projects/linux·blob v5.13 · refs

475 lines · 12.7 KiB

1#include <linux/bpf.h>
2#include <linux/btf.h>
3#include <linux/err.h>
4#include <linux/irq_work.h>
5#include <linux/slab.h>
6#include <linux/filter.h>
7#include <linux/mm.h>
8#include <linux/vmalloc.h>
9#include <linux/wait.h>
10#include <linux/poll.h>
11#include <uapi/linux/btf.h>
12
13#define RINGBUF_CREATE_FLAG_MASK (BPF_F_NUMA_NODE)
14
15/* non-mmap()'able part of bpf_ringbuf (everything up to consumer page) */
16#define RINGBUF_PGOFF \
17 (offsetof(struct bpf_ringbuf, consumer_pos) >> PAGE_SHIFT)
18/* consumer page and producer page */
19#define RINGBUF_POS_PAGES 2
20
21#define RINGBUF_MAX_RECORD_SZ (UINT_MAX/4)
22
23/* Maximum size of ring buffer area is limited by 32-bit page offset within
24 * record header, counted in pages. Reserve 8 bits for extensibility, and take
25 * into account few extra pages for consumer/producer pages and
26 * non-mmap()'able parts. This gives 64GB limit, which seems plenty for single
27 * ring buffer.
28 */
29#define RINGBUF_MAX_DATA_SZ \
30 (((1ULL << 24) - RINGBUF_POS_PAGES - RINGBUF_PGOFF) * PAGE_SIZE)
31
32struct bpf_ringbuf {
33 wait_queue_head_t waitq;
34 struct irq_work work;
35 u64 mask;
36 struct page **pages;
37 int nr_pages;
38 spinlock_t spinlock ____cacheline_aligned_in_smp;
39 /* Consumer and producer counters are put into separate pages to allow
40 * mapping consumer page as r/w, but restrict producer page to r/o.
41 * This protects producer position from being modified by user-space
42 * application and ruining in-kernel position tracking.
43 */
44 unsigned long consumer_pos __aligned(PAGE_SIZE);
45 unsigned long producer_pos __aligned(PAGE_SIZE);
46 char data[] __aligned(PAGE_SIZE);
47};
48
49struct bpf_ringbuf_map {
50 struct bpf_map map;
51 struct bpf_ringbuf *rb;
52};
53
54/* 8-byte ring buffer record header structure */
55struct bpf_ringbuf_hdr {
56 u32 len;
57 u32 pg_off;
58};
59
60static struct bpf_ringbuf *bpf_ringbuf_area_alloc(size_t data_sz, int numa_node)
61{
62 const gfp_t flags = GFP_KERNEL_ACCOUNT | __GFP_RETRY_MAYFAIL |
63 __GFP_NOWARN | __GFP_ZERO;
64 int nr_meta_pages = RINGBUF_PGOFF + RINGBUF_POS_PAGES;
65 int nr_data_pages = data_sz >> PAGE_SHIFT;
66 int nr_pages = nr_meta_pages + nr_data_pages;
67 struct page **pages, *page;
68 struct bpf_ringbuf *rb;
69 size_t array_size;
70 int i;
71
72 /* Each data page is mapped twice to allow "virtual"
73 * continuous read of samples wrapping around the end of ring
74 * buffer area:
75 * ------------------------------------------------------
76 * | meta pages | real data pages | same data pages |
77 * ------------------------------------------------------
78 * | | 1 2 3 4 5 6 7 8 9 | 1 2 3 4 5 6 7 8 9 |
79 * ------------------------------------------------------
80 * | | TA DA | TA DA |
81 * ------------------------------------------------------
82 * ^^^^^^^
83 * |
84 * Here, no need to worry about special handling of wrapped-around
85 * data due to double-mapped data pages. This works both in kernel and
86 * when mmap()'ed in user-space, simplifying both kernel and
87 * user-space implementations significantly.
88 */
89 array_size = (nr_meta_pages + 2 * nr_data_pages) * sizeof(*pages);
90 pages = bpf_map_area_alloc(array_size, numa_node);
91 if (!pages)
92 return NULL;
93
94 for (i = 0; i < nr_pages; i++) {
95 page = alloc_pages_node(numa_node, flags, 0);
96 if (!page) {
97 nr_pages = i;
98 goto err_free_pages;
99 }
100 pages[i] = page;
101 if (i >= nr_meta_pages)
102 pages[nr_data_pages + i] = page;
103 }
104
105 rb = vmap(pages, nr_meta_pages + 2 * nr_data_pages,
106 VM_ALLOC | VM_USERMAP, PAGE_KERNEL);
107 if (rb) {
108 rb->pages = pages;
109 rb->nr_pages = nr_pages;
110 return rb;
111 }
112
113err_free_pages:
114 for (i = 0; i < nr_pages; i++)
115 __free_page(pages[i]);
116 kvfree(pages);
117 return NULL;
118}
119
120static void bpf_ringbuf_notify(struct irq_work *work)
121{
122 struct bpf_ringbuf *rb = container_of(work, struct bpf_ringbuf, work);
123
124 wake_up_all(&rb->waitq);
125}
126
127static struct bpf_ringbuf *bpf_ringbuf_alloc(size_t data_sz, int numa_node)
128{
129 struct bpf_ringbuf *rb;
130
131 rb = bpf_ringbuf_area_alloc(data_sz, numa_node);
132 if (!rb)
133 return NULL;
134
135 spin_lock_init(&rb->spinlock);
136 init_waitqueue_head(&rb->waitq);
137 init_irq_work(&rb->work, bpf_ringbuf_notify);
138
139 rb->mask = data_sz - 1;
140 rb->consumer_pos = 0;
141 rb->producer_pos = 0;
142
143 return rb;
144}
145
146static struct bpf_map *ringbuf_map_alloc(union bpf_attr *attr)
147{
148 struct bpf_ringbuf_map *rb_map;
149
150 if (attr->map_flags & ~RINGBUF_CREATE_FLAG_MASK)
151 return ERR_PTR(-EINVAL);
152
153 if (attr->key_size || attr->value_size ||
154 !is_power_of_2(attr->max_entries) ||
155 !PAGE_ALIGNED(attr->max_entries))
156 return ERR_PTR(-EINVAL);
157
158#ifdef CONFIG_64BIT
159 /* on 32-bit arch, it's impossible to overflow record's hdr->pgoff */
160 if (attr->max_entries > RINGBUF_MAX_DATA_SZ)
161 return ERR_PTR(-E2BIG);
162#endif
163
164 rb_map = kzalloc(sizeof(*rb_map), GFP_USER | __GFP_ACCOUNT);
165 if (!rb_map)
166 return ERR_PTR(-ENOMEM);
167
168 bpf_map_init_from_attr(&rb_map->map, attr);
169
170 rb_map->rb = bpf_ringbuf_alloc(attr->max_entries, rb_map->map.numa_node);
171 if (!rb_map->rb) {
172 kfree(rb_map);
173 return ERR_PTR(-ENOMEM);
174 }
175
176 return &rb_map->map;
177}
178
179static void bpf_ringbuf_free(struct bpf_ringbuf *rb)
180{
181 /* copy pages pointer and nr_pages to local variable, as we are going
182 * to unmap rb itself with vunmap() below
183 */
184 struct page **pages = rb->pages;
185 int i, nr_pages = rb->nr_pages;
186
187 vunmap(rb);
188 for (i = 0; i < nr_pages; i++)
189 __free_page(pages[i]);
190 kvfree(pages);
191}
192
193static void ringbuf_map_free(struct bpf_map *map)
194{
195 struct bpf_ringbuf_map *rb_map;
196
197 rb_map = container_of(map, struct bpf_ringbuf_map, map);
198 bpf_ringbuf_free(rb_map->rb);
199 kfree(rb_map);
200}
201
202static void *ringbuf_map_lookup_elem(struct bpf_map *map, void *key)
203{
204 return ERR_PTR(-ENOTSUPP);
205}
206
207static int ringbuf_map_update_elem(struct bpf_map *map, void *key, void *value,
208 u64 flags)
209{
210 return -ENOTSUPP;
211}
212
213static int ringbuf_map_delete_elem(struct bpf_map *map, void *key)
214{
215 return -ENOTSUPP;
216}
217
218static int ringbuf_map_get_next_key(struct bpf_map *map, void *key,
219 void *next_key)
220{
221 return -ENOTSUPP;
222}
223
224static int ringbuf_map_mmap(struct bpf_map *map, struct vm_area_struct *vma)
225{
226 struct bpf_ringbuf_map *rb_map;
227
228 rb_map = container_of(map, struct bpf_ringbuf_map, map);
229
230 if (vma->vm_flags & VM_WRITE) {
231 /* allow writable mapping for the consumer_pos only */
232 if (vma->vm_pgoff != 0 || vma->vm_end - vma->vm_start != PAGE_SIZE)
233 return -EPERM;
234 } else {
235 vma->vm_flags &= ~VM_MAYWRITE;
236 }
237 /* remap_vmalloc_range() checks size and offset constraints */
238 return remap_vmalloc_range(vma, rb_map->rb,
239 vma->vm_pgoff + RINGBUF_PGOFF);
240}
241
242static unsigned long ringbuf_avail_data_sz(struct bpf_ringbuf *rb)
243{
244 unsigned long cons_pos, prod_pos;
245
246 cons_pos = smp_load_acquire(&rb->consumer_pos);
247 prod_pos = smp_load_acquire(&rb->producer_pos);
248 return prod_pos - cons_pos;
249}
250
251static __poll_t ringbuf_map_poll(struct bpf_map *map, struct file *filp,
252 struct poll_table_struct *pts)
253{
254 struct bpf_ringbuf_map *rb_map;
255
256 rb_map = container_of(map, struct bpf_ringbuf_map, map);
257 poll_wait(filp, &rb_map->rb->waitq, pts);
258
259 if (ringbuf_avail_data_sz(rb_map->rb))
260 return EPOLLIN | EPOLLRDNORM;
261 return 0;
262}
263
264static int ringbuf_map_btf_id;
265const struct bpf_map_ops ringbuf_map_ops = {
266 .map_meta_equal = bpf_map_meta_equal,
267 .map_alloc = ringbuf_map_alloc,
268 .map_free = ringbuf_map_free,
269 .map_mmap = ringbuf_map_mmap,
270 .map_poll = ringbuf_map_poll,
271 .map_lookup_elem = ringbuf_map_lookup_elem,
272 .map_update_elem = ringbuf_map_update_elem,
273 .map_delete_elem = ringbuf_map_delete_elem,
274 .map_get_next_key = ringbuf_map_get_next_key,
275 .map_btf_name = "bpf_ringbuf_map",
276 .map_btf_id = &ringbuf_map_btf_id,
277};
278
279/* Given pointer to ring buffer record metadata and struct bpf_ringbuf itself,
280 * calculate offset from record metadata to ring buffer in pages, rounded
281 * down. This page offset is stored as part of record metadata and allows to
282 * restore struct bpf_ringbuf * from record pointer. This page offset is
283 * stored at offset 4 of record metadata header.
284 */
285static size_t bpf_ringbuf_rec_pg_off(struct bpf_ringbuf *rb,
286 struct bpf_ringbuf_hdr *hdr)
287{
288 return ((void *)hdr - (void *)rb) >> PAGE_SHIFT;
289}
290
291/* Given pointer to ring buffer record header, restore pointer to struct
292 * bpf_ringbuf itself by using page offset stored at offset 4
293 */
294static struct bpf_ringbuf *
295bpf_ringbuf_restore_from_rec(struct bpf_ringbuf_hdr *hdr)
296{
297 unsigned long addr = (unsigned long)(void *)hdr;
298 unsigned long off = (unsigned long)hdr->pg_off << PAGE_SHIFT;
299
300 return (void*)((addr & PAGE_MASK) - off);
301}
302
303static void *__bpf_ringbuf_reserve(struct bpf_ringbuf *rb, u64 size)
304{
305 unsigned long cons_pos, prod_pos, new_prod_pos, flags;
306 u32 len, pg_off;
307 struct bpf_ringbuf_hdr *hdr;
308
309 if (unlikely(size > RINGBUF_MAX_RECORD_SZ))
310 return NULL;
311
312 len = round_up(size + BPF_RINGBUF_HDR_SZ, 8);
313 if (len > rb->mask + 1)
314 return NULL;
315
316 cons_pos = smp_load_acquire(&rb->consumer_pos);
317
318 if (in_nmi()) {
319 if (!spin_trylock_irqsave(&rb->spinlock, flags))
320 return NULL;
321 } else {
322 spin_lock_irqsave(&rb->spinlock, flags);
323 }
324
325 prod_pos = rb->producer_pos;
326 new_prod_pos = prod_pos + len;
327
328 /* check for out of ringbuf space by ensuring producer position
329 * doesn't advance more than (ringbuf_size - 1) ahead
330 */
331 if (new_prod_pos - cons_pos > rb->mask) {
332 spin_unlock_irqrestore(&rb->spinlock, flags);
333 return NULL;
334 }
335
336 hdr = (void *)rb->data + (prod_pos & rb->mask);
337 pg_off = bpf_ringbuf_rec_pg_off(rb, hdr);
338 hdr->len = size | BPF_RINGBUF_BUSY_BIT;
339 hdr->pg_off = pg_off;
340
341 /* pairs with consumer's smp_load_acquire() */
342 smp_store_release(&rb->producer_pos, new_prod_pos);
343
344 spin_unlock_irqrestore(&rb->spinlock, flags);
345
346 return (void *)hdr + BPF_RINGBUF_HDR_SZ;
347}
348
349BPF_CALL_3(bpf_ringbuf_reserve, struct bpf_map *, map, u64, size, u64, flags)
350{
351 struct bpf_ringbuf_map *rb_map;
352
353 if (unlikely(flags))
354 return 0;
355
356 rb_map = container_of(map, struct bpf_ringbuf_map, map);
357 return (unsigned long)__bpf_ringbuf_reserve(rb_map->rb, size);
358}
359
360const struct bpf_func_proto bpf_ringbuf_reserve_proto = {
361 .func = bpf_ringbuf_reserve,
362 .ret_type = RET_PTR_TO_ALLOC_MEM_OR_NULL,
363 .arg1_type = ARG_CONST_MAP_PTR,
364 .arg2_type = ARG_CONST_ALLOC_SIZE_OR_ZERO,
365 .arg3_type = ARG_ANYTHING,
366};
367
368static void bpf_ringbuf_commit(void *sample, u64 flags, bool discard)
369{
370 unsigned long rec_pos, cons_pos;
371 struct bpf_ringbuf_hdr *hdr;
372 struct bpf_ringbuf *rb;
373 u32 new_len;
374
375 hdr = sample - BPF_RINGBUF_HDR_SZ;
376 rb = bpf_ringbuf_restore_from_rec(hdr);
377 new_len = hdr->len ^ BPF_RINGBUF_BUSY_BIT;
378 if (discard)
379 new_len |= BPF_RINGBUF_DISCARD_BIT;
380
381 /* update record header with correct final size prefix */
382 xchg(&hdr->len, new_len);
383
384 /* if consumer caught up and is waiting for our record, notify about
385 * new data availability
386 */
387 rec_pos = (void *)hdr - (void *)rb->data;
388 cons_pos = smp_load_acquire(&rb->consumer_pos) & rb->mask;
389
390 if (flags & BPF_RB_FORCE_WAKEUP)
391 irq_work_queue(&rb->work);
392 else if (cons_pos == rec_pos && !(flags & BPF_RB_NO_WAKEUP))
393 irq_work_queue(&rb->work);
394}
395
396BPF_CALL_2(bpf_ringbuf_submit, void *, sample, u64, flags)
397{
398 bpf_ringbuf_commit(sample, flags, false /* discard */);
399 return 0;
400}
401
402const struct bpf_func_proto bpf_ringbuf_submit_proto = {
403 .func = bpf_ringbuf_submit,
404 .ret_type = RET_VOID,
405 .arg1_type = ARG_PTR_TO_ALLOC_MEM,
406 .arg2_type = ARG_ANYTHING,
407};
408
409BPF_CALL_2(bpf_ringbuf_discard, void *, sample, u64, flags)
410{
411 bpf_ringbuf_commit(sample, flags, true /* discard */);
412 return 0;
413}
414
415const struct bpf_func_proto bpf_ringbuf_discard_proto = {
416 .func = bpf_ringbuf_discard,
417 .ret_type = RET_VOID,
418 .arg1_type = ARG_PTR_TO_ALLOC_MEM,
419 .arg2_type = ARG_ANYTHING,
420};
421
422BPF_CALL_4(bpf_ringbuf_output, struct bpf_map *, map, void *, data, u64, size,
423 u64, flags)
424{
425 struct bpf_ringbuf_map *rb_map;
426 void *rec;
427
428 if (unlikely(flags & ~(BPF_RB_NO_WAKEUP | BPF_RB_FORCE_WAKEUP)))
429 return -EINVAL;
430
431 rb_map = container_of(map, struct bpf_ringbuf_map, map);
432 rec = __bpf_ringbuf_reserve(rb_map->rb, size);
433 if (!rec)
434 return -EAGAIN;
435
436 memcpy(rec, data, size);
437 bpf_ringbuf_commit(rec, flags, false /* discard */);
438 return 0;
439}
440
441const struct bpf_func_proto bpf_ringbuf_output_proto = {
442 .func = bpf_ringbuf_output,
443 .ret_type = RET_INTEGER,
444 .arg1_type = ARG_CONST_MAP_PTR,
445 .arg2_type = ARG_PTR_TO_MEM,
446 .arg3_type = ARG_CONST_SIZE_OR_ZERO,
447 .arg4_type = ARG_ANYTHING,
448};
449
450BPF_CALL_2(bpf_ringbuf_query, struct bpf_map *, map, u64, flags)
451{
452 struct bpf_ringbuf *rb;
453
454 rb = container_of(map, struct bpf_ringbuf_map, map)->rb;
455
456 switch (flags) {
457 case BPF_RB_AVAIL_DATA:
458 return ringbuf_avail_data_sz(rb);
459 case BPF_RB_RING_SIZE:
460 return rb->mask + 1;
461 case BPF_RB_CONS_POS:
462 return smp_load_acquire(&rb->consumer_pos);
463 case BPF_RB_PROD_POS:
464 return smp_load_acquire(&rb->producer_pos);
465 default:
466 return 0;
467 }
468}
469
470const struct bpf_func_proto bpf_ringbuf_query_proto = {
471 .func = bpf_ringbuf_query,
472 .ret_type = RET_INTEGER,
473 .arg1_type = ARG_CONST_MAP_PTR,
474 .arg2_type = ARG_ANYTHING,
475};