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TOMOYO Linux Cross Reference
Linux/kernel/kprobes.c

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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/export.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/sysctl.h>
 46 #include <linux/kdebug.h>
 47 #include <linux/memory.h>
 48 #include <linux/ftrace.h>
 49 #include <linux/cpu.h>
 50 #include <linux/jump_label.h>
 51 
 52 #include <asm/sections.h>
 53 #include <asm/cacheflush.h>
 54 #include <asm/errno.h>
 55 #include <linux/uaccess.h>
 56 
 57 #define KPROBE_HASH_BITS 6
 58 #define KPROBE_TABLE_SIZE (1 << KPROBE_HASH_BITS)
 59 
 60 
 61 static int kprobes_initialized;
 62 static struct hlist_head kprobe_table[KPROBE_TABLE_SIZE];
 63 static struct hlist_head kretprobe_inst_table[KPROBE_TABLE_SIZE];
 64 
 65 /* NOTE: change this value only with kprobe_mutex held */
 66 static bool kprobes_all_disarmed;
 67 
 68 /* This protects kprobe_table and optimizing_list */
 69 static DEFINE_MUTEX(kprobe_mutex);
 70 static DEFINE_PER_CPU(struct kprobe *, kprobe_instance) = NULL;
 71 static struct {
 72         raw_spinlock_t lock ____cacheline_aligned_in_smp;
 73 } kretprobe_table_locks[KPROBE_TABLE_SIZE];
 74 
 75 kprobe_opcode_t * __weak kprobe_lookup_name(const char *name,
 76                                         unsigned int __unused)
 77 {
 78         return ((kprobe_opcode_t *)(kallsyms_lookup_name(name)));
 79 }
 80 
 81 static raw_spinlock_t *kretprobe_table_lock_ptr(unsigned long hash)
 82 {
 83         return &(kretprobe_table_locks[hash].lock);
 84 }
 85 
 86 /* Blacklist -- list of struct kprobe_blacklist_entry */
 87 static LIST_HEAD(kprobe_blacklist);
 88 
 89 #ifdef __ARCH_WANT_KPROBES_INSN_SLOT
 90 /*
 91  * kprobe->ainsn.insn points to the copy of the instruction to be
 92  * single-stepped. x86_64, POWER4 and above have no-exec support and
 93  * stepping on the instruction on a vmalloced/kmalloced/data page
 94  * is a recipe for disaster
 95  */
 96 struct kprobe_insn_page {
 97         struct list_head list;
 98         kprobe_opcode_t *insns;         /* Page of instruction slots */
 99         struct kprobe_insn_cache *cache;
100         int nused;
101         int ngarbage;
102         char slot_used[];
103 };
104 
105 #define KPROBE_INSN_PAGE_SIZE(slots)                    \
106         (offsetof(struct kprobe_insn_page, slot_used) + \
107          (sizeof(char) * (slots)))
108 
109 static int slots_per_page(struct kprobe_insn_cache *c)
110 {
111         return PAGE_SIZE/(c->insn_size * sizeof(kprobe_opcode_t));
112 }
113 
114 enum kprobe_slot_state {
115         SLOT_CLEAN = 0,
116         SLOT_DIRTY = 1,
117         SLOT_USED = 2,
118 };
119 
120 void __weak *alloc_insn_page(void)
121 {
122         return module_alloc(PAGE_SIZE);
123 }
124 
125 void __weak free_insn_page(void *page)
126 {
127         module_memfree(page);
128 }
129 
130 struct kprobe_insn_cache kprobe_insn_slots = {
131         .mutex = __MUTEX_INITIALIZER(kprobe_insn_slots.mutex),
132         .alloc = alloc_insn_page,
133         .free = free_insn_page,
134         .pages = LIST_HEAD_INIT(kprobe_insn_slots.pages),
135         .insn_size = MAX_INSN_SIZE,
136         .nr_garbage = 0,
137 };
138 static int collect_garbage_slots(struct kprobe_insn_cache *c);
139 
140 /**
141  * __get_insn_slot() - Find a slot on an executable page for an instruction.
142  * We allocate an executable page if there's no room on existing ones.
143  */
144 kprobe_opcode_t *__get_insn_slot(struct kprobe_insn_cache *c)
145 {
146         struct kprobe_insn_page *kip;
147         kprobe_opcode_t *slot = NULL;
148 
149         /* Since the slot array is not protected by rcu, we need a mutex */
150         mutex_lock(&c->mutex);
151  retry:
152         rcu_read_lock();
153         list_for_each_entry_rcu(kip, &c->pages, list) {
154                 if (kip->nused < slots_per_page(c)) {
155                         int i;
156                         for (i = 0; i < slots_per_page(c); i++) {
157                                 if (kip->slot_used[i] == SLOT_CLEAN) {
158                                         kip->slot_used[i] = SLOT_USED;
159                                         kip->nused++;
160                                         slot = kip->insns + (i * c->insn_size);
161                                         rcu_read_unlock();
162                                         goto out;
163                                 }
164                         }
165                         /* kip->nused is broken. Fix it. */
166                         kip->nused = slots_per_page(c);
167                         WARN_ON(1);
168                 }
169         }
170         rcu_read_unlock();
171 
172         /* If there are any garbage slots, collect it and try again. */
173         if (c->nr_garbage && collect_garbage_slots(c) == 0)
174                 goto retry;
175 
176         /* All out of space.  Need to allocate a new page. */
177         kip = kmalloc(KPROBE_INSN_PAGE_SIZE(slots_per_page(c)), GFP_KERNEL);
178         if (!kip)
179                 goto out;
180 
181         /*
182          * Use module_alloc so this page is within +/- 2GB of where the
183          * kernel image and loaded module images reside. This is required
184          * so x86_64 can correctly handle the %rip-relative fixups.
185          */
186         kip->insns = c->alloc();
187         if (!kip->insns) {
188                 kfree(kip);
189                 goto out;
190         }
191         INIT_LIST_HEAD(&kip->list);
192         memset(kip->slot_used, SLOT_CLEAN, slots_per_page(c));
193         kip->slot_used[0] = SLOT_USED;
194         kip->nused = 1;
195         kip->ngarbage = 0;
196         kip->cache = c;
197         list_add_rcu(&kip->list, &c->pages);
198         slot = kip->insns;
199 out:
200         mutex_unlock(&c->mutex);
201         return slot;
202 }
203 
204 /* Return 1 if all garbages are collected, otherwise 0. */
205 static int collect_one_slot(struct kprobe_insn_page *kip, int idx)
206 {
207         kip->slot_used[idx] = SLOT_CLEAN;
208         kip->nused--;
209         if (kip->nused == 0) {
210                 /*
211                  * Page is no longer in use.  Free it unless
212                  * it's the last one.  We keep the last one
213                  * so as not to have to set it up again the
214                  * next time somebody inserts a probe.
215                  */
216                 if (!list_is_singular(&kip->list)) {
217                         list_del_rcu(&kip->list);
218                         synchronize_rcu();
219                         kip->cache->free(kip->insns);
220                         kfree(kip);
221                 }
222                 return 1;
223         }
224         return 0;
225 }
226 
227 static int collect_garbage_slots(struct kprobe_insn_cache *c)
228 {
229         struct kprobe_insn_page *kip, *next;
230 
231         /* Ensure no-one is interrupted on the garbages */
232         synchronize_sched();
233 
234         list_for_each_entry_safe(kip, next, &c->pages, list) {
235                 int i;
236                 if (kip->ngarbage == 0)
237                         continue;
238                 kip->ngarbage = 0;      /* we will collect all garbages */
239                 for (i = 0; i < slots_per_page(c); i++) {
240                         if (kip->slot_used[i] == SLOT_DIRTY && collect_one_slot(kip, i))
241                                 break;
242                 }
243         }
244         c->nr_garbage = 0;
245         return 0;
246 }
247 
248 void __free_insn_slot(struct kprobe_insn_cache *c,
249                       kprobe_opcode_t *slot, int dirty)
250 {
251         struct kprobe_insn_page *kip;
252         long idx;
253 
254         mutex_lock(&c->mutex);
255         rcu_read_lock();
256         list_for_each_entry_rcu(kip, &c->pages, list) {
257                 idx = ((long)slot - (long)kip->insns) /
258                         (c->insn_size * sizeof(kprobe_opcode_t));
259                 if (idx >= 0 && idx < slots_per_page(c))
260                         goto out;
261         }
262         /* Could not find this slot. */
263         WARN_ON(1);
264         kip = NULL;
265 out:
266         rcu_read_unlock();
267         /* Mark and sweep: this may sleep */
268         if (kip) {
269                 /* Check double free */
270                 WARN_ON(kip->slot_used[idx] != SLOT_USED);
271                 if (dirty) {
272                         kip->slot_used[idx] = SLOT_DIRTY;
273                         kip->ngarbage++;
274                         if (++c->nr_garbage > slots_per_page(c))
275                                 collect_garbage_slots(c);
276                 } else {
277                         collect_one_slot(kip, idx);
278                 }
279         }
280         mutex_unlock(&c->mutex);
281 }
282 
283 /*
284  * Check given address is on the page of kprobe instruction slots.
285  * This will be used for checking whether the address on a stack
286  * is on a text area or not.
287  */
288 bool __is_insn_slot_addr(struct kprobe_insn_cache *c, unsigned long addr)
289 {
290         struct kprobe_insn_page *kip;
291         bool ret = false;
292 
293         rcu_read_lock();
294         list_for_each_entry_rcu(kip, &c->pages, list) {
295                 if (addr >= (unsigned long)kip->insns &&
296                     addr < (unsigned long)kip->insns + PAGE_SIZE) {
297                         ret = true;
298                         break;
299                 }
300         }
301         rcu_read_unlock();
302 
303         return ret;
304 }
305 
306 #ifdef CONFIG_OPTPROBES
307 /* For optimized_kprobe buffer */
308 struct kprobe_insn_cache kprobe_optinsn_slots = {
309         .mutex = __MUTEX_INITIALIZER(kprobe_optinsn_slots.mutex),
310         .alloc = alloc_insn_page,
311         .free = free_insn_page,
312         .pages = LIST_HEAD_INIT(kprobe_optinsn_slots.pages),
313         /* .insn_size is initialized later */
314         .nr_garbage = 0,
315 };
316 #endif
317 #endif
318 
319 /* We have preemption disabled.. so it is safe to use __ versions */
320 static inline void set_kprobe_instance(struct kprobe *kp)
321 {
322         __this_cpu_write(kprobe_instance, kp);
323 }
324 
325 static inline void reset_kprobe_instance(void)
326 {
327         __this_cpu_write(kprobe_instance, NULL);
328 }
329 
330 /*
331  * This routine is called either:
332  *      - under the kprobe_mutex - during kprobe_[un]register()
333  *                              OR
334  *      - with preemption disabled - from arch/xxx/kernel/kprobes.c
335  */
336 struct kprobe *get_kprobe(void *addr)
337 {
338         struct hlist_head *head;
339         struct kprobe *p;
340 
341         head = &kprobe_table[hash_ptr(addr, KPROBE_HASH_BITS)];
342         hlist_for_each_entry_rcu(p, head, hlist) {
343                 if (p->addr == addr)
344                         return p;
345         }
346 
347         return NULL;
348 }
349 NOKPROBE_SYMBOL(get_kprobe);
350 
351 static int aggr_pre_handler(struct kprobe *p, struct pt_regs *regs);
352 
353 /* Return true if the kprobe is an aggregator */
354 static inline int kprobe_aggrprobe(struct kprobe *p)
355 {
356         return p->pre_handler == aggr_pre_handler;
357 }
358 
359 /* Return true(!0) if the kprobe is unused */
360 static inline int kprobe_unused(struct kprobe *p)
361 {
362         return kprobe_aggrprobe(p) && kprobe_disabled(p) &&
363                list_empty(&p->list);
364 }
365 
366 /*
367  * Keep all fields in the kprobe consistent
368  */
369 static inline void copy_kprobe(struct kprobe *ap, struct kprobe *p)
370 {
371         memcpy(&p->opcode, &ap->opcode, sizeof(kprobe_opcode_t));
372         memcpy(&p->ainsn, &ap->ainsn, sizeof(struct arch_specific_insn));
373 }
374 
375 #ifdef CONFIG_OPTPROBES
376 /* NOTE: change this value only with kprobe_mutex held */
377 static bool kprobes_allow_optimization;
378 
379 /*
380  * Call all pre_handler on the list, but ignores its return value.
381  * This must be called from arch-dep optimized caller.
382  */
383 void opt_pre_handler(struct kprobe *p, struct pt_regs *regs)
384 {
385         struct kprobe *kp;
386 
387         list_for_each_entry_rcu(kp, &p->list, list) {
388                 if (kp->pre_handler && likely(!kprobe_disabled(kp))) {
389                         set_kprobe_instance(kp);
390                         kp->pre_handler(kp, regs);
391                 }
392                 reset_kprobe_instance();
393         }
394 }
395 NOKPROBE_SYMBOL(opt_pre_handler);
396 
397 /* Free optimized instructions and optimized_kprobe */
398 static void free_aggr_kprobe(struct kprobe *p)
399 {
400         struct optimized_kprobe *op;
401 
402         op = container_of(p, struct optimized_kprobe, kp);
403         arch_remove_optimized_kprobe(op);
404         arch_remove_kprobe(p);
405         kfree(op);
406 }
407 
408 /* Return true(!0) if the kprobe is ready for optimization. */
409 static inline int kprobe_optready(struct kprobe *p)
410 {
411         struct optimized_kprobe *op;
412 
413         if (kprobe_aggrprobe(p)) {
414                 op = container_of(p, struct optimized_kprobe, kp);
415                 return arch_prepared_optinsn(&op->optinsn);
416         }
417 
418         return 0;
419 }
420 
421 /* Return true(!0) if the kprobe is disarmed. Note: p must be on hash list */
422 static inline int kprobe_disarmed(struct kprobe *p)
423 {
424         struct optimized_kprobe *op;
425 
426         /* If kprobe is not aggr/opt probe, just return kprobe is disabled */
427         if (!kprobe_aggrprobe(p))
428                 return kprobe_disabled(p);
429 
430         op = container_of(p, struct optimized_kprobe, kp);
431 
432         return kprobe_disabled(p) && list_empty(&op->list);
433 }
434 
435 /* Return true(!0) if the probe is queued on (un)optimizing lists */
436 static int kprobe_queued(struct kprobe *p)
437 {
438         struct optimized_kprobe *op;
439 
440         if (kprobe_aggrprobe(p)) {
441                 op = container_of(p, struct optimized_kprobe, kp);
442                 if (!list_empty(&op->list))
443                         return 1;
444         }
445         return 0;
446 }
447 
448 /*
449  * Return an optimized kprobe whose optimizing code replaces
450  * instructions including addr (exclude breakpoint).
451  */
452 static struct kprobe *get_optimized_kprobe(unsigned long addr)
453 {
454         int i;
455         struct kprobe *p = NULL;
456         struct optimized_kprobe *op;
457 
458         /* Don't check i == 0, since that is a breakpoint case. */
459         for (i = 1; !p && i < MAX_OPTIMIZED_LENGTH; i++)
460                 p = get_kprobe((void *)(addr - i));
461 
462         if (p && kprobe_optready(p)) {
463                 op = container_of(p, struct optimized_kprobe, kp);
464                 if (arch_within_optimized_kprobe(op, addr))
465                         return p;
466         }
467 
468         return NULL;
469 }
470 
471 /* Optimization staging list, protected by kprobe_mutex */
472 static LIST_HEAD(optimizing_list);
473 static LIST_HEAD(unoptimizing_list);
474 static LIST_HEAD(freeing_list);
475 
476 static void kprobe_optimizer(struct work_struct *work);
477 static DECLARE_DELAYED_WORK(optimizing_work, kprobe_optimizer);
478 #define OPTIMIZE_DELAY 5
479 
480 /*
481  * Optimize (replace a breakpoint with a jump) kprobes listed on
482  * optimizing_list.
483  */
484 static void do_optimize_kprobes(void)
485 {
486         /*
487          * The optimization/unoptimization refers online_cpus via
488          * stop_machine() and cpu-hotplug modifies online_cpus.
489          * And same time, text_mutex will be held in cpu-hotplug and here.
490          * This combination can cause a deadlock (cpu-hotplug try to lock
491          * text_mutex but stop_machine can not be done because online_cpus
492          * has been changed)
493          * To avoid this deadlock, caller must have locked cpu hotplug
494          * for preventing cpu-hotplug outside of text_mutex locking.
495          */
496         lockdep_assert_cpus_held();
497 
498         /* Optimization never be done when disarmed */
499         if (kprobes_all_disarmed || !kprobes_allow_optimization ||
500             list_empty(&optimizing_list))
501                 return;
502 
503         mutex_lock(&text_mutex);
504         arch_optimize_kprobes(&optimizing_list);
505         mutex_unlock(&text_mutex);
506 }
507 
508 /*
509  * Unoptimize (replace a jump with a breakpoint and remove the breakpoint
510  * if need) kprobes listed on unoptimizing_list.
511  */
512 static void do_unoptimize_kprobes(void)
513 {
514         struct optimized_kprobe *op, *tmp;
515 
516         /* See comment in do_optimize_kprobes() */
517         lockdep_assert_cpus_held();
518 
519         /* Unoptimization must be done anytime */
520         if (list_empty(&unoptimizing_list))
521                 return;
522 
523         mutex_lock(&text_mutex);
524         arch_unoptimize_kprobes(&unoptimizing_list, &freeing_list);
525         /* Loop free_list for disarming */
526         list_for_each_entry_safe(op, tmp, &freeing_list, list) {
527                 /* Disarm probes if marked disabled */
528                 if (kprobe_disabled(&op->kp))
529                         arch_disarm_kprobe(&op->kp);
530                 if (kprobe_unused(&op->kp)) {
531                         /*
532                          * Remove unused probes from hash list. After waiting
533                          * for synchronization, these probes are reclaimed.
534                          * (reclaiming is done by do_free_cleaned_kprobes.)
535                          */
536                         hlist_del_rcu(&op->kp.hlist);
537                 } else
538                         list_del_init(&op->list);
539         }
540         mutex_unlock(&text_mutex);
541 }
542 
543 /* Reclaim all kprobes on the free_list */
544 static void do_free_cleaned_kprobes(void)
545 {
546         struct optimized_kprobe *op, *tmp;
547 
548         list_for_each_entry_safe(op, tmp, &freeing_list, list) {
549                 BUG_ON(!kprobe_unused(&op->kp));
550                 list_del_init(&op->list);
551                 free_aggr_kprobe(&op->kp);
552         }
553 }
554 
555 /* Start optimizer after OPTIMIZE_DELAY passed */
556 static void kick_kprobe_optimizer(void)
557 {
558         schedule_delayed_work(&optimizing_work, OPTIMIZE_DELAY);
559 }
560 
561 /* Kprobe jump optimizer */
562 static void kprobe_optimizer(struct work_struct *work)
563 {
564         mutex_lock(&kprobe_mutex);
565         cpus_read_lock();
566         /* Lock modules while optimizing kprobes */
567         mutex_lock(&module_mutex);
568 
569         /*
570          * Step 1: Unoptimize kprobes and collect cleaned (unused and disarmed)
571          * kprobes before waiting for quiesence period.
572          */
573         do_unoptimize_kprobes();
574 
575         /*
576          * Step 2: Wait for quiesence period to ensure all potentially
577          * preempted tasks to have normally scheduled. Because optprobe
578          * may modify multiple instructions, there is a chance that Nth
579          * instruction is preempted. In that case, such tasks can return
580          * to 2nd-Nth byte of jump instruction. This wait is for avoiding it.
581          * Note that on non-preemptive kernel, this is transparently converted
582          * to synchronoze_sched() to wait for all interrupts to have completed.
583          */
584         synchronize_rcu_tasks();
585 
586         /* Step 3: Optimize kprobes after quiesence period */
587         do_optimize_kprobes();
588 
589         /* Step 4: Free cleaned kprobes after quiesence period */
590         do_free_cleaned_kprobes();
591 
592         mutex_unlock(&module_mutex);
593         cpus_read_unlock();
594         mutex_unlock(&kprobe_mutex);
595 
596         /* Step 5: Kick optimizer again if needed */
597         if (!list_empty(&optimizing_list) || !list_empty(&unoptimizing_list))
598                 kick_kprobe_optimizer();
599 }
600 
601 /* Wait for completing optimization and unoptimization */
602 void wait_for_kprobe_optimizer(void)
603 {
604         mutex_lock(&kprobe_mutex);
605 
606         while (!list_empty(&optimizing_list) || !list_empty(&unoptimizing_list)) {
607                 mutex_unlock(&kprobe_mutex);
608 
609                 /* this will also make optimizing_work execute immmediately */
610                 flush_delayed_work(&optimizing_work);
611                 /* @optimizing_work might not have been queued yet, relax */
612                 cpu_relax();
613 
614                 mutex_lock(&kprobe_mutex);
615         }
616 
617         mutex_unlock(&kprobe_mutex);
618 }
619 
620 /* Optimize kprobe if p is ready to be optimized */
621 static void optimize_kprobe(struct kprobe *p)
622 {
623         struct optimized_kprobe *op;
624 
625         /* Check if the kprobe is disabled or not ready for optimization. */
626         if (!kprobe_optready(p) || !kprobes_allow_optimization ||
627             (kprobe_disabled(p) || kprobes_all_disarmed))
628                 return;
629 
630         /* kprobes with post_handler can not be optimized */
631         if (p->post_handler)
632                 return;
633 
634         op = container_of(p, struct optimized_kprobe, kp);
635 
636         /* Check there is no other kprobes at the optimized instructions */
637         if (arch_check_optimized_kprobe(op) < 0)
638                 return;
639 
640         /* Check if it is already optimized. */
641         if (op->kp.flags & KPROBE_FLAG_OPTIMIZED)
642                 return;
643         op->kp.flags |= KPROBE_FLAG_OPTIMIZED;
644 
645         if (!list_empty(&op->list))
646                 /* This is under unoptimizing. Just dequeue the probe */
647                 list_del_init(&op->list);
648         else {
649                 list_add(&op->list, &optimizing_list);
650                 kick_kprobe_optimizer();
651         }
652 }
653 
654 /* Short cut to direct unoptimizing */
655 static void force_unoptimize_kprobe(struct optimized_kprobe *op)
656 {
657         lockdep_assert_cpus_held();
658         arch_unoptimize_kprobe(op);
659         if (kprobe_disabled(&op->kp))
660                 arch_disarm_kprobe(&op->kp);
661 }
662 
663 /* Unoptimize a kprobe if p is optimized */
664 static void unoptimize_kprobe(struct kprobe *p, bool force)
665 {
666         struct optimized_kprobe *op;
667 
668         if (!kprobe_aggrprobe(p) || kprobe_disarmed(p))
669                 return; /* This is not an optprobe nor optimized */
670 
671         op = container_of(p, struct optimized_kprobe, kp);
672         if (!kprobe_optimized(p)) {
673                 /* Unoptimized or unoptimizing case */
674                 if (force && !list_empty(&op->list)) {
675                         /*
676                          * Only if this is unoptimizing kprobe and forced,
677                          * forcibly unoptimize it. (No need to unoptimize
678                          * unoptimized kprobe again :)
679                          */
680                         list_del_init(&op->list);
681                         force_unoptimize_kprobe(op);
682                 }
683                 return;
684         }
685 
686         op->kp.flags &= ~KPROBE_FLAG_OPTIMIZED;
687         if (!list_empty(&op->list)) {
688                 /* Dequeue from the optimization queue */
689                 list_del_init(&op->list);
690                 return;
691         }
692         /* Optimized kprobe case */
693         if (force)
694                 /* Forcibly update the code: this is a special case */
695                 force_unoptimize_kprobe(op);
696         else {
697                 list_add(&op->list, &unoptimizing_list);
698                 kick_kprobe_optimizer();
699         }
700 }
701 
702 /* Cancel unoptimizing for reusing */
703 static void reuse_unused_kprobe(struct kprobe *ap)
704 {
705         struct optimized_kprobe *op;
706 
707         BUG_ON(!kprobe_unused(ap));
708         /*
709          * Unused kprobe MUST be on the way of delayed unoptimizing (means
710          * there is still a relative jump) and disabled.
711          */
712         op = container_of(ap, struct optimized_kprobe, kp);
713         WARN_ON_ONCE(list_empty(&op->list));
714         /* Enable the probe again */
715         ap->flags &= ~KPROBE_FLAG_DISABLED;
716         /* Optimize it again (remove from op->list) */
717         BUG_ON(!kprobe_optready(ap));
718         optimize_kprobe(ap);
719 }
720 
721 /* Remove optimized instructions */
722 static void kill_optimized_kprobe(struct kprobe *p)
723 {
724         struct optimized_kprobe *op;
725 
726         op = container_of(p, struct optimized_kprobe, kp);
727         if (!list_empty(&op->list))
728                 /* Dequeue from the (un)optimization queue */
729                 list_del_init(&op->list);
730         op->kp.flags &= ~KPROBE_FLAG_OPTIMIZED;
731 
732         if (kprobe_unused(p)) {
733                 /* Enqueue if it is unused */
734                 list_add(&op->list, &freeing_list);
735                 /*
736                  * Remove unused probes from the hash list. After waiting
737                  * for synchronization, this probe is reclaimed.
738                  * (reclaiming is done by do_free_cleaned_kprobes().)
739                  */
740                 hlist_del_rcu(&op->kp.hlist);
741         }
742 
743         /* Don't touch the code, because it is already freed. */
744         arch_remove_optimized_kprobe(op);
745 }
746 
747 static inline
748 void __prepare_optimized_kprobe(struct optimized_kprobe *op, struct kprobe *p)
749 {
750         if (!kprobe_ftrace(p))
751                 arch_prepare_optimized_kprobe(op, p);
752 }
753 
754 /* Try to prepare optimized instructions */
755 static void prepare_optimized_kprobe(struct kprobe *p)
756 {
757         struct optimized_kprobe *op;
758 
759         op = container_of(p, struct optimized_kprobe, kp);
760         __prepare_optimized_kprobe(op, p);
761 }
762 
763 /* Allocate new optimized_kprobe and try to prepare optimized instructions */
764 static struct kprobe *alloc_aggr_kprobe(struct kprobe *p)
765 {
766         struct optimized_kprobe *op;
767 
768         op = kzalloc(sizeof(struct optimized_kprobe), GFP_KERNEL);
769         if (!op)
770                 return NULL;
771 
772         INIT_LIST_HEAD(&op->list);
773         op->kp.addr = p->addr;
774         __prepare_optimized_kprobe(op, p);
775 
776         return &op->kp;
777 }
778 
779 static void init_aggr_kprobe(struct kprobe *ap, struct kprobe *p);
780 
781 /*
782  * Prepare an optimized_kprobe and optimize it
783  * NOTE: p must be a normal registered kprobe
784  */
785 static void try_to_optimize_kprobe(struct kprobe *p)
786 {
787         struct kprobe *ap;
788         struct optimized_kprobe *op;
789 
790         /* Impossible to optimize ftrace-based kprobe */
791         if (kprobe_ftrace(p))
792                 return;
793 
794         /* For preparing optimization, jump_label_text_reserved() is called */
795         cpus_read_lock();
796         jump_label_lock();
797         mutex_lock(&text_mutex);
798 
799         ap = alloc_aggr_kprobe(p);
800         if (!ap)
801                 goto out;
802 
803         op = container_of(ap, struct optimized_kprobe, kp);
804         if (!arch_prepared_optinsn(&op->optinsn)) {
805                 /* If failed to setup optimizing, fallback to kprobe */
806                 arch_remove_optimized_kprobe(op);
807                 kfree(op);
808                 goto out;
809         }
810 
811         init_aggr_kprobe(ap, p);
812         optimize_kprobe(ap);    /* This just kicks optimizer thread */
813 
814 out:
815         mutex_unlock(&text_mutex);
816         jump_label_unlock();
817         cpus_read_unlock();
818 }
819 
820 #ifdef CONFIG_SYSCTL
821 static void optimize_all_kprobes(void)
822 {
823         struct hlist_head *head;
824         struct kprobe *p;
825         unsigned int i;
826 
827         mutex_lock(&kprobe_mutex);
828         /* If optimization is already allowed, just return */
829         if (kprobes_allow_optimization)
830                 goto out;
831 
832         cpus_read_lock();
833         kprobes_allow_optimization = true;
834         for (i = 0; i < KPROBE_TABLE_SIZE; i++) {
835                 head = &kprobe_table[i];
836                 hlist_for_each_entry_rcu(p, head, hlist)
837                         if (!kprobe_disabled(p))
838                                 optimize_kprobe(p);
839         }
840         cpus_read_unlock();
841         printk(KERN_INFO "Kprobes globally optimized\n");
842 out:
843         mutex_unlock(&kprobe_mutex);
844 }
845 
846 static void unoptimize_all_kprobes(void)
847 {
848         struct hlist_head *head;
849         struct kprobe *p;
850         unsigned int i;
851 
852         mutex_lock(&kprobe_mutex);
853         /* If optimization is already prohibited, just return */
854         if (!kprobes_allow_optimization) {
855                 mutex_unlock(&kprobe_mutex);
856                 return;
857         }
858 
859         cpus_read_lock();
860         kprobes_allow_optimization = false;
861         for (i = 0; i < KPROBE_TABLE_SIZE; i++) {
862                 head = &kprobe_table[i];
863                 hlist_for_each_entry_rcu(p, head, hlist) {
864                         if (!kprobe_disabled(p))
865                                 unoptimize_kprobe(p, false);
866                 }
867         }
868         cpus_read_unlock();
869         mutex_unlock(&kprobe_mutex);
870 
871         /* Wait for unoptimizing completion */
872         wait_for_kprobe_optimizer();
873         printk(KERN_INFO "Kprobes globally unoptimized\n");
874 }
875 
876 static DEFINE_MUTEX(kprobe_sysctl_mutex);
877 int sysctl_kprobes_optimization;
878 int proc_kprobes_optimization_handler(struct ctl_table *table, int write,
879                                       void __user *buffer, size_t *length,
880                                       loff_t *ppos)
881 {
882         int ret;
883 
884         mutex_lock(&kprobe_sysctl_mutex);
885         sysctl_kprobes_optimization = kprobes_allow_optimization ? 1 : 0;
886         ret = proc_dointvec_minmax(table, write, buffer, length, ppos);
887 
888         if (sysctl_kprobes_optimization)
889                 optimize_all_kprobes();
890         else
891                 unoptimize_all_kprobes();
892         mutex_unlock(&kprobe_sysctl_mutex);
893 
894         return ret;
895 }
896 #endif /* CONFIG_SYSCTL */
897 
898 /* Put a breakpoint for a probe. Must be called with text_mutex locked */
899 static void __arm_kprobe(struct kprobe *p)
900 {
901         struct kprobe *_p;
902 
903         /* Check collision with other optimized kprobes */
904         _p = get_optimized_kprobe((unsigned long)p->addr);
905         if (unlikely(_p))
906                 /* Fallback to unoptimized kprobe */
907                 unoptimize_kprobe(_p, true);
908 
909         arch_arm_kprobe(p);
910         optimize_kprobe(p);     /* Try to optimize (add kprobe to a list) */
911 }
912 
913 /* Remove the breakpoint of a probe. Must be called with text_mutex locked */
914 static void __disarm_kprobe(struct kprobe *p, bool reopt)
915 {
916         struct kprobe *_p;
917 
918         /* Try to unoptimize */
919         unoptimize_kprobe(p, kprobes_all_disarmed);
920 
921         if (!kprobe_queued(p)) {
922                 arch_disarm_kprobe(p);
923                 /* If another kprobe was blocked, optimize it. */
924                 _p = get_optimized_kprobe((unsigned long)p->addr);
925                 if (unlikely(_p) && reopt)
926                         optimize_kprobe(_p);
927         }
928         /* TODO: reoptimize others after unoptimized this probe */
929 }
930 
931 #else /* !CONFIG_OPTPROBES */
932 
933 #define optimize_kprobe(p)                      do {} while (0)
934 #define unoptimize_kprobe(p, f)                 do {} while (0)
935 #define kill_optimized_kprobe(p)                do {} while (0)
936 #define prepare_optimized_kprobe(p)             do {} while (0)
937 #define try_to_optimize_kprobe(p)               do {} while (0)
938 #define __arm_kprobe(p)                         arch_arm_kprobe(p)
939 #define __disarm_kprobe(p, o)                   arch_disarm_kprobe(p)
940 #define kprobe_disarmed(p)                      kprobe_disabled(p)
941 #define wait_for_kprobe_optimizer()             do {} while (0)
942 
943 /* There should be no unused kprobes can be reused without optimization */
944 static void reuse_unused_kprobe(struct kprobe *ap)
945 {
946         printk(KERN_ERR "Error: There should be no unused kprobe here.\n");
947         BUG_ON(kprobe_unused(ap));
948 }
949 
950 static void free_aggr_kprobe(struct kprobe *p)
951 {
952         arch_remove_kprobe(p);
953         kfree(p);
954 }
955 
956 static struct kprobe *alloc_aggr_kprobe(struct kprobe *p)
957 {
958         return kzalloc(sizeof(struct kprobe), GFP_KERNEL);
959 }
960 #endif /* CONFIG_OPTPROBES */
961 
962 #ifdef CONFIG_KPROBES_ON_FTRACE
963 static struct ftrace_ops kprobe_ftrace_ops __read_mostly = {
964         .func = kprobe_ftrace_handler,
965         .flags = FTRACE_OPS_FL_SAVE_REGS | FTRACE_OPS_FL_IPMODIFY,
966 };
967 static int kprobe_ftrace_enabled;
968 
969 /* Must ensure p->addr is really on ftrace */
970 static int prepare_kprobe(struct kprobe *p)
971 {
972         if (!kprobe_ftrace(p))
973                 return arch_prepare_kprobe(p);
974 
975         return arch_prepare_kprobe_ftrace(p);
976 }
977 
978 /* Caller must lock kprobe_mutex */
979 static int arm_kprobe_ftrace(struct kprobe *p)
980 {
981         int ret = 0;
982 
983         ret = ftrace_set_filter_ip(&kprobe_ftrace_ops,
984                                    (unsigned long)p->addr, 0, 0);
985         if (ret) {
986                 pr_debug("Failed to arm kprobe-ftrace at %pS (%d)\n",
987                          p->addr, ret);
988                 return ret;
989         }
990 
991         if (kprobe_ftrace_enabled == 0) {
992                 ret = register_ftrace_function(&kprobe_ftrace_ops);
993                 if (ret) {
994                         pr_debug("Failed to init kprobe-ftrace (%d)\n", ret);
995                         goto err_ftrace;
996                 }
997         }
998 
999         kprobe_ftrace_enabled++;
1000         return ret;
1001 
1002 err_ftrace:
1003         /*
1004          * Note: Since kprobe_ftrace_ops has IPMODIFY set, and ftrace requires a
1005          * non-empty filter_hash for IPMODIFY ops, we're safe from an accidental
1006          * empty filter_hash which would undesirably trace all functions.
1007          */
1008         ftrace_set_filter_ip(&kprobe_ftrace_ops, (unsigned long)p->addr, 1, 0);
1009         return ret;
1010 }
1011 
1012 /* Caller must lock kprobe_mutex */
1013 static int disarm_kprobe_ftrace(struct kprobe *p)
1014 {
1015         int ret = 0;
1016 
1017         if (kprobe_ftrace_enabled == 1) {
1018                 ret = unregister_ftrace_function(&kprobe_ftrace_ops);
1019                 if (WARN(ret < 0, "Failed to unregister kprobe-ftrace (%d)\n", ret))
1020                         return ret;
1021         }
1022 
1023         kprobe_ftrace_enabled--;
1024 
1025         ret = ftrace_set_filter_ip(&kprobe_ftrace_ops,
1026                            (unsigned long)p->addr, 1, 0);
1027         WARN_ONCE(ret < 0, "Failed to disarm kprobe-ftrace at %pS (%d)\n",
1028                   p->addr, ret);
1029         return ret;
1030 }
1031 #else   /* !CONFIG_KPROBES_ON_FTRACE */
1032 #define prepare_kprobe(p)       arch_prepare_kprobe(p)
1033 #define arm_kprobe_ftrace(p)    (-ENODEV)
1034 #define disarm_kprobe_ftrace(p) (-ENODEV)
1035 #endif
1036 
1037 /* Arm a kprobe with text_mutex */
1038 static int arm_kprobe(struct kprobe *kp)
1039 {
1040         if (unlikely(kprobe_ftrace(kp)))
1041                 return arm_kprobe_ftrace(kp);
1042 
1043         cpus_read_lock();
1044         mutex_lock(&text_mutex);
1045         __arm_kprobe(kp);
1046         mutex_unlock(&text_mutex);
1047         cpus_read_unlock();
1048 
1049         return 0;
1050 }
1051 
1052 /* Disarm a kprobe with text_mutex */
1053 static int disarm_kprobe(struct kprobe *kp, bool reopt)
1054 {
1055         if (unlikely(kprobe_ftrace(kp)))
1056                 return disarm_kprobe_ftrace(kp);
1057 
1058         cpus_read_lock();
1059         mutex_lock(&text_mutex);
1060         __disarm_kprobe(kp, reopt);
1061         mutex_unlock(&text_mutex);
1062         cpus_read_unlock();
1063 
1064         return 0;
1065 }
1066 
1067 /*
1068  * Aggregate handlers for multiple kprobes support - these handlers
1069  * take care of invoking the individual kprobe handlers on p->list
1070  */
1071 static int aggr_pre_handler(struct kprobe *p, struct pt_regs *regs)
1072 {
1073         struct kprobe *kp;
1074 
1075         list_for_each_entry_rcu(kp, &p->list, list) {
1076                 if (kp->pre_handler && likely(!kprobe_disabled(kp))) {
1077                         set_kprobe_instance(kp);
1078                         if (kp->pre_handler(kp, regs))
1079                                 return 1;
1080                 }
1081                 reset_kprobe_instance();
1082         }
1083         return 0;
1084 }
1085 NOKPROBE_SYMBOL(aggr_pre_handler);
1086 
1087 static void aggr_post_handler(struct kprobe *p, struct pt_regs *regs,
1088                               unsigned long flags)
1089 {
1090         struct kprobe *kp;
1091 
1092         list_for_each_entry_rcu(kp, &p->list, list) {
1093                 if (kp->post_handler && likely(!kprobe_disabled(kp))) {
1094                         set_kprobe_instance(kp);
1095                         kp->post_handler(kp, regs, flags);
1096                         reset_kprobe_instance();
1097                 }
1098         }
1099 }
1100 NOKPROBE_SYMBOL(aggr_post_handler);
1101 
1102 static int aggr_fault_handler(struct kprobe *p, struct pt_regs *regs,
1103                               int trapnr)
1104 {
1105         struct kprobe *cur = __this_cpu_read(kprobe_instance);
1106 
1107         /*
1108          * if we faulted "during" the execution of a user specified
1109          * probe handler, invoke just that probe's fault handler
1110          */
1111         if (cur && cur->fault_handler) {
1112                 if (cur->fault_handler(cur, regs, trapnr))
1113                         return 1;
1114         }
1115         return 0;
1116 }
1117 NOKPROBE_SYMBOL(aggr_fault_handler);
1118 
1119 /* Walks the list and increments nmissed count for multiprobe case */
1120 void kprobes_inc_nmissed_count(struct kprobe *p)
1121 {
1122         struct kprobe *kp;
1123         if (!kprobe_aggrprobe(p)) {
1124                 p->nmissed++;
1125         } else {
1126                 list_for_each_entry_rcu(kp, &p->list, list)
1127                         kp->nmissed++;
1128         }
1129         return;
1130 }
1131 NOKPROBE_SYMBOL(kprobes_inc_nmissed_count);
1132 
1133 void recycle_rp_inst(struct kretprobe_instance *ri,
1134                      struct hlist_head *head)
1135 {
1136         struct kretprobe *rp = ri->rp;
1137 
1138         /* remove rp inst off the rprobe_inst_table */
1139         hlist_del(&ri->hlist);
1140         INIT_HLIST_NODE(&ri->hlist);
1141         if (likely(rp)) {
1142                 raw_spin_lock(&rp->lock);
1143                 hlist_add_head(&ri->hlist, &rp->free_instances);
1144                 raw_spin_unlock(&rp->lock);
1145         } else
1146                 /* Unregistering */
1147                 hlist_add_head(&ri->hlist, head);
1148 }
1149 NOKPROBE_SYMBOL(recycle_rp_inst);
1150 
1151 void kretprobe_hash_lock(struct task_struct *tsk,
1152                          struct hlist_head **head, unsigned long *flags)
1153 __acquires(hlist_lock)
1154 {
1155         unsigned long hash = hash_ptr(tsk, KPROBE_HASH_BITS);
1156         raw_spinlock_t *hlist_lock;
1157 
1158         *head = &kretprobe_inst_table[hash];
1159         hlist_lock = kretprobe_table_lock_ptr(hash);
1160         raw_spin_lock_irqsave(hlist_lock, *flags);
1161 }
1162 NOKPROBE_SYMBOL(kretprobe_hash_lock);
1163 
1164 static void kretprobe_table_lock(unsigned long hash,
1165                                  unsigned long *flags)
1166 __acquires(hlist_lock)
1167 {
1168         raw_spinlock_t *hlist_lock = kretprobe_table_lock_ptr(hash);
1169         raw_spin_lock_irqsave(hlist_lock, *flags);
1170 }
1171 NOKPROBE_SYMBOL(kretprobe_table_lock);
1172 
1173 void kretprobe_hash_unlock(struct task_struct *tsk,
1174                            unsigned long *flags)
1175 __releases(hlist_lock)
1176 {
1177         unsigned long hash = hash_ptr(tsk, KPROBE_HASH_BITS);
1178         raw_spinlock_t *hlist_lock;
1179 
1180         hlist_lock = kretprobe_table_lock_ptr(hash);
1181         raw_spin_unlock_irqrestore(hlist_lock, *flags);
1182 }
1183 NOKPROBE_SYMBOL(kretprobe_hash_unlock);
1184 
1185 static void kretprobe_table_unlock(unsigned long hash,
1186                                    unsigned long *flags)
1187 __releases(hlist_lock)
1188 {
1189         raw_spinlock_t *hlist_lock = kretprobe_table_lock_ptr(hash);
1190         raw_spin_unlock_irqrestore(hlist_lock, *flags);
1191 }
1192 NOKPROBE_SYMBOL(kretprobe_table_unlock);
1193 
1194 /*
1195  * This function is called from finish_task_switch when task tk becomes dead,
1196  * so that we can recycle any function-return probe instances associated
1197  * with this task. These left over instances represent probed functions
1198  * that have been called but will never return.
1199  */
1200 void kprobe_flush_task(struct task_struct *tk)
1201 {
1202         struct kretprobe_instance *ri;
1203         struct hlist_head *head, empty_rp;
1204         struct hlist_node *tmp;
1205         unsigned long hash, flags = 0;
1206 
1207         if (unlikely(!kprobes_initialized))
1208                 /* Early boot.  kretprobe_table_locks not yet initialized. */
1209                 return;
1210 
1211         INIT_HLIST_HEAD(&empty_rp);
1212         hash = hash_ptr(tk, KPROBE_HASH_BITS);
1213         head = &kretprobe_inst_table[hash];
1214         kretprobe_table_lock(hash, &flags);
1215         hlist_for_each_entry_safe(ri, tmp, head, hlist) {
1216                 if (ri->task == tk)
1217                         recycle_rp_inst(ri, &empty_rp);
1218         }
1219         kretprobe_table_unlock(hash, &flags);
1220         hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {
1221                 hlist_del(&ri->hlist);
1222                 kfree(ri);
1223         }
1224 }
1225 NOKPROBE_SYMBOL(kprobe_flush_task);
1226 
1227 static inline void free_rp_inst(struct kretprobe *rp)
1228 {
1229         struct kretprobe_instance *ri;
1230         struct hlist_node *next;
1231 
1232         hlist_for_each_entry_safe(ri, next, &rp->free_instances, hlist) {
1233                 hlist_del(&ri->hlist);
1234                 kfree(ri);
1235         }
1236 }
1237 
1238 static void cleanup_rp_inst(struct kretprobe *rp)
1239 {
1240         unsigned long flags, hash;
1241         struct kretprobe_instance *ri;
1242         struct hlist_node *next;
1243         struct hlist_head *head;
1244 
1245         /* No race here */
1246         for (hash = 0; hash < KPROBE_TABLE_SIZE; hash++) {
1247                 kretprobe_table_lock(hash, &flags);
1248                 head = &kretprobe_inst_table[hash];
1249                 hlist_for_each_entry_safe(ri, next, head, hlist) {
1250                         if (ri->rp == rp)
1251                                 ri->rp = NULL;
1252                 }
1253                 kretprobe_table_unlock(hash, &flags);
1254         }
1255         free_rp_inst(rp);
1256 }
1257 NOKPROBE_SYMBOL(cleanup_rp_inst);
1258 
1259 /* Add the new probe to ap->list */
1260 static int add_new_kprobe(struct kprobe *ap, struct kprobe *p)
1261 {
1262         BUG_ON(kprobe_gone(ap) || kprobe_gone(p));
1263 
1264         if (p->post_handler)
1265                 unoptimize_kprobe(ap, true);    /* Fall back to normal kprobe */
1266 
1267         list_add_rcu(&p->list, &ap->list);
1268         if (p->post_handler && !ap->post_handler)
1269                 ap->post_handler = aggr_post_handler;
1270 
1271         return 0;
1272 }
1273 
1274 /*
1275  * Fill in the required fields of the "manager kprobe". Replace the
1276  * earlier kprobe in the hlist with the manager kprobe
1277  */
1278 static void init_aggr_kprobe(struct kprobe *ap, struct kprobe *p)
1279 {
1280         /* Copy p's insn slot to ap */
1281         copy_kprobe(p, ap);
1282         flush_insn_slot(ap);
1283         ap->addr = p->addr;
1284         ap->flags = p->flags & ~KPROBE_FLAG_OPTIMIZED;
1285         ap->pre_handler = aggr_pre_handler;
1286         ap->fault_handler = aggr_fault_handler;
1287         /* We don't care the kprobe which has gone. */
1288         if (p->post_handler && !kprobe_gone(p))
1289                 ap->post_handler = aggr_post_handler;
1290 
1291         INIT_LIST_HEAD(&ap->list);
1292         INIT_HLIST_NODE(&ap->hlist);
1293 
1294         list_add_rcu(&p->list, &ap->list);
1295         hlist_replace_rcu(&p->hlist, &ap->hlist);
1296 }
1297 
1298 /*
1299  * This is the second or subsequent kprobe at the address - handle
1300  * the intricacies
1301  */
1302 static int register_aggr_kprobe(struct kprobe *orig_p, struct kprobe *p)
1303 {
1304         int ret = 0;
1305         struct kprobe *ap = orig_p;
1306 
1307         cpus_read_lock();
1308 
1309         /* For preparing optimization, jump_label_text_reserved() is called */
1310         jump_label_lock();
1311         mutex_lock(&text_mutex);
1312 
1313         if (!kprobe_aggrprobe(orig_p)) {
1314                 /* If orig_p is not an aggr_kprobe, create new aggr_kprobe. */
1315                 ap = alloc_aggr_kprobe(orig_p);
1316                 if (!ap) {
1317                         ret = -ENOMEM;
1318                         goto out;
1319                 }
1320                 init_aggr_kprobe(ap, orig_p);
1321         } else if (kprobe_unused(ap))
1322                 /* This probe is going to die. Rescue it */
1323                 reuse_unused_kprobe(ap);
1324 
1325         if (kprobe_gone(ap)) {
1326                 /*
1327                  * Attempting to insert new probe at the same location that
1328                  * had a probe in the module vaddr area which already
1329                  * freed. So, the instruction slot has already been
1330                  * released. We need a new slot for the new probe.
1331                  */
1332                 ret = arch_prepare_kprobe(ap);
1333                 if (ret)
1334                         /*
1335                          * Even if fail to allocate new slot, don't need to
1336                          * free aggr_probe. It will be used next time, or
1337                          * freed by unregister_kprobe.
1338                          */
1339                         goto out;
1340 
1341                 /* Prepare optimized instructions if possible. */
1342                 prepare_optimized_kprobe(ap);
1343 
1344                 /*
1345                  * Clear gone flag to prevent allocating new slot again, and
1346                  * set disabled flag because it is not armed yet.
1347                  */
1348                 ap->flags = (ap->flags & ~KPROBE_FLAG_GONE)
1349                             | KPROBE_FLAG_DISABLED;
1350         }
1351 
1352         /* Copy ap's insn slot to p */
1353         copy_kprobe(ap, p);
1354         ret = add_new_kprobe(ap, p);
1355 
1356 out:
1357         mutex_unlock(&text_mutex);
1358         jump_label_unlock();
1359         cpus_read_unlock();
1360 
1361         if (ret == 0 && kprobe_disabled(ap) && !kprobe_disabled(p)) {
1362                 ap->flags &= ~KPROBE_FLAG_DISABLED;
1363                 if (!kprobes_all_disarmed) {
1364                         /* Arm the breakpoint again. */
1365                         ret = arm_kprobe(ap);
1366                         if (ret) {
1367                                 ap->flags |= KPROBE_FLAG_DISABLED;
1368                                 list_del_rcu(&p->list);
1369                                 synchronize_sched();
1370                         }
1371                 }
1372         }
1373         return ret;
1374 }
1375 
1376 bool __weak arch_within_kprobe_blacklist(unsigned long addr)
1377 {
1378         /* The __kprobes marked functions and entry code must not be probed */
1379         return addr >= (unsigned long)__kprobes_text_start &&
1380                addr < (unsigned long)__kprobes_text_end;
1381 }
1382 
1383 bool within_kprobe_blacklist(unsigned long addr)
1384 {
1385         struct kprobe_blacklist_entry *ent;
1386 
1387         if (arch_within_kprobe_blacklist(addr))
1388                 return true;
1389         /*
1390          * If there exists a kprobe_blacklist, verify and
1391          * fail any probe registration in the prohibited area
1392          */
1393         list_for_each_entry(ent, &kprobe_blacklist, list) {
1394                 if (addr >= ent->start_addr && addr < ent->end_addr)
1395                         return true;
1396         }
1397 
1398         return false;
1399 }
1400 
1401 /*
1402  * If we have a symbol_name argument, look it up and add the offset field
1403  * to it. This way, we can specify a relative address to a symbol.
1404  * This returns encoded errors if it fails to look up symbol or invalid
1405  * combination of parameters.
1406  */
1407 static kprobe_opcode_t *_kprobe_addr(kprobe_opcode_t *addr,
1408                         const char *symbol_name, unsigned int offset)
1409 {
1410         if ((symbol_name && addr) || (!symbol_name && !addr))
1411                 goto invalid;
1412 
1413         if (symbol_name) {
1414                 addr = kprobe_lookup_name(symbol_name, offset);
1415                 if (!addr)
1416                         return ERR_PTR(-ENOENT);
1417         }
1418 
1419         addr = (kprobe_opcode_t *)(((char *)addr) + offset);
1420         if (addr)
1421                 return addr;
1422 
1423 invalid:
1424         return ERR_PTR(-EINVAL);
1425 }
1426 
1427 static kprobe_opcode_t *kprobe_addr(struct kprobe *p)
1428 {
1429         return _kprobe_addr(p->addr, p->symbol_name, p->offset);
1430 }
1431 
1432 /* Check passed kprobe is valid and return kprobe in kprobe_table. */
1433 static struct kprobe *__get_valid_kprobe(struct kprobe *p)
1434 {
1435         struct kprobe *ap, *list_p;
1436 
1437         ap = get_kprobe(p->addr);
1438         if (unlikely(!ap))
1439                 return NULL;
1440 
1441         if (p != ap) {
1442                 list_for_each_entry_rcu(list_p, &ap->list, list)
1443                         if (list_p == p)
1444                         /* kprobe p is a valid probe */
1445                                 goto valid;
1446                 return NULL;
1447         }
1448 valid:
1449         return ap;
1450 }
1451 
1452 /* Return error if the kprobe is being re-registered */
1453 static inline int check_kprobe_rereg(struct kprobe *p)
1454 {
1455         int ret = 0;
1456 
1457         mutex_lock(&kprobe_mutex);
1458         if (__get_valid_kprobe(p))
1459                 ret = -EINVAL;
1460         mutex_unlock(&kprobe_mutex);
1461 
1462         return ret;
1463 }
1464 
1465 int __weak arch_check_ftrace_location(struct kprobe *p)
1466 {
1467         unsigned long ftrace_addr;
1468 
1469         ftrace_addr = ftrace_location((unsigned long)p->addr);
1470         if (ftrace_addr) {
1471 #ifdef CONFIG_KPROBES_ON_FTRACE
1472                 /* Given address is not on the instruction boundary */
1473                 if ((unsigned long)p->addr != ftrace_addr)
1474                         return -EILSEQ;
1475                 p->flags |= KPROBE_FLAG_FTRACE;
1476 #else   /* !CONFIG_KPROBES_ON_FTRACE */
1477                 return -EINVAL;
1478 #endif
1479         }
1480         return 0;
1481 }
1482 
1483 static int check_kprobe_address_safe(struct kprobe *p,
1484                                      struct module **probed_mod)
1485 {
1486         int ret;
1487 
1488         ret = arch_check_ftrace_location(p);
1489         if (ret)
1490                 return ret;
1491         jump_label_lock();
1492         preempt_disable();
1493 
1494         /* Ensure it is not in reserved area nor out of text */
1495         if (!kernel_text_address((unsigned long) p->addr) ||
1496             within_kprobe_blacklist((unsigned long) p->addr) ||
1497             jump_label_text_reserved(p->addr, p->addr)) {
1498                 ret = -EINVAL;
1499                 goto out;
1500         }
1501 
1502         /* Check if are we probing a module */
1503         *probed_mod = __module_text_address((unsigned long) p->addr);
1504         if (*probed_mod) {
1505                 /*
1506                  * We must hold a refcount of the probed module while updating
1507                  * its code to prohibit unexpected unloading.
1508                  */
1509                 if (unlikely(!try_module_get(*probed_mod))) {
1510                         ret = -ENOENT;
1511                         goto out;
1512                 }
1513 
1514                 /*
1515                  * If the module freed .init.text, we couldn't insert
1516                  * kprobes in there.
1517                  */
1518                 if (within_module_init((unsigned long)p->addr, *probed_mod) &&
1519                     (*probed_mod)->state != MODULE_STATE_COMING) {
1520                         module_put(*probed_mod);
1521                         *probed_mod = NULL;
1522                         ret = -ENOENT;
1523                 }
1524         }
1525 out:
1526         preempt_enable();
1527         jump_label_unlock();
1528 
1529         return ret;
1530 }
1531 
1532 int register_kprobe(struct kprobe *p)
1533 {
1534         int ret;
1535         struct kprobe *old_p;
1536         struct module *probed_mod;
1537         kprobe_opcode_t *addr;
1538 
1539         /* Adjust probe address from symbol */
1540         addr = kprobe_addr(p);
1541         if (IS_ERR(addr))
1542                 return PTR_ERR(addr);
1543         p->addr = addr;
1544 
1545         ret = check_kprobe_rereg(p);
1546         if (ret)
1547                 return ret;
1548 
1549         /* User can pass only KPROBE_FLAG_DISABLED to register_kprobe */
1550         p->flags &= KPROBE_FLAG_DISABLED;
1551         p->nmissed = 0;
1552         INIT_LIST_HEAD(&p->list);
1553 
1554         ret = check_kprobe_address_safe(p, &probed_mod);
1555         if (ret)
1556                 return ret;
1557 
1558         mutex_lock(&kprobe_mutex);
1559 
1560         old_p = get_kprobe(p->addr);
1561         if (old_p) {
1562                 /* Since this may unoptimize old_p, locking text_mutex. */
1563                 ret = register_aggr_kprobe(old_p, p);
1564                 goto out;
1565         }
1566 
1567         cpus_read_lock();
1568         /* Prevent text modification */
1569         mutex_lock(&text_mutex);
1570         ret = prepare_kprobe(p);
1571         mutex_unlock(&text_mutex);
1572         cpus_read_unlock();
1573         if (ret)
1574                 goto out;
1575 
1576         INIT_HLIST_NODE(&p->hlist);
1577         hlist_add_head_rcu(&p->hlist,
1578                        &kprobe_table[hash_ptr(p->addr, KPROBE_HASH_BITS)]);
1579 
1580         if (!kprobes_all_disarmed && !kprobe_disabled(p)) {
1581                 ret = arm_kprobe(p);
1582                 if (ret) {
1583                         hlist_del_rcu(&p->hlist);
1584                         synchronize_sched();
1585                         goto out;
1586                 }
1587         }
1588 
1589         /* Try to optimize kprobe */
1590         try_to_optimize_kprobe(p);
1591 out:
1592         mutex_unlock(&kprobe_mutex);
1593 
1594         if (probed_mod)
1595                 module_put(probed_mod);
1596 
1597         return ret;
1598 }
1599 EXPORT_SYMBOL_GPL(register_kprobe);
1600 
1601 /* Check if all probes on the aggrprobe are disabled */
1602 static int aggr_kprobe_disabled(struct kprobe *ap)
1603 {
1604         struct kprobe *kp;
1605 
1606         list_for_each_entry_rcu(kp, &ap->list, list)
1607                 if (!kprobe_disabled(kp))
1608                         /*
1609                          * There is an active probe on the list.
1610                          * We can't disable this ap.
1611                          */
1612                         return 0;
1613 
1614         return 1;
1615 }
1616 
1617 /* Disable one kprobe: Make sure called under kprobe_mutex is locked */
1618 static struct kprobe *__disable_kprobe(struct kprobe *p)
1619 {
1620         struct kprobe *orig_p;
1621         int ret;
1622 
1623         /* Get an original kprobe for return */
1624         orig_p = __get_valid_kprobe(p);
1625         if (unlikely(orig_p == NULL))
1626                 return ERR_PTR(-EINVAL);
1627 
1628         if (!kprobe_disabled(p)) {
1629                 /* Disable probe if it is a child probe */
1630                 if (p != orig_p)
1631                         p->flags |= KPROBE_FLAG_DISABLED;
1632 
1633                 /* Try to disarm and disable this/parent probe */
1634                 if (p == orig_p || aggr_kprobe_disabled(orig_p)) {
1635                         /*
1636                          * If kprobes_all_disarmed is set, orig_p
1637                          * should have already been disarmed, so
1638                          * skip unneed disarming process.
1639                          */
1640                         if (!kprobes_all_disarmed) {
1641                                 ret = disarm_kprobe(orig_p, true);
1642                                 if (ret) {
1643                                         p->flags &= ~KPROBE_FLAG_DISABLED;
1644                                         return ERR_PTR(ret);
1645                                 }
1646                         }
1647                         orig_p->flags |= KPROBE_FLAG_DISABLED;
1648                 }
1649         }
1650 
1651         return orig_p;
1652 }
1653 
1654 /*
1655  * Unregister a kprobe without a scheduler synchronization.
1656  */
1657 static int __unregister_kprobe_top(struct kprobe *p)
1658 {
1659         struct kprobe *ap, *list_p;
1660 
1661         /* Disable kprobe. This will disarm it if needed. */
1662         ap = __disable_kprobe(p);
1663         if (IS_ERR(ap))
1664                 return PTR_ERR(ap);
1665 
1666         if (ap == p)
1667                 /*
1668                  * This probe is an independent(and non-optimized) kprobe
1669                  * (not an aggrprobe). Remove from the hash list.
1670                  */
1671                 goto disarmed;
1672 
1673         /* Following process expects this probe is an aggrprobe */
1674         WARN_ON(!kprobe_aggrprobe(ap));
1675 
1676         if (list_is_singular(&ap->list) && kprobe_disarmed(ap))
1677                 /*
1678                  * !disarmed could be happen if the probe is under delayed
1679                  * unoptimizing.
1680                  */
1681                 goto disarmed;
1682         else {
1683                 /* If disabling probe has special handlers, update aggrprobe */
1684                 if (p->post_handler && !kprobe_gone(p)) {
1685                         list_for_each_entry_rcu(list_p, &ap->list, list) {
1686                                 if ((list_p != p) && (list_p->post_handler))
1687                                         goto noclean;
1688                         }
1689                         ap->post_handler = NULL;
1690                 }
1691 noclean:
1692                 /*
1693                  * Remove from the aggrprobe: this path will do nothing in
1694                  * __unregister_kprobe_bottom().
1695                  */
1696                 list_del_rcu(&p->list);
1697                 if (!kprobe_disabled(ap) && !kprobes_all_disarmed)
1698                         /*
1699                          * Try to optimize this probe again, because post
1700                          * handler may have been changed.
1701                          */
1702                         optimize_kprobe(ap);
1703         }
1704         return 0;
1705 
1706 disarmed:
1707         BUG_ON(!kprobe_disarmed(ap));
1708         hlist_del_rcu(&ap->hlist);
1709         return 0;
1710 }
1711 
1712 static void __unregister_kprobe_bottom(struct kprobe *p)
1713 {
1714         struct kprobe *ap;
1715 
1716         if (list_empty(&p->list))
1717                 /* This is an independent kprobe */
1718                 arch_remove_kprobe(p);
1719         else if (list_is_singular(&p->list)) {
1720                 /* This is the last child of an aggrprobe */
1721                 ap = list_entry(p->list.next, struct kprobe, list);
1722                 list_del(&p->list);
1723                 free_aggr_kprobe(ap);
1724         }
1725         /* Otherwise, do nothing. */
1726 }
1727 
1728 int register_kprobes(struct kprobe **kps, int num)
1729 {
1730         int i, ret = 0;
1731 
1732         if (num <= 0)
1733                 return -EINVAL;
1734         for (i = 0; i < num; i++) {
1735                 ret = register_kprobe(kps[i]);
1736                 if (ret < 0) {
1737                         if (i > 0)
1738                                 unregister_kprobes(kps, i);
1739                         break;
1740                 }
1741         }
1742         return ret;
1743 }
1744 EXPORT_SYMBOL_GPL(register_kprobes);
1745 
1746 void unregister_kprobe(struct kprobe *p)
1747 {
1748         unregister_kprobes(&p, 1);
1749 }
1750 EXPORT_SYMBOL_GPL(unregister_kprobe);
1751 
1752 void unregister_kprobes(struct kprobe **kps, int num)
1753 {
1754         int i;
1755 
1756         if (num <= 0)
1757                 return;
1758         mutex_lock(&kprobe_mutex);
1759         for (i = 0; i < num; i++)
1760                 if (__unregister_kprobe_top(kps[i]) < 0)
1761                         kps[i]->addr = NULL;
1762         mutex_unlock(&kprobe_mutex);
1763 
1764         synchronize_sched();
1765         for (i = 0; i < num; i++)
1766                 if (kps[i]->addr)
1767                         __unregister_kprobe_bottom(kps[i]);
1768 }
1769 EXPORT_SYMBOL_GPL(unregister_kprobes);
1770 
1771 int __weak kprobe_exceptions_notify(struct notifier_block *self,
1772                                         unsigned long val, void *data)
1773 {
1774         return NOTIFY_DONE;
1775 }
1776 NOKPROBE_SYMBOL(kprobe_exceptions_notify);
1777 
1778 static struct notifier_block kprobe_exceptions_nb = {
1779         .notifier_call = kprobe_exceptions_notify,
1780         .priority = 0x7fffffff /* we need to be notified first */
1781 };
1782 
1783 unsigned long __weak arch_deref_entry_point(void *entry)
1784 {
1785         return (unsigned long)entry;
1786 }
1787 
1788 #ifdef CONFIG_KRETPROBES
1789 /*
1790  * This kprobe pre_handler is registered with every kretprobe. When probe
1791  * hits it will set up the return probe.
1792  */
1793 static int pre_handler_kretprobe(struct kprobe *p, struct pt_regs *regs)
1794 {
1795         struct kretprobe *rp = container_of(p, struct kretprobe, kp);
1796         unsigned long hash, flags = 0;
1797         struct kretprobe_instance *ri;
1798 
1799         /*
1800          * To avoid deadlocks, prohibit return probing in NMI contexts,
1801          * just skip the probe and increase the (inexact) 'nmissed'
1802          * statistical counter, so that the user is informed that
1803          * something happened:
1804          */
1805         if (unlikely(in_nmi())) {
1806                 rp->nmissed++;
1807                 return 0;
1808         }
1809 
1810         /* TODO: consider to only swap the RA after the last pre_handler fired */
1811         hash = hash_ptr(current, KPROBE_HASH_BITS);
1812         raw_spin_lock_irqsave(&rp->lock, flags);
1813         if (!hlist_empty(&rp->free_instances)) {
1814                 ri = hlist_entry(rp->free_instances.first,
1815                                 struct kretprobe_instance, hlist);
1816                 hlist_del(&ri->hlist);
1817                 raw_spin_unlock_irqrestore(&rp->lock, flags);
1818 
1819                 ri->rp = rp;
1820                 ri->task = current;
1821 
1822                 if (rp->entry_handler && rp->entry_handler(ri, regs)) {
1823                         raw_spin_lock_irqsave(&rp->lock, flags);
1824                         hlist_add_head(&ri->hlist, &rp->free_instances);
1825                         raw_spin_unlock_irqrestore(&rp->lock, flags);
1826                         return 0;
1827                 }
1828 
1829                 arch_prepare_kretprobe(ri, regs);
1830 
1831                 /* XXX(hch): why is there no hlist_move_head? */
1832                 INIT_HLIST_NODE(&ri->hlist);
1833                 kretprobe_table_lock(hash, &flags);
1834                 hlist_add_head(&ri->hlist, &kretprobe_inst_table[hash]);
1835                 kretprobe_table_unlock(hash, &flags);
1836         } else {
1837                 rp->nmissed++;
1838                 raw_spin_unlock_irqrestore(&rp->lock, flags);
1839         }
1840         return 0;
1841 }
1842 NOKPROBE_SYMBOL(pre_handler_kretprobe);
1843 
1844 bool __weak arch_kprobe_on_func_entry(unsigned long offset)
1845 {
1846         return !offset;
1847 }
1848 
1849 bool kprobe_on_func_entry(kprobe_opcode_t *addr, const char *sym, unsigned long offset)
1850 {
1851         kprobe_opcode_t *kp_addr = _kprobe_addr(addr, sym, offset);
1852 
1853         if (IS_ERR(kp_addr))
1854                 return false;
1855 
1856         if (!kallsyms_lookup_size_offset((unsigned long)kp_addr, NULL, &offset) ||
1857                                                 !arch_kprobe_on_func_entry(offset))
1858                 return false;
1859 
1860         return true;
1861 }
1862 
1863 int register_kretprobe(struct kretprobe *rp)
1864 {
1865         int ret = 0;
1866         struct kretprobe_instance *inst;
1867         int i;
1868         void *addr;
1869 
1870         if (!kprobe_on_func_entry(rp->kp.addr, rp->kp.symbol_name, rp->kp.offset))
1871                 return -EINVAL;
1872 
1873         if (kretprobe_blacklist_size) {
1874                 addr = kprobe_addr(&rp->kp);
1875                 if (IS_ERR(addr))
1876                         return PTR_ERR(addr);
1877 
1878                 for (i = 0; kretprobe_blacklist[i].name != NULL; i++) {
1879                         if (kretprobe_blacklist[i].addr == addr)
1880                                 return -EINVAL;
1881                 }
1882         }
1883 
1884         rp->kp.pre_handler = pre_handler_kretprobe;
1885         rp->kp.post_handler = NULL;
1886         rp->kp.fault_handler = NULL;
1887 
1888         /* Pre-allocate memory for max kretprobe instances */
1889         if (rp->maxactive <= 0) {
1890 #ifdef CONFIG_PREEMPT
1891                 rp->maxactive = max_t(unsigned int, 10, 2*num_possible_cpus());
1892 #else
1893                 rp->maxactive = num_possible_cpus();
1894 #endif
1895         }
1896         raw_spin_lock_init(&rp->lock);
1897         INIT_HLIST_HEAD(&rp->free_instances);
1898         for (i = 0; i < rp->maxactive; i++) {
1899                 inst = kmalloc(sizeof(struct kretprobe_instance) +
1900                                rp->data_size, GFP_KERNEL);
1901                 if (inst == NULL) {
1902                         free_rp_inst(rp);
1903                         return -ENOMEM;
1904                 }
1905                 INIT_HLIST_NODE(&inst->hlist);
1906                 hlist_add_head(&inst->hlist, &rp->free_instances);
1907         }
1908 
1909         rp->nmissed = 0;
1910         /* Establish function entry probe point */
1911         ret = register_kprobe(&rp->kp);
1912         if (ret != 0)
1913                 free_rp_inst(rp);
1914         return ret;
1915 }
1916 EXPORT_SYMBOL_GPL(register_kretprobe);
1917 
1918 int register_kretprobes(struct kretprobe **rps, int num)
1919 {
1920         int ret = 0, i;
1921 
1922         if (num <= 0)
1923                 return -EINVAL;
1924         for (i = 0; i < num; i++) {
1925                 ret = register_kretprobe(rps[i]);
1926                 if (ret < 0) {
1927                         if (i > 0)
1928                                 unregister_kretprobes(rps, i);
1929                         break;
1930                 }
1931         }
1932         return ret;
1933 }
1934 EXPORT_SYMBOL_GPL(register_kretprobes);
1935 
1936 void unregister_kretprobe(struct kretprobe *rp)
1937 {
1938         unregister_kretprobes(&rp, 1);
1939 }
1940 EXPORT_SYMBOL_GPL(unregister_kretprobe);
1941 
1942 void unregister_kretprobes(struct kretprobe **rps, int num)
1943 {
1944         int i;
1945 
1946         if (num <= 0)
1947                 return;
1948         mutex_lock(&kprobe_mutex);
1949         for (i = 0; i < num; i++)
1950                 if (__unregister_kprobe_top(&rps[i]->kp) < 0)
1951                         rps[i]->kp.addr = NULL;
1952         mutex_unlock(&kprobe_mutex);
1953 
1954         synchronize_sched();
1955         for (i = 0; i < num; i++) {
1956                 if (rps[i]->kp.addr) {
1957                         __unregister_kprobe_bottom(&rps[i]->kp);
1958                         cleanup_rp_inst(rps[i]);
1959                 }
1960         }
1961 }
1962 EXPORT_SYMBOL_GPL(unregister_kretprobes);
1963 
1964 #else /* CONFIG_KRETPROBES */
1965 int register_kretprobe(struct kretprobe *rp)
1966 {
1967         return -ENOSYS;
1968 }
1969 EXPORT_SYMBOL_GPL(register_kretprobe);
1970 
1971 int register_kretprobes(struct kretprobe **rps, int num)
1972 {
1973         return -ENOSYS;
1974 }
1975 EXPORT_SYMBOL_GPL(register_kretprobes);
1976 
1977 void unregister_kretprobe(struct kretprobe *rp)
1978 {
1979 }
1980 EXPORT_SYMBOL_GPL(unregister_kretprobe);
1981 
1982 void unregister_kretprobes(struct kretprobe **rps, int num)
1983 {
1984 }
1985 EXPORT_SYMBOL_GPL(unregister_kretprobes);
1986 
1987 static int pre_handler_kretprobe(struct kprobe *p, struct pt_regs *regs)
1988 {
1989         return 0;
1990 }
1991 NOKPROBE_SYMBOL(pre_handler_kretprobe);
1992 
1993 #endif /* CONFIG_KRETPROBES */
1994 
1995 /* Set the kprobe gone and remove its instruction buffer. */
1996 static void kill_kprobe(struct kprobe *p)
1997 {
1998         struct kprobe *kp;
1999 
2000         p->flags |= KPROBE_FLAG_GONE;
2001         if (kprobe_aggrprobe(p)) {
2002                 /*
2003                  * If this is an aggr_kprobe, we have to list all the
2004                  * chained probes and mark them GONE.
2005                  */
2006                 list_for_each_entry_rcu(kp, &p->list, list)
2007                         kp->flags |= KPROBE_FLAG_GONE;
2008                 p->post_handler = NULL;
2009                 kill_optimized_kprobe(p);
2010         }
2011         /*
2012          * Here, we can remove insn_slot safely, because no thread calls
2013          * the original probed function (which will be freed soon) any more.
2014          */
2015         arch_remove_kprobe(p);
2016 }
2017 
2018 /* Disable one kprobe */
2019 int disable_kprobe(struct kprobe *kp)
2020 {
2021         int ret = 0;
2022         struct kprobe *p;
2023 
2024         mutex_lock(&kprobe_mutex);
2025 
2026         /* Disable this kprobe */
2027         p = __disable_kprobe(kp);
2028         if (IS_ERR(p))
2029                 ret = PTR_ERR(p);
2030 
2031         mutex_unlock(&kprobe_mutex);
2032         return ret;
2033 }
2034 EXPORT_SYMBOL_GPL(disable_kprobe);
2035 
2036 /* Enable one kprobe */
2037 int enable_kprobe(struct kprobe *kp)
2038 {
2039         int ret = 0;
2040         struct kprobe *p;
2041 
2042         mutex_lock(&kprobe_mutex);
2043 
2044         /* Check whether specified probe is valid. */
2045         p = __get_valid_kprobe(kp);
2046         if (unlikely(p == NULL)) {
2047                 ret = -EINVAL;
2048                 goto out;
2049         }
2050 
2051         if (kprobe_gone(kp)) {
2052                 /* This kprobe has gone, we couldn't enable it. */
2053                 ret = -EINVAL;
2054                 goto out;
2055         }
2056 
2057         if (p != kp)
2058                 kp->flags &= ~KPROBE_FLAG_DISABLED;
2059 
2060         if (!kprobes_all_disarmed && kprobe_disabled(p)) {
2061                 p->flags &= ~KPROBE_FLAG_DISABLED;
2062                 ret = arm_kprobe(p);
2063                 if (ret)
2064                         p->flags |= KPROBE_FLAG_DISABLED;
2065         }
2066 out:
2067         mutex_unlock(&kprobe_mutex);
2068         return ret;
2069 }
2070 EXPORT_SYMBOL_GPL(enable_kprobe);
2071 
2072 /* Caller must NOT call this in usual path. This is only for critical case */
2073 void dump_kprobe(struct kprobe *kp)
2074 {
2075         pr_err("Dumping kprobe:\n");
2076         pr_err("Name: %s\nOffset: %x\nAddress: %pS\n",
2077                kp->symbol_name, kp->offset, kp->addr);
2078 }
2079 NOKPROBE_SYMBOL(dump_kprobe);
2080 
2081 /*
2082  * Lookup and populate the kprobe_blacklist.
2083  *
2084  * Unlike the kretprobe blacklist, we'll need to determine
2085  * the range of addresses that belong to the said functions,
2086  * since a kprobe need not necessarily be at the beginning
2087  * of a function.
2088  */
2089 static int __init populate_kprobe_blacklist(unsigned long *start,
2090                                              unsigned long *end)
2091 {
2092         unsigned long *iter;
2093         struct kprobe_blacklist_entry *ent;
2094         unsigned long entry, offset = 0, size = 0;
2095 
2096         for (iter = start; iter < end; iter++) {
2097                 entry = arch_deref_entry_point((void *)*iter);
2098 
2099                 if (!kernel_text_address(entry) ||
2100                     !kallsyms_lookup_size_offset(entry, &size, &offset))
2101                         continue;
2102 
2103                 ent = kmalloc(sizeof(*ent), GFP_KERNEL);
2104                 if (!ent)
2105                         return -ENOMEM;
2106                 ent->start_addr = entry;
2107                 ent->end_addr = entry + size;
2108                 INIT_LIST_HEAD(&ent->list);
2109                 list_add_tail(&ent->list, &kprobe_blacklist);
2110         }
2111         return 0;
2112 }
2113 
2114 /* Module notifier call back, checking kprobes on the module */
2115 static int kprobes_module_callback(struct notifier_block *nb,
2116                                    unsigned long val, void *data)
2117 {
2118         struct module *mod = data;
2119         struct hlist_head *head;
2120         struct kprobe *p;
2121         unsigned int i;
2122         int checkcore = (val == MODULE_STATE_GOING);
2123 
2124         if (val != MODULE_STATE_GOING && val != MODULE_STATE_LIVE)
2125                 return NOTIFY_DONE;
2126 
2127         /*
2128          * When MODULE_STATE_GOING was notified, both of module .text and
2129          * .init.text sections would be freed. When MODULE_STATE_LIVE was
2130          * notified, only .init.text section would be freed. We need to
2131          * disable kprobes which have been inserted in the sections.
2132          */
2133         mutex_lock(&kprobe_mutex);
2134         for (i = 0; i < KPROBE_TABLE_SIZE; i++) {
2135                 head = &kprobe_table[i];
2136                 hlist_for_each_entry_rcu(p, head, hlist)
2137                         if (within_module_init((unsigned long)p->addr, mod) ||
2138                             (checkcore &&
2139                              within_module_core((unsigned long)p->addr, mod))) {
2140                                 /*
2141                                  * The vaddr this probe is installed will soon
2142                                  * be vfreed buy not synced to disk. Hence,
2143                                  * disarming the breakpoint isn't needed.
2144                                  *
2145                                  * Note, this will also move any optimized probes
2146                                  * that are pending to be removed from their
2147                                  * corresponding lists to the freeing_list and
2148                                  * will not be touched by the delayed
2149                                  * kprobe_optimizer work handler.
2150                                  */
2151                                 kill_kprobe(p);
2152                         }
2153         }
2154         mutex_unlock(&kprobe_mutex);
2155         return NOTIFY_DONE;
2156 }
2157 
2158 static struct notifier_block kprobe_module_nb = {
2159         .notifier_call = kprobes_module_callback,
2160         .priority = 0
2161 };
2162 
2163 /* Markers of _kprobe_blacklist section */
2164 extern unsigned long __start_kprobe_blacklist[];
2165 extern unsigned long __stop_kprobe_blacklist[];
2166 
2167 static int __init init_kprobes(void)
2168 {
2169         int i, err = 0;
2170 
2171         /* FIXME allocate the probe table, currently defined statically */
2172         /* initialize all list heads */
2173         for (i = 0; i < KPROBE_TABLE_SIZE; i++) {
2174                 INIT_HLIST_HEAD(&kprobe_table[i]);
2175                 INIT_HLIST_HEAD(&kretprobe_inst_table[i]);
2176                 raw_spin_lock_init(&(kretprobe_table_locks[i].lock));
2177         }
2178 
2179         err = populate_kprobe_blacklist(__start_kprobe_blacklist,
2180                                         __stop_kprobe_blacklist);
2181         if (err) {
2182                 pr_err("kprobes: failed to populate blacklist: %d\n", err);
2183                 pr_err("Please take care of using kprobes.\n");
2184         }
2185 
2186         if (kretprobe_blacklist_size) {
2187                 /* lookup the function address from its name */
2188                 for (i = 0; kretprobe_blacklist[i].name != NULL; i++) {
2189                         kretprobe_blacklist[i].addr =
2190                                 kprobe_lookup_name(kretprobe_blacklist[i].name, 0);
2191                         if (!kretprobe_blacklist[i].addr)
2192                                 printk("kretprobe: lookup failed: %s\n",
2193                                        kretprobe_blacklist[i].name);
2194                 }
2195         }
2196 
2197 #if defined(CONFIG_OPTPROBES)
2198 #if defined(__ARCH_WANT_KPROBES_INSN_SLOT)
2199         /* Init kprobe_optinsn_slots */
2200         kprobe_optinsn_slots.insn_size = MAX_OPTINSN_SIZE;
2201 #endif
2202         /* By default, kprobes can be optimized */
2203         kprobes_allow_optimization = true;
2204 #endif
2205 
2206         /* By default, kprobes are armed */
2207         kprobes_all_disarmed = false;
2208 
2209         err = arch_init_kprobes();
2210         if (!err)
2211                 err = register_die_notifier(&kprobe_exceptions_nb);
2212         if (!err)
2213                 err = register_module_notifier(&kprobe_module_nb);
2214 
2215         kprobes_initialized = (err == 0);
2216 
2217         if (!err)
2218                 init_test_probes();
2219         return err;
2220 }
2221 
2222 #ifdef CONFIG_DEBUG_FS
2223 static void report_probe(struct seq_file *pi, struct kprobe *p,
2224                 const char *sym, int offset, char *modname, struct kprobe *pp)
2225 {
2226         char *kprobe_type;
2227         void *addr = p->addr;
2228 
2229         if (p->pre_handler == pre_handler_kretprobe)
2230                 kprobe_type = "r";
2231         else
2232                 kprobe_type = "k";
2233 
2234         if (!kallsyms_show_value())
2235                 addr = NULL;
2236 
2237         if (sym)
2238                 seq_printf(pi, "%px  %s  %s+0x%x  %s ",
2239                         addr, kprobe_type, sym, offset,
2240                         (modname ? modname : " "));
2241         else    /* try to use %pS */
2242                 seq_printf(pi, "%px  %s  %pS ",
2243                         addr, kprobe_type, p->addr);
2244 
2245         if (!pp)
2246                 pp = p;
2247         seq_printf(pi, "%s%s%s%s\n",
2248                 (kprobe_gone(p) ? "[GONE]" : ""),
2249                 ((kprobe_disabled(p) && !kprobe_gone(p)) ?  "[DISABLED]" : ""),
2250                 (kprobe_optimized(pp) ? "[OPTIMIZED]" : ""),
2251                 (kprobe_ftrace(pp) ? "[FTRACE]" : ""));
2252 }
2253 
2254 static void *kprobe_seq_start(struct seq_file *f, loff_t *pos)
2255 {
2256         return (*pos < KPROBE_TABLE_SIZE) ? pos : NULL;
2257 }
2258 
2259 static void *kprobe_seq_next(struct seq_file *f, void *v, loff_t *pos)
2260 {
2261         (*pos)++;
2262         if (*pos >= KPROBE_TABLE_SIZE)
2263                 return NULL;
2264         return pos;
2265 }
2266 
2267 static void kprobe_seq_stop(struct seq_file *f, void *v)
2268 {
2269         /* Nothing to do */
2270 }
2271 
2272 static int show_kprobe_addr(struct seq_file *pi, void *v)
2273 {
2274         struct hlist_head *head;
2275         struct kprobe *p, *kp;
2276         const char *sym = NULL;
2277         unsigned int i = *(loff_t *) v;
2278         unsigned long offset = 0;
2279         char *modname, namebuf[KSYM_NAME_LEN];
2280 
2281         head = &kprobe_table[i];
2282         preempt_disable();
2283         hlist_for_each_entry_rcu(p, head, hlist) {
2284                 sym = kallsyms_lookup((unsigned long)p->addr, NULL,
2285                                         &offset, &modname, namebuf);
2286                 if (kprobe_aggrprobe(p)) {
2287                         list_for_each_entry_rcu(kp, &p->list, list)
2288                                 report_probe(pi, kp, sym, offset, modname, p);
2289                 } else
2290                         report_probe(pi, p, sym, offset, modname, NULL);
2291         }
2292         preempt_enable();
2293         return 0;
2294 }
2295 
2296 static const struct seq_operations kprobes_seq_ops = {
2297         .start = kprobe_seq_start,
2298         .next  = kprobe_seq_next,
2299         .stop  = kprobe_seq_stop,
2300         .show  = show_kprobe_addr
2301 };
2302 
2303 static int kprobes_open(struct inode *inode, struct file *filp)
2304 {
2305         return seq_open(filp, &kprobes_seq_ops);
2306 }
2307 
2308 static const struct file_operations debugfs_kprobes_operations = {
2309         .open           = kprobes_open,
2310         .read           = seq_read,
2311         .llseek         = seq_lseek,
2312         .release        = seq_release,
2313 };
2314 
2315 /* kprobes/blacklist -- shows which functions can not be probed */
2316 static void *kprobe_blacklist_seq_start(struct seq_file *m, loff_t *pos)
2317 {
2318         return seq_list_start(&kprobe_blacklist, *pos);
2319 }
2320 
2321 static void *kprobe_blacklist_seq_next(struct seq_file *m, void *v, loff_t *pos)
2322 {
2323         return seq_list_next(v, &kprobe_blacklist, pos);
2324 }
2325 
2326 static int kprobe_blacklist_seq_show(struct seq_file *m, void *v)
2327 {
2328         struct kprobe_blacklist_entry *ent =
2329                 list_entry(v, struct kprobe_blacklist_entry, list);
2330 
2331         /*
2332          * If /proc/kallsyms is not showing kernel address, we won't
2333          * show them here either.
2334          */
2335         if (!kallsyms_show_value())
2336                 seq_printf(m, "0x%px-0x%px\t%ps\n", NULL, NULL,
2337                            (void *)ent->start_addr);
2338         else
2339                 seq_printf(m, "0x%px-0x%px\t%ps\n", (void *)ent->start_addr,
2340                            (void *)ent->end_addr, (void *)ent->start_addr);
2341         return 0;
2342 }
2343 
2344 static const struct seq_operations kprobe_blacklist_seq_ops = {
2345         .start = kprobe_blacklist_seq_start,
2346         .next  = kprobe_blacklist_seq_next,
2347         .stop  = kprobe_seq_stop,       /* Reuse void function */
2348         .show  = kprobe_blacklist_seq_show,
2349 };
2350 
2351 static int kprobe_blacklist_open(struct inode *inode, struct file *filp)
2352 {
2353         return seq_open(filp, &kprobe_blacklist_seq_ops);
2354 }
2355 
2356 static const struct file_operations debugfs_kprobe_blacklist_ops = {
2357         .open           = kprobe_blacklist_open,
2358         .read           = seq_read,
2359         .llseek         = seq_lseek,
2360         .release        = seq_release,
2361 };
2362 
2363 static int arm_all_kprobes(void)
2364 {
2365         struct hlist_head *head;
2366         struct kprobe *p;
2367         unsigned int i, total = 0, errors = 0;
2368         int err, ret = 0;
2369 
2370         mutex_lock(&kprobe_mutex);
2371 
2372         /* If kprobes are armed, just return */
2373         if (!kprobes_all_disarmed)
2374                 goto already_enabled;
2375 
2376         /*
2377          * optimize_kprobe() called by arm_kprobe() checks
2378          * kprobes_all_disarmed, so set kprobes_all_disarmed before
2379          * arm_kprobe.
2380          */
2381         kprobes_all_disarmed = false;
2382         /* Arming kprobes doesn't optimize kprobe itself */
2383         for (i = 0; i < KPROBE_TABLE_SIZE; i++) {
2384                 head = &kprobe_table[i];
2385                 /* Arm all kprobes on a best-effort basis */
2386                 hlist_for_each_entry_rcu(p, head, hlist) {
2387                         if (!kprobe_disabled(p)) {
2388                                 err = arm_kprobe(p);
2389                                 if (err)  {
2390                                         errors++;
2391                                         ret = err;
2392                                 }
2393                                 total++;
2394                         }
2395                 }
2396         }
2397 
2398         if (errors)
2399                 pr_warn("Kprobes globally enabled, but failed to arm %d out of %d probes\n",
2400                         errors, total);
2401         else
2402                 pr_info("Kprobes globally enabled\n");
2403 
2404 already_enabled:
2405         mutex_unlock(&kprobe_mutex);
2406         return ret;
2407 }
2408 
2409 static int disarm_all_kprobes(void)
2410 {
2411         struct hlist_head *head;
2412         struct kprobe *p;
2413         unsigned int i, total = 0, errors = 0;
2414         int err, ret = 0;
2415 
2416         mutex_lock(&kprobe_mutex);
2417 
2418         /* If kprobes are already disarmed, just return */
2419         if (kprobes_all_disarmed) {
2420                 mutex_unlock(&kprobe_mutex);
2421                 return 0;
2422         }
2423 
2424         kprobes_all_disarmed = true;
2425 
2426         for (i = 0; i < KPROBE_TABLE_SIZE; i++) {
2427                 head = &kprobe_table[i];
2428                 /* Disarm all kprobes on a best-effort basis */
2429                 hlist_for_each_entry_rcu(p, head, hlist) {
2430                         if (!arch_trampoline_kprobe(p) && !kprobe_disabled(p)) {
2431                                 err = disarm_kprobe(p, false);
2432                                 if (err) {
2433                                         errors++;
2434                                         ret = err;
2435                                 }
2436                                 total++;
2437                         }
2438                 }
2439         }
2440 
2441         if (errors)
2442                 pr_warn("Kprobes globally disabled, but failed to disarm %d out of %d probes\n",
2443                         errors, total);
2444         else
2445                 pr_info("Kprobes globally disabled\n");
2446 
2447         mutex_unlock(&kprobe_mutex);
2448 
2449         /* Wait for disarming all kprobes by optimizer */
2450         wait_for_kprobe_optimizer();
2451 
2452         return ret;
2453 }
2454 
2455 /*
2456  * XXX: The debugfs bool file interface doesn't allow for callbacks
2457  * when the bool state is switched. We can reuse that facility when
2458  * available
2459  */
2460 static ssize_t read_enabled_file_bool(struct file *file,
2461                char __user *user_buf, size_t count, loff_t *ppos)
2462 {
2463         char buf[3];
2464 
2465         if (!kprobes_all_disarmed)
2466                 buf[0] = '1';
2467         else
2468                 buf[0] = '';
2469         buf[1] = '\n';
2470         buf[2] = 0x00;
2471         return simple_read_from_buffer(user_buf, count, ppos, buf, 2);
2472 }
2473 
2474 static ssize_t write_enabled_file_bool(struct file *file,
2475                const char __user *user_buf, size_t count, loff_t *ppos)
2476 {
2477         char buf[32];
2478         size_t buf_size;
2479         int ret = 0;
2480 
2481         buf_size = min(count, (sizeof(buf)-1));
2482         if (copy_from_user(buf, user_buf, buf_size))
2483                 return -EFAULT;
2484 
2485         buf[buf_size] = '\0';
2486         switch (buf[0]) {
2487         case 'y':
2488         case 'Y':
2489         case '1':
2490                 ret = arm_all_kprobes();
2491                 break;
2492         case 'n':
2493         case 'N':
2494         case '':
2495                 ret = disarm_all_kprobes();
2496                 break;
2497         default:
2498                 return -EINVAL;
2499         }
2500 
2501         if (ret)
2502                 return ret;
2503 
2504         return count;
2505 }
2506 
2507 static const struct file_operations fops_kp = {
2508         .read =         read_enabled_file_bool,
2509         .write =        write_enabled_file_bool,
2510         .llseek =       default_llseek,
2511 };
2512 
2513 static int __init debugfs_kprobe_init(void)
2514 {
2515         struct dentry *dir, *file;
2516         unsigned int value = 1;
2517 
2518         dir = debugfs_create_dir("kprobes", NULL);
2519         if (!dir)
2520                 return -ENOMEM;
2521 
2522         file = debugfs_create_file("list", 0400, dir, NULL,
2523                                 &debugfs_kprobes_operations);
2524         if (!file)
2525                 goto error;
2526 
2527         file = debugfs_create_file("enabled", 0600, dir,
2528                                         &value, &fops_kp);
2529         if (!file)
2530                 goto error;
2531 
2532         file = debugfs_create_file("blacklist", 0400, dir, NULL,
2533                                 &debugfs_kprobe_blacklist_ops);
2534         if (!file)
2535                 goto error;
2536 
2537         return 0;
2538 
2539 error:
2540         debugfs_remove(dir);
2541         return -ENOMEM;
2542 }
2543 
2544 late_initcall(debugfs_kprobe_init);
2545 #endif /* CONFIG_DEBUG_FS */
2546 
2547 module_init(init_kprobes);
2548 

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