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 #pragma once
18
19 #include <linux/bpf.h>
20
21 #include <android-base/result.h>
22 #include <android-base/stringprintf.h>
23 #include <android-base/unique_fd.h>
24 #include <utils/Log.h>
25 #include "bpf/BpfUtils.h"
26
27 namespace android {
28 namespace bpf {
29
30 // This is a class wrapper for eBPF maps. The eBPF map is a special in-kernel
31 // data structure that stores data in <Key, Value> pairs. It can be read/write
32 // from userspace by passing syscalls with the map file descriptor. This class
33 // is used to generalize the procedure of interacting with eBPF maps and hide
34 // the implementation detail from other process. Besides the basic syscalls
35 // wrapper, it also provides some useful helper functions as well as an iterator
36 // nested class to iterate the map more easily.
37 //
38 // NOTE: A kernel eBPF map may be accessed by both kernel and userspace
39 // processes at the same time. Or if the map is pinned as a virtual file, it can
40 // be obtained by multiple eBPF map class object and accessed concurrently.
41 // Though the map class object and the underlying kernel map are thread safe, it
42 // is not safe to iterate over a map while another thread or process is deleting
43 // from it. In this case the iteration can return duplicate entries.
44 template <class Key, class Value>
45 class BpfMap {
46 public:
47 BpfMap<Key, Value>() {};
48
49 protected:
50 // flag must be within BPF_OBJ_FLAG_MASK, ie. 0, BPF_F_RDONLY, BPF_F_WRONLY
51 BpfMap<Key, Value>(const char* pathname, uint32_t flags) {
52 mMapFd.reset(mapRetrieve(pathname, flags));
53 if (mMapFd < 0) abort();
54 if (isAtLeastKernelVersion(4, 14, 0)) {
55 if (bpfGetFdKeySize(mMapFd) != sizeof(Key)) abort();
56 if (bpfGetFdValueSize(mMapFd) != sizeof(Value)) abort();
57 }
58 }
59
60 public:
61 explicit BpfMap<Key, Value>(const char* pathname) : BpfMap<Key, Value>(pathname, 0) {}
62
63 BpfMap<Key, Value>(bpf_map_type map_type, uint32_t max_entries, uint32_t map_flags = 0) {
64 mMapFd.reset(createMap(map_type, sizeof(Key), sizeof(Value), max_entries, map_flags));
65 if (mMapFd < 0) abort();
66 }
67
getFirstKey()68 base::Result<Key> getFirstKey() const {
69 Key firstKey;
70 if (getFirstMapKey(mMapFd, &firstKey)) {
71 return ErrnoErrorf("Get firstKey map {} failed", mMapFd.get());
72 }
73 return firstKey;
74 }
75
getNextKey(const Key & key)76 base::Result<Key> getNextKey(const Key& key) const {
77 Key nextKey;
78 if (getNextMapKey(mMapFd, &key, &nextKey)) {
79 return ErrnoErrorf("Get next key of map {} failed", mMapFd.get());
80 }
81 return nextKey;
82 }
83
writeValue(const Key & key,const Value & value,uint64_t flags)84 base::Result<void> writeValue(const Key& key, const Value& value, uint64_t flags) {
85 if (writeToMapEntry(mMapFd, &key, &value, flags)) {
86 return ErrnoErrorf("Write to map {} failed", mMapFd.get());
87 }
88 return {};
89 }
90
readValue(const Key key)91 base::Result<Value> readValue(const Key key) const {
92 Value value;
93 if (findMapEntry(mMapFd, &key, &value)) {
94 return ErrnoErrorf("Read value of map {} failed", mMapFd.get());
95 }
96 return value;
97 }
98
deleteValue(const Key & key)99 base::Result<void> deleteValue(const Key& key) {
100 if (deleteMapEntry(mMapFd, &key)) {
101 return ErrnoErrorf("Delete entry from map {} failed", mMapFd.get());
102 }
103 return {};
104 }
105
106 protected:
init(const char * path,int fd)107 [[clang::reinitializes]] base::Result<void> init(const char* path, int fd) {
108 mMapFd.reset(fd);
109 if (mMapFd == -1) {
110 return ErrnoErrorf("Pinned map not accessible or does not exist: ({})", path);
111 }
112 if (isAtLeastKernelVersion(4, 14, 0)) {
113 // Normally we should return an error here instead of calling abort,
114 // but this cannot happen at runtime without a massive code bug (K/V type mismatch)
115 // and as such it's better to just blow the system up and let the developer fix it.
116 // Crashes are much more likely to be noticed than logs and missing functionality.
117 if (bpfGetFdKeySize(mMapFd) != sizeof(Key)) abort();
118 if (bpfGetFdValueSize(mMapFd) != sizeof(Value)) abort();
119 }
120 return {};
121 }
122
123 public:
124 // Function that tries to get map from a pinned path.
init(const char * path)125 [[clang::reinitializes]] base::Result<void> init(const char* path) {
126 return init(path, mapRetrieveRW(path));
127 }
128
129
130 #ifdef TEST_BPF_MAP
131 // due to Android SELinux limitations which prevent map creation by anyone besides the bpfloader
132 // this should only ever be used by test code, it is equivalent to:
133 // .reset(createMap(type, keysize, valuesize, max_entries, map_flags)
134 // TODO: derive map_flags from BpfMap vs BpfMapRO
135 [[clang::reinitializes]] base::Result<void> resetMap(bpf_map_type map_type,
136 uint32_t max_entries,
137 uint32_t map_flags = 0) {
138 int map_fd = createMap(map_type, sizeof(Key), sizeof(Value), max_entries, map_flags);
139 if (map_fd < 0) {
140 auto err = ErrnoErrorf("Unable to create map.");
141 mMapFd.reset();
142 return err;
143 };
144 mMapFd.reset(map_fd);
145 return {};
146 }
147 #endif
148
149 // Iterate through the map and handle each key retrieved based on the filter
150 // without modification of map content.
151 base::Result<void> iterate(
152 const std::function<base::Result<void>(const Key& key, const BpfMap<Key, Value>& map)>&
153 filter) const;
154
155 // Iterate through the map and get each <key, value> pair, handle each <key,
156 // value> pair based on the filter without modification of map content.
157 base::Result<void> iterateWithValue(
158 const std::function<base::Result<void>(const Key& key, const Value& value,
159 const BpfMap<Key, Value>& map)>& filter) const;
160
161 // Iterate through the map and handle each key retrieved based on the filter
162 base::Result<void> iterate(
163 const std::function<base::Result<void>(const Key& key, BpfMap<Key, Value>& map)>&
164 filter);
165
166 // Iterate through the map and get each <key, value> pair, handle each <key,
167 // value> pair based on the filter.
168 base::Result<void> iterateWithValue(
169 const std::function<base::Result<void>(const Key& key, const Value& value,
170 BpfMap<Key, Value>& map)>& filter);
171
getMap()172 const base::unique_fd& getMap() const { return mMapFd; };
173
174 // Copy assignment operator
175 BpfMap<Key, Value>& operator=(const BpfMap<Key, Value>& other) {
176 if (this != &other) mMapFd.reset(fcntl(other.mMapFd.get(), F_DUPFD_CLOEXEC, 0));
177 return *this;
178 }
179
180 // Move assignment operator
181 BpfMap<Key, Value>& operator=(BpfMap<Key, Value>&& other) noexcept {
182 if (this != &other) {
183 mMapFd = std::move(other.mMapFd);
184 other.reset();
185 }
186 return *this;
187 }
188
189 void reset(base::unique_fd fd) = delete;
190
191 [[clang::reinitializes]] void reset(int fd = -1) {
192 mMapFd.reset(fd);
193 if ((fd >= 0) && isAtLeastKernelVersion(4, 14, 0)) {
194 if (bpfGetFdKeySize(mMapFd) != sizeof(Key)) abort();
195 if (bpfGetFdValueSize(mMapFd) != sizeof(Value)) abort();
196 if (bpfGetFdMapFlags(mMapFd) != 0) abort(); // TODO: fix for BpfMapRO
197 }
198 }
199
isValid()200 bool isValid() const { return mMapFd != -1; }
201
clear()202 base::Result<void> clear() {
203 while (true) {
204 auto key = getFirstKey();
205 if (!key.ok()) {
206 if (key.error().code() == ENOENT) return {}; // empty: success
207 return key.error(); // Anything else is an error
208 }
209 auto res = deleteValue(key.value());
210 if (!res.ok()) {
211 // Someone else could have deleted the key, so ignore ENOENT
212 if (res.error().code() == ENOENT) continue;
213 ALOGE("Failed to delete data %s", strerror(res.error().code()));
214 return res.error();
215 }
216 }
217 }
218
isEmpty()219 base::Result<bool> isEmpty() const {
220 auto key = getFirstKey();
221 if (!key.ok()) {
222 // Return error code ENOENT means the map is empty
223 if (key.error().code() == ENOENT) return true;
224 return key.error();
225 }
226 return false;
227 }
228
229 private:
230 base::unique_fd mMapFd;
231 };
232
233 template <class Key, class Value>
iterate(const std::function<base::Result<void> (const Key & key,const BpfMap<Key,Value> & map)> & filter)234 base::Result<void> BpfMap<Key, Value>::iterate(
235 const std::function<base::Result<void>(const Key& key, const BpfMap<Key, Value>& map)>&
236 filter) const {
237 base::Result<Key> curKey = getFirstKey();
238 while (curKey.ok()) {
239 const base::Result<Key>& nextKey = getNextKey(curKey.value());
240 base::Result<void> status = filter(curKey.value(), *this);
241 if (!status.ok()) return status;
242 curKey = nextKey;
243 }
244 if (curKey.error().code() == ENOENT) return {};
245 return curKey.error();
246 }
247
248 template <class Key, class Value>
iterateWithValue(const std::function<base::Result<void> (const Key & key,const Value & value,const BpfMap<Key,Value> & map)> & filter)249 base::Result<void> BpfMap<Key, Value>::iterateWithValue(
250 const std::function<base::Result<void>(const Key& key, const Value& value,
251 const BpfMap<Key, Value>& map)>& filter) const {
252 base::Result<Key> curKey = getFirstKey();
253 while (curKey.ok()) {
254 const base::Result<Key>& nextKey = getNextKey(curKey.value());
255 base::Result<Value> curValue = readValue(curKey.value());
256 if (!curValue.ok()) return curValue.error();
257 base::Result<void> status = filter(curKey.value(), curValue.value(), *this);
258 if (!status.ok()) return status;
259 curKey = nextKey;
260 }
261 if (curKey.error().code() == ENOENT) return {};
262 return curKey.error();
263 }
264
265 template <class Key, class Value>
iterate(const std::function<base::Result<void> (const Key & key,BpfMap<Key,Value> & map)> & filter)266 base::Result<void> BpfMap<Key, Value>::iterate(
267 const std::function<base::Result<void>(const Key& key, BpfMap<Key, Value>& map)>& filter) {
268 base::Result<Key> curKey = getFirstKey();
269 while (curKey.ok()) {
270 const base::Result<Key>& nextKey = getNextKey(curKey.value());
271 base::Result<void> status = filter(curKey.value(), *this);
272 if (!status.ok()) return status;
273 curKey = nextKey;
274 }
275 if (curKey.error().code() == ENOENT) return {};
276 return curKey.error();
277 }
278
279 template <class Key, class Value>
iterateWithValue(const std::function<base::Result<void> (const Key & key,const Value & value,BpfMap<Key,Value> & map)> & filter)280 base::Result<void> BpfMap<Key, Value>::iterateWithValue(
281 const std::function<base::Result<void>(const Key& key, const Value& value,
282 BpfMap<Key, Value>& map)>& filter) {
283 base::Result<Key> curKey = getFirstKey();
284 while (curKey.ok()) {
285 const base::Result<Key>& nextKey = getNextKey(curKey.value());
286 base::Result<Value> curValue = readValue(curKey.value());
287 if (!curValue.ok()) return curValue.error();
288 base::Result<void> status = filter(curKey.value(), curValue.value(), *this);
289 if (!status.ok()) return status;
290 curKey = nextKey;
291 }
292 if (curKey.error().code() == ENOENT) return {};
293 return curKey.error();
294 }
295
296 template <class Key, class Value>
297 class BpfMapRO : public BpfMap<Key, Value> {
298 public:
299 BpfMapRO<Key, Value>() {};
300
301 explicit BpfMapRO<Key, Value>(const char* pathname)
302 : BpfMap<Key, Value>(pathname, BPF_F_RDONLY) {}
303
304 // Function that tries to get map from a pinned path.
init(const char * path)305 [[clang::reinitializes]] base::Result<void> init(const char* path) {
306 return BpfMap<Key,Value>::init(path, mapRetrieveRO(path));
307 }
308 };
309
310 } // namespace bpf
311 } // namespace android
312