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// 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;
/*
* We check that 'regs + sizeof(struct pt_regs)' (that is,
* ®s[1]) does not exceed the bottom of the stack to avoid
* accessing data outside the task's stack. This may happen
* when frame->ex_frame is a false positive.
*/
if ((unsigned long)®s[1] > ALIGN(frame->sp, THREAD_SIZE))
return -EINVAL;
frame->pc = regs->ARM_pc;
frame->ex_frame = false;
return 0;
}
/* restore the registers from the stack frame */
#ifdef CONFIG_CC_IS_CLANG
frame->sp = frame->fp;
frame->fp = READ_ONCE_NOCHECK(*(unsigned long *)(fp));
frame->pc = READ_ONCE_NOCHECK(*(unsigned long *)(fp + 4));
#else
frame->fp = READ_ONCE_NOCHECK(*(unsigned long *)(fp - 12));
frame->sp = READ_ONCE_NOCHECK(*(unsigned long *)(fp - 8));
frame->pc = READ_ONCE_NOCHECK(*(unsigned long *)(fp - 4));
#endif
#ifdef CONFIG_KRETPROBES
if (is_kretprobe_trampoline(frame->pc))
frame->pc = kretprobe_find_ret_addr(frame->tsk,
(void *)frame->fp, &frame->kr_cur);
#endif
if (in_entry_text(frame->pc))
frame->ex_frame = true;
return 0;
}
#endif
void notrace walk_stackframe(struct stackframe *frame,
bool (*fn)(void *, unsigned long), void *data)
{
while (1) {
int ret;
if (!fn(data, frame->pc))
break;
ret = unwind_frame(frame);
if (ret < 0)
break;
}
}
EXPORT_SYMBOL(walk_stackframe);
#ifdef CONFIG_STACKTRACE
static void start_stack_trace(struct stackframe *frame, struct task_struct *task,
unsigned long fp, unsigned long sp,
unsigned long lr, unsigned long pc)
{
frame->fp = fp;
frame->sp = sp;
frame->lr = lr;
frame->pc = pc;
#ifdef CONFIG_KRETPROBES
frame->kr_cur = NULL;
frame->tsk = task;
#endif
#ifdef CONFIG_UNWINDER_FRAME_POINTER
frame->ex_frame = in_entry_text(frame->pc);
#endif
}
void arch_stack_walk(stack_trace_consume_fn consume_entry, void *cookie,
struct task_struct *task, struct pt_regs *regs)
{
struct stackframe frame;
if (regs) {
start_stack_trace(&frame, NULL, regs->ARM_fp, regs->ARM_sp,
regs->ARM_lr, regs->ARM_pc);
} else if (task != current) {
#ifdef CONFIG_SMP
/*
* What guarantees do we have here that 'tsk' is not
* running on another CPU? For now, ignore it as we
* can't guarantee we won't explode.
*/
return;
#else
start_stack_trace(&frame, task, thread_saved_fp(task),
thread_saved_sp(task), 0,
thread_saved_pc(task));
#endif
} else {
here:
start_stack_trace(&frame, task,
(unsigned long)__builtin_frame_address(0),
current_stack_pointer,
(unsigned long)__builtin_return_address(0),
(unsigned long)&&here);
/* skip this function */
if (unwind_frame(&frame))
return;
}
walk_stackframe(&frame, consume_entry, cookie);
}
#endif
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