Remove stack unwinder for now

It has caused more problems than it ever really solved, and is
apparently not getting cleaned up and fixed. We can put it back when
it's stable and isn't likely to make warning or bug events worse.

In the meantime, enable frame pointers for more readable stack traces.

Signed-off-by: Linus Torvalds <[e-mail]>

Makefile

···
 CFLAGS		+= -fomit-frame-pointer
 endif
 
-ifdef CONFIG_UNWIND_INFO
-CFLAGS		+= -fasynchronous-unwind-tables
-LDFLAGS_vmlinux	+= --eh-frame-hdr
-endif
-
 ifdef CONFIG_DEBUG_INFO
 CFLAGS		+= -g
 endif

arch/i386/defconfig

···
 # CONFIG_DEBUG_VM is not set
 # CONFIG_DEBUG_LIST is not set
 # CONFIG_FRAME_POINTER is not set
-CONFIG_UNWIND_INFO=y
-CONFIG_STACK_UNWIND=y
 # CONFIG_FORCED_INLINING is not set
 # CONFIG_HEADERS_CHECK is not set
 # CONFIG_RCU_TORTURE_TEST is not set

arch/i386/kernel/entry.S

···
 	jmp error_code
 	CFI_ENDPROC
 
-#ifdef CONFIG_STACK_UNWIND
-ENTRY(arch_unwind_init_running)
-	CFI_STARTPROC
-	movl	4(%esp), %edx
-	movl	(%esp), %ecx
-	leal	4(%esp), %eax
-	movl	%ebx, PT_EBX(%edx)
-	xorl	%ebx, %ebx
-	movl	%ebx, PT_ECX(%edx)
-	movl	%ebx, PT_EDX(%edx)
-	movl	%esi, PT_ESI(%edx)
-	movl	%edi, PT_EDI(%edx)
-	movl	%ebp, PT_EBP(%edx)
-	movl	%ebx, PT_EAX(%edx)
-	movl	$__USER_DS, PT_DS(%edx)
-	movl	$__USER_DS, PT_ES(%edx)
-	movl	$0, PT_GS(%edx)
-	movl	%ebx, PT_ORIG_EAX(%edx)
-	movl	%ecx, PT_EIP(%edx)
-	movl	12(%esp), %ecx
-	movl	$__KERNEL_CS, PT_CS(%edx)
-	movl	%ebx, PT_EFLAGS(%edx)
-	movl	%eax, PT_OLDESP(%edx)
-	movl	8(%esp), %eax
-	movl	%ecx, 8(%esp)
-	movl	PT_EBX(%edx), %ebx
-	movl	$__KERNEL_DS, PT_OLDSS(%edx)
-	jmpl	*%eax
-	CFI_ENDPROC
-ENDPROC(arch_unwind_init_running)
-#endif
-
 ENTRY(kernel_thread_helper)
 	pushl $0		# fake return address for unwinder
 	CFI_STARTPROC

arch/i386/kernel/traps.c

···
 asmlinkage void machine_check(void);
 
 int kstack_depth_to_print = 24;
-#ifdef CONFIG_STACK_UNWIND
-static int call_trace = 1;
-#else
-#define call_trace (-1)
-#endif
 ATOMIC_NOTIFIER_HEAD(i386die_chain);
 
 int register_die_notifier(struct notifier_block *nb)
···
 	return ebp;
 }
 
-struct ops_and_data {
-	struct stacktrace_ops *ops;
-	void *data;
-};
-
-static asmlinkage int
-dump_trace_unwind(struct unwind_frame_info *info, void *data)
-{
-	struct ops_and_data *oad = (struct ops_and_data *)data;
-	int n = 0;
-	unsigned long sp = UNW_SP(info);
-
-	if (arch_unw_user_mode(info))
-		return -1;
-	while (unwind(info) == 0 && UNW_PC(info)) {
-		n++;
-		oad->ops->address(oad->data, UNW_PC(info));
-		if (arch_unw_user_mode(info))
-			break;
-		if ((sp & ~(PAGE_SIZE - 1)) == (UNW_SP(info) & ~(PAGE_SIZE - 1))
-		    && sp > UNW_SP(info))
-			break;
-		sp = UNW_SP(info);
-	}
-	return n;
-}
-
 #define MSG(msg) ops->warning(data, msg)
 
 void dump_trace(struct task_struct *task, struct pt_regs *regs,
···
 	if (!task)
 		task = current;
 
-	if (call_trace >= 0) {
-		int unw_ret = 0;
-		struct unwind_frame_info info;
-		struct ops_and_data oad = { .ops = ops, .data = data };
-
-		if (regs) {
-			if (unwind_init_frame_info(&info, task, regs) == 0)
-				unw_ret = dump_trace_unwind(&info, &oad);
-		} else if (task == current)
-			unw_ret = unwind_init_running(&info, dump_trace_unwind,
-						      &oad);
-		else {
-			if (unwind_init_blocked(&info, task) == 0)
-				unw_ret = dump_trace_unwind(&info, &oad);
-		}
-		if (unw_ret > 0) {
-			if (call_trace == 1 && !arch_unw_user_mode(&info)) {
-				ops->warning_symbol(data,
-					     "DWARF2 unwinder stuck at %s",
-					     UNW_PC(&info));
-				if (UNW_SP(&info) >= PAGE_OFFSET) {
-					MSG("Leftover inexact backtrace:");
-					stack = (void *)UNW_SP(&info);
-					if (!stack)
-						return;
-					ebp = UNW_FP(&info);
-				} else
-					MSG("Full inexact backtrace again:");
-			} else if (call_trace >= 1)
-				return;
-			else
-				MSG("Full inexact backtrace again:");
-		} else
-			MSG("Inexact backtrace:");
-	}
 	if (!stack) {
 		unsigned long dummy;
 		stack = &dummy;
···
 	return 1;
 }
 __setup("kstack=", kstack_setup);
-
-#ifdef CONFIG_STACK_UNWIND
-static int __init call_trace_setup(char *s)
-{
-	if (strcmp(s, "old") == 0)
-		call_trace = -1;
-	else if (strcmp(s, "both") == 0)
-		call_trace = 0;
-	else if (strcmp(s, "newfallback") == 0)
-		call_trace = 1;
-	else if (strcmp(s, "new") == 2)
-		call_trace = 2;
-	return 1;
-}
-__setup("call_trace=", call_trace_setup);
-#endif

arch/x86_64/Makefile

···
 # actually it makes the kernel smaller too.
 cflags-y += -fno-reorder-blocks
 cflags-y += -Wno-sign-compare
-ifneq ($(CONFIG_UNWIND_INFO),y)
 cflags-y += -fno-asynchronous-unwind-tables
-endif
 ifneq ($(CONFIG_DEBUG_INFO),y)
 # -fweb shrinks the kernel a bit, but the difference is very small
 # it also messes up debugging, so don't use it for now.

arch/x86_64/defconfig

···
 # CONFIG_DEBUG_VM is not set
 # CONFIG_DEBUG_LIST is not set
 # CONFIG_FRAME_POINTER is not set
-CONFIG_UNWIND_INFO=y
-CONFIG_STACK_UNWIND=y
 # CONFIG_FORCED_INLINING is not set
 # CONFIG_HEADERS_CHECK is not set
 # CONFIG_RCU_TORTURE_TEST is not set

arch/x86_64/kernel/entry.S

···
 	ret
 	CFI_ENDPROC
 ENDPROC(call_softirq)
-
-#ifdef CONFIG_STACK_UNWIND
-ENTRY(arch_unwind_init_running)
-	CFI_STARTPROC
-	movq	%r15, R15(%rdi)
-	movq	%r14, R14(%rdi)
-	xchgq	%rsi, %rdx
-	movq	%r13, R13(%rdi)
-	movq	%r12, R12(%rdi)
-	xorl	%eax, %eax
-	movq	%rbp, RBP(%rdi)
-	movq	%rbx, RBX(%rdi)
-	movq	(%rsp), %rcx
-	movq	%rax, R11(%rdi)
-	movq	%rax, R10(%rdi)
-	movq	%rax, R9(%rdi)
-	movq	%rax, R8(%rdi)
-	movq	%rax, RAX(%rdi)
-	movq	%rax, RCX(%rdi)
-	movq	%rax, RDX(%rdi)
-	movq	%rax, RSI(%rdi)
-	movq	%rax, RDI(%rdi)
-	movq	%rax, ORIG_RAX(%rdi)
-	movq	%rcx, RIP(%rdi)
-	leaq	8(%rsp), %rcx
-	movq	$__KERNEL_CS, CS(%rdi)
-	movq	%rax, EFLAGS(%rdi)
-	movq	%rcx, RSP(%rdi)
-	movq	$__KERNEL_DS, SS(%rdi)
-	jmpq	*%rdx
-	CFI_ENDPROC
-ENDPROC(arch_unwind_init_running)
-#endif

arch/x86_64/kernel/traps.c

···
 }
 
 int kstack_depth_to_print = 12;
-#ifdef CONFIG_STACK_UNWIND
-static int call_trace = 1;
-#else
-#define call_trace (-1)
-#endif
 
 #ifdef CONFIG_KALLSYMS
 void printk_address(unsigned long address)
···
 	return NULL;
 }
 
-struct ops_and_data {
-	struct stacktrace_ops *ops;
-	void *data;
-};
-
-static int dump_trace_unwind(struct unwind_frame_info *info, void *context)
-{
-	struct ops_and_data *oad = (struct ops_and_data *)context;
-	int n = 0;
-	unsigned long sp = UNW_SP(info);
-
-	if (arch_unw_user_mode(info))
-		return -1;
-	while (unwind(info) == 0 && UNW_PC(info)) {
-		n++;
-		oad->ops->address(oad->data, UNW_PC(info));
-		if (arch_unw_user_mode(info))
-			break;
-		if ((sp & ~(PAGE_SIZE - 1)) == (UNW_SP(info) & ~(PAGE_SIZE - 1))
-		    && sp > UNW_SP(info))
-			break;
-		sp = UNW_SP(info);
-	}
-	return n;
-}
-
 #define MSG(txt) ops->warning(data, txt)
 
 /*
···
 	if (!tsk)
 		tsk = current;
 
-	if (call_trace >= 0) {
-		int unw_ret = 0;
-		struct unwind_frame_info info;
-		struct ops_and_data oad = { .ops = ops, .data = data };
-
-		if (regs) {
-			if (unwind_init_frame_info(&info, tsk, regs) == 0)
-				unw_ret = dump_trace_unwind(&info, &oad);
-		} else if (tsk == current)
-			unw_ret = unwind_init_running(&info, dump_trace_unwind,
-						      &oad);
-		else {
-			if (unwind_init_blocked(&info, tsk) == 0)
-				unw_ret = dump_trace_unwind(&info, &oad);
-		}
-		if (unw_ret > 0) {
-			if (call_trace == 1 && !arch_unw_user_mode(&info)) {
-				ops->warning_symbol(data,
-					     "DWARF2 unwinder stuck at %s",
-					     UNW_PC(&info));
-				if ((long)UNW_SP(&info) < 0) {
-					MSG("Leftover inexact backtrace:");
-					stack = (unsigned long *)UNW_SP(&info);
-					if (!stack)
-						goto out;
-				} else
-					MSG("Full inexact backtrace again:");
-			} else if (call_trace >= 1)
-				goto out;
-			else
-				MSG("Full inexact backtrace again:");
-		} else
-			MSG("Inexact backtrace:");
-	}
 	if (!stack) {
 		unsigned long dummy;
 		stack = &dummy;
···
 	tinfo = current_thread_info();
 	HANDLE_STACK (valid_stack_ptr(tinfo, stack));
 #undef HANDLE_STACK
-out:
 	put_cpu();
 }
 EXPORT_SYMBOL(dump_trace);
···
 	return 0;
 }
 early_param("kstack", kstack_setup);
-
-#ifdef CONFIG_STACK_UNWIND
-static int __init call_trace_setup(char *s)
-{
-	if (!s)
-		return -EINVAL;
-	if (strcmp(s, "old") == 0)
-		call_trace = -1;
-	else if (strcmp(s, "both") == 0)
-		call_trace = 0;
-	else if (strcmp(s, "newfallback") == 0)
-		call_trace = 1;
-	else if (strcmp(s, "new") == 0)
-		call_trace = 2;
-	return 0;
-}
-early_param("call_trace", call_trace_setup);
-#endif

arch/x86_64/kernel/vmlinux.lds.S

···
   /* Sections to be discarded */
   /DISCARD/ : {
 	*(.exitcall.exit)
-#ifndef CONFIG_UNWIND_INFO
 	*(.eh_frame)
-#endif
 	}
 
   STABS_DEBUG

include/asm-generic/vmlinux.lds.h

···
 		*(__ksymtab_strings)					\
 	}								\
 									\
-	EH_FRAME							\
-									\
 	/* Built-in module parameters. */				\
 	__param : AT(ADDR(__param) - LOAD_OFFSET) {			\
 		VMLINUX_SYMBOL(__start___param) = .;			\
···
 		VMLINUX_SYMBOL(__kprobes_text_start) = .;		\
 		*(.kprobes.text)					\
 		VMLINUX_SYMBOL(__kprobes_text_end) = .;
-
-#ifdef CONFIG_STACK_UNWIND
-#define EH_FRAME							\
-		/* Unwind data binary search table */			\
-		. = ALIGN(8);						\
-        	.eh_frame_hdr : AT(ADDR(.eh_frame_hdr) - LOAD_OFFSET) {	\
-			VMLINUX_SYMBOL(__start_unwind_hdr) = .;		\
-			*(.eh_frame_hdr)				\
-			VMLINUX_SYMBOL(__end_unwind_hdr) = .;		\
-		}							\
-		/* Unwind data */					\
-		. = ALIGN(8);						\
-		.eh_frame : AT(ADDR(.eh_frame) - LOAD_OFFSET) {		\
-			VMLINUX_SYMBOL(__start_unwind) = .;		\
-		  	*(.eh_frame)					\
-			VMLINUX_SYMBOL(__end_unwind) = .;		\
-		}
-#else
-#define EH_FRAME
-#endif
 
 		/* DWARF debug sections.
 		Symbols in the DWARF debugging sections are relative to

include/asm-i386/unwind.h

···
 #ifndef _ASM_I386_UNWIND_H
 #define _ASM_I386_UNWIND_H
 
-/*
- * Copyright (C) 2002-2006 Novell, Inc.
- *	Jan Beulich <[e-mail]>
- * This code is released under version 2 of the GNU GPL.
- */
-
-#ifdef CONFIG_STACK_UNWIND
-
-#include <linux/sched.h>
-#include <asm/fixmap.h>
-#include <asm/ptrace.h>
-#include <asm/uaccess.h>
-
-struct unwind_frame_info
-{
-	struct pt_regs regs;
-	struct task_struct *task;
-	unsigned call_frame:1;
-};
-
-#define UNW_PC(frame)        (frame)->regs.eip
-#define UNW_SP(frame)        (frame)->regs.esp
-#ifdef CONFIG_FRAME_POINTER
-#define UNW_FP(frame)        (frame)->regs.ebp
-#define FRAME_RETADDR_OFFSET 4
-#define FRAME_LINK_OFFSET    0
-#define STACK_BOTTOM(tsk)    STACK_LIMIT((tsk)->thread.esp0)
-#define STACK_TOP(tsk)       ((tsk)->thread.esp0)
-#else
-#define UNW_FP(frame) ((void)(frame), 0)
-#endif
-#define STACK_LIMIT(ptr)     (((ptr) - 1) & ~(THREAD_SIZE - 1))
-
-#define UNW_REGISTER_INFO \
-	PTREGS_INFO(eax), \
-	PTREGS_INFO(ecx), \
-	PTREGS_INFO(edx), \
-	PTREGS_INFO(ebx), \
-	PTREGS_INFO(esp), \
-	PTREGS_INFO(ebp), \
-	PTREGS_INFO(esi), \
-	PTREGS_INFO(edi), \
-	PTREGS_INFO(eip)
-
-#define UNW_DEFAULT_RA(raItem, dataAlign) \
-	((raItem).where == Memory && \
-	 !((raItem).value * (dataAlign) + 4))
-
-static inline void arch_unw_init_frame_info(struct unwind_frame_info *info,
-                                            /*const*/ struct pt_regs *regs)
-{
-	if (user_mode_vm(regs))
-		info->regs = *regs;
-	else {
-		memcpy(&info->regs, regs, offsetof(struct pt_regs, esp));
-		info->regs.esp = (unsigned long)&regs->esp;
-		info->regs.xss = __KERNEL_DS;
-	}
-}
-
-static inline void arch_unw_init_blocked(struct unwind_frame_info *info)
-{
-	memset(&info->regs, 0, sizeof(info->regs));
-	info->regs.eip = info->task->thread.eip;
-	info->regs.xcs = __KERNEL_CS;
-	__get_user(info->regs.ebp, (long *)info->task->thread.esp);
-	info->regs.esp = info->task->thread.esp;
-	info->regs.xss = __KERNEL_DS;
-	info->regs.xds = __USER_DS;
-	info->regs.xes = __USER_DS;
-	info->regs.xgs = __KERNEL_PDA;
-}
-
-extern asmlinkage int arch_unwind_init_running(struct unwind_frame_info *,
-                                               asmlinkage int (*callback)(struct unwind_frame_info *,
-                                                                          void *arg),
-                                               void *arg);
-
-static inline int arch_unw_user_mode(/*const*/ struct unwind_frame_info *info)
-{
-	return user_mode_vm(&info->regs)
-	       || info->regs.eip < PAGE_OFFSET
-	       || (info->regs.eip >= __fix_to_virt(FIX_VDSO)
-	           && info->regs.eip < __fix_to_virt(FIX_VDSO) + PAGE_SIZE)
-	       || info->regs.esp < PAGE_OFFSET;
-}
-
-#else
-
 #define UNW_PC(frame) ((void)(frame), 0)
 #define UNW_SP(frame) ((void)(frame), 0)
 #define UNW_FP(frame) ((void)(frame), 0)
···
 {
 	return 0;
 }
-
-#endif
 
 #endif /* _ASM_I386_UNWIND_H */

include/asm-x86_64/unwind.h

···
 #ifndef _ASM_X86_64_UNWIND_H
 #define _ASM_X86_64_UNWIND_H
 
-/*
- * Copyright (C) 2002-2006 Novell, Inc.
- *	Jan Beulich <[e-mail]>
- * This code is released under version 2 of the GNU GPL.
- */
-
-#ifdef CONFIG_STACK_UNWIND
-
-#include <linux/sched.h>
-#include <asm/ptrace.h>
-#include <asm/uaccess.h>
-#include <asm/vsyscall.h>
-
-struct unwind_frame_info
-{
-	struct pt_regs regs;
-	struct task_struct *task;
-	unsigned call_frame:1;
-};
-
-#define UNW_PC(frame)        (frame)->regs.rip
-#define UNW_SP(frame)        (frame)->regs.rsp
-#ifdef CONFIG_FRAME_POINTER
-#define UNW_FP(frame)        (frame)->regs.rbp
-#define FRAME_RETADDR_OFFSET 8
-#define FRAME_LINK_OFFSET    0
-#define STACK_BOTTOM(tsk)    (((tsk)->thread.rsp0 - 1) & ~(THREAD_SIZE - 1))
-#define STACK_TOP(tsk)       ((tsk)->thread.rsp0)
-#endif
-/* Might need to account for the special exception and interrupt handling
-   stacks here, since normally
-	EXCEPTION_STACK_ORDER < THREAD_ORDER < IRQSTACK_ORDER,
-   but the construct is needed only for getting across the stack switch to
-   the interrupt stack - thus considering the IRQ stack itself is unnecessary,
-   and the overhead of comparing against all exception handling stacks seems
-   not desirable. */
-#define STACK_LIMIT(ptr)     (((ptr) - 1) & ~(THREAD_SIZE - 1))
-
-#define UNW_REGISTER_INFO \
-	PTREGS_INFO(rax), \
-	PTREGS_INFO(rdx), \
-	PTREGS_INFO(rcx), \
-	PTREGS_INFO(rbx), \
-	PTREGS_INFO(rsi), \
-	PTREGS_INFO(rdi), \
-	PTREGS_INFO(rbp), \
-	PTREGS_INFO(rsp), \
-	PTREGS_INFO(r8), \
-	PTREGS_INFO(r9), \
-	PTREGS_INFO(r10), \
-	PTREGS_INFO(r11), \
-	PTREGS_INFO(r12), \
-	PTREGS_INFO(r13), \
-	PTREGS_INFO(r14), \
-	PTREGS_INFO(r15), \
-	PTREGS_INFO(rip)
-
-#define UNW_DEFAULT_RA(raItem, dataAlign) \
-	((raItem).where == Memory && \
-	 !((raItem).value * (dataAlign) + 8))
-
-static inline void arch_unw_init_frame_info(struct unwind_frame_info *info,
-                                            /*const*/ struct pt_regs *regs)
-{
-	info->regs = *regs;
-}
-
-static inline void arch_unw_init_blocked(struct unwind_frame_info *info)
-{
-	extern const char thread_return[];
-
-	memset(&info->regs, 0, sizeof(info->regs));
-	info->regs.rip = (unsigned long)thread_return;
-	info->regs.cs = __KERNEL_CS;
-	__get_user(info->regs.rbp, (unsigned long *)info->task->thread.rsp);
-	info->regs.rsp = info->task->thread.rsp;
-	info->regs.ss = __KERNEL_DS;
-}
-
-extern int arch_unwind_init_running(struct unwind_frame_info *,
-                                    int (*callback)(struct unwind_frame_info *,
-                                                    void *arg),
-                                    void *arg);
-
-static inline int arch_unw_user_mode(const struct unwind_frame_info *info)
-{
-	return user_mode(&info->regs)
-	       || (long)info->regs.rip >= 0
-	       || (info->regs.rip >= VSYSCALL_START && info->regs.rip < VSYSCALL_END)
-	       || (long)info->regs.rsp >= 0;
-}
-
-#else
-
 #define UNW_PC(frame) ((void)(frame), 0UL)
 #define UNW_SP(frame) ((void)(frame), 0UL)
 
···
 {
 	return 0;
 }
-
-#endif
 
 #endif /* _ASM_X86_64_UNWIND_H */

include/linux/unwind.h

···
 
 struct module;
 
-#ifdef CONFIG_STACK_UNWIND
-
-#include <asm/unwind.h>
-
-#ifndef ARCH_UNWIND_SECTION_NAME
-#define ARCH_UNWIND_SECTION_NAME ".eh_frame"
-#endif
-
-/*
- * Initialize unwind support.
- */
-extern void unwind_init(void);
-extern void unwind_setup(void);
-
-#ifdef CONFIG_MODULES
-
-extern void *unwind_add_table(struct module *,
-                              const void *table_start,
-                              unsigned long table_size);
-
-extern void unwind_remove_table(void *handle, int init_only);
-
-#endif
-
-extern int unwind_init_frame_info(struct unwind_frame_info *,
-                                  struct task_struct *,
-                                  /*const*/ struct pt_regs *);
-
-/*
- * Prepare to unwind a blocked task.
- */
-extern int unwind_init_blocked(struct unwind_frame_info *,
-                               struct task_struct *);
-
-/*
- * Prepare to unwind the currently running thread.
- */
-extern int unwind_init_running(struct unwind_frame_info *,
-                               asmlinkage int (*callback)(struct unwind_frame_info *,
-                                                          void *arg),
-                               void *arg);
-
-/*
- * Unwind to previous to frame.  Returns 0 if successful, negative
- * number in case of an error.
- */
-extern int unwind(struct unwind_frame_info *);
-
-/*
- * Unwind until the return pointer is in user-land (or until an error
- * occurs).  Returns 0 if successful, negative number in case of
- * error.
- */
-extern int unwind_to_user(struct unwind_frame_info *);
-
-#else
-
 struct unwind_frame_info {};
 
 static inline void unwind_init(void) {}
···
 	return NULL;
 }
 
-#endif
-
 static inline void unwind_remove_table(void *handle, int init_only)
 {
 }
+
+#endif
 
 static inline int unwind_init_frame_info(struct unwind_frame_info *info,
                                          struct task_struct *tsk,
···
 {
 	return -ENOSYS;
 }
-
-#endif
 
 #endif /* _LINUX_UNWIND_H */

kernel/Makefile

···
 obj-$(CONFIG_UID16) += uid16.o
 obj-$(CONFIG_MODULES) += module.o
 obj-$(CONFIG_KALLSYMS) += kallsyms.o
-obj-$(CONFIG_STACK_UNWIND) += unwind.o
 obj-$(CONFIG_PM) += power/
 obj-$(CONFIG_BSD_PROCESS_ACCT) += acct.o
 obj-$(CONFIG_KEXEC) += kexec.o

kernel/unwind.c

···
-/*
- * Copyright (C) 2002-2006 Novell, Inc.
- *	Jan Beulich <[e-mail]>
- * This code is released under version 2 of the GNU GPL.
- *
- * A simple API for unwinding kernel stacks.  This is used for
- * debugging and error reporting purposes.  The kernel doesn't need
- * full-blown stack unwinding with all the bells and whistles, so there
- * is not much point in implementing the full Dwarf2 unwind API.
- */
-
-#include <linux/unwind.h>
-#include <linux/module.h>
-#include <linux/bootmem.h>
-#include <linux/sort.h>
-#include <linux/stop_machine.h>
-#include <linux/uaccess.h>
-#include <asm/sections.h>
-#include <asm/uaccess.h>
-#include <asm/unaligned.h>
-
-extern const char __start_unwind[], __end_unwind[];
-extern const u8 __start_unwind_hdr[], __end_unwind_hdr[];
-
-#define MAX_STACK_DEPTH 8
-
-#define EXTRA_INFO(f) { \
-		BUILD_BUG_ON_ZERO(offsetof(struct unwind_frame_info, f) \
-		                  % FIELD_SIZEOF(struct unwind_frame_info, f)) \
-		+ offsetof(struct unwind_frame_info, f) \
-		  / FIELD_SIZEOF(struct unwind_frame_info, f), \
-		FIELD_SIZEOF(struct unwind_frame_info, f) \
-	}
-#define PTREGS_INFO(f) EXTRA_INFO(regs.f)
-
-static const struct {
-	unsigned offs:BITS_PER_LONG / 2;
-	unsigned width:BITS_PER_LONG / 2;
-} reg_info[] = {
-	UNW_REGISTER_INFO
-};
-
-#undef PTREGS_INFO
-#undef EXTRA_INFO
-
-#ifndef REG_INVALID
-#define REG_INVALID(r) (reg_info[r].width == 0)
-#endif
-
-#define DW_CFA_nop                          0x00
-#define DW_CFA_set_loc                      0x01
-#define DW_CFA_advance_loc1                 0x02
-#define DW_CFA_advance_loc2                 0x03
-#define DW_CFA_advance_loc4                 0x04
-#define DW_CFA_offset_extended              0x05
-#define DW_CFA_restore_extended             0x06
-#define DW_CFA_undefined                    0x07
-#define DW_CFA_same_value                   0x08
-#define DW_CFA_register                     0x09
-#define DW_CFA_remember_state               0x0a
-#define DW_CFA_restore_state                0x0b
-#define DW_CFA_def_cfa                      0x0c
-#define DW_CFA_def_cfa_register             0x0d
-#define DW_CFA_def_cfa_offset               0x0e
-#define DW_CFA_def_cfa_expression           0x0f
-#define DW_CFA_expression                   0x10
-#define DW_CFA_offset_extended_sf           0x11
-#define DW_CFA_def_cfa_sf                   0x12
-#define DW_CFA_def_cfa_offset_sf            0x13
-#define DW_CFA_val_offset                   0x14
-#define DW_CFA_val_offset_sf                0x15
-#define DW_CFA_val_expression               0x16
-#define DW_CFA_lo_user                      0x1c
-#define DW_CFA_GNU_window_save              0x2d
-#define DW_CFA_GNU_args_size                0x2e
-#define DW_CFA_GNU_negative_offset_extended 0x2f
-#define DW_CFA_hi_user                      0x3f
-
-#define DW_EH_PE_FORM     0x07
-#define DW_EH_PE_native   0x00
-#define DW_EH_PE_leb128   0x01
-#define DW_EH_PE_data2    0x02
-#define DW_EH_PE_data4    0x03
-#define DW_EH_PE_data8    0x04
-#define DW_EH_PE_signed   0x08
-#define DW_EH_PE_ADJUST   0x70
-#define DW_EH_PE_abs      0x00
-#define DW_EH_PE_pcrel    0x10
-#define DW_EH_PE_textrel  0x20
-#define DW_EH_PE_datarel  0x30
-#define DW_EH_PE_funcrel  0x40
-#define DW_EH_PE_aligned  0x50
-#define DW_EH_PE_indirect 0x80
-#define DW_EH_PE_omit     0xff
-
-typedef unsigned long uleb128_t;
-typedef   signed long sleb128_t;
-#define sleb128abs __builtin_labs
-
-static struct unwind_table {
-	struct {
-		unsigned long pc;
-		unsigned long range;
-	} core, init;
-	const void *address;
-	unsigned long size;
-	const unsigned char *header;
-	unsigned long hdrsz;
-	struct unwind_table *link;
-	const char *name;
-} root_table;
-
-struct unwind_item {
-	enum item_location {
-		Nowhere,
-		Memory,
-		Register,
-		Value
-	} where;
-	uleb128_t value;
-};
-
-struct unwind_state {
-	uleb128_t loc, org;
-	const u8 *cieStart, *cieEnd;
-	uleb128_t codeAlign;
-	sleb128_t dataAlign;
-	struct cfa {
-		uleb128_t reg, offs;
-	} cfa;
-	struct unwind_item regs[ARRAY_SIZE(reg_info)];
-	unsigned stackDepth:8;
-	unsigned version:8;
-	const u8 *label;
-	const u8 *stack[MAX_STACK_DEPTH];
-};
-
-static const struct cfa badCFA = { ARRAY_SIZE(reg_info), 1 };
-
-static unsigned unwind_debug;
-static int __init unwind_debug_setup(char *s)
-{
-	unwind_debug = simple_strtoul(s, NULL, 0);
-	return 1;
-}
-__setup("unwind_debug=", unwind_debug_setup);
-#define dprintk(lvl, fmt, args...) \
-	((void)(lvl > unwind_debug \
-	 || printk(KERN_DEBUG "unwind: " fmt "\n", ##args)))
-
-static struct unwind_table *find_table(unsigned long pc)
-{
-	struct unwind_table *table;
-
-	for (table = &root_table; table; table = table->link)
-		if ((pc >= table->core.pc
-		     && pc < table->core.pc + table->core.range)
-		    || (pc >= table->init.pc
-		        && pc < table->init.pc + table->init.range))
-			break;
-
-	return table;
-}
-
-static unsigned long read_pointer(const u8 **pLoc,
-                                  const void *end,
-                                  signed ptrType,
-                                  unsigned long text_base,
-                                  unsigned long data_base);
-
-static void init_unwind_table(struct unwind_table *table,
-                              const char *name,
-                              const void *core_start,
-                              unsigned long core_size,
-                              const void *init_start,
-                              unsigned long init_size,
-                              const void *table_start,
-                              unsigned long table_size,
-                              const u8 *header_start,
-                              unsigned long header_size)
-{
-	const u8 *ptr = header_start + 4;
-	const u8 *end = header_start + header_size;
-
-	table->core.pc = (unsigned long)core_start;
-	table->core.range = core_size;
-	table->init.pc = (unsigned long)init_start;
-	table->init.range = init_size;
-	table->address = table_start;
-	table->size = table_size;
-	/* See if the linker provided table looks valid. */
-	if (header_size <= 4
-	    || header_start[0] != 1
-	    || (void *)read_pointer(&ptr, end, header_start[1], 0, 0)
-	       != table_start
-	    || !read_pointer(&ptr, end, header_start[2], 0, 0)
-	    || !read_pointer(&ptr, end, header_start[3], 0,
-	                     (unsigned long)header_start)
-	    || !read_pointer(&ptr, end, header_start[3], 0,
-	                     (unsigned long)header_start))
-		header_start = NULL;
-	table->hdrsz = header_size;
-	smp_wmb();
-	table->header = header_start;
-	table->link = NULL;
-	table->name = name;
-}
-
-void __init unwind_init(void)
-{
-	init_unwind_table(&root_table, "kernel",
-	                  _text, _end - _text,
-	                  NULL, 0,
-	                  __start_unwind, __end_unwind - __start_unwind,
-	                  __start_unwind_hdr, __end_unwind_hdr - __start_unwind_hdr);
-}
-
-static const u32 bad_cie, not_fde;
-static const u32 *cie_for_fde(const u32 *fde, const struct unwind_table *);
-static signed fde_pointer_type(const u32 *cie);
-
-struct eh_frame_hdr_table_entry {
-	unsigned long start, fde;
-};
-
-static int cmp_eh_frame_hdr_table_entries(const void *p1, const void *p2)
-{
-	const struct eh_frame_hdr_table_entry *e1 = p1;
-	const struct eh_frame_hdr_table_entry *e2 = p2;
-
-	return (e1->start > e2->start) - (e1->start < e2->start);
-}
-
-static void swap_eh_frame_hdr_table_entries(void *p1, void *p2, int size)
-{
-	struct eh_frame_hdr_table_entry *e1 = p1;
-	struct eh_frame_hdr_table_entry *e2 = p2;
-	unsigned long v;
-
-	v = e1->start;
-	e1->start = e2->start;
-	e2->start = v;
-	v = e1->fde;
-	e1->fde = e2->fde;
-	e2->fde = v;
-}
-
-static void __init setup_unwind_table(struct unwind_table *table,
-					void *(*alloc)(unsigned long))
-{
-	const u8 *ptr;
-	unsigned long tableSize = table->size, hdrSize;
-	unsigned n;
-	const u32 *fde;
-	struct {
-		u8 version;
-		u8 eh_frame_ptr_enc;
-		u8 fde_count_enc;
-		u8 table_enc;
-		unsigned long eh_frame_ptr;
-		unsigned int fde_count;
-		struct eh_frame_hdr_table_entry table[];
-	} __attribute__((__packed__)) *header;
-
-	if (table->header)
-		return;
-
-	if (table->hdrsz)
-		printk(KERN_WARNING ".eh_frame_hdr for '%s' present but unusable\n",
-		       table->name);
-
-	if (tableSize & (sizeof(*fde) - 1))
-		return;
-
-	for (fde = table->address, n = 0;
-	     tableSize > sizeof(*fde) && tableSize - sizeof(*fde) >= *fde;
-	     tableSize -= sizeof(*fde) + *fde, fde += 1 + *fde / sizeof(*fde)) {
-		const u32 *cie = cie_for_fde(fde, table);
-		signed ptrType;
-
-		if (cie == &not_fde)
-			continue;
-		if (cie == NULL
-		    || cie == &bad_cie
-		    || (ptrType = fde_pointer_type(cie)) < 0)
-			return;
-		ptr = (const u8 *)(fde + 2);
-		if (!read_pointer(&ptr,
-		                  (const u8 *)(fde + 1) + *fde,
-		                  ptrType, 0, 0))
-			return;
-		++n;
-	}
-
-	if (tableSize || !n)
-		return;
-
-	hdrSize = 4 + sizeof(unsigned long) + sizeof(unsigned int)
-	        + 2 * n * sizeof(unsigned long);
-	dprintk(2, "Binary lookup table size for %s: %lu bytes", table->name, hdrSize);
-	header = alloc(hdrSize);
-	if (!header)
-		return;
-	header->version          = 1;
-	header->eh_frame_ptr_enc = DW_EH_PE_abs|DW_EH_PE_native;
-	header->fde_count_enc    = DW_EH_PE_abs|DW_EH_PE_data4;
-	header->table_enc        = DW_EH_PE_abs|DW_EH_PE_native;
-	put_unaligned((unsigned long)table->address, &header->eh_frame_ptr);
-	BUILD_BUG_ON(offsetof(typeof(*header), fde_count)
-	             % __alignof(typeof(header->fde_count)));
-	header->fde_count        = n;
-
-	BUILD_BUG_ON(offsetof(typeof(*header), table)
-	             % __alignof(typeof(*header->table)));
-	for (fde = table->address, tableSize = table->size, n = 0;
-	     tableSize;
-	     tableSize -= sizeof(*fde) + *fde, fde += 1 + *fde / sizeof(*fde)) {
-		const u32 *cie = fde + 1 - fde[1] / sizeof(*fde);
-
-		if (!fde[1])
-			continue; /* this is a CIE */
-		ptr = (const u8 *)(fde + 2);
-		header->table[n].start = read_pointer(&ptr,
-		                                      (const u8 *)(fde + 1) + *fde,
-		                                      fde_pointer_type(cie), 0, 0);
-		header->table[n].fde = (unsigned long)fde;
-		++n;
-	}
-	WARN_ON(n != header->fde_count);
-
-	sort(header->table,
-	     n,
-	     sizeof(*header->table),
-	     cmp_eh_frame_hdr_table_entries,
-	     swap_eh_frame_hdr_table_entries);
-
-	table->hdrsz = hdrSize;
-	smp_wmb();
-	table->header = (const void *)header;
-}
-
-static void *__init balloc(unsigned long sz)
-{
-	return __alloc_bootmem_nopanic(sz,
-	                               sizeof(unsigned int),
-	                               __pa(MAX_DMA_ADDRESS));
-}
-
-void __init unwind_setup(void)
-{
-	setup_unwind_table(&root_table, balloc);
-}
-
-#ifdef CONFIG_MODULES
-
-static struct unwind_table *last_table;
-
-/* Must be called with module_mutex held. */
-void *unwind_add_table(struct module *module,
-                       const void *table_start,
-                       unsigned long table_size)
-{
-	struct unwind_table *table;
-
-	if (table_size <= 0)
-		return NULL;
-
-	table = kmalloc(sizeof(*table), GFP_KERNEL);
-	if (!table)
-		return NULL;
-
-	init_unwind_table(table, module->name,
-	                  module->module_core, module->core_size,
-	                  module->module_init, module->init_size,
-	                  table_start, table_size,
-	                  NULL, 0);
-
-	if (last_table)
-		last_table->link = table;
-	else
-		root_table.link = table;
-	last_table = table;
-
-	return table;
-}
-
-struct unlink_table_info
-{
-	struct unwind_table *table;
-	int init_only;
-};
-
-static int unlink_table(void *arg)
-{
-	struct unlink_table_info *info = arg;
-	struct unwind_table *table = info->table, *prev;
-
-	for (prev = &root_table; prev->link && prev->link != table; prev = prev->link)
-		;
-
-	if (prev->link) {
-		if (info->init_only) {
-			table->init.pc = 0;
-			table->init.range = 0;
-			info->table = NULL;
-		} else {
-			prev->link = table->link;
-			if (!prev->link)
-				last_table = prev;
-		}
-	} else
-		info->table = NULL;
-
-	return 0;
-}
-
-/* Must be called with module_mutex held. */
-void unwind_remove_table(void *handle, int init_only)
-{
-	struct unwind_table *table = handle;
-	struct unlink_table_info info;
-
-	if (!table || table == &root_table)
-		return;
-
-	if (init_only && table == last_table) {
-		table->init.pc = 0;
-		table->init.range = 0;
-		return;
-	}
-
-	info.table = table;
-	info.init_only = init_only;
-	stop_machine_run(unlink_table, &info, NR_CPUS);
-
-	if (info.table)
-		kfree(table);
-}
-
-#endif /* CONFIG_MODULES */
-
-static uleb128_t get_uleb128(const u8 **pcur, const u8 *end)
-{
-	const u8 *cur = *pcur;
-	uleb128_t value;
-	unsigned shift;
-
-	for (shift = 0, value = 0; cur < end; shift += 7) {
-		if (shift + 7 > 8 * sizeof(value)
-		    && (*cur & 0x7fU) >= (1U << (8 * sizeof(value) - shift))) {
-			cur = end + 1;
-			break;
-		}
-		value |= (uleb128_t)(*cur & 0x7f) << shift;
-		if (!(*cur++ & 0x80))
-			break;
-	}
-	*pcur = cur;
-
-	return value;
-}
-
-static sleb128_t get_sleb128(const u8 **pcur, const u8 *end)
-{
-	const u8 *cur = *pcur;
-	sleb128_t value;
-	unsigned shift;
-
-	for (shift = 0, value = 0; cur < end; shift += 7) {
-		if (shift + 7 > 8 * sizeof(value)
-		    && (*cur & 0x7fU) >= (1U << (8 * sizeof(value) - shift))) {
-			cur = end + 1;
-			break;
-		}
-		value |= (sleb128_t)(*cur & 0x7f) << shift;
-		if (!(*cur & 0x80)) {
-			value |= -(*cur++ & 0x40) << shift;
-			break;
-		}
-	}
-	*pcur = cur;
-
-	return value;
-}
-
-static const u32 *cie_for_fde(const u32 *fde, const struct unwind_table *table)
-{
-	const u32 *cie;
-
-	if (!*fde || (*fde & (sizeof(*fde) - 1)))
-		return &bad_cie;
-	if (!fde[1])
-		return &not_fde; /* this is a CIE */
-	if ((fde[1] & (sizeof(*fde) - 1))
-	    || fde[1] > (unsigned long)(fde + 1) - (unsigned long)table->address)
-		return NULL; /* this is not a valid FDE */
-	cie = fde + 1 - fde[1] / sizeof(*fde);
-	if (*cie <= sizeof(*cie) + 4
-	    || *cie >= fde[1] - sizeof(*fde)
-	    || (*cie & (sizeof(*cie) - 1))
-	    || cie[1])
-		return NULL; /* this is not a (valid) CIE */
-	return cie;
-}
-
-static unsigned long read_pointer(const u8 **pLoc,
-                                  const void *end,
-                                  signed ptrType,
-                                  unsigned long text_base,
-                                  unsigned long data_base)
-{
-	unsigned long value = 0;
-	union {
-		const u8 *p8;
-		const u16 *p16u;
-		const s16 *p16s;
-		const u32 *p32u;
-		const s32 *p32s;
-		const unsigned long *pul;
-	} ptr;
-
-	if (ptrType < 0 || ptrType == DW_EH_PE_omit) {
-		dprintk(1, "Invalid pointer encoding %02X (%p,%p).", ptrType, *pLoc, end);
-		return 0;
-	}
-	ptr.p8 = *pLoc;
-	switch(ptrType & DW_EH_PE_FORM) {
-	case DW_EH_PE_data2:
-		if (end < (const void *)(ptr.p16u + 1)) {
-			dprintk(1, "Data16 overrun (%p,%p).", ptr.p8, end);
-			return 0;
-		}
-		if(ptrType & DW_EH_PE_signed)
-			value = get_unaligned(ptr.p16s++);
-		else
-			value = get_unaligned(ptr.p16u++);
-		break;
-	case DW_EH_PE_data4:
-#ifdef CONFIG_64BIT
-		if (end < (const void *)(ptr.p32u + 1)) {
-			dprintk(1, "Data32 overrun (%p,%p).", ptr.p8, end);
-			return 0;
-		}
-		if(ptrType & DW_EH_PE_signed)
-			value = get_unaligned(ptr.p32s++);
-		else
-			value = get_unaligned(ptr.p32u++);
-		break;
-	case DW_EH_PE_data8:
-		BUILD_BUG_ON(sizeof(u64) != sizeof(value));
-#else
-		BUILD_BUG_ON(sizeof(u32) != sizeof(value));
-#endif
-	case DW_EH_PE_native:
-		if (end < (const void *)(ptr.pul + 1)) {
-			dprintk(1, "DataUL overrun (%p,%p).", ptr.p8, end);
-			return 0;
-		}
-		value = get_unaligned(ptr.pul++);
-		break;
-	case DW_EH_PE_leb128:
-		BUILD_BUG_ON(sizeof(uleb128_t) > sizeof(value));
-		value = ptrType & DW_EH_PE_signed
-		        ? get_sleb128(&ptr.p8, end)
-		        : get_uleb128(&ptr.p8, end);
-		if ((const void *)ptr.p8 > end) {
-			dprintk(1, "DataLEB overrun (%p,%p).", ptr.p8, end);
-			return 0;
-		}
-		break;
-	default:
-		dprintk(2, "Cannot decode pointer type %02X (%p,%p).",
-		        ptrType, ptr.p8, end);
-		return 0;
-	}
-	switch(ptrType & DW_EH_PE_ADJUST) {
-	case DW_EH_PE_abs:
-		break;
-	case DW_EH_PE_pcrel:
-		value += (unsigned long)*pLoc;
-		break;
-	case DW_EH_PE_textrel:
-		if (likely(text_base)) {
-			value += text_base;
-			break;
-		}
-		dprintk(2, "Text-relative encoding %02X (%p,%p), but zero text base.",
-		        ptrType, *pLoc, end);
-		return 0;
-	case DW_EH_PE_datarel:
-		if (likely(data_base)) {
-			value += data_base;
-			break;
-		}
-		dprintk(2, "Data-relative encoding %02X (%p,%p), but zero data base.",
-		        ptrType, *pLoc, end);
-		return 0;
-	default:
-		dprintk(2, "Cannot adjust pointer type %02X (%p,%p).",
-		        ptrType, *pLoc, end);
-		return 0;
-	}
-	if ((ptrType & DW_EH_PE_indirect)
-	    && probe_kernel_address((unsigned long *)value, value)) {
-		dprintk(1, "Cannot read indirect value %lx (%p,%p).",
-		        value, *pLoc, end);
-		return 0;
-	}
-	*pLoc = ptr.p8;
-
-	return value;
-}
-
-static signed fde_pointer_type(const u32 *cie)
-{
-	const u8 *ptr = (const u8 *)(cie + 2);
-	unsigned version = *ptr;
-
-	if (version != 1)
-		return -1; /* unsupported */
-	if (*++ptr) {
-		const char *aug;
-		const u8 *end = (const u8 *)(cie + 1) + *cie;
-		uleb128_t len;
-
-		/* check if augmentation size is first (and thus present) */
-		if (*ptr != 'z')
-			return -1;
-		/* check if augmentation string is nul-terminated */
-		if ((ptr = memchr(aug = (const void *)ptr, 0, end - ptr)) == NULL)
-			return -1;
-		++ptr; /* skip terminator */
-		get_uleb128(&ptr, end); /* skip code alignment */
-		get_sleb128(&ptr, end); /* skip data alignment */
-		/* skip return address column */
-		version <= 1 ? (void)++ptr : (void)get_uleb128(&ptr, end);
-		len = get_uleb128(&ptr, end); /* augmentation length */
-		if (ptr + len < ptr || ptr + len > end)
-			return -1;
-		end = ptr + len;
-		while (*++aug) {
-			if (ptr >= end)
-				return -1;
-			switch(*aug) {
-			case 'L':
-				++ptr;
-				break;
-			case 'P': {
-					signed ptrType = *ptr++;
-
-					if (!read_pointer(&ptr, end, ptrType, 0, 0)
-					    || ptr > end)
-						return -1;
-				}
-				break;
-			case 'R':
-				return *ptr;
-			default:
-				return -1;
-			}
-		}
-	}
-	return DW_EH_PE_native|DW_EH_PE_abs;
-}
-
-static int advance_loc(unsigned long delta, struct unwind_state *state)
-{
-	state->loc += delta * state->codeAlign;
-
-	return delta > 0;
-}
-
-static void set_rule(uleb128_t reg,
-                     enum item_location where,
-                     uleb128_t value,
-                     struct unwind_state *state)
-{
-	if (reg < ARRAY_SIZE(state->regs)) {
-		state->regs[reg].where = where;
-		state->regs[reg].value = value;
-	}
-}
-
-static int processCFI(const u8 *start,
-                      const u8 *end,
-                      unsigned long targetLoc,
-                      signed ptrType,
-                      struct unwind_state *state)
-{
-	union {
-		const u8 *p8;
-		const u16 *p16;
-		const u32 *p32;
-	} ptr;
-	int result = 1;
-
-	if (start != state->cieStart) {
-		state->loc = state->org;
-		result = processCFI(state->cieStart, state->cieEnd, 0, ptrType, state);
-		if (targetLoc == 0 && state->label == NULL)
-			return result;
-	}
-	for (ptr.p8 = start; result && ptr.p8 < end; ) {
-		switch(*ptr.p8 >> 6) {
-			uleb128_t value;
-
-		case 0:
-			switch(*ptr.p8++) {
-			case DW_CFA_nop:
-				break;
-			case DW_CFA_set_loc:
-				state->loc = read_pointer(&ptr.p8, end, ptrType, 0, 0);
-				if (state->loc == 0)
-					result = 0;
-				break;
-			case DW_CFA_advance_loc1:
-				result = ptr.p8 < end && advance_loc(*ptr.p8++, state);
-				break;
-			case DW_CFA_advance_loc2:
-				result = ptr.p8 <= end + 2
-				         && advance_loc(*ptr.p16++, state);
-				break;
-			case DW_CFA_advance_loc4:
-				result = ptr.p8 <= end + 4
-				         && advance_loc(*ptr.p32++, state);
-				break;
-			case DW_CFA_offset_extended:
-				value = get_uleb128(&ptr.p8, end);
-				set_rule(value, Memory, get_uleb128(&ptr.p8, end), state);
-				break;
-			case DW_CFA_val_offset:
-				value = get_uleb128(&ptr.p8, end);
-				set_rule(value, Value, get_uleb128(&ptr.p8, end), state);
-				break;
-			case DW_CFA_offset_extended_sf:
-				value = get_uleb128(&ptr.p8, end);
-				set_rule(value, Memory, get_sleb128(&ptr.p8, end), state);
-				break;
-			case DW_CFA_val_offset_sf:
-				value = get_uleb128(&ptr.p8, end);
-				set_rule(value, Value, get_sleb128(&ptr.p8, end), state);
-				break;
-			case DW_CFA_restore_extended:
-			case DW_CFA_undefined:
-			case DW_CFA_same_value:
-				set_rule(get_uleb128(&ptr.p8, end), Nowhere, 0, state);
-				break;
-			case DW_CFA_register:
-				value = get_uleb128(&ptr.p8, end);
-				set_rule(value,
-				         Register,
-				         get_uleb128(&ptr.p8, end), state);
-				break;
-			case DW_CFA_remember_state:
-				if (ptr.p8 == state->label) {
-					state->label = NULL;
-					return 1;
-				}
-				if (state->stackDepth >= MAX_STACK_DEPTH) {
-					dprintk(1, "State stack overflow (%p,%p).", ptr.p8, end);
-					return 0;
-				}
-				state->stack[state->stackDepth++] = ptr.p8;
-				break;
-			case DW_CFA_restore_state:
-				if (state->stackDepth) {
-					const uleb128_t loc = state->loc;
-					const u8 *label = state->label;
-
-					state->label = state->stack[state->stackDepth - 1];
-					memcpy(&state->cfa, &badCFA, sizeof(state->cfa));
-					memset(state->regs, 0, sizeof(state->regs));
-					state->stackDepth = 0;
-					result = processCFI(start, end, 0, ptrType, state);
-					state->loc = loc;
-					state->label = label;
-				} else {
-					dprintk(1, "State stack underflow (%p,%p).", ptr.p8, end);
-					return 0;
-				}
-				break;
-			case DW_CFA_def_cfa:
-				state->cfa.reg = get_uleb128(&ptr.p8, end);
-				/*nobreak*/
-			case DW_CFA_def_cfa_offset:
-				state->cfa.offs = get_uleb128(&ptr.p8, end);
-				break;
-			case DW_CFA_def_cfa_sf:
-				state->cfa.reg = get_uleb128(&ptr.p8, end);
-				/*nobreak*/
-			case DW_CFA_def_cfa_offset_sf:
-				state->cfa.offs = get_sleb128(&ptr.p8, end)
-				                  * state->dataAlign;
-				break;
-			case DW_CFA_def_cfa_register:
-				state->cfa.reg = get_uleb128(&ptr.p8, end);
-				break;
-			/*todo case DW_CFA_def_cfa_expression: */
-			/*todo case DW_CFA_expression: */
-			/*todo case DW_CFA_val_expression: */
-			case DW_CFA_GNU_args_size:
-				get_uleb128(&ptr.p8, end);
-				break;
-			case DW_CFA_GNU_negative_offset_extended:
-				value = get_uleb128(&ptr.p8, end);
-				set_rule(value,
-				         Memory,
-				         (uleb128_t)0 - get_uleb128(&ptr.p8, end), state);
-				break;
-			case DW_CFA_GNU_window_save:
-			default:
-				dprintk(1, "Unrecognized CFI op %02X (%p,%p).", ptr.p8[-1], ptr.p8 - 1, end);
-				result = 0;
-				break;
-			}
-			break;
-		case 1:
-			result = advance_loc(*ptr.p8++ & 0x3f, state);
-			break;
-		case 2:
-			value = *ptr.p8++ & 0x3f;
-			set_rule(value, Memory, get_uleb128(&ptr.p8, end), state);
-			break;
-		case 3:
-			set_rule(*ptr.p8++ & 0x3f, Nowhere, 0, state);
-			break;
-		}
-		if (ptr.p8 > end) {
-			dprintk(1, "Data overrun (%p,%p).", ptr.p8, end);
-			result = 0;
-		}
-		if (result && targetLoc != 0 && targetLoc < state->loc)
-			return 1;
-	}
-
-	if (result && ptr.p8 < end)
-		dprintk(1, "Data underrun (%p,%p).", ptr.p8, end);
-
-	return result
-	   && ptr.p8 == end
-	   && (targetLoc == 0
-	    || (/*todo While in theory this should apply, gcc in practice omits
-	          everything past the function prolog, and hence the location
-	          never reaches the end of the function.
-	        targetLoc < state->loc &&*/ state->label == NULL));
-}
-
-/* Unwind to previous to frame.  Returns 0 if successful, negative
- * number in case of an error. */
-int unwind(struct unwind_frame_info *frame)
-{
-#define FRAME_REG(r, t) (((t *)frame)[reg_info[r].offs])
-	const u32 *fde = NULL, *cie = NULL;
-	const u8 *ptr = NULL, *end = NULL;
-	unsigned long pc = UNW_PC(frame) - frame->call_frame, sp;
-	unsigned long startLoc = 0, endLoc = 0, cfa;
-	unsigned i;
-	signed ptrType = -1;
-	uleb128_t retAddrReg = 0;
-	const struct unwind_table *table;
-	struct unwind_state state;
-
-	if (UNW_PC(frame) == 0)
-		return -EINVAL;
-	if ((table = find_table(pc)) != NULL
-	    && !(table->size & (sizeof(*fde) - 1))) {
-		const u8 *hdr = table->header;
-		unsigned long tableSize;
-
-		smp_rmb();
-		if (hdr && hdr[0] == 1) {
-			switch(hdr[3] & DW_EH_PE_FORM) {
-			case DW_EH_PE_native: tableSize = sizeof(unsigned long); break;
-			case DW_EH_PE_data2: tableSize = 2; break;
-			case DW_EH_PE_data4: tableSize = 4; break;
-			case DW_EH_PE_data8: tableSize = 8; break;
-			default: tableSize = 0; break;
-			}
-			ptr = hdr + 4;
-			end = hdr + table->hdrsz;
-			if (tableSize
-			    && read_pointer(&ptr, end, hdr[1], 0, 0)
-			       == (unsigned long)table->address
-			    && (i = read_pointer(&ptr, end, hdr[2], 0, 0)) > 0
-			    && i == (end - ptr) / (2 * tableSize)
-			    && !((end - ptr) % (2 * tableSize))) {
-				do {
-					const u8 *cur = ptr + (i / 2) * (2 * tableSize);
-
-					startLoc = read_pointer(&cur,
-					                        cur + tableSize,
-					                        hdr[3], 0,
-					                        (unsigned long)hdr);
-					if (pc < startLoc)
-						i /= 2;
-					else {
-						ptr = cur - tableSize;
-						i = (i + 1) / 2;
-					}
-				} while (startLoc && i > 1);
-				if (i == 1
-				    && (startLoc = read_pointer(&ptr,
-				                                ptr + tableSize,
-				                                hdr[3], 0,
-				                                (unsigned long)hdr)) != 0
-				    && pc >= startLoc)
-					fde = (void *)read_pointer(&ptr,
-					                           ptr + tableSize,
-					                           hdr[3], 0,
-					                           (unsigned long)hdr);
-			}
-		}
-		if(hdr && !fde)
-			dprintk(3, "Binary lookup for %lx failed.", pc);
-
-		if (fde != NULL) {
-			cie = cie_for_fde(fde, table);
-			ptr = (const u8 *)(fde + 2);
-			if(cie != NULL
-			   && cie != &bad_cie
-			   && cie != &not_fde
-			   && (ptrType = fde_pointer_type(cie)) >= 0
-			   && read_pointer(&ptr,
-			                   (const u8 *)(fde + 1) + *fde,
-			                   ptrType, 0, 0) == startLoc) {
-				if (!(ptrType & DW_EH_PE_indirect))
-					ptrType &= DW_EH_PE_FORM|DW_EH_PE_signed;
-				endLoc = startLoc
-				         + read_pointer(&ptr,
-				                        (const u8 *)(fde + 1) + *fde,
-				                        ptrType, 0, 0);
-				if(pc >= endLoc)
-					fde = NULL;
-			} else
-				fde = NULL;
-			if(!fde)
-				dprintk(1, "Binary lookup result for %lx discarded.", pc);
-		}
-		if (fde == NULL) {
-			for (fde = table->address, tableSize = table->size;
-			     cie = NULL, tableSize > sizeof(*fde)
-			     && tableSize - sizeof(*fde) >= *fde;
-			     tableSize -= sizeof(*fde) + *fde,
-			     fde += 1 + *fde / sizeof(*fde)) {
-				cie = cie_for_fde(fde, table);
-				if (cie == &bad_cie) {
-					cie = NULL;
-					break;
-				}
-				if (cie == NULL
-				    || cie == &not_fde
-				    || (ptrType = fde_pointer_type(cie)) < 0)
-					continue;
-				ptr = (const u8 *)(fde + 2);
-				startLoc = read_pointer(&ptr,
-				                        (const u8 *)(fde + 1) + *fde,
-				                        ptrType, 0, 0);
-				if (!startLoc)
-					continue;
-				if (!(ptrType & DW_EH_PE_indirect))
-					ptrType &= DW_EH_PE_FORM|DW_EH_PE_signed;
-				endLoc = startLoc
-				         + read_pointer(&ptr,
-				                        (const u8 *)(fde + 1) + *fde,
-				                        ptrType, 0, 0);
-				if (pc >= startLoc && pc < endLoc)
-					break;
-			}
-			if(!fde)
-				dprintk(3, "Linear lookup for %lx failed.", pc);
-		}
-	}
-	if (cie != NULL) {
-		memset(&state, 0, sizeof(state));
-		state.cieEnd = ptr; /* keep here temporarily */
-		ptr = (const u8 *)(cie + 2);
-		end = (const u8 *)(cie + 1) + *cie;
-		frame->call_frame = 1;
-		if ((state.version = *ptr) != 1)
-			cie = NULL; /* unsupported version */
-		else if (*++ptr) {
-			/* check if augmentation size is first (and thus present) */
-			if (*ptr == 'z') {
-				while (++ptr < end && *ptr) {
-					switch(*ptr) {
-					/* check for ignorable (or already handled)
-					 * nul-terminated augmentation string */
-					case 'L':
-					case 'P':
-					case 'R':
-						continue;
-					case 'S':
-						frame->call_frame = 0;
-						continue;
-					default:
-						break;
-					}
-					break;
-				}
-			}
-			if (ptr >= end || *ptr)
-				cie = NULL;
-		}
-		if(!cie)
-			dprintk(1, "CIE unusable (%p,%p).", ptr, end);
-		++ptr;
-	}
-	if (cie != NULL) {
-		/* get code aligment factor */
-		state.codeAlign = get_uleb128(&ptr, end);
-		/* get data aligment factor */
-		state.dataAlign = get_sleb128(&ptr, end);
-		if (state.codeAlign == 0 || state.dataAlign == 0 || ptr >= end)
-			cie = NULL;
-		else if (UNW_PC(frame) % state.codeAlign
-		         || UNW_SP(frame) % sleb128abs(state.dataAlign)) {
-			dprintk(1, "Input pointer(s) misaligned (%lx,%lx).",
-			        UNW_PC(frame), UNW_SP(frame));
-			return -EPERM;
-		} else {
-			retAddrReg = state.version <= 1 ? *ptr++ : get_uleb128(&ptr, end);
-			/* skip augmentation */
-			if (((const char *)(cie + 2))[1] == 'z') {
-				uleb128_t augSize = get_uleb128(&ptr, end);
-
-				ptr += augSize;
-			}
-			if (ptr > end
-			   || retAddrReg >= ARRAY_SIZE(reg_info)
-			   || REG_INVALID(retAddrReg)
-			   || reg_info[retAddrReg].width != sizeof(unsigned long))
-				cie = NULL;
-		}
-		if(!cie)
-			dprintk(1, "CIE validation failed (%p,%p).", ptr, end);
-	}
-	if (cie != NULL) {
-		state.cieStart = ptr;
-		ptr = state.cieEnd;
-		state.cieEnd = end;
-		end = (const u8 *)(fde + 1) + *fde;
-		/* skip augmentation */
-		if (((const char *)(cie + 2))[1] == 'z') {
-			uleb128_t augSize = get_uleb128(&ptr, end);
-
-			if ((ptr += augSize) > end)
-				fde = NULL;
-		}
-		if(!fde)
-			dprintk(1, "FDE validation failed (%p,%p).", ptr, end);
-	}
-	if (cie == NULL || fde == NULL) {
-#ifdef CONFIG_FRAME_POINTER
-		unsigned long top, bottom;
-
-		if ((UNW_SP(frame) | UNW_FP(frame)) % sizeof(unsigned long))
-			return -EPERM;
-		top = STACK_TOP(frame->task);
-		bottom = STACK_BOTTOM(frame->task);
-# if FRAME_RETADDR_OFFSET < 0
-		if (UNW_SP(frame) < top
-		    && UNW_FP(frame) <= UNW_SP(frame)
-		    && bottom < UNW_FP(frame)
-# else
-		if (UNW_SP(frame) > top
-		    && UNW_FP(frame) >= UNW_SP(frame)
-		    && bottom > UNW_FP(frame)
-# endif
-		   && !((UNW_SP(frame) | UNW_FP(frame))
-		        & (sizeof(unsigned long) - 1))) {
-			unsigned long link;
-
-			if (!probe_kernel_address(
-			                (unsigned long *)(UNW_FP(frame)
-			                                  + FRAME_LINK_OFFSET),
-						  link)
-# if FRAME_RETADDR_OFFSET < 0
-			   && link > bottom && link < UNW_FP(frame)
-# else
-			   && link > UNW_FP(frame) && link < bottom
-# endif
-			   && !(link & (sizeof(link) - 1))
-			   && !probe_kernel_address(
-			                  (unsigned long *)(UNW_FP(frame)
-			                                    + FRAME_RETADDR_OFFSET), UNW_PC(frame))) {
-				UNW_SP(frame) = UNW_FP(frame) + FRAME_RETADDR_OFFSET
-# if FRAME_RETADDR_OFFSET < 0
-					-
-# else
-					+
-# endif
-					  sizeof(UNW_PC(frame));
-				UNW_FP(frame) = link;
-				return 0;
-			}
-		}
-#endif
-		return -ENXIO;
-	}
-	state.org = startLoc;
-	memcpy(&state.cfa, &badCFA, sizeof(state.cfa));
-	/* process instructions */
-	if (!processCFI(ptr, end, pc, ptrType, &state)
-	   || state.loc > endLoc
-	   || state.regs[retAddrReg].where == Nowhere
-	   || state.cfa.reg >= ARRAY_SIZE(reg_info)
-	   || reg_info[state.cfa.reg].width != sizeof(unsigned long)
-	   || FRAME_REG(state.cfa.reg, unsigned long) % sizeof(unsigned long)
-	   || state.cfa.offs % sizeof(unsigned long)) {
-		dprintk(1, "Unusable unwind info (%p,%p).", ptr, end);
-		return -EIO;
-	}
-	/* update frame */
-#ifndef CONFIG_AS_CFI_SIGNAL_FRAME
-	if(frame->call_frame
-	   && !UNW_DEFAULT_RA(state.regs[retAddrReg], state.dataAlign))
-		frame->call_frame = 0;
-#endif
-	cfa = FRAME_REG(state.cfa.reg, unsigned long) + state.cfa.offs;
-	startLoc = min((unsigned long)UNW_SP(frame), cfa);
-	endLoc = max((unsigned long)UNW_SP(frame), cfa);
-	if (STACK_LIMIT(startLoc) != STACK_LIMIT(endLoc)) {
-		startLoc = min(STACK_LIMIT(cfa), cfa);
-		endLoc = max(STACK_LIMIT(cfa), cfa);
-	}
-#ifndef CONFIG_64BIT
-# define CASES CASE(8); CASE(16); CASE(32)
-#else
-# define CASES CASE(8); CASE(16); CASE(32); CASE(64)
-#endif
-	pc = UNW_PC(frame);
-	sp = UNW_SP(frame);
-	for (i = 0; i < ARRAY_SIZE(state.regs); ++i) {
-		if (REG_INVALID(i)) {
-			if (state.regs[i].where == Nowhere)
-				continue;
-			dprintk(1, "Cannot restore register %u (%d).",
-			        i, state.regs[i].where);
-			return -EIO;
-		}
-		switch(state.regs[i].where) {
-		default:
-			break;
-		case Register:
-			if (state.regs[i].value >= ARRAY_SIZE(reg_info)
-			   || REG_INVALID(state.regs[i].value)
-			   || reg_info[i].width > reg_info[state.regs[i].value].width) {
-				dprintk(1, "Cannot restore register %u from register %lu.",
-				        i, state.regs[i].value);
-				return -EIO;
-			}
-			switch(reg_info[state.regs[i].value].width) {
-#define CASE(n) \
-			case sizeof(u##n): \
-				state.regs[i].value = FRAME_REG(state.regs[i].value, \
-				                                const u##n); \
-				break
-			CASES;
-#undef CASE
-			default:
-				dprintk(1, "Unsupported register size %u (%lu).",
-				        reg_info[state.regs[i].value].width,
-				        state.regs[i].value);
-				return -EIO;
-			}
-			break;
-		}
-	}
-	for (i = 0; i < ARRAY_SIZE(state.regs); ++i) {
-		if (REG_INVALID(i))
-			continue;
-		switch(state.regs[i].where) {
-		case Nowhere:
-			if (reg_info[i].width != sizeof(UNW_SP(frame))
-			   || &FRAME_REG(i, __typeof__(UNW_SP(frame)))
-			      != &UNW_SP(frame))
-				continue;
-			UNW_SP(frame) = cfa;
-			break;
-		case Register:
-			switch(reg_info[i].width) {
-#define CASE(n) case sizeof(u##n): \
-				FRAME_REG(i, u##n) = state.regs[i].value; \
-				break
-			CASES;
-#undef CASE
-			default:
-				dprintk(1, "Unsupported register size %u (%u).",
-				        reg_info[i].width, i);
-				return -EIO;
-			}
-			break;
-		case Value:
-			if (reg_info[i].width != sizeof(unsigned long)) {
-				dprintk(1, "Unsupported value size %u (%u).",
-				        reg_info[i].width, i);
-				return -EIO;
-			}
-			FRAME_REG(i, unsigned long) = cfa + state.regs[i].value
-			                                    * state.dataAlign;
-			break;
-		case Memory: {
-				unsigned long addr = cfa + state.regs[i].value
-				                           * state.dataAlign;
-
-				if ((state.regs[i].value * state.dataAlign)
-				    % sizeof(unsigned long)
-				    || addr < startLoc
-				    || addr + sizeof(unsigned long) < addr
-				    || addr + sizeof(unsigned long) > endLoc) {
-					dprintk(1, "Bad memory location %lx (%lx).",
-					        addr, state.regs[i].value);
-					return -EIO;
-				}
-				switch(reg_info[i].width) {
-#define CASE(n)     case sizeof(u##n): \
-					probe_kernel_address((u##n *)addr, FRAME_REG(i, u##n)); \
-					break
-				CASES;
-#undef CASE
-				default:
-					dprintk(1, "Unsupported memory size %u (%u).",
-					        reg_info[i].width, i);
-					return -EIO;
-				}
-			}
-			break;
-		}
-	}
-
-	if (UNW_PC(frame) % state.codeAlign
-	    || UNW_SP(frame) % sleb128abs(state.dataAlign)) {
-		dprintk(1, "Output pointer(s) misaligned (%lx,%lx).",
-		        UNW_PC(frame), UNW_SP(frame));
-		return -EIO;
-	}
-	if (pc == UNW_PC(frame) && sp == UNW_SP(frame)) {
-		dprintk(1, "No progress (%lx,%lx).", pc, sp);
-		return -EIO;
-	}
-
-	return 0;
-#undef CASES
-#undef FRAME_REG
-}
-EXPORT_SYMBOL(unwind);
-
-int unwind_init_frame_info(struct unwind_frame_info *info,
-                           struct task_struct *tsk,
-                           /*const*/ struct pt_regs *regs)
-{
-	info->task = tsk;
-	info->call_frame = 0;
-	arch_unw_init_frame_info(info, regs);
-
-	return 0;
-}
-EXPORT_SYMBOL(unwind_init_frame_info);
-
-/*
- * Prepare to unwind a blocked task.
- */
-int unwind_init_blocked(struct unwind_frame_info *info,
-                        struct task_struct *tsk)
-{
-	info->task = tsk;
-	info->call_frame = 0;
-	arch_unw_init_blocked(info);
-
-	return 0;
-}
-EXPORT_SYMBOL(unwind_init_blocked);
-
-/*
- * Prepare to unwind the currently running thread.
- */
-int unwind_init_running(struct unwind_frame_info *info,
-                        asmlinkage int (*callback)(struct unwind_frame_info *,
-                                                   void *arg),
-                        void *arg)
-{
-	info->task = current;
-	info->call_frame = 0;
-
-	return arch_unwind_init_running(info, callback, arg);
-}
-EXPORT_SYMBOL(unwind_init_running);
-
-/*
- * Unwind until the return pointer is in user-land (or until an error
- * occurs).  Returns 0 if successful, negative number in case of
- * error.
- */
-int unwind_to_user(struct unwind_frame_info *info)
-{
-	while (!arch_unw_user_mode(info)) {
-		int err = unwind(info);
-
-		if (err < 0)
-			return err;
-	}
-
-	return 0;
-}
-EXPORT_SYMBOL(unwind_to_user);

lib/Kconfig.debug

···
 	  some architectures or if you use external debuggers.
 	  If you don't debug the kernel, you can say N.
 
-config UNWIND_INFO
-	bool "Compile the kernel with frame unwind information"
-	depends on !IA64 && !PARISC && !ARM
-	depends on !MODULES || !(MIPS || PPC || SUPERH || V850)
-	help
-	  If you say Y here the resulting kernel image will be slightly larger
-	  but not slower, and it will give very useful debugging information.
-	  If you don't debug the kernel, you can say N, but we may not be able
-	  to solve problems without frame unwind information or frame pointers.
-
-config STACK_UNWIND
-	bool "Stack unwind support"
-	depends on UNWIND_INFO
-	depends on X86
-	help
-	  This enables more precise stack traces, omitting all unrelated
-	  occurrences of pointers into kernel code from the dump.
-
 config FORCED_INLINING
 	bool "Force gcc to inline functions marked 'inline'"
 	depends on DEBUG_KERNEL

lib/fault-inject.c

···
 
 #define MAX_STACK_TRACE_DEPTH 32
 
-#ifdef CONFIG_STACK_UNWIND
-
-static asmlinkage int fail_stacktrace_callback(struct unwind_frame_info *info,
-						void *arg)
-{
-	int depth;
-	struct fault_attr *attr = arg;
-	bool found = (attr->require_start == 0 && attr->require_end == ULONG_MAX);
-
-	for (depth = 0; depth < attr->stacktrace_depth
-			&& unwind(info) == 0 && UNW_PC(info); depth++) {
-		if (arch_unw_user_mode(info))
-			break;
-		if (attr->reject_start <= UNW_PC(info) &&
-			       UNW_PC(info) < attr->reject_end)
-			return false;
-		if (attr->require_start <= UNW_PC(info) &&
-			       UNW_PC(info) < attr->require_end)
-			found = true;
-	}
-	return found;
-}
-
-static bool fail_stacktrace(struct fault_attr *attr)
-{
-	struct unwind_frame_info info;
-
-	return unwind_init_running(&info, fail_stacktrace_callback, attr);
-}
-
-#elif defined(CONFIG_STACKTRACE)
+#if defined(CONFIG_STACKTRACE)
 
 static bool fail_stacktrace(struct fault_attr *attr)
 {