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_TASKS_RCU))
 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         err = arch_protect_bpf_trampoline(im->image, im->size);
 460         if (err)
 461                 goto out_free;
 462
 463         WARN_ON(tr->cur_image && total == 0);
 464         if (tr->cur_image)
 465                 /* progs already running at this address */
 466                 err = modify_fentry(tr, tr->cur_image->image, im->image, lock_direct_mutex);
 467         else
 468                 /* first time registering */
 469                 err = register_fentry(tr, im->image);
 470
 471 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
 472         if (err == -EAGAIN) {
 473                 /* -EAGAIN from bpf_tramp_ftrace_ops_func. Now
 474                  * BPF_TRAMP_F_SHARE_IPMODIFY is set, we can generate the
 475                  * trampoline again, and retry register.
 476                  */
 477                 /* reset fops->func and fops->trampoline for re-register */
 478                 tr->fops->func = NULL;
 479                 tr->fops->trampoline = 0;
 480
 481                 /* free im memory and reallocate later */
 482                 bpf_tramp_image_free(im);
 483                 goto again;
 484         }
 485 #endif
 486         if (err)
 487                 goto out_free;
 488
 489         if (tr->cur_image)
 490                 bpf_tramp_image_put(tr->cur_image);
 491         tr->cur_image = im;
 492 out:
 493         /* If any error happens, restore previous flags */
 494         if (err)
 495                 tr->flags = orig_flags;
 496         kfree(tlinks);
 497         return err;
 498
 499 out_free:
 500         bpf_tramp_image_free(im);
 501         goto out;
 502 }
 503
 504 static enum bpf_tramp_prog_type bpf_attach_type_to_tramp(struct bpf_prog *prog)
 505 {
 506         switch (prog->expected_attach_type) {
 507         case BPF_TRACE_FENTRY:
 508                 return BPF_TRAMP_FENTRY;
 509         case BPF_MODIFY_RETURN:
 510                 return BPF_TRAMP_MODIFY_RETURN;
 511         case BPF_TRACE_FEXIT:
 512                 return BPF_TRAMP_FEXIT;
 513         case BPF_LSM_MAC:
 514                 if (!prog->aux->attach_func_proto->type)
 515                         /* The function returns void, we cannot modify its
 516                          * return value.
 517                          */
 518                         return BPF_TRAMP_FEXIT;
 519                 else
 520                         return BPF_TRAMP_MODIFY_RETURN;
 521         default:
 522                 return BPF_TRAMP_REPLACE;
 523         }
 524 }
 525
 526 static int __bpf_trampoline_link_prog(struct bpf_tramp_link *link, struct bpf_trampoline *tr)
 527 {
 528         enum bpf_tramp_prog_type kind;
 529         struct bpf_tramp_link *link_exiting;
 530         int err = 0;
 531         int cnt = 0, i;
 532
 533         kind = bpf_attach_type_to_tramp(link->link.prog);
 534         if (tr->extension_prog)
 535                 /* cannot attach fentry/fexit if extension prog is attached.
 536                  * cannot overwrite extension prog either.
 537                  */
 538                 return -EBUSY;
 539
 540         for (i = 0; i < BPF_TRAMP_MAX; i++)
 541                 cnt += tr->progs_cnt[i];
 542
 543         if (kind == BPF_TRAMP_REPLACE) {
 544                 /* Cannot attach extension if fentry/fexit are in use. */
 545                 if (cnt)
 546                         return -EBUSY;
 547                 tr->extension_prog = link->link.prog;
 548                 return bpf_arch_text_poke(tr->func.addr, BPF_MOD_JUMP, NULL,
 549                                           link->link.prog->bpf_func);
 550         }
 551         if (cnt >= BPF_MAX_TRAMP_LINKS)
 552                 return -E2BIG;
 553         if (!hlist_unhashed(&link->tramp_hlist))
 554                 /* prog already linked */
 555                 return -EBUSY;
 556         hlist_for_each_entry(link_exiting, &tr->progs_hlist[kind], tramp_hlist) {
 557                 if (link_exiting->link.prog != link->link.prog)
 558                         continue;
 559                 /* prog already linked */
 560                 return -EBUSY;
 561         }
 562
 563         hlist_add_head(&link->tramp_hlist, &tr->progs_hlist[kind]);
 564         tr->progs_cnt[kind]++;
 565         err = bpf_trampoline_update(tr, true /* lock_direct_mutex */);
 566         if (err) {
 567                 hlist_del_init(&link->tramp_hlist);
 568                 tr->progs_cnt[kind]--;
 569         }
 570         return err;
 571 }
 572
 573 int bpf_trampoline_link_prog(struct bpf_tramp_link *link, struct bpf_trampoline *tr)
 574 {
 575         int err;
 576
 577         mutex_lock(&tr->mutex);
 578         err = __bpf_trampoline_link_prog(link, tr);
 579         mutex_unlock(&tr->mutex);
 580         return err;
 581 }
 582
 583 static int __bpf_trampoline_unlink_prog(struct bpf_tramp_link *link, struct bpf_trampoline *tr)
 584 {
 585         enum bpf_tramp_prog_type kind;
 586         int err;
 587
 588         kind = bpf_attach_type_to_tramp(link->link.prog);
 589         if (kind == BPF_TRAMP_REPLACE) {
 590                 WARN_ON_ONCE(!tr->extension_prog);
 591                 err = bpf_arch_text_poke(tr->func.addr, BPF_MOD_JUMP,
 592                                          tr->extension_prog->bpf_func, NULL);
 593                 tr->extension_prog = NULL;
 594                 return err;
 595         }
 596         hlist_del_init(&link->tramp_hlist);
 597         tr->progs_cnt[kind]--;
 598         return bpf_trampoline_update(tr, true /* lock_direct_mutex */);
 599 }
 600
 601 /* bpf_trampoline_unlink_prog() should never fail. */
 602 int bpf_trampoline_unlink_prog(struct bpf_tramp_link *link, struct bpf_trampoline *tr)
 603 {
 604         int err;
 605
 606         mutex_lock(&tr->mutex);
 607         err = __bpf_trampoline_unlink_prog(link, tr);
 608         mutex_unlock(&tr->mutex);
 609         return err;
 610 }
 611
 612 #if defined(CONFIG_CGROUP_BPF) && defined(CONFIG_BPF_LSM)
 613 static void bpf_shim_tramp_link_release(struct bpf_link *link)
 614 {
 615         struct bpf_shim_tramp_link *shim_link =
 616                 container_of(link, struct bpf_shim_tramp_link, link.link);
 617
 618         /* paired with 'shim_link->trampoline = tr' in bpf_trampoline_link_cgroup_shim */
 619         if (!shim_link->trampoline)
 620                 return;
 621
 622         WARN_ON_ONCE(bpf_trampoline_unlink_prog(&shim_link->link, shim_link->trampoline));
 623         bpf_trampoline_put(shim_link->trampoline);
 624 }
 625
 626 static void bpf_shim_tramp_link_dealloc(struct bpf_link *link)
 627 {
 628         struct bpf_shim_tramp_link *shim_link =
 629                 container_of(link, struct bpf_shim_tramp_link, link.link);
 630
 631         kfree(shim_link);
 632 }
 633
 634 static const struct bpf_link_ops bpf_shim_tramp_link_lops = {
 635         .release = bpf_shim_tramp_link_release,
 636         .dealloc = bpf_shim_tramp_link_dealloc,
 637 };
 638
 639 static struct bpf_shim_tramp_link *cgroup_shim_alloc(const struct bpf_prog *prog,
 640                                                      bpf_func_t bpf_func,
 641                                                      int cgroup_atype)
 642 {
 643         struct bpf_shim_tramp_link *shim_link = NULL;
 644         struct bpf_prog *p;
 645
 646         shim_link = kzalloc(sizeof(*shim_link), GFP_USER);
 647         if (!shim_link)
 648                 return NULL;
 649
 650         p = bpf_prog_alloc(1, 0);
 651         if (!p) {
 652                 kfree(shim_link);
 653                 return NULL;
 654         }
 655
 656         p->jited = false;
 657         p->bpf_func = bpf_func;
 658
 659         p->aux->cgroup_atype = cgroup_atype;
 660         p->aux->attach_func_proto = prog->aux->attach_func_proto;
 661         p->aux->attach_btf_id = prog->aux->attach_btf_id;
 662         p->aux->attach_btf = prog->aux->attach_btf;
 663         btf_get(p->aux->attach_btf);
 664         p->type = BPF_PROG_TYPE_LSM;
 665         p->expected_attach_type = BPF_LSM_MAC;
 666         bpf_prog_inc(p);
 667         bpf_link_init(&shim_link->link.link, BPF_LINK_TYPE_UNSPEC,
 668                       &bpf_shim_tramp_link_lops, p);
 669         bpf_cgroup_atype_get(p->aux->attach_btf_id, cgroup_atype);
 670
 671         return shim_link;
 672 }
 673
 674 static struct bpf_shim_tramp_link *cgroup_shim_find(struct bpf_trampoline *tr,
 675                                                     bpf_func_t bpf_func)
 676 {
 677         struct bpf_tramp_link *link;
 678         int kind;
 679
 680         for (kind = 0; kind < BPF_TRAMP_MAX; kind++) {
 681                 hlist_for_each_entry(link, &tr->progs_hlist[kind], tramp_hlist) {
 682                         struct bpf_prog *p = link->link.prog;
 683
 684                         if (p->bpf_func == bpf_func)
 685                                 return container_of(link, struct bpf_shim_tramp_link, link);
 686                 }
 687         }
 688
 689         return NULL;
 690 }
 691
 692 int bpf_trampoline_link_cgroup_shim(struct bpf_prog *prog,
 693                                     int cgroup_atype)
 694 {
 695         struct bpf_shim_tramp_link *shim_link = NULL;
 696         struct bpf_attach_target_info tgt_info = {};
 697         struct bpf_trampoline *tr;
 698         bpf_func_t bpf_func;
 699         u64 key;
 700         int err;
 701
 702         err = bpf_check_attach_target(NULL, prog, NULL,
 703                                       prog->aux->attach_btf_id,
 704                                       &tgt_info);
 705         if (err)
 706                 return err;
 707
 708         key = bpf_trampoline_compute_key(NULL, prog->aux->attach_btf,
 709                                          prog->aux->attach_btf_id);
 710
 711         bpf_lsm_find_cgroup_shim(prog, &bpf_func);
 712         tr = bpf_trampoline_get(key, &tgt_info);
 713         if (!tr)
 714                 return  -ENOMEM;
 715
 716         mutex_lock(&tr->mutex);
 717
 718         shim_link = cgroup_shim_find(tr, bpf_func);
 719         if (shim_link) {
 720                 /* Reusing existing shim attached by the other program. */
 721                 bpf_link_inc(&shim_link->link.link);
 722
 723                 mutex_unlock(&tr->mutex);
 724                 bpf_trampoline_put(tr); /* bpf_trampoline_get above */
 725                 return 0;
 726         }
 727
 728         /* Allocate and install new shim. */
 729
 730         shim_link = cgroup_shim_alloc(prog, bpf_func, cgroup_atype);
 731         if (!shim_link) {
 732                 err = -ENOMEM;
 733                 goto err;
 734         }
 735
 736         err = __bpf_trampoline_link_prog(&shim_link->link, tr);
 737         if (err)
 738                 goto err;
 739
 740         shim_link->trampoline = tr;
 741         /* note, we're still holding tr refcnt from above */
 742
 743         mutex_unlock(&tr->mutex);
 744
 745         return 0;
 746 err:
 747         mutex_unlock(&tr->mutex);
 748
 749         if (shim_link)
 750                 bpf_link_put(&shim_link->link.link);
 751
 752         /* have to release tr while _not_ holding its mutex */
 753         bpf_trampoline_put(tr); /* bpf_trampoline_get above */
 754
 755         return err;
 756 }
 757
 758 void bpf_trampoline_unlink_cgroup_shim(struct bpf_prog *prog)
 759 {
 760         struct bpf_shim_tramp_link *shim_link = NULL;
 761         struct bpf_trampoline *tr;
 762         bpf_func_t bpf_func;
 763         u64 key;
 764
 765         key = bpf_trampoline_compute_key(NULL, prog->aux->attach_btf,
 766                                          prog->aux->attach_btf_id);
 767
 768         bpf_lsm_find_cgroup_shim(prog, &bpf_func);
 769         tr = bpf_trampoline_lookup(key);
 770         if (WARN_ON_ONCE(!tr))
 771                 return;
 772
 773         mutex_lock(&tr->mutex);
 774         shim_link = cgroup_shim_find(tr, bpf_func);
 775         mutex_unlock(&tr->mutex);
 776
 777         if (shim_link)
 778                 bpf_link_put(&shim_link->link.link);
 779
 780         bpf_trampoline_put(tr); /* bpf_trampoline_lookup above */
 781 }
 782 #endif
 783
 784 struct bpf_trampoline *bpf_trampoline_get(u64 key,
 785                                           struct bpf_attach_target_info *tgt_info)
 786 {
 787         struct bpf_trampoline *tr;
 788
 789         tr = bpf_trampoline_lookup(key);
 790         if (!tr)
 791                 return NULL;
 792
 793         mutex_lock(&tr->mutex);
 794         if (tr->func.addr)
 795                 goto out;
 796
 797         memcpy(&tr->func.model, &tgt_info->fmodel, sizeof(tgt_info->fmodel));
 798         tr->func.addr = (void *)tgt_info->tgt_addr;
 799 out:
 800         mutex_unlock(&tr->mutex);
 801         return tr;
 802 }
 803
 804 void bpf_trampoline_put(struct bpf_trampoline *tr)
 805 {
 806         int i;
 807
 808         if (!tr)
 809                 return;
 810         mutex_lock(&trampoline_mutex);
 811         if (!refcount_dec_and_test(&tr->refcnt))
 812                 goto out;
 813         WARN_ON_ONCE(mutex_is_locked(&tr->mutex));
 814
 815         for (i = 0; i < BPF_TRAMP_MAX; i++)
 816                 if (WARN_ON_ONCE(!hlist_empty(&tr->progs_hlist[i])))
 817                         goto out;
 818
 819         /* This code will be executed even when the last bpf_tramp_image
 820          * is alive. All progs are detached from the trampoline and the
 821          * trampoline image is patched with jmp into epilogue to skip
 822          * fexit progs. The fentry-only trampoline will be freed via
 823          * multiple rcu callbacks.
 824          */
 825         hlist_del(&tr->hlist);
 826         if (tr->fops) {
 827                 ftrace_free_filter(tr->fops);
 828                 kfree(tr->fops);
 829         }
 830         kfree(tr);
 831 out:
 832         mutex_unlock(&trampoline_mutex);
 833 }
 834
 835 #define NO_START_TIME 1
 836 static __always_inline u64 notrace bpf_prog_start_time(void)
 837 {
 838         u64 start = NO_START_TIME;
 839
 840         if (static_branch_unlikely(&bpf_stats_enabled_key)) {
 841                 start = sched_clock();
 842                 if (unlikely(!start))
 843                         start = NO_START_TIME;
 844         }
 845         return start;
 846 }
 847
 848 /* The logic is similar to bpf_prog_run(), but with an explicit
 849  * rcu_read_lock() and migrate_disable() which are required
 850  * for the trampoline. The macro is split into
 851  * call __bpf_prog_enter
 852  * call prog->bpf_func
 853  * call __bpf_prog_exit
 854  *
 855  * __bpf_prog_enter returns:
 856  * 0 - skip execution of the bpf prog
 857  * 1 - execute bpf prog
 858  * [2..MAX_U64] - execute bpf prog and record execution time.
 859  *     This is start time.
 860  */
 861 static u64 notrace __bpf_prog_enter_recur(struct bpf_prog *prog, struct bpf_tramp_run_ctx *run_ctx)
 862         __acquires(RCU)
 863 {
 864         rcu_read_lock();
 865         migrate_disable();
 866
 867         run_ctx->saved_run_ctx = bpf_set_run_ctx(&run_ctx->run_ctx);
 868
 869         if (unlikely(this_cpu_inc_return(*(prog->active)) != 1)) {
 870                 bpf_prog_inc_misses_counter(prog);
 871                 return 0;
 872         }
 873         return bpf_prog_start_time();
 874 }
 875
 876 static void notrace update_prog_stats(struct bpf_prog *prog,
 877                                       u64 start)
 878 {
 879         struct bpf_prog_stats *stats;
 880
 881         if (static_branch_unlikely(&bpf_stats_enabled_key) &&
 882             /* static_key could be enabled in __bpf_prog_enter*
 883              * and disabled in __bpf_prog_exit*.
 884              * And vice versa.
 885              * Hence check that 'start' is valid.
 886              */
 887             start > NO_START_TIME) {
 888                 u64 duration = sched_clock() - start;
 889                 unsigned long flags;
 890
 891                 stats = this_cpu_ptr(prog->stats);
 892                 flags = u64_stats_update_begin_irqsave(&stats->syncp);
 893                 u64_stats_inc(&stats->cnt);
 894                 u64_stats_add(&stats->nsecs, duration);
 895                 u64_stats_update_end_irqrestore(&stats->syncp, flags);
 896         }
 897 }
 898
 899 static void notrace __bpf_prog_exit_recur(struct bpf_prog *prog, u64 start,
 900                                           struct bpf_tramp_run_ctx *run_ctx)
 901         __releases(RCU)
 902 {
 903         bpf_reset_run_ctx(run_ctx->saved_run_ctx);
 904
 905         update_prog_stats(prog, start);
 906         this_cpu_dec(*(prog->active));
 907         migrate_enable();
 908         rcu_read_unlock();
 909 }
 910
 911 static u64 notrace __bpf_prog_enter_lsm_cgroup(struct bpf_prog *prog,
 912                                                struct bpf_tramp_run_ctx *run_ctx)
 913         __acquires(RCU)
 914 {
 915         /* Runtime stats are exported via actual BPF_LSM_CGROUP
 916          * programs, not the shims.
 917          */
 918         rcu_read_lock();
 919         migrate_disable();
 920
 921         run_ctx->saved_run_ctx = bpf_set_run_ctx(&run_ctx->run_ctx);
 922
 923         return NO_START_TIME;
 924 }
 925
 926 static void notrace __bpf_prog_exit_lsm_cgroup(struct bpf_prog *prog, u64 start,
 927                                                struct bpf_tramp_run_ctx *run_ctx)
 928         __releases(RCU)
 929 {
 930         bpf_reset_run_ctx(run_ctx->saved_run_ctx);
 931
 932         migrate_enable();
 933         rcu_read_unlock();
 934 }
 935
 936 u64 notrace __bpf_prog_enter_sleepable_recur(struct bpf_prog *prog,
 937                                              struct bpf_tramp_run_ctx *run_ctx)
 938 {
 939         rcu_read_lock_trace();
 940         migrate_disable();
 941         might_fault();
 942
 943         run_ctx->saved_run_ctx = bpf_set_run_ctx(&run_ctx->run_ctx);
 944
 945         if (unlikely(this_cpu_inc_return(*(prog->active)) != 1)) {
 946                 bpf_prog_inc_misses_counter(prog);
 947                 return 0;
 948         }
 949         return bpf_prog_start_time();
 950 }
 951
 952 void notrace __bpf_prog_exit_sleepable_recur(struct bpf_prog *prog, u64 start,
 953                                              struct bpf_tramp_run_ctx *run_ctx)
 954 {
 955         bpf_reset_run_ctx(run_ctx->saved_run_ctx);
 956
 957         update_prog_stats(prog, start);
 958         this_cpu_dec(*(prog->active));
 959         migrate_enable();
 960         rcu_read_unlock_trace();
 961 }
 962
 963 static u64 notrace __bpf_prog_enter_sleepable(struct bpf_prog *prog,
 964                                               struct bpf_tramp_run_ctx *run_ctx)
 965 {
 966         rcu_read_lock_trace();
 967         migrate_disable();
 968         might_fault();
 969
 970         run_ctx->saved_run_ctx = bpf_set_run_ctx(&run_ctx->run_ctx);
 971
 972         return bpf_prog_start_time();
 973 }
 974
 975 static void notrace __bpf_prog_exit_sleepable(struct bpf_prog *prog, u64 start,
 976                                               struct bpf_tramp_run_ctx *run_ctx)
 977 {
 978         bpf_reset_run_ctx(run_ctx->saved_run_ctx);
 979
 980         update_prog_stats(prog, start);
 981         migrate_enable();
 982         rcu_read_unlock_trace();
 983 }
 984
 985 static u64 notrace __bpf_prog_enter(struct bpf_prog *prog,
 986                                     struct bpf_tramp_run_ctx *run_ctx)
 987         __acquires(RCU)
 988 {
 989         rcu_read_lock();
 990         migrate_disable();
 991
 992         run_ctx->saved_run_ctx = bpf_set_run_ctx(&run_ctx->run_ctx);
 993
 994         return bpf_prog_start_time();
 995 }
 996
 997 static void notrace __bpf_prog_exit(struct bpf_prog *prog, u64 start,
 998                                     struct bpf_tramp_run_ctx *run_ctx)
 999         __releases(RCU)
1000 {
1001         bpf_reset_run_ctx(run_ctx->saved_run_ctx);
1002
1003         update_prog_stats(prog, start);
1004         migrate_enable();
1005         rcu_read_unlock();
1006 }
1007
1008 void notrace __bpf_tramp_enter(struct bpf_tramp_image *tr)
1009 {
1010         percpu_ref_get(&tr->pcref);
1011 }
1012
1013 void notrace __bpf_tramp_exit(struct bpf_tramp_image *tr)
1014 {
1015         percpu_ref_put(&tr->pcref);
1016 }
1017
1018 bpf_trampoline_enter_t bpf_trampoline_enter(const struct bpf_prog *prog)
1019 {
1020         bool sleepable = prog->sleepable;
1021
1022         if (bpf_prog_check_recur(prog))
1023                 return sleepable ? __bpf_prog_enter_sleepable_recur :
1024                         __bpf_prog_enter_recur;
1025
1026         if (resolve_prog_type(prog) == BPF_PROG_TYPE_LSM &&
1027             prog->expected_attach_type == BPF_LSM_CGROUP)
1028                 return __bpf_prog_enter_lsm_cgroup;
1029
1030         return sleepable ? __bpf_prog_enter_sleepable : __bpf_prog_enter;
1031 }
1032
1033 bpf_trampoline_exit_t bpf_trampoline_exit(const struct bpf_prog *prog)
1034 {
1035         bool sleepable = prog->sleepable;
1036
1037         if (bpf_prog_check_recur(prog))
1038                 return sleepable ? __bpf_prog_exit_sleepable_recur :
1039                         __bpf_prog_exit_recur;
1040
1041         if (resolve_prog_type(prog) == BPF_PROG_TYPE_LSM &&
1042             prog->expected_attach_type == BPF_LSM_CGROUP)
1043                 return __bpf_prog_exit_lsm_cgroup;
1044
1045         return sleepable ? __bpf_prog_exit_sleepable : __bpf_prog_exit;
1046 }
1047
1048 int __weak
1049 arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *image_end,
1050                             const struct btf_func_model *m, u32 flags,
1051                             struct bpf_tramp_links *tlinks,
1052                             void *func_addr)
1053 {
1054         return -ENOTSUPP;
1055 }
1056
1057 void * __weak arch_alloc_bpf_trampoline(unsigned int size)
1058 {
1059         void *image;
1060
1061         if (WARN_ON_ONCE(size > PAGE_SIZE))
1062                 return NULL;
1063         image = bpf_jit_alloc_exec(PAGE_SIZE);
1064         if (image)
1065                 set_vm_flush_reset_perms(image);
1066         return image;
1067 }
1068
1069 void __weak arch_free_bpf_trampoline(void *image, unsigned int size)
1070 {
1071         WARN_ON_ONCE(size > PAGE_SIZE);
1072         /* bpf_jit_free_exec doesn't need "size", but
1073          * bpf_prog_pack_free() needs it.
1074          */
1075         bpf_jit_free_exec(image);
1076 }
1077
1078 int __weak arch_protect_bpf_trampoline(void *image, unsigned int size)
1079 {
1080         WARN_ON_ONCE(size > PAGE_SIZE);
1081         return set_memory_rox((long)image, 1);
1082 }
1083
1084 int __weak arch_bpf_trampoline_size(const struct btf_func_model *m, u32 flags,
1085                                     struct bpf_tramp_links *tlinks, void *func_addr)
1086 {
1087         return -ENOTSUPP;
1088 }
1089
1090 static int __init init_trampolines(void)
1091 {
1092         int i;
1093
1094         for (i = 0; i < TRAMPOLINE_TABLE_SIZE; i++)
1095                 INIT_HLIST_HEAD(&trampoline_table[i]);
1096         return 0;
1097 }
1098 late_initcall(init_trampolines);