arch/arm/kernel/stacktrace.c

Source file repositories/reference/linux-study-clean/arch/arm/kernel/stacktrace.c

File Facts

System
Linux kernel
Corpus path
arch/arm/kernel/stacktrace.c
Extension
.c
Size
5093 bytes
Lines
198
Domain
Architecture Layer
Bucket
arch/arm
Inferred role
Architecture Layer: exported/initcall integration point
Status
integration implementation candidate

Why This File Exists

CPU and platform-specific kernel glue: boot entry, traps, syscall entry, interrupts, page tables, context switch, and low-level barriers.

Dependency Surface

Detected Declarations

Annotated Snippet

// SPDX-License-Identifier: GPL-2.0-only
#include <linux/export.h>
#include <linux/kprobes.h>
#include <linux/sched.h>
#include <linux/sched/debug.h>
#include <linux/stacktrace.h>

#include <asm/sections.h>
#include <asm/stacktrace.h>
#include <asm/traps.h>

#include "reboot.h"

#if defined(CONFIG_FRAME_POINTER) && !defined(CONFIG_ARM_UNWIND)
/*
 * Unwind the current stack frame and store the new register values in the
 * structure passed as argument. Unwinding is equivalent to a function return,
 * hence the new PC value rather than LR should be used for backtrace.
 *
 * With framepointer enabled, a simple function prologue looks like this:
 *	mov	ip, sp
 *	stmdb	sp!, {fp, ip, lr, pc}
 *	sub	fp, ip, #4
 *
 * A simple function epilogue looks like this:
 *	ldm	sp, {fp, sp, pc}
 *
 * When compiled with clang, pc and sp are not pushed. A simple function
 * prologue looks like this when built with clang:
 *
 *	stmdb	{..., fp, lr}
 *	add	fp, sp, #x
 *	sub	sp, sp, #y
 *
 * A simple function epilogue looks like this when built with clang:
 *
 *	sub	sp, fp, #x
 *	ldm	{..., fp, pc}
 *
 *
 * Note that with framepointer enabled, even the leaf functions have the same
 * prologue and epilogue, therefore we can ignore the LR value in this case.
 */

extern unsigned long call_with_stack_end;

static int frame_pointer_check(struct stackframe *frame)
{
	unsigned long high, low;
	unsigned long fp = frame->fp;
	unsigned long pc = frame->pc;

	/*
	 * call_with_stack() is the only place we allow SP to jump from one
	 * stack to another, with FP and SP pointing to different stacks,
	 * skipping the FP boundary check at this point.
	 */
	if (pc >= (unsigned long)&call_with_stack &&
			pc < (unsigned long)&call_with_stack_end)
		return 0;

	/* only go to a higher address on the stack */
	low = frame->sp;
	high = ALIGN(low, THREAD_SIZE);

	/* check current frame pointer is within bounds */
#ifdef CONFIG_CC_IS_CLANG
	if (fp < low + 4 || fp > high - 4)
		return -EINVAL;
#else
	if (fp < low + 12 || fp > high - 4)
		return -EINVAL;
#endif

	return 0;
}

int notrace unwind_frame(struct stackframe *frame)
{
	unsigned long fp = frame->fp;

	if (frame_pointer_check(frame))
		return -EINVAL;

	/*
	 * When we unwind through an exception stack, include the saved PC
	 * value into the stack trace.
	 */
	if (frame->ex_frame) {
		struct pt_regs *regs = (struct pt_regs *)frame->sp;

Annotation

Implementation Notes