gnu/dist/gettext/gettext-tools/lib/fatal-signal.c

   1 /* Emergency actions in case of a fatal signal.
   2    Copyright (C) 2003-2004 Free Software Foundation, Inc.
   3    Written by Bruno Haible <bruno@clisp.org>, 2003.
   4
   5    This program is free software; you can redistribute it and/or modify
   6    it under the terms of the GNU General Public License as published by
   7    the Free Software Foundation; either version 2, or (at your option)
   8    any later version.
   9
  10    This program is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13    GNU General Public License for more details.
  14
  15    You should have received a copy of the GNU General Public License
  16    along with this program; if not, write to the Free Software Foundation,
  17    Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
  18
  19
  20 #ifdef HAVE_CONFIG_H
  21 # include "config.h"
  22 #endif
  23
  24 /* Specification.  */
  25 #include "fatal-signal.h"
  26
  27 #include <stdbool.h>
  28 #include <stdlib.h>
  29 #include <signal.h>
  30 #include <string.h>
  31 #if HAVE_UNISTD_H
  32 # include <unistd.h>
  33 #endif
  34
  35 #include "xalloc.h"
  36
  37 #define SIZEOF(a) (sizeof(a) / sizeof(a[0]))
  38
  39
  40 /* ========================================================================= */
  41
  42
  43 /* The list of fatal signals.
  44    These are those signals whose default action is to terminate the process
  45    without a core dump, except
  46      SIGKILL - because it cannot be caught,
  47      SIGALRM SIGUSR1 SIGUSR2 SIGPOLL SIGIO SIGLOST - because applications
  48        often use them for their own purpose,
  49      SIGPROF SIGVTALRM - because they are used for profiling,
  50      SIGSTKFLT - because it is more similar to SIGFPE, SIGSEGV, SIGBUS,
  51      SIGSYS - because it is more similar to SIGABRT, SIGSEGV,
  52      SIGPWR - because it of too special use,
  53      SIGRTMIN...SIGRTMAX - because they are reserved for application use.
  54    plus
  55      SIGXCPU, SIGXFSZ - because they are quite similar to SIGTERM.  */
  56
  57 static int fatal_signals[] =
  58   {
  59     /* ISO C 99 signals.  */
  60 #ifdef SIGINT
  61     SIGINT,
  62 #endif
  63 #ifdef SIGTERM
  64     SIGTERM,
  65 #endif
  66     /* POSIX:2001 signals.  */
  67 #ifdef SIGHUP
  68     SIGHUP,
  69 #endif
  70 #ifdef SIGPIPE
  71     SIGPIPE,
  72 #endif
  73     /* BSD signals.  */
  74 #ifdef SIGXCPU
  75     SIGXCPU,
  76 #endif
  77 #ifdef SIGXFSZ
  78     SIGXFSZ,
  79 #endif
  80     0
  81   };
  82
  83 #define num_fatal_signals (SIZEOF (fatal_signals) - 1)
  84
  85 /* Eliminate signals whose signal handler is SIG_IGN.  */
  86
  87 static void
  88 init_fatal_signals (void)
  89 {
  90   static bool fatal_signals_initialized = false;
  91   if (!fatal_signals_initialized)
  92     {
  93 #if HAVE_SIGACTION
  94       size_t i;
  95
  96       for (i = 0; i < num_fatal_signals; i++)
  97         {
  98           struct sigaction action;
  99
 100           if (sigaction (fatal_signals[i], NULL, &action) >= 0
 101               && action.sa_handler == SIG_IGN)
 102             fatal_signals[i] = -1;
 103         }
 104 #endif
 105
 106       fatal_signals_initialized = true;
 107     }
 108 }
 109
 110
 111 /* ========================================================================= */
 112
 113
 114 typedef void (*action_t) (void);
 115
 116 /* Type of an entry in the actions array.
 117    The 'action' field is accessed from within the fatal_signal_handler(),
 118    therefore we mark it as 'volatile'.  */
 119 typedef struct
 120 {
 121   volatile action_t action;
 122 }
 123 actions_entry_t;
 124
 125 /* The registered cleanup actions.  */
 126 static actions_entry_t static_actions[32];
 127 static actions_entry_t * volatile actions = static_actions;
 128 static sig_atomic_t volatile actions_count = 0;
 129 static size_t actions_allocated = SIZEOF (static_actions);
 130
 131
 132 /* Uninstall the handlers.  */
 133 static inline void
 134 uninstall_handlers ()
 135 {
 136   size_t i;
 137
 138   for (i = 0; i < num_fatal_signals; i++)
 139     if (fatal_signals[i] >= 0)
 140       signal (fatal_signals[i], SIG_DFL);
 141 }
 142
 143
 144 /* The signal handler.  It gets called asynchronously.  */
 145 static void
 146 fatal_signal_handler (int sig)
 147 {
 148   for (;;)
 149     {
 150       /* Get the last registered cleanup action, in a reentrant way.  */
 151       action_t action;
 152       size_t n = actions_count;
 153       if (n == 0)
 154         break;
 155       n--;
 156       actions_count = n;
 157       action = actions[n].action;
 158       /* Execute the action.  */
 159       action ();
 160     }
 161
 162   /* Now execute the signal's default action.
 163      If signal() blocks the signal being delivered for the duration of the
 164      signal handler's execution, the re-raised signal is delivered when this
 165      handler returns; otherwise it is delivered already during raise().  */
 166   uninstall_handlers ();
 167 #if HAVE_RAISE
 168   raise (sig);
 169 #else
 170   kill (getpid (), sig);
 171 #endif
 172 }
 173
 174
 175 /* Install the handlers.  */
 176 static inline void
 177 install_handlers ()
 178 {
 179   size_t i;
 180
 181   for (i = 0; i < num_fatal_signals; i++)
 182     if (fatal_signals[i] >= 0)
 183       signal (fatal_signals[i], &fatal_signal_handler);
 184 }
 185
 186
 187 /* Register a cleanup function to be executed when a catchable fatal signal
 188    occurs.  */
 189 void
 190 at_fatal_signal (action_t action)
 191 {
 192   static bool cleanup_initialized = false;
 193   if (!cleanup_initialized)
 194     {
 195       init_fatal_signals ();
 196       install_handlers ();
 197       cleanup_initialized = true;
 198     }
 199
 200   if (actions_count == actions_allocated)
 201     {
 202       /* Extend the actions array.  Note that we cannot use xrealloc(),
 203          because then the cleanup() function could access an already
 204          deallocated array.  */
 205       actions_entry_t *old_actions = actions;
 206       size_t new_actions_allocated = 2 * actions_allocated;
 207       actions_entry_t *new_actions =
 208         xmalloc (new_actions_allocated * sizeof (actions_entry_t));
 209
 210       memcpy (new_actions, old_actions,
 211               actions_allocated * sizeof (actions_entry_t));
 212       actions = new_actions;
 213       actions_allocated = new_actions_allocated;
 214       /* Now we can free the old actions array.  */
 215       if (old_actions != static_actions)
 216         free (old_actions);
 217     }
 218   /* The two uses of 'volatile' in the types above (and ISO C 99 section
 219      5.1.2.3.(5)) ensure that we increment the actions_count only after
 220      the new action has been written to the memory location
 221      actions[actions_count].  */
 222   actions[actions_count].action = action;
 223   actions_count++;
 224 }
 225
 226
 227 /* ========================================================================= */
 228
 229
 230 #if HAVE_POSIX_SIGNALBLOCKING
 231
 232 static sigset_t fatal_signal_set;
 233
 234 static void
 235 init_fatal_signal_set ()
 236 {
 237   static bool fatal_signal_set_initialized = false;
 238   if (!fatal_signal_set_initialized)
 239     {
 240       size_t i;
 241
 242       init_fatal_signals ();
 243
 244       sigemptyset (&fatal_signal_set);
 245       for (i = 0; i < num_fatal_signals; i++)
 246         if (fatal_signals[i] >= 0)
 247           sigaddset (&fatal_signal_set, fatal_signals[i]);
 248
 249       fatal_signal_set_initialized = true;
 250     }
 251 }
 252
 253 /* Temporarily delay the catchable fatal signals.  */
 254 void
 255 block_fatal_signals ()
 256 {
 257   init_fatal_signal_set ();
 258   sigprocmask (SIG_BLOCK, &fatal_signal_set, NULL);
 259 }
 260
 261 /* Stop delaying the catchable fatal signals.  */
 262 void
 263 unblock_fatal_signals ()
 264 {
 265   init_fatal_signal_set ();
 266   sigprocmask (SIG_UNBLOCK, &fatal_signal_set, NULL);
 267 }
 268
 269 #else
 270
 271 /* Don't bother caring about the old systems which don't have POSIX signal
 272    blocking.  */
 273
 274 void
 275 block_fatal_signals ()
 276 {
 277 }
 278
 279 void
 280 unblock_fatal_signals ()
 281 {
 282 }
 283
 284 #endif