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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.
Contributed by David S. Miller <davem@davemloft.net>
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public License as
published by the Free Software Foundation; either version 2 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
Library General Public License for more details.
You should have received a copy of the GNU Library General Public
License along with the GNU C Library; see the file COPYING.LIB. If
not, see <http://www.gnu.org/licenses/>. */
#include <execinfo.h>
#include <stddef.h>
#include <sysdep.h>
#include <sys/trap.h>
#include <dlfcn.h>
#include <unwind.h>
#include <backtrace.h>
struct layout
{
unsigned long locals[8];
unsigned long ins[6];
unsigned long next;
void *return_address;
};
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.1");
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;
_Unwind_Ptr ip;
/* We are first called with address in the __backtrace function.
Skip it. */
if (arg->cnt != -1)
{
ip = unwind_getip (ctx);
arg->array[arg->cnt] = (void *) ip;
/* 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 };
bool use_unwinder;
int count;
if (size <= 0)
return 0;
use_unwinder = true;
#ifdef SHARED
__libc_once_define (static, once);
__libc_once (once, init);
if (unwind_backtrace == NULL)
use_unwinder = false;
#endif
if (use_unwinder == false)
{
struct layout *current;
unsigned long fp, i7;
asm volatile ("mov %%fp, %0" : "=r"(fp));
asm volatile ("mov %%i7, %0" : "=r"(i7));
current = (struct layout *) (fp + BACKTRACE_STACK_BIAS);
array[0] = (void *) i7;
if (size == 1)
return 1;
backtrace_flush_register_windows();
for (count = 1; count < size; count++)
{
array[count] = current->return_address;
if (!current->next)
break;
current = (struct layout *) (current->next + BACKTRACE_STACK_BIAS);
}
}
else
{
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;
count = arg.cnt != -1 ? arg.cnt : 0;
}
return count;
}
weak_alias (__backtrace, backtrace)
libc_hidden_def (__backtrace)
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