Merge tag 'objtool-core-2025-03-22' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull objtool updates from Ingo Molnar:

- The biggest change is the new option to automatically fail the build
on objtool warnings: CONFIG_OBJTOOL_WERROR.

While there are no currently known unfixed false positives left, such
an expansion in the severity of objtool warnings inevitably creates a
risk of build failures, so it's disabled by default and depends on
!COMPILE_TEST, so it shouldn't be enabled on
allyesconfig/allmodconfig builds and won't be forced on people who
just accept build-time defaults in 'make oldconfig'.

While the option is strongly recommended, only people who enable it
explicitly should see it.

(Josh Poimboeuf)

- Disable branch profiling in noinstr code with a broad brush that
includes all of arch/x86/ and kernel/sched/. (Josh Poimboeuf)

- Create backup object files on objtool errors and print exact objtool
arguments to make failure analysis easier (Josh Poimboeuf)

- Improve noreturn handling (Josh Poimboeuf)

- Improve rodata handling (Tiezhu Yang)

- Support jump tables, switch tables and goto tables on LoongArch
(Tiezhu Yang)

- Misc cleanups and fixes (Josh Poimboeuf, David Engraf, Ingo Molnar)

* tag 'objtool-core-2025-03-22' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (22 commits)
tracing: Disable branch profiling in noinstr code
objtool: Use O_CREAT with explicit mode mask
objtool: Add CONFIG_OBJTOOL_WERROR
objtool: Create backup on error and print args
objtool: Change "warning:" to "error:" for --Werror
objtool: Add --Werror option
objtool: Add --output option
objtool: Upgrade "Linked object detected" warning to error
objtool: Consolidate option validation
objtool: Remove --unret dependency on --rethunk
objtool: Increase per-function WARN_FUNC() rate limit
objtool: Update documentation
objtool: Improve __noreturn annotation warning
objtool: Fix error handling inconsistencies in check()
x86/traps: Make exc_double_fault() consistently noreturn
LoongArch: Enable jump table for objtool
objtool/LoongArch: Add support for goto table
objtool/LoongArch: Add support for switch table
objtool: Handle PC relative relocation type
objtool: Handle different entry size of rodata
...

arch/loongarch/Kconfig

···
 config AS_HAS_LVZ_EXTENSION
 	def_bool $(as-instr,hvcl 0)
 
+config CC_HAS_ANNOTATE_TABLEJUMP
+	def_bool $(cc-option,-mannotate-tablejump)
+
 menu "Kernel type and options"
 
 source "kernel/Kconfig.hz"

arch/loongarch/Makefile

···
 KBUILD_CFLAGS			+= $(call cc-option,-mthin-add-sub) $(call cc-option,-Wa$(comma)-mthin-add-sub)
 
 ifdef CONFIG_OBJTOOL
-KBUILD_CFLAGS			+= -fno-jump-tables
+ifdef CONFIG_CC_HAS_ANNOTATE_TABLEJUMP
+KBUILD_CFLAGS			+= -mannotate-tablejump
+else
+KBUILD_CFLAGS			+= -fno-jump-tables # keep compatibility with older compilers
+endif
 endif
 
 KBUILD_RUSTFLAGS		+= --target=loongarch64-unknown-none-softfloat -Ccode-model=small

arch/x86/Kbuild

···
 # SPDX-License-Identifier: GPL-2.0
+
+# Branch profiling isn't noinstr-safe.  Disable it for arch/x86/*
+subdir-ccflags-$(CONFIG_TRACE_BRANCH_PROFILING) += -DDISABLE_BRANCH_PROFILING
+
 obj-$(CONFIG_ARCH_HAS_CC_PLATFORM) += coco/
 
 obj-y += entry/

arch/x86/coco/sev/core.c

···
 
 #define pr_fmt(fmt)	"SEV: " fmt
 
-#define DISABLE_BRANCH_PROFILING
-
 #include <linux/sched/debug.h>	/* For show_regs() */
 #include <linux/percpu-defs.h>
 #include <linux/cc_platform.h>

arch/x86/kernel/head64.c

···
  *  Copyright (C) 2000 Andrea Arcangeli <[e-mail]> SuSE
  */
 
-#define DISABLE_BRANCH_PROFILING
-
 /* cpu_feature_enabled() cannot be used this early */
 #define USE_EARLY_PGTABLE_L5
 

arch/x86/kernel/traps.c

···
 #endif
 
 /*
+ * Prevent the compiler and/or objtool from marking the !CONFIG_X86_ESPFIX64
+ * version of exc_double_fault() as noreturn.  Otherwise the noreturn mismatch
+ * between configs triggers objtool warnings.
+ *
+ * This is a temporary hack until we have compiler or plugin support for
+ * annotating noreturns.
+ */
+#ifdef CONFIG_X86_ESPFIX64
+#define always_true() true
+#else
+bool always_true(void);
+bool __weak always_true(void) { return true; }
+#endif
+
+/*
  * Runs on an IST stack for x86_64 and on a special task stack for x86_32.
  *
  * On x86_64, this is more or less a normal kernel entry.  Notwithstanding the
···
 
 	pr_emerg("PANIC: double fault, error_code: 0x%lx\n", error_code);
 	die("double fault", regs, error_code);
-	panic("Machine halted.");
+	if (always_true())
+		panic("Machine halted.");
 	instrumentation_end();
 }
 

arch/x86/mm/kasan_init_64.c

···
 // SPDX-License-Identifier: GPL-2.0
-#define DISABLE_BRANCH_PROFILING
 #define pr_fmt(fmt) "kasan: " fmt
 
 /* cpu_feature_enabled() cannot be used this early */

arch/x86/mm/mem_encrypt_amd.c

···
  * Author: Tom Lendacky <[e-mail]>
  */
 
-#define DISABLE_BRANCH_PROFILING
-
 #include <linux/linkage.h>
 #include <linux/init.h>
 #include <linux/mm.h>

arch/x86/mm/mem_encrypt_identity.c

···
  * Author: Tom Lendacky <[e-mail]>
  */
 
-#define DISABLE_BRANCH_PROFILING
-
 /*
  * Since we're dealing with identity mappings, physical and virtual
  * addresses are the same, so override these defines which are ultimately

drivers/acpi/Makefile

···
 
 ccflags-$(CONFIG_ACPI_DEBUG)	+= -DACPI_DEBUG_OUTPUT
 
+ifdef CONFIG_TRACE_BRANCH_PROFILING
+CFLAGS_processor_idle.o += -DDISABLE_BRANCH_PROFILING
+endif
+
 #
 # ACPI Boot-Time Table Parsing
 #

drivers/cpuidle/Makefile

···
 # Makefile for cpuidle.
 #
 
+# Branch profiling isn't noinstr-safe
+ccflags-$(CONFIG_TRACE_BRANCH_PROFILING) += -DDISABLE_BRANCH_PROFILING
+
 obj-y += cpuidle.o driver.o governor.o sysfs.o governors/
 obj-$(CONFIG_ARCH_NEEDS_CPU_IDLE_COUPLED) += coupled.o
 obj-$(CONFIG_DT_IDLE_STATES)		  += dt_idle_states.o

drivers/idle/Makefile

···
 # SPDX-License-Identifier: GPL-2.0-only
-obj-$(CONFIG_INTEL_IDLE)			+= intel_idle.o
 
+# Branch profiling isn't noinstr-safe
+ccflags-$(CONFIG_TRACE_BRANCH_PROFILING) += -DDISABLE_BRANCH_PROFILING
+
+obj-$(CONFIG_INTEL_IDLE)			+= intel_idle.o

kernel/Makefile

···
 CFLAGS_REMOVE_irq_work.o = $(CC_FLAGS_FTRACE)
 endif
 
+# Branch profiling isn't noinstr-safe
+ifdef CONFIG_TRACE_BRANCH_PROFILING
+CFLAGS_context_tracking.o += -DDISABLE_BRANCH_PROFILING
+endif
+
 # Prevents flicker of uninteresting __do_softirq()/__local_bh_disable_ip()
 # in coverage traces.
 KCOV_INSTRUMENT_softirq.o := n

kernel/entry/Makefile

···
 UBSAN_SANITIZE := n
 KCOV_INSTRUMENT := n
 
+# Branch profiling isn't noinstr-safe
+ccflags-$(CONFIG_TRACE_BRANCH_PROFILING) += -DDISABLE_BRANCH_PROFILING
+
 CFLAGS_REMOVE_common.o	 = -fstack-protector -fstack-protector-strong
 CFLAGS_common.o		+= -fno-stack-protector
 

kernel/sched/Makefile

···
 CFLAGS_core.o := $(PROFILING) -fno-omit-frame-pointer
 endif
 
+# Branch profiling isn't noinstr-safe
+ifdef CONFIG_TRACE_BRANCH_PROFILING
+CFLAGS_build_policy.o += -DDISABLE_BRANCH_PROFILING
+CFLAGS_build_utility.o += -DDISABLE_BRANCH_PROFILING
+endif
 #
 # Build efficiency:
 #

kernel/time/Makefile

···
 # SPDX-License-Identifier: GPL-2.0
+
+# Branch profiling isn't noinstr-safe
+ifdef CONFIG_TRACE_BRANCH_PROFILING
+CFLAGS_sched_clock.o += -DDISABLE_BRANCH_PROFILING
+endif
+
 obj-y += time.o timer.o hrtimer.o sleep_timeout.o
 obj-y += timekeeping.o ntp.o clocksource.o jiffies.o timer_list.o
 obj-y += timeconv.o timecounter.o alarmtimer.o

lib/Kconfig.debug

···
 config OBJTOOL
 	bool
 
+config OBJTOOL_WERROR
+	bool "Upgrade objtool warnings to errors"
+	depends on OBJTOOL && !COMPILE_TEST
+	help
+	  Fail the build on objtool warnings.
+
+	  Objtool warnings can indicate kernel instability, including boot
+	  failures.  This option is highly recommended.
+
+	  If unsure, say Y.
+
 config STACK_VALIDATION
 	bool "Compile-time stack metadata validation"
 	depends on HAVE_STACK_VALIDATION && UNWINDER_FRAME_POINTER

lib/Makefile

···
 
 ccflags-remove-$(CONFIG_FUNCTION_TRACER) += $(CC_FLAGS_FTRACE)
 
+# Branch profiling isn't noinstr-safe
+ifdef CONFIG_TRACE_BRANCH_PROFILING
+CFLAGS_smp_processor_id.o += -DDISABLE_BRANCH_PROFILING
+endif
+
 # These files are disabled because they produce lots of non-interesting and/or
 # flaky coverage that is not a function of syscall inputs. For example,
 # rbtree can be global and individual rotations don't correlate with inputs.

scripts/Makefile.lib

···
 objtool-args-$(CONFIG_HAVE_UACCESS_VALIDATION)		+= --uaccess
 objtool-args-$(CONFIG_GCOV_KERNEL)			+= --no-unreachable
 objtool-args-$(CONFIG_PREFIX_SYMBOLS)			+= --prefix=$(CONFIG_FUNCTION_PADDING_BYTES)
+objtool-args-$(CONFIG_OBJTOOL_WERROR)			+= --Werror --backtrace
 
 objtool-args = $(objtool-args-y)					\
 	$(if $(delay-objtool), --link)					\

tools/objtool/Documentation/objtool.txt

···
   sites, enabling the kernel to patch them inline, to prevent "thunk
   funneling" for both security and performance reasons
 
+- Return thunk validation -- validates return thunks are used for
+  certain CPU mitigations including Retbleed and SRSO
+
+- Return thunk annotation -- annotates all return thunk sites so kernel
+  can patch them inline, depending on enabled mitigations
+
+- Return thunk training valiation -- validate that all entry paths
+  untrain a "safe return" before the first return (or call)
+
 - Non-instrumentation validation -- validates non-instrumentable
   ("noinstr") code rules, preventing instrumentation in low-level C
   entry code
···
 
 - Function entry annotation -- annotates function entries, enabling
   kernel function tracing
+
+- Function preamble (prefix) annotation and/or symbol generation -- used
+  for FineIBT and call depth tracking
 
 - Other toolchain hacks which will go unmentioned at this time...
 
···
 
 1. Each callable function must be annotated as such with the ELF
    function type.  In asm code, this is typically done using the
-   ENTRY/ENDPROC macros.  If objtool finds a return instruction
+   SYM_FUNC_{START,END} macros.  If objtool finds a return instruction
    outside of a function, it flags an error since that usually indicates
    callable code which should be annotated accordingly.
 
    This rule is needed so that objtool can properly identify each
    callable function in order to analyze its stack metadata.
 
-2. Conversely, each section of code which is *not* callable should *not*
-   be annotated as an ELF function.  The ENDPROC macro shouldn't be used
-   in this case.
-
-   This rule is needed so that objtool can ignore non-callable code.
-   Such code doesn't have to follow any of the other rules.
+2. Conversely, each section of code which is *not* callable, or is
+   otherwise doing funny things with the stack or registers, should
+   *not* be annotated as an ELF function.  Rather, SYM_CODE_{START,END}
+   should be used along with unwind hints.
 
 3. Each callable function which calls another function must have the
    correct frame pointer logic, if required by CONFIG_FRAME_POINTER or
···
    function B, the _caller_ of function A will be skipped on the stack
    trace.
 
-4. Dynamic jumps and jumps to undefined symbols are only allowed if:
+4. Indirect jumps and jumps to undefined symbols are only allowed if:
 
    a) the jump is part of a switch statement; or
 
···
    001e    2823e:  80 ce 02                or     $0x2,%dh
    ...
 
+
 2. file.o: warning: objtool: .text+0x53: unreachable instruction
 
    Objtool couldn't find a code path to reach the instruction.
 
    If the error is for an asm file, and the instruction is inside (or
    reachable from) a callable function, the function should be annotated
-   with the ENTRY/ENDPROC macros (ENDPROC is the important one).
-   Otherwise, the code should probably be annotated with the unwind hint
-   macros in asm/unwind_hints.h so objtool and the unwinder can know the
-   stack state associated with the code.
+   with the SYM_FUNC_START and SYM_FUNC_END macros.
 
-   If you're 100% sure the code won't affect stack traces, or if you're
-   a just a bad person, you can tell objtool to ignore it.  See the
-   "Adding exceptions" section below.
+   Otherwise, SYM_CODE_START can be used.  In that case the code needs
+   to be annotated with unwind hint macros.
 
-   If it's not actually in a callable function (e.g. kernel entry code),
-   change ENDPROC to END.
+   If you're sure the code won't affect the reliability of runtime stack
+   traces and want objtool to ignore it, see "Adding exceptions" below.
 
-3. file.o: warning: objtool: foo+0x48c: bar() is missing a __noreturn annotation
 
-   The call from foo() to bar() doesn't return, but bar() is missing the
-   __noreturn annotation.  NOTE: In addition to annotating the function
-   with __noreturn, please also add it to tools/objtool/noreturns.h.
+3. file.o: warning: objtool: foo+0x48c: bar() missing __noreturn in .c/.h or NORETURN() in noreturns.h
+
+   The call from foo() to bar() doesn't return, but bar() is incorrectly
+   annotated.  A noreturn function must be marked __noreturn in both its
+   declaration and its definition, and must have a NORETURN() annotation
+   in tools/objtool/noreturns.h.
+
 
 4. file.o: warning: objtool: func(): can't find starting instruction
    or
···
 
    This is a kernel entry/exit instruction like sysenter or iret.  Such
    instructions aren't allowed in a callable function, and are most
-   likely part of the kernel entry code.  They should usually not have
-   the callable function annotation (ENDPROC) and should always be
-   annotated with the unwind hint macros in asm/unwind_hints.h.
+   likely part of the kernel entry code.  Such code should probably be
+   placed in a SYM_FUNC_CODE block with unwind hints.
 
 
 6. file.o: warning: objtool: func()+0x26: sibling call from callable instruction with modified stack frame
 
-   This is a dynamic jump or a jump to an undefined symbol.  Objtool
-   assumed it's a sibling call and detected that the frame pointer
-   wasn't first restored to its original state.
+   This is a branch to an UNDEF symbol.  Objtool assumed it's a
+   sibling call and detected that the stack wasn't first restored to its
+   original state.
 
-   If it's not really a sibling call, you may need to move the
-   destination code to the local file.
+   If it's not really a sibling call, you may need to use unwind hints
+   and/or move the destination code to the local file.
 
    If the instruction is not actually in a callable function (e.g.
-   kernel entry code), change ENDPROC to END and annotate manually with
-   the unwind hint macros in asm/unwind_hints.h.
+   kernel entry code), use SYM_CODE_{START,END} and unwind hints.
 
 
 7. file: warning: objtool: func()+0x5c: stack state mismatch
···
 
    Another possibility is that the code has some asm or inline asm which
    does some unusual things to the stack or the frame pointer.  In such
-   cases it's probably appropriate to use the unwind hint macros in
-   asm/unwind_hints.h.
+   cases it's probably appropriate to use SYM_FUNC_CODE with unwind
+   hints.
 
 
 8. file.o: warning: objtool: funcA() falls through to next function funcB()
···
    can fall through into the next function.  There could be different
    reasons for this:
 
-   1) funcA()'s last instruction is a call to a "noreturn" function like
+   a) funcA()'s last instruction is a call to a "noreturn" function like
       panic().  In this case the noreturn function needs to be added to
       objtool's hard-coded global_noreturns array.  Feel free to bug the
       objtool maintainer, or you can submit a patch.
 
-   2) funcA() uses the unreachable() annotation in a section of code
+   b) funcA() uses the unreachable() annotation in a section of code
       that is actually reachable.
 
-   3) If funcA() calls an inline function, the object code for funcA()
-      might be corrupt due to a gcc bug.  For more details, see:
-      https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70646
+   c) Some undefined behavior like divide by zero.
+
 
 9. file.o: warning: objtool: funcA() call to funcB() with UACCESS enabled
 
···
     This limitation can be overcome by massaging the alternatives with
     NOPs to shift the stack changes around so they no longer conflict.
 
+
 11. file.o: warning: unannotated intra-function call
 
-   This warning means that a direct call is done to a destination which
-   is not at the beginning of a function. If this is a legit call, you
-   can remove this warning by putting the ANNOTATE_INTRA_FUNCTION_CALL
-   directive right before the call.
+    This warning means that a direct call is done to a destination which
+    is not at the beginning of a function. If this is a legit call, you
+    can remove this warning by putting the ANNOTATE_INTRA_FUNCTION_CALL
+    directive right before the call.
+
 
 12. file.o: warning: func(): not an indirect call target
 
-   This means that objtool is running with --ibt and a function expected
-   to be an indirect call target is not. In particular, this happens for
-   init_module() or cleanup_module() if a module relies on these special
-   names and does not use module_init() / module_exit() macros to create
-   them.
+    This means that objtool is running with --ibt and a function
+    expected to be an indirect call target is not. In particular, this
+    happens for init_module() or cleanup_module() if a module relies on
+    these special names and does not use module_init() / module_exit()
+    macros to create them.
 
 
 If the error doesn't seem to make sense, it could be a bug in objtool.
-Feel free to ask the objtool maintainer for help.
+Feel free to ask objtool maintainers for help.
 
 
 Adding exceptions

tools/objtool/Makefile

···
 OBJTOOL_LDFLAGS := $(LIBELF_LIBS) $(LIBSUBCMD) $(KBUILD_HOSTLDFLAGS)
 
 # Allow old libelf to be used:
-elfshdr := $(shell echo '$(pound)include <libelf.h>' | $(HOSTCC) $(OBJTOOL_CFLAGS) -x c -E - | grep elf_getshdr)
+elfshdr := $(shell echo '$(pound)include <libelf.h>' | $(HOSTCC) $(OBJTOOL_CFLAGS) -x c -E - 2>/dev/null | grep elf_getshdr)
 OBJTOOL_CFLAGS += $(if $(elfshdr),,-DLIBELF_USE_DEPRECATED)
 
 # Always want host compilation.

tools/objtool/arch/loongarch/decode.c

···
 #include <asm/inst.h>
 #include <asm/orc_types.h>
 #include <linux/objtool_types.h>
-
-#ifndef EM_LOONGARCH
-#define EM_LOONGARCH	258
-#endif
+#include <arch/elf.h>
 
 int arch_ftrace_match(char *name)
 {
···
 	/* initial CFA (call frame address) */
 	state->cfa.base = CFI_SP;
 	state->cfa.offset = 0;
+}
+
+unsigned int arch_reloc_size(struct reloc *reloc)
+{
+	switch (reloc_type(reloc)) {
+	case R_LARCH_32:
+	case R_LARCH_32_PCREL:
+		return 4;
+	default:
+		return 8;
+	}
+}
+
+unsigned long arch_jump_table_sym_offset(struct reloc *reloc, struct reloc *table)
+{
+	switch (reloc_type(reloc)) {
+	case R_LARCH_32_PCREL:
+	case R_LARCH_64_PCREL:
+		return reloc->sym->offset + reloc_addend(reloc) -
+		       (reloc_offset(reloc) - reloc_offset(table));
+	default:
+		return reloc->sym->offset + reloc_addend(reloc);
+	}
 }

tools/objtool/arch/loongarch/include/arch/elf.h

···
 #ifndef R_LARCH_32_PCREL
 #define R_LARCH_32_PCREL	99
 #endif
+#ifndef R_LARCH_64_PCREL
+#define R_LARCH_64_PCREL	109
+#endif
+
+#ifndef EM_LOONGARCH
+#define EM_LOONGARCH		258
+#endif
 
 #define R_NONE			R_LARCH_NONE
 #define R_ABS32			R_LARCH_32

tools/objtool/arch/loongarch/special.c

···
 // SPDX-License-Identifier: GPL-2.0-or-later
+#include <string.h>
 #include <objtool/special.h>
+#include <objtool/warn.h>
 
 bool arch_support_alt_relocation(struct special_alt *special_alt,
 				 struct instruction *insn,
···
 	return false;
 }
 
+struct table_info {
+	struct list_head jump_info;
+	unsigned long insn_offset;
+	unsigned long rodata_offset;
+};
+
+static void get_rodata_table_size_by_table_annotate(struct objtool_file *file,
+						    struct instruction *insn,
+						    unsigned long *table_size)
+{
+	struct section *rsec;
+	struct reloc *reloc;
+	struct list_head table_list;
+	struct table_info *orig_table;
+	struct table_info *next_table;
+	unsigned long tmp_insn_offset;
+	unsigned long tmp_rodata_offset;
+
+	rsec = find_section_by_name(file->elf, ".rela.discard.tablejump_annotate");
+	if (!rsec)
+		return;
+
+	INIT_LIST_HEAD(&table_list);
+
+	for_each_reloc(rsec, reloc) {
+		orig_table = malloc(sizeof(struct table_info));
+		if (!orig_table) {
+			WARN("malloc failed");
+			return;
+		}
+
+		orig_table->insn_offset = reloc->sym->offset + reloc_addend(reloc);
+		reloc++;
+		orig_table->rodata_offset = reloc->sym->offset + reloc_addend(reloc);
+
+		list_add_tail(&orig_table->jump_info, &table_list);
+
+		if (reloc_idx(reloc) + 1 == sec_num_entries(rsec))
+			break;
+	}
+
+	list_for_each_entry(orig_table, &table_list, jump_info) {
+		next_table = list_next_entry(orig_table, jump_info);
+		list_for_each_entry_from(next_table, &table_list, jump_info) {
+			if (next_table->rodata_offset < orig_table->rodata_offset) {
+				tmp_insn_offset = next_table->insn_offset;
+				tmp_rodata_offset = next_table->rodata_offset;
+				next_table->insn_offset = orig_table->insn_offset;
+				next_table->rodata_offset = orig_table->rodata_offset;
+				orig_table->insn_offset = tmp_insn_offset;
+				orig_table->rodata_offset = tmp_rodata_offset;
+			}
+		}
+	}
+
+	list_for_each_entry(orig_table, &table_list, jump_info) {
+		if (insn->offset == orig_table->insn_offset) {
+			next_table = list_next_entry(orig_table, jump_info);
+			if (&next_table->jump_info == &table_list) {
+				*table_size = 0;
+				return;
+			}
+
+			while (next_table->rodata_offset == orig_table->rodata_offset) {
+				next_table = list_next_entry(next_table, jump_info);
+				if (&next_table->jump_info == &table_list) {
+					*table_size = 0;
+					return;
+				}
+			}
+
+			*table_size = next_table->rodata_offset - orig_table->rodata_offset;
+		}
+	}
+}
+
+static struct reloc *find_reloc_by_table_annotate(struct objtool_file *file,
+						  struct instruction *insn,
+						  unsigned long *table_size)
+{
+	struct section *rsec;
+	struct reloc *reloc;
+	unsigned long offset;
+
+	rsec = find_section_by_name(file->elf, ".rela.discard.tablejump_annotate");
+	if (!rsec)
+		return NULL;
+
+	for_each_reloc(rsec, reloc) {
+		if (reloc->sym->sec->rodata)
+			continue;
+
+		if (strcmp(insn->sec->name, reloc->sym->sec->name))
+			continue;
+
+		offset = reloc->sym->offset + reloc_addend(reloc);
+		if (insn->offset == offset) {
+			get_rodata_table_size_by_table_annotate(file, insn, table_size);
+			reloc++;
+			return reloc;
+		}
+	}
+
+	return NULL;
+}
+
+static struct reloc *find_reloc_of_rodata_c_jump_table(struct section *sec,
+						       unsigned long offset,
+						       unsigned long *table_size)
+{
+	struct section *rsec;
+	struct reloc *reloc;
+
+	rsec = sec->rsec;
+	if (!rsec)
+		return NULL;
+
+	for_each_reloc(rsec, reloc) {
+		if (reloc_offset(reloc) > offset)
+			break;
+
+		if (!strcmp(reloc->sym->sec->name, C_JUMP_TABLE_SECTION)) {
+			*table_size = 0;
+			return reloc;
+		}
+	}
+
+	return NULL;
+}
+
 struct reloc *arch_find_switch_table(struct objtool_file *file,
 				     struct instruction *insn,
 				     unsigned long *table_size)
 {
-	return NULL;
+	struct reloc *annotate_reloc;
+	struct reloc *rodata_reloc;
+	struct section *table_sec;
+	unsigned long table_offset;
+
+	annotate_reloc = find_reloc_by_table_annotate(file, insn, table_size);
+	if (!annotate_reloc) {
+		annotate_reloc = find_reloc_of_rodata_c_jump_table(
+				 insn->sec, insn->offset, table_size);
+		if (!annotate_reloc)
+			return NULL;
+	}
+
+	table_sec = annotate_reloc->sym->sec;
+	table_offset = annotate_reloc->sym->offset + reloc_addend(annotate_reloc);
+
+	/*
+	 * Each table entry has a rela associated with it.  The rela
+	 * should reference text in the same function as the original
+	 * instruction.
+	 */
+	rodata_reloc = find_reloc_by_dest(file->elf, table_sec, table_offset);
+	if (!rodata_reloc)
+		return NULL;
+
+	return rodata_reloc;
 }

tools/objtool/arch/powerpc/decode.c

···
 	state->regs[CFI_RA].base = CFI_CFA;
 	state->regs[CFI_RA].offset = 0;
 }
+
+unsigned int arch_reloc_size(struct reloc *reloc)
+{
+	switch (reloc_type(reloc)) {
+	case R_PPC_REL32:
+	case R_PPC_ADDR32:
+	case R_PPC_UADDR32:
+	case R_PPC_PLT32:
+	case R_PPC_PLTREL32:
+		return 4;
+	default:
+		return 8;
+	}
+}

tools/objtool/arch/x86/decode.c

···
 	return !strcmp(sym->name, "retbleed_return_thunk") ||
 	       !strcmp(sym->name, "srso_safe_ret");
 }
+
+unsigned int arch_reloc_size(struct reloc *reloc)
+{
+	switch (reloc_type(reloc)) {
+	case R_X86_64_32:
+	case R_X86_64_32S:
+	case R_X86_64_PC32:
+	case R_X86_64_PLT32:
+		return 4;
+	default:
+		return 8;
+	}
+}

tools/objtool/builtin-check.c

···
 #include <subcmd/parse-options.h>
 #include <string.h>
 #include <stdlib.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <sys/stat.h>
+#include <sys/sendfile.h>
 #include <objtool/builtin.h>
 #include <objtool/objtool.h>
 
···
 	fprintf(stderr,					\
 		"error: objtool: " format "\n",		\
 		##__VA_ARGS__)
+
+const char *objname;
 
 struct opts opts;
 
···
 	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('o', "orc", &opts.orc, "generate ORC metadata"),
+	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_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, "backup", &opts.backup, "create .orig files before modification"),
-	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_BOOLEAN(0, "sec-address", &opts.sec_address, "print section addresses in warnings"),
-	OPT_BOOLEAN(0, "stats", &opts.stats, "print statistics"),
+	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_END(),
 };
···
 
 static bool opts_valid(void)
 {
+	if (opts.mnop && !opts.mcount) {
+		ERROR("--mnop requires --mcount");
+		return false;
+	}
+
+	if (opts.noinstr && !opts.link) {
+		ERROR("--noinstr requires --link");
+		return false;
+	}
+
+	if (opts.ibt && !opts.link) {
+		ERROR("--ibt requires --link");
+		return false;
+	}
+
+	if (opts.unret && !opts.link) {
+		ERROR("--unret requires --link");
+		return false;
+	}
+
 	if (opts.hack_jump_label	||
 	    opts.hack_noinstr		||
 	    opts.ibt			||
···
 		return true;
 	}
 
-	if (opts.unret && !opts.rethunk) {
-		ERROR("--unret requires --rethunk");
-		return false;
-	}
-
 	if (opts.dump_orc)
 		return true;
 
···
 	return false;
 }
 
-static bool mnop_opts_valid(void)
+static int copy_file(const char *src, const char *dst)
 {
-	if (opts.mnop && !opts.mcount) {
-		ERROR("--mnop requires --mcount");
-		return false;
+	size_t to_copy, copied;
+	int dst_fd, src_fd;
+	struct stat stat;
+	off_t offset = 0;
+
+	src_fd = open(src, O_RDONLY);
+	if (src_fd == -1) {
+		ERROR("can't open '%s' for reading", src);
+		return 1;
 	}
 
-	return true;
+	dst_fd = open(dst, O_WRONLY | O_CREAT | O_TRUNC, 0400);
+	if (dst_fd == -1) {
+		ERROR("can't open '%s' for writing", dst);
+		return 1;
+	}
+
+	if (fstat(src_fd, &stat) == -1) {
+		perror("fstat");
+		return 1;
+	}
+
+	if (fchmod(dst_fd, stat.st_mode) == -1) {
+		perror("fchmod");
+		return 1;
+	}
+
+	for (to_copy = stat.st_size; to_copy > 0; to_copy -= copied) {
+		copied = sendfile(dst_fd, src_fd, &offset, to_copy);
+		if (copied == -1) {
+			perror("sendfile");
+			return 1;
+		}
+	}
+
+	close(dst_fd);
+	close(src_fd);
+	return 0;
 }
 
-static bool link_opts_valid(struct objtool_file *file)
+static char **save_argv(int argc, const char **argv)
 {
-	if (opts.link)
-		return true;
+	char **orig_argv;
 
-	if (has_multiple_files(file->elf)) {
-		ERROR("Linked object detected, forcing --link");
-		opts.link = true;
-		return true;
+	orig_argv = calloc(argc, sizeof(char *));
+	if (!orig_argv) {
+		perror("calloc");
+		return NULL;
 	}
 
-	if (opts.noinstr) {
-		ERROR("--noinstr requires --link");
-		return false;
-	}
+	for (int i = 0; i < argc; i++) {
+		orig_argv[i] = strdup(argv[i]);
+		if (!orig_argv[i]) {
+			perror("strdup");
+			return NULL;
+		}
+	};
 
-	if (opts.ibt) {
-		ERROR("--ibt requires --link");
-		return false;
-	}
-
-	if (opts.unret) {
-		ERROR("--unret requires --link");
-		return false;
-	}
-
-	return true;
+	return orig_argv;
 }
+
+#define ORIG_SUFFIX ".orig"
 
 int objtool_run(int argc, const char **argv)
 {
-	const char *objname;
 	struct objtool_file *file;
-	int ret;
+	char *backup = NULL;
+	char **orig_argv;
+	int ret = 0;
 
-	argc = cmd_parse_options(argc, argv, check_usage);
-	objname = argv[0];
+	orig_argv = save_argv(argc, argv);
+	if (!orig_argv)
+		return 1;
+
+	cmd_parse_options(argc, argv, check_usage);
 
 	if (!opts_valid())
 		return 1;
 
+	objname = argv[0];
+
 	if (opts.dump_orc)
 		return orc_dump(objname);
 
+	if (!opts.dryrun && opts.output) {
+		/* copy original .o file to output file */
+		if (copy_file(objname, opts.output))
+			return 1;
+
+		/* from here on, work directly on the output file */
+		objname = opts.output;
+	}
+
 	file = objtool_open_read(objname);
 	if (!file)
-		return 1;
+		goto err;
 
-	if (!mnop_opts_valid())
-		return 1;
-
-	if (!link_opts_valid(file))
-		return 1;
+	if (!opts.link && has_multiple_files(file->elf)) {
+		ERROR("Linked object requires --link");
+		goto err;
+	}
 
 	ret = check(file);
 	if (ret)
-		return ret;
+		goto err;
 
-	if (file->elf->changed)
-		return elf_write(file->elf);
+	if (!opts.dryrun && file->elf->changed && elf_write(file->elf))
+		goto err;
 
 	return 0;
+
+err:
+	if (opts.dryrun)
+		goto err_msg;
+
+	if (opts.output) {
+		unlink(opts.output);
+		goto err_msg;
+	}
+
+	/*
+	 * Make a backup before kbuild deletes the file so the error
+	 * can be recreated without recompiling or relinking.
+	 */
+	backup = malloc(strlen(objname) + strlen(ORIG_SUFFIX) + 1);
+	if (!backup) {
+		perror("malloc");
+		return 1;
+	}
+
+	strcpy(backup, objname);
+	strcat(backup, ORIG_SUFFIX);
+	if (copy_file(objname, backup))
+		return 1;
+
+err_msg:
+	fprintf(stderr, "%s", orig_argv[0]);
+
+	for (int i = 1; i < argc; i++) {
+		char *arg = orig_argv[i];
+
+		if (backup && !strcmp(arg, objname))
+			fprintf(stderr, " %s -o %s", backup, objname);
+		else
+			fprintf(stderr, " %s", arg);
+	}
+
+	fprintf(stderr, "\n");
+
+	return 1;
 }

tools/objtool/check.c

···
 	return ret;
 }
 
+__weak unsigned long arch_jump_table_sym_offset(struct reloc *reloc, struct reloc *table)
+{
+	return reloc->sym->offset + reloc_addend(reloc);
+}
+
 static int add_jump_table(struct objtool_file *file, struct instruction *insn,
 			  struct reloc *next_table)
 {
···
 	unsigned int prev_offset = 0;
 	struct reloc *reloc = table;
 	struct alternative *alt;
+	unsigned long sym_offset;
 
 	/*
 	 * Each @reloc is a switch table relocation which points to the target
···
 			break;
 
 		/* Make sure the table entries are consecutive: */
-		if (prev_offset && reloc_offset(reloc) != prev_offset + 8)
+		if (prev_offset && reloc_offset(reloc) != prev_offset + arch_reloc_size(reloc))
 			break;
 
+		sym_offset = arch_jump_table_sym_offset(reloc, table);
+
 		/* Detect function pointers from contiguous objects: */
-		if (reloc->sym->sec == pfunc->sec &&
-		    reloc_addend(reloc) == pfunc->offset)
+		if (reloc->sym->sec == pfunc->sec && sym_offset == pfunc->offset)
 			break;
 
 		/*
···
 		 * which point to the end of the function.  Ignore them.
 		 */
 		if (reloc->sym->sec == pfunc->sec &&
-		    reloc_addend(reloc) == pfunc->offset + pfunc->len)
+		    sym_offset == pfunc->offset + pfunc->len)
 			goto next;
 
-		dest_insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
+		dest_insn = find_insn(file, reloc->sym->sec, sym_offset);
 		if (!dest_insn)
 			break;
 
···
 	struct reloc *table_reloc;
 	struct instruction *dest_insn, *orig_insn = insn;
 	unsigned long table_size;
+	unsigned long sym_offset;
 
 	/*
 	 * Backward search using the @first_jump_src links, these help avoid
···
 		table_reloc = arch_find_switch_table(file, insn, &table_size);
 		if (!table_reloc)
 			continue;
-		dest_insn = find_insn(file, table_reloc->sym->sec, reloc_addend(table_reloc));
+
+		sym_offset = table_reloc->sym->offset + reloc_addend(table_reloc);
+
+		dest_insn = find_insn(file, table_reloc->sym->sec, sym_offset);
 		if (!dest_insn || !insn_func(dest_insn) || insn_func(dest_insn)->pfunc != func)
 			continue;
 
···
 	return warnings;
 }
 
-static bool ignore_noreturn_call(struct instruction *insn)
-{
-	struct symbol *call_dest = insn_call_dest(insn);
-
-	/*
-	 * FIXME: hack, we need a real noreturn solution
-	 *
-	 * Problem is, exc_double_fault() may or may not return, depending on
-	 * whether CONFIG_X86_ESPFIX64 is set.  But objtool has no visibility
-	 * to the kernel config.
-	 *
-	 * Other potential ways to fix it:
-	 *
-	 *   - have compiler communicate __noreturn functions somehow
-	 *   - remove CONFIG_X86_ESPFIX64
-	 *   - read the .config file
-	 *   - add a cmdline option
-	 *   - create a generic objtool annotation format (vs a bunch of custom
-	 *     formats) and annotate it
-	 */
-	if (!strcmp(call_dest->name, "exc_double_fault")) {
-		/* prevent further unreachable warnings for the caller */
-		insn->sym->warned = 1;
-		return true;
-	}
-
-	return false;
-}
-
 static int validate_reachable_instructions(struct objtool_file *file)
 {
 	struct instruction *insn, *prev_insn;
···
 		prev_insn = prev_insn_same_sec(file, insn);
 		if (prev_insn && prev_insn->dead_end) {
 			call_dest = insn_call_dest(prev_insn);
-			if (call_dest && !ignore_noreturn_call(prev_insn)) {
-				WARN_INSN(insn, "%s() is missing a __noreturn annotation",
+			if (call_dest) {
+				WARN_INSN(insn, "%s() missing __noreturn in .c/.h or NORETURN() in noreturns.h",
 					  call_dest->name);
 				warnings++;
 				continue;
···
 	char *funcs = NULL, *tmp;
 
 	for_each_sym(file, sym) {
-		if (sym->warned) {
+		if (sym->warnings) {
 			if (!funcs) {
 				funcs = malloc(strlen(sym->name) + 1);
 				strcpy(funcs, sym->name);
···
 	init_cfi_state(&force_undefined_cfi);
 	force_undefined_cfi.force_undefined = true;
 
-	if (!cfi_hash_alloc(1UL << (file->elf->symbol_bits - 3)))
+	if (!cfi_hash_alloc(1UL << (file->elf->symbol_bits - 3))) {
+		ret = -1;
 		goto out;
+	}
 
 	cfi_hash_add(&init_cfi);
 	cfi_hash_add(&func_cfi);
···
 	if (opts.retpoline) {
 		ret = validate_retpoline(file);
 		if (ret < 0)
-			return ret;
+			goto out;
 		warnings += ret;
 	}
 
···
 		 */
 		ret = validate_unrets(file);
 		if (ret < 0)
-			return ret;
+			goto out;
 		warnings += ret;
 	}
 
···
 	if (opts.prefix) {
 		ret = add_prefix_symbols(file);
 		if (ret < 0)
-			return ret;
+			goto out;
 		warnings += ret;
 	}
 
···
 
 out:
 	/*
-	 *  For now, don't fail the kernel build on fatal warnings.  These
-	 *  errors are still fairly common due to the growing matrix of
-	 *  supported toolchains and their recent pace of change.
+	 * CONFIG_OBJTOOL_WERROR upgrades all warnings (and errors) to actual
+	 * errors.
+	 *
+	 * Note that even "fatal" type errors don't actually return an error
+	 * without CONFIG_OBJTOOL_WERROR.  That probably needs improved at some
+	 * point.
 	 */
+	if (opts.werror && (ret || warnings)) {
+		if (warnings)
+			WARN("%d warning(s) upgraded to errors", warnings);
+		return 1;
+	}
+
 	return 0;
 }

tools/objtool/elf.c

···
 	struct section *sec;
 	Elf_Scn *s;
 
-	if (opts.dryrun)
-		return 0;
-
 	/* Update changed relocation sections and section headers: */
 	list_for_each_entry(sec, &elf->sections, list) {
 		if (sec->truncate)

tools/objtool/include/objtool/arch.h

···
 
 bool arch_pc_relative_reloc(struct reloc *reloc);
 
+unsigned int arch_reloc_size(struct reloc *reloc);
+unsigned long arch_jump_table_sym_offset(struct reloc *reloc, struct reloc *table);
+
 #endif /* _ARCH_H */

tools/objtool/include/objtool/builtin.h

···
 
 	/* options: */
 	bool backtrace;
-	bool backup;
 	bool dryrun;
 	bool link;
 	bool mnop;
 	bool module;
 	bool no_unreachable;
+	const char *output;
 	bool sec_address;
 	bool stats;
 	bool verbose;
+	bool werror;
 };
 
 extern struct opts opts;

tools/objtool/include/objtool/elf.h

···
 	u8 return_thunk      : 1;
 	u8 fentry            : 1;
 	u8 profiling_func    : 1;
-	u8 warned	     : 1;
 	u8 embedded_insn     : 1;
 	u8 local_label       : 1;
 	u8 frame_pointer     : 1;
+	u8 warnings	     : 2;
 	struct list_head pv_target;
 	struct reloc *relocs;
 };

tools/objtool/include/objtool/warn.h

···
 
 #define WARN(format, ...)				\
 	fprintf(stderr,					\
-		"%s: warning: objtool: " format "\n",	\
-		objname, ##__VA_ARGS__)
+		"%s: %s: objtool: " format "\n",	\
+		objname,				\
+		opts.werror ? "error" : "warning",	\
+		##__VA_ARGS__)
 
 #define WARN_FUNC(format, sec, offset, ...)		\
 ({							\
···
 	free(_str);					\
 })
 
+#define WARN_LIMIT 2
+
 #define WARN_INSN(insn, format, ...)					\
 ({									\
 	struct instruction *_insn = (insn);				\
-	if (!_insn->sym || !_insn->sym->warned)				\
+	BUILD_BUG_ON(WARN_LIMIT > 2);					\
+	if (!_insn->sym || _insn->sym->warnings < WARN_LIMIT) {		\
 		WARN_FUNC(format, _insn->sec, _insn->offset,		\
 			  ##__VA_ARGS__);				\
-	if (_insn->sym)							\
-		_insn->sym->warned = 1;					\
+		if (_insn->sym)						\
+			_insn->sym->warnings++;				\
+	} else if (_insn->sym && _insn->sym->warnings == WARN_LIMIT) {	\
+		WARN_FUNC("skipping duplicate warning(s)",		\
+			  _insn->sec, _insn->offset);			\
+		_insn->sym->warnings++;					\
+	}								\
 })
 
 #define BT_INSN(insn, format, ...)				\

tools/objtool/objtool.c

···
 
 bool help;
 
-const char *objname;
 static struct objtool_file file;
 
-static bool objtool_create_backup(const char *_objname)
+struct objtool_file *objtool_open_read(const char *filename)
 {
-	int len = strlen(_objname);
-	char *buf, *base, *name = malloc(len+6);
-	int s, d, l, t;
-
-	if (!name) {
-		perror("failed backup name malloc");
-		return false;
+	if (file.elf) {
+		WARN("won't handle more than one file at a time");
+		return NULL;
 	}
 
-	strcpy(name, _objname);
-	strcpy(name + len, ".orig");
-
-	d = open(name, O_CREAT|O_WRONLY|O_TRUNC, 0644);
-	if (d < 0) {
-		perror("failed to create backup file");
-		return false;
-	}
-
-	s = open(_objname, O_RDONLY);
-	if (s < 0) {
-		perror("failed to open orig file");
-		return false;
-	}
-
-	buf = malloc(4096);
-	if (!buf) {
-		perror("failed backup data malloc");
-		return false;
-	}
-
-	while ((l = read(s, buf, 4096)) > 0) {
-		base = buf;
-		do {
-			t = write(d, base, l);
-			if (t < 0) {
-				perror("failed backup write");
-				return false;
-			}
-			base += t;
-			l -= t;
-		} while (l);
-	}
-
-	if (l < 0) {
-		perror("failed backup read");
-		return false;
-	}
-
-	free(name);
-	free(buf);
-	close(d);
-	close(s);
-
-	return true;
-}
-
-struct objtool_file *objtool_open_read(const char *_objname)
-{
-	if (objname) {
-		if (strcmp(objname, _objname)) {
-			WARN("won't handle more than one file at a time");
-			return NULL;
-		}
-		return &file;
-	}
-	objname = _objname;
-
-	file.elf = elf_open_read(objname, O_RDWR);
+	file.elf = elf_open_read(filename, O_RDWR);
 	if (!file.elf)
 		return NULL;
-
-	if (opts.backup && !objtool_create_backup(objname)) {
-		WARN("can't create backup file");
-		return NULL;
-	}
 
 	hash_init(file.insn_hash);
 	INIT_LIST_HEAD(&file.retpoline_call_list);

tools/objtool/orc_dump.c

···
 #include <objtool/warn.h>
 #include <objtool/endianness.h>
 
-int orc_dump(const char *_objname)
+int orc_dump(const char *filename)
 {
 	int fd, nr_entries, i, *orc_ip = NULL, orc_size = 0;
 	struct orc_entry *orc = NULL;
···
 	Elf_Data *data, *symtab = NULL, *rela_orc_ip = NULL;
 	struct elf dummy_elf = {};
 
-
-	objname = _objname;
-
 	elf_version(EV_CURRENT);
 
-	fd = open(objname, O_RDONLY);
+	fd = open(filename, O_RDONLY);
 	if (fd == -1) {
 		perror("open");
 		return -1;