src/third_party/android_crazy_linker/src/src/crazy_linker_globals.cpp

// Copyright 2014 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 "crazy_linker_globals.h"

#include <new>

#include <pthread.h>

namespace crazy {

namespace {

// Implement lazy-initialized static variable without a C++ constructor.
// Note that this is leaky, i.e. the instance is never destroyed, but
// this was also the case with the previous heap-based implementation.
pthread_once_t s_once = PTHREAD_ONCE_INIT;

union Storage {
  char dummy;
  Globals globals;

  Storage() {}
  ~Storage() {}
};

Storage s_storage;

void InitGlobals() {
  new (&s_storage.globals) Globals();
}

}  // namespace

Globals::Globals() {
  // IMPORTANT: The global mutex must be recursive to allow for recursive
  // dlopen() calls. See http://crbug.com/843804.
  pthread_mutexattr_t attr;
  pthread_mutexattr_init(&attr);
  pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_RECURSIVE);
  pthread_mutex_init(&lock_, &attr);
  pthread_mutexattr_destroy(&attr);

  search_paths_.ResetFromEnv("LD_LIBRARY_PATH");
}

Globals::~Globals() {
  pthread_mutex_destroy(&lock_);
}

void Globals::Lock() {
  pthread_mutex_lock(&lock_);
}

void Globals::Unlock() {
  pthread_mutex_unlock(&lock_);
}

// static
Globals* Globals::Get() {
  pthread_once(&s_once, InitGlobals);
  return &s_storage.globals;
}

// TECHNICAL NOTE: The mutex below does not have to be recursive, unlike the
// other one, because it should be only operated on during the following
// operations:
//
//   - Acquired before, and released after, calling one of the system linker's
//     functions that may modify the global link-map. Note that these should
//     never call back into the crazy linker.
//
//   - Acquired and released when modifying the global link-map in
//     crazy::RDebug::AddEntryImpl() and crazy::RDebug::DelEntryImpl(). These
//     do not call the system linker, or make any kind of recursive calls.

// static
pthread_mutex_t ScopedLinkMapLocker::s_lock_ = PTHREAD_MUTEX_INITIALIZER;

}  // namespace crazy