.\" .\" Copyright (C) 2002 Chad David . All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice(s), this list of conditions and the following disclaimer as .\" the first lines of this file unmodified other than the possible .\" addition of one or more copyright notices. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice(s), this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" .\" THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY .\" EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED .\" WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE .\" DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE LIABLE FOR ANY .\" DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES .\" (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR .\" SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER .\" CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH .\" DAMAGE. .\" .\" $FreeBSD: src/share/man/man9/signal.9,v 1.10.22.1.6.1 2010/12/21 17:09:25 kensmith Exp $ .\" .Dd November 20, 2004 .Dt SIGNAL 9 .Os .Sh NAME .Nm signal , .Nm SIGADDSET , .Nm SIGDELSET , .Nm SETEMPTYSET , .Nm SIGFILLSET , .Nm SIGISMEMBER , .Nm SIGISEMPTY , .Nm SIGNOTEMPTY , .Nm SIGSETEQ , .Nm SIGSETNEQ , .Nm SIGSETOR , .Nm SIGSETAND , .Nm SIGSETNAND , .Nm SIGSETCANTMASK , .Nm SIG_STOPSIGMASK , .Nm SIG_CONTSIGMASK , .Nm SIGPENDING , .Nm cursig , .Nm execsigs , .Nm issignal , .Nm killproc , .Nm pgsigio , .Nm postsig , .Nm sigexit , .Nm siginit , .Nm signotify , .Nm trapsignal .Nd "kernel signal functions" .Sh SYNOPSIS .In sys/param.h .In sys/proc.h .In sys/signalvar.h .Ft void .Fn SIGADDSET "sigset_t set" "int signo" .Ft void .Fn SIGDELSET "sigset_t set" "int signo" .Ft void .Fn SIGEMPTYSET "sigset_t set" .Ft void .Fn SIGFILLSET "sigset_t set" .Ft int .Fn SIGISMEMBER "sigset_t set" "int signo" .Ft int .Fn SIGISEMPTY "sigset_t set" .Ft int .Fn SIGNOTEMPTY "sigset_t set" .Ft int .Fn SIGSETEQ "sigset_t set1" "sigset_t set2" .Ft int .Fn SIGSETNEQ "sigset_t set1" "sigset_t set2" .Ft void .Fn SIGSETOR "sigset_t set1" "sigset_t set2" .Ft void .Fn SIGSETAND "sigset_t set1" "sigset_t set2" .Ft void .Fn SIGSETNAND "sigset_t set1" "sigset_t set2" .Ft void .Fn SIG_CANTMASK "sigset_t set" .Ft void .Fn SIG_STOPSIGMASK "sigset_t set" .Ft void .Fn SIG_CONTSIGMASK "sigset_t set" .Ft int .Fn SIGPENDING "struct proc *p" .Ft int .Fn cursig "struct thread *td" .Ft void .Fn execsigs "struct proc *p" .Ft int .Fn issignal "struct thread *td" .Ft void .Fn killproc "struct proc *p" "char *why" .Ft void .Fn pgsigio "struct sigio **sigiop" "int sig" "int checkctty" .Ft void .Fn postsig "int sig" .Ft void .Fn sigexit "struct thread *td" "int signum" .Ft void .Fn siginit "struct proc *p" .Ft void .Fn signotify "struct thread *td" .Ft void .Fn trapsignal "struct thread *td" "int sig" "u_long code" .Sh DESCRIPTION The .Fn SIGADDSET macro adds .Fa signo to .Fa set . No effort is made to ensure that .Fa signo is a valid signal number. .Pp The .Fn SIGDELSET macro removes .Fa signo from .Fa set . No effort is made to ensure that .Fa signo is a valid signal number. .Pp The .Fn SIGEMPTYSET macro clears all signals in .Fa set . .Pp The .Fn SIGFILLSET macro sets all signals in .Fa set . .Pp The .Fn SIGISMEMBER macro determines if .Fa signo is set in .Fa set . .Pp The .Fn SIGISEMPTY macro determines if .Fa set does not have any signals set. .Pp The .Fn SIGNOTEMPTY macro determines if .Fa set has any signals set. .Pp The .Fn SIGSETEQ macro determines if two signal sets are equal; that is, the same signals are set in both. .Pp The .Fn SIGSETNEQ macro determines if two signal sets differ; that is, if any signal set in one is not set in the other. .Pp The .Fn SIGSETOR macro ORs the signals set in .Fa set2 into .Fa set1 . .Pp The .Fn SIGSETAND macro ANDs the signals set in .Fa set2 into .Fa set1 . .Pp The .Fn SIGSETNAND macro NANDs the signals set in .Fa set2 into .Fa set1 . .Pp The .Fn SIG_CANTMASK macro clears the .Dv SIGKILL and .Dv SIGSTOP signals from .Fa set . These two signals cannot be blocked or caught and .Fn SIG_CANTMASK is used in code where signals are manipulated to ensure this policy is enforced. .Pp The .Fn SIG_STOPSIGMASK macro clears the .Dv SIGSTOP , .Dv SIGTSTP , .Dv SIGTTIN , and .Dv SIGTTOU signals from .Fa set . .Fn SIG_STOPSIGMASK is used to clear stop signals when a process is waiting for a child to exit or exec, and when a process is continuing after having been suspended. .Pp The .Fn SIG_CONTSIGMASK macro clears the .Dv SIGCONT signal from .Fa set . .Fn SIG_CONTSIGMASK is called when a process is stopped. .Pp The .Fn SIGPENDING macro determines if the given process has any pending signals that are not masked. If the process has a pending signal and the process is currently being traced, .Fn SIGPENDING will return true even if the signal is masked. .Pp The .Fn cursig function returns the signal number that should be delivered to process .Fa td->td_proc . If there are no signals pending, zero is returned. .Pp The .Fn execsigs function resets the signal set and signal stack of a process in preparation for an .Xr execve 2 . The lock for .Fa p must be held before .Fn execsigs is called. .Pp The .Fn issignal function determines if there are any pending signals for process .Fa td->td_proc that should be caught, or cause this process to terminate or interrupt its current system call. If process .Fa td->td_proc is currently being traced, ignored signals will be handled and the process is always stopped. Stop signals are handled and cleared right away by .Fn issignal unless the process is a member of an orphaned process group and the stop signal originated from a TTY. The .Va sched_lock lock may be acquired and released, and if .Va Giant is held, it may be released and reacquired. The .Vt sigacts structure .Fa td->td_proc->p_sigacts must be locked before calling .Fn issignal and may be released and reacquired during the call. The process lock for .Fa td->td_proc must be acquired before calling .Fn issignal and may be released and reacquired during the call. The lock for the parent of .Fa td->td_proc may also be acquired and released. Default signal actions are not taken for system processes and init. .Pp The .Fn killproc function delivers .Dv SIGKILL to .Fa p . .Fa why is logged as the reason .Em why the process was killed. .Pp The .Fn pgsigio function sends the signal .Fa sig to the process or process group .Fa sigiop->sio_pgid . If .Fa checkctty is non-zero, the signal is only delivered to processes in the process group that have a controlling terminal. If .Fa sigiop->sio_pgid is for a process (> 0), the lock for .Fa sigiop->sio_proc is acquired and released. If .Fa sigiop->sio_pgid is for a process group (< 0), the process group lock for .Fa sigiop->sio_pgrp is acquired and released. The lock .Va sigio_lock is acquired and released. .Pp The .Fn postsig function handles the actual delivery of the signal .Fa sig . .Fn postsig is called from .Fn ast after the kernel has been notified that a signal should be delivered (via a call to .Fn signotify , which causes the flag .Dv PS_NEEDSIGCHK to be set). The lock for process that owns .Va curthread must be held before .Fn postsig is called, and the current process cannot be 0. The lock for the .Va p_sigacts field of the current process must be held before .Fn postsig is called, and may be released and reacquired. .Pp The .Fn sigexit function causes the process that owns .Fa td to exit with a return value of signal number .Fa sig . If required, the process will dump core. The lock for the process that owns .Fa td must be held before .Fn sigexit is called. .Pp The .Fn siginit function is called during system initialization to cause every signal with a default property of .Dv SA_IGNORE (except .Dv SIGCONT ) to be ignored by .Fa p . The process lock for .Fa p is acquired and released by .Fn siginit . The only process that .Fn siginit is ever called for is .Va proc0 . .Pp The .Fn signotify function flags that there are unmasked signals pending that .Fn ast should handle. The lock for process .Fa td->td_proc must be held before .Fn signotify is called, and .Va sched_lock is acquired and released. .Pp The .Fn trapsignal function sends a signal that is the result of a trap to process .Fa td->td_proc . If the process is not being traced and the signal can be delivered immediately, .Fn trapsignal will deliver it directly; otherwise, .Fn trapsignal will call .Xr psignal 9 to cause the signal to be delivered. The .Va sched_lock lock is acquired and released, as is the lock for .Fa td->td_proc . The lock for the .Va p_sigacts field of .Fa td->td_proc is acquired and released. .Sh RETURN VALUES The .Fn SIGISMEMBER , .Fn SIGISEMPTY , .Fn SIGNOTEMPTY , .Fn SIGSETEQ , .Fn SIGSETNEQ , and .Fn SIGPENDING macros all return non-zero (true) if the condition they are checking is found to be true; otherwise, zero (false) is returned. .Pp The .Fn cursig function returns either a valid signal number or zero. .Pp .Fn issignal returns either a valid signal number or zero. .Sh SEE ALSO .Xr gsignal 9 , .Xr pgsignal 9 , .Xr psignal 9 .Sh AUTHORS This manual page was written by .An Chad David Aq davidc@FreeBSD.org .