1 /*
2 * Copyright (C) 2017 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 "src/tracing/ipc/posix_shared_memory.h"
18
19 #include <fcntl.h>
20 #include <stdint.h>
21 #include <stdio.h>
22 #include <stdlib.h>
23 #include <sys/mman.h>
24 #include <sys/stat.h>
25 #include <unistd.h>
26
27 #include <memory>
28 #include <utility>
29
30 #include "perfetto/base/compiler.h"
31 #include "perfetto/base/logging.h"
32 #include "perfetto/ext/base/temp_file.h"
33 #include "src/tracing/ipc/memfd.h"
34
35 namespace perfetto {
36
37 namespace {
38 int kFileSeals = F_SEAL_SHRINK | F_SEAL_GROW | F_SEAL_SEAL;
39 } // namespace
40
41 // static
Create(size_t size)42 std::unique_ptr<PosixSharedMemory> PosixSharedMemory::Create(size_t size) {
43 base::ScopedFile fd =
44 CreateMemfd("perfetto_shmem", MFD_CLOEXEC | MFD_ALLOW_SEALING);
45 bool is_memfd = !!fd;
46
47 // In-tree builds only allow mem_fd, so we can inspect the seals to verify the
48 // fd is appropriately sealed. We'll crash in the PERFETTO_CHECK(fd) below if
49 // memfd_create failed.
50 #if !PERFETTO_BUILDFLAG(PERFETTO_ANDROID_BUILD)
51 if (!fd) {
52 // TODO: if this fails on Android we should fall back on ashmem.
53 PERFETTO_DPLOG("memfd_create() failed");
54 fd = base::TempFile::CreateUnlinked().ReleaseFD();
55 }
56 #endif
57
58 PERFETTO_CHECK(fd);
59 int res = ftruncate(fd.get(), static_cast<off_t>(size));
60 PERFETTO_CHECK(res == 0);
61
62 if (is_memfd) {
63 // When memfd is supported, file seals should be, too.
64 res = fcntl(*fd, F_ADD_SEALS, kFileSeals);
65 PERFETTO_DCHECK(res == 0);
66 }
67
68 return MapFD(std::move(fd), size);
69 }
70
71 // static
AttachToFd(base::ScopedFile fd,bool require_seals_if_supported)72 std::unique_ptr<PosixSharedMemory> PosixSharedMemory::AttachToFd(
73 base::ScopedFile fd,
74 bool require_seals_if_supported) {
75 bool requires_seals = require_seals_if_supported;
76
77 #if PERFETTO_BUILDFLAG(PERFETTO_ANDROID_BUILD)
78 // In-tree kernels all support memfd.
79 PERFETTO_CHECK(HasMemfdSupport());
80 #else
81 // In out-of-tree builds, we only require seals if the kernel supports memfd.
82 if (requires_seals)
83 requires_seals = HasMemfdSupport();
84 #endif
85
86 if (requires_seals) {
87 // If the system supports memfd, we require a sealed memfd.
88 int res = fcntl(*fd, F_GET_SEALS);
89 if (res == -1 || (res & kFileSeals) != kFileSeals) {
90 PERFETTO_PLOG("Couldn't verify file seals on shmem FD");
91 return nullptr;
92 }
93 }
94
95 struct stat stat_buf = {};
96 int res = fstat(fd.get(), &stat_buf);
97 PERFETTO_CHECK(res == 0 && stat_buf.st_size > 0);
98 return MapFD(std::move(fd), static_cast<size_t>(stat_buf.st_size));
99 }
100
101 // static
MapFD(base::ScopedFile fd,size_t size)102 std::unique_ptr<PosixSharedMemory> PosixSharedMemory::MapFD(base::ScopedFile fd,
103 size_t size) {
104 PERFETTO_DCHECK(fd);
105 PERFETTO_DCHECK(size > 0);
106 void* start =
107 mmap(nullptr, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd.get(), 0);
108 PERFETTO_CHECK(start != MAP_FAILED);
109 return std::unique_ptr<PosixSharedMemory>(
110 new PosixSharedMemory(start, size, std::move(fd)));
111 }
112
PosixSharedMemory(void * start,size_t size,base::ScopedFile fd)113 PosixSharedMemory::PosixSharedMemory(void* start,
114 size_t size,
115 base::ScopedFile fd)
116 : start_(start), size_(size), fd_(std::move(fd)) {}
117
~PosixSharedMemory()118 PosixSharedMemory::~PosixSharedMemory() {
119 munmap(start(), size());
120 }
121
~Factory()122 PosixSharedMemory::Factory::~Factory() {}
123
CreateSharedMemory(size_t size)124 std::unique_ptr<SharedMemory> PosixSharedMemory::Factory::CreateSharedMemory(
125 size_t size) {
126 return PosixSharedMemory::Create(size);
127 }
128
129 } // namespace perfetto
130