sysdeps/generic/segfault.c

   1 /* Catch segmentation faults and print backtrace.
   2    Copyright (C) 1998, 1999, 2000, 2001, 2002, 2004
   3    Free Software Foundation, Inc.
   4    This file is part of the GNU C Library.
   5    Contributed by Ulrich Drepper <drepper@cygnus.com>, 1998.
   6
   7    The GNU C Library is free software; you can redistribute it and/or
   8    modify it under the terms of the GNU Lesser General Public
   9    License as published by the Free Software Foundation; either
  10    version 2.1 of the License, or (at your option) any later version.
  11
  12    The GNU C Library is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15    Lesser General Public License for more details.
  16
  17    You should have received a copy of the GNU Lesser General Public
  18    License along with the GNU C Library; if not, write to the Free
  19    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  20    02111-1307 USA.  */
  21
  22 #include <ctype.h>
  23 #include <errno.h>
  24 #include <execinfo.h>
  25 #include <fcntl.h>
  26 #include <signal.h>
  27 #include <stdio.h>
  28 #include <stdlib.h>
  29 #include <string.h>
  30 #include <unistd.h>
  31 #include <stdio-common/_itoa.h>
  32 #include <ldsodefs.h>
  33
  34 #include <bp-checks.h>
  35
  36 /* Get the definition of "struct layout".  */
  37 #include <frame.h>
  38
  39 /* This file defines macros to access the content of the sigcontext element
  40    passed up by the signal handler.  */
  41 #include <sigcontextinfo.h>
  42
  43 /* Get code to possibly dump the content of all registers.  */
  44 #include <register-dump.h>
  45
  46 /* This implementation assumes a stack layout that matches the defaults
  47    used by gcc's `__builtin_frame_address' and `__builtin_return_address'
  48    (FP is the frame pointer register):
  49
  50           +-----------------+     +-----------------+
  51     FP -> | previous FP --------> | previous FP ------>...
  52           |                 |     |                 |
  53           | return address  |     | return address  |
  54           +-----------------+     +-----------------+
  55
  56   */
  57
  58 /* Get some notion of the current stack.  Need not be exactly the top
  59    of the stack, just something somewhere in the current frame.  */
  60 #ifndef CURRENT_STACK_FRAME
  61 # define CURRENT_STACK_FRAME  ({ char __csf; &__csf; })
  62 #endif
  63
  64 /* By default we assume that the stack grows downward.  */
  65 #ifndef INNER_THAN
  66 # define INNER_THAN <
  67 #endif
  68
  69 /* By default assume the `next' pointer in struct layout points to the
  70    next struct layout.  */
  71 #ifndef ADVANCE_STACK_FRAME
  72 # define ADVANCE_STACK_FRAME(next) BOUNDED_1 ((struct layout *) (next))
  73 #endif
  74
  75 /* We'll use tis a lot.  */
  76 #define WRITE_STRING(s) write (fd, s, strlen (s))
  77
  78 /* Name of the output file.  */
  79 static const char *fname;
  80
  81
  82 /* We better should not use `strerror' since it can call far too many
  83    other functions which might fail.  Do it here ourselves.  */
  84 static void
  85 write_strsignal (int fd, int signal)
  86 {
  87   if (signal < 0 || signal >= _NSIG || _sys_siglist[signal] == NULL)
  88     {
  89       char buf[30];
  90       char *ptr = _itoa_word (signal, &buf[sizeof (buf)], 10, 0);
  91       WRITE_STRING ("signal ");
  92       write (fd, buf, &buf[sizeof (buf)] - ptr);
  93     }
  94   else
  95     WRITE_STRING (_sys_siglist[signal]);
  96 }
  97
  98
  99 /* This function is called when a segmentation fault is caught.  The system
 100    is in an instable state now.  This means especially that malloc() might
 101    not work anymore.  */
 102 static void
 103 catch_segfault (int signal, SIGCONTEXT ctx)
 104 {
 105   struct layout *current;
 106   void *__unbounded top_frame;
 107   void *__unbounded top_stack;
 108   int fd;
 109   void **arr;
 110   size_t cnt;
 111   struct sigaction sa;
 112
 113   /* This is the name of the file we are writing to.  If none is given
 114      or we cannot write to this file write to stderr.  */
 115   fd = 2;
 116   if (fname != NULL)
 117     {
 118       fd = open (fname, O_TRUNC | O_WRONLY | O_CREAT, 0666);
 119       if (fd == -1)
 120         fd = 2;
 121     }
 122
 123   WRITE_STRING ("*** ");
 124   write_strsignal (fd, signal);
 125   WRITE_STRING ("\n");
 126
 127 #ifdef REGISTER_DUMP
 128   REGISTER_DUMP;
 129 #endif
 130
 131   WRITE_STRING ("\nBacktrace:\n");
 132
 133   top_frame = GET_FRAME (ctx);
 134   top_stack = GET_STACK (ctx);
 135
 136   /* First count how many entries we'll have.  */
 137   cnt = 1;
 138   current = BOUNDED_1 ((struct layout *) top_frame);
 139   while (!((void *) current INNER_THAN top_stack
 140            || !((void *) current INNER_THAN __libc_stack_end)))
 141     {
 142       ++cnt;
 143
 144       current = ADVANCE_STACK_FRAME (current->next);
 145     }
 146
 147   arr = alloca (cnt * sizeof (void *));
 148
 149   /* First handle the program counter from the structure.  */
 150   arr[0] = GET_PC (ctx);
 151
 152   current = BOUNDED_1 ((struct layout *) top_frame);
 153   cnt = 1;
 154   while (!((void *) current INNER_THAN top_stack
 155            || !((void *) current INNER_THAN __libc_stack_end)))
 156     {
 157       arr[cnt++] = current->return_address;
 158
 159       current = ADVANCE_STACK_FRAME (current->next);
 160     }
 161
 162   /* If the last return address was NULL, assume that it doesn't count.  */
 163   if (arr[cnt-1] == NULL)
 164     cnt--;
 165
 166   /* Now generate nicely formatted output.  */
 167   __backtrace_symbols_fd (arr, cnt, fd);
 168
 169 #ifdef HAVE_PROC_SELF
 170   /* Now the link map.  */
 171   int mapfd = open ("/proc/self/maps", O_RDONLY);
 172   if (mapfd != -1)
 173     {
 174       write (fd, "\nMemory map:\n\n", 14);
 175
 176       char buf[256];
 177       ssize_t n;
 178
 179       while ((n = TEMP_FAILURE_RETRY (read (mapfd, buf, sizeof (buf)))) > 0)
 180         TEMP_FAILURE_RETRY (write (fd, buf, n));
 181
 182       close (mapfd);
 183     }
 184 #endif
 185
 186   /* Pass on the signal (so that a core file is produced).  */
 187   sa.sa_handler = SIG_DFL;
 188   sigemptyset (&sa.sa_mask);
 189   sa.sa_flags = 0;
 190   sigaction (signal, &sa, NULL);
 191   raise (signal);
 192 }
 193
 194
 195 static void
 196 __attribute__ ((constructor))
 197 install_handler (void)
 198 {
 199   struct sigaction sa;
 200   const char *sigs = getenv ("SEGFAULT_SIGNALS");
 201   const char *name;
 202
 203   sa.sa_handler = (void *) catch_segfault;
 204   sigemptyset (&sa.sa_mask);
 205   sa.sa_flags = SA_RESTART;
 206
 207   /* Maybe we are expected to use an alternative stack.  */
 208   if (getenv ("SEGFAULT_USE_ALTSTACK") != 0)
 209     {
 210       void *stack_mem = malloc (2 * SIGSTKSZ);
 211       struct sigaltstack ss;
 212
 213       if (stack_mem != NULL)
 214         {
 215           ss.ss_sp = stack_mem;
 216           ss.ss_flags = 0;
 217           ss.ss_size = 2 * SIGSTKSZ;
 218
 219           if (sigaltstack (&ss, NULL) == 0)
 220             sa.sa_flags |= SA_ONSTACK;
 221         }
 222     }
 223
 224   if (sigs == NULL)
 225     sigaction (SIGSEGV, &sa, NULL);
 226   else if (sigs[0] == '\0')
 227     /* Do not do anything.  */
 228     return;
 229   else
 230     {
 231       const char *where;
 232       int all = __strcasecmp (sigs, "all") == 0;
 233
 234 #define INSTALL_FOR_SIG(sig, name) \
 235       where = __strcasestr (sigs, name);                                      \
 236       if (all || (where != NULL                                               \
 237                   && (where == sigs || !isalnum (where[-1]))                  \
 238                   && !isalnum (where[sizeof (name) - 1])))                    \
 239         sigaction (sig, &sa, NULL);
 240
 241       INSTALL_FOR_SIG (SIGSEGV, "segv");
 242       INSTALL_FOR_SIG (SIGILL, "ill");
 243 #ifdef SIGBUS
 244       INSTALL_FOR_SIG (SIGBUS, "bus");
 245 #endif
 246 #ifdef SIGSTKFLT
 247       INSTALL_FOR_SIG (SIGSTKFLT, "stkflt");
 248 #endif
 249       INSTALL_FOR_SIG (SIGABRT, "abrt");
 250       INSTALL_FOR_SIG (SIGFPE, "fpe");
 251     }
 252
 253   /* Preserve the output file name if there is any given.  */
 254   name = getenv ("SEGFAULT_OUTPUT_NAME");
 255   if (name != NULL && name[0] != '\0')
 256     {
 257       int ret = access (name, R_OK | W_OK);
 258
 259       if (ret == 0 || (ret == -1 && errno == ENOENT))
 260         fname = __strdup (name);
 261     }
 262 }