// 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/heap_profiler_allocation_register.h"

#include <stddef.h>
#include <sys/mman.h>
#include <unistd.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 internal {

namespace {
size_t GetGuardSize() {
  return GetPageSize();
}
}

void* AllocateGuardedVirtualMemory(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;
}

void FreeGuardedVirtualMemory(void* address, size_t allocated_size) {
  size_t size = bits::Align(allocated_size, GetPageSize()) + GetGuardSize();
  munmap(address, size);
}

}  // namespace internal
}  // namespace trace_event
}  // namespace base