Edit
kc3-lang/gnulib/lib/fatal-signal.c
Jim Meyering
- lib/fatal-signal.c
-
/* Emergency actions in case of a fatal signal. Copyright (C) 2003-2004, 2006-2010 Free Software Foundation, Inc. Written by Bruno Haible <bruno@clisp.org>, 2003. This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program. If not, see <http://www.gnu.org/licenses/>. */ #include <config.h> /* Specification. */ #include "fatal-signal.h" #include <stdbool.h> #include <stdlib.h> #include <signal.h> #include <unistd.h> #include "sig-handler.h" #include "xalloc.h" #define SIZEOF(a) (sizeof(a) / sizeof(a[0])) /* ========================================================================= */ /* The list of fatal signals. These are those signals whose default action is to terminate the process without a core dump, except SIGKILL - because it cannot be caught, SIGALRM SIGUSR1 SIGUSR2 SIGPOLL SIGIO SIGLOST - because applications often use them for their own purpose, SIGPROF SIGVTALRM - because they are used for profiling, SIGSTKFLT - because it is more similar to SIGFPE, SIGSEGV, SIGBUS, SIGSYS - because it is more similar to SIGABRT, SIGSEGV, SIGPWR - because it of too special use, SIGRTMIN...SIGRTMAX - because they are reserved for application use. plus SIGXCPU, SIGXFSZ - because they are quite similar to SIGTERM. */ static int fatal_signals[] = { /* ISO C 99 signals. */ #ifdef SIGINT SIGINT, #endif #ifdef SIGTERM SIGTERM, #endif /* POSIX:2001 signals. */ #ifdef SIGHUP SIGHUP, #endif #ifdef SIGPIPE SIGPIPE, #endif /* BSD signals. */ #ifdef SIGXCPU SIGXCPU, #endif #ifdef SIGXFSZ SIGXFSZ, #endif /* Woe32 signals. */ #ifdef SIGBREAK SIGBREAK, #endif 0 }; #define num_fatal_signals (SIZEOF (fatal_signals) - 1) /* Eliminate signals whose signal handler is SIG_IGN. */ static void init_fatal_signals (void) { static bool fatal_signals_initialized = false; if (!fatal_signals_initialized) { size_t i; for (i = 0; i < num_fatal_signals; i++) { struct sigaction action; if (sigaction (fatal_signals[i], NULL, &action) >= 0 && get_handler (&action) == SIG_IGN) fatal_signals[i] = -1; } fatal_signals_initialized = true; } } /* ========================================================================= */ typedef void (*action_t) (void); /* Type of an entry in the actions array. The 'action' field is accessed from within the fatal_signal_handler(), therefore we mark it as 'volatile'. */ typedef struct { volatile action_t action; } actions_entry_t; /* The registered cleanup actions. */ static actions_entry_t static_actions[32]; static actions_entry_t * volatile actions = static_actions; static sig_atomic_t volatile actions_count = 0; static size_t actions_allocated = SIZEOF (static_actions); /* The saved signal handlers. Size 32 would not be sufficient: On HP-UX, SIGXCPU = 33, SIGXFSZ = 34. */ static struct sigaction saved_sigactions[64]; /* Uninstall the handlers. */ static inline void uninstall_handlers () { size_t i; for (i = 0; i < num_fatal_signals; i++) if (fatal_signals[i] >= 0) { int sig = fatal_signals[i]; if (saved_sigactions[sig].sa_handler == SIG_IGN) saved_sigactions[sig].sa_handler = SIG_DFL; sigaction (sig, &saved_sigactions[sig], NULL); } } /* The signal handler. It gets called asynchronously. */ static void fatal_signal_handler (int sig) { for (;;) { /* Get the last registered cleanup action, in a reentrant way. */ action_t action; size_t n = actions_count; if (n == 0) break; n--; actions_count = n; action = actions[n].action; /* Execute the action. */ action (); } /* Now execute the signal's default action. If the signal being delivered was blocked, the re-raised signal would be delivered when this handler returns. But the way we install this handler, no signal is blocked, and the re-raised signal is delivered already during raise(). */ uninstall_handlers (); raise (sig); } /* Install the handlers. */ static inline void install_handlers () { size_t i; struct sigaction action; action.sa_handler = &fatal_signal_handler; /* If we get a fatal signal while executing fatal_signal_handler, enter fatal_signal_handler recursively, since it is reentrant. Hence no SA_RESETHAND. */ action.sa_flags = SA_NODEFER; sigemptyset (&action.sa_mask); for (i = 0; i < num_fatal_signals; i++) if (fatal_signals[i] >= 0) { int sig = fatal_signals[i]; if (!(sig < sizeof (saved_sigactions) / sizeof (saved_sigactions[0]))) abort (); sigaction (sig, &action, &saved_sigactions[sig]); } } /* Register a cleanup function to be executed when a catchable fatal signal occurs. */ void at_fatal_signal (action_t action) { static bool cleanup_initialized = false; if (!cleanup_initialized) { init_fatal_signals (); install_handlers (); cleanup_initialized = true; } if (actions_count == actions_allocated) { /* Extend the actions array. Note that we cannot use xrealloc(), because then the cleanup() function could access an already deallocated array. */ actions_entry_t *old_actions = actions; size_t old_actions_allocated = actions_allocated; size_t new_actions_allocated = 2 * actions_allocated; actions_entry_t *new_actions = XNMALLOC (new_actions_allocated, actions_entry_t); size_t k; /* Don't use memcpy() here, because memcpy takes non-volatile arguments and is therefore not guaranteed to complete all memory stores before the next statement. */ for (k = 0; k < old_actions_allocated; k++) new_actions[k] = old_actions[k]; actions = new_actions; actions_allocated = new_actions_allocated; /* Now we can free the old actions array. */ if (old_actions != static_actions) free (old_actions); } /* The two uses of 'volatile' in the types above (and ISO C 99 section 5.1.2.3.(5)) ensure that we increment the actions_count only after the new action has been written to the memory location actions[actions_count]. */ actions[actions_count].action = action; actions_count++; } /* ========================================================================= */ static sigset_t fatal_signal_set; static void init_fatal_signal_set () { static bool fatal_signal_set_initialized = false; if (!fatal_signal_set_initialized) { size_t i; init_fatal_signals (); sigemptyset (&fatal_signal_set); for (i = 0; i < num_fatal_signals; i++) if (fatal_signals[i] >= 0) sigaddset (&fatal_signal_set, fatal_signals[i]); fatal_signal_set_initialized = true; } } /* Temporarily delay the catchable fatal signals. */ void block_fatal_signals () { init_fatal_signal_set (); sigprocmask (SIG_BLOCK, &fatal_signal_set, NULL); } /* Stop delaying the catchable fatal signals. */ void unblock_fatal_signals () { init_fatal_signal_set (); sigprocmask (SIG_UNBLOCK, &fatal_signal_set, NULL); }