1
2
3#include <linux/hash.h>
4#include <linux/bpf.h>
5#include <linux/filter.h>
6#include <linux/ftrace.h>
7#include <linux/rbtree_latch.h>
8#include <linux/perf_event.h>
9#include <linux/btf.h>
10#include <linux/rcupdate_trace.h>
11#include <linux/rcupdate_wait.h>
12#include <linux/module.h>
13
14
15const struct bpf_verifier_ops bpf_extension_verifier_ops = {
16};
17const struct bpf_prog_ops bpf_extension_prog_ops = {
18};
19
20
21#define TRAMPOLINE_HASH_BITS 10
22#define TRAMPOLINE_TABLE_SIZE (1 << TRAMPOLINE_HASH_BITS)
23
24static struct hlist_head trampoline_table[TRAMPOLINE_TABLE_SIZE];
25
26
27static DEFINE_MUTEX(trampoline_mutex);
28
29void *bpf_jit_alloc_exec_page(void)
30{
31 void *image;
32
33 image = bpf_jit_alloc_exec(PAGE_SIZE);
34 if (!image)
35 return NULL;
36
37 set_vm_flush_reset_perms(image);
38
39
40
41 set_memory_x((long)image, 1);
42 return image;
43}
44
45void bpf_image_ksym_add(void *data, struct bpf_ksym *ksym)
46{
47 ksym->start = (unsigned long) data;
48 ksym->end = ksym->start + PAGE_SIZE;
49 bpf_ksym_add(ksym);
50 perf_event_ksymbol(PERF_RECORD_KSYMBOL_TYPE_BPF, ksym->start,
51 PAGE_SIZE, false, ksym->name);
52}
53
54void bpf_image_ksym_del(struct bpf_ksym *ksym)
55{
56 bpf_ksym_del(ksym);
57 perf_event_ksymbol(PERF_RECORD_KSYMBOL_TYPE_BPF, ksym->start,
58 PAGE_SIZE, true, ksym->name);
59}
60
61static struct bpf_trampoline *bpf_trampoline_lookup(u64 key)
62{
63 struct bpf_trampoline *tr;
64 struct hlist_head *head;
65 int i;
66
67 mutex_lock(&trampoline_mutex);
68 head = &trampoline_table[hash_64(key, TRAMPOLINE_HASH_BITS)];
69 hlist_for_each_entry(tr, head, hlist) {
70 if (tr->key == key) {
71 refcount_inc(&tr->refcnt);
72 goto out;
73 }
74 }
75 tr = kzalloc(sizeof(*tr), GFP_KERNEL);
76 if (!tr)
77 goto out;
78
79 tr->key = key;
80 INIT_HLIST_NODE(&tr->hlist);
81 hlist_add_head(&tr->hlist, head);
82 refcount_set(&tr->refcnt, 1);
83 mutex_init(&tr->mutex);
84 for (i = 0; i < BPF_TRAMP_MAX; i++)
85 INIT_HLIST_HEAD(&tr->progs_hlist[i]);
86out:
87 mutex_unlock(&trampoline_mutex);
88 return tr;
89}
90
91static int bpf_trampoline_module_get(struct bpf_trampoline *tr)
92{
93 struct module *mod;
94 int err = 0;
95
96 preempt_disable();
97 mod = __module_text_address((unsigned long) tr->func.addr);
98 if (mod && !try_module_get(mod))
99 err = -ENOENT;
100 preempt_enable();
101 tr->mod = mod;
102 return err;
103}
104
105static void bpf_trampoline_module_put(struct bpf_trampoline *tr)
106{
107 module_put(tr->mod);
108 tr->mod = NULL;
109}
110
111static int is_ftrace_location(void *ip)
112{
113 long addr;
114
115 addr = ftrace_location((long)ip);
116 if (!addr)
117 return 0;
118 if (WARN_ON_ONCE(addr != (long)ip))
119 return -EFAULT;
120 return 1;
121}
122
123static int unregister_fentry(struct bpf_trampoline *tr, void *old_addr)
124{
125 void *ip = tr->func.addr;
126 int ret;
127
128 if (tr->func.ftrace_managed)
129 ret = unregister_ftrace_direct((long)ip, (long)old_addr);
130 else
131 ret = bpf_arch_text_poke(ip, BPF_MOD_CALL, old_addr, NULL);
132
133 if (!ret)
134 bpf_trampoline_module_put(tr);
135 return ret;
136}
137
138static int modify_fentry(struct bpf_trampoline *tr, void *old_addr, void *new_addr)
139{
140 void *ip = tr->func.addr;
141 int ret;
142
143 if (tr->func.ftrace_managed)
144 ret = modify_ftrace_direct((long)ip, (long)old_addr, (long)new_addr);
145 else
146 ret = bpf_arch_text_poke(ip, BPF_MOD_CALL, old_addr, new_addr);
147 return ret;
148}
149
150
151static int register_fentry(struct bpf_trampoline *tr, void *new_addr)
152{
153 void *ip = tr->func.addr;
154 int ret;
155
156 ret = is_ftrace_location(ip);
157 if (ret < 0)
158 return ret;
159 tr->func.ftrace_managed = ret;
160
161 if (bpf_trampoline_module_get(tr))
162 return -ENOENT;
163
164 if (tr->func.ftrace_managed)
165 ret = register_ftrace_direct((long)ip, (long)new_addr);
166 else
167 ret = bpf_arch_text_poke(ip, BPF_MOD_CALL, NULL, new_addr);
168
169 if (ret)
170 bpf_trampoline_module_put(tr);
171 return ret;
172}
173
174static struct bpf_tramp_progs *
175bpf_trampoline_get_progs(const struct bpf_trampoline *tr, int *total, bool *ip_arg)
176{
177 const struct bpf_prog_aux *aux;
178 struct bpf_tramp_progs *tprogs;
179 struct bpf_prog **progs;
180 int kind;
181
182 *total = 0;
183 tprogs = kcalloc(BPF_TRAMP_MAX, sizeof(*tprogs), GFP_KERNEL);
184 if (!tprogs)
185 return ERR_PTR(-ENOMEM);
186
187 for (kind = 0; kind < BPF_TRAMP_MAX; kind++) {
188 tprogs[kind].nr_progs = tr->progs_cnt[kind];
189 *total += tr->progs_cnt[kind];
190 progs = tprogs[kind].progs;
191
192 hlist_for_each_entry(aux, &tr->progs_hlist[kind], tramp_hlist) {
193 *ip_arg |= aux->prog->call_get_func_ip;
194 *progs++ = aux->prog;
195 }
196 }
197 return tprogs;
198}
199
200static void __bpf_tramp_image_put_deferred(struct work_struct *work)
201{
202 struct bpf_tramp_image *im;
203
204 im = container_of(work, struct bpf_tramp_image, work);
205 bpf_image_ksym_del(&im->ksym);
206 bpf_jit_free_exec(im->image);
207 bpf_jit_uncharge_modmem(1);
208 percpu_ref_exit(&im->pcref);
209 kfree_rcu(im, rcu);
210}
211
212
213static void __bpf_tramp_image_put_rcu(struct rcu_head *rcu)
214{
215 struct bpf_tramp_image *im;
216
217 im = container_of(rcu, struct bpf_tramp_image, rcu);
218 INIT_WORK(&im->work, __bpf_tramp_image_put_deferred);
219 schedule_work(&im->work);
220}
221
222
223static void __bpf_tramp_image_release(struct percpu_ref *pcref)
224{
225 struct bpf_tramp_image *im;
226
227 im = container_of(pcref, struct bpf_tramp_image, pcref);
228 call_rcu_tasks(&im->rcu, __bpf_tramp_image_put_rcu);
229}
230
231
232static void __bpf_tramp_image_put_rcu_tasks(struct rcu_head *rcu)
233{
234 struct bpf_tramp_image *im;
235
236 im = container_of(rcu, struct bpf_tramp_image, rcu);
237 if (im->ip_after_call)
238
239 percpu_ref_kill(&im->pcref);
240 else
241
242 call_rcu_tasks(&im->rcu, __bpf_tramp_image_put_rcu);
243}
244
245static void bpf_tramp_image_put(struct bpf_tramp_image *im)
246{
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273 if (im->ip_after_call) {
274 int err = bpf_arch_text_poke(im->ip_after_call, BPF_MOD_JUMP,
275 NULL, im->ip_epilogue);
276 WARN_ON(err);
277 if (IS_ENABLED(CONFIG_PREEMPTION))
278 call_rcu_tasks(&im->rcu, __bpf_tramp_image_put_rcu_tasks);
279 else
280 percpu_ref_kill(&im->pcref);
281 return;
282 }
283
284
285
286
287
288
289
290 call_rcu_tasks_trace(&im->rcu, __bpf_tramp_image_put_rcu_tasks);
291}
292
293static struct bpf_tramp_image *bpf_tramp_image_alloc(u64 key, u32 idx)
294{
295 struct bpf_tramp_image *im;
296 struct bpf_ksym *ksym;
297 void *image;
298 int err = -ENOMEM;
299
300 im = kzalloc(sizeof(*im), GFP_KERNEL);
301 if (!im)
302 goto out;
303
304 err = bpf_jit_charge_modmem(1);
305 if (err)
306 goto out_free_im;
307
308 err = -ENOMEM;
309 im->image = image = bpf_jit_alloc_exec_page();
310 if (!image)
311 goto out_uncharge;
312
313 err = percpu_ref_init(&im->pcref, __bpf_tramp_image_release, 0, GFP_KERNEL);
314 if (err)
315 goto out_free_image;
316
317 ksym = &im->ksym;
318 INIT_LIST_HEAD_RCU(&ksym->lnode);
319 snprintf(ksym->name, KSYM_NAME_LEN, "bpf_trampoline_%llu_%u", key, idx);
320 bpf_image_ksym_add(image, ksym);
321 return im;
322
323out_free_image:
324 bpf_jit_free_exec(im->image);
325out_uncharge:
326 bpf_jit_uncharge_modmem(1);
327out_free_im:
328 kfree(im);
329out:
330 return ERR_PTR(err);
331}
332
333static int bpf_trampoline_update(struct bpf_trampoline *tr)
334{
335 struct bpf_tramp_image *im;
336 struct bpf_tramp_progs *tprogs;
337 u32 flags = BPF_TRAMP_F_RESTORE_REGS;
338 bool ip_arg = false;
339 int err, total;
340
341 tprogs = bpf_trampoline_get_progs(tr, &total, &ip_arg);
342 if (IS_ERR(tprogs))
343 return PTR_ERR(tprogs);
344
345 if (total == 0) {
346 err = unregister_fentry(tr, tr->cur_image->image);
347 bpf_tramp_image_put(tr->cur_image);
348 tr->cur_image = NULL;
349 tr->selector = 0;
350 goto out;
351 }
352
353 im = bpf_tramp_image_alloc(tr->key, tr->selector);
354 if (IS_ERR(im)) {
355 err = PTR_ERR(im);
356 goto out;
357 }
358
359 if (tprogs[BPF_TRAMP_FEXIT].nr_progs ||
360 tprogs[BPF_TRAMP_MODIFY_RETURN].nr_progs)
361 flags = BPF_TRAMP_F_CALL_ORIG | BPF_TRAMP_F_SKIP_FRAME;
362
363 if (ip_arg)
364 flags |= BPF_TRAMP_F_IP_ARG;
365
366 err = arch_prepare_bpf_trampoline(im, im->image, im->image + PAGE_SIZE,
367 &tr->func.model, flags, tprogs,
368 tr->func.addr);
369 if (err < 0)
370 goto out;
371
372 WARN_ON(tr->cur_image && tr->selector == 0);
373 WARN_ON(!tr->cur_image && tr->selector);
374 if (tr->cur_image)
375
376 err = modify_fentry(tr, tr->cur_image->image, im->image);
377 else
378
379 err = register_fentry(tr, im->image);
380 if (err)
381 goto out;
382 if (tr->cur_image)
383 bpf_tramp_image_put(tr->cur_image);
384 tr->cur_image = im;
385 tr->selector++;
386out:
387 kfree(tprogs);
388 return err;
389}
390
391static enum bpf_tramp_prog_type bpf_attach_type_to_tramp(struct bpf_prog *prog)
392{
393 switch (prog->expected_attach_type) {
394 case BPF_TRACE_FENTRY:
395 return BPF_TRAMP_FENTRY;
396 case BPF_MODIFY_RETURN:
397 return BPF_TRAMP_MODIFY_RETURN;
398 case BPF_TRACE_FEXIT:
399 return BPF_TRAMP_FEXIT;
400 case BPF_LSM_MAC:
401 if (!prog->aux->attach_func_proto->type)
402
403
404
405 return BPF_TRAMP_FEXIT;
406 else
407 return BPF_TRAMP_MODIFY_RETURN;
408 default:
409 return BPF_TRAMP_REPLACE;
410 }
411}
412
413int bpf_trampoline_link_prog(struct bpf_prog *prog, struct bpf_trampoline *tr)
414{
415 enum bpf_tramp_prog_type kind;
416 int err = 0;
417 int cnt;
418
419 kind = bpf_attach_type_to_tramp(prog);
420 mutex_lock(&tr->mutex);
421 if (tr->extension_prog) {
422
423
424
425 err = -EBUSY;
426 goto out;
427 }
428 cnt = tr->progs_cnt[BPF_TRAMP_FENTRY] + tr->progs_cnt[BPF_TRAMP_FEXIT];
429 if (kind == BPF_TRAMP_REPLACE) {
430
431 if (cnt) {
432 err = -EBUSY;
433 goto out;
434 }
435 tr->extension_prog = prog;
436 err = bpf_arch_text_poke(tr->func.addr, BPF_MOD_JUMP, NULL,
437 prog->bpf_func);
438 goto out;
439 }
440 if (cnt >= BPF_MAX_TRAMP_PROGS) {
441 err = -E2BIG;
442 goto out;
443 }
444 if (!hlist_unhashed(&prog->aux->tramp_hlist)) {
445
446 err = -EBUSY;
447 goto out;
448 }
449 hlist_add_head(&prog->aux->tramp_hlist, &tr->progs_hlist[kind]);
450 tr->progs_cnt[kind]++;
451 err = bpf_trampoline_update(tr);
452 if (err) {
453 hlist_del_init(&prog->aux->tramp_hlist);
454 tr->progs_cnt[kind]--;
455 }
456out:
457 mutex_unlock(&tr->mutex);
458 return err;
459}
460
461
462int bpf_trampoline_unlink_prog(struct bpf_prog *prog, struct bpf_trampoline *tr)
463{
464 enum bpf_tramp_prog_type kind;
465 int err;
466
467 kind = bpf_attach_type_to_tramp(prog);
468 mutex_lock(&tr->mutex);
469 if (kind == BPF_TRAMP_REPLACE) {
470 WARN_ON_ONCE(!tr->extension_prog);
471 err = bpf_arch_text_poke(tr->func.addr, BPF_MOD_JUMP,
472 tr->extension_prog->bpf_func, NULL);
473 tr->extension_prog = NULL;
474 goto out;
475 }
476 hlist_del_init(&prog->aux->tramp_hlist);
477 tr->progs_cnt[kind]--;
478 err = bpf_trampoline_update(tr);
479out:
480 mutex_unlock(&tr->mutex);
481 return err;
482}
483
484struct bpf_trampoline *bpf_trampoline_get(u64 key,
485 struct bpf_attach_target_info *tgt_info)
486{
487 struct bpf_trampoline *tr;
488
489 tr = bpf_trampoline_lookup(key);
490 if (!tr)
491 return NULL;
492
493 mutex_lock(&tr->mutex);
494 if (tr->func.addr)
495 goto out;
496
497 memcpy(&tr->func.model, &tgt_info->fmodel, sizeof(tgt_info->fmodel));
498 tr->func.addr = (void *)tgt_info->tgt_addr;
499out:
500 mutex_unlock(&tr->mutex);
501 return tr;
502}
503
504void bpf_trampoline_put(struct bpf_trampoline *tr)
505{
506 if (!tr)
507 return;
508 mutex_lock(&trampoline_mutex);
509 if (!refcount_dec_and_test(&tr->refcnt))
510 goto out;
511 WARN_ON_ONCE(mutex_is_locked(&tr->mutex));
512 if (WARN_ON_ONCE(!hlist_empty(&tr->progs_hlist[BPF_TRAMP_FENTRY])))
513 goto out;
514 if (WARN_ON_ONCE(!hlist_empty(&tr->progs_hlist[BPF_TRAMP_FEXIT])))
515 goto out;
516
517
518
519
520
521
522 hlist_del(&tr->hlist);
523 kfree(tr);
524out:
525 mutex_unlock(&trampoline_mutex);
526}
527
528#define NO_START_TIME 1
529static u64 notrace bpf_prog_start_time(void)
530{
531 u64 start = NO_START_TIME;
532
533 if (static_branch_unlikely(&bpf_stats_enabled_key)) {
534 start = sched_clock();
535 if (unlikely(!start))
536 start = NO_START_TIME;
537 }
538 return start;
539}
540
541static void notrace inc_misses_counter(struct bpf_prog *prog)
542{
543 struct bpf_prog_stats *stats;
544
545 stats = this_cpu_ptr(prog->stats);
546 u64_stats_update_begin(&stats->syncp);
547 stats->misses++;
548 u64_stats_update_end(&stats->syncp);
549}
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564u64 notrace __bpf_prog_enter(struct bpf_prog *prog)
565 __acquires(RCU)
566{
567 rcu_read_lock();
568 migrate_disable();
569 if (unlikely(__this_cpu_inc_return(*(prog->active)) != 1)) {
570 inc_misses_counter(prog);
571 return 0;
572 }
573 return bpf_prog_start_time();
574}
575
576static void notrace update_prog_stats(struct bpf_prog *prog,
577 u64 start)
578{
579 struct bpf_prog_stats *stats;
580
581 if (static_branch_unlikely(&bpf_stats_enabled_key) &&
582
583
584
585
586
587 start > NO_START_TIME) {
588 stats = this_cpu_ptr(prog->stats);
589 u64_stats_update_begin(&stats->syncp);
590 stats->cnt++;
591 stats->nsecs += sched_clock() - start;
592 u64_stats_update_end(&stats->syncp);
593 }
594}
595
596void notrace __bpf_prog_exit(struct bpf_prog *prog, u64 start)
597 __releases(RCU)
598{
599 update_prog_stats(prog, start);
600 __this_cpu_dec(*(prog->active));
601 migrate_enable();
602 rcu_read_unlock();
603}
604
605u64 notrace __bpf_prog_enter_sleepable(struct bpf_prog *prog)
606{
607 rcu_read_lock_trace();
608 migrate_disable();
609 might_fault();
610 if (unlikely(__this_cpu_inc_return(*(prog->active)) != 1)) {
611 inc_misses_counter(prog);
612 return 0;
613 }
614 return bpf_prog_start_time();
615}
616
617void notrace __bpf_prog_exit_sleepable(struct bpf_prog *prog, u64 start)
618{
619 update_prog_stats(prog, start);
620 __this_cpu_dec(*(prog->active));
621 migrate_enable();
622 rcu_read_unlock_trace();
623}
624
625void notrace __bpf_tramp_enter(struct bpf_tramp_image *tr)
626{
627 percpu_ref_get(&tr->pcref);
628}
629
630void notrace __bpf_tramp_exit(struct bpf_tramp_image *tr)
631{
632 percpu_ref_put(&tr->pcref);
633}
634
635int __weak
636arch_prepare_bpf_trampoline(struct bpf_tramp_image *tr, void *image, void *image_end,
637 const struct btf_func_model *m, u32 flags,
638 struct bpf_tramp_progs *tprogs,
639 void *orig_call)
640{
641 return -ENOTSUPP;
642}
643
644static int __init init_trampolines(void)
645{
646 int i;
647
648 for (i = 0; i < TRAMPOLINE_TABLE_SIZE; i++)
649 INIT_HLIST_HEAD(&trampoline_table[i]);
650 return 0;
651}
652late_initcall(init_trampolines);
653