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trap.c revision 1.29 
      1 /*	$NetBSD: trap.c,v 1.29 2003/08/07 09:05:39 agc 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. Neither the name of the University nor the names of its contributors
     19  *    may be used to endorse or promote products derived from this software
     20  *    without specific prior written permission.
     21  *
     22  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     23  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     24  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     25  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     26  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     27  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     28  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     29  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     30  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     31  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     32  * SUCH DAMAGE.
     33  */
     34 
     35 #include <sys/cdefs.h>
     36 #ifndef lint
     37 #if 0
     38 static char sccsid[] = "@(#)trap.c	8.5 (Berkeley) 6/5/95";
     39 #else
     40 __RCSID("$NetBSD: trap.c,v 1.29 2003/08/07 09:05:39 agc Exp $");
     41 #endif
     42 #endif /* not lint */
     43 
     44 #include <signal.h>
     45 #include <unistd.h>
     46 #include <stdlib.h>
     47 
     48 #include "shell.h"
     49 #include "main.h"
     50 #include "nodes.h"	/* for other headers */
     51 #include "eval.h"
     52 #include "jobs.h"
     53 #include "show.h"
     54 #include "options.h"
     55 #include "syntax.h"
     56 #include "output.h"
     57 #include "memalloc.h"
     58 #include "error.h"
     59 #include "trap.h"
     60 #include "mystring.h"
     61 
     62 
     63 /*
     64  * Sigmode records the current value of the signal handlers for the various
     65  * modes.  A value of zero means that the current handler is not known.
     66  * S_HARD_IGN indicates that the signal was ignored on entry to the shell,
     67  */
     68 
     69 #define S_DFL 1			/* default signal handling (SIG_DFL) */
     70 #define S_CATCH 2		/* signal is caught */
     71 #define S_IGN 3			/* signal is ignored (SIG_IGN) */
     72 #define S_HARD_IGN 4		/* signal is ignored permenantly */
     73 #define S_RESET 5		/* temporary - to reset a hard ignored sig */
     74 
     75 
     76 char *trap[NSIG+1];		/* trap handler commands */
     77 MKINIT char sigmode[NSIG];	/* current value of signal */
     78 char gotsig[NSIG];		/* indicates specified signal received */
     79 int pendingsigs;		/* indicates some signal received */
     80 
     81 static int getsigaction(int, sig_t *);
     82 
     83 /*
     84  * return the signal number described by `p' (as a number or a name)
     85  * or -1 if it isn't one
     86  */
     87 
     88 static int
     89 signame_to_signum(const char *p)
     90 {
     91 	int i;
     92 
     93 	if (is_number(p))
     94 		return number(p);
     95 
     96 	if (strcasecmp(p, "exit") == 0 )
     97 		return 0;
     98 
     99 	if (strncasecmp(p, "sig", 3) == 0)
    100 		p += 3;
    101 
    102 	for (i = 0; i < NSIG; ++i)
    103 		if (strcasecmp (p, sys_signame[i]) == 0)
    104 			return i;
    105 	return -1;
    106 }
    107 
    108 /*
    109  * Print a list of valid signal names
    110  */
    111 static void
    112 printsignals(void)
    113 {
    114 	int n;
    115 
    116 	out1str("EXIT ");
    117 
    118 	for (n = 1; n < NSIG; n++) {
    119 		out1fmt("%s", sys_signame[n]);
    120 		if ((n == NSIG/2) ||  n == (NSIG - 1))
    121 			out1str("\n");
    122 		else
    123 			out1c(' ');
    124 	}
    125 }
    126 
    127 /*
    128  * The trap builtin.
    129  */
    130 
    131 int
    132 trapcmd(int argc, char **argv)
    133 {
    134 	char *action;
    135 	char **ap;
    136 	int signo;
    137 
    138 	if (argc <= 1) {
    139 		for (signo = 0 ; signo <= NSIG ; signo++) {
    140 			if (trap[signo] != NULL)
    141 				out1fmt("trap -- '%s' %s\n", trap[signo],
    142 				    (signo) ? sys_signame[signo] : "EXIT");
    143 		}
    144 		return 0;
    145 	}
    146 	ap = argv + 1;
    147 
    148 	action = NULL;
    149 
    150 	if (strcmp(*ap, "--") == 0)
    151 		if (*++ap == NULL)
    152 			return 0;
    153 
    154 	if (signame_to_signum(*ap) == -1) {
    155 		if ((*ap)[0] =='-') {
    156 			if ((*ap)[1] == NULL)
    157 				ap++;
    158 			else if ((*ap)[1] == 'l' && (*ap)[2] == NULL) {
    159 				printsignals();
    160 				return 0;
    161 			}
    162 			else
    163 				error("bad option %s\n", *ap);
    164 		}
    165 		else
    166 			action = *ap++;
    167 	}
    168 
    169 	while (*ap) {
    170 		if (is_number(*ap))
    171 			signo = number(*ap);
    172 		else
    173 			signo = signame_to_signum(*ap);
    174 
    175 		if (signo < 0 || signo > NSIG)
    176 			error("%s: bad trap", *ap);
    177 
    178 		INTOFF;
    179 		if (action)
    180 			action = savestr(action);
    181 
    182 		if (trap[signo])
    183 			ckfree(trap[signo]);
    184 
    185 		trap[signo] = action;
    186 
    187 		if (signo != 0)
    188 			setsignal(signo, 0);
    189 		INTON;
    190 		ap++;
    191 	}
    192 	return 0;
    193 }
    194 
    195 
    196 
    197 /*
    198  * Clear traps on a fork or vfork.
    199  * Takes one arg vfork, to tell it to not be destructive of
    200  * the parents variables.
    201  */
    202 
    203 void
    204 clear_traps(int vforked)
    205 {
    206 	char **tp;
    207 
    208 	for (tp = trap ; tp <= &trap[NSIG] ; tp++) {
    209 		if (*tp && **tp) {	/* trap not NULL or SIG_IGN */
    210 			INTOFF;
    211 			if (!vforked) {
    212 				ckfree(*tp);
    213 				*tp = NULL;
    214 			}
    215 			if (tp != &trap[0])
    216 				setsignal(tp - trap, vforked);
    217 			INTON;
    218 		}
    219 	}
    220 }
    221 
    222 
    223 
    224 /*
    225  * Set the signal handler for the specified signal.  The routine figures
    226  * out what it should be set to.
    227  */
    228 
    229 long
    230 setsignal(int signo, int vforked)
    231 {
    232 	int action;
    233 	sig_t sigact = SIG_DFL;
    234 	char *t, tsig;
    235 
    236 	if ((t = trap[signo]) == NULL)
    237 		action = S_DFL;
    238 	else if (*t != '\0')
    239 		action = S_CATCH;
    240 	else
    241 		action = S_IGN;
    242 	if (rootshell && !vforked && action == S_DFL) {
    243 		switch (signo) {
    244 		case SIGINT:
    245 			if (iflag || minusc || sflag == 0)
    246 				action = S_CATCH;
    247 			break;
    248 		case SIGQUIT:
    249 #ifdef DEBUG
    250 			if (debug)
    251 				break;
    252 #endif
    253 			/* FALLTHROUGH */
    254 		case SIGTERM:
    255 			if (iflag)
    256 				action = S_IGN;
    257 			break;
    258 #if JOBS
    259 		case SIGTSTP:
    260 		case SIGTTOU:
    261 			if (mflag)
    262 				action = S_IGN;
    263 			break;
    264 #endif
    265 		}
    266 	}
    267 
    268 	t = &sigmode[signo - 1];
    269 	tsig = *t;
    270 	if (tsig == 0) {
    271 		/*
    272 		 * current setting unknown
    273 		 */
    274 		if (!getsigaction(signo, &sigact)) {
    275 			/*
    276 			 * Pretend it worked; maybe we should give a warning
    277 			 * here, but other shells don't. We don't alter
    278 			 * sigmode, so that we retry every time.
    279 			 */
    280 			return 0;
    281 		}
    282 		if (sigact == SIG_IGN) {
    283 			if (mflag && (signo == SIGTSTP ||
    284 			     signo == SIGTTIN || signo == SIGTTOU)) {
    285 				tsig = S_IGN;	/* don't hard ignore these */
    286 			} else
    287 				tsig = S_HARD_IGN;
    288 		} else {
    289 			tsig = S_RESET;	/* force to be set */
    290 		}
    291 	}
    292 	if (tsig == S_HARD_IGN || tsig == action)
    293 		return 0;
    294 	switch (action) {
    295 		case S_DFL:	sigact = SIG_DFL;	break;
    296 		case S_CATCH:  	sigact = onsig;		break;
    297 		case S_IGN:	sigact = SIG_IGN;	break;
    298 	}
    299 	if (!vforked)
    300 		*t = action;
    301 	siginterrupt(signo, 1);
    302 	return (long)signal(signo, sigact);
    303 }
    304 
    305 /*
    306  * Return the current setting for sig w/o changing it.
    307  */
    308 static int
    309 getsigaction(int signo, sig_t *sigact)
    310 {
    311 	struct sigaction sa;
    312 
    313 	if (sigaction(signo, (struct sigaction *)0, &sa) == -1)
    314 		return 0;
    315 	*sigact = (sig_t) sa.sa_handler;
    316 	return 1;
    317 }
    318 
    319 /*
    320  * Ignore a signal.
    321  */
    322 
    323 void
    324 ignoresig(int signo, int vforked)
    325 {
    326 	if (sigmode[signo - 1] != S_IGN && sigmode[signo - 1] != S_HARD_IGN) {
    327 		signal(signo, SIG_IGN);
    328 	}
    329 	if (!vforked)
    330 		sigmode[signo - 1] = S_HARD_IGN;
    331 }
    332 
    333 
    334 #ifdef mkinit
    335 INCLUDE <signal.h>
    336 INCLUDE "trap.h"
    337 
    338 SHELLPROC {
    339 	char *sm;
    340 
    341 	clear_traps(0);
    342 	for (sm = sigmode ; sm < sigmode + NSIG ; sm++) {
    343 		if (*sm == S_IGN)
    344 			*sm = S_HARD_IGN;
    345 	}
    346 }
    347 #endif
    348 
    349 
    350 
    351 /*
    352  * Signal handler.
    353  */
    354 
    355 void
    356 onsig(int signo)
    357 {
    358 	signal(signo, onsig);
    359 	if (signo == SIGINT && trap[SIGINT] == NULL) {
    360 		onint();
    361 		return;
    362 	}
    363 	gotsig[signo - 1] = 1;
    364 	pendingsigs++;
    365 }
    366 
    367 
    368 
    369 /*
    370  * Called to execute a trap.  Perhaps we should avoid entering new trap
    371  * handlers while we are executing a trap handler.
    372  */
    373 
    374 void
    375 dotrap(void)
    376 {
    377 	int i;
    378 	int savestatus;
    379 
    380 	for (;;) {
    381 		for (i = 1 ; ; i++) {
    382 			if (gotsig[i - 1])
    383 				break;
    384 			if (i >= NSIG)
    385 				goto done;
    386 		}
    387 		gotsig[i - 1] = 0;
    388 		savestatus=exitstatus;
    389 		evalstring(trap[i], 0);
    390 		exitstatus=savestatus;
    391 	}
    392 done:
    393 	pendingsigs = 0;
    394 }
    395 
    396 
    397 
    398 /*
    399  * Controls whether the shell is interactive or not.
    400  */
    401 
    402 
    403 void
    404 setinteractive(int on)
    405 {
    406 	static int is_interactive;
    407 
    408 	if (on == is_interactive)
    409 		return;
    410 	setsignal(SIGINT, 0);
    411 	setsignal(SIGQUIT, 0);
    412 	setsignal(SIGTERM, 0);
    413 	is_interactive = on;
    414 }
    415 
    416 
    417 
    418 /*
    419  * Called to exit the shell.
    420  */
    421 
    422 void
    423 exitshell(int status)
    424 {
    425 	struct jmploc loc1, loc2;
    426 	char *p;
    427 
    428 	TRACE(("pid %d, exitshell(%d)\n", getpid(), status));
    429 	if (setjmp(loc1.loc)) {
    430 		goto l1;
    431 	}
    432 	if (setjmp(loc2.loc)) {
    433 		goto l2;
    434 	}
    435 	handler = &loc1;
    436 	if ((p = trap[0]) != NULL && *p != '\0') {
    437 		trap[0] = NULL;
    438 		evalstring(p, 0);
    439 	}
    440 l1:   handler = &loc2;			/* probably unnecessary */
    441 	flushall();
    442 #if JOBS
    443 	setjobctl(0);
    444 #endif
    445 l2:   _exit(status);
    446 	/* NOTREACHED */
    447 }
    448