Revision: 5169
Author: [email protected]
Date: Mon Aug 2 08:27:25 2010
Log: VirtualAlloc on Windows 7 does not currently provide sufficient
randomization to protect JIT code from being aligned in large regions at a
predictable location.
This patch manually randomizes the allocation address for
PAGE_EXECUTE_READWRITE regions between kAllocationRandomAddressMin and
kAllocationRandomAddressMax.
BUG=none
TEST=allocate lots of javascript code and check for contiguous allocations
Patch by Paul Mehta <[email protected]>
Review URL: http://codereview.chromium.org/2832095
http://code.google.com/p/v8/source/detail?r=5169
Modified:
/branches/bleeding_edge/src/platform-linux.cc
/branches/bleeding_edge/src/platform-win32.cc
=======================================
--- /branches/bleeding_edge/src/platform-linux.cc Mon May 31 03:09:07 2010
+++ /branches/bleeding_edge/src/platform-linux.cc Mon Aug 2 08:27:25 2010
@@ -236,6 +236,7 @@
void* OS::Allocate(const size_t requested,
size_t* allocated,
bool is_executable) {
+ // TODO(805): Port randomization of allocated executable memory to Linux.
const size_t msize = RoundUp(requested, sysconf(_SC_PAGESIZE));
int prot = PROT_READ | PROT_WRITE | (is_executable ? PROT_EXEC : 0);
void* mbase = mmap(NULL, msize, prot, MAP_PRIVATE | MAP_ANONYMOUS, -1,
0);
=======================================
--- /branches/bleeding_edge/src/platform-win32.cc Fri May 21 22:27:19 2010
+++ /branches/bleeding_edge/src/platform-win32.cc Mon Aug 2 08:27:25 2010
@@ -838,12 +838,38 @@
void* OS::Allocate(const size_t requested,
size_t* allocated,
bool is_executable) {
+ // The address range used to randomize RWX allocations in OS::Allocate
+ // Try not to map pages into the default range that windows loads DLLs
+ // Note: This does not guarantee RWX regions will be within the
+ // range kAllocationRandomAddressMin to kAllocationRandomAddressMax
+#ifdef V8_HOST_ARCH_64_BIT
+ static const intptr_t kAllocationRandomAddressMin = 0x0000000080000000;
+ static const intptr_t kAllocationRandomAddressMax = 0x000004FFFFFFFFFF;
+#else
+ static const intptr_t kAllocationRandomAddressMin = 0x04000000;
+ static const intptr_t kAllocationRandomAddressMax = 0x4FFFFFFF;
+#endif
+
// VirtualAlloc rounds allocated size to page size automatically.
size_t msize = RoundUp(requested, static_cast<int>(GetPageSize()));
+ intptr_t address = NULL;
// Windows XP SP2 allows Data Excution Prevention (DEP).
int prot = is_executable ? PAGE_EXECUTE_READWRITE : PAGE_READWRITE;
- LPVOID mbase = VirtualAlloc(NULL, msize, MEM_COMMIT | MEM_RESERVE, prot);
+
+ // For exectutable pages try and randomize the allocation address
+ if (prot == PAGE_EXECUTE_READWRITE && msize >= Page::kPageSize) {
+ address = (V8::Random() << kPageSizeBits) |
kAllocationRandomAddressMin;
+ address &= kAllocationRandomAddressMax;
+ }
+
+ LPVOID mbase = VirtualAlloc(reinterpret_cast<void *>(address),
+ msize,
+ MEM_COMMIT | MEM_RESERVE,
+ prot);
+ if (mbase == NULL && address != NULL)
+ mbase = VirtualAlloc(NULL, msize, MEM_COMMIT | MEM_RESERVE, prot);
+
if (mbase == NULL) {
LOG(StringEvent("OS::Allocate", "VirtualAlloc failed"));
return NULL;
--
v8-dev mailing list
[email protected]
http://groups.google.com/group/v8-dev
