X-Git-Url: http://git.lttng.org/?a=blobdiff_plain;f=liblttng-ust%2Fjhash.h;h=fef55a1f9599c5938348a09ab2f43f8b2d4d7ccf;hb=9560f5ebf55ec70baefe6da3e3d644fc7d497b63;hp=da1e7dd02c7b994bbdda9e5f8f7ce6eae27d4f5b;hpb=e3feda7db3de3530e7c9c511536c36cccf317013;p=lttng-ust.git

diff --git a/liblttng-ust/jhash.h b/liblttng-ust/jhash.h
index da1e7dd0..fef55a1f 100644
--- a/liblttng-ust/jhash.h
+++ b/liblttng-ust/jhash.h
@@ -16,6 +16,8 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301 USA
  */
 
+#include <stddef.h>
+#include <stdint.h>
 #include <urcu/compiler.h>
 #include <lttng/ust-endian.h>
 
@@ -63,19 +65,19 @@ do { \
  * Returns a 32-bit value.  Every bit of the key affects every bit of
  * the return value.  Two keys differing by one or two bits will have
  * totally different hash values.
- * 
+ *
  * The best hash table sizes are powers of 2.  There is no need to do
  * mod a prime (mod is sooo slow!).  If you need less than 32 bits,
  * use a bitmask.  For example, if you need only 10 bits, do
  *   h = (h & hashmask(10));
  * In which case, the hash table should have hashsize(10) elements.
- * 
+ *
  * If you are hashing n strings (uint8_t **)k, do it like this:
  *   for (i = 0, h = 0; i < n; ++i) h = hashlittle(k[i], len[i], h);
- * 
+ *
  * By Bob Jenkins, 2006.  bob_jenkins@burtleburtle.net.  You may use this
  * code any way you wish, private, educational, or commercial.  It's free.
- * 
+ *
  * Use for hash table lookup, or anything where one collision in 2^^32 is
  * acceptable.  Do NOT use for cryptographic purposes.
  */
@@ -106,34 +108,14 @@ uint32_t hashlittle(const void *key, size_t length, uint32_t initval)
 		}
 
 		/*----------------------------- handle the last (probably partial) block */
-		/* 
-		 * "k[2]&0xffffff" actually reads beyond the end of the string, but
-		 * then masks off the part it's not allowed to read.	Because the
-		 * string is aligned, the masked-off tail is in the same word as the
-		 * rest of the string.	Every machine with memory protection I've seen
-		 * does it on word boundaries, so is OK with this.	But VALGRIND will
-		 * still catch it and complain.	The masking trick does make the hash
-		 * noticably faster for short strings (like English words).
+		/*
+		 * The original jhash.h reads beyond the end of string, and implements
+		 * a special code path for VALGRIND. It seems to make ASan unhappy too
+		 * though, so considering that hashing event names is not a fast-path
+		 * in lttng-ust, remove the "fast" code entirely and use the slower
+		 * but verifiable VALGRIND version of the code which does not issue
+		 * out-of-bound reads.
 		 */
-#ifndef VALGRIND
-
-		switch (length) {
-		case 12: c+=k[2]; b+=k[1]; a+=k[0]; break;
-		case 11: c+=k[2]&0xffffff; b+=k[1]; a+=k[0]; break;
-		case 10: c+=k[2]&0xffff; b+=k[1]; a+=k[0]; break;
-		case 9 : c+=k[2]&0xff; b+=k[1]; a+=k[0]; break;
-		case 8 : b+=k[1]; a+=k[0]; break;
-		case 7 : b+=k[1]&0xffffff; a+=k[0]; break;
-		case 6 : b+=k[1]&0xffff; a+=k[0]; break;
-		case 5 : b+=k[1]&0xff; a+=k[0]; break;
-		case 4 : a+=k[0]; break;
-		case 3 : a+=k[0]&0xffffff; break;
-		case 2 : a+=k[0]&0xffff; break;
-		case 1 : a+=k[0]&0xff; break;
-		case 0 : return c;		/* zero length strings require no mixing */
-		}
-
-#else /* make valgrind happy */
 		{
 			const uint8_t *k8;
 
@@ -154,7 +136,6 @@ uint32_t hashlittle(const void *key, size_t length, uint32_t initval)
 			case 0 : return c;
 			}
 		}
-#endif /* !valgrind */
 
 	} else if (HASH_LITTLE_ENDIAN && ((u.i & 0x1) == 0)) {
 		const uint16_t *k = (const uint16_t *) key;	/* read 16-bit chunks */