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trap.c revision 1.26 
      1 /*	$NetBSD: trap.c,v 1.26 2001/03/18 04:04:23 wulf 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 1.26 2001/03/18 04:04:23 wulf 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 char *trap[NSIG+1];		/* trap handler commands */
     81 MKINIT char sigmode[NSIG];	/* current value of signal */
     82 char gotsig[NSIG];		/* indicates specified signal received */
     83 int pendingsigs;			/* indicates some signal received */
     84 
     85 static int getsigaction __P((int, sig_t *));
     86 static int signame_to_signum __P((const char *));
     87 void printsignals __P((void));
     88 
     89 /*
     90  * return the signal number described by `p' (as a number or a name)
     91  * or -1 if it isn't one
     92  */
     93 
     94 static int
     95 signame_to_signum(p)
     96 	const char *p;
     97 {
     98 	int i;
     99 
    100 	if (is_number(p))
    101 		return number(p);
    102 
    103 	if (strcasecmp(p, "exit") == 0 )
    104 		return 0;
    105 
    106 	if (strncasecmp(p, "sig", 3) == 0)
    107 		p += 3;
    108 
    109 	for (i = 0; i < NSIG; ++i)
    110 		if (strcasecmp (p, sys_signame[i]) == 0)
    111 			return i;
    112 	return -1;
    113 }
    114 
    115 /*
    116  * Print a list of valid signal names
    117  */
    118 void
    119 printsignals(void)
    120 {
    121 	int n;
    122 
    123 	out1str("EXIT ");
    124 
    125 	for (n = 1; n < NSIG; n++) {
    126 		out1fmt("%s", sys_signame[n]);
    127 		if ((n == NSIG/2) ||  n == (NSIG - 1))
    128 			out1str("\n");
    129 		else
    130 			out1c(' ');
    131 	}
    132 }
    133 
    134 /*
    135  * The trap builtin.
    136  */
    137 
    138 int
    139 trapcmd(argc, argv)
    140 	int argc;
    141 	char **argv;
    142 {
    143 	char *action;
    144 	char **ap;
    145 	int signo;
    146 
    147 	if (argc <= 1) {
    148 		for (signo = 0 ; signo <= NSIG ; signo++) {
    149 			if (trap[signo] != NULL)
    150 				out1fmt("trap -- '%s' %s\n", trap[signo],
    151 				    (signo) ? sys_signame[signo] : "EXIT");
    152 		}
    153 		return 0;
    154 	}
    155 	ap = argv + 1;
    156 
    157 	action = NULL;
    158 
    159 	if (strcmp(*ap, "--") == 0)
    160 		if (*++ap == NULL)
    161 			return 0;
    162 
    163 	if (signame_to_signum(*ap) == -1) {
    164 		if ((*ap)[0] =='-') {
    165 			if ((*ap)[1] == NULL)
    166 				ap++;
    167 			else if ((*ap)[1] == 'l' && (*ap)[2] == NULL) {
    168 				printsignals();
    169 				return 0;
    170 			}
    171 			else
    172 				error("bad option %s\n", *ap);
    173 		}
    174 		else
    175 			action = *ap++;
    176 	}
    177 
    178 	while (*ap) {
    179 		if (is_number(*ap))
    180 			signo = number(*ap);
    181 		else
    182 			signo = signame_to_signum(*ap);
    183 
    184 		if (signo < 0 || signo > NSIG)
    185 			error("%s: bad trap", *ap);
    186 
    187 		INTOFF;
    188 		if (action)
    189 			action = savestr(action);
    190 
    191 		if (trap[signo])
    192 			ckfree(trap[signo]);
    193 
    194 		trap[signo] = action;
    195 
    196 		if (signo != 0)
    197 			setsignal(signo);
    198 		INTON;
    199 		ap++;
    200 	}
    201 	return 0;
    202 }
    203 
    204 
    205 
    206 /*
    207  * Clear traps on a fork.
    208  */
    209 
    210 void
    211 clear_traps() {
    212 	char **tp;
    213 
    214 	for (tp = trap ; tp <= &trap[NSIG] ; tp++) {
    215 		if (*tp && **tp) {	/* trap not NULL or SIG_IGN */
    216 			INTOFF;
    217 			ckfree(*tp);
    218 			*tp = NULL;
    219 			if (tp != &trap[0])
    220 				setsignal(tp - trap);
    221 			INTON;
    222 		}
    223 	}
    224 }
    225 
    226 
    227 
    228 /*
    229  * Set the signal handler for the specified signal.  The routine figures
    230  * out what it should be set to.
    231  */
    232 
    233 long
    234 setsignal(signo)
    235 	int signo;
    236 {
    237 	int action;
    238 	sig_t sigact = SIG_DFL;
    239 	char *t;
    240 
    241 	if ((t = trap[signo]) == NULL)
    242 		action = S_DFL;
    243 	else if (*t != '\0')
    244 		action = S_CATCH;
    245 	else
    246 		action = S_IGN;
    247 	if (rootshell && action == S_DFL) {
    248 		switch (signo) {
    249 		case SIGINT:
    250 			if (iflag || minusc || sflag == 0)
    251 				action = S_CATCH;
    252 			break;
    253 		case SIGQUIT:
    254 #ifdef DEBUG
    255 			{
    256 			extern int debug;
    257 
    258 			if (debug)
    259 				break;
    260 			}
    261 #endif
    262 			/* FALLTHROUGH */
    263 		case SIGTERM:
    264 			if (iflag)
    265 				action = S_IGN;
    266 			break;
    267 #if JOBS
    268 		case SIGTSTP:
    269 		case SIGTTOU:
    270 			if (mflag)
    271 				action = S_IGN;
    272 			break;
    273 #endif
    274 		}
    275 	}
    276 
    277 	t = &sigmode[signo - 1];
    278 	if (*t == 0) {
    279 		/*
    280 		 * current setting unknown
    281 		 */
    282 		if (!getsigaction(signo, &sigact)) {
    283 			/*
    284 			 * Pretend it worked; maybe we should give a warning
    285 			 * here, but other shells don't. We don't alter
    286 			 * sigmode, so that we retry every time.
    287 			 */
    288 			return 0;
    289 		}
    290 		if (sigact == SIG_IGN) {
    291 			if (mflag && (signo == SIGTSTP ||
    292 			     signo == SIGTTIN || signo == SIGTTOU)) {
    293 				*t = S_IGN;	/* don't hard ignore these */
    294 			} else
    295 				*t = S_HARD_IGN;
    296 		} else {
    297 			*t = S_RESET;	/* force to be set */
    298 		}
    299 	}
    300 	if (*t == S_HARD_IGN || *t == action)
    301 		return 0;
    302 	switch (action) {
    303 		case S_DFL:	sigact = SIG_DFL;	break;
    304 		case S_CATCH:  	sigact = onsig;		break;
    305 		case S_IGN:	sigact = SIG_IGN;	break;
    306 	}
    307 	*t = action;
    308 	siginterrupt(signo, 1);
    309 	return (long)signal(signo, sigact);
    310 }
    311 
    312 /*
    313  * Return the current setting for sig w/o changing it.
    314  */
    315 static int
    316 getsigaction(signo, sigact)
    317 	int signo;
    318 	sig_t *sigact;
    319 {
    320 	struct sigaction sa;
    321 
    322 	if (sigaction(signo, (struct sigaction *)0, &sa) == -1)
    323 		return 0;
    324 	*sigact = (sig_t) sa.sa_handler;
    325 	return 1;
    326 }
    327 
    328 /*
    329  * Ignore a signal.
    330  */
    331 
    332 void
    333 ignoresig(signo)
    334 	int signo;
    335 {
    336 	if (sigmode[signo - 1] != S_IGN && sigmode[signo - 1] != S_HARD_IGN) {
    337 		signal(signo, SIG_IGN);
    338 	}
    339 	sigmode[signo - 1] = S_HARD_IGN;
    340 }
    341 
    342 
    343 #ifdef mkinit
    344 INCLUDE <signal.h>
    345 INCLUDE "trap.h"
    346 
    347 SHELLPROC {
    348 	char *sm;
    349 
    350 	clear_traps();
    351 	for (sm = sigmode ; sm < sigmode + NSIG ; sm++) {
    352 		if (*sm == S_IGN)
    353 			*sm = S_HARD_IGN;
    354 	}
    355 }
    356 #endif
    357 
    358 
    359 
    360 /*
    361  * Signal handler.
    362  */
    363 
    364 void
    365 onsig(signo)
    366 	int signo;
    367 {
    368 	signal(signo, onsig);
    369 	if (signo == SIGINT && trap[SIGINT] == NULL) {
    370 		onint();
    371 		return;
    372 	}
    373 	gotsig[signo - 1] = 1;
    374 	pendingsigs++;
    375 }
    376 
    377 
    378 
    379 /*
    380  * Called to execute a trap.  Perhaps we should avoid entering new trap
    381  * handlers while we are executing a trap handler.
    382  */
    383 
    384 void
    385 dotrap() {
    386 	int i;
    387 	int savestatus;
    388 
    389 	for (;;) {
    390 		for (i = 1 ; ; i++) {
    391 			if (gotsig[i - 1])
    392 				break;
    393 			if (i >= NSIG)
    394 				goto done;
    395 		}
    396 		gotsig[i - 1] = 0;
    397 		savestatus=exitstatus;
    398 		evalstring(trap[i], 0);
    399 		exitstatus=savestatus;
    400 	}
    401 done:
    402 	pendingsigs = 0;
    403 }
    404 
    405 
    406 
    407 /*
    408  * Controls whether the shell is interactive or not.
    409  */
    410 
    411 
    412 void
    413 setinteractive(on)
    414 	int on;
    415 {
    416 	static int is_interactive;
    417 
    418 	if (on == is_interactive)
    419 		return;
    420 	setsignal(SIGINT);
    421 	setsignal(SIGQUIT);
    422 	setsignal(SIGTERM);
    423 	is_interactive = on;
    424 }
    425 
    426 
    427 
    428 /*
    429  * Called to exit the shell.
    430  */
    431 
    432 void
    433 exitshell(status)
    434 	int status;
    435 {
    436 	struct jmploc loc1, loc2;
    437 	char *p;
    438 
    439 	TRACE(("exitshell(%d) pid=%d\n", status, getpid()));
    440 	if (setjmp(loc1.loc)) {
    441 		goto l1;
    442 	}
    443 	if (setjmp(loc2.loc)) {
    444 		goto l2;
    445 	}
    446 	handler = &loc1;
    447 	if ((p = trap[0]) != NULL && *p != '\0') {
    448 		trap[0] = NULL;
    449 		evalstring(p, 0);
    450 	}
    451 l1:   handler = &loc2;			/* probably unnecessary */
    452 	flushall();
    453 #if JOBS
    454 	setjobctl(0);
    455 #endif
    456 l2:   _exit(status);
    457 	/* NOTREACHED */
    458 }
    459