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Linux/kernel/bpf/arraymap.c

  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/err.h>
 14 #include <linux/slab.h>
 15 #include <linux/mm.h>
 16 #include <linux/filter.h>
 17 #include <linux/perf_event.h>
 18 
 19 static void bpf_array_free_percpu(struct bpf_array *array)
 20 {
 21         int i;
 22 
 23         for (i = 0; i < array->map.max_entries; i++)
 24                 free_percpu(array->pptrs[i]);
 25 }
 26 
 27 static int bpf_array_alloc_percpu(struct bpf_array *array)
 28 {
 29         void __percpu *ptr;
 30         int i;
 31 
 32         for (i = 0; i < array->map.max_entries; i++) {
 33                 ptr = __alloc_percpu_gfp(array->elem_size, 8,
 34                                          GFP_USER | __GFP_NOWARN);
 35                 if (!ptr) {
 36                         bpf_array_free_percpu(array);
 37                         return -ENOMEM;
 38                 }
 39                 array->pptrs[i] = ptr;
 40         }
 41 
 42         return 0;
 43 }
 44 
 45 /* Called from syscall */
 46 static struct bpf_map *array_map_alloc(union bpf_attr *attr)
 47 {
 48         bool percpu = attr->map_type == BPF_MAP_TYPE_PERCPU_ARRAY;
 49         struct bpf_array *array;
 50         u64 array_size;
 51         u32 elem_size;
 52 
 53         /* check sanity of attributes */
 54         if (attr->max_entries == 0 || attr->key_size != 4 ||
 55             attr->value_size == 0 || attr->map_flags)
 56                 return ERR_PTR(-EINVAL);
 57 
 58         if (attr->value_size > KMALLOC_MAX_SIZE)
 59                 /* if value_size is bigger, the user space won't be able to
 60                  * access the elements.
 61                  */
 62                 return ERR_PTR(-E2BIG);
 63 
 64         elem_size = round_up(attr->value_size, 8);
 65 
 66         array_size = sizeof(*array);
 67         if (percpu)
 68                 array_size += (u64) attr->max_entries * sizeof(void *);
 69         else
 70                 array_size += (u64) attr->max_entries * elem_size;
 71 
 72         /* make sure there is no u32 overflow later in round_up() */
 73         if (array_size >= U32_MAX - PAGE_SIZE)
 74                 return ERR_PTR(-ENOMEM);
 75 
 76         /* allocate all map elements and zero-initialize them */
 77         array = bpf_map_area_alloc(array_size);
 78         if (!array)
 79                 return ERR_PTR(-ENOMEM);
 80 
 81         /* copy mandatory map attributes */
 82         array->map.map_type = attr->map_type;
 83         array->map.key_size = attr->key_size;
 84         array->map.value_size = attr->value_size;
 85         array->map.max_entries = attr->max_entries;
 86         array->elem_size = elem_size;
 87 
 88         if (!percpu)
 89                 goto out;
 90 
 91         array_size += (u64) attr->max_entries * elem_size * num_possible_cpus();
 92 
 93         if (array_size >= U32_MAX - PAGE_SIZE ||
 94             elem_size > PCPU_MIN_UNIT_SIZE || bpf_array_alloc_percpu(array)) {
 95                 bpf_map_area_free(array);
 96                 return ERR_PTR(-ENOMEM);
 97         }
 98 out:
 99         array->map.pages = round_up(array_size, PAGE_SIZE) >> PAGE_SHIFT;
100 
101         return &array->map;
102 }
103 
104 /* Called from syscall or from eBPF program */
105 static void *array_map_lookup_elem(struct bpf_map *map, void *key)
106 {
107         struct bpf_array *array = container_of(map, struct bpf_array, map);
108         u32 index = *(u32 *)key;
109 
110         if (unlikely(index >= array->map.max_entries))
111                 return NULL;
112 
113         return array->value + array->elem_size * index;
114 }
115 
116 /* Called from eBPF program */
117 static void *percpu_array_map_lookup_elem(struct bpf_map *map, void *key)
118 {
119         struct bpf_array *array = container_of(map, struct bpf_array, map);
120         u32 index = *(u32 *)key;
121 
122         if (unlikely(index >= array->map.max_entries))
123                 return NULL;
124 
125         return this_cpu_ptr(array->pptrs[index]);
126 }
127 
128 int bpf_percpu_array_copy(struct bpf_map *map, void *key, void *value)
129 {
130         struct bpf_array *array = container_of(map, struct bpf_array, map);
131         u32 index = *(u32 *)key;
132         void __percpu *pptr;
133         int cpu, off = 0;
134         u32 size;
135 
136         if (unlikely(index >= array->map.max_entries))
137                 return -ENOENT;
138 
139         /* per_cpu areas are zero-filled and bpf programs can only
140          * access 'value_size' of them, so copying rounded areas
141          * will not leak any kernel data
142          */
143         size = round_up(map->value_size, 8);
144         rcu_read_lock();
145         pptr = array->pptrs[index];
146         for_each_possible_cpu(cpu) {
147                 bpf_long_memcpy(value + off, per_cpu_ptr(pptr, cpu), size);
148                 off += size;
149         }
150         rcu_read_unlock();
151         return 0;
152 }
153 
154 /* Called from syscall */
155 static int array_map_get_next_key(struct bpf_map *map, void *key, void *next_key)
156 {
157         struct bpf_array *array = container_of(map, struct bpf_array, map);
158         u32 index = *(u32 *)key;
159         u32 *next = (u32 *)next_key;
160 
161         if (index >= array->map.max_entries) {
162                 *next = 0;
163                 return 0;
164         }
165 
166         if (index == array->map.max_entries - 1)
167                 return -ENOENT;
168 
169         *next = index + 1;
170         return 0;
171 }
172 
173 /* Called from syscall or from eBPF program */
174 static int array_map_update_elem(struct bpf_map *map, void *key, void *value,
175                                  u64 map_flags)
176 {
177         struct bpf_array *array = container_of(map, struct bpf_array, map);
178         u32 index = *(u32 *)key;
179 
180         if (unlikely(map_flags > BPF_EXIST))
181                 /* unknown flags */
182                 return -EINVAL;
183 
184         if (unlikely(index >= array->map.max_entries))
185                 /* all elements were pre-allocated, cannot insert a new one */
186                 return -E2BIG;
187 
188         if (unlikely(map_flags == BPF_NOEXIST))
189                 /* all elements already exist */
190                 return -EEXIST;
191 
192         if (array->map.map_type == BPF_MAP_TYPE_PERCPU_ARRAY)
193                 memcpy(this_cpu_ptr(array->pptrs[index]),
194                        value, map->value_size);
195         else
196                 memcpy(array->value + array->elem_size * index,
197                        value, map->value_size);
198         return 0;
199 }
200 
201 int bpf_percpu_array_update(struct bpf_map *map, void *key, void *value,
202                             u64 map_flags)
203 {
204         struct bpf_array *array = container_of(map, struct bpf_array, map);
205         u32 index = *(u32 *)key;
206         void __percpu *pptr;
207         int cpu, off = 0;
208         u32 size;
209 
210         if (unlikely(map_flags > BPF_EXIST))
211                 /* unknown flags */
212                 return -EINVAL;
213 
214         if (unlikely(index >= array->map.max_entries))
215                 /* all elements were pre-allocated, cannot insert a new one */
216                 return -E2BIG;
217 
218         if (unlikely(map_flags == BPF_NOEXIST))
219                 /* all elements already exist */
220                 return -EEXIST;
221 
222         /* the user space will provide round_up(value_size, 8) bytes that
223          * will be copied into per-cpu area. bpf programs can only access
224          * value_size of it. During lookup the same extra bytes will be
225          * returned or zeros which were zero-filled by percpu_alloc,
226          * so no kernel data leaks possible
227          */
228         size = round_up(map->value_size, 8);
229         rcu_read_lock();
230         pptr = array->pptrs[index];
231         for_each_possible_cpu(cpu) {
232                 bpf_long_memcpy(per_cpu_ptr(pptr, cpu), value + off, size);
233                 off += size;
234         }
235         rcu_read_unlock();
236         return 0;
237 }
238 
239 /* Called from syscall or from eBPF program */
240 static int array_map_delete_elem(struct bpf_map *map, void *key)
241 {
242         return -EINVAL;
243 }
244 
245 /* Called when map->refcnt goes to zero, either from workqueue or from syscall */
246 static void array_map_free(struct bpf_map *map)
247 {
248         struct bpf_array *array = container_of(map, struct bpf_array, map);
249 
250         /* at this point bpf_prog->aux->refcnt == 0 and this map->refcnt == 0,
251          * so the programs (can be more than one that used this map) were
252          * disconnected from events. Wait for outstanding programs to complete
253          * and free the array
254          */
255         synchronize_rcu();
256 
257         if (array->map.map_type == BPF_MAP_TYPE_PERCPU_ARRAY)
258                 bpf_array_free_percpu(array);
259 
260         bpf_map_area_free(array);
261 }
262 
263 static const struct bpf_map_ops array_ops = {
264         .map_alloc = array_map_alloc,
265         .map_free = array_map_free,
266         .map_get_next_key = array_map_get_next_key,
267         .map_lookup_elem = array_map_lookup_elem,
268         .map_update_elem = array_map_update_elem,
269         .map_delete_elem = array_map_delete_elem,
270 };
271 
272 static struct bpf_map_type_list array_type __read_mostly = {
273         .ops = &array_ops,
274         .type = BPF_MAP_TYPE_ARRAY,
275 };
276 
277 static const struct bpf_map_ops percpu_array_ops = {
278         .map_alloc = array_map_alloc,
279         .map_free = array_map_free,
280         .map_get_next_key = array_map_get_next_key,
281         .map_lookup_elem = percpu_array_map_lookup_elem,
282         .map_update_elem = array_map_update_elem,
283         .map_delete_elem = array_map_delete_elem,
284 };
285 
286 static struct bpf_map_type_list percpu_array_type __read_mostly = {
287         .ops = &percpu_array_ops,
288         .type = BPF_MAP_TYPE_PERCPU_ARRAY,
289 };
290 
291 static int __init register_array_map(void)
292 {
293         bpf_register_map_type(&array_type);
294         bpf_register_map_type(&percpu_array_type);
295         return 0;
296 }
297 late_initcall(register_array_map);
298 
299 static struct bpf_map *fd_array_map_alloc(union bpf_attr *attr)
300 {
301         /* only file descriptors can be stored in this type of map */
302         if (attr->value_size != sizeof(u32))
303                 return ERR_PTR(-EINVAL);
304         return array_map_alloc(attr);
305 }
306 
307 static void fd_array_map_free(struct bpf_map *map)
308 {
309         struct bpf_array *array = container_of(map, struct bpf_array, map);
310         int i;
311 
312         synchronize_rcu();
313 
314         /* make sure it's empty */
315         for (i = 0; i < array->map.max_entries; i++)
316                 BUG_ON(array->ptrs[i] != NULL);
317 
318         bpf_map_area_free(array);
319 }
320 
321 static void *fd_array_map_lookup_elem(struct bpf_map *map, void *key)
322 {
323         return NULL;
324 }
325 
326 /* only called from syscall */
327 int bpf_fd_array_map_update_elem(struct bpf_map *map, struct file *map_file,
328                                  void *key, void *value, u64 map_flags)
329 {
330         struct bpf_array *array = container_of(map, struct bpf_array, map);
331         void *new_ptr, *old_ptr;
332         u32 index = *(u32 *)key, ufd;
333 
334         if (map_flags != BPF_ANY)
335                 return -EINVAL;
336 
337         if (index >= array->map.max_entries)
338                 return -E2BIG;
339 
340         ufd = *(u32 *)value;
341         new_ptr = map->ops->map_fd_get_ptr(map, map_file, ufd);
342         if (IS_ERR(new_ptr))
343                 return PTR_ERR(new_ptr);
344 
345         old_ptr = xchg(array->ptrs + index, new_ptr);
346         if (old_ptr)
347                 map->ops->map_fd_put_ptr(old_ptr);
348 
349         return 0;
350 }
351 
352 static int fd_array_map_delete_elem(struct bpf_map *map, void *key)
353 {
354         struct bpf_array *array = container_of(map, struct bpf_array, map);
355         void *old_ptr;
356         u32 index = *(u32 *)key;
357 
358         if (index >= array->map.max_entries)
359                 return -E2BIG;
360 
361         old_ptr = xchg(array->ptrs + index, NULL);
362         if (old_ptr) {
363                 map->ops->map_fd_put_ptr(old_ptr);
364                 return 0;
365         } else {
366                 return -ENOENT;
367         }
368 }
369 
370 static void *prog_fd_array_get_ptr(struct bpf_map *map,
371                                    struct file *map_file, int fd)
372 {
373         struct bpf_array *array = container_of(map, struct bpf_array, map);
374         struct bpf_prog *prog = bpf_prog_get(fd);
375 
376         if (IS_ERR(prog))
377                 return prog;
378 
379         if (!bpf_prog_array_compatible(array, prog)) {
380                 bpf_prog_put(prog);
381                 return ERR_PTR(-EINVAL);
382         }
383 
384         return prog;
385 }
386 
387 static void prog_fd_array_put_ptr(void *ptr)
388 {
389         bpf_prog_put(ptr);
390 }
391 
392 /* decrement refcnt of all bpf_progs that are stored in this map */
393 void bpf_fd_array_map_clear(struct bpf_map *map)
394 {
395         struct bpf_array *array = container_of(map, struct bpf_array, map);
396         int i;
397 
398         for (i = 0; i < array->map.max_entries; i++)
399                 fd_array_map_delete_elem(map, &i);
400 }
401 
402 static const struct bpf_map_ops prog_array_ops = {
403         .map_alloc = fd_array_map_alloc,
404         .map_free = fd_array_map_free,
405         .map_get_next_key = array_map_get_next_key,
406         .map_lookup_elem = fd_array_map_lookup_elem,
407         .map_delete_elem = fd_array_map_delete_elem,
408         .map_fd_get_ptr = prog_fd_array_get_ptr,
409         .map_fd_put_ptr = prog_fd_array_put_ptr,
410 };
411 
412 static struct bpf_map_type_list prog_array_type __read_mostly = {
413         .ops = &prog_array_ops,
414         .type = BPF_MAP_TYPE_PROG_ARRAY,
415 };
416 
417 static int __init register_prog_array_map(void)
418 {
419         bpf_register_map_type(&prog_array_type);
420         return 0;
421 }
422 late_initcall(register_prog_array_map);
423 
424 static struct bpf_event_entry *bpf_event_entry_gen(struct file *perf_file,
425                                                    struct file *map_file)
426 {
427         struct bpf_event_entry *ee;
428 
429         ee = kzalloc(sizeof(*ee), GFP_ATOMIC);
430         if (ee) {
431                 ee->event = perf_file->private_data;
432                 ee->perf_file = perf_file;
433                 ee->map_file = map_file;
434         }
435 
436         return ee;
437 }
438 
439 static void __bpf_event_entry_free(struct rcu_head *rcu)
440 {
441         struct bpf_event_entry *ee;
442 
443         ee = container_of(rcu, struct bpf_event_entry, rcu);
444         fput(ee->perf_file);
445         kfree(ee);
446 }
447 
448 static void bpf_event_entry_free_rcu(struct bpf_event_entry *ee)
449 {
450         call_rcu(&ee->rcu, __bpf_event_entry_free);
451 }
452 
453 static void *perf_event_fd_array_get_ptr(struct bpf_map *map,
454                                          struct file *map_file, int fd)
455 {
456         const struct perf_event_attr *attr;
457         struct bpf_event_entry *ee;
458         struct perf_event *event;
459         struct file *perf_file;
460 
461         perf_file = perf_event_get(fd);
462         if (IS_ERR(perf_file))
463                 return perf_file;
464 
465         event = perf_file->private_data;
466         ee = ERR_PTR(-EINVAL);
467 
468         attr = perf_event_attrs(event);
469         if (IS_ERR(attr) || attr->inherit)
470                 goto err_out;
471 
472         switch (attr->type) {
473         case PERF_TYPE_SOFTWARE:
474                 if (attr->config != PERF_COUNT_SW_BPF_OUTPUT)
475                         goto err_out;
476                 /* fall-through */
477         case PERF_TYPE_RAW:
478         case PERF_TYPE_HARDWARE:
479                 ee = bpf_event_entry_gen(perf_file, map_file);
480                 if (ee)
481                         return ee;
482                 ee = ERR_PTR(-ENOMEM);
483                 /* fall-through */
484         default:
485                 break;
486         }
487 
488 err_out:
489         fput(perf_file);
490         return ee;
491 }
492 
493 static void perf_event_fd_array_put_ptr(void *ptr)
494 {
495         bpf_event_entry_free_rcu(ptr);
496 }
497 
498 static void perf_event_fd_array_release(struct bpf_map *map,
499                                         struct file *map_file)
500 {
501         struct bpf_array *array = container_of(map, struct bpf_array, map);
502         struct bpf_event_entry *ee;
503         int i;
504 
505         rcu_read_lock();
506         for (i = 0; i < array->map.max_entries; i++) {
507                 ee = READ_ONCE(array->ptrs[i]);
508                 if (ee && ee->map_file == map_file)
509                         fd_array_map_delete_elem(map, &i);
510         }
511         rcu_read_unlock();
512 }
513 
514 static const struct bpf_map_ops perf_event_array_ops = {
515         .map_alloc = fd_array_map_alloc,
516         .map_free = fd_array_map_free,
517         .map_get_next_key = array_map_get_next_key,
518         .map_lookup_elem = fd_array_map_lookup_elem,
519         .map_delete_elem = fd_array_map_delete_elem,
520         .map_fd_get_ptr = perf_event_fd_array_get_ptr,
521         .map_fd_put_ptr = perf_event_fd_array_put_ptr,
522         .map_release = perf_event_fd_array_release,
523 };
524 
525 static struct bpf_map_type_list perf_event_array_type __read_mostly = {
526         .ops = &perf_event_array_ops,
527         .type = BPF_MAP_TYPE_PERF_EVENT_ARRAY,
528 };
529 
530 static int __init register_perf_event_array_map(void)
531 {
532         bpf_register_map_type(&perf_event_array_type);
533         return 0;
534 }
535 late_initcall(register_perf_event_array_map);
536 
537 #ifdef CONFIG_CGROUPS
538 static void *cgroup_fd_array_get_ptr(struct bpf_map *map,
539                                      struct file *map_file /* not used */,
540                                      int fd)
541 {
542         return cgroup_get_from_fd(fd);
543 }
544 
545 static void cgroup_fd_array_put_ptr(void *ptr)
546 {
547         /* cgroup_put free cgrp after a rcu grace period */
548         cgroup_put(ptr);
549 }
550 
551 static void cgroup_fd_array_free(struct bpf_map *map)
552 {
553         bpf_fd_array_map_clear(map);
554         fd_array_map_free(map);
555 }
556 
557 static const struct bpf_map_ops cgroup_array_ops = {
558         .map_alloc = fd_array_map_alloc,
559         .map_free = cgroup_fd_array_free,
560         .map_get_next_key = array_map_get_next_key,
561         .map_lookup_elem = fd_array_map_lookup_elem,
562         .map_delete_elem = fd_array_map_delete_elem,
563         .map_fd_get_ptr = cgroup_fd_array_get_ptr,
564         .map_fd_put_ptr = cgroup_fd_array_put_ptr,
565 };
566 
567 static struct bpf_map_type_list cgroup_array_type __read_mostly = {
568         .ops = &cgroup_array_ops,
569         .type = BPF_MAP_TYPE_CGROUP_ARRAY,
570 };
571 
572 static int __init register_cgroup_array_map(void)
573 {
574         bpf_register_map_type(&cgroup_array_type);
575         return 0;
576 }
577 late_initcall(register_cgroup_array_map);
578 #endif
579 

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