SharedMemoryUnix.cpp [plain text]
#include "config.h"
#if USE(UNIX_DOMAIN_SOCKETS)
#include "SharedMemory.h"
#include "Decoder.h"
#include "Encoder.h"
#include <errno.h>
#include <fcntl.h>
#include <stdlib.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
#include <wtf/Assertions.h>
#include <wtf/RandomNumber.h>
#include <wtf/UniStdExtras.h>
#include <wtf/text/CString.h>
#include <wtf/text/WTFString.h>
#if HAVE(LINUX_MEMFD_H)
#include <linux/memfd.h>
#include <sys/syscall.h>
#endif
namespace WebKit {
SharedMemory::Handle::Handle()
{
}
SharedMemory::Handle::~Handle()
{
}
SharedMemory::Handle::Handle(Handle&&) = default;
SharedMemory::Handle& SharedMemory::Handle::operator=(Handle&& other) = default;
void SharedMemory::Handle::clear()
{
m_attachment = IPC::Attachment();
}
bool SharedMemory::Handle::isNull() const
{
return m_attachment.fileDescriptor() == -1;
}
void SharedMemory::IPCHandle::encode(IPC::Encoder& encoder) const
{
encoder << handle.releaseAttachment();
encoder << dataSize;
}
bool SharedMemory::IPCHandle::decode(IPC::Decoder& decoder, IPCHandle& ipcHandle)
{
ASSERT_ARG(ipcHandle.handle, ipcHandle.handle.isNull());
IPC::Attachment attachment;
if (!decoder.decode(attachment))
return false;
uint64_t dataSize;
if (!decoder.decode(dataSize))
return false;
ipcHandle.handle.adoptAttachment(WTFMove(attachment));
ipcHandle.dataSize = dataSize;
return true;
}
IPC::Attachment SharedMemory::Handle::releaseAttachment() const
{
return WTFMove(m_attachment);
}
void SharedMemory::Handle::adoptAttachment(IPC::Attachment&& attachment)
{
ASSERT(isNull());
m_attachment = WTFMove(attachment);
}
static inline int accessModeMMap(SharedMemory::Protection protection)
{
switch (protection) {
case SharedMemory::Protection::ReadOnly:
return PROT_READ;
case SharedMemory::Protection::ReadWrite:
return PROT_READ | PROT_WRITE;
}
ASSERT_NOT_REACHED();
return PROT_READ | PROT_WRITE;
}
static int createSharedMemory()
{
int fileDescriptor = -1;
#if HAVE(LINUX_MEMFD_H)
static bool isMemFdAvailable = true;
if (isMemFdAvailable) {
do {
fileDescriptor = syscall(__NR_memfd_create, "WebKitSharedMemory", MFD_CLOEXEC);
} while (fileDescriptor == -1 && errno == EINTR);
if (fileDescriptor != -1)
return fileDescriptor;
if (errno != ENOSYS)
return fileDescriptor;
isMemFdAvailable = false;
}
#endif
CString tempName;
for (int tries = 0; fileDescriptor == -1 && tries < 10; ++tries) {
String name = String("/WK2SharedMemory.") + String::number(static_cast<unsigned>(WTF::randomNumber() * (std::numeric_limits<unsigned>::max() + 1.0)));
tempName = name.utf8();
do {
fileDescriptor = shm_open(tempName.data(), O_CREAT | O_RDWR, S_IRUSR | S_IWUSR);
} while (fileDescriptor == -1 && errno == EINTR);
}
if (fileDescriptor != -1)
shm_unlink(tempName.data());
return fileDescriptor;
}
RefPtr<SharedMemory> SharedMemory::allocate(size_t size)
{
int fileDescriptor = createSharedMemory();
if (fileDescriptor == -1) {
WTFLogAlways("Failed to create shared memory: %s", strerror(errno));
return nullptr;
}
while (ftruncate(fileDescriptor, size) == -1) {
if (errno != EINTR) {
closeWithRetry(fileDescriptor);
return nullptr;
}
}
void* data = mmap(nullptr, size, PROT_READ | PROT_WRITE, MAP_SHARED, fileDescriptor, 0);
if (data == MAP_FAILED) {
closeWithRetry(fileDescriptor);
return nullptr;
}
RefPtr<SharedMemory> instance = adoptRef(new SharedMemory());
instance->m_data = data;
instance->m_fileDescriptor = fileDescriptor;
instance->m_size = size;
return instance;
}
RefPtr<SharedMemory> SharedMemory::map(const Handle& handle, Protection protection)
{
ASSERT(!handle.isNull());
int fd = handle.m_attachment.releaseFileDescriptor();
void* data = mmap(0, handle.m_attachment.size(), accessModeMMap(protection), MAP_SHARED, fd, 0);
closeWithRetry(fd);
if (data == MAP_FAILED)
return nullptr;
RefPtr<SharedMemory> instance = wrapMap(data, handle.m_attachment.size(), -1);
instance->m_fileDescriptor = WTF::nullopt;
instance->m_isWrappingMap = false;
return instance;
}
RefPtr<SharedMemory> SharedMemory::wrapMap(void* data, size_t size, int fileDescriptor)
{
RefPtr<SharedMemory> instance = adoptRef(new SharedMemory());
instance->m_data = data;
instance->m_size = size;
instance->m_fileDescriptor = fileDescriptor;
instance->m_isWrappingMap = true;
return instance;
}
SharedMemory::~SharedMemory()
{
if (m_isWrappingMap)
return;
munmap(m_data, m_size);
if (m_fileDescriptor)
closeWithRetry(m_fileDescriptor.value());
}
bool SharedMemory::createHandle(Handle& handle, Protection)
{
ASSERT_ARG(handle, handle.isNull());
ASSERT(m_fileDescriptor);
int duplicatedHandle = dupCloseOnExec(m_fileDescriptor.value());
if (duplicatedHandle == -1) {
ASSERT_NOT_REACHED();
return false;
}
handle.m_attachment = IPC::Attachment(duplicatedHandle, m_size);
return true;
}
unsigned SharedMemory::systemPageSize()
{
static unsigned pageSize = 0;
if (!pageSize)
pageSize = getpagesize();
return pageSize;
}
}
#endif