99 lines
3.3 KiB
C++
99 lines
3.3 KiB
C++
// Copyright (c) 2012 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.
|
|
|
|
#ifndef BASE_POSIX_GLOBAL_DESCRIPTORS_H_
|
|
#define BASE_POSIX_GLOBAL_DESCRIPTORS_H_
|
|
|
|
#include "build/build_config.h"
|
|
|
|
#include <vector>
|
|
#include <utility>
|
|
|
|
#include <stdint.h>
|
|
|
|
#include "base/files/memory_mapped_file.h"
|
|
#include "base/files/scoped_file.h"
|
|
#include "base/memory/singleton.h"
|
|
|
|
namespace base {
|
|
|
|
// It's common practice to install file descriptors into well known slot
|
|
// numbers before execing a child; stdin, stdout and stderr are ubiqutous
|
|
// examples.
|
|
//
|
|
// However, when using a zygote model, this becomes troublesome. Since the
|
|
// descriptors which need to be in these slots generally aren't known, any code
|
|
// could open a resource and take one of the reserved descriptors. Simply
|
|
// overwriting the slot isn't a viable solution.
|
|
//
|
|
// We could try to fill the reserved slots as soon as possible, but this is a
|
|
// fragile solution since global constructors etc are able to open files.
|
|
//
|
|
// Instead, we retreat from the idea of installing descriptors in specific
|
|
// slots and add a layer of indirection in the form of this singleton object.
|
|
// It maps from an abstract key to a descriptor. If independent modules each
|
|
// need to define keys, then values should be chosen randomly so as not to
|
|
// collide.
|
|
//
|
|
// Note that this class is deprecated and passing file descriptor should ideally
|
|
// be done through the command line and using FileDescriptorStore.
|
|
// See https://crbugs.com/detail?id=692619
|
|
class BASE_EXPORT GlobalDescriptors {
|
|
public:
|
|
typedef uint32_t Key;
|
|
struct Descriptor {
|
|
Descriptor(Key key, int fd);
|
|
Descriptor(Key key, int fd, base::MemoryMappedFile::Region region);
|
|
|
|
// Globally unique key.
|
|
Key key;
|
|
// Actual FD.
|
|
int fd;
|
|
// Optional region, defaults to kWholeFile.
|
|
base::MemoryMappedFile::Region region;
|
|
};
|
|
typedef std::vector<Descriptor> Mapping;
|
|
|
|
// Often we want a canonical descriptor for a given Key. In this case, we add
|
|
// the following constant to the key value:
|
|
static const int kBaseDescriptor = 3; // 0, 1, 2 are already taken.
|
|
|
|
// Return the singleton instance of GlobalDescriptors.
|
|
static GlobalDescriptors* GetInstance();
|
|
|
|
// Get a descriptor given a key. It is a fatal error if the key is not known.
|
|
int Get(Key key) const;
|
|
|
|
// Get a descriptor given a key. Returns -1 on error.
|
|
int MaybeGet(Key key) const;
|
|
|
|
// Returns a descriptor given a key and removes it from this class mappings.
|
|
// Also populates |region|.
|
|
// It is a fatal error if the key is not known.
|
|
base::ScopedFD TakeFD(Key key, base::MemoryMappedFile::Region* region);
|
|
|
|
// Get a region given a key. It is a fatal error if the key is not known.
|
|
base::MemoryMappedFile::Region GetRegion(Key key) const;
|
|
|
|
// Set the descriptor for the given |key|. This sets the region associated
|
|
// with |key| to kWholeFile.
|
|
void Set(Key key, int fd);
|
|
|
|
// Set the descriptor and |region| for the given |key|.
|
|
void Set(Key key, int fd, base::MemoryMappedFile::Region region);
|
|
|
|
void Reset(const Mapping& mapping);
|
|
|
|
private:
|
|
friend struct DefaultSingletonTraits<GlobalDescriptors>;
|
|
GlobalDescriptors();
|
|
~GlobalDescriptors();
|
|
|
|
Mapping descriptors_;
|
|
};
|
|
|
|
} // namespace base
|
|
|
|
#endif // BASE_POSIX_GLOBAL_DESCRIPTORS_H_
|