4.3BSD-Tahoe/usr/src/ucb/Mail/sigretro.c
/*
* Copyright (c) 1980 Regents of the University of California.
* All rights reserved.
*
* Redistribution and use in source and binary forms are permitted
* provided that this notice is preserved and that due credit is given
* to the University of California at Berkeley. The name of the University
* may not be used to endorse or promote products derived from this
* software without specific prior written permission. This software
* is provided ``as is'' without express or implied warranty.
*/
#ifdef notdef
static char sccsid[] = "@(#)sigretro.c 5.3 (Berkeley) 2/18/88";
#endif /* notdef */
#include <signal.h>
#include <errno.h>
#include <setjmp.h>
#include "sigretro.h"
/*
* Retrofit new signal interface to old signal primitives.
* Supported routines:
* sigsys(sig, func)
* sigset(sig, func)
* sighold(sig)
* sigrelse(sig)
* sigignore(sig)
* sigpause(sig)
* Also,
* sigchild()
* to set all held signals to ignored signals in the
* child process after fork(2)
*/
typedef int (*sigtype)();
sigtype sigdisp(), sighold(), sigignore();
/*
* The following helps us keep the extended signal semantics together.
* We remember for each signal the address of the function we're
* supposed to call. s_func is SIG_DFL / SIG_IGN if appropriate.
*/
struct sigtable {
sigtype s_func; /* What to call */
int s_flag; /* Signal flags; see below */
} sigtable[NSIG + 1];
/*
* Signal flag values.
*/
#define SHELD 1 /* Signal is being held */
#define SDEFER 2 /* Signal occured while held */
#define SSET 4 /* s_func is believable */
#define SPAUSE 8 /* are pausing, waiting for sig */
jmp_buf _pause; /* For doing sigpause() */
/*
* Approximate sigsys() system call
* This is almost useless since one only calls sigsys()
* in the child of a vfork(). If you have vfork(), you have new signals
* anyway. The real sigsys() does all the stuff needed to support
* the real sigset() library. We don't bother here, assuming that
* you are either ignoring or defaulting a signal in the child.
*/
sigtype
sigsys(sig, func)
sigtype func;
{
sigtype old;
old = sigdisp(sig);
signal(sig, func);
return(old);
}
/*
* Set the (permanent) disposition of a signal.
* If the signal is subsequently (or even now) held,
* the action you set here can be enabled using sigrelse().
*/
sigtype
sigset(sig, func)
sigtype func;
{
sigtype old;
int _sigtramp();
extern int errno;
if (sig < 1 || sig > NSIG) {
errno = EINVAL;
return(BADSIG);
}
old = sigdisp(sig);
/*
* Does anyone actually call sigset with SIG_HOLD!?
*/
if (func == SIG_HOLD) {
sighold(sig);
return(old);
}
sigtable[sig].s_flag |= SSET;
sigtable[sig].s_func = func;
if (func == SIG_DFL) {
/*
* If signal has been held, must retain
* the catch so that we can note occurrance
* of signal.
*/
if ((sigtable[sig].s_flag & SHELD) == 0)
signal(sig, SIG_DFL);
else
signal(sig, _sigtramp);
return(old);
}
if (func == SIG_IGN) {
/*
* Clear pending signal
*/
signal(sig, SIG_IGN);
sigtable[sig].s_flag &= ~SDEFER;
return(old);
}
signal(sig, _sigtramp);
return(old);
}
/*
* Hold a signal.
* This CAN be tricky if the signal's disposition is SIG_DFL.
* In that case, we still catch the signal so we can note it
* happened and do something crazy later.
*/
sigtype
sighold(sig)
{
sigtype old;
extern int errno;
if (sig < 1 || sig > NSIG) {
errno = EINVAL;
return(BADSIG);
}
old = sigdisp(sig);
if (sigtable[sig].s_flag & SHELD)
return(old);
/*
* When the default action is required, we have to
* set up to catch the signal to note signal's occurrance.
*/
if (old == SIG_DFL) {
sigtable[sig].s_flag |= SSET;
signal(sig, _sigtramp);
}
sigtable[sig].s_flag |= SHELD;
return(old);
}
/*
* Release a signal
* If the signal occurred while we had it held, cause the signal.
*/
sigtype
sigrelse(sig)
{
sigtype old;
extern int errno;
int _sigtramp();
if (sig < 1 || sig > NSIG) {
errno = EINVAL;
return(BADSIG);
}
old = sigdisp(sig);
if ((sigtable[sig].s_flag & SHELD) == 0)
return(old);
sigtable[sig].s_flag &= ~SHELD;
if (sigtable[sig].s_flag & SDEFER)
_sigtramp(sig);
/*
* If disposition was the default, then we can unset the
* catch to _sigtramp() and let the system do the work.
*/
if (sigtable[sig].s_func == SIG_DFL)
signal(sig, SIG_DFL);
return(old);
}
/*
* Ignore a signal.
*/
sigtype
sigignore(sig)
{
return(sigset(sig, SIG_IGN));
}
/*
* Pause, waiting for sig to occur.
* We assume LUSER called us with the signal held.
* When we got the signal, mark the signal as having
* occurred. It will actually cause something when
* the signal is released.
*
* This is probably useless without job control anyway.
*/
sigpause(sig)
{
extern int errno;
if (sig < 1 || sig > NSIG) {
errno = EINVAL;
return;
}
sigtable[sig].s_flag |= SHELD|SPAUSE;
if (setjmp(_pause) == 0)
pause();
sigtable[sig].s_flag &= ~SPAUSE;
sigtable[sig].s_flag |= SDEFER;
}
/*
* In the child process after fork(2), set the disposition of all held
* signals to SIG_IGN. This is a new procedure not in the real sigset()
* package, provided for retrofitting purposes.
*/
sigchild()
{
register int i;
for (i = 1; i <= NSIG; i++)
if (sigtable[i].s_flag & SHELD)
signal(i, SIG_IGN);
}
/*
* Return the current disposition of a signal
* If we have not set this signal before, we have to
* ask the system
*/
sigtype
sigdisp(sig)
{
extern int errno;
sigtype old;
if (sig < 1 || sig > NSIG) {
errno = EINVAL;
return(BADSIG);
}
/*
* If we have no knowledge of this signal,
* ask the system, then save the result for later.
*/
if ((sigtable[sig].s_flag & SSET) == 0) {
old = signal(sig, SIG_IGN);
sigtable[sig].s_func = old;
sigtable[sig].s_flag |= SSET;
signal(sig, old);
return(old);
}
/*
* If we have set this signal before, then sigset()
* will have been careful to leave something meaningful
* in s_func.
*/
return(sigtable[sig].s_func);
}
/*
* The following routine gets called for any signal
* that is to be trapped to a user function.
*/
_sigtramp(sig)
{
extern int errno;
sigtype old;
if (sig < 1 || sig > NSIG) {
errno = EINVAL;
return;
}
top:
old = signal(sig, SIG_IGN);
/*
* If signal being paused on, wakeup sigpause()
*/
if (sigtable[sig].s_flag & SPAUSE)
longjmp(_pause, 1);
/*
* If signal being held, mark its table entry
* so we can trigger it when signal released.
* Then just return.
*/
if (sigtable[sig].s_flag & SHELD) {
sigtable[sig].s_flag |= SDEFER;
signal(sig, _sigtramp);
return;
}
/*
* If the signal is being ignored, just return.
* This would make SIGCONT more normal, but of course
* any system with SIGCONT also has the new signal pkg, so...
*/
if (sigtable[sig].s_func == SIG_IGN)
return;
/*
* If the signal is SIG_DFL, then we probably got here
* by holding the signal, having it happen, then releasing
* the signal. I wonder if a process is allowed to send
* a signal to itself?
*/
if (sigtable[sig].s_func == SIG_DFL) {
signal(sig, SIG_DFL);
kill(getpid(), sig);
/* Will we get back here? */
return;
}
/*
* Looks like we should just cause the signal...
* We hold the signal for the duration of the user's
* code with the signal re-enabled. If the signal
* happens again while in user code, we will recursively
* trap here and mark that we had another occurance
* and return to the user's trap code. When we return
* from there, we can cause the signal again.
*/
sigtable[sig].s_flag &= ~SDEFER;
sigtable[sig].s_flag |= SHELD;
signal(sig, _sigtramp);
(*sigtable[sig].s_func)(sig);
/*
* If the signal re-occurred while in the user's routine,
* just go try it again...
*/
sigtable[sig].s_flag &= ~SHELD;
if (sigtable[sig].s_flag & SDEFER)
goto top;
}