freebsd-dev/bin/sh/trap.c

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/*-
* Copyright (c) 1991, 1993
* The Regents of the University of California. All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* Kenneth Almquist.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 4. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#ifndef lint
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#if 0
static char sccsid[] = "@(#)trap.c 8.5 (Berkeley) 6/5/95";
#endif
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#endif /* not lint */
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#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
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#include <signal.h>
#include <unistd.h>
#include <stdlib.h>
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#include "shell.h"
#include "main.h"
#include "nodes.h" /* for other headers */
#include "eval.h"
#include "jobs.h"
#include "show.h"
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#include "options.h"
#include "syntax.h"
#include "output.h"
#include "memalloc.h"
#include "error.h"
#include "trap.h"
#include "mystring.h"
#include "myhistedit.h"
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/*
* Sigmode records the current value of the signal handlers for the various
* modes. A value of zero means that the current handler is not known.
* S_HARD_IGN indicates that the signal was ignored on entry to the shell,
*/
#define S_DFL 1 /* default signal handling (SIG_DFL) */
#define S_CATCH 2 /* signal is caught */
#define S_IGN 3 /* signal is ignored (SIG_IGN) */
#define S_HARD_IGN 4 /* signal is ignored permanently */
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#define S_RESET 5 /* temporary - to reset a hard ignored sig */
MKINIT char sigmode[NSIG]; /* current value of signal */
int pendingsigs; /* indicates some signal received */
int in_dotrap; /* do we execute in a trap handler? */
static char *volatile trap[NSIG]; /* trap handler commands */
static volatile sig_atomic_t gotsig[NSIG];
/* indicates specified signal received */
static int ignore_sigchld; /* Used while handling SIGCHLD traps. */
volatile sig_atomic_t gotwinch;
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static int getsigaction(int, sig_t *);
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/*
* Map a string to a signal number.
*
* Note: the signal number may exceed NSIG.
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*/
static int
sigstring_to_signum(char *sig)
{
if (is_number(sig)) {
int signo;
signo = atoi(sig);
return ((signo >= 0 && signo < NSIG) ? signo : (-1));
} else if (strcasecmp(sig, "exit") == 0) {
return (0);
} else {
int n;
if (strncasecmp(sig, "sig", 3) == 0)
sig += 3;
for (n = 1; n < sys_nsig; n++)
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if (sys_signame[n] &&
strcasecmp(sys_signame[n], sig) == 0)
return (n);
}
return (-1);
}
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/*
* Print a list of valid signal names.
*/
static void
printsignals(void)
{
int n, outlen;
outlen = 0;
for (n = 1; n < sys_nsig; n++) {
if (sys_signame[n]) {
out1fmt("%s", sys_signame[n]);
outlen += strlen(sys_signame[n]);
} else {
out1fmt("%d", n);
outlen += 3; /* good enough */
}
++outlen;
if (outlen > 70 || n == sys_nsig - 1) {
out1str("\n");
outlen = 0;
} else {
out1c(' ');
}
}
}
/*
* The trap builtin.
*/
int
trapcmd(int argc, char **argv)
{
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char *action;
int signo;
if (argc <= 1) {
for (signo = 0 ; signo < sys_nsig ; signo++) {
if (signo < NSIG && trap[signo] != NULL) {
out1str("trap -- ");
out1qstr(trap[signo]);
if (signo == 0) {
out1str(" exit\n");
} else if (sys_signame[signo]) {
out1fmt(" %s\n", sys_signame[signo]);
} else {
out1fmt(" %d\n", signo);
}
}
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}
return 0;
}
action = NULL;
if (*++argv && strcmp(*argv, "--") == 0)
argv++;
if (*argv && sigstring_to_signum(*argv) == -1) {
if ((*argv)[0] != '-') {
action = *argv;
argv++;
} else if ((*argv)[1] == '\0') {
argv++;
} else if ((*argv)[1] == 'l' && (*argv)[2] == '\0') {
printsignals();
return 0;
} else {
error("bad option %s", *argv);
}
}
while (*argv) {
if ((signo = sigstring_to_signum(*argv)) == -1)
error("bad signal %s", *argv);
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INTOFF;
if (action)
action = savestr(action);
if (trap[signo])
ckfree(trap[signo]);
trap[signo] = action;
if (signo != 0)
setsignal(signo);
INTON;
argv++;
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}
return 0;
}
/*
* Clear traps on a fork.
*/
void
clear_traps(void)
{
char *volatile *tp;
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for (tp = trap ; tp <= &trap[NSIG - 1] ; tp++) {
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if (*tp && **tp) { /* trap not NULL or SIG_IGN */
INTOFF;
ckfree(*tp);
*tp = NULL;
if (tp != &trap[0])
setsignal(tp - trap);
INTON;
}
}
}
/*
* Set the signal handler for the specified signal. The routine figures
* out what it should be set to.
*/
void
setsignal(int signo)
{
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int action;
sig_t sig, sigact = SIG_DFL;
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char *t;
if ((t = trap[signo]) == NULL)
action = S_DFL;
else if (*t != '\0')
action = S_CATCH;
else
action = S_IGN;
if (action == S_DFL) {
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switch (signo) {
case SIGINT:
action = S_CATCH;
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break;
case SIGQUIT:
#ifdef DEBUG
{
extern int debug;
if (debug)
break;
}
#endif
action = S_CATCH;
break;
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case SIGTERM:
if (rootshell && iflag)
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action = S_IGN;
break;
#if JOBS
case SIGTSTP:
case SIGTTOU:
if (rootshell && mflag)
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action = S_IGN;
break;
#endif
#ifndef NO_HISTORY
case SIGWINCH:
if (rootshell && iflag)
action = S_CATCH;
break;
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#endif
}
}
t = &sigmode[signo];
if (*t == 0) {
/*
* current setting unknown
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*/
if (!getsigaction(signo, &sigact)) {
/*
* Pretend it worked; maybe we should give a warning
* here, but other shells don't. We don't alter
* sigmode, so that we retry every time.
*/
return;
}
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if (sigact == SIG_IGN) {
if (mflag && (signo == SIGTSTP ||
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signo == SIGTTIN || signo == SIGTTOU)) {
*t = S_IGN; /* don't hard ignore these */
} else
*t = S_HARD_IGN;
} else {
*t = S_RESET; /* force to be set */
}
}
if (*t == S_HARD_IGN || *t == action)
return;
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switch (action) {
case S_DFL: sigact = SIG_DFL; break;
case S_CATCH: sigact = onsig; break;
case S_IGN: sigact = SIG_IGN; break;
}
*t = action;
sig = signal(signo, sigact);
if (sig != SIG_ERR && action == S_CATCH)
siginterrupt(signo, 1);
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}
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/*
* Return the current setting for sig w/o changing it.
*/
static int
getsigaction(int signo, sig_t *sigact)
{
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struct sigaction sa;
if (sigaction(signo, (struct sigaction *)0, &sa) == -1)
return 0;
*sigact = (sig_t) sa.sa_handler;
return 1;
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}
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/*
* Ignore a signal.
*/
void
ignoresig(int signo)
{
if (sigmode[signo] != S_IGN && sigmode[signo] != S_HARD_IGN) {
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signal(signo, SIG_IGN);
}
sigmode[signo] = S_HARD_IGN;
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}
#ifdef mkinit
INCLUDE <signal.h>
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INCLUDE "trap.h"
SHELLPROC {
char *sm;
clear_traps();
for (sm = sigmode ; sm < sigmode + NSIG ; sm++) {
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if (*sm == S_IGN)
*sm = S_HARD_IGN;
}
}
#endif
/*
* Signal handler.
*/
void
onsig(int signo)
{
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if (signo == SIGINT && trap[SIGINT] == NULL) {
onint();
return;
}
if (signo != SIGCHLD || !ignore_sigchld)
gotsig[signo] = 1;
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pendingsigs++;
/* If we are currently in a wait builtin, prepare to break it */
if ((signo == SIGINT || signo == SIGQUIT) && in_waitcmd != 0)
breakwaitcmd = 1;
/*
* If a trap is set, not ignored and not the null command, we need
* to make sure traps are executed even when a child blocks signals.
*/
if (Tflag &&
trap[signo] != NULL &&
Various small code cleanups resulting from a code reviewing and linting procedure: 1. Remove useless sub-expression: - if (*start || (!ifsspc && start > string && (nulonly || 1))) { + if (*start || (!ifsspc && start > string)) { The sub-expression "(nulonly || 1)" always evaluates to true and according to CVS logs seems to be just a left-over from some debugging and introduced by accident. Removing the sub-expression doesn't change semantics and a code inspection showed that the variable "nulonly" is also not necessary here in any way (and the expression would require fixing instead of removing). 2. Remove dead code: - if (backslash && c == '\\') { - if (read(STDIN_FILENO, &c, 1) != 1) { - status = 1; - break; - } - STPUTC(c, p); - } else if (ap[1] != NULL && strchr(ifs, c) != NULL) { + if (ap[1] != NULL && strchr(ifs, c) != NULL) { Inspection of the control and data flow showed that variable "backslash" is always false (0) when the "if"-expression is evaluated, hence the whole block is effectively dead code. Additionally, the skipping of characters after a backslash is already performed correctly a few lines above, so this code is also not needed at all. According to the CVS logs and the ASH 0.2 sources, this code existed in this way already since its early days. 3. Cleanup Style: - ! trap[signo][0] == '\0' && + ! (trap[signo][0] == '\0') && The expression wants to ensure the trap is not assigned the empty string. But the "!" operator has higher precedence than "==", so the comparison should be put into parenthesis to form the intended way of expression. Nevertheless the code was effectively not really broken as both particular NUL comparisons are semantically equal, of course. But the parenthesized version is a lot more intuitive. 4. Remove shadowing variable declaration: - char *q; The declaration of symbol "q" hides another identical declaration of "q" in the same context. As the other "q" is already reused multiple times and also can be reused again without negative side-effects, just remove the shadowing declaration. 5. Just small cosmetics: - if (ifsset() != 0) + if (ifsset()) The ifsset() macro is already coded by returning the boolean result of a comparison operator, so no need to compare this boolean result again against a numerical value. This also aligns the macros usage to the remaining existing code. Reviewed by: stefanf@
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! (trap[signo][0] == '\0') &&
! (trap[signo][0] == ':' && trap[signo][1] == '\0'))
breakwaitcmd = 1;
#ifndef NO_HISTORY
if (signo == SIGWINCH)
gotwinch = 1;
#endif
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}
/*
* Called to execute a trap. Perhaps we should avoid entering new trap
* handlers while we are executing a trap handler.
*/
void
dotrap(void)
{
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int i;
int savestatus;
in_dotrap++;
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for (;;) {
for (i = 1; i < NSIG; i++) {
if (gotsig[i]) {
gotsig[i] = 0;
if (trap[i]) {
/*
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* Ignore SIGCHLD to avoid infinite
* recursion if the trap action does
* a fork.
*/
if (i == SIGCHLD)
ignore_sigchld++;
savestatus = exitstatus;
evalstring(trap[i]);
exitstatus = savestatus;
if (i == SIGCHLD)
ignore_sigchld--;
}
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break;
}
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}
if (i >= NSIG)
break;
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}
in_dotrap--;
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pendingsigs = 0;
}
/*
* Controls whether the shell is interactive or not.
*/
void
setinteractive(int on)
{
static int is_interactive = -1;
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if (on == is_interactive)
return;
setsignal(SIGINT);
setsignal(SIGQUIT);
setsignal(SIGTERM);
#ifndef NO_HISTORY
setsignal(SIGWINCH);
#endif
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is_interactive = on;
}
/*
* Called to exit the shell.
*/
void
exitshell(int status)
{
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struct jmploc loc1, loc2;
char *p;
TRACE(("exitshell(%d) pid=%d\n", status, getpid()));
if (setjmp(loc1.loc)) {
goto l1;
}
if (setjmp(loc2.loc)) {
goto l2;
}
handler = &loc1;
if ((p = trap[0]) != NULL && *p != '\0') {
trap[0] = NULL;
evalstring(p);
}
l1: handler = &loc2; /* probably unnecessary */
flushall();
#if JOBS
setjobctl(0);
#endif
l2: _exit(status);
}