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/*
* Copyright (C) 2017 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "src/tracing/ipc/posix_shared_memory.h"
#if PERFETTO_BUILDFLAG(PERFETTO_OS_LINUX) || \
PERFETTO_BUILDFLAG(PERFETTO_OS_ANDROID) || \
PERFETTO_BUILDFLAG(PERFETTO_OS_APPLE)
#include <fcntl.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <unistd.h>
#include <memory>
#include <utility>
#include "perfetto/base/compiler.h"
#include "perfetto/base/logging.h"
#include "perfetto/ext/base/temp_file.h"
#include "src/tracing/ipc/memfd.h"
namespace perfetto {
namespace {
int kFileSeals = F_SEAL_SHRINK | F_SEAL_GROW | F_SEAL_SEAL;
} // namespace
// static
std::unique_ptr<PosixSharedMemory> PosixSharedMemory::Create(size_t size) {
base::ScopedFile fd =
CreateMemfd("perfetto_shmem", MFD_CLOEXEC | MFD_ALLOW_SEALING);
bool is_memfd = !!fd;
// In-tree builds only allow mem_fd, so we can inspect the seals to verify the
// fd is appropriately sealed. We'll crash in the PERFETTO_CHECK(fd) below if
// memfd_create failed.
#if !PERFETTO_BUILDFLAG(PERFETTO_ANDROID_BUILD)
if (!fd) {
// TODO: if this fails on Android we should fall back on ashmem.
PERFETTO_DPLOG("memfd_create() failed");
fd = base::TempFile::CreateUnlinked().ReleaseFD();
}
#endif
PERFETTO_CHECK(fd);
int res = ftruncate(fd.get(), static_cast<off_t>(size));
PERFETTO_CHECK(res == 0);
if (is_memfd) {
// When memfd is supported, file seals should be, too.
res = fcntl(*fd, F_ADD_SEALS, kFileSeals);
PERFETTO_DCHECK(res == 0);
}
return MapFD(std::move(fd), size);
}
// static
std::unique_ptr<PosixSharedMemory> PosixSharedMemory::AttachToFd(
base::ScopedFile fd,
bool require_seals_if_supported) {
bool requires_seals = require_seals_if_supported;
#if PERFETTO_BUILDFLAG(PERFETTO_ANDROID_BUILD)
// In-tree kernels all support memfd.
PERFETTO_CHECK(HasMemfdSupport());
#else
// In out-of-tree builds, we only require seals if the kernel supports memfd.
if (requires_seals)
requires_seals = HasMemfdSupport();
#endif
if (requires_seals) {
// If the system supports memfd, we require a sealed memfd.
int res = fcntl(*fd, F_GET_SEALS);
if (res == -1 || (res & kFileSeals) != kFileSeals) {
PERFETTO_PLOG("Couldn't verify file seals on shmem FD");
return nullptr;
}
}
struct stat stat_buf = {};
int res = fstat(fd.get(), &stat_buf);
PERFETTO_CHECK(res == 0 && stat_buf.st_size > 0);
return MapFD(std::move(fd), static_cast<size_t>(stat_buf.st_size));
}
// static
std::unique_ptr<PosixSharedMemory> PosixSharedMemory::MapFD(base::ScopedFile fd,
size_t size) {
PERFETTO_DCHECK(fd);
PERFETTO_DCHECK(size > 0);
void* start =
mmap(nullptr, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd.get(), 0);
PERFETTO_CHECK(start != MAP_FAILED);
return std::unique_ptr<PosixSharedMemory>(
new PosixSharedMemory(start, size, std::move(fd)));
}
PosixSharedMemory::PosixSharedMemory(void* start,
size_t size,
base::ScopedFile fd)
: start_(start), size_(size), fd_(std::move(fd)) {}
PosixSharedMemory::~PosixSharedMemory() {
munmap(start(), size());
}
PosixSharedMemory::Factory::~Factory() {}
std::unique_ptr<SharedMemory> PosixSharedMemory::Factory::CreateSharedMemory(
size_t size) {
return PosixSharedMemory::Create(size);
}
} // namespace perfetto
#endif // OS_LINUX || OS_ANDROID || OS_APPLE