[Tracing] Add allocation register for heap profiling

base/trace_event/memory_profiler_allocation_register_posix.cc

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "base/trace_event/memory_profiler_allocation_register.h"
+
+#include <sys/mman.h>
+#include <unistd.h>
+
+#include "base/basictypes.h"
+#include "base/bits.h"
+#include "base/logging.h"
+#include "base/process/process_metrics.h"
+
+#ifndef MAP_ANONYMOUS
+#define MAP_ANONYMOUS MAP_ANON
+#endif
+
+namespace base {
+namespace trace_event {
+
+namespace {
+size_t GetGuardSize() {
+  return GetPageSize();
+}
+}
+
+// static
+void* AllocationRegister::AllocateVirtualMemory(size_t size) {
+  size = bits::Align(size, GetPageSize());
+
+  // Add space for a guard page at the end.
+  size_t map_size = size + GetGuardSize();
+
+  void* addr = mmap(nullptr, map_size, PROT_READ | PROT_WRITE,
+                    MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+
+  PCHECK(addr != MAP_FAILED);
+
+  // Mark the last page of the allocated address space as inaccessible
+  // (PROT_NONE). The read/write accessible space is still at least |min_size|
+  // bytes.
+  void* guard_addr =
+      reinterpret_cast<void*>(reinterpret_cast<uintptr_t>(addr) + size);
+  int result = mprotect(guard_addr, GetGuardSize(), PROT_NONE);
+  PCHECK(result == 0);
+
+  return addr;
+}
+
+// static
+void AllocationRegister::FreeVirtualMemory(void* address,
+                                           size_t allocated_size) {
+  size_t size = bits::Align(allocated_size, GetPageSize()) + GetGuardSize();
+  munmap(address, size);
+}
+
+}  // namespace trace_event
+}  // namespace base