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authorRich Felker <dalias@aerifal.cx>2014-03-24 16:57:11 -0400
committerRich Felker <dalias@aerifal.cx>2014-03-24 16:57:11 -0400
commitdab441aea240f3b7c18a26d2ef51979ea36c301c (patch)
tree9bb6c68bc3b025020a15d0d92b2b6aeff84a4d8c /src/signal
parent98221c36119d2abfc55fe1d919705f625709fe3b (diff)
downloadmusl-dab441aea240f3b7c18a26d2ef51979ea36c301c.tar.gz
always initialize thread pointer at program start
this is the first step in an overhaul aimed at greatly simplifying and optimizing everything dealing with thread-local state. previously, the thread pointer was initialized lazily on first access, or at program startup if stack protector was in use, or at certain random places where inconsistent state could be reached if it were not initialized early. while believed to be fully correct, the logic was fragile and non-obvious. in the first phase of the thread pointer overhaul, support is retained (and in some cases improved) for systems/situation where loading the thread pointer fails, e.g. old kernels. some notes on specific changes: - the confusing use of libc.main_thread as an indicator that the thread pointer is initialized is eliminated in favor of an explicit has_thread_pointer predicate. - sigaction no longer needs to ensure that the thread pointer is initialized before installing a signal handler (this was needed to prevent a situation where the signal handler caused the thread pointer to be initialized and the subsequent sigreturn cleared it again) but it still needs to ensure that implementation-internal thread-related signals are not blocked. - pthread tsd initialization for the main thread is deferred in a new manner to minimize bloat in the static-linked __init_tp code. - pthread_setcancelstate no longer needs special handling for the situation before the thread pointer is initialized. it simply fails on systems that cannot support a thread pointer, which are non-conforming anyway. - pthread_cleanup_push/pop now check for missing thread pointer and nop themselves out in this case, so stdio no longer needs to avoid the cancellable path when the thread pointer is not available. a number of cases remain where certain interfaces may crash if the system does not support a thread pointer. at this point, these should be limited to pthread interfaces, and the number of such cases should be fewer than before.
Diffstat (limited to 'src/signal')
-rw-r--r--src/signal/sigaction.c19
1 files changed, 15 insertions, 4 deletions
diff --git a/src/signal/sigaction.c b/src/signal/sigaction.c
index f7ff4a61..d5f47741 100644
--- a/src/signal/sigaction.c
+++ b/src/signal/sigaction.c
@@ -8,9 +8,7 @@
void __restore(), __restore_rt();
-static pthread_t dummy(void) { return 0; }
-weak_alias(dummy, __pthread_self_def);
-
+static int unmask_done;
static unsigned long handler_set[_NSIG/(8*sizeof(long))];
void __get_handler_set(sigset_t *set)
@@ -29,7 +27,20 @@ int __libc_sigaction(int sig, const struct sigaction *restrict sa, struct sigact
if ((uintptr_t)sa->sa_handler > 1UL) {
a_or_l(handler_set+(sig-1)/(8*sizeof(long)),
1UL<<(sig-1)%(8*sizeof(long)));
- __pthread_self_def();
+
+ /* If pthread_create has not yet been called,
+ * implementation-internal signals might not
+ * yet have been unblocked. They must be
+ * unblocked before any signal handler is
+ * installed, so that an application cannot
+ * receive an illegal sigset_t (with them
+ * blocked) as part of the ucontext_t passed
+ * to the signal handler. */
+ if (!libc.threaded && !unmask_done) {
+ __syscall(SYS_rt_sigprocmask, SIG_UNBLOCK,
+ SIGPT_SET, 0, _NSIG/8);
+ unmask_done = 1;
+ }
}
ksa.handler = sa->sa_handler;
ksa.flags = sa->sa_flags | SA_RESTORER;