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 <linux/kmemleak.h>
 12#include <uapi/linux/btf.h>
 13#include <linux/btf_ids.h>
 14
 15#define RINGBUF_CREATE_FLAG_MASK (BPF_F_NUMA_NODE)
 16
 17/* non-mmap()'able part of bpf_ringbuf (everything up to consumer page) */
 18#define RINGBUF_PGOFF \
 19	(offsetof(struct bpf_ringbuf, consumer_pos) >> PAGE_SHIFT)
 20/* consumer page and producer page */
 21#define RINGBUF_POS_PAGES 2
 22#define RINGBUF_NR_META_PAGES (RINGBUF_PGOFF + RINGBUF_POS_PAGES)
 23
 24#define RINGBUF_MAX_RECORD_SZ (UINT_MAX/4)
 25
 
 
 
 
 
 
 
 
 
 26struct bpf_ringbuf {
 27	wait_queue_head_t waitq;
 28	struct irq_work work;
 29	u64 mask;
 30	struct page **pages;
 31	int nr_pages;
 32	raw_spinlock_t spinlock ____cacheline_aligned_in_smp;
 33	/* For user-space producer ring buffers, an atomic_t busy bit is used
 34	 * to synchronize access to the ring buffers in the kernel, rather than
 35	 * the spinlock that is used for kernel-producer ring buffers. This is
 36	 * done because the ring buffer must hold a lock across a BPF program's
 37	 * callback:
 38	 *
 39	 *    __bpf_user_ringbuf_peek() // lock acquired
 40	 * -> program callback_fn()
 41	 * -> __bpf_user_ringbuf_sample_release() // lock released
 42	 *
 43	 * It is unsafe and incorrect to hold an IRQ spinlock across what could
 44	 * be a long execution window, so we instead simply disallow concurrent
 45	 * access to the ring buffer by kernel consumers, and return -EBUSY from
 46	 * __bpf_user_ringbuf_peek() if the busy bit is held by another task.
 47	 */
 48	atomic_t busy ____cacheline_aligned_in_smp;
 49	/* Consumer and producer counters are put into separate pages to
 50	 * allow each position to be mapped with different permissions.
 51	 * This prevents a user-space application from modifying the
 52	 * position and ruining in-kernel tracking. The permissions of the
 53	 * pages depend on who is producing samples: user-space or the
 54	 * kernel. Note that the pending counter is placed in the same
 55	 * page as the producer, so that it shares the same cache line.
 56	 *
 57	 * Kernel-producer
 58	 * ---------------
 59	 * The producer position and data pages are mapped as r/o in
 60	 * userspace. For this approach, bits in the header of samples are
 61	 * used to signal to user-space, and to other producers, whether a
 62	 * sample is currently being written.
 63	 *
 64	 * User-space producer
 65	 * -------------------
 66	 * Only the page containing the consumer position is mapped r/o in
 67	 * user-space. User-space producers also use bits of the header to
 68	 * communicate to the kernel, but the kernel must carefully check and
 69	 * validate each sample to ensure that they're correctly formatted, and
 70	 * fully contained within the ring buffer.
 71	 */
 72	unsigned long consumer_pos __aligned(PAGE_SIZE);
 73	unsigned long producer_pos __aligned(PAGE_SIZE);
 74	unsigned long pending_pos;
 75	char data[] __aligned(PAGE_SIZE);
 76};
 77
 78struct bpf_ringbuf_map {
 79	struct bpf_map map;
 80	struct bpf_ringbuf *rb;
 81};
 82
 83/* 8-byte ring buffer record header structure */
 84struct bpf_ringbuf_hdr {
 85	u32 len;
 86	u32 pg_off;
 87};
 88
 89static struct bpf_ringbuf *bpf_ringbuf_area_alloc(size_t data_sz, int numa_node)
 90{
 91	const gfp_t flags = GFP_KERNEL_ACCOUNT | __GFP_RETRY_MAYFAIL |
 92			    __GFP_NOWARN | __GFP_ZERO;
 93	int nr_meta_pages = RINGBUF_NR_META_PAGES;
 94	int nr_data_pages = data_sz >> PAGE_SHIFT;
 95	int nr_pages = nr_meta_pages + nr_data_pages;
 96	struct page **pages, *page;
 97	struct bpf_ringbuf *rb;
 98	size_t array_size;
 99	int i;
100
101	/* Each data page is mapped twice to allow "virtual"
102	 * continuous read of samples wrapping around the end of ring
103	 * buffer area:
104	 * ------------------------------------------------------
105	 * | meta pages |  real data pages  |  same data pages  |
106	 * ------------------------------------------------------
107	 * |            | 1 2 3 4 5 6 7 8 9 | 1 2 3 4 5 6 7 8 9 |
108	 * ------------------------------------------------------
109	 * |            | TA             DA | TA             DA |
110	 * ------------------------------------------------------
111	 *                               ^^^^^^^
112	 *                                  |
113	 * Here, no need to worry about special handling of wrapped-around
114	 * data due to double-mapped data pages. This works both in kernel and
115	 * when mmap()'ed in user-space, simplifying both kernel and
116	 * user-space implementations significantly.
117	 */
118	array_size = (nr_meta_pages + 2 * nr_data_pages) * sizeof(*pages);
119	pages = bpf_map_area_alloc(array_size, numa_node);
120	if (!pages)
121		return NULL;
122
123	for (i = 0; i < nr_pages; i++) {
124		page = alloc_pages_node(numa_node, flags, 0);
125		if (!page) {
126			nr_pages = i;
127			goto err_free_pages;
128		}
129		pages[i] = page;
130		if (i >= nr_meta_pages)
131			pages[nr_data_pages + i] = page;
132	}
133
134	rb = vmap(pages, nr_meta_pages + 2 * nr_data_pages,
135		  VM_MAP | VM_USERMAP, PAGE_KERNEL);
136	if (rb) {
137		kmemleak_not_leak(pages);
138		rb->pages = pages;
139		rb->nr_pages = nr_pages;
140		return rb;
141	}
142
143err_free_pages:
144	for (i = 0; i < nr_pages; i++)
145		__free_page(pages[i]);
146	bpf_map_area_free(pages);
147	return NULL;
148}
149
150static void bpf_ringbuf_notify(struct irq_work *work)
151{
152	struct bpf_ringbuf *rb = container_of(work, struct bpf_ringbuf, work);
153
154	wake_up_all(&rb->waitq);
155}
156
157/* Maximum size of ring buffer area is limited by 32-bit page offset within
158 * record header, counted in pages. Reserve 8 bits for extensibility, and
159 * take into account few extra pages for consumer/producer pages and
160 * non-mmap()'able parts, the current maximum size would be:
161 *
162 *     (((1ULL << 24) - RINGBUF_POS_PAGES - RINGBUF_PGOFF) * PAGE_SIZE)
163 *
164 * This gives 64GB limit, which seems plenty for single ring buffer. Now
165 * considering that the maximum value of data_sz is (4GB - 1), there
166 * will be no overflow, so just note the size limit in the comments.
167 */
168static struct bpf_ringbuf *bpf_ringbuf_alloc(size_t data_sz, int numa_node)
169{
170	struct bpf_ringbuf *rb;
171
172	rb = bpf_ringbuf_area_alloc(data_sz, numa_node);
173	if (!rb)
174		return NULL;
175
176	raw_spin_lock_init(&rb->spinlock);
177	atomic_set(&rb->busy, 0);
178	init_waitqueue_head(&rb->waitq);
179	init_irq_work(&rb->work, bpf_ringbuf_notify);
180
181	rb->mask = data_sz - 1;
182	rb->consumer_pos = 0;
183	rb->producer_pos = 0;
184	rb->pending_pos = 0;
185
186	return rb;
187}
188
189static struct bpf_map *ringbuf_map_alloc(union bpf_attr *attr)
190{
191	struct bpf_ringbuf_map *rb_map;
192
193	if (attr->map_flags & ~RINGBUF_CREATE_FLAG_MASK)
194		return ERR_PTR(-EINVAL);
195
196	if (attr->key_size || attr->value_size ||
197	    !is_power_of_2(attr->max_entries) ||
198	    !PAGE_ALIGNED(attr->max_entries))
199		return ERR_PTR(-EINVAL);
200
201	rb_map = bpf_map_area_alloc(sizeof(*rb_map), NUMA_NO_NODE);
 
 
 
 
 
 
202	if (!rb_map)
203		return ERR_PTR(-ENOMEM);
204
205	bpf_map_init_from_attr(&rb_map->map, attr);
206
207	rb_map->rb = bpf_ringbuf_alloc(attr->max_entries, rb_map->map.numa_node);
208	if (!rb_map->rb) {
209		bpf_map_area_free(rb_map);
210		return ERR_PTR(-ENOMEM);
211	}
212
213	return &rb_map->map;
214}
215
216static void bpf_ringbuf_free(struct bpf_ringbuf *rb)
217{
218	/* copy pages pointer and nr_pages to local variable, as we are going
219	 * to unmap rb itself with vunmap() below
220	 */
221	struct page **pages = rb->pages;
222	int i, nr_pages = rb->nr_pages;
223
224	vunmap(rb);
225	for (i = 0; i < nr_pages; i++)
226		__free_page(pages[i]);
227	bpf_map_area_free(pages);
228}
229
230static void ringbuf_map_free(struct bpf_map *map)
231{
232	struct bpf_ringbuf_map *rb_map;
233
234	rb_map = container_of(map, struct bpf_ringbuf_map, map);
235	bpf_ringbuf_free(rb_map->rb);
236	bpf_map_area_free(rb_map);
237}
238
239static void *ringbuf_map_lookup_elem(struct bpf_map *map, void *key)
240{
241	return ERR_PTR(-ENOTSUPP);
242}
243
244static long ringbuf_map_update_elem(struct bpf_map *map, void *key, void *value,
245				    u64 flags)
246{
247	return -ENOTSUPP;
248}
249
250static long ringbuf_map_delete_elem(struct bpf_map *map, void *key)
251{
252	return -ENOTSUPP;
253}
254
255static int ringbuf_map_get_next_key(struct bpf_map *map, void *key,
256				    void *next_key)
257{
258	return -ENOTSUPP;
259}
260
261static int ringbuf_map_mmap_kern(struct bpf_map *map, struct vm_area_struct *vma)
262{
263	struct bpf_ringbuf_map *rb_map;
264
265	rb_map = container_of(map, struct bpf_ringbuf_map, map);
266
267	if (vma->vm_flags & VM_WRITE) {
268		/* allow writable mapping for the consumer_pos only */
269		if (vma->vm_pgoff != 0 || vma->vm_end - vma->vm_start != PAGE_SIZE)
270			return -EPERM;
 
 
271	}
272	/* remap_vmalloc_range() checks size and offset constraints */
273	return remap_vmalloc_range(vma, rb_map->rb,
274				   vma->vm_pgoff + RINGBUF_PGOFF);
275}
276
277static int ringbuf_map_mmap_user(struct bpf_map *map, struct vm_area_struct *vma)
278{
279	struct bpf_ringbuf_map *rb_map;
280
281	rb_map = container_of(map, struct bpf_ringbuf_map, map);
282
283	if (vma->vm_flags & VM_WRITE) {
284		if (vma->vm_pgoff == 0)
285			/* Disallow writable mappings to the consumer pointer,
286			 * and allow writable mappings to both the producer
287			 * position, and the ring buffer data itself.
288			 */
289			return -EPERM;
290	}
291	/* remap_vmalloc_range() checks size and offset constraints */
292	return remap_vmalloc_range(vma, rb_map->rb, vma->vm_pgoff + RINGBUF_PGOFF);
293}
294
295static unsigned long ringbuf_avail_data_sz(struct bpf_ringbuf *rb)
296{
297	unsigned long cons_pos, prod_pos;
298
299	cons_pos = smp_load_acquire(&rb->consumer_pos);
300	prod_pos = smp_load_acquire(&rb->producer_pos);
301	return prod_pos - cons_pos;
302}
303
304static u32 ringbuf_total_data_sz(const struct bpf_ringbuf *rb)
305{
306	return rb->mask + 1;
307}
308
309static __poll_t ringbuf_map_poll_kern(struct bpf_map *map, struct file *filp,
310				      struct poll_table_struct *pts)
311{
312	struct bpf_ringbuf_map *rb_map;
313
314	rb_map = container_of(map, struct bpf_ringbuf_map, map);
315	poll_wait(filp, &rb_map->rb->waitq, pts);
316
317	if (ringbuf_avail_data_sz(rb_map->rb))
318		return EPOLLIN | EPOLLRDNORM;
319	return 0;
320}
321
322static __poll_t ringbuf_map_poll_user(struct bpf_map *map, struct file *filp,
323				      struct poll_table_struct *pts)
324{
325	struct bpf_ringbuf_map *rb_map;
326
327	rb_map = container_of(map, struct bpf_ringbuf_map, map);
328	poll_wait(filp, &rb_map->rb->waitq, pts);
329
330	if (ringbuf_avail_data_sz(rb_map->rb) < ringbuf_total_data_sz(rb_map->rb))
331		return EPOLLOUT | EPOLLWRNORM;
332	return 0;
333}
334
335static u64 ringbuf_map_mem_usage(const struct bpf_map *map)
336{
337	struct bpf_ringbuf *rb;
338	int nr_data_pages;
339	int nr_meta_pages;
340	u64 usage = sizeof(struct bpf_ringbuf_map);
341
342	rb = container_of(map, struct bpf_ringbuf_map, map)->rb;
343	usage += (u64)rb->nr_pages << PAGE_SHIFT;
344	nr_meta_pages = RINGBUF_NR_META_PAGES;
345	nr_data_pages = map->max_entries >> PAGE_SHIFT;
346	usage += (nr_meta_pages + 2 * nr_data_pages) * sizeof(struct page *);
347	return usage;
348}
349
350BTF_ID_LIST_SINGLE(ringbuf_map_btf_ids, struct, bpf_ringbuf_map)
351const struct bpf_map_ops ringbuf_map_ops = {
352	.map_meta_equal = bpf_map_meta_equal,
353	.map_alloc = ringbuf_map_alloc,
354	.map_free = ringbuf_map_free,
355	.map_mmap = ringbuf_map_mmap_kern,
356	.map_poll = ringbuf_map_poll_kern,
357	.map_lookup_elem = ringbuf_map_lookup_elem,
358	.map_update_elem = ringbuf_map_update_elem,
359	.map_delete_elem = ringbuf_map_delete_elem,
360	.map_get_next_key = ringbuf_map_get_next_key,
361	.map_mem_usage = ringbuf_map_mem_usage,
362	.map_btf_id = &ringbuf_map_btf_ids[0],
363};
364
365BTF_ID_LIST_SINGLE(user_ringbuf_map_btf_ids, struct, bpf_ringbuf_map)
366const struct bpf_map_ops user_ringbuf_map_ops = {
367	.map_meta_equal = bpf_map_meta_equal,
368	.map_alloc = ringbuf_map_alloc,
369	.map_free = ringbuf_map_free,
370	.map_mmap = ringbuf_map_mmap_user,
371	.map_poll = ringbuf_map_poll_user,
372	.map_lookup_elem = ringbuf_map_lookup_elem,
373	.map_update_elem = ringbuf_map_update_elem,
374	.map_delete_elem = ringbuf_map_delete_elem,
375	.map_get_next_key = ringbuf_map_get_next_key,
376	.map_mem_usage = ringbuf_map_mem_usage,
377	.map_btf_id = &user_ringbuf_map_btf_ids[0],
378};
379
380/* Given pointer to ring buffer record metadata and struct bpf_ringbuf itself,
381 * calculate offset from record metadata to ring buffer in pages, rounded
382 * down. This page offset is stored as part of record metadata and allows to
383 * restore struct bpf_ringbuf * from record pointer. This page offset is
384 * stored at offset 4 of record metadata header.
385 */
386static size_t bpf_ringbuf_rec_pg_off(struct bpf_ringbuf *rb,
387				     struct bpf_ringbuf_hdr *hdr)
388{
389	return ((void *)hdr - (void *)rb) >> PAGE_SHIFT;
390}
391
392/* Given pointer to ring buffer record header, restore pointer to struct
393 * bpf_ringbuf itself by using page offset stored at offset 4
394 */
395static struct bpf_ringbuf *
396bpf_ringbuf_restore_from_rec(struct bpf_ringbuf_hdr *hdr)
397{
398	unsigned long addr = (unsigned long)(void *)hdr;
399	unsigned long off = (unsigned long)hdr->pg_off << PAGE_SHIFT;
400
401	return (void*)((addr & PAGE_MASK) - off);
402}
403
404static void *__bpf_ringbuf_reserve(struct bpf_ringbuf *rb, u64 size)
405{
406	unsigned long cons_pos, prod_pos, new_prod_pos, pend_pos, flags;
 
407	struct bpf_ringbuf_hdr *hdr;
408	u32 len, pg_off, tmp_size, hdr_len;
409
410	if (unlikely(size > RINGBUF_MAX_RECORD_SZ))
411		return NULL;
412
413	len = round_up(size + BPF_RINGBUF_HDR_SZ, 8);
414	if (len > ringbuf_total_data_sz(rb))
415		return NULL;
416
417	cons_pos = smp_load_acquire(&rb->consumer_pos);
418
419	if (in_nmi()) {
420		if (!raw_spin_trylock_irqsave(&rb->spinlock, flags))
421			return NULL;
422	} else {
423		raw_spin_lock_irqsave(&rb->spinlock, flags);
424	}
425
426	pend_pos = rb->pending_pos;
427	prod_pos = rb->producer_pos;
428	new_prod_pos = prod_pos + len;
429
430	while (pend_pos < prod_pos) {
431		hdr = (void *)rb->data + (pend_pos & rb->mask);
432		hdr_len = READ_ONCE(hdr->len);
433		if (hdr_len & BPF_RINGBUF_BUSY_BIT)
434			break;
435		tmp_size = hdr_len & ~BPF_RINGBUF_DISCARD_BIT;
436		tmp_size = round_up(tmp_size + BPF_RINGBUF_HDR_SZ, 8);
437		pend_pos += tmp_size;
438	}
439	rb->pending_pos = pend_pos;
440
441	/* check for out of ringbuf space:
442	 * - by ensuring producer position doesn't advance more than
443	 *   (ringbuf_size - 1) ahead
444	 * - by ensuring oldest not yet committed record until newest
445	 *   record does not span more than (ringbuf_size - 1)
446	 */
447	if (new_prod_pos - cons_pos > rb->mask ||
448	    new_prod_pos - pend_pos > rb->mask) {
449		raw_spin_unlock_irqrestore(&rb->spinlock, flags);
450		return NULL;
451	}
452
453	hdr = (void *)rb->data + (prod_pos & rb->mask);
454	pg_off = bpf_ringbuf_rec_pg_off(rb, hdr);
455	hdr->len = size | BPF_RINGBUF_BUSY_BIT;
456	hdr->pg_off = pg_off;
457
458	/* pairs with consumer's smp_load_acquire() */
459	smp_store_release(&rb->producer_pos, new_prod_pos);
460
461	raw_spin_unlock_irqrestore(&rb->spinlock, flags);
462
463	return (void *)hdr + BPF_RINGBUF_HDR_SZ;
464}
465
466BPF_CALL_3(bpf_ringbuf_reserve, struct bpf_map *, map, u64, size, u64, flags)
467{
468	struct bpf_ringbuf_map *rb_map;
469
470	if (unlikely(flags))
471		return 0;
472
473	rb_map = container_of(map, struct bpf_ringbuf_map, map);
474	return (unsigned long)__bpf_ringbuf_reserve(rb_map->rb, size);
475}
476
477const struct bpf_func_proto bpf_ringbuf_reserve_proto = {
478	.func		= bpf_ringbuf_reserve,
479	.ret_type	= RET_PTR_TO_RINGBUF_MEM_OR_NULL,
480	.arg1_type	= ARG_CONST_MAP_PTR,
481	.arg2_type	= ARG_CONST_ALLOC_SIZE_OR_ZERO,
482	.arg3_type	= ARG_ANYTHING,
483};
484
485static void bpf_ringbuf_commit(void *sample, u64 flags, bool discard)
486{
487	unsigned long rec_pos, cons_pos;
488	struct bpf_ringbuf_hdr *hdr;
489	struct bpf_ringbuf *rb;
490	u32 new_len;
491
492	hdr = sample - BPF_RINGBUF_HDR_SZ;
493	rb = bpf_ringbuf_restore_from_rec(hdr);
494	new_len = hdr->len ^ BPF_RINGBUF_BUSY_BIT;
495	if (discard)
496		new_len |= BPF_RINGBUF_DISCARD_BIT;
497
498	/* update record header with correct final size prefix */
499	xchg(&hdr->len, new_len);
500
501	/* if consumer caught up and is waiting for our record, notify about
502	 * new data availability
503	 */
504	rec_pos = (void *)hdr - (void *)rb->data;
505	cons_pos = smp_load_acquire(&rb->consumer_pos) & rb->mask;
506
507	if (flags & BPF_RB_FORCE_WAKEUP)
508		irq_work_queue(&rb->work);
509	else if (cons_pos == rec_pos && !(flags & BPF_RB_NO_WAKEUP))
510		irq_work_queue(&rb->work);
511}
512
513BPF_CALL_2(bpf_ringbuf_submit, void *, sample, u64, flags)
514{
515	bpf_ringbuf_commit(sample, flags, false /* discard */);
516	return 0;
517}
518
519const struct bpf_func_proto bpf_ringbuf_submit_proto = {
520	.func		= bpf_ringbuf_submit,
521	.ret_type	= RET_VOID,
522	.arg1_type	= ARG_PTR_TO_RINGBUF_MEM | OBJ_RELEASE,
523	.arg2_type	= ARG_ANYTHING,
524};
525
526BPF_CALL_2(bpf_ringbuf_discard, void *, sample, u64, flags)
527{
528	bpf_ringbuf_commit(sample, flags, true /* discard */);
529	return 0;
530}
531
532const struct bpf_func_proto bpf_ringbuf_discard_proto = {
533	.func		= bpf_ringbuf_discard,
534	.ret_type	= RET_VOID,
535	.arg1_type	= ARG_PTR_TO_RINGBUF_MEM | OBJ_RELEASE,
536	.arg2_type	= ARG_ANYTHING,
537};
538
539BPF_CALL_4(bpf_ringbuf_output, struct bpf_map *, map, void *, data, u64, size,
540	   u64, flags)
541{
542	struct bpf_ringbuf_map *rb_map;
543	void *rec;
544
545	if (unlikely(flags & ~(BPF_RB_NO_WAKEUP | BPF_RB_FORCE_WAKEUP)))
546		return -EINVAL;
547
548	rb_map = container_of(map, struct bpf_ringbuf_map, map);
549	rec = __bpf_ringbuf_reserve(rb_map->rb, size);
550	if (!rec)
551		return -EAGAIN;
552
553	memcpy(rec, data, size);
554	bpf_ringbuf_commit(rec, flags, false /* discard */);
555	return 0;
556}
557
558const struct bpf_func_proto bpf_ringbuf_output_proto = {
559	.func		= bpf_ringbuf_output,
560	.ret_type	= RET_INTEGER,
561	.arg1_type	= ARG_CONST_MAP_PTR,
562	.arg2_type	= ARG_PTR_TO_MEM | MEM_RDONLY,
563	.arg3_type	= ARG_CONST_SIZE_OR_ZERO,
564	.arg4_type	= ARG_ANYTHING,
565};
566
567BPF_CALL_2(bpf_ringbuf_query, struct bpf_map *, map, u64, flags)
568{
569	struct bpf_ringbuf *rb;
570
571	rb = container_of(map, struct bpf_ringbuf_map, map)->rb;
572
573	switch (flags) {
574	case BPF_RB_AVAIL_DATA:
575		return ringbuf_avail_data_sz(rb);
576	case BPF_RB_RING_SIZE:
577		return ringbuf_total_data_sz(rb);
578	case BPF_RB_CONS_POS:
579		return smp_load_acquire(&rb->consumer_pos);
580	case BPF_RB_PROD_POS:
581		return smp_load_acquire(&rb->producer_pos);
582	default:
583		return 0;
584	}
585}
586
587const struct bpf_func_proto bpf_ringbuf_query_proto = {
588	.func		= bpf_ringbuf_query,
589	.ret_type	= RET_INTEGER,
590	.arg1_type	= ARG_CONST_MAP_PTR,
591	.arg2_type	= ARG_ANYTHING,
592};
593
594BPF_CALL_4(bpf_ringbuf_reserve_dynptr, struct bpf_map *, map, u32, size, u64, flags,
595	   struct bpf_dynptr_kern *, ptr)
596{
597	struct bpf_ringbuf_map *rb_map;
598	void *sample;
599	int err;
600
601	if (unlikely(flags)) {
602		bpf_dynptr_set_null(ptr);
603		return -EINVAL;
604	}
605
606	err = bpf_dynptr_check_size(size);
607	if (err) {
608		bpf_dynptr_set_null(ptr);
609		return err;
610	}
611
612	rb_map = container_of(map, struct bpf_ringbuf_map, map);
613
614	sample = __bpf_ringbuf_reserve(rb_map->rb, size);
615	if (!sample) {
616		bpf_dynptr_set_null(ptr);
617		return -EINVAL;
618	}
619
620	bpf_dynptr_init(ptr, sample, BPF_DYNPTR_TYPE_RINGBUF, 0, size);
621
622	return 0;
623}
624
625const struct bpf_func_proto bpf_ringbuf_reserve_dynptr_proto = {
626	.func		= bpf_ringbuf_reserve_dynptr,
627	.ret_type	= RET_INTEGER,
628	.arg1_type	= ARG_CONST_MAP_PTR,
629	.arg2_type	= ARG_ANYTHING,
630	.arg3_type	= ARG_ANYTHING,
631	.arg4_type	= ARG_PTR_TO_DYNPTR | DYNPTR_TYPE_RINGBUF | MEM_UNINIT | MEM_WRITE,
632};
633
634BPF_CALL_2(bpf_ringbuf_submit_dynptr, struct bpf_dynptr_kern *, ptr, u64, flags)
635{
636	if (!ptr->data)
637		return 0;
638
639	bpf_ringbuf_commit(ptr->data, flags, false /* discard */);
640
641	bpf_dynptr_set_null(ptr);
642
643	return 0;
644}
645
646const struct bpf_func_proto bpf_ringbuf_submit_dynptr_proto = {
647	.func		= bpf_ringbuf_submit_dynptr,
648	.ret_type	= RET_VOID,
649	.arg1_type	= ARG_PTR_TO_DYNPTR | DYNPTR_TYPE_RINGBUF | OBJ_RELEASE,
650	.arg2_type	= ARG_ANYTHING,
651};
652
653BPF_CALL_2(bpf_ringbuf_discard_dynptr, struct bpf_dynptr_kern *, ptr, u64, flags)
654{
655	if (!ptr->data)
656		return 0;
657
658	bpf_ringbuf_commit(ptr->data, flags, true /* discard */);
659
660	bpf_dynptr_set_null(ptr);
661
662	return 0;
663}
664
665const struct bpf_func_proto bpf_ringbuf_discard_dynptr_proto = {
666	.func		= bpf_ringbuf_discard_dynptr,
667	.ret_type	= RET_VOID,
668	.arg1_type	= ARG_PTR_TO_DYNPTR | DYNPTR_TYPE_RINGBUF | OBJ_RELEASE,
669	.arg2_type	= ARG_ANYTHING,
670};
671
672static int __bpf_user_ringbuf_peek(struct bpf_ringbuf *rb, void **sample, u32 *size)
673{
674	int err;
675	u32 hdr_len, sample_len, total_len, flags, *hdr;
676	u64 cons_pos, prod_pos;
677
678	/* Synchronizes with smp_store_release() in user-space producer. */
679	prod_pos = smp_load_acquire(&rb->producer_pos);
680	if (prod_pos % 8)
681		return -EINVAL;
682
683	/* Synchronizes with smp_store_release() in __bpf_user_ringbuf_sample_release() */
684	cons_pos = smp_load_acquire(&rb->consumer_pos);
685	if (cons_pos >= prod_pos)
686		return -ENODATA;
687
688	hdr = (u32 *)((uintptr_t)rb->data + (uintptr_t)(cons_pos & rb->mask));
689	/* Synchronizes with smp_store_release() in user-space producer. */
690	hdr_len = smp_load_acquire(hdr);
691	flags = hdr_len & (BPF_RINGBUF_BUSY_BIT | BPF_RINGBUF_DISCARD_BIT);
692	sample_len = hdr_len & ~flags;
693	total_len = round_up(sample_len + BPF_RINGBUF_HDR_SZ, 8);
694
695	/* The sample must fit within the region advertised by the producer position. */
696	if (total_len > prod_pos - cons_pos)
697		return -EINVAL;
698
699	/* The sample must fit within the data region of the ring buffer. */
700	if (total_len > ringbuf_total_data_sz(rb))
701		return -E2BIG;
702
703	/* The sample must fit into a struct bpf_dynptr. */
704	err = bpf_dynptr_check_size(sample_len);
705	if (err)
706		return -E2BIG;
707
708	if (flags & BPF_RINGBUF_DISCARD_BIT) {
709		/* If the discard bit is set, the sample should be skipped.
710		 *
711		 * Update the consumer pos, and return -EAGAIN so the caller
712		 * knows to skip this sample and try to read the next one.
713		 */
714		smp_store_release(&rb->consumer_pos, cons_pos + total_len);
715		return -EAGAIN;
716	}
717
718	if (flags & BPF_RINGBUF_BUSY_BIT)
719		return -ENODATA;
720
721	*sample = (void *)((uintptr_t)rb->data +
722			   (uintptr_t)((cons_pos + BPF_RINGBUF_HDR_SZ) & rb->mask));
723	*size = sample_len;
724	return 0;
725}
726
727static void __bpf_user_ringbuf_sample_release(struct bpf_ringbuf *rb, size_t size, u64 flags)
728{
729	u64 consumer_pos;
730	u32 rounded_size = round_up(size + BPF_RINGBUF_HDR_SZ, 8);
731
732	/* Using smp_load_acquire() is unnecessary here, as the busy-bit
733	 * prevents another task from writing to consumer_pos after it was read
734	 * by this task with smp_load_acquire() in __bpf_user_ringbuf_peek().
735	 */
736	consumer_pos = rb->consumer_pos;
737	 /* Synchronizes with smp_load_acquire() in user-space producer. */
738	smp_store_release(&rb->consumer_pos, consumer_pos + rounded_size);
739}
740
741BPF_CALL_4(bpf_user_ringbuf_drain, struct bpf_map *, map,
742	   void *, callback_fn, void *, callback_ctx, u64, flags)
743{
744	struct bpf_ringbuf *rb;
745	long samples, discarded_samples = 0, ret = 0;
746	bpf_callback_t callback = (bpf_callback_t)callback_fn;
747	u64 wakeup_flags = BPF_RB_NO_WAKEUP | BPF_RB_FORCE_WAKEUP;
748	int busy = 0;
749
750	if (unlikely(flags & ~wakeup_flags))
751		return -EINVAL;
752
753	rb = container_of(map, struct bpf_ringbuf_map, map)->rb;
754
755	/* If another consumer is already consuming a sample, wait for them to finish. */
756	if (!atomic_try_cmpxchg(&rb->busy, &busy, 1))
757		return -EBUSY;
758
759	for (samples = 0; samples < BPF_MAX_USER_RINGBUF_SAMPLES && ret == 0; samples++) {
760		int err;
761		u32 size;
762		void *sample;
763		struct bpf_dynptr_kern dynptr;
764
765		err = __bpf_user_ringbuf_peek(rb, &sample, &size);
766		if (err) {
767			if (err == -ENODATA) {
768				break;
769			} else if (err == -EAGAIN) {
770				discarded_samples++;
771				continue;
772			} else {
773				ret = err;
774				goto schedule_work_return;
775			}
776		}
777
778		bpf_dynptr_init(&dynptr, sample, BPF_DYNPTR_TYPE_LOCAL, 0, size);
779		ret = callback((uintptr_t)&dynptr, (uintptr_t)callback_ctx, 0, 0, 0);
780		__bpf_user_ringbuf_sample_release(rb, size, flags);
781	}
782	ret = samples - discarded_samples;
783
784schedule_work_return:
785	/* Prevent the clearing of the busy-bit from being reordered before the
786	 * storing of any rb consumer or producer positions.
787	 */
788	atomic_set_release(&rb->busy, 0);
789
790	if (flags & BPF_RB_FORCE_WAKEUP)
791		irq_work_queue(&rb->work);
792	else if (!(flags & BPF_RB_NO_WAKEUP) && samples > 0)
793		irq_work_queue(&rb->work);
794	return ret;
795}
796
797const struct bpf_func_proto bpf_user_ringbuf_drain_proto = {
798	.func		= bpf_user_ringbuf_drain,
799	.ret_type	= RET_INTEGER,
800	.arg1_type	= ARG_CONST_MAP_PTR,
801	.arg2_type	= ARG_PTR_TO_FUNC,
802	.arg3_type	= ARG_PTR_TO_STACK_OR_NULL,
803	.arg4_type	= ARG_ANYTHING,
804};