static already_AddRefed<SharedMemory>
ReadSegment(const IPC::Message& aDescriptor, Shmem::id_t* aId, size_t* aNBytes, size_t aExtraSize)
{
if (SHMEM_CREATED_MESSAGE_TYPE != aDescriptor.type()) {
NS_ERROR("expected 'shmem created' message");
return nullptr;
}
SharedMemory::SharedMemoryType type;
PickleIterator iter(aDescriptor);
if (!ShmemCreated::ReadInfo(&aDescriptor, &iter, aId, aNBytes, &type)) {
return nullptr;
}
RefPtr<SharedMemory> segment = NewSegment(type);
if (!segment) {
return nullptr;
}
if (!segment->ReadHandle(&aDescriptor, &iter)) {
NS_ERROR("trying to open invalid handle");
return nullptr;
}
aDescriptor.EndRead(iter);
size_t size = SharedMemory::PageAlignedSize(*aNBytes + aExtraSize);
if (!segment->Map(size)) {
return nullptr;
}
// close the handle to the segment after it is mapped
segment->CloseHandle();
return segment.forget();
}
// static
already_AddRefed<Shmem::SharedMemory>
Shmem::OpenExisting(IHadBetterBeIPDLCodeCallingThis_OtherwiseIAmADoodyhead,
const IPC::Message& aDescriptor,
id_t* aId,
bool /*unused*/)
{
if (SHMEM_CREATED_MESSAGE_TYPE != aDescriptor.type()) {
return nullptr;
}
SharedMemory::SharedMemoryType type;
void* iter = nullptr;
size_t size;
if (!ShmemCreated::ReadInfo(&aDescriptor, &iter, aId, &size, &type))
return nullptr;
nsRefPtr<SharedMemory> segment;
size_t segmentSize = SharedMemory::PageAlignedSize(size + sizeof(uint32_t));
if (SharedMemory::TYPE_BASIC == type) {
SharedMemoryBasic::Handle handle;
if (!ShmemCreated::ReadHandle(&aDescriptor, &iter, &handle))
return nullptr;
if (!SharedMemoryBasic::IsHandleValid(handle)) {
return nullptr;
}
segment = CreateSegment(segmentSize, handle);
}
#ifdef MOZ_HAVE_SHAREDMEMORYSYSV
else if (SharedMemory::TYPE_SYSV == type) {
SharedMemorySysV::Handle handle;
if (!ShmemCreated::ReadHandle(&aDescriptor, &iter, &handle))
return nullptr;
if (!SharedMemorySysV::IsHandleValid(handle)) {
return nullptr;
}
segment = CreateSegment(segmentSize, handle);
}
#endif
else {
return nullptr;
}
if (!segment)
return nullptr;
// this is the only validity check done in non-DEBUG builds
if (size != static_cast<size_t>(*PtrToSize(segment))) {
return nullptr;
}
return segment.forget();
}
// static
already_AddRefed<Shmem::SharedMemory>
Shmem::OpenExisting(IHadBetterBeIPDLCodeCallingThis_OtherwiseIAmADoodyhead,
const IPC::Message& aDescriptor,
id_t* aId,
bool aProtect)
{
if (SHMEM_CREATED_MESSAGE_TYPE != aDescriptor.type()) {
NS_ERROR("expected 'shmem created' message");
return nullptr;
}
void* iter = nullptr;
SharedMemory::SharedMemoryType type;
size_t size;
if (!ShmemCreated::ReadInfo(&aDescriptor, &iter, aId, &size, &type))
return nullptr;
nsRefPtr<SharedMemory> segment;
size_t pageSize = SharedMemory::SystemPageSize();
// |2*pageSize| is for the front and back sentinels
size_t segmentSize = SharedMemory::PageAlignedSize(size + 2*pageSize);
if (SharedMemory::TYPE_BASIC == type) {
SharedMemoryBasic::Handle handle;
if (!ShmemCreated::ReadHandle(&aDescriptor, &iter, &handle))
return nullptr;
if (!SharedMemoryBasic::IsHandleValid(handle)) {
NS_ERROR("trying to open invalid handle");
return nullptr;
}
segment = CreateSegment(segmentSize, handle);
}
#ifdef MOZ_HAVE_SHAREDMEMORYSYSV
else if (SharedMemory::TYPE_SYSV == type) {
SharedMemorySysV::Handle handle;
if (!ShmemCreated::ReadHandle(&aDescriptor, &iter, &handle))
return nullptr;
if (!SharedMemorySysV::IsHandleValid(handle)) {
NS_ERROR("trying to open invalid handle");
return nullptr;
}
segment = CreateSegment(segmentSize, handle);
}
#endif
else {
NS_ERROR("unknown shmem type");
return nullptr;
}
if (!segment)
return nullptr;
Header* header = GetHeader(segment);
if (size != header->mSize) {
NS_ERROR("Wrong size for this Shmem!");
return nullptr;
}
// The caller of this function may not know whether the segment is
// unsafe or not
if (!header->mUnsafe && aProtect)
Protect(segment);
return segment.forget();
}