Reviewers: Chris Evans,
Description:
Revert "Implement mapping randomization for 64-bit Linux."
Causes sputnik test failures.
[email protected]
BUG=
TEST=
Please review this at http://codereview.chromium.org/7468023/
SVN Base: https://v8.googlecode.com/svn/branches/bleeding_edge
Affected files:
M src/platform-linux.cc
Index: src/platform-linux.cc
diff --git a/src/platform-linux.cc b/src/platform-linux.cc
index
37330be82ba3b16146be383ba451e560c5accc32..bc280ea0a06069474e45e3d19e85a5b65ca49c8b
100644
--- a/src/platform-linux.cc
+++ b/src/platform-linux.cc
@@ -78,33 +78,13 @@ double ceiling(double x) {
static Mutex* limit_mutex = NULL;
-static void* GetRandomMmapAddr() {
- Isolate* isolate = Isolate::UncheckedCurrent();
- // Note that the current isolate isn't set up in a call path via
- // CpuFeatures::Probe. We don't care about randomization in this case
because
- // the code page is immediately freed.
- if (isolate != NULL) {
-#ifdef V8_TARGET_ARCH_X64
- uint64_t rnd1 = V8::RandomPrivate(isolate);
- uint64_t rnd2 = V8::RandomPrivate(isolate);
- uint64_t raw_addr = (rnd1 << 32) ^ rnd2;
- raw_addr &= V8_UINT64_C(0x3ffffffff000);
-#else
- uint32_t raw_addr = V8::RandomPrivate(isolate);
- // The range 0x20000000 - 0x60000000 is relatively unpopulated across a
- // variety of ASLR modes (PAE kernel, NX compat mode, etc).
- raw_addr &= 0x3ffff000;
- raw_addr += 0x20000000;
-#endif
- return reinterpret_cast<void*>(raw_addr);
- }
- return NULL;
-}
-
-
void OS::Setup() {
- // Seed the random number generator. We preserve microsecond resolution.
- uint64_t seed = Ticks() ^ (getpid() << 16);
+ // Seed the random number generator.
+ // Convert the current time to a 64-bit integer first, before converting
it
+ // to an unsigned. Going directly can cause an overflow and the seed to
be
+ // set to all ones. The seed will be identical for different instances
that
+ // call this setup code within the same millisecond.
+ uint64_t seed = static_cast<uint64_t>(TimeCurrentMillis());
srandom(static_cast<unsigned int>(seed));
limit_mutex = CreateMutex();
@@ -387,10 +367,10 @@ size_t OS::AllocateAlignment() {
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* addr = GetRandomMmapAddr();
- void* mbase = mmap(addr, msize, prot, MAP_PRIVATE | MAP_ANONYMOUS, -1,
0);
+ void* mbase = mmap(NULL, msize, prot, MAP_PRIVATE | MAP_ANONYMOUS, -1,
0);
if (mbase == MAP_FAILED) {
LOG(i::Isolate::Current(),
StringEvent("OS::Allocate", "mmap failed"));
@@ -606,7 +586,7 @@ static const int kMmapFdOffset = 0;
VirtualMemory::VirtualMemory(size_t size) {
- address_ = mmap(GetRandomMmapAddr(), size, PROT_NONE,
+ address_ = mmap(NULL, size, PROT_NONE,
MAP_PRIVATE | MAP_ANONYMOUS | MAP_NORESERVE,
kMmapFd, kMmapFdOffset);
size_ = size;
--
v8-dev mailing list
[email protected]
http://groups.google.com/group/v8-dev
