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/* Return backtrace of current program state.
Copyright (C) 2003-2020 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Jakub Jelinek <jakub@redhat.com>, 2003.
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 <libc-lock.h>
#include <dlfcn.h>
#include <execinfo.h>
#include <gnu/lib-names.h>
#include <stdlib.h>
#include <unwind.h>
struct trace_arg
{
void **array;
_Unwind_Word cfa;
int cnt;
int size;
};
#ifdef SHARED
static _Unwind_Reason_Code (*unwind_backtrace) (_Unwind_Trace_Fn, void *);
static _Unwind_Ptr (*unwind_getip) (struct _Unwind_Context *);
static _Unwind_Word (*unwind_getcfa) (struct _Unwind_Context *);
static void *libgcc_handle;
/* Dummy version in case libgcc_s does not contain the real code. */
static _Unwind_Word
dummy_getcfa (struct _Unwind_Context *ctx __attribute__ ((unused)))
{
return 0;
}
static void
init (void)
{
libgcc_handle = __libc_dlopen (LIBGCC_S_SO);
if (libgcc_handle == NULL)
return;
unwind_backtrace = __libc_dlsym (libgcc_handle, "_Unwind_Backtrace");
unwind_getip = __libc_dlsym (libgcc_handle, "_Unwind_GetIP");
if (unwind_getip == NULL)
unwind_backtrace = NULL;
unwind_getcfa = (__libc_dlsym (libgcc_handle, "_Unwind_GetCFA")
?: dummy_getcfa);
}
#else
# define unwind_backtrace _Unwind_Backtrace
# define unwind_getip _Unwind_GetIP
# define unwind_getcfa _Unwind_GetCFA
#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);
/* Check whether we make any progress. */
_Unwind_Word cfa = unwind_getcfa (ctx);
if (arg->cnt > 0 && arg->array[arg->cnt - 1] == arg->array[arg->cnt]
&& cfa == arg->cfa)
return _URC_END_OF_STACK;
arg->cfa = cfa;
}
if (++arg->cnt == arg->size)
return _URC_END_OF_STACK;
return _URC_NO_REASON;
}
int
__backtrace (void **array, int size)
{
struct trace_arg arg = { .array = array, .cfa = 0, .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);
/* _Unwind_Backtrace seems to put NULL address above
_start. Fix it up here. */
if (arg.cnt > 1 && arg.array[arg.cnt - 1] == NULL)
--arg.cnt;
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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