sysdeps/generic/segfault.c

   1 /* Catch segmentation faults and print backtrace.
   2    Copyright (C) 1998 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 <stdlib.h>
  26 #include <string.h>
  27 #include <unistd.h>
  28
  29 /* This file defines macros to access the content of the sigcontext element
  30    passed up by the signal handler.  */
  31 #include <sigcontextinfo.h>
  32
  33 /* Get code to possibly dump the content of all registers.  */
  34 #include <register-dump.h>
  35
  36 /* This is a global variable set at program start time.  It marks the
  37    highest used stack address.  */
  38 extern void *__libc_stack_end;
  39
  40
  41 /* This implementation assumes a stack layout that matches the defaults
  42    used by gcc's `__builtin_frame_address' and `__builtin_return_address'
  43    (FP is the frame pointer register):
  44
  45           +-----------------+     +-----------------+
  46     FP -> | previous FP --------> | previous FP ------>...
  47           |                 |     |                 |
  48           | return address  |     | return address  |
  49           +-----------------+     +-----------------+
  50
  51   */
  52
  53 /* Get some notion of the current stack.  Need not be exactly the top
  54    of the stack, just something somewhere in the current frame.  */
  55 #ifndef CURRENT_STACK_FRAME
  56 # define CURRENT_STACK_FRAME  ({ char __csf; &__csf; })
  57 #endif
  58
  59 /* By default we assume that the stack grows downward.  */
  60 #ifndef INNER_THAN
  61 # define INNER_THAN <
  62 #endif
  63
  64 struct layout
  65 {
  66   struct layout *next;
  67   void *return_address;
  68 };
  69
  70
  71 /* This function is called when a segmentation fault is caught.  The system
  72    is in an instable state now.  This means especially that malloc() might
  73    not work anymore.  */
  74 static void
  75 catch_segfault (int signal, SIGCONTEXT ctx)
  76 {
  77   struct layout *current;
  78   void *top_frame;
  79   void *top_stack;
  80   const char *fname;
  81   int fd;
  82   void **arr;
  83   size_t cnt;
  84   struct sigaction sa;
  85   const char *sigstring;
  86
  87   /* This is the name of the file we are writing to.  If none is given
  88      or we cannot write to this file write to stderr.  */
  89   fd = 2;
  90   fname = getenv ("SEGFAULT_OUTPUT_NAME");
  91   if (fname != NULL && fname[0] != '\0')
  92     {
  93       fd = open (fname, O_TRUNC | O_WRONLY | O_CREAT, 0666);
  94       if (fd == -1)
  95         fd = 2;
  96     }
  97
  98 #define WRITE_STRING(s) write (fd, s, strlen (s))
  99   WRITE_STRING ("*** ");
 100   sigstring = strsignal (signal);
 101   WRITE_STRING (sigstring);
 102   WRITE_STRING ("\n");
 103
 104 #ifdef REGISTER_DUMP
 105   REGISTER_DUMP;
 106 #endif
 107
 108   WRITE_STRING ("\nBacktrace:\n");
 109
 110   top_frame = GET_FRAME (ctx);
 111   top_stack = GET_STACK (ctx);
 112
 113   /* First count how many entries we'll have.  */
 114   cnt = 1;
 115   current = (struct layout *) top_frame;
 116   while (!((void *) current INNER_THAN top_stack
 117            || !((void *) current INNER_THAN __libc_stack_end)))
 118     {
 119       ++cnt;
 120
 121       current = current->next;
 122     }
 123
 124   arr = alloca (cnt * sizeof (void *));
 125
 126   /* First handle the program counter from the structure.  */
 127   arr[0] = GET_PC (ctx);
 128
 129   current = (struct layout *) top_frame;
 130   cnt = 1;
 131   while (!((void *) current INNER_THAN top_stack
 132            || !((void *) current INNER_THAN __libc_stack_end)))
 133     {
 134       arr[cnt++] = current->return_address;
 135
 136       current = current->next;
 137     }
 138
 139   /* If the last return address was NULL, assume that it doesn't count.  */
 140   if (arr[cnt-1] == NULL)
 141     cnt--;
 142
 143   /* Now generate nicely formatted output.  */
 144   __backtrace_symbols_fd (arr, cnt, fd);
 145
 146   /* Pass on the signal (so that a core file is produced).  */
 147   sa.sa_handler = SIG_DFL;
 148   sigemptyset (&sa.sa_mask);
 149   sa.sa_flags = 0;
 150   sigaction (signal, &sa, NULL);
 151   raise (signal);
 152 }
 153
 154
 155 static void
 156 __attribute__ ((constructor))
 157 install_handler (void)
 158 {
 159   struct sigaction sa;
 160   const char *sigs = getenv ("SEGFAULT_SIGNALS");
 161
 162   sa.sa_handler = (void *) catch_segfault;
 163   sigemptyset (&sa.sa_mask);
 164   sa.sa_flags = SA_RESTART;
 165
 166   /* Maybe we are expected to use an alternative stack.  */
 167   if (getenv ("SEGFAULT_USE_ALTSTACK") != 0)
 168     {
 169       void *stack_mem = malloc (2 * SIGSTKSZ);
 170       struct sigaltstack ss;
 171
 172       if (stack_mem != NULL)
 173         {
 174           ss.ss_sp = stack_mem;
 175           ss.ss_flags = 0;
 176           ss.ss_size = 2 * SIGSTKSZ;
 177
 178           if (sigaltstack (&ss, NULL) == 0)
 179             sa.sa_flags |= SA_ONSTACK;
 180         }
 181     }
 182
 183   if (sigs == NULL)
 184     sigaction (SIGSEGV, &sa, NULL);
 185   else if (sigs[0] == '\0')
 186     /* Do not do anything.  */
 187     return;
 188   else
 189     {
 190       const char *where;
 191       int all = __strcasecmp (sigs, "all");
 192
 193 #define INSTALL_FOR_SIG(sig, name) \
 194       where = __strcasestr (sigs, name);                                      \
 195       if (all || (where != NULL                                               \
 196                   && (where == sigs || !isalnum (where[-1]))                  \
 197                   && !isalnum (where[sizeof (name) - 1])))                    \
 198         sigaction (sig, &sa, NULL);
 199
 200       INSTALL_FOR_SIG (SIGSEGV, "segv");
 201       INSTALL_FOR_SIG (SIGILL, "ill");
 202 #ifdef SIGBUS
 203       INSTALL_FOR_SIG (SIGBUS, "bus");
 204 #endif
 205 #ifdef SIGSTKFLT
 206       INSTALL_FOR_SIG (SIGSTKFLT, "stkflt");
 207 #endif
 208       INSTALL_FOR_SIG (SIGABRT, "abrt");
 209       INSTALL_FOR_SIG (SIGFPE, "fpe");
 210     }
 211 }