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

src/platform-linux.cc

Index: src/platform-linux.cc
===================================================================
--- src/platform-linux.cc	(revision 9508)
+++ src/platform-linux.cc	(working copy)
@@ -77,34 +77,6 @@
 
 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;
-    // 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).
-    raw_addr &= 0x3ffff000;
-    raw_addr += 0x20000000;
-#endif
-    return reinterpret_cast<void*>(raw_addr);
-  }
-  return NULL;
-}
-

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

accidentally deleted new line

-
 void OS::Setup() {
   // Seed the random number generator. We preserve microsecond resolution.
   uint64_t seed = Ticks() ^ (getpid() << 16);
@@ -386,7 +358,7 @@
                    bool is_executable) {
   const size_t msize = RoundUp(requested, AllocateAlignment());
   int prot = PROT_READ | PROT_WRITE | (is_executable ? PROT_EXEC : 0);
-  void* addr = GetRandomMmapAddr();
+  void* addr = OS::GetRandomMmapAddr();
   void* mbase = mmap(addr, msize, prot, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
   if (mbase == MAP_FAILED) {
     LOG(i::Isolate::Current(),
@@ -456,7 +428,12 @@
   int size = ftell(file);
 
   void* memory =
-      mmap(0, size, PROT_READ | PROT_WRITE, MAP_SHARED, fileno(file), 0);
+      mmap(OS::GetRandomMmapAddr(),
+           size,
+           PROT_READ | PROT_WRITE,
+           MAP_SHARED,
+           fileno(file),
+           0);
   return new PosixMemoryMappedFile(file, memory, size);
 }
 
@@ -471,7 +448,12 @@
     return NULL;
   }
   void* memory =
-      mmap(0, size, PROT_READ | PROT_WRITE, MAP_SHARED, fileno(file), 0);
+      mmap(OS::GetRandomMmapAddr(),
+           size,
+           PROT_READ | PROT_WRITE,
+           MAP_SHARED,
+           fileno(file),
+           0);
   return new PosixMemoryMappedFile(file, memory, size);
 }
 
@@ -556,8 +538,12 @@
   // kernel log.
   int size = sysconf(_SC_PAGESIZE);
   FILE* f = fopen(kGCFakeMmap, "w+");
-  void* addr = mmap(NULL, size, PROT_READ | PROT_EXEC, MAP_PRIVATE,
-                    fileno(f), 0);
+  void* addr = mmap(OS::GetRandomMmapAddr(),
+                    size,
+                    PROT_READ | PROT_EXEC,
+                    MAP_PRIVATE,
+                    fileno(f),
+                    0);
   ASSERT(addr != MAP_FAILED);
   OS::Free(addr, size);
   fclose(f);
@@ -614,7 +600,7 @@
   ASSERT(IsAligned(alignment, static_cast<intptr_t>(OS::AllocateAlignment())));
   size_t request_size = RoundUp(size + alignment,
                                 static_cast<intptr_t>(OS::AllocateAlignment()));
-  void* reservation = mmap(GetRandomMmapAddr(),
+  void* reservation = mmap(OS::GetRandomMmapAddr(),
                            request_size,
                            PROT_NONE,
                            MAP_PRIVATE | MAP_ANONYMOUS | MAP_NORESERVE,
@@ -680,7 +666,7 @@
 
 
 void* VirtualMemory::ReserveRegion(size_t size) {
-  void* result = mmap(GetRandomMmapAddr(),
+  void* result = mmap(OS::GetRandomMmapAddr(),
                       size,
                       PROT_NONE,
                       MAP_PRIVATE | MAP_ANONYMOUS | MAP_NORESERVE,