/* NAME:
* sigact.c - fake sigaction(2)
*
* SYNOPSIS:
* #include "sigact.h"
*
* int sigaction(int sig, struct sigaction *act,
* struct sigaction *oact);
* int sigaddset(sigset_t *mask, int sig);
* int sigdelset(sigset_t *mask, int sig);
* int sigemptyset(sigset_t *mask);
* int sigfillset(sigset_t *mask);
* int sigismember(sigset_t *mask, int sig);
* int sigpending(sigset_t *set);
* int sigprocmask(int how, sigset_t *set, sigset_t *oset);
* int sigsuspend(sigset_t *mask);
*
* SIG_HDLR (*Signal(int sig, SIG_HDLR (*disp)(int)))(int);
*
* DESCRIPTION:
* This is a fake sigaction implementation. It uses
* sigsetmask(2) et al or sigset(2) and friends if
* available, otherwise it just uses signal(2). If it
* thinks sigaction(2) really exists it compiles to "almost"
* nothing.
*
* In any case it provides a Signal() function that is
* implemented in terms of sigaction().
* If not using signal(2) as part of the underlying
* implementation (USE_SIGNAL or USE_SIGMASK), and
* NO_SIGNAL is not defined, it also provides a signal()
* function that calls Signal().
*
* The need for all this mucking about is the problems
* caused by mixing various signal handling mechanisms in
* the one process. This module allows for a consistent
* POSIX compliant interface to whatever is actually
* available.
*
* sigaction() allows the caller to examine and/or set the
* action to be associated with a given signal. "act" and
* "oact" are pointers to 'sigaction structs':
*.nf
*
* struct sigaction
* {
* SIG_HDLR (*sa_handler)();
* sigset_t sa_mask;
* int sa_flags;
* };
*.fi
*
* SIG_HDLR is normally 'void' in the POSIX implementation
* and for most current systems. On some older UNIX
* systems, signal handlers do not return 'void', so
* this implementation keeps 'sa_handler' inline with the
* hosts normal signal handling conventions.
* 'sa_mask' controls which signals will be blocked while
* the selected signal handler is active. It is not used
* in this implementation.
* 'sa_flags' controls various semantics such as whether
* system calls should be automagically restarted
* (SA_RESTART) etc. It is not used in this
* implementation.
* Either "act" or "oact" may be NULL in which case the
* appropriate operation is skipped.
*
* sigaddset() adds "sig" to the sigset_t pointed to by "mask".
*
* sigdelset() removes "sig" from the sigset_t pointed to
* by "mask".
*
* sigemptyset() makes the sigset_t pointed to by "mask" empty.
*
* sigfillset() makes the sigset_t pointed to by "mask"
* full ie. match all signals.
*
* sigismember() returns true if "sig" is found in "*mask".
*
* sigpending() is supposed to return "set" loaded with the
* set of signals that are blocked and pending for the
* calling process. It does nothing in this impementation.
*
* sigprocmask() is used to examine and/or change the
* signal mask for the calling process. Either "set" or
* "oset" may be NULL in which case the appropriate
* operation is skipped. "how" may be one of SIG_BLOCK,
* SIG_UNBLOCK or SIG_SETMASK. If this package is built
* with USE_SIGNAL, then this routine achieves nothing.
*
* sigsuspend() sets the signal mask to "*mask" and waits
* for a signal to be delivered after which the previous
* mask is restored.
*
*
* RETURN VALUE:
* 0==success, -1==failure
*
* BUGS:
* Since we fake most of this, don't expect fancy usage to
* work.
*
* AUTHOR:
* Simon J. Gerraty <sjg@crufty.net>
*/
/* COPYRIGHT:
* @(#)Copyright (c) 1992-2021, Simon J. Gerraty
*
* This is free software. It comes with NO WARRANTY.
* Permission to use, modify and distribute this source code
* is granted subject to the following conditions.
* 1/ that that the above copyright notice and this notice
* are preserved in all copies and that due credit be given
* to the author.
* 2/ that any changes to this code are clearly commented
* as such so that the author does get blamed for bugs
* other than his own.
*
* Please send copies of changes and bug-fixes to:
* sjg@crufty.net
*
*/
#ifndef lint
static char *RCSid = "$Id: sigact.c,v 1.8 2021/10/14 19:39:17 sjg Exp $";
#endif
#undef _ANSI_SOURCE /* causes problems */
#include <signal.h>
#include <sys/cdefs.h>
#ifdef HAVE_CONFIG_H
# include "config.h"
# ifdef NO_SIGSET
# undef HAVE_SIGSET
# endif
# ifndef HAVE_SIGACTION
# ifdef HAVE_SIGSETMASK
# define USE_SIGMASK
# else
# ifdef HAVE_SIGSET
# define USE_SIGSET
# else
# define USE_SIGNAL
# endif
# endif
# endif
#endif
/*
* some systems have a faulty sigaction() implementation!
* Allow us to bypass it.
* Or they may have installed sigact.h as signal.h which is why
* we have SA_NOCLDSTOP defined.
*/
#if !defined(SA_NOCLDSTOP) || defined(_SIGACT_H) || defined(USE_SIGNAL) || defined(USE_SIGSET) || defined(USE_SIGMASK)
/*
* if we haven't been told,
* try and guess what we should implement with.
*/
#if !defined(USE_SIGSET) && !defined(USE_SIGMASK) && !defined(USE_SIGNAL)
# if defined(sigmask) || defined(BSD) || defined(_BSD) && !defined(BSD41)
# define USE_SIGMASK
# else
# ifndef NO_SIGSET
# define USE_SIGSET
# else
# define USE_SIGNAL
# endif
# endif
#endif
/*
* if we still don't know, we're in trouble
*/
#if !defined(USE_SIGSET) && !defined(USE_SIGMASK) && !defined(USE_SIGNAL)
error must know what to implement with
#endif
#include "sigact.h"
/*
* in case signal() has been mapped to our Signal().
*/
#undef signal
int
sigaction(int sig,
const struct sigaction *act,
struct sigaction *oact)
{
SIG_HDLR(*oldh) ();
if (act) {
#ifdef USE_SIGSET
oldh = sigset(sig, act->sa_handler);
#else
oldh = signal(sig, act->sa_handler);
#endif
} else {
if (oact) {
#ifdef USE_SIGSET
oldh = sigset(sig, SIG_IGN);
#else
oldh = signal(sig, SIG_IGN);
#endif
if (oldh != SIG_IGN && oldh != SIG_ERR) {
#ifdef USE_SIGSET
(void) sigset(sig, oldh);
#else
(void) signal(sig, oldh);
#endif
}
}
}
if (oact) {
oact->sa_handler = oldh;
}
return 0; /* hey we're faking it */
}
#ifndef HAVE_SIGADDSET
int
sigaddset(sigset_t *mask, int sig)
{
*mask |= sigmask(sig);
return 0;
}
int
sigdelset(sigset_t *mask, int sig)
{
*mask &= ~(sigmask(sig));
return 0;
}
int
sigemptyset(sigset_t *mask)
{
*mask = 0;
return 0;
}
int
sigfillset(sigset_t *mask)
{
*mask = ~0;
return 0;
}
int
sigismember(const sigset_t *mask, int sig)
{
return ((*mask) & sigmask(sig));
}
#endif
#ifndef HAVE_SIGPENDING
int
sigpending(sigset_t *set)
{
return 0; /* faking it! */
}
#endif
#ifndef HAVE_SIGPROCMASK
int
sigprocmask(int how, const sigset_t *set, sigset_t *oset)
{
#ifdef USE_SIGSET
int i;
#endif
static sigset_t sm;
static int once = 0;
if (!once) {
/*
* initally we clear sm,
* there after, it represents the last
* thing we did.
*/
once++;
#ifdef USE_SIGMASK
sm = sigblock(0);
#else
sm = 0;
#endif
}
if (oset)
*oset = sm;
if (set) {
switch (how) {
case SIG_BLOCK:
sm |= *set;
break;
case SIG_UNBLOCK:
sm &= ~(*set);
break;
case SIG_SETMASK:
sm = *set;
break;
}
#ifdef USE_SIGMASK
(void) sigsetmask(sm);
#else
#ifdef USE_SIGSET
for (i = 1; i < NSIG; i++) {
if (how == SIG_UNBLOCK) {
if (*set & sigmask(i))
sigrelse(i);
} else
if (sm & sigmask(i)) {
sighold(i);
}
}
#endif
#endif
}
return 0;
}
#endif
#ifndef HAVE_SIGSUSPEND
int
sigsuspend(sigset_t *mask)
{
#ifdef USE_SIGMASK
sigpause(*mask);
#else
int i;
#ifdef USE_SIGSET
for (i = 1; i < NSIG; i++) {
if (*mask & sigmask(i)) {
/* not the same sigpause() as above! */
sigpause(i);
break;
}
}
#else /* signal(2) only */
SIG_HDLR(*oldh) ();
/*
* make sure that signals in mask will not
* be ignored.
*/
for (i = 1; i < NSIG; i++) {
if (*mask & sigmask(i)) {
if ((oldh = signal(i, SIG_DFL)) != SIG_ERR &&
oldh != SIG_IGN &&
oldh != SIG_DFL)
(void) signal(i, oldh); /* restore handler */
}
}
pause(); /* wait for a signal */
#endif
#endif
return 0;
}
#endif
#endif /* ! SA_NOCLDSTOP */
#if 0
#if !defined(SIG_HDLR)
#define SIG_HDLR void
#endif
#if !defined(SIG_ERR)
#define SIG_ERR (SIG_HDLR (*)())-1
#endif
#if !defined(USE_SIGNAL) && !defined(USE_SIGMASK) && !defined(NO_SIGNAL)
/*
* ensure we avoid signal mayhem
*/
extern void (*Signal (int sig, void (*handler) (int)))(int);
SIG_HDLR(*signal(int sig, SIG_HDLR(*handler)(int))
{
return (Signal(sig, handler));
}
#endif
#endif
/* This lot (for GNU-Emacs) goes at the end of the file. */
/*
* Local Variables:
* version-control:t
* comment-column:40
* End:
*/