fix sigset_t size for mips (it's the only arch with 128 signals).

fix _NSIG for it.
better document what's going on in sigaction().
seems to not induce any actual code changes (sans mips).

1 files changed, 13 insertions, 7 deletions

diff --git a/libc/sysdeps/linux/x86_64/sigaction.c b/libc/sysdeps/linux/x86_64/sigaction.c
index 3d9e4ea29..e53e30442 100644
--- a/libc/sysdeps/linux/x86_64/sigaction.c
+++ b/libc/sysdeps/linux/x86_64/sigaction.c
@@ -50,23 +50,29 @@ __libc_sigaction (int sig, const struct sigaction *act, struct sigaction *oact)
 {
 	int result;
 	struct kernel_sigaction kact, koact;
+	enum {
+		SIGSET_MIN_SIZE = sizeof(kact.sa_mask) < sizeof(act->sa_mask)
+				? sizeof(kact.sa_mask) : sizeof(act->sa_mask)
+	};
 
 	if (act) {
 		kact.k_sa_handler = act->sa_handler;
-		memcpy (&kact.sa_mask, &act->sa_mask, sizeof (sigset_t));
+		memcpy (&kact.sa_mask, &act->sa_mask, SIGSET_MIN_SIZE);
 		kact.sa_flags = act->sa_flags | SA_RESTORER;
 
 		kact.sa_restorer = &restore_rt;
 	}
 
-	/* XXX The size argument hopefully will have to be changed to the
-	   real size of the user-level sigset_t.  */
-	result = INLINE_SYSCALL (rt_sigaction, 4,
-	                         sig, act ? __ptrvalue (&kact) : NULL,
-	                         oact ? __ptrvalue (&koact) : NULL, _NSIG / 8);
+	/* NB: kernel (as of 2.6.25) will return EINVAL
+	 * if sizeof(kact.sa_mask) does not match kernel's sizeof(sigset_t) */
+	result = INLINE_SYSCALL (rt_sigaction, 4, sig,
+	                act ? __ptrvalue (&kact) : NULL,
+	                oact ? __ptrvalue (&koact) : NULL,
+			sizeof(kact.sa_mask));
+
 	if (oact && result >= 0) {
 		oact->sa_handler = koact.k_sa_handler;
-		memcpy (&oact->sa_mask, &koact.sa_mask, sizeof (sigset_t));
+		memcpy (&oact->sa_mask, &koact.sa_mask, SIGSET_MIN_SIZE);
 		oact->sa_flags = koact.sa_flags;
 		oact->sa_restorer = koact.sa_restorer;
 	}