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/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         kfree(tr->fops);
 845         kfree(tr);
 846 out:
 847         mutex_unlock(&trampoline_mutex);
 848 }
 849
 850 #define NO_START_TIME 1
 851 static __always_inline u64 notrace bpf_prog_start_time(void)
 852 {
 853         u64 start = NO_START_TIME;
 854
 855         if (static_branch_unlikely(&bpf_stats_enabled_key)) {
 856                 start = sched_clock();
 857                 if (unlikely(!start))
 858                         start = NO_START_TIME;
 859         }
 860         return start;
 861 }
 862
 863 static void notrace inc_misses_counter(struct bpf_prog *prog)
 864 {
 865         struct bpf_prog_stats *stats;
 866         unsigned int flags;
 867
 868         stats = this_cpu_ptr(prog->stats);
 869         flags = u64_stats_update_begin_irqsave(&stats->syncp);
 870         u64_stats_inc(&stats->misses);
 871         u64_stats_update_end_irqrestore(&stats->syncp, flags);
 872 }
 873
 874 /* The logic is similar to bpf_prog_run(), but with an explicit
 875  * rcu_read_lock() and migrate_disable() which are required
 876  * for the trampoline. The macro is split into
 877  * call __bpf_prog_enter
 878  * call prog->bpf_func
 879  * call __bpf_prog_exit
 880  *
 881  * __bpf_prog_enter returns:
 882  * 0 - skip execution of the bpf prog
 883  * 1 - execute bpf prog
 884  * [2..MAX_U64] - execute bpf prog and record execution time.
 885  *     This is start time.
 886  */
 887 u64 notrace __bpf_prog_enter(struct bpf_prog *prog, struct bpf_tramp_run_ctx *run_ctx)
 888         __acquires(RCU)
 889 {
 890         rcu_read_lock();
 891         migrate_disable();
 892
 893         run_ctx->saved_run_ctx = bpf_set_run_ctx(&run_ctx->run_ctx);
 894
 895         if (unlikely(__this_cpu_inc_return(*(prog->active)) != 1)) {
 896                 inc_misses_counter(prog);
 897                 return 0;
 898         }
 899         return bpf_prog_start_time();
 900 }
 901
 902 static void notrace update_prog_stats(struct bpf_prog *prog,
 903                                       u64 start)
 904 {
 905         struct bpf_prog_stats *stats;
 906
 907         if (static_branch_unlikely(&bpf_stats_enabled_key) &&
 908             /* static_key could be enabled in __bpf_prog_enter*
 909              * and disabled in __bpf_prog_exit*.
 910              * And vice versa.
 911              * Hence check that 'start' is valid.
 912              */
 913             start > NO_START_TIME) {
 914                 unsigned long flags;
 915
 916                 stats = this_cpu_ptr(prog->stats);
 917                 flags = u64_stats_update_begin_irqsave(&stats->syncp);
 918                 u64_stats_inc(&stats->cnt);
 919                 u64_stats_add(&stats->nsecs, sched_clock() - start);
 920                 u64_stats_update_end_irqrestore(&stats->syncp, flags);
 921         }
 922 }
 923
 924 void notrace __bpf_prog_exit(struct bpf_prog *prog, u64 start, struct bpf_tramp_run_ctx *run_ctx)
 925         __releases(RCU)
 926 {
 927         bpf_reset_run_ctx(run_ctx->saved_run_ctx);
 928
 929         update_prog_stats(prog, start);
 930         __this_cpu_dec(*(prog->active));
 931         migrate_enable();
 932         rcu_read_unlock();
 933 }
 934
 935 u64 notrace __bpf_prog_enter_lsm_cgroup(struct bpf_prog *prog,
 936                                         struct bpf_tramp_run_ctx *run_ctx)
 937         __acquires(RCU)
 938 {
 939         /* Runtime stats are exported via actual BPF_LSM_CGROUP
 940          * programs, not the shims.
 941          */
 942         rcu_read_lock();
 943         migrate_disable();
 944
 945         run_ctx->saved_run_ctx = bpf_set_run_ctx(&run_ctx->run_ctx);
 946
 947         return NO_START_TIME;
 948 }
 949
 950 void notrace __bpf_prog_exit_lsm_cgroup(struct bpf_prog *prog, u64 start,
 951                                         struct bpf_tramp_run_ctx *run_ctx)
 952         __releases(RCU)
 953 {
 954         bpf_reset_run_ctx(run_ctx->saved_run_ctx);
 955
 956         migrate_enable();
 957         rcu_read_unlock();
 958 }
 959
 960 u64 notrace __bpf_prog_enter_sleepable(struct bpf_prog *prog, struct bpf_tramp_run_ctx *run_ctx)
 961 {
 962         rcu_read_lock_trace();
 963         migrate_disable();
 964         might_fault();
 965
 966         if (unlikely(__this_cpu_inc_return(*(prog->active)) != 1)) {
 967                 inc_misses_counter(prog);
 968                 return 0;
 969         }
 970
 971         run_ctx->saved_run_ctx = bpf_set_run_ctx(&run_ctx->run_ctx);
 972
 973         return bpf_prog_start_time();
 974 }
 975
 976 void notrace __bpf_prog_exit_sleepable(struct bpf_prog *prog, u64 start,
 977                                        struct bpf_tramp_run_ctx *run_ctx)
 978 {
 979         bpf_reset_run_ctx(run_ctx->saved_run_ctx);
 980
 981         update_prog_stats(prog, start);
 982         __this_cpu_dec(*(prog->active));
 983         migrate_enable();
 984         rcu_read_unlock_trace();
 985 }
 986
 987 void notrace __bpf_tramp_enter(struct bpf_tramp_image *tr)
 988 {
 989         percpu_ref_get(&tr->pcref);
 990 }
 991
 992 void notrace __bpf_tramp_exit(struct bpf_tramp_image *tr)
 993 {
 994         percpu_ref_put(&tr->pcref);
 995 }
 996
 997 int __weak
 998 arch_prepare_bpf_trampoline(struct bpf_tramp_image *tr, void *image, void *image_end,
 999                             const struct btf_func_model *m, u32 flags,
1000                             struct bpf_tramp_links *tlinks,
1001                             void *orig_call)
1002 {
1003         return -ENOTSUPP;
1004 }
1005
1006 static int __init init_trampolines(void)
1007 {
1008         int i;
1009
1010         for (i = 0; i < TRAMPOLINE_TABLE_SIZE; i++)
1011                 INIT_HLIST_HEAD(&trampoline_table[i]);
1012         return 0;
1013 }
1014 late_initcall(init_trampolines);