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1// SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
2/*
3 * Ring buffer operations.
4 *
5 * Copyright (C) 2020 Facebook, Inc.
6 */
7#ifndef _GNU_SOURCE
8#define _GNU_SOURCE
9#endif
10#include <stdlib.h>
11#include <stdio.h>
12#include <errno.h>
13#include <unistd.h>
14#include <linux/err.h>
15#include <linux/bpf.h>
16#include <asm/barrier.h>
17#include <sys/mman.h>
18#include <sys/epoll.h>
19#include <time.h>
20
21#include "libbpf.h"
22#include "libbpf_internal.h"
23#include "bpf.h"
24
25struct ring {
26 ring_buffer_sample_fn sample_cb;
27 void *ctx;
28 void *data;
29 unsigned long *consumer_pos;
30 unsigned long *producer_pos;
31 unsigned long mask;
32 int map_fd;
33};
34
35struct ring_buffer {
36 struct epoll_event *events;
37 struct ring *rings;
38 size_t page_size;
39 int epoll_fd;
40 int ring_cnt;
41};
42
43struct user_ring_buffer {
44 struct epoll_event event;
45 unsigned long *consumer_pos;
46 unsigned long *producer_pos;
47 void *data;
48 unsigned long mask;
49 size_t page_size;
50 int map_fd;
51 int epoll_fd;
52};
53
54/* 8-byte ring buffer header structure */
55struct ringbuf_hdr {
56 __u32 len;
57 __u32 pad;
58};
59
60static void ringbuf_unmap_ring(struct ring_buffer *rb, struct ring *r)
61{
62 if (r->consumer_pos) {
63 munmap(r->consumer_pos, rb->page_size);
64 r->consumer_pos = NULL;
65 }
66 if (r->producer_pos) {
67 munmap(r->producer_pos, rb->page_size + 2 * (r->mask + 1));
68 r->producer_pos = NULL;
69 }
70}
71
72/* Add extra RINGBUF maps to this ring buffer manager */
73int ring_buffer__add(struct ring_buffer *rb, int map_fd,
74 ring_buffer_sample_fn sample_cb, void *ctx)
75{
76 struct bpf_map_info info;
77 __u32 len = sizeof(info);
78 struct epoll_event *e;
79 struct ring *r;
80 __u64 mmap_sz;
81 void *tmp;
82 int err;
83
84 memset(&info, 0, sizeof(info));
85
86 err = bpf_obj_get_info_by_fd(map_fd, &info, &len);
87 if (err) {
88 err = -errno;
89 pr_warn("ringbuf: failed to get map info for fd=%d: %d\n",
90 map_fd, err);
91 return libbpf_err(err);
92 }
93
94 if (info.type != BPF_MAP_TYPE_RINGBUF) {
95 pr_warn("ringbuf: map fd=%d is not BPF_MAP_TYPE_RINGBUF\n",
96 map_fd);
97 return libbpf_err(-EINVAL);
98 }
99
100 tmp = libbpf_reallocarray(rb->rings, rb->ring_cnt + 1, sizeof(*rb->rings));
101 if (!tmp)
102 return libbpf_err(-ENOMEM);
103 rb->rings = tmp;
104
105 tmp = libbpf_reallocarray(rb->events, rb->ring_cnt + 1, sizeof(*rb->events));
106 if (!tmp)
107 return libbpf_err(-ENOMEM);
108 rb->events = tmp;
109
110 r = &rb->rings[rb->ring_cnt];
111 memset(r, 0, sizeof(*r));
112
113 r->map_fd = map_fd;
114 r->sample_cb = sample_cb;
115 r->ctx = ctx;
116 r->mask = info.max_entries - 1;
117
118 /* Map writable consumer page */
119 tmp = mmap(NULL, rb->page_size, PROT_READ | PROT_WRITE, MAP_SHARED, map_fd, 0);
120 if (tmp == MAP_FAILED) {
121 err = -errno;
122 pr_warn("ringbuf: failed to mmap consumer page for map fd=%d: %d\n",
123 map_fd, err);
124 return libbpf_err(err);
125 }
126 r->consumer_pos = tmp;
127
128 /* Map read-only producer page and data pages. We map twice as big
129 * data size to allow simple reading of samples that wrap around the
130 * end of a ring buffer. See kernel implementation for details.
131 */
132 mmap_sz = rb->page_size + 2 * (__u64)info.max_entries;
133 if (mmap_sz != (__u64)(size_t)mmap_sz) {
134 pr_warn("ringbuf: ring buffer size (%u) is too big\n", info.max_entries);
135 return libbpf_err(-E2BIG);
136 }
137 tmp = mmap(NULL, (size_t)mmap_sz, PROT_READ, MAP_SHARED, map_fd, rb->page_size);
138 if (tmp == MAP_FAILED) {
139 err = -errno;
140 ringbuf_unmap_ring(rb, r);
141 pr_warn("ringbuf: failed to mmap data pages for map fd=%d: %d\n",
142 map_fd, err);
143 return libbpf_err(err);
144 }
145 r->producer_pos = tmp;
146 r->data = tmp + rb->page_size;
147
148 e = &rb->events[rb->ring_cnt];
149 memset(e, 0, sizeof(*e));
150
151 e->events = EPOLLIN;
152 e->data.fd = rb->ring_cnt;
153 if (epoll_ctl(rb->epoll_fd, EPOLL_CTL_ADD, map_fd, e) < 0) {
154 err = -errno;
155 ringbuf_unmap_ring(rb, r);
156 pr_warn("ringbuf: failed to epoll add map fd=%d: %d\n",
157 map_fd, err);
158 return libbpf_err(err);
159 }
160
161 rb->ring_cnt++;
162 return 0;
163}
164
165void ring_buffer__free(struct ring_buffer *rb)
166{
167 int i;
168
169 if (!rb)
170 return;
171
172 for (i = 0; i < rb->ring_cnt; ++i)
173 ringbuf_unmap_ring(rb, &rb->rings[i]);
174 if (rb->epoll_fd >= 0)
175 close(rb->epoll_fd);
176
177 free(rb->events);
178 free(rb->rings);
179 free(rb);
180}
181
182struct ring_buffer *
183ring_buffer__new(int map_fd, ring_buffer_sample_fn sample_cb, void *ctx,
184 const struct ring_buffer_opts *opts)
185{
186 struct ring_buffer *rb;
187 int err;
188
189 if (!OPTS_VALID(opts, ring_buffer_opts))
190 return errno = EINVAL, NULL;
191
192 rb = calloc(1, sizeof(*rb));
193 if (!rb)
194 return errno = ENOMEM, NULL;
195
196 rb->page_size = getpagesize();
197
198 rb->epoll_fd = epoll_create1(EPOLL_CLOEXEC);
199 if (rb->epoll_fd < 0) {
200 err = -errno;
201 pr_warn("ringbuf: failed to create epoll instance: %d\n", err);
202 goto err_out;
203 }
204
205 err = ring_buffer__add(rb, map_fd, sample_cb, ctx);
206 if (err)
207 goto err_out;
208
209 return rb;
210
211err_out:
212 ring_buffer__free(rb);
213 return errno = -err, NULL;
214}
215
216static inline int roundup_len(__u32 len)
217{
218 /* clear out top 2 bits (discard and busy, if set) */
219 len <<= 2;
220 len >>= 2;
221 /* add length prefix */
222 len += BPF_RINGBUF_HDR_SZ;
223 /* round up to 8 byte alignment */
224 return (len + 7) / 8 * 8;
225}
226
227static int64_t ringbuf_process_ring(struct ring *r)
228{
229 int *len_ptr, len, err;
230 /* 64-bit to avoid overflow in case of extreme application behavior */
231 int64_t cnt = 0;
232 unsigned long cons_pos, prod_pos;
233 bool got_new_data;
234 void *sample;
235
236 cons_pos = smp_load_acquire(r->consumer_pos);
237 do {
238 got_new_data = false;
239 prod_pos = smp_load_acquire(r->producer_pos);
240 while (cons_pos < prod_pos) {
241 len_ptr = r->data + (cons_pos & r->mask);
242 len = smp_load_acquire(len_ptr);
243
244 /* sample not committed yet, bail out for now */
245 if (len & BPF_RINGBUF_BUSY_BIT)
246 goto done;
247
248 got_new_data = true;
249 cons_pos += roundup_len(len);
250
251 if ((len & BPF_RINGBUF_DISCARD_BIT) == 0) {
252 sample = (void *)len_ptr + BPF_RINGBUF_HDR_SZ;
253 err = r->sample_cb(r->ctx, sample, len);
254 if (err < 0) {
255 /* update consumer pos and bail out */
256 smp_store_release(r->consumer_pos,
257 cons_pos);
258 return err;
259 }
260 cnt++;
261 }
262
263 smp_store_release(r->consumer_pos, cons_pos);
264 }
265 } while (got_new_data);
266done:
267 return cnt;
268}
269
270/* Consume available ring buffer(s) data without event polling.
271 * Returns number of records consumed across all registered ring buffers (or
272 * INT_MAX, whichever is less), or negative number if any of the callbacks
273 * return error.
274 */
275int ring_buffer__consume(struct ring_buffer *rb)
276{
277 int64_t err, res = 0;
278 int i;
279
280 for (i = 0; i < rb->ring_cnt; i++) {
281 struct ring *ring = &rb->rings[i];
282
283 err = ringbuf_process_ring(ring);
284 if (err < 0)
285 return libbpf_err(err);
286 res += err;
287 }
288 if (res > INT_MAX)
289 return INT_MAX;
290 return res;
291}
292
293/* Poll for available data and consume records, if any are available.
294 * Returns number of records consumed (or INT_MAX, whichever is less), or
295 * negative number, if any of the registered callbacks returned error.
296 */
297int ring_buffer__poll(struct ring_buffer *rb, int timeout_ms)
298{
299 int i, cnt;
300 int64_t err, res = 0;
301
302 cnt = epoll_wait(rb->epoll_fd, rb->events, rb->ring_cnt, timeout_ms);
303 if (cnt < 0)
304 return libbpf_err(-errno);
305
306 for (i = 0; i < cnt; i++) {
307 __u32 ring_id = rb->events[i].data.fd;
308 struct ring *ring = &rb->rings[ring_id];
309
310 err = ringbuf_process_ring(ring);
311 if (err < 0)
312 return libbpf_err(err);
313 res += err;
314 }
315 if (res > INT_MAX)
316 return INT_MAX;
317 return res;
318}
319
320/* Get an fd that can be used to sleep until data is available in the ring(s) */
321int ring_buffer__epoll_fd(const struct ring_buffer *rb)
322{
323 return rb->epoll_fd;
324}
325
326static void user_ringbuf_unmap_ring(struct user_ring_buffer *rb)
327{
328 if (rb->consumer_pos) {
329 munmap(rb->consumer_pos, rb->page_size);
330 rb->consumer_pos = NULL;
331 }
332 if (rb->producer_pos) {
333 munmap(rb->producer_pos, rb->page_size + 2 * (rb->mask + 1));
334 rb->producer_pos = NULL;
335 }
336}
337
338void user_ring_buffer__free(struct user_ring_buffer *rb)
339{
340 if (!rb)
341 return;
342
343 user_ringbuf_unmap_ring(rb);
344
345 if (rb->epoll_fd >= 0)
346 close(rb->epoll_fd);
347
348 free(rb);
349}
350
351static int user_ringbuf_map(struct user_ring_buffer *rb, int map_fd)
352{
353 struct bpf_map_info info;
354 __u32 len = sizeof(info);
355 __u64 mmap_sz;
356 void *tmp;
357 struct epoll_event *rb_epoll;
358 int err;
359
360 memset(&info, 0, sizeof(info));
361
362 err = bpf_obj_get_info_by_fd(map_fd, &info, &len);
363 if (err) {
364 err = -errno;
365 pr_warn("user ringbuf: failed to get map info for fd=%d: %d\n", map_fd, err);
366 return err;
367 }
368
369 if (info.type != BPF_MAP_TYPE_USER_RINGBUF) {
370 pr_warn("user ringbuf: map fd=%d is not BPF_MAP_TYPE_USER_RINGBUF\n", map_fd);
371 return -EINVAL;
372 }
373
374 rb->map_fd = map_fd;
375 rb->mask = info.max_entries - 1;
376
377 /* Map read-only consumer page */
378 tmp = mmap(NULL, rb->page_size, PROT_READ, MAP_SHARED, map_fd, 0);
379 if (tmp == MAP_FAILED) {
380 err = -errno;
381 pr_warn("user ringbuf: failed to mmap consumer page for map fd=%d: %d\n",
382 map_fd, err);
383 return err;
384 }
385 rb->consumer_pos = tmp;
386
387 /* Map read-write the producer page and data pages. We map the data
388 * region as twice the total size of the ring buffer to allow the
389 * simple reading and writing of samples that wrap around the end of
390 * the buffer. See the kernel implementation for details.
391 */
392 mmap_sz = rb->page_size + 2 * (__u64)info.max_entries;
393 if (mmap_sz != (__u64)(size_t)mmap_sz) {
394 pr_warn("user ringbuf: ring buf size (%u) is too big\n", info.max_entries);
395 return -E2BIG;
396 }
397 tmp = mmap(NULL, (size_t)mmap_sz, PROT_READ | PROT_WRITE, MAP_SHARED,
398 map_fd, rb->page_size);
399 if (tmp == MAP_FAILED) {
400 err = -errno;
401 pr_warn("user ringbuf: failed to mmap data pages for map fd=%d: %d\n",
402 map_fd, err);
403 return err;
404 }
405
406 rb->producer_pos = tmp;
407 rb->data = tmp + rb->page_size;
408
409 rb_epoll = &rb->event;
410 rb_epoll->events = EPOLLOUT;
411 if (epoll_ctl(rb->epoll_fd, EPOLL_CTL_ADD, map_fd, rb_epoll) < 0) {
412 err = -errno;
413 pr_warn("user ringbuf: failed to epoll add map fd=%d: %d\n", map_fd, err);
414 return err;
415 }
416
417 return 0;
418}
419
420struct user_ring_buffer *
421user_ring_buffer__new(int map_fd, const struct user_ring_buffer_opts *opts)
422{
423 struct user_ring_buffer *rb;
424 int err;
425
426 if (!OPTS_VALID(opts, user_ring_buffer_opts))
427 return errno = EINVAL, NULL;
428
429 rb = calloc(1, sizeof(*rb));
430 if (!rb)
431 return errno = ENOMEM, NULL;
432
433 rb->page_size = getpagesize();
434
435 rb->epoll_fd = epoll_create1(EPOLL_CLOEXEC);
436 if (rb->epoll_fd < 0) {
437 err = -errno;
438 pr_warn("user ringbuf: failed to create epoll instance: %d\n", err);
439 goto err_out;
440 }
441
442 err = user_ringbuf_map(rb, map_fd);
443 if (err)
444 goto err_out;
445
446 return rb;
447
448err_out:
449 user_ring_buffer__free(rb);
450 return errno = -err, NULL;
451}
452
453static void user_ringbuf_commit(struct user_ring_buffer *rb, void *sample, bool discard)
454{
455 __u32 new_len;
456 struct ringbuf_hdr *hdr;
457 uintptr_t hdr_offset;
458
459 hdr_offset = rb->mask + 1 + (sample - rb->data) - BPF_RINGBUF_HDR_SZ;
460 hdr = rb->data + (hdr_offset & rb->mask);
461
462 new_len = hdr->len & ~BPF_RINGBUF_BUSY_BIT;
463 if (discard)
464 new_len |= BPF_RINGBUF_DISCARD_BIT;
465
466 /* Synchronizes with smp_load_acquire() in __bpf_user_ringbuf_peek() in
467 * the kernel.
468 */
469 __atomic_exchange_n(&hdr->len, new_len, __ATOMIC_ACQ_REL);
470}
471
472void user_ring_buffer__discard(struct user_ring_buffer *rb, void *sample)
473{
474 user_ringbuf_commit(rb, sample, true);
475}
476
477void user_ring_buffer__submit(struct user_ring_buffer *rb, void *sample)
478{
479 user_ringbuf_commit(rb, sample, false);
480}
481
482void *user_ring_buffer__reserve(struct user_ring_buffer *rb, __u32 size)
483{
484 __u32 avail_size, total_size, max_size;
485 /* 64-bit to avoid overflow in case of extreme application behavior */
486 __u64 cons_pos, prod_pos;
487 struct ringbuf_hdr *hdr;
488
489 /* The top two bits are used as special flags */
490 if (size & (BPF_RINGBUF_BUSY_BIT | BPF_RINGBUF_DISCARD_BIT))
491 return errno = E2BIG, NULL;
492
493 /* Synchronizes with smp_store_release() in __bpf_user_ringbuf_peek() in
494 * the kernel.
495 */
496 cons_pos = smp_load_acquire(rb->consumer_pos);
497 /* Synchronizes with smp_store_release() in user_ringbuf_commit() */
498 prod_pos = smp_load_acquire(rb->producer_pos);
499
500 max_size = rb->mask + 1;
501 avail_size = max_size - (prod_pos - cons_pos);
502 /* Round up total size to a multiple of 8. */
503 total_size = (size + BPF_RINGBUF_HDR_SZ + 7) / 8 * 8;
504
505 if (total_size > max_size)
506 return errno = E2BIG, NULL;
507
508 if (avail_size < total_size)
509 return errno = ENOSPC, NULL;
510
511 hdr = rb->data + (prod_pos & rb->mask);
512 hdr->len = size | BPF_RINGBUF_BUSY_BIT;
513 hdr->pad = 0;
514
515 /* Synchronizes with smp_load_acquire() in __bpf_user_ringbuf_peek() in
516 * the kernel.
517 */
518 smp_store_release(rb->producer_pos, prod_pos + total_size);
519
520 return (void *)rb->data + ((prod_pos + BPF_RINGBUF_HDR_SZ) & rb->mask);
521}
522
523static __u64 ns_elapsed_timespec(const struct timespec *start, const struct timespec *end)
524{
525 __u64 start_ns, end_ns, ns_per_s = 1000000000;
526
527 start_ns = (__u64)start->tv_sec * ns_per_s + start->tv_nsec;
528 end_ns = (__u64)end->tv_sec * ns_per_s + end->tv_nsec;
529
530 return end_ns - start_ns;
531}
532
533void *user_ring_buffer__reserve_blocking(struct user_ring_buffer *rb, __u32 size, int timeout_ms)
534{
535 void *sample;
536 int err, ms_remaining = timeout_ms;
537 struct timespec start;
538
539 if (timeout_ms < 0 && timeout_ms != -1)
540 return errno = EINVAL, NULL;
541
542 if (timeout_ms != -1) {
543 err = clock_gettime(CLOCK_MONOTONIC, &start);
544 if (err)
545 return NULL;
546 }
547
548 do {
549 int cnt, ms_elapsed;
550 struct timespec curr;
551 __u64 ns_per_ms = 1000000;
552
553 sample = user_ring_buffer__reserve(rb, size);
554 if (sample)
555 return sample;
556 else if (errno != ENOSPC)
557 return NULL;
558
559 /* The kernel guarantees at least one event notification
560 * delivery whenever at least one sample is drained from the
561 * ring buffer in an invocation to bpf_ringbuf_drain(). Other
562 * additional events may be delivered at any time, but only one
563 * event is guaranteed per bpf_ringbuf_drain() invocation,
564 * provided that a sample is drained, and the BPF program did
565 * not pass BPF_RB_NO_WAKEUP to bpf_ringbuf_drain(). If
566 * BPF_RB_FORCE_WAKEUP is passed to bpf_ringbuf_drain(), a
567 * wakeup event will be delivered even if no samples are
568 * drained.
569 */
570 cnt = epoll_wait(rb->epoll_fd, &rb->event, 1, ms_remaining);
571 if (cnt < 0)
572 return NULL;
573
574 if (timeout_ms == -1)
575 continue;
576
577 err = clock_gettime(CLOCK_MONOTONIC, &curr);
578 if (err)
579 return NULL;
580
581 ms_elapsed = ns_elapsed_timespec(&start, &curr) / ns_per_ms;
582 ms_remaining = timeout_ms - ms_elapsed;
583 } while (ms_remaining > 0);
584
585 /* Try one more time to reserve a sample after the specified timeout has elapsed. */
586 return user_ring_buffer__reserve(rb, size);
587}
1// SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
2/*
3 * Ring buffer operations.
4 *
5 * Copyright (C) 2020 Facebook, Inc.
6 */
7#ifndef _GNU_SOURCE
8#define _GNU_SOURCE
9#endif
10#include <stdlib.h>
11#include <stdio.h>
12#include <errno.h>
13#include <unistd.h>
14#include <linux/err.h>
15#include <linux/bpf.h>
16#include <asm/barrier.h>
17#include <sys/mman.h>
18#include <sys/epoll.h>
19#include <time.h>
20
21#include "libbpf.h"
22#include "libbpf_internal.h"
23#include "bpf.h"
24#include "str_error.h"
25
26struct ring {
27 ring_buffer_sample_fn sample_cb;
28 void *ctx;
29 void *data;
30 unsigned long *consumer_pos;
31 unsigned long *producer_pos;
32 unsigned long mask;
33 int map_fd;
34};
35
36struct ring_buffer {
37 struct epoll_event *events;
38 struct ring **rings;
39 size_t page_size;
40 int epoll_fd;
41 int ring_cnt;
42};
43
44struct user_ring_buffer {
45 struct epoll_event event;
46 unsigned long *consumer_pos;
47 unsigned long *producer_pos;
48 void *data;
49 unsigned long mask;
50 size_t page_size;
51 int map_fd;
52 int epoll_fd;
53};
54
55/* 8-byte ring buffer header structure */
56struct ringbuf_hdr {
57 __u32 len;
58 __u32 pad;
59};
60
61static void ringbuf_free_ring(struct ring_buffer *rb, struct ring *r)
62{
63 if (r->consumer_pos) {
64 munmap(r->consumer_pos, rb->page_size);
65 r->consumer_pos = NULL;
66 }
67 if (r->producer_pos) {
68 munmap(r->producer_pos, rb->page_size + 2 * (r->mask + 1));
69 r->producer_pos = NULL;
70 }
71
72 free(r);
73}
74
75/* Add extra RINGBUF maps to this ring buffer manager */
76int ring_buffer__add(struct ring_buffer *rb, int map_fd,
77 ring_buffer_sample_fn sample_cb, void *ctx)
78{
79 struct bpf_map_info info;
80 __u32 len = sizeof(info);
81 struct epoll_event *e;
82 struct ring *r;
83 __u64 mmap_sz;
84 void *tmp;
85 int err;
86
87 memset(&info, 0, sizeof(info));
88
89 err = bpf_map_get_info_by_fd(map_fd, &info, &len);
90 if (err) {
91 err = -errno;
92 pr_warn("ringbuf: failed to get map info for fd=%d: %s\n",
93 map_fd, errstr(err));
94 return libbpf_err(err);
95 }
96
97 if (info.type != BPF_MAP_TYPE_RINGBUF) {
98 pr_warn("ringbuf: map fd=%d is not BPF_MAP_TYPE_RINGBUF\n",
99 map_fd);
100 return libbpf_err(-EINVAL);
101 }
102
103 tmp = libbpf_reallocarray(rb->rings, rb->ring_cnt + 1, sizeof(*rb->rings));
104 if (!tmp)
105 return libbpf_err(-ENOMEM);
106 rb->rings = tmp;
107
108 tmp = libbpf_reallocarray(rb->events, rb->ring_cnt + 1, sizeof(*rb->events));
109 if (!tmp)
110 return libbpf_err(-ENOMEM);
111 rb->events = tmp;
112
113 r = calloc(1, sizeof(*r));
114 if (!r)
115 return libbpf_err(-ENOMEM);
116 rb->rings[rb->ring_cnt] = r;
117
118 r->map_fd = map_fd;
119 r->sample_cb = sample_cb;
120 r->ctx = ctx;
121 r->mask = info.max_entries - 1;
122
123 /* Map writable consumer page */
124 tmp = mmap(NULL, rb->page_size, PROT_READ | PROT_WRITE, MAP_SHARED, map_fd, 0);
125 if (tmp == MAP_FAILED) {
126 err = -errno;
127 pr_warn("ringbuf: failed to mmap consumer page for map fd=%d: %s\n",
128 map_fd, errstr(err));
129 goto err_out;
130 }
131 r->consumer_pos = tmp;
132
133 /* Map read-only producer page and data pages. We map twice as big
134 * data size to allow simple reading of samples that wrap around the
135 * end of a ring buffer. See kernel implementation for details.
136 */
137 mmap_sz = rb->page_size + 2 * (__u64)info.max_entries;
138 if (mmap_sz != (__u64)(size_t)mmap_sz) {
139 err = -E2BIG;
140 pr_warn("ringbuf: ring buffer size (%u) is too big\n", info.max_entries);
141 goto err_out;
142 }
143 tmp = mmap(NULL, (size_t)mmap_sz, PROT_READ, MAP_SHARED, map_fd, rb->page_size);
144 if (tmp == MAP_FAILED) {
145 err = -errno;
146 pr_warn("ringbuf: failed to mmap data pages for map fd=%d: %s\n",
147 map_fd, errstr(err));
148 goto err_out;
149 }
150 r->producer_pos = tmp;
151 r->data = tmp + rb->page_size;
152
153 e = &rb->events[rb->ring_cnt];
154 memset(e, 0, sizeof(*e));
155
156 e->events = EPOLLIN;
157 e->data.fd = rb->ring_cnt;
158 if (epoll_ctl(rb->epoll_fd, EPOLL_CTL_ADD, map_fd, e) < 0) {
159 err = -errno;
160 pr_warn("ringbuf: failed to epoll add map fd=%d: %s\n",
161 map_fd, errstr(err));
162 goto err_out;
163 }
164
165 rb->ring_cnt++;
166 return 0;
167
168err_out:
169 ringbuf_free_ring(rb, r);
170 return libbpf_err(err);
171}
172
173void ring_buffer__free(struct ring_buffer *rb)
174{
175 int i;
176
177 if (!rb)
178 return;
179
180 for (i = 0; i < rb->ring_cnt; ++i)
181 ringbuf_free_ring(rb, rb->rings[i]);
182 if (rb->epoll_fd >= 0)
183 close(rb->epoll_fd);
184
185 free(rb->events);
186 free(rb->rings);
187 free(rb);
188}
189
190struct ring_buffer *
191ring_buffer__new(int map_fd, ring_buffer_sample_fn sample_cb, void *ctx,
192 const struct ring_buffer_opts *opts)
193{
194 struct ring_buffer *rb;
195 int err;
196
197 if (!OPTS_VALID(opts, ring_buffer_opts))
198 return errno = EINVAL, NULL;
199
200 rb = calloc(1, sizeof(*rb));
201 if (!rb)
202 return errno = ENOMEM, NULL;
203
204 rb->page_size = getpagesize();
205
206 rb->epoll_fd = epoll_create1(EPOLL_CLOEXEC);
207 if (rb->epoll_fd < 0) {
208 err = -errno;
209 pr_warn("ringbuf: failed to create epoll instance: %s\n", errstr(err));
210 goto err_out;
211 }
212
213 err = ring_buffer__add(rb, map_fd, sample_cb, ctx);
214 if (err)
215 goto err_out;
216
217 return rb;
218
219err_out:
220 ring_buffer__free(rb);
221 return errno = -err, NULL;
222}
223
224static inline int roundup_len(__u32 len)
225{
226 /* clear out top 2 bits (discard and busy, if set) */
227 len <<= 2;
228 len >>= 2;
229 /* add length prefix */
230 len += BPF_RINGBUF_HDR_SZ;
231 /* round up to 8 byte alignment */
232 return (len + 7) / 8 * 8;
233}
234
235static int64_t ringbuf_process_ring(struct ring *r, size_t n)
236{
237 int *len_ptr, len, err;
238 /* 64-bit to avoid overflow in case of extreme application behavior */
239 int64_t cnt = 0;
240 unsigned long cons_pos, prod_pos;
241 bool got_new_data;
242 void *sample;
243
244 cons_pos = smp_load_acquire(r->consumer_pos);
245 do {
246 got_new_data = false;
247 prod_pos = smp_load_acquire(r->producer_pos);
248 while (cons_pos < prod_pos) {
249 len_ptr = r->data + (cons_pos & r->mask);
250 len = smp_load_acquire(len_ptr);
251
252 /* sample not committed yet, bail out for now */
253 if (len & BPF_RINGBUF_BUSY_BIT)
254 goto done;
255
256 got_new_data = true;
257 cons_pos += roundup_len(len);
258
259 if ((len & BPF_RINGBUF_DISCARD_BIT) == 0) {
260 sample = (void *)len_ptr + BPF_RINGBUF_HDR_SZ;
261 err = r->sample_cb(r->ctx, sample, len);
262 if (err < 0) {
263 /* update consumer pos and bail out */
264 smp_store_release(r->consumer_pos,
265 cons_pos);
266 return err;
267 }
268 cnt++;
269 }
270
271 smp_store_release(r->consumer_pos, cons_pos);
272
273 if (cnt >= n)
274 goto done;
275 }
276 } while (got_new_data);
277done:
278 return cnt;
279}
280
281/* Consume available ring buffer(s) data without event polling, up to n
282 * records.
283 *
284 * Returns number of records consumed across all registered ring buffers (or
285 * n, whichever is less), or negative number if any of the callbacks return
286 * error.
287 */
288int ring_buffer__consume_n(struct ring_buffer *rb, size_t n)
289{
290 int64_t err, res = 0;
291 int i;
292
293 for (i = 0; i < rb->ring_cnt; i++) {
294 struct ring *ring = rb->rings[i];
295
296 err = ringbuf_process_ring(ring, n);
297 if (err < 0)
298 return libbpf_err(err);
299 res += err;
300 n -= err;
301
302 if (n == 0)
303 break;
304 }
305 return res > INT_MAX ? INT_MAX : res;
306}
307
308/* Consume available ring buffer(s) data without event polling.
309 * Returns number of records consumed across all registered ring buffers (or
310 * INT_MAX, whichever is less), or negative number if any of the callbacks
311 * return error.
312 */
313int ring_buffer__consume(struct ring_buffer *rb)
314{
315 int64_t err, res = 0;
316 int i;
317
318 for (i = 0; i < rb->ring_cnt; i++) {
319 struct ring *ring = rb->rings[i];
320
321 err = ringbuf_process_ring(ring, INT_MAX);
322 if (err < 0)
323 return libbpf_err(err);
324 res += err;
325 if (res > INT_MAX) {
326 res = INT_MAX;
327 break;
328 }
329 }
330 return res;
331}
332
333/* Poll for available data and consume records, if any are available.
334 * Returns number of records consumed (or INT_MAX, whichever is less), or
335 * negative number, if any of the registered callbacks returned error.
336 */
337int ring_buffer__poll(struct ring_buffer *rb, int timeout_ms)
338{
339 int i, cnt;
340 int64_t err, res = 0;
341
342 cnt = epoll_wait(rb->epoll_fd, rb->events, rb->ring_cnt, timeout_ms);
343 if (cnt < 0)
344 return libbpf_err(-errno);
345
346 for (i = 0; i < cnt; i++) {
347 __u32 ring_id = rb->events[i].data.fd;
348 struct ring *ring = rb->rings[ring_id];
349
350 err = ringbuf_process_ring(ring, INT_MAX);
351 if (err < 0)
352 return libbpf_err(err);
353 res += err;
354 }
355 if (res > INT_MAX)
356 res = INT_MAX;
357 return res;
358}
359
360/* Get an fd that can be used to sleep until data is available in the ring(s) */
361int ring_buffer__epoll_fd(const struct ring_buffer *rb)
362{
363 return rb->epoll_fd;
364}
365
366struct ring *ring_buffer__ring(struct ring_buffer *rb, unsigned int idx)
367{
368 if (idx >= rb->ring_cnt)
369 return errno = ERANGE, NULL;
370
371 return rb->rings[idx];
372}
373
374unsigned long ring__consumer_pos(const struct ring *r)
375{
376 /* Synchronizes with smp_store_release() in ringbuf_process_ring(). */
377 return smp_load_acquire(r->consumer_pos);
378}
379
380unsigned long ring__producer_pos(const struct ring *r)
381{
382 /* Synchronizes with smp_store_release() in __bpf_ringbuf_reserve() in
383 * the kernel.
384 */
385 return smp_load_acquire(r->producer_pos);
386}
387
388size_t ring__avail_data_size(const struct ring *r)
389{
390 unsigned long cons_pos, prod_pos;
391
392 cons_pos = ring__consumer_pos(r);
393 prod_pos = ring__producer_pos(r);
394 return prod_pos - cons_pos;
395}
396
397size_t ring__size(const struct ring *r)
398{
399 return r->mask + 1;
400}
401
402int ring__map_fd(const struct ring *r)
403{
404 return r->map_fd;
405}
406
407int ring__consume_n(struct ring *r, size_t n)
408{
409 int64_t res;
410
411 res = ringbuf_process_ring(r, n);
412 if (res < 0)
413 return libbpf_err(res);
414
415 return res > INT_MAX ? INT_MAX : res;
416}
417
418int ring__consume(struct ring *r)
419{
420 return ring__consume_n(r, INT_MAX);
421}
422
423static void user_ringbuf_unmap_ring(struct user_ring_buffer *rb)
424{
425 if (rb->consumer_pos) {
426 munmap(rb->consumer_pos, rb->page_size);
427 rb->consumer_pos = NULL;
428 }
429 if (rb->producer_pos) {
430 munmap(rb->producer_pos, rb->page_size + 2 * (rb->mask + 1));
431 rb->producer_pos = NULL;
432 }
433}
434
435void user_ring_buffer__free(struct user_ring_buffer *rb)
436{
437 if (!rb)
438 return;
439
440 user_ringbuf_unmap_ring(rb);
441
442 if (rb->epoll_fd >= 0)
443 close(rb->epoll_fd);
444
445 free(rb);
446}
447
448static int user_ringbuf_map(struct user_ring_buffer *rb, int map_fd)
449{
450 struct bpf_map_info info;
451 __u32 len = sizeof(info);
452 __u64 mmap_sz;
453 void *tmp;
454 struct epoll_event *rb_epoll;
455 int err;
456
457 memset(&info, 0, sizeof(info));
458
459 err = bpf_map_get_info_by_fd(map_fd, &info, &len);
460 if (err) {
461 err = -errno;
462 pr_warn("user ringbuf: failed to get map info for fd=%d: %s\n",
463 map_fd, errstr(err));
464 return err;
465 }
466
467 if (info.type != BPF_MAP_TYPE_USER_RINGBUF) {
468 pr_warn("user ringbuf: map fd=%d is not BPF_MAP_TYPE_USER_RINGBUF\n", map_fd);
469 return -EINVAL;
470 }
471
472 rb->map_fd = map_fd;
473 rb->mask = info.max_entries - 1;
474
475 /* Map read-only consumer page */
476 tmp = mmap(NULL, rb->page_size, PROT_READ, MAP_SHARED, map_fd, 0);
477 if (tmp == MAP_FAILED) {
478 err = -errno;
479 pr_warn("user ringbuf: failed to mmap consumer page for map fd=%d: %s\n",
480 map_fd, errstr(err));
481 return err;
482 }
483 rb->consumer_pos = tmp;
484
485 /* Map read-write the producer page and data pages. We map the data
486 * region as twice the total size of the ring buffer to allow the
487 * simple reading and writing of samples that wrap around the end of
488 * the buffer. See the kernel implementation for details.
489 */
490 mmap_sz = rb->page_size + 2 * (__u64)info.max_entries;
491 if (mmap_sz != (__u64)(size_t)mmap_sz) {
492 pr_warn("user ringbuf: ring buf size (%u) is too big\n", info.max_entries);
493 return -E2BIG;
494 }
495 tmp = mmap(NULL, (size_t)mmap_sz, PROT_READ | PROT_WRITE, MAP_SHARED,
496 map_fd, rb->page_size);
497 if (tmp == MAP_FAILED) {
498 err = -errno;
499 pr_warn("user ringbuf: failed to mmap data pages for map fd=%d: %s\n",
500 map_fd, errstr(err));
501 return err;
502 }
503
504 rb->producer_pos = tmp;
505 rb->data = tmp + rb->page_size;
506
507 rb_epoll = &rb->event;
508 rb_epoll->events = EPOLLOUT;
509 if (epoll_ctl(rb->epoll_fd, EPOLL_CTL_ADD, map_fd, rb_epoll) < 0) {
510 err = -errno;
511 pr_warn("user ringbuf: failed to epoll add map fd=%d: %s\n", map_fd, errstr(err));
512 return err;
513 }
514
515 return 0;
516}
517
518struct user_ring_buffer *
519user_ring_buffer__new(int map_fd, const struct user_ring_buffer_opts *opts)
520{
521 struct user_ring_buffer *rb;
522 int err;
523
524 if (!OPTS_VALID(opts, user_ring_buffer_opts))
525 return errno = EINVAL, NULL;
526
527 rb = calloc(1, sizeof(*rb));
528 if (!rb)
529 return errno = ENOMEM, NULL;
530
531 rb->page_size = getpagesize();
532
533 rb->epoll_fd = epoll_create1(EPOLL_CLOEXEC);
534 if (rb->epoll_fd < 0) {
535 err = -errno;
536 pr_warn("user ringbuf: failed to create epoll instance: %s\n", errstr(err));
537 goto err_out;
538 }
539
540 err = user_ringbuf_map(rb, map_fd);
541 if (err)
542 goto err_out;
543
544 return rb;
545
546err_out:
547 user_ring_buffer__free(rb);
548 return errno = -err, NULL;
549}
550
551static void user_ringbuf_commit(struct user_ring_buffer *rb, void *sample, bool discard)
552{
553 __u32 new_len;
554 struct ringbuf_hdr *hdr;
555 uintptr_t hdr_offset;
556
557 hdr_offset = rb->mask + 1 + (sample - rb->data) - BPF_RINGBUF_HDR_SZ;
558 hdr = rb->data + (hdr_offset & rb->mask);
559
560 new_len = hdr->len & ~BPF_RINGBUF_BUSY_BIT;
561 if (discard)
562 new_len |= BPF_RINGBUF_DISCARD_BIT;
563
564 /* Synchronizes with smp_load_acquire() in __bpf_user_ringbuf_peek() in
565 * the kernel.
566 */
567 __atomic_exchange_n(&hdr->len, new_len, __ATOMIC_ACQ_REL);
568}
569
570void user_ring_buffer__discard(struct user_ring_buffer *rb, void *sample)
571{
572 user_ringbuf_commit(rb, sample, true);
573}
574
575void user_ring_buffer__submit(struct user_ring_buffer *rb, void *sample)
576{
577 user_ringbuf_commit(rb, sample, false);
578}
579
580void *user_ring_buffer__reserve(struct user_ring_buffer *rb, __u32 size)
581{
582 __u32 avail_size, total_size, max_size;
583 /* 64-bit to avoid overflow in case of extreme application behavior */
584 __u64 cons_pos, prod_pos;
585 struct ringbuf_hdr *hdr;
586
587 /* The top two bits are used as special flags */
588 if (size & (BPF_RINGBUF_BUSY_BIT | BPF_RINGBUF_DISCARD_BIT))
589 return errno = E2BIG, NULL;
590
591 /* Synchronizes with smp_store_release() in __bpf_user_ringbuf_peek() in
592 * the kernel.
593 */
594 cons_pos = smp_load_acquire(rb->consumer_pos);
595 /* Synchronizes with smp_store_release() in user_ringbuf_commit() */
596 prod_pos = smp_load_acquire(rb->producer_pos);
597
598 max_size = rb->mask + 1;
599 avail_size = max_size - (prod_pos - cons_pos);
600 /* Round up total size to a multiple of 8. */
601 total_size = (size + BPF_RINGBUF_HDR_SZ + 7) / 8 * 8;
602
603 if (total_size > max_size)
604 return errno = E2BIG, NULL;
605
606 if (avail_size < total_size)
607 return errno = ENOSPC, NULL;
608
609 hdr = rb->data + (prod_pos & rb->mask);
610 hdr->len = size | BPF_RINGBUF_BUSY_BIT;
611 hdr->pad = 0;
612
613 /* Synchronizes with smp_load_acquire() in __bpf_user_ringbuf_peek() in
614 * the kernel.
615 */
616 smp_store_release(rb->producer_pos, prod_pos + total_size);
617
618 return (void *)rb->data + ((prod_pos + BPF_RINGBUF_HDR_SZ) & rb->mask);
619}
620
621static __u64 ns_elapsed_timespec(const struct timespec *start, const struct timespec *end)
622{
623 __u64 start_ns, end_ns, ns_per_s = 1000000000;
624
625 start_ns = (__u64)start->tv_sec * ns_per_s + start->tv_nsec;
626 end_ns = (__u64)end->tv_sec * ns_per_s + end->tv_nsec;
627
628 return end_ns - start_ns;
629}
630
631void *user_ring_buffer__reserve_blocking(struct user_ring_buffer *rb, __u32 size, int timeout_ms)
632{
633 void *sample;
634 int err, ms_remaining = timeout_ms;
635 struct timespec start;
636
637 if (timeout_ms < 0 && timeout_ms != -1)
638 return errno = EINVAL, NULL;
639
640 if (timeout_ms != -1) {
641 err = clock_gettime(CLOCK_MONOTONIC, &start);
642 if (err)
643 return NULL;
644 }
645
646 do {
647 int cnt, ms_elapsed;
648 struct timespec curr;
649 __u64 ns_per_ms = 1000000;
650
651 sample = user_ring_buffer__reserve(rb, size);
652 if (sample)
653 return sample;
654 else if (errno != ENOSPC)
655 return NULL;
656
657 /* The kernel guarantees at least one event notification
658 * delivery whenever at least one sample is drained from the
659 * ring buffer in an invocation to bpf_ringbuf_drain(). Other
660 * additional events may be delivered at any time, but only one
661 * event is guaranteed per bpf_ringbuf_drain() invocation,
662 * provided that a sample is drained, and the BPF program did
663 * not pass BPF_RB_NO_WAKEUP to bpf_ringbuf_drain(). If
664 * BPF_RB_FORCE_WAKEUP is passed to bpf_ringbuf_drain(), a
665 * wakeup event will be delivered even if no samples are
666 * drained.
667 */
668 cnt = epoll_wait(rb->epoll_fd, &rb->event, 1, ms_remaining);
669 if (cnt < 0)
670 return NULL;
671
672 if (timeout_ms == -1)
673 continue;
674
675 err = clock_gettime(CLOCK_MONOTONIC, &curr);
676 if (err)
677 return NULL;
678
679 ms_elapsed = ns_elapsed_timespec(&start, &curr) / ns_per_ms;
680 ms_remaining = timeout_ms - ms_elapsed;
681 } while (ms_remaining > 0);
682
683 /* Try one more time to reserve a sample after the specified timeout has elapsed. */
684 return user_ring_buffer__reserve(rb, size);
685}