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trap.c revision 1.14 
      1 /*	$NetBSD: trap.c,v 1.14 1995/06/05 14:24:33 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 #ifndef lint
     40 #if 0
     41 static char sccsid[] = "@(#)trap.c	8.4 (Berkeley) 6/5/95";
     42 #else
     43 static char rcsid[] = "$NetBSD: trap.c,v 1.14 1995/06/05 14:24:33 christos Exp $";
     44 #endif
     45 #endif /* not lint */
     46 
     47 #include <signal.h>
     48 #include <unistd.h>
     49 #include <stdlib.h>
     50 
     51 #include "shell.h"
     52 #include "main.h"
     53 #include "nodes.h"	/* for other headers */
     54 #include "eval.h"
     55 #include "jobs.h"
     56 #include "show.h"
     57 #include "options.h"
     58 #include "syntax.h"
     59 #include "output.h"
     60 #include "memalloc.h"
     61 #include "error.h"
     62 #include "trap.h"
     63 #include "mystring.h"
     64 
     65 
     66 /*
     67  * Sigmode records the current value of the signal handlers for the various
     68  * modes.  A value of zero means that the current handler is not known.
     69  * S_HARD_IGN indicates that the signal was ignored on entry to the shell,
     70  */
     71 
     72 #define S_DFL 1			/* default signal handling (SIG_DFL) */
     73 #define S_CATCH 2		/* signal is caught */
     74 #define S_IGN 3			/* signal is ignored (SIG_IGN) */
     75 #define S_HARD_IGN 4		/* signal is ignored permenantly */
     76 #define S_RESET 5		/* temporary - to reset a hard ignored sig */
     77 
     78 
     79 extern char nullstr[1];		/* null string */
     80 
     81 char *trap[NSIG+1];		/* trap handler commands */
     82 MKINIT char sigmode[NSIG];	/* current value of signal */
     83 char gotsig[NSIG];		/* indicates specified signal received */
     84 int pendingsigs;			/* indicates some signal received */
     85 
     86 /*
     87  * The trap builtin.
     88  */
     89 
     90 int
     91 trapcmd(argc, argv)
     92 	int argc;
     93 	char **argv;
     94 {
     95 	char *action;
     96 	char **ap;
     97 	int signo;
     98 
     99 	if (argc <= 1) {
    100 		for (signo = 0 ; signo <= NSIG ; signo++) {
    101 			if (trap[signo] != NULL)
    102 				out1fmt("%d: %s\n", signo, trap[signo]);
    103 		}
    104 		return 0;
    105 	}
    106 	ap = argv + 1;
    107 	if (is_number(*ap))
    108 		action = NULL;
    109 	else
    110 		action = *ap++;
    111 	while (*ap) {
    112 		if ((signo = number(*ap)) < 0 || signo > NSIG)
    113 			error("%s: bad trap", *ap);
    114 		INTOFF;
    115 		if (action)
    116 			action = savestr(action);
    117 		if (trap[signo])
    118 			ckfree(trap[signo]);
    119 		trap[signo] = action;
    120 		if (signo != 0)
    121 			setsignal(signo);
    122 		INTON;
    123 		ap++;
    124 	}
    125 	return 0;
    126 }
    127 
    128 
    129 
    130 /*
    131  * Clear traps on a fork.
    132  */
    133 
    134 void
    135 clear_traps() {
    136 	char **tp;
    137 
    138 	for (tp = trap ; tp <= &trap[NSIG] ; tp++) {
    139 		if (*tp && **tp) {	/* trap not NULL or SIG_IGN */
    140 			INTOFF;
    141 			ckfree(*tp);
    142 			*tp = NULL;
    143 			if (tp != &trap[0])
    144 				setsignal(tp - trap);
    145 			INTON;
    146 		}
    147 	}
    148 }
    149 
    150 
    151 
    152 /*
    153  * Set the signal handler for the specified signal.  The routine figures
    154  * out what it should be set to.
    155  */
    156 
    157 long
    158 setsignal(signo)
    159 	int signo;
    160 {
    161 	int action;
    162 	sig_t sigact = SIG_DFL;
    163 	char *t;
    164 	extern void onsig();
    165 	extern sig_t getsigaction();
    166 
    167 	if ((t = trap[signo]) == NULL)
    168 		action = S_DFL;
    169 	else if (*t != '\0')
    170 		action = S_CATCH;
    171 	else
    172 		action = S_IGN;
    173 	if (rootshell && action == S_DFL) {
    174 		switch (signo) {
    175 		case SIGINT:
    176 			if (iflag)
    177 				action = S_CATCH;
    178 			break;
    179 		case SIGQUIT:
    180 #ifdef DEBUG
    181 			{
    182 			extern int debug;
    183 
    184 			if (debug)
    185 				break;
    186 			}
    187 #endif
    188 			/* FALLTHROUGH */
    189 		case SIGTERM:
    190 			if (iflag)
    191 				action = S_IGN;
    192 			break;
    193 #if JOBS
    194 		case SIGTSTP:
    195 		case SIGTTOU:
    196 			if (mflag)
    197 				action = S_IGN;
    198 			break;
    199 #endif
    200 		}
    201 	}
    202 
    203 	if (signo == SIGKILL)
    204 		/* Pretend it worked */
    205 		return 0;
    206 
    207 	t = &sigmode[signo - 1];
    208 	if (*t == 0) {
    209 		/*
    210 		 * current setting unknown
    211 		 */
    212 		sigact = getsigaction(signo);
    213 		if (sigact == SIG_IGN) {
    214 			if (mflag && (signo == SIGTSTP ||
    215 			     signo == SIGTTIN || signo == SIGTTOU)) {
    216 				*t = S_IGN;	/* don't hard ignore these */
    217 			} else
    218 				*t = S_HARD_IGN;
    219 		} else {
    220 			*t = S_RESET;	/* force to be set */
    221 		}
    222 	}
    223 	if (*t == S_HARD_IGN || *t == action)
    224 		return 0;
    225 	switch (action) {
    226 		case S_DFL:	sigact = SIG_DFL;	break;
    227 		case S_CATCH:  	sigact = onsig;		break;
    228 		case S_IGN:	sigact = SIG_IGN;	break;
    229 	}
    230 	*t = action;
    231 	return (long)signal(signo, sigact);
    232 }
    233 
    234 /*
    235  * Return the current setting for sig w/o changing it.
    236  */
    237 sig_t
    238 getsigaction(signo)
    239 	int signo;
    240 {
    241 	struct sigaction sa;
    242 
    243 	if (sigaction(signo, (struct sigaction *)0, &sa) == -1)
    244 		error("Sigaction system call failed");
    245 
    246 	return (sig_t) sa.sa_handler;
    247 }
    248 
    249 /*
    250  * Ignore a signal.
    251  */
    252 
    253 void
    254 ignoresig(signo)
    255 	int signo;
    256 {
    257 	if (sigmode[signo - 1] != S_IGN && sigmode[signo - 1] != S_HARD_IGN) {
    258 		signal(signo, SIG_IGN);
    259 	}
    260 	sigmode[signo - 1] = S_HARD_IGN;
    261 }
    262 
    263 
    264 #ifdef mkinit
    265 INCLUDE <signal.h>
    266 INCLUDE "trap.h"
    267 
    268 SHELLPROC {
    269 	char *sm;
    270 
    271 	clear_traps();
    272 	for (sm = sigmode ; sm < sigmode + NSIG ; sm++) {
    273 		if (*sm == S_IGN)
    274 			*sm = S_HARD_IGN;
    275 	}
    276 }
    277 #endif
    278 
    279 
    280 
    281 /*
    282  * Signal handler.
    283  */
    284 
    285 void
    286 onsig(signo)
    287 	int signo;
    288 {
    289 	signal(signo, onsig);
    290 	if (signo == SIGINT && trap[SIGINT] == NULL) {
    291 		onint();
    292 		return;
    293 	}
    294 	gotsig[signo - 1] = 1;
    295 	pendingsigs++;
    296 }
    297 
    298 
    299 
    300 /*
    301  * Called to execute a trap.  Perhaps we should avoid entering new trap
    302  * handlers while we are executing a trap handler.
    303  */
    304 
    305 void
    306 dotrap() {
    307 	int i;
    308 	int savestatus;
    309 
    310 	for (;;) {
    311 		for (i = 1 ; ; i++) {
    312 			if (gotsig[i - 1])
    313 				break;
    314 			if (i >= NSIG)
    315 				goto done;
    316 		}
    317 		gotsig[i - 1] = 0;
    318 		savestatus=exitstatus;
    319 		evalstring(trap[i]);
    320 		exitstatus=savestatus;
    321 	}
    322 done:
    323 	pendingsigs = 0;
    324 }
    325 
    326 
    327 
    328 /*
    329  * Controls whether the shell is interactive or not.
    330  */
    331 
    332 
    333 void
    334 setinteractive(on)
    335 	int on;
    336 {
    337 	static int is_interactive;
    338 
    339 	if (on == is_interactive)
    340 		return;
    341 	setsignal(SIGINT);
    342 	setsignal(SIGQUIT);
    343 	setsignal(SIGTERM);
    344 	is_interactive = on;
    345 }
    346 
    347 
    348 
    349 /*
    350  * Called to exit the shell.
    351  */
    352 
    353 void
    354 exitshell(status)
    355 	int status;
    356 {
    357 	struct jmploc loc1, loc2;
    358 	char *p;
    359 
    360 	TRACE(("exitshell(%d) pid=%d\n", status, getpid()));
    361 	if (setjmp(loc1.loc)) {
    362 		goto l1;
    363 	}
    364 	if (setjmp(loc2.loc)) {
    365 		goto l2;
    366 	}
    367 	handler = &loc1;
    368 	if ((p = trap[0]) != NULL && *p != '\0') {
    369 		trap[0] = NULL;
    370 		evalstring(p);
    371 	}
    372 l1:   handler = &loc2;			/* probably unnecessary */
    373 	flushall();
    374 #if JOBS
    375 	setjobctl(0);
    376 #endif
    377 l2:   _exit(status);
    378 }
    379