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.

8 files changed, 18 insertions, 29 deletions

diff --git a/src/signal/raise.c b/src/signal/raise.c
index 9948f418..71e0505b 100644
--- a/src/signal/raise.c
+++ b/src/signal/raise.c
@@ -1,18 +1,16 @@
 #include <signal.h>
 #include <errno.h>
+#include <stdint.h>
 #include "syscall.h"
 
-int __sigprocmask(int, const sigset_t *, sigset_t *);
-
 int raise(int sig)
 {
 	int pid, tid, ret;
 	sigset_t set;
-	sigfillset(&set);
-	__sigprocmask(SIG_BLOCK, &set, &set);
+	__syscall(SYS_rt_sigprocmask, SIG_BLOCK, (uint64_t[]){-1}, &set, 8);
 	tid = syscall(SYS_gettid);
 	pid = syscall(SYS_getpid);
 	ret = syscall(SYS_tgkill, pid, tid, sig);
-	__sigprocmask(SIG_SETMASK, &set, 0);
+	__syscall(SYS_rt_sigprocmask, SIG_SETMASK, &set, 0, 8);
 	return ret;
 }
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;
 	}
diff --git a/src/signal/sigaddset.c b/src/signal/sigaddset.c
index 23e655db..d632c6fb 100644
--- a/src/signal/sigaddset.c
+++ b/src/signal/sigaddset.c
@@ -4,7 +4,7 @@
 int sigaddset(sigset_t *set, int sig)
 {
 	unsigned s = sig-1;
-	if (s >= 8*sizeof(sigset_t)) {
+	if (s >= 8*sizeof(sigset_t) || s-32U<3) {
 		errno = EINVAL;
 		return -1;
 	}
diff --git a/src/signal/sigdelset.c b/src/signal/sigdelset.c
index 14042fb8..f8794ad6 100644
--- a/src/signal/sigdelset.c
+++ b/src/signal/sigdelset.c
@@ -4,7 +4,7 @@
 int sigdelset(sigset_t *set, int sig)
 {
 	unsigned s = sig-1;
-	if (s >= 8*sizeof(sigset_t)) {
+	if (s >= 8*sizeof(sigset_t) || s-32U<3) {
 		errno = EINVAL;
 		return -1;
 	}
diff --git a/src/signal/sigemptyset.c b/src/signal/sigemptyset.c
index 91f77adf..ca9b8920 100644
--- a/src/signal/sigemptyset.c
+++ b/src/signal/sigemptyset.c
@@ -3,6 +3,7 @@
 
 int sigemptyset(sigset_t *set)
 {
-	memset(set, 0, sizeof *set);
+	set->__bits[0] = 0;
+	if (sizeof(long)==4) set->__bits[1] = 0;
 	return 0;
 }
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;
 }
diff --git a/src/signal/sigismember.c b/src/signal/sigismember.c
index afd29e52..d3de6efb 100644
--- a/src/signal/sigismember.c
+++ b/src/signal/sigismember.c
@@ -4,7 +4,7 @@
 int sigismember(const sigset_t *set, int sig)
 {
 	unsigned s = sig-1;
-	if (s >= 8*sizeof(sigset_t)) {
+	if (s >= 8*sizeof(sigset_t) || s-32U<3) {
 		errno = EINVAL;
 		return -1;
 	}
diff --git a/src/signal/sigprocmask.c b/src/signal/sigprocmask.c
index a272c10d..3f003afb 100644
--- a/src/signal/sigprocmask.c
+++ b/src/signal/sigprocmask.c
@@ -4,27 +4,11 @@
 #include "libc.h"
 #include "pthread_impl.h"
 
-int __libc_sigprocmask(int how, const sigset_t *set, sigset_t *old)
+int sigprocmask(int how, const sigset_t *set, sigset_t *old)
 {
-	return syscall(SYS_rt_sigprocmask, how, set, old, 8);
-}
-
-int __sigprocmask(int how, const sigset_t *set, sigset_t *old)
-{
-	sigset_t tmp;
 	if (how > 2U) {
 		errno = EINVAL;
 		return -1;
 	}
-	/* Disallow blocking thread control signals */
-	if (set && how != SIG_UNBLOCK) {
-		tmp = *set;
-		set = &tmp;
-		sigdelset(&tmp, SIGCANCEL);
-		sigdelset(&tmp, SIGSYSCALL);
-		sigdelset(&tmp, SIGTIMER);
-	}
-	return __libc_sigprocmask(how, set, old);
+	return syscall(SYS_rt_sigprocmask, how, set, old, 8);
 }
-
-weak_alias(__sigprocmask, sigprocmask);