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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,
int (*fn)(struct stackframe *, void *), void *data)
{
while (1) {
int ret;
if (fn(frame, data))
break;
ret = unwind_frame(frame);
if (ret < 0)
break;
}
}
EXPORT_SYMBOL(walk_stackframe);
#ifdef CONFIG_STACKTRACE
struct stack_trace_data {
struct stack_trace *trace;
unsigned int no_sched_functions;
unsigned int skip;
};
static int save_trace(struct stackframe *frame, void *d)
{
struct stack_trace_data *data = d;
struct stack_trace *trace = data->trace;
unsigned long addr = frame->pc;
if (data->no_sched_functions && in_sched_functions(addr))
return 0;
if (data->skip) {
data->skip--;
return 0;
}
trace->entries[trace->nr_entries++] = addr;
return trace->nr_entries >= trace->max_entries;
}
/* This must be noinline to so that our skip calculation works correctly */
static noinline void __save_stack_trace(struct task_struct *tsk,
struct stack_trace *trace, unsigned int nosched)
{
struct stack_trace_data data;
struct stackframe frame;
data.trace = trace;
data.skip = trace->skip;
data.no_sched_functions = nosched;
if (tsk != 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
frame.fp = thread_saved_fp(tsk);
frame.sp = thread_saved_sp(tsk);
frame.lr = 0; /* recovered from the stack */
frame.pc = thread_saved_pc(tsk);
#endif
} else {
/* We don't want this function nor the caller */
data.skip += 2;
frame.fp = (unsigned long)__builtin_frame_address(0);
frame.sp = current_stack_pointer;
frame.lr = (unsigned long)__builtin_return_address(0);
here:
frame.pc = (unsigned long)&&here;
}
#ifdef CONFIG_KRETPROBES
frame.kr_cur = NULL;
frame.tsk = tsk;
#endif
#ifdef CONFIG_UNWINDER_FRAME_POINTER
frame.ex_frame = false;
#endif
walk_stackframe(&frame, save_trace, &data);
}
void save_stack_trace_regs(struct pt_regs *regs, struct stack_trace *trace)
{
struct stack_trace_data data;
struct stackframe frame;
data.trace = trace;
data.skip = trace->skip;
data.no_sched_functions = 0;
frame.fp = regs->ARM_fp;
frame.sp = regs->ARM_sp;
frame.lr = regs->ARM_lr;
frame.pc = regs->ARM_pc;
#ifdef CONFIG_KRETPROBES
frame.kr_cur = NULL;
frame.tsk = current;
#endif
#ifdef CONFIG_UNWINDER_FRAME_POINTER
frame.ex_frame = in_entry_text(frame.pc);
#endif
walk_stackframe(&frame, save_trace, &data);
}
void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
{
__save_stack_trace(tsk, trace, 1);
}
EXPORT_SYMBOL(save_stack_trace_tsk);
void save_stack_trace(struct stack_trace *trace)
{
__save_stack_trace(current, trace, 0);
}
EXPORT_SYMBOL_GPL(save_stack_trace);
#endif
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