1 /* Emergency actions in case of a fatal signal.
2 Copyright (C) 2003-2004, 2006 Free Software Foundation, Inc.
3 Written by Bruno Haible <bruno@clisp.org>, 2003.
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)
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.
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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
25 #include "fatal-signal.h"
35 #define SIZEOF(a) (sizeof(a) / sizeof(a[0]))
38 /* ========================================================================= */
41 /* The list of fatal signals.
42 These are those signals whose default action is to terminate the process
43 without a core dump, except
44 SIGKILL - because it cannot be caught,
45 SIGALRM SIGUSR1 SIGUSR2 SIGPOLL SIGIO SIGLOST - because applications
46 often use them for their own purpose,
47 SIGPROF SIGVTALRM - because they are used for profiling,
48 SIGSTKFLT - because it is more similar to SIGFPE, SIGSEGV, SIGBUS,
49 SIGSYS - because it is more similar to SIGABRT, SIGSEGV,
50 SIGPWR - because it of too special use,
51 SIGRTMIN...SIGRTMAX - because they are reserved for application use.
53 SIGXCPU, SIGXFSZ - because they are quite similar to SIGTERM. */
55 static int fatal_signals[] =
57 /* ISO C 99 signals. */
64 /* POSIX:2001 signals. */
81 #define num_fatal_signals (SIZEOF (fatal_signals) - 1)
83 /* Eliminate signals whose signal handler is SIG_IGN. */
86 init_fatal_signals (void)
88 static bool fatal_signals_initialized = false;
89 if (!fatal_signals_initialized)
94 for (i = 0; i < num_fatal_signals; i++)
96 struct sigaction action;
98 if (sigaction (fatal_signals[i], NULL, &action) >= 0
99 && action.sa_handler == SIG_IGN)
100 fatal_signals[i] = -1;
104 fatal_signals_initialized = true;
109 /* ========================================================================= */
112 typedef void (*action_t) (void);
114 /* Type of an entry in the actions array.
115 The 'action' field is accessed from within the fatal_signal_handler(),
116 therefore we mark it as 'volatile'. */
119 volatile action_t action;
123 /* The registered cleanup actions. */
124 static actions_entry_t static_actions[32];
125 static actions_entry_t * volatile actions = static_actions;
126 static sig_atomic_t volatile actions_count = 0;
127 static size_t actions_allocated = SIZEOF (static_actions);
130 /* Uninstall the handlers. */
132 uninstall_handlers ()
136 for (i = 0; i < num_fatal_signals; i++)
137 if (fatal_signals[i] >= 0)
138 signal (fatal_signals[i], SIG_DFL);
142 /* The signal handler. It gets called asynchronously. */
144 fatal_signal_handler (int sig)
148 /* Get the last registered cleanup action, in a reentrant way. */
150 size_t n = actions_count;
155 action = actions[n].action;
156 /* Execute the action. */
160 /* Now execute the signal's default action.
161 If signal() blocks the signal being delivered for the duration of the
162 signal handler's execution, the re-raised signal is delivered when this
163 handler returns; otherwise it is delivered already during raise(). */
164 uninstall_handlers ();
168 kill (getpid (), sig);
173 /* Install the handlers. */
179 for (i = 0; i < num_fatal_signals; i++)
180 if (fatal_signals[i] >= 0)
181 signal (fatal_signals[i], &fatal_signal_handler);
185 /* Register a cleanup function to be executed when a catchable fatal signal
188 at_fatal_signal (action_t action)
190 static bool cleanup_initialized = false;
191 if (!cleanup_initialized)
193 init_fatal_signals ();
195 cleanup_initialized = true;
198 if (actions_count == actions_allocated)
200 /* Extend the actions array. Note that we cannot use xrealloc(),
201 because then the cleanup() function could access an already
202 deallocated array. */
203 actions_entry_t *old_actions = actions;
204 size_t new_actions_allocated = 2 * actions_allocated;
205 actions_entry_t *new_actions =
206 xmalloc (new_actions_allocated * sizeof (actions_entry_t));
208 memcpy (new_actions, old_actions,
209 actions_allocated * sizeof (actions_entry_t));
210 actions = new_actions;
211 actions_allocated = new_actions_allocated;
212 /* Now we can free the old actions array. */
213 if (old_actions != static_actions)
216 /* The two uses of 'volatile' in the types above (and ISO C 99 section
217 5.1.2.3.(5)) ensure that we increment the actions_count only after
218 the new action has been written to the memory location
219 actions[actions_count]. */
220 actions[actions_count].action = action;
225 /* ========================================================================= */
228 #if HAVE_POSIX_SIGNALBLOCKING
230 static sigset_t fatal_signal_set;
233 init_fatal_signal_set ()
235 static bool fatal_signal_set_initialized = false;
236 if (!fatal_signal_set_initialized)
240 init_fatal_signals ();
242 sigemptyset (&fatal_signal_set);
243 for (i = 0; i < num_fatal_signals; i++)
244 if (fatal_signals[i] >= 0)
245 sigaddset (&fatal_signal_set, fatal_signals[i]);
247 fatal_signal_set_initialized = true;
251 /* Temporarily delay the catchable fatal signals. */
253 block_fatal_signals ()
255 init_fatal_signal_set ();
256 sigprocmask (SIG_BLOCK, &fatal_signal_set, NULL);
259 /* Stop delaying the catchable fatal signals. */
261 unblock_fatal_signals ()
263 init_fatal_signal_set ();
264 sigprocmask (SIG_UNBLOCK, &fatal_signal_set, NULL);
269 /* Don't bother caring about the old systems which don't have POSIX signal
273 block_fatal_signals ()
278 unblock_fatal_signals ()