optimize canary code a bit by storing offset of sizes table instead of

recomputing it all the time

1 files changed, 7 insertions, 5 deletions

diff --git a/src/lib/libc/stdlib/malloc.c b/src/lib/libc/stdlib/malloc.c
index ba3124eac6..fe80af08c5 100644
--- a/src/lib/libc/stdlib/malloc.c
+++ b/src/lib/libc/stdlib/malloc.c
@@ -1,4 +1,4 @@
-/*      $OpenBSD: malloc.c,v 1.199 2016/10/07 05:55:37 otto Exp $       */
+/*      $OpenBSD: malloc.c,v 1.200 2016/10/12 07:36:38 otto Exp $       */
 /*
  * Copyright (c) 2008, 2010, 2011, 2016 Otto Moerbeek <otto@drijf.net>
  * Copyright (c) 2012 Matthew Dempsky <matthew@openbsd.org>
@@ -165,6 +165,7 @@ struct chunk_info {
         u_short shift;                  /* how far to shift for this size */
         u_short free;                   /* how many free chunks */
         u_short total;                  /* how many chunks */
+        u_short offset;                 /* requested size table offset */
                                         /* which chunks are free */
         u_short bits[1];
 };
@@ -916,6 +917,7 @@ omalloc_make_chunks(struct dir_info *d, int bits, int listnum)
                 bp->size = 1U << bits;
                 bp->shift = bits;
                 bp->total = bp->free = MALLOC_PAGESIZE >> bits;
+                bp->offset = howmany(bp->total, MALLOC_BITS);
                 bp->page = pp;
         }
 
@@ -1025,7 +1027,7 @@ malloc_bytes(struct dir_info *d, size_t argsize, void *f)
         k += (lp - bp->bits) * MALLOC_BITS;
         
         if (mopts.chunk_canaries)
-                bp->bits[howmany(bp->total, MALLOC_BITS) + k] = argsize;
+                bp->bits[bp->offset + k] = argsize;
 
         k <<= bp->shift;
 
@@ -1056,8 +1058,7 @@ find_chunknum(struct dir_info *d, struct region_info *r, void *ptr, int check)
         /* Find the chunk number on the page */
         chunknum = ((uintptr_t)ptr & MALLOC_PAGEMASK) >> info->shift;
         if (check && mopts.chunk_canaries && info->size > 0) {
-                size_t sz = info->bits[howmany(info->total, MALLOC_BITS) +
-                    chunknum];
+                size_t sz = info->bits[info->offset + chunknum];
                 size_t check_sz = info->size - sz;
                 u_char *p, *q;
 
@@ -1280,7 +1281,8 @@ malloc(size_t size)
 /*DEF_STRONG(malloc);*/
 
 static void
-validate_junk(struct dir_info *pool, void *p) {
+validate_junk(struct dir_info *pool, void *p)
+{
         struct region_info *r;
         size_t byte, sz;