1 // SPDX-License-Identifier: GPL-2.0-only
2 /* Copyright (c) 2019 Facebook */
3 #include <linux/hash.h>
5 #include <linux/filter.h>
6 #include <linux/ftrace.h>
7 #include <linux/rbtree_latch.h>
8 #include <linux/perf_event.h>
10 #include <linux/rcupdate_trace.h>
11 #include <linux/rcupdate_wait.h>
12 #include <linux/module.h>
13 #include <linux/static_call.h>
14 #include <linux/bpf_verifier.h>
15 #include <linux/bpf_lsm.h>
16 #include <linux/delay.h>
18 /* dummy _ops. The verifier will operate on target program's ops. */
19 const struct bpf_verifier_ops bpf_extension_verifier_ops = {
21 const struct bpf_prog_ops bpf_extension_prog_ops = {
24 /* btf_vmlinux has ~22k attachable functions. 1k htab is enough. */
25 #define TRAMPOLINE_HASH_BITS 10
26 #define TRAMPOLINE_TABLE_SIZE (1 << TRAMPOLINE_HASH_BITS)
28 static struct hlist_head trampoline_table[TRAMPOLINE_TABLE_SIZE];
30 /* serializes access to trampoline_table */
31 static DEFINE_MUTEX(trampoline_mutex);
33 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
34 static int bpf_trampoline_update(struct bpf_trampoline *tr, bool lock_direct_mutex);
36 static int bpf_tramp_ftrace_ops_func(struct ftrace_ops *ops, enum ftrace_ops_cmd cmd)
38 struct bpf_trampoline *tr = ops->private;
41 if (cmd == FTRACE_OPS_CMD_ENABLE_SHARE_IPMODIFY_SELF) {
42 /* This is called inside register_ftrace_direct_multi(), so
43 * tr->mutex is already locked.
45 lockdep_assert_held_once(&tr->mutex);
47 /* Instead of updating the trampoline here, we propagate
48 * -EAGAIN to register_ftrace_direct_multi(). Then we can
49 * retry register_ftrace_direct_multi() after updating the
52 if ((tr->flags & BPF_TRAMP_F_CALL_ORIG) &&
53 !(tr->flags & BPF_TRAMP_F_ORIG_STACK)) {
54 if (WARN_ON_ONCE(tr->flags & BPF_TRAMP_F_SHARE_IPMODIFY))
57 tr->flags |= BPF_TRAMP_F_SHARE_IPMODIFY;
64 /* The normal locking order is
65 * tr->mutex => direct_mutex (ftrace.c) => ftrace_lock (ftrace.c)
67 * The following two commands are called from
69 * prepare_direct_functions_for_ipmodify
70 * cleanup_direct_functions_after_ipmodify
72 * In both cases, direct_mutex is already locked. Use
73 * mutex_trylock(&tr->mutex) to avoid deadlock in race condition
74 * (something else is making changes to this same trampoline).
76 if (!mutex_trylock(&tr->mutex)) {
77 /* sleep 1 ms to make sure whatever holding tr->mutex makes
85 case FTRACE_OPS_CMD_ENABLE_SHARE_IPMODIFY_PEER:
86 tr->flags |= BPF_TRAMP_F_SHARE_IPMODIFY;
88 if ((tr->flags & BPF_TRAMP_F_CALL_ORIG) &&
89 !(tr->flags & BPF_TRAMP_F_ORIG_STACK))
90 ret = bpf_trampoline_update(tr, false /* lock_direct_mutex */);
92 case FTRACE_OPS_CMD_DISABLE_SHARE_IPMODIFY_PEER:
93 tr->flags &= ~BPF_TRAMP_F_SHARE_IPMODIFY;
95 if (tr->flags & BPF_TRAMP_F_ORIG_STACK)
96 ret = bpf_trampoline_update(tr, false /* lock_direct_mutex */);
103 mutex_unlock(&tr->mutex);
108 bool bpf_prog_has_trampoline(const struct bpf_prog *prog)
110 enum bpf_attach_type eatype = prog->expected_attach_type;
111 enum bpf_prog_type ptype = prog->type;
113 return (ptype == BPF_PROG_TYPE_TRACING &&
114 (eatype == BPF_TRACE_FENTRY || eatype == BPF_TRACE_FEXIT ||
115 eatype == BPF_MODIFY_RETURN)) ||
116 (ptype == BPF_PROG_TYPE_LSM && eatype == BPF_LSM_MAC);
119 void bpf_image_ksym_add(void *data, struct bpf_ksym *ksym)
121 ksym->start = (unsigned long) data;
122 ksym->end = ksym->start + PAGE_SIZE;
124 perf_event_ksymbol(PERF_RECORD_KSYMBOL_TYPE_BPF, ksym->start,
125 PAGE_SIZE, false, ksym->name);
128 void bpf_image_ksym_del(struct bpf_ksym *ksym)
131 perf_event_ksymbol(PERF_RECORD_KSYMBOL_TYPE_BPF, ksym->start,
132 PAGE_SIZE, true, ksym->name);
135 static struct bpf_trampoline *bpf_trampoline_lookup(u64 key)
137 struct bpf_trampoline *tr;
138 struct hlist_head *head;
141 mutex_lock(&trampoline_mutex);
142 head = &trampoline_table[hash_64(key, TRAMPOLINE_HASH_BITS)];
143 hlist_for_each_entry(tr, head, hlist) {
144 if (tr->key == key) {
145 refcount_inc(&tr->refcnt);
149 tr = kzalloc(sizeof(*tr), GFP_KERNEL);
152 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
153 tr->fops = kzalloc(sizeof(struct ftrace_ops), GFP_KERNEL);
159 tr->fops->private = tr;
160 tr->fops->ops_func = bpf_tramp_ftrace_ops_func;
164 INIT_HLIST_NODE(&tr->hlist);
165 hlist_add_head(&tr->hlist, head);
166 refcount_set(&tr->refcnt, 1);
167 mutex_init(&tr->mutex);
168 for (i = 0; i < BPF_TRAMP_MAX; i++)
169 INIT_HLIST_HEAD(&tr->progs_hlist[i]);
171 mutex_unlock(&trampoline_mutex);
175 static int bpf_trampoline_module_get(struct bpf_trampoline *tr)
181 mod = __module_text_address((unsigned long) tr->func.addr);
182 if (mod && !try_module_get(mod))
189 static void bpf_trampoline_module_put(struct bpf_trampoline *tr)
195 static int unregister_fentry(struct bpf_trampoline *tr, void *old_addr)
197 void *ip = tr->func.addr;
200 if (tr->func.ftrace_managed)
201 ret = unregister_ftrace_direct_multi(tr->fops, (long)old_addr);
203 ret = bpf_arch_text_poke(ip, BPF_MOD_CALL, old_addr, NULL);
206 bpf_trampoline_module_put(tr);
210 static int modify_fentry(struct bpf_trampoline *tr, void *old_addr, void *new_addr,
211 bool lock_direct_mutex)
213 void *ip = tr->func.addr;
216 if (tr->func.ftrace_managed) {
217 if (lock_direct_mutex)
218 ret = modify_ftrace_direct_multi(tr->fops, (long)new_addr);
220 ret = modify_ftrace_direct_multi_nolock(tr->fops, (long)new_addr);
222 ret = bpf_arch_text_poke(ip, BPF_MOD_CALL, old_addr, new_addr);
227 /* first time registering */
228 static int register_fentry(struct bpf_trampoline *tr, void *new_addr)
230 void *ip = tr->func.addr;
234 faddr = ftrace_location((unsigned long)ip);
238 tr->func.ftrace_managed = true;
241 if (bpf_trampoline_module_get(tr))
244 if (tr->func.ftrace_managed) {
245 ftrace_set_filter_ip(tr->fops, (unsigned long)ip, 0, 1);
246 ret = register_ftrace_direct_multi(tr->fops, (long)new_addr);
248 ret = bpf_arch_text_poke(ip, BPF_MOD_CALL, NULL, new_addr);
252 bpf_trampoline_module_put(tr);
256 static struct bpf_tramp_links *
257 bpf_trampoline_get_progs(const struct bpf_trampoline *tr, int *total, bool *ip_arg)
259 struct bpf_tramp_link *link;
260 struct bpf_tramp_links *tlinks;
261 struct bpf_tramp_link **links;
265 tlinks = kcalloc(BPF_TRAMP_MAX, sizeof(*tlinks), GFP_KERNEL);
267 return ERR_PTR(-ENOMEM);
269 for (kind = 0; kind < BPF_TRAMP_MAX; kind++) {
270 tlinks[kind].nr_links = tr->progs_cnt[kind];
271 *total += tr->progs_cnt[kind];
272 links = tlinks[kind].links;
274 hlist_for_each_entry(link, &tr->progs_hlist[kind], tramp_hlist) {
275 *ip_arg |= link->link.prog->call_get_func_ip;
282 static void __bpf_tramp_image_put_deferred(struct work_struct *work)
284 struct bpf_tramp_image *im;
286 im = container_of(work, struct bpf_tramp_image, work);
287 bpf_image_ksym_del(&im->ksym);
288 bpf_jit_free_exec(im->image);
289 bpf_jit_uncharge_modmem(PAGE_SIZE);
290 percpu_ref_exit(&im->pcref);
294 /* callback, fexit step 3 or fentry step 2 */
295 static void __bpf_tramp_image_put_rcu(struct rcu_head *rcu)
297 struct bpf_tramp_image *im;
299 im = container_of(rcu, struct bpf_tramp_image, rcu);
300 INIT_WORK(&im->work, __bpf_tramp_image_put_deferred);
301 schedule_work(&im->work);
304 /* callback, fexit step 2. Called after percpu_ref_kill confirms. */
305 static void __bpf_tramp_image_release(struct percpu_ref *pcref)
307 struct bpf_tramp_image *im;
309 im = container_of(pcref, struct bpf_tramp_image, pcref);
310 call_rcu_tasks(&im->rcu, __bpf_tramp_image_put_rcu);
313 /* callback, fexit or fentry step 1 */
314 static void __bpf_tramp_image_put_rcu_tasks(struct rcu_head *rcu)
316 struct bpf_tramp_image *im;
318 im = container_of(rcu, struct bpf_tramp_image, rcu);
319 if (im->ip_after_call)
320 /* the case of fmod_ret/fexit trampoline and CONFIG_PREEMPTION=y */
321 percpu_ref_kill(&im->pcref);
323 /* the case of fentry trampoline */
324 call_rcu_tasks(&im->rcu, __bpf_tramp_image_put_rcu);
327 static void bpf_tramp_image_put(struct bpf_tramp_image *im)
329 /* The trampoline image that calls original function is using:
330 * rcu_read_lock_trace to protect sleepable bpf progs
331 * rcu_read_lock to protect normal bpf progs
332 * percpu_ref to protect trampoline itself
333 * rcu tasks to protect trampoline asm not covered by percpu_ref
334 * (which are few asm insns before __bpf_tramp_enter and
335 * after __bpf_tramp_exit)
337 * The trampoline is unreachable before bpf_tramp_image_put().
339 * First, patch the trampoline to avoid calling into fexit progs.
340 * The progs will be freed even if the original function is still
341 * executing or sleeping.
342 * In case of CONFIG_PREEMPT=y use call_rcu_tasks() to wait on
343 * first few asm instructions to execute and call into
344 * __bpf_tramp_enter->percpu_ref_get.
345 * Then use percpu_ref_kill to wait for the trampoline and the original
346 * function to finish.
347 * Then use call_rcu_tasks() to make sure few asm insns in
348 * the trampoline epilogue are done as well.
350 * In !PREEMPT case the task that got interrupted in the first asm
351 * insns won't go through an RCU quiescent state which the
352 * percpu_ref_kill will be waiting for. Hence the first
353 * call_rcu_tasks() is not necessary.
355 if (im->ip_after_call) {
356 int err = bpf_arch_text_poke(im->ip_after_call, BPF_MOD_JUMP,
357 NULL, im->ip_epilogue);
359 if (IS_ENABLED(CONFIG_PREEMPTION))
360 call_rcu_tasks(&im->rcu, __bpf_tramp_image_put_rcu_tasks);
362 percpu_ref_kill(&im->pcref);
366 /* The trampoline without fexit and fmod_ret progs doesn't call original
367 * function and doesn't use percpu_ref.
368 * Use call_rcu_tasks_trace() to wait for sleepable progs to finish.
369 * Then use call_rcu_tasks() to wait for the rest of trampoline asm
372 call_rcu_tasks_trace(&im->rcu, __bpf_tramp_image_put_rcu_tasks);
375 static struct bpf_tramp_image *bpf_tramp_image_alloc(u64 key, u32 idx)
377 struct bpf_tramp_image *im;
378 struct bpf_ksym *ksym;
382 im = kzalloc(sizeof(*im), GFP_KERNEL);
386 err = bpf_jit_charge_modmem(PAGE_SIZE);
391 im->image = image = bpf_jit_alloc_exec(PAGE_SIZE);
394 set_vm_flush_reset_perms(image);
396 err = percpu_ref_init(&im->pcref, __bpf_tramp_image_release, 0, GFP_KERNEL);
401 INIT_LIST_HEAD_RCU(&ksym->lnode);
402 snprintf(ksym->name, KSYM_NAME_LEN, "bpf_trampoline_%llu_%u", key, idx);
403 bpf_image_ksym_add(image, ksym);
407 bpf_jit_free_exec(im->image);
409 bpf_jit_uncharge_modmem(PAGE_SIZE);
416 static int bpf_trampoline_update(struct bpf_trampoline *tr, bool lock_direct_mutex)
418 struct bpf_tramp_image *im;
419 struct bpf_tramp_links *tlinks;
420 u32 orig_flags = tr->flags;
424 tlinks = bpf_trampoline_get_progs(tr, &total, &ip_arg);
426 return PTR_ERR(tlinks);
429 err = unregister_fentry(tr, tr->cur_image->image);
430 bpf_tramp_image_put(tr->cur_image);
431 tr->cur_image = NULL;
436 im = bpf_tramp_image_alloc(tr->key, tr->selector);
442 /* clear all bits except SHARE_IPMODIFY */
443 tr->flags &= BPF_TRAMP_F_SHARE_IPMODIFY;
445 if (tlinks[BPF_TRAMP_FEXIT].nr_links ||
446 tlinks[BPF_TRAMP_MODIFY_RETURN].nr_links) {
447 /* NOTE: BPF_TRAMP_F_RESTORE_REGS and BPF_TRAMP_F_SKIP_FRAME
448 * should not be set together.
450 tr->flags |= BPF_TRAMP_F_CALL_ORIG | BPF_TRAMP_F_SKIP_FRAME;
452 tr->flags |= BPF_TRAMP_F_RESTORE_REGS;
456 tr->flags |= BPF_TRAMP_F_IP_ARG;
458 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
460 if ((tr->flags & BPF_TRAMP_F_SHARE_IPMODIFY) &&
461 (tr->flags & BPF_TRAMP_F_CALL_ORIG))
462 tr->flags |= BPF_TRAMP_F_ORIG_STACK;
465 err = arch_prepare_bpf_trampoline(im, im->image, im->image + PAGE_SIZE,
466 &tr->func.model, tr->flags, tlinks,
471 set_memory_rox((long)im->image, 1);
473 WARN_ON(tr->cur_image && tr->selector == 0);
474 WARN_ON(!tr->cur_image && tr->selector);
476 /* progs already running at this address */
477 err = modify_fentry(tr, tr->cur_image->image, im->image, lock_direct_mutex);
479 /* first time registering */
480 err = register_fentry(tr, im->image);
482 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
483 if (err == -EAGAIN) {
484 /* -EAGAIN from bpf_tramp_ftrace_ops_func. Now
485 * BPF_TRAMP_F_SHARE_IPMODIFY is set, we can generate the
486 * trampoline again, and retry register.
488 /* reset fops->func and fops->trampoline for re-register */
489 tr->fops->func = NULL;
490 tr->fops->trampoline = 0;
492 /* reset im->image memory attr for arch_prepare_bpf_trampoline */
493 set_memory_nx((long)im->image, 1);
494 set_memory_rw((long)im->image, 1);
502 bpf_tramp_image_put(tr->cur_image);
506 /* If any error happens, restore previous flags */
508 tr->flags = orig_flags;
513 static enum bpf_tramp_prog_type bpf_attach_type_to_tramp(struct bpf_prog *prog)
515 switch (prog->expected_attach_type) {
516 case BPF_TRACE_FENTRY:
517 return BPF_TRAMP_FENTRY;
518 case BPF_MODIFY_RETURN:
519 return BPF_TRAMP_MODIFY_RETURN;
520 case BPF_TRACE_FEXIT:
521 return BPF_TRAMP_FEXIT;
523 if (!prog->aux->attach_func_proto->type)
524 /* The function returns void, we cannot modify its
527 return BPF_TRAMP_FEXIT;
529 return BPF_TRAMP_MODIFY_RETURN;
531 return BPF_TRAMP_REPLACE;
535 static int __bpf_trampoline_link_prog(struct bpf_tramp_link *link, struct bpf_trampoline *tr)
537 enum bpf_tramp_prog_type kind;
538 struct bpf_tramp_link *link_exiting;
542 kind = bpf_attach_type_to_tramp(link->link.prog);
543 if (tr->extension_prog)
544 /* cannot attach fentry/fexit if extension prog is attached.
545 * cannot overwrite extension prog either.
549 for (i = 0; i < BPF_TRAMP_MAX; i++)
550 cnt += tr->progs_cnt[i];
552 if (kind == BPF_TRAMP_REPLACE) {
553 /* Cannot attach extension if fentry/fexit are in use. */
556 tr->extension_prog = link->link.prog;
557 return bpf_arch_text_poke(tr->func.addr, BPF_MOD_JUMP, NULL,
558 link->link.prog->bpf_func);
560 if (cnt >= BPF_MAX_TRAMP_LINKS)
562 if (!hlist_unhashed(&link->tramp_hlist))
563 /* prog already linked */
565 hlist_for_each_entry(link_exiting, &tr->progs_hlist[kind], tramp_hlist) {
566 if (link_exiting->link.prog != link->link.prog)
568 /* prog already linked */
572 hlist_add_head(&link->tramp_hlist, &tr->progs_hlist[kind]);
573 tr->progs_cnt[kind]++;
574 err = bpf_trampoline_update(tr, true /* lock_direct_mutex */);
576 hlist_del_init(&link->tramp_hlist);
577 tr->progs_cnt[kind]--;
582 int bpf_trampoline_link_prog(struct bpf_tramp_link *link, struct bpf_trampoline *tr)
586 mutex_lock(&tr->mutex);
587 err = __bpf_trampoline_link_prog(link, tr);
588 mutex_unlock(&tr->mutex);
592 static int __bpf_trampoline_unlink_prog(struct bpf_tramp_link *link, struct bpf_trampoline *tr)
594 enum bpf_tramp_prog_type kind;
597 kind = bpf_attach_type_to_tramp(link->link.prog);
598 if (kind == BPF_TRAMP_REPLACE) {
599 WARN_ON_ONCE(!tr->extension_prog);
600 err = bpf_arch_text_poke(tr->func.addr, BPF_MOD_JUMP,
601 tr->extension_prog->bpf_func, NULL);
602 tr->extension_prog = NULL;
605 hlist_del_init(&link->tramp_hlist);
606 tr->progs_cnt[kind]--;
607 return bpf_trampoline_update(tr, true /* lock_direct_mutex */);
610 /* bpf_trampoline_unlink_prog() should never fail. */
611 int bpf_trampoline_unlink_prog(struct bpf_tramp_link *link, struct bpf_trampoline *tr)
615 mutex_lock(&tr->mutex);
616 err = __bpf_trampoline_unlink_prog(link, tr);
617 mutex_unlock(&tr->mutex);
621 #if defined(CONFIG_CGROUP_BPF) && defined(CONFIG_BPF_LSM)
622 static void bpf_shim_tramp_link_release(struct bpf_link *link)
624 struct bpf_shim_tramp_link *shim_link =
625 container_of(link, struct bpf_shim_tramp_link, link.link);
627 /* paired with 'shim_link->trampoline = tr' in bpf_trampoline_link_cgroup_shim */
628 if (!shim_link->trampoline)
631 WARN_ON_ONCE(bpf_trampoline_unlink_prog(&shim_link->link, shim_link->trampoline));
632 bpf_trampoline_put(shim_link->trampoline);
635 static void bpf_shim_tramp_link_dealloc(struct bpf_link *link)
637 struct bpf_shim_tramp_link *shim_link =
638 container_of(link, struct bpf_shim_tramp_link, link.link);
643 static const struct bpf_link_ops bpf_shim_tramp_link_lops = {
644 .release = bpf_shim_tramp_link_release,
645 .dealloc = bpf_shim_tramp_link_dealloc,
648 static struct bpf_shim_tramp_link *cgroup_shim_alloc(const struct bpf_prog *prog,
652 struct bpf_shim_tramp_link *shim_link = NULL;
655 shim_link = kzalloc(sizeof(*shim_link), GFP_USER);
659 p = bpf_prog_alloc(1, 0);
666 p->bpf_func = bpf_func;
668 p->aux->cgroup_atype = cgroup_atype;
669 p->aux->attach_func_proto = prog->aux->attach_func_proto;
670 p->aux->attach_btf_id = prog->aux->attach_btf_id;
671 p->aux->attach_btf = prog->aux->attach_btf;
672 btf_get(p->aux->attach_btf);
673 p->type = BPF_PROG_TYPE_LSM;
674 p->expected_attach_type = BPF_LSM_MAC;
676 bpf_link_init(&shim_link->link.link, BPF_LINK_TYPE_UNSPEC,
677 &bpf_shim_tramp_link_lops, p);
678 bpf_cgroup_atype_get(p->aux->attach_btf_id, cgroup_atype);
683 static struct bpf_shim_tramp_link *cgroup_shim_find(struct bpf_trampoline *tr,
686 struct bpf_tramp_link *link;
689 for (kind = 0; kind < BPF_TRAMP_MAX; kind++) {
690 hlist_for_each_entry(link, &tr->progs_hlist[kind], tramp_hlist) {
691 struct bpf_prog *p = link->link.prog;
693 if (p->bpf_func == bpf_func)
694 return container_of(link, struct bpf_shim_tramp_link, link);
701 int bpf_trampoline_link_cgroup_shim(struct bpf_prog *prog,
704 struct bpf_shim_tramp_link *shim_link = NULL;
705 struct bpf_attach_target_info tgt_info = {};
706 struct bpf_trampoline *tr;
711 err = bpf_check_attach_target(NULL, prog, NULL,
712 prog->aux->attach_btf_id,
717 key = bpf_trampoline_compute_key(NULL, prog->aux->attach_btf,
718 prog->aux->attach_btf_id);
720 bpf_lsm_find_cgroup_shim(prog, &bpf_func);
721 tr = bpf_trampoline_get(key, &tgt_info);
725 mutex_lock(&tr->mutex);
727 shim_link = cgroup_shim_find(tr, bpf_func);
729 /* Reusing existing shim attached by the other program. */
730 bpf_link_inc(&shim_link->link.link);
732 mutex_unlock(&tr->mutex);
733 bpf_trampoline_put(tr); /* bpf_trampoline_get above */
737 /* Allocate and install new shim. */
739 shim_link = cgroup_shim_alloc(prog, bpf_func, cgroup_atype);
745 err = __bpf_trampoline_link_prog(&shim_link->link, tr);
749 shim_link->trampoline = tr;
750 /* note, we're still holding tr refcnt from above */
752 mutex_unlock(&tr->mutex);
756 mutex_unlock(&tr->mutex);
759 bpf_link_put(&shim_link->link.link);
761 /* have to release tr while _not_ holding its mutex */
762 bpf_trampoline_put(tr); /* bpf_trampoline_get above */
767 void bpf_trampoline_unlink_cgroup_shim(struct bpf_prog *prog)
769 struct bpf_shim_tramp_link *shim_link = NULL;
770 struct bpf_trampoline *tr;
774 key = bpf_trampoline_compute_key(NULL, prog->aux->attach_btf,
775 prog->aux->attach_btf_id);
777 bpf_lsm_find_cgroup_shim(prog, &bpf_func);
778 tr = bpf_trampoline_lookup(key);
779 if (WARN_ON_ONCE(!tr))
782 mutex_lock(&tr->mutex);
783 shim_link = cgroup_shim_find(tr, bpf_func);
784 mutex_unlock(&tr->mutex);
787 bpf_link_put(&shim_link->link.link);
789 bpf_trampoline_put(tr); /* bpf_trampoline_lookup above */
793 struct bpf_trampoline *bpf_trampoline_get(u64 key,
794 struct bpf_attach_target_info *tgt_info)
796 struct bpf_trampoline *tr;
798 tr = bpf_trampoline_lookup(key);
802 mutex_lock(&tr->mutex);
806 memcpy(&tr->func.model, &tgt_info->fmodel, sizeof(tgt_info->fmodel));
807 tr->func.addr = (void *)tgt_info->tgt_addr;
809 mutex_unlock(&tr->mutex);
813 void bpf_trampoline_put(struct bpf_trampoline *tr)
819 mutex_lock(&trampoline_mutex);
820 if (!refcount_dec_and_test(&tr->refcnt))
822 WARN_ON_ONCE(mutex_is_locked(&tr->mutex));
824 for (i = 0; i < BPF_TRAMP_MAX; i++)
825 if (WARN_ON_ONCE(!hlist_empty(&tr->progs_hlist[i])))
828 /* This code will be executed even when the last bpf_tramp_image
829 * is alive. All progs are detached from the trampoline and the
830 * trampoline image is patched with jmp into epilogue to skip
831 * fexit progs. The fentry-only trampoline will be freed via
832 * multiple rcu callbacks.
834 hlist_del(&tr->hlist);
836 ftrace_free_filter(tr->fops);
841 mutex_unlock(&trampoline_mutex);
844 #define NO_START_TIME 1
845 static __always_inline u64 notrace bpf_prog_start_time(void)
847 u64 start = NO_START_TIME;
849 if (static_branch_unlikely(&bpf_stats_enabled_key)) {
850 start = sched_clock();
851 if (unlikely(!start))
852 start = NO_START_TIME;
857 /* The logic is similar to bpf_prog_run(), but with an explicit
858 * rcu_read_lock() and migrate_disable() which are required
859 * for the trampoline. The macro is split into
860 * call __bpf_prog_enter
861 * call prog->bpf_func
862 * call __bpf_prog_exit
864 * __bpf_prog_enter returns:
865 * 0 - skip execution of the bpf prog
866 * 1 - execute bpf prog
867 * [2..MAX_U64] - execute bpf prog and record execution time.
868 * This is start time.
870 static u64 notrace __bpf_prog_enter_recur(struct bpf_prog *prog, struct bpf_tramp_run_ctx *run_ctx)
876 run_ctx->saved_run_ctx = bpf_set_run_ctx(&run_ctx->run_ctx);
878 if (unlikely(this_cpu_inc_return(*(prog->active)) != 1)) {
879 bpf_prog_inc_misses_counter(prog);
882 return bpf_prog_start_time();
885 static void notrace update_prog_stats(struct bpf_prog *prog,
888 struct bpf_prog_stats *stats;
890 if (static_branch_unlikely(&bpf_stats_enabled_key) &&
891 /* static_key could be enabled in __bpf_prog_enter*
892 * and disabled in __bpf_prog_exit*.
894 * Hence check that 'start' is valid.
896 start > NO_START_TIME) {
899 stats = this_cpu_ptr(prog->stats);
900 flags = u64_stats_update_begin_irqsave(&stats->syncp);
901 u64_stats_inc(&stats->cnt);
902 u64_stats_add(&stats->nsecs, sched_clock() - start);
903 u64_stats_update_end_irqrestore(&stats->syncp, flags);
907 static void notrace __bpf_prog_exit_recur(struct bpf_prog *prog, u64 start,
908 struct bpf_tramp_run_ctx *run_ctx)
911 bpf_reset_run_ctx(run_ctx->saved_run_ctx);
913 update_prog_stats(prog, start);
914 this_cpu_dec(*(prog->active));
919 static u64 notrace __bpf_prog_enter_lsm_cgroup(struct bpf_prog *prog,
920 struct bpf_tramp_run_ctx *run_ctx)
923 /* Runtime stats are exported via actual BPF_LSM_CGROUP
924 * programs, not the shims.
929 run_ctx->saved_run_ctx = bpf_set_run_ctx(&run_ctx->run_ctx);
931 return NO_START_TIME;
934 static void notrace __bpf_prog_exit_lsm_cgroup(struct bpf_prog *prog, u64 start,
935 struct bpf_tramp_run_ctx *run_ctx)
938 bpf_reset_run_ctx(run_ctx->saved_run_ctx);
944 u64 notrace __bpf_prog_enter_sleepable_recur(struct bpf_prog *prog,
945 struct bpf_tramp_run_ctx *run_ctx)
947 rcu_read_lock_trace();
951 if (unlikely(this_cpu_inc_return(*(prog->active)) != 1)) {
952 bpf_prog_inc_misses_counter(prog);
956 run_ctx->saved_run_ctx = bpf_set_run_ctx(&run_ctx->run_ctx);
958 return bpf_prog_start_time();
961 void notrace __bpf_prog_exit_sleepable_recur(struct bpf_prog *prog, u64 start,
962 struct bpf_tramp_run_ctx *run_ctx)
964 bpf_reset_run_ctx(run_ctx->saved_run_ctx);
966 update_prog_stats(prog, start);
967 this_cpu_dec(*(prog->active));
969 rcu_read_unlock_trace();
972 static u64 notrace __bpf_prog_enter_sleepable(struct bpf_prog *prog,
973 struct bpf_tramp_run_ctx *run_ctx)
975 rcu_read_lock_trace();
979 run_ctx->saved_run_ctx = bpf_set_run_ctx(&run_ctx->run_ctx);
981 return bpf_prog_start_time();
984 static void notrace __bpf_prog_exit_sleepable(struct bpf_prog *prog, u64 start,
985 struct bpf_tramp_run_ctx *run_ctx)
987 bpf_reset_run_ctx(run_ctx->saved_run_ctx);
989 update_prog_stats(prog, start);
991 rcu_read_unlock_trace();
994 static u64 notrace __bpf_prog_enter(struct bpf_prog *prog,
995 struct bpf_tramp_run_ctx *run_ctx)
1001 run_ctx->saved_run_ctx = bpf_set_run_ctx(&run_ctx->run_ctx);
1003 return bpf_prog_start_time();
1006 static void notrace __bpf_prog_exit(struct bpf_prog *prog, u64 start,
1007 struct bpf_tramp_run_ctx *run_ctx)
1010 bpf_reset_run_ctx(run_ctx->saved_run_ctx);
1012 update_prog_stats(prog, start);
1017 void notrace __bpf_tramp_enter(struct bpf_tramp_image *tr)
1019 percpu_ref_get(&tr->pcref);
1022 void notrace __bpf_tramp_exit(struct bpf_tramp_image *tr)
1024 percpu_ref_put(&tr->pcref);
1027 bpf_trampoline_enter_t bpf_trampoline_enter(const struct bpf_prog *prog)
1029 bool sleepable = prog->aux->sleepable;
1031 if (bpf_prog_check_recur(prog))
1032 return sleepable ? __bpf_prog_enter_sleepable_recur :
1033 __bpf_prog_enter_recur;
1035 if (resolve_prog_type(prog) == BPF_PROG_TYPE_LSM &&
1036 prog->expected_attach_type == BPF_LSM_CGROUP)
1037 return __bpf_prog_enter_lsm_cgroup;
1039 return sleepable ? __bpf_prog_enter_sleepable : __bpf_prog_enter;
1042 bpf_trampoline_exit_t bpf_trampoline_exit(const struct bpf_prog *prog)
1044 bool sleepable = prog->aux->sleepable;
1046 if (bpf_prog_check_recur(prog))
1047 return sleepable ? __bpf_prog_exit_sleepable_recur :
1048 __bpf_prog_exit_recur;
1050 if (resolve_prog_type(prog) == BPF_PROG_TYPE_LSM &&
1051 prog->expected_attach_type == BPF_LSM_CGROUP)
1052 return __bpf_prog_exit_lsm_cgroup;
1054 return sleepable ? __bpf_prog_exit_sleepable : __bpf_prog_exit;
1058 arch_prepare_bpf_trampoline(struct bpf_tramp_image *tr, void *image, void *image_end,
1059 const struct btf_func_model *m, u32 flags,
1060 struct bpf_tramp_links *tlinks,
1066 static int __init init_trampolines(void)
1070 for (i = 0; i < TRAMPOLINE_TABLE_SIZE; i++)
1071 INIT_HLIST_HEAD(&trampoline_table[i]);
1074 late_initcall(init_trampolines);