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 	/* For user-space producer ring buffers, an atomic_t busy bit is used
42 	 * to synchronize access to the ring buffers in the kernel, rather than
43 	 * the spinlock that is used for kernel-producer ring buffers. This is
44 	 * done because the ring buffer must hold a lock across a BPF program's
45 	 * callback:
46 	 *
47 	 *    __bpf_user_ringbuf_peek() // lock acquired
48 	 * -> program callback_fn()
49 	 * -> __bpf_user_ringbuf_sample_release() // lock released
50 	 *
51 	 * It is unsafe and incorrect to hold an IRQ spinlock across what could
52 	 * be a long execution window, so we instead simply disallow concurrent
53 	 * access to the ring buffer by kernel consumers, and return -EBUSY from
54 	 * __bpf_user_ringbuf_peek() if the busy bit is held by another task.
55 	 */
56 	atomic_t busy ____cacheline_aligned_in_smp;
57 	/* Consumer and producer counters are put into separate pages to
58 	 * allow each position to be mapped with different permissions.
59 	 * This prevents a user-space application from modifying the
60 	 * position and ruining in-kernel tracking. The permissions of the
61 	 * pages depend on who is producing samples: user-space or the
62 	 * kernel.
63 	 *
64 	 * Kernel-producer
65 	 * ---------------
66 	 * The producer position and data pages are mapped as r/o in
67 	 * userspace. For this approach, bits in the header of samples are
68 	 * used to signal to user-space, and to other producers, whether a
69 	 * sample is currently being written.
70 	 *
71 	 * User-space producer
72 	 * -------------------
73 	 * Only the page containing the consumer position is mapped r/o in
74 	 * user-space. User-space producers also use bits of the header to
75 	 * communicate to the kernel, but the kernel must carefully check and
76 	 * validate each sample to ensure that they're correctly formatted, and
77 	 * fully contained within the ring buffer.
78 	 */
79 	unsigned long consumer_pos __aligned(PAGE_SIZE);
80 	unsigned long producer_pos __aligned(PAGE_SIZE);
81 	char data[] __aligned(PAGE_SIZE);
82 };
83 
84 struct bpf_ringbuf_map {
85 	struct bpf_map map;
86 	struct bpf_ringbuf *rb;
87 };
88 
89 /* 8-byte ring buffer record header structure */
90 struct bpf_ringbuf_hdr {
91 	u32 len;
92 	u32 pg_off;
93 };
94 
bpf_ringbuf_area_alloc(size_t data_sz,int numa_node)95 static struct bpf_ringbuf *bpf_ringbuf_area_alloc(size_t data_sz, int numa_node)
96 {
97 	const gfp_t flags = GFP_KERNEL_ACCOUNT | __GFP_RETRY_MAYFAIL |
98 			    __GFP_NOWARN | __GFP_ZERO;
99 	int nr_meta_pages = RINGBUF_PGOFF + RINGBUF_POS_PAGES;
100 	int nr_data_pages = data_sz >> PAGE_SHIFT;
101 	int nr_pages = nr_meta_pages + nr_data_pages;
102 	struct page **pages, *page;
103 	struct bpf_ringbuf *rb;
104 	size_t array_size;
105 	int i;
106 
107 	/* Each data page is mapped twice to allow "virtual"
108 	 * continuous read of samples wrapping around the end of ring
109 	 * buffer area:
110 	 * ------------------------------------------------------
111 	 * | meta pages |  real data pages  |  same data pages  |
112 	 * ------------------------------------------------------
113 	 * |            | 1 2 3 4 5 6 7 8 9 | 1 2 3 4 5 6 7 8 9 |
114 	 * ------------------------------------------------------
115 	 * |            | TA             DA | TA             DA |
116 	 * ------------------------------------------------------
117 	 *                               ^^^^^^^
118 	 *                                  |
119 	 * Here, no need to worry about special handling of wrapped-around
120 	 * data due to double-mapped data pages. This works both in kernel and
121 	 * when mmap()'ed in user-space, simplifying both kernel and
122 	 * user-space implementations significantly.
123 	 */
124 	array_size = (nr_meta_pages + 2 * nr_data_pages) * sizeof(*pages);
125 	pages = bpf_map_area_alloc(array_size, numa_node);
126 	if (!pages)
127 		return NULL;
128 
129 	for (i = 0; i < nr_pages; i++) {
130 		page = alloc_pages_node(numa_node, flags, 0);
131 		if (!page) {
132 			nr_pages = i;
133 			goto err_free_pages;
134 		}
135 		pages[i] = page;
136 		if (i >= nr_meta_pages)
137 			pages[nr_data_pages + i] = page;
138 	}
139 
140 	rb = vmap(pages, nr_meta_pages + 2 * nr_data_pages,
141 		  VM_MAP | VM_USERMAP, PAGE_KERNEL);
142 	if (rb) {
143 		kmemleak_not_leak(pages);
144 		rb->pages = pages;
145 		rb->nr_pages = nr_pages;
146 		return rb;
147 	}
148 
149 err_free_pages:
150 	for (i = 0; i < nr_pages; i++)
151 		__free_page(pages[i]);
152 	bpf_map_area_free(pages);
153 	return NULL;
154 }
155 
bpf_ringbuf_notify(struct irq_work * work)156 static void bpf_ringbuf_notify(struct irq_work *work)
157 {
158 	struct bpf_ringbuf *rb = container_of(work, struct bpf_ringbuf, work);
159 
160 	wake_up_all(&rb->waitq);
161 }
162 
bpf_ringbuf_alloc(size_t data_sz,int numa_node)163 static struct bpf_ringbuf *bpf_ringbuf_alloc(size_t data_sz, int numa_node)
164 {
165 	struct bpf_ringbuf *rb;
166 
167 	rb = bpf_ringbuf_area_alloc(data_sz, numa_node);
168 	if (!rb)
169 		return NULL;
170 
171 	spin_lock_init(&rb->spinlock);
172 	atomic_set(&rb->busy, 0);
173 	init_waitqueue_head(&rb->waitq);
174 	init_irq_work(&rb->work, bpf_ringbuf_notify);
175 
176 	rb->mask = data_sz - 1;
177 	rb->consumer_pos = 0;
178 	rb->producer_pos = 0;
179 
180 	return rb;
181 }
182 
ringbuf_map_alloc(union bpf_attr * attr)183 static struct bpf_map *ringbuf_map_alloc(union bpf_attr *attr)
184 {
185 	struct bpf_ringbuf_map *rb_map;
186 
187 	if (attr->map_flags & ~RINGBUF_CREATE_FLAG_MASK)
188 		return ERR_PTR(-EINVAL);
189 
190 	if (attr->key_size || attr->value_size ||
191 	    !is_power_of_2(attr->max_entries) ||
192 	    !PAGE_ALIGNED(attr->max_entries))
193 		return ERR_PTR(-EINVAL);
194 
195 #ifdef CONFIG_64BIT
196 	/* on 32-bit arch, it's impossible to overflow record's hdr->pgoff */
197 	if (attr->max_entries > RINGBUF_MAX_DATA_SZ)
198 		return ERR_PTR(-E2BIG);
199 #endif
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 
bpf_ringbuf_free(struct bpf_ringbuf * rb)216 static 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 
ringbuf_map_free(struct bpf_map * map)230 static 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 
ringbuf_map_lookup_elem(struct bpf_map * map,void * key)239 static void *ringbuf_map_lookup_elem(struct bpf_map *map, void *key)
240 {
241 	return ERR_PTR(-ENOTSUPP);
242 }
243 
ringbuf_map_update_elem(struct bpf_map * map,void * key,void * value,u64 flags)244 static int ringbuf_map_update_elem(struct bpf_map *map, void *key, void *value,
245 				   u64 flags)
246 {
247 	return -ENOTSUPP;
248 }
249 
ringbuf_map_delete_elem(struct bpf_map * map,void * key)250 static int ringbuf_map_delete_elem(struct bpf_map *map, void *key)
251 {
252 	return -ENOTSUPP;
253 }
254 
ringbuf_map_get_next_key(struct bpf_map * map,void * key,void * next_key)255 static int ringbuf_map_get_next_key(struct bpf_map *map, void *key,
256 				    void *next_key)
257 {
258 	return -ENOTSUPP;
259 }
260 
ringbuf_map_mmap_kern(struct bpf_map * map,struct vm_area_struct * vma)261 static 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 	} else {
272 		vma->vm_flags &= ~VM_MAYWRITE;
273 	}
274 	/* remap_vmalloc_range() checks size and offset constraints */
275 	return remap_vmalloc_range(vma, rb_map->rb,
276 				   vma->vm_pgoff + RINGBUF_PGOFF);
277 }
278 
ringbuf_map_mmap_user(struct bpf_map * map,struct vm_area_struct * vma)279 static int ringbuf_map_mmap_user(struct bpf_map *map, struct vm_area_struct *vma)
280 {
281 	struct bpf_ringbuf_map *rb_map;
282 
283 	rb_map = container_of(map, struct bpf_ringbuf_map, map);
284 
285 	if (vma->vm_flags & VM_WRITE) {
286 		if (vma->vm_pgoff == 0)
287 			/* Disallow writable mappings to the consumer pointer,
288 			 * and allow writable mappings to both the producer
289 			 * position, and the ring buffer data itself.
290 			 */
291 			return -EPERM;
292 	} else {
293 		vma->vm_flags &= ~VM_MAYWRITE;
294 	}
295 	/* remap_vmalloc_range() checks size and offset constraints */
296 	return remap_vmalloc_range(vma, rb_map->rb, vma->vm_pgoff + RINGBUF_PGOFF);
297 }
298 
ringbuf_avail_data_sz(struct bpf_ringbuf * rb)299 static unsigned long ringbuf_avail_data_sz(struct bpf_ringbuf *rb)
300 {
301 	unsigned long cons_pos, prod_pos;
302 
303 	cons_pos = smp_load_acquire(&rb->consumer_pos);
304 	prod_pos = smp_load_acquire(&rb->producer_pos);
305 	return prod_pos - cons_pos;
306 }
307 
ringbuf_total_data_sz(const struct bpf_ringbuf * rb)308 static u32 ringbuf_total_data_sz(const struct bpf_ringbuf *rb)
309 {
310 	return rb->mask + 1;
311 }
312 
ringbuf_map_poll_kern(struct bpf_map * map,struct file * filp,struct poll_table_struct * pts)313 static __poll_t ringbuf_map_poll_kern(struct bpf_map *map, struct file *filp,
314 				      struct poll_table_struct *pts)
315 {
316 	struct bpf_ringbuf_map *rb_map;
317 
318 	rb_map = container_of(map, struct bpf_ringbuf_map, map);
319 	poll_wait(filp, &rb_map->rb->waitq, pts);
320 
321 	if (ringbuf_avail_data_sz(rb_map->rb))
322 		return EPOLLIN | EPOLLRDNORM;
323 	return 0;
324 }
325 
ringbuf_map_poll_user(struct bpf_map * map,struct file * filp,struct poll_table_struct * pts)326 static __poll_t ringbuf_map_poll_user(struct bpf_map *map, struct file *filp,
327 				      struct poll_table_struct *pts)
328 {
329 	struct bpf_ringbuf_map *rb_map;
330 
331 	rb_map = container_of(map, struct bpf_ringbuf_map, map);
332 	poll_wait(filp, &rb_map->rb->waitq, pts);
333 
334 	if (ringbuf_avail_data_sz(rb_map->rb) < ringbuf_total_data_sz(rb_map->rb))
335 		return EPOLLOUT | EPOLLWRNORM;
336 	return 0;
337 }
338 
339 BTF_ID_LIST_SINGLE(ringbuf_map_btf_ids, struct, bpf_ringbuf_map)
340 const struct bpf_map_ops ringbuf_map_ops = {
341 	.map_meta_equal = bpf_map_meta_equal,
342 	.map_alloc = ringbuf_map_alloc,
343 	.map_free = ringbuf_map_free,
344 	.map_mmap = ringbuf_map_mmap_kern,
345 	.map_poll = ringbuf_map_poll_kern,
346 	.map_lookup_elem = ringbuf_map_lookup_elem,
347 	.map_update_elem = ringbuf_map_update_elem,
348 	.map_delete_elem = ringbuf_map_delete_elem,
349 	.map_get_next_key = ringbuf_map_get_next_key,
350 	.map_btf_id = &ringbuf_map_btf_ids[0],
351 };
352 
353 BTF_ID_LIST_SINGLE(user_ringbuf_map_btf_ids, struct, bpf_ringbuf_map)
354 const struct bpf_map_ops user_ringbuf_map_ops = {
355 	.map_meta_equal = bpf_map_meta_equal,
356 	.map_alloc = ringbuf_map_alloc,
357 	.map_free = ringbuf_map_free,
358 	.map_mmap = ringbuf_map_mmap_user,
359 	.map_poll = ringbuf_map_poll_user,
360 	.map_lookup_elem = ringbuf_map_lookup_elem,
361 	.map_update_elem = ringbuf_map_update_elem,
362 	.map_delete_elem = ringbuf_map_delete_elem,
363 	.map_get_next_key = ringbuf_map_get_next_key,
364 	.map_btf_id = &user_ringbuf_map_btf_ids[0],
365 };
366 
367 /* Given pointer to ring buffer record metadata and struct bpf_ringbuf itself,
368  * calculate offset from record metadata to ring buffer in pages, rounded
369  * down. This page offset is stored as part of record metadata and allows to
370  * restore struct bpf_ringbuf * from record pointer. This page offset is
371  * stored at offset 4 of record metadata header.
372  */
bpf_ringbuf_rec_pg_off(struct bpf_ringbuf * rb,struct bpf_ringbuf_hdr * hdr)373 static size_t bpf_ringbuf_rec_pg_off(struct bpf_ringbuf *rb,
374 				     struct bpf_ringbuf_hdr *hdr)
375 {
376 	return ((void *)hdr - (void *)rb) >> PAGE_SHIFT;
377 }
378 
379 /* Given pointer to ring buffer record header, restore pointer to struct
380  * bpf_ringbuf itself by using page offset stored at offset 4
381  */
382 static struct bpf_ringbuf *
bpf_ringbuf_restore_from_rec(struct bpf_ringbuf_hdr * hdr)383 bpf_ringbuf_restore_from_rec(struct bpf_ringbuf_hdr *hdr)
384 {
385 	unsigned long addr = (unsigned long)(void *)hdr;
386 	unsigned long off = (unsigned long)hdr->pg_off << PAGE_SHIFT;
387 
388 	return (void*)((addr & PAGE_MASK) - off);
389 }
390 
__bpf_ringbuf_reserve(struct bpf_ringbuf * rb,u64 size)391 static void *__bpf_ringbuf_reserve(struct bpf_ringbuf *rb, u64 size)
392 {
393 	unsigned long cons_pos, prod_pos, new_prod_pos, flags;
394 	u32 len, pg_off;
395 	struct bpf_ringbuf_hdr *hdr;
396 
397 	if (unlikely(size > RINGBUF_MAX_RECORD_SZ))
398 		return NULL;
399 
400 	len = round_up(size + BPF_RINGBUF_HDR_SZ, 8);
401 	if (len > ringbuf_total_data_sz(rb))
402 		return NULL;
403 
404 	cons_pos = smp_load_acquire(&rb->consumer_pos);
405 
406 	if (in_nmi()) {
407 		if (!spin_trylock_irqsave(&rb->spinlock, flags))
408 			return NULL;
409 	} else {
410 		spin_lock_irqsave(&rb->spinlock, flags);
411 	}
412 
413 	prod_pos = rb->producer_pos;
414 	new_prod_pos = prod_pos + len;
415 
416 	/* check for out of ringbuf space by ensuring producer position
417 	 * doesn't advance more than (ringbuf_size - 1) ahead
418 	 */
419 	if (new_prod_pos - cons_pos > rb->mask) {
420 		spin_unlock_irqrestore(&rb->spinlock, flags);
421 		return NULL;
422 	}
423 
424 	hdr = (void *)rb->data + (prod_pos & rb->mask);
425 	pg_off = bpf_ringbuf_rec_pg_off(rb, hdr);
426 	hdr->len = size | BPF_RINGBUF_BUSY_BIT;
427 	hdr->pg_off = pg_off;
428 
429 	/* pairs with consumer's smp_load_acquire() */
430 	smp_store_release(&rb->producer_pos, new_prod_pos);
431 
432 	spin_unlock_irqrestore(&rb->spinlock, flags);
433 
434 	return (void *)hdr + BPF_RINGBUF_HDR_SZ;
435 }
436 
BPF_CALL_3(bpf_ringbuf_reserve,struct bpf_map *,map,u64,size,u64,flags)437 BPF_CALL_3(bpf_ringbuf_reserve, struct bpf_map *, map, u64, size, u64, flags)
438 {
439 	struct bpf_ringbuf_map *rb_map;
440 
441 	if (unlikely(flags))
442 		return 0;
443 
444 	rb_map = container_of(map, struct bpf_ringbuf_map, map);
445 	return (unsigned long)__bpf_ringbuf_reserve(rb_map->rb, size);
446 }
447 
448 const struct bpf_func_proto bpf_ringbuf_reserve_proto = {
449 	.func		= bpf_ringbuf_reserve,
450 	.ret_type	= RET_PTR_TO_ALLOC_MEM_OR_NULL,
451 	.arg1_type	= ARG_CONST_MAP_PTR,
452 	.arg2_type	= ARG_CONST_ALLOC_SIZE_OR_ZERO,
453 	.arg3_type	= ARG_ANYTHING,
454 };
455 
bpf_ringbuf_commit(void * sample,u64 flags,bool discard)456 static void bpf_ringbuf_commit(void *sample, u64 flags, bool discard)
457 {
458 	unsigned long rec_pos, cons_pos;
459 	struct bpf_ringbuf_hdr *hdr;
460 	struct bpf_ringbuf *rb;
461 	u32 new_len;
462 
463 	hdr = sample - BPF_RINGBUF_HDR_SZ;
464 	rb = bpf_ringbuf_restore_from_rec(hdr);
465 	new_len = hdr->len ^ BPF_RINGBUF_BUSY_BIT;
466 	if (discard)
467 		new_len |= BPF_RINGBUF_DISCARD_BIT;
468 
469 	/* update record header with correct final size prefix */
470 	xchg(&hdr->len, new_len);
471 
472 	/* if consumer caught up and is waiting for our record, notify about
473 	 * new data availability
474 	 */
475 	rec_pos = (void *)hdr - (void *)rb->data;
476 	cons_pos = smp_load_acquire(&rb->consumer_pos) & rb->mask;
477 
478 	if (flags & BPF_RB_FORCE_WAKEUP)
479 		irq_work_queue(&rb->work);
480 	else if (cons_pos == rec_pos && !(flags & BPF_RB_NO_WAKEUP))
481 		irq_work_queue(&rb->work);
482 }
483 
BPF_CALL_2(bpf_ringbuf_submit,void *,sample,u64,flags)484 BPF_CALL_2(bpf_ringbuf_submit, void *, sample, u64, flags)
485 {
486 	bpf_ringbuf_commit(sample, flags, false /* discard */);
487 	return 0;
488 }
489 
490 const struct bpf_func_proto bpf_ringbuf_submit_proto = {
491 	.func		= bpf_ringbuf_submit,
492 	.ret_type	= RET_VOID,
493 	.arg1_type	= ARG_PTR_TO_ALLOC_MEM | OBJ_RELEASE,
494 	.arg2_type	= ARG_ANYTHING,
495 };
496 
BPF_CALL_2(bpf_ringbuf_discard,void *,sample,u64,flags)497 BPF_CALL_2(bpf_ringbuf_discard, void *, sample, u64, flags)
498 {
499 	bpf_ringbuf_commit(sample, flags, true /* discard */);
500 	return 0;
501 }
502 
503 const struct bpf_func_proto bpf_ringbuf_discard_proto = {
504 	.func		= bpf_ringbuf_discard,
505 	.ret_type	= RET_VOID,
506 	.arg1_type	= ARG_PTR_TO_ALLOC_MEM | OBJ_RELEASE,
507 	.arg2_type	= ARG_ANYTHING,
508 };
509 
BPF_CALL_4(bpf_ringbuf_output,struct bpf_map *,map,void *,data,u64,size,u64,flags)510 BPF_CALL_4(bpf_ringbuf_output, struct bpf_map *, map, void *, data, u64, size,
511 	   u64, flags)
512 {
513 	struct bpf_ringbuf_map *rb_map;
514 	void *rec;
515 
516 	if (unlikely(flags & ~(BPF_RB_NO_WAKEUP | BPF_RB_FORCE_WAKEUP)))
517 		return -EINVAL;
518 
519 	rb_map = container_of(map, struct bpf_ringbuf_map, map);
520 	rec = __bpf_ringbuf_reserve(rb_map->rb, size);
521 	if (!rec)
522 		return -EAGAIN;
523 
524 	memcpy(rec, data, size);
525 	bpf_ringbuf_commit(rec, flags, false /* discard */);
526 	return 0;
527 }
528 
529 const struct bpf_func_proto bpf_ringbuf_output_proto = {
530 	.func		= bpf_ringbuf_output,
531 	.ret_type	= RET_INTEGER,
532 	.arg1_type	= ARG_CONST_MAP_PTR,
533 	.arg2_type	= ARG_PTR_TO_MEM | MEM_RDONLY,
534 	.arg3_type	= ARG_CONST_SIZE_OR_ZERO,
535 	.arg4_type	= ARG_ANYTHING,
536 };
537 
BPF_CALL_2(bpf_ringbuf_query,struct bpf_map *,map,u64,flags)538 BPF_CALL_2(bpf_ringbuf_query, struct bpf_map *, map, u64, flags)
539 {
540 	struct bpf_ringbuf *rb;
541 
542 	rb = container_of(map, struct bpf_ringbuf_map, map)->rb;
543 
544 	switch (flags) {
545 	case BPF_RB_AVAIL_DATA:
546 		return ringbuf_avail_data_sz(rb);
547 	case BPF_RB_RING_SIZE:
548 		return ringbuf_total_data_sz(rb);
549 	case BPF_RB_CONS_POS:
550 		return smp_load_acquire(&rb->consumer_pos);
551 	case BPF_RB_PROD_POS:
552 		return smp_load_acquire(&rb->producer_pos);
553 	default:
554 		return 0;
555 	}
556 }
557 
558 const struct bpf_func_proto bpf_ringbuf_query_proto = {
559 	.func		= bpf_ringbuf_query,
560 	.ret_type	= RET_INTEGER,
561 	.arg1_type	= ARG_CONST_MAP_PTR,
562 	.arg2_type	= ARG_ANYTHING,
563 };
564 
BPF_CALL_4(bpf_ringbuf_reserve_dynptr,struct bpf_map *,map,u32,size,u64,flags,struct bpf_dynptr_kern *,ptr)565 BPF_CALL_4(bpf_ringbuf_reserve_dynptr, struct bpf_map *, map, u32, size, u64, flags,
566 	   struct bpf_dynptr_kern *, ptr)
567 {
568 	struct bpf_ringbuf_map *rb_map;
569 	void *sample;
570 	int err;
571 
572 	if (unlikely(flags)) {
573 		bpf_dynptr_set_null(ptr);
574 		return -EINVAL;
575 	}
576 
577 	err = bpf_dynptr_check_size(size);
578 	if (err) {
579 		bpf_dynptr_set_null(ptr);
580 		return err;
581 	}
582 
583 	rb_map = container_of(map, struct bpf_ringbuf_map, map);
584 
585 	sample = __bpf_ringbuf_reserve(rb_map->rb, size);
586 	if (!sample) {
587 		bpf_dynptr_set_null(ptr);
588 		return -EINVAL;
589 	}
590 
591 	bpf_dynptr_init(ptr, sample, BPF_DYNPTR_TYPE_RINGBUF, 0, size);
592 
593 	return 0;
594 }
595 
596 const struct bpf_func_proto bpf_ringbuf_reserve_dynptr_proto = {
597 	.func		= bpf_ringbuf_reserve_dynptr,
598 	.ret_type	= RET_INTEGER,
599 	.arg1_type	= ARG_CONST_MAP_PTR,
600 	.arg2_type	= ARG_ANYTHING,
601 	.arg3_type	= ARG_ANYTHING,
602 	.arg4_type	= ARG_PTR_TO_DYNPTR | DYNPTR_TYPE_RINGBUF | MEM_UNINIT,
603 };
604 
BPF_CALL_2(bpf_ringbuf_submit_dynptr,struct bpf_dynptr_kern *,ptr,u64,flags)605 BPF_CALL_2(bpf_ringbuf_submit_dynptr, struct bpf_dynptr_kern *, ptr, u64, flags)
606 {
607 	if (!ptr->data)
608 		return 0;
609 
610 	bpf_ringbuf_commit(ptr->data, flags, false /* discard */);
611 
612 	bpf_dynptr_set_null(ptr);
613 
614 	return 0;
615 }
616 
617 const struct bpf_func_proto bpf_ringbuf_submit_dynptr_proto = {
618 	.func		= bpf_ringbuf_submit_dynptr,
619 	.ret_type	= RET_VOID,
620 	.arg1_type	= ARG_PTR_TO_DYNPTR | DYNPTR_TYPE_RINGBUF | OBJ_RELEASE,
621 	.arg2_type	= ARG_ANYTHING,
622 };
623 
BPF_CALL_2(bpf_ringbuf_discard_dynptr,struct bpf_dynptr_kern *,ptr,u64,flags)624 BPF_CALL_2(bpf_ringbuf_discard_dynptr, struct bpf_dynptr_kern *, ptr, u64, flags)
625 {
626 	if (!ptr->data)
627 		return 0;
628 
629 	bpf_ringbuf_commit(ptr->data, flags, true /* discard */);
630 
631 	bpf_dynptr_set_null(ptr);
632 
633 	return 0;
634 }
635 
636 const struct bpf_func_proto bpf_ringbuf_discard_dynptr_proto = {
637 	.func		= bpf_ringbuf_discard_dynptr,
638 	.ret_type	= RET_VOID,
639 	.arg1_type	= ARG_PTR_TO_DYNPTR | DYNPTR_TYPE_RINGBUF | OBJ_RELEASE,
640 	.arg2_type	= ARG_ANYTHING,
641 };
642 
__bpf_user_ringbuf_peek(struct bpf_ringbuf * rb,void ** sample,u32 * size)643 static int __bpf_user_ringbuf_peek(struct bpf_ringbuf *rb, void **sample, u32 *size)
644 {
645 	int err;
646 	u32 hdr_len, sample_len, total_len, flags, *hdr;
647 	u64 cons_pos, prod_pos;
648 
649 	/* Synchronizes with smp_store_release() in user-space producer. */
650 	prod_pos = smp_load_acquire(&rb->producer_pos);
651 	if (prod_pos % 8)
652 		return -EINVAL;
653 
654 	/* Synchronizes with smp_store_release() in __bpf_user_ringbuf_sample_release() */
655 	cons_pos = smp_load_acquire(&rb->consumer_pos);
656 	if (cons_pos >= prod_pos)
657 		return -ENODATA;
658 
659 	hdr = (u32 *)((uintptr_t)rb->data + (uintptr_t)(cons_pos & rb->mask));
660 	/* Synchronizes with smp_store_release() in user-space producer. */
661 	hdr_len = smp_load_acquire(hdr);
662 	flags = hdr_len & (BPF_RINGBUF_BUSY_BIT | BPF_RINGBUF_DISCARD_BIT);
663 	sample_len = hdr_len & ~flags;
664 	total_len = round_up(sample_len + BPF_RINGBUF_HDR_SZ, 8);
665 
666 	/* The sample must fit within the region advertised by the producer position. */
667 	if (total_len > prod_pos - cons_pos)
668 		return -EINVAL;
669 
670 	/* The sample must fit within the data region of the ring buffer. */
671 	if (total_len > ringbuf_total_data_sz(rb))
672 		return -E2BIG;
673 
674 	/* The sample must fit into a struct bpf_dynptr. */
675 	err = bpf_dynptr_check_size(sample_len);
676 	if (err)
677 		return -E2BIG;
678 
679 	if (flags & BPF_RINGBUF_DISCARD_BIT) {
680 		/* If the discard bit is set, the sample should be skipped.
681 		 *
682 		 * Update the consumer pos, and return -EAGAIN so the caller
683 		 * knows to skip this sample and try to read the next one.
684 		 */
685 		smp_store_release(&rb->consumer_pos, cons_pos + total_len);
686 		return -EAGAIN;
687 	}
688 
689 	if (flags & BPF_RINGBUF_BUSY_BIT)
690 		return -ENODATA;
691 
692 	*sample = (void *)((uintptr_t)rb->data +
693 			   (uintptr_t)((cons_pos + BPF_RINGBUF_HDR_SZ) & rb->mask));
694 	*size = sample_len;
695 	return 0;
696 }
697 
__bpf_user_ringbuf_sample_release(struct bpf_ringbuf * rb,size_t size,u64 flags)698 static void __bpf_user_ringbuf_sample_release(struct bpf_ringbuf *rb, size_t size, u64 flags)
699 {
700 	u64 consumer_pos;
701 	u32 rounded_size = round_up(size + BPF_RINGBUF_HDR_SZ, 8);
702 
703 	/* Using smp_load_acquire() is unnecessary here, as the busy-bit
704 	 * prevents another task from writing to consumer_pos after it was read
705 	 * by this task with smp_load_acquire() in __bpf_user_ringbuf_peek().
706 	 */
707 	consumer_pos = rb->consumer_pos;
708 	 /* Synchronizes with smp_load_acquire() in user-space producer. */
709 	smp_store_release(&rb->consumer_pos, consumer_pos + rounded_size);
710 }
711 
BPF_CALL_4(bpf_user_ringbuf_drain,struct bpf_map *,map,void *,callback_fn,void *,callback_ctx,u64,flags)712 BPF_CALL_4(bpf_user_ringbuf_drain, struct bpf_map *, map,
713 	   void *, callback_fn, void *, callback_ctx, u64, flags)
714 {
715 	struct bpf_ringbuf *rb;
716 	long samples, discarded_samples = 0, ret = 0;
717 	bpf_callback_t callback = (bpf_callback_t)callback_fn;
718 	u64 wakeup_flags = BPF_RB_NO_WAKEUP | BPF_RB_FORCE_WAKEUP;
719 	int busy = 0;
720 
721 	if (unlikely(flags & ~wakeup_flags))
722 		return -EINVAL;
723 
724 	rb = container_of(map, struct bpf_ringbuf_map, map)->rb;
725 
726 	/* If another consumer is already consuming a sample, wait for them to finish. */
727 	if (!atomic_try_cmpxchg(&rb->busy, &busy, 1))
728 		return -EBUSY;
729 
730 	for (samples = 0; samples < BPF_MAX_USER_RINGBUF_SAMPLES && ret == 0; samples++) {
731 		int err;
732 		u32 size;
733 		void *sample;
734 		struct bpf_dynptr_kern dynptr;
735 
736 		err = __bpf_user_ringbuf_peek(rb, &sample, &size);
737 		if (err) {
738 			if (err == -ENODATA) {
739 				break;
740 			} else if (err == -EAGAIN) {
741 				discarded_samples++;
742 				continue;
743 			} else {
744 				ret = err;
745 				goto schedule_work_return;
746 			}
747 		}
748 
749 		bpf_dynptr_init(&dynptr, sample, BPF_DYNPTR_TYPE_LOCAL, 0, size);
750 		ret = callback((uintptr_t)&dynptr, (uintptr_t)callback_ctx, 0, 0, 0);
751 		__bpf_user_ringbuf_sample_release(rb, size, flags);
752 	}
753 	ret = samples - discarded_samples;
754 
755 schedule_work_return:
756 	/* Prevent the clearing of the busy-bit from being reordered before the
757 	 * storing of any rb consumer or producer positions.
758 	 */
759 	smp_mb__before_atomic();
760 	atomic_set(&rb->busy, 0);
761 
762 	if (flags & BPF_RB_FORCE_WAKEUP)
763 		irq_work_queue(&rb->work);
764 	else if (!(flags & BPF_RB_NO_WAKEUP) && samples > 0)
765 		irq_work_queue(&rb->work);
766 	return ret;
767 }
768 
769 const struct bpf_func_proto bpf_user_ringbuf_drain_proto = {
770 	.func		= bpf_user_ringbuf_drain,
771 	.ret_type	= RET_INTEGER,
772 	.arg1_type	= ARG_CONST_MAP_PTR,
773 	.arg2_type	= ARG_PTR_TO_FUNC,
774 	.arg3_type	= ARG_PTR_TO_STACK_OR_NULL,
775 	.arg4_type	= ARG_ANYTHING,
776 };
777