[haiku-commits] r35488 - haiku/trunk/src/system/libroot/posix/malloc_debug

From: mmlr@xxxxxxxx
To: haiku-commits@xxxxxxxxxxxxx
Date: Tue, 16 Feb 2010 00:48:51 +0100 (CET)
Author: mmlr
Date: 2010-02-16 00:48:51 +0100 (Tue, 16 Feb 2010)
New Revision: 35488
Changeset: http://dev.haiku-os.org/changeset/35488/haiku

Modified:
   haiku/trunk/src/system/libroot/posix/malloc_debug/heap.cpp
Log:
Finish the implementation of heap_debug_malloc_with_guard_page() using mprotect
to make the guard page inaccessible. Thanks Ingo for the pointer!


Modified: haiku/trunk/src/system/libroot/posix/malloc_debug/heap.cpp
===================================================================
--- haiku/trunk/src/system/libroot/posix/malloc_debug/heap.cpp  2010-02-15 
23:01:31 UTC (rev 35487)
+++ haiku/trunk/src/system/libroot/posix/malloc_debug/heap.cpp  2010-02-15 
23:48:51 UTC (rev 35488)
@@ -10,10 +10,14 @@
  */
 
 #include <malloc.h>
+#include <malloc_debug.h>
 #include <stdio.h>
 #include <string.h>
 #include <stdlib.h>
 
+#include <errno.h>
+#include <sys/mman.h>
+
 #include <locks.h>
 #include <syscalls.h>
 
@@ -1703,15 +1707,14 @@
 extern "C" void *
 heap_debug_malloc_with_guard_page(size_t size)
 {
-       size_t areaSize = ROUNDUP(size + sizeof(area_allocation_info), 
B_PAGE_SIZE);
+       size_t areaSize = ROUNDUP(size + sizeof(area_allocation_info) + 
B_PAGE_SIZE,
+               B_PAGE_SIZE);
        if (areaSize < size) {
                // the size overflowed
                return NULL;
        }
 
        void *address = NULL;
-       // TODO: this needs a kernel backend (flag) to enforce adding an 
unmapped
-       // page past the required pages so it will reliably crash
        area_id allocationArea = create_area("guarded area", &address,
                B_ANY_ADDRESS, areaSize, B_NO_LOCK, B_READ_AREA | B_WRITE_AREA);
        if (allocationArea < B_OK) {
@@ -1720,6 +1723,13 @@
                return NULL;
        }
 
+       if (mprotect((void *)((addr_t)address + areaSize - B_PAGE_SIZE),
+                       B_PAGE_SIZE, PROT_NONE) != 0) {
+               panic("heap: failed to protect guard page: %s\n", 
strerror(errno));
+               delete_area(allocationArea);
+               return NULL;
+       }
+
        area_allocation_info *info = (area_allocation_info *)address;
        info->magic = kAreaAllocationMagic;
        info->area = allocationArea;
@@ -1731,7 +1741,7 @@
 
        // the address is calculated so that the end of the allocation
        // is at the end of the usable space of the requested area
-       address = (void *)((addr_t)address + areaSize - size);
+       address = (void *)((addr_t)address + areaSize - B_PAGE_SIZE - size);
 
        INFO(("heap: allocated area %ld for guarded allocation of %lu bytes\n",
                allocationArea, size));
[haiku-commits] r35488 - haiku/trunk/src/system/libroot/posix/malloc_debug

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