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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_map_memory memory;
52 struct bpf_ringbuf *rb;
53};
54
55/* 8-byte ring buffer record header structure */
56struct bpf_ringbuf_hdr {
57 u32 len;
58 u32 pg_off;
59};
60
61static struct bpf_ringbuf *bpf_ringbuf_area_alloc(size_t data_sz, int numa_node)
62{
63 const gfp_t flags = GFP_KERNEL | __GFP_RETRY_MAYFAIL | __GFP_NOWARN |
64 __GFP_ZERO;
65 int nr_meta_pages = RINGBUF_PGOFF + RINGBUF_POS_PAGES;
66 int nr_data_pages = data_sz >> PAGE_SHIFT;
67 int nr_pages = nr_meta_pages + nr_data_pages;
68 struct page **pages, *page;
69 struct bpf_ringbuf *rb;
70 size_t array_size;
71 int i;
72
73 /* Each data page is mapped twice to allow "virtual"
74 * continuous read of samples wrapping around the end of ring
75 * buffer area:
76 * ------------------------------------------------------
77 * | meta pages | real data pages | same data pages |
78 * ------------------------------------------------------
79 * | | 1 2 3 4 5 6 7 8 9 | 1 2 3 4 5 6 7 8 9 |
80 * ------------------------------------------------------
81 * | | TA DA | TA DA |
82 * ------------------------------------------------------
83 * ^^^^^^^
84 * |
85 * Here, no need to worry about special handling of wrapped-around
86 * data due to double-mapped data pages. This works both in kernel and
87 * when mmap()'ed in user-space, simplifying both kernel and
88 * user-space implementations significantly.
89 */
90 array_size = (nr_meta_pages + 2 * nr_data_pages) * sizeof(*pages);
91 if (array_size > PAGE_SIZE)
92 pages = vmalloc_node(array_size, numa_node);
93 else
94 pages = kmalloc_node(array_size, flags, numa_node);
95 if (!pages)
96 return NULL;
97
98 for (i = 0; i < nr_pages; i++) {
99 page = alloc_pages_node(numa_node, flags, 0);
100 if (!page) {
101 nr_pages = i;
102 goto err_free_pages;
103 }
104 pages[i] = page;
105 if (i >= nr_meta_pages)
106 pages[nr_data_pages + i] = page;
107 }
108
109 rb = vmap(pages, nr_meta_pages + 2 * nr_data_pages,
110 VM_ALLOC | VM_USERMAP, PAGE_KERNEL);
111 if (rb) {
112 rb->pages = pages;
113 rb->nr_pages = nr_pages;
114 return rb;
115 }
116
117err_free_pages:
118 for (i = 0; i < nr_pages; i++)
119 __free_page(pages[i]);
120 kvfree(pages);
121 return NULL;
122}
123
124static void bpf_ringbuf_notify(struct irq_work *work)
125{
126 struct bpf_ringbuf *rb = container_of(work, struct bpf_ringbuf, work);
127
128 wake_up_all(&rb->waitq);
129}
130
131static struct bpf_ringbuf *bpf_ringbuf_alloc(size_t data_sz, int numa_node)
132{
133 struct bpf_ringbuf *rb;
134
135 rb = bpf_ringbuf_area_alloc(data_sz, numa_node);
136 if (!rb)
137 return ERR_PTR(-ENOMEM);
138
139 spin_lock_init(&rb->spinlock);
140 init_waitqueue_head(&rb->waitq);
141 init_irq_work(&rb->work, bpf_ringbuf_notify);
142
143 rb->mask = data_sz - 1;
144 rb->consumer_pos = 0;
145 rb->producer_pos = 0;
146
147 return rb;
148}
149
150static struct bpf_map *ringbuf_map_alloc(union bpf_attr *attr)
151{
152 struct bpf_ringbuf_map *rb_map;
153 u64 cost;
154 int err;
155
156 if (attr->map_flags & ~RINGBUF_CREATE_FLAG_MASK)
157 return ERR_PTR(-EINVAL);
158
159 if (attr->key_size || attr->value_size ||
160 !is_power_of_2(attr->max_entries) ||
161 !PAGE_ALIGNED(attr->max_entries))
162 return ERR_PTR(-EINVAL);
163
164#ifdef CONFIG_64BIT
165 /* on 32-bit arch, it's impossible to overflow record's hdr->pgoff */
166 if (attr->max_entries > RINGBUF_MAX_DATA_SZ)
167 return ERR_PTR(-E2BIG);
168#endif
169
170 rb_map = kzalloc(sizeof(*rb_map), GFP_USER);
171 if (!rb_map)
172 return ERR_PTR(-ENOMEM);
173
174 bpf_map_init_from_attr(&rb_map->map, attr);
175
176 cost = sizeof(struct bpf_ringbuf_map) +
177 sizeof(struct bpf_ringbuf) +
178 attr->max_entries;
179 err = bpf_map_charge_init(&rb_map->map.memory, cost);
180 if (err)
181 goto err_free_map;
182
183 rb_map->rb = bpf_ringbuf_alloc(attr->max_entries, rb_map->map.numa_node);
184 if (IS_ERR(rb_map->rb)) {
185 err = PTR_ERR(rb_map->rb);
186 goto err_uncharge;
187 }
188
189 return &rb_map->map;
190
191err_uncharge:
192 bpf_map_charge_finish(&rb_map->map.memory);
193err_free_map:
194 kfree(rb_map);
195 return ERR_PTR(err);
196}
197
198static void bpf_ringbuf_free(struct bpf_ringbuf *rb)
199{
200 /* copy pages pointer and nr_pages to local variable, as we are going
201 * to unmap rb itself with vunmap() below
202 */
203 struct page **pages = rb->pages;
204 int i, nr_pages = rb->nr_pages;
205
206 vunmap(rb);
207 for (i = 0; i < nr_pages; i++)
208 __free_page(pages[i]);
209 kvfree(pages);
210}
211
212static void ringbuf_map_free(struct bpf_map *map)
213{
214 struct bpf_ringbuf_map *rb_map;
215
216 rb_map = container_of(map, struct bpf_ringbuf_map, map);
217 bpf_ringbuf_free(rb_map->rb);
218 kfree(rb_map);
219}
220
221static void *ringbuf_map_lookup_elem(struct bpf_map *map, void *key)
222{
223 return ERR_PTR(-ENOTSUPP);
224}
225
226static int ringbuf_map_update_elem(struct bpf_map *map, void *key, void *value,
227 u64 flags)
228{
229 return -ENOTSUPP;
230}
231
232static int ringbuf_map_delete_elem(struct bpf_map *map, void *key)
233{
234 return -ENOTSUPP;
235}
236
237static int ringbuf_map_get_next_key(struct bpf_map *map, void *key,
238 void *next_key)
239{
240 return -ENOTSUPP;
241}
242
243static size_t bpf_ringbuf_mmap_page_cnt(const struct bpf_ringbuf *rb)
244{
245 size_t data_pages = (rb->mask + 1) >> PAGE_SHIFT;
246
247 /* consumer page + producer page + 2 x data pages */
248 return RINGBUF_POS_PAGES + 2 * data_pages;
249}
250
251static int ringbuf_map_mmap(struct bpf_map *map, struct vm_area_struct *vma)
252{
253 struct bpf_ringbuf_map *rb_map;
254 size_t mmap_sz;
255
256 rb_map = container_of(map, struct bpf_ringbuf_map, map);
257 mmap_sz = bpf_ringbuf_mmap_page_cnt(rb_map->rb) << PAGE_SHIFT;
258
259 if (vma->vm_pgoff * PAGE_SIZE + (vma->vm_end - vma->vm_start) > mmap_sz)
260 return -EINVAL;
261
262 return remap_vmalloc_range(vma, rb_map->rb,
263 vma->vm_pgoff + RINGBUF_PGOFF);
264}
265
266static unsigned long ringbuf_avail_data_sz(struct bpf_ringbuf *rb)
267{
268 unsigned long cons_pos, prod_pos;
269
270 cons_pos = smp_load_acquire(&rb->consumer_pos);
271 prod_pos = smp_load_acquire(&rb->producer_pos);
272 return prod_pos - cons_pos;
273}
274
275static __poll_t ringbuf_map_poll(struct bpf_map *map, struct file *filp,
276 struct poll_table_struct *pts)
277{
278 struct bpf_ringbuf_map *rb_map;
279
280 rb_map = container_of(map, struct bpf_ringbuf_map, map);
281 poll_wait(filp, &rb_map->rb->waitq, pts);
282
283 if (ringbuf_avail_data_sz(rb_map->rb))
284 return EPOLLIN | EPOLLRDNORM;
285 return 0;
286}
287
288static int ringbuf_map_btf_id;
289const struct bpf_map_ops ringbuf_map_ops = {
290 .map_alloc = ringbuf_map_alloc,
291 .map_free = ringbuf_map_free,
292 .map_mmap = ringbuf_map_mmap,
293 .map_poll = ringbuf_map_poll,
294 .map_lookup_elem = ringbuf_map_lookup_elem,
295 .map_update_elem = ringbuf_map_update_elem,
296 .map_delete_elem = ringbuf_map_delete_elem,
297 .map_get_next_key = ringbuf_map_get_next_key,
298 .map_btf_name = "bpf_ringbuf_map",
299 .map_btf_id = &ringbuf_map_btf_id,
300};
301
302/* Given pointer to ring buffer record metadata and struct bpf_ringbuf itself,
303 * calculate offset from record metadata to ring buffer in pages, rounded
304 * down. This page offset is stored as part of record metadata and allows to
305 * restore struct bpf_ringbuf * from record pointer. This page offset is
306 * stored at offset 4 of record metadata header.
307 */
308static size_t bpf_ringbuf_rec_pg_off(struct bpf_ringbuf *rb,
309 struct bpf_ringbuf_hdr *hdr)
310{
311 return ((void *)hdr - (void *)rb) >> PAGE_SHIFT;
312}
313
314/* Given pointer to ring buffer record header, restore pointer to struct
315 * bpf_ringbuf itself by using page offset stored at offset 4
316 */
317static struct bpf_ringbuf *
318bpf_ringbuf_restore_from_rec(struct bpf_ringbuf_hdr *hdr)
319{
320 unsigned long addr = (unsigned long)(void *)hdr;
321 unsigned long off = (unsigned long)hdr->pg_off << PAGE_SHIFT;
322
323 return (void*)((addr & PAGE_MASK) - off);
324}
325
326static void *__bpf_ringbuf_reserve(struct bpf_ringbuf *rb, u64 size)
327{
328 unsigned long cons_pos, prod_pos, new_prod_pos, flags;
329 u32 len, pg_off;
330 struct bpf_ringbuf_hdr *hdr;
331
332 if (unlikely(size > RINGBUF_MAX_RECORD_SZ))
333 return NULL;
334
335 len = round_up(size + BPF_RINGBUF_HDR_SZ, 8);
336 cons_pos = smp_load_acquire(&rb->consumer_pos);
337
338 if (in_nmi()) {
339 if (!spin_trylock_irqsave(&rb->spinlock, flags))
340 return NULL;
341 } else {
342 spin_lock_irqsave(&rb->spinlock, flags);
343 }
344
345 prod_pos = rb->producer_pos;
346 new_prod_pos = prod_pos + len;
347
348 /* check for out of ringbuf space by ensuring producer position
349 * doesn't advance more than (ringbuf_size - 1) ahead
350 */
351 if (new_prod_pos - cons_pos > rb->mask) {
352 spin_unlock_irqrestore(&rb->spinlock, flags);
353 return NULL;
354 }
355
356 hdr = (void *)rb->data + (prod_pos & rb->mask);
357 pg_off = bpf_ringbuf_rec_pg_off(rb, hdr);
358 hdr->len = size | BPF_RINGBUF_BUSY_BIT;
359 hdr->pg_off = pg_off;
360
361 /* pairs with consumer's smp_load_acquire() */
362 smp_store_release(&rb->producer_pos, new_prod_pos);
363
364 spin_unlock_irqrestore(&rb->spinlock, flags);
365
366 return (void *)hdr + BPF_RINGBUF_HDR_SZ;
367}
368
369BPF_CALL_3(bpf_ringbuf_reserve, struct bpf_map *, map, u64, size, u64, flags)
370{
371 struct bpf_ringbuf_map *rb_map;
372
373 if (unlikely(flags))
374 return 0;
375
376 rb_map = container_of(map, struct bpf_ringbuf_map, map);
377 return (unsigned long)__bpf_ringbuf_reserve(rb_map->rb, size);
378}
379
380const struct bpf_func_proto bpf_ringbuf_reserve_proto = {
381 .func = bpf_ringbuf_reserve,
382 .ret_type = RET_PTR_TO_ALLOC_MEM_OR_NULL,
383 .arg1_type = ARG_CONST_MAP_PTR,
384 .arg2_type = ARG_CONST_ALLOC_SIZE_OR_ZERO,
385 .arg3_type = ARG_ANYTHING,
386};
387
388static void bpf_ringbuf_commit(void *sample, u64 flags, bool discard)
389{
390 unsigned long rec_pos, cons_pos;
391 struct bpf_ringbuf_hdr *hdr;
392 struct bpf_ringbuf *rb;
393 u32 new_len;
394
395 hdr = sample - BPF_RINGBUF_HDR_SZ;
396 rb = bpf_ringbuf_restore_from_rec(hdr);
397 new_len = hdr->len ^ BPF_RINGBUF_BUSY_BIT;
398 if (discard)
399 new_len |= BPF_RINGBUF_DISCARD_BIT;
400
401 /* update record header with correct final size prefix */
402 xchg(&hdr->len, new_len);
403
404 /* if consumer caught up and is waiting for our record, notify about
405 * new data availability
406 */
407 rec_pos = (void *)hdr - (void *)rb->data;
408 cons_pos = smp_load_acquire(&rb->consumer_pos) & rb->mask;
409
410 if (flags & BPF_RB_FORCE_WAKEUP)
411 irq_work_queue(&rb->work);
412 else if (cons_pos == rec_pos && !(flags & BPF_RB_NO_WAKEUP))
413 irq_work_queue(&rb->work);
414}
415
416BPF_CALL_2(bpf_ringbuf_submit, void *, sample, u64, flags)
417{
418 bpf_ringbuf_commit(sample, flags, false /* discard */);
419 return 0;
420}
421
422const struct bpf_func_proto bpf_ringbuf_submit_proto = {
423 .func = bpf_ringbuf_submit,
424 .ret_type = RET_VOID,
425 .arg1_type = ARG_PTR_TO_ALLOC_MEM,
426 .arg2_type = ARG_ANYTHING,
427};
428
429BPF_CALL_2(bpf_ringbuf_discard, void *, sample, u64, flags)
430{
431 bpf_ringbuf_commit(sample, flags, true /* discard */);
432 return 0;
433}
434
435const struct bpf_func_proto bpf_ringbuf_discard_proto = {
436 .func = bpf_ringbuf_discard,
437 .ret_type = RET_VOID,
438 .arg1_type = ARG_PTR_TO_ALLOC_MEM,
439 .arg2_type = ARG_ANYTHING,
440};
441
442BPF_CALL_4(bpf_ringbuf_output, struct bpf_map *, map, void *, data, u64, size,
443 u64, flags)
444{
445 struct bpf_ringbuf_map *rb_map;
446 void *rec;
447
448 if (unlikely(flags & ~(BPF_RB_NO_WAKEUP | BPF_RB_FORCE_WAKEUP)))
449 return -EINVAL;
450
451 rb_map = container_of(map, struct bpf_ringbuf_map, map);
452 rec = __bpf_ringbuf_reserve(rb_map->rb, size);
453 if (!rec)
454 return -EAGAIN;
455
456 memcpy(rec, data, size);
457 bpf_ringbuf_commit(rec, flags, false /* discard */);
458 return 0;
459}
460
461const struct bpf_func_proto bpf_ringbuf_output_proto = {
462 .func = bpf_ringbuf_output,
463 .ret_type = RET_INTEGER,
464 .arg1_type = ARG_CONST_MAP_PTR,
465 .arg2_type = ARG_PTR_TO_MEM,
466 .arg3_type = ARG_CONST_SIZE_OR_ZERO,
467 .arg4_type = ARG_ANYTHING,
468};
469
470BPF_CALL_2(bpf_ringbuf_query, struct bpf_map *, map, u64, flags)
471{
472 struct bpf_ringbuf *rb;
473
474 rb = container_of(map, struct bpf_ringbuf_map, map)->rb;
475
476 switch (flags) {
477 case BPF_RB_AVAIL_DATA:
478 return ringbuf_avail_data_sz(rb);
479 case BPF_RB_RING_SIZE:
480 return rb->mask + 1;
481 case BPF_RB_CONS_POS:
482 return smp_load_acquire(&rb->consumer_pos);
483 case BPF_RB_PROD_POS:
484 return smp_load_acquire(&rb->producer_pos);
485 default:
486 return 0;
487 }
488}
489
490const struct bpf_func_proto bpf_ringbuf_query_proto = {
491 .func = bpf_ringbuf_query,
492 .ret_type = RET_INTEGER,
493 .arg1_type = ARG_CONST_MAP_PTR,
494 .arg2_type = ARG_ANYTHING,
495};