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 #if PERFETTO_BUILDFLAG(PERFETTO_OS_LINUX) || \
20 PERFETTO_BUILDFLAG(PERFETTO_OS_ANDROID) || \
21 PERFETTO_BUILDFLAG(PERFETTO_OS_APPLE) || \
22 PERFETTO_BUILDFLAG(PERFETTO_OS_FUCHSIA) || \
23 PERFETTO_BUILDFLAG(PERFETTO_OS_WASM)
24
25 #include <fcntl.h>
26 #include <stdint.h>
27 #include <stdio.h>
28 #include <stdlib.h>
29 #include <sys/mman.h>
30 #include <sys/stat.h>
31 #include <unistd.h>
32
33 #include <memory>
34 #include <utility>
35
36 #include "perfetto/base/compiler.h"
37 #include "perfetto/base/logging.h"
38 #include "perfetto/ext/base/temp_file.h"
39 #include "src/tracing/ipc/memfd.h"
40
41 namespace perfetto {
42
43 namespace {
44 int kFileSeals = F_SEAL_SHRINK | F_SEAL_GROW | F_SEAL_SEAL;
45 } // namespace
46
47 // static
Create(size_t size)48 std::unique_ptr<PosixSharedMemory> PosixSharedMemory::Create(size_t size) {
49 base::ScopedFile fd =
50 CreateMemfd("perfetto_shmem", MFD_CLOEXEC | MFD_ALLOW_SEALING);
51 bool is_memfd = !!fd;
52
53 // In-tree builds only allow mem_fd, so we can inspect the seals to verify the
54 // fd is appropriately sealed. We'll crash in the PERFETTO_CHECK(fd) below if
55 // memfd_create failed.
56 #if !PERFETTO_BUILDFLAG(PERFETTO_ANDROID_BUILD)
57 if (!fd) {
58 // TODO: if this fails on Android we should fall back on ashmem.
59 PERFETTO_DPLOG("memfd_create() failed");
60 fd = base::TempFile::CreateUnlinked().ReleaseFD();
61 }
62 #endif
63
64 PERFETTO_CHECK(fd);
65 int res = ftruncate(fd.get(), static_cast<off_t>(size));
66 PERFETTO_CHECK(res == 0);
67
68 if (is_memfd) {
69 // When memfd is supported, file seals should be, too.
70 res = fcntl(*fd, F_ADD_SEALS, kFileSeals);
71 PERFETTO_DCHECK(res == 0);
72 }
73
74 return MapFD(std::move(fd), size);
75 }
76
77 // static
AttachToFd(base::ScopedFile fd,bool require_seals_if_supported)78 std::unique_ptr<PosixSharedMemory> PosixSharedMemory::AttachToFd(
79 base::ScopedFile fd,
80 bool require_seals_if_supported) {
81 bool requires_seals = require_seals_if_supported;
82
83 #if PERFETTO_BUILDFLAG(PERFETTO_ANDROID_BUILD)
84 // In-tree kernels all support memfd.
85 PERFETTO_CHECK(HasMemfdSupport());
86 #else
87 // In out-of-tree builds, we only require seals if the kernel supports memfd.
88 if (requires_seals)
89 requires_seals = HasMemfdSupport();
90 #endif
91
92 if (requires_seals) {
93 // If the system supports memfd, we require a sealed memfd.
94 int res = fcntl(*fd, F_GET_SEALS);
95 if (res == -1 || (res & kFileSeals) != kFileSeals) {
96 PERFETTO_PLOG("Couldn't verify file seals on shmem FD");
97 return nullptr;
98 }
99 }
100
101 struct stat stat_buf = {};
102 int res = fstat(fd.get(), &stat_buf);
103 PERFETTO_CHECK(res == 0 && stat_buf.st_size > 0);
104 return MapFD(std::move(fd), static_cast<size_t>(stat_buf.st_size));
105 }
106
107 // static
MapFD(base::ScopedFile fd,size_t size)108 std::unique_ptr<PosixSharedMemory> PosixSharedMemory::MapFD(base::ScopedFile fd,
109 size_t size) {
110 PERFETTO_DCHECK(fd);
111 PERFETTO_DCHECK(size > 0);
112 void* start =
113 mmap(nullptr, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd.get(), 0);
114 PERFETTO_CHECK(start != MAP_FAILED);
115 return std::unique_ptr<PosixSharedMemory>(
116 new PosixSharedMemory(start, size, std::move(fd)));
117 }
118
PosixSharedMemory(void * start,size_t size,base::ScopedFile fd)119 PosixSharedMemory::PosixSharedMemory(void* start,
120 size_t size,
121 base::ScopedFile fd)
122 : start_(start), size_(size), fd_(std::move(fd)) {}
123
~PosixSharedMemory()124 PosixSharedMemory::~PosixSharedMemory() {
125 munmap(start(), size());
126 }
127
~Factory()128 PosixSharedMemory::Factory::~Factory() {}
129
CreateSharedMemory(size_t size)130 std::unique_ptr<SharedMemory> PosixSharedMemory::Factory::CreateSharedMemory(
131 size_t size) {
132 return PosixSharedMemory::Create(size);
133 }
134
135 } // namespace perfetto
136
137 #endif // OS_LINUX || OS_ANDROID || OS_APPLE
138