kernel/kprobes.c

   1 /*
   2  *  Kernel Probes (KProbes)
   3  *  kernel/kprobes.c
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License
  16  * along with this program; if not, write to the Free Software
  17  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  18  *
  19  * Copyright (C) IBM Corporation, 2002, 2004
  20  *
  21  * 2002-Oct     Created by Vamsi Krishna S <vamsi_krishna@in.ibm.com> Kernel
  22  *              Probes initial implementation (includes suggestions from
  23  *              Rusty Russell).
  24  * 2004-Aug     Updated by Prasanna S Panchamukhi <prasanna@in.ibm.com> with
  25  *              hlists and exceptions notifier as suggested by Andi Kleen.
  26  * 2004-July    Suparna Bhattacharya <suparna@in.ibm.com> added jumper probes
  27  *              interface to access function arguments.
  28  * 2004-Sep     Prasanna S Panchamukhi <prasanna@in.ibm.com> Changed Kprobes
  29  *              exceptions notifier to be first on the priority list.
  30  * 2005-May     Hien Nguyen <hien@us.ibm.com>, Jim Keniston
  31  *              <jkenisto@us.ibm.com> and Prasanna S Panchamukhi
  32  *              <prasanna@in.ibm.com> added function-return probes.
  33  */
  34 #include <linux/kprobes.h>
  35 #include <linux/hash.h>
  36 #include <linux/init.h>
  37 #include <linux/slab.h>
  38 #include <linux/module.h>
  39 #include <linux/moduleloader.h>
  40 #include <asm-generic/sections.h>
  41 #include <asm/cacheflush.h>
  42 #include <asm/errno.h>
  43 #include <asm/kdebug.h>
  44
  45 #define KPROBE_HASH_BITS 6
  46 #define KPROBE_TABLE_SIZE (1 << KPROBE_HASH_BITS)
  47
  48 static struct hlist_head kprobe_table[KPROBE_TABLE_SIZE];
  49 static struct hlist_head kretprobe_inst_table[KPROBE_TABLE_SIZE];
  50
  51 DECLARE_MUTEX(kprobe_mutex);            /* Protects kprobe_table */
  52 DEFINE_SPINLOCK(kretprobe_lock);        /* Protects kretprobe_inst_table */
  53 static DEFINE_PER_CPU(struct kprobe *, kprobe_instance) = NULL;
  54
  55 #ifdef __ARCH_WANT_KPROBES_INSN_SLOT
  56 /*
  57  * kprobe->ainsn.insn points to the copy of the instruction to be
  58  * single-stepped. x86_64, POWER4 and above have no-exec support and
  59  * stepping on the instruction on a vmalloced/kmalloced/data page
  60  * is a recipe for disaster
  61  */
  62 #define INSNS_PER_PAGE  (PAGE_SIZE/(MAX_INSN_SIZE * sizeof(kprobe_opcode_t)))
  63
  64 struct kprobe_insn_page {
  65         struct hlist_node hlist;
  66         kprobe_opcode_t *insns;         /* Page of instruction slots */
  67         char slot_used[INSNS_PER_PAGE];
  68         int nused;
  69 };
  70
  71 static struct hlist_head kprobe_insn_pages;
  72
  73 /**
  74  * get_insn_slot() - Find a slot on an executable page for an instruction.
  75  * We allocate an executable page if there's no room on existing ones.
  76  */
  77 kprobe_opcode_t __kprobes *get_insn_slot(void)
  78 {
  79         struct kprobe_insn_page *kip;
  80         struct hlist_node *pos;
  81
  82         hlist_for_each(pos, &kprobe_insn_pages) {
  83                 kip = hlist_entry(pos, struct kprobe_insn_page, hlist);
  84                 if (kip->nused < INSNS_PER_PAGE) {
  85                         int i;
  86                         for (i = 0; i < INSNS_PER_PAGE; i++) {
  87                                 if (!kip->slot_used[i]) {
  88                                         kip->slot_used[i] = 1;
  89                                         kip->nused++;
  90                                         return kip->insns + (i * MAX_INSN_SIZE);
  91                                 }
  92                         }
  93                         /* Surprise!  No unused slots.  Fix kip->nused. */
  94                         kip->nused = INSNS_PER_PAGE;
  95                 }
  96         }
  97
  98         /* All out of space.  Need to allocate a new page. Use slot 0.*/
  99         kip = kmalloc(sizeof(struct kprobe_insn_page), GFP_KERNEL);
 100         if (!kip) {
 101                 return NULL;
 102         }
 103
 104         /*
 105          * Use module_alloc so this page is within +/- 2GB of where the
 106          * kernel image and loaded module images reside. This is required
 107          * so x86_64 can correctly handle the %rip-relative fixups.
 108          */
 109         kip->insns = module_alloc(PAGE_SIZE);
 110         if (!kip->insns) {
 111                 kfree(kip);
 112                 return NULL;
 113         }
 114         INIT_HLIST_NODE(&kip->hlist);
 115         hlist_add_head(&kip->hlist, &kprobe_insn_pages);
 116         memset(kip->slot_used, 0, INSNS_PER_PAGE);
 117         kip->slot_used[0] = 1;
 118         kip->nused = 1;
 119         return kip->insns;
 120 }
 121
 122 void __kprobes free_insn_slot(kprobe_opcode_t *slot)
 123 {
 124         struct kprobe_insn_page *kip;
 125         struct hlist_node *pos;
 126
 127         hlist_for_each(pos, &kprobe_insn_pages) {
 128                 kip = hlist_entry(pos, struct kprobe_insn_page, hlist);
 129                 if (kip->insns <= slot &&
 130                     slot < kip->insns + (INSNS_PER_PAGE * MAX_INSN_SIZE)) {
 131                         int i = (slot - kip->insns) / MAX_INSN_SIZE;
 132                         kip->slot_used[i] = 0;
 133                         kip->nused--;
 134                         if (kip->nused == 0) {
 135                                 /*
 136                                  * Page is no longer in use.  Free it unless
 137                                  * it's the last one.  We keep the last one
 138                                  * so as not to have to set it up again the
 139                                  * next time somebody inserts a probe.
 140                                  */
 141                                 hlist_del(&kip->hlist);
 142                                 if (hlist_empty(&kprobe_insn_pages)) {
 143                                         INIT_HLIST_NODE(&kip->hlist);
 144                                         hlist_add_head(&kip->hlist,
 145                                                 &kprobe_insn_pages);
 146                                 } else {
 147                                         module_free(NULL, kip->insns);
 148                                         kfree(kip);
 149                                 }
 150                         }
 151                         return;
 152                 }
 153         }
 154 }
 155 #endif
 156
 157 /* We have preemption disabled.. so it is safe to use __ versions */
 158 static inline void set_kprobe_instance(struct kprobe *kp)
 159 {
 160         __get_cpu_var(kprobe_instance) = kp;
 161 }
 162
 163 static inline void reset_kprobe_instance(void)
 164 {
 165         __get_cpu_var(kprobe_instance) = NULL;
 166 }
 167
 168 /*
 169  * This routine is called either:
 170  *      - under the kprobe_mutex - during kprobe_[un]register()
 171  *                              OR
 172  *      - with preemption disabled - from arch/xxx/kernel/kprobes.c
 173  */
 174 struct kprobe __kprobes *get_kprobe(void *addr)
 175 {
 176         struct hlist_head *head;
 177         struct hlist_node *node;
 178         struct kprobe *p;
 179
 180         head = &kprobe_table[hash_ptr(addr, KPROBE_HASH_BITS)];
 181         hlist_for_each_entry_rcu(p, node, head, hlist) {
 182                 if (p->addr == addr)
 183                         return p;
 184         }
 185         return NULL;
 186 }
 187
 188 /*
 189  * Aggregate handlers for multiple kprobes support - these handlers
 190  * take care of invoking the individual kprobe handlers on p->list
 191  */
 192 static int __kprobes aggr_pre_handler(struct kprobe *p, struct pt_regs *regs)
 193 {
 194         struct kprobe *kp;
 195
 196         list_for_each_entry_rcu(kp, &p->list, list) {
 197                 if (kp->pre_handler) {
 198                         set_kprobe_instance(kp);
 199                         if (kp->pre_handler(kp, regs))
 200                                 return 1;
 201                 }
 202                 reset_kprobe_instance();
 203         }
 204         return 0;
 205 }
 206
 207 static void __kprobes aggr_post_handler(struct kprobe *p, struct pt_regs *regs,
 208                                         unsigned long flags)
 209 {
 210         struct kprobe *kp;
 211
 212         list_for_each_entry_rcu(kp, &p->list, list) {
 213                 if (kp->post_handler) {
 214                         set_kprobe_instance(kp);
 215                         kp->post_handler(kp, regs, flags);
 216                         reset_kprobe_instance();
 217                 }
 218         }
 219         return;
 220 }
 221
 222 static int __kprobes aggr_fault_handler(struct kprobe *p, struct pt_regs *regs,
 223                                         int trapnr)
 224 {
 225         struct kprobe *cur = __get_cpu_var(kprobe_instance);
 226
 227         /*
 228          * if we faulted "during" the execution of a user specified
 229          * probe handler, invoke just that probe's fault handler
 230          */
 231         if (cur && cur->fault_handler) {
 232                 if (cur->fault_handler(cur, regs, trapnr))
 233                         return 1;
 234         }
 235         return 0;
 236 }
 237
 238 static int __kprobes aggr_break_handler(struct kprobe *p, struct pt_regs *regs)
 239 {
 240         struct kprobe *cur = __get_cpu_var(kprobe_instance);
 241         int ret = 0;
 242
 243         if (cur && cur->break_handler) {
 244                 if (cur->break_handler(cur, regs))
 245                         ret = 1;
 246         }
 247         reset_kprobe_instance();
 248         return ret;
 249 }
 250
 251 /* Walks the list and increments nmissed count for multiprobe case */
 252 void __kprobes kprobes_inc_nmissed_count(struct kprobe *p)
 253 {
 254         struct kprobe *kp;
 255         if (p->pre_handler != aggr_pre_handler) {
 256                 p->nmissed++;
 257         } else {
 258                 list_for_each_entry_rcu(kp, &p->list, list)
 259                         kp->nmissed++;
 260         }
 261         return;
 262 }
 263
 264 /* Called with kretprobe_lock held */
 265 struct kretprobe_instance __kprobes *get_free_rp_inst(struct kretprobe *rp)
 266 {
 267         struct hlist_node *node;
 268         struct kretprobe_instance *ri;
 269         hlist_for_each_entry(ri, node, &rp->free_instances, uflist)
 270                 return ri;
 271         return NULL;
 272 }
 273
 274 /* Called with kretprobe_lock held */
 275 static struct kretprobe_instance __kprobes *get_used_rp_inst(struct kretprobe
 276                                                               *rp)
 277 {
 278         struct hlist_node *node;
 279         struct kretprobe_instance *ri;
 280         hlist_for_each_entry(ri, node, &rp->used_instances, uflist)
 281                 return ri;
 282         return NULL;
 283 }
 284
 285 /* Called with kretprobe_lock held */
 286 void __kprobes add_rp_inst(struct kretprobe_instance *ri)
 287 {
 288         /*
 289          * Remove rp inst off the free list -
 290          * Add it back when probed function returns
 291          */
 292         hlist_del(&ri->uflist);
 293
 294         /* Add rp inst onto table */
 295         INIT_HLIST_NODE(&ri->hlist);
 296         hlist_add_head(&ri->hlist,
 297                         &kretprobe_inst_table[hash_ptr(ri->task, KPROBE_HASH_BITS)]);
 298
 299         /* Also add this rp inst to the used list. */
 300         INIT_HLIST_NODE(&ri->uflist);
 301         hlist_add_head(&ri->uflist, &ri->rp->used_instances);
 302 }
 303
 304 /* Called with kretprobe_lock held */
 305 void __kprobes recycle_rp_inst(struct kretprobe_instance *ri)
 306 {
 307         /* remove rp inst off the rprobe_inst_table */
 308         hlist_del(&ri->hlist);
 309         if (ri->rp) {
 310                 /* remove rp inst off the used list */
 311                 hlist_del(&ri->uflist);
 312                 /* put rp inst back onto the free list */
 313                 INIT_HLIST_NODE(&ri->uflist);
 314                 hlist_add_head(&ri->uflist, &ri->rp->free_instances);
 315         } else
 316                 /* Unregistering */
 317                 kfree(ri);
 318 }
 319
 320 struct hlist_head __kprobes *kretprobe_inst_table_head(struct task_struct *tsk)
 321 {
 322         return &kretprobe_inst_table[hash_ptr(tsk, KPROBE_HASH_BITS)];
 323 }
 324
 325 /*
 326  * This function is called from exit_thread or flush_thread when task tk's
 327  * stack is being recycled so that we can recycle any function-return probe
 328  * instances associated with this task. These left over instances represent
 329  * probed functions that have been called but will never return.
 330  */
 331 void __kprobes kprobe_flush_task(struct task_struct *tk)
 332 {
 333         struct kretprobe_instance *ri;
 334         struct hlist_head *head;
 335         struct hlist_node *node, *tmp;
 336         unsigned long flags = 0;
 337
 338         spin_lock_irqsave(&kretprobe_lock, flags);
 339         head = kretprobe_inst_table_head(current);
 340         hlist_for_each_entry_safe(ri, node, tmp, head, hlist) {
 341                 if (ri->task == tk)
 342                         recycle_rp_inst(ri);
 343         }
 344         spin_unlock_irqrestore(&kretprobe_lock, flags);
 345 }
 346
 347 static inline void free_rp_inst(struct kretprobe *rp)
 348 {
 349         struct kretprobe_instance *ri;
 350         while ((ri = get_free_rp_inst(rp)) != NULL) {
 351                 hlist_del(&ri->uflist);
 352                 kfree(ri);
 353         }
 354 }
 355
 356 /*
 357  * Keep all fields in the kprobe consistent
 358  */
 359 static inline void copy_kprobe(struct kprobe *old_p, struct kprobe *p)
 360 {
 361         memcpy(&p->opcode, &old_p->opcode, sizeof(kprobe_opcode_t));
 362         memcpy(&p->ainsn, &old_p->ainsn, sizeof(struct arch_specific_insn));
 363 }
 364
 365 /*
 366 * Add the new probe to old_p->list. Fail if this is the
 367 * second jprobe at the address - two jprobes can't coexist
 368 */
 369 static int __kprobes add_new_kprobe(struct kprobe *old_p, struct kprobe *p)
 370 {
 371         struct kprobe *kp;
 372
 373         if (p->break_handler) {
 374                 list_for_each_entry_rcu(kp, &old_p->list, list) {
 375                         if (kp->break_handler)
 376                                 return -EEXIST;
 377                 }
 378                 list_add_tail_rcu(&p->list, &old_p->list);
 379         } else
 380                 list_add_rcu(&p->list, &old_p->list);
 381         return 0;
 382 }
 383
 384 /*
 385  * Fill in the required fields of the "manager kprobe". Replace the
 386  * earlier kprobe in the hlist with the manager kprobe
 387  */
 388 static inline void add_aggr_kprobe(struct kprobe *ap, struct kprobe *p)
 389 {
 390         copy_kprobe(p, ap);
 391         ap->addr = p->addr;
 392         ap->pre_handler = aggr_pre_handler;
 393         ap->post_handler = aggr_post_handler;
 394         ap->fault_handler = aggr_fault_handler;
 395         ap->break_handler = aggr_break_handler;
 396
 397         INIT_LIST_HEAD(&ap->list);
 398         list_add_rcu(&p->list, &ap->list);
 399
 400         hlist_replace_rcu(&p->hlist, &ap->hlist);
 401 }
 402
 403 /*
 404  * This is the second or subsequent kprobe at the address - handle
 405  * the intricacies
 406  */
 407 static int __kprobes register_aggr_kprobe(struct kprobe *old_p,
 408                                           struct kprobe *p)
 409 {
 410         int ret = 0;
 411         struct kprobe *ap;
 412
 413         if (old_p->pre_handler == aggr_pre_handler) {
 414                 copy_kprobe(old_p, p);
 415                 ret = add_new_kprobe(old_p, p);
 416         } else {
 417                 ap = kzalloc(sizeof(struct kprobe), GFP_KERNEL);
 418                 if (!ap)
 419                         return -ENOMEM;
 420                 add_aggr_kprobe(ap, old_p);
 421                 copy_kprobe(ap, p);
 422                 ret = add_new_kprobe(ap, p);
 423         }
 424         return ret;
 425 }
 426
 427 static int __kprobes in_kprobes_functions(unsigned long addr)
 428 {
 429         if (addr >= (unsigned long)__kprobes_text_start
 430                 && addr < (unsigned long)__kprobes_text_end)
 431                 return -EINVAL;
 432         return 0;
 433 }
 434
 435 static int __kprobes __register_kprobe(struct kprobe *p,
 436         unsigned long called_from)
 437 {
 438         int ret = 0;
 439         struct kprobe *old_p;
 440         struct module *probed_mod;
 441
 442         if ((!kernel_text_address((unsigned long) p->addr)) ||
 443                 in_kprobes_functions((unsigned long) p->addr))
 444                 return -EINVAL;
 445
 446         p->mod_refcounted = 0;
 447         /* Check are we probing a module */
 448         if ((probed_mod = module_text_address((unsigned long) p->addr))) {
 449                 struct module *calling_mod = module_text_address(called_from);
 450                 /* We must allow modules to probe themself and
 451                  * in this case avoid incrementing the module refcount,
 452                  * so as to allow unloading of self probing modules.
 453                  */
 454                 if (calling_mod && (calling_mod != probed_mod)) {
 455                         if (unlikely(!try_module_get(probed_mod)))
 456                                 return -EINVAL;
 457                         p->mod_refcounted = 1;
 458                 } else
 459                         probed_mod = NULL;
 460         }
 461
 462         p->nmissed = 0;
 463         down(&kprobe_mutex);
 464         old_p = get_kprobe(p->addr);
 465         if (old_p) {
 466                 ret = register_aggr_kprobe(old_p, p);
 467                 goto out;
 468         }
 469
 470         if ((ret = arch_prepare_kprobe(p)) != 0)
 471                 goto out;
 472
 473         INIT_HLIST_NODE(&p->hlist);
 474         hlist_add_head_rcu(&p->hlist,
 475                        &kprobe_table[hash_ptr(p->addr, KPROBE_HASH_BITS)]);
 476
 477         arch_arm_kprobe(p);
 478
 479 out:
 480         up(&kprobe_mutex);
 481
 482         if (ret && probed_mod)
 483                 module_put(probed_mod);
 484         return ret;
 485 }
 486
 487 int __kprobes register_kprobe(struct kprobe *p)
 488 {
 489         return __register_kprobe(p,
 490                 (unsigned long)__builtin_return_address(0));
 491 }
 492
 493 void __kprobes unregister_kprobe(struct kprobe *p)
 494 {
 495         struct module *mod;
 496         struct kprobe *old_p, *list_p;
 497         int cleanup_p;
 498
 499         down(&kprobe_mutex);
 500         old_p = get_kprobe(p->addr);
 501         if (unlikely(!old_p)) {
 502                 up(&kprobe_mutex);
 503                 return;
 504         }
 505         if (p != old_p) {
 506                 list_for_each_entry_rcu(list_p, &old_p->list, list)
 507                         if (list_p == p)
 508                         /* kprobe p is a valid probe */
 509                                 goto valid_p;
 510                 up(&kprobe_mutex);
 511                 return;
 512         }
 513 valid_p:
 514         if ((old_p == p) || ((old_p->pre_handler == aggr_pre_handler) &&
 515                 (p->list.next == &old_p->list) &&
 516                 (p->list.prev == &old_p->list))) {
 517                 /* Only probe on the hash list */
 518                 arch_disarm_kprobe(p);
 519                 hlist_del_rcu(&old_p->hlist);
 520                 cleanup_p = 1;
 521         } else {
 522                 list_del_rcu(&p->list);
 523                 cleanup_p = 0;
 524         }
 525
 526         up(&kprobe_mutex);
 527
 528         synchronize_sched();
 529         if (p->mod_refcounted &&
 530             (mod = module_text_address((unsigned long)p->addr)))
 531                 module_put(mod);
 532
 533         if (cleanup_p) {
 534                 if (p != old_p) {
 535                         list_del_rcu(&p->list);
 536                         kfree(old_p);
 537                 }
 538                 arch_remove_kprobe(p);
 539         }
 540 }
 541
 542 static struct notifier_block kprobe_exceptions_nb = {
 543         .notifier_call = kprobe_exceptions_notify,
 544         .priority = 0x7fffffff /* we need to notified first */
 545 };
 546
 547 int __kprobes register_jprobe(struct jprobe *jp)
 548 {
 549         /* Todo: Verify probepoint is a function entry point */
 550         jp->kp.pre_handler = setjmp_pre_handler;
 551         jp->kp.break_handler = longjmp_break_handler;
 552
 553         return __register_kprobe(&jp->kp,
 554                 (unsigned long)__builtin_return_address(0));
 555 }
 556
 557 void __kprobes unregister_jprobe(struct jprobe *jp)
 558 {
 559         unregister_kprobe(&jp->kp);
 560 }
 561
 562 #ifdef ARCH_SUPPORTS_KRETPROBES
 563
 564 /*
 565  * This kprobe pre_handler is registered with every kretprobe. When probe
 566  * hits it will set up the return probe.
 567  */
 568 static int __kprobes pre_handler_kretprobe(struct kprobe *p,
 569                                            struct pt_regs *regs)
 570 {
 571         struct kretprobe *rp = container_of(p, struct kretprobe, kp);
 572         unsigned long flags = 0;
 573
 574         /*TODO: consider to only swap the RA after the last pre_handler fired */
 575         spin_lock_irqsave(&kretprobe_lock, flags);
 576         arch_prepare_kretprobe(rp, regs);
 577         spin_unlock_irqrestore(&kretprobe_lock, flags);
 578         return 0;
 579 }
 580
 581 int __kprobes register_kretprobe(struct kretprobe *rp)
 582 {
 583         int ret = 0;
 584         struct kretprobe_instance *inst;
 585         int i;
 586
 587         rp->kp.pre_handler = pre_handler_kretprobe;
 588
 589         /* Pre-allocate memory for max kretprobe instances */
 590         if (rp->maxactive <= 0) {
 591 #ifdef CONFIG_PREEMPT
 592                 rp->maxactive = max(10, 2 * NR_CPUS);
 593 #else
 594                 rp->maxactive = NR_CPUS;
 595 #endif
 596         }
 597         INIT_HLIST_HEAD(&rp->used_instances);
 598         INIT_HLIST_HEAD(&rp->free_instances);
 599         for (i = 0; i < rp->maxactive; i++) {
 600                 inst = kmalloc(sizeof(struct kretprobe_instance), GFP_KERNEL);
 601                 if (inst == NULL) {
 602                         free_rp_inst(rp);
 603                         return -ENOMEM;
 604                 }
 605                 INIT_HLIST_NODE(&inst->uflist);
 606                 hlist_add_head(&inst->uflist, &rp->free_instances);
 607         }
 608
 609         rp->nmissed = 0;
 610         /* Establish function entry probe point */
 611         if ((ret = __register_kprobe(&rp->kp,
 612                 (unsigned long)__builtin_return_address(0))) != 0)
 613                 free_rp_inst(rp);
 614         return ret;
 615 }
 616
 617 #else /* ARCH_SUPPORTS_KRETPROBES */
 618
 619 int __kprobes register_kretprobe(struct kretprobe *rp)
 620 {
 621         return -ENOSYS;
 622 }
 623
 624 #endif /* ARCH_SUPPORTS_KRETPROBES */
 625
 626 void __kprobes unregister_kretprobe(struct kretprobe *rp)
 627 {
 628         unsigned long flags;
 629         struct kretprobe_instance *ri;
 630
 631         unregister_kprobe(&rp->kp);
 632         /* No race here */
 633         spin_lock_irqsave(&kretprobe_lock, flags);
 634         while ((ri = get_used_rp_inst(rp)) != NULL) {
 635                 ri->rp = NULL;
 636                 hlist_del(&ri->uflist);
 637         }
 638         spin_unlock_irqrestore(&kretprobe_lock, flags);
 639         free_rp_inst(rp);
 640 }
 641
 642 static int __init init_kprobes(void)
 643 {
 644         int i, err = 0;
 645
 646         /* FIXME allocate the probe table, currently defined statically */
 647         /* initialize all list heads */
 648         for (i = 0; i < KPROBE_TABLE_SIZE; i++) {
 649                 INIT_HLIST_HEAD(&kprobe_table[i]);
 650                 INIT_HLIST_HEAD(&kretprobe_inst_table[i]);
 651         }
 652
 653         err = arch_init_kprobes();
 654         if (!err)
 655                 err = register_die_notifier(&kprobe_exceptions_nb);
 656
 657         return err;
 658 }
 659
 660 __initcall(init_kprobes);
 661
 662 EXPORT_SYMBOL_GPL(register_kprobe);
 663 EXPORT_SYMBOL_GPL(unregister_kprobe);
 664 EXPORT_SYMBOL_GPL(register_jprobe);
 665 EXPORT_SYMBOL_GPL(unregister_jprobe);
 666 EXPORT_SYMBOL_GPL(jprobe_return);
 667 EXPORT_SYMBOL_GPL(register_kretprobe);
 668 EXPORT_SYMBOL_GPL(unregister_kretprobe);
 669