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/* Return backtrace of current program state.
Copyright (C) 2013-2019 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
<http://www.gnu.org/licenses/>. */
#include <libc-lock.h>
#include <dlfcn.h>
#include <execinfo.h>
#include <stdlib.h>
#include <unwind.h>
struct trace_arg
{
void **array;
int cnt, size;
void *lastfp, *lastsp;
};
#ifdef SHARED
static _Unwind_Reason_Code (*unwind_backtrace) (_Unwind_Trace_Fn, void *);
static _Unwind_Ptr (*unwind_getip) (struct _Unwind_Context *);
static _Unwind_Ptr (*unwind_getcfa) (struct _Unwind_Context *);
static _Unwind_Ptr (*unwind_getgr) (struct _Unwind_Context *, int);
static void *libgcc_handle;
static void
init (void)
{
libgcc_handle = __libc_dlopen ("libgcc_s.so.2");
if (libgcc_handle == NULL)
return;
unwind_backtrace = __libc_dlsym (libgcc_handle, "_Unwind_Backtrace");
unwind_getip = __libc_dlsym (libgcc_handle, "_Unwind_GetIP");
unwind_getcfa = __libc_dlsym (libgcc_handle, "_Unwind_GetCFA");
unwind_getgr = __libc_dlsym (libgcc_handle, "_Unwind_GetGR");
if (unwind_getip == NULL || unwind_getgr == NULL || unwind_getcfa == NULL)
{
unwind_backtrace = NULL;
__libc_dlclose (libgcc_handle);
libgcc_handle = NULL;
}
}
#else
# define unwind_backtrace _Unwind_Backtrace
# define unwind_getip _Unwind_GetIP
# define unwind_getcfa _Unwind_GetCFA
# define unwind_getgr _Unwind_GetGR
#endif
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_getip (ctx);
if (++arg->cnt == arg->size)
return _URC_END_OF_STACK;
/* %fp is DWARF2 register 14 on M68K. */
arg->lastfp = (void *) unwind_getgr (ctx, 14);
arg->lastsp = (void *) 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.
+-----------------+ +-----------------+
%fp -> | %fp last frame--------> | %fp 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 *fp;
void *ret;
};
int
__backtrace (void **array, int size)
{
struct trace_arg arg = { .array = array, .size = size, .cnt = -1 };
if (size <= 0)
return 0;
#ifdef SHARED
__libc_once_define (static, once);
__libc_once (once, init);
if (unwind_backtrace == NULL)
return 0;
#endif
unwind_backtrace (backtrace_helper, &arg);
if (arg.cnt > 1 && arg.array[arg.cnt - 1] == NULL)
--arg.cnt;
else if (arg.cnt < size)
{
struct layout *fp = (struct layout *) arg.lastfp;
while (arg.cnt < size)
{
/* Check for out of range. */
if ((void *) fp < arg.lastsp || (void *) fp > __libc_stack_end
|| ((long) fp & 1))
break;
array[arg.cnt++] = fp->ret;
fp = fp->fp;
}
}
return arg.cnt != -1 ? arg.cnt : 0;
}
weak_alias (__backtrace, backtrace)
libc_hidden_def (__backtrace)
#ifdef SHARED
/* Free all resources if necessary. */
libc_freeres_fn (free_mem)
{
unwind_backtrace = NULL;
if (libgcc_handle != NULL)
{
__libc_dlclose (libgcc_handle);
libgcc_handle = NULL;
}
}
#endif
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