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/* Catch segmentation faults and print backtrace.
Copyright (C) 1998 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Ulrich Drepper <drepper@cygnus.com>, 1998.
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,
write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA. */
#include <execinfo.h>
#include <fcntl.h>
#include <signal.h>
#include <stdlib.h>
#include <unistd.h>
/* This file defines macros to access the content of the sigcontext element
passed up by the signal handler. */
#include <sigcontextinfo.h>
/* This is a global variable set at program start time. It marks the
highest used stack address. */
extern void *__libc_stack_end;
/* This implementation assumes a stack layout that matches the defaults
used by gcc's `__builtin_frame_address' and `__builtin_return_address'
(FP is the frame pointer register):
+-----------------+ +-----------------+
FP -> | previous FP --------> | previous FP ------>...
| | | |
| return address | | return address |
+-----------------+ +-----------------+
*/
/* Get some notion of the current stack. Need not be exactly the top
of the stack, just something somewhere in the current frame. */
#ifndef CURRENT_STACK_FRAME
# define CURRENT_STACK_FRAME ({ char __csf; &__csf; })
#endif
/* By default we assume that the stack grows downward. */
#ifndef INNER_THAN
# define INNER_THAN <
#endif
struct layout
{
struct layout *next;
void *return_address;
};
/* This function is called when a segmentation fault is caught. The system
is in an instable state now. This means especially that malloc() might
not work anymore. */
static void
catch_segfault (int signal, SIGCONTEXT ctx)
{
struct layout *current;
void *top_frame;
void *top_stack;
const char *fname;
int fd;
void **arr;
size_t cnt;
/* This is the name of the file we are writing to. If none is given
or we cannot write to this file write to stderr. */
fd = 2;
fname = getenv ("SEGFAULT_OUTPUT_NAME");
if (fname != NULL && fname[0] != '\0')
{
fd = open (fname, O_TRUNC | O_WRONLY | O_CREAT);
if (fd == -1)
fd = 2;
}
#define WRITE_STRING(s) write (fd, s, sizeof (s) - 1)
WRITE_STRING ("*** Segmentation Fault\n");
WRITE_STRING ("Backtrace:\n");
top_frame = GET_FRAME (ctx);
top_stack = GET_STACK (ctx);
/* First count how many entries we'll have. */
cnt = 1;
current = (struct layout *) top_frame;
while (!((void *) current INNER_THAN top_stack
|| !((void *) current INNER_THAN __libc_stack_end)))
{
++cnt;
current = current->next;
}
arr = alloca (cnt * sizeof (void *));
/* First handle the program counter from the structure. */
arr[0] = GET_PC (ctx);
current = (struct layout *) top_frame;
cnt = 1;
while (!((void *) current INNER_THAN top_stack
|| !((void *) current INNER_THAN __libc_stack_end)))
{
arr[cnt++] = current->return_address;
current = current->next;
}
/* Now generate nicely formatted output. */
__backtrace_symbols_fd (arr, cnt, fd);
/* Nothing else to do. */
_exit (128 + SIGSEGV);
}
static void
__attribute__ ((constructor))
install_handler (void)
{
struct sigaction sa;
sa.sa_handler = (void *) catch_segfault;
sigemptyset (&sa.sa_mask);
sa.sa_flags = SA_RESTART;
sigaction (SIGSEGV, &sa, NULL);
/* Maybe we are expected to use an alternative stack. */
if (getenv ("SEGFAULT_USE_ALTSTACK") != 0)
{
void *stack_mem = malloc (2 * SIGSTKSZ);
struct sigaltstack ss;
if (stack_mem != NULL)
{
ss.ss_sp = stack_mem;
ss.ss_flags = SS_ONSTACK;
ss.ss_size = 2 * SIGSTKSZ;
sigaltstack (&ss, NULL);
}
}
}
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