To allow for easier playing with more strict settings introduce

a separate symbolic constant for the leeway we allow when moving
allocations towards the end of a page. No functional change.

1 files changed, 14 insertions, 5 deletions

diff --git a/src/lib/libc/stdlib/malloc.c b/src/lib/libc/stdlib/malloc.c
index f5f0ab730f..b6e4ada312 100644
--- a/src/lib/libc/stdlib/malloc.c
+++ b/src/lib/libc/stdlib/malloc.c
@@ -1,4 +1,4 @@
-/*      $OpenBSD: malloc.c,v 1.107 2008/11/12 09:41:49 otto Exp $       */
+/*      $OpenBSD: malloc.c,v 1.108 2008/11/13 07:38:45 otto Exp $       */
 /*
  * Copyright (c) 2008 Otto Moerbeek <otto@drijf.net>
  *
@@ -64,6 +64,13 @@
 #define MALLOC_MAXCHUNK         (1 << (MALLOC_PAGESHIFT-1))
 #define MALLOC_MAXCACHE         256
 #define MALLOC_DELAYED_CHUNKS   16      /* should be power of 2 */
+/*
+ * When the P option is active, we move allocations between half a page
+ * and a whole page towards the end, subject to alignment constraints.
+ * This is the extra headroom we allow. Set to zero to be the most
+ * strict.
+ */
+#define MALLOC_LEEWAY           16
 
 #define PAGEROUND(x)  (((x) + (MALLOC_PAGEMASK)) & ~MALLOC_PAGEMASK)
 
@@ -1081,12 +1088,12 @@ omalloc(size_t sz, int zero_fill)
                 }
 
                 if (malloc_move &&
-                    sz - malloc_guard < MALLOC_PAGESIZE - MALLOC_MINSIZE) {
+                    sz - malloc_guard < MALLOC_PAGESIZE - MALLOC_LEEWAY) {
                         /* fill whole allocation */
                         if (malloc_junk)
                                 memset(p, SOME_JUNK, psz - malloc_guard);
                         /* shift towards the end */
-                        p = ((char *)p) + ((MALLOC_PAGESIZE - MALLOC_MINSIZE -
+                        p = ((char *)p) + ((MALLOC_PAGESIZE - MALLOC_LEEWAY -
                             (sz - malloc_guard)) & ~(MALLOC_MINSIZE-1));
                         /* fill zeros if needed and overwritten above */
                         if (zero_fill && malloc_junk)
@@ -1177,9 +1184,11 @@ ofree(void *p)
         }
         REALSIZE(sz, r);
         if (sz > MALLOC_MAXCHUNK) {
-                if (sz - malloc_guard >= MALLOC_PAGESIZE - MALLOC_MINSIZE) {
-                        if (r->p != p)
+                if (sz - malloc_guard >= MALLOC_PAGESIZE - MALLOC_LEEWAY) {
+                        if (r->p != p) {
                                 wrterror("bogus pointer");
+                                return;
+                        }
                 } else {
 #if notyetbecause_of_realloc
                         /* shifted towards the end */