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0f8e4bd8 AS |
1 | /* Copyright (c) 2011-2014 PLUMgrid, http://plumgrid.com |
2 | * | |
3 | * This program is free software; you can redistribute it and/or | |
4 | * modify it under the terms of version 2 of the GNU General Public | |
5 | * License as published by the Free Software Foundation. | |
6 | * | |
7 | * This program is distributed in the hope that it will be useful, but | |
8 | * WITHOUT ANY WARRANTY; without even the implied warranty of | |
9 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
10 | * General Public License for more details. | |
11 | */ | |
12 | #include <linux/bpf.h> | |
13 | #include <linux/jhash.h> | |
14 | #include <linux/filter.h> | |
15 | #include <linux/vmalloc.h> | |
16 | ||
17 | struct bpf_htab { | |
18 | struct bpf_map map; | |
19 | struct hlist_head *buckets; | |
20 | spinlock_t lock; | |
21 | u32 count; /* number of elements in this hashtable */ | |
22 | u32 n_buckets; /* number of hash buckets */ | |
23 | u32 elem_size; /* size of each element in bytes */ | |
24 | }; | |
25 | ||
26 | /* each htab element is struct htab_elem + key + value */ | |
27 | struct htab_elem { | |
28 | struct hlist_node hash_node; | |
29 | struct rcu_head rcu; | |
30 | u32 hash; | |
31 | char key[0] __aligned(8); | |
32 | }; | |
33 | ||
34 | /* Called from syscall */ | |
35 | static struct bpf_map *htab_map_alloc(union bpf_attr *attr) | |
36 | { | |
37 | struct bpf_htab *htab; | |
38 | int err, i; | |
39 | ||
40 | htab = kzalloc(sizeof(*htab), GFP_USER); | |
41 | if (!htab) | |
42 | return ERR_PTR(-ENOMEM); | |
43 | ||
44 | /* mandatory map attributes */ | |
45 | htab->map.key_size = attr->key_size; | |
46 | htab->map.value_size = attr->value_size; | |
47 | htab->map.max_entries = attr->max_entries; | |
48 | ||
49 | /* check sanity of attributes. | |
50 | * value_size == 0 may be allowed in the future to use map as a set | |
51 | */ | |
52 | err = -EINVAL; | |
53 | if (htab->map.max_entries == 0 || htab->map.key_size == 0 || | |
54 | htab->map.value_size == 0) | |
55 | goto free_htab; | |
56 | ||
57 | /* hash table size must be power of 2 */ | |
58 | htab->n_buckets = roundup_pow_of_two(htab->map.max_entries); | |
59 | ||
60 | err = -E2BIG; | |
61 | if (htab->map.key_size > MAX_BPF_STACK) | |
62 | /* eBPF programs initialize keys on stack, so they cannot be | |
63 | * larger than max stack size | |
64 | */ | |
65 | goto free_htab; | |
66 | ||
67 | err = -ENOMEM; | |
daaf427c AS |
68 | /* prevent zero size kmalloc and check for u32 overflow */ |
69 | if (htab->n_buckets == 0 || | |
70 | htab->n_buckets > U32_MAX / sizeof(struct hlist_head)) | |
71 | goto free_htab; | |
72 | ||
0f8e4bd8 AS |
73 | htab->buckets = kmalloc_array(htab->n_buckets, sizeof(struct hlist_head), |
74 | GFP_USER | __GFP_NOWARN); | |
75 | ||
76 | if (!htab->buckets) { | |
77 | htab->buckets = vmalloc(htab->n_buckets * sizeof(struct hlist_head)); | |
78 | if (!htab->buckets) | |
79 | goto free_htab; | |
80 | } | |
81 | ||
82 | for (i = 0; i < htab->n_buckets; i++) | |
83 | INIT_HLIST_HEAD(&htab->buckets[i]); | |
84 | ||
85 | spin_lock_init(&htab->lock); | |
86 | htab->count = 0; | |
87 | ||
88 | htab->elem_size = sizeof(struct htab_elem) + | |
89 | round_up(htab->map.key_size, 8) + | |
90 | htab->map.value_size; | |
91 | return &htab->map; | |
92 | ||
93 | free_htab: | |
94 | kfree(htab); | |
95 | return ERR_PTR(err); | |
96 | } | |
97 | ||
98 | static inline u32 htab_map_hash(const void *key, u32 key_len) | |
99 | { | |
100 | return jhash(key, key_len, 0); | |
101 | } | |
102 | ||
103 | static inline struct hlist_head *select_bucket(struct bpf_htab *htab, u32 hash) | |
104 | { | |
105 | return &htab->buckets[hash & (htab->n_buckets - 1)]; | |
106 | } | |
107 | ||
108 | static struct htab_elem *lookup_elem_raw(struct hlist_head *head, u32 hash, | |
109 | void *key, u32 key_size) | |
110 | { | |
111 | struct htab_elem *l; | |
112 | ||
113 | hlist_for_each_entry_rcu(l, head, hash_node) | |
114 | if (l->hash == hash && !memcmp(&l->key, key, key_size)) | |
115 | return l; | |
116 | ||
117 | return NULL; | |
118 | } | |
119 | ||
120 | /* Called from syscall or from eBPF program */ | |
121 | static void *htab_map_lookup_elem(struct bpf_map *map, void *key) | |
122 | { | |
123 | struct bpf_htab *htab = container_of(map, struct bpf_htab, map); | |
124 | struct hlist_head *head; | |
125 | struct htab_elem *l; | |
126 | u32 hash, key_size; | |
127 | ||
128 | /* Must be called with rcu_read_lock. */ | |
129 | WARN_ON_ONCE(!rcu_read_lock_held()); | |
130 | ||
131 | key_size = map->key_size; | |
132 | ||
133 | hash = htab_map_hash(key, key_size); | |
134 | ||
135 | head = select_bucket(htab, hash); | |
136 | ||
137 | l = lookup_elem_raw(head, hash, key, key_size); | |
138 | ||
139 | if (l) | |
140 | return l->key + round_up(map->key_size, 8); | |
141 | ||
142 | return NULL; | |
143 | } | |
144 | ||
145 | /* Called from syscall */ | |
146 | static int htab_map_get_next_key(struct bpf_map *map, void *key, void *next_key) | |
147 | { | |
148 | struct bpf_htab *htab = container_of(map, struct bpf_htab, map); | |
149 | struct hlist_head *head; | |
150 | struct htab_elem *l, *next_l; | |
151 | u32 hash, key_size; | |
152 | int i; | |
153 | ||
154 | WARN_ON_ONCE(!rcu_read_lock_held()); | |
155 | ||
156 | key_size = map->key_size; | |
157 | ||
158 | hash = htab_map_hash(key, key_size); | |
159 | ||
160 | head = select_bucket(htab, hash); | |
161 | ||
162 | /* lookup the key */ | |
163 | l = lookup_elem_raw(head, hash, key, key_size); | |
164 | ||
165 | if (!l) { | |
166 | i = 0; | |
167 | goto find_first_elem; | |
168 | } | |
169 | ||
170 | /* key was found, get next key in the same bucket */ | |
171 | next_l = hlist_entry_safe(rcu_dereference_raw(hlist_next_rcu(&l->hash_node)), | |
172 | struct htab_elem, hash_node); | |
173 | ||
174 | if (next_l) { | |
175 | /* if next elem in this hash list is non-zero, just return it */ | |
176 | memcpy(next_key, next_l->key, key_size); | |
177 | return 0; | |
178 | } | |
179 | ||
180 | /* no more elements in this hash list, go to the next bucket */ | |
181 | i = hash & (htab->n_buckets - 1); | |
182 | i++; | |
183 | ||
184 | find_first_elem: | |
185 | /* iterate over buckets */ | |
186 | for (; i < htab->n_buckets; i++) { | |
187 | head = select_bucket(htab, i); | |
188 | ||
189 | /* pick first element in the bucket */ | |
190 | next_l = hlist_entry_safe(rcu_dereference_raw(hlist_first_rcu(head)), | |
191 | struct htab_elem, hash_node); | |
192 | if (next_l) { | |
193 | /* if it's not empty, just return it */ | |
194 | memcpy(next_key, next_l->key, key_size); | |
195 | return 0; | |
196 | } | |
197 | } | |
198 | ||
199 | /* itereated over all buckets and all elements */ | |
200 | return -ENOENT; | |
201 | } | |
202 | ||
203 | /* Called from syscall or from eBPF program */ | |
204 | static int htab_map_update_elem(struct bpf_map *map, void *key, void *value, | |
205 | u64 map_flags) | |
206 | { | |
207 | struct bpf_htab *htab = container_of(map, struct bpf_htab, map); | |
208 | struct htab_elem *l_new, *l_old; | |
209 | struct hlist_head *head; | |
210 | unsigned long flags; | |
211 | u32 key_size; | |
212 | int ret; | |
213 | ||
214 | if (map_flags > BPF_EXIST) | |
215 | /* unknown flags */ | |
216 | return -EINVAL; | |
217 | ||
218 | WARN_ON_ONCE(!rcu_read_lock_held()); | |
219 | ||
220 | /* allocate new element outside of lock */ | |
221 | l_new = kmalloc(htab->elem_size, GFP_ATOMIC); | |
222 | if (!l_new) | |
223 | return -ENOMEM; | |
224 | ||
225 | key_size = map->key_size; | |
226 | ||
227 | memcpy(l_new->key, key, key_size); | |
228 | memcpy(l_new->key + round_up(key_size, 8), value, map->value_size); | |
229 | ||
230 | l_new->hash = htab_map_hash(l_new->key, key_size); | |
231 | ||
232 | /* bpf_map_update_elem() can be called in_irq() */ | |
233 | spin_lock_irqsave(&htab->lock, flags); | |
234 | ||
235 | head = select_bucket(htab, l_new->hash); | |
236 | ||
237 | l_old = lookup_elem_raw(head, l_new->hash, key, key_size); | |
238 | ||
239 | if (!l_old && unlikely(htab->count >= map->max_entries)) { | |
240 | /* if elem with this 'key' doesn't exist and we've reached | |
241 | * max_entries limit, fail insertion of new elem | |
242 | */ | |
243 | ret = -E2BIG; | |
244 | goto err; | |
245 | } | |
246 | ||
247 | if (l_old && map_flags == BPF_NOEXIST) { | |
248 | /* elem already exists */ | |
249 | ret = -EEXIST; | |
250 | goto err; | |
251 | } | |
252 | ||
253 | if (!l_old && map_flags == BPF_EXIST) { | |
254 | /* elem doesn't exist, cannot update it */ | |
255 | ret = -ENOENT; | |
256 | goto err; | |
257 | } | |
258 | ||
259 | /* add new element to the head of the list, so that concurrent | |
260 | * search will find it before old elem | |
261 | */ | |
262 | hlist_add_head_rcu(&l_new->hash_node, head); | |
263 | if (l_old) { | |
264 | hlist_del_rcu(&l_old->hash_node); | |
265 | kfree_rcu(l_old, rcu); | |
266 | } else { | |
267 | htab->count++; | |
268 | } | |
269 | spin_unlock_irqrestore(&htab->lock, flags); | |
270 | ||
271 | return 0; | |
272 | err: | |
273 | spin_unlock_irqrestore(&htab->lock, flags); | |
274 | kfree(l_new); | |
275 | return ret; | |
276 | } | |
277 | ||
278 | /* Called from syscall or from eBPF program */ | |
279 | static int htab_map_delete_elem(struct bpf_map *map, void *key) | |
280 | { | |
281 | struct bpf_htab *htab = container_of(map, struct bpf_htab, map); | |
282 | struct hlist_head *head; | |
283 | struct htab_elem *l; | |
284 | unsigned long flags; | |
285 | u32 hash, key_size; | |
286 | int ret = -ENOENT; | |
287 | ||
288 | WARN_ON_ONCE(!rcu_read_lock_held()); | |
289 | ||
290 | key_size = map->key_size; | |
291 | ||
292 | hash = htab_map_hash(key, key_size); | |
293 | ||
294 | spin_lock_irqsave(&htab->lock, flags); | |
295 | ||
296 | head = select_bucket(htab, hash); | |
297 | ||
298 | l = lookup_elem_raw(head, hash, key, key_size); | |
299 | ||
300 | if (l) { | |
301 | hlist_del_rcu(&l->hash_node); | |
302 | htab->count--; | |
303 | kfree_rcu(l, rcu); | |
304 | ret = 0; | |
305 | } | |
306 | ||
307 | spin_unlock_irqrestore(&htab->lock, flags); | |
308 | return ret; | |
309 | } | |
310 | ||
311 | static void delete_all_elements(struct bpf_htab *htab) | |
312 | { | |
313 | int i; | |
314 | ||
315 | for (i = 0; i < htab->n_buckets; i++) { | |
316 | struct hlist_head *head = select_bucket(htab, i); | |
317 | struct hlist_node *n; | |
318 | struct htab_elem *l; | |
319 | ||
320 | hlist_for_each_entry_safe(l, n, head, hash_node) { | |
321 | hlist_del_rcu(&l->hash_node); | |
322 | htab->count--; | |
323 | kfree(l); | |
324 | } | |
325 | } | |
326 | } | |
327 | ||
328 | /* Called when map->refcnt goes to zero, either from workqueue or from syscall */ | |
329 | static void htab_map_free(struct bpf_map *map) | |
330 | { | |
331 | struct bpf_htab *htab = container_of(map, struct bpf_htab, map); | |
332 | ||
333 | /* at this point bpf_prog->aux->refcnt == 0 and this map->refcnt == 0, | |
334 | * so the programs (can be more than one that used this map) were | |
335 | * disconnected from events. Wait for outstanding critical sections in | |
336 | * these programs to complete | |
337 | */ | |
338 | synchronize_rcu(); | |
339 | ||
340 | /* some of kfree_rcu() callbacks for elements of this map may not have | |
341 | * executed. It's ok. Proceed to free residual elements and map itself | |
342 | */ | |
343 | delete_all_elements(htab); | |
344 | kvfree(htab->buckets); | |
345 | kfree(htab); | |
346 | } | |
347 | ||
a2c83fff | 348 | static const struct bpf_map_ops htab_ops = { |
0f8e4bd8 AS |
349 | .map_alloc = htab_map_alloc, |
350 | .map_free = htab_map_free, | |
351 | .map_get_next_key = htab_map_get_next_key, | |
352 | .map_lookup_elem = htab_map_lookup_elem, | |
353 | .map_update_elem = htab_map_update_elem, | |
354 | .map_delete_elem = htab_map_delete_elem, | |
355 | }; | |
356 | ||
a2c83fff | 357 | static struct bpf_map_type_list htab_type __read_mostly = { |
0f8e4bd8 AS |
358 | .ops = &htab_ops, |
359 | .type = BPF_MAP_TYPE_HASH, | |
360 | }; | |
361 | ||
362 | static int __init register_htab_map(void) | |
363 | { | |
a2c83fff | 364 | bpf_register_map_type(&htab_type); |
0f8e4bd8 AS |
365 | return 0; |
366 | } | |
367 | late_initcall(register_htab_map); |