[PATCH] Notify page fault call chain
[linux-2.6.git] / 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 static atomic_t kprobe_count;
51
52 DEFINE_MUTEX(kprobe_mutex);             /* Protects kprobe_table */
53 DEFINE_SPINLOCK(kretprobe_lock);        /* Protects kretprobe_inst_table */
54 static DEFINE_PER_CPU(struct kprobe *, kprobe_instance) = NULL;
55
56 static struct notifier_block kprobe_page_fault_nb = {
57         .notifier_call = kprobe_exceptions_notify,
58         .priority = 0x7fffffff /* we need to notified first */
59 };
60
61 #ifdef __ARCH_WANT_KPROBES_INSN_SLOT
62 /*
63  * kprobe->ainsn.insn points to the copy of the instruction to be
64  * single-stepped. x86_64, POWER4 and above have no-exec support and
65  * stepping on the instruction on a vmalloced/kmalloced/data page
66  * is a recipe for disaster
67  */
68 #define INSNS_PER_PAGE  (PAGE_SIZE/(MAX_INSN_SIZE * sizeof(kprobe_opcode_t)))
69
70 struct kprobe_insn_page {
71         struct hlist_node hlist;
72         kprobe_opcode_t *insns;         /* Page of instruction slots */
73         char slot_used[INSNS_PER_PAGE];
74         int nused;
75 };
76
77 static struct hlist_head kprobe_insn_pages;
78
79 /**
80  * get_insn_slot() - Find a slot on an executable page for an instruction.
81  * We allocate an executable page if there's no room on existing ones.
82  */
83 kprobe_opcode_t __kprobes *get_insn_slot(void)
84 {
85         struct kprobe_insn_page *kip;
86         struct hlist_node *pos;
87
88         hlist_for_each(pos, &kprobe_insn_pages) {
89                 kip = hlist_entry(pos, struct kprobe_insn_page, hlist);
90                 if (kip->nused < INSNS_PER_PAGE) {
91                         int i;
92                         for (i = 0; i < INSNS_PER_PAGE; i++) {
93                                 if (!kip->slot_used[i]) {
94                                         kip->slot_used[i] = 1;
95                                         kip->nused++;
96                                         return kip->insns + (i * MAX_INSN_SIZE);
97                                 }
98                         }
99                         /* Surprise!  No unused slots.  Fix kip->nused. */
100                         kip->nused = INSNS_PER_PAGE;
101                 }
102         }
103
104         /* All out of space.  Need to allocate a new page. Use slot 0.*/
105         kip = kmalloc(sizeof(struct kprobe_insn_page), GFP_KERNEL);
106         if (!kip) {
107                 return NULL;
108         }
109
110         /*
111          * Use module_alloc so this page is within +/- 2GB of where the
112          * kernel image and loaded module images reside. This is required
113          * so x86_64 can correctly handle the %rip-relative fixups.
114          */
115         kip->insns = module_alloc(PAGE_SIZE);
116         if (!kip->insns) {
117                 kfree(kip);
118                 return NULL;
119         }
120         INIT_HLIST_NODE(&kip->hlist);
121         hlist_add_head(&kip->hlist, &kprobe_insn_pages);
122         memset(kip->slot_used, 0, INSNS_PER_PAGE);
123         kip->slot_used[0] = 1;
124         kip->nused = 1;
125         return kip->insns;
126 }
127
128 void __kprobes free_insn_slot(kprobe_opcode_t *slot)
129 {
130         struct kprobe_insn_page *kip;
131         struct hlist_node *pos;
132
133         hlist_for_each(pos, &kprobe_insn_pages) {
134                 kip = hlist_entry(pos, struct kprobe_insn_page, hlist);
135                 if (kip->insns <= slot &&
136                     slot < kip->insns + (INSNS_PER_PAGE * MAX_INSN_SIZE)) {
137                         int i = (slot - kip->insns) / MAX_INSN_SIZE;
138                         kip->slot_used[i] = 0;
139                         kip->nused--;
140                         if (kip->nused == 0) {
141                                 /*
142                                  * Page is no longer in use.  Free it unless
143                                  * it's the last one.  We keep the last one
144                                  * so as not to have to set it up again the
145                                  * next time somebody inserts a probe.
146                                  */
147                                 hlist_del(&kip->hlist);
148                                 if (hlist_empty(&kprobe_insn_pages)) {
149                                         INIT_HLIST_NODE(&kip->hlist);
150                                         hlist_add_head(&kip->hlist,
151                                                 &kprobe_insn_pages);
152                                 } else {
153                                         module_free(NULL, kip->insns);
154                                         kfree(kip);
155                                 }
156                         }
157                         return;
158                 }
159         }
160 }
161 #endif
162
163 /* We have preemption disabled.. so it is safe to use __ versions */
164 static inline void set_kprobe_instance(struct kprobe *kp)
165 {
166         __get_cpu_var(kprobe_instance) = kp;
167 }
168
169 static inline void reset_kprobe_instance(void)
170 {
171         __get_cpu_var(kprobe_instance) = NULL;
172 }
173
174 /*
175  * This routine is called either:
176  *      - under the kprobe_mutex - during kprobe_[un]register()
177  *                              OR
178  *      - with preemption disabled - from arch/xxx/kernel/kprobes.c
179  */
180 struct kprobe __kprobes *get_kprobe(void *addr)
181 {
182         struct hlist_head *head;
183         struct hlist_node *node;
184         struct kprobe *p;
185
186         head = &kprobe_table[hash_ptr(addr, KPROBE_HASH_BITS)];
187         hlist_for_each_entry_rcu(p, node, head, hlist) {
188                 if (p->addr == addr)
189                         return p;
190         }
191         return NULL;
192 }
193
194 /*
195  * Aggregate handlers for multiple kprobes support - these handlers
196  * take care of invoking the individual kprobe handlers on p->list
197  */
198 static int __kprobes aggr_pre_handler(struct kprobe *p, struct pt_regs *regs)
199 {
200         struct kprobe *kp;
201
202         list_for_each_entry_rcu(kp, &p->list, list) {
203                 if (kp->pre_handler) {
204                         set_kprobe_instance(kp);
205                         if (kp->pre_handler(kp, regs))
206                                 return 1;
207                 }
208                 reset_kprobe_instance();
209         }
210         return 0;
211 }
212
213 static void __kprobes aggr_post_handler(struct kprobe *p, struct pt_regs *regs,
214                                         unsigned long flags)
215 {
216         struct kprobe *kp;
217
218         list_for_each_entry_rcu(kp, &p->list, list) {
219                 if (kp->post_handler) {
220                         set_kprobe_instance(kp);
221                         kp->post_handler(kp, regs, flags);
222                         reset_kprobe_instance();
223                 }
224         }
225         return;
226 }
227
228 static int __kprobes aggr_fault_handler(struct kprobe *p, struct pt_regs *regs,
229                                         int trapnr)
230 {
231         struct kprobe *cur = __get_cpu_var(kprobe_instance);
232
233         /*
234          * if we faulted "during" the execution of a user specified
235          * probe handler, invoke just that probe's fault handler
236          */
237         if (cur && cur->fault_handler) {
238                 if (cur->fault_handler(cur, regs, trapnr))
239                         return 1;
240         }
241         return 0;
242 }
243
244 static int __kprobes aggr_break_handler(struct kprobe *p, struct pt_regs *regs)
245 {
246         struct kprobe *cur = __get_cpu_var(kprobe_instance);
247         int ret = 0;
248
249         if (cur && cur->break_handler) {
250                 if (cur->break_handler(cur, regs))
251                         ret = 1;
252         }
253         reset_kprobe_instance();
254         return ret;
255 }
256
257 /* Walks the list and increments nmissed count for multiprobe case */
258 void __kprobes kprobes_inc_nmissed_count(struct kprobe *p)
259 {
260         struct kprobe *kp;
261         if (p->pre_handler != aggr_pre_handler) {
262                 p->nmissed++;
263         } else {
264                 list_for_each_entry_rcu(kp, &p->list, list)
265                         kp->nmissed++;
266         }
267         return;
268 }
269
270 /* Called with kretprobe_lock held */
271 struct kretprobe_instance __kprobes *get_free_rp_inst(struct kretprobe *rp)
272 {
273         struct hlist_node *node;
274         struct kretprobe_instance *ri;
275         hlist_for_each_entry(ri, node, &rp->free_instances, uflist)
276                 return ri;
277         return NULL;
278 }
279
280 /* Called with kretprobe_lock held */
281 static struct kretprobe_instance __kprobes *get_used_rp_inst(struct kretprobe
282                                                               *rp)
283 {
284         struct hlist_node *node;
285         struct kretprobe_instance *ri;
286         hlist_for_each_entry(ri, node, &rp->used_instances, uflist)
287                 return ri;
288         return NULL;
289 }
290
291 /* Called with kretprobe_lock held */
292 void __kprobes add_rp_inst(struct kretprobe_instance *ri)
293 {
294         /*
295          * Remove rp inst off the free list -
296          * Add it back when probed function returns
297          */
298         hlist_del(&ri->uflist);
299
300         /* Add rp inst onto table */
301         INIT_HLIST_NODE(&ri->hlist);
302         hlist_add_head(&ri->hlist,
303                         &kretprobe_inst_table[hash_ptr(ri->task, KPROBE_HASH_BITS)]);
304
305         /* Also add this rp inst to the used list. */
306         INIT_HLIST_NODE(&ri->uflist);
307         hlist_add_head(&ri->uflist, &ri->rp->used_instances);
308 }
309
310 /* Called with kretprobe_lock held */
311 void __kprobes recycle_rp_inst(struct kretprobe_instance *ri)
312 {
313         /* remove rp inst off the rprobe_inst_table */
314         hlist_del(&ri->hlist);
315         if (ri->rp) {
316                 /* remove rp inst off the used list */
317                 hlist_del(&ri->uflist);
318                 /* put rp inst back onto the free list */
319                 INIT_HLIST_NODE(&ri->uflist);
320                 hlist_add_head(&ri->uflist, &ri->rp->free_instances);
321         } else
322                 /* Unregistering */
323                 kfree(ri);
324 }
325
326 struct hlist_head __kprobes *kretprobe_inst_table_head(struct task_struct *tsk)
327 {
328         return &kretprobe_inst_table[hash_ptr(tsk, KPROBE_HASH_BITS)];
329 }
330
331 /*
332  * This function is called from finish_task_switch when task tk becomes dead,
333  * so that we can recycle any function-return probe instances associated
334  * with this task. These left over instances represent probed functions
335  * that have been called but will never return.
336  */
337 void __kprobes kprobe_flush_task(struct task_struct *tk)
338 {
339         struct kretprobe_instance *ri;
340         struct hlist_head *head;
341         struct hlist_node *node, *tmp;
342         unsigned long flags = 0;
343
344         spin_lock_irqsave(&kretprobe_lock, flags);
345         head = kretprobe_inst_table_head(tk);
346         hlist_for_each_entry_safe(ri, node, tmp, head, hlist) {
347                 if (ri->task == tk)
348                         recycle_rp_inst(ri);
349         }
350         spin_unlock_irqrestore(&kretprobe_lock, flags);
351 }
352
353 static inline void free_rp_inst(struct kretprobe *rp)
354 {
355         struct kretprobe_instance *ri;
356         while ((ri = get_free_rp_inst(rp)) != NULL) {
357                 hlist_del(&ri->uflist);
358                 kfree(ri);
359         }
360 }
361
362 /*
363  * Keep all fields in the kprobe consistent
364  */
365 static inline void copy_kprobe(struct kprobe *old_p, struct kprobe *p)
366 {
367         memcpy(&p->opcode, &old_p->opcode, sizeof(kprobe_opcode_t));
368         memcpy(&p->ainsn, &old_p->ainsn, sizeof(struct arch_specific_insn));
369 }
370
371 /*
372 * Add the new probe to old_p->list. Fail if this is the
373 * second jprobe at the address - two jprobes can't coexist
374 */
375 static int __kprobes add_new_kprobe(struct kprobe *old_p, struct kprobe *p)
376 {
377         if (p->break_handler) {
378                 if (old_p->break_handler)
379                         return -EEXIST;
380                 list_add_tail_rcu(&p->list, &old_p->list);
381                 old_p->break_handler = aggr_break_handler;
382         } else
383                 list_add_rcu(&p->list, &old_p->list);
384         if (p->post_handler && !old_p->post_handler)
385                 old_p->post_handler = aggr_post_handler;
386         return 0;
387 }
388
389 /*
390  * Fill in the required fields of the "manager kprobe". Replace the
391  * earlier kprobe in the hlist with the manager kprobe
392  */
393 static inline void add_aggr_kprobe(struct kprobe *ap, struct kprobe *p)
394 {
395         copy_kprobe(p, ap);
396         ap->addr = p->addr;
397         ap->pre_handler = aggr_pre_handler;
398         ap->fault_handler = aggr_fault_handler;
399         if (p->post_handler)
400                 ap->post_handler = aggr_post_handler;
401         if (p->break_handler)
402                 ap->break_handler = aggr_break_handler;
403
404         INIT_LIST_HEAD(&ap->list);
405         list_add_rcu(&p->list, &ap->list);
406
407         hlist_replace_rcu(&p->hlist, &ap->hlist);
408 }
409
410 /*
411  * This is the second or subsequent kprobe at the address - handle
412  * the intricacies
413  */
414 static int __kprobes register_aggr_kprobe(struct kprobe *old_p,
415                                           struct kprobe *p)
416 {
417         int ret = 0;
418         struct kprobe *ap;
419
420         if (old_p->pre_handler == aggr_pre_handler) {
421                 copy_kprobe(old_p, p);
422                 ret = add_new_kprobe(old_p, p);
423         } else {
424                 ap = kzalloc(sizeof(struct kprobe), GFP_KERNEL);
425                 if (!ap)
426                         return -ENOMEM;
427                 add_aggr_kprobe(ap, old_p);
428                 copy_kprobe(ap, p);
429                 ret = add_new_kprobe(ap, p);
430         }
431         return ret;
432 }
433
434 static int __kprobes in_kprobes_functions(unsigned long addr)
435 {
436         if (addr >= (unsigned long)__kprobes_text_start
437                 && addr < (unsigned long)__kprobes_text_end)
438                 return -EINVAL;
439         return 0;
440 }
441
442 static int __kprobes __register_kprobe(struct kprobe *p,
443         unsigned long called_from)
444 {
445         int ret = 0;
446         struct kprobe *old_p;
447         struct module *probed_mod;
448
449         if ((!kernel_text_address((unsigned long) p->addr)) ||
450                 in_kprobes_functions((unsigned long) p->addr))
451                 return -EINVAL;
452
453         p->mod_refcounted = 0;
454         /* Check are we probing a module */
455         if ((probed_mod = module_text_address((unsigned long) p->addr))) {
456                 struct module *calling_mod = module_text_address(called_from);
457                 /* We must allow modules to probe themself and
458                  * in this case avoid incrementing the module refcount,
459                  * so as to allow unloading of self probing modules.
460                  */
461                 if (calling_mod && (calling_mod != probed_mod)) {
462                         if (unlikely(!try_module_get(probed_mod)))
463                                 return -EINVAL;
464                         p->mod_refcounted = 1;
465                 } else
466                         probed_mod = NULL;
467         }
468
469         p->nmissed = 0;
470         mutex_lock(&kprobe_mutex);
471         old_p = get_kprobe(p->addr);
472         if (old_p) {
473                 ret = register_aggr_kprobe(old_p, p);
474                 if (!ret)
475                         atomic_inc(&kprobe_count);
476                 goto out;
477         }
478
479         if ((ret = arch_prepare_kprobe(p)) != 0)
480                 goto out;
481
482         INIT_HLIST_NODE(&p->hlist);
483         hlist_add_head_rcu(&p->hlist,
484                        &kprobe_table[hash_ptr(p->addr, KPROBE_HASH_BITS)]);
485
486         if (atomic_add_return(1, &kprobe_count) == \
487                                 (ARCH_INACTIVE_KPROBE_COUNT + 1))
488                 register_page_fault_notifier(&kprobe_page_fault_nb);
489
490         arch_arm_kprobe(p);
491
492 out:
493         mutex_unlock(&kprobe_mutex);
494
495         if (ret && probed_mod)
496                 module_put(probed_mod);
497         return ret;
498 }
499
500 int __kprobes register_kprobe(struct kprobe *p)
501 {
502         return __register_kprobe(p,
503                 (unsigned long)__builtin_return_address(0));
504 }
505
506 void __kprobes unregister_kprobe(struct kprobe *p)
507 {
508         struct module *mod;
509         struct kprobe *old_p, *list_p;
510         int cleanup_p;
511
512         mutex_lock(&kprobe_mutex);
513         old_p = get_kprobe(p->addr);
514         if (unlikely(!old_p)) {
515                 mutex_unlock(&kprobe_mutex);
516                 return;
517         }
518         if (p != old_p) {
519                 list_for_each_entry_rcu(list_p, &old_p->list, list)
520                         if (list_p == p)
521                         /* kprobe p is a valid probe */
522                                 goto valid_p;
523                 mutex_unlock(&kprobe_mutex);
524                 return;
525         }
526 valid_p:
527         if ((old_p == p) || ((old_p->pre_handler == aggr_pre_handler) &&
528                 (p->list.next == &old_p->list) &&
529                 (p->list.prev == &old_p->list))) {
530                 /* Only probe on the hash list */
531                 arch_disarm_kprobe(p);
532                 hlist_del_rcu(&old_p->hlist);
533                 cleanup_p = 1;
534         } else {
535                 list_del_rcu(&p->list);
536                 cleanup_p = 0;
537         }
538
539         mutex_unlock(&kprobe_mutex);
540
541         synchronize_sched();
542         if (p->mod_refcounted &&
543             (mod = module_text_address((unsigned long)p->addr)))
544                 module_put(mod);
545
546         if (cleanup_p) {
547                 if (p != old_p) {
548                         list_del_rcu(&p->list);
549                         kfree(old_p);
550                 }
551                 arch_remove_kprobe(p);
552         } else {
553                 mutex_lock(&kprobe_mutex);
554                 if (p->break_handler)
555                         old_p->break_handler = NULL;
556                 if (p->post_handler){
557                         list_for_each_entry_rcu(list_p, &old_p->list, list){
558                                 if (list_p->post_handler){
559                                         cleanup_p = 2;
560                                         break;
561                                 }
562                         }
563                         if (cleanup_p == 0)
564                                 old_p->post_handler = NULL;
565                 }
566                 mutex_unlock(&kprobe_mutex);
567         }
568
569         /* Call unregister_page_fault_notifier()
570          * if no probes are active
571          */
572         mutex_lock(&kprobe_mutex);
573         if (atomic_add_return(-1, &kprobe_count) == \
574                                 ARCH_INACTIVE_KPROBE_COUNT)
575                 unregister_page_fault_notifier(&kprobe_page_fault_nb);
576         mutex_unlock(&kprobe_mutex);
577         return;
578 }
579
580 static struct notifier_block kprobe_exceptions_nb = {
581         .notifier_call = kprobe_exceptions_notify,
582         .priority = 0x7fffffff /* we need to be notified first */
583 };
584
585
586 int __kprobes register_jprobe(struct jprobe *jp)
587 {
588         /* Todo: Verify probepoint is a function entry point */
589         jp->kp.pre_handler = setjmp_pre_handler;
590         jp->kp.break_handler = longjmp_break_handler;
591
592         return __register_kprobe(&jp->kp,
593                 (unsigned long)__builtin_return_address(0));
594 }
595
596 void __kprobes unregister_jprobe(struct jprobe *jp)
597 {
598         unregister_kprobe(&jp->kp);
599 }
600
601 #ifdef ARCH_SUPPORTS_KRETPROBES
602
603 /*
604  * This kprobe pre_handler is registered with every kretprobe. When probe
605  * hits it will set up the return probe.
606  */
607 static int __kprobes pre_handler_kretprobe(struct kprobe *p,
608                                            struct pt_regs *regs)
609 {
610         struct kretprobe *rp = container_of(p, struct kretprobe, kp);
611         unsigned long flags = 0;
612
613         /*TODO: consider to only swap the RA after the last pre_handler fired */
614         spin_lock_irqsave(&kretprobe_lock, flags);
615         arch_prepare_kretprobe(rp, regs);
616         spin_unlock_irqrestore(&kretprobe_lock, flags);
617         return 0;
618 }
619
620 int __kprobes register_kretprobe(struct kretprobe *rp)
621 {
622         int ret = 0;
623         struct kretprobe_instance *inst;
624         int i;
625
626         rp->kp.pre_handler = pre_handler_kretprobe;
627         rp->kp.post_handler = NULL;
628         rp->kp.fault_handler = NULL;
629         rp->kp.break_handler = NULL;
630
631         /* Pre-allocate memory for max kretprobe instances */
632         if (rp->maxactive <= 0) {
633 #ifdef CONFIG_PREEMPT
634                 rp->maxactive = max(10, 2 * NR_CPUS);
635 #else
636                 rp->maxactive = NR_CPUS;
637 #endif
638         }
639         INIT_HLIST_HEAD(&rp->used_instances);
640         INIT_HLIST_HEAD(&rp->free_instances);
641         for (i = 0; i < rp->maxactive; i++) {
642                 inst = kmalloc(sizeof(struct kretprobe_instance), GFP_KERNEL);
643                 if (inst == NULL) {
644                         free_rp_inst(rp);
645                         return -ENOMEM;
646                 }
647                 INIT_HLIST_NODE(&inst->uflist);
648                 hlist_add_head(&inst->uflist, &rp->free_instances);
649         }
650
651         rp->nmissed = 0;
652         /* Establish function entry probe point */
653         if ((ret = __register_kprobe(&rp->kp,
654                 (unsigned long)__builtin_return_address(0))) != 0)
655                 free_rp_inst(rp);
656         return ret;
657 }
658
659 #else /* ARCH_SUPPORTS_KRETPROBES */
660
661 int __kprobes register_kretprobe(struct kretprobe *rp)
662 {
663         return -ENOSYS;
664 }
665
666 #endif /* ARCH_SUPPORTS_KRETPROBES */
667
668 void __kprobes unregister_kretprobe(struct kretprobe *rp)
669 {
670         unsigned long flags;
671         struct kretprobe_instance *ri;
672
673         unregister_kprobe(&rp->kp);
674         /* No race here */
675         spin_lock_irqsave(&kretprobe_lock, flags);
676         while ((ri = get_used_rp_inst(rp)) != NULL) {
677                 ri->rp = NULL;
678                 hlist_del(&ri->uflist);
679         }
680         spin_unlock_irqrestore(&kretprobe_lock, flags);
681         free_rp_inst(rp);
682 }
683
684 static int __init init_kprobes(void)
685 {
686         int i, err = 0;
687
688         /* FIXME allocate the probe table, currently defined statically */
689         /* initialize all list heads */
690         for (i = 0; i < KPROBE_TABLE_SIZE; i++) {
691                 INIT_HLIST_HEAD(&kprobe_table[i]);
692                 INIT_HLIST_HEAD(&kretprobe_inst_table[i]);
693         }
694         atomic_set(&kprobe_count, 0);
695
696         err = arch_init_kprobes();
697         if (!err)
698                 err = register_die_notifier(&kprobe_exceptions_nb);
699
700         return err;
701 }
702
703 __initcall(init_kprobes);
704
705 EXPORT_SYMBOL_GPL(register_kprobe);
706 EXPORT_SYMBOL_GPL(unregister_kprobe);
707 EXPORT_SYMBOL_GPL(register_jprobe);
708 EXPORT_SYMBOL_GPL(unregister_jprobe);
709 EXPORT_SYMBOL_GPL(jprobe_return);
710 EXPORT_SYMBOL_GPL(register_kretprobe);
711 EXPORT_SYMBOL_GPL(unregister_kretprobe);
712