kernel/bpf/trampoline.c

   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/static_call.h>
  13 #include <linux/bpf_verifier.h>
  14 #include <linux/bpf_lsm.h>
  15 #include <linux/delay.h>
  16
  17 /* dummy _ops. The verifier will operate on target program's ops. */
  18 const struct bpf_verifier_ops bpf_extension_verifier_ops = {
  19 };
  20 const struct bpf_prog_ops bpf_extension_prog_ops = {
  21 };
  22
  23 /* btf_vmlinux has ~22k attachable functions. 1k htab is enough. */
  24 #define TRAMPOLINE_HASH_BITS 10
  25 #define TRAMPOLINE_TABLE_SIZE (1 << TRAMPOLINE_HASH_BITS)
  26
  27 static struct hlist_head trampoline_table[TRAMPOLINE_TABLE_SIZE];
  28
  29 /* serializes access to trampoline_table */
  30 static DEFINE_MUTEX(trampoline_mutex);
  31
  32 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
  33 static int bpf_trampoline_update(struct bpf_trampoline *tr, bool lock_direct_mutex);
  34
  35 static int bpf_tramp_ftrace_ops_func(struct ftrace_ops *ops, enum ftrace_ops_cmd cmd)
  36 {
  37         struct bpf_trampoline *tr = ops->private;
  38         int ret = 0;
  39
  40         if (cmd == FTRACE_OPS_CMD_ENABLE_SHARE_IPMODIFY_SELF) {
  41                 /* This is called inside register_ftrace_direct_multi(), so
  42                  * tr->mutex is already locked.
  43                  */
  44                 lockdep_assert_held_once(&tr->mutex);
  45
  46                 /* Instead of updating the trampoline here, we propagate
  47                  * -EAGAIN to register_ftrace_direct(). Then we can
  48                  * retry register_ftrace_direct() after updating the
  49                  * trampoline.
  50                  */
  51                 if ((tr->flags & BPF_TRAMP_F_CALL_ORIG) &&
  52                     !(tr->flags & BPF_TRAMP_F_ORIG_STACK)) {
  53                         if (WARN_ON_ONCE(tr->flags & BPF_TRAMP_F_SHARE_IPMODIFY))
  54                                 return -EBUSY;
  55
  56                         tr->flags |= BPF_TRAMP_F_SHARE_IPMODIFY;
  57                         return -EAGAIN;
  58                 }
  59
  60                 return 0;
  61         }
  62
  63         /* The normal locking order is
  64          *    tr->mutex => direct_mutex (ftrace.c) => ftrace_lock (ftrace.c)
  65          *
  66          * The following two commands are called from
  67          *
  68          *   prepare_direct_functions_for_ipmodify
  69          *   cleanup_direct_functions_after_ipmodify
  70          *
  71          * In both cases, direct_mutex is already locked. Use
  72          * mutex_trylock(&tr->mutex) to avoid deadlock in race condition
  73          * (something else is making changes to this same trampoline).
  74          */
  75         if (!mutex_trylock(&tr->mutex)) {
  76                 /* sleep 1 ms to make sure whatever holding tr->mutex makes
  77                  * some progress.
  78                  */
  79                 msleep(1);
  80                 return -EAGAIN;
  81         }
  82
  83         switch (cmd) {
  84         case FTRACE_OPS_CMD_ENABLE_SHARE_IPMODIFY_PEER:
  85                 tr->flags |= BPF_TRAMP_F_SHARE_IPMODIFY;
  86
  87                 if ((tr->flags & BPF_TRAMP_F_CALL_ORIG) &&
  88                     !(tr->flags & BPF_TRAMP_F_ORIG_STACK))
  89                         ret = bpf_trampoline_update(tr, false /* lock_direct_mutex */);
  90                 break;
  91         case FTRACE_OPS_CMD_DISABLE_SHARE_IPMODIFY_PEER:
  92                 tr->flags &= ~BPF_TRAMP_F_SHARE_IPMODIFY;
  93
  94                 if (tr->flags & BPF_TRAMP_F_ORIG_STACK)
  95                         ret = bpf_trampoline_update(tr, false /* lock_direct_mutex */);
  96                 break;
  97         default:
  98                 ret = -EINVAL;
  99                 break;
 100         }
 101
 102         mutex_unlock(&tr->mutex);
 103         return ret;
 104 }
 105 #endif
 106
 107 bool bpf_prog_has_trampoline(const struct bpf_prog *prog)
 108 {
 109         enum bpf_attach_type eatype = prog->expected_attach_type;
 110         enum bpf_prog_type ptype = prog->type;
 111
 112         return (ptype == BPF_PROG_TYPE_TRACING &&
 113                 (eatype == BPF_TRACE_FENTRY || eatype == BPF_TRACE_FEXIT ||
 114                  eatype == BPF_MODIFY_RETURN)) ||
 115                 (ptype == BPF_PROG_TYPE_LSM && eatype == BPF_LSM_MAC);
 116 }
 117
 118 void bpf_image_ksym_add(void *data, unsigned int size, struct bpf_ksym *ksym)
 119 {
 120         ksym->start = (unsigned long) data;
 121         ksym->end = ksym->start + size;
 122         bpf_ksym_add(ksym);
 123         perf_event_ksymbol(PERF_RECORD_KSYMBOL_TYPE_BPF, ksym->start,
 124                            PAGE_SIZE, false, ksym->name);
 125 }
 126
 127 void bpf_image_ksym_del(struct bpf_ksym *ksym)
 128 {
 129         bpf_ksym_del(ksym);
 130         perf_event_ksymbol(PERF_RECORD_KSYMBOL_TYPE_BPF, ksym->start,
 131                            PAGE_SIZE, true, ksym->name);
 132 }
 133
 134 static struct bpf_trampoline *bpf_trampoline_lookup(u64 key)
 135 {
 136         struct bpf_trampoline *tr;
 137         struct hlist_head *head;
 138         int i;
 139
 140         mutex_lock(&trampoline_mutex);
 141         head = &trampoline_table[hash_64(key, TRAMPOLINE_HASH_BITS)];
 142         hlist_for_each_entry(tr, head, hlist) {
 143                 if (tr->key == key) {
 144                         refcount_inc(&tr->refcnt);
 145                         goto out;
 146                 }
 147         }
 148         tr = kzalloc(sizeof(*tr), GFP_KERNEL);
 149         if (!tr)
 150                 goto out;
 151 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
 152         tr->fops = kzalloc(sizeof(struct ftrace_ops), GFP_KERNEL);
 153         if (!tr->fops) {
 154                 kfree(tr);
 155                 tr = NULL;
 156                 goto out;
 157         }
 158         tr->fops->private = tr;
 159         tr->fops->ops_func = bpf_tramp_ftrace_ops_func;
 160 #endif
 161
 162         tr->key = key;
 163         INIT_HLIST_NODE(&tr->hlist);
 164         hlist_add_head(&tr->hlist, head);
 165         refcount_set(&tr->refcnt, 1);
 166         mutex_init(&tr->mutex);
 167         for (i = 0; i < BPF_TRAMP_MAX; i++)
 168                 INIT_HLIST_HEAD(&tr->progs_hlist[i]);
 169 out:
 170         mutex_unlock(&trampoline_mutex);
 171         return tr;
 172 }
 173
 174 static int unregister_fentry(struct bpf_trampoline *tr, void *old_addr)
 175 {
 176         void *ip = tr->func.addr;
 177         int ret;
 178
 179         if (tr->func.ftrace_managed)
 180                 ret = unregister_ftrace_direct(tr->fops, (long)old_addr, false);
 181         else
 182                 ret = bpf_arch_text_poke(ip, BPF_MOD_CALL, old_addr, NULL);
 183
 184         return ret;
 185 }
 186
 187 static int modify_fentry(struct bpf_trampoline *tr, void *old_addr, void *new_addr,
 188                          bool lock_direct_mutex)
 189 {
 190         void *ip = tr->func.addr;
 191         int ret;
 192
 193         if (tr->func.ftrace_managed) {
 194                 if (lock_direct_mutex)
 195                         ret = modify_ftrace_direct(tr->fops, (long)new_addr);
 196                 else
 197                         ret = modify_ftrace_direct_nolock(tr->fops, (long)new_addr);
 198         } else {
 199                 ret = bpf_arch_text_poke(ip, BPF_MOD_CALL, old_addr, new_addr);
 200         }
 201         return ret;
 202 }
 203
 204 /* first time registering */
 205 static int register_fentry(struct bpf_trampoline *tr, void *new_addr)
 206 {
 207         void *ip = tr->func.addr;
 208         unsigned long faddr;
 209         int ret;
 210
 211         faddr = ftrace_location((unsigned long)ip);
 212         if (faddr) {
 213                 if (!tr->fops)
 214                         return -ENOTSUPP;
 215                 tr->func.ftrace_managed = true;
 216         }
 217
 218         if (tr->func.ftrace_managed) {
 219                 ftrace_set_filter_ip(tr->fops, (unsigned long)ip, 0, 1);
 220                 ret = register_ftrace_direct(tr->fops, (long)new_addr);
 221         } else {
 222                 ret = bpf_arch_text_poke(ip, BPF_MOD_CALL, NULL, new_addr);
 223         }
 224
 225         return ret;
 226 }
 227
 228 static struct bpf_tramp_links *
 229 bpf_trampoline_get_progs(const struct bpf_trampoline *tr, int *total, bool *ip_arg)
 230 {
 231         struct bpf_tramp_link *link;
 232         struct bpf_tramp_links *tlinks;
 233         struct bpf_tramp_link **links;
 234         int kind;
 235
 236         *total = 0;
 237         tlinks = kcalloc(BPF_TRAMP_MAX, sizeof(*tlinks), GFP_KERNEL);
 238         if (!tlinks)
 239                 return ERR_PTR(-ENOMEM);
 240
 241         for (kind = 0; kind < BPF_TRAMP_MAX; kind++) {
 242                 tlinks[kind].nr_links = tr->progs_cnt[kind];
 243                 *total += tr->progs_cnt[kind];
 244                 links = tlinks[kind].links;
 245
 246                 hlist_for_each_entry(link, &tr->progs_hlist[kind], tramp_hlist) {
 247                         *ip_arg |= link->link.prog->call_get_func_ip;
 248                         *links++ = link;
 249                 }
 250         }
 251         return tlinks;
 252 }
 253
 254 static void bpf_tramp_image_free(struct bpf_tramp_image *im)
 255 {
 256         bpf_image_ksym_del(&im->ksym);
 257         arch_free_bpf_trampoline(im->image, im->size);
 258         bpf_jit_uncharge_modmem(im->size);
 259         percpu_ref_exit(&im->pcref);
 260         kfree_rcu(im, rcu);
 261 }
 262
 263 static void __bpf_tramp_image_put_deferred(struct work_struct *work)
 264 {
 265         struct bpf_tramp_image *im;
 266
 267         im = container_of(work, struct bpf_tramp_image, work);
 268         bpf_tramp_image_free(im);
 269 }
 270
 271 /* callback, fexit step 3 or fentry step 2 */
 272 static void __bpf_tramp_image_put_rcu(struct rcu_head *rcu)
 273 {
 274         struct bpf_tramp_image *im;
 275
 276         im = container_of(rcu, struct bpf_tramp_image, rcu);
 277         INIT_WORK(&im->work, __bpf_tramp_image_put_deferred);
 278         schedule_work(&im->work);
 279 }
 280
 281 /* callback, fexit step 2. Called after percpu_ref_kill confirms. */
 282 static void __bpf_tramp_image_release(struct percpu_ref *pcref)
 283 {
 284         struct bpf_tramp_image *im;
 285
 286         im = container_of(pcref, struct bpf_tramp_image, pcref);
 287         call_rcu_tasks(&im->rcu, __bpf_tramp_image_put_rcu);
 288 }
 289
 290 /* callback, fexit or fentry step 1 */
 291 static void __bpf_tramp_image_put_rcu_tasks(struct rcu_head *rcu)
 292 {
 293         struct bpf_tramp_image *im;
 294
 295         im = container_of(rcu, struct bpf_tramp_image, rcu);
 296         if (im->ip_after_call)
 297                 /* the case of fmod_ret/fexit trampoline and CONFIG_PREEMPTION=y */
 298                 percpu_ref_kill(&im->pcref);
 299         else
 300                 /* the case of fentry trampoline */
 301                 call_rcu_tasks(&im->rcu, __bpf_tramp_image_put_rcu);
 302 }
 303
 304 static void bpf_tramp_image_put(struct bpf_tramp_image *im)
 305 {
 306         /* The trampoline image that calls original function is using:
 307          * rcu_read_lock_trace to protect sleepable bpf progs
 308          * rcu_read_lock to protect normal bpf progs
 309          * percpu_ref to protect trampoline itself
 310          * rcu tasks to protect trampoline asm not covered by percpu_ref
 311          * (which are few asm insns before __bpf_tramp_enter and
 312          *  after __bpf_tramp_exit)
 313          *
 314          * The trampoline is unreachable before bpf_tramp_image_put().
 315          *
 316          * First, patch the trampoline to avoid calling into fexit progs.
 317          * The progs will be freed even if the original function is still
 318          * executing or sleeping.
 319          * In case of CONFIG_PREEMPT=y use call_rcu_tasks() to wait on
 320          * first few asm instructions to execute and call into
 321          * __bpf_tramp_enter->percpu_ref_get.
 322          * Then use percpu_ref_kill to wait for the trampoline and the original
 323          * function to finish.
 324          * Then use call_rcu_tasks() to make sure few asm insns in
 325          * the trampoline epilogue are done as well.
 326          *
 327          * In !PREEMPT case the task that got interrupted in the first asm
 328          * insns won't go through an RCU quiescent state which the
 329          * percpu_ref_kill will be waiting for. Hence the first
 330          * call_rcu_tasks() is not necessary.
 331          */
 332         if (im->ip_after_call) {
 333                 int err = bpf_arch_text_poke(im->ip_after_call, BPF_MOD_JUMP,
 334                                              NULL, im->ip_epilogue);
 335                 WARN_ON(err);
 336                 if (IS_ENABLED(CONFIG_PREEMPTION))
 337                         call_rcu_tasks(&im->rcu, __bpf_tramp_image_put_rcu_tasks);
 338                 else
 339                         percpu_ref_kill(&im->pcref);
 340                 return;
 341         }
 342
 343         /* The trampoline without fexit and fmod_ret progs doesn't call original
 344          * function and doesn't use percpu_ref.
 345          * Use call_rcu_tasks_trace() to wait for sleepable progs to finish.
 346          * Then use call_rcu_tasks() to wait for the rest of trampoline asm
 347          * and normal progs.
 348          */
 349         call_rcu_tasks_trace(&im->rcu, __bpf_tramp_image_put_rcu_tasks);
 350 }
 351
 352 static struct bpf_tramp_image *bpf_tramp_image_alloc(u64 key, int size)
 353 {
 354         struct bpf_tramp_image *im;
 355         struct bpf_ksym *ksym;
 356         void *image;
 357         int err = -ENOMEM;
 358
 359         im = kzalloc(sizeof(*im), GFP_KERNEL);
 360         if (!im)
 361                 goto out;
 362
 363         err = bpf_jit_charge_modmem(size);
 364         if (err)
 365                 goto out_free_im;
 366         im->size = size;
 367
 368         err = -ENOMEM;
 369         im->image = image = arch_alloc_bpf_trampoline(size);
 370         if (!image)
 371                 goto out_uncharge;
 372
 373         err = percpu_ref_init(&im->pcref, __bpf_tramp_image_release, 0, GFP_KERNEL);
 374         if (err)
 375                 goto out_free_image;
 376
 377         ksym = &im->ksym;
 378         INIT_LIST_HEAD_RCU(&ksym->lnode);
 379         snprintf(ksym->name, KSYM_NAME_LEN, "bpf_trampoline_%llu", key);
 380         bpf_image_ksym_add(image, size, ksym);
 381         return im;
 382
 383 out_free_image:
 384         arch_free_bpf_trampoline(im->image, im->size);
 385 out_uncharge:
 386         bpf_jit_uncharge_modmem(size);
 387 out_free_im:
 388         kfree(im);
 389 out:
 390         return ERR_PTR(err);
 391 }
 392
 393 static int bpf_trampoline_update(struct bpf_trampoline *tr, bool lock_direct_mutex)
 394 {
 395         struct bpf_tramp_image *im;
 396         struct bpf_tramp_links *tlinks;
 397         u32 orig_flags = tr->flags;
 398         bool ip_arg = false;
 399         int err, total, size;
 400
 401         tlinks = bpf_trampoline_get_progs(tr, &total, &ip_arg);
 402         if (IS_ERR(tlinks))
 403                 return PTR_ERR(tlinks);
 404
 405         if (total == 0) {
 406                 err = unregister_fentry(tr, tr->cur_image->image);
 407                 bpf_tramp_image_put(tr->cur_image);
 408                 tr->cur_image = NULL;
 409                 goto out;
 410         }
 411
 412         /* clear all bits except SHARE_IPMODIFY and TAIL_CALL_CTX */
 413         tr->flags &= (BPF_TRAMP_F_SHARE_IPMODIFY | BPF_TRAMP_F_TAIL_CALL_CTX);
 414
 415         if (tlinks[BPF_TRAMP_FEXIT].nr_links ||
 416             tlinks[BPF_TRAMP_MODIFY_RETURN].nr_links) {
 417                 /* NOTE: BPF_TRAMP_F_RESTORE_REGS and BPF_TRAMP_F_SKIP_FRAME
 418                  * should not be set together.
 419                  */
 420                 tr->flags |= BPF_TRAMP_F_CALL_ORIG | BPF_TRAMP_F_SKIP_FRAME;
 421         } else {
 422                 tr->flags |= BPF_TRAMP_F_RESTORE_REGS;
 423         }
 424
 425         if (ip_arg)
 426                 tr->flags |= BPF_TRAMP_F_IP_ARG;
 427
 428 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
 429 again:
 430         if ((tr->flags & BPF_TRAMP_F_SHARE_IPMODIFY) &&
 431             (tr->flags & BPF_TRAMP_F_CALL_ORIG))
 432                 tr->flags |= BPF_TRAMP_F_ORIG_STACK;
 433 #endif
 434
 435         size = arch_bpf_trampoline_size(&tr->func.model, tr->flags,
 436                                         tlinks, tr->func.addr);
 437         if (size < 0) {
 438                 err = size;
 439                 goto out;
 440         }
 441
 442         if (size > PAGE_SIZE) {
 443                 err = -E2BIG;
 444                 goto out;
 445         }
 446
 447         im = bpf_tramp_image_alloc(tr->key, size);
 448         if (IS_ERR(im)) {
 449                 err = PTR_ERR(im);
 450                 goto out;
 451         }
 452
 453         err = arch_prepare_bpf_trampoline(im, im->image, im->image + size,
 454                                           &tr->func.model, tr->flags, tlinks,
 455                                           tr->func.addr);
 456         if (err < 0)
 457                 goto out_free;
 458
 459         arch_protect_bpf_trampoline(im->image, im->size);
 460
 461         WARN_ON(tr->cur_image && total == 0);
 462         if (tr->cur_image)
 463                 /* progs already running at this address */
 464                 err = modify_fentry(tr, tr->cur_image->image, im->image, lock_direct_mutex);
 465         else
 466                 /* first time registering */
 467                 err = register_fentry(tr, im->image);
 468
 469 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
 470         if (err == -EAGAIN) {
 471                 /* -EAGAIN from bpf_tramp_ftrace_ops_func. Now
 472                  * BPF_TRAMP_F_SHARE_IPMODIFY is set, we can generate the
 473                  * trampoline again, and retry register.
 474                  */
 475                 /* reset fops->func and fops->trampoline for re-register */
 476                 tr->fops->func = NULL;
 477                 tr->fops->trampoline = 0;
 478
 479                 /* free im memory and reallocate later */
 480                 bpf_tramp_image_free(im);
 481                 goto again;
 482         }
 483 #endif
 484         if (err)
 485                 goto out_free;
 486
 487         if (tr->cur_image)
 488                 bpf_tramp_image_put(tr->cur_image);
 489         tr->cur_image = im;
 490 out:
 491         /* If any error happens, restore previous flags */
 492         if (err)
 493                 tr->flags = orig_flags;
 494         kfree(tlinks);
 495         return err;
 496
 497 out_free:
 498         bpf_tramp_image_free(im);
 499         goto out;
 500 }
 501
 502 static enum bpf_tramp_prog_type bpf_attach_type_to_tramp(struct bpf_prog *prog)
 503 {
 504         switch (prog->expected_attach_type) {
 505         case BPF_TRACE_FENTRY:
 506                 return BPF_TRAMP_FENTRY;
 507         case BPF_MODIFY_RETURN:
 508                 return BPF_TRAMP_MODIFY_RETURN;
 509         case BPF_TRACE_FEXIT:
 510                 return BPF_TRAMP_FEXIT;
 511         case BPF_LSM_MAC:
 512                 if (!prog->aux->attach_func_proto->type)
 513                         /* The function returns void, we cannot modify its
 514                          * return value.
 515                          */
 516                         return BPF_TRAMP_FEXIT;
 517                 else
 518                         return BPF_TRAMP_MODIFY_RETURN;
 519         default:
 520                 return BPF_TRAMP_REPLACE;
 521         }
 522 }
 523
 524 static int __bpf_trampoline_link_prog(struct bpf_tramp_link *link, struct bpf_trampoline *tr)
 525 {
 526         enum bpf_tramp_prog_type kind;
 527         struct bpf_tramp_link *link_exiting;
 528         int err = 0;
 529         int cnt = 0, i;
 530
 531         kind = bpf_attach_type_to_tramp(link->link.prog);
 532         if (tr->extension_prog)
 533                 /* cannot attach fentry/fexit if extension prog is attached.
 534                  * cannot overwrite extension prog either.
 535                  */
 536                 return -EBUSY;
 537
 538         for (i = 0; i < BPF_TRAMP_MAX; i++)
 539                 cnt += tr->progs_cnt[i];
 540
 541         if (kind == BPF_TRAMP_REPLACE) {
 542                 /* Cannot attach extension if fentry/fexit are in use. */
 543                 if (cnt)
 544                         return -EBUSY;
 545                 tr->extension_prog = link->link.prog;
 546                 return bpf_arch_text_poke(tr->func.addr, BPF_MOD_JUMP, NULL,
 547                                           link->link.prog->bpf_func);
 548         }
 549         if (cnt >= BPF_MAX_TRAMP_LINKS)
 550                 return -E2BIG;
 551         if (!hlist_unhashed(&link->tramp_hlist))
 552                 /* prog already linked */
 553                 return -EBUSY;
 554         hlist_for_each_entry(link_exiting, &tr->progs_hlist[kind], tramp_hlist) {
 555                 if (link_exiting->link.prog != link->link.prog)
 556                         continue;
 557                 /* prog already linked */
 558                 return -EBUSY;
 559         }
 560
 561         hlist_add_head(&link->tramp_hlist, &tr->progs_hlist[kind]);
 562         tr->progs_cnt[kind]++;
 563         err = bpf_trampoline_update(tr, true /* lock_direct_mutex */);
 564         if (err) {
 565                 hlist_del_init(&link->tramp_hlist);
 566                 tr->progs_cnt[kind]--;
 567         }
 568         return err;
 569 }
 570
 571 int bpf_trampoline_link_prog(struct bpf_tramp_link *link, struct bpf_trampoline *tr)
 572 {
 573         int err;
 574
 575         mutex_lock(&tr->mutex);
 576         err = __bpf_trampoline_link_prog(link, tr);
 577         mutex_unlock(&tr->mutex);
 578         return err;
 579 }
 580
 581 static int __bpf_trampoline_unlink_prog(struct bpf_tramp_link *link, struct bpf_trampoline *tr)
 582 {
 583         enum bpf_tramp_prog_type kind;
 584         int err;
 585
 586         kind = bpf_attach_type_to_tramp(link->link.prog);
 587         if (kind == BPF_TRAMP_REPLACE) {
 588                 WARN_ON_ONCE(!tr->extension_prog);
 589                 err = bpf_arch_text_poke(tr->func.addr, BPF_MOD_JUMP,
 590                                          tr->extension_prog->bpf_func, NULL);
 591                 tr->extension_prog = NULL;
 592                 return err;
 593         }
 594         hlist_del_init(&link->tramp_hlist);
 595         tr->progs_cnt[kind]--;
 596         return bpf_trampoline_update(tr, true /* lock_direct_mutex */);
 597 }
 598
 599 /* bpf_trampoline_unlink_prog() should never fail. */
 600 int bpf_trampoline_unlink_prog(struct bpf_tramp_link *link, struct bpf_trampoline *tr)
 601 {
 602         int err;
 603
 604         mutex_lock(&tr->mutex);
 605         err = __bpf_trampoline_unlink_prog(link, tr);
 606         mutex_unlock(&tr->mutex);
 607         return err;
 608 }
 609
 610 #if defined(CONFIG_CGROUP_BPF) && defined(CONFIG_BPF_LSM)
 611 static void bpf_shim_tramp_link_release(struct bpf_link *link)
 612 {
 613         struct bpf_shim_tramp_link *shim_link =
 614                 container_of(link, struct bpf_shim_tramp_link, link.link);
 615
 616         /* paired with 'shim_link->trampoline = tr' in bpf_trampoline_link_cgroup_shim */
 617         if (!shim_link->trampoline)
 618                 return;
 619
 620         WARN_ON_ONCE(bpf_trampoline_unlink_prog(&shim_link->link, shim_link->trampoline));
 621         bpf_trampoline_put(shim_link->trampoline);
 622 }
 623
 624 static void bpf_shim_tramp_link_dealloc(struct bpf_link *link)
 625 {
 626         struct bpf_shim_tramp_link *shim_link =
 627                 container_of(link, struct bpf_shim_tramp_link, link.link);
 628
 629         kfree(shim_link);
 630 }
 631
 632 static const struct bpf_link_ops bpf_shim_tramp_link_lops = {
 633         .release = bpf_shim_tramp_link_release,
 634         .dealloc = bpf_shim_tramp_link_dealloc,
 635 };
 636
 637 static struct bpf_shim_tramp_link *cgroup_shim_alloc(const struct bpf_prog *prog,
 638                                                      bpf_func_t bpf_func,
 639                                                      int cgroup_atype)
 640 {
 641         struct bpf_shim_tramp_link *shim_link = NULL;
 642         struct bpf_prog *p;
 643
 644         shim_link = kzalloc(sizeof(*shim_link), GFP_USER);
 645         if (!shim_link)
 646                 return NULL;
 647
 648         p = bpf_prog_alloc(1, 0);
 649         if (!p) {
 650                 kfree(shim_link);
 651                 return NULL;
 652         }
 653
 654         p->jited = false;
 655         p->bpf_func = bpf_func;
 656
 657         p->aux->cgroup_atype = cgroup_atype;
 658         p->aux->attach_func_proto = prog->aux->attach_func_proto;
 659         p->aux->attach_btf_id = prog->aux->attach_btf_id;
 660         p->aux->attach_btf = prog->aux->attach_btf;
 661         btf_get(p->aux->attach_btf);
 662         p->type = BPF_PROG_TYPE_LSM;
 663         p->expected_attach_type = BPF_LSM_MAC;
 664         bpf_prog_inc(p);
 665         bpf_link_init(&shim_link->link.link, BPF_LINK_TYPE_UNSPEC,
 666                       &bpf_shim_tramp_link_lops, p);
 667         bpf_cgroup_atype_get(p->aux->attach_btf_id, cgroup_atype);
 668
 669         return shim_link;
 670 }
 671
 672 static struct bpf_shim_tramp_link *cgroup_shim_find(struct bpf_trampoline *tr,
 673                                                     bpf_func_t bpf_func)
 674 {
 675         struct bpf_tramp_link *link;
 676         int kind;
 677
 678         for (kind = 0; kind < BPF_TRAMP_MAX; kind++) {
 679                 hlist_for_each_entry(link, &tr->progs_hlist[kind], tramp_hlist) {
 680                         struct bpf_prog *p = link->link.prog;
 681
 682                         if (p->bpf_func == bpf_func)
 683                                 return container_of(link, struct bpf_shim_tramp_link, link);
 684                 }
 685         }
 686
 687         return NULL;
 688 }
 689
 690 int bpf_trampoline_link_cgroup_shim(struct bpf_prog *prog,
 691                                     int cgroup_atype)
 692 {
 693         struct bpf_shim_tramp_link *shim_link = NULL;
 694         struct bpf_attach_target_info tgt_info = {};
 695         struct bpf_trampoline *tr;
 696         bpf_func_t bpf_func;
 697         u64 key;
 698         int err;
 699
 700         err = bpf_check_attach_target(NULL, prog, NULL,
 701                                       prog->aux->attach_btf_id,
 702                                       &tgt_info);
 703         if (err)
 704                 return err;
 705
 706         key = bpf_trampoline_compute_key(NULL, prog->aux->attach_btf,
 707                                          prog->aux->attach_btf_id);
 708
 709         bpf_lsm_find_cgroup_shim(prog, &bpf_func);
 710         tr = bpf_trampoline_get(key, &tgt_info);
 711         if (!tr)
 712                 return  -ENOMEM;
 713
 714         mutex_lock(&tr->mutex);
 715
 716         shim_link = cgroup_shim_find(tr, bpf_func);
 717         if (shim_link) {
 718                 /* Reusing existing shim attached by the other program. */
 719                 bpf_link_inc(&shim_link->link.link);
 720
 721                 mutex_unlock(&tr->mutex);
 722                 bpf_trampoline_put(tr); /* bpf_trampoline_get above */
 723                 return 0;
 724         }
 725
 726         /* Allocate and install new shim. */
 727
 728         shim_link = cgroup_shim_alloc(prog, bpf_func, cgroup_atype);
 729         if (!shim_link) {
 730                 err = -ENOMEM;
 731                 goto err;
 732         }
 733
 734         err = __bpf_trampoline_link_prog(&shim_link->link, tr);
 735         if (err)
 736                 goto err;
 737
 738         shim_link->trampoline = tr;
 739         /* note, we're still holding tr refcnt from above */
 740
 741         mutex_unlock(&tr->mutex);
 742
 743         return 0;
 744 err:
 745         mutex_unlock(&tr->mutex);
 746
 747         if (shim_link)
 748                 bpf_link_put(&shim_link->link.link);
 749
 750         /* have to release tr while _not_ holding its mutex */
 751         bpf_trampoline_put(tr); /* bpf_trampoline_get above */
 752
 753         return err;
 754 }
 755
 756 void bpf_trampoline_unlink_cgroup_shim(struct bpf_prog *prog)
 757 {
 758         struct bpf_shim_tramp_link *shim_link = NULL;
 759         struct bpf_trampoline *tr;
 760         bpf_func_t bpf_func;
 761         u64 key;
 762
 763         key = bpf_trampoline_compute_key(NULL, prog->aux->attach_btf,
 764                                          prog->aux->attach_btf_id);
 765
 766         bpf_lsm_find_cgroup_shim(prog, &bpf_func);
 767         tr = bpf_trampoline_lookup(key);
 768         if (WARN_ON_ONCE(!tr))
 769                 return;
 770
 771         mutex_lock(&tr->mutex);
 772         shim_link = cgroup_shim_find(tr, bpf_func);
 773         mutex_unlock(&tr->mutex);
 774
 775         if (shim_link)
 776                 bpf_link_put(&shim_link->link.link);
 777
 778         bpf_trampoline_put(tr); /* bpf_trampoline_lookup above */
 779 }
 780 #endif
 781
 782 struct bpf_trampoline *bpf_trampoline_get(u64 key,
 783                                           struct bpf_attach_target_info *tgt_info)
 784 {
 785         struct bpf_trampoline *tr;
 786
 787         tr = bpf_trampoline_lookup(key);
 788         if (!tr)
 789                 return NULL;
 790
 791         mutex_lock(&tr->mutex);
 792         if (tr->func.addr)
 793                 goto out;
 794
 795         memcpy(&tr->func.model, &tgt_info->fmodel, sizeof(tgt_info->fmodel));
 796         tr->func.addr = (void *)tgt_info->tgt_addr;
 797 out:
 798         mutex_unlock(&tr->mutex);
 799         return tr;
 800 }
 801
 802 void bpf_trampoline_put(struct bpf_trampoline *tr)
 803 {
 804         int i;
 805
 806         if (!tr)
 807                 return;
 808         mutex_lock(&trampoline_mutex);
 809         if (!refcount_dec_and_test(&tr->refcnt))
 810                 goto out;
 811         WARN_ON_ONCE(mutex_is_locked(&tr->mutex));
 812
 813         for (i = 0; i < BPF_TRAMP_MAX; i++)
 814                 if (WARN_ON_ONCE(!hlist_empty(&tr->progs_hlist[i])))
 815                         goto out;
 816
 817         /* This code will be executed even when the last bpf_tramp_image
 818          * is alive. All progs are detached from the trampoline and the
 819          * trampoline image is patched with jmp into epilogue to skip
 820          * fexit progs. The fentry-only trampoline will be freed via
 821          * multiple rcu callbacks.
 822          */
 823         hlist_del(&tr->hlist);
 824         if (tr->fops) {
 825                 ftrace_free_filter(tr->fops);
 826                 kfree(tr->fops);
 827         }
 828         kfree(tr);
 829 out:
 830         mutex_unlock(&trampoline_mutex);
 831 }
 832
 833 #define NO_START_TIME 1
 834 static __always_inline u64 notrace bpf_prog_start_time(void)
 835 {
 836         u64 start = NO_START_TIME;
 837
 838         if (static_branch_unlikely(&bpf_stats_enabled_key)) {
 839                 start = sched_clock();
 840                 if (unlikely(!start))
 841                         start = NO_START_TIME;
 842         }
 843         return start;
 844 }
 845
 846 /* The logic is similar to bpf_prog_run(), but with an explicit
 847  * rcu_read_lock() and migrate_disable() which are required
 848  * for the trampoline. The macro is split into
 849  * call __bpf_prog_enter
 850  * call prog->bpf_func
 851  * call __bpf_prog_exit
 852  *
 853  * __bpf_prog_enter returns:
 854  * 0 - skip execution of the bpf prog
 855  * 1 - execute bpf prog
 856  * [2..MAX_U64] - execute bpf prog and record execution time.
 857  *     This is start time.
 858  */
 859 static u64 notrace __bpf_prog_enter_recur(struct bpf_prog *prog, struct bpf_tramp_run_ctx *run_ctx)
 860         __acquires(RCU)
 861 {
 862         rcu_read_lock();
 863         migrate_disable();
 864
 865         run_ctx->saved_run_ctx = bpf_set_run_ctx(&run_ctx->run_ctx);
 866
 867         if (unlikely(this_cpu_inc_return(*(prog->active)) != 1)) {
 868                 bpf_prog_inc_misses_counter(prog);
 869                 return 0;
 870         }
 871         return bpf_prog_start_time();
 872 }
 873
 874 static void notrace update_prog_stats(struct bpf_prog *prog,
 875                                       u64 start)
 876 {
 877         struct bpf_prog_stats *stats;
 878
 879         if (static_branch_unlikely(&bpf_stats_enabled_key) &&
 880             /* static_key could be enabled in __bpf_prog_enter*
 881              * and disabled in __bpf_prog_exit*.
 882              * And vice versa.
 883              * Hence check that 'start' is valid.
 884              */
 885             start > NO_START_TIME) {
 886                 unsigned long flags;
 887
 888                 stats = this_cpu_ptr(prog->stats);
 889                 flags = u64_stats_update_begin_irqsave(&stats->syncp);
 890                 u64_stats_inc(&stats->cnt);
 891                 u64_stats_add(&stats->nsecs, sched_clock() - start);
 892                 u64_stats_update_end_irqrestore(&stats->syncp, flags);
 893         }
 894 }
 895
 896 static void notrace __bpf_prog_exit_recur(struct bpf_prog *prog, u64 start,
 897                                           struct bpf_tramp_run_ctx *run_ctx)
 898         __releases(RCU)
 899 {
 900         bpf_reset_run_ctx(run_ctx->saved_run_ctx);
 901
 902         update_prog_stats(prog, start);
 903         this_cpu_dec(*(prog->active));
 904         migrate_enable();
 905         rcu_read_unlock();
 906 }
 907
 908 static u64 notrace __bpf_prog_enter_lsm_cgroup(struct bpf_prog *prog,
 909                                                struct bpf_tramp_run_ctx *run_ctx)
 910         __acquires(RCU)
 911 {
 912         /* Runtime stats are exported via actual BPF_LSM_CGROUP
 913          * programs, not the shims.
 914          */
 915         rcu_read_lock();
 916         migrate_disable();
 917
 918         run_ctx->saved_run_ctx = bpf_set_run_ctx(&run_ctx->run_ctx);
 919
 920         return NO_START_TIME;
 921 }
 922
 923 static void notrace __bpf_prog_exit_lsm_cgroup(struct bpf_prog *prog, u64 start,
 924                                                struct bpf_tramp_run_ctx *run_ctx)
 925         __releases(RCU)
 926 {
 927         bpf_reset_run_ctx(run_ctx->saved_run_ctx);
 928
 929         migrate_enable();
 930         rcu_read_unlock();
 931 }
 932
 933 u64 notrace __bpf_prog_enter_sleepable_recur(struct bpf_prog *prog,
 934                                              struct bpf_tramp_run_ctx *run_ctx)
 935 {
 936         rcu_read_lock_trace();
 937         migrate_disable();
 938         might_fault();
 939
 940         run_ctx->saved_run_ctx = bpf_set_run_ctx(&run_ctx->run_ctx);
 941
 942         if (unlikely(this_cpu_inc_return(*(prog->active)) != 1)) {
 943                 bpf_prog_inc_misses_counter(prog);
 944                 return 0;
 945         }
 946         return bpf_prog_start_time();
 947 }
 948
 949 void notrace __bpf_prog_exit_sleepable_recur(struct bpf_prog *prog, u64 start,
 950                                              struct bpf_tramp_run_ctx *run_ctx)
 951 {
 952         bpf_reset_run_ctx(run_ctx->saved_run_ctx);
 953
 954         update_prog_stats(prog, start);
 955         this_cpu_dec(*(prog->active));
 956         migrate_enable();
 957         rcu_read_unlock_trace();
 958 }
 959
 960 static u64 notrace __bpf_prog_enter_sleepable(struct bpf_prog *prog,
 961                                               struct bpf_tramp_run_ctx *run_ctx)
 962 {
 963         rcu_read_lock_trace();
 964         migrate_disable();
 965         might_fault();
 966
 967         run_ctx->saved_run_ctx = bpf_set_run_ctx(&run_ctx->run_ctx);
 968
 969         return bpf_prog_start_time();
 970 }
 971
 972 static void notrace __bpf_prog_exit_sleepable(struct bpf_prog *prog, u64 start,
 973                                               struct bpf_tramp_run_ctx *run_ctx)
 974 {
 975         bpf_reset_run_ctx(run_ctx->saved_run_ctx);
 976
 977         update_prog_stats(prog, start);
 978         migrate_enable();
 979         rcu_read_unlock_trace();
 980 }
 981
 982 static u64 notrace __bpf_prog_enter(struct bpf_prog *prog,
 983                                     struct bpf_tramp_run_ctx *run_ctx)
 984         __acquires(RCU)
 985 {
 986         rcu_read_lock();
 987         migrate_disable();
 988
 989         run_ctx->saved_run_ctx = bpf_set_run_ctx(&run_ctx->run_ctx);
 990
 991         return bpf_prog_start_time();
 992 }
 993
 994 static void notrace __bpf_prog_exit(struct bpf_prog *prog, u64 start,
 995                                     struct bpf_tramp_run_ctx *run_ctx)
 996         __releases(RCU)
 997 {
 998         bpf_reset_run_ctx(run_ctx->saved_run_ctx);
 999
1000         update_prog_stats(prog, start);
1001         migrate_enable();
1002         rcu_read_unlock();
1003 }
1004
1005 void notrace __bpf_tramp_enter(struct bpf_tramp_image *tr)
1006 {
1007         percpu_ref_get(&tr->pcref);
1008 }
1009
1010 void notrace __bpf_tramp_exit(struct bpf_tramp_image *tr)
1011 {
1012         percpu_ref_put(&tr->pcref);
1013 }
1014
1015 bpf_trampoline_enter_t bpf_trampoline_enter(const struct bpf_prog *prog)
1016 {
1017         bool sleepable = prog->sleepable;
1018
1019         if (bpf_prog_check_recur(prog))
1020                 return sleepable ? __bpf_prog_enter_sleepable_recur :
1021                         __bpf_prog_enter_recur;
1022
1023         if (resolve_prog_type(prog) == BPF_PROG_TYPE_LSM &&
1024             prog->expected_attach_type == BPF_LSM_CGROUP)
1025                 return __bpf_prog_enter_lsm_cgroup;
1026
1027         return sleepable ? __bpf_prog_enter_sleepable : __bpf_prog_enter;
1028 }
1029
1030 bpf_trampoline_exit_t bpf_trampoline_exit(const struct bpf_prog *prog)
1031 {
1032         bool sleepable = prog->sleepable;
1033
1034         if (bpf_prog_check_recur(prog))
1035                 return sleepable ? __bpf_prog_exit_sleepable_recur :
1036                         __bpf_prog_exit_recur;
1037
1038         if (resolve_prog_type(prog) == BPF_PROG_TYPE_LSM &&
1039             prog->expected_attach_type == BPF_LSM_CGROUP)
1040                 return __bpf_prog_exit_lsm_cgroup;
1041
1042         return sleepable ? __bpf_prog_exit_sleepable : __bpf_prog_exit;
1043 }
1044
1045 int __weak
1046 arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *image_end,
1047                             const struct btf_func_model *m, u32 flags,
1048                             struct bpf_tramp_links *tlinks,
1049                             void *func_addr)
1050 {
1051         return -ENOTSUPP;
1052 }
1053
1054 void * __weak arch_alloc_bpf_trampoline(unsigned int size)
1055 {
1056         void *image;
1057
1058         if (WARN_ON_ONCE(size > PAGE_SIZE))
1059                 return NULL;
1060         image = bpf_jit_alloc_exec(PAGE_SIZE);
1061         if (image)
1062                 set_vm_flush_reset_perms(image);
1063         return image;
1064 }
1065
1066 void __weak arch_free_bpf_trampoline(void *image, unsigned int size)
1067 {
1068         WARN_ON_ONCE(size > PAGE_SIZE);
1069         /* bpf_jit_free_exec doesn't need "size", but
1070          * bpf_prog_pack_free() needs it.
1071          */
1072         bpf_jit_free_exec(image);
1073 }
1074
1075 void __weak arch_protect_bpf_trampoline(void *image, unsigned int size)
1076 {
1077         WARN_ON_ONCE(size > PAGE_SIZE);
1078         set_memory_rox((long)image, 1);
1079 }
1080
1081 void __weak arch_unprotect_bpf_trampoline(void *image, unsigned int size)
1082 {
1083         WARN_ON_ONCE(size > PAGE_SIZE);
1084         set_memory_nx((long)image, 1);
1085         set_memory_rw((long)image, 1);
1086 }
1087
1088 int __weak arch_bpf_trampoline_size(const struct btf_func_model *m, u32 flags,
1089                                     struct bpf_tramp_links *tlinks, void *func_addr)
1090 {
1091         return -ENOTSUPP;
1092 }
1093
1094 static int __init init_trampolines(void)
1095 {
1096         int i;
1097
1098         for (i = 0; i < TRAMPOLINE_TABLE_SIZE; i++)
1099                 INIT_HLIST_HEAD(&trampoline_table[i]);
1100         return 0;
1101 }
1102 late_initcall(init_trampolines);