1 /*
2 * Copyright (C) 2018 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 #include "memfd.h"
18
19 #include <errno.h>
20 #include <stdio.h>
21 #if !defined(_WIN32)
22 #include <fcntl.h>
23 #include <sys/mman.h>
24 #include <sys/syscall.h>
25 #include <sys/utsname.h>
26 #include <unistd.h>
27 #endif
28
29 #include <android-base/logging.h>
30 #include <android-base/unique_fd.h>
31
32 #include "macros.h"
33
34 namespace art {
35
36 #if defined(__linux__)
37
memfd_create(const char * name,unsigned int flags)38 int memfd_create(const char* name, unsigned int flags) {
39 // Check kernel version supports memfd_create(). Some older kernels segfault executing
40 // memfd_create() rather than returning ENOSYS (b/116769556).
41 static constexpr int kRequiredMajor = 3;
42 static constexpr int kRequiredMinor = 17;
43 struct utsname uts;
44 int major, minor;
45 if (uname(&uts) != 0 ||
46 strcmp(uts.sysname, "Linux") != 0 ||
47 sscanf(uts.release, "%d.%d", &major, &minor) != 2 ||
48 (major < kRequiredMajor || (major == kRequiredMajor && minor < kRequiredMinor))) {
49 errno = ENOSYS;
50 return -1;
51 }
52
53 return syscall(__NR_memfd_create, name, flags);
54 }
55
IsSealFutureWriteSupportedInternal()56 static bool IsSealFutureWriteSupportedInternal() {
57 android::base::unique_fd fd(art::memfd_create("test_android_memfd", MFD_ALLOW_SEALING));
58 if (fd == -1) {
59 LOG(INFO) << "memfd_create failed: " << strerror(errno) << ", no memfd support.";
60 return false;
61 }
62
63 if (fcntl(fd, F_ADD_SEALS, F_SEAL_FUTURE_WRITE) == -1) {
64 LOG(INFO) << "fcntl(F_ADD_SEALS) failed: " << strerror(errno) << ", no memfd support.";
65 return false;
66 }
67
68 LOG(INFO) << "Using memfd for future sealing";
69 return true;
70 }
71
IsSealFutureWriteSupported()72 bool IsSealFutureWriteSupported() {
73 static bool is_seal_future_write_supported = IsSealFutureWriteSupportedInternal();
74 return is_seal_future_write_supported;
75 }
76
77 #else // __linux__
78
79 int memfd_create([[maybe_unused]] const char* name, [[maybe_unused]] unsigned int flags) {
80 errno = ENOSYS;
81 return -1;
82 }
83
84 bool IsSealFutureWriteSupported() {
85 return false;
86 }
87
88 #endif // __linux__
89
90 } // namespace art
91