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Diffstat (limited to 'lib/sigprocmask.c')
| -rw-r--r-- | lib/sigprocmask.c | 329 |
1 files changed, 329 insertions, 0 deletions
diff --git a/lib/sigprocmask.c b/lib/sigprocmask.c new file mode 100644 index 0000000..6780a37 --- /dev/null +++ b/lib/sigprocmask.c @@ -0,0 +1,329 @@ +/* POSIX compatible signal blocking. + Copyright (C) 2006-2011 Free Software Foundation, Inc. + Written by Bruno Haible <bruno@clisp.org>, 2006. + + 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 <signal.h> + +#include <errno.h> +#include <stdint.h> +#include <stdlib.h> + +/* We assume that a platform without POSIX signal blocking functions + also does not have the POSIX sigaction() function, only the + signal() function. We also assume signal() has SysV semantics, + where any handler is uninstalled prior to being invoked. This is + true for Woe32 platforms. */ + +/* We use raw signal(), but also provide a wrapper rpl_signal() so + that applications can query or change a blocked signal. */ +#undef signal + +/* Provide invalid signal numbers as fallbacks if the uncatchable + signals are not defined. */ +#ifndef SIGKILL +# define SIGKILL (-1) +#endif +#ifndef SIGSTOP +# define SIGSTOP (-1) +#endif + +/* On native Windows, as of 2008, the signal SIGABRT_COMPAT is an alias + for the signal SIGABRT. Only one signal handler is stored for both + SIGABRT and SIGABRT_COMPAT. SIGABRT_COMPAT is not a signal of its own. */ +#if (defined _WIN32 || defined __WIN32__) && ! defined __CYGWIN__ +# undef SIGABRT_COMPAT +# define SIGABRT_COMPAT 6 +#endif +#ifdef SIGABRT_COMPAT +# define SIGABRT_COMPAT_MASK (1U << SIGABRT_COMPAT) +#else +# define SIGABRT_COMPAT_MASK 0 +#endif + +typedef void (*handler_t) (int); + +/* Handling of gnulib defined signals. */ + +#if GNULIB_defined_SIGPIPE +static handler_t SIGPIPE_handler = SIG_DFL; +#endif + +#if GNULIB_defined_SIGPIPE +static handler_t +ext_signal (int sig, handler_t handler) +{ + switch (sig) + { + case SIGPIPE: + { + handler_t old_handler = SIGPIPE_handler; + SIGPIPE_handler = handler; + return old_handler; + } + default: /* System defined signal */ + return signal (sig, handler); + } +} +# define signal ext_signal +#endif + +int +sigismember (const sigset_t *set, int sig) +{ + if (sig >= 0 && sig < NSIG) + { + #ifdef SIGABRT_COMPAT + if (sig == SIGABRT_COMPAT) + sig = SIGABRT; + #endif + + return (*set >> sig) & 1; + } + else + return 0; +} + +int +sigemptyset (sigset_t *set) +{ + *set = 0; + return 0; +} + +int +sigaddset (sigset_t *set, int sig) +{ + if (sig >= 0 && sig < NSIG) + { + #ifdef SIGABRT_COMPAT + if (sig == SIGABRT_COMPAT) + sig = SIGABRT; + #endif + + *set |= 1U << sig; + return 0; + } + else + { + errno = EINVAL; + return -1; + } +} + +int +sigdelset (sigset_t *set, int sig) +{ + if (sig >= 0 && sig < NSIG) + { + #ifdef SIGABRT_COMPAT + if (sig == SIGABRT_COMPAT) + sig = SIGABRT; + #endif + + *set &= ~(1U << sig); + return 0; + } + else + { + errno = EINVAL; + return -1; + } +} + + +int +sigfillset (sigset_t *set) +{ + *set = ((2U << (NSIG - 1)) - 1) & ~ SIGABRT_COMPAT_MASK; + return 0; +} + +/* Set of currently blocked signals. */ +static volatile sigset_t blocked_set /* = 0 */; + +/* Set of currently blocked and pending signals. */ +static volatile sig_atomic_t pending_array[NSIG] /* = { 0 } */; + +/* Signal handler that is installed for blocked signals. */ +static void +blocked_handler (int sig) +{ + /* Reinstall the handler, in case the signal occurs multiple times + while blocked. There is an inherent race where an asynchronous + signal in between when the kernel uninstalled the handler and + when we reinstall it will trigger the default handler; oh + well. */ + signal (sig, blocked_handler); + if (sig >= 0 && sig < NSIG) + pending_array[sig] = 1; +} + +int +sigpending (sigset_t *set) +{ + sigset_t pending = 0; + int sig; + + for (sig = 0; sig < NSIG; sig++) + if (pending_array[sig]) + pending |= 1U << sig; + *set = pending; + return 0; +} + +/* The previous signal handlers. + Only the array elements corresponding to blocked signals are relevant. */ +static volatile handler_t old_handlers[NSIG]; + +int +sigprocmask (int operation, const sigset_t *set, sigset_t *old_set) +{ + if (old_set != NULL) + *old_set = blocked_set; + + if (set != NULL) + { + sigset_t new_blocked_set; + sigset_t to_unblock; + sigset_t to_block; + + switch (operation) + { + case SIG_BLOCK: + new_blocked_set = blocked_set | *set; + break; + case SIG_SETMASK: + new_blocked_set = *set; + break; + case SIG_UNBLOCK: + new_blocked_set = blocked_set & ~*set; + break; + default: + errno = EINVAL; + return -1; + } + to_unblock = blocked_set & ~new_blocked_set; + to_block = new_blocked_set & ~blocked_set; + + if (to_block != 0) + { + int sig; + + for (sig = 0; sig < NSIG; sig++) + if ((to_block >> sig) & 1) + { + pending_array[sig] = 0; + if ((old_handlers[sig] = signal (sig, blocked_handler)) != SIG_ERR) + blocked_set |= 1U << sig; + } + } + + if (to_unblock != 0) + { + sig_atomic_t received[NSIG]; + int sig; + + for (sig = 0; sig < NSIG; sig++) + if ((to_unblock >> sig) & 1) + { + if (signal (sig, old_handlers[sig]) != blocked_handler) + /* The application changed a signal handler while the signal + was blocked, bypassing our rpl_signal replacement. + We don't support this. */ + abort (); + received[sig] = pending_array[sig]; + blocked_set &= ~(1U << sig); + pending_array[sig] = 0; + } + else + received[sig] = 0; + + for (sig = 0; sig < NSIG; sig++) + if (received[sig]) + raise (sig); + } + } + return 0; +} + +/* Install the handler FUNC for signal SIG, and return the previous + handler. */ +handler_t +rpl_signal (int sig, handler_t handler) +{ + /* We must provide a wrapper, so that a user can query what handler + they installed even if that signal is currently blocked. */ + if (sig >= 0 && sig < NSIG && sig != SIGKILL && sig != SIGSTOP + && handler != SIG_ERR) + { + #ifdef SIGABRT_COMPAT + if (sig == SIGABRT_COMPAT) + sig = SIGABRT; + #endif + + if (blocked_set & (1U << sig)) + { + /* POSIX states that sigprocmask and signal are both + async-signal-safe. This is not true of our + implementation - there is a slight data race where an + asynchronous interrupt on signal A can occur after we + install blocked_handler but before we have updated + old_handlers for signal B, such that handler A can see + stale information if it calls signal(B). Oh well - + signal handlers really shouldn't try to manipulate the + installed handlers of unrelated signals. */ + handler_t result = old_handlers[sig]; + old_handlers[sig] = handler; + return result; + } + else + return signal (sig, handler); + } + else + { + errno = EINVAL; + return SIG_ERR; + } +} + +#if GNULIB_defined_SIGPIPE +/* Raise the signal SIG. */ +int +rpl_raise (int sig) +# undef raise +{ + switch (sig) + { + case SIGPIPE: + if (blocked_set & (1U << sig)) + pending_array[sig] = 1; + else + { + handler_t handler = SIGPIPE_handler; + if (handler == SIG_DFL) + exit (128 + SIGPIPE); + else if (handler != SIG_IGN) + (*handler) (sig); + } + return 0; + default: /* System defined signal */ + return raise (sig); + } +} +#endif |