sysdeps/generic/segfault.c

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