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>

1 files changed, 46 insertions, 0 deletions

diff --git a/security/selinux/include/hash.h b/security/selinux/include/hash.h
new file mode 100644
index 000000000000..5b429a873eb6
--- /dev/null
+++ b/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_ */