1 /* Emergency actions in case of a fatal signal.
2 Copyright (C) 2003-2004, 2006-2008 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 3 of the License, or
8 (at your option) any later version.
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, see <http://www.gnu.org/licenses/>. */
22 #include "fatal-signal.h"
29 #include "sig-handler.h"
32 #define SIZEOF(a) (sizeof(a) / sizeof(a[0]))
34 /* ========================================================================= */
37 /* The list of fatal signals.
38 These are those signals whose default action is to terminate the process
39 without a core dump, except
40 SIGKILL - because it cannot be caught,
41 SIGALRM SIGUSR1 SIGUSR2 SIGPOLL SIGIO SIGLOST - because applications
42 often use them for their own purpose,
43 SIGPROF SIGVTALRM - because they are used for profiling,
44 SIGSTKFLT - because it is more similar to SIGFPE, SIGSEGV, SIGBUS,
45 SIGSYS - because it is more similar to SIGABRT, SIGSEGV,
46 SIGPWR - because it of too special use,
47 SIGRTMIN...SIGRTMAX - because they are reserved for application use.
49 SIGXCPU, SIGXFSZ - because they are quite similar to SIGTERM. */
51 static int fatal_signals[] =
53 /* ISO C 99 signals. */
60 /* 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)
93 for (i = 0; i < num_fatal_signals; i++)
95 struct sigaction action;
97 if (sigaction (fatal_signals[i], NULL, &action) >= 0
98 && get_handler (&action) == SIG_IGN)
99 fatal_signals[i] = -1;
102 fatal_signals_initialized = true;
107 /* ========================================================================= */
110 typedef void (*action_t) (void);
112 /* Type of an entry in the actions array.
113 The 'action' field is accessed from within the fatal_signal_handler(),
114 therefore we mark it as 'volatile'. */
117 volatile action_t action;
121 /* The registered cleanup actions. */
122 static actions_entry_t static_actions[32];
123 static actions_entry_t * volatile actions = static_actions;
124 static sig_atomic_t volatile actions_count = 0;
125 static size_t actions_allocated = SIZEOF (static_actions);
128 /* Uninstall the handlers. */
130 uninstall_handlers ()
133 struct sigaction action;
135 action.sa_handler = SIG_DFL;
137 sigemptyset (&action.sa_mask);
138 for (i = 0; i < num_fatal_signals; i++)
139 if (fatal_signals[i] >= 0)
140 sigaction (fatal_signals[i], &action, NULL);
144 /* The signal handler. It gets called asynchronously. */
146 fatal_signal_handler (int sig)
150 /* Get the last registered cleanup action, in a reentrant way. */
152 size_t n = actions_count;
157 action = actions[n].action;
158 /* Execute the action. */
162 /* Now execute the signal's default action.
163 If any cleanup action blocks the signal that triggered the cleanup, the
164 re-raised signal is delivered when this handler returns; otherwise it
165 is delivered already during raise(). */
166 uninstall_handlers ();
171 /* Install the handlers. */
176 struct sigaction action;
178 action.sa_handler = &fatal_signal_handler;
179 /* One-shot handling - if we fault while handling a fault, the
180 cleanup actions are intentionally cut short. */
181 action.sa_flags = SA_NODEFER | SA_RESETHAND;
182 sigemptyset (&action.sa_mask);
183 for (i = 0; i < num_fatal_signals; i++)
184 if (fatal_signals[i] >= 0)
185 sigaction (fatal_signals[i], &action, NULL);
189 /* Register a cleanup function to be executed when a catchable fatal signal
192 at_fatal_signal (action_t action)
194 static bool cleanup_initialized = false;
195 if (!cleanup_initialized)
197 init_fatal_signals ();
199 cleanup_initialized = true;
202 if (actions_count == actions_allocated)
204 /* Extend the actions array. Note that we cannot use xrealloc(),
205 because then the cleanup() function could access an already
206 deallocated array. */
207 actions_entry_t *old_actions = actions;
208 size_t old_actions_allocated = actions_allocated;
209 size_t new_actions_allocated = 2 * actions_allocated;
210 actions_entry_t *new_actions =
211 XNMALLOC (new_actions_allocated, actions_entry_t);
214 /* Don't use memcpy() here, because memcpy takes non-volatile arguments
215 and is therefore not guaranteed to complete all memory stores before
216 the next statement. */
217 for (k = 0; k < old_actions_allocated; k++)
218 new_actions[k] = old_actions[k];
219 actions = new_actions;
220 actions_allocated = new_actions_allocated;
221 /* Now we can free the old actions array. */
222 if (old_actions != static_actions)
225 /* The two uses of 'volatile' in the types above (and ISO C 99 section
226 5.1.2.3.(5)) ensure that we increment the actions_count only after
227 the new action has been written to the memory location
228 actions[actions_count]. */
229 actions[actions_count].action = action;
234 /* ========================================================================= */
237 static sigset_t fatal_signal_set;
240 init_fatal_signal_set ()
242 static bool fatal_signal_set_initialized = false;
243 if (!fatal_signal_set_initialized)
247 init_fatal_signals ();
249 sigemptyset (&fatal_signal_set);
250 for (i = 0; i < num_fatal_signals; i++)
251 if (fatal_signals[i] >= 0)
252 sigaddset (&fatal_signal_set, fatal_signals[i]);
254 fatal_signal_set_initialized = true;
258 /* Temporarily delay the catchable fatal signals. */
260 block_fatal_signals ()
262 init_fatal_signal_set ();
263 sigprocmask (SIG_BLOCK, &fatal_signal_set, NULL);
266 /* Stop delaying the catchable fatal signals. */
268 unblock_fatal_signals ()
270 init_fatal_signal_set ();
271 sigprocmask (SIG_UNBLOCK, &fatal_signal_set, NULL);