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 int map_fd = mapRetrieve(pathname, flags);
53 if (map_fd >= 0) mMapFd.reset(map_fd);
54 }
55
56 public:
57 explicit BpfMap<Key, Value>(const char* pathname) : BpfMap<Key, Value>(pathname, 0) {}
58
59 BpfMap<Key, Value>(bpf_map_type map_type, uint32_t max_entries, uint32_t map_flags = 0) {
60 int map_fd = createMap(map_type, sizeof(Key), sizeof(Value), max_entries, map_flags);
61 if (map_fd >= 0) mMapFd.reset(map_fd);
62 }
63
getFirstKey()64 base::Result<Key> getFirstKey() const {
65 Key firstKey;
66 if (getFirstMapKey(mMapFd, &firstKey)) {
67 return ErrnoErrorf("Get firstKey map {} failed", mMapFd.get());
68 }
69 return firstKey;
70 }
71
getNextKey(const Key & key)72 base::Result<Key> getNextKey(const Key& key) const {
73 Key nextKey;
74 if (getNextMapKey(mMapFd, &key, &nextKey)) {
75 return ErrnoErrorf("Get next key of map {} failed", mMapFd.get());
76 }
77 return nextKey;
78 }
79
writeValue(const Key & key,const Value & value,uint64_t flags)80 base::Result<void> writeValue(const Key& key, const Value& value, uint64_t flags) {
81 if (writeToMapEntry(mMapFd, &key, &value, flags)) {
82 return ErrnoErrorf("Write to map {} failed", mMapFd.get());
83 }
84 return {};
85 }
86
readValue(const Key key)87 base::Result<Value> readValue(const Key key) const {
88 Value value;
89 if (findMapEntry(mMapFd, &key, &value)) {
90 return ErrnoErrorf("Read value of map {} failed", mMapFd.get());
91 }
92 return value;
93 }
94
deleteValue(const Key & key)95 base::Result<void> deleteValue(const Key& key) {
96 if (deleteMapEntry(mMapFd, &key)) {
97 return ErrnoErrorf("Delete entry from map {} failed", mMapFd.get());
98 }
99 return {};
100 }
101
102 // Function that tries to get map from a pinned path.
103 base::Result<void> init(const char* path);
104
105 // Iterate through the map and handle each key retrieved based on the filter
106 // without modification of map content.
107 base::Result<void> iterate(
108 const std::function<base::Result<void>(const Key& key, const BpfMap<Key, Value>& map)>&
109 filter) const;
110
111 // Iterate through the map and get each <key, value> pair, handle each <key,
112 // value> pair based on the filter without modification of map content.
113 base::Result<void> iterateWithValue(
114 const std::function<base::Result<void>(const Key& key, const Value& value,
115 const BpfMap<Key, Value>& map)>& filter) const;
116
117 // Iterate through the map and handle each key retrieved based on the filter
118 base::Result<void> iterate(
119 const std::function<base::Result<void>(const Key& key, BpfMap<Key, Value>& map)>&
120 filter);
121
122 // Iterate through the map and get each <key, value> pair, handle each <key,
123 // value> pair based on the filter.
124 base::Result<void> iterateWithValue(
125 const std::function<base::Result<void>(const Key& key, const Value& value,
126 BpfMap<Key, Value>& map)>& filter);
127
getMap()128 const base::unique_fd& getMap() const { return mMapFd; };
129
130 // Copy assignment operator
131 BpfMap<Key, Value>& operator=(const BpfMap<Key, Value>& other) {
132 if (this != &other) mMapFd.reset(fcntl(other.mMapFd.get(), F_DUPFD_CLOEXEC, 0));
133 return *this;
134 }
135
136 // Move assignment operator
137 BpfMap<Key, Value>& operator=(BpfMap<Key, Value>&& other) noexcept {
138 mMapFd = std::move(other.mMapFd);
139 other.reset(-1);
140 return *this;
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