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/* Return backtrace of current program state.
Copyright (C) 1998-2020 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 <stddef.h>
#include <string.h>
#include <signal.h>
#include <libc-vdso.h>
/* This is the stack layout we see with every stack frame.
Note that every routine is required by the ABI to lay out the stack
like this.
+----------------+ +-----------------+
%r1 -> | %r1 last frame--------> | %r1 last frame--->... --> NULL
| | | |
| (unused) | | return address |
+----------------+ +-----------------+
*/
struct layout
{
struct layout *next;
void *return_address;
};
#define SIGNAL_FRAMESIZE 64
/* Since the signal handler is just like any other function it needs to
save/restore its LR and it will save it into callers stack frame.
Since a signal handler doesn't have a caller, the kernel creates a
dummy frame to make it look like it has a caller. */
struct signal_frame_32 {
char dummy[SIGNAL_FRAMESIZE];
struct sigcontext sctx;
mcontext_t mctx;
/* We don't care about the rest, since IP value is at 'mctx' field. */
};
static inline int
is_sigtramp_address (void *nip)
{
#ifdef HAVE_SIGTRAMP_RT32
if (nip == VDSO_SYMBOL (sigtramp32))
return 1;
#endif
return 0;
}
struct rt_signal_frame_32 {
char dummy[SIGNAL_FRAMESIZE + 16];
siginfo_t info;
ucontext_t uc;
/* We don't care about the rest, since IP value is at 'uc' field. */
};
static inline int
is_sigtramp_address_rt (void * nip)
{
#ifdef HAVE_SIGTRAMP_32
if (nip == VDSO_SYMBOL (sigtramp_rt32))
return 1;
#endif
return 0;
}
int
__backtrace (void **array, int size)
{
struct layout *current;
int count;
/* Force gcc to spill LR. */
asm volatile ("" : "=l"(current));
/* Get the address on top-of-stack. */
asm volatile ("lwz %0,0(1)" : "=r"(current));
for ( count = 0;
current != NULL && count < size;
current = current->next, count++)
{
gregset_t *gregset = NULL;
array[count] = current->return_address;
/* Check if the symbol is the signal trampoline and get the interrupted
* symbol address from the trampoline saved area. */
if (is_sigtramp_address (current->return_address))
{
struct signal_frame_32 *sigframe =
(struct signal_frame_32*) current;
gregset = &sigframe->mctx.gregs;
}
else if (is_sigtramp_address_rt (current->return_address))
{
struct rt_signal_frame_32 *sigframe =
(struct rt_signal_frame_32*) current;
gregset = &sigframe->uc.uc_mcontext.uc_regs->gregs;
}
if (gregset)
{
array[++count] = (void*)((*gregset)[PT_NIP]);
current = (void*)((*gregset)[PT_R1]);
}
}
/* It's possible the second-last stack frame can't return
(that is, it's __libc_start_main), in which case
the CRT startup code will have set its LR to 'NULL'. */
if (count > 0 && array[count-1] == NULL)
count--;
return count;
}
weak_alias (__backtrace, backtrace)
libc_hidden_def (__backtrace)
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