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   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/stddef.h>
  39 #include <linux/module.h>
  40 #include <linux/moduleloader.h>
  41 #include <linux/kallsyms.h>
  42 #include <linux/freezer.h>
  43 #include <linux/seq_file.h>
  44 #include <linux/debugfs.h>
  45 #include <linux/kdebug.h>
  46
  47 #include <asm-generic/sections.h>
  48 #include <asm/cacheflush.h>
  49 #include <asm/errno.h>
  50 #include <asm/uaccess.h>
  51
  52 #define KPROBE_HASH_BITS 6
  53 #define KPROBE_TABLE_SIZE (1 << KPROBE_HASH_BITS)
  54
  55
  56 /*
  57  * Some oddball architectures like 64bit powerpc have function descriptors
  58  * so this must be overridable.
  59  */
  60 #ifndef kprobe_lookup_name
  61 #define kprobe_lookup_name(name, addr) \
  62         addr = ((kprobe_opcode_t *)(kallsyms_lookup_name(name)))
  63 #endif
  64
  65 static struct hlist_head kprobe_table[KPROBE_TABLE_SIZE];
  66 static struct hlist_head kretprobe_inst_table[KPROBE_TABLE_SIZE];
  67 static atomic_t kprobe_count;
  68
  69 /* NOTE: change this value only with kprobe_mutex held */
  70 static bool kprobe_enabled;
  71
  72 DEFINE_MUTEX(kprobe_mutex);             /* Protects kprobe_table */
  73 DEFINE_SPINLOCK(kretprobe_lock);        /* Protects kretprobe_inst_table */
  74 static DEFINE_PER_CPU(struct kprobe *, kprobe_instance) = NULL;
  75
  76 static struct notifier_block kprobe_page_fault_nb = {
  77         .notifier_call = kprobe_exceptions_notify,
  78         .priority = 0x7fffffff /* we need to notified first */
  79 };
  80
  81 #ifdef __ARCH_WANT_KPROBES_INSN_SLOT
  82 /*
  83  * kprobe->ainsn.insn points to the copy of the instruction to be
  84  * single-stepped. x86_64, POWER4 and above have no-exec support and
  85  * stepping on the instruction on a vmalloced/kmalloced/data page
  86  * is a recipe for disaster
  87  */
  88 #define INSNS_PER_PAGE  (PAGE_SIZE/(MAX_INSN_SIZE * sizeof(kprobe_opcode_t)))
  89
  90 struct kprobe_insn_page {
  91         struct hlist_node hlist;
  92         kprobe_opcode_t *insns;         /* Page of instruction slots */
  93         char slot_used[INSNS_PER_PAGE];
  94         int nused;
  95         int ngarbage;
  96 };
  97
  98 enum kprobe_slot_state {
  99         SLOT_CLEAN = 0,
 100         SLOT_DIRTY = 1,
 101         SLOT_USED = 2,
 102 };
 103
 104 static struct hlist_head kprobe_insn_pages;
 105 static int kprobe_garbage_slots;
 106 static int collect_garbage_slots(void);
 107
 108 static int __kprobes check_safety(void)
 109 {
 110         int ret = 0;
 111 #if defined(CONFIG_PREEMPT) && defined(CONFIG_PM)
 112         ret = freeze_processes();
 113         if (ret == 0) {
 114                 struct task_struct *p, *q;
 115                 do_each_thread(p, q) {
 116                         if (p != current && p->state == TASK_RUNNING &&
 117                             p->pid != 0) {
 118                                 printk("Check failed: %s is running\n",p->comm);
 119                                 ret = -1;
 120                                 goto loop_end;
 121                         }
 122                 } while_each_thread(p, q);
 123         }
 124 loop_end:
 125         thaw_processes();
 126 #else
 127         synchronize_sched();
 128 #endif
 129         return ret;
 130 }
 131
 132 /**
 133  * get_insn_slot() - Find a slot on an executable page for an instruction.
 134  * We allocate an executable page if there's no room on existing ones.
 135  */
 136 kprobe_opcode_t __kprobes *get_insn_slot(void)
 137 {
 138         struct kprobe_insn_page *kip;
 139         struct hlist_node *pos;
 140
 141  retry:
 142         hlist_for_each_entry(kip, pos, &kprobe_insn_pages, hlist) {
 143                 if (kip->nused < INSNS_PER_PAGE) {
 144                         int i;
 145                         for (i = 0; i < INSNS_PER_PAGE; i++) {
 146                                 if (kip->slot_used[i] == SLOT_CLEAN) {
 147                                         kip->slot_used[i] = SLOT_USED;
 148                                         kip->nused++;
 149                                         return kip->insns + (i * MAX_INSN_SIZE);
 150                                 }
 151                         }
 152                         /* Surprise!  No unused slots.  Fix kip->nused. */
 153                         kip->nused = INSNS_PER_PAGE;
 154                 }
 155         }
 156
 157         /* If there are any garbage slots, collect it and try again. */
 158         if (kprobe_garbage_slots && collect_garbage_slots() == 0) {
 159                 goto retry;
 160         }
 161         /* All out of space.  Need to allocate a new page. Use slot 0. */
 162         kip = kmalloc(sizeof(struct kprobe_insn_page), GFP_KERNEL);
 163         if (!kip)
 164                 return NULL;
 165
 166         /*
 167          * Use module_alloc so this page is within +/- 2GB of where the
 168          * kernel image and loaded module images reside. This is required
 169          * so x86_64 can correctly handle the %rip-relative fixups.
 170          */
 171         kip->insns = module_alloc(PAGE_SIZE);
 172         if (!kip->insns) {
 173                 kfree(kip);
 174                 return NULL;
 175         }
 176         INIT_HLIST_NODE(&kip->hlist);
 177         hlist_add_head(&kip->hlist, &kprobe_insn_pages);
 178         memset(kip->slot_used, SLOT_CLEAN, INSNS_PER_PAGE);
 179         kip->slot_used[0] = SLOT_USED;
 180         kip->nused = 1;
 181         kip->ngarbage = 0;
 182         return kip->insns;
 183 }
 184
 185 /* Return 1 if all garbages are collected, otherwise 0. */
 186 static int __kprobes collect_one_slot(struct kprobe_insn_page *kip, int idx)
 187 {
 188         kip->slot_used[idx] = SLOT_CLEAN;
 189         kip->nused--;
 190         if (kip->nused == 0) {
 191                 /*
 192                  * Page is no longer in use.  Free it unless
 193                  * it's the last one.  We keep the last one
 194                  * so as not to have to set it up again the
 195                  * next time somebody inserts a probe.
 196                  */
 197                 hlist_del(&kip->hlist);
 198                 if (hlist_empty(&kprobe_insn_pages)) {
 199                         INIT_HLIST_NODE(&kip->hlist);
 200                         hlist_add_head(&kip->hlist,
 201                                        &kprobe_insn_pages);
 202                 } else {
 203                         module_free(NULL, kip->insns);
 204                         kfree(kip);
 205                 }
 206                 return 1;
 207         }
 208         return 0;
 209 }
 210
 211 static int __kprobes collect_garbage_slots(void)
 212 {
 213         struct kprobe_insn_page *kip;
 214         struct hlist_node *pos, *next;
 215
 216         /* Ensure no-one is preepmted on the garbages */
 217         if (check_safety() != 0)
 218                 return -EAGAIN;
 219
 220         hlist_for_each_entry_safe(kip, pos, next, &kprobe_insn_pages, hlist) {
 221                 int i;
 222                 if (kip->ngarbage == 0)
 223                         continue;
 224                 kip->ngarbage = 0;      /* we will collect all garbages */
 225                 for (i = 0; i < INSNS_PER_PAGE; i++) {
 226                         if (kip->slot_used[i] == SLOT_DIRTY &&
 227                             collect_one_slot(kip, i))
 228                                 break;
 229                 }
 230         }
 231         kprobe_garbage_slots = 0;
 232         return 0;
 233 }
 234
 235 void __kprobes free_insn_slot(kprobe_opcode_t * slot, int dirty)
 236 {
 237         struct kprobe_insn_page *kip;
 238         struct hlist_node *pos;
 239
 240         hlist_for_each_entry(kip, pos, &kprobe_insn_pages, hlist) {
 241                 if (kip->insns <= slot &&
 242                     slot < kip->insns + (INSNS_PER_PAGE * MAX_INSN_SIZE)) {
 243                         int i = (slot - kip->insns) / MAX_INSN_SIZE;
 244                         if (dirty) {
 245                                 kip->slot_used[i] = SLOT_DIRTY;
 246                                 kip->ngarbage++;
 247                         } else {
 248                                 collect_one_slot(kip, i);
 249                         }
 250                         break;
 251                 }
 252         }
 253
 254         if (dirty && ++kprobe_garbage_slots > INSNS_PER_PAGE)
 255                 collect_garbage_slots();
 256 }
 257 #endif
 258
 259 /* We have preemption disabled.. so it is safe to use __ versions */
 260 static inline void set_kprobe_instance(struct kprobe *kp)
 261 {
 262         __get_cpu_var(kprobe_instance) = kp;
 263 }
 264
 265 static inline void reset_kprobe_instance(void)
 266 {
 267         __get_cpu_var(kprobe_instance) = NULL;
 268 }
 269
 270 /*
 271  * This routine is called either:
 272  *      - under the kprobe_mutex - during kprobe_[un]register()
 273  *                              OR
 274  *      - with preemption disabled - from arch/xxx/kernel/kprobes.c
 275  */
 276 struct kprobe __kprobes *get_kprobe(void *addr)
 277 {
 278         struct hlist_head *head;
 279         struct hlist_node *node;
 280         struct kprobe *p;
 281
 282         head = &kprobe_table[hash_ptr(addr, KPROBE_HASH_BITS)];
 283         hlist_for_each_entry_rcu(p, node, head, hlist) {
 284                 if (p->addr == addr)
 285                         return p;
 286         }
 287         return NULL;
 288 }
 289
 290 /*
 291  * Aggregate handlers for multiple kprobes support - these handlers
 292  * take care of invoking the individual kprobe handlers on p->list
 293  */
 294 static int __kprobes aggr_pre_handler(struct kprobe *p, struct pt_regs *regs)
 295 {
 296         struct kprobe *kp;
 297
 298         list_for_each_entry_rcu(kp, &p->list, list) {
 299                 if (kp->pre_handler) {
 300                         set_kprobe_instance(kp);
 301                         if (kp->pre_handler(kp, regs))
 302                                 return 1;
 303                 }
 304                 reset_kprobe_instance();
 305         }
 306         return 0;
 307 }
 308
 309 static void __kprobes aggr_post_handler(struct kprobe *p, struct pt_regs *regs,
 310                                         unsigned long flags)
 311 {
 312         struct kprobe *kp;
 313
 314         list_for_each_entry_rcu(kp, &p->list, list) {
 315                 if (kp->post_handler) {
 316                         set_kprobe_instance(kp);
 317                         kp->post_handler(kp, regs, flags);
 318                         reset_kprobe_instance();
 319                 }
 320         }
 321 }
 322
 323 static int __kprobes aggr_fault_handler(struct kprobe *p, struct pt_regs *regs,
 324                                         int trapnr)
 325 {
 326         struct kprobe *cur = __get_cpu_var(kprobe_instance);
 327
 328         /*
 329          * if we faulted "during" the execution of a user specified
 330          * probe handler, invoke just that probe's fault handler
 331          */
 332         if (cur && cur->fault_handler) {
 333                 if (cur->fault_handler(cur, regs, trapnr))
 334                         return 1;
 335         }
 336         return 0;
 337 }
 338
 339 static int __kprobes aggr_break_handler(struct kprobe *p, struct pt_regs *regs)
 340 {
 341         struct kprobe *cur = __get_cpu_var(kprobe_instance);
 342         int ret = 0;
 343
 344         if (cur && cur->break_handler) {
 345                 if (cur->break_handler(cur, regs))
 346                         ret = 1;
 347         }
 348         reset_kprobe_instance();
 349         return ret;
 350 }
 351
 352 /* Walks the list and increments nmissed count for multiprobe case */
 353 void __kprobes kprobes_inc_nmissed_count(struct kprobe *p)
 354 {
 355         struct kprobe *kp;
 356         if (p->pre_handler != aggr_pre_handler) {
 357                 p->nmissed++;
 358         } else {
 359                 list_for_each_entry_rcu(kp, &p->list, list)
 360                         kp->nmissed++;
 361         }
 362         return;
 363 }
 364
 365 /* Called with kretprobe_lock held */
 366 void __kprobes recycle_rp_inst(struct kretprobe_instance *ri,
 367                                 struct hlist_head *head)
 368 {
 369         /* remove rp inst off the rprobe_inst_table */
 370         hlist_del(&ri->hlist);
 371         if (ri->rp) {
 372                 /* remove rp inst off the used list */
 373                 hlist_del(&ri->uflist);
 374                 /* put rp inst back onto the free list */
 375                 INIT_HLIST_NODE(&ri->uflist);
 376                 hlist_add_head(&ri->uflist, &ri->rp->free_instances);
 377         } else
 378                 /* Unregistering */
 379                 hlist_add_head(&ri->hlist, head);
 380 }
 381
 382 struct hlist_head __kprobes *kretprobe_inst_table_head(struct task_struct *tsk)
 383 {
 384         return &kretprobe_inst_table[hash_ptr(tsk, KPROBE_HASH_BITS)];
 385 }
 386
 387 /*
 388  * This function is called from finish_task_switch when task tk becomes dead,
 389  * so that we can recycle any function-return probe instances associated
 390  * with this task. These left over instances represent probed functions
 391  * that have been called but will never return.
 392  */
 393 void __kprobes kprobe_flush_task(struct task_struct *tk)
 394 {
 395         struct kretprobe_instance *ri;
 396         struct hlist_head *head, empty_rp;
 397         struct hlist_node *node, *tmp;
 398         unsigned long flags = 0;
 399
 400         INIT_HLIST_HEAD(&empty_rp);
 401         spin_lock_irqsave(&kretprobe_lock, flags);
 402         head = kretprobe_inst_table_head(tk);
 403         hlist_for_each_entry_safe(ri, node, tmp, head, hlist) {
 404                 if (ri->task == tk)
 405                         recycle_rp_inst(ri, &empty_rp);
 406         }
 407         spin_unlock_irqrestore(&kretprobe_lock, flags);
 408
 409         hlist_for_each_entry_safe(ri, node, tmp, &empty_rp, hlist) {
 410                 hlist_del(&ri->hlist);
 411                 kfree(ri);
 412         }
 413 }
 414
 415 static inline void free_rp_inst(struct kretprobe *rp)
 416 {
 417         struct kretprobe_instance *ri;
 418         struct hlist_node *pos, *next;
 419
 420         hlist_for_each_entry_safe(ri, pos, next, &rp->free_instances, uflist) {
 421                 hlist_del(&ri->uflist);
 422                 kfree(ri);
 423         }
 424 }
 425
 426 /*
 427  * Keep all fields in the kprobe consistent
 428  */
 429 static inline void copy_kprobe(struct kprobe *old_p, struct kprobe *p)
 430 {
 431         memcpy(&p->opcode, &old_p->opcode, sizeof(kprobe_opcode_t));
 432         memcpy(&p->ainsn, &old_p->ainsn, sizeof(struct arch_specific_insn));
 433 }
 434
 435 /*
 436 * Add the new probe to old_p->list. Fail if this is the
 437 * second jprobe at the address - two jprobes can't coexist
 438 */
 439 static int __kprobes add_new_kprobe(struct kprobe *old_p, struct kprobe *p)
 440 {
 441         if (p->break_handler) {
 442                 if (old_p->break_handler)
 443                         return -EEXIST;
 444                 list_add_tail_rcu(&p->list, &old_p->list);
 445                 old_p->break_handler = aggr_break_handler;
 446         } else
 447                 list_add_rcu(&p->list, &old_p->list);
 448         if (p->post_handler && !old_p->post_handler)
 449                 old_p->post_handler = aggr_post_handler;
 450         return 0;
 451 }
 452
 453 /*
 454  * Fill in the required fields of the "manager kprobe". Replace the
 455  * earlier kprobe in the hlist with the manager kprobe
 456  */
 457 static inline void add_aggr_kprobe(struct kprobe *ap, struct kprobe *p)
 458 {
 459         copy_kprobe(p, ap);
 460         flush_insn_slot(ap);
 461         ap->addr = p->addr;
 462         ap->pre_handler = aggr_pre_handler;
 463         ap->fault_handler = aggr_fault_handler;
 464         if (p->post_handler)
 465                 ap->post_handler = aggr_post_handler;
 466         if (p->break_handler)
 467                 ap->break_handler = aggr_break_handler;
 468
 469         INIT_LIST_HEAD(&ap->list);
 470         list_add_rcu(&p->list, &ap->list);
 471
 472         hlist_replace_rcu(&p->hlist, &ap->hlist);
 473 }
 474
 475 /*
 476  * This is the second or subsequent kprobe at the address - handle
 477  * the intricacies
 478  */
 479 static int __kprobes register_aggr_kprobe(struct kprobe *old_p,
 480                                           struct kprobe *p)
 481 {
 482         int ret = 0;
 483         struct kprobe *ap;
 484
 485         if (old_p->pre_handler == aggr_pre_handler) {
 486                 copy_kprobe(old_p, p);
 487                 ret = add_new_kprobe(old_p, p);
 488         } else {
 489                 ap = kzalloc(sizeof(struct kprobe), GFP_KERNEL);
 490                 if (!ap)
 491                         return -ENOMEM;
 492                 add_aggr_kprobe(ap, old_p);
 493                 copy_kprobe(ap, p);
 494                 ret = add_new_kprobe(ap, p);
 495         }
 496         return ret;
 497 }
 498
 499 static int __kprobes in_kprobes_functions(unsigned long addr)
 500 {
 501         if (addr >= (unsigned long)__kprobes_text_start &&
 502             addr < (unsigned long)__kprobes_text_end)
 503                 return -EINVAL;
 504         return 0;
 505 }
 506
 507 static int __kprobes __register_kprobe(struct kprobe *p,
 508         unsigned long called_from)
 509 {
 510         int ret = 0;
 511         struct kprobe *old_p;
 512         struct module *probed_mod;
 513
 514         /*
 515          * If we have a symbol_name argument look it up,
 516          * and add it to the address.  That way the addr
 517          * field can either be global or relative to a symbol.
 518          */
 519         if (p->symbol_name) {
 520                 if (p->addr)
 521                         return -EINVAL;
 522                 kprobe_lookup_name(p->symbol_name, p->addr);
 523         }
 524
 525         if (!p->addr)
 526                 return -EINVAL;
 527         p->addr = (kprobe_opcode_t *)(((char *)p->addr)+ p->offset);
 528
 529         if (!kernel_text_address((unsigned long) p->addr) ||
 530             in_kprobes_functions((unsigned long) p->addr))
 531                 return -EINVAL;
 532
 533         p->mod_refcounted = 0;
 534
 535         /*
 536          * Check if are we probing a module.
 537          */
 538         probed_mod = module_text_address((unsigned long) p->addr);
 539         if (probed_mod) {
 540                 struct module *calling_mod = module_text_address(called_from);
 541                 /*
 542                  * We must allow modules to probe themself and in this case
 543                  * avoid incrementing the module refcount, so as to allow
 544                  * unloading of self probing modules.
 545                  */
 546                 if (calling_mod && calling_mod != probed_mod) {
 547                         if (unlikely(!try_module_get(probed_mod)))
 548                                 return -EINVAL;
 549                         p->mod_refcounted = 1;
 550                 } else
 551                         probed_mod = NULL;
 552         }
 553
 554         p->nmissed = 0;
 555         mutex_lock(&kprobe_mutex);
 556         old_p = get_kprobe(p->addr);
 557         if (old_p) {
 558                 ret = register_aggr_kprobe(old_p, p);
 559                 if (!ret)
 560                         atomic_inc(&kprobe_count);
 561                 goto out;
 562         }
 563
 564         ret = arch_prepare_kprobe(p);
 565         if (ret)
 566                 goto out;
 567
 568         INIT_HLIST_NODE(&p->hlist);
 569         hlist_add_head_rcu(&p->hlist,
 570                        &kprobe_table[hash_ptr(p->addr, KPROBE_HASH_BITS)]);
 571
 572         if (kprobe_enabled) {
 573                 if (atomic_add_return(1, &kprobe_count) == \
 574                                 (ARCH_INACTIVE_KPROBE_COUNT + 1))
 575                         register_page_fault_notifier(&kprobe_page_fault_nb);
 576
 577                 arch_arm_kprobe(p);
 578         }
 579 out:
 580         mutex_unlock(&kprobe_mutex);
 581
 582         if (ret && probed_mod)
 583                 module_put(probed_mod);
 584         return ret;
 585 }
 586
 587 int __kprobes register_kprobe(struct kprobe *p)
 588 {
 589         return __register_kprobe(p, (unsigned long)__builtin_return_address(0));
 590 }
 591
 592 void __kprobes unregister_kprobe(struct kprobe *p)
 593 {
 594         struct module *mod;
 595         struct kprobe *old_p, *list_p;
 596         int cleanup_p;
 597
 598         mutex_lock(&kprobe_mutex);
 599         old_p = get_kprobe(p->addr);
 600         if (unlikely(!old_p)) {
 601                 mutex_unlock(&kprobe_mutex);
 602                 return;
 603         }
 604         if (p != old_p) {
 605                 list_for_each_entry_rcu(list_p, &old_p->list, list)
 606                         if (list_p == p)
 607                         /* kprobe p is a valid probe */
 608                                 goto valid_p;
 609                 mutex_unlock(&kprobe_mutex);
 610                 return;
 611         }
 612 valid_p:
 613         if (old_p == p ||
 614             (old_p->pre_handler == aggr_pre_handler &&
 615              p->list.next == &old_p->list && p->list.prev == &old_p->list)) {
 616                 /*
 617                  * Only probe on the hash list. Disarm only if kprobes are
 618                  * enabled - otherwise, the breakpoint would already have
 619                  * been removed. We save on flushing icache.
 620                  */
 621                 if (kprobe_enabled)
 622                         arch_disarm_kprobe(p);
 623                 hlist_del_rcu(&old_p->hlist);
 624                 cleanup_p = 1;
 625         } else {
 626                 list_del_rcu(&p->list);
 627                 cleanup_p = 0;
 628         }
 629
 630         mutex_unlock(&kprobe_mutex);
 631
 632         synchronize_sched();
 633         if (p->mod_refcounted) {
 634                 mod = module_text_address((unsigned long)p->addr);
 635                 if (mod)
 636                         module_put(mod);
 637         }
 638
 639         if (cleanup_p) {
 640                 if (p != old_p) {
 641                         list_del_rcu(&p->list);
 642                         kfree(old_p);
 643                 }
 644                 arch_remove_kprobe(p);
 645         } else {
 646                 mutex_lock(&kprobe_mutex);
 647                 if (p->break_handler)
 648                         old_p->break_handler = NULL;
 649                 if (p->post_handler){
 650                         list_for_each_entry_rcu(list_p, &old_p->list, list){
 651                                 if (list_p->post_handler){
 652                                         cleanup_p = 2;
 653                                         break;
 654                                 }
 655                         }
 656                         if (cleanup_p == 0)
 657                                 old_p->post_handler = NULL;
 658                 }
 659                 mutex_unlock(&kprobe_mutex);
 660         }
 661
 662         /* Call unregister_page_fault_notifier()
 663          * if no probes are active
 664          */
 665         mutex_lock(&kprobe_mutex);
 666         if (atomic_add_return(-1, &kprobe_count) == \
 667                                 ARCH_INACTIVE_KPROBE_COUNT)
 668                 unregister_page_fault_notifier(&kprobe_page_fault_nb);
 669         mutex_unlock(&kprobe_mutex);
 670         return;
 671 }
 672
 673 static struct notifier_block kprobe_exceptions_nb = {
 674         .notifier_call = kprobe_exceptions_notify,
 675         .priority = 0x7fffffff /* we need to be notified first */
 676 };
 677
 678
 679 int __kprobes register_jprobe(struct jprobe *jp)
 680 {
 681         /* Todo: Verify probepoint is a function entry point */
 682         jp->kp.pre_handler = setjmp_pre_handler;
 683         jp->kp.break_handler = longjmp_break_handler;
 684
 685         return __register_kprobe(&jp->kp,
 686                 (unsigned long)__builtin_return_address(0));
 687 }
 688
 689 void __kprobes unregister_jprobe(struct jprobe *jp)
 690 {
 691         unregister_kprobe(&jp->kp);
 692 }
 693
 694 #ifdef ARCH_SUPPORTS_KRETPROBES
 695
 696 /*
 697  * This kprobe pre_handler is registered with every kretprobe. When probe
 698  * hits it will set up the return probe.
 699  */
 700 static int __kprobes pre_handler_kretprobe(struct kprobe *p,
 701                                            struct pt_regs *regs)
 702 {
 703         struct kretprobe *rp = container_of(p, struct kretprobe, kp);
 704         unsigned long flags = 0;
 705
 706         /*TODO: consider to only swap the RA after the last pre_handler fired */
 707         spin_lock_irqsave(&kretprobe_lock, flags);
 708         if (!hlist_empty(&rp->free_instances)) {
 709                 struct kretprobe_instance *ri;
 710
 711                 ri = hlist_entry(rp->free_instances.first,
 712                                  struct kretprobe_instance, uflist);
 713                 ri->rp = rp;
 714                 ri->task = current;
 715                 arch_prepare_kretprobe(ri, regs);
 716
 717                 /* XXX(hch): why is there no hlist_move_head? */
 718                 hlist_del(&ri->uflist);
 719                 hlist_add_head(&ri->uflist, &ri->rp->used_instances);
 720                 hlist_add_head(&ri->hlist, kretprobe_inst_table_head(ri->task));
 721         } else
 722                 rp->nmissed++;
 723         spin_unlock_irqrestore(&kretprobe_lock, flags);
 724         return 0;
 725 }
 726
 727 int __kprobes register_kretprobe(struct kretprobe *rp)
 728 {
 729         int ret = 0;
 730         struct kretprobe_instance *inst;
 731         int i;
 732
 733         rp->kp.pre_handler = pre_handler_kretprobe;
 734         rp->kp.post_handler = NULL;
 735         rp->kp.fault_handler = NULL;
 736         rp->kp.break_handler = NULL;
 737
 738         /* Pre-allocate memory for max kretprobe instances */
 739         if (rp->maxactive <= 0) {
 740 #ifdef CONFIG_PREEMPT
 741                 rp->maxactive = max(10, 2 * NR_CPUS);
 742 #else
 743                 rp->maxactive = NR_CPUS;
 744 #endif
 745         }
 746         INIT_HLIST_HEAD(&rp->used_instances);
 747         INIT_HLIST_HEAD(&rp->free_instances);
 748         for (i = 0; i < rp->maxactive; i++) {
 749                 inst = kmalloc(sizeof(struct kretprobe_instance), GFP_KERNEL);
 750                 if (inst == NULL) {
 751                         free_rp_inst(rp);
 752                         return -ENOMEM;
 753                 }
 754                 INIT_HLIST_NODE(&inst->uflist);
 755                 hlist_add_head(&inst->uflist, &rp->free_instances);
 756         }
 757
 758         rp->nmissed = 0;
 759         /* Establish function entry probe point */
 760         if ((ret = __register_kprobe(&rp->kp,
 761                 (unsigned long)__builtin_return_address(0))) != 0)
 762                 free_rp_inst(rp);
 763         return ret;
 764 }
 765
 766 #else /* ARCH_SUPPORTS_KRETPROBES */
 767
 768 int __kprobes register_kretprobe(struct kretprobe *rp)
 769 {
 770         return -ENOSYS;
 771 }
 772
 773 static int __kprobes pre_handler_kretprobe(struct kprobe *p,
 774                                            struct pt_regs *regs)
 775 {
 776         return 0;
 777 }
 778
 779 #endif /* ARCH_SUPPORTS_KRETPROBES */
 780
 781 void __kprobes unregister_kretprobe(struct kretprobe *rp)
 782 {
 783         unsigned long flags;
 784         struct kretprobe_instance *ri;
 785         struct hlist_node *pos, *next;
 786
 787         unregister_kprobe(&rp->kp);
 788
 789         /* No race here */
 790         spin_lock_irqsave(&kretprobe_lock, flags);
 791         hlist_for_each_entry_safe(ri, pos, next, &rp->used_instances, uflist) {
 792                 ri->rp = NULL;
 793                 hlist_del(&ri->uflist);
 794         }
 795         spin_unlock_irqrestore(&kretprobe_lock, flags);
 796         free_rp_inst(rp);
 797 }
 798
 799 static int __init init_kprobes(void)
 800 {
 801         int i, err = 0;
 802
 803         /* FIXME allocate the probe table, currently defined statically */
 804         /* initialize all list heads */
 805         for (i = 0; i < KPROBE_TABLE_SIZE; i++) {
 806                 INIT_HLIST_HEAD(&kprobe_table[i]);
 807                 INIT_HLIST_HEAD(&kretprobe_inst_table[i]);
 808         }
 809         atomic_set(&kprobe_count, 0);
 810
 811         /* By default, kprobes are enabled */
 812         kprobe_enabled = true;
 813
 814         err = arch_init_kprobes();
 815         if (!err)
 816                 err = register_die_notifier(&kprobe_exceptions_nb);
 817
 818         return err;
 819 }
 820
 821 #ifdef CONFIG_DEBUG_FS
 822 static void __kprobes report_probe(struct seq_file *pi, struct kprobe *p,
 823                 const char *sym, int offset,char *modname)
 824 {
 825         char *kprobe_type;
 826
 827         if (p->pre_handler == pre_handler_kretprobe)
 828                 kprobe_type = "r";
 829         else if (p->pre_handler == setjmp_pre_handler)
 830                 kprobe_type = "j";
 831         else
 832                 kprobe_type = "k";
 833         if (sym)
 834                 seq_printf(pi, "%p  %s  %s+0x%x  %s\n", p->addr, kprobe_type,
 835                         sym, offset, (modname ? modname : " "));
 836         else
 837                 seq_printf(pi, "%p  %s  %p\n", p->addr, kprobe_type, p->addr);
 838 }
 839
 840 static void __kprobes *kprobe_seq_start(struct seq_file *f, loff_t *pos)
 841 {
 842         return (*pos < KPROBE_TABLE_SIZE) ? pos : NULL;
 843 }
 844
 845 static void __kprobes *kprobe_seq_next(struct seq_file *f, void *v, loff_t *pos)
 846 {
 847         (*pos)++;
 848         if (*pos >= KPROBE_TABLE_SIZE)
 849                 return NULL;
 850         return pos;
 851 }
 852
 853 static void __kprobes kprobe_seq_stop(struct seq_file *f, void *v)
 854 {
 855         /* Nothing to do */
 856 }
 857
 858 static int __kprobes show_kprobe_addr(struct seq_file *pi, void *v)
 859 {
 860         struct hlist_head *head;
 861         struct hlist_node *node;
 862         struct kprobe *p, *kp;
 863         const char *sym = NULL;
 864         unsigned int i = *(loff_t *) v;
 865         unsigned long offset = 0;
 866         char *modname, namebuf[128];
 867
 868         head = &kprobe_table[i];
 869         preempt_disable();
 870         hlist_for_each_entry_rcu(p, node, head, hlist) {
 871                 sym = kallsyms_lookup((unsigned long)p->addr, NULL,
 872                                         &offset, &modname, namebuf);
 873                 if (p->pre_handler == aggr_pre_handler) {
 874                         list_for_each_entry_rcu(kp, &p->list, list)
 875                                 report_probe(pi, kp, sym, offset, modname);
 876                 } else
 877                         report_probe(pi, p, sym, offset, modname);
 878         }
 879         preempt_enable();
 880         return 0;
 881 }
 882
 883 static struct seq_operations kprobes_seq_ops = {
 884         .start = kprobe_seq_start,
 885         .next  = kprobe_seq_next,
 886         .stop  = kprobe_seq_stop,
 887         .show  = show_kprobe_addr
 888 };
 889
 890 static int __kprobes kprobes_open(struct inode *inode, struct file *filp)
 891 {
 892         return seq_open(filp, &kprobes_seq_ops);
 893 }
 894
 895 static struct file_operations debugfs_kprobes_operations = {
 896         .open           = kprobes_open,
 897         .read           = seq_read,
 898         .llseek         = seq_lseek,
 899         .release        = seq_release,
 900 };
 901
 902 static void __kprobes enable_all_kprobes(void)
 903 {
 904         struct hlist_head *head;
 905         struct hlist_node *node;
 906         struct kprobe *p;
 907         unsigned int i;
 908
 909         mutex_lock(&kprobe_mutex);
 910
 911         /* If kprobes are already enabled, just return */
 912         if (kprobe_enabled)
 913                 goto already_enabled;
 914
 915         /*
 916          * Re-register the page fault notifier only if there are any
 917          * active probes at the time of enabling kprobes globally
 918          */
 919         if (atomic_read(&kprobe_count) > ARCH_INACTIVE_KPROBE_COUNT)
 920                 register_page_fault_notifier(&kprobe_page_fault_nb);
 921
 922         for (i = 0; i < KPROBE_TABLE_SIZE; i++) {
 923                 head = &kprobe_table[i];
 924                 hlist_for_each_entry_rcu(p, node, head, hlist)
 925                         arch_arm_kprobe(p);
 926         }
 927
 928         kprobe_enabled = true;
 929         printk(KERN_INFO "Kprobes globally enabled\n");
 930
 931 already_enabled:
 932         mutex_unlock(&kprobe_mutex);
 933         return;
 934 }
 935
 936 static void __kprobes disable_all_kprobes(void)
 937 {
 938         struct hlist_head *head;
 939         struct hlist_node *node;
 940         struct kprobe *p;
 941         unsigned int i;
 942
 943         mutex_lock(&kprobe_mutex);
 944
 945         /* If kprobes are already disabled, just return */
 946         if (!kprobe_enabled)
 947                 goto already_disabled;
 948
 949         kprobe_enabled = false;
 950         printk(KERN_INFO "Kprobes globally disabled\n");
 951         for (i = 0; i < KPROBE_TABLE_SIZE; i++) {
 952                 head = &kprobe_table[i];
 953                 hlist_for_each_entry_rcu(p, node, head, hlist) {
 954                         if (!arch_trampoline_kprobe(p))
 955                                 arch_disarm_kprobe(p);
 956                 }
 957         }
 958
 959         mutex_unlock(&kprobe_mutex);
 960         /* Allow all currently running kprobes to complete */
 961         synchronize_sched();
 962
 963         mutex_lock(&kprobe_mutex);
 964         /* Unconditionally unregister the page_fault notifier */
 965         unregister_page_fault_notifier(&kprobe_page_fault_nb);
 966
 967 already_disabled:
 968         mutex_unlock(&kprobe_mutex);
 969         return;
 970 }
 971
 972 /*
 973  * XXX: The debugfs bool file interface doesn't allow for callbacks
 974  * when the bool state is switched. We can reuse that facility when
 975  * available
 976  */
 977 static ssize_t read_enabled_file_bool(struct file *file,
 978                char __user *user_buf, size_t count, loff_t *ppos)
 979 {
 980         char buf[3];
 981
 982         if (kprobe_enabled)
 983                 buf[0] = '1';
 984         else
 985                 buf[0] = '0';
 986         buf[1] = '\n';
 987         buf[2] = 0x00;
 988         return simple_read_from_buffer(user_buf, count, ppos, buf, 2);
 989 }
 990
 991 static ssize_t write_enabled_file_bool(struct file *file,
 992                const char __user *user_buf, size_t count, loff_t *ppos)
 993 {
 994         char buf[32];
 995         int buf_size;
 996
 997         buf_size = min(count, (sizeof(buf)-1));
 998         if (copy_from_user(buf, user_buf, buf_size))
 999                 return -EFAULT;
1000
1001         switch (buf[0]) {
1002         case 'y':
1003         case 'Y':
1004         case '1':
1005                 enable_all_kprobes();
1006                 break;
1007         case 'n':
1008         case 'N':
1009         case '0':
1010                 disable_all_kprobes();
1011                 break;
1012         }
1013
1014         return count;
1015 }
1016
1017 static struct file_operations fops_kp = {
1018         .read =         read_enabled_file_bool,
1019         .write =        write_enabled_file_bool,
1020 };
1021
1022 static int __kprobes debugfs_kprobe_init(void)
1023 {
1024         struct dentry *dir, *file;
1025         unsigned int value = 1;
1026
1027         dir = debugfs_create_dir("kprobes", NULL);
1028         if (!dir)
1029                 return -ENOMEM;
1030
1031         file = debugfs_create_file("list", 0444, dir, NULL,
1032                                 &debugfs_kprobes_operations);
1033         if (!file) {
1034                 debugfs_remove(dir);
1035                 return -ENOMEM;
1036         }
1037
1038         file = debugfs_create_file("enabled", 0600, dir,
1039                                         &value, &fops_kp);
1040         if (!file) {
1041                 debugfs_remove(dir);
1042                 return -ENOMEM;
1043         }
1044
1045         return 0;
1046 }
1047
1048 late_initcall(debugfs_kprobe_init);
1049 #endif /* CONFIG_DEBUG_FS */
1050
1051 module_init(init_kprobes);
1052
1053 EXPORT_SYMBOL_GPL(register_kprobe);
1054 EXPORT_SYMBOL_GPL(unregister_kprobe);
1055 EXPORT_SYMBOL_GPL(register_jprobe);
1056 EXPORT_SYMBOL_GPL(unregister_jprobe);
1057 EXPORT_SYMBOL_GPL(jprobe_return);
1058 EXPORT_SYMBOL_GPL(register_kretprobe);
1059 EXPORT_SYMBOL_GPL(unregister_kretprobe);