Revert r16648, r16641, r16638 and r16637.

src/platform-cygwin.cc

Index: src/platform-cygwin.cc
diff --git a/src/platform-cygwin.cc b/src/platform-cygwin.cc
index 081f1954d2b9c4359376aa2c1da19a5c6b3f7d90..4d3b1e313e631d8e0ba498c11bc35b257cebee47 100644
--- a/src/platform-cygwin.cc
+++ b/src/platform-cygwin.cc
@@ -73,6 +73,21 @@ double OS::LocalTimeOffset() {
 }
 
 
+void* OS::Allocate(const size_t requested,
+                   size_t* allocated,
+                   bool is_executable) {
+  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);
+  if (mbase == MAP_FAILED) {
+    LOG(Isolate::Current(), StringEvent("OS::Allocate", "mmap failed"));
+    return NULL;
+  }
+  *allocated = msize;
+  return mbase;
+}
+
+
 void OS::DumpBacktrace() {
   // Currently unsupported.
 }
@@ -208,8 +223,7 @@ static void* GetRandomAddr() {
   // CpuFeatures::Probe. We don't care about randomization in this case because
   // the code page is immediately freed.
   if (isolate != NULL) {
-    // The address range used to randomize RWX allocations in
-    // VirtualMemory::AllocateRegion().
+    // The address range used to randomize RWX allocations in OS::Allocate
     // Try not to map pages into the default range that windows loads DLLs
     // Use a multiple of 64k to prevent committing unused memory.
     // Note: This does not guarantee RWX regions will be within the
@@ -230,4 +244,126 @@ static void* GetRandomAddr() {
   return NULL;
 }
 
+
+static void* RandomizedVirtualAlloc(size_t size, int action, int protection) {
+  LPVOID base = NULL;
+
+  if (protection == PAGE_EXECUTE_READWRITE || protection == PAGE_NOACCESS) {
+    // For exectutable pages try and randomize the allocation address
+    for (size_t attempts = 0; base == NULL && attempts < 3; ++attempts) {
+      base = VirtualAlloc(GetRandomAddr(), size, action, protection);
+    }
+  }
+
+  // After three attempts give up and let the OS find an address to use.
+  if (base == NULL) base = VirtualAlloc(NULL, size, action, protection);
+
+  return base;
+}
+
+
+VirtualMemory::VirtualMemory() : address_(NULL), size_(0) { }
+
+
+VirtualMemory::VirtualMemory(size_t size)
+    : 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* address = ReserveRegion(request_size);
+  if (address == NULL) return;
+  Address base = RoundUp(static_cast<Address>(address), alignment);
+  // Try reducing the size by freeing and then reallocating a specific area.
+  bool result = ReleaseRegion(address, request_size);
+  USE(result);
+  ASSERT(result);
+  address = VirtualAlloc(base, size, MEM_RESERVE, PAGE_NOACCESS);
+  if (address != NULL) {
+    request_size = size;
+    ASSERT(base == static_cast<Address>(address));
+  } else {
+    // Resizing failed, just go with a bigger area.
+    address = ReserveRegion(request_size);
+    if (address == NULL) return;
+  }
+  address_ = address;
+  size_ = request_size;
+}
+
+
+VirtualMemory::~VirtualMemory() {
+  if (IsReserved()) {
+    bool result = ReleaseRegion(address_, size_);
+    ASSERT(result);
+    USE(result);
+  }
+}
+
+
+bool VirtualMemory::IsReserved() {
+  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) {
+  ASSERT(IsReserved());
+  return UncommitRegion(address, size);
+}
+
+
+void* VirtualMemory::ReserveRegion(size_t size) {
+  return RandomizedVirtualAlloc(size, MEM_RESERVE, PAGE_NOACCESS);
+}
+
+
+bool VirtualMemory::CommitRegion(void* base, size_t size, bool is_executable) {
+  int prot = is_executable ? PAGE_EXECUTE_READWRITE : PAGE_READWRITE;
+  if (NULL == VirtualAlloc(base, size, MEM_COMMIT, prot)) {
+    return false;
+  }
+  return true;
+}
+
+
+bool VirtualMemory::Guard(void* address) {
+  if (NULL == VirtualAlloc(address,
+                           OS::CommitPageSize(),
+                           MEM_COMMIT,
+                           PAGE_NOACCESS)) {
+    return false;
+  }
+  return true;
+}
+
+
+bool VirtualMemory::UncommitRegion(void* base, size_t size) {
+  return VirtualFree(base, size, MEM_DECOMMIT) != 0;
+}
+
+
+bool VirtualMemory::ReleaseRegion(void* base, size_t size) {
+  return VirtualFree(base, 0, MEM_RELEASE) != 0;
+}
+
+
+bool VirtualMemory::HasLazyCommits() {
+  // TODO(alph): implement for the platform.
+  return false;
+}
+
 } }  // namespace v8::internal