Merge branch 'objtool/core' of https://git.kernel.org/pub/scm/linux/kernel/git/jpoimboe/linux

This series introduces new objtool features and a klp-build script to
generate livepatch modules using a source .patch as input.

This builds on concepts from the longstanding out-of-tree kpatch [1]
project which began in 2012 and has been used for many years to generate
livepatch modules for production kernels. However, this is a complete
rewrite which incorporates hard-earned lessons from 12+ years of
maintaining kpatch.

Key improvements compared to kpatch-build:

- Integrated with objtool: Leverages objtool's existing control-flow
graph analysis to help detect changed functions.

- Works on vmlinux.o: Supports late-linked objects, making it
compatible with LTO, IBT, and similar.

- Simplified code base: ~3k fewer lines of code.

- Upstream: No more out-of-tree #ifdef hacks, far less cruft.

- Cleaner internals: Vastly simplified logic for symbol/section/reloc
inclusion and special section extraction.

- Robust __LINE__ macro handling: Avoids false positive binary diffs
caused by the __LINE__ macro by introducing a fix-patch-lines script
which injects #line directives into the source .patch to preserve
the original line numbers at compile time.

The primary user interface is the klp-build script which does the
following:

- Builds an original kernel with -function-sections and
-fdata-sections, plus objtool function checksumming.

- Applies the .patch file and rebuilds the kernel using the same
options.

- Runs 'objtool klp diff' to detect changed functions and generate
intermediate binary diff objects.

- Builds a kernel module which links the diff objects with some
livepatch module init code (scripts/livepatch/init.c).

- Finalizes the livepatch module (aka work around linker wreckage)
using 'objtool klp post-link'.

I've tested with a variety of patches on defconfig and Fedora-config
kernels with both GCC and Clang.

MAINTAINERS

···
 F:	Documentation/ABI/testing/sysfs-kernel-livepatch
 F:	Documentation/livepatch/
 F:	arch/powerpc/include/asm/livepatch.h
-F:	include/linux/livepatch.h
+F:	include/linux/livepatch*.h
 F:	kernel/livepatch/
 F:	kernel/module/livepatch.c
 F:	samples/livepatch/
+F:	scripts/livepatch/
 F:	tools/testing/selftests/livepatch/
 
 LLC (802.2)

arch/s390/include/asm/nospec-insn.h

···
 #ifdef CONFIG_EXPOLINE_EXTERN
 	SYM_CODE_START(\name)
 #else
-	.pushsection .text.\name,"axG",@progbits,\name,comdat
+	.pushsection .text..\name,"axG",@progbits,\name,comdat
 	.globl \name
 	.hidden \name
 	.type \name,@function

arch/s390/kernel/vmlinux.lds.S

···
 		IRQENTRY_TEXT
 		SOFTIRQENTRY_TEXT
 		FTRACE_HOTPATCH_TRAMPOLINES_TEXT
-		*(.text.*_indirect_*)
+		*(.text..*_indirect_*)
 		*(.gnu.warning)
 		. = ALIGN(PAGE_SIZE);
 		_etext = .;		/* End of text section */

arch/x86/Kconfig

···
 	select HAVE_FUNCTION_ERROR_INJECTION
 	select HAVE_KRETPROBES
 	select HAVE_RETHOOK
+	select HAVE_KLP_BUILD			if X86_64
 	select HAVE_LIVEPATCH			if X86_64
 	select HAVE_MIXED_BREAKPOINTS_REGS
 	select HAVE_MOD_ARCH_SPECIFIC

arch/x86/include/asm/alternative.h

···
 
 #define ALTINSTR_ENTRY(ft_flags)					      \
 	".pushsection .altinstructions,\"a\"\n"				      \
+	ANNOTATE_DATA_SPECIAL						      \
 	" .long 771b - .\n"				/* label           */ \
 	" .long 774f - .\n"				/* new instruction */ \
 	" .4byte " __stringify(ft_flags) "\n"		/* feature + flags */ \
···
 
 #define ALTINSTR_REPLACEMENT(newinstr)		/* replacement */	\
 	".pushsection .altinstr_replacement, \"ax\"\n"			\
+	ANNOTATE_DATA_SPECIAL						\
 	"# ALT: replacement\n"						\
 	"774:\n\t" newinstr "\n775:\n"					\
 	".popsection\n"
···
  * instruction. See apply_alternatives().
  */
 .macro altinstr_entry orig alt ft_flags orig_len alt_len
+	ANNOTATE_DATA_SPECIAL
 	.long \orig - .
 	.long \alt - .
 	.4byte \ft_flags
···
 	.popsection ;							\
 	.pushsection .altinstr_replacement,"ax"	;			\
 743:									\
+	ANNOTATE_DATA_SPECIAL ;						\
 	newinst	;							\
 744:									\
 	.popsection ;

arch/x86/include/asm/asm.h

···
 #ifndef _ASM_X86_ASM_H
 #define _ASM_X86_ASM_H
 
+#include <linux/annotate.h>
+
 #ifdef __ASSEMBLER__
 # define __ASM_FORM(x, ...)		x,## __VA_ARGS__
 # define __ASM_FORM_RAW(x, ...)		x,## __VA_ARGS__
···
 # define _ASM_EXTABLE_TYPE(from, to, type)			\
 	.pushsection "__ex_table","a" ;				\
 	.balign 4 ;						\
+	ANNOTATE_DATA_SPECIAL ;					\
 	.long (from) - . ;					\
 	.long (to) - . ;					\
 	.long type ;						\
···
 # define _ASM_EXTABLE_TYPE(from, to, type)			\
 	" .pushsection \"__ex_table\",\"a\"\n"			\
 	" .balign 4\n"						\
+	ANNOTATE_DATA_SPECIAL					\
 	" .long (" #from ") - .\n"				\
 	" .long (" #to ") - .\n"				\
 	" .long " __stringify(type) " \n"			\
···
 # define _ASM_EXTABLE_TYPE_REG(from, to, type, reg)				\
 	" .pushsection \"__ex_table\",\"a\"\n"					\
 	" .balign 4\n"								\
+	ANNOTATE_DATA_SPECIAL							\
 	" .long (" #from ") - .\n"						\
 	" .long (" #to ") - .\n"						\
 	DEFINE_EXTABLE_TYPE_REG							\

arch/x86/include/asm/bug.h

···
 #define _BUG_FLAGS_ASM(ins, file, line, flags, size, extra)		\
 	"1:\t" ins "\n"							\
 	".pushsection __bug_table,\"aw\"\n"				\
+	ANNOTATE_DATA_SPECIAL						\
 	__BUG_ENTRY(file, line, flags)					\
 	"\t.org 2b + " size "\n"					\
 	".popsection\n"							\

arch/x86/include/asm/cpufeature.h

···
 	asm goto(ALTERNATIVE_TERNARY("jmp 6f", %c[feature], "", "jmp %l[t_no]")
 		".pushsection .altinstr_aux,\"ax\"\n"
 		"6:\n"
+		ANNOTATE_DATA_SPECIAL
 		" testb %[bitnum], %a[cap_byte]\n"
 		" jnz %l[t_yes]\n"
 		" jmp %l[t_no]\n"

arch/x86/include/asm/jump_label.h

···
 #define JUMP_TABLE_ENTRY(key, label)			\
 	".pushsection __jump_table,  \"aw\" \n\t"	\
 	_ASM_ALIGN "\n\t"				\
+	ANNOTATE_DATA_SPECIAL				\
 	".long 1b - . \n\t"				\
 	".long " label " - . \n\t"			\
 	_ASM_PTR " " key " - . \n\t"			\

arch/x86/kernel/alternative.c

···
  * See entry_{32,64}.S for more details.
  */
 
-/*
- * We define the int3_magic() function in assembly to control the calling
- * convention such that we can 'call' it from assembly.
- */
-
-extern void int3_magic(unsigned int *ptr); /* defined in asm */
+extern void int3_selftest_asm(unsigned int *ptr);
 
 asm (
 "	.pushsection	.init.text, \"ax\", @progbits\n"
-"	.type		int3_magic, @function\n"
-"int3_magic:\n"
+"	.type		int3_selftest_asm, @function\n"
+"int3_selftest_asm:\n"
 	ANNOTATE_NOENDBR
-"	movl	$1, (%" _ASM_ARG1 ")\n"
+	/*
+	 * INT3 padded with NOP to CALL_INSN_SIZE. The INT3 triggers an
+	 * exception, then the int3_exception_nb notifier emulates a call to
+	 * int3_selftest_callee().
+	 */
+"	int3; nop; nop; nop; nop\n"
 	ASM_RET
-"	.size		int3_magic, .-int3_magic\n"
+"	.size		int3_selftest_asm, . - int3_selftest_asm\n"
+"	.popsection\n"
+);
+
+extern void int3_selftest_callee(unsigned int *ptr);
+
+asm (
+"	.pushsection	.init.text, \"ax\", @progbits\n"
+"	.type		int3_selftest_callee, @function\n"
+"int3_selftest_callee:\n"
+	ANNOTATE_NOENDBR
+"	movl	$0x1234, (%" _ASM_ARG1 ")\n"
+	ASM_RET
+"	.size		int3_selftest_callee, . - int3_selftest_callee\n"
 "	.popsection\n"
 );
 
···
 static int __init
 int3_exception_notify(struct notifier_block *self, unsigned long val, void *data)
 {
-	unsigned long selftest = (unsigned long)&int3_selftest_ip;
+	unsigned long selftest = (unsigned long)&int3_selftest_asm;
 	struct die_args *args = data;
 	struct pt_regs *regs = args->regs;
 
···
 	if (regs->ip - INT3_INSN_SIZE != selftest)
 		return NOTIFY_DONE;
 
-	int3_emulate_call(regs, (unsigned long)&int3_magic);
+	int3_emulate_call(regs, (unsigned long)&int3_selftest_callee);
 	return NOTIFY_STOP;
 }
 
···
 	BUG_ON(register_die_notifier(&int3_exception_nb));
 
 	/*
-	 * Basically: int3_magic(&val); but really complicated :-)
-	 *
-	 * INT3 padded with NOP to CALL_INSN_SIZE. The int3_exception_nb
-	 * notifier above will emulate CALL for us.
+	 * Basically: int3_selftest_callee(&val); but really complicated :-)
 	 */
-	asm volatile ("int3_selftest_ip:\n\t"
-		      ANNOTATE_NOENDBR
-		      "    int3; nop; nop; nop; nop\n\t"
-		      : ASM_CALL_CONSTRAINT
-		      : __ASM_SEL_RAW(a, D) (&val)
-		      : "memory");
+	int3_selftest_asm(&val);
 
-	BUG_ON(val != 1);
+	BUG_ON(val != 0x1234);
 
 	unregister_die_notifier(&int3_exception_nb);
 }

arch/x86/kernel/kprobes/opt.c

···
 
 asm (
 			".pushsection .rodata\n"
-			"optprobe_template_func:\n"
 			".global optprobe_template_entry\n"
 			"optprobe_template_entry:\n"
 #ifdef CONFIG_X86_64
···
 			".global optprobe_template_end\n"
 			"optprobe_template_end:\n"
 			".popsection\n");
-
-void optprobe_template_func(void);
-STACK_FRAME_NON_STANDARD(optprobe_template_func);
 
 #define TMPL_CLAC_IDX \
 	((long)optprobe_template_clac - (long)optprobe_template_entry)

arch/x86/kernel/module.c

···
 	DEBUGP("%s relocate section %u to %u\n",
 	       apply ? "Applying" : "Clearing",
 	       relsec, sechdrs[relsec].sh_info);
+
 	for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) {
 		size_t size;
 
···
 
 		if (apply) {
 			if (memcmp(loc, &zero, size)) {
-				pr_err("x86/modules: Invalid relocation target, existing value is nonzero for type %d, loc %p, val %Lx\n",
-				       (int)ELF64_R_TYPE(rel[i].r_info), loc, val);
+				pr_err("x86/modules: Invalid relocation target, existing value is nonzero for sec %u, idx %u, type %d, loc %lx, val %llx\n",
+				       relsec, i, (int)ELF64_R_TYPE(rel[i].r_info),
+				       (unsigned long)loc, val);
 				return -ENOEXEC;
 			}
 			write(loc, &val, size);
 		} else {
 			if (memcmp(loc, &val, size)) {
-				pr_warn("x86/modules: Invalid relocation target, existing value does not match expected value for type %d, loc %p, val %Lx\n",
-					(int)ELF64_R_TYPE(rel[i].r_info), loc, val);
+				pr_warn("x86/modules: Invalid relocation target, existing value does not match expected value for sec %u, idx %u, type %d, loc %lx, val %llx\n",
+					relsec, i, (int)ELF64_R_TYPE(rel[i].r_info),
+					(unsigned long)loc, val);
 				return -ENOEXEC;
 			}
 			write(loc, &zero, size);
···
 	return 0;
 
 overflow:
-	pr_err("overflow in relocation type %d val %Lx\n",
-	       (int)ELF64_R_TYPE(rel[i].r_info), val);
+	pr_err("overflow in relocation type %d val %llx sec %u idx %d\n",
+	       (int)ELF64_R_TYPE(rel[i].r_info), val, relsec, i);
 	pr_err("`%s' likely not compiled with -mcmodel=kernel\n",
 	       me->name);
 	return -ENOEXEC;

drivers/infiniband/hw/usnic/usnic_uiom_interval_tree.h

···
 usnic_uiom_interval_tree_remove(struct usnic_uiom_interval_node *node,
 					struct rb_root_cached *root);
 extern struct usnic_uiom_interval_node *
+usnic_uiom_interval_tree_subtree_search(struct usnic_uiom_interval_node *node,
+					unsigned long start,
+					unsigned long last);
+extern struct usnic_uiom_interval_node *
 usnic_uiom_interval_tree_iter_first(struct rb_root_cached *root,
 					unsigned long start,
 					unsigned long last);

include/asm-generic/vmlinux.lds.h

···
 #define ALIGN_FUNCTION()  . = ALIGN(CONFIG_FUNCTION_ALIGNMENT)
 
 /*
- * LD_DEAD_CODE_DATA_ELIMINATION option enables -fdata-sections, which
- * generates .data.identifier sections, which need to be pulled in with
- * .data. We don't want to pull in .data..other sections, which Linux
- * has defined. Same for text and bss.
+ * Support -ffunction-sections by matching .text and .text.*,
+ * but exclude '.text..*'.
  *
- * With LTO_CLANG, the linker also splits sections by default, so we need
- * these macros to combine the sections during the final link.
- *
- * With AUTOFDO_CLANG and PROPELLER_CLANG, by default, the linker splits
- * text sections and regroups functions into subsections.
- *
- * RODATA_MAIN is not used because existing code already defines .rodata.x
- * sections to be brought in with rodata.
+ * Special .text.* sections that are typically grouped separately, such as
+ * .text.unlikely or .text.hot, must be matched explicitly before using
+ * TEXT_MAIN.
  */
-#if defined(CONFIG_LD_DEAD_CODE_DATA_ELIMINATION) || defined(CONFIG_LTO_CLANG) || \
-defined(CONFIG_AUTOFDO_CLANG) || defined(CONFIG_PROPELLER_CLANG)
 #define TEXT_MAIN .text .text.[0-9a-zA-Z_]*
-#else
-#define TEXT_MAIN .text
-#endif
-#if defined(CONFIG_LD_DEAD_CODE_DATA_ELIMINATION) || defined(CONFIG_LTO_CLANG)
+
+/*
+ * Support -fdata-sections by matching .data, .data.*, and others,
+ * but exclude '.data..*'.
+ */
 #define DATA_MAIN .data .data.[0-9a-zA-Z_]* .data.rel.* .data..L* .data..compoundliteral* .data.$__unnamed_* .data.$L*
 #define SDATA_MAIN .sdata .sdata.[0-9a-zA-Z_]*
 #define RODATA_MAIN .rodata .rodata.[0-9a-zA-Z_]* .rodata..L*
 #define BSS_MAIN .bss .bss.[0-9a-zA-Z_]* .bss..L* .bss..compoundliteral*
 #define SBSS_MAIN .sbss .sbss.[0-9a-zA-Z_]*
-#else
-#define DATA_MAIN .data .data.rel .data.rel.local
-#define SDATA_MAIN .sdata
-#define RODATA_MAIN .rodata
-#define BSS_MAIN .bss
-#define SBSS_MAIN .sbss
-#endif
 
 /*
  * GCC 4.5 and later have a 32 bytes section alignment for structures.
···
  * during second ld run in second ld pass when generating System.map
  *
  * TEXT_MAIN here will match symbols with a fixed pattern (for example,
- * .text.hot or .text.unlikely) if dead code elimination or
- * function-section is enabled. Match these symbols first before
- * TEXT_MAIN to ensure they are grouped together.
+ * .text.hot or .text.unlikely).  Match those before TEXT_MAIN to ensure
+ * they get grouped together.
  *
  * Also placing .text.hot section at the beginning of a page, this
  * would help the TLB performance.

include/linux/annotate.h

···
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_ANNOTATE_H
+#define _LINUX_ANNOTATE_H
+
+#include <linux/objtool_types.h>
+
+#ifdef CONFIG_OBJTOOL
+
+#ifndef __ASSEMBLY__
+
+#define __ASM_ANNOTATE(section, label, type)				\
+	".pushsection " section ",\"M\", @progbits, 8\n\t"		\
+	".long " __stringify(label) " - .\n\t"				\
+	".long " __stringify(type) "\n\t"				\
+	".popsection\n\t"
+
+#define ASM_ANNOTATE_LABEL(label, type)					\
+	__ASM_ANNOTATE(".discard.annotate_insn", label, type)
+
+#define ASM_ANNOTATE(type)						\
+	"911:\n\t"							\
+	ASM_ANNOTATE_LABEL(911b, type)
+
+#define ASM_ANNOTATE_DATA(type)						\
+	"912:\n\t"							\
+	__ASM_ANNOTATE(".discard.annotate_data", 912b, type)
+
+#else /* __ASSEMBLY__ */
+
+.macro __ANNOTATE section, type
+.Lhere_\@:
+	.pushsection \section, "M", @progbits, 8
+	.long	.Lhere_\@ - .
+	.long	\type
+	.popsection
+.endm
+
+.macro ANNOTATE type
+	__ANNOTATE ".discard.annotate_insn", \type
+.endm
+
+.macro ANNOTATE_DATA type
+	__ANNOTATE ".discard.annotate_data", \type
+.endm
+
+#endif /* __ASSEMBLY__ */
+
+#else /* !CONFIG_OBJTOOL */
+#ifndef __ASSEMBLY__
+#define ASM_ANNOTATE_LABEL(label, type) ""
+#define ASM_ANNOTATE(type)
+#define ASM_ANNOTATE_DATA(type)
+#else /* __ASSEMBLY__ */
+.macro ANNOTATE type
+.endm
+.macro ANNOTATE_DATA type
+.endm
+#endif /* __ASSEMBLY__ */
+#endif /* !CONFIG_OBJTOOL */
+
+#ifndef __ASSEMBLY__
+
+/*
+ * Annotate away the various 'relocation to !ENDBR` complaints; knowing that
+ * these relocations will never be used for indirect calls.
+ */
+#define ANNOTATE_NOENDBR		ASM_ANNOTATE(ANNOTYPE_NOENDBR)
+#define ANNOTATE_NOENDBR_SYM(sym)	asm(ASM_ANNOTATE_LABEL(sym, ANNOTYPE_NOENDBR))
+
+/*
+ * This should be used immediately before an indirect jump/call. It tells
+ * objtool the subsequent indirect jump/call is vouched safe for retpoline
+ * builds.
+ */
+#define ANNOTATE_RETPOLINE_SAFE		ASM_ANNOTATE(ANNOTYPE_RETPOLINE_SAFE)
+/*
+ * See linux/instrumentation.h
+ */
+#define ANNOTATE_INSTR_BEGIN(label)	ASM_ANNOTATE_LABEL(label, ANNOTYPE_INSTR_BEGIN)
+#define ANNOTATE_INSTR_END(label)	ASM_ANNOTATE_LABEL(label, ANNOTYPE_INSTR_END)
+/*
+ * objtool annotation to ignore the alternatives and only consider the original
+ * instruction(s).
+ */
+#define ANNOTATE_IGNORE_ALTERNATIVE	ASM_ANNOTATE(ANNOTYPE_IGNORE_ALTS)
+/*
+ * This macro indicates that the following intra-function call is valid.
+ * Any non-annotated intra-function call will cause objtool to issue a warning.
+ */
+#define ANNOTATE_INTRA_FUNCTION_CALL	ASM_ANNOTATE(ANNOTYPE_INTRA_FUNCTION_CALL)
+/*
+ * Use objtool to validate the entry requirement that all code paths do
+ * VALIDATE_UNRET_END before RET.
+ *
+ * NOTE: The macro must be used at the beginning of a global symbol, otherwise
+ * it will be ignored.
+ */
+#define ANNOTATE_UNRET_BEGIN		ASM_ANNOTATE(ANNOTYPE_UNRET_BEGIN)
+/*
+ * This should be used to refer to an instruction that is considered
+ * terminating, like a noreturn CALL or UD2 when we know they are not -- eg
+ * WARN using UD2.
+ */
+#define ANNOTATE_REACHABLE(label)	ASM_ANNOTATE_LABEL(label, ANNOTYPE_REACHABLE)
+/*
+ * This should not be used; it annotates away CFI violations. There are a few
+ * valid use cases like kexec handover to the next kernel image, and there is
+ * no security concern there.
+ *
+ * There are also a few real issues annotated away, like EFI because we can't
+ * control the EFI code.
+ */
+#define ANNOTATE_NOCFI_SYM(sym)		asm(ASM_ANNOTATE_LABEL(sym, ANNOTYPE_NOCFI))
+
+/*
+ * Annotate a special section entry.  This emables livepatch module generation
+ * to find and extract individual special section entries as needed.
+ */
+#define ANNOTATE_DATA_SPECIAL		ASM_ANNOTATE_DATA(ANNOTYPE_DATA_SPECIAL)
+
+#else /* __ASSEMBLY__ */
+#define ANNOTATE_NOENDBR		ANNOTATE type=ANNOTYPE_NOENDBR
+#define ANNOTATE_RETPOLINE_SAFE		ANNOTATE type=ANNOTYPE_RETPOLINE_SAFE
+/*	ANNOTATE_INSTR_BEGIN		ANNOTATE type=ANNOTYPE_INSTR_BEGIN */
+/*	ANNOTATE_INSTR_END		ANNOTATE type=ANNOTYPE_INSTR_END */
+#define ANNOTATE_IGNORE_ALTERNATIVE	ANNOTATE type=ANNOTYPE_IGNORE_ALTS
+#define ANNOTATE_INTRA_FUNCTION_CALL	ANNOTATE type=ANNOTYPE_INTRA_FUNCTION_CALL
+#define ANNOTATE_UNRET_BEGIN		ANNOTATE type=ANNOTYPE_UNRET_BEGIN
+#define ANNOTATE_REACHABLE		ANNOTATE type=ANNOTYPE_REACHABLE
+#define ANNOTATE_NOCFI_SYM		ANNOTATE type=ANNOTYPE_NOCFI
+#define ANNOTATE_DATA_SPECIAL		ANNOTATE_DATA type=ANNOTYPE_DATA_SPECIAL
+#endif /* __ASSEMBLY__ */
+
+#endif /* _LINUX_ANNOTATE_H */

include/linux/compiler.h

···
 	__asm__ ("" : "=r" (var) : "0" (var))
 #endif
 
-#define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
+/* Format: __UNIQUE_ID_<name>_<__COUNTER__> */
+#define __UNIQUE_ID(name)					\
+	__PASTE(__UNIQUE_ID_,					\
+	__PASTE(name,						\
+	__PASTE(_, __COUNTER__)))
 
 /**
  * data_race - mark an expression as containing intentional data races
···
  */
 #define ___ADDRESSABLE(sym, __attrs)						\
 	static void * __used __attrs						\
-	__UNIQUE_ID(__PASTE(__addressable_,sym)) = (void *)(uintptr_t)&sym;
+	__UNIQUE_ID(__PASTE(addressable_, sym)) = (void *)(uintptr_t)&sym;
 
 #define __ADDRESSABLE(sym) \
 	___ADDRESSABLE(sym, __section(".discard.addressable"))

include/linux/elfnote.h

···
 
 #else	/* !__ASSEMBLER__ */
 #include <uapi/linux/elf.h>
+#include <linux/compiler.h>
 /*
  * Use an anonymous structure which matches the shape of
  * Elf{32,64}_Nhdr, but includes the name and desc data.  The size and
  * type of name and desc depend on the macro arguments.  "name" must
- * be a literal string, and "desc" must be passed by value.  You may
- * only define one note per line, since __LINE__ is used to generate
- * unique symbols.
+ * be a literal string, and "desc" must be passed by value.
  */
-#define _ELFNOTE_PASTE(a,b)	a##b
-#define _ELFNOTE(size, name, unique, type, desc)			\
+#define ELFNOTE(size, name, type, desc)					\
 	static const struct {						\
 		struct elf##size##_note _nhdr;				\
 		unsigned char _name[sizeof(name)]			\
 		__attribute__((aligned(sizeof(Elf##size##_Word))));	\
 		typeof(desc) _desc					\
 			     __attribute__((aligned(sizeof(Elf##size##_Word)))); \
-	} _ELFNOTE_PASTE(_note_, unique)				\
+	} __UNIQUE_ID(note)						\
 		__used							\
 		__attribute__((section(".note." name),			\
 			       aligned(sizeof(Elf##size##_Word)),	\
···
 		name,							\
 		desc							\
 	}
-#define ELFNOTE(size, name, type, desc)		\
-	_ELFNOTE(size, name, __LINE__, type, desc)
 
 #define ELFNOTE32(name, type, desc) ELFNOTE(32, name, type, desc)
 #define ELFNOTE64(name, type, desc) ELFNOTE(64, name, type, desc)
+
 #endif	/* __ASSEMBLER__ */
 
 #endif /* _LINUX_ELFNOTE_H */

include/linux/init.h

···
 
 /* Format: <modname>__<counter>_<line>_<fn> */
 #define __initcall_id(fn)					\
+	__PASTE(kmod_,						\
 	__PASTE(__KBUILD_MODNAME,				\
 	__PASTE(__,						\
 	__PASTE(__COUNTER__,					\
 	__PASTE(_,						\
 	__PASTE(__LINE__,					\
-	__PASTE(_, fn))))))
+	__PASTE(_, fn)))))))
 
 /* Format: __<prefix>__<iid><id> */
 #define __initcall_name(prefix, __iid, id)			\

include/linux/interval_tree.h

···
 		     struct rb_root_cached *root);
 
 extern struct interval_tree_node *
+interval_tree_subtree_search(struct interval_tree_node *node,
+			     unsigned long start, unsigned long last);
+
+extern struct interval_tree_node *
 interval_tree_iter_first(struct rb_root_cached *root,
 			 unsigned long start, unsigned long last);
 

include/linux/interval_tree_generic.h

···
  *   Cond2: start <= ITLAST(node)					      \
  */									      \
 									      \
-static ITSTRUCT *							      \
+ITSTATIC ITSTRUCT *							      \
 ITPREFIX ## _subtree_search(ITSTRUCT *node, ITTYPE start, ITTYPE last)	      \
 {									      \
 	while (true) {							      \

include/linux/livepatch.h

···
 #include <linux/ftrace.h>
 #include <linux/completion.h>
 #include <linux/list.h>
+#include <linux/livepatch_external.h>
 #include <linux/livepatch_sched.h>
 
 #if IS_ENABLED(CONFIG_LIVEPATCH)
···
 	bool nop;
 	bool patched;
 	bool transition;
-};
-
-struct klp_object;
-
-/**
- * struct klp_callbacks - pre/post live-(un)patch callback structure
- * @pre_patch:		executed before code patching
- * @post_patch:		executed after code patching
- * @pre_unpatch:	executed before code unpatching
- * @post_unpatch:	executed after code unpatching
- * @post_unpatch_enabled:	flag indicating if post-unpatch callback
- * 				should run
- *
- * All callbacks are optional.  Only the pre-patch callback, if provided,
- * will be unconditionally executed.  If the parent klp_object fails to
- * patch for any reason, including a non-zero error status returned from
- * the pre-patch callback, no further callbacks will be executed.
- */
-struct klp_callbacks {
-	int (*pre_patch)(struct klp_object *obj);
-	void (*post_patch)(struct klp_object *obj);
-	void (*pre_unpatch)(struct klp_object *obj);
-	void (*post_unpatch)(struct klp_object *obj);
-	bool post_unpatch_enabled;
 };
 
 /**

include/linux/livepatch_external.h

···
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * External livepatch interfaces for patch creation tooling
+ */
+
+#ifndef _LINUX_LIVEPATCH_EXTERNAL_H_
+#define _LINUX_LIVEPATCH_EXTERNAL_H_
+
+#include <linux/types.h>
+
+#define KLP_RELOC_SEC_PREFIX		".klp.rela."
+#define KLP_SYM_PREFIX			".klp.sym."
+
+#define __KLP_PRE_PATCH_PREFIX		__klp_pre_patch_callback_
+#define __KLP_POST_PATCH_PREFIX		__klp_post_patch_callback_
+#define __KLP_PRE_UNPATCH_PREFIX	__klp_pre_unpatch_callback_
+#define __KLP_POST_UNPATCH_PREFIX	__klp_post_unpatch_callback_
+
+#define KLP_PRE_PATCH_PREFIX		__stringify(__KLP_PRE_PATCH_PREFIX)
+#define KLP_POST_PATCH_PREFIX		__stringify(__KLP_POST_PATCH_PREFIX)
+#define KLP_PRE_UNPATCH_PREFIX		__stringify(__KLP_PRE_UNPATCH_PREFIX)
+#define KLP_POST_UNPATCH_PREFIX		__stringify(__KLP_POST_UNPATCH_PREFIX)
+
+struct klp_object;
+
+typedef int (*klp_pre_patch_t)(struct klp_object *obj);
+typedef void (*klp_post_patch_t)(struct klp_object *obj);
+typedef void (*klp_pre_unpatch_t)(struct klp_object *obj);
+typedef void (*klp_post_unpatch_t)(struct klp_object *obj);
+
+/**
+ * struct klp_callbacks - pre/post live-(un)patch callback structure
+ * @pre_patch:		executed before code patching
+ * @post_patch:		executed after code patching
+ * @pre_unpatch:	executed before code unpatching
+ * @post_unpatch:	executed after code unpatching
+ * @post_unpatch_enabled:	flag indicating if post-unpatch callback
+ *				should run
+ *
+ * All callbacks are optional.  Only the pre-patch callback, if provided,
+ * will be unconditionally executed.  If the parent klp_object fails to
+ * patch for any reason, including a non-zero error status returned from
+ * the pre-patch callback, no further callbacks will be executed.
+ */
+struct klp_callbacks {
+	klp_pre_patch_t		pre_patch;
+	klp_post_patch_t	post_patch;
+	klp_pre_unpatch_t	pre_unpatch;
+	klp_post_unpatch_t	post_unpatch;
+	bool post_unpatch_enabled;
+};
+
+/*
+ * 'struct klp_{func,object}_ext' are compact "external" representations of
+ * 'struct klp_{func,object}'.   They are used by objtool for livepatch
+ * generation.  The structs are then read by the livepatch module and converted
+ * to the real structs before calling klp_enable_patch().
+ *
+ * TODO make these the official API for klp_enable_patch().  That should
+ * simplify livepatch's interface as well as its data structure lifetime
+ * management.
+ */
+struct klp_func_ext {
+	const char *old_name;
+	void *new_func;
+	unsigned long sympos;
+};
+
+struct klp_object_ext {
+	const char *name;
+	struct klp_func_ext *funcs;
+	struct klp_callbacks callbacks;
+	unsigned int nr_funcs;
+};
+
+#endif /* _LINUX_LIVEPATCH_EXTERNAL_H_ */

include/linux/livepatch_helpers.h

···
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_LIVEPATCH_HELPERS_H
+#define _LINUX_LIVEPATCH_HELPERS_H
+
+/*
+ * Interfaces for use by livepatch patches
+ */
+
+#include <linux/syscalls.h>
+#include <linux/livepatch.h>
+
+#ifdef MODULE
+#define KLP_OBJNAME __KBUILD_MODNAME
+#else
+#define KLP_OBJNAME vmlinux
+#endif
+
+/* Livepatch callback registration */
+
+#define KLP_CALLBACK_PTRS ".discard.klp_callback_ptrs"
+
+#define KLP_PRE_PATCH_CALLBACK(func)						\
+	klp_pre_patch_t __used __section(KLP_CALLBACK_PTRS)			\
+		__PASTE(__KLP_PRE_PATCH_PREFIX, KLP_OBJNAME) = func
+
+#define KLP_POST_PATCH_CALLBACK(func)						\
+	klp_post_patch_t __used __section(KLP_CALLBACK_PTRS)			\
+		__PASTE(__KLP_POST_PATCH_PREFIX, KLP_OBJNAME) = func
+
+#define KLP_PRE_UNPATCH_CALLBACK(func)						\
+	klp_pre_unpatch_t __used __section(KLP_CALLBACK_PTRS)			\
+		__PASTE(__KLP_PRE_UNPATCH_PREFIX, KLP_OBJNAME) = func
+
+#define KLP_POST_UNPATCH_CALLBACK(func)						\
+	klp_post_unpatch_t __used __section(KLP_CALLBACK_PTRS)			\
+		__PASTE(__KLP_POST_UNPATCH_PREFIX, KLP_OBJNAME) = func
+
+/*
+ * Replace static_call() usage with this macro when create-diff-object
+ * recommends it due to the original static call key living in a module.
+ *
+ * This converts the static call to a regular indirect call.
+ */
+#define KLP_STATIC_CALL(name) \
+	((typeof(STATIC_CALL_TRAMP(name))*)(STATIC_CALL_KEY(name).func))
+
+/* Syscall patching */
+
+#define KLP_SYSCALL_DEFINE1(name, ...) KLP_SYSCALL_DEFINEx(1, _##name, __VA_ARGS__)
+#define KLP_SYSCALL_DEFINE2(name, ...) KLP_SYSCALL_DEFINEx(2, _##name, __VA_ARGS__)
+#define KLP_SYSCALL_DEFINE3(name, ...) KLP_SYSCALL_DEFINEx(3, _##name, __VA_ARGS__)
+#define KLP_SYSCALL_DEFINE4(name, ...) KLP_SYSCALL_DEFINEx(4, _##name, __VA_ARGS__)
+#define KLP_SYSCALL_DEFINE5(name, ...) KLP_SYSCALL_DEFINEx(5, _##name, __VA_ARGS__)
+#define KLP_SYSCALL_DEFINE6(name, ...) KLP_SYSCALL_DEFINEx(6, _##name, __VA_ARGS__)
+
+#define KLP_SYSCALL_DEFINEx(x, sname, ...)				\
+	__KLP_SYSCALL_DEFINEx(x, sname, __VA_ARGS__)
+
+#ifdef CONFIG_X86_64
+// TODO move this to arch/x86/include/asm/syscall_wrapper.h and share code
+#define __KLP_SYSCALL_DEFINEx(x, name, ...)			\
+	static long __se_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__));	\
+	static inline long __klp_do_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__));\
+	__X64_SYS_STUBx(x, name, __VA_ARGS__)				\
+	__IA32_SYS_STUBx(x, name, __VA_ARGS__)				\
+	static long __se_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__))	\
+	{								\
+		long ret = __klp_do_sys##name(__MAP(x,__SC_CAST,__VA_ARGS__));\
+		__MAP(x,__SC_TEST,__VA_ARGS__);				\
+		__PROTECT(x, ret,__MAP(x,__SC_ARGS,__VA_ARGS__));	\
+		return ret;						\
+	}								\
+	static inline long __klp_do_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__))
+
+#endif
+
+#endif /* _LINUX_LIVEPATCH_HELPERS_H */

include/linux/mm.h

···
 				    struct rb_root_cached *root);
 void vma_interval_tree_remove(struct vm_area_struct *node,
 			      struct rb_root_cached *root);
+struct vm_area_struct *vma_interval_tree_subtree_search(struct vm_area_struct *node,
+				unsigned long start, unsigned long last);
 struct vm_area_struct *vma_interval_tree_iter_first(struct rb_root_cached *root,
 				unsigned long start, unsigned long last);
 struct vm_area_struct *vma_interval_tree_iter_next(struct vm_area_struct *node,

include/linux/objtool.h

···
 #define _LINUX_OBJTOOL_H
 
 #include <linux/objtool_types.h>
+#include <linux/annotate.h>
 
 #ifdef CONFIG_OBJTOOL
 
-#include <asm/asm.h>
-
 #ifndef __ASSEMBLY__
 
-#define UNWIND_HINT(type, sp_reg, sp_offset, signal)	\
+#define UNWIND_HINT(type, sp_reg, sp_offset, signal)		\
 	"987: \n\t"						\
 	".pushsection .discard.unwind_hints\n\t"		\
+	ANNOTATE_DATA_SPECIAL					\
 	/* struct unwind_hint */				\
 	".long 987b - .\n\t"					\
 	".short " __stringify(sp_offset) "\n\t"			\
···
 
 #define __ASM_BREF(label)	label ## b
 
-#define __ASM_ANNOTATE(label, type)					\
-	".pushsection .discard.annotate_insn,\"M\",@progbits,8\n\t"	\
-	".long " __stringify(label) " - .\n\t"			\
-	".long " __stringify(type) "\n\t"				\
-	".popsection\n\t"
-
-#define ASM_ANNOTATE(type)						\
-	"911:\n\t"						\
-	__ASM_ANNOTATE(911b, type)
-
 #else /* __ASSEMBLY__ */
 
 /*
···
 .macro UNWIND_HINT type:req sp_reg=0 sp_offset=0 signal=0
 .Lhere_\@:
 	.pushsection .discard.unwind_hints
+		ANNOTATE_DATA_SPECIAL
 		/* struct unwind_hint */
 		.long .Lhere_\@ - .
 		.short \sp_offset
···
 
 .macro STACK_FRAME_NON_STANDARD func:req
 	.pushsection .discard.func_stack_frame_non_standard, "aw"
-	.long \func - .
+	.quad \func
 	.popsection
 .endm
 
···
 #ifdef CONFIG_FRAME_POINTER
 	STACK_FRAME_NON_STANDARD \func
 #endif
-.endm
-
-.macro ANNOTATE type:req
-.Lhere_\@:
-	.pushsection .discard.annotate_insn,"M",@progbits,8
-	.long	.Lhere_\@ - .
-	.long	\type
-	.popsection
 .endm
 
 #endif /* __ASSEMBLY__ */
···
 #define UNWIND_HINT(type, sp_reg, sp_offset, signal) "\n\t"
 #define STACK_FRAME_NON_STANDARD(func)
 #define STACK_FRAME_NON_STANDARD_FP(func)
-#define __ASM_ANNOTATE(label, type) ""
-#define ASM_ANNOTATE(type)
 #else
 .macro UNWIND_HINT type:req sp_reg=0 sp_offset=0 signal=0
 .endm
 .macro STACK_FRAME_NON_STANDARD func:req
 .endm
-.macro ANNOTATE type:req
-.endm
 #endif
 
 #endif /* CONFIG_OBJTOOL */
-
-#ifndef __ASSEMBLY__
-/*
- * Annotate away the various 'relocation to !ENDBR` complaints; knowing that
- * these relocations will never be used for indirect calls.
- */
-#define ANNOTATE_NOENDBR		ASM_ANNOTATE(ANNOTYPE_NOENDBR)
-#define ANNOTATE_NOENDBR_SYM(sym)	asm(__ASM_ANNOTATE(sym, ANNOTYPE_NOENDBR))
-
-/*
- * This should be used immediately before an indirect jump/call. It tells
- * objtool the subsequent indirect jump/call is vouched safe for retpoline
- * builds.
- */
-#define ANNOTATE_RETPOLINE_SAFE		ASM_ANNOTATE(ANNOTYPE_RETPOLINE_SAFE)
-/*
- * See linux/instrumentation.h
- */
-#define ANNOTATE_INSTR_BEGIN(label)	__ASM_ANNOTATE(label, ANNOTYPE_INSTR_BEGIN)
-#define ANNOTATE_INSTR_END(label)	__ASM_ANNOTATE(label, ANNOTYPE_INSTR_END)
-/*
- * objtool annotation to ignore the alternatives and only consider the original
- * instruction(s).
- */
-#define ANNOTATE_IGNORE_ALTERNATIVE	ASM_ANNOTATE(ANNOTYPE_IGNORE_ALTS)
-/*
- * This macro indicates that the following intra-function call is valid.
- * Any non-annotated intra-function call will cause objtool to issue a warning.
- */
-#define ANNOTATE_INTRA_FUNCTION_CALL	ASM_ANNOTATE(ANNOTYPE_INTRA_FUNCTION_CALL)
-/*
- * Use objtool to validate the entry requirement that all code paths do
- * VALIDATE_UNRET_END before RET.
- *
- * NOTE: The macro must be used at the beginning of a global symbol, otherwise
- * it will be ignored.
- */
-#define ANNOTATE_UNRET_BEGIN		ASM_ANNOTATE(ANNOTYPE_UNRET_BEGIN)
-/*
- * This should be used to refer to an instruction that is considered
- * terminating, like a noreturn CALL or UD2 when we know they are not -- eg
- * WARN using UD2.
- */
-#define ANNOTATE_REACHABLE(label)	__ASM_ANNOTATE(label, ANNOTYPE_REACHABLE)
-/*
- * This should not be used; it annotates away CFI violations. There are a few
- * valid use cases like kexec handover to the next kernel image, and there is
- * no security concern there.
- *
- * There are also a few real issues annotated away, like EFI because we can't
- * control the EFI code.
- */
-#define ANNOTATE_NOCFI_SYM(sym)		asm(__ASM_ANNOTATE(sym, ANNOTYPE_NOCFI))
-
-#else
-#define ANNOTATE_NOENDBR		ANNOTATE type=ANNOTYPE_NOENDBR
-#define ANNOTATE_RETPOLINE_SAFE		ANNOTATE type=ANNOTYPE_RETPOLINE_SAFE
-/*	ANNOTATE_INSTR_BEGIN		ANNOTATE type=ANNOTYPE_INSTR_BEGIN */
-/*	ANNOTATE_INSTR_END		ANNOTATE type=ANNOTYPE_INSTR_END */
-#define ANNOTATE_IGNORE_ALTERNATIVE	ANNOTATE type=ANNOTYPE_IGNORE_ALTS
-#define ANNOTATE_INTRA_FUNCTION_CALL	ANNOTATE type=ANNOTYPE_INTRA_FUNCTION_CALL
-#define ANNOTATE_UNRET_BEGIN		ANNOTATE type=ANNOTYPE_UNRET_BEGIN
-#define ANNOTATE_REACHABLE		ANNOTATE type=ANNOTYPE_REACHABLE
-#define ANNOTATE_NOCFI_SYM		ANNOTATE type=ANNOTYPE_NOCFI
-#endif
 
 #if defined(CONFIG_NOINSTR_VALIDATION) && \
 	(defined(CONFIG_MITIGATION_UNRET_ENTRY) || defined(CONFIG_MITIGATION_SRSO))

include/linux/objtool_types.h

···
 #define ANNOTYPE_REACHABLE		8
 #define ANNOTYPE_NOCFI			9
 
+#define ANNOTYPE_DATA_SPECIAL		1
+
 #endif /* _LINUX_OBJTOOL_TYPES_H */

kernel/livepatch/Kconfig

···
 	  module uses the interface provided by this option to register
 	  a patch, causing calls to patched functions to be redirected
 	  to new function code contained in the patch module.
+
+config HAVE_KLP_BUILD
+	bool
+	help
+	  Arch supports klp-build
+
+config KLP_BUILD
+	def_bool y
+	depends on LIVEPATCH && HAVE_KLP_BUILD
+	select OBJTOOL
+	help
+	  Enable klp-build support

kernel/livepatch/core.c

···
 	for (i = 0; i < relasec->sh_size / sizeof(Elf_Rela); i++) {
 		sym = (Elf_Sym *)sechdrs[symndx].sh_addr + ELF_R_SYM(relas[i].r_info);
 		if (sym->st_shndx != SHN_LIVEPATCH) {
-			pr_err("symbol %s is not marked as a livepatch symbol\n",
-			       strtab + sym->st_name);
+			pr_err("symbol %s at rela sec %u idx %d is not marked as a livepatch symbol\n",
+			       strtab + sym->st_name, symndx, i);
 			return -EINVAL;
 		}
 
 		/* Format: .klp.sym.sym_objname.sym_name,sympos */
 		cnt = sscanf(strtab + sym->st_name,
-			     ".klp.sym.%55[^.].%511[^,],%lu",
+			     KLP_SYM_PREFIX "%55[^.].%511[^,],%lu",
 			     sym_objname, sym_name, &sympos);
 		if (cnt != 3) {
 			pr_err("symbol %s has an incorrectly formatted name\n",
···
 	 * See comment in klp_resolve_symbols() for an explanation
 	 * of the selected field width value.
 	 */
-	cnt = sscanf(shstrtab + sec->sh_name, ".klp.rela.%55[^.]",
+	cnt = sscanf(shstrtab + sec->sh_name, KLP_RELOC_SEC_PREFIX "%55[^.]",
 		     sec_objname);
 	if (cnt != 1) {
 		pr_err("section %s has an incorrectly formatted name\n",

lib/interval_tree.c

···
 
 EXPORT_SYMBOL_GPL(interval_tree_insert);
 EXPORT_SYMBOL_GPL(interval_tree_remove);
+EXPORT_SYMBOL_GPL(interval_tree_subtree_search);
 EXPORT_SYMBOL_GPL(interval_tree_iter_first);
 EXPORT_SYMBOL_GPL(interval_tree_iter_next);
 

scripts/Makefile.lib

···
 name-fix = $(call stringify,$(call name-fix-token,$1))
 basename_flags = -DKBUILD_BASENAME=$(call name-fix,$(basetarget))
 modname_flags  = -DKBUILD_MODNAME=$(call name-fix,$(modname)) \
-		 -D__KBUILD_MODNAME=kmod_$(call name-fix-token,$(modname))
+		 -D__KBUILD_MODNAME=$(call name-fix-token,$(modname))
 modfile_flags  = -DKBUILD_MODFILE=$(call stringify,$(modfile))
 
 _c_flags       = $(filter-out $(CFLAGS_REMOVE_$(target-stem).o), \
···
 
 objtool := $(objtree)/tools/objtool/objtool
 
+objtool-args-$(CONFIG_KLP_BUILD)			+= --checksum
 objtool-args-$(CONFIG_HAVE_JUMP_LABEL_HACK)		+= --hacks=jump_label
 objtool-args-$(CONFIG_HAVE_NOINSTR_HACK)		+= --hacks=noinstr
 objtool-args-$(CONFIG_MITIGATION_CALL_DEPTH_TRACKING)	+= --hacks=skylake
···
 objtool-args-$(CONFIG_HAVE_UACCESS_VALIDATION)		+= --uaccess
 objtool-args-$(or $(CONFIG_GCOV_KERNEL),$(CONFIG_KCOV))	+= --no-unreachable
 objtool-args-$(CONFIG_PREFIX_SYMBOLS)			+= --prefix=$(CONFIG_FUNCTION_PADDING_BYTES)
-objtool-args-$(CONFIG_OBJTOOL_WERROR)			+= --Werror
+objtool-args-$(CONFIG_OBJTOOL_WERROR)			+= --werror
 
 objtool-args = $(objtool-args-y)					\
 	$(if $(delay-objtool), --link)					\
 	$(if $(part-of-module), --module)
 
-delay-objtool := $(or $(CONFIG_LTO_CLANG),$(CONFIG_X86_KERNEL_IBT))
+delay-objtool := $(or $(CONFIG_LTO_CLANG),$(CONFIG_X86_KERNEL_IBT),$(CONFIG_KLP_BUILD))
 
 cmd_objtool = $(if $(objtool-enabled), ; $(objtool) $(objtool-args) $@)
 cmd_gen_objtooldep = $(if $(objtool-enabled), { echo ; echo '$@: $$(wildcard $(objtool))' ; } >> $(dot-target).cmd)

scripts/Makefile.vmlinux_o

···
 ifeq ($(delay-objtool),y)
 vmlinux-objtool-args-y					+= $(objtool-args-y)
 else
-vmlinux-objtool-args-$(CONFIG_OBJTOOL_WERROR)		+= --Werror
+vmlinux-objtool-args-$(CONFIG_OBJTOOL_WERROR)		+= --werror
 endif
 
 vmlinux-objtool-args-$(CONFIG_NOINSTR_VALIDATION)	+= --noinstr \

scripts/faddr2line

···
-#!/bin/bash
+#!/usr/bin/env bash
 # SPDX-License-Identifier: GPL-2.0
 #
 # Translate stack dump function offsets.
···
 AWK="awk"
 GREP="grep"
 
+# Enforce ASCII-only output from tools like readelf
+# ensuring sed processes strings correctly.
+export LANG=C
+
 command -v ${AWK} >/dev/null 2>&1 || die "${AWK} isn't installed"
 command -v ${READELF} >/dev/null 2>&1 || die "${READELF} isn't installed"
 command -v ${ADDR2LINE} >/dev/null 2>&1 || die "${ADDR2LINE} isn't installed"
···
 
 run_readelf() {
 	local objfile=$1
-	local out=$(${READELF} --file-header --section-headers --symbols --wide $objfile)
+	local tmpfile
+	tmpfile=$(mktemp)
+
+	${READELF} --file-header --section-headers --symbols --wide "$objfile" > "$tmpfile"
 
 	# This assumes that readelf first prints the file header, then the section headers, then the symbols.
 	# Note: It seems that GNU readelf does not prefix section headers with the "There are X section headers"
 	# line when multiple options are given, so let's also match with the "Section Headers:" line.
-	ELF_FILEHEADER=$(echo "${out}" | sed -n '/There are [0-9]* section headers, starting at offset\|Section Headers:/q;p')
-	ELF_SECHEADERS=$(echo "${out}" | sed -n '/There are [0-9]* section headers, starting at offset\|Section Headers:/,$p' | sed -n '/Symbol table .* contains [0-9]* entries:/q;p')
-	ELF_SYMS=$(echo "${out}" | sed -n '/Symbol table .* contains [0-9]* entries:/,$p')
+	ELF_FILEHEADER=$(sed -n '/There are [0-9]* section headers, starting at offset\|Section Headers:/q;p' "$tmpfile")
+	ELF_SECHEADERS=$(sed -n '/There are [0-9]* section headers, starting at offset\|Section Headers:/,$p' "$tmpfile" | sed -n '/Symbol table .* contains [0-9]* entries:/q;p')
+	ELF_SYMS=$(sed -n '/Symbol table .* contains [0-9]* entries:/,$p' "$tmpfile")
+
+	rm -f -- "$tmpfile"
 }
 
 check_vmlinux() {

scripts/link-vmlinux.sh

···
 	# skip output file argument
 	shift
 
-	if is_enabled CONFIG_LTO_CLANG || is_enabled CONFIG_X86_KERNEL_IBT; then
+	if is_enabled CONFIG_LTO_CLANG || is_enabled CONFIG_X86_KERNEL_IBT ||
+	   is_enabled CONFIG_KLP_BUILD; then
 		# Use vmlinux.o instead of performing the slow LTO link again.
 		objs=vmlinux.o
 		libs=

scripts/livepatch/fix-patch-lines

···
+#!/usr/bin/awk -f
+# SPDX-License-Identifier: GPL-2.0
+#
+# Use #line directives to preserve original __LINE__ numbers across patches to
+# avoid unwanted compilation changes.
+
+BEGIN {
+	in_hunk = 0
+	skip    = 0
+}
+
+/^--- / {
+	skip = $2 !~ /\.(c|h)$/
+	print
+	next
+}
+
+/^@@/ {
+	if (skip) {
+		print
+		next
+	}
+
+	in_hunk = 1
+
+	# @@ -1,3 +1,4 @@:
+	#   1: line number in old file
+	#   3: how many lines the hunk covers in old file
+	#   1: line number in new file
+	#   4: how many lines the hunk covers in new file
+
+	match($0, /^@@ -([0-9]+)(,([0-9]+))? \+([0-9]+)(,([0-9]+))? @@/, m)
+
+	# Set 'cur' to the old file's line number at the start of the hunk.  It
+	# gets incremented for every context line and every line removal, so
+	# that it always represents the old file's current line number.
+	cur = m[1]
+
+	# last = last line number of current hunk
+	last = cur + (m[3] ? m[3] : 1) - 1
+
+	need_line_directive = 0
+
+	print
+	next
+}
+
+{
+	if (skip || !in_hunk || $0 ~ /^\\ No newline at end of file/) {
+		print
+		next
+	}
+
+	# change line
+	if ($0 ~ /^[+-]/) {
+		# inject #line after this group of changes
+		need_line_directive = 1
+
+		if ($0 ~ /^-/)
+			cur++
+
+		print
+		next
+	}
+
+	# If this is the first context line after a group of changes, inject
+	# the #line directive to force the compiler to correct the line
+	# numbering to match the original file.
+	if (need_line_directive) {
+		print "+#line " cur
+		need_line_directive = 0
+	}
+
+	if (cur == last)
+		in_hunk = 0
+
+	cur++
+	print
+}

scripts/livepatch/init.c

···
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Init code for a livepatch kernel module
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/livepatch.h>
+
+extern struct klp_object_ext __start_klp_objects[];
+extern struct klp_object_ext __stop_klp_objects[];
+
+static struct klp_patch *patch;
+
+static int __init livepatch_mod_init(void)
+{
+	struct klp_object *objs;
+	unsigned int nr_objs;
+	int ret;
+
+	nr_objs = __stop_klp_objects - __start_klp_objects;
+
+	if (!nr_objs) {
+		pr_err("nothing to patch!\n");
+		ret = -EINVAL;
+		goto err;
+	}
+
+	patch = kzalloc(sizeof(*patch), GFP_KERNEL);
+	if (!patch) {
+		ret = -ENOMEM;
+		goto err;
+	}
+
+	objs = kzalloc(sizeof(struct klp_object) * (nr_objs + 1),  GFP_KERNEL);
+	if (!objs) {
+		ret = -ENOMEM;
+		goto err_free_patch;
+	}
+
+	for (int i = 0; i < nr_objs; i++) {
+		struct klp_object_ext *obj_ext = __start_klp_objects + i;
+		struct klp_func_ext *funcs_ext = obj_ext->funcs;
+		unsigned int nr_funcs = obj_ext->nr_funcs;
+		struct klp_func *funcs = objs[i].funcs;
+		struct klp_object *obj = objs + i;
+
+		funcs = kzalloc(sizeof(struct klp_func) * (nr_funcs + 1), GFP_KERNEL);
+		if (!funcs) {
+			ret = -ENOMEM;
+			for (int j = 0; j < i; j++)
+				kfree(objs[i].funcs);
+			goto err_free_objs;
+		}
+
+		for (int j = 0; j < nr_funcs; j++) {
+			funcs[j].old_name   = funcs_ext[j].old_name;
+			funcs[j].new_func   = funcs_ext[j].new_func;
+			funcs[j].old_sympos = funcs_ext[j].sympos;
+		}
+
+		obj->name = obj_ext->name;
+		obj->funcs = funcs;
+
+		memcpy(&obj->callbacks, &obj_ext->callbacks, sizeof(struct klp_callbacks));
+	}
+
+	patch->mod = THIS_MODULE;
+	patch->objs = objs;
+
+	/* TODO patch->states */
+
+#ifdef KLP_NO_REPLACE
+	patch->replace = false;
+#else
+	patch->replace = true;
+#endif
+
+	return klp_enable_patch(patch);
+
+err_free_objs:
+	kfree(objs);
+err_free_patch:
+	kfree(patch);
+err:
+	return ret;
+}
+
+static void __exit livepatch_mod_exit(void)
+{
+	unsigned int nr_objs;
+
+	nr_objs = __stop_klp_objects - __start_klp_objects;
+
+	for (int i = 0; i < nr_objs; i++)
+		kfree(patch->objs[i].funcs);
+
+	kfree(patch->objs);
+	kfree(patch);
+}
+
+module_init(livepatch_mod_init);
+module_exit(livepatch_mod_exit);
+MODULE_LICENSE("GPL");
+MODULE_INFO(livepatch, "Y");
+MODULE_DESCRIPTION("Livepatch module");

scripts/livepatch/klp-build

···
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+#
+# Build a livepatch module
+
+# shellcheck disable=SC1090,SC2155
+
+if (( BASH_VERSINFO[0]  < 4 || \
+     (BASH_VERSINFO[0] == 4 && BASH_VERSINFO[1] < 4) )); then
+		echo "error: this script requires bash 4.4+" >&2
+	exit 1
+fi
+
+set -o errexit
+set -o errtrace
+set -o pipefail
+set -o nounset
+
+# Allow doing 'cmd | mapfile -t array' instead of 'mapfile -t array < <(cmd)'.
+# This helps keep execution in pipes so pipefail+errexit can catch errors.
+shopt -s lastpipe
+
+unset DEBUG_CLONE DIFF_CHECKSUM SKIP_CLEANUP XTRACE
+
+REPLACE=1
+SHORT_CIRCUIT=0
+JOBS="$(getconf _NPROCESSORS_ONLN)"
+VERBOSE="-s"
+shopt -o xtrace | grep -q 'on' && XTRACE=1
+
+# Avoid removing the previous $TMP_DIR until args have been fully processed.
+KEEP_TMP=1
+
+SCRIPT="$(basename "$0")"
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+FIX_PATCH_LINES="$SCRIPT_DIR/fix-patch-lines"
+
+SRC="$(pwd)"
+OBJ="$(pwd)"
+
+CONFIG="$OBJ/.config"
+TMP_DIR="$OBJ/klp-tmp"
+
+ORIG_DIR="$TMP_DIR/orig"
+PATCHED_DIR="$TMP_DIR/patched"
+DIFF_DIR="$TMP_DIR/diff"
+KMOD_DIR="$TMP_DIR/kmod"
+
+STASH_DIR="$TMP_DIR/stash"
+TIMESTAMP="$TMP_DIR/timestamp"
+PATCH_TMP_DIR="$TMP_DIR/tmp"
+
+KLP_DIFF_LOG="$DIFF_DIR/diff.log"
+
+grep0() {
+	command grep "$@" || true
+}
+
+status() {
+	echo "$*"
+}
+
+warn() {
+	echo "error: $SCRIPT: $*" >&2
+}
+
+die() {
+	warn "$@"
+	exit 1
+}
+
+declare -a STASHED_FILES
+
+stash_file() {
+	local file="$1"
+	local rel_file="${file#"$SRC"/}"
+
+	[[ ! -e "$file" ]] && die "no file to stash: $file"
+
+	mkdir -p "$STASH_DIR/$(dirname "$rel_file")"
+	cp -f "$file" "$STASH_DIR/$rel_file"
+
+	STASHED_FILES+=("$rel_file")
+}
+
+restore_files() {
+	local file
+
+	for file in "${STASHED_FILES[@]}"; do
+		mv -f "$STASH_DIR/$file" "$SRC/$file" || warn "can't restore file: $file"
+	done
+
+	STASHED_FILES=()
+}
+
+cleanup() {
+	set +o nounset
+	revert_patches "--recount"
+	restore_files
+	[[ "$KEEP_TMP" -eq 0 ]] && rm -rf "$TMP_DIR"
+	return 0
+}
+
+trap_err() {
+	warn "line ${BASH_LINENO[0]}: '$BASH_COMMAND'"
+}
+
+trap cleanup  EXIT INT TERM HUP
+trap trap_err ERR
+
+__usage() {
+	cat <<EOF
+Usage: $SCRIPT [OPTIONS] PATCH_FILE(s)
+Generate a livepatch module.
+
+Options:
+   -f, --show-first-changed	Show address of first changed instruction
+   -j, --jobs=<jobs>		Build jobs to run simultaneously [default: $JOBS]
+   -o, --output=<file.ko>	Output file [default: livepatch-<patch-name>.ko]
+       --no-replace		Disable livepatch atomic replace
+   -v, --verbose		Pass V=1 to kernel/module builds
+
+Advanced Options:
+   -d, --debug			Show symbol/reloc cloning decisions
+   -S, --short-circuit=STEP	Start at build step (requires prior --keep-tmp)
+				   1|orig	Build original kernel (default)
+				   2|patched	Build patched kernel
+				   3|diff	Diff objects
+				   4|kmod	Build patch module
+   -T, --keep-tmp		Preserve tmp dir on exit
+
+EOF
+}
+
+usage() {
+	__usage >&2
+}
+
+process_args() {
+	local keep_tmp=0
+	local short
+	local long
+	local args
+
+	short="hfj:o:vdS:T"
+	long="help,show-first-changed,jobs:,output:,no-replace,verbose,debug,short-circuit:,keep-tmp"
+
+	args=$(getopt --options "$short" --longoptions "$long" -- "$@") || {
+		echo; usage; exit
+	}
+	eval set -- "$args"
+
+	while true; do
+		case "$1" in
+			-h | --help)
+				usage
+				exit 0
+				;;
+			-f | --show-first-changed)
+				DIFF_CHECKSUM=1
+				shift
+				;;
+			-j | --jobs)
+				JOBS="$2"
+				shift 2
+				;;
+			-o | --output)
+				[[ "$2" != *.ko ]] && die "output filename should end with .ko"
+				OUTFILE="$2"
+				NAME="$(basename "$OUTFILE")"
+				NAME="${NAME%.ko}"
+				NAME="$(module_name_string "$NAME")"
+				shift 2
+				;;
+			--no-replace)
+				REPLACE=0
+				shift
+				;;
+			-v | --verbose)
+				VERBOSE="V=1"
+				shift
+				;;
+			-d | --debug)
+				DEBUG_CLONE=1
+				keep_tmp=1
+				shift
+				;;
+			-S | --short-circuit)
+				[[ ! -d "$TMP_DIR" ]] && die "--short-circuit requires preserved klp-tmp dir"
+				keep_tmp=1
+				case "$2" in
+					1 | orig)	SHORT_CIRCUIT=1; ;;
+					2 | patched)	SHORT_CIRCUIT=2; ;;
+					3 | diff)	SHORT_CIRCUIT=3; ;;
+					4 | mod)	SHORT_CIRCUIT=4; ;;
+					*)		die "invalid short-circuit step '$2'" ;;
+				esac
+				shift 2
+				;;
+			-T | --keep-tmp)
+				keep_tmp=1
+				shift
+				;;
+			--)
+				shift
+				break
+				;;
+			*)
+				usage
+				exit 1
+				;;
+		esac
+	done
+
+	if [[ $# -eq 0 ]]; then
+		usage
+		exit 1
+	fi
+
+	KEEP_TMP="$keep_tmp"
+	PATCHES=("$@")
+}
+
+# temporarily disable xtrace for especially verbose code
+xtrace_save() {
+	[[ -v XTRACE ]] && set +x
+	return 0
+}
+
+xtrace_restore() {
+	[[ -v XTRACE ]] && set -x
+	return 0
+}
+
+validate_config() {
+	xtrace_save "reading .config"
+	source "$CONFIG" || die "no .config file in $(dirname "$CONFIG")"
+	xtrace_restore
+
+	[[ -v CONFIG_LIVEPATCH ]] ||			\
+		die "CONFIG_LIVEPATCH not enabled"
+
+	[[ -v CONFIG_KLP_BUILD ]] ||			\
+		die "CONFIG_KLP_BUILD not enabled"
+
+	[[ -v CONFIG_GCC_PLUGIN_LATENT_ENTROPY ]] &&	\
+		die "kernel option 'CONFIG_GCC_PLUGIN_LATENT_ENTROPY' not supported"
+
+	[[ -v CONFIG_GCC_PLUGIN_RANDSTRUCT ]] &&	\
+		die "kernel option 'CONFIG_GCC_PLUGIN_RANDSTRUCT' not supported"
+
+	return 0
+}
+
+# Only allow alphanumerics and '_' and '-' in the module name.  Everything else
+# is replaced with '-'.  Also truncate to 55 chars so the full name + NUL
+# terminator fits in the kernel's 56-byte module name array.
+module_name_string() {
+	echo "${1//[^a-zA-Z0-9_-]/-}" | cut -c 1-55
+}
+
+# If the module name wasn't specified on the cmdline with --output, give it a
+# name based on the patch name.
+set_module_name() {
+	[[ -v NAME ]] && return 0
+
+	if [[ "${#PATCHES[@]}" -eq 1 ]]; then
+		NAME="$(basename "${PATCHES[0]}")"
+		NAME="${NAME%.*}"
+	else
+		NAME="patch"
+	fi
+
+	NAME="livepatch-$NAME"
+	NAME="$(module_name_string "$NAME")"
+
+	OUTFILE="$NAME.ko"
+}
+
+# Hardcode the value printed by the localversion script to prevent patch
+# application from appending it with '+' due to a dirty git working tree.
+set_kernelversion() {
+	local file="$SRC/scripts/setlocalversion"
+	local localversion
+
+	stash_file "$file"
+
+	localversion="$(cd "$SRC" && make --no-print-directory kernelversion)"
+	localversion="$(cd "$SRC" && KERNELVERSION="$localversion" ./scripts/setlocalversion)"
+	[[ -z "$localversion" ]] && die "setlocalversion failed"
+
+	sed -i "2i echo $localversion; exit 0" scripts/setlocalversion
+}
+
+get_patch_files() {
+	local patch="$1"
+
+	grep0 -E '^(--- |\+\+\+ )' "$patch"			\
+		| gawk '{print $2}'				\
+		| sed 's|^[^/]*/||'				\
+		| sort -u
+}
+
+# Make sure git re-stats the changed files
+git_refresh() {
+	local patch="$1"
+	local files=()
+
+	[[ ! -e "$SRC/.git" ]] && return
+
+	get_patch_files "$patch" | mapfile -t files
+
+	(
+		cd "$SRC"
+		git update-index -q --refresh -- "${files[@]}"
+	)
+}
+
+check_unsupported_patches() {
+	local patch
+
+	for patch in "${PATCHES[@]}"; do
+		local files=()
+
+		get_patch_files "$patch" | mapfile -t files
+
+		for file in "${files[@]}"; do
+			case "$file" in
+				lib/*|*.S)
+					die "unsupported patch to $file"
+					;;
+			esac
+		done
+	done
+}
+
+apply_patch() {
+	local patch="$1"
+	shift
+	local extra_args=("$@")
+
+	[[ ! -f "$patch" ]] && die "$patch doesn't exist"
+
+	(
+		cd "$SRC"
+
+		# The sed strips the version signature from 'git format-patch',
+		# otherwise 'git apply --recount' warns.
+		sed -n '/^-- /q;p' "$patch" |
+			git apply "${extra_args[@]}"
+	)
+
+	APPLIED_PATCHES+=("$patch")
+}
+
+revert_patch() {
+	local patch="$1"
+	shift
+	local extra_args=("$@")
+	local tmp=()
+
+	(
+		cd "$SRC"
+
+		sed -n '/^-- /q;p' "$patch" |
+			git apply --reverse "${extra_args[@]}"
+	)
+	git_refresh "$patch"
+
+	for p in "${APPLIED_PATCHES[@]}"; do
+		[[ "$p" == "$patch" ]] && continue
+		tmp+=("$p")
+	done
+
+	APPLIED_PATCHES=("${tmp[@]}")
+}
+
+apply_patches() {
+	local patch
+
+	for patch in "${PATCHES[@]}"; do
+		apply_patch "$patch"
+	done
+}
+
+revert_patches() {
+	local extra_args=("$@")
+	local patches=("${APPLIED_PATCHES[@]}")
+
+	for (( i=${#patches[@]}-1 ; i>=0 ; i-- )) ; do
+		revert_patch "${patches[$i]}" "${extra_args[@]}"
+	done
+
+	APPLIED_PATCHES=()
+}
+
+validate_patches() {
+	check_unsupported_patches
+	apply_patches
+	revert_patches
+}
+
+do_init() {
+	# We're not yet smart enough to handle anything other than in-tree
+	# builds in pwd.
+	[[ ! "$SRC" -ef "$SCRIPT_DIR/../.." ]] && die "please run from the kernel root directory"
+	[[ ! "$OBJ" -ef "$SCRIPT_DIR/../.." ]] && die "please run from the kernel root directory"
+
+	(( SHORT_CIRCUIT <= 1 )) && rm -rf "$TMP_DIR"
+	mkdir -p "$TMP_DIR"
+
+	APPLIED_PATCHES=()
+
+	[[ -x "$FIX_PATCH_LINES" ]] || die "can't find fix-patch-lines"
+
+	validate_config
+	set_module_name
+	set_kernelversion
+}
+
+# Refresh the patch hunk headers, specifically the line numbers and counts.
+refresh_patch() {
+	local patch="$1"
+	local tmpdir="$PATCH_TMP_DIR"
+	local files=()
+
+	rm -rf "$tmpdir"
+	mkdir -p "$tmpdir/a"
+	mkdir -p "$tmpdir/b"
+
+	# Get all source files affected by the patch
+	get_patch_files "$patch" | mapfile -t files
+
+	# Copy orig source files to 'a'
+	( cd "$SRC" && echo "${files[@]}" | xargs cp --parents --target-directory="$tmpdir/a" )
+
+	# Copy patched source files to 'b'
+	apply_patch "$patch" --recount
+	( cd "$SRC" && echo "${files[@]}" | xargs cp --parents --target-directory="$tmpdir/b" )
+	revert_patch "$patch" --recount
+
+	# Diff 'a' and 'b' to make a clean patch
+	( cd "$tmpdir" && git diff --no-index --no-prefix a b > "$patch" ) || true
+}
+
+# Copy the patches to a temporary directory, fix their lines so as not to
+# affect the __LINE__ macro for otherwise unchanged functions further down the
+# file, and update $PATCHES to point to the fixed patches.
+fix_patches() {
+	local idx
+	local i
+
+	rm -f "$TMP_DIR"/*.patch
+
+	idx=0001
+	for i in "${!PATCHES[@]}"; do
+		local old_patch="${PATCHES[$i]}"
+		local tmp_patch="$TMP_DIR/tmp.patch"
+		local patch="${PATCHES[$i]}"
+		local new_patch
+
+		new_patch="$TMP_DIR/$idx-fixed-$(basename "$patch")"
+
+		cp -f "$old_patch" "$tmp_patch"
+		refresh_patch "$tmp_patch"
+		"$FIX_PATCH_LINES" "$tmp_patch" > "$new_patch"
+		refresh_patch "$new_patch"
+
+		PATCHES[i]="$new_patch"
+
+		rm -f "$tmp_patch"
+		idx=$(printf "%04d" $(( 10#$idx + 1 )))
+	done
+}
+
+clean_kernel() {
+	local cmd=()
+
+	cmd=("make")
+	cmd+=("--silent")
+	cmd+=("-j$JOBS")
+	cmd+=("clean")
+
+	(
+		cd "$SRC"
+		"${cmd[@]}"
+	)
+}
+
+build_kernel() {
+	local log="$TMP_DIR/build.log"
+	local cmd=()
+
+	cmd=("make")
+
+	# When a patch to a kernel module references a newly created unexported
+	# symbol which lives in vmlinux or another kernel module, the patched
+	# kernel build fails with the following error:
+	#
+	#   ERROR: modpost: "klp_string" [fs/xfs/xfs.ko] undefined!
+	#
+	# The undefined symbols are working as designed in that case.  They get
+	# resolved later when the livepatch module build link pulls all the
+	# disparate objects together into the same kernel module.
+	#
+	# It would be good to have a way to tell modpost to skip checking for
+	# undefined symbols altogether.  For now, just convert the error to a
+	# warning with KBUILD_MODPOST_WARN, and grep out the warning to avoid
+	# confusing the user.
+	#
+	cmd+=("KBUILD_MODPOST_WARN=1")
+
+	cmd+=("$VERBOSE")
+	cmd+=("-j$JOBS")
+	cmd+=("KCFLAGS=-ffunction-sections -fdata-sections")
+	cmd+=("vmlinux")
+	cmd+=("modules")
+
+	(
+		cd "$SRC"
+		"${cmd[@]}"							\
+			1> >(tee -a "$log")					\
+			2> >(tee -a "$log" | grep0 -v "modpost.*undefined!" >&2)
+	)
+}
+
+find_objects() {
+	local opts=("$@")
+
+	# Find root-level vmlinux.o and non-root-level .ko files,
+	# excluding klp-tmp/ and .git/
+	find "$OBJ" \( -path "$TMP_DIR" -o -path "$OBJ/.git" -o	-regex "$OBJ/[^/][^/]*\.ko" \) -prune -o \
+		    -type f "${opts[@]}"				\
+		    \( -name "*.ko" -o -path "$OBJ/vmlinux.o" \)	\
+		    -printf '%P\n'
+}
+
+# Copy all .o archives to $ORIG_DIR
+copy_orig_objects() {
+	local files=()
+
+	rm -rf "$ORIG_DIR"
+	mkdir -p "$ORIG_DIR"
+
+	find_objects | mapfile -t files
+
+	xtrace_save "copying orig objects"
+	for _file in "${files[@]}"; do
+		local rel_file="${_file/.ko/.o}"
+		local file="$OBJ/$rel_file"
+		local file_dir="$(dirname "$file")"
+		local orig_file="$ORIG_DIR/$rel_file"
+		local orig_dir="$(dirname "$orig_file")"
+		local cmd_file="$file_dir/.$(basename "$file").cmd"
+
+		[[ ! -f "$file" ]] && die "missing $(basename "$file") for $_file"
+
+		mkdir -p "$orig_dir"
+		cp -f "$file" "$orig_dir"
+		[[ -e "$cmd_file" ]] && cp -f "$cmd_file" "$orig_dir"
+	done
+	xtrace_restore
+
+	mv -f "$TMP_DIR/build.log" "$ORIG_DIR"
+	touch "$TIMESTAMP"
+}
+
+# Copy all changed objects to $PATCHED_DIR
+copy_patched_objects() {
+	local files=()
+	local opts=()
+	local found=0
+
+	rm -rf "$PATCHED_DIR"
+	mkdir -p "$PATCHED_DIR"
+
+	# Note this doesn't work with some configs, thus the 'cmp' below.
+	opts=("-newer")
+	opts+=("$TIMESTAMP")
+
+	find_objects "${opts[@]}" | mapfile -t files
+
+	xtrace_save "copying changed objects"
+	for _file in "${files[@]}"; do
+		local rel_file="${_file/.ko/.o}"
+		local file="$OBJ/$rel_file"
+		local orig_file="$ORIG_DIR/$rel_file"
+		local patched_file="$PATCHED_DIR/$rel_file"
+		local patched_dir="$(dirname "$patched_file")"
+
+		[[ ! -f "$file" ]] && die "missing $(basename "$file") for $_file"
+
+		cmp -s "$orig_file" "$file" && continue
+
+		mkdir -p "$patched_dir"
+		cp -f "$file" "$patched_dir"
+		found=1
+	done
+	xtrace_restore
+
+	(( found == 0 )) && die "no changes detected"
+
+	mv -f "$TMP_DIR/build.log" "$PATCHED_DIR"
+}
+
+# Diff changed objects, writing output object to $DIFF_DIR
+diff_objects() {
+	local log="$KLP_DIFF_LOG"
+	local files=()
+	local opts=()
+
+	rm -rf "$DIFF_DIR"
+	mkdir -p "$DIFF_DIR"
+
+	find "$PATCHED_DIR" -type f -name "*.o" | mapfile -t files
+	[[ ${#files[@]} -eq 0 ]] && die "no changes detected"
+
+	[[ -v DEBUG_CLONE ]] && opts=("--debug")
+
+	# Diff all changed objects
+	for file in "${files[@]}"; do
+		local rel_file="${file#"$PATCHED_DIR"/}"
+		local orig_file="$rel_file"
+		local patched_file="$PATCHED_DIR/$rel_file"
+		local out_file="$DIFF_DIR/$rel_file"
+		local filter=()
+		local cmd=()
+
+		mkdir -p "$(dirname "$out_file")"
+
+		cmd=("$SRC/tools/objtool/objtool")
+		cmd+=("klp")
+		cmd+=("diff")
+		(( ${#opts[@]} > 0 )) && cmd+=("${opts[@]}")
+		cmd+=("$orig_file")
+		cmd+=("$patched_file")
+		cmd+=("$out_file")
+
+		if [[ -v DIFF_CHECKSUM ]]; then
+			filter=("grep0")
+			filter+=("-Ev")
+			filter+=("DEBUG: .*checksum: ")
+		else
+			filter=("cat")
+		fi
+
+		(
+			cd "$ORIG_DIR"
+			"${cmd[@]}"							\
+				1> >(tee -a "$log")					\
+				2> >(tee -a "$log" | "${filter[@]}" >&2) ||		\
+				die "objtool klp diff failed"
+		)
+	done
+}
+
+# For each changed object, run objtool with --debug-checksum to get the
+# per-instruction checksums, and then diff those to find the first changed
+# instruction for each function.
+diff_checksums() {
+	local orig_log="$ORIG_DIR/checksum.log"
+	local patched_log="$PATCHED_DIR/checksum.log"
+	local -A funcs
+	local cmd=()
+	local line
+	local file
+	local func
+
+	gawk '/\.o: changed function: / {
+		sub(/:$/, "", $1)
+		print $1, $NF
+	}' "$KLP_DIFF_LOG" | mapfile -t lines
+
+	for line in "${lines[@]}"; do
+		read -r file func <<< "$line"
+		if [[ ! -v funcs["$file"] ]]; then
+			funcs["$file"]="$func"
+		else
+			funcs["$file"]+=" $func"
+		fi
+	done
+
+	cmd=("$SRC/tools/objtool/objtool")
+	cmd+=("--checksum")
+	cmd+=("--link")
+	cmd+=("--dry-run")
+
+	for file in "${!funcs[@]}"; do
+		local opt="--debug-checksum=${funcs[$file]// /,}"
+
+		(
+			cd "$ORIG_DIR"
+			"${cmd[@]}" "$opt" "$file" &> "$orig_log" || \
+				( cat "$orig_log" >&2; die "objtool --debug-checksum failed" )
+
+			cd "$PATCHED_DIR"
+			"${cmd[@]}" "$opt" "$file" &> "$patched_log" ||	\
+				( cat "$patched_log" >&2; die "objtool --debug-checksum failed" )
+		)
+
+		for func in ${funcs[$file]}; do
+			diff <( grep0 -E "^DEBUG: .*checksum: $func " "$orig_log"    | sed "s|$ORIG_DIR/||")	\
+			     <( grep0 -E "^DEBUG: .*checksum: $func " "$patched_log" | sed "s|$PATCHED_DIR/||")	\
+				| gawk '/^< DEBUG: / {
+					gsub(/:/, "")
+					printf "%s: %s: %s\n", $3, $5, $6
+					exit
+			}' || true
+		done
+	done
+}
+
+# Build and post-process livepatch module in $KMOD_DIR
+build_patch_module() {
+	local makefile="$KMOD_DIR/Kbuild"
+	local log="$KMOD_DIR/build.log"
+	local kmod_file
+	local cflags=()
+	local files=()
+	local cmd=()
+
+	rm -rf "$KMOD_DIR"
+	mkdir -p "$KMOD_DIR"
+
+	cp -f "$SRC/scripts/livepatch/init.c" "$KMOD_DIR"
+
+	echo "obj-m := $NAME.o" > "$makefile"
+	echo -n "$NAME-y := init.o" >> "$makefile"
+
+	find "$DIFF_DIR" -type f -name "*.o" | mapfile -t files
+	[[ ${#files[@]} -eq 0 ]] && die "no changes detected"
+
+	for file in "${files[@]}"; do
+		local rel_file="${file#"$DIFF_DIR"/}"
+		local orig_file="$ORIG_DIR/$rel_file"
+		local orig_dir="$(dirname "$orig_file")"
+		local kmod_file="$KMOD_DIR/$rel_file"
+		local kmod_dir="$(dirname "$kmod_file")"
+		local cmd_file="$orig_dir/.$(basename "$file").cmd"
+
+		mkdir -p "$kmod_dir"
+		cp -f "$file" "$kmod_dir"
+		[[ -e "$cmd_file" ]] && cp -f "$cmd_file" "$kmod_dir"
+
+		# Tell kbuild this is a prebuilt object
+		cp -f "$file" "${kmod_file}_shipped"
+
+		echo -n " $rel_file" >> "$makefile"
+	done
+
+	echo >> "$makefile"
+
+	cflags=("-ffunction-sections")
+	cflags+=("-fdata-sections")
+	[[ $REPLACE -eq 0 ]] && cflags+=("-DKLP_NO_REPLACE")
+
+	cmd=("make")
+	cmd+=("$VERBOSE")
+	cmd+=("-j$JOBS")
+	cmd+=("--directory=.")
+	cmd+=("M=$KMOD_DIR")
+	cmd+=("KCFLAGS=${cflags[*]}")
+
+	# Build a "normal" kernel module with init.c and the diffed objects
+	(
+		cd "$SRC"
+		"${cmd[@]}"							\
+			1> >(tee -a "$log")					\
+			2> >(tee -a "$log" >&2)
+	)
+
+	kmod_file="$KMOD_DIR/$NAME.ko"
+
+	# Save off the intermediate binary for debugging
+	cp -f "$kmod_file" "$kmod_file.orig"
+
+	# Work around issue where slight .config change makes corrupt BTF
+	objcopy --remove-section=.BTF "$kmod_file"
+
+	# Fix (and work around) linker wreckage for klp syms / relocs
+	"$SRC/tools/objtool/objtool" klp post-link "$kmod_file" || die "objtool klp post-link failed"
+
+	cp -f "$kmod_file" "$OUTFILE"
+}
+
+
+################################################################################
+
+process_args "$@"
+do_init
+
+if (( SHORT_CIRCUIT <= 1 )); then
+	status "Validating patch(es)"
+	validate_patches
+	status "Building original kernel"
+	clean_kernel
+	build_kernel
+	status "Copying original object files"
+	copy_orig_objects
+fi
+
+if (( SHORT_CIRCUIT <= 2 )); then
+	status "Fixing patch(es)"
+	fix_patches
+	apply_patches
+	status "Building patched kernel"
+	build_kernel
+	revert_patches
+	status "Copying patched object files"
+	copy_patched_objects
+fi
+
+if (( SHORT_CIRCUIT <= 3 )); then
+	status "Diffing objects"
+	diff_objects
+	if [[ -v DIFF_CHECKSUM ]]; then
+		status "Finding first changed instructions"
+		diff_checksums
+	fi
+fi
+
+if (( SHORT_CIRCUIT <= 4 )); then
+	status "Building patch module: $OUTFILE"
+	build_patch_module
+fi
+
+status "SUCCESS"

scripts/mod/modpost.c

···
 		    strstarts(symname, "_savevr_") ||
 		    strcmp(symname, ".TOC.") == 0)
 			return 1;
+
+	/* ignore linker-created section bounds variables */
+	if (strstarts(symname, "__start_") || strstarts(symname, "__stop_"))
+		return 1;
+
 	/* Do not ignore this symbol */
 	return 0;
 }

scripts/module.lds.S

···
 
 	__patchable_function_entries : { *(__patchable_function_entries) }
 
+	__klp_funcs		0: ALIGN(8) { KEEP(*(__klp_funcs)) }
+
+	__klp_objects		0: ALIGN(8) {
+		__start_klp_objects = .;
+		KEEP(*(__klp_objects))
+		__stop_klp_objects = .;
+	}
+
 #ifdef CONFIG_ARCH_USES_CFI_TRAPS
-	__kcfi_traps 		: { KEEP(*(.kcfi_traps)) }
+	__kcfi_traps		: { KEEP(*(.kcfi_traps)) }
 #endif
 
-#ifdef CONFIG_LTO_CLANG
-	/*
-	 * With CONFIG_LTO_CLANG, LLD always enables -fdata-sections and
-	 * -ffunction-sections, which increases the size of the final module.
-	 * Merge the split sections in the final binary.
-	 */
+	.text : {
+		*(.text .text.[0-9a-zA-Z_]*)
+	}
+
 	.bss : {
 		*(.bss .bss.[0-9a-zA-Z_]*)
 		*(.bss..L*)
···
 		*(.rodata .rodata.[0-9a-zA-Z_]*)
 		*(.rodata..L*)
 	}
-#endif
+
 	MOD_SEPARATE_CODETAG_SECTIONS()
 }
 

tools/build/Build

···
+hostprogs	:= fixdep
+fixdep-y	:= fixdep.o

tools/build/Makefile

···
 	$(Q)$(MAKE) -C feature OUTPUT=$(TMP_O) clean >/dev/null
 endif
 
-$(OUTPUT)fixdep: $(srctree)/tools/build/fixdep.c
-	$(QUIET_CC)$(HOSTCC) $(KBUILD_HOSTCFLAGS) $(KBUILD_HOSTLDFLAGS) -o $@ $<
+include $(srctree)/tools/build/Makefile.include
+
+FIXDEP		:= $(OUTPUT)fixdep
+FIXDEP_IN	:= $(OUTPUT)fixdep-in.o
+
+# To track fixdep's dependencies properly, fixdep needs to run on itself.
+# Build it twice the first time.
+$(FIXDEP_IN): FORCE
+	$(Q)if [ ! -f $(FIXDEP) ]; then						\
+		$(MAKE) $(build)=fixdep HOSTCFLAGS="$(KBUILD_HOSTCFLAGS)";	\
+		rm -f $(FIXDEP).o;						\
+	fi
+	$(Q)$(MAKE) $(build)=fixdep HOSTCFLAGS="$(KBUILD_HOSTCFLAGS)"
+
+
+$(FIXDEP): $(FIXDEP_IN)
+	$(QUIET_LINK)$(HOSTCC) $(FIXDEP_IN) $(KBUILD_HOSTLDFLAGS) -o $@
+
+FORCE:
+
+.PHONY: FORCE

tools/include/linux/interval_tree_generic.h

···
  *   Cond2: start <= ITLAST(node)					      \
  */									      \
 									      \
-static ITSTRUCT *							      \
+ITSTATIC ITSTRUCT *							      \
 ITPREFIX ## _subtree_search(ITSTRUCT *node, ITTYPE start, ITTYPE last)	      \
 {									      \
 	while (true) {							      \
···
 		if (ITSTART(node) <= last) {		/* Cond1 */	      \
 			if (start <= ITLAST(node))	/* Cond2 */	      \
 				return node;	/* node is leftmost match */  \
-			if (node->ITRB.rb_right) {			      \
-				node = rb_entry(node->ITRB.rb_right,	      \
-						ITSTRUCT, ITRB);	      \
-				if (start <= node->ITSUBTREE)		      \
-					continue;			      \
-			}						      \
+			node = rb_entry(node->ITRB.rb_right, ITSTRUCT, ITRB); \
+			continue;					      \
 		}							      \
 		return NULL;	/* No match */				      \
 	}								      \

tools/include/linux/livepatch_external.h

···
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * External livepatch interfaces for patch creation tooling
+ */
+
+#ifndef _LINUX_LIVEPATCH_EXTERNAL_H_
+#define _LINUX_LIVEPATCH_EXTERNAL_H_
+
+#include <linux/types.h>
+
+#define KLP_RELOC_SEC_PREFIX		".klp.rela."
+#define KLP_SYM_PREFIX			".klp.sym."
+
+#define __KLP_PRE_PATCH_PREFIX		__klp_pre_patch_callback_
+#define __KLP_POST_PATCH_PREFIX		__klp_post_patch_callback_
+#define __KLP_PRE_UNPATCH_PREFIX	__klp_pre_unpatch_callback_
+#define __KLP_POST_UNPATCH_PREFIX	__klp_post_unpatch_callback_
+
+#define KLP_PRE_PATCH_PREFIX		__stringify(__KLP_PRE_PATCH_PREFIX)
+#define KLP_POST_PATCH_PREFIX		__stringify(__KLP_POST_PATCH_PREFIX)
+#define KLP_PRE_UNPATCH_PREFIX		__stringify(__KLP_PRE_UNPATCH_PREFIX)
+#define KLP_POST_UNPATCH_PREFIX		__stringify(__KLP_POST_UNPATCH_PREFIX)
+
+struct klp_object;
+
+typedef int (*klp_pre_patch_t)(struct klp_object *obj);
+typedef void (*klp_post_patch_t)(struct klp_object *obj);
+typedef void (*klp_pre_unpatch_t)(struct klp_object *obj);
+typedef void (*klp_post_unpatch_t)(struct klp_object *obj);
+
+/**
+ * struct klp_callbacks - pre/post live-(un)patch callback structure
+ * @pre_patch:		executed before code patching
+ * @post_patch:		executed after code patching
+ * @pre_unpatch:	executed before code unpatching
+ * @post_unpatch:	executed after code unpatching
+ * @post_unpatch_enabled:	flag indicating if post-unpatch callback
+ *				should run
+ *
+ * All callbacks are optional.  Only the pre-patch callback, if provided,
+ * will be unconditionally executed.  If the parent klp_object fails to
+ * patch for any reason, including a non-zero error status returned from
+ * the pre-patch callback, no further callbacks will be executed.
+ */
+struct klp_callbacks {
+	klp_pre_patch_t		pre_patch;
+	klp_post_patch_t	post_patch;
+	klp_pre_unpatch_t	pre_unpatch;
+	klp_post_unpatch_t	post_unpatch;
+	bool post_unpatch_enabled;
+};
+
+/*
+ * 'struct klp_{func,object}_ext' are compact "external" representations of
+ * 'struct klp_{func,object}'.   They are used by objtool for livepatch
+ * generation.  The structs are then read by the livepatch module and converted
+ * to the real structs before calling klp_enable_patch().
+ *
+ * TODO make these the official API for klp_enable_patch().  That should
+ * simplify livepatch's interface as well as its data structure lifetime
+ * management.
+ */
+struct klp_func_ext {
+	const char *old_name;
+	void *new_func;
+	unsigned long sympos;
+};
+
+struct klp_object_ext {
+	const char *name;
+	struct klp_func_ext *funcs;
+	struct klp_callbacks callbacks;
+	unsigned int nr_funcs;
+};
+
+#endif /* _LINUX_LIVEPATCH_EXTERNAL_H_ */

tools/include/linux/objtool_types.h

···
 #define ANNOTYPE_REACHABLE		8
 #define ANNOTYPE_NOCFI			9
 
+#define ANNOTYPE_DATA_SPECIAL		1
+
 #endif /* _LINUX_OBJTOOL_TYPES_H */

tools/include/linux/string.h

···
 	return strncmp(str, prefix, strlen(prefix)) == 0;
 }
 
+/*
+ * Checks if a string ends with another.
+ */
+static inline bool str_ends_with(const char *str, const char *substr)
+{
+	size_t len = strlen(str);
+	size_t sublen = strlen(substr);
+
+	if (sublen > len)
+		return false;
+
+	return !strcmp(str + len - sublen, substr);
+}
+
 extern char * __must_check skip_spaces(const char *);
 
 extern char *strim(char *);

tools/objtool/Build

···
 objtool-y += elf.o
 objtool-y += objtool.o
 
-objtool-$(BUILD_ORC) += orc_gen.o
-objtool-$(BUILD_ORC) += orc_dump.o
+objtool-$(BUILD_ORC) += orc_gen.o orc_dump.o
+objtool-$(BUILD_KLP) += builtin-klp.o klp-diff.o klp-post-link.o
 
 objtool-y += libstring.o
 objtool-y += libctype.o

tools/objtool/Makefile

···
 include ../scripts/Makefile.include
 include ../scripts/Makefile.arch
 
+ifeq ($(SRCARCH),x86)
+	BUILD_ORC    := y
+	ARCH_HAS_KLP := y
+endif
+
+ifeq ($(SRCARCH),loongarch)
+	BUILD_ORC	   := y
+endif
+
+ifeq ($(ARCH_HAS_KLP),y)
+	HAVE_XXHASH = $(shell echo "int main() {}" | \
+		      $(HOSTCC) -xc - -o /dev/null -lxxhash 2> /dev/null && echo y || echo n)
+	ifeq ($(HAVE_XXHASH),y)
+		BUILD_KLP	 := y
+		LIBXXHASH_CFLAGS := $(shell $(HOSTPKG_CONFIG) libxxhash --cflags 2>/dev/null) \
+				    -DBUILD_KLP
+		LIBXXHASH_LIBS   := $(shell $(HOSTPKG_CONFIG) libxxhash --libs 2>/dev/null || echo -lxxhash)
+	endif
+endif
+
+export BUILD_ORC BUILD_KLP
+
 ifeq ($(srctree),)
 srctree := $(patsubst %/,%,$(dir $(CURDIR)))
 srctree := $(patsubst %/,%,$(dir $(srctree)))
···
 
 all: $(OBJTOOL)
 
+WARNINGS := -Werror -Wall -Wextra -Wmissing-prototypes			\
+	    -Wmissing-declarations -Wwrite-strings			\
+	    -Wno-implicit-fallthrough -Wno-sign-compare			\
+	    -Wno-unused-parameter
+
 INCLUDES := -I$(srctree)/tools/include \
 	    -I$(srctree)/tools/include/uapi \
 	    -I$(srctree)/tools/arch/$(HOSTARCH)/include/uapi \
···
 	    -I$(srctree)/tools/objtool/include \
 	    -I$(srctree)/tools/objtool/arch/$(SRCARCH)/include \
 	    -I$(LIBSUBCMD_OUTPUT)/include
-# Note, EXTRA_WARNINGS here was determined for CC and not HOSTCC, it
-# is passed here to match a legacy behavior.
-WARNINGS := $(EXTRA_WARNINGS) -Wno-switch-default -Wno-switch-enum -Wno-packed -Wno-nested-externs
-OBJTOOL_CFLAGS := -Werror $(WARNINGS) $(KBUILD_HOSTCFLAGS) -g $(INCLUDES) $(LIBELF_FLAGS)
-OBJTOOL_LDFLAGS := $(LIBELF_LIBS) $(LIBSUBCMD) $(KBUILD_HOSTLDFLAGS)
+
+OBJTOOL_CFLAGS  := -std=gnu11 -fomit-frame-pointer -O2 -g $(WARNINGS)	\
+		   $(INCLUDES) $(LIBELF_FLAGS) $(LIBXXHASH_CFLAGS) $(HOSTCFLAGS)
+
+OBJTOOL_LDFLAGS := $(LIBSUBCMD) $(LIBELF_LIBS) $(LIBXXHASH_LIBS) $(HOSTLDFLAGS)
 
 # Allow old libelf to be used:
 elfshdr := $(shell echo '$(pound)include <libelf.h>' | $(HOSTCC) $(OBJTOOL_CFLAGS) -x c -E - 2>/dev/null | grep elf_getshdr)
···
 AWK = awk
 MKDIR = mkdir
 
-BUILD_ORC := n
-
-ifeq ($(SRCARCH),x86)
-	BUILD_ORC := y
-endif
-
-ifeq ($(SRCARCH),loongarch)
-	BUILD_ORC := y
-endif
-
-export BUILD_ORC
 export srctree OUTPUT CFLAGS SRCARCH AWK
 include $(srctree)/tools/build/Makefile.include
 

tools/objtool/arch/loongarch/decode.c

···
 #include <linux/objtool_types.h>
 #include <arch/elf.h>
 
-int arch_ftrace_match(char *name)
+int arch_ftrace_match(const char *name)
 {
 	return !strcmp(name, "_mcount");
 }
···
 	return insn->offset + (insn->immediate << 2);
 }
 
-unsigned long arch_dest_reloc_offset(int addend)
+s64 arch_insn_adjusted_addend(struct instruction *insn, struct reloc *reloc)
 {
-	return addend;
+	return reloc_addend(reloc);
 }
 
 bool arch_pc_relative_reloc(struct reloc *reloc)

tools/objtool/arch/loongarch/orc.c

···
 #include <objtool/check.h>
 #include <objtool/orc.h>
 #include <objtool/warn.h>
-#include <objtool/endianness.h>
 
 int init_orc_entry(struct orc_entry *orc, struct cfi_state *cfi, struct instruction *insn)
 {

tools/objtool/arch/powerpc/decode.c

···
 #include <objtool/arch.h>
 #include <objtool/warn.h>
 #include <objtool/builtin.h>
-#include <objtool/endianness.h>
 
-int arch_ftrace_match(char *name)
+int arch_ftrace_match(const char *name)
 {
 	return !strcmp(name, "_mcount");
 }
 
-unsigned long arch_dest_reloc_offset(int addend)
+s64 arch_insn_adjusted_addend(struct instruction *insn, struct reloc *reloc)
 {
-	return addend;
+	return reloc_addend(reloc);
 }
 
 bool arch_callee_saved_reg(unsigned char reg)

tools/objtool/arch/x86/decode.c

···
 #include <objtool/elf.h>
 #include <objtool/arch.h>
 #include <objtool/warn.h>
-#include <objtool/endianness.h>
 #include <objtool/builtin.h>
 #include <arch/elf.h>
 
-int arch_ftrace_match(char *name)
+int arch_ftrace_match(const char *name)
 {
 	return !strcmp(name, "__fentry__");
 }
···
 	}
 }
 
-unsigned long arch_dest_reloc_offset(int addend)
+/* Undo the effects of __pa_symbol() if necessary */
+static unsigned long phys_to_virt(unsigned long pa)
 {
-	return addend + 4;
+	s64 va = pa;
+
+	if (va > 0)
+		va &= ~(0x80000000);
+
+	return va;
+}
+
+s64 arch_insn_adjusted_addend(struct instruction *insn, struct reloc *reloc)
+{
+	s64 addend = reloc_addend(reloc);
+
+	if (arch_pc_relative_reloc(reloc))
+		addend += insn->offset + insn->len - reloc_offset(reloc);
+
+	return phys_to_virt(addend);
+}
+
+static void scan_for_insn(struct section *sec, unsigned long offset,
+			  unsigned long *insn_off, unsigned int *insn_len)
+{
+	unsigned long o = 0;
+	struct insn insn;
+
+	while (1) {
+
+		insn_decode(&insn, sec->data->d_buf + o, sec_size(sec) - o,
+			    INSN_MODE_64);
+
+		if (o + insn.length > offset) {
+			*insn_off = o;
+			*insn_len = insn.length;
+			return;
+		}
+
+		o += insn.length;
+	}
+}
+
+u64 arch_adjusted_addend(struct reloc *reloc)
+{
+	unsigned int type = reloc_type(reloc);
+	s64 addend = reloc_addend(reloc);
+	unsigned long insn_off;
+	unsigned int insn_len;
+
+	if (type == R_X86_64_PLT32)
+		return addend + 4;
+
+	if (type != R_X86_64_PC32 || !is_text_sec(reloc->sec->base))
+		return addend;
+
+	scan_for_insn(reloc->sec->base, reloc_offset(reloc),
+		      &insn_off, &insn_len);
+
+	return addend + insn_off + insn_len - reloc_offset(reloc);
 }
 
 unsigned long arch_jump_destination(struct instruction *insn)

tools/objtool/arch/x86/orc.c

···
 #include <objtool/check.h>
 #include <objtool/orc.h>
 #include <objtool/warn.h>
-#include <objtool/endianness.h>
 
 int init_orc_entry(struct orc_entry *orc, struct cfi_state *cfi, struct instruction *insn)
 {

tools/objtool/arch/x86/special.c

···
 	/* look for a relocation which references .rodata */
 	text_reloc = find_reloc_by_dest_range(file->elf, insn->sec,
 					      insn->offset, insn->len);
-	if (!text_reloc || text_reloc->sym->type != STT_SECTION ||
+	if (!text_reloc || !is_sec_sym(text_reloc->sym) ||
 	    !text_reloc->sym->sec->rodata)
 		return NULL;
 

tools/objtool/builtin-check.c

···
 
 static const struct option check_options[] = {
 	OPT_GROUP("Actions:"),
+	OPT_BOOLEAN(0,		 "checksum", &opts.checksum, "generate per-function checksums"),
+	OPT_BOOLEAN(0,		 "cfi", &opts.cfi, "annotate kernel control flow integrity (kCFI) function preambles"),
 	OPT_CALLBACK_OPTARG('h', "hacks", NULL, NULL, "jump_label,noinstr,skylake", "patch toolchain bugs/limitations", parse_hacks),
-	OPT_BOOLEAN('i', "ibt", &opts.ibt, "validate and annotate IBT"),
-	OPT_BOOLEAN('m', "mcount", &opts.mcount, "annotate mcount/fentry calls for ftrace"),
-	OPT_BOOLEAN('n', "noinstr", &opts.noinstr, "validate noinstr rules"),
-	OPT_BOOLEAN(0,   "orc", &opts.orc, "generate ORC metadata"),
-	OPT_BOOLEAN('r', "retpoline", &opts.retpoline, "validate and annotate retpoline usage"),
-	OPT_BOOLEAN(0,   "rethunk", &opts.rethunk, "validate and annotate rethunk usage"),
-	OPT_BOOLEAN(0,   "unret", &opts.unret, "validate entry unret placement"),
-	OPT_INTEGER(0,   "prefix", &opts.prefix, "generate prefix symbols"),
-	OPT_BOOLEAN('l', "sls", &opts.sls, "validate straight-line-speculation mitigations"),
-	OPT_BOOLEAN('s', "stackval", &opts.stackval, "validate frame pointer rules"),
-	OPT_BOOLEAN('t', "static-call", &opts.static_call, "annotate static calls"),
-	OPT_BOOLEAN('u', "uaccess", &opts.uaccess, "validate uaccess rules for SMAP"),
-	OPT_BOOLEAN(0  , "cfi", &opts.cfi, "annotate kernel control flow integrity (kCFI) function preambles"),
-	OPT_BOOLEAN(0  , "noabs", &opts.noabs, "reject absolute references in allocatable sections"),
-	OPT_CALLBACK_OPTARG(0, "dump", NULL, NULL, "orc", "dump metadata", parse_dump),
+	OPT_BOOLEAN('i',	 "ibt", &opts.ibt, "validate and annotate IBT"),
+	OPT_BOOLEAN('m',	 "mcount", &opts.mcount, "annotate mcount/fentry calls for ftrace"),
+	OPT_BOOLEAN(0,		 "noabs", &opts.noabs, "reject absolute references in allocatable sections"),
+	OPT_BOOLEAN('n',	 "noinstr", &opts.noinstr, "validate noinstr rules"),
+	OPT_BOOLEAN(0,		 "orc", &opts.orc, "generate ORC metadata"),
+	OPT_BOOLEAN('r',	 "retpoline", &opts.retpoline, "validate and annotate retpoline usage"),
+	OPT_BOOLEAN(0,		 "rethunk", &opts.rethunk, "validate and annotate rethunk usage"),
+	OPT_BOOLEAN(0,		 "unret", &opts.unret, "validate entry unret placement"),
+	OPT_INTEGER(0,		 "prefix", &opts.prefix, "generate prefix symbols"),
+	OPT_BOOLEAN('l',	 "sls", &opts.sls, "validate straight-line-speculation mitigations"),
+	OPT_BOOLEAN('s',	 "stackval", &opts.stackval, "validate frame pointer rules"),
+	OPT_BOOLEAN('t',	 "static-call", &opts.static_call, "annotate static calls"),
+	OPT_BOOLEAN('u',	 "uaccess", &opts.uaccess, "validate uaccess rules for SMAP"),
+	OPT_CALLBACK_OPTARG(0,	 "dump", NULL, NULL, "orc", "dump metadata", parse_dump),
 
 	OPT_GROUP("Options:"),
-	OPT_BOOLEAN(0,   "backtrace", &opts.backtrace, "unwind on error"),
-	OPT_BOOLEAN(0,   "dry-run", &opts.dryrun, "don't write modifications"),
-	OPT_BOOLEAN(0,   "link", &opts.link, "object is a linked object"),
-	OPT_BOOLEAN(0,   "module", &opts.module, "object is part of a kernel module"),
-	OPT_BOOLEAN(0,   "mnop", &opts.mnop, "nop out mcount call sites"),
-	OPT_BOOLEAN(0,   "no-unreachable", &opts.no_unreachable, "skip 'unreachable instruction' warnings"),
-	OPT_STRING('o',  "output", &opts.output, "file", "output file name"),
-	OPT_BOOLEAN(0,   "sec-address", &opts.sec_address, "print section addresses in warnings"),
-	OPT_BOOLEAN(0,   "stats", &opts.stats, "print statistics"),
-	OPT_BOOLEAN('v', "verbose", &opts.verbose, "verbose warnings"),
-	OPT_BOOLEAN(0,   "Werror", &opts.werror, "return error on warnings"),
+	OPT_BOOLEAN(0,		 "backtrace", &opts.backtrace, "unwind on error"),
+	OPT_BOOLEAN(0,		 "backup", &opts.backup, "create backup (.orig) file on warning/error"),
+	OPT_STRING(0,		 "debug-checksum", &opts.debug_checksum,  "funcs", "enable checksum debug output"),
+	OPT_BOOLEAN(0,		 "dry-run", &opts.dryrun, "don't write modifications"),
+	OPT_BOOLEAN(0,		 "link", &opts.link, "object is a linked object"),
+	OPT_BOOLEAN(0,		 "module", &opts.module, "object is part of a kernel module"),
+	OPT_BOOLEAN(0,		 "mnop", &opts.mnop, "nop out mcount call sites"),
+	OPT_BOOLEAN(0,		 "no-unreachable", &opts.no_unreachable, "skip 'unreachable instruction' warnings"),
+	OPT_STRING('o',		 "output", &opts.output, "file", "output file name"),
+	OPT_BOOLEAN(0,		 "sec-address", &opts.sec_address, "print section addresses in warnings"),
+	OPT_BOOLEAN(0,		 "stats", &opts.stats, "print statistics"),
+	OPT_BOOLEAN('v',	 "verbose", &opts.verbose, "verbose warnings"),
+	OPT_BOOLEAN(0,		 "werror", &opts.werror, "return error on warnings"),
 
 	OPT_END(),
 };
···
 		return false;
 	}
 
-	if (opts.hack_jump_label	||
+#ifndef BUILD_KLP
+	if (opts.checksum) {
+		ERROR("--checksum not supported; install xxhash-devel and recompile");
+		return false;
+	}
+#endif
+
+	if (opts.debug_checksum && !opts.checksum) {
+		ERROR("--debug-checksum requires --checksum");
+		return false;
+	}
+
+	if (opts.checksum		||
+	    opts.hack_jump_label	||
 	    opts.hack_noinstr		||
 	    opts.ibt			||
 	    opts.mcount			||
···
 			ERROR_GLIBC("strdup(%s)", argv[i]);
 			exit(1);
 		}
-	};
+	}
 }
 
-void print_args(void)
+int make_backup(void)
 {
-	char *backup = NULL;
-
-	if (opts.output || opts.dryrun)
-		goto print;
+	char *backup;
 
 	/*
 	 * Make a backup before kbuild deletes the file so the error
···
 	backup = malloc(strlen(objname) + strlen(ORIG_SUFFIX) + 1);
 	if (!backup) {
 		ERROR_GLIBC("malloc");
-		goto print;
+		return 1;
 	}
 
 	strcpy(backup, objname);
 	strcat(backup, ORIG_SUFFIX);
-	if (copy_file(objname, backup)) {
-		backup = NULL;
-		goto print;
-	}
+	if (copy_file(objname, backup))
+		return 1;
 
-print:
 	/*
-	 * Print the cmdline args to make it easier to recreate.  If '--output'
-	 * wasn't used, add it to the printed args with the backup as input.
+	 * Print the cmdline args to make it easier to recreate.
 	 */
+
 	fprintf(stderr, "%s", orig_argv[0]);
 
 	for (int i = 1; i < orig_argc; i++) {
 		char *arg = orig_argv[i];
 
-		if (backup && !strcmp(arg, objname))
+		/* Modify the printed args to use the backup */
+		if (!opts.output && !strcmp(arg, objname))
 			fprintf(stderr, " %s -o %s", backup, objname);
 		else
 			fprintf(stderr, " %s", arg);
 	}
 
 	fprintf(stderr, "\n");
+	return 0;
 }
 
 int objtool_run(int argc, const char **argv)
···
 	if (!opts.dryrun && file->elf->changed && elf_write(file->elf))
 		return 1;
 
-	return 0;
+	return elf_close(file->elf);
 }

tools/objtool/builtin-klp.c

···
+// SPDX-License-Identifier: GPL-2.0-or-later
+#include <subcmd/parse-options.h>
+#include <string.h>
+#include <stdlib.h>
+#include <objtool/builtin.h>
+#include <objtool/objtool.h>
+#include <objtool/klp.h>
+
+struct subcmd {
+	const char *name;
+	const char *description;
+	int (*fn)(int, const char **);
+};
+
+static struct subcmd subcmds[] = {
+	{ "diff",		"Generate binary diff of two object files",		cmd_klp_diff, },
+	{ "post-link",		"Finalize klp symbols/relocs after module linking",	cmd_klp_post_link, },
+};
+
+static void cmd_klp_usage(void)
+{
+	fprintf(stderr, "usage: objtool klp <subcommand> [<options>]\n\n");
+	fprintf(stderr, "Subcommands:\n");
+
+	for (int i = 0; i < ARRAY_SIZE(subcmds); i++) {
+		struct subcmd *cmd = &subcmds[i];
+
+		fprintf(stderr, "  %s\t%s\n", cmd->name, cmd->description);
+	}
+
+	exit(1);
+}
+
+int cmd_klp(int argc, const char **argv)
+{
+	argc--;
+	argv++;
+
+	if (!argc)
+		cmd_klp_usage();
+
+	if (argc) {
+		for (int i = 0; i < ARRAY_SIZE(subcmds); i++) {
+			struct subcmd *cmd = &subcmds[i];
+
+			if (!strcmp(cmd->name, argv[0]))
+				return cmd->fn(argc, argv);
+		}
+	}
+
+	cmd_klp_usage();
+	return 0;
+}

tools/objtool/check.c

···
  * Copyright (C) 2015-2017 Josh Poimboeuf <[e-mail]>
  */
 
+#define _GNU_SOURCE /* memmem() */
 #include <string.h>
 #include <stdlib.h>
 #include <inttypes.h>
···
 #include <objtool/check.h>
 #include <objtool/special.h>
 #include <objtool/warn.h>
-#include <objtool/endianness.h>
+#include <objtool/checksum.h>
+#include <objtool/util.h>
 
 #include <linux/objtool_types.h>
 #include <linux/hashtable.h>
···
 #define for_each_insn(file, insn)					\
 	for (struct section *__sec, *__fake = (struct section *)1;	\
 	     __fake; __fake = NULL)					\
-		for_each_sec(file, __sec)				\
+		for_each_sec(file->elf, __sec)				\
 			sec_for_each_insn(file, __sec, insn)
 
 #define func_for_each_insn(file, func, insn)				\
···
 }
 
 /*
- * Checks if a string ends with another.
- */
-static bool str_ends_with(const char *s, const char *sub)
-{
-	const int slen = strlen(s);
-	const int sublen = strlen(sub);
-
-	if (sublen > slen)
-		return 0;
-
-	return !memcmp(s + slen - sublen, sub, sublen);
-}
-
-/*
  * Checks if a function is a Rust "noreturn" one.
  */
 static bool is_rust_noreturn(const struct symbol *func)
···
 	if (!func)
 		return false;
 
-	if (func->bind == STB_GLOBAL || func->bind == STB_WEAK) {
+	if (!is_local_sym(func)) {
 		if (is_rust_noreturn(func))
 			return true;
 
···
 				return true;
 	}
 
-	if (func->bind == STB_WEAK)
+	if (is_weak_sym(func))
 		return false;
 
 	if (!func->len)
···
 	struct symbol *func;
 	unsigned long offset;
 	struct instruction *insn;
-	int ret;
 
-	for_each_sec(file, sec) {
+	for_each_sec(file->elf, sec) {
 		struct instruction *insns = NULL;
 		u8 prev_len = 0;
 		u8 idx = 0;
 
-		if (!(sec->sh.sh_flags & SHF_EXECINSTR))
+		if (!is_text_sec(sec))
 			continue;
 
 		if (strcmp(sec->name, ".altinstr_replacement") &&
···
 		if (!strcmp(sec->name, ".init.text") && !opts.module)
 			sec->init = true;
 
-		for (offset = 0; offset < sec->sh.sh_size; offset += insn->len) {
+		for (offset = 0; offset < sec_size(sec); offset += insn->len) {
 			if (!insns || idx == INSN_CHUNK_MAX) {
-				insns = calloc(sizeof(*insn), INSN_CHUNK_SIZE);
+				insns = calloc(INSN_CHUNK_SIZE, sizeof(*insn));
 				if (!insns) {
 					ERROR_GLIBC("calloc");
 					return -1;
···
 			insn->offset = offset;
 			insn->prev_len = prev_len;
 
-			ret = arch_decode_instruction(file, sec, offset,
-						      sec->sh.sh_size - offset,
-						      insn);
-			if (ret)
-				return ret;
+			if (arch_decode_instruction(file, sec, offset, sec_size(sec) - offset, insn))
+				return -1;
 
 			prev_len = insn->len;
 
···
 		}
 
 		sec_for_each_sym(sec, func) {
-			if (func->type != STT_NOTYPE && func->type != STT_FUNC)
+			if (!is_notype_sym(func) && !is_func_sym(func))
 				continue;
 
-			if (func->offset == sec->sh.sh_size) {
+			if (func->offset == sec_size(sec)) {
 				/* Heuristic: likely an "end" symbol */
-				if (func->type == STT_NOTYPE)
+				if (is_notype_sym(func))
 					continue;
 				ERROR("%s(): STT_FUNC at end of section", func->name);
 				return -1;
···
 
 			sym_for_each_insn(file, func, insn) {
 				insn->sym = func;
-				if (func->type == STT_FUNC &&
+				if (is_func_sym(func) &&
 				    insn->type == INSN_ENDBR &&
 				    list_empty(&insn->call_node)) {
 					if (insn->offset == func->offset) {
···
 		idx = (reloc_offset(reloc) - sym->offset) / sizeof(unsigned long);
 
 		func = reloc->sym;
-		if (func->type == STT_SECTION)
+		if (is_sec_sym(func))
 			func = find_symbol_by_offset(reloc->sym->sec,
 						     reloc_addend(reloc));
 		if (!func) {
···
 	};
 	const char *pv_ops;
 	struct symbol *sym;
-	int idx, nr, ret;
+	int idx, nr;
 
 	if (!opts.noinstr)
 		return 0;
···
 		return 0;
 
 	nr = sym->len / sizeof(unsigned long);
-	file->pv_ops = calloc(sizeof(struct pv_state), nr);
+	file->pv_ops = calloc(nr, sizeof(struct pv_state));
 	if (!file->pv_ops) {
 		ERROR_GLIBC("calloc");
 		return -1;
···
 		INIT_LIST_HEAD(&file->pv_ops[idx].targets);
 
 	for (idx = 0; (pv_ops = pv_ops_tables[idx]); idx++) {
-		ret = add_pv_ops(file, pv_ops);
-		if (ret)
-			return ret;
+		if (add_pv_ops(file, pv_ops))
+			return -1;
 	}
 
 	return 0;
+}
+
+static bool is_livepatch_module(struct objtool_file *file)
+{
+	struct section *sec;
+
+	if (!opts.module)
+		return false;
+
+	sec = find_section_by_name(file->elf, ".modinfo");
+	if (!sec)
+		return false;
+
+	return memmem(sec->data->d_buf, sec_size(sec), "\0livepatch=Y", 12);
 }
 
 static int create_static_call_sections(struct objtool_file *file)
···
 
 	sec = find_section_by_name(file->elf, ".static_call_sites");
 	if (sec) {
-		INIT_LIST_HEAD(&file->static_call_list);
-		WARN("file already has .static_call_sites section, skipping");
+		/*
+		 * Livepatch modules may have already extracted the static call
+		 * site entries to take advantage of vmlinux static call
+		 * privileges.
+		 */
+		if (!file->klp)
+			WARN("file already has .static_call_sites section, skipping");
+
 		return 0;
 	}
 
···
 
 		key_sym = find_symbol_by_name(file->elf, tmp);
 		if (!key_sym) {
-			if (!opts.module) {
+			if (!opts.module || file->klp) {
 				ERROR("static_call: can't find static_call_key symbol: %s", tmp);
 				return -1;
 			}
···
 		struct symbol *sym = insn->sym;
 		*site = 0;
 
-		if (opts.module && sym && sym->type == STT_FUNC &&
+		if (opts.module && sym && is_func_sym(sym) &&
 		    insn->offset == sym->offset &&
 		    (!strcmp(sym->name, "init_module") ||
 		     !strcmp(sym->name, "cleanup_module"))) {
···
 
 	sec = find_section_by_name(file->elf, ".cfi_sites");
 	if (sec) {
-		INIT_LIST_HEAD(&file->call_list);
 		WARN("file already has .cfi_sites section, skipping");
 		return 0;
 	}
 
 	idx = 0;
-	for_each_sym(file, sym) {
-		if (sym->type != STT_FUNC)
+	for_each_sym(file->elf, sym) {
+		if (!is_func_sym(sym))
 			continue;
 
 		if (strncmp(sym->name, "__cfi_", 6))
···
 		return -1;
 
 	idx = 0;
-	for_each_sym(file, sym) {
-		if (sym->type != STT_FUNC)
+	for_each_sym(file->elf, sym) {
+		if (!is_func_sym(sym))
 			continue;
 
 		if (strncmp(sym->name, "__cfi_", 6))
···
 
 	sec = find_section_by_name(file->elf, "__mcount_loc");
 	if (sec) {
-		INIT_LIST_HEAD(&file->mcount_loc_list);
-		WARN("file already has __mcount_loc section, skipping");
+		/*
+		 * Livepatch modules have already extracted their __mcount_loc
+		 * entries to cover the !CONFIG_FTRACE_MCOUNT_USE_OBJTOOL case.
+		 */
+		if (!file->klp)
+			WARN("file already has __mcount_loc section, skipping");
+
 		return 0;
 	}
 
···
 
 	sec = find_section_by_name(file->elf, ".call_sites");
 	if (sec) {
-		INIT_LIST_HEAD(&file->call_list);
 		WARN("file already has .call_sites section, skipping");
 		return 0;
 	}
···
 
 	return 0;
 }
+
+#ifdef BUILD_KLP
+static int create_sym_checksum_section(struct objtool_file *file)
+{
+	struct section *sec;
+	struct symbol *sym;
+	unsigned int idx = 0;
+	struct sym_checksum *checksum;
+	size_t entsize = sizeof(struct sym_checksum);
+
+	sec = find_section_by_name(file->elf, ".discard.sym_checksum");
+	if (sec) {
+		if (!opts.dryrun)
+			WARN("file already has .discard.sym_checksum section, skipping");
+
+		return 0;
+	}
+
+	for_each_sym(file->elf, sym)
+		if (sym->csum.checksum)
+			idx++;
+
+	if (!idx)
+		return 0;
+
+	sec = elf_create_section_pair(file->elf, ".discard.sym_checksum", entsize,
+				      idx, idx);
+	if (!sec)
+		return -1;
+
+	idx = 0;
+	for_each_sym(file->elf, sym) {
+		if (!sym->csum.checksum)
+			continue;
+
+		if (!elf_init_reloc(file->elf, sec->rsec, idx, idx * entsize,
+				    sym, 0, R_TEXT64))
+			return -1;
+
+		checksum = (struct sym_checksum *)sec->data->d_buf + idx;
+		checksum->addr = 0; /* reloc */
+		checksum->checksum = sym->csum.checksum;
+
+		mark_sec_changed(file->elf, sec, true);
+
+		idx++;
+	}
+
+	return 0;
+}
+#else
+static int create_sym_checksum_section(struct objtool_file *file) { return -EINVAL; }
+#endif
 
 /*
  * Warnings shouldn't be reported for ignored functions.
···
 }
 
 static bool is_first_func_insn(struct objtool_file *file,
-			       struct instruction *insn, struct symbol *sym)
+			       struct instruction *insn)
 {
-	if (insn->offset == sym->offset)
+	struct symbol *func = insn_func(insn);
+
+	if (!func)
+		return false;
+
+	if (insn->offset == func->offset)
 		return true;
 
 	/* Allow direct CALL/JMP past ENDBR */
···
 		struct instruction *prev = prev_insn_same_sym(file, insn);
 
 		if (prev && prev->type == INSN_ENDBR &&
-		    insn->offset == sym->offset + prev->len)
+		    insn->offset == func->offset + prev->len)
 			return true;
 	}
 
···
 }
 
 /*
- * A sibling call is a tail-call to another symbol -- to differentiate from a
- * recursive tail-call which is to the same symbol.
- */
-static bool jump_is_sibling_call(struct objtool_file *file,
-				 struct instruction *from, struct instruction *to)
-{
-	struct symbol *fs = from->sym;
-	struct symbol *ts = to->sym;
-
-	/* Not a sibling call if from/to a symbol hole */
-	if (!fs || !ts)
-		return false;
-
-	/* Not a sibling call if not targeting the start of a symbol. */
-	if (!is_first_func_insn(file, to, ts))
-		return false;
-
-	/* Disallow sibling calls into STT_NOTYPE */
-	if (ts->type == STT_NOTYPE)
-		return false;
-
-	/* Must not be self to be a sibling */
-	return fs->pfunc != ts->pfunc;
-}
-
-/*
  * Find the destination instructions for all jumps.
  */
 static int add_jump_destinations(struct objtool_file *file)
 {
-	struct instruction *insn, *jump_dest;
+	struct instruction *insn;
 	struct reloc *reloc;
-	struct section *dest_sec;
-	unsigned long dest_off;
-	int ret;
 
 	for_each_insn(file, insn) {
 		struct symbol *func = insn_func(insn);
+		struct instruction *dest_insn;
+		struct section *dest_sec;
+		struct symbol *dest_sym;
+		unsigned long dest_off;
+
+		if (!is_static_jump(insn))
+			continue;
 
 		if (insn->jump_dest) {
 			/*
···
 			 */
 			continue;
 		}
-		if (!is_static_jump(insn))
-			continue;
 
 		reloc = insn_reloc(file, insn);
 		if (!reloc) {
 			dest_sec = insn->sec;
 			dest_off = arch_jump_destination(insn);
-		} else if (reloc->sym->type == STT_SECTION) {
-			dest_sec = reloc->sym->sec;
-			dest_off = arch_dest_reloc_offset(reloc_addend(reloc));
-		} else if (reloc->sym->retpoline_thunk) {
-			ret = add_retpoline_call(file, insn);
-			if (ret)
-				return ret;
-			continue;
-		} else if (reloc->sym->return_thunk) {
-			add_return_call(file, insn, true);
-			continue;
-		} else if (func) {
-			/*
-			 * External sibling call or internal sibling call with
-			 * STT_FUNC reloc.
-			 */
-			ret = add_call_dest(file, insn, reloc->sym, true);
-			if (ret)
-				return ret;
-			continue;
-		} else if (reloc->sym->sec->idx) {
-			dest_sec = reloc->sym->sec;
-			dest_off = reloc->sym->sym.st_value +
-				   arch_dest_reloc_offset(reloc_addend(reloc));
+			dest_sym = dest_sec->sym;
 		} else {
-			/* non-func asm code jumping to another file */
-			continue;
+			dest_sym = reloc->sym;
+			if (is_undef_sym(dest_sym)) {
+				if (dest_sym->retpoline_thunk) {
+					if (add_retpoline_call(file, insn))
+						return -1;
+					continue;
+				}
+
+				if (dest_sym->return_thunk) {
+					add_return_call(file, insn, true);
+					continue;
+				}
+
+				/* External symbol */
+				if (func) {
+					/* External sibling call */
+					if (add_call_dest(file, insn, dest_sym, true))
+						return -1;
+					continue;
+				}
+
+				/* Non-func asm code jumping to external symbol */
+				continue;
+			}
+
+			dest_sec = dest_sym->sec;
+			dest_off = dest_sym->offset + arch_insn_adjusted_addend(insn, reloc);
 		}
 
-		jump_dest = find_insn(file, dest_sec, dest_off);
-		if (!jump_dest) {
+		dest_insn = find_insn(file, dest_sec, dest_off);
+		if (!dest_insn) {
 			struct symbol *sym = find_symbol_by_offset(dest_sec, dest_off);
 
 			/*
-			 * This is a special case for retbleed_untrain_ret().
-			 * It jumps to __x86_return_thunk(), but objtool
-			 * can't find the thunk's starting RET
-			 * instruction, because the RET is also in the
-			 * middle of another instruction.  Objtool only
-			 * knows about the outer instruction.
+			 * retbleed_untrain_ret() jumps to
+			 * __x86_return_thunk(), but objtool can't find
+			 * the thunk's starting RET instruction,
+			 * because the RET is also in the middle of
+			 * another instruction.  Objtool only knows
+			 * about the outer instruction.
 			 */
 			if (sym && sym->embedded_insn) {
 				add_return_call(file, insn, false);
···
 			}
 
 			/*
-			 * GCOV/KCOV dead code can jump to the end of the
-			 * function/section.
+			 * GCOV/KCOV dead code can jump to the end of
+			 * the function/section.
 			 */
 			if (file->ignore_unreachables && func &&
 			    dest_sec == insn->sec &&
 			    dest_off == func->offset + func->len)
 				continue;
 
-			ERROR_INSN(insn, "can't find jump dest instruction at %s+0x%lx",
-				   dest_sec->name, dest_off);
+			ERROR_INSN(insn, "can't find jump dest instruction at %s",
+				   offstr(dest_sec, dest_off));
 			return -1;
 		}
 
-		/*
-		 * An intra-TU jump in retpoline.o might not have a relocation
-		 * for its jump dest, in which case the above
-		 * add_{retpoline,return}_call() didn't happen.
-		 */
-		if (jump_dest->sym && jump_dest->offset == jump_dest->sym->offset) {
-			if (jump_dest->sym->retpoline_thunk) {
-				ret = add_retpoline_call(file, insn);
-				if (ret)
-					return ret;
-				continue;
-			}
-			if (jump_dest->sym->return_thunk) {
-				add_return_call(file, insn, true);
-				continue;
-			}
+		if (!dest_sym || is_sec_sym(dest_sym)) {
+			dest_sym = dest_insn->sym;
+			if (!dest_sym)
+				goto set_jump_dest;
 		}
 
-		/*
-		 * Cross-function jump.
-		 */
-		if (func && insn_func(jump_dest) && func != insn_func(jump_dest)) {
-
-			/*
-			 * For GCC 8+, create parent/child links for any cold
-			 * subfunctions.  This is _mostly_ redundant with a
-			 * similar initialization in read_symbols().
-			 *
-			 * If a function has aliases, we want the *first* such
-			 * function in the symbol table to be the subfunction's
-			 * parent.  In that case we overwrite the
-			 * initialization done in read_symbols().
-			 *
-			 * However this code can't completely replace the
-			 * read_symbols() code because this doesn't detect the
-			 * case where the parent function's only reference to a
-			 * subfunction is through a jump table.
-			 */
-			if (!strstr(func->name, ".cold") &&
-			    strstr(insn_func(jump_dest)->name, ".cold")) {
-				func->cfunc = insn_func(jump_dest);
-				insn_func(jump_dest)->pfunc = func;
-			}
-		}
-
-		if (jump_is_sibling_call(file, insn, jump_dest)) {
-			/*
-			 * Internal sibling call without reloc or with
-			 * STT_SECTION reloc.
-			 */
-			ret = add_call_dest(file, insn, insn_func(jump_dest), true);
-			if (ret)
-				return ret;
+		if (dest_sym->retpoline_thunk && dest_insn->offset == dest_sym->offset) {
+			if (add_retpoline_call(file, insn))
+				return -1;
 			continue;
 		}
 
-		insn->jump_dest = jump_dest;
+		if (dest_sym->return_thunk && dest_insn->offset == dest_sym->offset) {
+			add_return_call(file, insn, true);
+			continue;
+		}
+
+		if (!insn->sym || insn->sym == dest_insn->sym)
+			goto set_jump_dest;
+
+		/*
+		 * Internal cross-function jump.
+		 */
+
+		/*
+		 * For GCC 8+, create parent/child links for any cold
+		 * subfunctions.  This is _mostly_ redundant with a
+		 * similar initialization in read_symbols().
+		 *
+		 * If a function has aliases, we want the *first* such
+		 * function in the symbol table to be the subfunction's
+		 * parent.  In that case we overwrite the
+		 * initialization done in read_symbols().
+		 *
+		 * However this code can't completely replace the
+		 * read_symbols() code because this doesn't detect the
+		 * case where the parent function's only reference to a
+		 * subfunction is through a jump table.
+		 */
+		if (func && dest_sym->cold) {
+			func->cfunc = dest_sym;
+			dest_sym->pfunc = func;
+			goto set_jump_dest;
+		}
+
+		if (is_first_func_insn(file, dest_insn)) {
+			/* Internal sibling call */
+			if (add_call_dest(file, insn, dest_sym, true))
+				return -1;
+			continue;
+		}
+
+set_jump_dest:
+		insn->jump_dest = dest_insn;
 	}
 
 	return 0;
···
 	unsigned long dest_off;
 	struct symbol *dest;
 	struct reloc *reloc;
-	int ret;
 
 	for_each_insn(file, insn) {
 		struct symbol *func = insn_func(insn);
···
 			dest_off = arch_jump_destination(insn);
 			dest = find_call_destination(insn->sec, dest_off);
 
-			ret = add_call_dest(file, insn, dest, false);
-			if (ret)
-				return ret;
+			if (add_call_dest(file, insn, dest, false))
+				return -1;
 
 			if (func && func->ignore)
 				continue;
···
 				return -1;
 			}
 
-			if (func && insn_call_dest(insn)->type != STT_FUNC) {
+			if (func && !is_func_sym(insn_call_dest(insn))) {
 				ERROR_INSN(insn, "unsupported call to non-function");
 				return -1;
 			}
 
-		} else if (reloc->sym->type == STT_SECTION) {
-			dest_off = arch_dest_reloc_offset(reloc_addend(reloc));
+		} else if (is_sec_sym(reloc->sym)) {
+			dest_off = arch_insn_adjusted_addend(insn, reloc);
 			dest = find_call_destination(reloc->sym->sec, dest_off);
 			if (!dest) {
 				ERROR_INSN(insn, "can't find call dest symbol at %s+0x%lx",
···
 				return -1;
 			}
 
-			ret = add_call_dest(file, insn, dest, false);
-			if (ret)
-				return ret;
+			if (add_call_dest(file, insn, dest, false))
+				return -1;
 
 		} else if (reloc->sym->retpoline_thunk) {
-			ret = add_retpoline_call(file, insn);
-			if (ret)
-				return ret;
+			if (add_retpoline_call(file, insn))
+				return -1;
 
 		} else {
-			ret = add_call_dest(file, insn, reloc->sym, false);
-			if (ret)
-				return ret;
+			if (add_call_dest(file, insn, reloc->sym, false))
+				return -1;
 		}
 	}
 
···
 		nop->type = INSN_NOP;
 		nop->sym = orig_insn->sym;
 		nop->alt_group = new_alt_group;
+		nop->fake = 1;
 	}
 
 	if (!special_alt->new_len) {
···
 	struct instruction *orig_insn, *new_insn;
 	struct special_alt *special_alt, *tmp;
 	struct alternative *alt;
-	int ret;
 
 	if (special_get_alts(file->elf, &special_alts))
 		return -1;
···
 				continue;
 			}
 
-			ret = handle_group_alt(file, special_alt, orig_insn,
-					       &new_insn);
-			if (ret)
-				return ret;
+			if (handle_group_alt(file, special_alt, orig_insn, &new_insn))
+				return -1;
 
 		} else if (special_alt->jump_or_nop) {
-			ret = handle_jump_alt(file, special_alt, orig_insn,
-					      &new_insn);
-			if (ret)
-				return ret;
+			if (handle_jump_alt(file, special_alt, orig_insn, &new_insn))
+				return -1;
 		}
 
 		alt = calloc(1, sizeof(*alt));
···
 				  struct symbol *func)
 {
 	struct instruction *insn;
-	int ret;
 
 	func_for_each_insn(file, func, insn) {
 		if (!insn_jump_table(insn))
 			continue;
 
-		ret = add_jump_table(file, insn);
-		if (ret)
-			return ret;
+		if (add_jump_table(file, insn))
+			return -1;
 	}
 
 	return 0;
···
 static int add_jump_table_alts(struct objtool_file *file)
 {
 	struct symbol *func;
-	int ret;
 
 	if (!file->rodata)
 		return 0;
 
-	for_each_sym(file, func) {
-		if (func->type != STT_FUNC)
+	for_each_sym(file->elf, func) {
+		if (!is_func_sym(func))
 			continue;
 
 		mark_func_jump_tables(file, func);
-		ret = add_func_jump_tables(file, func);
-		if (ret)
-			return ret;
+		if (add_func_jump_tables(file, func))
+			return -1;
 	}
 
 	return 0;
···
 		return -1;
 	}
 
-	if (sec->sh.sh_size % sizeof(struct unwind_hint)) {
+	if (sec_size(sec) % sizeof(struct unwind_hint)) {
 		ERROR("struct unwind_hint size mismatch");
 		return -1;
 	}
 
 	file->hints = true;
 
-	for (i = 0; i < sec->sh.sh_size / sizeof(struct unwind_hint); i++) {
+	for (i = 0; i < sec_size(sec) / sizeof(struct unwind_hint); i++) {
 		hint = (struct unwind_hint *)sec->data->d_buf + i;
 
 		reloc = find_reloc_by_dest(file->elf, sec, i * sizeof(*hint));
···
 			return -1;
 		}
 
-		if (reloc->sym->type == STT_SECTION) {
-			offset = reloc_addend(reloc);
-		} else if (reloc->sym->local_label) {
-			offset = reloc->sym->offset;
-		} else {
-			ERROR("unexpected relocation symbol type in %s", sec->rsec->name);
-			return -1;
-		}
+		offset = reloc->sym->offset + reloc_addend(reloc);
 
 		insn = find_insn(file, reloc->sym->sec, offset);
 		if (!insn) {
···
 		if (hint->type == UNWIND_HINT_TYPE_REGS_PARTIAL) {
 			struct symbol *sym = find_symbol_by_offset(insn->sec, insn->offset);
 
-			if (sym && sym->bind == STB_GLOBAL) {
+			if (sym && is_global_sym(sym)) {
 				if (opts.ibt && insn->type != INSN_ENDBR && !insn->noendbr) {
 					ERROR_INSN(insn, "UNWIND_HINT_IRET_REGS without ENDBR");
 					return -1;
···
 	struct instruction *insn;
 	struct reloc *reloc;
 	uint64_t offset;
-	int type, ret;
+	int type;
 
 	sec = find_section_by_name(file->elf, ".discard.annotate_insn");
 	if (!sec)
···
 		sec->sh.sh_entsize = 8;
 	}
 
-	for_each_reloc(sec->rsec, reloc) {
-		type = *(u32 *)(sec->data->d_buf + (reloc_idx(reloc) * sec->sh.sh_entsize) + 4);
-		type = bswap_if_needed(file->elf, type);
+	if (sec_num_entries(sec) != sec_num_entries(sec->rsec)) {
+		ERROR("bad .discard.annotate_insn section: missing relocs");
+		return -1;
+	}
 
+	for_each_reloc(sec->rsec, reloc) {
+		type = annotype(file->elf, sec, reloc);
 		offset = reloc->sym->offset + reloc_addend(reloc);
 		insn = find_insn(file, reloc->sym->sec, offset);
 
···
 			return -1;
 		}
 
-		ret = func(file, type, insn);
-		if (ret < 0)
-			return ret;
+		if (func(file, type, insn))
+			return -1;
 	}
 
 	return 0;
···
 {
 	struct symbol *func;
 
-	for_each_sym(file, func) {
-		if (func->type == STT_NOTYPE && strstarts(func->name, ".L"))
+	for_each_sym(file->elf, func) {
+		if (is_notype_sym(func) && strstarts(func->name, ".L"))
 			func->local_label = true;
 
-		if (func->bind != STB_GLOBAL)
+		if (!is_global_sym(func))
 			continue;
 
 		if (!strncmp(func->name, STATIC_CALL_TRAMP_PREFIX_STR,
···
 	 *
 	 * .rodata.str1.* sections are ignored; they don't contain jump tables.
 	 */
-	for_each_sec(file, sec) {
+	for_each_sec(file->elf, sec) {
 		if ((!strncmp(sec->name, ".rodata", 7) &&
 		     !strstr(sec->name, ".str1.")) ||
 		    !strncmp(sec->name, ".data.rel.ro", 12)) {
···
 	file->rodata = found;
 }
 
+static void mark_holes(struct objtool_file *file)
+{
+	struct instruction *insn;
+	bool in_hole = false;
+
+	if (!opts.link)
+		return;
+
+	/*
+	 * Whole archive runs might encounter dead code from weak symbols.
+	 * This is where the linker will have dropped the weak symbol in
+	 * favour of a regular symbol, but leaves the code in place.
+	 */
+	for_each_insn(file, insn) {
+		if (insn->sym || !find_symbol_hole_containing(insn->sec, insn->offset)) {
+			in_hole = false;
+			continue;
+		}
+
+		/* Skip function padding and pfx code */
+		if (!in_hole && insn->type == INSN_NOP)
+			continue;
+
+		in_hole = true;
+		insn->hole = 1;
+
+		/*
+		 * If this hole jumps to a .cold function, mark it ignore.
+		 */
+		if (insn->jump_dest) {
+			struct symbol *dest_func = insn_func(insn->jump_dest);
+
+			if (dest_func && dest_func->cold)
+				dest_func->ignore = true;
+		}
+	}
+}
+
+static bool validate_branch_enabled(void)
+{
+	return opts.stackval ||
+	       opts.orc ||
+	       opts.uaccess ||
+	       opts.checksum;
+}
+
 static int decode_sections(struct objtool_file *file)
 {
-	int ret;
+	file->klp = is_livepatch_module(file);
 
 	mark_rodata(file);
 
-	ret = init_pv_ops(file);
-	if (ret)
-		return ret;
+	if (init_pv_ops(file))
+		return -1;
 
 	/*
 	 * Must be before add_{jump_call}_destination.
 	 */
-	ret = classify_symbols(file);
-	if (ret)
-		return ret;
+	if (classify_symbols(file))
+		return -1;
 
-	ret = decode_instructions(file);
-	if (ret)
-		return ret;
+	if (decode_instructions(file))
+		return -1;
 
-	ret = add_ignores(file);
-	if (ret)
-		return ret;
+	if (add_ignores(file))
+		return -1;
 
 	add_uaccess_safe(file);
 
-	ret = read_annotate(file, __annotate_early);
-	if (ret)
-		return ret;
+	if (read_annotate(file, __annotate_early))
+		return -1;
 
 	/*
 	 * Must be before add_jump_destinations(), which depends on 'func'
 	 * being set for alternatives, to enable proper sibling call detection.
 	 */
-	if (opts.stackval || opts.orc || opts.uaccess || opts.noinstr) {
-		ret = add_special_section_alts(file);
-		if (ret)
-			return ret;
+	if (validate_branch_enabled() || opts.noinstr || opts.hack_jump_label) {
+		if (add_special_section_alts(file))
+			return -1;
 	}
 
-	ret = add_jump_destinations(file);
-	if (ret)
-		return ret;
+	if (add_jump_destinations(file))
+		return -1;
 
 	/*
 	 * Must be before add_call_destination(); it changes INSN_CALL to
 	 * INSN_JUMP.
 	 */
-	ret = read_annotate(file, __annotate_ifc);
-	if (ret)
-		return ret;
+	if (read_annotate(file, __annotate_ifc))
+		return -1;
 
-	ret = add_call_destinations(file);
-	if (ret)
-		return ret;
+	if (add_call_destinations(file))
+		return -1;
 
-	ret = add_jump_table_alts(file);
-	if (ret)
-		return ret;
+	if (add_jump_table_alts(file))
+		return -1;
 
-	ret = read_unwind_hints(file);
-	if (ret)
-		return ret;
+	if (read_unwind_hints(file))
+		return -1;
+
+	/* Must be after add_jump_destinations() */
+	mark_holes(file);
 
 	/*
 	 * Must be after add_call_destinations() such that it can override
 	 * dead_end_function() marks.
 	 */
-	ret = read_annotate(file, __annotate_late);
-	if (ret)
-		return ret;
+	if (read_annotate(file, __annotate_late))
+		return -1;
 
 	return 0;
 }
···
 	if (!reloc || strcmp(reloc->sym->name, "pv_ops"))
 		return false;
 
-	idx = (arch_dest_reloc_offset(reloc_addend(reloc)) / sizeof(void *));
+	idx = arch_insn_adjusted_addend(insn, reloc) / sizeof(void *);
 
 	if (file->pv_ops[idx].clean)
 		return true;
···
 	return alt_insn->type == INSN_CLAC || alt_insn->type == INSN_STAC;
 }
 
+static int checksum_debug_init(struct objtool_file *file)
+{
+	char *dup, *s;
+
+	if (!opts.debug_checksum)
+		return 0;
+
+	dup = strdup(opts.debug_checksum);
+	if (!dup) {
+		ERROR_GLIBC("strdup");
+		return -1;
+	}
+
+	s = dup;
+	while (*s) {
+		struct symbol *func;
+		char *comma;
+
+		comma = strchr(s, ',');
+		if (comma)
+			*comma = '\0';
+
+		func = find_symbol_by_name(file->elf, s);
+		if (!func || !is_func_sym(func))
+			WARN("--debug-checksum: can't find '%s'", s);
+		else
+			func->debug_checksum = 1;
+
+		if (!comma)
+			break;
+
+		s = comma + 1;
+	}
+
+	free(dup);
+	return 0;
+}
+
+static void checksum_update_insn(struct objtool_file *file, struct symbol *func,
+				 struct instruction *insn)
+{
+	struct reloc *reloc = insn_reloc(file, insn);
+	unsigned long offset;
+	struct symbol *sym;
+
+	if (insn->fake)
+		return;
+
+	checksum_update(func, insn, insn->sec->data->d_buf + insn->offset, insn->len);
+
+	if (!reloc) {
+		struct symbol *call_dest = insn_call_dest(insn);
+
+		if (call_dest)
+			checksum_update(func, insn, call_dest->demangled_name,
+					strlen(call_dest->demangled_name));
+		return;
+	}
+
+	sym = reloc->sym;
+	offset = arch_insn_adjusted_addend(insn, reloc);
+
+	if (is_string_sec(sym->sec)) {
+		char *str;
+
+		str = sym->sec->data->d_buf + sym->offset + offset;
+		checksum_update(func, insn, str, strlen(str));
+		return;
+	}
+
+	if (is_sec_sym(sym)) {
+		sym = find_symbol_containing(reloc->sym->sec, offset);
+		if (!sym)
+			return;
+
+		offset -= sym->offset;
+	}
+
+	checksum_update(func, insn, sym->demangled_name, strlen(sym->demangled_name));
+	checksum_update(func, insn, &offset, sizeof(offset));
+}
+
 /*
  * Follow the branch starting at the given instruction, and recursively follow
  * any other branches (jumps).  Meanwhile, track the frame pointer state at
···
 {
 	struct alternative *alt;
 	struct instruction *next_insn, *prev_insn = NULL;
-	struct section *sec;
 	u8 visited;
 	int ret;
 
 	if (func && func->ignore)
 		return 0;
 
-	sec = insn->sec;
-
 	while (1) {
 		next_insn = next_insn_to_validate(file, insn);
 
+		if (opts.checksum && func && insn->sec)
+			checksum_update_insn(file, func, insn);
+
 		if (func && insn_func(insn) && func != insn_func(insn)->pfunc) {
 			/* Ignore KCFI type preambles, which always fall through */
-			if (!strncmp(func->name, "__cfi_", 6) ||
-			    !strncmp(func->name, "__pfx_", 6) ||
-			    !strncmp(func->name, "__pi___cfi_", 11) ||
-			    !strncmp(func->name, "__pi___pfx_", 11))
+			if (is_prefix_func(func))
 				return 0;
 
 			if (file->ignore_unreachables)
···
 
 			WARN("%s%sunexpected end of section %s",
 			     func ? func->name : "", func ? "(): " : "",
-			     sec->name);
+			     insn->sec->name);
 			return 1;
 		}
 
···
 				  struct insn_state *state)
 {
 	if (insn->hint && !insn->visited) {
-		int ret = validate_branch(file, insn_func(insn), insn, *state);
+		struct symbol *func = insn_func(insn);
+		int ret;
+
+		if (opts.checksum)
+			checksum_init(func);
+
+		ret = validate_branch(file, func, insn, *state);
 		if (ret)
 			BT_INSN(insn, "<=== (hint)");
 		return ret;
···
 	struct instruction *prev_insn;
 	int i;
 
-	if (insn->type == INSN_NOP || insn->type == INSN_TRAP || (func && func->ignore))
+	if (insn->type == INSN_NOP || insn->type == INSN_TRAP ||
+	    insn->hole || (func && func->ignore))
 		return true;
 
 	/*
···
 	if (!strcmp(insn->sec->name, ".altinstr_replacement") ||
 	    !strcmp(insn->sec->name, ".altinstr_aux"))
 		return true;
-
-	/*
-	 * Whole archive runs might encounter dead code from weak symbols.
-	 * This is where the linker will have dropped the weak symbol in
-	 * favour of a regular symbol, but leaves the code in place.
-	 *
-	 * In this case we'll find a piece of code (whole function) that is not
-	 * covered by a !section symbol. Ignore them.
-	 */
-	if (opts.link && !func) {
-		int size = find_symbol_hole_containing(insn->sec, insn->offset);
-		unsigned long end = insn->offset + size;
-
-		if (!size) /* not a hole */
-			return false;
-
-		if (size < 0) /* hole until the end */
-			return true;
-
-		sec_for_each_insn_continue(file, insn) {
-			/*
-			 * If we reach a visited instruction at or before the
-			 * end of the hole, ignore the unreachable.
-			 */
-			if (insn->visited)
-				return true;
-
-			if (insn->offset >= end)
-				break;
-
-			/*
-			 * If this hole jumps to a .cold function, mark it ignore too.
-			 */
-			if (insn->jump_dest && insn_func(insn->jump_dest) &&
-			    strstr(insn_func(insn->jump_dest)->name, ".cold")) {
-				insn_func(insn->jump_dest)->ignore = true;
-			}
-		}
-
-		return false;
-	}
 
 	if (!func)
 		return false;
···
 	return false;
 }
 
-static int add_prefix_symbol(struct objtool_file *file, struct symbol *func)
+/*
+ * For FineIBT or kCFI, a certain number of bytes preceding the function may be
+ * NOPs.  Those NOPs may be rewritten at runtime and executed, so give them a
+ * proper function name: __pfx_<func>.
+ *
+ * The NOPs may not exist for the following cases:
+ *
+ *   - compiler cloned functions (*.cold, *.part0, etc)
+ *   - asm functions created with inline asm or without SYM_FUNC_START()
+ *
+ * Also, the function may already have a prefix from a previous objtool run
+ * (livepatch extracted functions, or manually running objtool multiple times).
+ *
+ * So return 0 if the NOPs are missing or the function already has a prefix
+ * symbol.
+ */
+static int create_prefix_symbol(struct objtool_file *file, struct symbol *func)
 {
 	struct instruction *insn, *prev;
+	char name[SYM_NAME_LEN];
 	struct cfi_state *cfi;
 
-	insn = find_insn(file, func->sec, func->offset);
-	if (!insn)
+	if (!is_func_sym(func) || is_prefix_func(func) ||
+	    func->cold || func->static_call_tramp)
+		return 0;
+
+	if ((strlen(func->name) + sizeof("__pfx_") > SYM_NAME_LEN)) {
+		WARN("%s: symbol name too long, can't create __pfx_ symbol",
+		      func->name);
+		return 0;
+	}
+
+	if (snprintf_check(name, SYM_NAME_LEN, "__pfx_%s", func->name))
 		return -1;
+
+	if (file->klp) {
+		struct symbol *pfx;
+
+		pfx = find_symbol_by_offset(func->sec, func->offset - opts.prefix);
+		if (pfx && is_prefix_func(pfx) && !strcmp(pfx->name, name))
+			return 0;
+	}
+
+	insn = find_insn(file, func->sec, func->offset);
+	if (!insn) {
+		WARN("%s: can't find starting instruction", func->name);
+		return -1;
+	}
 
 	for (prev = prev_insn_same_sec(file, insn);
 	     prev;
···
 		u64 offset;
 
 		if (prev->type != INSN_NOP)
-			return -1;
+			return 0;
 
 		offset = func->offset - prev->offset;
 
 		if (offset > opts.prefix)
-			return -1;
+			return 0;
 
 		if (offset < opts.prefix)
 			continue;
 
-		elf_create_prefix_symbol(file->elf, func, opts.prefix);
+		if (!elf_create_symbol(file->elf, name, func->sec,
+				       GELF_ST_BIND(func->sym.st_info),
+				       GELF_ST_TYPE(func->sym.st_info),
+				       prev->offset, opts.prefix))
+			return -1;
+
 		break;
 	}
 
 	if (!prev)
-		return -1;
+		return 0;
 
 	if (!insn->cfi) {
 		/*
···
 	return 0;
 }
 
-static int add_prefix_symbols(struct objtool_file *file)
+static int create_prefix_symbols(struct objtool_file *file)
 {
 	struct section *sec;
 	struct symbol *func;
 
-	for_each_sec(file, sec) {
-		if (!(sec->sh.sh_flags & SHF_EXECINSTR))
+	for_each_sec(file->elf, sec) {
+		if (!is_text_sec(sec))
 			continue;
 
 		sec_for_each_sym(sec, func) {
-			if (func->type != STT_FUNC)
-				continue;
-
-			add_prefix_symbol(file, func);
+			if (create_prefix_symbol(file, func))
+				return -1;
 		}
 	}
 
···
 			   struct symbol *sym, struct insn_state *state)
 {
 	struct instruction *insn;
+	struct symbol *func;
 	int ret;
 
 	if (!sym->len) {
···
 	if (opts.uaccess)
 		state->uaccess = sym->uaccess_safe;
 
-	ret = validate_branch(file, insn_func(insn), insn, *state);
+	func = insn_func(insn);
+
+	if (opts.checksum)
+		checksum_init(func);
+
+	ret = validate_branch(file, func, insn, *state);
 	if (ret)
 		BT_INSN(insn, "<=== (sym)");
+
+	if (opts.checksum)
+		checksum_finish(func);
+
 	return ret;
 }
 
···
 	int warnings = 0;
 
 	sec_for_each_sym(sec, func) {
-		if (func->type != STT_FUNC)
+		if (!is_func_sym(func))
 			continue;
 
 		init_insn_state(file, &state, sec);
···
 	struct section *sec;
 	int warnings = 0;
 
-	for_each_sec(file, sec) {
-		if (!(sec->sh.sh_flags & SHF_EXECINSTR))
+	for_each_sec(file->elf, sec) {
+		if (!is_text_sec(sec))
 			continue;
 
 		warnings += validate_section(file, sec);
···
 					      reloc_offset(reloc) + 1,
 					      (insn->offset + insn->len) - (reloc_offset(reloc) + 1))) {
 
-		off = reloc->sym->offset;
-		if (reloc_type(reloc) == R_X86_64_PC32 ||
-		    reloc_type(reloc) == R_X86_64_PLT32)
-			off += arch_dest_reloc_offset(reloc_addend(reloc));
-		else
-			off += reloc_addend(reloc);
+		off = reloc->sym->offset + arch_insn_adjusted_addend(insn, reloc);
 
 		dest = find_insn(file, reloc->sym->sec, off);
 		if (!dest)
···
 	for_each_insn(file, insn)
 		warnings += validate_ibt_insn(file, insn);
 
-	for_each_sec(file, sec) {
+	for_each_sec(file->elf, sec) {
 
 		/* Already done by validate_ibt_insn() */
-		if (sec->sh.sh_flags & SHF_EXECINSTR)
+		if (is_text_sec(sec))
 			continue;
 
 		if (!sec->rsec)
···
 		    !strncmp(sec->name, ".debug", 6)			||
 		    !strcmp(sec->name, ".altinstructions")		||
 		    !strcmp(sec->name, ".ibt_endbr_seal")		||
+		    !strcmp(sec->name, ".kcfi_traps")			||
 		    !strcmp(sec->name, ".orc_unwind_ip")		||
-		    !strcmp(sec->name, ".parainstructions")		||
 		    !strcmp(sec->name, ".retpoline_sites")		||
 		    !strcmp(sec->name, ".smp_locks")			||
 		    !strcmp(sec->name, ".static_call_sites")		||
···
 		    !strcmp(sec->name, "__bug_table")			||
 		    !strcmp(sec->name, "__ex_table")			||
 		    !strcmp(sec->name, "__jump_table")			||
+		    !strcmp(sec->name, "__klp_funcs")			||
 		    !strcmp(sec->name, "__mcount_loc")			||
-		    !strcmp(sec->name, ".kcfi_traps")			||
 		    !strcmp(sec->name, ".llvm.call-graph-profile")	||
 		    !strcmp(sec->name, ".llvm_bb_addr_map")		||
 		    !strcmp(sec->name, "__tracepoints")			||
-		    strstr(sec->name, "__patchable_function_entries"))
+		    !strcmp(sec->name, "__patchable_function_entries"))
 			continue;
 
 		for_each_reloc(sec->rsec, reloc)
···
 	struct symbol *sym;
 	char *funcs = NULL, *tmp;
 
-	for_each_sym(file, sym) {
+	for_each_sym(file->elf, sym) {
 		if (sym->warned) {
 			if (!funcs) {
 				funcs = malloc(strlen(sym->name) + 1);
···
 	struct reloc *reloc;
 	int ret = 0;
 
-	for_each_sec(file, sec) {
+	for_each_sec(file->elf, sec) {
 		/* absolute references in non-loadable sections are fine */
 		if (!(sec->sh.sh_flags & SHF_ALLOC))
 			continue;
···
 	cfi_hash_add(&init_cfi);
 	cfi_hash_add(&func_cfi);
 
+	ret = checksum_debug_init(file);
+	if (ret)
+		goto out;
+
 	ret = decode_sections(file);
 	if (ret)
 		goto out;
···
 	if (opts.retpoline)
 		warnings += validate_retpoline(file);
 
-	if (opts.stackval || opts.orc || opts.uaccess) {
+	if (validate_branch_enabled()) {
 		int w = 0;
 
 		w += validate_functions(file);
···
 	}
 
 	if (opts.prefix) {
-		ret = add_prefix_symbols(file);
+		ret = create_prefix_symbols(file);
 		if (ret)
 			goto out;
 	}
···
 
 	if (opts.noabs)
 		warnings += check_abs_references(file);
+
+	if (opts.checksum) {
+		ret = create_sym_checksum_section(file);
+		if (ret)
+			goto out;
+	}
 
 	if (opts.orc && nr_insns) {
 		ret = orc_create(file);
···
 	if (opts.verbose) {
 		if (opts.werror && warnings)
 			WARN("%d warning(s) upgraded to errors", warnings);
-		print_args();
 		disas_warned_funcs(file);
 	}
+
+	if (opts.backup && make_backup())
+		return 1;
 
 	return ret;
 }

tools/objtool/elf.c

···
 #include <string.h>
 #include <unistd.h>
 #include <errno.h>
+#include <libgen.h>
+#include <ctype.h>
 #include <linux/interval_tree_generic.h>
 #include <objtool/builtin.h>
-
 #include <objtool/elf.h>
 #include <objtool/warn.h>
+
+#define ALIGN_UP(x, align_to) (((x) + ((align_to)-1)) & ~((align_to)-1))
+#define ALIGN_UP_POW2(x) (1U << ((8 * sizeof(x)) - __builtin_clz((x) - 1U)))
+#define MAX(a, b) ((a) > (b) ? (a) : (b))
 
 static inline u32 str_hash(const char *str)
 {
···
 
 static inline unsigned long __sym_last(struct symbol *s)
 {
-	return s->offset + s->len - 1;
+	return s->offset + (s->len ? s->len - 1 : 0);
 }
 
 INTERVAL_TREE_DEFINE(struct symbol, node, unsigned long, __subtree_last,
-		     __sym_start, __sym_last, static, __sym)
+		     __sym_start, __sym_last, static inline __maybe_unused,
+		     __sym)
 
 #define __sym_for_each(_iter, _tree, _start, _end)			\
 	for (_iter = __sym_iter_first((_tree), (_start), (_end));	\
···
 };
 
 /*
- * Find !section symbol where @offset is after it.
+ * Find the last symbol before @offset.
  */
 static int symbol_hole_by_offset(const void *key, const struct rb_node *node)
 {
···
 		return -1;
 
 	if (sh->key >= s->offset + s->len) {
-		if (s->type != STT_SECTION)
-			sh->sym = s;
+		sh->sym = s;
 		return 1;
 	}
 
···
 	struct symbol *iter;
 
 	__sym_for_each(iter, tree, offset, offset) {
-		if (iter->offset == offset && iter->type != STT_SECTION)
+		if (iter->offset == offset && !is_sec_sym(iter))
 			return iter;
 	}
 
···
 	struct symbol *iter;
 
 	__sym_for_each(iter, tree, offset, offset) {
-		if (iter->offset == offset && iter->type == STT_FUNC)
+		if (iter->offset == offset && is_func_sym(iter))
 			return iter;
 	}
 
···
 struct symbol *find_symbol_containing(const struct section *sec, unsigned long offset)
 {
 	struct rb_root_cached *tree = (struct rb_root_cached *)&sec->symbol_tree;
-	struct symbol *iter;
+	struct symbol *sym = NULL, *tmp;
 
-	__sym_for_each(iter, tree, offset, offset) {
-		if (iter->type != STT_SECTION)
-			return iter;
+	__sym_for_each(tmp, tree, offset, offset) {
+		if (tmp->len) {
+			if (!sym) {
+				sym = tmp;
+				continue;
+			}
+
+			if (sym->offset != tmp->offset || sym->len != tmp->len) {
+				/*
+				 * In the rare case of overlapping symbols,
+				 * pick the smaller one.
+				 *
+				 * TODO: outlaw overlapping symbols
+				 */
+				if (tmp->len < sym->len)
+					sym = tmp;
+			}
+		}
 	}
 
-	return NULL;
+	return sym;
 }
 
 /*
···
 	struct symbol *iter;
 
 	__sym_for_each(iter, tree, offset, offset) {
-		if (iter->type == STT_FUNC)
+		if (is_func_sym(iter))
 			return iter;
 	}
 
···
 
 	elf_hash_for_each_possible(symbol_name, sym, name_hash, str_hash(name)) {
 		if (!strcmp(sym->name, name))
+			return sym;
+	}
+
+	return NULL;
+}
+
+struct symbol *find_global_symbol_by_name(const struct elf *elf, const char *name)
+{
+	struct symbol *sym;
+
+	elf_hash_for_each_possible(symbol_name, sym, name_hash, str_hash(name)) {
+		if (!strcmp(sym->name, name) && !is_local_sym(sym))
 			return sym;
 	}
 
···
 			return -1;
 		}
 
-		if (sec->sh.sh_size != 0 && !is_dwarf_section(sec)) {
+		if (sec_size(sec) != 0 && !is_dwarf_section(sec)) {
 			sec->data = elf_getdata(s, NULL);
 			if (!sec->data) {
 				ERROR_ELF("elf_getdata");
 				return -1;
 			}
 			if (sec->data->d_off != 0 ||
-			    sec->data->d_size != sec->sh.sh_size) {
+			    sec->data->d_size != sec_size(sec)) {
 				ERROR("unexpected data attributes for %s", sec->name);
 				return -1;
 			}
···
 	return 0;
 }
 
-static void elf_add_symbol(struct elf *elf, struct symbol *sym)
+static const char *demangle_name(struct symbol *sym)
+{
+	char *str;
+
+	if (!is_local_sym(sym))
+		return sym->name;
+
+	if (!is_func_sym(sym) && !is_object_sym(sym))
+		return sym->name;
+
+	if (!strstarts(sym->name, "__UNIQUE_ID_") && !strchr(sym->name, '.'))
+		return sym->name;
+
+	str = strdup(sym->name);
+	if (!str) {
+		ERROR_GLIBC("strdup");
+		return NULL;
+	}
+
+	for (int i = strlen(str) - 1; i >= 0; i--) {
+		char c = str[i];
+
+		if (!isdigit(c) && c != '.') {
+			str[i + 1] = '\0';
+			break;
+		}
+	};
+
+	return str;
+}
+
+static int elf_add_symbol(struct elf *elf, struct symbol *sym)
 {
 	struct list_head *entry;
 	struct rb_node *pnode;
···
 	sym->type = GELF_ST_TYPE(sym->sym.st_info);
 	sym->bind = GELF_ST_BIND(sym->sym.st_info);
 
-	if (sym->type == STT_FILE)
+	if (is_file_sym(sym))
 		elf->num_files++;
 
 	sym->offset = sym->sym.st_value;
 	sym->len = sym->sym.st_size;
 
 	__sym_for_each(iter, &sym->sec->symbol_tree, sym->offset, sym->offset) {
-		if (iter->offset == sym->offset && iter->type == sym->type)
+		if (iter->offset == sym->offset && iter->type == sym->type &&
+		    iter->len == sym->len)
 			iter->alias = sym;
 	}
 
···
 	else
 		entry = &sym->sec->symbol_list;
 	list_add(&sym->list, entry);
+
+	list_add_tail(&sym->global_list, &elf->symbols);
 	elf_hash_add(symbol, &sym->hash, sym->idx);
 	elf_hash_add(symbol_name, &sym->name_hash, str_hash(sym->name));
 
-	/*
-	 * Don't store empty STT_NOTYPE symbols in the rbtree.  They
-	 * can exist within a function, confusing the sorting.
-	 */
-	if (!sym->len)
-		__sym_remove(sym, &sym->sec->symbol_tree);
+	if (is_func_sym(sym) &&
+	    (strstarts(sym->name, "__pfx_") ||
+	     strstarts(sym->name, "__cfi_") ||
+	     strstarts(sym->name, "__pi___pfx_") ||
+	     strstarts(sym->name, "__pi___cfi_")))
+		sym->prefix = 1;
+
+	if (strstarts(sym->name, ".klp.sym"))
+		sym->klp = 1;
+
+	if (!sym->klp && is_func_sym(sym) && strstr(sym->name, ".cold"))
+		sym->cold = 1;
+	sym->pfunc = sym->cfunc = sym;
+
+	sym->demangled_name = demangle_name(sym);
+	if (!sym->demangled_name)
+		return -1;
+
+	return 0;
 }
 
 static int read_symbols(struct elf *elf)
···
 		ERROR_GLIBC("calloc");
 		return -1;
 	}
+
+	INIT_LIST_HEAD(&elf->symbols);
+
 	for (i = 0; i < symbols_nr; i++) {
 		sym = &elf->symbol_data[i];
 
···
 		if (!gelf_getsymshndx(symtab->data, shndx_data, i, &sym->sym,
 				      &shndx)) {
 			ERROR_ELF("gelf_getsymshndx");
-			goto err;
+			return -1;
 		}
 
 		sym->name = elf_strptr(elf->elf, symtab->sh.sh_link,
 				       sym->sym.st_name);
 		if (!sym->name) {
 			ERROR_ELF("elf_strptr");
-			goto err;
+			return -1;
 		}
 
 		if ((sym->sym.st_shndx > SHN_UNDEF &&
···
 			sym->sec = find_section_by_index(elf, shndx);
 			if (!sym->sec) {
 				ERROR("couldn't find section for symbol %s", sym->name);
-				goto err;
+				return -1;
 			}
 			if (GELF_ST_TYPE(sym->sym.st_info) == STT_SECTION) {
 				sym->name = sym->sec->name;
···
 		} else
 			sym->sec = find_section_by_index(elf, 0);
 
-		elf_add_symbol(elf, sym);
+		if (elf_add_symbol(elf, sym))
+			return -1;
 	}
 
 	if (opts.stats) {
···
 		sec_for_each_sym(sec, sym) {
 			char *pname;
 			size_t pnamelen;
-			if (sym->type != STT_FUNC)
+
+			if (!sym->cold)
 				continue;
-
-			if (sym->pfunc == NULL)
-				sym->pfunc = sym;
-
-			if (sym->cfunc == NULL)
-				sym->cfunc = sym;
 
 			coldstr = strstr(sym->name, ".cold");
-			if (!coldstr)
-				continue;
+			if (!coldstr) {
+				ERROR("%s(): cold subfunction without \".cold\"?", sym->name);
+				return -1;
+			}
 
 			pnamelen = coldstr - sym->name;
 			pname = strndup(sym->name, pnamelen);
···
 	}
 
 	return 0;
-
-err:
-	free(sym);
-	return -1;
 }
 
 static int mark_group_syms(struct elf *elf)
···
 		return -1;
 	}
 
-	list_for_each_entry(sec, &elf->sections, list) {
+	for_each_sec(elf, sec) {
 		if (sec->sh.sh_type == SHT_GROUP &&
 		    sec->sh.sh_link == symtab->idx) {
 			sym = find_symbol_by_index(elf, sec->sh.sh_info);
···
 static int elf_update_symbol(struct elf *elf, struct section *symtab,
 			     struct section *symtab_shndx, struct symbol *sym)
 {
-	Elf32_Word shndx = sym->sec ? sym->sec->idx : SHN_UNDEF;
+	Elf32_Word shndx;
 	Elf_Data *symtab_data = NULL, *shndx_data = NULL;
 	Elf64_Xword entsize = symtab->sh.sh_entsize;
 	int max_idx, idx = sym->idx;
···
 	bool is_special_shndx = sym->sym.st_shndx >= SHN_LORESERVE &&
 				sym->sym.st_shndx != SHN_XINDEX;
 
-	if (is_special_shndx)
-		shndx = sym->sym.st_shndx;
+	shndx = is_special_shndx ? sym->sym.st_shndx : sym->sec->idx;
 
 	s = elf_getscn(elf->elf, symtab->idx);
 	if (!s) {
···
 	}
 
 	/* setup extended section index magic and write the symbol */
-	if ((shndx >= SHN_UNDEF && shndx < SHN_LORESERVE) || is_special_shndx) {
+	if (shndx < SHN_LORESERVE || is_special_shndx) {
 		sym->sym.st_shndx = shndx;
 		if (!shndx_data)
 			shndx = 0;
···
 	return 0;
 }
 
-static struct symbol *
-__elf_create_symbol(struct elf *elf, struct symbol *sym)
+struct symbol *elf_create_symbol(struct elf *elf, const char *name,
+				 struct section *sec, unsigned int bind,
+				 unsigned int type, unsigned long offset,
+				 size_t size)
 {
 	struct section *symtab, *symtab_shndx;
 	Elf32_Word first_non_local, new_idx;
-	struct symbol *old;
+	struct symbol *old, *sym;
+
+	sym = calloc(1, sizeof(*sym));
+	if (!sym) {
+		ERROR_GLIBC("calloc");
+		return NULL;
+	}
+
+	sym->name = strdup(name);
+	if (!sym->name) {
+		ERROR_GLIBC("strdup");
+		return NULL;
+	}
+
+	if (type != STT_SECTION) {
+		sym->sym.st_name = elf_add_string(elf, NULL, sym->name);
+		if (sym->sym.st_name == -1)
+			return NULL;
+	}
+
+	if (sec) {
+		sym->sec = sec;
+	} else {
+		sym->sec = find_section_by_index(elf, 0);
+		if (!sym->sec) {
+			ERROR("no NULL section");
+			return NULL;
+		}
+	}
+
+	sym->sym.st_info  = GELF_ST_INFO(bind, type);
+	sym->sym.st_value = offset;
+	sym->sym.st_size  = size;
 
 	symtab = find_section_by_name(elf, ".symtab");
-	if (symtab) {
-		symtab_shndx = find_section_by_name(elf, ".symtab_shndx");
-	} else {
+	if (!symtab) {
 		ERROR("no .symtab");
 		return NULL;
 	}
 
+	symtab_shndx = find_section_by_name(elf, ".symtab_shndx");
+
 	new_idx = sec_num_entries(symtab);
 
-	if (GELF_ST_BIND(sym->sym.st_info) != STB_LOCAL)
+	if (bind != STB_LOCAL)
 		goto non_local;
 
 	/*
···
 
 non_local:
 	sym->idx = new_idx;
-	if (elf_update_symbol(elf, symtab, symtab_shndx, sym)) {
-		ERROR("elf_update_symbol");
+	if (sym->idx && elf_update_symbol(elf, symtab, symtab_shndx, sym))
 		return NULL;
-	}
 
 	symtab->sh.sh_size += symtab->sh.sh_entsize;
 	mark_sec_changed(elf, symtab, true);
···
 		mark_sec_changed(elf, symtab_shndx, true);
 	}
 
+	if (elf_add_symbol(elf, sym))
+		return NULL;
+
 	return sym;
 }
 
-static struct symbol *
-elf_create_section_symbol(struct elf *elf, struct section *sec)
+struct symbol *elf_create_section_symbol(struct elf *elf, struct section *sec)
 {
 	struct symbol *sym = calloc(1, sizeof(*sym));
 
-	if (!sym) {
-		ERROR_GLIBC("malloc");
+	sym = elf_create_symbol(elf, sec->name, sec, STB_LOCAL, STT_SECTION, 0, 0);
+	if (!sym)
 		return NULL;
-	}
 
-	sym->name = sec->name;
-	sym->sec = sec;
-
-	// st_name 0
-	sym->sym.st_info = GELF_ST_INFO(STB_LOCAL, STT_SECTION);
-	// st_other 0
-	// st_value 0
-	// st_size 0
-
-	sym = __elf_create_symbol(elf, sym);
-	if (sym)
-		elf_add_symbol(elf, sym);
+	sec->sym = sym;
 
 	return sym;
 }
 
-static int elf_add_string(struct elf *elf, struct section *strtab, char *str);
-
-struct symbol *
-elf_create_prefix_symbol(struct elf *elf, struct symbol *orig, long size)
-{
-	struct symbol *sym = calloc(1, sizeof(*sym));
-	size_t namelen = strlen(orig->name) + sizeof("__pfx_");
-	char *name = malloc(namelen);
-
-	if (!sym || !name) {
-		ERROR_GLIBC("malloc");
-		return NULL;
-	}
-
-	snprintf(name, namelen, "__pfx_%s", orig->name);
-
-	sym->name = name;
-	sym->sec = orig->sec;
-
-	sym->sym.st_name = elf_add_string(elf, NULL, name);
-	sym->sym.st_info = orig->sym.st_info;
-	sym->sym.st_value = orig->sym.st_value - size;
-	sym->sym.st_size = size;
-
-	sym = __elf_create_symbol(elf, sym);
-	if (sym)
-		elf_add_symbol(elf, sym);
-
-	return sym;
-}
-
-static struct reloc *elf_init_reloc(struct elf *elf, struct section *rsec,
-				    unsigned int reloc_idx,
-				    unsigned long offset, struct symbol *sym,
-				    s64 addend, unsigned int type)
+struct reloc *elf_init_reloc(struct elf *elf, struct section *rsec,
+			     unsigned int reloc_idx, unsigned long offset,
+			     struct symbol *sym, s64 addend, unsigned int type)
 {
 	struct reloc *reloc, empty = { 0 };
 
···
 				      unsigned long insn_off)
 {
 	struct symbol *sym = insn_sec->sym;
-	int addend = insn_off;
+	s64 addend = insn_off;
 
-	if (!(insn_sec->sh.sh_flags & SHF_EXECINSTR)) {
+	if (!is_text_sec(insn_sec)) {
 		ERROR("bad call to %s() for data symbol %s", __func__, sym->name);
 		return NULL;
 	}
···
 		sym = elf_create_section_symbol(elf, insn_sec);
 		if (!sym)
 			return NULL;
-
-		insn_sec->sym = sym;
 	}
 
 	return elf_init_reloc(elf, sec->rsec, reloc_idx, offset, sym, addend,
···
 				      struct symbol *sym,
 				      s64 addend)
 {
-	if (sym->sec && (sec->sh.sh_flags & SHF_EXECINSTR)) {
+	if (is_text_sec(sec)) {
 		ERROR("bad call to %s() for text symbol %s", __func__, sym->name);
 		return NULL;
 	}
···
 
 		rsec->base->rsec = rsec;
 
-		nr_reloc = 0;
+		/* nr_alloc_relocs=0: libelf owns d_buf */
+		rsec->nr_alloc_relocs = 0;
+
 		rsec->relocs = calloc(sec_num_entries(rsec), sizeof(*reloc));
 		if (!rsec->relocs) {
 			ERROR_GLIBC("calloc");
 			return -1;
 		}
+
+		nr_reloc = 0;
 		for (i = 0; i < sec_num_entries(rsec); i++) {
 			reloc = &rsec->relocs[i];
 
···
 		goto err;
 	}
 
+	elf->name = strdup(name);
+	if (!elf->name) {
+		ERROR_GLIBC("strdup");
+		return NULL;
+	}
+
 	if ((flags & O_ACCMODE) == O_RDONLY)
 		cmd = ELF_C_READ_MMAP;
 	else if ((flags & O_ACCMODE) == O_RDWR)
···
 	return NULL;
 }
 
-static int elf_add_string(struct elf *elf, struct section *strtab, char *str)
+struct elf *elf_create_file(GElf_Ehdr *ehdr, const char *name)
 {
-	Elf_Data *data;
-	Elf_Scn *s;
-	int len;
+	struct section *null, *symtab, *strtab, *shstrtab;
+	char *dir, *base, *tmp_name;
+	struct symbol *sym;
+	struct elf *elf;
+
+	elf_version(EV_CURRENT);
+
+	elf = calloc(1, sizeof(*elf));
+	if (!elf) {
+		ERROR_GLIBC("calloc");
+		return NULL;
+	}
+
+	INIT_LIST_HEAD(&elf->sections);
+
+	dir = strdup(name);
+	if (!dir) {
+		ERROR_GLIBC("strdup");
+		return NULL;
+	}
+
+	dir = dirname(dir);
+
+	base = strdup(name);
+	if (!base) {
+		ERROR_GLIBC("strdup");
+		return NULL;
+	}
+
+	base = basename(base);
+
+	tmp_name = malloc(256);
+	if (!tmp_name) {
+		ERROR_GLIBC("malloc");
+		return NULL;
+	}
+
+	snprintf(tmp_name, 256, "%s/%s.XXXXXX", dir, base);
+
+	elf->fd = mkstemp(tmp_name);
+	if (elf->fd == -1) {
+		ERROR_GLIBC("can't create tmp file");
+		exit(1);
+	}
+
+	elf->tmp_name = tmp_name;
+
+	elf->name = strdup(name);
+	if (!elf->name) {
+		ERROR_GLIBC("strdup");
+		return NULL;
+	}
+
+	elf->elf = elf_begin(elf->fd, ELF_C_WRITE, NULL);
+	if (!elf->elf) {
+		ERROR_ELF("elf_begin");
+		return NULL;
+	}
+
+	if (!gelf_newehdr(elf->elf, ELFCLASS64)) {
+		ERROR_ELF("gelf_newehdr");
+		return NULL;
+	}
+
+	memcpy(&elf->ehdr, ehdr, sizeof(elf->ehdr));
+
+	if (!gelf_update_ehdr(elf->elf, &elf->ehdr)) {
+		ERROR_ELF("gelf_update_ehdr");
+		return NULL;
+	}
+
+	INIT_LIST_HEAD(&elf->symbols);
+
+	if (!elf_alloc_hash(section,		1000) ||
+	    !elf_alloc_hash(section_name,	1000) ||
+	    !elf_alloc_hash(symbol,		10000) ||
+	    !elf_alloc_hash(symbol_name,	10000) ||
+	    !elf_alloc_hash(reloc,		100000))
+		return NULL;
+
+	null		= elf_create_section(elf, NULL, 0, 0, SHT_NULL, 0, 0);
+	shstrtab	= elf_create_section(elf, NULL, 0, 0, SHT_STRTAB, 1, 0);
+	strtab		= elf_create_section(elf, NULL, 0, 0, SHT_STRTAB, 1, 0);
+
+	if (!null || !shstrtab || !strtab)
+		return NULL;
+
+	null->name	= "";
+	shstrtab->name	= ".shstrtab";
+	strtab->name	= ".strtab";
+
+	null->sh.sh_name	= elf_add_string(elf, shstrtab, null->name);
+	shstrtab->sh.sh_name	= elf_add_string(elf, shstrtab, shstrtab->name);
+	strtab->sh.sh_name	= elf_add_string(elf, shstrtab, strtab->name);
+
+	if (null->sh.sh_name == -1 || shstrtab->sh.sh_name == -1 || strtab->sh.sh_name == -1)
+		return NULL;
+
+	elf_hash_add(section_name, &null->name_hash,		str_hash(null->name));
+	elf_hash_add(section_name, &strtab->name_hash,		str_hash(strtab->name));
+	elf_hash_add(section_name, &shstrtab->name_hash,	str_hash(shstrtab->name));
+
+	if (elf_add_string(elf, strtab, "") == -1)
+		return NULL;
+
+	symtab = elf_create_section(elf, ".symtab", 0x18, 0x18, SHT_SYMTAB, 0x8, 0);
+	if (!symtab)
+		return NULL;
+
+	symtab->sh.sh_link = strtab->idx;
+	symtab->sh.sh_info = 1;
+
+	elf->ehdr.e_shstrndx = shstrtab->idx;
+	if (!gelf_update_ehdr(elf->elf, &elf->ehdr)) {
+		ERROR_ELF("gelf_update_ehdr");
+		return NULL;
+	}
+
+	sym = calloc(1, sizeof(*sym));
+	if (!sym) {
+		ERROR_GLIBC("calloc");
+		return NULL;
+	}
+
+	sym->name = "";
+	sym->sec = null;
+	elf_add_symbol(elf, sym);
+
+	return elf;
+}
+
+unsigned int elf_add_string(struct elf *elf, struct section *strtab, const char *str)
+{
+	unsigned int offset;
 
 	if (!strtab)
 		strtab = find_section_by_name(elf, ".strtab");
···
 		return -1;
 	}
 
-	s = elf_getscn(elf->elf, strtab->idx);
-	if (!s) {
-		ERROR_ELF("elf_getscn");
+	if (!strtab->sh.sh_addralign) {
+		ERROR("'%s': invalid sh_addralign", strtab->name);
 		return -1;
 	}
 
-	data = elf_newdata(s);
-	if (!data) {
-		ERROR_ELF("elf_newdata");
+	offset = ALIGN_UP(strtab->sh.sh_size, strtab->sh.sh_addralign);
+
+	if (!elf_add_data(elf, strtab, str, strlen(str) + 1))
 		return -1;
-	}
 
-	data->d_buf = str;
-	data->d_size = strlen(str) + 1;
-	data->d_align = 1;
-
-	len = strtab->sh.sh_size;
-	strtab->sh.sh_size += data->d_size;
-
-	mark_sec_changed(elf, strtab, true);
-
-	return len;
+	return offset;
 }
 
-struct section *elf_create_section(struct elf *elf, const char *name,
-				   size_t entsize, unsigned int nr)
+void *elf_add_data(struct elf *elf, struct section *sec, const void *data, size_t size)
 {
-	struct section *sec, *shstrtab;
-	size_t size = entsize * nr;
+	unsigned long offset;
 	Elf_Scn *s;
 
-	sec = malloc(sizeof(*sec));
-	if (!sec) {
-		ERROR_GLIBC("malloc");
+	if (!sec->sh.sh_addralign) {
+		ERROR("'%s': invalid sh_addralign", sec->name);
 		return NULL;
 	}
-	memset(sec, 0, sizeof(*sec));
 
-	INIT_LIST_HEAD(&sec->symbol_list);
-
-	s = elf_newscn(elf->elf);
+	s = elf_getscn(elf->elf, sec->idx);
 	if (!s) {
-		ERROR_ELF("elf_newscn");
+		ERROR_ELF("elf_getscn");
 		return NULL;
 	}
-
-	sec->name = strdup(name);
-	if (!sec->name) {
-		ERROR_GLIBC("strdup");
-		return NULL;
-	}
-
-	sec->idx = elf_ndxscn(s);
 
 	sec->data = elf_newdata(s);
 	if (!sec->data) {
···
 		return NULL;
 	}
 
+	sec->data->d_buf = calloc(1, size);
+	if (!sec->data->d_buf) {
+		ERROR_GLIBC("calloc");
+		return NULL;
+	}
+
+	if (data)
+		memcpy(sec->data->d_buf, data, size);
+
 	sec->data->d_size = size;
 	sec->data->d_align = 1;
 
+	offset = ALIGN_UP(sec->sh.sh_size, sec->sh.sh_addralign);
+	sec->sh.sh_size = offset + size;
+
+	mark_sec_changed(elf, sec, true);
+
+	return sec->data->d_buf;
+}
+
+struct section *elf_create_section(struct elf *elf, const char *name,
+				   size_t size, size_t entsize,
+				   unsigned int type, unsigned int align,
+				   unsigned int flags)
+{
+	struct section *sec, *shstrtab;
+	Elf_Scn *s;
+
+	if (name && find_section_by_name(elf, name)) {
+		ERROR("section '%s' already exists", name);
+		return NULL;
+	}
+
+	sec = calloc(1, sizeof(*sec));
+	if (!sec) {
+		ERROR_GLIBC("calloc");
+		return NULL;
+	}
+
+	INIT_LIST_HEAD(&sec->symbol_list);
+
+	/* don't actually create the section, just the data structures */
+	if (type == SHT_NULL)
+		goto add;
+
+	s = elf_newscn(elf->elf);
+	if (!s) {
+		ERROR_ELF("elf_newscn");
+		return NULL;
+	}
+
+	sec->idx = elf_ndxscn(s);
+
 	if (size) {
-		sec->data->d_buf = malloc(size);
-		if (!sec->data->d_buf) {
-			ERROR_GLIBC("malloc");
+		sec->data = elf_newdata(s);
+		if (!sec->data) {
+			ERROR_ELF("elf_newdata");
 			return NULL;
 		}
-		memset(sec->data->d_buf, 0, size);
+
+		sec->data->d_size = size;
+		sec->data->d_align = 1;
+
+		sec->data->d_buf = calloc(1, size);
+		if (!sec->data->d_buf) {
+			ERROR_GLIBC("calloc");
+			return NULL;
+		}
 	}
 
 	if (!gelf_getshdr(s, &sec->sh)) {
···
 
 	sec->sh.sh_size = size;
 	sec->sh.sh_entsize = entsize;
-	sec->sh.sh_type = SHT_PROGBITS;
-	sec->sh.sh_addralign = 1;
-	sec->sh.sh_flags = SHF_ALLOC;
+	sec->sh.sh_type = type;
+	sec->sh.sh_addralign = align;
+	sec->sh.sh_flags = flags;
 
-	/* Add section name to .shstrtab (or .strtab for Clang) */
-	shstrtab = find_section_by_name(elf, ".shstrtab");
-	if (!shstrtab)
-		shstrtab = find_section_by_name(elf, ".strtab");
-	if (!shstrtab) {
-		ERROR("can't find .shstrtab or .strtab section");
-		return NULL;
+	if (name) {
+		sec->name = strdup(name);
+		if (!sec->name) {
+			ERROR("strdup");
+			return NULL;
+		}
+
+		/* Add section name to .shstrtab (or .strtab for Clang) */
+		shstrtab = find_section_by_name(elf, ".shstrtab");
+		if (!shstrtab) {
+			shstrtab = find_section_by_name(elf, ".strtab");
+			if (!shstrtab) {
+				ERROR("can't find .shstrtab or .strtab");
+				return NULL;
+			}
+		}
+		sec->sh.sh_name = elf_add_string(elf, shstrtab, sec->name);
+		if (sec->sh.sh_name == -1)
+			return NULL;
+
+		elf_hash_add(section_name, &sec->name_hash, str_hash(sec->name));
 	}
-	sec->sh.sh_name = elf_add_string(elf, shstrtab, sec->name);
-	if (sec->sh.sh_name == -1)
-		return NULL;
 
+add:
 	list_add_tail(&sec->list, &elf->sections);
 	elf_hash_add(section, &sec->hash, sec->idx);
-	elf_hash_add(section_name, &sec->name_hash, str_hash(sec->name));
 
 	mark_sec_changed(elf, sec, true);
 
 	return sec;
 }
 
-static struct section *elf_create_rela_section(struct elf *elf,
-					       struct section *sec,
-					       unsigned int reloc_nr)
+static int elf_alloc_reloc(struct elf *elf, struct section *rsec)
+{
+	struct reloc *old_relocs, *old_relocs_end, *new_relocs;
+	unsigned int nr_relocs_old = sec_num_entries(rsec);
+	unsigned int nr_relocs_new = nr_relocs_old + 1;
+	unsigned long nr_alloc;
+	struct symbol *sym;
+
+	if (!rsec->data) {
+		rsec->data = elf_newdata(elf_getscn(elf->elf, rsec->idx));
+		if (!rsec->data) {
+			ERROR_ELF("elf_newdata");
+			return -1;
+		}
+
+		rsec->data->d_align = 1;
+		rsec->data->d_type = ELF_T_RELA;
+		rsec->data->d_buf = NULL;
+	}
+
+	rsec->data->d_size = nr_relocs_new * elf_rela_size(elf);
+	rsec->sh.sh_size   = rsec->data->d_size;
+
+	nr_alloc = MAX(64, ALIGN_UP_POW2(nr_relocs_new));
+	if (nr_alloc <= rsec->nr_alloc_relocs)
+		return 0;
+
+	if (rsec->data->d_buf && !rsec->nr_alloc_relocs) {
+		void *orig_buf = rsec->data->d_buf;
+
+		/*
+		 * The original d_buf is owned by libelf so it can't be
+		 * realloced.
+		 */
+		rsec->data->d_buf = malloc(nr_alloc * elf_rela_size(elf));
+		if (!rsec->data->d_buf) {
+			ERROR_GLIBC("malloc");
+			return -1;
+		}
+		memcpy(rsec->data->d_buf, orig_buf,
+		       nr_relocs_old * elf_rela_size(elf));
+	} else {
+		rsec->data->d_buf = realloc(rsec->data->d_buf,
+					    nr_alloc * elf_rela_size(elf));
+		if (!rsec->data->d_buf) {
+			ERROR_GLIBC("realloc");
+			return -1;
+		}
+	}
+
+	rsec->nr_alloc_relocs = nr_alloc;
+
+	old_relocs = rsec->relocs;
+	new_relocs = calloc(nr_alloc, sizeof(struct reloc));
+	if (!new_relocs) {
+		ERROR_GLIBC("calloc");
+		return -1;
+	}
+
+	if (!old_relocs)
+		goto done;
+
+	/*
+	 * The struct reloc's address has changed.  Update all the symbols and
+	 * relocs which reference it.
+	 */
+
+	old_relocs_end = &old_relocs[nr_relocs_old];
+	for_each_sym(elf, sym) {
+		struct reloc *reloc;
+
+		reloc = sym->relocs;
+		if (!reloc)
+			continue;
+
+		if (reloc >= old_relocs && reloc < old_relocs_end)
+			sym->relocs = &new_relocs[reloc - old_relocs];
+
+		while (1) {
+			struct reloc *next_reloc = sym_next_reloc(reloc);
+
+			if (!next_reloc)
+				break;
+
+			if (next_reloc >= old_relocs && next_reloc < old_relocs_end)
+				set_sym_next_reloc(reloc, &new_relocs[next_reloc - old_relocs]);
+
+			reloc = next_reloc;
+		}
+	}
+
+	memcpy(new_relocs, old_relocs, nr_relocs_old * sizeof(struct reloc));
+
+	for (int i = 0; i < nr_relocs_old; i++) {
+		struct reloc *old = &old_relocs[i];
+		struct reloc *new = &new_relocs[i];
+		u32 key = reloc_hash(old);
+
+		elf_hash_del(reloc, &old->hash, key);
+		elf_hash_add(reloc, &new->hash, key);
+	}
+
+	free(old_relocs);
+done:
+	rsec->relocs = new_relocs;
+	return 0;
+}
+
+struct section *elf_create_rela_section(struct elf *elf, struct section *sec,
+					unsigned int nr_relocs)
 {
 	struct section *rsec;
 	char *rsec_name;
···
 	strcpy(rsec_name, ".rela");
 	strcat(rsec_name, sec->name);
 
-	rsec = elf_create_section(elf, rsec_name, elf_rela_size(elf), reloc_nr);
+	rsec = elf_create_section(elf, rsec_name, nr_relocs * elf_rela_size(elf),
+				  elf_rela_size(elf), SHT_RELA, elf_addr_size(elf),
+				  SHF_INFO_LINK);
 	free(rsec_name);
 	if (!rsec)
 		return NULL;
 
-	rsec->data->d_type = ELF_T_RELA;
-	rsec->sh.sh_type = SHT_RELA;
-	rsec->sh.sh_addralign = elf_addr_size(elf);
+	if (nr_relocs) {
+		rsec->data->d_type = ELF_T_RELA;
+
+		rsec->nr_alloc_relocs = nr_relocs;
+		rsec->relocs = calloc(nr_relocs, sizeof(struct reloc));
+		if (!rsec->relocs) {
+			ERROR_GLIBC("calloc");
+			return NULL;
+		}
+	}
+
 	rsec->sh.sh_link = find_section_by_name(elf, ".symtab")->idx;
 	rsec->sh.sh_info = sec->idx;
-	rsec->sh.sh_flags = SHF_INFO_LINK;
-
-	rsec->relocs = calloc(sec_num_entries(rsec), sizeof(struct reloc));
-	if (!rsec->relocs) {
-		ERROR_GLIBC("calloc");
-		return NULL;
-	}
 
 	sec->rsec = rsec;
 	rsec->base = sec;
···
 	return rsec;
 }
 
+struct reloc *elf_create_reloc(struct elf *elf, struct section *sec,
+			       unsigned long offset,
+			       struct symbol *sym, s64 addend,
+			       unsigned int type)
+{
+	struct section *rsec = sec->rsec;
+
+	if (!rsec) {
+		rsec = elf_create_rela_section(elf, sec, 0);
+		if (!rsec)
+			return NULL;
+	}
+
+	if (find_reloc_by_dest(elf, sec, offset)) {
+		ERROR_FUNC(sec, offset, "duplicate reloc");
+		return NULL;
+	}
+
+	if (elf_alloc_reloc(elf, rsec))
+		return NULL;
+
+	mark_sec_changed(elf, rsec, true);
+
+	return elf_init_reloc(elf, rsec, sec_num_entries(rsec) - 1, offset, sym,
+			      addend, type);
+}
+
 struct section *elf_create_section_pair(struct elf *elf, const char *name,
 					size_t entsize, unsigned int nr,
-					unsigned int reloc_nr)
+					unsigned int nr_relocs)
 {
 	struct section *sec;
 
-	sec = elf_create_section(elf, name, entsize, nr);
+	sec = elf_create_section(elf, name, nr * entsize, entsize,
+				 SHT_PROGBITS, 1, SHF_ALLOC);
 	if (!sec)
 		return NULL;
 
-	if (!elf_create_rela_section(elf, sec, reloc_nr))
+	if (!elf_create_rela_section(elf, sec, nr_relocs))
 		return NULL;
 
 	return sec;
···
  */
 static int elf_truncate_section(struct elf *elf, struct section *sec)
 {
-	u64 size = sec->sh.sh_size;
+	u64 size = sec_size(sec);
 	bool truncated = false;
 	Elf_Data *data = NULL;
 	Elf_Scn *s;
···
 	for (;;) {
 		/* get next data descriptor for the relevant section */
 		data = elf_getdata(s, data);
-
 		if (!data) {
 			if (size) {
 				ERROR("end of section data but non-zero size left\n");
···
 
 	/* Update changed relocation sections and section headers: */
 	list_for_each_entry(sec, &elf->sections, list) {
-		if (sec->truncate)
-			elf_truncate_section(elf, sec);
+		if (sec->truncate && elf_truncate_section(elf, sec))
+			return -1;
 
 		if (sec_changed(sec)) {
 			s = elf_getscn(elf->elf, sec->idx);
···
 	return 0;
 }
 
-void elf_close(struct elf *elf)
+int elf_close(struct elf *elf)
 {
 	if (elf->elf)
 		elf_end(elf->elf);
···
 	if (elf->fd > 0)
 		close(elf->fd);
 
+	if (elf->tmp_name && rename(elf->tmp_name, elf->name))
+		return -1;
+
 	/*
 	 * NOTE: All remaining allocations are leaked on purpose.  Objtool is
 	 * about to exit anyway.
 	 */
+	return 0;
 }

tools/objtool/include/objtool/arch.h

···
 
 struct instruction;
 
-int arch_ftrace_match(char *name);
+int arch_ftrace_match(const char *name);
 
 void arch_initial_func_cfi_state(struct cfi_init_state *state);
 
···
 
 unsigned long arch_jump_destination(struct instruction *insn);
 
-unsigned long arch_dest_reloc_offset(int addend);
+s64 arch_insn_adjusted_addend(struct instruction *insn, struct reloc *reloc);
+u64 arch_adjusted_addend(struct reloc *reloc);
 
 const char *arch_nop_insn(int len);
 const char *arch_ret_insn(int len);

tools/objtool/include/objtool/builtin.h

···
 
 struct opts {
 	/* actions: */
+	bool cfi;
+	bool checksum;
 	bool dump_orc;
 	bool hack_jump_label;
 	bool hack_noinstr;
 	bool hack_skylake;
 	bool ibt;
 	bool mcount;
+	bool noabs;
 	bool noinstr;
 	bool orc;
 	bool retpoline;
···
 	bool static_call;
 	bool uaccess;
 	int prefix;
-	bool cfi;
-	bool noabs;
 
 	/* options: */
 	bool backtrace;
+	bool backup;
+	const char *debug_checksum;
 	bool dryrun;
 	bool link;
 	bool mnop;
···
 
 int objtool_run(int argc, const char **argv);
 
-void print_args(void);
+int make_backup(void);
+
+int cmd_klp(int argc, const char **argv);
 
 #endif /* _BUILTIN_H */

tools/objtool/include/objtool/check.h

···
 	    noendbr		: 1,
 	    unret		: 1,
 	    visited		: 4,
-	    no_reloc		: 1;
-		/* 10 bit hole */
+	    no_reloc		: 1,
+	    hole		: 1,
+	    fake		: 1;
+		/* 9 bit hole */
 
 	struct alt_group *alt_group;
 	struct instruction *jump_dest;

tools/objtool/include/objtool/checksum.h

···
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+#ifndef _OBJTOOL_CHECKSUM_H
+#define _OBJTOOL_CHECKSUM_H
+
+#include <objtool/elf.h>
+
+#ifdef BUILD_KLP
+
+static inline void checksum_init(struct symbol *func)
+{
+	if (func && !func->csum.state) {
+		func->csum.state = XXH3_createState();
+		XXH3_64bits_reset(func->csum.state);
+	}
+}
+
+static inline void checksum_update(struct symbol *func,
+				   struct instruction *insn,
+				   const void *data, size_t size)
+{
+	XXH3_64bits_update(func->csum.state, data, size);
+	dbg_checksum(func, insn, XXH3_64bits_digest(func->csum.state));
+}
+
+static inline void checksum_finish(struct symbol *func)
+{
+	if (func && func->csum.state) {
+		func->csum.checksum = XXH3_64bits_digest(func->csum.state);
+		func->csum.state = NULL;
+	}
+}
+
+#else /* !BUILD_KLP */
+
+static inline void checksum_init(struct symbol *func) {}
+static inline void checksum_update(struct symbol *func,
+				   struct instruction *insn,
+				   const void *data, size_t size) {}
+static inline void checksum_finish(struct symbol *func) {}
+
+#endif /* !BUILD_KLP */
+
+#endif /* _OBJTOOL_CHECKSUM_H */

tools/objtool/include/objtool/checksum_types.h

···
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _OBJTOOL_CHECKSUM_TYPES_H
+#define _OBJTOOL_CHECKSUM_TYPES_H
+
+struct sym_checksum {
+	u64 addr;
+	u64 checksum;
+};
+
+#ifdef BUILD_KLP
+
+#include <xxhash.h>
+
+struct checksum {
+	XXH3_state_t *state;
+	XXH64_hash_t checksum;
+};
+
+#else /* !BUILD_KLP */
+
+struct checksum {};
+
+#endif /* !BUILD_KLP */
+
+#endif /* _OBJTOOL_CHECKSUM_TYPES_H */

tools/objtool/include/objtool/elf.h

···
 
 #include <stdio.h>
 #include <gelf.h>
+#include <linux/string.h>
 #include <linux/list.h>
 #include <linux/hashtable.h>
 #include <linux/rbtree.h>
 #include <linux/jhash.h>
+
+#include <objtool/endianness.h>
+#include <objtool/checksum_types.h>
 #include <arch/elf.h>
+
+#define SEC_NAME_LEN		1024
+#define SYM_NAME_LEN		512
+
+#define bswap_if_needed(elf, val) __bswap_if_needed(&elf->ehdr, val)
 
 #ifdef LIBELF_USE_DEPRECATED
 # define elf_getshdrnum    elf_getshnum
···
 	struct section *base, *rsec;
 	struct symbol *sym;
 	Elf_Data *data;
-	char *name;
+	const char *name;
 	int idx;
 	bool _changed, text, rodata, noinstr, init, truncate;
 	struct reloc *relocs;
+	unsigned long nr_alloc_relocs;
+	struct section *twin;
 };
 
 struct symbol {
 	struct list_head list;
+	struct list_head global_list;
 	struct rb_node node;
 	struct elf_hash_node hash;
 	struct elf_hash_node name_hash;
 	GElf_Sym sym;
 	struct section *sec;
-	char *name;
+	const char *name, *demangled_name;
 	unsigned int idx, len;
 	unsigned long offset;
 	unsigned long __subtree_last;
···
 	u8 frame_pointer     : 1;
 	u8 ignore	     : 1;
 	u8 nocfi             : 1;
+	u8 cold		     : 1;
+	u8 prefix	     : 1;
+	u8 debug_checksum    : 1;
+	u8 changed	     : 1;
+	u8 included	     : 1;
+	u8 klp		     : 1;
 	struct list_head pv_target;
 	struct reloc *relocs;
 	struct section *group_sec;
+	struct checksum csum;
+	struct symbol *twin, *clone;
 };
 
 struct reloc {
···
 	GElf_Ehdr ehdr;
 	int fd;
 	bool changed;
-	char *name;
+	const char *name, *tmp_name;
 	unsigned int num_files;
 	struct list_head sections;
+	struct list_head symbols;
 	unsigned long num_relocs;
 
 	int symbol_bits;
···
 };
 
 struct elf *elf_open_read(const char *name, int flags);
+struct elf *elf_create_file(GElf_Ehdr *ehdr, const char *name);
 
 struct section *elf_create_section(struct elf *elf, const char *name,
-				   size_t entsize, unsigned int nr);
+				   size_t size, size_t entsize,
+				   unsigned int type, unsigned int align,
+				   unsigned int flags);
 struct section *elf_create_section_pair(struct elf *elf, const char *name,
 					size_t entsize, unsigned int nr,
 					unsigned int reloc_nr);
 
-struct symbol *elf_create_prefix_symbol(struct elf *elf, struct symbol *orig, long size);
+struct section *elf_create_rela_section(struct elf *elf, struct section *sec,
+					unsigned int reloc_nr);
+
+struct symbol *elf_create_symbol(struct elf *elf, const char *name,
+				 struct section *sec, unsigned int bind,
+				 unsigned int type, unsigned long offset,
+				 size_t size);
+struct symbol *elf_create_section_symbol(struct elf *elf, struct section *sec);
+
+void *elf_add_data(struct elf *elf, struct section *sec, const void *data,
+		   size_t size);
+
+unsigned int elf_add_string(struct elf *elf, struct section *strtab, const char *str);
+
+struct reloc *elf_create_reloc(struct elf *elf, struct section *sec,
+			       unsigned long offset, struct symbol *sym,
+			       s64 addend, unsigned int type);
+
+struct reloc *elf_init_reloc(struct elf *elf, struct section *rsec,
+			     unsigned int reloc_idx, unsigned long offset,
+			     struct symbol *sym, s64 addend, unsigned int type);
 
 struct reloc *elf_init_reloc_text_sym(struct elf *elf, struct section *sec,
 				      unsigned long offset,
···
 				      struct symbol *sym,
 				      s64 addend);
 
-int elf_write_insn(struct elf *elf, struct section *sec,
-		   unsigned long offset, unsigned int len,
-		   const char *insn);
+int elf_write_insn(struct elf *elf, struct section *sec, unsigned long offset,
+		   unsigned int len, const char *insn);
+
 int elf_write(struct elf *elf);
-void elf_close(struct elf *elf);
+int elf_close(struct elf *elf);
 
 struct section *find_section_by_name(const struct elf *elf, const char *name);
 struct symbol *find_func_by_offset(struct section *sec, unsigned long offset);
 struct symbol *find_symbol_by_offset(struct section *sec, unsigned long offset);
 struct symbol *find_symbol_by_name(const struct elf *elf, const char *name);
+struct symbol *find_global_symbol_by_name(const struct elf *elf, const char *name);
 struct symbol *find_symbol_containing(const struct section *sec, unsigned long offset);
 int find_symbol_hole_containing(const struct section *sec, unsigned long offset);
 struct reloc *find_reloc_by_dest(const struct elf *elf, struct section *sec, unsigned long offset);
···
 	return elf_addr_size(elf) == 4 ? R_TEXT32 : R_TEXT64;
 }
 
+static inline bool is_undef_sym(struct symbol *sym)
+{
+	return !sym->sec->idx;
+}
+
+static inline bool is_null_sym(struct symbol *sym)
+{
+	return !sym->idx;
+}
+
+static inline bool is_sec_sym(struct symbol *sym)
+{
+	return sym->type == STT_SECTION;
+}
+
+static inline bool is_object_sym(struct symbol *sym)
+{
+	return sym->type == STT_OBJECT;
+}
+
+static inline bool is_func_sym(struct symbol *sym)
+{
+	return sym->type == STT_FUNC;
+}
+
+static inline bool is_file_sym(struct symbol *sym)
+{
+	return sym->type == STT_FILE;
+}
+
+static inline bool is_notype_sym(struct symbol *sym)
+{
+	return sym->type == STT_NOTYPE;
+}
+
+static inline bool is_global_sym(struct symbol *sym)
+{
+	return sym->bind == STB_GLOBAL;
+}
+
+static inline bool is_weak_sym(struct symbol *sym)
+{
+	return sym->bind == STB_WEAK;
+}
+
+static inline bool is_local_sym(struct symbol *sym)
+{
+	return sym->bind == STB_LOCAL;
+}
+
+static inline bool is_prefix_func(struct symbol *sym)
+{
+	return sym->prefix;
+}
+
 static inline bool is_reloc_sec(struct section *sec)
 {
 	return sec->sh.sh_type == SHT_RELA || sec->sh.sh_type == SHT_REL;
+}
+
+static inline bool is_string_sec(struct section *sec)
+{
+	return sec->sh.sh_flags & SHF_STRINGS;
+}
+
+static inline bool is_text_sec(struct section *sec)
+{
+	return sec->sh.sh_flags & SHF_EXECINSTR;
 }
 
 static inline bool sec_changed(struct section *sec)
···
 	 * Elf64_Rela: 24 bytes
 	 */
 	return reloc->sec->sh.sh_entsize < 16;
+}
+
+static inline unsigned long sec_size(struct section *sec)
+{
+	return sec->sh.sh_size;
 }
 
 #define __get_reloc_field(reloc, field)					\
···
 	mark_sec_changed(elf, reloc->sec, true);
 }
 
+static inline unsigned int annotype(struct elf *elf, struct section *sec,
+				    struct reloc *reloc)
+{
+	unsigned int type;
+
+	type = *(u32 *)(sec->data->d_buf + (reloc_idx(reloc) * 8) + 4);
+	return bswap_if_needed(elf, type);
+}
+
 #define RELOC_JUMP_TABLE_BIT 1UL
 
 /* Does reloc mark the beginning of a jump table? */
···
 	reloc->_sym_next_reloc = (unsigned long)next | bit;
 }
 
-#define for_each_sec(file, sec)						\
-	list_for_each_entry(sec, &file->elf->sections, list)
+#define for_each_sec(elf, sec)						\
+	list_for_each_entry(sec, &elf->sections, list)
 
 #define sec_for_each_sym(sec, sym)					\
 	list_for_each_entry(sym, &sec->symbol_list, list)
 
-#define for_each_sym(file, sym)						\
-	for (struct section *__sec, *__fake = (struct section *)1;	\
-	     __fake; __fake = NULL)					\
-		for_each_sec(file, __sec)				\
-			sec_for_each_sym(__sec, sym)
+#define sec_prev_sym(sym)						\
+	sym->sec && sym->list.prev != &sym->sec->symbol_list ?		\
+	list_prev_entry(sym, list) : NULL
+
+#define for_each_sym(elf, sym)						\
+	list_for_each_entry(sym, &elf->symbols, global_list)
+
+#define for_each_sym_continue(elf, sym)					\
+	list_for_each_entry_continue(sym, &elf->symbols, global_list)
+
+#define rsec_next_reloc(rsec, reloc)					\
+	reloc_idx(reloc) < sec_num_entries(rsec) - 1 ? reloc + 1 : NULL
 
 #define for_each_reloc(rsec, reloc)					\
-	for (int __i = 0, __fake = 1; __fake; __fake = 0)		\
-		for (reloc = rsec->relocs;				\
-		     __i < sec_num_entries(rsec);			\
-		     __i++, reloc++)
+	for (reloc = rsec->relocs; reloc; reloc = rsec_next_reloc(rsec, reloc))
 
 #define for_each_reloc_from(rsec, reloc)				\
-	for (int __i = reloc_idx(reloc);				\
-	     __i < sec_num_entries(rsec);				\
-	     __i++, reloc++)
+	for (; reloc; reloc = rsec_next_reloc(rsec, reloc))
+
+#define for_each_reloc_continue(rsec, reloc)				\
+	for (reloc = rsec_next_reloc(rsec, reloc); reloc;		\
+	     reloc = rsec_next_reloc(rsec, reloc))
+
+#define sym_for_each_reloc(elf, sym, reloc)				\
+	for (reloc = find_reloc_by_dest_range(elf, sym->sec,		\
+					      sym->offset, sym->len);	\
+	     reloc && reloc_offset(reloc) <  sym->offset + sym->len;	\
+	     reloc = rsec_next_reloc(sym->sec->rsec, reloc))
+
+static inline struct symbol *get_func_prefix(struct symbol *func)
+{
+	struct symbol *prev;
+
+	if (!is_func_sym(func))
+		return NULL;
+
+	prev = sec_prev_sym(func);
+	if (prev && is_prefix_func(prev))
+		return prev;
+
+	return NULL;
+}
 
 #define OFFSET_STRIDE_BITS	4
 #define OFFSET_STRIDE		(1UL << OFFSET_STRIDE_BITS)

tools/objtool/include/objtool/endianness.h

···
 
 #include <linux/kernel.h>
 #include <endian.h>
-#include <objtool/elf.h>
 
 /*
  * Does a byte swap if target file endianness doesn't match the host, i.e. cross
···
  * To be used for multi-byte values conversion, which are read from / about
  * to be written to a target native endianness ELF file.
  */
-static inline bool need_bswap(struct elf *elf)
+static inline bool need_bswap(GElf_Ehdr *ehdr)
 {
 	return (__BYTE_ORDER == __LITTLE_ENDIAN) ^
-	       (elf->ehdr.e_ident[EI_DATA] == ELFDATA2LSB);
+	       (ehdr->e_ident[EI_DATA] == ELFDATA2LSB);
 }
 
-#define bswap_if_needed(elf, val)					\
+#define __bswap_if_needed(ehdr, val)					\
 ({									\
 	__typeof__(val) __ret;						\
-	bool __need_bswap = need_bswap(elf);				\
+	bool __need_bswap = need_bswap(ehdr);				\
 	switch (sizeof(val)) {						\
 	case 8:								\
 		__ret = __need_bswap ? bswap_64(val) : (val); break;	\

tools/objtool/include/objtool/klp.h

···
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+#ifndef _OBJTOOL_KLP_H
+#define _OBJTOOL_KLP_H
+
+#define SHF_RELA_LIVEPATCH	0x00100000
+#define SHN_LIVEPATCH		0xff20
+
+/*
+ * __klp_objects and __klp_funcs are created by klp diff and used by the patch
+ * module init code to build the klp_patch, klp_object and klp_func structs
+ * needed by the livepatch API.
+ */
+#define KLP_OBJECTS_SEC	"__klp_objects"
+#define KLP_FUNCS_SEC	"__klp_funcs"
+
+/*
+ * __klp_relocs is an intermediate section which are created by klp diff and
+ * converted into KLP symbols/relas by "objtool klp post-link".  This is needed
+ * to work around the linker, which doesn't preserve SHN_LIVEPATCH or
+ * SHF_RELA_LIVEPATCH, nor does it support having two RELA sections for a
+ * single PROGBITS section.
+ */
+#define KLP_RELOCS_SEC	"__klp_relocs"
+#define KLP_STRINGS_SEC	".rodata.klp.str1.1"
+
+struct klp_reloc {
+	void *offset;
+	void *sym;
+	u32 type;
+};
+
+int cmd_klp_diff(int argc, const char **argv);
+int cmd_klp_post_link(int argc, const char **argv);
+
+#endif /* _OBJTOOL_KLP_H */

tools/objtool/include/objtool/objtool.h

···
 	struct list_head mcount_loc_list;
 	struct list_head endbr_list;
 	struct list_head call_list;
-	bool ignore_unreachables, hints, rodata;
+	bool ignore_unreachables, hints, rodata, klp;
 
 	unsigned int nr_endbr;
 	unsigned int nr_endbr_int;
···
 
 	struct pv_state *pv_ops;
 };
+
+char *top_level_dir(const char *file);
 
 struct objtool_file *objtool_open_read(const char *_objname);
 

tools/objtool/include/objtool/util.h

···
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+#ifndef _UTIL_H
+#define _UTIL_H
+
+#include <objtool/warn.h>
+
+#define snprintf_check(str, size, format, args...)			\
+({									\
+	int __ret = snprintf(str, size, format, args);			\
+	if (__ret < 0)							\
+		ERROR_GLIBC("snprintf");				\
+	else if (__ret >= size)						\
+		ERROR("snprintf() failed for '" format "'", args);	\
+	else								\
+		__ret = 0;						\
+	__ret;								\
+})
+
+#endif /* _UTIL_H */

tools/objtool/include/objtool/warn.h

···
 #define ERROR_FUNC(sec, offset, format, ...) __WARN_FUNC(ERROR_STR, sec, offset, format, ##__VA_ARGS__)
 #define ERROR_INSN(insn, format, ...) WARN_FUNC(insn->sec, insn->offset, format, ##__VA_ARGS__)
 
+extern bool debug;
+extern int indent;
+
+static inline void unindent(int *unused) { indent--; }
+
+#define __dbg(format, ...)						\
+	fprintf(stderr,							\
+		"DEBUG: %s%s" format "\n",				\
+		objname ?: "",						\
+		objname ? ": " : "",					\
+		##__VA_ARGS__)
+
+#define dbg(args...)							\
+({									\
+	if (unlikely(debug))						\
+		__dbg(args);						\
+})
+
+#define __dbg_indent(format, ...)					\
+({									\
+	if (unlikely(debug))						\
+		__dbg("%*s" format, indent * 8, "", ##__VA_ARGS__);	\
+})
+
+#define dbg_indent(args...)						\
+	int __attribute__((cleanup(unindent))) __dummy_##__COUNTER__;	\
+	__dbg_indent(args);						\
+	indent++
+
+#define dbg_checksum(func, insn, checksum)				\
+({									\
+	if (unlikely(insn->sym && insn->sym->pfunc &&			\
+		     insn->sym->pfunc->debug_checksum)) {		\
+		char *insn_off = offstr(insn->sec, insn->offset);	\
+		__dbg("checksum: %s %s %016lx",				\
+		      func->name, insn_off, checksum);			\
+		free(insn_off);						\
+	}								\
+})
+
 #endif /* _WARN_H */

tools/objtool/klp-diff.c

···
+// SPDX-License-Identifier: GPL-2.0-or-later
+#define _GNU_SOURCE /* memmem() */
+#include <subcmd/parse-options.h>
+#include <stdlib.h>
+#include <string.h>
+#include <libgen.h>
+#include <stdio.h>
+#include <ctype.h>
+
+#include <objtool/objtool.h>
+#include <objtool/warn.h>
+#include <objtool/arch.h>
+#include <objtool/klp.h>
+#include <objtool/util.h>
+#include <arch/special.h>
+
+#include <linux/objtool_types.h>
+#include <linux/livepatch_external.h>
+#include <linux/stringify.h>
+#include <linux/string.h>
+#include <linux/jhash.h>
+
+#define sizeof_field(TYPE, MEMBER) sizeof((((TYPE *)0)->MEMBER))
+
+struct elfs {
+	struct elf *orig, *patched, *out;
+	const char *modname;
+};
+
+struct export {
+	struct hlist_node hash;
+	char *mod, *sym;
+};
+
+static const char * const klp_diff_usage[] = {
+	"objtool klp diff [<options>] <in1.o> <in2.o> <out.o>",
+	NULL,
+};
+
+static const struct option klp_diff_options[] = {
+	OPT_GROUP("Options:"),
+	OPT_BOOLEAN('d', "debug", &debug, "enable debug output"),
+	OPT_END(),
+};
+
+static DEFINE_HASHTABLE(exports, 15);
+
+static inline u32 str_hash(const char *str)
+{
+	return jhash(str, strlen(str), 0);
+}
+
+static char *escape_str(const char *orig)
+{
+	size_t len = 0;
+	const char *a;
+	char *b, *new;
+
+	for (a = orig; *a; a++) {
+		switch (*a) {
+		case '\001': len += 5; break;
+		case '\n':
+		case '\t':   len += 2; break;
+		default: len++;
+		}
+	}
+
+	new = malloc(len + 1);
+	if (!new)
+		return NULL;
+
+	for (a = orig, b = new; *a; a++) {
+		switch (*a) {
+		case '\001': memcpy(b, "<SOH>", 5); b += 5; break;
+		case '\n': *b++ = '\\'; *b++ = 'n'; break;
+		case '\t': *b++ = '\\'; *b++ = 't'; break;
+		default:   *b++ = *a;
+		}
+	}
+
+	*b = '\0';
+	return new;
+}
+
+static int read_exports(void)
+{
+	const char *symvers = "Module.symvers";
+	char line[1024], *path = NULL;
+	unsigned int line_num = 1;
+	FILE *file;
+
+	file = fopen(symvers, "r");
+	if (!file) {
+		path = top_level_dir(symvers);
+		if (!path) {
+			ERROR("can't open '%s', \"objtool diff\" should be run from the kernel tree", symvers);
+			return -1;
+		}
+
+		file = fopen(path, "r");
+		if (!file) {
+			ERROR_GLIBC("fopen");
+			return -1;
+		}
+	}
+
+	while (fgets(line, 1024, file)) {
+		char *sym, *mod, *type;
+		struct export *export;
+
+		sym = strchr(line, '\t');
+		if (!sym) {
+			ERROR("malformed Module.symvers (sym) at line %d", line_num);
+			return -1;
+		}
+
+		*sym++ = '\0';
+
+		mod = strchr(sym, '\t');
+		if (!mod) {
+			ERROR("malformed Module.symvers (mod) at line %d", line_num);
+			return -1;
+		}
+
+		*mod++ = '\0';
+
+		type = strchr(mod, '\t');
+		if (!type) {
+			ERROR("malformed Module.symvers (type) at line %d", line_num);
+			return -1;
+		}
+
+		*type++ = '\0';
+
+		if (*sym == '\0' || *mod == '\0') {
+			ERROR("malformed Module.symvers at line %d", line_num);
+			return -1;
+		}
+
+		export = calloc(1, sizeof(*export));
+		if (!export) {
+			ERROR_GLIBC("calloc");
+			return -1;
+		}
+
+		export->mod = strdup(mod);
+		if (!export->mod) {
+			ERROR_GLIBC("strdup");
+			return -1;
+		}
+
+		export->sym = strdup(sym);
+		if (!export->sym) {
+			ERROR_GLIBC("strdup");
+			return -1;
+		}
+
+		hash_add(exports, &export->hash, str_hash(sym));
+	}
+
+	free(path);
+	fclose(file);
+
+	return 0;
+}
+
+static int read_sym_checksums(struct elf *elf)
+{
+	struct section *sec;
+
+	sec = find_section_by_name(elf, ".discard.sym_checksum");
+	if (!sec) {
+		ERROR("'%s' missing .discard.sym_checksum section, file not processed by 'objtool --checksum'?",
+		      elf->name);
+		return -1;
+	}
+
+	if (!sec->rsec) {
+		ERROR("missing reloc section for .discard.sym_checksum");
+		return -1;
+	}
+
+	if (sec_size(sec) % sizeof(struct sym_checksum)) {
+		ERROR("struct sym_checksum size mismatch");
+		return -1;
+	}
+
+	for (int i = 0; i < sec_size(sec) / sizeof(struct sym_checksum); i++) {
+		struct sym_checksum *sym_checksum;
+		struct reloc *reloc;
+		struct symbol *sym;
+
+		sym_checksum = (struct sym_checksum *)sec->data->d_buf + i;
+
+		reloc = find_reloc_by_dest(elf, sec, i * sizeof(*sym_checksum));
+		if (!reloc) {
+			ERROR("can't find reloc for sym_checksum[%d]", i);
+			return -1;
+		}
+
+		sym = reloc->sym;
+
+		if (is_sec_sym(sym)) {
+			ERROR("not sure how to handle section %s", sym->name);
+			return -1;
+		}
+
+		if (is_func_sym(sym))
+			sym->csum.checksum = sym_checksum->checksum;
+	}
+
+	return 0;
+}
+
+static struct symbol *first_file_symbol(struct elf *elf)
+{
+	struct symbol *sym;
+
+	for_each_sym(elf, sym) {
+		if (is_file_sym(sym))
+			return sym;
+	}
+
+	return NULL;
+}
+
+static struct symbol *next_file_symbol(struct elf *elf, struct symbol *sym)
+{
+	for_each_sym_continue(elf, sym) {
+		if (is_file_sym(sym))
+			return sym;
+	}
+
+	return NULL;
+}
+
+/*
+ * Certain static local variables should never be correlated.  They will be
+ * used in place rather than referencing the originals.
+ */
+static bool is_uncorrelated_static_local(struct symbol *sym)
+{
+	static const char * const vars[] = {
+		"__already_done.",
+		"__func__.",
+		"__key.",
+		"__warned.",
+		"_entry.",
+		"_entry_ptr.",
+		"_rs.",
+		"descriptor.",
+		"CSWTCH.",
+	};
+
+	if (!is_object_sym(sym) || !is_local_sym(sym))
+		return false;
+
+	if (!strcmp(sym->sec->name, ".data.once"))
+		return true;
+
+	for (int i = 0; i < ARRAY_SIZE(vars); i++) {
+		if (strstarts(sym->name, vars[i]))
+			return true;
+	}
+
+	return false;
+}
+
+/*
+ * Clang emits several useless .Ltmp_* code labels.
+ */
+static bool is_clang_tmp_label(struct symbol *sym)
+{
+	return sym->type == STT_NOTYPE &&
+	       is_text_sec(sym->sec) &&
+	       strstarts(sym->name, ".Ltmp") &&
+	       isdigit(sym->name[5]);
+}
+
+static bool is_special_section(struct section *sec)
+{
+	static const char * const specials[] = {
+		".altinstructions",
+		".smp_locks",
+		"__bug_table",
+		"__ex_table",
+		"__jump_table",
+		"__mcount_loc",
+
+		/*
+		 * Extract .static_call_sites here to inherit non-module
+		 * preferential treatment.  The later static call processing
+		 * during klp module build will be skipped when it sees this
+		 * section already exists.
+		 */
+		".static_call_sites",
+	};
+
+	static const char * const non_special_discards[] = {
+		".discard.addressable",
+		".discard.sym_checksum",
+	};
+
+	if (is_text_sec(sec))
+		return false;
+
+	for (int i = 0; i < ARRAY_SIZE(specials); i++) {
+		if (!strcmp(sec->name, specials[i]))
+			return true;
+	}
+
+	/* Most .discard data sections are special */
+	for (int i = 0; i < ARRAY_SIZE(non_special_discards); i++) {
+		if (!strcmp(sec->name, non_special_discards[i]))
+			return false;
+	}
+
+	return strstarts(sec->name, ".discard.");
+}
+
+/*
+ * These sections are referenced by special sections but aren't considered
+ * special sections themselves.
+ */
+static bool is_special_section_aux(struct section *sec)
+{
+	static const char * const specials_aux[] = {
+		".altinstr_replacement",
+		".altinstr_aux",
+	};
+
+	for (int i = 0; i < ARRAY_SIZE(specials_aux); i++) {
+		if (!strcmp(sec->name, specials_aux[i]))
+			return true;
+	}
+
+	return false;
+}
+
+/*
+ * These symbols should never be correlated, so their local patched versions
+ * are used instead of linking to the originals.
+ */
+static bool dont_correlate(struct symbol *sym)
+{
+	return is_file_sym(sym) ||
+	       is_null_sym(sym) ||
+	       is_sec_sym(sym) ||
+	       is_prefix_func(sym) ||
+	       is_uncorrelated_static_local(sym) ||
+	       is_clang_tmp_label(sym) ||
+	       is_string_sec(sym->sec) ||
+	       is_special_section(sym->sec) ||
+	       is_special_section_aux(sym->sec) ||
+	       strstarts(sym->name, "__initcall__");
+}
+
+/*
+ * For each symbol in the original kernel, find its corresponding "twin" in the
+ * patched kernel.
+ */
+static int correlate_symbols(struct elfs *e)
+{
+	struct symbol *file1_sym, *file2_sym;
+	struct symbol *sym1, *sym2;
+
+	/* Correlate locals */
+	for (file1_sym = first_file_symbol(e->orig),
+	     file2_sym = first_file_symbol(e->patched); ;
+	     file1_sym = next_file_symbol(e->orig, file1_sym),
+	     file2_sym = next_file_symbol(e->patched, file2_sym)) {
+
+		if (!file1_sym && file2_sym) {
+			ERROR("FILE symbol mismatch: NULL != %s", file2_sym->name);
+			return -1;
+		}
+
+		if (file1_sym && !file2_sym) {
+			ERROR("FILE symbol mismatch: %s != NULL", file1_sym->name);
+			return -1;
+		}
+
+		if (!file1_sym)
+			break;
+
+		if (strcmp(file1_sym->name, file2_sym->name)) {
+			ERROR("FILE symbol mismatch: %s != %s", file1_sym->name, file2_sym->name);
+			return -1;
+		}
+
+		file1_sym->twin = file2_sym;
+		file2_sym->twin = file1_sym;
+
+		sym1 = file1_sym;
+
+		for_each_sym_continue(e->orig, sym1) {
+			if (is_file_sym(sym1) || !is_local_sym(sym1))
+				break;
+
+			if (dont_correlate(sym1))
+				continue;
+
+			sym2 = file2_sym;
+			for_each_sym_continue(e->patched, sym2) {
+				if (is_file_sym(sym2) || !is_local_sym(sym2))
+					break;
+
+				if (sym2->twin || dont_correlate(sym2))
+					continue;
+
+				if (strcmp(sym1->demangled_name, sym2->demangled_name))
+					continue;
+
+				sym1->twin = sym2;
+				sym2->twin = sym1;
+				break;
+			}
+		}
+	}
+
+	/* Correlate globals */
+	for_each_sym(e->orig, sym1) {
+		if (sym1->bind == STB_LOCAL)
+			continue;
+
+		sym2 = find_global_symbol_by_name(e->patched, sym1->name);
+
+		if (sym2 && !sym2->twin && !strcmp(sym1->name, sym2->name)) {
+			sym1->twin = sym2;
+			sym2->twin = sym1;
+		}
+	}
+
+	for_each_sym(e->orig, sym1) {
+		if (sym1->twin || dont_correlate(sym1))
+			continue;
+		WARN("no correlation: %s", sym1->name);
+	}
+
+	return 0;
+}
+
+/* "sympos" is used by livepatch to disambiguate duplicate symbol names */
+static unsigned long find_sympos(struct elf *elf, struct symbol *sym)
+{
+	bool vmlinux = str_ends_with(objname, "vmlinux.o");
+	unsigned long sympos = 0, nr_matches = 0;
+	bool has_dup = false;
+	struct symbol *s;
+
+	if (sym->bind != STB_LOCAL)
+		return 0;
+
+	if (vmlinux && sym->type == STT_FUNC) {
+		/*
+		 * HACK: Unfortunately, symbol ordering can differ between
+		 * vmlinux.o and vmlinux due to the linker script emitting
+		 * .text.unlikely* before .text*.  Count .text.unlikely* first.
+		 *
+		 * TODO: Disambiguate symbols more reliably (checksums?)
+		 */
+		for_each_sym(elf, s) {
+			if (strstarts(s->sec->name, ".text.unlikely") &&
+			    !strcmp(s->name, sym->name)) {
+				nr_matches++;
+				if (s == sym)
+					sympos = nr_matches;
+				else
+					has_dup = true;
+			}
+		}
+		for_each_sym(elf, s) {
+			if (!strstarts(s->sec->name, ".text.unlikely") &&
+			    !strcmp(s->name, sym->name)) {
+				nr_matches++;
+				if (s == sym)
+					sympos = nr_matches;
+				else
+					has_dup = true;
+			}
+		}
+	} else {
+		for_each_sym(elf, s) {
+			if (!strcmp(s->name, sym->name)) {
+				nr_matches++;
+				if (s == sym)
+					sympos = nr_matches;
+				else
+					has_dup = true;
+			}
+		}
+	}
+
+	if (!sympos) {
+		ERROR("can't find sympos for %s", sym->name);
+		return ULONG_MAX;
+	}
+
+	return has_dup ? sympos : 0;
+}
+
+static int clone_sym_relocs(struct elfs *e, struct symbol *patched_sym);
+
+static struct symbol *__clone_symbol(struct elf *elf, struct symbol *patched_sym,
+				     bool data_too)
+{
+	struct section *out_sec = NULL;
+	unsigned long offset = 0;
+	struct symbol *out_sym;
+
+	if (data_too && !is_undef_sym(patched_sym)) {
+		struct section *patched_sec = patched_sym->sec;
+
+		out_sec = find_section_by_name(elf, patched_sec->name);
+		if (!out_sec) {
+			out_sec = elf_create_section(elf, patched_sec->name, 0,
+						     patched_sec->sh.sh_entsize,
+						     patched_sec->sh.sh_type,
+						     patched_sec->sh.sh_addralign,
+						     patched_sec->sh.sh_flags);
+			if (!out_sec)
+				return NULL;
+		}
+
+		if (is_string_sec(patched_sym->sec)) {
+			out_sym = elf_create_section_symbol(elf, out_sec);
+			if (!out_sym)
+				return NULL;
+
+			goto sym_created;
+		}
+
+		if (!is_sec_sym(patched_sym))
+			offset = sec_size(out_sec);
+
+		if (patched_sym->len || is_sec_sym(patched_sym)) {
+			void *data = NULL;
+			size_t size;
+
+			/* bss doesn't have data */
+			if (patched_sym->sec->data->d_buf)
+				data = patched_sym->sec->data->d_buf + patched_sym->offset;
+
+			if (is_sec_sym(patched_sym))
+				size = sec_size(patched_sym->sec);
+			else
+				size = patched_sym->len;
+
+			if (!elf_add_data(elf, out_sec, data, size))
+				return NULL;
+		}
+	}
+
+	out_sym = elf_create_symbol(elf, patched_sym->name, out_sec,
+				    patched_sym->bind, patched_sym->type,
+				    offset, patched_sym->len);
+	if (!out_sym)
+		return NULL;
+
+sym_created:
+	patched_sym->clone = out_sym;
+	out_sym->clone = patched_sym;
+
+	return out_sym;
+}
+
+static const char *sym_type(struct symbol *sym)
+{
+	switch (sym->type) {
+	case STT_NOTYPE:  return "NOTYPE";
+	case STT_OBJECT:  return "OBJECT";
+	case STT_FUNC:    return "FUNC";
+	case STT_SECTION: return "SECTION";
+	case STT_FILE:    return "FILE";
+	default:	  return "UNKNOWN";
+	}
+}
+
+static const char *sym_bind(struct symbol *sym)
+{
+	switch (sym->bind) {
+	case STB_LOCAL:   return "LOCAL";
+	case STB_GLOBAL:  return "GLOBAL";
+	case STB_WEAK:    return "WEAK";
+	default:	  return "UNKNOWN";
+	}
+}
+
+/*
+ * Copy a symbol to the output object, optionally including its data and
+ * relocations.
+ */
+static struct symbol *clone_symbol(struct elfs *e, struct symbol *patched_sym,
+				   bool data_too)
+{
+	struct symbol *pfx;
+
+	if (patched_sym->clone)
+		return patched_sym->clone;
+
+	dbg_indent("%s%s", patched_sym->name, data_too ? " [+DATA]" : "");
+
+	/* Make sure the prefix gets cloned first */
+	if (is_func_sym(patched_sym) && data_too) {
+		pfx = get_func_prefix(patched_sym);
+		if (pfx)
+			clone_symbol(e, pfx, true);
+	}
+
+	if (!__clone_symbol(e->out, patched_sym, data_too))
+		return NULL;
+
+	if (data_too && clone_sym_relocs(e, patched_sym))
+		return NULL;
+
+	return patched_sym->clone;
+}
+
+static void mark_included_function(struct symbol *func)
+{
+	struct symbol *pfx;
+
+	func->included = 1;
+
+	/* Include prefix function */
+	pfx = get_func_prefix(func);
+	if (pfx)
+		pfx->included = 1;
+
+	/* Make sure .cold parent+child always stay together */
+	if (func->cfunc && func->cfunc != func)
+		func->cfunc->included = 1;
+	if (func->pfunc && func->pfunc != func)
+		func->pfunc->included = 1;
+}
+
+/*
+ * Copy all changed functions (and their dependencies) from the patched object
+ * to the output object.
+ */
+static int mark_changed_functions(struct elfs *e)
+{
+	struct symbol *sym_orig, *patched_sym;
+	bool changed = false;
+
+	/* Find changed functions */
+	for_each_sym(e->orig, sym_orig) {
+		if (!is_func_sym(sym_orig) || is_prefix_func(sym_orig))
+			continue;
+
+		patched_sym = sym_orig->twin;
+		if (!patched_sym)
+			continue;
+
+		if (sym_orig->csum.checksum != patched_sym->csum.checksum) {
+			patched_sym->changed = 1;
+			mark_included_function(patched_sym);
+			changed = true;
+		}
+	}
+
+	/* Find added functions and print them */
+	for_each_sym(e->patched, patched_sym) {
+		if (!is_func_sym(patched_sym) || is_prefix_func(patched_sym))
+			continue;
+
+		if (!patched_sym->twin) {
+			printf("%s: new function: %s\n", objname, patched_sym->name);
+			mark_included_function(patched_sym);
+			changed = true;
+		}
+	}
+
+	/* Print changed functions */
+	for_each_sym(e->patched, patched_sym) {
+		if (patched_sym->changed)
+			printf("%s: changed function: %s\n", objname, patched_sym->name);
+	}
+
+	return !changed ? -1 : 0;
+}
+
+static int clone_included_functions(struct elfs *e)
+{
+	struct symbol *patched_sym;
+
+	for_each_sym(e->patched, patched_sym) {
+		if (patched_sym->included) {
+			if (!clone_symbol(e, patched_sym, true))
+				return -1;
+		}
+	}
+
+	return 0;
+}
+
+/*
+ * Determine whether a relocation should reference the section rather than the
+ * underlying symbol.
+ */
+static bool section_reference_needed(struct section *sec)
+{
+	/*
+	 * String symbols are zero-length and uncorrelated.  It's easier to
+	 * deal with them as section symbols.
+	 */
+	if (is_string_sec(sec))
+		return true;
+
+	/*
+	 * .rodata has mostly anonymous data so there's no way to determine the
+	 * length of a needed reference.  just copy the whole section if needed.
+	 */
+	if (strstarts(sec->name, ".rodata"))
+		return true;
+
+	/* UBSAN anonymous data */
+	if (strstarts(sec->name, ".data..Lubsan") ||	/* GCC */
+	    strstarts(sec->name, ".data..L__unnamed_"))	/* Clang */
+		return true;
+
+	return false;
+}
+
+static bool is_reloc_allowed(struct reloc *reloc)
+{
+	return section_reference_needed(reloc->sym->sec) == is_sec_sym(reloc->sym);
+}
+
+static struct export *find_export(struct symbol *sym)
+{
+	struct export *export;
+
+	hash_for_each_possible(exports, export, hash, str_hash(sym->name)) {
+		if (!strcmp(export->sym, sym->name))
+			return export;
+	}
+
+	return NULL;
+}
+
+static const char *__find_modname(struct elfs *e)
+{
+	struct section *sec;
+	char *name;
+
+	sec = find_section_by_name(e->orig, ".modinfo");
+	if (!sec) {
+		ERROR("missing .modinfo section");
+		return NULL;
+	}
+
+	name = memmem(sec->data->d_buf, sec_size(sec), "\0name=", 6);
+	if (name)
+		return name + 6;
+
+	name = strdup(e->orig->name);
+	if (!name) {
+		ERROR_GLIBC("strdup");
+		return NULL;
+	}
+
+	for (char *c = name; *c; c++) {
+		if (*c == '/')
+			name = c + 1;
+		else if (*c == '-')
+			*c = '_';
+		else if (*c == '.') {
+			*c = '\0';
+			break;
+		}
+	}
+
+	return name;
+}
+
+/* Get the object's module name as defined by the kernel (and klp_object) */
+static const char *find_modname(struct elfs *e)
+{
+	const char *modname;
+
+	if (e->modname)
+		return e->modname;
+
+	modname = __find_modname(e);
+	e->modname = modname;
+	return modname;
+}
+
+/*
+ * Copying a function from its native compiled environment to a kernel module
+ * removes its natural access to local functions/variables and unexported
+ * globals.  References to such symbols need to be converted to KLP relocs so
+ * the kernel arch relocation code knows to apply them and where to find the
+ * symbols.  Particularly, duplicate static symbols need to be disambiguated.
+ */
+static bool klp_reloc_needed(struct reloc *patched_reloc)
+{
+	struct symbol *patched_sym = patched_reloc->sym;
+	struct export *export;
+
+	/* no external symbol to reference */
+	if (dont_correlate(patched_sym))
+		return false;
+
+	/* For included functions, a regular reloc will do. */
+	if (patched_sym->included)
+		return false;
+
+	/*
+	 * If exported by a module, it has to be a klp reloc.  Thanks to the
+	 * clusterfunk that is late module patching, the patch module is
+	 * allowed to be loaded before any modules it depends on.
+	 *
+	 * If exported by vmlinux, a normal reloc will do.
+	 */
+	export = find_export(patched_sym);
+	if (export)
+		return strcmp(export->mod, "vmlinux");
+
+	if (!patched_sym->twin) {
+		/*
+		 * Presumably the symbol and its reference were added by the
+		 * patch.  The symbol could be defined in this .o or in another
+		 * .o in the patch module.
+		 *
+		 * This check needs to be *after* the export check due to the
+		 * possibility of the patch adding a new UNDEF reference to an
+		 * exported symbol.
+		 */
+		return false;
+	}
+
+	/* Unexported symbol which lives in the original vmlinux or module. */
+	return true;
+}
+
+static int convert_reloc_sym_to_secsym(struct elf *elf, struct reloc *reloc)
+{
+	struct symbol *sym = reloc->sym;
+	struct section *sec = sym->sec;
+
+	if (!sec->sym && !elf_create_section_symbol(elf, sec))
+		return -1;
+
+	reloc->sym = sec->sym;
+	set_reloc_sym(elf, reloc, sym->idx);
+	set_reloc_addend(elf, reloc, sym->offset + reloc_addend(reloc));
+	return 0;
+}
+
+static int convert_reloc_secsym_to_sym(struct elf *elf, struct reloc *reloc)
+{
+	struct symbol *sym = reloc->sym;
+	struct section *sec = sym->sec;
+
+	/* If the symbol has a dedicated section, it's easy to find */
+	sym = find_symbol_by_offset(sec, 0);
+	if (sym && sym->len == sec_size(sec))
+		goto found_sym;
+
+	/* No dedicated section; find the symbol manually */
+	sym = find_symbol_containing(sec, arch_adjusted_addend(reloc));
+	if (!sym) {
+		/*
+		 * This can happen for special section references to weak code
+		 * whose symbol has been stripped by the linker.
+		 */
+		return -1;
+	}
+
+found_sym:
+	reloc->sym = sym;
+	set_reloc_sym(elf, reloc, sym->idx);
+	set_reloc_addend(elf, reloc, reloc_addend(reloc) - sym->offset);
+	return 0;
+}
+
+/*
+ * Convert a relocation symbol reference to the needed format: either a section
+ * symbol or the underlying symbol itself.
+ */
+static int convert_reloc_sym(struct elf *elf, struct reloc *reloc)
+{
+	if (is_reloc_allowed(reloc))
+		return 0;
+
+	if (section_reference_needed(reloc->sym->sec))
+		return convert_reloc_sym_to_secsym(elf, reloc);
+	else
+		return convert_reloc_secsym_to_sym(elf, reloc);
+}
+
+/*
+ * Convert a regular relocation to a klp relocation (sort of).
+ */
+static int clone_reloc_klp(struct elfs *e, struct reloc *patched_reloc,
+			   struct section *sec, unsigned long offset,
+			   struct export *export)
+{
+	struct symbol *patched_sym = patched_reloc->sym;
+	s64 addend = reloc_addend(patched_reloc);
+	const char *sym_modname, *sym_orig_name;
+	static struct section *klp_relocs;
+	struct symbol *sym, *klp_sym;
+	unsigned long klp_reloc_off;
+	char sym_name[SYM_NAME_LEN];
+	struct klp_reloc klp_reloc;
+	unsigned long sympos;
+
+	if (!patched_sym->twin) {
+		ERROR("unexpected klp reloc for new symbol %s", patched_sym->name);
+		return -1;
+	}
+
+	/*
+	 * Keep the original reloc intact for now to avoid breaking objtool run
+	 * which relies on proper relocations for many of its features.  This
+	 * will be disabled later by "objtool klp post-link".
+	 *
+	 * Convert it to UNDEF (and WEAK to avoid modpost warnings).
+	 */
+
+	sym = patched_sym->clone;
+	if (!sym) {
+		/* STB_WEAK: avoid modpost undefined symbol warnings */
+		sym = elf_create_symbol(e->out, patched_sym->name, NULL,
+					STB_WEAK, patched_sym->type, 0, 0);
+		if (!sym)
+			return -1;
+
+		patched_sym->clone = sym;
+		sym->clone = patched_sym;
+	}
+
+	if (!elf_create_reloc(e->out, sec, offset, sym, addend, reloc_type(patched_reloc)))
+		return -1;
+
+	/*
+	 * Create the KLP symbol.
+	 */
+
+	if (export) {
+		sym_modname = export->mod;
+		sym_orig_name = export->sym;
+		sympos = 0;
+	} else {
+		sym_modname = find_modname(e);
+		if (!sym_modname)
+			return -1;
+
+		sym_orig_name = patched_sym->twin->name;
+		sympos = find_sympos(e->orig, patched_sym->twin);
+		if (sympos == ULONG_MAX)
+			return -1;
+	}
+
+	/* symbol format: .klp.sym.modname.sym_name,sympos */
+	if (snprintf_check(sym_name, SYM_NAME_LEN, KLP_SYM_PREFIX "%s.%s,%ld",
+		      sym_modname, sym_orig_name, sympos))
+		return -1;
+
+	klp_sym = find_symbol_by_name(e->out, sym_name);
+	if (!klp_sym) {
+		__dbg_indent("%s", sym_name);
+
+		/* STB_WEAK: avoid modpost undefined symbol warnings */
+		klp_sym = elf_create_symbol(e->out, sym_name, NULL,
+					    STB_WEAK, patched_sym->type, 0, 0);
+		if (!klp_sym)
+			return -1;
+	}
+
+	/*
+	 * Create the __klp_relocs entry.  This will be converted to an actual
+	 * KLP rela by "objtool klp post-link".
+	 *
+	 * This intermediate step is necessary to prevent corruption by the
+	 * linker, which doesn't know how to properly handle two rela sections
+	 * applying to the same base section.
+	 */
+
+	if (!klp_relocs) {
+		klp_relocs = elf_create_section(e->out, KLP_RELOCS_SEC, 0,
+						0, SHT_PROGBITS, 8, SHF_ALLOC);
+		if (!klp_relocs)
+			return -1;
+	}
+
+	klp_reloc_off = sec_size(klp_relocs);
+	memset(&klp_reloc, 0, sizeof(klp_reloc));
+
+	klp_reloc.type = reloc_type(patched_reloc);
+	if (!elf_add_data(e->out, klp_relocs, &klp_reloc, sizeof(klp_reloc)))
+		return -1;
+
+	/* klp_reloc.offset */
+	if (!sec->sym && !elf_create_section_symbol(e->out, sec))
+		return -1;
+
+	if (!elf_create_reloc(e->out, klp_relocs,
+			      klp_reloc_off + offsetof(struct klp_reloc, offset),
+			      sec->sym, offset, R_ABS64))
+		return -1;
+
+	/* klp_reloc.sym */
+	if (!elf_create_reloc(e->out, klp_relocs,
+			      klp_reloc_off + offsetof(struct klp_reloc, sym),
+			      klp_sym, addend, R_ABS64))
+		return -1;
+
+	return 0;
+}
+
+#define dbg_clone_reloc(sec, offset, patched_sym, addend, export, klp)			\
+	dbg_indent("%s+0x%lx: %s%s0x%lx [%s%s%s%s%s%s]",				\
+		   sec->name, offset, patched_sym->name,				\
+		   addend >= 0 ? "+" : "-", labs(addend),				\
+		   sym_type(patched_sym),						\
+		   patched_sym->type == STT_SECTION ? "" : " ",				\
+		   patched_sym->type == STT_SECTION ? "" : sym_bind(patched_sym),	\
+		   is_undef_sym(patched_sym) ? " UNDEF" : "",				\
+		   export ? " EXPORTED" : "",						\
+		   klp ? " KLP" : "")
+
+/* Copy a reloc and its symbol to the output object */
+static int clone_reloc(struct elfs *e, struct reloc *patched_reloc,
+			struct section *sec, unsigned long offset)
+{
+	struct symbol *patched_sym = patched_reloc->sym;
+	struct export *export = find_export(patched_sym);
+	long addend = reloc_addend(patched_reloc);
+	struct symbol *out_sym;
+	bool klp;
+
+	if (!is_reloc_allowed(patched_reloc)) {
+		ERROR_FUNC(patched_reloc->sec->base, reloc_offset(patched_reloc),
+			   "missing symbol for reference to %s+%ld",
+			   patched_sym->name, addend);
+		return -1;
+	}
+
+	klp = klp_reloc_needed(patched_reloc);
+
+	dbg_clone_reloc(sec, offset, patched_sym, addend, export, klp);
+
+	if (klp) {
+		if (clone_reloc_klp(e, patched_reloc, sec, offset, export))
+			return -1;
+
+		return 0;
+	}
+
+	/*
+	 * Why !export sets 'data_too':
+	 *
+	 * Unexported non-klp symbols need to live in the patch module,
+	 * otherwise there will be unresolved symbols.  Notably, this includes:
+	 *
+	 *   - New functions/data
+	 *   - String sections
+	 *   - Special section entries
+	 *   - Uncorrelated static local variables
+	 *   - UBSAN sections
+	 */
+	out_sym = clone_symbol(e, patched_sym, patched_sym->included || !export);
+	if (!out_sym)
+		return -1;
+
+	/*
+	 * For strings, all references use section symbols, thanks to
+	 * section_reference_needed().  clone_symbol() has cloned an empty
+	 * version of the string section.  Now copy the string itself.
+	 */
+	if (is_string_sec(patched_sym->sec)) {
+		const char *str = patched_sym->sec->data->d_buf + addend;
+
+		__dbg_indent("\"%s\"", escape_str(str));
+
+		addend = elf_add_string(e->out, out_sym->sec, str);
+		if (addend == -1)
+			return -1;
+	}
+
+	if (!elf_create_reloc(e->out, sec, offset, out_sym, addend,
+			      reloc_type(patched_reloc)))
+		return -1;
+
+	return 0;
+}
+
+/* Copy all relocs needed for a symbol's contents */
+static int clone_sym_relocs(struct elfs *e, struct symbol *patched_sym)
+{
+	struct section *patched_rsec = patched_sym->sec->rsec;
+	struct reloc *patched_reloc;
+	unsigned long start, end;
+	struct symbol *out_sym;
+
+	out_sym = patched_sym->clone;
+	if (!out_sym) {
+		ERROR("no clone for %s", patched_sym->name);
+		return -1;
+	}
+
+	if (!patched_rsec)
+		return 0;
+
+	if (!is_sec_sym(patched_sym) && !patched_sym->len)
+		return 0;
+
+	if (is_string_sec(patched_sym->sec))
+		return 0;
+
+	if (is_sec_sym(patched_sym)) {
+		start = 0;
+		end = sec_size(patched_sym->sec);
+	} else {
+		start = patched_sym->offset;
+		end = start + patched_sym->len;
+	}
+
+	for_each_reloc(patched_rsec, patched_reloc) {
+		unsigned long offset;
+
+		if (reloc_offset(patched_reloc) < start ||
+		    reloc_offset(patched_reloc) >= end)
+			continue;
+
+		/*
+		 * Skip any reloc referencing .altinstr_aux.  Its code is
+		 * always patched by alternatives.  See ALTERNATIVE_TERNARY().
+		 */
+		if (patched_reloc->sym->sec &&
+		    !strcmp(patched_reloc->sym->sec->name, ".altinstr_aux"))
+			continue;
+
+		if (convert_reloc_sym(e->patched, patched_reloc)) {
+			ERROR_FUNC(patched_rsec->base, reloc_offset(patched_reloc),
+				   "failed to convert reloc sym '%s' to its proper format",
+				   patched_reloc->sym->name);
+			return -1;
+		}
+
+		offset = out_sym->offset + (reloc_offset(patched_reloc) - patched_sym->offset);
+
+		if (clone_reloc(e, patched_reloc, out_sym->sec, offset))
+			return -1;
+	}
+	return 0;
+
+}
+
+static int create_fake_symbol(struct elf *elf, struct section *sec,
+			      unsigned long offset, size_t size)
+{
+	char name[SYM_NAME_LEN];
+	unsigned int type;
+	static int ctr;
+	char *c;
+
+	if (snprintf_check(name, SYM_NAME_LEN, "%s_%d", sec->name, ctr++))
+		return -1;
+
+	for (c = name; *c; c++)
+		if (*c == '.')
+			*c = '_';
+
+	/*
+	 * STT_NOTYPE: Prevent objtool from validating .altinstr_replacement
+	 *	       while still allowing objdump to disassemble it.
+	 */
+	type = is_text_sec(sec) ? STT_NOTYPE : STT_OBJECT;
+	return elf_create_symbol(elf, name, sec, STB_LOCAL, type, offset, size) ? 0 : -1;
+}
+
+/*
+ * Special sections (alternatives, etc) are basically arrays of structs.
+ * For all the special sections, create a symbol for each struct entry.  This
+ * is a bit cumbersome, but it makes the extracting of the individual entries
+ * much more straightforward.
+ *
+ * There are three ways to identify the entry sizes for a special section:
+ *
+ * 1) ELF section header sh_entsize: Ideally this would be used almost
+ *    everywhere.  But unfortunately the toolchains make it difficult.  The
+ *    assembler .[push]section directive syntax only takes entsize when
+ *    combined with SHF_MERGE.  But Clang disallows combining SHF_MERGE with
+ *    SHF_WRITE.  And some special sections do need to be writable.
+ *
+ *    Another place this wouldn't work is .altinstr_replacement, whose entries
+ *    don't have a fixed size.
+ *
+ * 2) ANNOTATE_DATA_SPECIAL: This is a lightweight objtool annotation which
+ *    points to the beginning of each entry.  The size of the entry is then
+ *    inferred by the location of the subsequent annotation (or end of
+ *    section).
+ *
+ * 3) Simple array of pointers: If the special section is just a basic array of
+ *    pointers, the entry size can be inferred by the number of relocations.
+ *    No annotations needed.
+ *
+ * Note I also tried to create per-entry symbols at the time of creation, in
+ * the original [inline] asm.  Unfortunately, creating uniquely named symbols
+ * is trickier than one might think, especially with Clang inline asm.  I
+ * eventually just gave up trying to make that work, in favor of using
+ * ANNOTATE_DATA_SPECIAL and creating the symbols here after the fact.
+ */
+static int create_fake_symbols(struct elf *elf)
+{
+	struct section *sec;
+	struct reloc *reloc;
+
+	/*
+	 * 1) Make symbols for all the ANNOTATE_DATA_SPECIAL entries:
+	 */
+
+	sec = find_section_by_name(elf, ".discard.annotate_data");
+	if (!sec || !sec->rsec)
+		return 0;
+
+	for_each_reloc(sec->rsec, reloc) {
+		unsigned long offset, size;
+		struct reloc *next_reloc;
+
+		if (annotype(elf, sec, reloc) != ANNOTYPE_DATA_SPECIAL)
+			continue;
+
+		offset = reloc_addend(reloc);
+
+		size = 0;
+		next_reloc = reloc;
+		for_each_reloc_continue(sec->rsec, next_reloc) {
+			if (annotype(elf, sec, next_reloc) != ANNOTYPE_DATA_SPECIAL ||
+			    next_reloc->sym->sec != reloc->sym->sec)
+				continue;
+
+			size = reloc_addend(next_reloc) - offset;
+			break;
+		}
+
+		if (!size)
+			size = sec_size(reloc->sym->sec) - offset;
+
+		if (create_fake_symbol(elf, reloc->sym->sec, offset, size))
+			return -1;
+	}
+
+	/*
+	 * 2) Make symbols for sh_entsize, and simple arrays of pointers:
+	 */
+
+	for_each_sec(elf, sec) {
+		unsigned int entry_size;
+		unsigned long offset;
+
+		if (!is_special_section(sec) || find_symbol_by_offset(sec, 0))
+			continue;
+
+		if (!sec->rsec) {
+			ERROR("%s: missing special section relocations", sec->name);
+			return -1;
+		}
+
+		entry_size = sec->sh.sh_entsize;
+		if (!entry_size) {
+			entry_size = arch_reloc_size(sec->rsec->relocs);
+			if (sec_size(sec) != entry_size * sec_num_entries(sec->rsec)) {
+				ERROR("%s: missing special section entsize or annotations", sec->name);
+				return -1;
+			}
+		}
+
+		for (offset = 0; offset < sec_size(sec); offset += entry_size) {
+			if (create_fake_symbol(elf, sec, offset, entry_size))
+				return -1;
+		}
+	}
+
+	return 0;
+}
+
+/* Keep a special section entry if it references an included function */
+static bool should_keep_special_sym(struct elf *elf, struct symbol *sym)
+{
+	struct reloc *reloc;
+
+	if (is_sec_sym(sym) || !sym->sec->rsec)
+		return false;
+
+	sym_for_each_reloc(elf, sym, reloc) {
+		if (convert_reloc_sym(elf, reloc))
+			continue;
+
+		if (is_func_sym(reloc->sym) && reloc->sym->included)
+			return true;
+	}
+
+	return false;
+}
+
+/*
+ * Klp relocations aren't allowed for __jump_table and .static_call_sites if
+ * the referenced symbol lives in a kernel module, because such klp relocs may
+ * be applied after static branch/call init, resulting in code corruption.
+ *
+ * Validate a special section entry to avoid that.  Note that an inert
+ * tracepoint is harmless enough, in that case just skip the entry and print a
+ * warning.  Otherwise, return an error.
+ *
+ * This is only a temporary limitation which will be fixed when livepatch adds
+ * support for submodules: fully self-contained modules which are embedded in
+ * the top-level livepatch module's data and which can be loaded on demand when
+ * their corresponding to-be-patched module gets loaded.  Then klp relocs can
+ * be retired.
+ *
+ * Return:
+ *   -1: error: validation failed
+ *    1: warning: tracepoint skipped
+ *    0: success
+ */
+static int validate_special_section_klp_reloc(struct elfs *e, struct symbol *sym)
+{
+	bool static_branch = !strcmp(sym->sec->name, "__jump_table");
+	bool static_call   = !strcmp(sym->sec->name, ".static_call_sites");
+	struct symbol *code_sym = NULL;
+	unsigned long code_offset = 0;
+	struct reloc *reloc;
+	int ret = 0;
+
+	if (!static_branch && !static_call)
+		return 0;
+
+	sym_for_each_reloc(e->patched, sym, reloc) {
+		const char *sym_modname;
+		struct export *export;
+
+		/* Static branch/call keys are always STT_OBJECT */
+		if (reloc->sym->type != STT_OBJECT) {
+
+			/* Save code location which can be printed below */
+			if (reloc->sym->type == STT_FUNC && !code_sym) {
+				code_sym = reloc->sym;
+				code_offset = reloc_addend(reloc);
+			}
+
+			continue;
+		}
+
+		if (!klp_reloc_needed(reloc))
+			continue;
+
+		export = find_export(reloc->sym);
+		if (export) {
+			sym_modname = export->mod;
+		} else {
+			sym_modname = find_modname(e);
+			if (!sym_modname)
+				return -1;
+		}
+
+		/* vmlinux keys are ok */
+		if (!strcmp(sym_modname, "vmlinux"))
+			continue;
+
+		if (static_branch) {
+			if (strstarts(reloc->sym->name, "__tracepoint_")) {
+				WARN("%s: disabling unsupported tracepoint %s",
+				     code_sym->name, reloc->sym->name + 13);
+				ret = 1;
+				continue;
+			}
+
+			ERROR("%s+0x%lx: unsupported static branch key %s.  Use static_key_enabled() instead",
+			      code_sym->name, code_offset, reloc->sym->name);
+			return -1;
+		}
+
+		/* static call */
+		if (strstarts(reloc->sym->name, "__SCK__tp_func_")) {
+			ret = 1;
+			continue;
+		}
+
+		ERROR("%s()+0x%lx: unsupported static call key %s.  Use KLP_STATIC_CALL() instead",
+		      code_sym->name, code_offset, reloc->sym->name);
+		return -1;
+	}
+
+	return ret;
+}
+
+static int clone_special_section(struct elfs *e, struct section *patched_sec)
+{
+	struct symbol *patched_sym;
+
+	/*
+	 * Extract all special section symbols (and their dependencies) which
+	 * reference included functions.
+	 */
+	sec_for_each_sym(patched_sec, patched_sym) {
+		int ret;
+
+		if (!is_object_sym(patched_sym))
+			continue;
+
+		if (!should_keep_special_sym(e->patched, patched_sym))
+			continue;
+
+		ret = validate_special_section_klp_reloc(e, patched_sym);
+		if (ret < 0)
+			return -1;
+		if (ret > 0)
+			continue;
+
+		if (!clone_symbol(e, patched_sym, true))
+			return -1;
+	}
+
+	return 0;
+}
+
+/* Extract only the needed bits from special sections */
+static int clone_special_sections(struct elfs *e)
+{
+	struct section *patched_sec;
+
+	if (create_fake_symbols(e->patched))
+		return -1;
+
+	for_each_sec(e->patched, patched_sec) {
+		if (is_special_section(patched_sec)) {
+			if (clone_special_section(e, patched_sec))
+				return -1;
+		}
+	}
+
+	return 0;
+}
+
+/*
+ * Create __klp_objects and __klp_funcs sections which are intermediate
+ * sections provided as input to the patch module's init code for building the
+ * klp_patch, klp_object and klp_func structs for the livepatch API.
+ */
+static int create_klp_sections(struct elfs *e)
+{
+	size_t obj_size  = sizeof(struct klp_object_ext);
+	size_t func_size = sizeof(struct klp_func_ext);
+	struct section *obj_sec, *funcs_sec, *str_sec;
+	struct symbol *funcs_sym, *str_sym, *sym;
+	char sym_name[SYM_NAME_LEN];
+	unsigned int nr_funcs = 0;
+	const char *modname;
+	void *obj_data;
+	s64 addend;
+
+	obj_sec  = elf_create_section_pair(e->out, KLP_OBJECTS_SEC, obj_size, 0, 0);
+	if (!obj_sec)
+		return -1;
+
+	funcs_sec = elf_create_section_pair(e->out, KLP_FUNCS_SEC, func_size, 0, 0);
+	if (!funcs_sec)
+		return -1;
+
+	funcs_sym = elf_create_section_symbol(e->out, funcs_sec);
+	if (!funcs_sym)
+		return -1;
+
+	str_sec = elf_create_section(e->out, KLP_STRINGS_SEC, 0, 0,
+				     SHT_PROGBITS, 1,
+				     SHF_ALLOC | SHF_STRINGS | SHF_MERGE);
+	if (!str_sec)
+		return -1;
+
+	if (elf_add_string(e->out, str_sec, "") == -1)
+		return -1;
+
+	str_sym = elf_create_section_symbol(e->out, str_sec);
+	if (!str_sym)
+		return -1;
+
+	/* allocate klp_object_ext */
+	obj_data = elf_add_data(e->out, obj_sec, NULL, obj_size);
+	if (!obj_data)
+		return -1;
+
+	modname = find_modname(e);
+	if (!modname)
+		return -1;
+
+	/* klp_object_ext.name */
+	if (strcmp(modname, "vmlinux")) {
+		addend = elf_add_string(e->out, str_sec, modname);
+		if (addend == -1)
+			return -1;
+
+		if (!elf_create_reloc(e->out, obj_sec,
+				      offsetof(struct klp_object_ext, name),
+				      str_sym, addend, R_ABS64))
+			return -1;
+	}
+
+	/* klp_object_ext.funcs */
+	if (!elf_create_reloc(e->out, obj_sec, offsetof(struct klp_object_ext, funcs),
+			      funcs_sym, 0, R_ABS64))
+		return -1;
+
+	for_each_sym(e->out, sym) {
+		unsigned long offset = nr_funcs * func_size;
+		unsigned long sympos;
+		void *func_data;
+
+		if (!is_func_sym(sym) || sym->cold || !sym->clone || !sym->clone->changed)
+			continue;
+
+		/* allocate klp_func_ext */
+		func_data = elf_add_data(e->out, funcs_sec, NULL, func_size);
+		if (!func_data)
+			return -1;
+
+		/* klp_func_ext.old_name */
+		addend = elf_add_string(e->out, str_sec, sym->clone->twin->name);
+		if (addend == -1)
+			return -1;
+
+		if (!elf_create_reloc(e->out, funcs_sec,
+				      offset + offsetof(struct klp_func_ext, old_name),
+				      str_sym, addend, R_ABS64))
+			return -1;
+
+		/* klp_func_ext.new_func */
+		if (!elf_create_reloc(e->out, funcs_sec,
+				      offset + offsetof(struct klp_func_ext, new_func),
+				      sym, 0, R_ABS64))
+			return -1;
+
+		/* klp_func_ext.sympos */
+		BUILD_BUG_ON(sizeof(sympos) != sizeof_field(struct klp_func_ext, sympos));
+		sympos = find_sympos(e->orig, sym->clone->twin);
+		if (sympos == ULONG_MAX)
+			return -1;
+		memcpy(func_data + offsetof(struct klp_func_ext, sympos), &sympos,
+		       sizeof_field(struct klp_func_ext, sympos));
+
+		nr_funcs++;
+	}
+
+	/* klp_object_ext.nr_funcs */
+	BUILD_BUG_ON(sizeof(nr_funcs) != sizeof_field(struct klp_object_ext, nr_funcs));
+	memcpy(obj_data + offsetof(struct klp_object_ext, nr_funcs), &nr_funcs,
+	       sizeof_field(struct klp_object_ext, nr_funcs));
+
+	/*
+	 * Find callback pointers created by KLP_PRE_PATCH_CALLBACK() and
+	 * friends, and add them to the klp object.
+	 */
+
+	if (snprintf_check(sym_name, SYM_NAME_LEN, KLP_PRE_PATCH_PREFIX "%s", modname))
+		return -1;
+
+	sym = find_symbol_by_name(e->out, sym_name);
+	if (sym) {
+		struct reloc *reloc;
+
+		reloc = find_reloc_by_dest(e->out, sym->sec, sym->offset);
+
+		if (!elf_create_reloc(e->out, obj_sec,
+				      offsetof(struct klp_object_ext, callbacks) +
+				      offsetof(struct klp_callbacks, pre_patch),
+				      reloc->sym, reloc_addend(reloc), R_ABS64))
+			return -1;
+	}
+
+	if (snprintf_check(sym_name, SYM_NAME_LEN, KLP_POST_PATCH_PREFIX "%s", modname))
+		return -1;
+
+	sym = find_symbol_by_name(e->out, sym_name);
+	if (sym) {
+		struct reloc *reloc;
+
+		reloc = find_reloc_by_dest(e->out, sym->sec, sym->offset);
+
+		if (!elf_create_reloc(e->out, obj_sec,
+				      offsetof(struct klp_object_ext, callbacks) +
+				      offsetof(struct klp_callbacks, post_patch),
+				      reloc->sym, reloc_addend(reloc), R_ABS64))
+			return -1;
+	}
+
+	if (snprintf_check(sym_name, SYM_NAME_LEN, KLP_PRE_UNPATCH_PREFIX "%s", modname))
+		return -1;
+
+	sym = find_symbol_by_name(e->out, sym_name);
+	if (sym) {
+		struct reloc *reloc;
+
+		reloc = find_reloc_by_dest(e->out, sym->sec, sym->offset);
+
+		if (!elf_create_reloc(e->out, obj_sec,
+				      offsetof(struct klp_object_ext, callbacks) +
+				      offsetof(struct klp_callbacks, pre_unpatch),
+				      reloc->sym, reloc_addend(reloc), R_ABS64))
+			return -1;
+	}
+
+	if (snprintf_check(sym_name, SYM_NAME_LEN, KLP_POST_UNPATCH_PREFIX "%s", modname))
+		return -1;
+
+	sym = find_symbol_by_name(e->out, sym_name);
+	if (sym) {
+		struct reloc *reloc;
+
+		reloc = find_reloc_by_dest(e->out, sym->sec, sym->offset);
+
+		if (!elf_create_reloc(e->out, obj_sec,
+				      offsetof(struct klp_object_ext, callbacks) +
+				      offsetof(struct klp_callbacks, post_unpatch),
+				      reloc->sym, reloc_addend(reloc), R_ABS64))
+			return -1;
+	}
+
+	return 0;
+}
+
+/*
+ * Copy all .modinfo import_ns= tags to ensure all namespaced exported symbols
+ * can be accessed via normal relocs.
+ */
+static int copy_import_ns(struct elfs *e)
+{
+	struct section *patched_sec, *out_sec = NULL;
+	char *import_ns, *data_end;
+
+	patched_sec = find_section_by_name(e->patched, ".modinfo");
+	if (!patched_sec)
+		return 0;
+
+	import_ns = patched_sec->data->d_buf;
+	if (!import_ns)
+		return 0;
+
+	for (data_end = import_ns + sec_size(patched_sec);
+	     import_ns < data_end;
+	     import_ns += strlen(import_ns) + 1) {
+
+		import_ns = memmem(import_ns, data_end - import_ns, "import_ns=", 10);
+		if (!import_ns)
+			return 0;
+
+		if (!out_sec) {
+			out_sec = find_section_by_name(e->out, ".modinfo");
+			if (!out_sec) {
+				out_sec = elf_create_section(e->out, ".modinfo", 0,
+							     patched_sec->sh.sh_entsize,
+							     patched_sec->sh.sh_type,
+							     patched_sec->sh.sh_addralign,
+							     patched_sec->sh.sh_flags);
+				if (!out_sec)
+					return -1;
+			}
+		}
+
+		if (!elf_add_data(e->out, out_sec, import_ns, strlen(import_ns) + 1))
+			return -1;
+	}
+
+	return 0;
+}
+
+int cmd_klp_diff(int argc, const char **argv)
+{
+	struct elfs e = {0};
+
+	argc = parse_options(argc, argv, klp_diff_options, klp_diff_usage, 0);
+	if (argc != 3)
+		usage_with_options(klp_diff_usage, klp_diff_options);
+
+	objname = argv[0];
+
+	e.orig = elf_open_read(argv[0], O_RDONLY);
+	e.patched = elf_open_read(argv[1], O_RDONLY);
+	e.out = NULL;
+
+	if (!e.orig || !e.patched)
+		return -1;
+
+	if (read_exports())
+		return -1;
+
+	if (read_sym_checksums(e.orig))
+		return -1;
+
+	if (read_sym_checksums(e.patched))
+		return -1;
+
+	if (correlate_symbols(&e))
+		return -1;
+
+	if (mark_changed_functions(&e))
+		return 0;
+
+	e.out = elf_create_file(&e.orig->ehdr, argv[2]);
+	if (!e.out)
+		return -1;
+
+	if (clone_included_functions(&e))
+		return -1;
+
+	if (clone_special_sections(&e))
+		return -1;
+
+	if (create_klp_sections(&e))
+		return -1;
+
+	if (copy_import_ns(&e))
+		return -1;
+
+	if  (elf_write(e.out))
+		return -1;
+
+	return elf_close(e.out);
+}

tools/objtool/klp-post-link.c

···
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Read the intermediate KLP reloc/symbol representations created by klp diff
+ * and convert them to the proper format required by livepatch.  This needs to
+ * run last to avoid linker wreckage.  Linkers don't tend to handle the "two
+ * rela sections for a single base section" case very well, nor do they like
+ * SHN_LIVEPATCH.
+ *
+ * This is the final tool in the livepatch module generation pipeline:
+ *
+ *   kernel builds -> objtool klp diff -> module link -> objtool klp post-link
+ */
+
+#include <fcntl.h>
+#include <gelf.h>
+#include <objtool/objtool.h>
+#include <objtool/warn.h>
+#include <objtool/klp.h>
+#include <objtool/util.h>
+#include <linux/livepatch_external.h>
+
+static int fix_klp_relocs(struct elf *elf)
+{
+	struct section *symtab, *klp_relocs;
+
+	klp_relocs = find_section_by_name(elf, KLP_RELOCS_SEC);
+	if (!klp_relocs)
+		return 0;
+
+	symtab = find_section_by_name(elf, ".symtab");
+	if (!symtab) {
+		ERROR("missing .symtab");
+		return -1;
+	}
+
+	for (int i = 0; i < sec_size(klp_relocs) / sizeof(struct klp_reloc); i++) {
+		struct klp_reloc *klp_reloc;
+		unsigned long klp_reloc_off;
+		struct section *sec, *tmp, *klp_rsec;
+		unsigned long offset;
+		struct reloc *reloc;
+		char sym_modname[64];
+		char rsec_name[SEC_NAME_LEN];
+		u64 addend;
+		struct symbol *sym, *klp_sym;
+
+		klp_reloc_off = i * sizeof(*klp_reloc);
+		klp_reloc = klp_relocs->data->d_buf + klp_reloc_off;
+
+		/*
+		 * Read __klp_relocs[i]:
+		 */
+
+		/* klp_reloc.sec_offset */
+		reloc = find_reloc_by_dest(elf, klp_relocs,
+					   klp_reloc_off + offsetof(struct klp_reloc, offset));
+		if (!reloc) {
+			ERROR("malformed " KLP_RELOCS_SEC " section");
+			return -1;
+		}
+
+		sec = reloc->sym->sec;
+		offset = reloc_addend(reloc);
+
+		/* klp_reloc.sym */
+		reloc = find_reloc_by_dest(elf, klp_relocs,
+					   klp_reloc_off + offsetof(struct klp_reloc, sym));
+		if (!reloc) {
+			ERROR("malformed " KLP_RELOCS_SEC " section");
+			return -1;
+		}
+
+		klp_sym = reloc->sym;
+		addend = reloc_addend(reloc);
+
+		/* symbol format: .klp.sym.modname.sym_name,sympos */
+		if (sscanf(klp_sym->name + strlen(KLP_SYM_PREFIX), "%55[^.]", sym_modname) != 1)
+			ERROR("can't find modname in klp symbol '%s'", klp_sym->name);
+
+		/*
+		 * Create the KLP rela:
+		 */
+
+		/* section format: .klp.rela.sec_objname.section_name */
+		if (snprintf_check(rsec_name, SEC_NAME_LEN,
+				   KLP_RELOC_SEC_PREFIX "%s.%s",
+				   sym_modname, sec->name))
+			return -1;
+
+		klp_rsec = find_section_by_name(elf, rsec_name);
+		if (!klp_rsec) {
+			klp_rsec = elf_create_section(elf, rsec_name, 0,
+						      elf_rela_size(elf),
+						      SHT_RELA, elf_addr_size(elf),
+						      SHF_ALLOC | SHF_INFO_LINK | SHF_RELA_LIVEPATCH);
+			if (!klp_rsec)
+				return -1;
+
+			klp_rsec->sh.sh_link = symtab->idx;
+			klp_rsec->sh.sh_info = sec->idx;
+			klp_rsec->base = sec;
+		}
+
+		tmp = sec->rsec;
+		sec->rsec = klp_rsec;
+		if (!elf_create_reloc(elf, sec, offset, klp_sym, addend, klp_reloc->type))
+			return -1;
+		sec->rsec = tmp;
+
+		/*
+		 * Fix up the corresponding KLP symbol:
+		 */
+
+		klp_sym->sym.st_shndx = SHN_LIVEPATCH;
+		if (!gelf_update_sym(symtab->data, klp_sym->idx, &klp_sym->sym)) {
+			ERROR_ELF("gelf_update_sym");
+			return -1;
+		}
+
+		/*
+		 * Disable the original non-KLP reloc by converting it to R_*_NONE:
+		 */
+
+		reloc = find_reloc_by_dest(elf, sec, offset);
+		sym = reloc->sym;
+		sym->sym.st_shndx = SHN_LIVEPATCH;
+		set_reloc_type(elf, reloc, 0);
+		if (!gelf_update_sym(symtab->data, sym->idx, &sym->sym)) {
+			ERROR_ELF("gelf_update_sym");
+			return -1;
+		}
+	}
+
+	return 0;
+}
+
+/*
+ * This runs on the livepatch module after all other linking has been done.  It
+ * converts the intermediate __klp_relocs section into proper KLP relocs to be
+ * processed by livepatch.  This needs to run last to avoid linker wreckage.
+ * Linkers don't tend to handle the "two rela sections for a single base
+ * section" case very well, nor do they appreciate SHN_LIVEPATCH.
+ */
+int cmd_klp_post_link(int argc, const char **argv)
+{
+	struct elf *elf;
+
+	argc--;
+	argv++;
+
+	if (argc != 1) {
+		fprintf(stderr, "%d\n", argc);
+		fprintf(stderr, "usage: objtool link <file.ko>\n");
+		return -1;
+	}
+
+	elf = elf_open_read(argv[0], O_RDWR);
+	if (!elf)
+		return -1;
+
+	if (fix_klp_relocs(elf))
+		return -1;
+
+	if (elf_write(elf))
+		return -1;
+
+	return elf_close(elf);
+}

tools/objtool/objtool.c

···
 #include <objtool/objtool.h>
 #include <objtool/warn.h>
 
-bool help;
+bool debug;
+int indent;
 
 static struct objtool_file file;
 
···
 	return 0;
 }
 
+char *top_level_dir(const char *file)
+{
+	ssize_t len, self_len, file_len;
+	char self[PATH_MAX], *str;
+	int i;
+
+	len = readlink("/proc/self/exe", self, sizeof(self) - 1);
+	if (len <= 0)
+		return NULL;
+	self[len] = '\0';
+
+	for (i = 0; i < 3; i++) {
+		char *s = strrchr(self, '/');
+		if (!s)
+			return NULL;
+		*s = '\0';
+	}
+
+	self_len = strlen(self);
+	file_len = strlen(file);
+
+	str = malloc(self_len + file_len + 2);
+	if (!str)
+		return NULL;
+
+	memcpy(str, self, self_len);
+	str[self_len] = '/';
+	strcpy(str + self_len + 1, file);
+
+	return str;
+}
+
+
 int main(int argc, const char **argv)
 {
 	static const char *UNUSED = "OBJTOOL_NOT_IMPLEMENTED";
···
 	/* libsubcmd init */
 	exec_cmd_init("objtool", UNUSED, UNUSED, UNUSED);
 	pager_init(UNUSED);
+
+	if (argc > 1 && !strcmp(argv[1], "klp")) {
+		argc--;
+		argv++;
+		return cmd_klp(argc, argv);
+	}
 
 	return objtool_run(argc, argv);
 }

tools/objtool/orc_dump.c

···
 #include <objtool/objtool.h>
 #include <objtool/orc.h>
 #include <objtool/warn.h>
-#include <objtool/endianness.h>
 
 int orc_dump(const char *filename)
 {

tools/objtool/orc_gen.c

···
 #include <objtool/check.h>
 #include <objtool/orc.h>
 #include <objtool/warn.h>
-#include <objtool/endianness.h>
 
 struct orc_list_entry {
 	struct list_head list;
···
 
 	/* Build a deduplicated list of ORC entries: */
 	INIT_LIST_HEAD(&orc_list);
-	for_each_sec(file, sec) {
+	for_each_sec(file->elf, sec) {
 		struct orc_entry orc, prev_orc = {0};
 		struct instruction *insn;
 		bool empty = true;
···
 		return -1;
 	}
 	orc_sec = elf_create_section(file->elf, ".orc_unwind",
-				     sizeof(struct orc_entry), nr);
+				     nr * sizeof(struct orc_entry),
+				     sizeof(struct orc_entry),
+				     SHT_PROGBITS,
+				     1,
+				     SHF_ALLOC);
 	if (!orc_sec)
 		return -1;
 

tools/objtool/special.c

···
 #include <objtool/builtin.h>
 #include <objtool/special.h>
 #include <objtool/warn.h>
-#include <objtool/endianness.h>
 
 struct special_entry {
 	const char *sec;
···
 	struct section *sec;
 	unsigned int nr_entries;
 	struct special_alt *alt;
-	int idx, ret;
+	int idx;
 
 	INIT_LIST_HEAD(alts);
 
···
 		if (!sec)
 			continue;
 
-		if (sec->sh.sh_size % entry->size != 0) {
+		if (sec_size(sec) % entry->size != 0) {
 			ERROR("%s size not a multiple of %d", sec->name, entry->size);
 			return -1;
 		}
 
-		nr_entries = sec->sh.sh_size / entry->size;
+		nr_entries = sec_size(sec) / entry->size;
 
 		for (idx = 0; idx < nr_entries; idx++) {
 			alt = malloc(sizeof(*alt));
···
 			}
 			memset(alt, 0, sizeof(*alt));
 
-			ret = get_alt_entry(elf, entry, sec, idx, alt);
-			if (ret > 0)
-				continue;
-			if (ret < 0)
-				return ret;
+			if (get_alt_entry(elf, entry, sec, idx, alt))
+				return -1;
 
 			list_add_tail(&alt->list, alts);
 		}

tools/objtool/sync-check.sh

···
 arch/x86/include/asm/emulate_prefix.h
 arch/x86/lib/x86-opcode-map.txt
 arch/x86/tools/gen-insn-attr-x86.awk
+include/linux/interval_tree_generic.h
+include/linux/livepatch_external.h
 include/linux/static_call_types.h
 "
 

tools/objtool/weak.c

···
 #include <stdbool.h>
 #include <errno.h>
 #include <objtool/objtool.h>
+#include <objtool/arch.h>
+#include <objtool/builtin.h>
 
 #define UNSUPPORTED(name)						\
 ({									\
···
 int __weak orc_create(struct objtool_file *file)
 {
 	UNSUPPORTED("ORC");
+}
+
+int __weak cmd_klp(int argc, const char **argv)
+{
+	UNSUPPORTED("klp");
 }