Merge experimental/gc branch to the bleeding_edge.

src/platform-linux.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 70 matching lines @@
 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);
   }
@@ skipping 273 matching lines @@
 
 
 size_t OS::AllocateAlignment() {
   return sysconf(_SC_PAGESIZE);
 }
 
 
 void* OS::Allocate(const size_t requested,
                    size_t* allocated,
                    bool is_executable) {
-  const size_t msize = RoundUp(requested, sysconf(_SC_PAGESIZE));
+  const size_t msize = RoundUp(requested, AllocateAlignment());
   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);
   if (mbase == MAP_FAILED) {
     LOG(i::Isolate::Current(),
         StringEvent("OS::Allocate", "mmap failed"));
     return NULL;
   }
   *allocated = msize;
   UpdateAllocatedSpaceLimits(mbase, msize);
@@ skipping 196 matching lines @@
 #else  // ndef __GLIBC__
   return 0;
 #endif  // ndef __GLIBC__
 }
 
 
 // Constants used for mmap.
 static const int kMmapFd = -1;
 static const int kMmapFdOffset = 0;
 
+VirtualMemory::VirtualMemory() : address_(NULL), size_(0) { }
 
 VirtualMemory::VirtualMemory(size_t size) {
-  address_ = mmap(GetRandomMmapAddr(), size, PROT_NONE,
-                  MAP_PRIVATE | MAP_ANONYMOUS | MAP_NORESERVE,
-                  kMmapFd, kMmapFdOffset);
+  address_ = ReserveRegion(size);
+  size_ = size;
+}
+
+
+VirtualMemory::VirtualMemory(size_t size, size_t alignment)
+    : address_(NULL), size_(0) {
+  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(),
+                           request_size,
+                           PROT_NONE,
+                           MAP_PRIVATE | MAP_ANONYMOUS | MAP_NORESERVE,
+                           kMmapFd,
+                           kMmapFdOffset);
+  if (reservation == MAP_FAILED) return;
+  Address base = static_cast<Address>(reservation);
+  Address aligned_base = RoundUp(base, alignment);
+  ASSERT(base <= aligned_base);
+
+  // Unmap extra memory reserved before and after the desired block.
+  size_t bytes_prior = static_cast<size_t>(aligned_base - base);
+  if (bytes_prior > 0) {
+    munmap(base, bytes_prior);
+  }
+  if (static_cast<size_t>(aligned_base - base) < request_size - size) {
+    munmap(aligned_base + size, request_size - size - bytes_prior);
+  }
+
+  address_ = static_cast<void*>(aligned_base);
   size_ = size;
 }
 
 
 VirtualMemory::~VirtualMemory() {
   if (IsReserved()) {
-    if (0 == munmap(address(), size())) address_ = MAP_FAILED;
+    bool result = ReleaseRegion(address(), size());
+    ASSERT(result);
+    USE(result);
   }
 }
 
 
 bool VirtualMemory::IsReserved() {
-  return address_ != MAP_FAILED;
+  return address_ != NULL;
+}
+
+
+void VirtualMemory::Reset() {
+  address_ = NULL;
+  size_ = 0;
 }
 
 
 bool VirtualMemory::Commit(void* address, size_t size, bool is_executable) {
+  return CommitRegion(address, size, is_executable);
+}
+
+
+bool VirtualMemory::Uncommit(void* address, size_t size) {
+  return UncommitRegion(address, size);
+}
+
+
+void* VirtualMemory::ReserveRegion(size_t size) {
+  void* result = mmap(GetRandomMmapAddr(),
+                      size,
+                      PROT_NONE,
+                      MAP_PRIVATE | MAP_ANONYMOUS | MAP_NORESERVE,
+                      kMmapFd,
+                      kMmapFdOffset);
+
+  if (result == MAP_FAILED) return NULL;
+
+  return result;
+}
+
+
+bool VirtualMemory::CommitRegion(void* base, size_t size, bool is_executable) {
   int prot = PROT_READ | PROT_WRITE | (is_executable ? PROT_EXEC : 0);
-  if (MAP_FAILED == mmap(address, size, prot,
+  if (MAP_FAILED == mmap(base,
+                         size,
+                         prot,
                          MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED,
-                         kMmapFd, kMmapFdOffset)) {
+                         kMmapFd,
+                         kMmapFdOffset)) {
     return false;
   }
 
-  UpdateAllocatedSpaceLimits(address, size);
+  UpdateAllocatedSpaceLimits(base, size);
   return true;
 }
 
 
-bool VirtualMemory::Uncommit(void* address, size_t size) {
-  return mmap(address, size, PROT_NONE,
+bool VirtualMemory::UncommitRegion(void* base, size_t size) {
+  return mmap(base,
+              size,
+              PROT_NONE,
               MAP_PRIVATE | MAP_ANONYMOUS | MAP_NORESERVE | MAP_FIXED,
-              kMmapFd, kMmapFdOffset) != MAP_FAILED;
+              kMmapFd,
+              kMmapFdOffset) != MAP_FAILED;
+}
+
+
+bool VirtualMemory::ReleaseRegion(void* base, size_t size) {
+  return munmap(base, size) == 0;
 }
 
 
 class Thread::PlatformData : public Malloced {
  public:
   PlatformData() : thread_(kNoThread) {}
 
   pthread_t thread_;  // Thread handle for pthread.
 };
 
@@ skipping 488 matching lines @@
 
 
 void Sampler::Stop() {
   ASSERT(IsActive());
   SignalSender::RemoveActiveSampler(this);
   SetActive(false);
 }
 
 
 } }  // namespace v8::internal