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trap.c revision 1.28 
      1 /*	$NetBSD: trap.c,v 1.28 2002/11/24 22:35:43 christos 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 1.28 2002/11/24 22:35:43 christos 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(int, sig_t *);
     86 
     87 /*
     88  * return the signal number described by `p' (as a number or a name)
     89  * or -1 if it isn't one
     90  */
     91 
     92 static int
     93 signame_to_signum(const char *p)
     94 {
     95 	int i;
     96 
     97 	if (is_number(p))
     98 		return number(p);
     99 
    100 	if (strcasecmp(p, "exit") == 0 )
    101 		return 0;
    102 
    103 	if (strncasecmp(p, "sig", 3) == 0)
    104 		p += 3;
    105 
    106 	for (i = 0; i < NSIG; ++i)
    107 		if (strcasecmp (p, sys_signame[i]) == 0)
    108 			return i;
    109 	return -1;
    110 }
    111 
    112 /*
    113  * Print a list of valid signal names
    114  */
    115 static void
    116 printsignals(void)
    117 {
    118 	int n;
    119 
    120 	out1str("EXIT ");
    121 
    122 	for (n = 1; n < NSIG; n++) {
    123 		out1fmt("%s", sys_signame[n]);
    124 		if ((n == NSIG/2) ||  n == (NSIG - 1))
    125 			out1str("\n");
    126 		else
    127 			out1c(' ');
    128 	}
    129 }
    130 
    131 /*
    132  * The trap builtin.
    133  */
    134 
    135 int
    136 trapcmd(int argc, char **argv)
    137 {
    138 	char *action;
    139 	char **ap;
    140 	int signo;
    141 
    142 	if (argc <= 1) {
    143 		for (signo = 0 ; signo <= NSIG ; signo++) {
    144 			if (trap[signo] != NULL)
    145 				out1fmt("trap -- '%s' %s\n", trap[signo],
    146 				    (signo) ? sys_signame[signo] : "EXIT");
    147 		}
    148 		return 0;
    149 	}
    150 	ap = argv + 1;
    151 
    152 	action = NULL;
    153 
    154 	if (strcmp(*ap, "--") == 0)
    155 		if (*++ap == NULL)
    156 			return 0;
    157 
    158 	if (signame_to_signum(*ap) == -1) {
    159 		if ((*ap)[0] =='-') {
    160 			if ((*ap)[1] == NULL)
    161 				ap++;
    162 			else if ((*ap)[1] == 'l' && (*ap)[2] == NULL) {
    163 				printsignals();
    164 				return 0;
    165 			}
    166 			else
    167 				error("bad option %s\n", *ap);
    168 		}
    169 		else
    170 			action = *ap++;
    171 	}
    172 
    173 	while (*ap) {
    174 		if (is_number(*ap))
    175 			signo = number(*ap);
    176 		else
    177 			signo = signame_to_signum(*ap);
    178 
    179 		if (signo < 0 || signo > NSIG)
    180 			error("%s: bad trap", *ap);
    181 
    182 		INTOFF;
    183 		if (action)
    184 			action = savestr(action);
    185 
    186 		if (trap[signo])
    187 			ckfree(trap[signo]);
    188 
    189 		trap[signo] = action;
    190 
    191 		if (signo != 0)
    192 			setsignal(signo, 0);
    193 		INTON;
    194 		ap++;
    195 	}
    196 	return 0;
    197 }
    198 
    199 
    200 
    201 /*
    202  * Clear traps on a fork or vfork.
    203  * Takes one arg vfork, to tell it to not be destructive of
    204  * the parents variables.
    205  */
    206 
    207 void
    208 clear_traps(int vforked)
    209 {
    210 	char **tp;
    211 
    212 	for (tp = trap ; tp <= &trap[NSIG] ; tp++) {
    213 		if (*tp && **tp) {	/* trap not NULL or SIG_IGN */
    214 			INTOFF;
    215 			if (!vforked) {
    216 				ckfree(*tp);
    217 				*tp = NULL;
    218 			}
    219 			if (tp != &trap[0])
    220 				setsignal(tp - trap, vforked);
    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(int signo, int vforked)
    235 {
    236 	int action;
    237 	sig_t sigact = SIG_DFL;
    238 	char *t, tsig;
    239 
    240 	if ((t = trap[signo]) == NULL)
    241 		action = S_DFL;
    242 	else if (*t != '\0')
    243 		action = S_CATCH;
    244 	else
    245 		action = S_IGN;
    246 	if (rootshell && !vforked && action == S_DFL) {
    247 		switch (signo) {
    248 		case SIGINT:
    249 			if (iflag || minusc || sflag == 0)
    250 				action = S_CATCH;
    251 			break;
    252 		case SIGQUIT:
    253 #ifdef DEBUG
    254 			if (debug)
    255 				break;
    256 #endif
    257 			/* FALLTHROUGH */
    258 		case SIGTERM:
    259 			if (iflag)
    260 				action = S_IGN;
    261 			break;
    262 #if JOBS
    263 		case SIGTSTP:
    264 		case SIGTTOU:
    265 			if (mflag)
    266 				action = S_IGN;
    267 			break;
    268 #endif
    269 		}
    270 	}
    271 
    272 	t = &sigmode[signo - 1];
    273 	tsig = *t;
    274 	if (tsig == 0) {
    275 		/*
    276 		 * current setting unknown
    277 		 */
    278 		if (!getsigaction(signo, &sigact)) {
    279 			/*
    280 			 * Pretend it worked; maybe we should give a warning
    281 			 * here, but other shells don't. We don't alter
    282 			 * sigmode, so that we retry every time.
    283 			 */
    284 			return 0;
    285 		}
    286 		if (sigact == SIG_IGN) {
    287 			if (mflag && (signo == SIGTSTP ||
    288 			     signo == SIGTTIN || signo == SIGTTOU)) {
    289 				tsig = S_IGN;	/* don't hard ignore these */
    290 			} else
    291 				tsig = S_HARD_IGN;
    292 		} else {
    293 			tsig = S_RESET;	/* force to be set */
    294 		}
    295 	}
    296 	if (tsig == S_HARD_IGN || tsig == action)
    297 		return 0;
    298 	switch (action) {
    299 		case S_DFL:	sigact = SIG_DFL;	break;
    300 		case S_CATCH:  	sigact = onsig;		break;
    301 		case S_IGN:	sigact = SIG_IGN;	break;
    302 	}
    303 	if (!vforked)
    304 		*t = action;
    305 	siginterrupt(signo, 1);
    306 	return (long)signal(signo, sigact);
    307 }
    308 
    309 /*
    310  * Return the current setting for sig w/o changing it.
    311  */
    312 static int
    313 getsigaction(int signo, sig_t *sigact)
    314 {
    315 	struct sigaction sa;
    316 
    317 	if (sigaction(signo, (struct sigaction *)0, &sa) == -1)
    318 		return 0;
    319 	*sigact = (sig_t) sa.sa_handler;
    320 	return 1;
    321 }
    322 
    323 /*
    324  * Ignore a signal.
    325  */
    326 
    327 void
    328 ignoresig(int signo, int vforked)
    329 {
    330 	if (sigmode[signo - 1] != S_IGN && sigmode[signo - 1] != S_HARD_IGN) {
    331 		signal(signo, SIG_IGN);
    332 	}
    333 	if (!vforked)
    334 		sigmode[signo - 1] = S_HARD_IGN;
    335 }
    336 
    337 
    338 #ifdef mkinit
    339 INCLUDE <signal.h>
    340 INCLUDE "trap.h"
    341 
    342 SHELLPROC {
    343 	char *sm;
    344 
    345 	clear_traps(0);
    346 	for (sm = sigmode ; sm < sigmode + NSIG ; sm++) {
    347 		if (*sm == S_IGN)
    348 			*sm = S_HARD_IGN;
    349 	}
    350 }
    351 #endif
    352 
    353 
    354 
    355 /*
    356  * Signal handler.
    357  */
    358 
    359 void
    360 onsig(int signo)
    361 {
    362 	signal(signo, onsig);
    363 	if (signo == SIGINT && trap[SIGINT] == NULL) {
    364 		onint();
    365 		return;
    366 	}
    367 	gotsig[signo - 1] = 1;
    368 	pendingsigs++;
    369 }
    370 
    371 
    372 
    373 /*
    374  * Called to execute a trap.  Perhaps we should avoid entering new trap
    375  * handlers while we are executing a trap handler.
    376  */
    377 
    378 void
    379 dotrap(void)
    380 {
    381 	int i;
    382 	int savestatus;
    383 
    384 	for (;;) {
    385 		for (i = 1 ; ; i++) {
    386 			if (gotsig[i - 1])
    387 				break;
    388 			if (i >= NSIG)
    389 				goto done;
    390 		}
    391 		gotsig[i - 1] = 0;
    392 		savestatus=exitstatus;
    393 		evalstring(trap[i], 0);
    394 		exitstatus=savestatus;
    395 	}
    396 done:
    397 	pendingsigs = 0;
    398 }
    399 
    400 
    401 
    402 /*
    403  * Controls whether the shell is interactive or not.
    404  */
    405 
    406 
    407 void
    408 setinteractive(int on)
    409 {
    410 	static int is_interactive;
    411 
    412 	if (on == is_interactive)
    413 		return;
    414 	setsignal(SIGINT, 0);
    415 	setsignal(SIGQUIT, 0);
    416 	setsignal(SIGTERM, 0);
    417 	is_interactive = on;
    418 }
    419 
    420 
    421 
    422 /*
    423  * Called to exit the shell.
    424  */
    425 
    426 void
    427 exitshell(int status)
    428 {
    429 	struct jmploc loc1, loc2;
    430 	char *p;
    431 
    432 	TRACE(("pid %d, exitshell(%d)\n", getpid(), status));
    433 	if (setjmp(loc1.loc)) {
    434 		goto l1;
    435 	}
    436 	if (setjmp(loc2.loc)) {
    437 		goto l2;
    438 	}
    439 	handler = &loc1;
    440 	if ((p = trap[0]) != NULL && *p != '\0') {
    441 		trap[0] = NULL;
    442 		evalstring(p, 0);
    443 	}
    444 l1:   handler = &loc2;			/* probably unnecessary */
    445 	flushall();
    446 #if JOBS
    447 	setjobctl(0);
    448 #endif
    449 l2:   _exit(status);
    450 	/* NOTREACHED */
    451 }
    452