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hush: install signal handlers with filled sigmask

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function                                             old     new   delta
install_sighandler                                     -      39     +39
hush_main                                           1001    1031     +30
builtin_trap                                         386     392      +6
install_sighandlers                                  121     123      +2
switch_off_special_sigs                               87      86      -1
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 3/1 up/down: 77/-1)              Total: 76 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko 2011-05-12 23:06:20 +02:00
parent b1ab283f0b
commit 0806e401d6
1 changed files with 28 additions and 9 deletions
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37
shell/hush.c
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@ -815,6 +815,7 @@ struct globals {
unsigned long memleak_value;
int debug_indent;
#endif
struct sigaction sa;
char user_input_buf[ENABLE_FEATURE_EDITING ? CONFIG_FEATURE_EDITING_MAX_LEN : 2];
};
#define G (*ptr_to_globals)
@ -823,6 +824,9 @@ struct globals {
* is global, thus "G." prefix is a useful hint */
#define INIT_G() do { \
SET_PTR_TO_GLOBALS(xzalloc(sizeof(G))); \
/* memset(&G.sa, 0, sizeof(G.sa)); */ \
sigfillset(&G.sa.sa_mask); \
G.sa.sa_flags = SA_RESTART; \
} while (0)
@ -1414,9 +1418,6 @@ static void restore_G_args(save_arg_t *sv, char **argv)
* 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.
*
* TODO: don't use signal() to install sighandlers: need to mask ALL signals
* while handler runs. I saw signal nesting in one strace, race window isn't small.
*/
enum {
SPECIAL_INTERACTIVE_SIGS = 0
@ -1444,6 +1445,24 @@ static void record_pending_signo(int sig)
#endif
}
static sighandler_t install_sighandler(int sig, sighandler_t handler)
{
struct sigaction old_sa;
/* We could use signal() to install handlers... almost:
* except that we need to mask ALL signals while handlers run.
* I saw signal nesting in strace, race window isn't small.
* SA_RESTART is also needed, but in Linux, signal()
* sets SA_RESTART too.
*/
/* memset(&G.sa, 0, sizeof(G.sa)); - already done */
/* sigfillset(&G.sa.sa_mask); - already done */
/* G.sa.sa_flags = SA_RESTART; - already done */
G.sa.sa_handler = handler;
sigaction(sig, &G.sa, &old_sa);
return old_sa.sa_handler;
}
#if ENABLE_HUSH_JOB
/* After [v]fork, in child: do not restore tty pgrp on xfunc death */
@ -5451,7 +5470,7 @@ static void switch_off_special_sigs(unsigned mask)
G.traps[sig] = NULL;
}
/* We are here only if no trap or trap was not '' */
signal(sig, SIG_DFL);
install_sighandler(sig, SIG_DFL);
}
}
@ -5496,7 +5515,7 @@ static void reset_traps_to_defaults(void)
/* There is no signal for trap 0 (EXIT) */
if (sig == 0)
continue;
signal(sig, pick_sighandler(sig));
install_sighandler(sig, pick_sighandler(sig));
}
}
@ -7524,7 +7543,7 @@ static void install_sighandlers(unsigned mask)
sig++;
if (!(mask & 1))
continue;
old_handler = signal(sig, pick_sighandler(sig));
old_handler = install_sighandler(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:
@ -7533,7 +7552,7 @@ static void install_sighandlers(unsigned mask)
continue;
if (old_handler == SIG_IGN) {
/* oops... restore back to IGN, and record this fact */
signal(sig, old_handler);
install_sighandler(sig, old_handler);
if (!G.traps)
G.traps = xzalloc(sizeof(G.traps[0]) * NSIG);
free(G.traps[sig]);
@ -7854,7 +7873,7 @@ int hush_main(int argc, char **argv)
for (sig = 1; sig < NSIG; sig++) {
if (empty_trap_mask & (1LL << sig)) {
G.traps[sig] = xzalloc(1); /* == xstrdup(""); */
signal(sig, SIG_IGN);
install_sighandler(sig, SIG_IGN);
}
}
}
@ -8389,7 +8408,7 @@ static int FAST_FUNC builtin_trap(char **argv)
else
/* We are removing trap handler */
handler = pick_sighandler(sig);
signal(sig, handler);
install_sighandler(sig, handler);
}
return ret;
}