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, struct bpf_ksym *ksym)
 119 {
 120         ksym->start = (unsigned long) data;
 121         ksym->end = ksym->start + PAGE_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         bpf_jit_free_exec(im->image);
 258         bpf_jit_uncharge_modmem(PAGE_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)
 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(PAGE_SIZE);
 364         if (err)
 365                 goto out_free_im;
 366
 367         err = -ENOMEM;
 368         im->image = image = bpf_jit_alloc_exec(PAGE_SIZE);
 369         if (!image)
 370                 goto out_uncharge;
 371         set_vm_flush_reset_perms(image);
 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, ksym);
 381         return im;
 382
 383 out_free_image:
 384         bpf_jit_free_exec(im->image);
 385 out_uncharge:
 386         bpf_jit_uncharge_modmem(PAGE_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;
 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         im = bpf_tramp_image_alloc(tr->key);
 413         if (IS_ERR(im)) {
 414                 err = PTR_ERR(im);
 415                 goto out;
 416         }
 417
 418         /* clear all bits except SHARE_IPMODIFY */
 419         tr->flags &= BPF_TRAMP_F_SHARE_IPMODIFY;
 420
 421         if (tlinks[BPF_TRAMP_FEXIT].nr_links ||
 422             tlinks[BPF_TRAMP_MODIFY_RETURN].nr_links) {
 423                 /* NOTE: BPF_TRAMP_F_RESTORE_REGS and BPF_TRAMP_F_SKIP_FRAME
 424                  * should not be set together.
 425                  */
 426                 tr->flags |= BPF_TRAMP_F_CALL_ORIG | BPF_TRAMP_F_SKIP_FRAME;
 427         } else {
 428                 tr->flags |= BPF_TRAMP_F_RESTORE_REGS;
 429         }
 430
 431         if (ip_arg)
 432                 tr->flags |= BPF_TRAMP_F_IP_ARG;
 433
 434 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
 435 again:
 436         if ((tr->flags & BPF_TRAMP_F_SHARE_IPMODIFY) &&
 437             (tr->flags & BPF_TRAMP_F_CALL_ORIG))
 438                 tr->flags |= BPF_TRAMP_F_ORIG_STACK;
 439 #endif
 440
 441         err = arch_prepare_bpf_trampoline(im, im->image, im->image + PAGE_SIZE,
 442                                           &tr->func.model, tr->flags, tlinks,
 443                                           tr->func.addr);
 444         if (err < 0)
 445                 goto out_free;
 446
 447         set_memory_rox((long)im->image, 1);
 448
 449         WARN_ON(tr->cur_image && total == 0);
 450         if (tr->cur_image)
 451                 /* progs already running at this address */
 452                 err = modify_fentry(tr, tr->cur_image->image, im->image, lock_direct_mutex);
 453         else
 454                 /* first time registering */
 455                 err = register_fentry(tr, im->image);
 456
 457 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
 458         if (err == -EAGAIN) {
 459                 /* -EAGAIN from bpf_tramp_ftrace_ops_func. Now
 460                  * BPF_TRAMP_F_SHARE_IPMODIFY is set, we can generate the
 461                  * trampoline again, and retry register.
 462                  */
 463                 /* reset fops->func and fops->trampoline for re-register */
 464                 tr->fops->func = NULL;
 465                 tr->fops->trampoline = 0;
 466
 467                 /* reset im->image memory attr for arch_prepare_bpf_trampoline */
 468                 set_memory_nx((long)im->image, 1);
 469                 set_memory_rw((long)im->image, 1);
 470                 goto again;
 471         }
 472 #endif
 473         if (err)
 474                 goto out_free;
 475
 476         if (tr->cur_image)
 477                 bpf_tramp_image_put(tr->cur_image);
 478         tr->cur_image = im;
 479 out:
 480         /* If any error happens, restore previous flags */
 481         if (err)
 482                 tr->flags = orig_flags;
 483         kfree(tlinks);
 484         return err;
 485
 486 out_free:
 487         bpf_tramp_image_free(im);
 488         goto out;
 489 }
 490
 491 static enum bpf_tramp_prog_type bpf_attach_type_to_tramp(struct bpf_prog *prog)
 492 {
 493         switch (prog->expected_attach_type) {
 494         case BPF_TRACE_FENTRY:
 495                 return BPF_TRAMP_FENTRY;
 496         case BPF_MODIFY_RETURN:
 497                 return BPF_TRAMP_MODIFY_RETURN;
 498         case BPF_TRACE_FEXIT:
 499                 return BPF_TRAMP_FEXIT;
 500         case BPF_LSM_MAC:
 501                 if (!prog->aux->attach_func_proto->type)
 502                         /* The function returns void, we cannot modify its
 503                          * return value.
 504                          */
 505                         return BPF_TRAMP_FEXIT;
 506                 else
 507                         return BPF_TRAMP_MODIFY_RETURN;
 508         default:
 509                 return BPF_TRAMP_REPLACE;
 510         }
 511 }
 512
 513 static int __bpf_trampoline_link_prog(struct bpf_tramp_link *link, struct bpf_trampoline *tr)
 514 {
 515         enum bpf_tramp_prog_type kind;
 516         struct bpf_tramp_link *link_exiting;
 517         int err = 0;
 518         int cnt = 0, i;
 519
 520         kind = bpf_attach_type_to_tramp(link->link.prog);
 521         if (tr->extension_prog)
 522                 /* cannot attach fentry/fexit if extension prog is attached.
 523                  * cannot overwrite extension prog either.
 524                  */
 525                 return -EBUSY;
 526
 527         for (i = 0; i < BPF_TRAMP_MAX; i++)
 528                 cnt += tr->progs_cnt[i];
 529
 530         if (kind == BPF_TRAMP_REPLACE) {
 531                 /* Cannot attach extension if fentry/fexit are in use. */
 532                 if (cnt)
 533                         return -EBUSY;
 534                 tr->extension_prog = link->link.prog;
 535                 return bpf_arch_text_poke(tr->func.addr, BPF_MOD_JUMP, NULL,
 536                                           link->link.prog->bpf_func);
 537         }
 538         if (cnt >= BPF_MAX_TRAMP_LINKS)
 539                 return -E2BIG;
 540         if (!hlist_unhashed(&link->tramp_hlist))
 541                 /* prog already linked */
 542                 return -EBUSY;
 543         hlist_for_each_entry(link_exiting, &tr->progs_hlist[kind], tramp_hlist) {
 544                 if (link_exiting->link.prog != link->link.prog)
 545                         continue;
 546                 /* prog already linked */
 547                 return -EBUSY;
 548         }
 549
 550         hlist_add_head(&link->tramp_hlist, &tr->progs_hlist[kind]);
 551         tr->progs_cnt[kind]++;
 552         err = bpf_trampoline_update(tr, true /* lock_direct_mutex */);
 553         if (err) {
 554                 hlist_del_init(&link->tramp_hlist);
 555                 tr->progs_cnt[kind]--;
 556         }
 557         return err;
 558 }
 559
 560 int bpf_trampoline_link_prog(struct bpf_tramp_link *link, struct bpf_trampoline *tr)
 561 {
 562         int err;
 563
 564         mutex_lock(&tr->mutex);
 565         err = __bpf_trampoline_link_prog(link, tr);
 566         mutex_unlock(&tr->mutex);
 567         return err;
 568 }
 569
 570 static int __bpf_trampoline_unlink_prog(struct bpf_tramp_link *link, struct bpf_trampoline *tr)
 571 {
 572         enum bpf_tramp_prog_type kind;
 573         int err;
 574
 575         kind = bpf_attach_type_to_tramp(link->link.prog);
 576         if (kind == BPF_TRAMP_REPLACE) {
 577                 WARN_ON_ONCE(!tr->extension_prog);
 578                 err = bpf_arch_text_poke(tr->func.addr, BPF_MOD_JUMP,
 579                                          tr->extension_prog->bpf_func, NULL);
 580                 tr->extension_prog = NULL;
 581                 return err;
 582         }
 583         hlist_del_init(&link->tramp_hlist);
 584         tr->progs_cnt[kind]--;
 585         return bpf_trampoline_update(tr, true /* lock_direct_mutex */);
 586 }
 587
 588 /* bpf_trampoline_unlink_prog() should never fail. */
 589 int bpf_trampoline_unlink_prog(struct bpf_tramp_link *link, struct bpf_trampoline *tr)
 590 {
 591         int err;
 592
 593         mutex_lock(&tr->mutex);
 594         err = __bpf_trampoline_unlink_prog(link, tr);
 595         mutex_unlock(&tr->mutex);
 596         return err;
 597 }
 598
 599 #if defined(CONFIG_CGROUP_BPF) && defined(CONFIG_BPF_LSM)
 600 static void bpf_shim_tramp_link_release(struct bpf_link *link)
 601 {
 602         struct bpf_shim_tramp_link *shim_link =
 603                 container_of(link, struct bpf_shim_tramp_link, link.link);
 604
 605         /* paired with 'shim_link->trampoline = tr' in bpf_trampoline_link_cgroup_shim */
 606         if (!shim_link->trampoline)
 607                 return;
 608
 609         WARN_ON_ONCE(bpf_trampoline_unlink_prog(&shim_link->link, shim_link->trampoline));
 610         bpf_trampoline_put(shim_link->trampoline);
 611 }
 612
 613 static void bpf_shim_tramp_link_dealloc(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         kfree(shim_link);
 619 }
 620
 621 static const struct bpf_link_ops bpf_shim_tramp_link_lops = {
 622         .release = bpf_shim_tramp_link_release,
 623         .dealloc = bpf_shim_tramp_link_dealloc,
 624 };
 625
 626 static struct bpf_shim_tramp_link *cgroup_shim_alloc(const struct bpf_prog *prog,
 627                                                      bpf_func_t bpf_func,
 628                                                      int cgroup_atype)
 629 {
 630         struct bpf_shim_tramp_link *shim_link = NULL;
 631         struct bpf_prog *p;
 632
 633         shim_link = kzalloc(sizeof(*shim_link), GFP_USER);
 634         if (!shim_link)
 635                 return NULL;
 636
 637         p = bpf_prog_alloc(1, 0);
 638         if (!p) {
 639                 kfree(shim_link);
 640                 return NULL;
 641         }
 642
 643         p->jited = false;
 644         p->bpf_func = bpf_func;
 645
 646         p->aux->cgroup_atype = cgroup_atype;
 647         p->aux->attach_func_proto = prog->aux->attach_func_proto;
 648         p->aux->attach_btf_id = prog->aux->attach_btf_id;
 649         p->aux->attach_btf = prog->aux->attach_btf;
 650         btf_get(p->aux->attach_btf);
 651         p->type = BPF_PROG_TYPE_LSM;
 652         p->expected_attach_type = BPF_LSM_MAC;
 653         bpf_prog_inc(p);
 654         bpf_link_init(&shim_link->link.link, BPF_LINK_TYPE_UNSPEC,
 655                       &bpf_shim_tramp_link_lops, p);
 656         bpf_cgroup_atype_get(p->aux->attach_btf_id, cgroup_atype);
 657
 658         return shim_link;
 659 }
 660
 661 static struct bpf_shim_tramp_link *cgroup_shim_find(struct bpf_trampoline *tr,
 662                                                     bpf_func_t bpf_func)
 663 {
 664         struct bpf_tramp_link *link;
 665         int kind;
 666
 667         for (kind = 0; kind < BPF_TRAMP_MAX; kind++) {
 668                 hlist_for_each_entry(link, &tr->progs_hlist[kind], tramp_hlist) {
 669                         struct bpf_prog *p = link->link.prog;
 670
 671                         if (p->bpf_func == bpf_func)
 672                                 return container_of(link, struct bpf_shim_tramp_link, link);
 673                 }
 674         }
 675
 676         return NULL;
 677 }
 678
 679 int bpf_trampoline_link_cgroup_shim(struct bpf_prog *prog,
 680                                     int cgroup_atype)
 681 {
 682         struct bpf_shim_tramp_link *shim_link = NULL;
 683         struct bpf_attach_target_info tgt_info = {};
 684         struct bpf_trampoline *tr;
 685         bpf_func_t bpf_func;
 686         u64 key;
 687         int err;
 688
 689         err = bpf_check_attach_target(NULL, prog, NULL,
 690                                       prog->aux->attach_btf_id,
 691                                       &tgt_info);
 692         if (err)
 693                 return err;
 694
 695         key = bpf_trampoline_compute_key(NULL, prog->aux->attach_btf,
 696                                          prog->aux->attach_btf_id);
 697
 698         bpf_lsm_find_cgroup_shim(prog, &bpf_func);
 699         tr = bpf_trampoline_get(key, &tgt_info);
 700         if (!tr)
 701                 return  -ENOMEM;
 702
 703         mutex_lock(&tr->mutex);
 704
 705         shim_link = cgroup_shim_find(tr, bpf_func);
 706         if (shim_link) {
 707                 /* Reusing existing shim attached by the other program. */
 708                 bpf_link_inc(&shim_link->link.link);
 709
 710                 mutex_unlock(&tr->mutex);
 711                 bpf_trampoline_put(tr); /* bpf_trampoline_get above */
 712                 return 0;
 713         }
 714
 715         /* Allocate and install new shim. */
 716
 717         shim_link = cgroup_shim_alloc(prog, bpf_func, cgroup_atype);
 718         if (!shim_link) {
 719                 err = -ENOMEM;
 720                 goto err;
 721         }
 722
 723         err = __bpf_trampoline_link_prog(&shim_link->link, tr);
 724         if (err)
 725                 goto err;
 726
 727         shim_link->trampoline = tr;
 728         /* note, we're still holding tr refcnt from above */
 729
 730         mutex_unlock(&tr->mutex);
 731
 732         return 0;
 733 err:
 734         mutex_unlock(&tr->mutex);
 735
 736         if (shim_link)
 737                 bpf_link_put(&shim_link->link.link);
 738
 739         /* have to release tr while _not_ holding its mutex */
 740         bpf_trampoline_put(tr); /* bpf_trampoline_get above */
 741
 742         return err;
 743 }
 744
 745 void bpf_trampoline_unlink_cgroup_shim(struct bpf_prog *prog)
 746 {
 747         struct bpf_shim_tramp_link *shim_link = NULL;
 748         struct bpf_trampoline *tr;
 749         bpf_func_t bpf_func;
 750         u64 key;
 751
 752         key = bpf_trampoline_compute_key(NULL, prog->aux->attach_btf,
 753                                          prog->aux->attach_btf_id);
 754
 755         bpf_lsm_find_cgroup_shim(prog, &bpf_func);
 756         tr = bpf_trampoline_lookup(key);
 757         if (WARN_ON_ONCE(!tr))
 758                 return;
 759
 760         mutex_lock(&tr->mutex);
 761         shim_link = cgroup_shim_find(tr, bpf_func);
 762         mutex_unlock(&tr->mutex);
 763
 764         if (shim_link)
 765                 bpf_link_put(&shim_link->link.link);
 766
 767         bpf_trampoline_put(tr); /* bpf_trampoline_lookup above */
 768 }
 769 #endif
 770
 771 struct bpf_trampoline *bpf_trampoline_get(u64 key,
 772                                           struct bpf_attach_target_info *tgt_info)
 773 {
 774         struct bpf_trampoline *tr;
 775
 776         tr = bpf_trampoline_lookup(key);
 777         if (!tr)
 778                 return NULL;
 779
 780         mutex_lock(&tr->mutex);
 781         if (tr->func.addr)
 782                 goto out;
 783
 784         memcpy(&tr->func.model, &tgt_info->fmodel, sizeof(tgt_info->fmodel));
 785         tr->func.addr = (void *)tgt_info->tgt_addr;
 786 out:
 787         mutex_unlock(&tr->mutex);
 788         return tr;
 789 }
 790
 791 void bpf_trampoline_put(struct bpf_trampoline *tr)
 792 {
 793         int i;
 794
 795         if (!tr)
 796                 return;
 797         mutex_lock(&trampoline_mutex);
 798         if (!refcount_dec_and_test(&tr->refcnt))
 799                 goto out;
 800         WARN_ON_ONCE(mutex_is_locked(&tr->mutex));
 801
 802         for (i = 0; i < BPF_TRAMP_MAX; i++)
 803                 if (WARN_ON_ONCE(!hlist_empty(&tr->progs_hlist[i])))
 804                         goto out;
 805
 806         /* This code will be executed even when the last bpf_tramp_image
 807          * is alive. All progs are detached from the trampoline and the
 808          * trampoline image is patched with jmp into epilogue to skip
 809          * fexit progs. The fentry-only trampoline will be freed via
 810          * multiple rcu callbacks.
 811          */
 812         hlist_del(&tr->hlist);
 813         if (tr->fops) {
 814                 ftrace_free_filter(tr->fops);
 815                 kfree(tr->fops);
 816         }
 817         kfree(tr);
 818 out:
 819         mutex_unlock(&trampoline_mutex);
 820 }
 821
 822 #define NO_START_TIME 1
 823 static __always_inline u64 notrace bpf_prog_start_time(void)
 824 {
 825         u64 start = NO_START_TIME;
 826
 827         if (static_branch_unlikely(&bpf_stats_enabled_key)) {
 828                 start = sched_clock();
 829                 if (unlikely(!start))
 830                         start = NO_START_TIME;
 831         }
 832         return start;
 833 }
 834
 835 /* The logic is similar to bpf_prog_run(), but with an explicit
 836  * rcu_read_lock() and migrate_disable() which are required
 837  * for the trampoline. The macro is split into
 838  * call __bpf_prog_enter
 839  * call prog->bpf_func
 840  * call __bpf_prog_exit
 841  *
 842  * __bpf_prog_enter returns:
 843  * 0 - skip execution of the bpf prog
 844  * 1 - execute bpf prog
 845  * [2..MAX_U64] - execute bpf prog and record execution time.
 846  *     This is start time.
 847  */
 848 static u64 notrace __bpf_prog_enter_recur(struct bpf_prog *prog, struct bpf_tramp_run_ctx *run_ctx)
 849         __acquires(RCU)
 850 {
 851         rcu_read_lock();
 852         migrate_disable();
 853
 854         run_ctx->saved_run_ctx = bpf_set_run_ctx(&run_ctx->run_ctx);
 855
 856         if (unlikely(this_cpu_inc_return(*(prog->active)) != 1)) {
 857                 bpf_prog_inc_misses_counter(prog);
 858                 return 0;
 859         }
 860         return bpf_prog_start_time();
 861 }
 862
 863 static void notrace update_prog_stats(struct bpf_prog *prog,
 864                                       u64 start)
 865 {
 866         struct bpf_prog_stats *stats;
 867
 868         if (static_branch_unlikely(&bpf_stats_enabled_key) &&
 869             /* static_key could be enabled in __bpf_prog_enter*
 870              * and disabled in __bpf_prog_exit*.
 871              * And vice versa.
 872              * Hence check that 'start' is valid.
 873              */
 874             start > NO_START_TIME) {
 875                 unsigned long flags;
 876
 877                 stats = this_cpu_ptr(prog->stats);
 878                 flags = u64_stats_update_begin_irqsave(&stats->syncp);
 879                 u64_stats_inc(&stats->cnt);
 880                 u64_stats_add(&stats->nsecs, sched_clock() - start);
 881                 u64_stats_update_end_irqrestore(&stats->syncp, flags);
 882         }
 883 }
 884
 885 static void notrace __bpf_prog_exit_recur(struct bpf_prog *prog, u64 start,
 886                                           struct bpf_tramp_run_ctx *run_ctx)
 887         __releases(RCU)
 888 {
 889         bpf_reset_run_ctx(run_ctx->saved_run_ctx);
 890
 891         update_prog_stats(prog, start);
 892         this_cpu_dec(*(prog->active));
 893         migrate_enable();
 894         rcu_read_unlock();
 895 }
 896
 897 static u64 notrace __bpf_prog_enter_lsm_cgroup(struct bpf_prog *prog,
 898                                                struct bpf_tramp_run_ctx *run_ctx)
 899         __acquires(RCU)
 900 {
 901         /* Runtime stats are exported via actual BPF_LSM_CGROUP
 902          * programs, not the shims.
 903          */
 904         rcu_read_lock();
 905         migrate_disable();
 906
 907         run_ctx->saved_run_ctx = bpf_set_run_ctx(&run_ctx->run_ctx);
 908
 909         return NO_START_TIME;
 910 }
 911
 912 static void notrace __bpf_prog_exit_lsm_cgroup(struct bpf_prog *prog, u64 start,
 913                                                struct bpf_tramp_run_ctx *run_ctx)
 914         __releases(RCU)
 915 {
 916         bpf_reset_run_ctx(run_ctx->saved_run_ctx);
 917
 918         migrate_enable();
 919         rcu_read_unlock();
 920 }
 921
 922 u64 notrace __bpf_prog_enter_sleepable_recur(struct bpf_prog *prog,
 923                                              struct bpf_tramp_run_ctx *run_ctx)
 924 {
 925         rcu_read_lock_trace();
 926         migrate_disable();
 927         might_fault();
 928
 929         run_ctx->saved_run_ctx = bpf_set_run_ctx(&run_ctx->run_ctx);
 930
 931         if (unlikely(this_cpu_inc_return(*(prog->active)) != 1)) {
 932                 bpf_prog_inc_misses_counter(prog);
 933                 return 0;
 934         }
 935         return bpf_prog_start_time();
 936 }
 937
 938 void notrace __bpf_prog_exit_sleepable_recur(struct bpf_prog *prog, u64 start,
 939                                              struct bpf_tramp_run_ctx *run_ctx)
 940 {
 941         bpf_reset_run_ctx(run_ctx->saved_run_ctx);
 942
 943         update_prog_stats(prog, start);
 944         this_cpu_dec(*(prog->active));
 945         migrate_enable();
 946         rcu_read_unlock_trace();
 947 }
 948
 949 static u64 notrace __bpf_prog_enter_sleepable(struct bpf_prog *prog,
 950                                               struct bpf_tramp_run_ctx *run_ctx)
 951 {
 952         rcu_read_lock_trace();
 953         migrate_disable();
 954         might_fault();
 955
 956         run_ctx->saved_run_ctx = bpf_set_run_ctx(&run_ctx->run_ctx);
 957
 958         return bpf_prog_start_time();
 959 }
 960
 961 static void notrace __bpf_prog_exit_sleepable(struct bpf_prog *prog, u64 start,
 962                                               struct bpf_tramp_run_ctx *run_ctx)
 963 {
 964         bpf_reset_run_ctx(run_ctx->saved_run_ctx);
 965
 966         update_prog_stats(prog, start);
 967         migrate_enable();
 968         rcu_read_unlock_trace();
 969 }
 970
 971 static u64 notrace __bpf_prog_enter(struct bpf_prog *prog,
 972                                     struct bpf_tramp_run_ctx *run_ctx)
 973         __acquires(RCU)
 974 {
 975         rcu_read_lock();
 976         migrate_disable();
 977
 978         run_ctx->saved_run_ctx = bpf_set_run_ctx(&run_ctx->run_ctx);
 979
 980         return bpf_prog_start_time();
 981 }
 982
 983 static void notrace __bpf_prog_exit(struct bpf_prog *prog, u64 start,
 984                                     struct bpf_tramp_run_ctx *run_ctx)
 985         __releases(RCU)
 986 {
 987         bpf_reset_run_ctx(run_ctx->saved_run_ctx);
 988
 989         update_prog_stats(prog, start);
 990         migrate_enable();
 991         rcu_read_unlock();
 992 }
 993
 994 void notrace __bpf_tramp_enter(struct bpf_tramp_image *tr)
 995 {
 996         percpu_ref_get(&tr->pcref);
 997 }
 998
 999 void notrace __bpf_tramp_exit(struct bpf_tramp_image *tr)
1000 {
1001         percpu_ref_put(&tr->pcref);
1002 }
1003
1004 bpf_trampoline_enter_t bpf_trampoline_enter(const struct bpf_prog *prog)
1005 {
1006         bool sleepable = prog->aux->sleepable;
1007
1008         if (bpf_prog_check_recur(prog))
1009                 return sleepable ? __bpf_prog_enter_sleepable_recur :
1010                         __bpf_prog_enter_recur;
1011
1012         if (resolve_prog_type(prog) == BPF_PROG_TYPE_LSM &&
1013             prog->expected_attach_type == BPF_LSM_CGROUP)
1014                 return __bpf_prog_enter_lsm_cgroup;
1015
1016         return sleepable ? __bpf_prog_enter_sleepable : __bpf_prog_enter;
1017 }
1018
1019 bpf_trampoline_exit_t bpf_trampoline_exit(const struct bpf_prog *prog)
1020 {
1021         bool sleepable = prog->aux->sleepable;
1022
1023         if (bpf_prog_check_recur(prog))
1024                 return sleepable ? __bpf_prog_exit_sleepable_recur :
1025                         __bpf_prog_exit_recur;
1026
1027         if (resolve_prog_type(prog) == BPF_PROG_TYPE_LSM &&
1028             prog->expected_attach_type == BPF_LSM_CGROUP)
1029                 return __bpf_prog_exit_lsm_cgroup;
1030
1031         return sleepable ? __bpf_prog_exit_sleepable : __bpf_prog_exit;
1032 }
1033
1034 int __weak
1035 arch_prepare_bpf_trampoline(struct bpf_tramp_image *tr, void *image, void *image_end,
1036                             const struct btf_func_model *m, u32 flags,
1037                             struct bpf_tramp_links *tlinks,
1038                             void *orig_call)
1039 {
1040         return -ENOTSUPP;
1041 }
1042
1043 static int __init init_trampolines(void)
1044 {
1045         int i;
1046
1047         for (i = 0; i < TRAMPOLINE_TABLE_SIZE; i++)
1048                 INIT_HLIST_HEAD(&trampoline_table[i]);
1049         return 0;
1050 }
1051 late_initcall(init_trampolines);