1 // SPDX-License-Identifier: GPL-2.0-only 2 /* Copyright (c) 2019 Facebook */ 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 #include <linux/static_call.h> 14 #include <linux/bpf_verifier.h> 15 #include <linux/bpf_lsm.h> 16 #include <linux/delay.h> 17 18 /* dummy _ops. The verifier will operate on target program's ops. */ 19 const struct bpf_verifier_ops bpf_extension_verifier_ops = { 20 }; 21 const struct bpf_prog_ops bpf_extension_prog_ops = { 22 }; 23 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) 27 28 static struct hlist_head trampoline_table[TRAMPOLINE_TABLE_SIZE]; 29 30 /* serializes access to trampoline_table */ 31 static DEFINE_MUTEX(trampoline_mutex); 32 33 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS 34 static int bpf_trampoline_update(struct bpf_trampoline *tr, bool lock_direct_mutex); 35 36 static int bpf_tramp_ftrace_ops_func(struct ftrace_ops *ops, enum ftrace_ops_cmd cmd) 37 { 38 struct bpf_trampoline *tr = ops->private; 39 int ret = 0; 40 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. 44 */ 45 lockdep_assert_held_once(&tr->mutex); 46 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 50 * trampoline. 51 */ 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)) 55 return -EBUSY; 56 57 tr->flags |= BPF_TRAMP_F_SHARE_IPMODIFY; 58 return -EAGAIN; 59 } 60 61 return 0; 62 } 63 64 /* The normal locking order is 65 * tr->mutex => direct_mutex (ftrace.c) => ftrace_lock (ftrace.c) 66 * 67 * The following two commands are called from 68 * 69 * prepare_direct_functions_for_ipmodify 70 * cleanup_direct_functions_after_ipmodify 71 * 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). 75 */ 76 if (!mutex_trylock(&tr->mutex)) { 77 /* sleep 1 ms to make sure whatever holding tr->mutex makes 78 * some progress. 79 */ 80 msleep(1); 81 return -EAGAIN; 82 } 83 84 switch (cmd) { 85 case FTRACE_OPS_CMD_ENABLE_SHARE_IPMODIFY_PEER: 86 tr->flags |= BPF_TRAMP_F_SHARE_IPMODIFY; 87 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 */); 91 break; 92 case FTRACE_OPS_CMD_DISABLE_SHARE_IPMODIFY_PEER: 93 tr->flags &= ~BPF_TRAMP_F_SHARE_IPMODIFY; 94 95 if (tr->flags & BPF_TRAMP_F_ORIG_STACK) 96 ret = bpf_trampoline_update(tr, false /* lock_direct_mutex */); 97 break; 98 default: 99 ret = -EINVAL; 100 break; 101 } 102 103 mutex_unlock(&tr->mutex); 104 return ret; 105 } 106 #endif 107 108 bool bpf_prog_has_trampoline(const struct bpf_prog *prog) 109 { 110 enum bpf_attach_type eatype = prog->expected_attach_type; 111 enum bpf_prog_type ptype = prog->type; 112 113 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); 117 } 118 119 void *bpf_jit_alloc_exec_page(void) 120 { 121 void *image; 122 123 image = bpf_jit_alloc_exec(PAGE_SIZE); 124 if (!image) 125 return NULL; 126 127 set_vm_flush_reset_perms(image); 128 /* Keep image as writeable. The alternative is to keep flipping ro/rw 129 * every time new program is attached or detached. 130 */ 131 set_memory_x((long)image, 1); 132 return image; 133 } 134 135 void bpf_image_ksym_add(void *data, struct bpf_ksym *ksym) 136 { 137 ksym->start = (unsigned long) data; 138 ksym->end = ksym->start + PAGE_SIZE; 139 bpf_ksym_add(ksym); 140 perf_event_ksymbol(PERF_RECORD_KSYMBOL_TYPE_BPF, ksym->start, 141 PAGE_SIZE, false, ksym->name); 142 } 143 144 void bpf_image_ksym_del(struct bpf_ksym *ksym) 145 { 146 bpf_ksym_del(ksym); 147 perf_event_ksymbol(PERF_RECORD_KSYMBOL_TYPE_BPF, ksym->start, 148 PAGE_SIZE, true, ksym->name); 149 } 150 151 static struct bpf_trampoline *bpf_trampoline_lookup(u64 key) 152 { 153 struct bpf_trampoline *tr; 154 struct hlist_head *head; 155 int i; 156 157 mutex_lock(&trampoline_mutex); 158 head = &trampoline_table[hash_64(key, TRAMPOLINE_HASH_BITS)]; 159 hlist_for_each_entry(tr, head, hlist) { 160 if (tr->key == key) { 161 refcount_inc(&tr->refcnt); 162 goto out; 163 } 164 } 165 tr = kzalloc(sizeof(*tr), GFP_KERNEL); 166 if (!tr) 167 goto out; 168 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS 169 tr->fops = kzalloc(sizeof(struct ftrace_ops), GFP_KERNEL); 170 if (!tr->fops) { 171 kfree(tr); 172 tr = NULL; 173 goto out; 174 } 175 tr->fops->private = tr; 176 tr->fops->ops_func = bpf_tramp_ftrace_ops_func; 177 #endif 178 179 tr->key = key; 180 INIT_HLIST_NODE(&tr->hlist); 181 hlist_add_head(&tr->hlist, head); 182 refcount_set(&tr->refcnt, 1); 183 mutex_init(&tr->mutex); 184 for (i = 0; i < BPF_TRAMP_MAX; i++) 185 INIT_HLIST_HEAD(&tr->progs_hlist[i]); 186 out: 187 mutex_unlock(&trampoline_mutex); 188 return tr; 189 } 190 191 static int bpf_trampoline_module_get(struct bpf_trampoline *tr) 192 { 193 struct module *mod; 194 int err = 0; 195 196 preempt_disable(); 197 mod = __module_text_address((unsigned long) tr->func.addr); 198 if (mod && !try_module_get(mod)) 199 err = -ENOENT; 200 preempt_enable(); 201 tr->mod = mod; 202 return err; 203 } 204 205 static void bpf_trampoline_module_put(struct bpf_trampoline *tr) 206 { 207 module_put(tr->mod); 208 tr->mod = NULL; 209 } 210 211 static int unregister_fentry(struct bpf_trampoline *tr, void *old_addr) 212 { 213 void *ip = tr->func.addr; 214 int ret; 215 216 if (tr->func.ftrace_managed) 217 ret = unregister_ftrace_direct_multi(tr->fops, (long)old_addr); 218 else 219 ret = bpf_arch_text_poke(ip, BPF_MOD_CALL, old_addr, NULL); 220 221 if (!ret) 222 bpf_trampoline_module_put(tr); 223 return ret; 224 } 225 226 static int modify_fentry(struct bpf_trampoline *tr, void *old_addr, void *new_addr, 227 bool lock_direct_mutex) 228 { 229 void *ip = tr->func.addr; 230 int ret; 231 232 if (tr->func.ftrace_managed) { 233 if (lock_direct_mutex) 234 ret = modify_ftrace_direct_multi(tr->fops, (long)new_addr); 235 else 236 ret = modify_ftrace_direct_multi_nolock(tr->fops, (long)new_addr); 237 } else { 238 ret = bpf_arch_text_poke(ip, BPF_MOD_CALL, old_addr, new_addr); 239 } 240 return ret; 241 } 242 243 /* first time registering */ 244 static int register_fentry(struct bpf_trampoline *tr, void *new_addr) 245 { 246 void *ip = tr->func.addr; 247 unsigned long faddr; 248 int ret; 249 250 faddr = ftrace_location((unsigned long)ip); 251 if (faddr) { 252 if (!tr->fops) 253 return -ENOTSUPP; 254 tr->func.ftrace_managed = true; 255 } 256 257 if (bpf_trampoline_module_get(tr)) 258 return -ENOENT; 259 260 if (tr->func.ftrace_managed) { 261 ftrace_set_filter_ip(tr->fops, (unsigned long)ip, 0, 1); 262 ret = register_ftrace_direct_multi(tr->fops, (long)new_addr); 263 } else { 264 ret = bpf_arch_text_poke(ip, BPF_MOD_CALL, NULL, new_addr); 265 } 266 267 if (ret) 268 bpf_trampoline_module_put(tr); 269 return ret; 270 } 271 272 static struct bpf_tramp_links * 273 bpf_trampoline_get_progs(const struct bpf_trampoline *tr, int *total, bool *ip_arg) 274 { 275 struct bpf_tramp_link *link; 276 struct bpf_tramp_links *tlinks; 277 struct bpf_tramp_link **links; 278 int kind; 279 280 *total = 0; 281 tlinks = kcalloc(BPF_TRAMP_MAX, sizeof(*tlinks), GFP_KERNEL); 282 if (!tlinks) 283 return ERR_PTR(-ENOMEM); 284 285 for (kind = 0; kind < BPF_TRAMP_MAX; kind++) { 286 tlinks[kind].nr_links = tr->progs_cnt[kind]; 287 *total += tr->progs_cnt[kind]; 288 links = tlinks[kind].links; 289 290 hlist_for_each_entry(link, &tr->progs_hlist[kind], tramp_hlist) { 291 *ip_arg |= link->link.prog->call_get_func_ip; 292 *links++ = link; 293 } 294 } 295 return tlinks; 296 } 297 298 static void __bpf_tramp_image_put_deferred(struct work_struct *work) 299 { 300 struct bpf_tramp_image *im; 301 302 im = container_of(work, struct bpf_tramp_image, work); 303 bpf_image_ksym_del(&im->ksym); 304 bpf_jit_free_exec(im->image); 305 bpf_jit_uncharge_modmem(PAGE_SIZE); 306 percpu_ref_exit(&im->pcref); 307 kfree_rcu(im, rcu); 308 } 309 310 /* callback, fexit step 3 or fentry step 2 */ 311 static void __bpf_tramp_image_put_rcu(struct rcu_head *rcu) 312 { 313 struct bpf_tramp_image *im; 314 315 im = container_of(rcu, struct bpf_tramp_image, rcu); 316 INIT_WORK(&im->work, __bpf_tramp_image_put_deferred); 317 schedule_work(&im->work); 318 } 319 320 /* callback, fexit step 2. Called after percpu_ref_kill confirms. */ 321 static void __bpf_tramp_image_release(struct percpu_ref *pcref) 322 { 323 struct bpf_tramp_image *im; 324 325 im = container_of(pcref, struct bpf_tramp_image, pcref); 326 call_rcu_tasks(&im->rcu, __bpf_tramp_image_put_rcu); 327 } 328 329 /* callback, fexit or fentry step 1 */ 330 static void __bpf_tramp_image_put_rcu_tasks(struct rcu_head *rcu) 331 { 332 struct bpf_tramp_image *im; 333 334 im = container_of(rcu, struct bpf_tramp_image, rcu); 335 if (im->ip_after_call) 336 /* the case of fmod_ret/fexit trampoline and CONFIG_PREEMPTION=y */ 337 percpu_ref_kill(&im->pcref); 338 else 339 /* the case of fentry trampoline */ 340 call_rcu_tasks(&im->rcu, __bpf_tramp_image_put_rcu); 341 } 342 343 static void bpf_tramp_image_put(struct bpf_tramp_image *im) 344 { 345 /* The trampoline image that calls original function is using: 346 * rcu_read_lock_trace to protect sleepable bpf progs 347 * rcu_read_lock to protect normal bpf progs 348 * percpu_ref to protect trampoline itself 349 * rcu tasks to protect trampoline asm not covered by percpu_ref 350 * (which are few asm insns before __bpf_tramp_enter and 351 * after __bpf_tramp_exit) 352 * 353 * The trampoline is unreachable before bpf_tramp_image_put(). 354 * 355 * First, patch the trampoline to avoid calling into fexit progs. 356 * The progs will be freed even if the original function is still 357 * executing or sleeping. 358 * In case of CONFIG_PREEMPT=y use call_rcu_tasks() to wait on 359 * first few asm instructions to execute and call into 360 * __bpf_tramp_enter->percpu_ref_get. 361 * Then use percpu_ref_kill to wait for the trampoline and the original 362 * function to finish. 363 * Then use call_rcu_tasks() to make sure few asm insns in 364 * the trampoline epilogue are done as well. 365 * 366 * In !PREEMPT case the task that got interrupted in the first asm 367 * insns won't go through an RCU quiescent state which the 368 * percpu_ref_kill will be waiting for. Hence the first 369 * call_rcu_tasks() is not necessary. 370 */ 371 if (im->ip_after_call) { 372 int err = bpf_arch_text_poke(im->ip_after_call, BPF_MOD_JUMP, 373 NULL, im->ip_epilogue); 374 WARN_ON(err); 375 if (IS_ENABLED(CONFIG_PREEMPTION)) 376 call_rcu_tasks(&im->rcu, __bpf_tramp_image_put_rcu_tasks); 377 else 378 percpu_ref_kill(&im->pcref); 379 return; 380 } 381 382 /* The trampoline without fexit and fmod_ret progs doesn't call original 383 * function and doesn't use percpu_ref. 384 * Use call_rcu_tasks_trace() to wait for sleepable progs to finish. 385 * Then use call_rcu_tasks() to wait for the rest of trampoline asm 386 * and normal progs. 387 */ 388 call_rcu_tasks_trace(&im->rcu, __bpf_tramp_image_put_rcu_tasks); 389 } 390 391 static struct bpf_tramp_image *bpf_tramp_image_alloc(u64 key, u32 idx) 392 { 393 struct bpf_tramp_image *im; 394 struct bpf_ksym *ksym; 395 void *image; 396 int err = -ENOMEM; 397 398 im = kzalloc(sizeof(*im), GFP_KERNEL); 399 if (!im) 400 goto out; 401 402 err = bpf_jit_charge_modmem(PAGE_SIZE); 403 if (err) 404 goto out_free_im; 405 406 err = -ENOMEM; 407 im->image = image = bpf_jit_alloc_exec_page(); 408 if (!image) 409 goto out_uncharge; 410 411 err = percpu_ref_init(&im->pcref, __bpf_tramp_image_release, 0, GFP_KERNEL); 412 if (err) 413 goto out_free_image; 414 415 ksym = &im->ksym; 416 INIT_LIST_HEAD_RCU(&ksym->lnode); 417 snprintf(ksym->name, KSYM_NAME_LEN, "bpf_trampoline_%llu_%u", key, idx); 418 bpf_image_ksym_add(image, ksym); 419 return im; 420 421 out_free_image: 422 bpf_jit_free_exec(im->image); 423 out_uncharge: 424 bpf_jit_uncharge_modmem(PAGE_SIZE); 425 out_free_im: 426 kfree(im); 427 out: 428 return ERR_PTR(err); 429 } 430 431 static int bpf_trampoline_update(struct bpf_trampoline *tr, bool lock_direct_mutex) 432 { 433 struct bpf_tramp_image *im; 434 struct bpf_tramp_links *tlinks; 435 u32 orig_flags = tr->flags; 436 bool ip_arg = false; 437 int err, total; 438 439 tlinks = bpf_trampoline_get_progs(tr, &total, &ip_arg); 440 if (IS_ERR(tlinks)) 441 return PTR_ERR(tlinks); 442 443 if (total == 0) { 444 err = unregister_fentry(tr, tr->cur_image->image); 445 bpf_tramp_image_put(tr->cur_image); 446 tr->cur_image = NULL; 447 tr->selector = 0; 448 goto out; 449 } 450 451 im = bpf_tramp_image_alloc(tr->key, tr->selector); 452 if (IS_ERR(im)) { 453 err = PTR_ERR(im); 454 goto out; 455 } 456 457 /* clear all bits except SHARE_IPMODIFY */ 458 tr->flags &= BPF_TRAMP_F_SHARE_IPMODIFY; 459 460 if (tlinks[BPF_TRAMP_FEXIT].nr_links || 461 tlinks[BPF_TRAMP_MODIFY_RETURN].nr_links) { 462 /* NOTE: BPF_TRAMP_F_RESTORE_REGS and BPF_TRAMP_F_SKIP_FRAME 463 * should not be set together. 464 */ 465 tr->flags |= BPF_TRAMP_F_CALL_ORIG | BPF_TRAMP_F_SKIP_FRAME; 466 } else { 467 tr->flags |= BPF_TRAMP_F_RESTORE_REGS; 468 } 469 470 if (ip_arg) 471 tr->flags |= BPF_TRAMP_F_IP_ARG; 472 473 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS 474 again: 475 if ((tr->flags & BPF_TRAMP_F_SHARE_IPMODIFY) && 476 (tr->flags & BPF_TRAMP_F_CALL_ORIG)) 477 tr->flags |= BPF_TRAMP_F_ORIG_STACK; 478 #endif 479 480 err = arch_prepare_bpf_trampoline(im, im->image, im->image + PAGE_SIZE, 481 &tr->func.model, tr->flags, tlinks, 482 tr->func.addr); 483 if (err < 0) 484 goto out; 485 486 WARN_ON(tr->cur_image && tr->selector == 0); 487 WARN_ON(!tr->cur_image && tr->selector); 488 if (tr->cur_image) 489 /* progs already running at this address */ 490 err = modify_fentry(tr, tr->cur_image->image, im->image, lock_direct_mutex); 491 else 492 /* first time registering */ 493 err = register_fentry(tr, im->image); 494 495 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS 496 if (err == -EAGAIN) { 497 /* -EAGAIN from bpf_tramp_ftrace_ops_func. Now 498 * BPF_TRAMP_F_SHARE_IPMODIFY is set, we can generate the 499 * trampoline again, and retry register. 500 */ 501 /* reset fops->func and fops->trampoline for re-register */ 502 tr->fops->func = NULL; 503 tr->fops->trampoline = 0; 504 goto again; 505 } 506 #endif 507 if (err) 508 goto out; 509 510 if (tr->cur_image) 511 bpf_tramp_image_put(tr->cur_image); 512 tr->cur_image = im; 513 tr->selector++; 514 out: 515 /* If any error happens, restore previous flags */ 516 if (err) 517 tr->flags = orig_flags; 518 kfree(tlinks); 519 return err; 520 } 521 522 static enum bpf_tramp_prog_type bpf_attach_type_to_tramp(struct bpf_prog *prog) 523 { 524 switch (prog->expected_attach_type) { 525 case BPF_TRACE_FENTRY: 526 return BPF_TRAMP_FENTRY; 527 case BPF_MODIFY_RETURN: 528 return BPF_TRAMP_MODIFY_RETURN; 529 case BPF_TRACE_FEXIT: 530 return BPF_TRAMP_FEXIT; 531 case BPF_LSM_MAC: 532 if (!prog->aux->attach_func_proto->type) 533 /* The function returns void, we cannot modify its 534 * return value. 535 */ 536 return BPF_TRAMP_FEXIT; 537 else 538 return BPF_TRAMP_MODIFY_RETURN; 539 default: 540 return BPF_TRAMP_REPLACE; 541 } 542 } 543 544 static int __bpf_trampoline_link_prog(struct bpf_tramp_link *link, struct bpf_trampoline *tr) 545 { 546 enum bpf_tramp_prog_type kind; 547 struct bpf_tramp_link *link_exiting; 548 int err = 0; 549 int cnt = 0, i; 550 551 kind = bpf_attach_type_to_tramp(link->link.prog); 552 if (tr->extension_prog) 553 /* cannot attach fentry/fexit if extension prog is attached. 554 * cannot overwrite extension prog either. 555 */ 556 return -EBUSY; 557 558 for (i = 0; i < BPF_TRAMP_MAX; i++) 559 cnt += tr->progs_cnt[i]; 560 561 if (kind == BPF_TRAMP_REPLACE) { 562 /* Cannot attach extension if fentry/fexit are in use. */ 563 if (cnt) 564 return -EBUSY; 565 tr->extension_prog = link->link.prog; 566 return bpf_arch_text_poke(tr->func.addr, BPF_MOD_JUMP, NULL, 567 link->link.prog->bpf_func); 568 } 569 if (cnt >= BPF_MAX_TRAMP_LINKS) 570 return -E2BIG; 571 if (!hlist_unhashed(&link->tramp_hlist)) 572 /* prog already linked */ 573 return -EBUSY; 574 hlist_for_each_entry(link_exiting, &tr->progs_hlist[kind], tramp_hlist) { 575 if (link_exiting->link.prog != link->link.prog) 576 continue; 577 /* prog already linked */ 578 return -EBUSY; 579 } 580 581 hlist_add_head(&link->tramp_hlist, &tr->progs_hlist[kind]); 582 tr->progs_cnt[kind]++; 583 err = bpf_trampoline_update(tr, true /* lock_direct_mutex */); 584 if (err) { 585 hlist_del_init(&link->tramp_hlist); 586 tr->progs_cnt[kind]--; 587 } 588 return err; 589 } 590 591 int bpf_trampoline_link_prog(struct bpf_tramp_link *link, struct bpf_trampoline *tr) 592 { 593 int err; 594 595 mutex_lock(&tr->mutex); 596 err = __bpf_trampoline_link_prog(link, tr); 597 mutex_unlock(&tr->mutex); 598 return err; 599 } 600 601 static int __bpf_trampoline_unlink_prog(struct bpf_tramp_link *link, struct bpf_trampoline *tr) 602 { 603 enum bpf_tramp_prog_type kind; 604 int err; 605 606 kind = bpf_attach_type_to_tramp(link->link.prog); 607 if (kind == BPF_TRAMP_REPLACE) { 608 WARN_ON_ONCE(!tr->extension_prog); 609 err = bpf_arch_text_poke(tr->func.addr, BPF_MOD_JUMP, 610 tr->extension_prog->bpf_func, NULL); 611 tr->extension_prog = NULL; 612 return err; 613 } 614 hlist_del_init(&link->tramp_hlist); 615 tr->progs_cnt[kind]--; 616 return bpf_trampoline_update(tr, true /* lock_direct_mutex */); 617 } 618 619 /* bpf_trampoline_unlink_prog() should never fail. */ 620 int bpf_trampoline_unlink_prog(struct bpf_tramp_link *link, struct bpf_trampoline *tr) 621 { 622 int err; 623 624 mutex_lock(&tr->mutex); 625 err = __bpf_trampoline_unlink_prog(link, tr); 626 mutex_unlock(&tr->mutex); 627 return err; 628 } 629 630 #if defined(CONFIG_CGROUP_BPF) && defined(CONFIG_BPF_LSM) 631 static void bpf_shim_tramp_link_release(struct bpf_link *link) 632 { 633 struct bpf_shim_tramp_link *shim_link = 634 container_of(link, struct bpf_shim_tramp_link, link.link); 635 636 /* paired with 'shim_link->trampoline = tr' in bpf_trampoline_link_cgroup_shim */ 637 if (!shim_link->trampoline) 638 return; 639 640 WARN_ON_ONCE(bpf_trampoline_unlink_prog(&shim_link->link, shim_link->trampoline)); 641 bpf_trampoline_put(shim_link->trampoline); 642 } 643 644 static void bpf_shim_tramp_link_dealloc(struct bpf_link *link) 645 { 646 struct bpf_shim_tramp_link *shim_link = 647 container_of(link, struct bpf_shim_tramp_link, link.link); 648 649 kfree(shim_link); 650 } 651 652 static const struct bpf_link_ops bpf_shim_tramp_link_lops = { 653 .release = bpf_shim_tramp_link_release, 654 .dealloc = bpf_shim_tramp_link_dealloc, 655 }; 656 657 static struct bpf_shim_tramp_link *cgroup_shim_alloc(const struct bpf_prog *prog, 658 bpf_func_t bpf_func, 659 int cgroup_atype) 660 { 661 struct bpf_shim_tramp_link *shim_link = NULL; 662 struct bpf_prog *p; 663 664 shim_link = kzalloc(sizeof(*shim_link), GFP_USER); 665 if (!shim_link) 666 return NULL; 667 668 p = bpf_prog_alloc(1, 0); 669 if (!p) { 670 kfree(shim_link); 671 return NULL; 672 } 673 674 p->jited = false; 675 p->bpf_func = bpf_func; 676 677 p->aux->cgroup_atype = cgroup_atype; 678 p->aux->attach_func_proto = prog->aux->attach_func_proto; 679 p->aux->attach_btf_id = prog->aux->attach_btf_id; 680 p->aux->attach_btf = prog->aux->attach_btf; 681 btf_get(p->aux->attach_btf); 682 p->type = BPF_PROG_TYPE_LSM; 683 p->expected_attach_type = BPF_LSM_MAC; 684 bpf_prog_inc(p); 685 bpf_link_init(&shim_link->link.link, BPF_LINK_TYPE_UNSPEC, 686 &bpf_shim_tramp_link_lops, p); 687 bpf_cgroup_atype_get(p->aux->attach_btf_id, cgroup_atype); 688 689 return shim_link; 690 } 691 692 static struct bpf_shim_tramp_link *cgroup_shim_find(struct bpf_trampoline *tr, 693 bpf_func_t bpf_func) 694 { 695 struct bpf_tramp_link *link; 696 int kind; 697 698 for (kind = 0; kind < BPF_TRAMP_MAX; kind++) { 699 hlist_for_each_entry(link, &tr->progs_hlist[kind], tramp_hlist) { 700 struct bpf_prog *p = link->link.prog; 701 702 if (p->bpf_func == bpf_func) 703 return container_of(link, struct bpf_shim_tramp_link, link); 704 } 705 } 706 707 return NULL; 708 } 709 710 int bpf_trampoline_link_cgroup_shim(struct bpf_prog *prog, 711 int cgroup_atype) 712 { 713 struct bpf_shim_tramp_link *shim_link = NULL; 714 struct bpf_attach_target_info tgt_info = {}; 715 struct bpf_trampoline *tr; 716 bpf_func_t bpf_func; 717 u64 key; 718 int err; 719 720 err = bpf_check_attach_target(NULL, prog, NULL, 721 prog->aux->attach_btf_id, 722 &tgt_info); 723 if (err) 724 return err; 725 726 key = bpf_trampoline_compute_key(NULL, prog->aux->attach_btf, 727 prog->aux->attach_btf_id); 728 729 bpf_lsm_find_cgroup_shim(prog, &bpf_func); 730 tr = bpf_trampoline_get(key, &tgt_info); 731 if (!tr) 732 return -ENOMEM; 733 734 mutex_lock(&tr->mutex); 735 736 shim_link = cgroup_shim_find(tr, bpf_func); 737 if (shim_link) { 738 /* Reusing existing shim attached by the other program. */ 739 bpf_link_inc(&shim_link->link.link); 740 741 mutex_unlock(&tr->mutex); 742 bpf_trampoline_put(tr); /* bpf_trampoline_get above */ 743 return 0; 744 } 745 746 /* Allocate and install new shim. */ 747 748 shim_link = cgroup_shim_alloc(prog, bpf_func, cgroup_atype); 749 if (!shim_link) { 750 err = -ENOMEM; 751 goto err; 752 } 753 754 err = __bpf_trampoline_link_prog(&shim_link->link, tr); 755 if (err) 756 goto err; 757 758 shim_link->trampoline = tr; 759 /* note, we're still holding tr refcnt from above */ 760 761 mutex_unlock(&tr->mutex); 762 763 return 0; 764 err: 765 mutex_unlock(&tr->mutex); 766 767 if (shim_link) 768 bpf_link_put(&shim_link->link.link); 769 770 /* have to release tr while _not_ holding its mutex */ 771 bpf_trampoline_put(tr); /* bpf_trampoline_get above */ 772 773 return err; 774 } 775 776 void bpf_trampoline_unlink_cgroup_shim(struct bpf_prog *prog) 777 { 778 struct bpf_shim_tramp_link *shim_link = NULL; 779 struct bpf_trampoline *tr; 780 bpf_func_t bpf_func; 781 u64 key; 782 783 key = bpf_trampoline_compute_key(NULL, prog->aux->attach_btf, 784 prog->aux->attach_btf_id); 785 786 bpf_lsm_find_cgroup_shim(prog, &bpf_func); 787 tr = bpf_trampoline_lookup(key); 788 if (WARN_ON_ONCE(!tr)) 789 return; 790 791 mutex_lock(&tr->mutex); 792 shim_link = cgroup_shim_find(tr, bpf_func); 793 mutex_unlock(&tr->mutex); 794 795 if (shim_link) 796 bpf_link_put(&shim_link->link.link); 797 798 bpf_trampoline_put(tr); /* bpf_trampoline_lookup above */ 799 } 800 #endif 801 802 struct bpf_trampoline *bpf_trampoline_get(u64 key, 803 struct bpf_attach_target_info *tgt_info) 804 { 805 struct bpf_trampoline *tr; 806 807 tr = bpf_trampoline_lookup(key); 808 if (!tr) 809 return NULL; 810 811 mutex_lock(&tr->mutex); 812 if (tr->func.addr) 813 goto out; 814 815 memcpy(&tr->func.model, &tgt_info->fmodel, sizeof(tgt_info->fmodel)); 816 tr->func.addr = (void *)tgt_info->tgt_addr; 817 out: 818 mutex_unlock(&tr->mutex); 819 return tr; 820 } 821 822 void bpf_trampoline_put(struct bpf_trampoline *tr) 823 { 824 int i; 825 826 if (!tr) 827 return; 828 mutex_lock(&trampoline_mutex); 829 if (!refcount_dec_and_test(&tr->refcnt)) 830 goto out; 831 WARN_ON_ONCE(mutex_is_locked(&tr->mutex)); 832 833 for (i = 0; i < BPF_TRAMP_MAX; i++) 834 if (WARN_ON_ONCE(!hlist_empty(&tr->progs_hlist[i]))) 835 goto out; 836 837 /* This code will be executed even when the last bpf_tramp_image 838 * is alive. All progs are detached from the trampoline and the 839 * trampoline image is patched with jmp into epilogue to skip 840 * fexit progs. The fentry-only trampoline will be freed via 841 * multiple rcu callbacks. 842 */ 843 hlist_del(&tr->hlist); 844 if (tr->fops) { 845 ftrace_free_filter(tr->fops); 846 kfree(tr->fops); 847 } 848 kfree(tr); 849 out: 850 mutex_unlock(&trampoline_mutex); 851 } 852 853 #define NO_START_TIME 1 854 static __always_inline u64 notrace bpf_prog_start_time(void) 855 { 856 u64 start = NO_START_TIME; 857 858 if (static_branch_unlikely(&bpf_stats_enabled_key)) { 859 start = sched_clock(); 860 if (unlikely(!start)) 861 start = NO_START_TIME; 862 } 863 return start; 864 } 865 866 static void notrace inc_misses_counter(struct bpf_prog *prog) 867 { 868 struct bpf_prog_stats *stats; 869 unsigned int flags; 870 871 stats = this_cpu_ptr(prog->stats); 872 flags = u64_stats_update_begin_irqsave(&stats->syncp); 873 u64_stats_inc(&stats->misses); 874 u64_stats_update_end_irqrestore(&stats->syncp, flags); 875 } 876 877 /* The logic is similar to bpf_prog_run(), but with an explicit 878 * rcu_read_lock() and migrate_disable() which are required 879 * for the trampoline. The macro is split into 880 * call __bpf_prog_enter 881 * call prog->bpf_func 882 * call __bpf_prog_exit 883 * 884 * __bpf_prog_enter returns: 885 * 0 - skip execution of the bpf prog 886 * 1 - execute bpf prog 887 * [2..MAX_U64] - execute bpf prog and record execution time. 888 * This is start time. 889 */ 890 u64 notrace __bpf_prog_enter(struct bpf_prog *prog, struct bpf_tramp_run_ctx *run_ctx) 891 __acquires(RCU) 892 { 893 rcu_read_lock(); 894 migrate_disable(); 895 896 run_ctx->saved_run_ctx = bpf_set_run_ctx(&run_ctx->run_ctx); 897 898 if (unlikely(__this_cpu_inc_return(*(prog->active)) != 1)) { 899 inc_misses_counter(prog); 900 return 0; 901 } 902 return bpf_prog_start_time(); 903 } 904 905 static void notrace update_prog_stats(struct bpf_prog *prog, 906 u64 start) 907 { 908 struct bpf_prog_stats *stats; 909 910 if (static_branch_unlikely(&bpf_stats_enabled_key) && 911 /* static_key could be enabled in __bpf_prog_enter* 912 * and disabled in __bpf_prog_exit*. 913 * And vice versa. 914 * Hence check that 'start' is valid. 915 */ 916 start > NO_START_TIME) { 917 unsigned long flags; 918 919 stats = this_cpu_ptr(prog->stats); 920 flags = u64_stats_update_begin_irqsave(&stats->syncp); 921 u64_stats_inc(&stats->cnt); 922 u64_stats_add(&stats->nsecs, sched_clock() - start); 923 u64_stats_update_end_irqrestore(&stats->syncp, flags); 924 } 925 } 926 927 void notrace __bpf_prog_exit(struct bpf_prog *prog, u64 start, struct bpf_tramp_run_ctx *run_ctx) 928 __releases(RCU) 929 { 930 bpf_reset_run_ctx(run_ctx->saved_run_ctx); 931 932 update_prog_stats(prog, start); 933 __this_cpu_dec(*(prog->active)); 934 migrate_enable(); 935 rcu_read_unlock(); 936 } 937 938 u64 notrace __bpf_prog_enter_lsm_cgroup(struct bpf_prog *prog, 939 struct bpf_tramp_run_ctx *run_ctx) 940 __acquires(RCU) 941 { 942 /* Runtime stats are exported via actual BPF_LSM_CGROUP 943 * programs, not the shims. 944 */ 945 rcu_read_lock(); 946 migrate_disable(); 947 948 run_ctx->saved_run_ctx = bpf_set_run_ctx(&run_ctx->run_ctx); 949 950 return NO_START_TIME; 951 } 952 953 void notrace __bpf_prog_exit_lsm_cgroup(struct bpf_prog *prog, u64 start, 954 struct bpf_tramp_run_ctx *run_ctx) 955 __releases(RCU) 956 { 957 bpf_reset_run_ctx(run_ctx->saved_run_ctx); 958 959 migrate_enable(); 960 rcu_read_unlock(); 961 } 962 963 u64 notrace __bpf_prog_enter_sleepable(struct bpf_prog *prog, struct bpf_tramp_run_ctx *run_ctx) 964 { 965 rcu_read_lock_trace(); 966 migrate_disable(); 967 might_fault(); 968 969 if (unlikely(__this_cpu_inc_return(*(prog->active)) != 1)) { 970 inc_misses_counter(prog); 971 return 0; 972 } 973 974 run_ctx->saved_run_ctx = bpf_set_run_ctx(&run_ctx->run_ctx); 975 976 return bpf_prog_start_time(); 977 } 978 979 void notrace __bpf_prog_exit_sleepable(struct bpf_prog *prog, u64 start, 980 struct bpf_tramp_run_ctx *run_ctx) 981 { 982 bpf_reset_run_ctx(run_ctx->saved_run_ctx); 983 984 update_prog_stats(prog, start); 985 __this_cpu_dec(*(prog->active)); 986 migrate_enable(); 987 rcu_read_unlock_trace(); 988 } 989 990 void notrace __bpf_tramp_enter(struct bpf_tramp_image *tr) 991 { 992 percpu_ref_get(&tr->pcref); 993 } 994 995 void notrace __bpf_tramp_exit(struct bpf_tramp_image *tr) 996 { 997 percpu_ref_put(&tr->pcref); 998 } 999 1000 int __weak 1001 arch_prepare_bpf_trampoline(struct bpf_tramp_image *tr, void *image, void *image_end, 1002 const struct btf_func_model *m, u32 flags, 1003 struct bpf_tramp_links *tlinks, 1004 void *orig_call) 1005 { 1006 return -ENOTSUPP; 1007 } 1008 1009 static int __init init_trampolines(void) 1010 { 1011 int i; 1012 1013 for (i = 0; i < TRAMPOLINE_TABLE_SIZE; i++) 1014 INIT_HLIST_HEAD(&trampoline_table[i]); 1015 return 0; 1016 } 1017 late_initcall(init_trampolines); 1018