jprobes: make jprobes a little safer for users
[linux-3.10.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/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 unsigned long __weak arch_deref_entry_point(void *entry)
679 {
680         return (unsigned long)entry;
681 }
682
683 int __kprobes register_jprobe(struct jprobe *jp)
684 {
685         unsigned long addr = arch_deref_entry_point(jp->entry);
686
687         if (!kernel_text_address(addr))
688                 return -EINVAL;
689
690         /* Todo: Verify probepoint is a function entry point */
691         jp->kp.pre_handler = setjmp_pre_handler;
692         jp->kp.break_handler = longjmp_break_handler;
693
694         return __register_kprobe(&jp->kp,
695                 (unsigned long)__builtin_return_address(0));
696 }
697
698 void __kprobes unregister_jprobe(struct jprobe *jp)
699 {
700         unregister_kprobe(&jp->kp);
701 }
702
703 #ifdef ARCH_SUPPORTS_KRETPROBES
704
705 /*
706  * This kprobe pre_handler is registered with every kretprobe. When probe
707  * hits it will set up the return probe.
708  */
709 static int __kprobes pre_handler_kretprobe(struct kprobe *p,
710                                            struct pt_regs *regs)
711 {
712         struct kretprobe *rp = container_of(p, struct kretprobe, kp);
713         unsigned long flags = 0;
714
715         /*TODO: consider to only swap the RA after the last pre_handler fired */
716         spin_lock_irqsave(&kretprobe_lock, flags);
717         if (!hlist_empty(&rp->free_instances)) {
718                 struct kretprobe_instance *ri;
719
720                 ri = hlist_entry(rp->free_instances.first,
721                                  struct kretprobe_instance, uflist);
722                 ri->rp = rp;
723                 ri->task = current;
724                 arch_prepare_kretprobe(ri, regs);
725
726                 /* XXX(hch): why is there no hlist_move_head? */
727                 hlist_del(&ri->uflist);
728                 hlist_add_head(&ri->uflist, &ri->rp->used_instances);
729                 hlist_add_head(&ri->hlist, kretprobe_inst_table_head(ri->task));
730         } else
731                 rp->nmissed++;
732         spin_unlock_irqrestore(&kretprobe_lock, flags);
733         return 0;
734 }
735
736 int __kprobes register_kretprobe(struct kretprobe *rp)
737 {
738         int ret = 0;
739         struct kretprobe_instance *inst;
740         int i;
741
742         rp->kp.pre_handler = pre_handler_kretprobe;
743         rp->kp.post_handler = NULL;
744         rp->kp.fault_handler = NULL;
745         rp->kp.break_handler = NULL;
746
747         /* Pre-allocate memory for max kretprobe instances */
748         if (rp->maxactive <= 0) {
749 #ifdef CONFIG_PREEMPT
750                 rp->maxactive = max(10, 2 * NR_CPUS);
751 #else
752                 rp->maxactive = NR_CPUS;
753 #endif
754         }
755         INIT_HLIST_HEAD(&rp->used_instances);
756         INIT_HLIST_HEAD(&rp->free_instances);
757         for (i = 0; i < rp->maxactive; i++) {
758                 inst = kmalloc(sizeof(struct kretprobe_instance), GFP_KERNEL);
759                 if (inst == NULL) {
760                         free_rp_inst(rp);
761                         return -ENOMEM;
762                 }
763                 INIT_HLIST_NODE(&inst->uflist);
764                 hlist_add_head(&inst->uflist, &rp->free_instances);
765         }
766
767         rp->nmissed = 0;
768         /* Establish function entry probe point */
769         if ((ret = __register_kprobe(&rp->kp,
770                 (unsigned long)__builtin_return_address(0))) != 0)
771                 free_rp_inst(rp);
772         return ret;
773 }
774
775 #else /* ARCH_SUPPORTS_KRETPROBES */
776
777 int __kprobes register_kretprobe(struct kretprobe *rp)
778 {
779         return -ENOSYS;
780 }
781
782 static int __kprobes pre_handler_kretprobe(struct kprobe *p,
783                                            struct pt_regs *regs)
784 {
785         return 0;
786 }
787
788 #endif /* ARCH_SUPPORTS_KRETPROBES */
789
790 void __kprobes unregister_kretprobe(struct kretprobe *rp)
791 {
792         unsigned long flags;
793         struct kretprobe_instance *ri;
794         struct hlist_node *pos, *next;
795
796         unregister_kprobe(&rp->kp);
797
798         /* No race here */
799         spin_lock_irqsave(&kretprobe_lock, flags);
800         hlist_for_each_entry_safe(ri, pos, next, &rp->used_instances, uflist) {
801                 ri->rp = NULL;
802                 hlist_del(&ri->uflist);
803         }
804         spin_unlock_irqrestore(&kretprobe_lock, flags);
805         free_rp_inst(rp);
806 }
807
808 static int __init init_kprobes(void)
809 {
810         int i, err = 0;
811
812         /* FIXME allocate the probe table, currently defined statically */
813         /* initialize all list heads */
814         for (i = 0; i < KPROBE_TABLE_SIZE; i++) {
815                 INIT_HLIST_HEAD(&kprobe_table[i]);
816                 INIT_HLIST_HEAD(&kretprobe_inst_table[i]);
817         }
818         atomic_set(&kprobe_count, 0);
819
820         /* By default, kprobes are enabled */
821         kprobe_enabled = true;
822
823         err = arch_init_kprobes();
824         if (!err)
825                 err = register_die_notifier(&kprobe_exceptions_nb);
826
827         return err;
828 }
829
830 #ifdef CONFIG_DEBUG_FS
831 static void __kprobes report_probe(struct seq_file *pi, struct kprobe *p,
832                 const char *sym, int offset,char *modname)
833 {
834         char *kprobe_type;
835
836         if (p->pre_handler == pre_handler_kretprobe)
837                 kprobe_type = "r";
838         else if (p->pre_handler == setjmp_pre_handler)
839                 kprobe_type = "j";
840         else
841                 kprobe_type = "k";
842         if (sym)
843                 seq_printf(pi, "%p  %s  %s+0x%x  %s\n", p->addr, kprobe_type,
844                         sym, offset, (modname ? modname : " "));
845         else
846                 seq_printf(pi, "%p  %s  %p\n", p->addr, kprobe_type, p->addr);
847 }
848
849 static void __kprobes *kprobe_seq_start(struct seq_file *f, loff_t *pos)
850 {
851         return (*pos < KPROBE_TABLE_SIZE) ? pos : NULL;
852 }
853
854 static void __kprobes *kprobe_seq_next(struct seq_file *f, void *v, loff_t *pos)
855 {
856         (*pos)++;
857         if (*pos >= KPROBE_TABLE_SIZE)
858                 return NULL;
859         return pos;
860 }
861
862 static void __kprobes kprobe_seq_stop(struct seq_file *f, void *v)
863 {
864         /* Nothing to do */
865 }
866
867 static int __kprobes show_kprobe_addr(struct seq_file *pi, void *v)
868 {
869         struct hlist_head *head;
870         struct hlist_node *node;
871         struct kprobe *p, *kp;
872         const char *sym = NULL;
873         unsigned int i = *(loff_t *) v;
874         unsigned long offset = 0;
875         char *modname, namebuf[128];
876
877         head = &kprobe_table[i];
878         preempt_disable();
879         hlist_for_each_entry_rcu(p, node, head, hlist) {
880                 sym = kallsyms_lookup((unsigned long)p->addr, NULL,
881                                         &offset, &modname, namebuf);
882                 if (p->pre_handler == aggr_pre_handler) {
883                         list_for_each_entry_rcu(kp, &p->list, list)
884                                 report_probe(pi, kp, sym, offset, modname);
885                 } else
886                         report_probe(pi, p, sym, offset, modname);
887         }
888         preempt_enable();
889         return 0;
890 }
891
892 static struct seq_operations kprobes_seq_ops = {
893         .start = kprobe_seq_start,
894         .next  = kprobe_seq_next,
895         .stop  = kprobe_seq_stop,
896         .show  = show_kprobe_addr
897 };
898
899 static int __kprobes kprobes_open(struct inode *inode, struct file *filp)
900 {
901         return seq_open(filp, &kprobes_seq_ops);
902 }
903
904 static struct file_operations debugfs_kprobes_operations = {
905         .open           = kprobes_open,
906         .read           = seq_read,
907         .llseek         = seq_lseek,
908         .release        = seq_release,
909 };
910
911 static void __kprobes enable_all_kprobes(void)
912 {
913         struct hlist_head *head;
914         struct hlist_node *node;
915         struct kprobe *p;
916         unsigned int i;
917
918         mutex_lock(&kprobe_mutex);
919
920         /* If kprobes are already enabled, just return */
921         if (kprobe_enabled)
922                 goto already_enabled;
923
924         /*
925          * Re-register the page fault notifier only if there are any
926          * active probes at the time of enabling kprobes globally
927          */
928         if (atomic_read(&kprobe_count) > ARCH_INACTIVE_KPROBE_COUNT)
929                 register_page_fault_notifier(&kprobe_page_fault_nb);
930
931         for (i = 0; i < KPROBE_TABLE_SIZE; i++) {
932                 head = &kprobe_table[i];
933                 hlist_for_each_entry_rcu(p, node, head, hlist)
934                         arch_arm_kprobe(p);
935         }
936
937         kprobe_enabled = true;
938         printk(KERN_INFO "Kprobes globally enabled\n");
939
940 already_enabled:
941         mutex_unlock(&kprobe_mutex);
942         return;
943 }
944
945 static void __kprobes disable_all_kprobes(void)
946 {
947         struct hlist_head *head;
948         struct hlist_node *node;
949         struct kprobe *p;
950         unsigned int i;
951
952         mutex_lock(&kprobe_mutex);
953
954         /* If kprobes are already disabled, just return */
955         if (!kprobe_enabled)
956                 goto already_disabled;
957
958         kprobe_enabled = false;
959         printk(KERN_INFO "Kprobes globally disabled\n");
960         for (i = 0; i < KPROBE_TABLE_SIZE; i++) {
961                 head = &kprobe_table[i];
962                 hlist_for_each_entry_rcu(p, node, head, hlist) {
963                         if (!arch_trampoline_kprobe(p))
964                                 arch_disarm_kprobe(p);
965                 }
966         }
967
968         mutex_unlock(&kprobe_mutex);
969         /* Allow all currently running kprobes to complete */
970         synchronize_sched();
971
972         mutex_lock(&kprobe_mutex);
973         /* Unconditionally unregister the page_fault notifier */
974         unregister_page_fault_notifier(&kprobe_page_fault_nb);
975
976 already_disabled:
977         mutex_unlock(&kprobe_mutex);
978         return;
979 }
980
981 /*
982  * XXX: The debugfs bool file interface doesn't allow for callbacks
983  * when the bool state is switched. We can reuse that facility when
984  * available
985  */
986 static ssize_t read_enabled_file_bool(struct file *file,
987                char __user *user_buf, size_t count, loff_t *ppos)
988 {
989         char buf[3];
990
991         if (kprobe_enabled)
992                 buf[0] = '1';
993         else
994                 buf[0] = '0';
995         buf[1] = '\n';
996         buf[2] = 0x00;
997         return simple_read_from_buffer(user_buf, count, ppos, buf, 2);
998 }
999
1000 static ssize_t write_enabled_file_bool(struct file *file,
1001                const char __user *user_buf, size_t count, loff_t *ppos)
1002 {
1003         char buf[32];
1004         int buf_size;
1005
1006         buf_size = min(count, (sizeof(buf)-1));
1007         if (copy_from_user(buf, user_buf, buf_size))
1008                 return -EFAULT;
1009
1010         switch (buf[0]) {
1011         case 'y':
1012         case 'Y':
1013         case '1':
1014                 enable_all_kprobes();
1015                 break;
1016         case 'n':
1017         case 'N':
1018         case '0':
1019                 disable_all_kprobes();
1020                 break;
1021         }
1022
1023         return count;
1024 }
1025
1026 static struct file_operations fops_kp = {
1027         .read =         read_enabled_file_bool,
1028         .write =        write_enabled_file_bool,
1029 };
1030
1031 static int __kprobes debugfs_kprobe_init(void)
1032 {
1033         struct dentry *dir, *file;
1034         unsigned int value = 1;
1035
1036         dir = debugfs_create_dir("kprobes", NULL);
1037         if (!dir)
1038                 return -ENOMEM;
1039
1040         file = debugfs_create_file("list", 0444, dir, NULL,
1041                                 &debugfs_kprobes_operations);
1042         if (!file) {
1043                 debugfs_remove(dir);
1044                 return -ENOMEM;
1045         }
1046
1047         file = debugfs_create_file("enabled", 0600, dir,
1048                                         &value, &fops_kp);
1049         if (!file) {
1050                 debugfs_remove(dir);
1051                 return -ENOMEM;
1052         }
1053
1054         return 0;
1055 }
1056
1057 late_initcall(debugfs_kprobe_init);
1058 #endif /* CONFIG_DEBUG_FS */
1059
1060 module_init(init_kprobes);
1061
1062 EXPORT_SYMBOL_GPL(register_kprobe);
1063 EXPORT_SYMBOL_GPL(unregister_kprobe);
1064 EXPORT_SYMBOL_GPL(register_jprobe);
1065 EXPORT_SYMBOL_GPL(unregister_jprobe);
1066 EXPORT_SYMBOL_GPL(jprobe_return);
1067 EXPORT_SYMBOL_GPL(register_kretprobe);
1068 EXPORT_SYMBOL_GPL(unregister_kretprobe);