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download PDF document: trapsignal.9.pdf

SIGNAL(9) FreeBSD Kernel Developer's Manual SIGNAL(9)
NAME signal, SIGADDSET, SIGDELSET, SETEMPTYSET, SIGFILLSET, SIGISMEMBER, SIGISEMPTY, SIGNOTEMPTY, SIGSETEQ, SIGSETNEQ, SIGSETOR, SIGSETAND, SIGSETNAND, SIGSETCANTMASK, SIG_STOPSIGMASK, SIG_CONTSIGMASK, SIGPENDING, cursig, execsigs, issignal, killproc, pgsigio, postsig, sigexit, siginit, signotify, trapsignal - kernel signal functions
SYNOPSIS #include <sys/param.h> #include <sys/proc.h> #include <sys/signalvar.h>
void SIGADDSET(sigset_t set, int signo);
void SIGDELSET(sigset_t set, int signo);
void SIGEMPTYSET(sigset_t set);
void SIGFILLSET(sigset_t set);
int SIGISMEMBER(sigset_t set, int signo);
int SIGISEMPTY(sigset_t set);
int SIGNOTEMPTY(sigset_t set);
int SIGSETEQ(sigset_t set1, sigset_t set2);
int SIGSETNEQ(sigset_t set1, sigset_t set2);
void SIGSETOR(sigset_t set1, sigset_t set2);
void SIGSETAND(sigset_t set1, sigset_t set2);
void SIGSETNAND(sigset_t set1, sigset_t set2);
void SIG_CANTMASK(sigset_t set);
void SIG_STOPSIGMASK(sigset_t set);
void SIG_CONTSIGMASK(sigset_t set);
execsigs(struct proc *p);
int issignal(struct thread *td);
void killproc(struct proc *p, char *why);
void pgsigio(struct sigio **sigiop, int sig, int checkctty);
void postsig(int sig);
void sigexit(struct thread *td, int signum);
void siginit(struct proc *p);
void signotify(struct thread *td);
void trapsignal(struct thread *td, int sig, u_long code);
DESCRIPTION The SIGADDSET() macro adds signo to set. No effort is made to ensure that signo is a valid signal number.
The SIGDELSET() macro removes signo from set. No effort is made to ensure that signo is a valid signal number.
The SIGEMPTYSET() macro clears all signals in set.
The SIGFILLSET() macro sets all signals in set.
The SIGISMEMBER() macro determines if signo is set in set.
The SIGISEMPTY() macro determines if set does not have any signals set.
The SIGNOTEMPTY() macro determines if set has any signals set.
The SIGSETEQ() macro determines if two signal sets are equal; that is, the same signals are set in both.
The SIGSETNEQ() macro determines if two signal sets differ; that is, if any signal set in one is not set in the other.
The SIGSETOR() macro ORs the signals set in set2 into set1.
The SIGSETAND() macro ANDs the signals set in set2 into set1.
The SIGSETNAND() macro NANDs the signals set in set2 into set1.
The SIG_CANTMASK() macro clears the SIGKILL and SIGSTOP signals from set. These two signals cannot be blocked or caught and SIG_CANTMASK() is used in code where signals are manipulated to ensure this policy is enforced.

The 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, SIGPENDING() will return true even if the signal is masked.
The cursig() function returns the signal number that should be delivered to process td->td_proc. If there are no signals pending, zero is returned.
The execsigs() function resets the signal set and signal stack of a process in preparation for an execve(2). The process lock for p must be held before execsigs() is called.
The issignal() function determines if there are any pending signals for process td->td_proc that should be caught, or cause this process to terminate or interrupt its current system call. If process 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 issignal() unless the process is a member of an orphaned process group and the stop signal originated from a TTY. The process spin lock for td->td_proc may be acquired and released. The sigacts structure td->td_proc->p_sigacts must be locked before calling issignal() and may be released and reacquired during the call. The process lock for td->td_proc must be acquired before calling issignal() and may be released and reacquired during the call. Default signal actions are not taken for system processes and init.
The killproc() function delivers SIGKILL to p. why is logged as the reason why the process was killed.
The pgsigio() function sends the signal sig to the process or process group sigiop->sio_pgid. If checkctty is non-zero, the signal is only delivered to processes in the process group that have a controlling terminal. If sigiop->sio_pgid is for a process (> 0), the lock for sigiop->sio_proc is acquired and released. If sigiop->sio_pgid is for a process group (< 0), the process group lock for sigiop->sio_pgrp is acquired and released. The lock sigio_lock is acquired and released.
The postsig() function handles the actual delivery of the signal sig. postsig() is called from ast() after the kernel has been notified that a signal should be delivered (via a call to signotify(), which causes the flag PS_NEEDSIGCHK to be set). The process lock for process that owns curthread must be held before postsig() is called, and the current process cannot be 0. The lock for the p_sigacts field of the current process must be held before postsig() is called, and may be released and reacquired.
The sigexit() function causes the process that owns td to exit with a return value of signal number sig. If required, the process will dump core. The process lock for the process that owns td must be held before sigexit() is called.
The siginit() function is called during system initialization to cause every signal with a default property of SA_IGNORE (except SIGCONT) to be ignored by p. The process lock for p is acquired and released, as is the lock for sigacts structure p->p_sigacts. The only process that siginit() is ever called for is proc0.
can be delivered immediately, trapsignal() will deliver it directly; otherwise, trapsignal() will call psignal(9) to cause the signal to be delivered. The process lock for td->td_proc is acquired and released. The lock for the p_sigacts field of td->td_proc is acquired and released.
RETURN VALUES The SIGISMEMBER(), SIGISEMPTY(), SIGNOTEMPTY(), SIGSETEQ(), SIGSETNEQ(), and SIGPENDING() macros all return non-zero (true) if the condition they are checking is found to be true; otherwise, zero (false) is returned.
The cursig() function returns either a valid signal number or zero.
issignal() returns either a valid signal number or zero.
SEE ALSO pgsignal(9), psignal(9)
AUTHORS This manual page was written by Chad David <davidc@FreeBSD.org>.
FreeBSD 14.0-RELEASE-p11 July 14, 2023 FreeBSD 14.0-RELEASE-p11