Reviewers: fschneider, Chris Evans,
Description:
Re-apply: Implement mapping randomization for 64-bit Linux.
- 32-bit Linux already seems to scatter the mmap() chunks around;
64-bit didn't.
- Seed the system random number generator a little better (we needlessly
trunctaed microsecond resolution to millisecond resolution).
- Will automatically take advantage of better entropy when V8::RandomPrivate
uses it.
[email protected],[email protected]
BUG=v8:805
TEST=
Please review this at http://codereview.chromium.org/7464022/
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
bc280ea0a06069474e45e3d19e85a5b65ca49c8b..37330be82ba3b16146be383ba451e560c5accc32
100644
--- a/src/platform-linux.cc
+++ b/src/platform-linux.cc
@@ -78,13 +78,33 @@ 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.
- // 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());
+ // Seed the random number generator. We preserve microsecond resolution.
+ uint64_t seed = Ticks() ^ (getpid() << 16);
srandom(static_cast<unsigned int>(seed));
limit_mutex = CreateMutex();
@@ -367,10 +387,10 @@ 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* mbase = mmap(NULL, msize, prot, MAP_PRIVATE | MAP_ANONYMOUS, -1,
0);
+ void* addr = GetRandomMmapAddr();
+ void* mbase = mmap(addr, msize, prot, MAP_PRIVATE | MAP_ANONYMOUS, -1,
0);
if (mbase == MAP_FAILED) {
LOG(i::Isolate::Current(),
StringEvent("OS::Allocate", "mmap failed"));
@@ -586,7 +606,7 @@ static const int kMmapFdOffset = 0;
VirtualMemory::VirtualMemory(size_t size) {
- address_ = mmap(NULL, size, PROT_NONE,
+ address_ = mmap(GetRandomMmapAddr(), size, PROT_NONE,
MAP_PRIVATE | MAP_ANONYMOUS | MAP_NORESERVE,
kMmapFd, kMmapFdOffset);
size_ = size;
--
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