[RFC PATCH 5/8] signals: Better support cases where _NSIG_WORDS is greater than 2

[Walt Drummond <walt@drummond.us>]

Directly handle the now more common cases where _NSIG_WORDS could be 3
or 4.

Signed-off-by: Walt Drummond <walt@drummond.us>
---
 fs/proc/array.c        |  3 +-
 include/linux/signal.h | 74 +++++++++++++++++++++++++++---------------
 kernel/signal.c        |  5 +++
 3 files changed, 55 insertions(+), 27 deletions(-)

diff --git a/fs/proc/array.c b/fs/proc/array.c
index 49be8c8ef555..f37c03077b58 100644
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -223,7 +223,8 @@ void render_sigset_t(struct seq_file *m, const char *header,
 
 	seq_puts(m, header);
 
-	i = _NSIG;
+	/* Round up when _NSIG isn't a multiple of 4 */
+	i = (_NSIG + 3) & ~0x03;
 	do {
 		int x = 0;
 
diff --git a/include/linux/signal.h b/include/linux/signal.h
index eaf7991fffee..4084b765a6cc 100644
--- a/include/linux/signal.h
+++ b/include/linux/signal.h
@@ -168,18 +168,22 @@ do {					        \
 static inline int sigequalsets(const sigset_t *set1, const sigset_t *set2)
 {
 	switch (_NSIG_WORDS) {
+	default:
+		return memcmp(set1, set2, sizeof(sigset_t)) == 0;
 	case 4:
 		return	(set1->sig[3] == set2->sig[3]) &&
 			(set1->sig[2] == set2->sig[2]) &&
 			(set1->sig[1] == set2->sig[1]) &&
 			(set1->sig[0] == set2->sig[0]);
+	case 3:
+		return  (set1->sig[2] == set2->sig[2]) &&
+			(set1->sig[1] == set2->sig[1]) &&
+			(set1->sig[0] == set2->sig[0]);
 	case 2:
 		return	(set1->sig[1] == set2->sig[1]) &&
 			(set1->sig[0] == set2->sig[0]);
 	case 1:
 		return	set1->sig[0] == set2->sig[0];
-	default:
-		return memcmp(set1, set2, sizeof(sigset_t)) == 0;
 	}
 	return 0;
 }
@@ -197,27 +201,24 @@ static inline int sigisemptyset(sigset_t *set)
 #define _SIG_SET_BINOP(name, op)					\
 static inline void name(sigset_t *r, const sigset_t *a, const sigset_t *b) \
 {									\
-	unsigned long a0, a1, a2, a3, b0, b1, b2, b3;			\
 	int i;								\
 									\
 	switch (_NSIG_WORDS) {						\
+	default:							\
+		for (i = 0; i < _NSIG_WORDS; i++)			\
+			r->sig[i] = op(a->sig[i], b->sig[i]);		\
+		break;							\
 	case 4:								\
-		a3 = a->sig[3]; a2 = a->sig[2];				\
-		b3 = b->sig[3]; b2 = b->sig[2];				\
-		r->sig[3] = op(a3, b3);					\
-		r->sig[2] = op(a2, b2);					\
+		r->sig[3] = op(a->sig[3], b->sig[3]);			\
+		fallthrough;						\
+	case 3:								\
+		r->sig[2] = op(a->sig[2], b->sig[2]);			\
 		fallthrough;						\
 	case 2:								\
-		a1 = a->sig[1]; b1 = b->sig[1];				\
-		r->sig[1] = op(a1, b1);					\
+		r->sig[1] = op(a->sig[1], b->sig[1]);			\
 		fallthrough;						\
 	case 1:								\
-		a0 = a->sig[0]; b0 = b->sig[0];				\
-		r->sig[0] = op(a0, b0);					\
-		break;							\
-	default:							\
-		for (i = 0; i < _NSIG_WORDS; i++)			\
-			r->sig[i] = op(a->sig[i], b->sig[i]);		\
+		r->sig[0] = op(a->sig[0], b->sig[0]);			\
 		break;							\
 	}								\
 }
@@ -242,17 +243,22 @@ static inline void name(sigset_t *set)					\
 	int i;								\
 									\
 	switch (_NSIG_WORDS) {						\
-	case 4:	set->sig[3] = op(set->sig[3]);				\
-		set->sig[2] = op(set->sig[2]);				\
-		fallthrough;						\
-	case 2:	set->sig[1] = op(set->sig[1]);				\
-		fallthrough;						\
-	case 1:	set->sig[0] = op(set->sig[0]);				\
-		    break;						\
 	default:							\
 		for (i = 0; i < _NSIG_WORDS; i++)			\
 			set->sig[i] = op(set->sig[i]);			\
 		break;							\
+	case 4:								\
+		set->sig[3] = op(set->sig[3]);				\
+		fallthrough;						\
+	case 3:								\
+		set->sig[2] = op(set->sig[2]);				\
+		fallthrough;						\
+	case 2:								\
+		set->sig[1] = op(set->sig[1]);				\
+		fallthrough;						\
+	case 1:								\
+		set->sig[0] = op(set->sig[0]);				\
+		break;							\
 	}								\
 }
 
@@ -268,9 +274,17 @@ static inline void sigemptyset(sigset_t *set)
 	default:
 		memset(set, 0, sizeof(sigset_t));
 		break;
-	case 2: set->sig[1] = 0;
+	case 4:
+		set->sig[3] = 0;
+		fallthrough;
+	case 3:
+		set->sig[2] = 0;
 		fallthrough;
-	case 1:	set->sig[0] = 0;
+	case 2:
+		set->sig[1] = 0;
+		fallthrough;
+	case 1:
+		set->sig[0] = 0;
 		break;
 	}
 }
@@ -281,9 +295,17 @@ static inline void sigfillset(sigset_t *set)
 	default:
 		memset(set, -1, sizeof(sigset_t));
 		break;
-	case 2: set->sig[1] = -1;
+	case 4:
+		set->sig[3] = -1;
 		fallthrough;
-	case 1:	set->sig[0] = -1;
+	case 3:
+		set->sig[2] = -1;
+		fallthrough;
+	case 2:
+		set->sig[1] = -1;
+		fallthrough;
+	case 1:
+		set->sig[0] = -1;
 		break;
 	}
 }
diff --git a/kernel/signal.c b/kernel/signal.c
index 9421f1112b20..9c846a017201 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -143,6 +143,11 @@ static inline bool has_pending_signals(sigset_t *signal, sigset_t *blocked)
 		ready |= signal->sig[0] &~ blocked->sig[0];
 		break;
 
+	case 3: ready  = signal->sig[2] &~ blocked->sig[2];
+		ready |= signal->sig[1] &~ blocked->sig[1];
+		ready |= signal->sig[0] &~ blocked->sig[0];
+		break;
+
 	case 2: ready  = signal->sig[1] &~ blocked->sig[1];
 		ready |= signal->sig[0] &~ blocked->sig[0];
 		break;
-- 
2.30.2