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trap.c revision 1.37 
      1 /*	$NetBSD: trap.c,v 1.37 2015/08/22 12:12:47 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. 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 1.37 2015/08/22 12:12:47 christos 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 "builtins.h"
     56 #include "syntax.h"
     57 #include "output.h"
     58 #include "memalloc.h"
     59 #include "error.h"
     60 #include "trap.h"
     61 #include "mystring.h"
     62 #include "var.h"
     63 
     64 
     65 /*
     66  * Sigmode records the current value of the signal handlers for the various
     67  * modes.  A value of zero means that the current handler is not known.
     68  * S_HARD_IGN indicates that the signal was ignored on entry to the shell,
     69  */
     70 
     71 #define S_DFL 1			/* default signal handling (SIG_DFL) */
     72 #define S_CATCH 2		/* signal is caught */
     73 #define S_IGN 3			/* signal is ignored (SIG_IGN) */
     74 #define S_HARD_IGN 4		/* signal is ignored permenantly */
     75 #define S_RESET 5		/* temporary - to reset a hard ignored sig */
     76 
     77 
     78 char *trap[NSIG+1];		/* trap handler commands */
     79 MKINIT char sigmode[NSIG];	/* current value of signal */
     80 static volatile char gotsig[NSIG];/* indicates specified signal received */
     81 volatile int pendingsigs;	/* indicates some signal received */
     82 
     83 static int getsigaction(int, sig_t *);
     84 
     85 /*
     86  * return the signal number described by `p' (as a number or a name)
     87  * or -1 if it isn't one
     88  */
     89 
     90 static int
     91 signame_to_signum(const char *p)
     92 {
     93 	int i;
     94 
     95 	if (is_number(p))
     96 		return number(p);
     97 
     98 	if (strcasecmp(p, "exit") == 0 )
     99 		return 0;
    100 
    101 	if (strncasecmp(p, "sig", 3) == 0)
    102 		p += 3;
    103 
    104 	for (i = 0; i < NSIG; ++i)
    105 		if (strcasecmp (p, sys_signame[i]) == 0)
    106 			return i;
    107 	return -1;
    108 }
    109 
    110 /*
    111  * Print a list of valid signal names
    112  */
    113 static void
    114 printsignals(void)
    115 {
    116 	int n;
    117 
    118 	out1str("EXIT ");
    119 
    120 	for (n = 1; n < NSIG; n++) {
    121 		out1fmt("%s", sys_signame[n]);
    122 		if ((n == NSIG/2) ||  n == (NSIG - 1))
    123 			out1str("\n");
    124 		else
    125 			out1c(' ');
    126 	}
    127 }
    128 
    129 /*
    130  * The trap builtin.
    131  */
    132 
    133 int
    134 trapcmd(int argc, char **argv)
    135 {
    136 	char *action;
    137 	char **ap;
    138 	int signo;
    139 
    140 	if (argc <= 1) {
    141 		for (signo = 0 ; signo <= NSIG ; signo++)
    142 			if (trap[signo] != NULL) {
    143 				out1fmt("trap -- ");
    144 				print_quoted(trap[signo]);
    145 				out1fmt(" %s\n",
    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] == '\0')
    161 				ap++;
    162 			else if ((*ap)[1] == 'l' && (*ap)[2] == '\0') {
    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 sig_t
    234 setsignal(int signo, int vforked)
    235 {
    236 	int action;
    237 	sig_t sigact = SIG_DFL, sig;
    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 			/*
    288 			 * POSIX 3.14.13 states that non-interactive shells
    289 			 * should ignore trap commands for signals that were
    290 			 * ignored upon entry, and leaves the behavior
    291 			 * unspecified for interactive shells. On interactive
    292 			 * shells, or if job control is on, and we have a job
    293 			 * control related signal, we allow the trap to work.
    294 			 *
    295 			 * This change allows us to be POSIX compliant, and
    296 			 * at the same time override the default behavior if
    297 			 * we need to by setting the interactive flag.
    298 			 */
    299 			if ((mflag && (signo == SIGTSTP ||
    300 			     signo == SIGTTIN || signo == SIGTTOU)) || iflag) {
    301 				tsig = S_IGN;
    302 			} else
    303 				tsig = S_HARD_IGN;
    304 		} else {
    305 			tsig = S_RESET;	/* force to be set */
    306 		}
    307 	}
    308 	if (tsig == S_HARD_IGN || tsig == action)
    309 		return 0;
    310 	switch (action) {
    311 		case S_DFL:	sigact = SIG_DFL;	break;
    312 		case S_CATCH:  	sigact = onsig;		break;
    313 		case S_IGN:	sigact = SIG_IGN;	break;
    314 	}
    315 	sig = signal(signo, sigact);
    316 	if (sig != SIG_ERR) {
    317 		sigset_t ss;
    318 		if (!vforked)
    319 			*t = action;
    320 		if (action == S_CATCH)
    321 			(void)siginterrupt(signo, 1);
    322 		/*
    323 		 * If our parent accidentally blocked signals for
    324 		 * us make sure we unblock them
    325 		 */
    326 		(void)sigemptyset(&ss);
    327 		(void)sigaddset(&ss, signo);
    328 		(void)sigprocmask(SIG_UNBLOCK, &ss, NULL);
    329 	}
    330 	return sig;
    331 }
    332 
    333 /*
    334  * Return the current setting for sig w/o changing it.
    335  */
    336 static int
    337 getsigaction(int signo, sig_t *sigact)
    338 {
    339 	struct sigaction sa;
    340 
    341 	if (sigaction(signo, (struct sigaction *)0, &sa) == -1)
    342 		return 0;
    343 	*sigact = (sig_t) sa.sa_handler;
    344 	return 1;
    345 }
    346 
    347 /*
    348  * Ignore a signal.
    349  */
    350 
    351 void
    352 ignoresig(int signo, int vforked)
    353 {
    354 	if (sigmode[signo - 1] != S_IGN && sigmode[signo - 1] != S_HARD_IGN) {
    355 		signal(signo, SIG_IGN);
    356 	}
    357 	if (!vforked)
    358 		sigmode[signo - 1] = S_HARD_IGN;
    359 }
    360 
    361 
    362 #ifdef mkinit
    363 INCLUDE <signal.h>
    364 INCLUDE "trap.h"
    365 
    366 SHELLPROC {
    367 	char *sm;
    368 
    369 	clear_traps(0);
    370 	for (sm = sigmode ; sm < sigmode + NSIG ; sm++) {
    371 		if (*sm == S_IGN)
    372 			*sm = S_HARD_IGN;
    373 	}
    374 }
    375 #endif
    376 
    377 
    378 
    379 /*
    380  * Signal handler.
    381  */
    382 
    383 void
    384 onsig(int signo)
    385 {
    386 	signal(signo, onsig);
    387 	if (signo == SIGINT && trap[SIGINT] == NULL) {
    388 		onint();
    389 		return;
    390 	}
    391 	gotsig[signo - 1] = 1;
    392 	pendingsigs++;
    393 }
    394 
    395 
    396 
    397 /*
    398  * Called to execute a trap.  Perhaps we should avoid entering new trap
    399  * handlers while we are executing a trap handler.
    400  */
    401 
    402 void
    403 dotrap(void)
    404 {
    405 	int i;
    406 	int savestatus;
    407 
    408 	for (;;) {
    409 		for (i = 1 ; ; i++) {
    410 			if (gotsig[i - 1])
    411 				break;
    412 			if (i >= NSIG)
    413 				goto done;
    414 		}
    415 		gotsig[i - 1] = 0;
    416 		savestatus=exitstatus;
    417 		evalstring(trap[i], 0);
    418 		exitstatus=savestatus;
    419 	}
    420 done:
    421 	pendingsigs = 0;
    422 }
    423 
    424 int
    425 lastsig(void)
    426 {
    427 	int i;
    428 
    429 	for (i = NSIG; i > 0; i--)
    430 		if (gotsig[i - 1])
    431 			return i;
    432 	return SIGINT;	/* XXX */
    433 }
    434 
    435 /*
    436  * Controls whether the shell is interactive or not.
    437  */
    438 
    439 
    440 void
    441 setinteractive(int on)
    442 {
    443 	static int is_interactive;
    444 
    445 	if (on == is_interactive)
    446 		return;
    447 	setsignal(SIGINT, 0);
    448 	setsignal(SIGQUIT, 0);
    449 	setsignal(SIGTERM, 0);
    450 	is_interactive = on;
    451 }
    452 
    453 
    454 
    455 /*
    456  * Called to exit the shell.
    457  */
    458 
    459 void
    460 exitshell(int status)
    461 {
    462 	struct jmploc loc1, loc2;
    463 	char *p;
    464 
    465 	TRACE(("pid %d, exitshell(%d)\n", getpid(), status));
    466 	if (setjmp(loc1.loc)) {
    467 		goto l1;
    468 	}
    469 	if (setjmp(loc2.loc)) {
    470 		goto l2;
    471 	}
    472 	handler = &loc1;
    473 	if ((p = trap[0]) != NULL && *p != '\0') {
    474 		trap[0] = NULL;
    475 		evalstring(p, 0);
    476 	}
    477 l1:   handler = &loc2;			/* probably unnecessary */
    478 	flushall();
    479 #if JOBS
    480 	setjobctl(0);
    481 #endif
    482 l2:   _exit(status);
    483 	/* NOTREACHED */
    484 }
    485