selinux: Move avtab_hash() to a shared location for future reuse

This is a preparation patch, no functional change.

Signed-off-by: Hongru Zhang <zhanghongru@xiaomi.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>

Author: Hongru Zhang

security/selinux/include/hash.h

@@ -0,0 +1,46 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#ifndef _SELINUX_HASH_H_
+#define _SELINUX_HASH_H_
+
+/* Based on MurmurHash3, written by Austin Appleby and placed in the
+ * public domain.
+ */
+static inline u32 avtab_hash(const struct avtab_key *keyp, u32 mask)
+{
+	static const u32 c1 = 0xcc9e2d51;
+	static const u32 c2 = 0x1b873593;
+	static const u32 r1 = 15;
+	static const u32 r2 = 13;
+	static const u32 m = 5;
+	static const u32 n = 0xe6546b64;
+
+	u32 hash = 0;
+
+#define mix(input)                                         \
+	do {                                               \
+		u32 v = input;                             \
+		v *= c1;                                   \
+		v = (v << r1) | (v >> (32 - r1));          \
+		v *= c2;                                   \
+		hash ^= v;                                 \
+		hash = (hash << r2) | (hash >> (32 - r2)); \
+		hash = hash * m + n;                       \
+	} while (0)
+
+	mix(keyp->target_class);
+	mix(keyp->target_type);
+	mix(keyp->source_type);
+
+#undef mix
+
+	hash ^= hash >> 16;
+	hash *= 0x85ebca6b;
+	hash ^= hash >> 13;
+	hash *= 0xc2b2ae35;
+	hash ^= hash >> 16;
+
+	return hash & mask;
+}
+
+#endif /* _SELINUX_HASH_H_ */

security/selinux/ss/avtab.c

@@ -20,50 +20,11 @@
 #include <linux/errno.h>
 #include "avtab.h"
 #include "policydb.h"
+#include "hash.h"
 
 static struct kmem_cache *avtab_node_cachep __ro_after_init;
 static struct kmem_cache *avtab_xperms_cachep __ro_after_init;
 
-/* Based on MurmurHash3, written by Austin Appleby and placed in the
- * public domain.
- */
-static inline u32 avtab_hash(const struct avtab_key *keyp, u32 mask)
-{
-	static const u32 c1 = 0xcc9e2d51;
-	static const u32 c2 = 0x1b873593;
-	static const u32 r1 = 15;
-	static const u32 r2 = 13;
-	static const u32 m = 5;
-	static const u32 n = 0xe6546b64;
-
-	u32 hash = 0;
-
-#define mix(input)                                         \
-	do {                                               \
-		u32 v = input;                             \
-		v *= c1;                                   \
-		v = (v << r1) | (v >> (32 - r1));          \
-		v *= c2;                                   \
-		hash ^= v;                                 \
-		hash = (hash << r2) | (hash >> (32 - r2)); \
-		hash = hash * m + n;                       \
-	} while (0)
-
-	mix(keyp->target_class);
-	mix(keyp->target_type);
-	mix(keyp->source_type);
-
-#undef mix
-
-	hash ^= hash >> 16;
-	hash *= 0x85ebca6b;
-	hash ^= hash >> 13;
-	hash *= 0xc2b2ae35;
-	hash ^= hash >> 16;
-
-	return hash & mask;
-}
-
 static struct avtab_node *avtab_insert_node(struct avtab *h,
 					    struct avtab_node **dst,
 					    const struct avtab_key *key,