When built without NPTL support (or for a sparc target), the system()
function doesn't conform to its specification. Namely, it uses signal()
to install/save/restore signal handlers, which may break applications
using custom handlers installed with sigaction(). In addition, it resets
the SIGCHLD handler to SIG_DFL instead of blocking the signal, which may
result in "lost" signals if a custom handler was installed.
Fix system() by replacing uses of signal() with appropriate calls to
sigaction() and sigprocmask().
Signed-off-by: Richard Braun <rbr...@sceen.net>
---
libc/stdlib/system.c | 37 ++++++++++++++++++++-----------------
1 files changed, 20 insertions(+), 17 deletions(-)
diff --git a/libc/stdlib/system.c b/libc/stdlib/system.c
index a0ff726..a92c307 100644
--- a/libc/stdlib/system.c
+++ b/libc/stdlib/system.c
@@ -33,32 +33,34 @@ extern __typeof(system) __libc_system;
int __libc_system(const char *command)
{
int wait_val, pid;
- __sighandler_t save_quit, save_int, save_chld;
+ struct sigaction sa, save_quit, save_int;
+ sigset_t save_mask;
if (command == 0)
return 1;
- save_quit = signal(SIGQUIT, SIG_IGN);
- save_int = signal(SIGINT, SIG_IGN);
- save_chld = signal(SIGCHLD, SIG_DFL);
+ memset(&sa, 0, sizeof(sa));
+ sa.sa_handler = SIG_IGN;
+ /* __sigemptyset(&sa.sa_mask); - done by memset() */
+ /* sa.sa_flags = 0; - done by memset() */
+
+ sigaction(SIGQUIT, &sa, &save_quit);
+ sigaction(SIGINT, &sa, &save_int);
+ __sigaddset(&sa.sa_mask, SIGCHLD);
+ sigprocmask(SIG_BLOCK, &sa.sa_mask, &save_mask);
if ((pid = vfork()) < 0) {
- signal(SIGQUIT, save_quit);
- signal(SIGINT, save_int);
- signal(SIGCHLD, save_chld);
- return -1;
+ wait_val = -1;
+ goto out;
}
if (pid == 0) {
- signal(SIGQUIT, SIG_DFL);
- signal(SIGINT, SIG_DFL);
- signal(SIGCHLD, SIG_DFL);
+ sigaction(SIGQUIT, &save_quit, NULL);
+ sigaction(SIGINT, &save_int, NULL);
+ sigprocmask(SIG_SETMASK, &save_mask, NULL);
execl("/bin/sh", "sh", "-c", command, (char *) 0);
_exit(127);
}
- /* Signals are not absolutly guarenteed with vfork */
- signal(SIGQUIT, SIG_IGN);
- signal(SIGINT, SIG_IGN);
#if 0
__printf("Waiting for child %d\n", pid);
@@ -67,9 +69,10 @@ int __libc_system(const char *command)
if (wait4(pid, &wait_val, 0, 0) == -1)
wait_val = -1;
- signal(SIGQUIT, save_quit);
- signal(SIGINT, save_int);
- signal(SIGCHLD, save_chld);
+out:
+ sigaction(SIGQUIT, &save_quit, NULL);
+ sigaction(SIGINT, &save_int, NULL);
+ sigprocmask(SIG_SETMASK, &save_mask, NULL);
return wait_val;
}
#else
--
1.7.2.5
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