libmemunreachable/ScopedDisableMalloc.h

/*
 * Copyright (C) 2016 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#ifndef LIBMEMUNREACHABLE_SCOPED_DISABLE_MALLOC_H_
#define LIBMEMUNREACHABLE_SCOPED_DISABLE_MALLOC_H_

#include <memory>

#include "android-base/macros.h"

#include "ScopedAlarm.h"
#include "bionic.h"
#include "log.h"

namespace android {

class DisableMallocGuard {
 public:
  DisableMallocGuard() : disabled_(false) {}
  ~DisableMallocGuard() { Enable(); }

  void Disable() {
    if (!disabled_) {
      malloc_disable();
      disabled_ = true;
    }
  }

  void Enable() {
    if (disabled_) {
      malloc_enable();
      disabled_ = false;
    }
  }

 private:
  DISALLOW_COPY_AND_ASSIGN(DisableMallocGuard);
  bool disabled_;
};

// Any calls to malloc or free from this thread will deadlock as long as this
// object is in scope.  Calls to malloc from other threads may succeed (for
// example if the allocation is satisfied out of the thread's tcache), or may
// block until the object is destroyed.
//
// Don't call fork() while malloc is disabled, it needs the same locks held
// here.
class ScopedDisableMalloc {
 public:
  ScopedDisableMalloc() { disable_malloc_.Disable(); }

  ~ScopedDisableMalloc() { disable_malloc_.Enable(); }

 private:
  DISALLOW_COPY_AND_ASSIGN(ScopedDisableMalloc);
  DisableMallocGuard disable_malloc_;
};

class ScopedDisableMallocTimeout {
 public:
  explicit ScopedDisableMallocTimeout(
      std::chrono::milliseconds timeout = std::chrono::milliseconds(2000))
      : timeout_(timeout), timed_out_(false), disable_malloc_() {
    Disable();
  }

  ~ScopedDisableMallocTimeout() { Enable(); }

  bool timed_out() { return timed_out_; }

  void Enable() {
    disable_malloc_.Enable();
    alarm_ = nullptr;
  }

  void Disable() {
    // set up the alarm before disabling malloc so unique_ptr can be used
    alarm_ = std::make_unique<ScopedAlarm>(timeout_, [&]() {
      disable_malloc_.Enable();
      timed_out_ = true;
    });

    disable_malloc_.Disable();
  }

 private:
  DISALLOW_COPY_AND_ASSIGN(ScopedDisableMallocTimeout);
  std::chrono::milliseconds timeout_;
  bool timed_out_;
  std::unique_ptr<ScopedAlarm> alarm_;
  DisableMallocGuard disable_malloc_;
};

}  // namespace android

#endif  // LIBMEMUNREACHABLE_SCOPED_DISABLE_MALLOC_H_