Add hinting to improve ASLR for macos (all allocations) and linux (newly added allocation types).

src/platform-posix.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 64 matching lines @@
 void OS::ProtectCode(void* address, const size_t size) {
   mprotect(address, size, PROT_READ | PROT_EXEC);
 }
 
 
 // Create guard pages.
 void OS::Guard(void* address, const size_t size) {
   mprotect(address, size, PROT_NONE);
 }
 #endif  // __CYGWIN__
 

[Vyacheslav Egorov (Chromium), 2011/10/10 14:13:14]

one more new line required

+void* OS::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;
+    // Currently available CPUs have 48 bits of virtual addressing.  Truncate
+    // the hint address to 46 bits to give the kernel a fighting chance of
+    // fulfilling our placement request.
+    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) and on macos
+    // 10.6 and 10.7.
+    raw_addr &= 0x3ffff000;
+    raw_addr += 0x20000000;
+#endif
+    return reinterpret_cast<void*>(raw_addr);
+  }
+  return NULL;
+}
+
 
 // ----------------------------------------------------------------------------
 // Math functions
 
 double modulo(double x, double y) {
   return fmod(x, y);
 }
 
 
 double OS::nan_value() {
@@ skipping 361 matching lines @@
   return ntohl(value);
 }
 
 
 Socket* OS::CreateSocket() {
   return new POSIXSocket();
 }
 
 
 } }  // namespace v8::internal