musl/src/signal/raise.c

#include <signal.h>
#include <stdint.h>
#include "syscall.h"
#include "pthread_impl.h"

int raise(int sig)
{
	int tid, ret;
	sigset_t set;
	__block_app_sigs(&set);
	tid = __syscall(SYS_gettid);
	ret = syscall(SYS_tkill, tid, sig);
	__restore_sigs(&set);
	return ret;
}
initial check-in, version 0.5.0 2011-02-12 00:22:29 -05:00			`#include <signal.h>`
overhaul implementation-internal signal protections the new approach relies on the fact that the only ways to create sigset_t objects without invoking UB are to use the sigset() functions, or from the masks returned by sigprocmask, sigaction, etc. or in the ucontext_t argument to a signal handler. thus, as long as sigfillset and sigaddset avoid adding the "protected" signals, there is no way the application will ever obtain a sigset_t including these bits, and thus no need to add the overhead of checking/clearing them when sigprocmask or sigaction is called. note that the old code actually failed* to remove the bits from sa_mask when sigaction was called. the new implementations are also significantly smaller, simpler, and faster due to ignoring the useless "GNU HURD signals" 65-1024, which are not used and, if there's any sanity in the world, never will be used. 2011-05-07 23:23:58 -04:00			`#include <stdint.h>`
initial check-in, version 0.5.0 2011-02-12 00:22:29 -05:00			`#include "syscall.h"`
fix (hopefully) all hard-coded 8's for kernel sigset_t size some minor changes to how hard-coded sets for thread-related purposes are handled were also needed, since the old object sizes were not necessarily sufficient. things have gotten a bit ugly in this area, and i think a cleanup is in order at some point, but for now the goal is just to get the code working on all supported archs including mips, which was badly broken by linux rejecting syscalls with the wrong sigset_t size. 2012-08-09 22:52:13 -04:00			`#include "pthread_impl.h"`
initial check-in, version 0.5.0 2011-02-12 00:22:29 -05:00
			`int raise(int sig)`
			`{`
use tkill instead of tgkill in implementing raise this shaves off a useless syscall for getting the caller's pid and brings raise into alignment with other functions which were adapted to use tkill rather than tgkill. commit 83dc6eb087633abcf5608ad651d3b525ca2ec35e documents the rationale for this change, and in particular why the tgkill syscall is useless for its designed purpose of avoiding races. 2014-12-18 20:44:51 -05:00			`int tid, ret;`
fix race condition in raise - just mask signals a signal handler could fork after the pid/tid were read, causing the wrong process to be signalled. i'm not sure if this is supposed to have UB or not, but raise is async-signal-safe, so it probably is allowed. the current solution is slightly expensive so this implementation is likely to be changed in the future. 2011-03-09 20:07:24 -05:00			`sigset_t set;`
transition to using functions for internal signal blocking/restoring there are several reasons for this change. one is getting rid of the repetition of the syscall signature all over the place. another is sharing the constant masks without costly GOT accesses in PIC. the main motivation, however, is accurately representing whether we want to block signals that might be handled by the application, or all signals. 2013-04-26 19:48:01 -04:00			`__block_app_sigs(&set);`
optimize/debloat raise use __syscall rather than syscall when failure is not possible or not to be considered. 2013-04-26 19:02:23 -04:00			`tid = __syscall(SYS_gettid);`
use tkill instead of tgkill in implementing raise this shaves off a useless syscall for getting the caller's pid and brings raise into alignment with other functions which were adapted to use tkill rather than tgkill. commit 83dc6eb087633abcf5608ad651d3b525ca2ec35e documents the rationale for this change, and in particular why the tgkill syscall is useless for its designed purpose of avoiding races. 2014-12-18 20:44:51 -05:00			`ret = syscall(SYS_tkill, tid, sig);`
transition to using functions for internal signal blocking/restoring there are several reasons for this change. one is getting rid of the repetition of the syscall signature all over the place. another is sharing the constant masks without costly GOT accesses in PIC. the main motivation, however, is accurately representing whether we want to block signals that might be handled by the application, or all signals. 2013-04-26 19:48:01 -04:00			`__restore_sigs(&set);`
fix raise semantics with threads. 2011-03-09 19:42:06 -05:00			`return ret;`
initial check-in, version 0.5.0 2011-02-12 00:22:29 -05:00			`}`