/* Catch segmentation faults and print backtrace. Copyright (C) 1998-2017 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 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 <alloca.h> #include <ctype.h> #include <errno.h> #include <execinfo.h> #include <fcntl.h> #include <signal.h> #include <stdint.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <_itoa.h> #include <ldsodefs.h> /* This file defines macros to access the content of the sigcontext element passed up by the signal handler. */ #include <sigcontextinfo.h> /* Get code to possibly dump the content of all registers. */ #include <register-dump.h> /* We'll use this a lot. */ #define WRITE_STRING(s) write (fd, s, strlen (s)) /* Name of the output file. */ static const char *fname; /* We better should not use `strerror' since it can call far too many other functions which might fail. Do it here ourselves. */ static void write_strsignal (int fd, int signal) { if (signal < 0 || signal >= _NSIG || _sys_siglist[signal] == NULL) { char buf[30]; char *ptr = _itoa_word (signal, &buf[sizeof (buf)], 10, 0); WRITE_STRING ("signal "); write (fd, buf, &buf[sizeof (buf)] - ptr); } else WRITE_STRING (_sys_siglist[signal]); } /* This function is called when a segmentation fault is caught. The system is in an unstable state now. This means especially that malloc() might not work anymore. */ static void catch_segfault (int signal, SIGCONTEXT ctx) { int fd, cnt, i; void **arr; struct sigaction sa; uintptr_t pc; /* 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; if (fname != NULL) { fd = open (fname, O_TRUNC | O_WRONLY | O_CREAT, 0666); if (fd == -1) fd = 2; } WRITE_STRING ("*** "); write_strsignal (fd, signal); WRITE_STRING ("\n"); #ifdef REGISTER_DUMP REGISTER_DUMP; #endif WRITE_STRING ("\nBacktrace:\n"); /* Get the backtrace. */ arr = alloca (256 * sizeof (void *)); cnt = backtrace (arr, 256); /* Now try to locate the PC from signal context in the backtrace. Normally it will be found at arr[2], but it might appear later if there were some signal handler wrappers. Allow a few bytes difference to cope with as many arches as possible. */ pc = (uintptr_t) GET_PC (ctx); for (i = 0; i < cnt; ++i) if ((uintptr_t) arr[i] >= pc - 16 && (uintptr_t) arr[i] <= pc + 16) break; /* If we haven't found it, better dump full backtrace even including the signal handler frames instead of not dumping anything. */ if (i == cnt) i = 0; /* Now generate nicely formatted output. */ __backtrace_symbols_fd (arr + i, cnt - i, fd); #ifdef HAVE_PROC_SELF /* Now the link map. */ int mapfd = open ("/proc/self/maps", O_RDONLY); if (mapfd != -1) { write (fd, "\nMemory map:\n\n", 14); char buf[256]; ssize_t n; while ((n = TEMP_FAILURE_RETRY (read (mapfd, buf, sizeof (buf)))) > 0) TEMP_FAILURE_RETRY (write (fd, buf, n)); close (mapfd); } #endif /* Pass on the signal (so that a core file is produced). */ sa.sa_handler = SIG_DFL; sigemptyset (&sa.sa_mask); sa.sa_flags = 0; sigaction (signal, &sa, NULL); raise (signal); } static void __attribute__ ((constructor)) install_handler (void) { struct sigaction sa; const char *sigs = getenv ("SEGFAULT_SIGNALS"); const char *name; sa.sa_handler = (void *) catch_segfault; sigemptyset (&sa.sa_mask); sa.sa_flags = SA_RESTART; /* Maybe we are expected to use an alternative stack. */ if (getenv ("SEGFAULT_USE_ALTSTACK") != 0) { void *stack_mem = malloc (2 * SIGSTKSZ); stack_t ss; if (stack_mem != NULL) { ss.ss_sp = stack_mem; ss.ss_flags = 0; ss.ss_size = 2 * SIGSTKSZ; if (sigaltstack (&ss, NULL) == 0) sa.sa_flags |= SA_ONSTACK; } } if (sigs == NULL) sigaction (SIGSEGV, &sa, NULL); else if (sigs[0] == '\0') /* Do not do anything. */ return; else { const char *where; int all = __strcasecmp (sigs, "all") == 0; #define INSTALL_FOR_SIG(sig, name) \ where = __strcasestr (sigs, name); \ if (all || (where != NULL \ && (where == sigs || !isalnum (where[-1])) \ && !isalnum (where[sizeof (name) - 1]))) \ sigaction (sig, &sa, NULL); INSTALL_FOR_SIG (SIGSEGV, "segv"); INSTALL_FOR_SIG (SIGILL, "ill"); #ifdef SIGBUS INSTALL_FOR_SIG (SIGBUS, "bus"); #endif #ifdef SIGSTKFLT INSTALL_FOR_SIG (SIGSTKFLT, "stkflt"); #endif INSTALL_FOR_SIG (SIGABRT, "abrt"); INSTALL_FOR_SIG (SIGFPE, "fpe"); } /* Preserve the output file name if there is any given. */ name = getenv ("SEGFAULT_OUTPUT_NAME"); if (name != NULL && name[0] != '\0') { int ret = access (name, R_OK | W_OK); if (ret == 0 || (ret == -1 && errno == ENOENT)) fname = __strdup (name); } }