sandboxed-api/sandboxed_api/sandbox2/buffer.cc

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// Copyright 2019 Google LLC. All Rights Reserved.
//
// 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 "sandboxed_api/sandbox2/buffer.h"
#include <sys/mman.h>
#include <sys/stat.h>
#include <unistd.h>
#include <cerrno>
#include "absl/memory/memory.h"
#include "absl/strings/str_cat.h"
#include "sandboxed_api/sandbox2/util.h"
#include "sandboxed_api/sandbox2/util/strerror.h"
#include "sandboxed_api/util/canonical_errors.h"
namespace sandbox2 {
// Creates a new Buffer that is backed by the specified file descriptor.
::sapi::StatusOr<std::unique_ptr<Buffer>> Buffer::CreateFromFd(int fd) {
auto buffer = absl::WrapUnique(new Buffer{});
struct stat stat_buf;
if (fstat(fd, &stat_buf) != 0) {
return ::sapi::InternalError(
absl::StrCat("Could not stat buffer fd: ", StrError(errno)));
}
size_t size = stat_buf.st_size;
int prot = PROT_READ | PROT_WRITE;
int flags = MAP_SHARED;
off_t offset = 0;
buffer->buf_ =
reinterpret_cast<uint8_t*>(mmap(nullptr, size, prot, flags, fd, offset));
if (buffer->buf_ == MAP_FAILED) {
return ::sapi::InternalError(
absl::StrCat("Could not map buffer fd: ", StrError(errno)));
}
buffer->fd_ = fd;
buffer->size_ = size;
return buffer;
}
// Creates a new Buffer of the specified size, backed by a temporary file that
// will be immediately deleted.
::sapi::StatusOr<std::unique_ptr<Buffer>> Buffer::CreateWithSize(int64_t size) {
int fd;
if (!util::CreateMemFd(&fd)) {
return ::sapi::InternalError("Could not create buffer temp file");
}
if (ftruncate(fd, size) != 0) {
return ::sapi::InternalError(
absl::StrCat("Could not extend buffer fd: ", StrError(errno)));
}
return CreateFromFd(fd);
}
Buffer::~Buffer() {
if (buf_ != nullptr) {
munmap(buf_, size_);
}
if (fd_ != -1) {
close(fd_);
}
}
} // namespace sandbox2