* malloc/arena.c (heap_info): Add mprotect_size field, adjust pad.

(new_heap): Initialize mprotect_size. 
(grow_heap): When growing, only mprotect from mprotect_size till 
new_size if mprotect_size is smaller.  When shrinking, use PROT_NONE 
MMAP for __libc_enable_secure only, otherwise use MADV_DONTNEED.
2007-05-07  Ulrich Drepper  <drepper@redhat.com>
	    Jakub Jelinek  <jakub@redhat.com>

	* malloc/arena.c (heap_info): Add mprotect_size field, adjust pad.
	(new_heap): Initialize mprotect_size.
	(grow_heap): When growing, only mprotect from mprotect_size till
	new_size if mprotect_size is smaller.  When shrinking, use PROT_NONE
	MMAP for __libc_enable_secure only, otherwise use MADV_DONTNEED.

1 files changed, 29 insertions, 8 deletions

diff --git a/malloc/arena.c b/malloc/arena.c
index 1d9f952..ce64335 100644
--- a/malloc/arena.c
+++ b/malloc/arena.c
@@ -1,5 +1,6 @@
 /* Malloc implementation for multiple threads without lock contention.
-   Copyright (C) 2001,2002,2003,2004,2005,2006 Free Software Foundation, Inc.
+   Copyright (C) 2001,2002,2003,2004,2005,2006,2007
+   Free Software Foundation, Inc.
    This file is part of the GNU C Library.
    Contributed by Wolfram Gloger <wg@malloc.de>, 2001.
 
@@ -59,10 +60,12 @@ typedef struct _heap_info {
   mstate ar_ptr; /* Arena for this heap. */
   struct _heap_info *prev; /* Previous heap. */
   size_t size;   /* Current size in bytes. */
+  size_t mprotect_size;	/* Size in bytes that has been mprotected
+			   PROT_READ|PROT_WRITE.  */
   /* Make sure the following data is properly aligned, particularly
      that sizeof (heap_info) + 2 * SIZE_SZ is a multiple of
-     MALLOG_ALIGNMENT. */
-  char pad[-5 * SIZE_SZ & MALLOC_ALIGN_MASK];
+     MALLOC_ALIGNMENT. */
+  char pad[-6 * SIZE_SZ & MALLOC_ALIGN_MASK];
 } heap_info;
 
 /* Get a compile-time error if the heap_info padding is not correct
@@ -692,6 +695,7 @@ new_heap(size, top_pad) size_t size, top_pad;
   }
   h = (heap_info *)p2;
   h->size = size;
+  h->mprotect_size = size;
   THREAD_STAT(stat_n_heaps++);
   return h;
 }
@@ -714,17 +718,34 @@ grow_heap(h, diff) heap_info *h; long diff;
     new_size = (long)h->size + diff;
     if((unsigned long) new_size > (unsigned long) HEAP_MAX_SIZE)
       return -1;
-    if(mprotect((char *)h + h->size, diff, PROT_READ|PROT_WRITE) != 0)
-      return -2;
+    if((unsigned long) new_size > h->mprotect_size) {
+      if (mprotect((char *)h + h->mprotect_size,
+		   (unsigned long) new_size - h->mprotect_size,
+		   PROT_READ|PROT_WRITE) != 0)
+	return -2;
+      h->mprotect_size = new_size;
+    }
   } else {
     new_size = (long)h->size + diff;
     if(new_size < (long)sizeof(*h))
       return -1;
     /* Try to re-map the extra heap space freshly to save memory, and
        make it inaccessible. */
-    if((char *)MMAP((char *)h + new_size, -diff, PROT_NONE,
-                    MAP_PRIVATE|MAP_FIXED) == (char *) MAP_FAILED)
-      return -2;
+#ifdef _LIBC
+    if (__builtin_expect (__libc_enable_secure, 0))
+#else
+    if (1)
+#endif
+      {
+	if((char *)MMAP((char *)h + new_size, -diff, PROT_NONE,
+			MAP_PRIVATE|MAP_FIXED) == (char *) MAP_FAILED)
+	  return -2;
+	h->mprotect_size = new_size;
+      }
+#ifdef _LIBC
+    else
+      madvise ((char *)h + new_size, -diff, MADV_DONTNEED);
+#endif
     /*fprintf(stderr, "shrink %p %08lx\n", h, new_size);*/
   }
   h->size = new_size;