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trap.c revision 1.23 
      1 /*	$NetBSD: trap.c,v 1.23 2000/05/13 20:50:15 elric Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 1991, 1993
      5  *	The Regents of the University of California.  All rights reserved.
      6  *
      7  * This code is derived from software contributed to Berkeley by
      8  * Kenneth Almquist.
      9  *
     10  * Redistribution and use in source and binary forms, with or without
     11  * modification, are permitted provided that the following conditions
     12  * are met:
     13  * 1. Redistributions of source code must retain the above copyright
     14  *    notice, this list of conditions and the following disclaimer.
     15  * 2. Redistributions in binary form must reproduce the above copyright
     16  *    notice, this list of conditions and the following disclaimer in the
     17  *    documentation and/or other materials provided with the distribution.
     18  * 3. All advertising materials mentioning features or use of this software
     19  *    must display the following acknowledgement:
     20  *	This product includes software developed by the University of
     21  *	California, Berkeley and its contributors.
     22  * 4. Neither the name of the University nor the names of its contributors
     23  *    may be used to endorse or promote products derived from this software
     24  *    without specific prior written permission.
     25  *
     26  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     27  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     28  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     29  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     30  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     31  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     32  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     33  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     34  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     35  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     36  * SUCH DAMAGE.
     37  */
     38 
     39 #include <sys/cdefs.h>
     40 #ifndef lint
     41 #if 0
     42 static char sccsid[] = "@(#)trap.c	8.5 (Berkeley) 6/5/95";
     43 #else
     44 __RCSID("$NetBSD: trap.c,v 1.23 2000/05/13 20:50:15 elric Exp $");
     45 #endif
     46 #endif /* not lint */
     47 
     48 #include <signal.h>
     49 #include <unistd.h>
     50 #include <stdlib.h>
     51 
     52 #include "shell.h"
     53 #include "main.h"
     54 #include "nodes.h"	/* for other headers */
     55 #include "eval.h"
     56 #include "jobs.h"
     57 #include "show.h"
     58 #include "options.h"
     59 #include "syntax.h"
     60 #include "output.h"
     61 #include "memalloc.h"
     62 #include "error.h"
     63 #include "trap.h"
     64 #include "mystring.h"
     65 
     66 
     67 /*
     68  * Sigmode records the current value of the signal handlers for the various
     69  * modes.  A value of zero means that the current handler is not known.
     70  * S_HARD_IGN indicates that the signal was ignored on entry to the shell,
     71  */
     72 
     73 #define S_DFL 1			/* default signal handling (SIG_DFL) */
     74 #define S_CATCH 2		/* signal is caught */
     75 #define S_IGN 3			/* signal is ignored (SIG_IGN) */
     76 #define S_HARD_IGN 4		/* signal is ignored permenantly */
     77 #define S_RESET 5		/* temporary - to reset a hard ignored sig */
     78 
     79 
     80 extern char nullstr[1];		/* null string */
     81 
     82 char *trap[NSIG+1];		/* trap handler commands */
     83 MKINIT char sigmode[NSIG];	/* current value of signal */
     84 char gotsig[NSIG];		/* indicates specified signal received */
     85 int pendingsigs;			/* indicates some signal received */
     86 
     87 static int getsigaction __P((int, sig_t *));
     88 
     89 /*
     90  * The trap builtin.
     91  */
     92 
     93 int
     94 trapcmd(argc, argv)
     95 	int argc;
     96 	char **argv;
     97 {
     98 	char *action;
     99 	char **ap;
    100 	int signo;
    101 
    102 	if (argc <= 1) {
    103 		for (signo = 0 ; signo <= NSIG ; signo++) {
    104 			if (trap[signo] != NULL)
    105 				out1fmt("%d: %s\n", signo, trap[signo]);
    106 		}
    107 		return 0;
    108 	}
    109 	ap = argv + 1;
    110 	if (is_number(*ap))
    111 		action = NULL;
    112 	else
    113 		action = *ap++;
    114 	while (*ap) {
    115 		if ((signo = number(*ap)) < 0 || signo > NSIG)
    116 			error("%s: bad trap", *ap);
    117 		INTOFF;
    118 		if (action)
    119 			action = savestr(action);
    120 		if (trap[signo])
    121 			ckfree(trap[signo]);
    122 		trap[signo] = action;
    123 		if (signo != 0)
    124 			setsignal(signo, 0);
    125 		INTON;
    126 		ap++;
    127 	}
    128 	return 0;
    129 }
    130 
    131 
    132 
    133 /*
    134  * Clear traps on a fork or vfork.
    135  * Takes one arg vfork, to tell it to not be destructive of
    136  * the parents variables.
    137  */
    138 
    139 void
    140 clear_traps(vforked)
    141 	int vforked;
    142 {
    143 	char **tp;
    144 
    145 	for (tp = trap ; tp <= &trap[NSIG] ; tp++) {
    146 		if (*tp && **tp) {	/* trap not NULL or SIG_IGN */
    147 			INTOFF;
    148 			if (!vforked) {
    149 				ckfree(*tp);
    150 				*tp = NULL;
    151 			}
    152 			if (tp != &trap[0])
    153 				setsignal(tp - trap, vforked);
    154 			INTON;
    155 		}
    156 	}
    157 }
    158 
    159 
    160 
    161 /*
    162  * Set the signal handler for the specified signal.  The routine figures
    163  * out what it should be set to.
    164  */
    165 
    166 long
    167 setsignal(signo, vforked)
    168 	int signo;
    169 	int vforked;
    170 {
    171 	int action;
    172 	sig_t sigact = SIG_DFL;
    173 	char *t, tsig;
    174 
    175 	if ((t = trap[signo]) == NULL)
    176 		action = S_DFL;
    177 	else if (*t != '\0')
    178 		action = S_CATCH;
    179 	else
    180 		action = S_IGN;
    181 	if (rootshell && !vforked && action == S_DFL) {
    182 		switch (signo) {
    183 		case SIGINT:
    184 			if (iflag || minusc || sflag == 0)
    185 				action = S_CATCH;
    186 			break;
    187 		case SIGQUIT:
    188 #ifdef DEBUG
    189 			{
    190 			extern int debug;
    191 
    192 			if (debug)
    193 				break;
    194 			}
    195 #endif
    196 			/* FALLTHROUGH */
    197 		case SIGTERM:
    198 			if (iflag)
    199 				action = S_IGN;
    200 			break;
    201 #if JOBS
    202 		case SIGTSTP:
    203 		case SIGTTOU:
    204 			if (mflag)
    205 				action = S_IGN;
    206 			break;
    207 #endif
    208 		}
    209 	}
    210 
    211 	t = &sigmode[signo - 1];
    212 	tsig = *t;
    213 	if (tsig == 0) {
    214 		/*
    215 		 * current setting unknown
    216 		 */
    217 		if (!getsigaction(signo, &sigact)) {
    218 			/*
    219 			 * Pretend it worked; maybe we should give a warning
    220 			 * here, but other shells don't. We don't alter
    221 			 * sigmode, so that we retry every time.
    222 			 */
    223 			return 0;
    224 		}
    225 		if (sigact == SIG_IGN) {
    226 			if (mflag && (signo == SIGTSTP ||
    227 			     signo == SIGTTIN || signo == SIGTTOU)) {
    228 				tsig = S_IGN;	/* don't hard ignore these */
    229 			} else
    230 				tsig = S_HARD_IGN;
    231 		} else {
    232 			tsig = S_RESET;	/* force to be set */
    233 		}
    234 	}
    235 	if (tsig == S_HARD_IGN || tsig == action)
    236 		return 0;
    237 	switch (action) {
    238 		case S_DFL:	sigact = SIG_DFL;	break;
    239 		case S_CATCH:  	sigact = onsig;		break;
    240 		case S_IGN:	sigact = SIG_IGN;	break;
    241 	}
    242 	if (!vforked)
    243 		*t = action;
    244 	siginterrupt(signo, 1);
    245 	return (long)signal(signo, sigact);
    246 }
    247 
    248 /*
    249  * Return the current setting for sig w/o changing it.
    250  */
    251 static int
    252 getsigaction(signo, sigact)
    253 	int signo;
    254 	sig_t *sigact;
    255 {
    256 	struct sigaction sa;
    257 
    258 	if (sigaction(signo, (struct sigaction *)0, &sa) == -1)
    259 		return 0;
    260 	*sigact = (sig_t) sa.sa_handler;
    261 	return 1;
    262 }
    263 
    264 /*
    265  * Ignore a signal.
    266  */
    267 
    268 void
    269 ignoresig(signo, vforked)
    270 	int signo;
    271 	int vforked;
    272 {
    273 	if (sigmode[signo - 1] != S_IGN && sigmode[signo - 1] != S_HARD_IGN) {
    274 		signal(signo, SIG_IGN);
    275 	}
    276 	if (!vforked)
    277 		sigmode[signo - 1] = S_HARD_IGN;
    278 }
    279 
    280 
    281 #ifdef mkinit
    282 INCLUDE <signal.h>
    283 INCLUDE "trap.h"
    284 
    285 SHELLPROC {
    286 	char *sm;
    287 
    288 	clear_traps(0);
    289 	for (sm = sigmode ; sm < sigmode + NSIG ; sm++) {
    290 		if (*sm == S_IGN)
    291 			*sm = S_HARD_IGN;
    292 	}
    293 }
    294 #endif
    295 
    296 
    297 
    298 /*
    299  * Signal handler.
    300  */
    301 
    302 void
    303 onsig(signo)
    304 	int signo;
    305 {
    306 	signal(signo, onsig);
    307 	if (signo == SIGINT && trap[SIGINT] == NULL) {
    308 		onint();
    309 		return;
    310 	}
    311 	gotsig[signo - 1] = 1;
    312 	pendingsigs++;
    313 }
    314 
    315 
    316 
    317 /*
    318  * Called to execute a trap.  Perhaps we should avoid entering new trap
    319  * handlers while we are executing a trap handler.
    320  */
    321 
    322 void
    323 dotrap() {
    324 	int i;
    325 	int savestatus;
    326 
    327 	for (;;) {
    328 		for (i = 1 ; ; i++) {
    329 			if (gotsig[i - 1])
    330 				break;
    331 			if (i >= NSIG)
    332 				goto done;
    333 		}
    334 		gotsig[i - 1] = 0;
    335 		savestatus=exitstatus;
    336 		evalstring(trap[i], 0);
    337 		exitstatus=savestatus;
    338 	}
    339 done:
    340 	pendingsigs = 0;
    341 }
    342 
    343 
    344 
    345 /*
    346  * Controls whether the shell is interactive or not.
    347  */
    348 
    349 
    350 void
    351 setinteractive(on)
    352 	int on;
    353 {
    354 	static int is_interactive;
    355 
    356 	if (on == is_interactive)
    357 		return;
    358 	setsignal(SIGINT, 0);
    359 	setsignal(SIGQUIT, 0);
    360 	setsignal(SIGTERM, 0);
    361 	is_interactive = on;
    362 }
    363 
    364 
    365 
    366 /*
    367  * Called to exit the shell.
    368  */
    369 
    370 void
    371 exitshell(status)
    372 	int status;
    373 {
    374 	struct jmploc loc1, loc2;
    375 	char *p;
    376 
    377 	TRACE(("exitshell(%d) pid=%d\n", status, getpid()));
    378 	if (setjmp(loc1.loc)) {
    379 		goto l1;
    380 	}
    381 	if (setjmp(loc2.loc)) {
    382 		goto l2;
    383 	}
    384 	handler = &loc1;
    385 	if ((p = trap[0]) != NULL && *p != '\0') {
    386 		trap[0] = NULL;
    387 		evalstring(p, 0);
    388 	}
    389 l1:   handler = &loc2;			/* probably unnecessary */
    390 	flushall();
    391 #if JOBS
    392 	setjobctl(0);
    393 #endif
    394 l2:   _exit(status);
    395 	/* NOTREACHED */
    396 }
    397