overhaul implementation-internal signal protections

the new approach relies on the fact that the only ways to create
sigset_t objects without invoking UB are to use the sig*set()
functions, or from the masks returned by sigprocmask, sigaction, etc.
or in the ucontext_t argument to a signal handler. thus, as long as
sigfillset and sigaddset avoid adding the "protected" signals, there
is no way the application will ever obtain a sigset_t including these
bits, and thus no need to add the overhead of checking/clearing them
when sigprocmask or sigaction is called.

note that the old code actually *failed* to remove the bits from
sa_mask when sigaction was called.

the new implementations are also significantly smaller, simpler, and
faster due to ignoring the useless "GNU HURD signals" 65-1024, which
are not used and, if there's any sanity in the world, never will be
used.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/signal/sigaction.c b/src/signal/sigaction.c
index 887bbc4f..18956c6b 100644
--- a/src/signal/sigaction.c
+++ b/src/signal/sigaction.c
@@ -35,7 +35,7 @@ int __libc_sigaction(int sig, const struct sigaction *sa, struct sigaction *old)
 
 int __sigaction(int sig, const struct sigaction *sa, struct sigaction *old)
 {
-	if (sig-SIGCANCEL < 3U) {
+	if (sig-32U < 3) {
 		errno = EINVAL;
 		return -1;
 	}