mirror of
https://github.com/mozilla/gecko-dev.git
synced 2024-11-26 14:22:01 +00:00
315 lines
8.6 KiB
C++
315 lines
8.6 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
|
|
* vim: sw=2 ts=8 et :
|
|
*/
|
|
/* This Source Code Form is subject to the terms of the Mozilla Public
|
|
* License, v. 2.0. If a copy of the MPL was not distributed with this
|
|
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
|
|
|
|
#ifndef mozilla_ipc_Shmem_h
|
|
#define mozilla_ipc_Shmem_h
|
|
|
|
#include "mozilla/Attributes.h"
|
|
|
|
#include "base/basictypes.h"
|
|
#include "base/process.h"
|
|
|
|
#include "nscore.h"
|
|
#include "nsDebug.h"
|
|
#include "nsAutoPtr.h"
|
|
|
|
#include "ipc/IPCMessageUtils.h"
|
|
#include "mozilla/ipc/SharedMemory.h"
|
|
|
|
/**
|
|
* |Shmem| is one agent in the IPDL shared memory scheme. The way it
|
|
works is essentially
|
|
*
|
|
* (1) C++ code calls, say, |parentActor->AllocShmem(size)|
|
|
|
|
* (2) IPDL-generated code creates a |mozilla::ipc::SharedMemory|
|
|
* wrapping the bare OS shmem primitives. The code then adds the new
|
|
* SharedMemory to the set of shmem segments being managed by IPDL.
|
|
*
|
|
* (3) IPDL-generated code "shares" the new SharedMemory to the child
|
|
* process, and then sends a special asynchronous IPC message to the
|
|
* child notifying it of the creation of the segment. (What this
|
|
* means is OS specific.)
|
|
*
|
|
* (4a) The child receives the special IPC message, and using the
|
|
* |SharedMemory{SysV,Basic}::Handle| it was passed, creates a
|
|
* |mozilla::ipc::SharedMemory| in the child
|
|
* process.
|
|
*
|
|
* (4b) After sending the "shmem-created" IPC message, IPDL-generated
|
|
* code in the parent returns a |mozilla::ipc::Shmem| back to the C++
|
|
* caller of |parentActor->AllocShmem()|. The |Shmem| is a "weak
|
|
* reference" to the underlying |SharedMemory|, which is managed by
|
|
* IPDL-generated code. C++ consumers of |Shmem| can't get at the
|
|
* underlying |SharedMemory|.
|
|
*
|
|
* If parent code wants to give access rights to the Shmem to the
|
|
* child, it does so by sending its |Shmem| to the child, in an IPDL
|
|
* message. The parent's |Shmem| then "dies", i.e. becomes
|
|
* inaccessible. This process could be compared to passing a
|
|
* "shmem-access baton" between parent and child.
|
|
*/
|
|
|
|
namespace mozilla {
|
|
namespace layers {
|
|
class ShadowLayerForwarder;
|
|
}
|
|
|
|
namespace ipc {
|
|
|
|
class Shmem MOZ_FINAL
|
|
{
|
|
friend struct IPC::ParamTraits<mozilla::ipc::Shmem>;
|
|
#ifdef DEBUG
|
|
// For ShadowLayerForwarder::CheckSurfaceDescriptor
|
|
friend class mozilla::layers::ShadowLayerForwarder;
|
|
#endif
|
|
|
|
public:
|
|
typedef int32_t id_t;
|
|
// Low-level wrapper around platform shmem primitives.
|
|
typedef mozilla::ipc::SharedMemory SharedMemory;
|
|
typedef SharedMemory::SharedMemoryType SharedMemoryType;
|
|
struct IHadBetterBeIPDLCodeCallingThis_OtherwiseIAmADoodyhead {};
|
|
|
|
Shmem() :
|
|
mSegment(nullptr),
|
|
mData(nullptr),
|
|
mSize(0),
|
|
mId(0)
|
|
{
|
|
}
|
|
|
|
Shmem(const Shmem& aOther) :
|
|
mSegment(aOther.mSegment),
|
|
mData(aOther.mData),
|
|
mSize(aOther.mSize),
|
|
mId(aOther.mId)
|
|
{
|
|
}
|
|
|
|
#if !defined(DEBUG)
|
|
Shmem(IHadBetterBeIPDLCodeCallingThis_OtherwiseIAmADoodyhead,
|
|
SharedMemory* aSegment, id_t aId) :
|
|
mSegment(aSegment),
|
|
mData(aSegment->memory()),
|
|
mSize(0),
|
|
mId(aId)
|
|
{
|
|
mSize = static_cast<size_t>(*PtrToSize(mSegment));
|
|
}
|
|
#else
|
|
Shmem(IHadBetterBeIPDLCodeCallingThis_OtherwiseIAmADoodyhead,
|
|
SharedMemory* aSegment, id_t aId);
|
|
#endif
|
|
|
|
~Shmem()
|
|
{
|
|
// Shmem only holds a "weak ref" to the actual segment, which is
|
|
// owned by IPDL. So there's nothing interesting to be done here
|
|
forget(IHadBetterBeIPDLCodeCallingThis_OtherwiseIAmADoodyhead());
|
|
}
|
|
|
|
Shmem& operator=(const Shmem& aRhs)
|
|
{
|
|
mSegment = aRhs.mSegment;
|
|
mData = aRhs.mData;
|
|
mSize = aRhs.mSize;
|
|
mId = aRhs.mId;
|
|
return *this;
|
|
}
|
|
|
|
bool operator==(const Shmem& aRhs) const
|
|
{
|
|
// need to compare IDs because of AdoptShmem(); two Shmems might
|
|
// refer to the same segment but with different IDs for different
|
|
// protocol trees. (NB: it's possible for this method to
|
|
// spuriously return true if AdoptShmem() gives the same ID for
|
|
// two protocol trees, but I don't think that can cause any
|
|
// problems since the Shmems really would be indistinguishable.)
|
|
return mSegment == aRhs.mSegment && mId == aRhs.mId;
|
|
}
|
|
|
|
// Returns whether this Shmem is writable by you, and thus whether you can
|
|
// transfer writability to another actor.
|
|
bool
|
|
IsWritable() const
|
|
{
|
|
return mSegment != nullptr;
|
|
}
|
|
|
|
// Returns whether this Shmem is readable by you, and thus whether you can
|
|
// transfer readability to another actor.
|
|
bool
|
|
IsReadable() const
|
|
{
|
|
return mSegment != nullptr;
|
|
}
|
|
|
|
// Return a pointer to the user-visible data segment.
|
|
template<typename T>
|
|
T*
|
|
get() const
|
|
{
|
|
AssertInvariants();
|
|
AssertAligned<T>();
|
|
|
|
return reinterpret_cast<T*>(mData);
|
|
}
|
|
|
|
// Return the size of the segment as requested when this shmem
|
|
// segment was allocated, in units of T. The underlying mapping may
|
|
// actually be larger because of page alignment and private data,
|
|
// but this isn't exposed to clients.
|
|
template<typename T>
|
|
size_t
|
|
Size() const
|
|
{
|
|
AssertInvariants();
|
|
AssertAligned<T>();
|
|
|
|
return mSize / sizeof(T);
|
|
}
|
|
|
|
int GetSysVID() const;
|
|
|
|
// These shouldn't be used directly, use the IPDL interface instead.
|
|
id_t Id(IHadBetterBeIPDLCodeCallingThis_OtherwiseIAmADoodyhead) const {
|
|
return mId;
|
|
}
|
|
|
|
SharedMemory* Segment(IHadBetterBeIPDLCodeCallingThis_OtherwiseIAmADoodyhead) const {
|
|
return mSegment;
|
|
}
|
|
|
|
#ifndef DEBUG
|
|
void RevokeRights(IHadBetterBeIPDLCodeCallingThis_OtherwiseIAmADoodyhead)
|
|
{
|
|
}
|
|
#else
|
|
void RevokeRights(IHadBetterBeIPDLCodeCallingThis_OtherwiseIAmADoodyhead);
|
|
#endif
|
|
|
|
void forget(IHadBetterBeIPDLCodeCallingThis_OtherwiseIAmADoodyhead)
|
|
{
|
|
mSegment = nullptr;
|
|
mData = nullptr;
|
|
mSize = 0;
|
|
mId = 0;
|
|
}
|
|
|
|
static already_AddRefed<Shmem::SharedMemory>
|
|
Alloc(IHadBetterBeIPDLCodeCallingThis_OtherwiseIAmADoodyhead,
|
|
size_t aNBytes,
|
|
SharedMemoryType aType,
|
|
bool aUnsafe,
|
|
bool aProtect=false);
|
|
|
|
// Prepare this to be shared with |aProcess|. Return an IPC message
|
|
// that contains enough information for the other process to map
|
|
// this segment in OpenExisting() below. Return a new message if
|
|
// successful (owned by the caller), nullptr if not.
|
|
IPC::Message*
|
|
ShareTo(IHadBetterBeIPDLCodeCallingThis_OtherwiseIAmADoodyhead,
|
|
base::ProcessHandle aProcess,
|
|
int32_t routingId);
|
|
|
|
// Stop sharing this with |aProcess|. Return an IPC message that
|
|
// contains enough information for the other process to unmap this
|
|
// segment. Return a new message if successful (owned by the
|
|
// caller), nullptr if not.
|
|
IPC::Message*
|
|
UnshareFrom(IHadBetterBeIPDLCodeCallingThis_OtherwiseIAmADoodyhead,
|
|
base::ProcessHandle aProcess,
|
|
int32_t routingId);
|
|
|
|
// Return a SharedMemory instance in this process using the
|
|
// descriptor shared to us by the process that created the
|
|
// underlying OS shmem resource. The contents of the descriptor
|
|
// depend on the type of SharedMemory that was passed to us.
|
|
static already_AddRefed<SharedMemory>
|
|
OpenExisting(IHadBetterBeIPDLCodeCallingThis_OtherwiseIAmADoodyhead,
|
|
const IPC::Message& aDescriptor,
|
|
id_t* aId,
|
|
bool aProtect=false);
|
|
|
|
static void
|
|
Dealloc(IHadBetterBeIPDLCodeCallingThis_OtherwiseIAmADoodyhead,
|
|
SharedMemory* aSegment);
|
|
|
|
private:
|
|
template<typename T>
|
|
void AssertAligned() const
|
|
{
|
|
if (0 != (mSize % sizeof(T)))
|
|
NS_RUNTIMEABORT("shmem is not T-aligned");
|
|
}
|
|
|
|
#if !defined(DEBUG)
|
|
void AssertInvariants() const
|
|
{ }
|
|
|
|
static uint32_t*
|
|
PtrToSize(SharedMemory* aSegment)
|
|
{
|
|
char* endOfSegment =
|
|
reinterpret_cast<char*>(aSegment->memory()) + aSegment->Size();
|
|
return reinterpret_cast<uint32_t*>(endOfSegment - sizeof(uint32_t));
|
|
}
|
|
|
|
#else
|
|
void AssertInvariants() const;
|
|
#endif
|
|
|
|
SharedMemory* MOZ_NON_OWNING_REF mSegment;
|
|
void* mData;
|
|
size_t mSize;
|
|
id_t mId;
|
|
};
|
|
|
|
|
|
} // namespace ipc
|
|
} // namespace mozilla
|
|
|
|
|
|
namespace IPC {
|
|
|
|
template<>
|
|
struct ParamTraits<mozilla::ipc::Shmem>
|
|
{
|
|
typedef mozilla::ipc::Shmem paramType;
|
|
|
|
// NB: Read()/Write() look creepy in that Shmems have a pointer
|
|
// member, but IPDL internally uses mId to properly initialize a
|
|
// "real" Shmem
|
|
|
|
static void Write(Message* aMsg, const paramType& aParam)
|
|
{
|
|
WriteParam(aMsg, aParam.mId);
|
|
}
|
|
|
|
static bool Read(const Message* aMsg, void** aIter, paramType* aResult)
|
|
{
|
|
paramType::id_t id;
|
|
if (!ReadParam(aMsg, aIter, &id))
|
|
return false;
|
|
aResult->mId = id;
|
|
return true;
|
|
}
|
|
|
|
static void Log(const paramType& aParam, std::wstring* aLog)
|
|
{
|
|
aLog->append(L"(shmem segment)");
|
|
}
|
|
};
|
|
|
|
|
|
} // namespace IPC
|
|
|
|
|
|
#endif // ifndef mozilla_ipc_Shmem_h
|