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 #ifndef BPF_BPFMAP_H
18 #define BPF_BPFMAP_H
19
20 #include <linux/bpf.h>
21
22 #include <android-base/result.h>
23 #include <android-base/stringprintf.h>
24 #include <android-base/unique_fd.h>
25 #include <utils/Log.h>
26 #include "bpf/BpfUtils.h"
27
28 namespace android {
29 namespace bpf {
30
31 // This is a class wrapper for eBPF maps. The eBPF map is a special in-kernel
32 // data structure that stores data in <Key, Value> pairs. It can be read/write
33 // from userspace by passing syscalls with the map file descriptor. This class
34 // is used to generalize the procedure of interacting with eBPF maps and hide
35 // the implementation detail from other process. Besides the basic syscalls
36 // wrapper, it also provides some useful helper functions as well as an iterator
37 // nested class to iterate the map more easily.
38 //
39 // NOTE: A kernel eBPF map may be accessed by both kernel and userspace
40 // processes at the same time. Or if the map is pinned as a virtual file, it can
41 // be obtained by multiple eBPF map class object and accessed concurrently.
42 // Though the map class object and the underlying kernel map are thread safe, it
43 // is not safe to iterate over a map while another thread or process is deleting
44 // from it. In this case the iteration can return duplicate entries.
45 template <class Key, class Value>
46 class BpfMap {
47 public:
48 BpfMap<Key, Value>() {};
49
50 protected:
51 // flag must be within BPF_OBJ_FLAG_MASK, ie. 0, BPF_F_RDONLY, BPF_F_WRONLY
52 BpfMap<Key, Value>(const char* pathname, uint32_t flags) {
53 int map_fd = mapRetrieve(pathname, flags);
54 if (map_fd >= 0) mMapFd.reset(map_fd);
55 }
56
57 public:
58 explicit BpfMap<Key, Value>(const char* pathname) : BpfMap<Key, Value>(pathname, 0) {}
59
60 BpfMap<Key, Value>(bpf_map_type map_type, uint32_t max_entries, uint32_t map_flags = 0) {
61 int map_fd = createMap(map_type, sizeof(Key), sizeof(Value), max_entries, map_flags);
62 if (map_fd >= 0) mMapFd.reset(map_fd);
63 }
64
getFirstKey()65 base::Result<Key> getFirstKey() const {
66 Key firstKey;
67 if (getFirstMapKey(mMapFd, &firstKey)) {
68 return ErrnoErrorf("Get firstKey map {} failed", mMapFd.get());
69 }
70 return firstKey;
71 }
72
getNextKey(const Key & key)73 base::Result<Key> getNextKey(const Key& key) const {
74 Key nextKey;
75 if (getNextMapKey(mMapFd, &key, &nextKey)) {
76 return ErrnoErrorf("Get next key of map {} failed", mMapFd.get());
77 }
78 return nextKey;
79 }
80
writeValue(const Key & key,const Value & value,uint64_t flags)81 base::Result<void> writeValue(const Key& key, const Value& value, uint64_t flags) {
82 if (writeToMapEntry(mMapFd, &key, &value, flags)) {
83 return ErrnoErrorf("Write to map {} failed", mMapFd.get());
84 }
85 return {};
86 }
87
readValue(const Key key)88 base::Result<Value> readValue(const Key key) const {
89 Value value;
90 if (findMapEntry(mMapFd, &key, &value)) {
91 return ErrnoErrorf("Read value of map {} failed", mMapFd.get());
92 }
93 return value;
94 }
95
deleteValue(const Key & key)96 base::Result<void> deleteValue(const Key& key) {
97 if (deleteMapEntry(mMapFd, &key)) {
98 return ErrnoErrorf("Delete entry from map {} failed", mMapFd.get());
99 }
100 return {};
101 }
102
103 // Function that tries to get map from a pinned path.
104 base::Result<void> init(const char* path);
105
106 // Iterate through the map and handle each key retrieved based on the filter
107 // without modification of map content.
108 base::Result<void> iterate(
109 const std::function<base::Result<void>(const Key& key, const BpfMap<Key, Value>& map)>&
110 filter) const;
111
112 // Iterate through the map and get each <key, value> pair, handle each <key,
113 // value> pair based on the filter without modification of map content.
114 base::Result<void> iterateWithValue(
115 const std::function<base::Result<void>(const Key& key, const Value& value,
116 const BpfMap<Key, Value>& map)>& filter) const;
117
118 // Iterate through the map and handle each key retrieved based on the filter
119 base::Result<void> iterate(
120 const std::function<base::Result<void>(const Key& key, BpfMap<Key, Value>& map)>&
121 filter);
122
123 // Iterate through the map and get each <key, value> pair, handle each <key,
124 // value> pair based on the filter.
125 base::Result<void> iterateWithValue(
126 const std::function<base::Result<void>(const Key& key, const Value& value,
127 BpfMap<Key, Value>& map)>& filter);
128
getMap()129 const base::unique_fd& getMap() const { return mMapFd; };
130
131 // Copy assignment operator
132 BpfMap<Key, Value>& operator=(const BpfMap<Key, Value>& other) {
133 if (this != &other) mMapFd.reset(fcntl(other.mMapFd.get(), F_DUPFD_CLOEXEC, 0));
134 return *this;
135 }
136
137 // Move constructor
138 void operator=(BpfMap<Key, Value>&& other) noexcept {
139 mMapFd = std::move(other.mMapFd);
140 other.reset(-1);
141 }
142
143 void reset(base::unique_fd fd) = delete;
144
reset(int fd)145 void reset(int fd) { mMapFd.reset(fd); }
146
isValid()147 bool isValid() const { return mMapFd != -1; }
148
clear()149 base::Result<void> clear() {
150 while (true) {
151 auto key = getFirstKey();
152 if (!key.ok()) {
153 if (key.error().code() == ENOENT) return {}; // empty: success
154 return key.error(); // Anything else is an error
155 }
156 auto res = deleteValue(key.value());
157 if (!res.ok()) {
158 // Someone else could have deleted the key, so ignore ENOENT
159 if (res.error().code() == ENOENT) continue;
160 ALOGE("Failed to delete data %s", strerror(res.error().code()));
161 return res.error();
162 }
163 }
164 }
165
isEmpty()166 base::Result<bool> isEmpty() const {
167 auto key = getFirstKey();
168 if (!key.ok()) {
169 // Return error code ENOENT means the map is empty
170 if (key.error().code() == ENOENT) return true;
171 return key.error();
172 }
173 return false;
174 }
175
176 private:
177 base::unique_fd mMapFd;
178 };
179
180 template <class Key, class Value>
init(const char * path)181 base::Result<void> BpfMap<Key, Value>::init(const char* path) {
182 mMapFd = base::unique_fd(mapRetrieveRW(path));
183 if (mMapFd == -1) {
184 return ErrnoErrorf("Pinned map not accessible or does not exist: ({})", path);
185 }
186 return {};
187 }
188
189 template <class Key, class Value>
iterate(const std::function<base::Result<void> (const Key & key,const BpfMap<Key,Value> & map)> & filter)190 base::Result<void> BpfMap<Key, Value>::iterate(
191 const std::function<base::Result<void>(const Key& key, const BpfMap<Key, Value>& map)>&
192 filter) const {
193 base::Result<Key> curKey = getFirstKey();
194 while (curKey.ok()) {
195 const base::Result<Key>& nextKey = getNextKey(curKey.value());
196 base::Result<void> status = filter(curKey.value(), *this);
197 if (!status.ok()) return status;
198 curKey = nextKey;
199 }
200 if (curKey.error().code() == ENOENT) return {};
201 return curKey.error();
202 }
203
204 template <class Key, class Value>
iterateWithValue(const std::function<base::Result<void> (const Key & key,const Value & value,const BpfMap<Key,Value> & map)> & filter)205 base::Result<void> BpfMap<Key, Value>::iterateWithValue(
206 const std::function<base::Result<void>(const Key& key, const Value& value,
207 const BpfMap<Key, Value>& map)>& filter) const {
208 base::Result<Key> curKey = getFirstKey();
209 while (curKey.ok()) {
210 const base::Result<Key>& nextKey = getNextKey(curKey.value());
211 base::Result<Value> curValue = readValue(curKey.value());
212 if (!curValue.ok()) return curValue.error();
213 base::Result<void> status = filter(curKey.value(), curValue.value(), *this);
214 if (!status.ok()) return status;
215 curKey = nextKey;
216 }
217 if (curKey.error().code() == ENOENT) return {};
218 return curKey.error();
219 }
220
221 template <class Key, class Value>
iterate(const std::function<base::Result<void> (const Key & key,BpfMap<Key,Value> & map)> & filter)222 base::Result<void> BpfMap<Key, Value>::iterate(
223 const std::function<base::Result<void>(const Key& key, BpfMap<Key, Value>& map)>& filter) {
224 base::Result<Key> curKey = getFirstKey();
225 while (curKey.ok()) {
226 const base::Result<Key>& nextKey = getNextKey(curKey.value());
227 base::Result<void> status = filter(curKey.value(), *this);
228 if (!status.ok()) return status;
229 curKey = nextKey;
230 }
231 if (curKey.error().code() == ENOENT) return {};
232 return curKey.error();
233 }
234
235 template <class Key, class Value>
iterateWithValue(const std::function<base::Result<void> (const Key & key,const Value & value,BpfMap<Key,Value> & map)> & filter)236 base::Result<void> BpfMap<Key, Value>::iterateWithValue(
237 const std::function<base::Result<void>(const Key& key, const Value& value,
238 BpfMap<Key, Value>& map)>& filter) {
239 base::Result<Key> curKey = getFirstKey();
240 while (curKey.ok()) {
241 const base::Result<Key>& nextKey = getNextKey(curKey.value());
242 base::Result<Value> curValue = readValue(curKey.value());
243 if (!curValue.ok()) return curValue.error();
244 base::Result<void> status = filter(curKey.value(), curValue.value(), *this);
245 if (!status.ok()) return status;
246 curKey = nextKey;
247 }
248 if (curKey.error().code() == ENOENT) return {};
249 return curKey.error();
250 }
251
252 template <class Key, class Value>
253 class BpfMapRO : public BpfMap<Key, Value> {
254 public:
255 explicit BpfMapRO<Key, Value>(const char* pathname)
256 : BpfMap<Key, Value>(pathname, BPF_F_RDONLY) {}
257 };
258
259 } // namespace bpf
260 } // namespace android
261
262 #endif
263