1 /*
2 * Copyright (C) 2021 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 // File operations without libc. Most important is not touching thread-local errno.
18
19 #ifndef BERBERIS_BASE_FD_H_
20 #define BERBERIS_BASE_FD_H_
21
22 #include <linux/unistd.h>
23 #include <sys/mman.h>
24 #include <unistd.h>
25
26 #include "berberis/base/bit_util.h"
27 #include "berberis/base/logging.h"
28 #include "berberis/base/raw_syscall.h"
29
30 namespace berberis {
31
CreateMemfdOrDie(const char * name)32 inline int CreateMemfdOrDie(const char* name) {
33 // Use MFD_CLOEXEC to avoid leaking the file descriptor to child processes.
34 int fd = static_cast<int>(RawSyscall(__NR_memfd_create, bit_cast<long>(name), MFD_CLOEXEC));
35 CHECK(fd >= 0);
36 return fd;
37 }
38
FtruncateOrDie(int fd,off64_t size)39 inline void FtruncateOrDie(int fd, off64_t size) {
40 // Call libc instead of syscall because we want 64 version and do not want to
41 // do ifdefs for 32/64/glibc/bionic in order to get the correct one.
42 CHECK_EQ(ftruncate64(fd, size), 0);
43 }
44
WriteFullyOrDie(int fd,const void * data,size_t size)45 inline void WriteFullyOrDie(int fd, const void* data, size_t size) {
46 auto* curr = reinterpret_cast<const uint8_t*>(data);
47 auto* end = curr + size;
48 while (curr < end) {
49 auto written = RawSyscall(__NR_write, fd, bit_cast<long>(curr), end - curr);
50 // It is not clear if write syscall can return 0 when writing more than 0 bytes.
51 if (written >= 0) {
52 curr += written;
53 } else {
54 CHECK(written == -EINTR);
55 }
56 }
57 }
58
CloseUnsafe(int fd)59 inline void CloseUnsafe(int fd) {
60 RawSyscall(__NR_close, fd);
61 }
62
63 } // namespace berberis
64
65 #endif // BERBERIS_BASE_FD_H_
66