X-Git-Url: http://git.lttng.org/?a=blobdiff_plain;f=liblttng-ust%2Fjhash.h;h=91993e8bf64ea6d5c6a45ae210a4bd1f4145b3ad;hb=c0c0989ab70574e09b2f7e8b48c2da6af664a849;hp=fe785bd5a9560572c0442eb0bee2ae6b8100b580;hpb=a60af3a5ee5d990c867ef190acfa81c180301ea2;p=lttng-ust.git

diff --git a/liblttng-ust/jhash.h b/liblttng-ust/jhash.h
index fe785bd5..91993e8b 100644
--- a/liblttng-ust/jhash.h
+++ b/liblttng-ust/jhash.h
@@ -1,19 +1,7 @@
 /*
- * Copyright (C) 2011 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
- *
- * This library is free software; you can redistribute it and/or
- * modify it under the terms of the GNU Lesser General Public
- * License as published by the Free Software Foundation;
- * version 2.1 of the License.
+ * SPDX-License-Identifier: LGPL-2.1-only
  *
- * This library is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
- * Lesser General Public License for more details.
- *
- * You should have received a copy of the GNU Lesser General Public
- * License along with this library; if not, write to the Free Software
- * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301 USA
+ * Copyright (C) 2011 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
  */
 
 #include <stddef.h>
@@ -109,33 +97,13 @@ 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;
 
@@ -156,7 +124,6 @@ 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 */