[mmalloc] Use mremap to expand heaps (heap collision prevention)

[simgrid.git] / src / xbt / mmalloc / mmorecore.c

diff --git a/src/xbt/mmalloc/mmorecore.c b/src/xbt/mmalloc/mmorecore.c
index 197341d..f47c539 100644 (file)
--- a/src/xbt/mmalloc/mmorecore.c
+++ b/src/xbt/mmalloc/mmorecore.c
@@ -1,17 +1,14 @@
-/* Support for an sbrk-like function that uses mmap.
-   Copyright 1992, 2000 Free Software Foundation, Inc.
+/* Support for an sbrk-like function that uses mmap. */
 
-   Contributed by Fred Fish at Cygnus Support.   fnf@cygnus.com */
-
-/* Copyright (c) 2010-2012. The SimGrid Team.
+/* Copyright (c) 2010-2014. The SimGrid Team.
  * All rights reserved.                                                     */
 
 /* This program is free software; you can redistribute it and/or modify it
  * under the terms of the license (GNU LGPL) which comes with this package. */
 
-#ifndef MAP_ANONYMOUS
-#define MAP_ANONYMOUS MAP_ANON
-#endif
+/* Copyright 1992, 2000 Free Software Foundation, Inc.
+
+   Contributed by Fred Fish at Cygnus Support.   fnf@cygnus.com */
 
 #ifdef HAVE_UNISTD_H
 #include <unistd.h>             /* Prototypes for lseek */
@@ -19,18 +16,16 @@
 #include <stdio.h>
 #include <fcntl.h>
 #include <sys/mman.h>
+#include <sys/wait.h>
 
 #include "mmprivate.h"
 
-/* Cache the pagesize for the current host machine.  Note that if the host
-   does not readily provide a getpagesize() function, we need to emulate it
-   elsewhere, not clutter up this file with lots of kluges to try to figure
-   it out. */
-
-static size_t pagesize;
+#ifndef MAP_ANONYMOUS
+#define MAP_ANONYMOUS MAP_ANON
+#endif
 
-#define PAGE_ALIGN(addr) (void*) (((long)(addr) + pagesize - 1) & \
-                                  ~(pagesize - 1))
+#define PAGE_ALIGN(addr) (void*) (((long)(addr) + xbt_pagesize - 1) &   \
+                                  ~((long)xbt_pagesize - 1))
 
 /* Return MAP_PRIVATE if MDP represents /dev/zero.  Otherwise, return
    MAP_SHARED.  */
@@ -65,8 +60,6 @@ void *mmorecore(struct mdesc *mdp, ssize_t size)
   char buf = 0;                 /* Single byte to write to extend mapped file */
 
 //  fprintf(stderr,"increase %p by %u\n",mdp,size);
-  if (pagesize == 0)
-    pagesize = getpagesize();
 
   if (size == 0) {
     /* Just return the current "break" value. */
@@ -116,9 +109,14 @@ void *mmorecore(struct mdesc *mdp, ssize_t size)
 
       /* Let's call mmap. Note that it is possible that mdp->top
          is 0. In this case mmap will choose the address for us */
-      mapto = mmap(mdp->top, mapbytes, PROT_READ | PROT_WRITE,
+      if(mdp->base==mdp->top)
+        mapto = mmap(mdp->top, mapbytes, PROT_READ | PROT_WRITE,
                    MAP_PRIVATE_OR_SHARED(mdp) | MAP_IS_ANONYMOUS(mdp) |
                    MAP_FIXED, MAP_ANON_OR_FD(mdp), foffset);
+      else {
+        size_t old_size = (char*)mdp->top - (char*)mdp->base;
+        mapto = mremap(mdp->base, old_size, old_size+size, 0);
+      }
 
       if (mapto == (void *) -1/* That's MAP_FAILED */) {
         char buff[1024];
@@ -131,9 +129,6 @@ void *mmorecore(struct mdesc *mdp, ssize_t size)
         abort();
       }
 
-      if (mdp->top == 0)
-        mdp->base = mdp->breakval = mapto;
-
       mdp->top = PAGE_ALIGN((char *) mdp->breakval + size);
       result = (void *) mdp->breakval;
       mdp->breakval = (char *) mdp->breakval + size;