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