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hush: replace signal handling machinery

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With new version of signal handling, read builtin should be less buggy
wrt signals.

function                                             old     new   delta
install_sighandlers                                    -     121    +121
switch_off_special_sigs                                -      84     +84
pick_sighandler                                        -      58     +58
install_special_sighandlers                            -      47     +47
builtin_wait                                         284     319     +35
record_pending_signo                                   -      21     +21
execvp_or_die                                         43      48      +5
file_get                                             290     288      -2
run_list                                            1004     998      -6
static.zero_timespec                                   8       -      -8
sigprocmask_set                                       14       -     -14
sigwaitinfo                                           23       -     -23
record_signal                                         23       -     -23
__GI_sigwaitinfo                                      23       -     -23
sigtimedwait                                          25       -     -25
builtin_trap                                         417     392     -25
__GI_sigtimedwait                                     25       -     -25
hush_main                                           1003     965     -38
check_and_run_traps                                  263     217     -46
__rt_sigtimedwait                                     52       -     -52
reset_traps_to_defaults                              213     126     -87
init_sigmasks                                        198       -    -198
builtin_read                                         536     197    -339
------------------------------------------------------------------------------
(add/remove: 5/10 grow/shrink: 2/7 up/down: 371/-934)        Total: -563 bytes
   text	   data	    bss	    dec	    hex	filename
 903075	    936	  17736	 921747	  e1093	busybox_old
 902547	    936	  17736	 921219	  e0e83	busybox_unstripped

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko 2011-05-11 23:56:11 +02:00
parent 10c0131a8a
commit 9d6cbafe72
1 changed files with 279 additions and 233 deletions
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512
shell/hush.c
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@ -106,6 +106,10 @@
# define PIPE_BUF 4096 /* amount of buffering in a pipe */ # define PIPE_BUF 4096 /* amount of buffering in a pipe */
#endif #endif
/* Not every libc has sighandler_t. Fix it */
typedef void (*hush_sighandler_t)(int);
#define sighandler_t hush_sighandler_t
//config:config HUSH //config:config HUSH
//config: bool "hush" //config: bool "hush"
//config: default y //config: default y
@ -764,7 +768,6 @@ struct globals {
smalluint last_exitcode; smalluint last_exitcode;
/* are global_argv and global_argv[1..n] malloced? (note: not [0]) */ /* are global_argv and global_argv[1..n] malloced? (note: not [0]) */
smalluint global_args_malloced; smalluint global_args_malloced;
smalluint inherited_set_is_saved;
/* how many non-NULL argv's we have. NB: $# + 1 */ /* how many non-NULL argv's we have. NB: $# + 1 */
int global_argc; int global_argc;
char **global_argv; char **global_argv;
@ -794,21 +797,20 @@ struct globals {
#endif #endif
/* Which signals have non-DFL handler (even with no traps set)? /* Which signals have non-DFL handler (even with no traps set)?
* Set at the start to: * Set at the start to:
* (SIGQUIT + maybe SPECIAL_INTERACTIVE_SIGS + maybe SPECIAL_JOB_SIGS) * (SIGQUIT + maybe SPECIAL_INTERACTIVE_SIGS + maybe SPECIAL_JOBSTOP_SIGS)
* SPECIAL_INTERACTIVE_SIGS are cleared after fork. * SPECIAL_INTERACTIVE_SIGS are cleared after fork.
* The rest is cleared right before execv syscalls.
* Other than these two times, never modified. * Other than these two times, never modified.
*/ */
unsigned special_sig_mask; unsigned special_sig_mask;
#if ENABLE_HUSH_JOB
unsigned fatal_sig_mask;
#define G_fatal_sig_mask G.fatal_sig_mask
#else
#define G_fatal_sig_mask 0
#endif
char **traps; /* char *traps[NSIG] */ char **traps; /* char *traps[NSIG] */
/* Signal mask on the entry to the (top-level) shell. Never modified. */ sigset_t pending_set;
sigset_t inherited_set;
/* Starts equal to inherited_set,
* but shell-special signals are added and SIGCHLD is removed.
* When a trap is set/cleared, signal is added to/removed from it:
*/
sigset_t blocked_set;
/* Used by read() */
sigset_t detected_set;
#if HUSH_DEBUG #if HUSH_DEBUG
unsigned long memleak_value; unsigned long memleak_value;
int debug_indent; int debug_indent;
@ -1337,8 +1339,8 @@ static void restore_G_args(save_arg_t *sv, char **argv)
* (What happens to signals which are IGN on shell start?) * (What happens to signals which are IGN on shell start?)
* (What happens with signal mask on shell start?) * (What happens with signal mask on shell start?)
* *
* Implementation in hush * Old implementation
* ====================== * ==================
* We use in-kernel pending signal mask to determine which signals were sent. * We use in-kernel pending signal mask to determine which signals were sent.
* We block all signals which we don't want to take action immediately, * We block all signals which we don't want to take action immediately,
* i.e. we block all signals which need to have special handling as described * i.e. we block all signals which need to have special handling as described
@ -1369,6 +1371,49 @@ static void restore_G_args(save_arg_t *sv, char **argv)
* Standard says "When a subshell is entered, traps that are not being ignored * Standard says "When a subshell is entered, traps that are not being ignored
* are set to the default actions". bash interprets it so that traps which * are set to the default actions". bash interprets it so that traps which
* are set to '' (ignore) are NOT reset to defaults. We do the same. * are set to '' (ignore) are NOT reset to defaults. We do the same.
*
* Problem: the above approach makes it unwieldy to catch signals while
* we are in read builtin, of while we read commands from stdin:
* masked signals are not visible!
*
* New implementation
* ==================
* We record each signal we are interested in by installing signal handler
* for them - a bit like emulating kernel pending signal mask in userspace.
* We are interested in: signals which need to have special handling
* as described above, and all signals which have traps set.
* Signals are rocorded in pending_set.
* After each pipe execution, we extract any pending signals
* and act on them.
*
* unsigned special_sig_mask: a mask of shell-special signals.
* unsigned fatal_sig_mask: a mask of signals on which we restore tty pgrp.
* char *traps[sig] if trap for sig is set (even if it's '').
* sigset_t pending_set: set of sigs we received.
*
* "trap - SIGxxx":
* if sig is in special_sig_mask, set handler back to:
* record_pending_signo, or to IGN if it's a tty stop signal
* if sig is in fatal_sig_mask, set handler back to sigexit.
* else: set handler back to SIG_DFL
* "trap 'cmd' SIGxxx":
* set handler to record_pending_signo.
* "trap '' SIGxxx":
* set handler to SIG_IGN.
* after [v]fork, if we plan to be a shell:
* set signals with special interactive handling to SIG_DFL
* (because child shell is not interactive),
* unset all traps except '' (note: regardless of child shell's type - {}, (), etc)
* after [v]fork, if we plan to exec:
* POSIX says fork clears pending signal mask in child - no need to clear it.
*
* To make wait builtin interruptible, we handle SIGCHLD as special signal,
* otherwise (if we leave it SIG_DFL) sigsuspend in wait builtin will not wake up on it.
*
* Note (compat):
* Standard says "When a subshell is entered, traps that are not being ignored
* are set to the default actions". bash interprets it so that traps which
* are set to '' (ignore) are NOT reset to defaults. We do the same.
*/ */
enum { enum {
SPECIAL_INTERACTIVE_SIGS = 0 SPECIAL_INTERACTIVE_SIGS = 0
@ -1376,26 +1421,25 @@ enum {
| (1 << SIGINT) | (1 << SIGINT)
| (1 << SIGHUP) | (1 << SIGHUP)
, ,
SPECIAL_JOB_SIGS = 0 SPECIAL_JOBSTOP_SIGS = 0
#if ENABLE_HUSH_JOB #if ENABLE_HUSH_JOB
| (1 << SIGTTIN) | (1 << SIGTTIN)
| (1 << SIGTTOU) | (1 << SIGTTOU)
| (1 << SIGTSTP) | (1 << SIGTSTP)
#endif #endif
,
}; };
static void sigprocmask_set(sigset_t *set) static void record_pending_signo(int sig)
{ {
sigprocmask(SIG_SETMASK, set, NULL); sigaddset(&G.pending_set, sig);
}
#if ENABLE_HUSH_FAST #if ENABLE_HUSH_FAST
static void SIGCHLD_handler(int sig UNUSED_PARAM) if (sig == SIGCHLD) {
{ G.count_SIGCHLD++;
G.count_SIGCHLD++;
//bb_error_msg("[%d] SIGCHLD_handler: G.count_SIGCHLD:%d G.handled_SIGCHLD:%d", getpid(), G.count_SIGCHLD, G.handled_SIGCHLD); //bb_error_msg("[%d] SIGCHLD_handler: G.count_SIGCHLD:%d G.handled_SIGCHLD:%d", getpid(), G.count_SIGCHLD, G.handled_SIGCHLD);
} }
#endif #endif
}
#if ENABLE_HUSH_JOB #if ENABLE_HUSH_JOB
@ -1433,6 +1477,31 @@ static void sigexit(int sig)
#endif #endif
static sighandler_t pick_sighandler(unsigned sig)
{
sighandler_t handler = SIG_DFL;
if (sig < sizeof(unsigned)*8) {
unsigned sigmask = (1 << sig);
#if ENABLE_HUSH_JOB
/* sig is fatal? */
if (G_fatal_sig_mask & sigmask)
handler = sigexit;
#endif
/* sig has special handling? */
else if (G.special_sig_mask & sigmask)
handler = record_pending_signo;
/* TTIN/TTOU/TSTS can't be set to record_pending_signo
* in order to ignore them: they will be raised
* in an endless loop then when we try to do some
* terminal ioctls! We do nave to _ignore_ these.
*/
if (SPECIAL_JOBSTOP_SIGS & sigmask)
handler = SIG_IGN;
}
return handler;
}
/* Restores tty foreground process group, and exits. */ /* Restores tty foreground process group, and exits. */
static void hush_exit(int exitcode) NORETURN; static void hush_exit(int exitcode) NORETURN;
static void hush_exit(int exitcode) static void hush_exit(int exitcode)
@ -1478,39 +1547,30 @@ static void hush_exit(int exitcode)
} }
static int check_and_run_traps(int sig) //TODO: return a mask of ALL handled sigs?
static int check_and_run_traps(void)
{ {
/* I want it in rodata, not in bss.
* gcc 4.2.1 puts it in rodata only if it has { 0, 0 }
* initializer. But other compilers may still use bss.
* TODO: find more portable solution.
*/
static const struct timespec zero_timespec = { 0, 0 };
smalluint save_rcode;
int last_sig = 0; int last_sig = 0;
if (sig)
goto got_sig;
while (1) { while (1) {
if (!sigisemptyset(&G.detected_set)) { int sig;
sig = 0;
do {
sig++;
if (sigismember(&G.detected_set, sig)) {
sigdelset(&G.detected_set, sig);
goto got_sig;
}
} while (sig < NSIG);
}
sig = sigtimedwait(&G.blocked_set, NULL, &zero_timespec); if (sigisemptyset(&G.pending_set))
if (sig <= 0)
break; break;
sig = 0;
do {
sig++;
if (sigismember(&G.pending_set, sig)) {
sigdelset(&G.pending_set, sig);
goto got_sig;
}
} while (sig < NSIG);
break;
got_sig: got_sig:
if (G.traps && G.traps[sig]) { if (G.traps && G.traps[sig]) {
if (G.traps[sig][0]) { if (G.traps[sig][0]) {
/* We have user-defined handler */ /* We have user-defined handler */
smalluint save_rcode;
char *argv[3]; char *argv[3];
/* argv[0] is unused */ /* argv[0] is unused */
argv[1] = G.traps[sig]; argv[1] = G.traps[sig];
@ -1524,12 +1584,6 @@ static int check_and_run_traps(int sig)
} }
/* not a trap: special action */ /* not a trap: special action */
switch (sig) { switch (sig) {
#if ENABLE_HUSH_FAST
case SIGCHLD:
G.count_SIGCHLD++;
//bb_error_msg("[%d] check_and_run_traps: G.count_SIGCHLD:%d G.handled_SIGCHLD:%d", getpid(), G.count_SIGCHLD, G.handled_SIGCHLD);
break;
#endif
case SIGINT: case SIGINT:
/* Builtin was ^C'ed, make it look prettier: */ /* Builtin was ^C'ed, make it look prettier: */
bb_putchar('\n'); bb_putchar('\n');
@ -1550,12 +1604,22 @@ static int check_and_run_traps(int sig)
} }
sigexit(SIGHUP); sigexit(SIGHUP);
} }
#endif
#if ENABLE_HUSH_FAST
case SIGCHLD:
G.count_SIGCHLD++;
//bb_error_msg("[%d] check_and_run_traps: G.count_SIGCHLD:%d G.handled_SIGCHLD:%d", getpid(), G.count_SIGCHLD, G.handled_SIGCHLD);
/* Note:
* We dont do 'last_sig = sig' here -> NOT returning this sig.
* This simplifies wait builtin a bit.
*/
break;
#endif #endif
default: /* ignored: */ default: /* ignored: */
/* SIGTERM, SIGQUIT, SIGTTIN, SIGTTOU, SIGTSTP */ /* SIGTERM, SIGQUIT, SIGTTIN, SIGTTOU, SIGTSTP */
/* note: /* Note:
* we dont do 'last_sig = sig' here -> NOT returning this sig. * We dont do 'last_sig = sig' here -> NOT returning this sig.
* example: wait is not interrupted by TERM * Example: wait is not interrupted by TERM
* in interactive shell, because TERM is ignored. * in interactive shell, because TERM is ignored.
*/ */
break; break;
@ -1948,7 +2012,7 @@ static void get_user_input(struct in_str *i)
* only after <Enter>. (^C will work) */ * only after <Enter>. (^C will work) */
r = read_line_input(G.line_input_state, prompt_str, G.user_input_buf, CONFIG_FEATURE_EDITING_MAX_LEN-1, /*timeout*/ -1); r = read_line_input(G.line_input_state, prompt_str, G.user_input_buf, CONFIG_FEATURE_EDITING_MAX_LEN-1, /*timeout*/ -1);
/* catch *SIGINT* etc (^C is handled by read_line_input) */ /* catch *SIGINT* etc (^C is handled by read_line_input) */
check_and_run_traps(0); check_and_run_traps();
} while (r == 0 || G.flag_SIGINT); /* repeat if ^C or SIGINT */ } while (r == 0 || G.flag_SIGINT); /* repeat if ^C or SIGINT */
i->eof_flag = (r < 0); i->eof_flag = (r < 0);
if (i->eof_flag) { /* EOF/error detected */ if (i->eof_flag) { /* EOF/error detected */
@ -1964,7 +2028,7 @@ static void get_user_input(struct in_str *i)
* $ <[enter], repeatedly...> * $ <[enter], repeatedly...>
* Without check_and_run_traps, handler never runs. * Without check_and_run_traps, handler never runs.
*/ */
check_and_run_traps(0); check_and_run_traps();
fputs(prompt_str, stdout); fputs(prompt_str, stdout);
} }
fflush_all(); fflush_all();
@ -5368,6 +5432,25 @@ void re_execute_shell(char ***to_free, const char *s,
char *g_argv0, char **g_argv, char *g_argv0, char **g_argv,
char **builtin_argv) NORETURN; char **builtin_argv) NORETURN;
static void switch_off_special_sigs(unsigned mask)
{
unsigned sig = 0;
while ((mask >>= 1) != 0) {
sig++;
if (!(mask & 1))
continue;
if (G.traps) {
if (G.traps[sig] && !G.traps[sig][0])
/* trap is '', has to remain SIG_IGN */
continue;
free(G.traps[sig]);
G.traps[sig] = NULL;
}
/* We are here only if no trap or trap was not '' */
signal(sig, SIG_DFL);
}
}
static void reset_traps_to_defaults(void) static void reset_traps_to_defaults(void)
{ {
/* This function is always called in a child shell /* This function is always called in a child shell
@ -5381,44 +5464,35 @@ static void reset_traps_to_defaults(void)
* Testcase: (while :; do :; done) + ^Z should background. * Testcase: (while :; do :; done) + ^Z should background.
* Same goes for SIGTERM, SIGHUP, SIGINT. * Same goes for SIGTERM, SIGHUP, SIGINT.
*/ */
if (!G.traps && !(G.special_sig_mask & SPECIAL_INTERACTIVE_SIGS)) mask = (G.special_sig_mask & SPECIAL_INTERACTIVE_SIGS) | G_fatal_sig_mask;
return; /* already no traps and no SPECIAL_INTERACTIVE_SIGS */ if (!G.traps && !mask)
return; /* already no traps and no special sigs */
/* Switching off SPECIAL_INTERACTIVE_SIGS. /* Switch off special sigs */
* Stupid. It can be done with *single* &= op, but we can't use switch_off_special_sigs(mask);
* the fact that G.blocked_set is implemented as a bitmask #if ENABLE_HUSH_JOB
* in libc... */ G_fatal_sig_mask = 0;
mask = SPECIAL_INTERACTIVE_SIGS; #endif
sig = 0;
while ((mask >>= 1) != 0) {
sig++;
if (mask & 1) {
/* Careful. Only if no trap or trap is not "" */
if (!G.traps || !G.traps[sig] || G.traps[sig][0])
sigdelset(&G.blocked_set, sig);
}
}
/* Our homegrown sig mask is saner to work with :) */
G.special_sig_mask &= ~SPECIAL_INTERACTIVE_SIGS; G.special_sig_mask &= ~SPECIAL_INTERACTIVE_SIGS;
/* SIGQUIT and maybe SPECIAL_JOBSTOP_SIGS remain set in G.special_sig_mask */
/* Resetting all traps to default except empty ones */ if (!G.traps)
mask = G.special_sig_mask; return;
if (G.traps) for (sig = 0; sig < NSIG; sig++, mask >>= 1) {
if (!G.traps[sig] || !G.traps[sig][0]) /* Reset all sigs to default except ones with empty traps */
continue; for (sig = 0; sig < NSIG; sig++) {
if (!G.traps[sig])
continue; /* no trap: nothing to do */
if (!G.traps[sig][0])
continue; /* empty trap: has to remain SIG_IGN */
/* sig has non-empty trap, reset it: */
free(G.traps[sig]); free(G.traps[sig]);
G.traps[sig] = NULL; G.traps[sig] = NULL;
/* There is no signal for 0 (EXIT) */ /* There is no signal for trap 0 (EXIT) */
if (sig == 0) if (sig == 0)
continue; continue;
/* There was a trap handler, we just removed it. signal(sig, pick_sighandler(sig));
* But if sig still has non-DFL handling,
* we should not unblock the sig. */
if (mask & 1)
continue;
sigdelset(&G.blocked_set, sig);
} }
sigprocmask_set(&G.blocked_set);
} }
#else /* !BB_MMU */ #else /* !BB_MMU */
@ -5463,6 +5537,7 @@ static void re_execute_shell(char ***to_free, const char *s,
for (sig = 1; sig < NSIG; sig++) { for (sig = 1; sig < NSIG; sig++) {
if (G.traps[sig] && !G.traps[sig][0]) if (G.traps[sig] && !G.traps[sig][0])
empty_trap_mask |= 1LL << sig; empty_trap_mask |= 1LL << sig;
///vda: optimize
} }
} }
@ -5548,7 +5623,7 @@ static void re_execute_shell(char ***to_free, const char *s,
do_exec: do_exec:
debug_printf_exec("re_execute_shell pid:%d cmd:'%s'\n", getpid(), s); debug_printf_exec("re_execute_shell pid:%d cmd:'%s'\n", getpid(), s);
sigprocmask_set(&G.inherited_set); switch_off_special_sigs(G.special_sig_mask & SPECIAL_JOBSTOP_SIGS);
execve(bb_busybox_exec_path, argv, pp); execve(bb_busybox_exec_path, argv, pp);
/* Fallback. Useful for init=/bin/hush usage etc */ /* Fallback. Useful for init=/bin/hush usage etc */
if (argv[0][0] == '/') if (argv[0][0] == '/')
@ -6202,7 +6277,7 @@ static void execvp_or_die(char **argv) NORETURN;
static void execvp_or_die(char **argv) static void execvp_or_die(char **argv)
{ {
debug_printf_exec("execing '%s'\n", argv[0]); debug_printf_exec("execing '%s'\n", argv[0]);
sigprocmask_set(&G.inherited_set); switch_off_special_sigs(G.special_sig_mask & SPECIAL_JOBSTOP_SIGS);
execvp(argv[0], argv); execvp(argv[0], argv);
bb_perror_msg("can't execute '%s'", argv[0]); bb_perror_msg("can't execute '%s'", argv[0]);
_exit(127); /* bash compat */ _exit(127); /* bash compat */
@ -6334,7 +6409,7 @@ static NOINLINE void pseudo_exec_argv(nommu_save_t *nommu_save,
# endif # endif
/* Re-exec ourselves */ /* Re-exec ourselves */
debug_printf_exec("re-execing applet '%s'\n", argv[0]); debug_printf_exec("re-execing applet '%s'\n", argv[0]);
sigprocmask_set(&G.inherited_set); switch_off_special_sigs(G.special_sig_mask & SPECIAL_JOBSTOP_SIGS);
execv(bb_busybox_exec_path, argv); execv(bb_busybox_exec_path, argv);
/* If they called chroot or otherwise made the binary no longer /* If they called chroot or otherwise made the binary no longer
* executable, fall through */ * executable, fall through */
@ -7033,9 +7108,6 @@ static NOINLINE int run_pipe(struct pipe *pi)
if (setup_redirects(command, NULL)) if (setup_redirects(command, NULL))
_exit(1); _exit(1);
/* Restore default handlers just prior to exec */
/*signal(SIGCHLD, SIG_DFL); - so far we don't have any handlers */
/* Stores to nommu_save list of env vars putenv'ed /* Stores to nommu_save list of env vars putenv'ed
* (NOMMU, on MMU we don't need that) */ * (NOMMU, on MMU we don't need that) */
/* cast away volatility... */ /* cast away volatility... */
@ -7313,7 +7385,7 @@ static int run_list(struct pipe *pi)
* and we don't need to wait for anything. */ * and we don't need to wait for anything. */
G.last_exitcode = rcode; G.last_exitcode = rcode;
debug_printf_exec(": builtin/func exitcode %d\n", rcode); debug_printf_exec(": builtin/func exitcode %d\n", rcode);
check_and_run_traps(0); check_and_run_traps();
#if ENABLE_HUSH_LOOPS #if ENABLE_HUSH_LOOPS
/* Was it "break" or "continue"? */ /* Was it "break" or "continue"? */
if (G.flag_break_continue) { if (G.flag_break_continue) {
@ -7345,7 +7417,7 @@ static int run_list(struct pipe *pi)
/* even bash 3.2 doesn't do that well with nested bg: /* even bash 3.2 doesn't do that well with nested bg:
* try "{ { sleep 10; echo DEEP; } & echo HERE; } &". * try "{ { sleep 10; echo DEEP; } & echo HERE; } &".
* I'm NOT treating inner &'s as jobs */ * I'm NOT treating inner &'s as jobs */
check_and_run_traps(0); check_and_run_traps();
#if ENABLE_HUSH_JOB #if ENABLE_HUSH_JOB
if (G.run_list_level == 1) if (G.run_list_level == 1)
insert_bg_job(pi); insert_bg_job(pi);
@ -7360,13 +7432,13 @@ static int run_list(struct pipe *pi)
/* Waits for completion, then fg's main shell */ /* Waits for completion, then fg's main shell */
rcode = checkjobs_and_fg_shell(pi); rcode = checkjobs_and_fg_shell(pi);
debug_printf_exec(": checkjobs_and_fg_shell exitcode %d\n", rcode); debug_printf_exec(": checkjobs_and_fg_shell exitcode %d\n", rcode);
check_and_run_traps(0); check_and_run_traps();
} else } else
#endif #endif
{ /* This one just waits for completion */ { /* This one just waits for completion */
rcode = checkjobs(pi); rcode = checkjobs(pi);
debug_printf_exec(": checkjobs exitcode %d\n", rcode); debug_printf_exec(": checkjobs exitcode %d\n", rcode);
check_and_run_traps(0); check_and_run_traps();
} }
G.last_exitcode = rcode; G.last_exitcode = rcode;
} }
@ -7437,58 +7509,61 @@ static int run_and_free_list(struct pipe *pi)
} }
/* Called a few times only (or even once if "sh -c") */ static void install_sighandlers(unsigned mask)
static void init_sigmasks(void) {
sighandler_t old_handler;
unsigned sig = 0;
while ((mask >>= 1) != 0) {
sig++;
if (!(mask & 1))
continue;
old_handler = signal(sig, pick_sighandler(sig));
/* POSIX allows shell to re-enable SIGCHLD
* even if it was SIG_IGN on entry.
* Therefore we skip IGN check for it:
*/
if (sig == SIGCHLD)
continue;
if (old_handler == SIG_IGN) {
/* oops... restore back to IGN, and record this fact */
signal(sig, old_handler);
if (!G.traps)
G.traps = xzalloc(sizeof(G.traps[0]) * NSIG);
free(G.traps[sig]);
G.traps[sig] = xzalloc(1); /* == xstrdup(""); */
}
}
}
/* Called a few times only (or even once if "sh -c") */
static void install_special_sighandlers(void)
{ {
unsigned sig;
unsigned mask; unsigned mask;
/* POSIX allows shell to re-enable SIGCHLD if (G.special_sig_mask != 0)
* even if it was SIG_IGN on entry */ return;
if (!G.inherited_set_is_saved) {
#if ENABLE_HUSH_FAST
signal(SIGCHLD, SIGCHLD_handler);
#else
signal(SIGCHLD, SIG_DFL);
#endif
sigprocmask(SIG_SETMASK, NULL, &G.blocked_set);
G.inherited_set = G.blocked_set;
}
/* Which signals are shell-special? */ /* Which signals are shell-special? */
mask = (1 << SIGQUIT); mask = (1 << SIGQUIT) | (1 << SIGCHLD);
if (G_interactive_fd) { if (G_interactive_fd) {
mask |= SPECIAL_INTERACTIVE_SIGS; mask |= SPECIAL_INTERACTIVE_SIGS;
if (G_saved_tty_pgrp) /* we have ctty, job control sigs work */ if (G_saved_tty_pgrp) /* we have ctty, job control sigs work */
mask |= SPECIAL_JOB_SIGS; mask |= SPECIAL_JOBSTOP_SIGS;
} }
G.special_sig_mask = mask; G.special_sig_mask = mask;
/* Block them. And unblock SIGCHLD */ install_sighandlers(mask);
sig = 0;
while ((mask >>= 1) != 0) {
sig++;
if (mask & 1)
sigaddset(&G.blocked_set, sig);
}
sigdelset(&G.blocked_set, SIGCHLD);
if (memcmp(&G.inherited_set, &G.blocked_set, sizeof(G.inherited_set)) != 0)
sigprocmask_set(&G.blocked_set);
G.inherited_set_is_saved = 1;
} }
#if ENABLE_HUSH_JOB #if ENABLE_HUSH_JOB
/* helper */ /* helper */
/* Set handlers to restore tty pgrp and exit */ /* Set handlers to restore tty pgrp and exit */
static void set_fatal_handlers_to_sigexit(void) static void install_fatal_sighandlers(void)
{ {
void (*handler)(int); unsigned mask;
unsigned fatal_sigs, sig;
/* We will restore tty pgrp on these signals */ /* We will restore tty pgrp on these signals */
fatal_sigs = 0 mask = 0
+ (1 << SIGILL ) * HUSH_DEBUG + (1 << SIGILL ) * HUSH_DEBUG
+ (1 << SIGFPE ) * HUSH_DEBUG + (1 << SIGFPE ) * HUSH_DEBUG
+ (1 << SIGBUS ) * HUSH_DEBUG + (1 << SIGBUS ) * HUSH_DEBUG
@ -7505,22 +7580,13 @@ static void set_fatal_handlers_to_sigexit(void)
/*+ (1 << SIGTERM)*/ /*+ (1 << SIGTERM)*/
/*+ (1 << SIGINT )*/ /*+ (1 << SIGINT )*/
; ;
/* special_sig_mask'ed signals are set to record_pending_signo
/* special_sig_mask'ed signals are, well, masked,
* no need to set handler for them. * no need to set handler for them.
*/ */
fatal_sigs &= ~G.special_sig_mask; /*mask &= ~G.special_sig_mask; - they never overlap */
G_fatal_sig_mask = mask;
/* For each sig in fatal_sigs... */ install_sighandlers(mask);
sig = 0;
while ((fatal_sigs >>= 1) != 0) {
sig++;
if (!(fatal_sigs & 1))
continue;
handler = signal(sig, sigexit);
if (handler == SIG_IGN) /* oops... restore back to IGN! */
signal(sig, handler);
}
} }
#endif #endif
@ -7682,10 +7748,11 @@ int hush_main(int argc, char **argv)
} }
/* Shell is non-interactive at first. We need to call /* Shell is non-interactive at first. We need to call
* init_sigmasks() if we are going to execute "sh <script>", * install_special_sighandlers() if we are going to execute "sh <script>",
* "sh -c <cmds>" or login shell's /etc/profile and friends. * "sh -c <cmds>" or login shell's /etc/profile and friends.
* If we later decide that we are interactive, we run init_sigmasks() * If we later decide that we are interactive, we run install_special_sighandlers()
* in order to intercept (more) signals. * in order to intercept (more) signals.
//FIXME: re-running is currently most likely broken, it's a no-op.
*/ */
/* Parse options */ /* Parse options */
@ -7724,7 +7791,7 @@ int hush_main(int argc, char **argv)
/* -c 'builtin' [BARGV...] "" ARG0 [ARG1...] */ /* -c 'builtin' [BARGV...] "" ARG0 [ARG1...] */
const struct built_in_command *x; const struct built_in_command *x;
init_sigmasks(); install_special_sighandlers();
x = find_builtin(optarg); x = find_builtin(optarg);
if (x) { /* paranoia */ if (x) { /* paranoia */
G.global_argc -= builtin_argc; /* skip [BARGV...] "" */ G.global_argc -= builtin_argc; /* skip [BARGV...] "" */
@ -7741,7 +7808,7 @@ int hush_main(int argc, char **argv)
G.global_argv[0] = argv[0]; G.global_argv[0] = argv[0];
G.global_argc++; G.global_argc++;
} /* else -c 'script' ARG0 [ARG1...]: $0 is ARG0 */ } /* else -c 'script' ARG0 [ARG1...]: $0 is ARG0 */
init_sigmasks(); install_special_sighandlers();
parse_and_run_string(optarg); parse_and_run_string(optarg);
goto final_return; goto final_return;
case 'i': case 'i':
@ -7773,15 +7840,15 @@ int hush_main(int argc, char **argv)
empty_trap_mask = bb_strtoull(optarg, &optarg, 16); empty_trap_mask = bb_strtoull(optarg, &optarg, 16);
if (empty_trap_mask != 0) { if (empty_trap_mask != 0) {
int sig; int sig;
init_sigmasks(); install_special_sighandlers();
G.traps = xzalloc(sizeof(G.traps[0]) * NSIG); G.traps = xzalloc(sizeof(G.traps[0]) * NSIG);
for (sig = 1; sig < NSIG; sig++) { for (sig = 1; sig < NSIG; sig++) {
///vda: fixme: more efficient code
if (empty_trap_mask & (1LL << sig)) { if (empty_trap_mask & (1LL << sig)) {
G.traps[sig] = xzalloc(1); /* == xstrdup(""); */ G.traps[sig] = xzalloc(1); /* == xstrdup(""); */
sigaddset(&G.blocked_set, sig); signal(sig, SIG_IGN);
} }
} }
sigprocmask_set(&G.blocked_set);
} }
# if ENABLE_HUSH_LOOPS # if ENABLE_HUSH_LOOPS
optarg++; optarg++;
@ -7831,7 +7898,7 @@ int hush_main(int argc, char **argv)
input = fopen_for_read("/etc/profile"); input = fopen_for_read("/etc/profile");
if (input != NULL) { if (input != NULL) {
close_on_exec_on(fileno(input)); close_on_exec_on(fileno(input));
init_sigmasks(); install_special_sighandlers();
parse_and_run_file(input); parse_and_run_file(input);
fclose(input); fclose(input);
} }
@ -7856,7 +7923,7 @@ int hush_main(int argc, char **argv)
G.global_argc = argc - optind; G.global_argc = argc - optind;
input = xfopen_for_read(argv[optind]); input = xfopen_for_read(argv[optind]);
close_on_exec_on(fileno(input)); close_on_exec_on(fileno(input));
init_sigmasks(); install_special_sighandlers();
parse_and_run_file(input); parse_and_run_file(input);
#if ENABLE_FEATURE_CLEAN_UP #if ENABLE_FEATURE_CLEAN_UP
fclose(input); fclose(input);
@ -7865,7 +7932,7 @@ int hush_main(int argc, char **argv)
} }
/* Up to here, shell was non-interactive. Now it may become one. /* Up to here, shell was non-interactive. Now it may become one.
* NB: don't forget to (re)run init_sigmasks() as needed. * NB: don't forget to (re)run install_special_sighandlers() as needed.
*/ */
/* A shell is interactive if the '-i' flag was given, /* A shell is interactive if the '-i' flag was given,
@ -7918,11 +7985,11 @@ int hush_main(int argc, char **argv)
} }
/* Block some signals */ /* Block some signals */
init_sigmasks(); install_special_sighandlers();
if (G_saved_tty_pgrp) { if (G_saved_tty_pgrp) {
/* Set other signals to restore saved_tty_pgrp */ /* Set other signals to restore saved_tty_pgrp */
set_fatal_handlers_to_sigexit(); install_fatal_sighandlers();
/* Put ourselves in our own process group /* Put ourselves in our own process group
* (bash, too, does this only if ctty is available) */ * (bash, too, does this only if ctty is available) */
bb_setpgrp(); /* is the same as setpgid(our_pid, our_pid); */ bb_setpgrp(); /* is the same as setpgid(our_pid, our_pid); */
@ -7933,7 +8000,7 @@ int hush_main(int argc, char **argv)
* (we reset die_sleep = 0 whereever we [v]fork) */ * (we reset die_sleep = 0 whereever we [v]fork) */
enable_restore_tty_pgrp_on_exit(); /* sets die_sleep = -1 */ enable_restore_tty_pgrp_on_exit(); /* sets die_sleep = -1 */
} else { } else {
init_sigmasks(); install_special_sighandlers();
} }
#elif ENABLE_HUSH_INTERACTIVE #elif ENABLE_HUSH_INTERACTIVE
/* No job control compiled in, only prompt/line editing */ /* No job control compiled in, only prompt/line editing */
@ -7950,10 +8017,10 @@ int hush_main(int argc, char **argv)
if (G_interactive_fd) { if (G_interactive_fd) {
close_on_exec_on(G_interactive_fd); close_on_exec_on(G_interactive_fd);
} }
init_sigmasks(); install_special_sighandlers();
#else #else
/* We have interactiveness code disabled */ /* We have interactiveness code disabled */
init_sigmasks(); install_special_sighandlers();
#endif #endif
/* bash: /* bash:
* if interactive but not a login shell, sources ~/.bashrc * if interactive but not a login shell, sources ~/.bashrc
@ -8087,7 +8154,7 @@ static int FAST_FUNC builtin_exec(char **argv)
tcsetpgrp(G_interactive_fd, G_saved_tty_pgrp); tcsetpgrp(G_interactive_fd, G_saved_tty_pgrp);
/* TODO: if exec fails, bash does NOT exit! We do. /* TODO: if exec fails, bash does NOT exit! We do.
* We'll need to undo sigprocmask (it's inside execvp_or_die) * We'll need to undo trap cleanup (it's inside execvp_or_die)
* and tcsetpgrp, and this is inherently racy. * and tcsetpgrp, and this is inherently racy.
*/ */
execvp_or_die(argv); execvp_or_die(argv);
@ -8284,6 +8351,8 @@ static int FAST_FUNC builtin_trap(char **argv)
process_sig_list: process_sig_list:
ret = EXIT_SUCCESS; ret = EXIT_SUCCESS;
while (*argv) { while (*argv) {
sighandler_t handler;
sig = get_signum(*argv++); sig = get_signum(*argv++);
if (sig < 0 || sig >= NSIG) { if (sig < 0 || sig >= NSIG) {
ret = EXIT_FAILURE; ret = EXIT_FAILURE;
@ -8302,18 +8371,13 @@ static int FAST_FUNC builtin_trap(char **argv)
if (sig == 0) if (sig == 0)
continue; continue;
if (new_cmd) { if (new_cmd)
sigaddset(&G.blocked_set, sig); handler = (new_cmd[0] ? record_pending_signo : SIG_IGN);
} else { else
/* There was a trap handler, we are removing it /* We are removing trap handler */
* (if sig has non-DFL handling, handler = pick_sighandler(sig);
* we don't need to do anything) */ signal(sig, handler);
if (sig < sizeof(G.special_sig_mask)*8 && (G.special_sig_mask & (1 << sig)))
continue;
sigdelset(&G.blocked_set, sig);
}
} }
sigprocmask_set(&G.blocked_set);
return ret; return ret;
} }
@ -8535,11 +8599,6 @@ static int FAST_FUNC builtin_pwd(char **argv UNUSED_PARAM)
* if it has non-empty trap: * if it has non-empty trap:
* - executes trap and returns to read; * - executes trap and returns to read;
*/ */
/* helper */
static void record_signal(int sig)
{
sigaddset(&G.detected_set, sig);
}
static int FAST_FUNC builtin_read(char **argv) static int FAST_FUNC builtin_read(char **argv)
{ {
const char *r; const char *r;
@ -8549,7 +8608,6 @@ static int FAST_FUNC builtin_read(char **argv)
char *opt_u = NULL; char *opt_u = NULL;
const char *ifs; const char *ifs;
int read_flags; int read_flags;
sigset_t saved_blkd_set;
/* "!": do not abort on errors. /* "!": do not abort on errors.
* Option string must start with "sr" to match BUILTIN_READ_xxx * Option string must start with "sr" to match BUILTIN_READ_xxx
@ -8561,41 +8619,6 @@ static int FAST_FUNC builtin_read(char **argv)
ifs = get_local_var_value("IFS"); /* can be NULL */ ifs = get_local_var_value("IFS"); /* can be NULL */
again: again:
/* We need to temporarily unblock and record signals around read */
saved_blkd_set = G.blocked_set;
{
unsigned sig;
struct sigaction sa, old_sa;
memset(&sa, 0, sizeof(sa));
sigfillset(&sa.sa_mask);
sa.sa_flags = SA_RESTART;
sa.sa_handler = record_signal;
sig = 0;
do {
sig++;
if (sigismember(&G.blocked_set, sig)) {
char *sig_trap = (G.traps && G.traps[sig]) ? G.traps[sig] : NULL;
/* If has a nonempty trap... */
if ((sig_trap && sig_trap[0])
/* ...or has no trap and is SIGINT or SIGHUP */
|| (!sig_trap && (sig == SIGINT || sig == SIGHUP))
) {
sigaction(sig, &sa, &old_sa);
if (old_sa.sa_handler == SIG_IGN) /* oops... restore back to IGN! */
sigaction_set(sig, &old_sa);
else
sigdelset(&G.blocked_set, sig);
}
}
} while (sig < NSIG-1);
}
if (memcmp(&saved_blkd_set, &G.blocked_set, sizeof(saved_blkd_set)) != 0)
sigprocmask_set(&G.blocked_set);
r = shell_builtin_read(set_local_var_from_halves, r = shell_builtin_read(set_local_var_from_halves,
argv, argv,
ifs, ifs,
@ -8606,13 +8629,8 @@ static int FAST_FUNC builtin_read(char **argv)
opt_u opt_u
); );
if (memcmp(&saved_blkd_set, &G.blocked_set, sizeof(saved_blkd_set)) != 0) {
G.blocked_set = saved_blkd_set;
sigprocmask_set(&G.blocked_set);
}
if ((uintptr_t)r == 1 && errno == EINTR) { if ((uintptr_t)r == 1 && errno == EINTR) {
unsigned sig = check_and_run_traps(0); unsigned sig = check_and_run_traps();
if (sig && sig != SIGINT) if (sig && sig != SIGINT)
goto again; goto again;
} }
@ -8849,7 +8867,7 @@ static int FAST_FUNC builtin_unset(char **argv)
static int FAST_FUNC builtin_wait(char **argv) static int FAST_FUNC builtin_wait(char **argv)
{ {
int ret = EXIT_SUCCESS; int ret = EXIT_SUCCESS;
int status, sig; int status;
argv = skip_dash_dash(argv); argv = skip_dash_dash(argv);
if (argv[0] == NULL) { if (argv[0] == NULL) {
@ -8869,25 +8887,53 @@ static int FAST_FUNC builtin_wait(char **argv)
* ^C <-- after ~4 sec from keyboard * ^C <-- after ~4 sec from keyboard
* $ * $
*/ */
sigaddset(&G.blocked_set, SIGCHLD);
sigprocmask_set(&G.blocked_set);
while (1) { while (1) {
checkjobs(NULL); int sig;
if (errno == ECHILD) sigset_t oldset, allsigs;
break;
/* Wait for SIGCHLD or any other signal of interest */ /* waitpid is not interruptible by SA_RESTARTed
/* sigtimedwait with infinite timeout: */ * signals which we use. Thus, this ugly dance:
sig = sigwaitinfo(&G.blocked_set, NULL); */
if (sig > 0) {
sig = check_and_run_traps(sig); /* Make sure possible SIGCHLD is stored in kernel's
if (sig && sig != SIGCHLD) { /* see note 2 */ * pending signal mask before we call waitpid.
ret = 128 + sig; * Or else we may race with SIGCHLD, lose it,
break; * and get stuck in sigwaitinfo...
} */
sigfillset(&allsigs);
sigprocmask(SIG_SETMASK, &allsigs, &oldset);
if (!sigisemptyset(&G.pending_set)) {
/* Crap! we raced with some signal! */
// sig = 0;
goto restore;
} }
checkjobs(NULL); /* waitpid(WNOHANG) inside */
if (errno == ECHILD) {
sigprocmask(SIG_SETMASK, &oldset, NULL);
break;
}
/* Wait for SIGCHLD or any other signal */
//sig = sigwaitinfo(&allsigs, NULL);
/* It is vitally important for sigsuspend that SIGCHLD has non-DFL handler! */
/* Note: sigsuspend invokes signal handler */
sigsuspend(&oldset);
restore:
sigprocmask(SIG_SETMASK, &oldset, NULL);
/* So, did we get a signal? */
//if (sig > 0)
// raise(sig); /* run handler */
sig = check_and_run_traps();
if (sig /*&& sig != SIGCHLD - always true */) {
/* see note 2 */
ret = 128 + sig;
break;
}
/* SIGCHLD, or no signal, or ignored one, such as SIGQUIT. Repeat */
} }
sigdelset(&G.blocked_set, SIGCHLD);
sigprocmask_set(&G.blocked_set);
return ret; return ret;
} }