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, 2 insertions, 3 deletions

diff --git a/src/thread/__rsyscall.c b/src/thread/__rsyscall.c
index 61d41df7..e885d9e7 100644
--- a/src/thread/__rsyscall.c
+++ b/src/thread/__rsyscall.c
@@ -56,8 +56,7 @@ int __rsyscall(int nr, long a, long b, long c, long d, long e, long f)
 	while ((i=rs.blocks))
 		__wait(&rs.blocks, 0, i, 1);
 
-	sigfillset(&set);
-	__libc_sigprocmask(SIG_BLOCK, &set, &set);
+	__syscall(SYS_rt_sigprocmask, SIG_BLOCK, (uint64_t[]){-1}, &set, 8);
 
 	if (!rs.init) {
 		struct sigaction sa = {
@@ -88,7 +87,7 @@ int __rsyscall(int nr, long a, long b, long c, long d, long e, long f)
 	}
 
 	/* Handle any lingering signals with no-op */
-	__libc_sigprocmask(SIG_UNBLOCK, &set, &set);
+	__syscall(SYS_rt_sigprocmask, SIG_SETMASK, &set, &set, 8);
 
 	/* Resume other threads' signal handlers and wait for them */
 	rs.hold = 0;