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/* Return backtrace of current program state.
Copyright (C) 1998-2021 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#include <execinfo.h>
#include <stdlib.h>
#include <unwind-link.h>
struct trace_arg
{
void **array;
struct unwind_link *unwind_link;
int cnt, size;
void *lastebp, *lastesp;
};
static _Unwind_Reason_Code
backtrace_helper (struct _Unwind_Context *ctx, void *a)
{
struct trace_arg *arg = a;
/* We are first called with address in the __backtrace function.
Skip it. */
if (arg->cnt != -1)
arg->array[arg->cnt]
= (void *) UNWIND_LINK_PTR (arg->unwind_link, _Unwind_GetIP) (ctx);
if (++arg->cnt == arg->size)
return _URC_END_OF_STACK;
/* %ebp is DWARF2 register 5 on IA-32. */
arg->lastebp
= (void *) UNWIND_LINK_PTR (arg->unwind_link, _Unwind_GetGR) (ctx, 5);
arg->lastesp
= (void *) UNWIND_LINK_PTR (arg->unwind_link, _Unwind_GetCFA) (ctx);
return _URC_NO_REASON;
}
/* This is a global variable set at program start time. It marks the
highest used stack address. */
extern void *__libc_stack_end;
/* This is the stack layout we see with every stack frame
if not compiled without frame pointer.
+-----------------+ +-----------------+
%ebp -> | %ebp last frame--------> | %ebp last frame--->...
| | | |
| return address | | return address |
+-----------------+ +-----------------+
First try as far to get as far as possible using
_Unwind_Backtrace which handles -fomit-frame-pointer
as well, but requires .eh_frame info. Then fall back to
walking the stack manually. */
struct layout
{
struct layout *ebp;
void *ret;
};
int
__backtrace (void **array, int size)
{
struct trace_arg arg =
{
.array = array,
.unwind_link = __libc_unwind_link_get (),
.size = size,
.cnt = -1,
};
if (size <= 0 || arg.unwind_link == NULL)
return 0;
UNWIND_LINK_PTR (arg.unwind_link, _Unwind_Backtrace)
(backtrace_helper, &arg);
if (arg.cnt > 1 && arg.array[arg.cnt - 1] == NULL)
--arg.cnt;
else if (arg.cnt < size)
{
struct layout *ebp = (struct layout *) arg.lastebp;
while (arg.cnt < size)
{
/* Check for out of range. */
if ((void *) ebp < arg.lastesp || (void *) ebp > __libc_stack_end
|| ((long) ebp & 3))
break;
array[arg.cnt++] = ebp->ret;
ebp = ebp->ebp;
}
}
return arg.cnt != -1 ? arg.cnt : 0;
}
weak_alias (__backtrace, backtrace)
libc_hidden_def (__backtrace)
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