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 
23 #define RINGBUF_MAX_RECORD_SZ (UINT_MAX/4)
24 
25 /* Maximum size of ring buffer area is limited by 32-bit page offset within
26  * record header, counted in pages. Reserve 8 bits for extensibility, and take
27  * into account few extra pages for consumer/producer pages and
28  * non-mmap()'able parts. This gives 64GB limit, which seems plenty for single
29  * ring buffer.
30  */
31 #define RINGBUF_MAX_DATA_SZ \
32 	(((1ULL << 24) - RINGBUF_POS_PAGES - RINGBUF_PGOFF) * PAGE_SIZE)
33 
34 struct bpf_ringbuf {
35 	wait_queue_head_t waitq;
36 	struct irq_work work;
37 	u64 mask;
38 	struct page **pages;
39 	int nr_pages;
40 	spinlock_t spinlock ____cacheline_aligned_in_smp;
41 	/* Consumer and producer counters are put into separate pages to allow
42 	 * mapping consumer page as r/w, but restrict producer page to r/o.
43 	 * This protects producer position from being modified by user-space
44 	 * application and ruining in-kernel position tracking.
45 	 */
46 	unsigned long consumer_pos __aligned(PAGE_SIZE);
47 	unsigned long producer_pos __aligned(PAGE_SIZE);
48 	char data[] __aligned(PAGE_SIZE);
49 };
50 
51 struct bpf_ringbuf_map {
52 	struct bpf_map map;
53 	struct bpf_ringbuf *rb;
54 };
55 
56 /* 8-byte ring buffer record header structure */
57 struct bpf_ringbuf_hdr {
58 	u32 len;
59 	u32 pg_off;
60 };
61 
bpf_ringbuf_area_alloc(size_t data_sz,int numa_node)62 static struct bpf_ringbuf *bpf_ringbuf_area_alloc(size_t data_sz, int numa_node)
63 {
64 	const gfp_t flags = GFP_KERNEL_ACCOUNT | __GFP_RETRY_MAYFAIL |
65 			    __GFP_NOWARN | __GFP_ZERO;
66 	int nr_meta_pages = RINGBUF_PGOFF + RINGBUF_POS_PAGES;
67 	int nr_data_pages = data_sz >> PAGE_SHIFT;
68 	int nr_pages = nr_meta_pages + nr_data_pages;
69 	struct page **pages, *page;
70 	struct bpf_ringbuf *rb;
71 	size_t array_size;
72 	int i;
73 
74 	/* Each data page is mapped twice to allow "virtual"
75 	 * continuous read of samples wrapping around the end of ring
76 	 * buffer area:
77 	 * ------------------------------------------------------
78 	 * | meta pages |  real data pages  |  same data pages  |
79 	 * ------------------------------------------------------
80 	 * |            | 1 2 3 4 5 6 7 8 9 | 1 2 3 4 5 6 7 8 9 |
81 	 * ------------------------------------------------------
82 	 * |            | TA             DA | TA             DA |
83 	 * ------------------------------------------------------
84 	 *                               ^^^^^^^
85 	 *                                  |
86 	 * Here, no need to worry about special handling of wrapped-around
87 	 * data due to double-mapped data pages. This works both in kernel and
88 	 * when mmap()'ed in user-space, simplifying both kernel and
89 	 * user-space implementations significantly.
90 	 */
91 	array_size = (nr_meta_pages + 2 * nr_data_pages) * sizeof(*pages);
92 	pages = bpf_map_area_alloc(array_size, numa_node);
93 	if (!pages)
94 		return NULL;
95 
96 	for (i = 0; i < nr_pages; i++) {
97 		page = alloc_pages_node(numa_node, flags, 0);
98 		if (!page) {
99 			nr_pages = i;
100 			goto err_free_pages;
101 		}
102 		pages[i] = page;
103 		if (i >= nr_meta_pages)
104 			pages[nr_data_pages + i] = page;
105 	}
106 
107 	rb = vmap(pages, nr_meta_pages + 2 * nr_data_pages,
108 		  VM_MAP | VM_USERMAP, PAGE_KERNEL);
109 	if (rb) {
110 		kmemleak_not_leak(pages);
111 		rb->pages = pages;
112 		rb->nr_pages = nr_pages;
113 		return rb;
114 	}
115 
116 err_free_pages:
117 	for (i = 0; i < nr_pages; i++)
118 		__free_page(pages[i]);
119 	kvfree(pages);
120 	return NULL;
121 }
122 
bpf_ringbuf_notify(struct irq_work * work)123 static void bpf_ringbuf_notify(struct irq_work *work)
124 {
125 	struct bpf_ringbuf *rb = container_of(work, struct bpf_ringbuf, work);
126 
127 	wake_up_all(&rb->waitq);
128 }
129 
bpf_ringbuf_alloc(size_t data_sz,int numa_node)130 static struct bpf_ringbuf *bpf_ringbuf_alloc(size_t data_sz, int numa_node)
131 {
132 	struct bpf_ringbuf *rb;
133 
134 	rb = bpf_ringbuf_area_alloc(data_sz, numa_node);
135 	if (!rb)
136 		return NULL;
137 
138 	spin_lock_init(&rb->spinlock);
139 	init_waitqueue_head(&rb->waitq);
140 	init_irq_work(&rb->work, bpf_ringbuf_notify);
141 
142 	rb->mask = data_sz - 1;
143 	rb->consumer_pos = 0;
144 	rb->producer_pos = 0;
145 
146 	return rb;
147 }
148 
ringbuf_map_alloc(union bpf_attr * attr)149 static struct bpf_map *ringbuf_map_alloc(union bpf_attr *attr)
150 {
151 	struct bpf_ringbuf_map *rb_map;
152 
153 	if (attr->map_flags & ~RINGBUF_CREATE_FLAG_MASK)
154 		return ERR_PTR(-EINVAL);
155 
156 	if (attr->key_size || attr->value_size ||
157 	    !is_power_of_2(attr->max_entries) ||
158 	    !PAGE_ALIGNED(attr->max_entries))
159 		return ERR_PTR(-EINVAL);
160 
161 #ifdef CONFIG_64BIT
162 	/* on 32-bit arch, it's impossible to overflow record's hdr->pgoff */
163 	if (attr->max_entries > RINGBUF_MAX_DATA_SZ)
164 		return ERR_PTR(-E2BIG);
165 #endif
166 
167 	rb_map = kzalloc(sizeof(*rb_map), GFP_USER | __GFP_ACCOUNT);
168 	if (!rb_map)
169 		return ERR_PTR(-ENOMEM);
170 
171 	bpf_map_init_from_attr(&rb_map->map, attr);
172 
173 	rb_map->rb = bpf_ringbuf_alloc(attr->max_entries, rb_map->map.numa_node);
174 	if (!rb_map->rb) {
175 		kfree(rb_map);
176 		return ERR_PTR(-ENOMEM);
177 	}
178 
179 	return &rb_map->map;
180 }
181 
bpf_ringbuf_free(struct bpf_ringbuf * rb)182 static void bpf_ringbuf_free(struct bpf_ringbuf *rb)
183 {
184 	/* copy pages pointer and nr_pages to local variable, as we are going
185 	 * to unmap rb itself with vunmap() below
186 	 */
187 	struct page **pages = rb->pages;
188 	int i, nr_pages = rb->nr_pages;
189 
190 	vunmap(rb);
191 	for (i = 0; i < nr_pages; i++)
192 		__free_page(pages[i]);
193 	kvfree(pages);
194 }
195 
ringbuf_map_free(struct bpf_map * map)196 static void ringbuf_map_free(struct bpf_map *map)
197 {
198 	struct bpf_ringbuf_map *rb_map;
199 
200 	rb_map = container_of(map, struct bpf_ringbuf_map, map);
201 	bpf_ringbuf_free(rb_map->rb);
202 	kfree(rb_map);
203 }
204 
ringbuf_map_lookup_elem(struct bpf_map * map,void * key)205 static void *ringbuf_map_lookup_elem(struct bpf_map *map, void *key)
206 {
207 	return ERR_PTR(-ENOTSUPP);
208 }
209 
ringbuf_map_update_elem(struct bpf_map * map,void * key,void * value,u64 flags)210 static int ringbuf_map_update_elem(struct bpf_map *map, void *key, void *value,
211 				   u64 flags)
212 {
213 	return -ENOTSUPP;
214 }
215 
ringbuf_map_delete_elem(struct bpf_map * map,void * key)216 static int ringbuf_map_delete_elem(struct bpf_map *map, void *key)
217 {
218 	return -ENOTSUPP;
219 }
220 
ringbuf_map_get_next_key(struct bpf_map * map,void * key,void * next_key)221 static int ringbuf_map_get_next_key(struct bpf_map *map, void *key,
222 				    void *next_key)
223 {
224 	return -ENOTSUPP;
225 }
226 
ringbuf_map_mmap(struct bpf_map * map,struct vm_area_struct * vma)227 static int ringbuf_map_mmap(struct bpf_map *map, struct vm_area_struct *vma)
228 {
229 	struct bpf_ringbuf_map *rb_map;
230 
231 	rb_map = container_of(map, struct bpf_ringbuf_map, map);
232 
233 	if (vma->vm_flags & VM_WRITE) {
234 		/* allow writable mapping for the consumer_pos only */
235 		if (vma->vm_pgoff != 0 || vma->vm_end - vma->vm_start != PAGE_SIZE)
236 			return -EPERM;
237 	} else {
238 		vma->vm_flags &= ~VM_MAYWRITE;
239 	}
240 	/* remap_vmalloc_range() checks size and offset constraints */
241 	return remap_vmalloc_range(vma, rb_map->rb,
242 				   vma->vm_pgoff + RINGBUF_PGOFF);
243 }
244 
ringbuf_avail_data_sz(struct bpf_ringbuf * rb)245 static unsigned long ringbuf_avail_data_sz(struct bpf_ringbuf *rb)
246 {
247 	unsigned long cons_pos, prod_pos;
248 
249 	cons_pos = smp_load_acquire(&rb->consumer_pos);
250 	prod_pos = smp_load_acquire(&rb->producer_pos);
251 	return prod_pos - cons_pos;
252 }
253 
ringbuf_map_poll(struct bpf_map * map,struct file * filp,struct poll_table_struct * pts)254 static __poll_t ringbuf_map_poll(struct bpf_map *map, struct file *filp,
255 				 struct poll_table_struct *pts)
256 {
257 	struct bpf_ringbuf_map *rb_map;
258 
259 	rb_map = container_of(map, struct bpf_ringbuf_map, map);
260 	poll_wait(filp, &rb_map->rb->waitq, pts);
261 
262 	if (ringbuf_avail_data_sz(rb_map->rb))
263 		return EPOLLIN | EPOLLRDNORM;
264 	return 0;
265 }
266 
267 BTF_ID_LIST_SINGLE(ringbuf_map_btf_ids, struct, bpf_ringbuf_map)
268 const struct bpf_map_ops ringbuf_map_ops = {
269 	.map_meta_equal = bpf_map_meta_equal,
270 	.map_alloc = ringbuf_map_alloc,
271 	.map_free = ringbuf_map_free,
272 	.map_mmap = ringbuf_map_mmap,
273 	.map_poll = ringbuf_map_poll,
274 	.map_lookup_elem = ringbuf_map_lookup_elem,
275 	.map_update_elem = ringbuf_map_update_elem,
276 	.map_delete_elem = ringbuf_map_delete_elem,
277 	.map_get_next_key = ringbuf_map_get_next_key,
278 	.map_btf_id = &ringbuf_map_btf_ids[0],
279 };
280 
281 /* Given pointer to ring buffer record metadata and struct bpf_ringbuf itself,
282  * calculate offset from record metadata to ring buffer in pages, rounded
283  * down. This page offset is stored as part of record metadata and allows to
284  * restore struct bpf_ringbuf * from record pointer. This page offset is
285  * stored at offset 4 of record metadata header.
286  */
bpf_ringbuf_rec_pg_off(struct bpf_ringbuf * rb,struct bpf_ringbuf_hdr * hdr)287 static size_t bpf_ringbuf_rec_pg_off(struct bpf_ringbuf *rb,
288 				     struct bpf_ringbuf_hdr *hdr)
289 {
290 	return ((void *)hdr - (void *)rb) >> PAGE_SHIFT;
291 }
292 
293 /* Given pointer to ring buffer record header, restore pointer to struct
294  * bpf_ringbuf itself by using page offset stored at offset 4
295  */
296 static struct bpf_ringbuf *
bpf_ringbuf_restore_from_rec(struct bpf_ringbuf_hdr * hdr)297 bpf_ringbuf_restore_from_rec(struct bpf_ringbuf_hdr *hdr)
298 {
299 	unsigned long addr = (unsigned long)(void *)hdr;
300 	unsigned long off = (unsigned long)hdr->pg_off << PAGE_SHIFT;
301 
302 	return (void*)((addr & PAGE_MASK) - off);
303 }
304 
__bpf_ringbuf_reserve(struct bpf_ringbuf * rb,u64 size)305 static void *__bpf_ringbuf_reserve(struct bpf_ringbuf *rb, u64 size)
306 {
307 	unsigned long cons_pos, prod_pos, new_prod_pos, flags;
308 	u32 len, pg_off;
309 	struct bpf_ringbuf_hdr *hdr;
310 
311 	if (unlikely(size > RINGBUF_MAX_RECORD_SZ))
312 		return NULL;
313 
314 	len = round_up(size + BPF_RINGBUF_HDR_SZ, 8);
315 	if (len > rb->mask + 1)
316 		return NULL;
317 
318 	cons_pos = smp_load_acquire(&rb->consumer_pos);
319 
320 	if (in_nmi()) {
321 		if (!spin_trylock_irqsave(&rb->spinlock, flags))
322 			return NULL;
323 	} else {
324 		spin_lock_irqsave(&rb->spinlock, flags);
325 	}
326 
327 	prod_pos = rb->producer_pos;
328 	new_prod_pos = prod_pos + len;
329 
330 	/* check for out of ringbuf space by ensuring producer position
331 	 * doesn't advance more than (ringbuf_size - 1) ahead
332 	 */
333 	if (new_prod_pos - cons_pos > rb->mask) {
334 		spin_unlock_irqrestore(&rb->spinlock, flags);
335 		return NULL;
336 	}
337 
338 	hdr = (void *)rb->data + (prod_pos & rb->mask);
339 	pg_off = bpf_ringbuf_rec_pg_off(rb, hdr);
340 	hdr->len = size | BPF_RINGBUF_BUSY_BIT;
341 	hdr->pg_off = pg_off;
342 
343 	/* pairs with consumer's smp_load_acquire() */
344 	smp_store_release(&rb->producer_pos, new_prod_pos);
345 
346 	spin_unlock_irqrestore(&rb->spinlock, flags);
347 
348 	return (void *)hdr + BPF_RINGBUF_HDR_SZ;
349 }
350 
BPF_CALL_3(bpf_ringbuf_reserve,struct bpf_map *,map,u64,size,u64,flags)351 BPF_CALL_3(bpf_ringbuf_reserve, struct bpf_map *, map, u64, size, u64, flags)
352 {
353 	struct bpf_ringbuf_map *rb_map;
354 
355 	if (unlikely(flags))
356 		return 0;
357 
358 	rb_map = container_of(map, struct bpf_ringbuf_map, map);
359 	return (unsigned long)__bpf_ringbuf_reserve(rb_map->rb, size);
360 }
361 
362 const struct bpf_func_proto bpf_ringbuf_reserve_proto = {
363 	.func		= bpf_ringbuf_reserve,
364 	.ret_type	= RET_PTR_TO_ALLOC_MEM_OR_NULL,
365 	.arg1_type	= ARG_CONST_MAP_PTR,
366 	.arg2_type	= ARG_CONST_ALLOC_SIZE_OR_ZERO,
367 	.arg3_type	= ARG_ANYTHING,
368 };
369 
bpf_ringbuf_commit(void * sample,u64 flags,bool discard)370 static void bpf_ringbuf_commit(void *sample, u64 flags, bool discard)
371 {
372 	unsigned long rec_pos, cons_pos;
373 	struct bpf_ringbuf_hdr *hdr;
374 	struct bpf_ringbuf *rb;
375 	u32 new_len;
376 
377 	hdr = sample - BPF_RINGBUF_HDR_SZ;
378 	rb = bpf_ringbuf_restore_from_rec(hdr);
379 	new_len = hdr->len ^ BPF_RINGBUF_BUSY_BIT;
380 	if (discard)
381 		new_len |= BPF_RINGBUF_DISCARD_BIT;
382 
383 	/* update record header with correct final size prefix */
384 	xchg(&hdr->len, new_len);
385 
386 	/* if consumer caught up and is waiting for our record, notify about
387 	 * new data availability
388 	 */
389 	rec_pos = (void *)hdr - (void *)rb->data;
390 	cons_pos = smp_load_acquire(&rb->consumer_pos) & rb->mask;
391 
392 	if (flags & BPF_RB_FORCE_WAKEUP)
393 		irq_work_queue(&rb->work);
394 	else if (cons_pos == rec_pos && !(flags & BPF_RB_NO_WAKEUP))
395 		irq_work_queue(&rb->work);
396 }
397 
BPF_CALL_2(bpf_ringbuf_submit,void *,sample,u64,flags)398 BPF_CALL_2(bpf_ringbuf_submit, void *, sample, u64, flags)
399 {
400 	bpf_ringbuf_commit(sample, flags, false /* discard */);
401 	return 0;
402 }
403 
404 const struct bpf_func_proto bpf_ringbuf_submit_proto = {
405 	.func		= bpf_ringbuf_submit,
406 	.ret_type	= RET_VOID,
407 	.arg1_type	= ARG_PTR_TO_ALLOC_MEM | OBJ_RELEASE,
408 	.arg2_type	= ARG_ANYTHING,
409 };
410 
BPF_CALL_2(bpf_ringbuf_discard,void *,sample,u64,flags)411 BPF_CALL_2(bpf_ringbuf_discard, void *, sample, u64, flags)
412 {
413 	bpf_ringbuf_commit(sample, flags, true /* discard */);
414 	return 0;
415 }
416 
417 const struct bpf_func_proto bpf_ringbuf_discard_proto = {
418 	.func		= bpf_ringbuf_discard,
419 	.ret_type	= RET_VOID,
420 	.arg1_type	= ARG_PTR_TO_ALLOC_MEM | OBJ_RELEASE,
421 	.arg2_type	= ARG_ANYTHING,
422 };
423 
BPF_CALL_4(bpf_ringbuf_output,struct bpf_map *,map,void *,data,u64,size,u64,flags)424 BPF_CALL_4(bpf_ringbuf_output, struct bpf_map *, map, void *, data, u64, size,
425 	   u64, flags)
426 {
427 	struct bpf_ringbuf_map *rb_map;
428 	void *rec;
429 
430 	if (unlikely(flags & ~(BPF_RB_NO_WAKEUP | BPF_RB_FORCE_WAKEUP)))
431 		return -EINVAL;
432 
433 	rb_map = container_of(map, struct bpf_ringbuf_map, map);
434 	rec = __bpf_ringbuf_reserve(rb_map->rb, size);
435 	if (!rec)
436 		return -EAGAIN;
437 
438 	memcpy(rec, data, size);
439 	bpf_ringbuf_commit(rec, flags, false /* discard */);
440 	return 0;
441 }
442 
443 const struct bpf_func_proto bpf_ringbuf_output_proto = {
444 	.func		= bpf_ringbuf_output,
445 	.ret_type	= RET_INTEGER,
446 	.arg1_type	= ARG_CONST_MAP_PTR,
447 	.arg2_type	= ARG_PTR_TO_MEM | MEM_RDONLY,
448 	.arg3_type	= ARG_CONST_SIZE_OR_ZERO,
449 	.arg4_type	= ARG_ANYTHING,
450 };
451 
BPF_CALL_2(bpf_ringbuf_query,struct bpf_map *,map,u64,flags)452 BPF_CALL_2(bpf_ringbuf_query, struct bpf_map *, map, u64, flags)
453 {
454 	struct bpf_ringbuf *rb;
455 
456 	rb = container_of(map, struct bpf_ringbuf_map, map)->rb;
457 
458 	switch (flags) {
459 	case BPF_RB_AVAIL_DATA:
460 		return ringbuf_avail_data_sz(rb);
461 	case BPF_RB_RING_SIZE:
462 		return rb->mask + 1;
463 	case BPF_RB_CONS_POS:
464 		return smp_load_acquire(&rb->consumer_pos);
465 	case BPF_RB_PROD_POS:
466 		return smp_load_acquire(&rb->producer_pos);
467 	default:
468 		return 0;
469 	}
470 }
471 
472 const struct bpf_func_proto bpf_ringbuf_query_proto = {
473 	.func		= bpf_ringbuf_query,
474 	.ret_type	= RET_INTEGER,
475 	.arg1_type	= ARG_CONST_MAP_PTR,
476 	.arg2_type	= ARG_ANYTHING,
477 };
478 
BPF_CALL_4(bpf_ringbuf_reserve_dynptr,struct bpf_map *,map,u32,size,u64,flags,struct bpf_dynptr_kern *,ptr)479 BPF_CALL_4(bpf_ringbuf_reserve_dynptr, struct bpf_map *, map, u32, size, u64, flags,
480 	   struct bpf_dynptr_kern *, ptr)
481 {
482 	struct bpf_ringbuf_map *rb_map;
483 	void *sample;
484 	int err;
485 
486 	if (unlikely(flags)) {
487 		bpf_dynptr_set_null(ptr);
488 		return -EINVAL;
489 	}
490 
491 	err = bpf_dynptr_check_size(size);
492 	if (err) {
493 		bpf_dynptr_set_null(ptr);
494 		return err;
495 	}
496 
497 	rb_map = container_of(map, struct bpf_ringbuf_map, map);
498 
499 	sample = __bpf_ringbuf_reserve(rb_map->rb, size);
500 	if (!sample) {
501 		bpf_dynptr_set_null(ptr);
502 		return -EINVAL;
503 	}
504 
505 	bpf_dynptr_init(ptr, sample, BPF_DYNPTR_TYPE_RINGBUF, 0, size);
506 
507 	return 0;
508 }
509 
510 const struct bpf_func_proto bpf_ringbuf_reserve_dynptr_proto = {
511 	.func		= bpf_ringbuf_reserve_dynptr,
512 	.ret_type	= RET_INTEGER,
513 	.arg1_type	= ARG_CONST_MAP_PTR,
514 	.arg2_type	= ARG_ANYTHING,
515 	.arg3_type	= ARG_ANYTHING,
516 	.arg4_type	= ARG_PTR_TO_DYNPTR | DYNPTR_TYPE_RINGBUF | MEM_UNINIT,
517 };
518 
BPF_CALL_2(bpf_ringbuf_submit_dynptr,struct bpf_dynptr_kern *,ptr,u64,flags)519 BPF_CALL_2(bpf_ringbuf_submit_dynptr, struct bpf_dynptr_kern *, ptr, u64, flags)
520 {
521 	if (!ptr->data)
522 		return 0;
523 
524 	bpf_ringbuf_commit(ptr->data, flags, false /* discard */);
525 
526 	bpf_dynptr_set_null(ptr);
527 
528 	return 0;
529 }
530 
531 const struct bpf_func_proto bpf_ringbuf_submit_dynptr_proto = {
532 	.func		= bpf_ringbuf_submit_dynptr,
533 	.ret_type	= RET_VOID,
534 	.arg1_type	= ARG_PTR_TO_DYNPTR | DYNPTR_TYPE_RINGBUF | OBJ_RELEASE,
535 	.arg2_type	= ARG_ANYTHING,
536 };
537 
BPF_CALL_2(bpf_ringbuf_discard_dynptr,struct bpf_dynptr_kern *,ptr,u64,flags)538 BPF_CALL_2(bpf_ringbuf_discard_dynptr, struct bpf_dynptr_kern *, ptr, u64, flags)
539 {
540 	if (!ptr->data)
541 		return 0;
542 
543 	bpf_ringbuf_commit(ptr->data, flags, true /* discard */);
544 
545 	bpf_dynptr_set_null(ptr);
546 
547 	return 0;
548 }
549 
550 const struct bpf_func_proto bpf_ringbuf_discard_dynptr_proto = {
551 	.func		= bpf_ringbuf_discard_dynptr,
552 	.ret_type	= RET_VOID,
553 	.arg1_type	= ARG_PTR_TO_DYNPTR | DYNPTR_TYPE_RINGBUF | OBJ_RELEASE,
554 	.arg2_type	= ARG_ANYTHING,
555 };
556