1 // SPDX-License-Identifier: GPL-2.0-only
2 /* Copyright (c) 2019 Facebook */
3
4 #include <linux/bpf.h>
5 #include <linux/bpf_verifier.h>
6 #include <linux/btf.h>
7 #include <linux/filter.h>
8 #include <linux/slab.h>
9 #include <linux/numa.h>
10 #include <linux/seq_file.h>
11 #include <linux/refcount.h>
12 #include <linux/mutex.h>
13 #include <linux/btf_ids.h>
14 #include <linux/rcupdate_wait.h>
15
16 enum bpf_struct_ops_state {
17 BPF_STRUCT_OPS_STATE_INIT,
18 BPF_STRUCT_OPS_STATE_INUSE,
19 BPF_STRUCT_OPS_STATE_TOBEFREE,
20 BPF_STRUCT_OPS_STATE_READY,
21 };
22
23 #define BPF_STRUCT_OPS_COMMON_VALUE \
24 refcount_t refcnt; \
25 enum bpf_struct_ops_state state
26
27 struct bpf_struct_ops_value {
28 BPF_STRUCT_OPS_COMMON_VALUE;
29 char data[] ____cacheline_aligned_in_smp;
30 };
31
32 struct bpf_struct_ops_map {
33 struct bpf_map map;
34 struct rcu_head rcu;
35 const struct bpf_struct_ops *st_ops;
36 /* protect map_update */
37 struct mutex lock;
38 /* link has all the bpf_links that is populated
39 * to the func ptr of the kernel's struct
40 * (in kvalue.data).
41 */
42 struct bpf_link **links;
43 /* image is a page that has all the trampolines
44 * that stores the func args before calling the bpf_prog.
45 * A PAGE_SIZE "image" is enough to store all trampoline for
46 * "links[]".
47 */
48 void *image;
49 /* uvalue->data stores the kernel struct
50 * (e.g. tcp_congestion_ops) that is more useful
51 * to userspace than the kvalue. For example,
52 * the bpf_prog's id is stored instead of the kernel
53 * address of a func ptr.
54 */
55 struct bpf_struct_ops_value *uvalue;
56 /* kvalue.data stores the actual kernel's struct
57 * (e.g. tcp_congestion_ops) that will be
58 * registered to the kernel subsystem.
59 */
60 struct bpf_struct_ops_value kvalue;
61 };
62
63 struct bpf_struct_ops_link {
64 struct bpf_link link;
65 struct bpf_map __rcu *map;
66 };
67
68 static DEFINE_MUTEX(update_mutex);
69
70 #define VALUE_PREFIX "bpf_struct_ops_"
71 #define VALUE_PREFIX_LEN (sizeof(VALUE_PREFIX) - 1)
72
73 /* bpf_struct_ops_##_name (e.g. bpf_struct_ops_tcp_congestion_ops) is
74 * the map's value exposed to the userspace and its btf-type-id is
75 * stored at the map->btf_vmlinux_value_type_id.
76 *
77 */
78 #define BPF_STRUCT_OPS_TYPE(_name) \
79 extern struct bpf_struct_ops bpf_##_name; \
80 \
81 struct bpf_struct_ops_##_name { \
82 BPF_STRUCT_OPS_COMMON_VALUE; \
83 struct _name data ____cacheline_aligned_in_smp; \
84 };
85 #include "bpf_struct_ops_types.h"
86 #undef BPF_STRUCT_OPS_TYPE
87
88 enum {
89 #define BPF_STRUCT_OPS_TYPE(_name) BPF_STRUCT_OPS_TYPE_##_name,
90 #include "bpf_struct_ops_types.h"
91 #undef BPF_STRUCT_OPS_TYPE
92 __NR_BPF_STRUCT_OPS_TYPE,
93 };
94
95 static struct bpf_struct_ops * const bpf_struct_ops[] = {
96 #define BPF_STRUCT_OPS_TYPE(_name) \
97 [BPF_STRUCT_OPS_TYPE_##_name] = &bpf_##_name,
98 #include "bpf_struct_ops_types.h"
99 #undef BPF_STRUCT_OPS_TYPE
100 };
101
102 const struct bpf_verifier_ops bpf_struct_ops_verifier_ops = {
103 };
104
105 const struct bpf_prog_ops bpf_struct_ops_prog_ops = {
106 #ifdef CONFIG_NET
107 .test_run = bpf_struct_ops_test_run,
108 #endif
109 };
110
111 static const struct btf_type *module_type;
112
bpf_struct_ops_init(struct btf * btf,struct bpf_verifier_log * log)113 void bpf_struct_ops_init(struct btf *btf, struct bpf_verifier_log *log)
114 {
115 s32 type_id, value_id, module_id;
116 const struct btf_member *member;
117 struct bpf_struct_ops *st_ops;
118 const struct btf_type *t;
119 char value_name[128];
120 const char *mname;
121 u32 i, j;
122
123 /* Ensure BTF type is emitted for "struct bpf_struct_ops_##_name" */
124 #define BPF_STRUCT_OPS_TYPE(_name) BTF_TYPE_EMIT(struct bpf_struct_ops_##_name);
125 #include "bpf_struct_ops_types.h"
126 #undef BPF_STRUCT_OPS_TYPE
127
128 module_id = btf_find_by_name_kind(btf, "module", BTF_KIND_STRUCT);
129 if (module_id < 0) {
130 pr_warn("Cannot find struct module in btf_vmlinux\n");
131 return;
132 }
133 module_type = btf_type_by_id(btf, module_id);
134
135 for (i = 0; i < ARRAY_SIZE(bpf_struct_ops); i++) {
136 st_ops = bpf_struct_ops[i];
137
138 if (strlen(st_ops->name) + VALUE_PREFIX_LEN >=
139 sizeof(value_name)) {
140 pr_warn("struct_ops name %s is too long\n",
141 st_ops->name);
142 continue;
143 }
144 sprintf(value_name, "%s%s", VALUE_PREFIX, st_ops->name);
145
146 value_id = btf_find_by_name_kind(btf, value_name,
147 BTF_KIND_STRUCT);
148 if (value_id < 0) {
149 pr_warn("Cannot find struct %s in btf_vmlinux\n",
150 value_name);
151 continue;
152 }
153
154 type_id = btf_find_by_name_kind(btf, st_ops->name,
155 BTF_KIND_STRUCT);
156 if (type_id < 0) {
157 pr_warn("Cannot find struct %s in btf_vmlinux\n",
158 st_ops->name);
159 continue;
160 }
161 t = btf_type_by_id(btf, type_id);
162 if (btf_type_vlen(t) > BPF_STRUCT_OPS_MAX_NR_MEMBERS) {
163 pr_warn("Cannot support #%u members in struct %s\n",
164 btf_type_vlen(t), st_ops->name);
165 continue;
166 }
167
168 for_each_member(j, t, member) {
169 const struct btf_type *func_proto;
170
171 mname = btf_name_by_offset(btf, member->name_off);
172 if (!*mname) {
173 pr_warn("anon member in struct %s is not supported\n",
174 st_ops->name);
175 break;
176 }
177
178 if (__btf_member_bitfield_size(t, member)) {
179 pr_warn("bit field member %s in struct %s is not supported\n",
180 mname, st_ops->name);
181 break;
182 }
183
184 func_proto = btf_type_resolve_func_ptr(btf,
185 member->type,
186 NULL);
187 if (func_proto &&
188 btf_distill_func_proto(log, btf,
189 func_proto, mname,
190 &st_ops->func_models[j])) {
191 pr_warn("Error in parsing func ptr %s in struct %s\n",
192 mname, st_ops->name);
193 break;
194 }
195 }
196
197 if (j == btf_type_vlen(t)) {
198 if (st_ops->init(btf)) {
199 pr_warn("Error in init bpf_struct_ops %s\n",
200 st_ops->name);
201 } else {
202 st_ops->type_id = type_id;
203 st_ops->type = t;
204 st_ops->value_id = value_id;
205 st_ops->value_type = btf_type_by_id(btf,
206 value_id);
207 }
208 }
209 }
210 }
211
212 extern struct btf *btf_vmlinux;
213
214 static const struct bpf_struct_ops *
bpf_struct_ops_find_value(u32 value_id)215 bpf_struct_ops_find_value(u32 value_id)
216 {
217 unsigned int i;
218
219 if (!value_id || !btf_vmlinux)
220 return NULL;
221
222 for (i = 0; i < ARRAY_SIZE(bpf_struct_ops); i++) {
223 if (bpf_struct_ops[i]->value_id == value_id)
224 return bpf_struct_ops[i];
225 }
226
227 return NULL;
228 }
229
bpf_struct_ops_find(u32 type_id)230 const struct bpf_struct_ops *bpf_struct_ops_find(u32 type_id)
231 {
232 unsigned int i;
233
234 if (!type_id || !btf_vmlinux)
235 return NULL;
236
237 for (i = 0; i < ARRAY_SIZE(bpf_struct_ops); i++) {
238 if (bpf_struct_ops[i]->type_id == type_id)
239 return bpf_struct_ops[i];
240 }
241
242 return NULL;
243 }
244
bpf_struct_ops_map_get_next_key(struct bpf_map * map,void * key,void * next_key)245 static int bpf_struct_ops_map_get_next_key(struct bpf_map *map, void *key,
246 void *next_key)
247 {
248 if (key && *(u32 *)key == 0)
249 return -ENOENT;
250
251 *(u32 *)next_key = 0;
252 return 0;
253 }
254
bpf_struct_ops_map_sys_lookup_elem(struct bpf_map * map,void * key,void * value)255 int bpf_struct_ops_map_sys_lookup_elem(struct bpf_map *map, void *key,
256 void *value)
257 {
258 struct bpf_struct_ops_map *st_map = (struct bpf_struct_ops_map *)map;
259 struct bpf_struct_ops_value *uvalue, *kvalue;
260 enum bpf_struct_ops_state state;
261 s64 refcnt;
262
263 if (unlikely(*(u32 *)key != 0))
264 return -ENOENT;
265
266 kvalue = &st_map->kvalue;
267 /* Pair with smp_store_release() during map_update */
268 state = smp_load_acquire(&kvalue->state);
269 if (state == BPF_STRUCT_OPS_STATE_INIT) {
270 memset(value, 0, map->value_size);
271 return 0;
272 }
273
274 /* No lock is needed. state and refcnt do not need
275 * to be updated together under atomic context.
276 */
277 uvalue = value;
278 memcpy(uvalue, st_map->uvalue, map->value_size);
279 uvalue->state = state;
280
281 /* This value offers the user space a general estimate of how
282 * many sockets are still utilizing this struct_ops for TCP
283 * congestion control. The number might not be exact, but it
284 * should sufficiently meet our present goals.
285 */
286 refcnt = atomic64_read(&map->refcnt) - atomic64_read(&map->usercnt);
287 refcount_set(&uvalue->refcnt, max_t(s64, refcnt, 0));
288
289 return 0;
290 }
291
bpf_struct_ops_map_lookup_elem(struct bpf_map * map,void * key)292 static void *bpf_struct_ops_map_lookup_elem(struct bpf_map *map, void *key)
293 {
294 return ERR_PTR(-EINVAL);
295 }
296
bpf_struct_ops_map_put_progs(struct bpf_struct_ops_map * st_map)297 static void bpf_struct_ops_map_put_progs(struct bpf_struct_ops_map *st_map)
298 {
299 const struct btf_type *t = st_map->st_ops->type;
300 u32 i;
301
302 for (i = 0; i < btf_type_vlen(t); i++) {
303 if (st_map->links[i]) {
304 bpf_link_put(st_map->links[i]);
305 st_map->links[i] = NULL;
306 }
307 }
308 }
309
check_zero_holes(const struct btf_type * t,void * data)310 static int check_zero_holes(const struct btf_type *t, void *data)
311 {
312 const struct btf_member *member;
313 u32 i, moff, msize, prev_mend = 0;
314 const struct btf_type *mtype;
315
316 for_each_member(i, t, member) {
317 moff = __btf_member_bit_offset(t, member) / 8;
318 if (moff > prev_mend &&
319 memchr_inv(data + prev_mend, 0, moff - prev_mend))
320 return -EINVAL;
321
322 mtype = btf_type_by_id(btf_vmlinux, member->type);
323 mtype = btf_resolve_size(btf_vmlinux, mtype, &msize);
324 if (IS_ERR(mtype))
325 return PTR_ERR(mtype);
326 prev_mend = moff + msize;
327 }
328
329 if (t->size > prev_mend &&
330 memchr_inv(data + prev_mend, 0, t->size - prev_mend))
331 return -EINVAL;
332
333 return 0;
334 }
335
bpf_struct_ops_link_release(struct bpf_link * link)336 static void bpf_struct_ops_link_release(struct bpf_link *link)
337 {
338 }
339
bpf_struct_ops_link_dealloc(struct bpf_link * link)340 static void bpf_struct_ops_link_dealloc(struct bpf_link *link)
341 {
342 struct bpf_tramp_link *tlink = container_of(link, struct bpf_tramp_link, link);
343
344 kfree(tlink);
345 }
346
347 const struct bpf_link_ops bpf_struct_ops_link_lops = {
348 .release = bpf_struct_ops_link_release,
349 .dealloc = bpf_struct_ops_link_dealloc,
350 };
351
bpf_struct_ops_prepare_trampoline(struct bpf_tramp_links * tlinks,struct bpf_tramp_link * link,const struct btf_func_model * model,void * image,void * image_end)352 int bpf_struct_ops_prepare_trampoline(struct bpf_tramp_links *tlinks,
353 struct bpf_tramp_link *link,
354 const struct btf_func_model *model,
355 void *image, void *image_end)
356 {
357 u32 flags;
358
359 tlinks[BPF_TRAMP_FENTRY].links[0] = link;
360 tlinks[BPF_TRAMP_FENTRY].nr_links = 1;
361 /* BPF_TRAMP_F_RET_FENTRY_RET is only used by bpf_struct_ops,
362 * and it must be used alone.
363 */
364 flags = model->ret_size > 0 ? BPF_TRAMP_F_RET_FENTRY_RET : 0;
365 return arch_prepare_bpf_trampoline(NULL, image, image_end,
366 model, flags, tlinks, NULL);
367 }
368
bpf_struct_ops_map_update_elem(struct bpf_map * map,void * key,void * value,u64 flags)369 static long bpf_struct_ops_map_update_elem(struct bpf_map *map, void *key,
370 void *value, u64 flags)
371 {
372 struct bpf_struct_ops_map *st_map = (struct bpf_struct_ops_map *)map;
373 const struct bpf_struct_ops *st_ops = st_map->st_ops;
374 struct bpf_struct_ops_value *uvalue, *kvalue;
375 const struct btf_member *member;
376 const struct btf_type *t = st_ops->type;
377 struct bpf_tramp_links *tlinks;
378 void *udata, *kdata;
379 int prog_fd, err;
380 void *image, *image_end;
381 u32 i;
382
383 if (flags)
384 return -EINVAL;
385
386 if (*(u32 *)key != 0)
387 return -E2BIG;
388
389 err = check_zero_holes(st_ops->value_type, value);
390 if (err)
391 return err;
392
393 uvalue = value;
394 err = check_zero_holes(t, uvalue->data);
395 if (err)
396 return err;
397
398 if (uvalue->state || refcount_read(&uvalue->refcnt))
399 return -EINVAL;
400
401 tlinks = kcalloc(BPF_TRAMP_MAX, sizeof(*tlinks), GFP_KERNEL);
402 if (!tlinks)
403 return -ENOMEM;
404
405 uvalue = (struct bpf_struct_ops_value *)st_map->uvalue;
406 kvalue = (struct bpf_struct_ops_value *)&st_map->kvalue;
407
408 mutex_lock(&st_map->lock);
409
410 if (kvalue->state != BPF_STRUCT_OPS_STATE_INIT) {
411 err = -EBUSY;
412 goto unlock;
413 }
414
415 memcpy(uvalue, value, map->value_size);
416
417 udata = &uvalue->data;
418 kdata = &kvalue->data;
419 image = st_map->image;
420 image_end = st_map->image + PAGE_SIZE;
421
422 for_each_member(i, t, member) {
423 const struct btf_type *mtype, *ptype;
424 struct bpf_prog *prog;
425 struct bpf_tramp_link *link;
426 u32 moff;
427
428 moff = __btf_member_bit_offset(t, member) / 8;
429 ptype = btf_type_resolve_ptr(btf_vmlinux, member->type, NULL);
430 if (ptype == module_type) {
431 if (*(void **)(udata + moff))
432 goto reset_unlock;
433 *(void **)(kdata + moff) = BPF_MODULE_OWNER;
434 continue;
435 }
436
437 err = st_ops->init_member(t, member, kdata, udata);
438 if (err < 0)
439 goto reset_unlock;
440
441 /* The ->init_member() has handled this member */
442 if (err > 0)
443 continue;
444
445 /* If st_ops->init_member does not handle it,
446 * we will only handle func ptrs and zero-ed members
447 * here. Reject everything else.
448 */
449
450 /* All non func ptr member must be 0 */
451 if (!ptype || !btf_type_is_func_proto(ptype)) {
452 u32 msize;
453
454 mtype = btf_type_by_id(btf_vmlinux, member->type);
455 mtype = btf_resolve_size(btf_vmlinux, mtype, &msize);
456 if (IS_ERR(mtype)) {
457 err = PTR_ERR(mtype);
458 goto reset_unlock;
459 }
460
461 if (memchr_inv(udata + moff, 0, msize)) {
462 err = -EINVAL;
463 goto reset_unlock;
464 }
465
466 continue;
467 }
468
469 prog_fd = (int)(*(unsigned long *)(udata + moff));
470 /* Similar check as the attr->attach_prog_fd */
471 if (!prog_fd)
472 continue;
473
474 prog = bpf_prog_get(prog_fd);
475 if (IS_ERR(prog)) {
476 err = PTR_ERR(prog);
477 goto reset_unlock;
478 }
479
480 if (prog->type != BPF_PROG_TYPE_STRUCT_OPS ||
481 prog->aux->attach_btf_id != st_ops->type_id ||
482 prog->expected_attach_type != i) {
483 bpf_prog_put(prog);
484 err = -EINVAL;
485 goto reset_unlock;
486 }
487
488 link = kzalloc(sizeof(*link), GFP_USER);
489 if (!link) {
490 bpf_prog_put(prog);
491 err = -ENOMEM;
492 goto reset_unlock;
493 }
494 bpf_link_init(&link->link, BPF_LINK_TYPE_STRUCT_OPS,
495 &bpf_struct_ops_link_lops, prog);
496 st_map->links[i] = &link->link;
497
498 err = bpf_struct_ops_prepare_trampoline(tlinks, link,
499 &st_ops->func_models[i],
500 image, image_end);
501 if (err < 0)
502 goto reset_unlock;
503
504 *(void **)(kdata + moff) = image;
505 image += err;
506
507 /* put prog_id to udata */
508 *(unsigned long *)(udata + moff) = prog->aux->id;
509 }
510
511 if (st_map->map.map_flags & BPF_F_LINK) {
512 err = 0;
513 if (st_ops->validate) {
514 err = st_ops->validate(kdata);
515 if (err)
516 goto reset_unlock;
517 }
518 set_memory_rox((long)st_map->image, 1);
519 /* Let bpf_link handle registration & unregistration.
520 *
521 * Pair with smp_load_acquire() during lookup_elem().
522 */
523 smp_store_release(&kvalue->state, BPF_STRUCT_OPS_STATE_READY);
524 goto unlock;
525 }
526
527 set_memory_rox((long)st_map->image, 1);
528 err = st_ops->reg(kdata);
529 if (likely(!err)) {
530 /* This refcnt increment on the map here after
531 * 'st_ops->reg()' is secure since the state of the
532 * map must be set to INIT at this moment, and thus
533 * bpf_struct_ops_map_delete_elem() can't unregister
534 * or transition it to TOBEFREE concurrently.
535 */
536 bpf_map_inc(map);
537 /* Pair with smp_load_acquire() during lookup_elem().
538 * It ensures the above udata updates (e.g. prog->aux->id)
539 * can be seen once BPF_STRUCT_OPS_STATE_INUSE is set.
540 */
541 smp_store_release(&kvalue->state, BPF_STRUCT_OPS_STATE_INUSE);
542 goto unlock;
543 }
544
545 /* Error during st_ops->reg(). Can happen if this struct_ops needs to be
546 * verified as a whole, after all init_member() calls. Can also happen if
547 * there was a race in registering the struct_ops (under the same name) to
548 * a sub-system through different struct_ops's maps.
549 */
550 set_memory_nx((long)st_map->image, 1);
551 set_memory_rw((long)st_map->image, 1);
552
553 reset_unlock:
554 bpf_struct_ops_map_put_progs(st_map);
555 memset(uvalue, 0, map->value_size);
556 memset(kvalue, 0, map->value_size);
557 unlock:
558 kfree(tlinks);
559 mutex_unlock(&st_map->lock);
560 return err;
561 }
562
bpf_struct_ops_map_delete_elem(struct bpf_map * map,void * key)563 static long bpf_struct_ops_map_delete_elem(struct bpf_map *map, void *key)
564 {
565 enum bpf_struct_ops_state prev_state;
566 struct bpf_struct_ops_map *st_map;
567
568 st_map = (struct bpf_struct_ops_map *)map;
569 if (st_map->map.map_flags & BPF_F_LINK)
570 return -EOPNOTSUPP;
571
572 prev_state = cmpxchg(&st_map->kvalue.state,
573 BPF_STRUCT_OPS_STATE_INUSE,
574 BPF_STRUCT_OPS_STATE_TOBEFREE);
575 switch (prev_state) {
576 case BPF_STRUCT_OPS_STATE_INUSE:
577 st_map->st_ops->unreg(&st_map->kvalue.data);
578 bpf_map_put(map);
579 return 0;
580 case BPF_STRUCT_OPS_STATE_TOBEFREE:
581 return -EINPROGRESS;
582 case BPF_STRUCT_OPS_STATE_INIT:
583 return -ENOENT;
584 default:
585 WARN_ON_ONCE(1);
586 /* Should never happen. Treat it as not found. */
587 return -ENOENT;
588 }
589 }
590
bpf_struct_ops_map_seq_show_elem(struct bpf_map * map,void * key,struct seq_file * m)591 static void bpf_struct_ops_map_seq_show_elem(struct bpf_map *map, void *key,
592 struct seq_file *m)
593 {
594 void *value;
595 int err;
596
597 value = kmalloc(map->value_size, GFP_USER | __GFP_NOWARN);
598 if (!value)
599 return;
600
601 err = bpf_struct_ops_map_sys_lookup_elem(map, key, value);
602 if (!err) {
603 btf_type_seq_show(btf_vmlinux, map->btf_vmlinux_value_type_id,
604 value, m);
605 seq_puts(m, "\n");
606 }
607
608 kfree(value);
609 }
610
__bpf_struct_ops_map_free(struct bpf_map * map)611 static void __bpf_struct_ops_map_free(struct bpf_map *map)
612 {
613 struct bpf_struct_ops_map *st_map = (struct bpf_struct_ops_map *)map;
614
615 if (st_map->links)
616 bpf_struct_ops_map_put_progs(st_map);
617 bpf_map_area_free(st_map->links);
618 bpf_jit_free_exec(st_map->image);
619 bpf_map_area_free(st_map->uvalue);
620 bpf_map_area_free(st_map);
621 }
622
bpf_struct_ops_map_free(struct bpf_map * map)623 static void bpf_struct_ops_map_free(struct bpf_map *map)
624 {
625 /* The struct_ops's function may switch to another struct_ops.
626 *
627 * For example, bpf_tcp_cc_x->init() may switch to
628 * another tcp_cc_y by calling
629 * setsockopt(TCP_CONGESTION, "tcp_cc_y").
630 * During the switch, bpf_struct_ops_put(tcp_cc_x) is called
631 * and its refcount may reach 0 which then free its
632 * trampoline image while tcp_cc_x is still running.
633 *
634 * A vanilla rcu gp is to wait for all bpf-tcp-cc prog
635 * to finish. bpf-tcp-cc prog is non sleepable.
636 * A rcu_tasks gp is to wait for the last few insn
637 * in the tramopline image to finish before releasing
638 * the trampoline image.
639 */
640 synchronize_rcu_mult(call_rcu, call_rcu_tasks);
641
642 __bpf_struct_ops_map_free(map);
643 }
644
bpf_struct_ops_map_alloc_check(union bpf_attr * attr)645 static int bpf_struct_ops_map_alloc_check(union bpf_attr *attr)
646 {
647 if (attr->key_size != sizeof(unsigned int) || attr->max_entries != 1 ||
648 (attr->map_flags & ~BPF_F_LINK) || !attr->btf_vmlinux_value_type_id)
649 return -EINVAL;
650 return 0;
651 }
652
bpf_struct_ops_map_alloc(union bpf_attr * attr)653 static struct bpf_map *bpf_struct_ops_map_alloc(union bpf_attr *attr)
654 {
655 const struct bpf_struct_ops *st_ops;
656 size_t st_map_size;
657 struct bpf_struct_ops_map *st_map;
658 const struct btf_type *t, *vt;
659 struct bpf_map *map;
660
661 st_ops = bpf_struct_ops_find_value(attr->btf_vmlinux_value_type_id);
662 if (!st_ops)
663 return ERR_PTR(-ENOTSUPP);
664
665 vt = st_ops->value_type;
666 if (attr->value_size != vt->size)
667 return ERR_PTR(-EINVAL);
668
669 t = st_ops->type;
670
671 st_map_size = sizeof(*st_map) +
672 /* kvalue stores the
673 * struct bpf_struct_ops_tcp_congestions_ops
674 */
675 (vt->size - sizeof(struct bpf_struct_ops_value));
676
677 st_map = bpf_map_area_alloc(st_map_size, NUMA_NO_NODE);
678 if (!st_map)
679 return ERR_PTR(-ENOMEM);
680
681 st_map->st_ops = st_ops;
682 map = &st_map->map;
683
684 st_map->uvalue = bpf_map_area_alloc(vt->size, NUMA_NO_NODE);
685 st_map->links =
686 bpf_map_area_alloc(btf_type_vlen(t) * sizeof(struct bpf_links *),
687 NUMA_NO_NODE);
688 st_map->image = bpf_jit_alloc_exec(PAGE_SIZE);
689 if (!st_map->uvalue || !st_map->links || !st_map->image) {
690 __bpf_struct_ops_map_free(map);
691 return ERR_PTR(-ENOMEM);
692 }
693
694 mutex_init(&st_map->lock);
695 set_vm_flush_reset_perms(st_map->image);
696 bpf_map_init_from_attr(map, attr);
697
698 return map;
699 }
700
bpf_struct_ops_map_mem_usage(const struct bpf_map * map)701 static u64 bpf_struct_ops_map_mem_usage(const struct bpf_map *map)
702 {
703 struct bpf_struct_ops_map *st_map = (struct bpf_struct_ops_map *)map;
704 const struct bpf_struct_ops *st_ops = st_map->st_ops;
705 const struct btf_type *vt = st_ops->value_type;
706 u64 usage;
707
708 usage = sizeof(*st_map) +
709 vt->size - sizeof(struct bpf_struct_ops_value);
710 usage += vt->size;
711 usage += btf_type_vlen(vt) * sizeof(struct bpf_links *);
712 usage += PAGE_SIZE;
713 return usage;
714 }
715
716 BTF_ID_LIST_SINGLE(bpf_struct_ops_map_btf_ids, struct, bpf_struct_ops_map)
717 const struct bpf_map_ops bpf_struct_ops_map_ops = {
718 .map_alloc_check = bpf_struct_ops_map_alloc_check,
719 .map_alloc = bpf_struct_ops_map_alloc,
720 .map_free = bpf_struct_ops_map_free,
721 .map_get_next_key = bpf_struct_ops_map_get_next_key,
722 .map_lookup_elem = bpf_struct_ops_map_lookup_elem,
723 .map_delete_elem = bpf_struct_ops_map_delete_elem,
724 .map_update_elem = bpf_struct_ops_map_update_elem,
725 .map_seq_show_elem = bpf_struct_ops_map_seq_show_elem,
726 .map_mem_usage = bpf_struct_ops_map_mem_usage,
727 .map_btf_id = &bpf_struct_ops_map_btf_ids[0],
728 };
729
730 /* "const void *" because some subsystem is
731 * passing a const (e.g. const struct tcp_congestion_ops *)
732 */
bpf_struct_ops_get(const void * kdata)733 bool bpf_struct_ops_get(const void *kdata)
734 {
735 struct bpf_struct_ops_value *kvalue;
736 struct bpf_struct_ops_map *st_map;
737 struct bpf_map *map;
738
739 kvalue = container_of(kdata, struct bpf_struct_ops_value, data);
740 st_map = container_of(kvalue, struct bpf_struct_ops_map, kvalue);
741
742 map = __bpf_map_inc_not_zero(&st_map->map, false);
743 return !IS_ERR(map);
744 }
745
bpf_struct_ops_put(const void * kdata)746 void bpf_struct_ops_put(const void *kdata)
747 {
748 struct bpf_struct_ops_value *kvalue;
749 struct bpf_struct_ops_map *st_map;
750
751 kvalue = container_of(kdata, struct bpf_struct_ops_value, data);
752 st_map = container_of(kvalue, struct bpf_struct_ops_map, kvalue);
753
754 bpf_map_put(&st_map->map);
755 }
756
bpf_struct_ops_valid_to_reg(struct bpf_map * map)757 static bool bpf_struct_ops_valid_to_reg(struct bpf_map *map)
758 {
759 struct bpf_struct_ops_map *st_map = (struct bpf_struct_ops_map *)map;
760
761 return map->map_type == BPF_MAP_TYPE_STRUCT_OPS &&
762 map->map_flags & BPF_F_LINK &&
763 /* Pair with smp_store_release() during map_update */
764 smp_load_acquire(&st_map->kvalue.state) == BPF_STRUCT_OPS_STATE_READY;
765 }
766
bpf_struct_ops_map_link_dealloc(struct bpf_link * link)767 static void bpf_struct_ops_map_link_dealloc(struct bpf_link *link)
768 {
769 struct bpf_struct_ops_link *st_link;
770 struct bpf_struct_ops_map *st_map;
771
772 st_link = container_of(link, struct bpf_struct_ops_link, link);
773 st_map = (struct bpf_struct_ops_map *)
774 rcu_dereference_protected(st_link->map, true);
775 if (st_map) {
776 /* st_link->map can be NULL if
777 * bpf_struct_ops_link_create() fails to register.
778 */
779 st_map->st_ops->unreg(&st_map->kvalue.data);
780 bpf_map_put(&st_map->map);
781 }
782 kfree(st_link);
783 }
784
bpf_struct_ops_map_link_show_fdinfo(const struct bpf_link * link,struct seq_file * seq)785 static void bpf_struct_ops_map_link_show_fdinfo(const struct bpf_link *link,
786 struct seq_file *seq)
787 {
788 struct bpf_struct_ops_link *st_link;
789 struct bpf_map *map;
790
791 st_link = container_of(link, struct bpf_struct_ops_link, link);
792 rcu_read_lock();
793 map = rcu_dereference(st_link->map);
794 seq_printf(seq, "map_id:\t%d\n", map->id);
795 rcu_read_unlock();
796 }
797
bpf_struct_ops_map_link_fill_link_info(const struct bpf_link * link,struct bpf_link_info * info)798 static int bpf_struct_ops_map_link_fill_link_info(const struct bpf_link *link,
799 struct bpf_link_info *info)
800 {
801 struct bpf_struct_ops_link *st_link;
802 struct bpf_map *map;
803
804 st_link = container_of(link, struct bpf_struct_ops_link, link);
805 rcu_read_lock();
806 map = rcu_dereference(st_link->map);
807 info->struct_ops.map_id = map->id;
808 rcu_read_unlock();
809 return 0;
810 }
811
bpf_struct_ops_map_link_update(struct bpf_link * link,struct bpf_map * new_map,struct bpf_map * expected_old_map)812 static int bpf_struct_ops_map_link_update(struct bpf_link *link, struct bpf_map *new_map,
813 struct bpf_map *expected_old_map)
814 {
815 struct bpf_struct_ops_map *st_map, *old_st_map;
816 struct bpf_map *old_map;
817 struct bpf_struct_ops_link *st_link;
818 int err;
819
820 st_link = container_of(link, struct bpf_struct_ops_link, link);
821 st_map = container_of(new_map, struct bpf_struct_ops_map, map);
822
823 if (!bpf_struct_ops_valid_to_reg(new_map))
824 return -EINVAL;
825
826 if (!st_map->st_ops->update)
827 return -EOPNOTSUPP;
828
829 mutex_lock(&update_mutex);
830
831 old_map = rcu_dereference_protected(st_link->map, lockdep_is_held(&update_mutex));
832 if (expected_old_map && old_map != expected_old_map) {
833 err = -EPERM;
834 goto err_out;
835 }
836
837 old_st_map = container_of(old_map, struct bpf_struct_ops_map, map);
838 /* The new and old struct_ops must be the same type. */
839 if (st_map->st_ops != old_st_map->st_ops) {
840 err = -EINVAL;
841 goto err_out;
842 }
843
844 err = st_map->st_ops->update(st_map->kvalue.data, old_st_map->kvalue.data);
845 if (err)
846 goto err_out;
847
848 bpf_map_inc(new_map);
849 rcu_assign_pointer(st_link->map, new_map);
850 bpf_map_put(old_map);
851
852 err_out:
853 mutex_unlock(&update_mutex);
854
855 return err;
856 }
857
858 static const struct bpf_link_ops bpf_struct_ops_map_lops = {
859 .dealloc = bpf_struct_ops_map_link_dealloc,
860 .show_fdinfo = bpf_struct_ops_map_link_show_fdinfo,
861 .fill_link_info = bpf_struct_ops_map_link_fill_link_info,
862 .update_map = bpf_struct_ops_map_link_update,
863 };
864
bpf_struct_ops_link_create(union bpf_attr * attr)865 int bpf_struct_ops_link_create(union bpf_attr *attr)
866 {
867 struct bpf_struct_ops_link *link = NULL;
868 struct bpf_link_primer link_primer;
869 struct bpf_struct_ops_map *st_map;
870 struct bpf_map *map;
871 int err;
872
873 map = bpf_map_get(attr->link_create.map_fd);
874 if (IS_ERR(map))
875 return PTR_ERR(map);
876
877 st_map = (struct bpf_struct_ops_map *)map;
878
879 if (!bpf_struct_ops_valid_to_reg(map)) {
880 err = -EINVAL;
881 goto err_out;
882 }
883
884 link = kzalloc(sizeof(*link), GFP_USER);
885 if (!link) {
886 err = -ENOMEM;
887 goto err_out;
888 }
889 bpf_link_init(&link->link, BPF_LINK_TYPE_STRUCT_OPS, &bpf_struct_ops_map_lops, NULL);
890
891 err = bpf_link_prime(&link->link, &link_primer);
892 if (err)
893 goto err_out;
894
895 err = st_map->st_ops->reg(st_map->kvalue.data);
896 if (err) {
897 bpf_link_cleanup(&link_primer);
898 link = NULL;
899 goto err_out;
900 }
901 RCU_INIT_POINTER(link->map, map);
902
903 return bpf_link_settle(&link_primer);
904
905 err_out:
906 bpf_map_put(map);
907 kfree(link);
908 return err;
909 }
910
911