[deoptimizer] Make deoptimizer entry code memory rx.

Bug: chromium:774108,v8:6792
Change-Id: If91b709779912c37b88f3c57e46f7910b59cc240
Reviewed-on: https://chromium-review.googlesource.com/737870
Commit-Queue: Hannes Payer <hpayer@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48967}

src/deoptimizer.cc

@@ -24,9 +24,15 @@ namespace v8 {
 namespace internal {
 
 static MemoryChunk* AllocateCodeChunk(MemoryAllocator* allocator) {
-  return allocator->AllocateChunk(Deoptimizer::GetMaxDeoptTableSize(),
-                                  MemoryAllocator::GetCommitPageSize(),
-                                  EXECUTABLE, nullptr);
+  MemoryChunk* chunk = allocator->AllocateChunk(
+      Deoptimizer::GetMaxDeoptTableSize(), MemoryAllocator::GetCommitPageSize(),
+      EXECUTABLE, nullptr);
+  if (FLAG_write_protect_code_memory) {
+    // TODO(hpayer): Ensure code memory chunk allocation gives us rx by default.
+    chunk->SetReadAndWritable();
+    chunk->SetReadAndExecutable();
+  }
+  return chunk;
 }
 
 DeoptimizerData::DeoptimizerData(MemoryAllocator* allocator)
@@ -2009,6 +2015,11 @@ void Deoptimizer::EnsureCodeForDeoptimizationEntry(Isolate* isolate,
   DCHECK(!RelocInfo::RequiresRelocation(isolate, desc));
 
   MemoryChunk* chunk = data->deopt_entry_code_[type];
+
+  // TODO(mstarzinger,6792): This code-space modification section should be
+  // moved into {Heap} eventually and a safe wrapper be provided.
+  CodePageMemoryModificationScope modification_scope(chunk);
+
   CHECK(static_cast<int>(Deoptimizer::GetMaxDeoptTableSize()) >=
         desc.instr_size);
   if (!chunk->CommitArea(desc.instr_size)) {

src/heap/spaces.cc

@@ -530,7 +530,10 @@ void MemoryChunk::InitializationMemoryFence() {
 
 void MemoryChunk::SetReadAndExecutable() {
   DCHECK(IsFlagSet(MemoryChunk::IS_EXECUTABLE));
-  DCHECK(owner()->identity() == CODE_SPACE || owner()->identity() == LO_SPACE);
+  // TODO(hpayer): owner() can only be null if we use the MemoryChunk outside
+  // of spaces. We actually should not do that and we should untangle this.
+  DCHECK(owner() == nullptr || owner()->identity() == CODE_SPACE ||
+         owner()->identity() == LO_SPACE);
   // Decrementing the write_unprotect_counter_ and changing the page
   // protection mode has to be atomic.
   base::LockGuard<base::Mutex> guard(page_protection_change_mutex_);