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, 7 insertions, 1 deletions

diff --git a/src/signal/sigfillset.c b/src/signal/sigfillset.c
index fab50a52..6c84b9b7 100644
--- a/src/signal/sigfillset.c
+++ b/src/signal/sigfillset.c
@@ -1,8 +1,14 @@
 #include <signal.h>
 #include <string.h>
+#include <limits.h>
 
 int sigfillset(sigset_t *set)
 {
-	memset(set, -1, sizeof *set);
+#if ULONG_MAX == 0xffffffff
+	set->__bits[0] = 0x7ffffffful;
+	set->__bits[1] = 0xfffffffcul;
+#else
+	set->__bits[0] = 0xfffffffc7ffffffful;
+#endif
 	return 0;
 }