Root/kernel/kprobes.c

1/*
2 * Kernel Probes (KProbes)
3 * kernel/kprobes.c
4 *
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License as published by
7 * the Free Software Foundation; either version 2 of the License, or
8 * (at your option) any later version.
9 *
10 * This program is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 * GNU General Public License for more details.
14 *
15 * You should have received a copy of the GNU General Public License
16 * along with this program; if not, write to the Free Software
17 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
18 *
19 * Copyright (C) IBM Corporation, 2002, 2004
20 *
21 * 2002-Oct Created by Vamsi Krishna S <vamsi_krishna@in.ibm.com> Kernel
22 * Probes initial implementation (includes suggestions from
23 * Rusty Russell).
24 * 2004-Aug Updated by Prasanna S Panchamukhi <prasanna@in.ibm.com> with
25 * hlists and exceptions notifier as suggested by Andi Kleen.
26 * 2004-July Suparna Bhattacharya <suparna@in.ibm.com> added jumper probes
27 * interface to access function arguments.
28 * 2004-Sep Prasanna S Panchamukhi <prasanna@in.ibm.com> Changed Kprobes
29 * exceptions notifier to be first on the priority list.
30 * 2005-May Hien Nguyen <hien@us.ibm.com>, Jim Keniston
31 * <jkenisto@us.ibm.com> and Prasanna S Panchamukhi
32 * <prasanna@in.ibm.com> added function-return probes.
33 */
34#include <linux/kprobes.h>
35#include <linux/hash.h>
36#include <linux/init.h>
37#include <linux/slab.h>
38#include <linux/stddef.h>
39#include <linux/module.h>
40#include <linux/moduleloader.h>
41#include <linux/kallsyms.h>
42#include <linux/freezer.h>
43#include <linux/seq_file.h>
44#include <linux/debugfs.h>
45#include <linux/sysctl.h>
46#include <linux/kdebug.h>
47#include <linux/memory.h>
48#include <linux/ftrace.h>
49#include <linux/cpu.h>
50
51#include <asm-generic/sections.h>
52#include <asm/cacheflush.h>
53#include <asm/errno.h>
54#include <asm/uaccess.h>
55
56#define KPROBE_HASH_BITS 6
57#define KPROBE_TABLE_SIZE (1 << KPROBE_HASH_BITS)
58
59
60/*
61 * Some oddball architectures like 64bit powerpc have function descriptors
62 * so this must be overridable.
63 */
64#ifndef kprobe_lookup_name
65#define kprobe_lookup_name(name, addr) \
66    addr = ((kprobe_opcode_t *)(kallsyms_lookup_name(name)))
67#endif
68
69static int kprobes_initialized;
70static struct hlist_head kprobe_table[KPROBE_TABLE_SIZE];
71static struct hlist_head kretprobe_inst_table[KPROBE_TABLE_SIZE];
72
73/* NOTE: change this value only with kprobe_mutex held */
74static bool kprobes_all_disarmed;
75
76static DEFINE_MUTEX(kprobe_mutex); /* Protects kprobe_table */
77static DEFINE_PER_CPU(struct kprobe *, kprobe_instance) = NULL;
78static struct {
79    spinlock_t lock ____cacheline_aligned_in_smp;
80} kretprobe_table_locks[KPROBE_TABLE_SIZE];
81
82static spinlock_t *kretprobe_table_lock_ptr(unsigned long hash)
83{
84    return &(kretprobe_table_locks[hash].lock);
85}
86
87/*
88 * Normally, functions that we'd want to prohibit kprobes in, are marked
89 * __kprobes. But, there are cases where such functions already belong to
90 * a different section (__sched for preempt_schedule)
91 *
92 * For such cases, we now have a blacklist
93 */
94static struct kprobe_blackpoint kprobe_blacklist[] = {
95    {"preempt_schedule",},
96    {"native_get_debugreg",},
97    {"irq_entries_start",},
98    {"common_interrupt",},
99    {"mcount",}, /* mcount can be called from everywhere */
100    {NULL} /* Terminator */
101};
102
103#ifdef __ARCH_WANT_KPROBES_INSN_SLOT
104/*
105 * kprobe->ainsn.insn points to the copy of the instruction to be
106 * single-stepped. x86_64, POWER4 and above have no-exec support and
107 * stepping on the instruction on a vmalloced/kmalloced/data page
108 * is a recipe for disaster
109 */
110struct kprobe_insn_page {
111    struct list_head list;
112    kprobe_opcode_t *insns; /* Page of instruction slots */
113    int nused;
114    int ngarbage;
115    char slot_used[];
116};
117
118#define KPROBE_INSN_PAGE_SIZE(slots) \
119    (offsetof(struct kprobe_insn_page, slot_used) + \
120     (sizeof(char) * (slots)))
121
122struct kprobe_insn_cache {
123    struct list_head pages; /* list of kprobe_insn_page */
124    size_t insn_size; /* size of instruction slot */
125    int nr_garbage;
126};
127
128static int slots_per_page(struct kprobe_insn_cache *c)
129{
130    return PAGE_SIZE/(c->insn_size * sizeof(kprobe_opcode_t));
131}
132
133enum kprobe_slot_state {
134    SLOT_CLEAN = 0,
135    SLOT_DIRTY = 1,
136    SLOT_USED = 2,
137};
138
139static DEFINE_MUTEX(kprobe_insn_mutex); /* Protects kprobe_insn_slots */
140static struct kprobe_insn_cache kprobe_insn_slots = {
141    .pages = LIST_HEAD_INIT(kprobe_insn_slots.pages),
142    .insn_size = MAX_INSN_SIZE,
143    .nr_garbage = 0,
144};
145static int __kprobes collect_garbage_slots(struct kprobe_insn_cache *c);
146
147/**
148 * __get_insn_slot() - Find a slot on an executable page for an instruction.
149 * We allocate an executable page if there's no room on existing ones.
150 */
151static kprobe_opcode_t __kprobes *__get_insn_slot(struct kprobe_insn_cache *c)
152{
153    struct kprobe_insn_page *kip;
154
155 retry:
156    list_for_each_entry(kip, &c->pages, list) {
157        if (kip->nused < slots_per_page(c)) {
158            int i;
159            for (i = 0; i < slots_per_page(c); i++) {
160                if (kip->slot_used[i] == SLOT_CLEAN) {
161                    kip->slot_used[i] = SLOT_USED;
162                    kip->nused++;
163                    return kip->insns + (i * c->insn_size);
164                }
165            }
166            /* kip->nused is broken. Fix it. */
167            kip->nused = slots_per_page(c);
168            WARN_ON(1);
169        }
170    }
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        return NULL;
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 = module_alloc(PAGE_SIZE);
187    if (!kip->insns) {
188        kfree(kip);
189        return NULL;
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    list_add(&kip->list, &c->pages);
197    return kip->insns;
198}
199
200
201kprobe_opcode_t __kprobes *get_insn_slot(void)
202{
203    kprobe_opcode_t *ret = NULL;
204
205    mutex_lock(&kprobe_insn_mutex);
206    ret = __get_insn_slot(&kprobe_insn_slots);
207    mutex_unlock(&kprobe_insn_mutex);
208
209    return ret;
210}
211
212/* Return 1 if all garbages are collected, otherwise 0. */
213static int __kprobes collect_one_slot(struct kprobe_insn_page *kip, int idx)
214{
215    kip->slot_used[idx] = SLOT_CLEAN;
216    kip->nused--;
217    if (kip->nused == 0) {
218        /*
219         * Page is no longer in use. Free it unless
220         * it's the last one. We keep the last one
221         * so as not to have to set it up again the
222         * next time somebody inserts a probe.
223         */
224        if (!list_is_singular(&kip->list)) {
225            list_del(&kip->list);
226            module_free(NULL, kip->insns);
227            kfree(kip);
228        }
229        return 1;
230    }
231    return 0;
232}
233
234static int __kprobes collect_garbage_slots(struct kprobe_insn_cache *c)
235{
236    struct kprobe_insn_page *kip, *next;
237
238    /* Ensure no-one is interrupted on the garbages */
239    synchronize_sched();
240
241    list_for_each_entry_safe(kip, next, &c->pages, list) {
242        int i;
243        if (kip->ngarbage == 0)
244            continue;
245        kip->ngarbage = 0; /* we will collect all garbages */
246        for (i = 0; i < slots_per_page(c); i++) {
247            if (kip->slot_used[i] == SLOT_DIRTY &&
248                collect_one_slot(kip, i))
249                break;
250        }
251    }
252    c->nr_garbage = 0;
253    return 0;
254}
255
256static void __kprobes __free_insn_slot(struct kprobe_insn_cache *c,
257                       kprobe_opcode_t *slot, int dirty)
258{
259    struct kprobe_insn_page *kip;
260
261    list_for_each_entry(kip, &c->pages, list) {
262        long idx = ((long)slot - (long)kip->insns) /
263                (c->insn_size * sizeof(kprobe_opcode_t));
264        if (idx >= 0 && idx < slots_per_page(c)) {
265            WARN_ON(kip->slot_used[idx] != SLOT_USED);
266            if (dirty) {
267                kip->slot_used[idx] = SLOT_DIRTY;
268                kip->ngarbage++;
269                if (++c->nr_garbage > slots_per_page(c))
270                    collect_garbage_slots(c);
271            } else
272                collect_one_slot(kip, idx);
273            return;
274        }
275    }
276    /* Could not free this slot. */
277    WARN_ON(1);
278}
279
280void __kprobes free_insn_slot(kprobe_opcode_t * slot, int dirty)
281{
282    mutex_lock(&kprobe_insn_mutex);
283    __free_insn_slot(&kprobe_insn_slots, slot, dirty);
284    mutex_unlock(&kprobe_insn_mutex);
285}
286#ifdef CONFIG_OPTPROBES
287/* For optimized_kprobe buffer */
288static DEFINE_MUTEX(kprobe_optinsn_mutex); /* Protects kprobe_optinsn_slots */
289static struct kprobe_insn_cache kprobe_optinsn_slots = {
290    .pages = LIST_HEAD_INIT(kprobe_optinsn_slots.pages),
291    /* .insn_size is initialized later */
292    .nr_garbage = 0,
293};
294/* Get a slot for optimized_kprobe buffer */
295kprobe_opcode_t __kprobes *get_optinsn_slot(void)
296{
297    kprobe_opcode_t *ret = NULL;
298
299    mutex_lock(&kprobe_optinsn_mutex);
300    ret = __get_insn_slot(&kprobe_optinsn_slots);
301    mutex_unlock(&kprobe_optinsn_mutex);
302
303    return ret;
304}
305
306void __kprobes free_optinsn_slot(kprobe_opcode_t * slot, int dirty)
307{
308    mutex_lock(&kprobe_optinsn_mutex);
309    __free_insn_slot(&kprobe_optinsn_slots, slot, dirty);
310    mutex_unlock(&kprobe_optinsn_mutex);
311}
312#endif
313#endif
314
315/* We have preemption disabled.. so it is safe to use __ versions */
316static inline void set_kprobe_instance(struct kprobe *kp)
317{
318    __get_cpu_var(kprobe_instance) = kp;
319}
320
321static inline void reset_kprobe_instance(void)
322{
323    __get_cpu_var(kprobe_instance) = NULL;
324}
325
326/*
327 * This routine is called either:
328 * - under the kprobe_mutex - during kprobe_[un]register()
329 * OR
330 * - with preemption disabled - from arch/xxx/kernel/kprobes.c
331 */
332struct kprobe __kprobes *get_kprobe(void *addr)
333{
334    struct hlist_head *head;
335    struct hlist_node *node;
336    struct kprobe *p;
337
338    head = &kprobe_table[hash_ptr(addr, KPROBE_HASH_BITS)];
339    hlist_for_each_entry_rcu(p, node, head, hlist) {
340        if (p->addr == addr)
341            return p;
342    }
343
344    return NULL;
345}
346
347static int __kprobes aggr_pre_handler(struct kprobe *p, struct pt_regs *regs);
348
349/* Return true if the kprobe is an aggregator */
350static inline int kprobe_aggrprobe(struct kprobe *p)
351{
352    return p->pre_handler == aggr_pre_handler;
353}
354
355/*
356 * Keep all fields in the kprobe consistent
357 */
358static inline void copy_kprobe(struct kprobe *old_p, struct kprobe *p)
359{
360    memcpy(&p->opcode, &old_p->opcode, sizeof(kprobe_opcode_t));
361    memcpy(&p->ainsn, &old_p->ainsn, sizeof(struct arch_specific_insn));
362}
363
364#ifdef CONFIG_OPTPROBES
365/* NOTE: change this value only with kprobe_mutex held */
366static bool kprobes_allow_optimization;
367
368/*
369 * Call all pre_handler on the list, but ignores its return value.
370 * This must be called from arch-dep optimized caller.
371 */
372void __kprobes opt_pre_handler(struct kprobe *p, struct pt_regs *regs)
373{
374    struct kprobe *kp;
375
376    list_for_each_entry_rcu(kp, &p->list, list) {
377        if (kp->pre_handler && likely(!kprobe_disabled(kp))) {
378            set_kprobe_instance(kp);
379            kp->pre_handler(kp, regs);
380        }
381        reset_kprobe_instance();
382    }
383}
384
385/* Return true(!0) if the kprobe is ready for optimization. */
386static inline int kprobe_optready(struct kprobe *p)
387{
388    struct optimized_kprobe *op;
389
390    if (kprobe_aggrprobe(p)) {
391        op = container_of(p, struct optimized_kprobe, kp);
392        return arch_prepared_optinsn(&op->optinsn);
393    }
394
395    return 0;
396}
397
398/*
399 * Return an optimized kprobe whose optimizing code replaces
400 * instructions including addr (exclude breakpoint).
401 */
402struct kprobe *__kprobes get_optimized_kprobe(unsigned long addr)
403{
404    int i;
405    struct kprobe *p = NULL;
406    struct optimized_kprobe *op;
407
408    /* Don't check i == 0, since that is a breakpoint case. */
409    for (i = 1; !p && i < MAX_OPTIMIZED_LENGTH; i++)
410        p = get_kprobe((void *)(addr - i));
411
412    if (p && kprobe_optready(p)) {
413        op = container_of(p, struct optimized_kprobe, kp);
414        if (arch_within_optimized_kprobe(op, addr))
415            return p;
416    }
417
418    return NULL;
419}
420
421/* Optimization staging list, protected by kprobe_mutex */
422static LIST_HEAD(optimizing_list);
423
424static void kprobe_optimizer(struct work_struct *work);
425static DECLARE_DELAYED_WORK(optimizing_work, kprobe_optimizer);
426#define OPTIMIZE_DELAY 5
427
428/* Kprobe jump optimizer */
429static __kprobes void kprobe_optimizer(struct work_struct *work)
430{
431    struct optimized_kprobe *op, *tmp;
432
433    /* Lock modules while optimizing kprobes */
434    mutex_lock(&module_mutex);
435    mutex_lock(&kprobe_mutex);
436    if (kprobes_all_disarmed || !kprobes_allow_optimization)
437        goto end;
438
439    /*
440     * Wait for quiesence period to ensure all running interrupts
441     * are done. Because optprobe may modify multiple instructions
442     * there is a chance that Nth instruction is interrupted. In that
443     * case, running interrupt can return to 2nd-Nth byte of jump
444     * instruction. This wait is for avoiding it.
445     */
446    synchronize_sched();
447
448    /*
449     * The optimization/unoptimization refers online_cpus via
450     * stop_machine() and cpu-hotplug modifies online_cpus.
451     * And same time, text_mutex will be held in cpu-hotplug and here.
452     * This combination can cause a deadlock (cpu-hotplug try to lock
453     * text_mutex but stop_machine can not be done because online_cpus
454     * has been changed)
455     * To avoid this deadlock, we need to call get_online_cpus()
456     * for preventing cpu-hotplug outside of text_mutex locking.
457     */
458    get_online_cpus();
459    mutex_lock(&text_mutex);
460    list_for_each_entry_safe(op, tmp, &optimizing_list, list) {
461        WARN_ON(kprobe_disabled(&op->kp));
462        if (arch_optimize_kprobe(op) < 0)
463            op->kp.flags &= ~KPROBE_FLAG_OPTIMIZED;
464        list_del_init(&op->list);
465    }
466    mutex_unlock(&text_mutex);
467    put_online_cpus();
468end:
469    mutex_unlock(&kprobe_mutex);
470    mutex_unlock(&module_mutex);
471}
472
473/* Optimize kprobe if p is ready to be optimized */
474static __kprobes void optimize_kprobe(struct kprobe *p)
475{
476    struct optimized_kprobe *op;
477
478    /* Check if the kprobe is disabled or not ready for optimization. */
479    if (!kprobe_optready(p) || !kprobes_allow_optimization ||
480        (kprobe_disabled(p) || kprobes_all_disarmed))
481        return;
482
483    /* Both of break_handler and post_handler are not supported. */
484    if (p->break_handler || p->post_handler)
485        return;
486
487    op = container_of(p, struct optimized_kprobe, kp);
488
489    /* Check there is no other kprobes at the optimized instructions */
490    if (arch_check_optimized_kprobe(op) < 0)
491        return;
492
493    /* Check if it is already optimized. */
494    if (op->kp.flags & KPROBE_FLAG_OPTIMIZED)
495        return;
496
497    op->kp.flags |= KPROBE_FLAG_OPTIMIZED;
498    list_add(&op->list, &optimizing_list);
499    if (!delayed_work_pending(&optimizing_work))
500        schedule_delayed_work(&optimizing_work, OPTIMIZE_DELAY);
501}
502
503/* Unoptimize a kprobe if p is optimized */
504static __kprobes void unoptimize_kprobe(struct kprobe *p)
505{
506    struct optimized_kprobe *op;
507
508    if ((p->flags & KPROBE_FLAG_OPTIMIZED) && kprobe_aggrprobe(p)) {
509        op = container_of(p, struct optimized_kprobe, kp);
510        if (!list_empty(&op->list))
511            /* Dequeue from the optimization queue */
512            list_del_init(&op->list);
513        else
514            /* Replace jump with break */
515            arch_unoptimize_kprobe(op);
516        op->kp.flags &= ~KPROBE_FLAG_OPTIMIZED;
517    }
518}
519
520/* Remove optimized instructions */
521static void __kprobes kill_optimized_kprobe(struct kprobe *p)
522{
523    struct optimized_kprobe *op;
524
525    op = container_of(p, struct optimized_kprobe, kp);
526    if (!list_empty(&op->list)) {
527        /* Dequeue from the optimization queue */
528        list_del_init(&op->list);
529        op->kp.flags &= ~KPROBE_FLAG_OPTIMIZED;
530    }
531    /* Don't unoptimize, because the target code will be freed. */
532    arch_remove_optimized_kprobe(op);
533}
534
535/* Try to prepare optimized instructions */
536static __kprobes void prepare_optimized_kprobe(struct kprobe *p)
537{
538    struct optimized_kprobe *op;
539
540    op = container_of(p, struct optimized_kprobe, kp);
541    arch_prepare_optimized_kprobe(op);
542}
543
544/* Free optimized instructions and optimized_kprobe */
545static __kprobes void free_aggr_kprobe(struct kprobe *p)
546{
547    struct optimized_kprobe *op;
548
549    op = container_of(p, struct optimized_kprobe, kp);
550    arch_remove_optimized_kprobe(op);
551    kfree(op);
552}
553
554/* Allocate new optimized_kprobe and try to prepare optimized instructions */
555static __kprobes struct kprobe *alloc_aggr_kprobe(struct kprobe *p)
556{
557    struct optimized_kprobe *op;
558
559    op = kzalloc(sizeof(struct optimized_kprobe), GFP_KERNEL);
560    if (!op)
561        return NULL;
562
563    INIT_LIST_HEAD(&op->list);
564    op->kp.addr = p->addr;
565    arch_prepare_optimized_kprobe(op);
566
567    return &op->kp;
568}
569
570static void __kprobes init_aggr_kprobe(struct kprobe *ap, struct kprobe *p);
571
572/*
573 * Prepare an optimized_kprobe and optimize it
574 * NOTE: p must be a normal registered kprobe
575 */
576static __kprobes void try_to_optimize_kprobe(struct kprobe *p)
577{
578    struct kprobe *ap;
579    struct optimized_kprobe *op;
580
581    ap = alloc_aggr_kprobe(p);
582    if (!ap)
583        return;
584
585    op = container_of(ap, struct optimized_kprobe, kp);
586    if (!arch_prepared_optinsn(&op->optinsn)) {
587        /* If failed to setup optimizing, fallback to kprobe */
588        free_aggr_kprobe(ap);
589        return;
590    }
591
592    init_aggr_kprobe(ap, p);
593    optimize_kprobe(ap);
594}
595
596#ifdef CONFIG_SYSCTL
597static void __kprobes optimize_all_kprobes(void)
598{
599    struct hlist_head *head;
600    struct hlist_node *node;
601    struct kprobe *p;
602    unsigned int i;
603
604    /* If optimization is already allowed, just return */
605    if (kprobes_allow_optimization)
606        return;
607
608    kprobes_allow_optimization = true;
609    mutex_lock(&text_mutex);
610    for (i = 0; i < KPROBE_TABLE_SIZE; i++) {
611        head = &kprobe_table[i];
612        hlist_for_each_entry_rcu(p, node, head, hlist)
613            if (!kprobe_disabled(p))
614                optimize_kprobe(p);
615    }
616    mutex_unlock(&text_mutex);
617    printk(KERN_INFO "Kprobes globally optimized\n");
618}
619
620static void __kprobes unoptimize_all_kprobes(void)
621{
622    struct hlist_head *head;
623    struct hlist_node *node;
624    struct kprobe *p;
625    unsigned int i;
626
627    /* If optimization is already prohibited, just return */
628    if (!kprobes_allow_optimization)
629        return;
630
631    kprobes_allow_optimization = false;
632    printk(KERN_INFO "Kprobes globally unoptimized\n");
633    get_online_cpus(); /* For avoiding text_mutex deadlock */
634    mutex_lock(&text_mutex);
635    for (i = 0; i < KPROBE_TABLE_SIZE; i++) {
636        head = &kprobe_table[i];
637        hlist_for_each_entry_rcu(p, node, head, hlist) {
638            if (!kprobe_disabled(p))
639                unoptimize_kprobe(p);
640        }
641    }
642
643    mutex_unlock(&text_mutex);
644    put_online_cpus();
645    /* Allow all currently running kprobes to complete */
646    synchronize_sched();
647}
648
649int sysctl_kprobes_optimization;
650int proc_kprobes_optimization_handler(struct ctl_table *table, int write,
651                      void __user *buffer, size_t *length,
652                      loff_t *ppos)
653{
654    int ret;
655
656    mutex_lock(&kprobe_mutex);
657    sysctl_kprobes_optimization = kprobes_allow_optimization ? 1 : 0;
658    ret = proc_dointvec_minmax(table, write, buffer, length, ppos);
659
660    if (sysctl_kprobes_optimization)
661        optimize_all_kprobes();
662    else
663        unoptimize_all_kprobes();
664    mutex_unlock(&kprobe_mutex);
665
666    return ret;
667}
668#endif /* CONFIG_SYSCTL */
669
670static void __kprobes __arm_kprobe(struct kprobe *p)
671{
672    struct kprobe *old_p;
673
674    /* Check collision with other optimized kprobes */
675    old_p = get_optimized_kprobe((unsigned long)p->addr);
676    if (unlikely(old_p))
677        unoptimize_kprobe(old_p); /* Fallback to unoptimized kprobe */
678
679    arch_arm_kprobe(p);
680    optimize_kprobe(p); /* Try to optimize (add kprobe to a list) */
681}
682
683static void __kprobes __disarm_kprobe(struct kprobe *p)
684{
685    struct kprobe *old_p;
686
687    unoptimize_kprobe(p); /* Try to unoptimize */
688    arch_disarm_kprobe(p);
689
690    /* If another kprobe was blocked, optimize it. */
691    old_p = get_optimized_kprobe((unsigned long)p->addr);
692    if (unlikely(old_p))
693        optimize_kprobe(old_p);
694}
695
696#else /* !CONFIG_OPTPROBES */
697
698#define optimize_kprobe(p) do {} while (0)
699#define unoptimize_kprobe(p) do {} while (0)
700#define kill_optimized_kprobe(p) do {} while (0)
701#define prepare_optimized_kprobe(p) do {} while (0)
702#define try_to_optimize_kprobe(p) do {} while (0)
703#define __arm_kprobe(p) arch_arm_kprobe(p)
704#define __disarm_kprobe(p) arch_disarm_kprobe(p)
705
706static __kprobes void free_aggr_kprobe(struct kprobe *p)
707{
708    kfree(p);
709}
710
711static __kprobes struct kprobe *alloc_aggr_kprobe(struct kprobe *p)
712{
713    return kzalloc(sizeof(struct kprobe), GFP_KERNEL);
714}
715#endif /* CONFIG_OPTPROBES */
716
717/* Arm a kprobe with text_mutex */
718static void __kprobes arm_kprobe(struct kprobe *kp)
719{
720    /*
721     * Here, since __arm_kprobe() doesn't use stop_machine(),
722     * this doesn't cause deadlock on text_mutex. So, we don't
723     * need get_online_cpus().
724     */
725    mutex_lock(&text_mutex);
726    __arm_kprobe(kp);
727    mutex_unlock(&text_mutex);
728}
729
730/* Disarm a kprobe with text_mutex */
731static void __kprobes disarm_kprobe(struct kprobe *kp)
732{
733    get_online_cpus(); /* For avoiding text_mutex deadlock */
734    mutex_lock(&text_mutex);
735    __disarm_kprobe(kp);
736    mutex_unlock(&text_mutex);
737    put_online_cpus();
738}
739
740/*
741 * Aggregate handlers for multiple kprobes support - these handlers
742 * take care of invoking the individual kprobe handlers on p->list
743 */
744static int __kprobes aggr_pre_handler(struct kprobe *p, struct pt_regs *regs)
745{
746    struct kprobe *kp;
747
748    list_for_each_entry_rcu(kp, &p->list, list) {
749        if (kp->pre_handler && likely(!kprobe_disabled(kp))) {
750            set_kprobe_instance(kp);
751            if (kp->pre_handler(kp, regs))
752                return 1;
753        }
754        reset_kprobe_instance();
755    }
756    return 0;
757}
758
759static void __kprobes aggr_post_handler(struct kprobe *p, struct pt_regs *regs,
760                    unsigned long flags)
761{
762    struct kprobe *kp;
763
764    list_for_each_entry_rcu(kp, &p->list, list) {
765        if (kp->post_handler && likely(!kprobe_disabled(kp))) {
766            set_kprobe_instance(kp);
767            kp->post_handler(kp, regs, flags);
768            reset_kprobe_instance();
769        }
770    }
771}
772
773static int __kprobes aggr_fault_handler(struct kprobe *p, struct pt_regs *regs,
774                    int trapnr)
775{
776    struct kprobe *cur = __get_cpu_var(kprobe_instance);
777
778    /*
779     * if we faulted "during" the execution of a user specified
780     * probe handler, invoke just that probe's fault handler
781     */
782    if (cur && cur->fault_handler) {
783        if (cur->fault_handler(cur, regs, trapnr))
784            return 1;
785    }
786    return 0;
787}
788
789static int __kprobes aggr_break_handler(struct kprobe *p, struct pt_regs *regs)
790{
791    struct kprobe *cur = __get_cpu_var(kprobe_instance);
792    int ret = 0;
793
794    if (cur && cur->break_handler) {
795        if (cur->break_handler(cur, regs))
796            ret = 1;
797    }
798    reset_kprobe_instance();
799    return ret;
800}
801
802/* Walks the list and increments nmissed count for multiprobe case */
803void __kprobes kprobes_inc_nmissed_count(struct kprobe *p)
804{
805    struct kprobe *kp;
806    if (!kprobe_aggrprobe(p)) {
807        p->nmissed++;
808    } else {
809        list_for_each_entry_rcu(kp, &p->list, list)
810            kp->nmissed++;
811    }
812    return;
813}
814
815void __kprobes recycle_rp_inst(struct kretprobe_instance *ri,
816                struct hlist_head *head)
817{
818    struct kretprobe *rp = ri->rp;
819
820    /* remove rp inst off the rprobe_inst_table */
821    hlist_del(&ri->hlist);
822    INIT_HLIST_NODE(&ri->hlist);
823    if (likely(rp)) {
824        spin_lock(&rp->lock);
825        hlist_add_head(&ri->hlist, &rp->free_instances);
826        spin_unlock(&rp->lock);
827    } else
828        /* Unregistering */
829        hlist_add_head(&ri->hlist, head);
830}
831
832void __kprobes kretprobe_hash_lock(struct task_struct *tsk,
833             struct hlist_head **head, unsigned long *flags)
834{
835    unsigned long hash = hash_ptr(tsk, KPROBE_HASH_BITS);
836    spinlock_t *hlist_lock;
837
838    *head = &kretprobe_inst_table[hash];
839    hlist_lock = kretprobe_table_lock_ptr(hash);
840    spin_lock_irqsave(hlist_lock, *flags);
841}
842
843static void __kprobes kretprobe_table_lock(unsigned long hash,
844    unsigned long *flags)
845{
846    spinlock_t *hlist_lock = kretprobe_table_lock_ptr(hash);
847    spin_lock_irqsave(hlist_lock, *flags);
848}
849
850void __kprobes kretprobe_hash_unlock(struct task_struct *tsk,
851    unsigned long *flags)
852{
853    unsigned long hash = hash_ptr(tsk, KPROBE_HASH_BITS);
854    spinlock_t *hlist_lock;
855
856    hlist_lock = kretprobe_table_lock_ptr(hash);
857    spin_unlock_irqrestore(hlist_lock, *flags);
858}
859
860void __kprobes kretprobe_table_unlock(unsigned long hash, unsigned long *flags)
861{
862    spinlock_t *hlist_lock = kretprobe_table_lock_ptr(hash);
863    spin_unlock_irqrestore(hlist_lock, *flags);
864}
865
866/*
867 * This function is called from finish_task_switch when task tk becomes dead,
868 * so that we can recycle any function-return probe instances associated
869 * with this task. These left over instances represent probed functions
870 * that have been called but will never return.
871 */
872void __kprobes kprobe_flush_task(struct task_struct *tk)
873{
874    struct kretprobe_instance *ri;
875    struct hlist_head *head, empty_rp;
876    struct hlist_node *node, *tmp;
877    unsigned long hash, flags = 0;
878
879    if (unlikely(!kprobes_initialized))
880        /* Early boot. kretprobe_table_locks not yet initialized. */
881        return;
882
883    hash = hash_ptr(tk, KPROBE_HASH_BITS);
884    head = &kretprobe_inst_table[hash];
885    kretprobe_table_lock(hash, &flags);
886    hlist_for_each_entry_safe(ri, node, tmp, head, hlist) {
887        if (ri->task == tk)
888            recycle_rp_inst(ri, &empty_rp);
889    }
890    kretprobe_table_unlock(hash, &flags);
891    INIT_HLIST_HEAD(&empty_rp);
892    hlist_for_each_entry_safe(ri, node, tmp, &empty_rp, hlist) {
893        hlist_del(&ri->hlist);
894        kfree(ri);
895    }
896}
897
898static inline void free_rp_inst(struct kretprobe *rp)
899{
900    struct kretprobe_instance *ri;
901    struct hlist_node *pos, *next;
902
903    hlist_for_each_entry_safe(ri, pos, next, &rp->free_instances, hlist) {
904        hlist_del(&ri->hlist);
905        kfree(ri);
906    }
907}
908
909static void __kprobes cleanup_rp_inst(struct kretprobe *rp)
910{
911    unsigned long flags, hash;
912    struct kretprobe_instance *ri;
913    struct hlist_node *pos, *next;
914    struct hlist_head *head;
915
916    /* No race here */
917    for (hash = 0; hash < KPROBE_TABLE_SIZE; hash++) {
918        kretprobe_table_lock(hash, &flags);
919        head = &kretprobe_inst_table[hash];
920        hlist_for_each_entry_safe(ri, pos, next, head, hlist) {
921            if (ri->rp == rp)
922                ri->rp = NULL;
923        }
924        kretprobe_table_unlock(hash, &flags);
925    }
926    free_rp_inst(rp);
927}
928
929/*
930* Add the new probe to ap->list. Fail if this is the
931* second jprobe at the address - two jprobes can't coexist
932*/
933static int __kprobes add_new_kprobe(struct kprobe *ap, struct kprobe *p)
934{
935    BUG_ON(kprobe_gone(ap) || kprobe_gone(p));
936
937    if (p->break_handler || p->post_handler)
938        unoptimize_kprobe(ap); /* Fall back to normal kprobe */
939
940    if (p->break_handler) {
941        if (ap->break_handler)
942            return -EEXIST;
943        list_add_tail_rcu(&p->list, &ap->list);
944        ap->break_handler = aggr_break_handler;
945    } else
946        list_add_rcu(&p->list, &ap->list);
947    if (p->post_handler && !ap->post_handler)
948        ap->post_handler = aggr_post_handler;
949
950    if (kprobe_disabled(ap) && !kprobe_disabled(p)) {
951        ap->flags &= ~KPROBE_FLAG_DISABLED;
952        if (!kprobes_all_disarmed)
953            /* Arm the breakpoint again. */
954            __arm_kprobe(ap);
955    }
956    return 0;
957}
958
959/*
960 * Fill in the required fields of the "manager kprobe". Replace the
961 * earlier kprobe in the hlist with the manager kprobe
962 */
963static void __kprobes init_aggr_kprobe(struct kprobe *ap, struct kprobe *p)
964{
965    /* Copy p's insn slot to ap */
966    copy_kprobe(p, ap);
967    flush_insn_slot(ap);
968    ap->addr = p->addr;
969    ap->flags = p->flags & ~KPROBE_FLAG_OPTIMIZED;
970    ap->pre_handler = aggr_pre_handler;
971    ap->fault_handler = aggr_fault_handler;
972    /* We don't care the kprobe which has gone. */
973    if (p->post_handler && !kprobe_gone(p))
974        ap->post_handler = aggr_post_handler;
975    if (p->break_handler && !kprobe_gone(p))
976        ap->break_handler = aggr_break_handler;
977
978    INIT_LIST_HEAD(&ap->list);
979    INIT_HLIST_NODE(&ap->hlist);
980
981    list_add_rcu(&p->list, &ap->list);
982    hlist_replace_rcu(&p->hlist, &ap->hlist);
983}
984
985/*
986 * This is the second or subsequent kprobe at the address - handle
987 * the intricacies
988 */
989static int __kprobes register_aggr_kprobe(struct kprobe *old_p,
990                      struct kprobe *p)
991{
992    int ret = 0;
993    struct kprobe *ap = old_p;
994
995    if (!kprobe_aggrprobe(old_p)) {
996        /* If old_p is not an aggr_kprobe, create new aggr_kprobe. */
997        ap = alloc_aggr_kprobe(old_p);
998        if (!ap)
999            return -ENOMEM;
1000        init_aggr_kprobe(ap, old_p);
1001    }
1002
1003    if (kprobe_gone(ap)) {
1004        /*
1005         * Attempting to insert new probe at the same location that
1006         * had a probe in the module vaddr area which already
1007         * freed. So, the instruction slot has already been
1008         * released. We need a new slot for the new probe.
1009         */
1010        ret = arch_prepare_kprobe(ap);
1011        if (ret)
1012            /*
1013             * Even if fail to allocate new slot, don't need to
1014             * free aggr_probe. It will be used next time, or
1015             * freed by unregister_kprobe.
1016             */
1017            return ret;
1018
1019        /* Prepare optimized instructions if possible. */
1020        prepare_optimized_kprobe(ap);
1021
1022        /*
1023         * Clear gone flag to prevent allocating new slot again, and
1024         * set disabled flag because it is not armed yet.
1025         */
1026        ap->flags = (ap->flags & ~KPROBE_FLAG_GONE)
1027                | KPROBE_FLAG_DISABLED;
1028    }
1029
1030    /* Copy ap's insn slot to p */
1031    copy_kprobe(ap, p);
1032    return add_new_kprobe(ap, p);
1033}
1034
1035/* Try to disable aggr_kprobe, and return 1 if succeeded.*/
1036static int __kprobes try_to_disable_aggr_kprobe(struct kprobe *p)
1037{
1038    struct kprobe *kp;
1039
1040    list_for_each_entry_rcu(kp, &p->list, list) {
1041        if (!kprobe_disabled(kp))
1042            /*
1043             * There is an active probe on the list.
1044             * We can't disable aggr_kprobe.
1045             */
1046            return 0;
1047    }
1048    p->flags |= KPROBE_FLAG_DISABLED;
1049    return 1;
1050}
1051
1052static int __kprobes in_kprobes_functions(unsigned long addr)
1053{
1054    struct kprobe_blackpoint *kb;
1055
1056    if (addr >= (unsigned long)__kprobes_text_start &&
1057        addr < (unsigned long)__kprobes_text_end)
1058        return -EINVAL;
1059    /*
1060     * If there exists a kprobe_blacklist, verify and
1061     * fail any probe registration in the prohibited area
1062     */
1063    for (kb = kprobe_blacklist; kb->name != NULL; kb++) {
1064        if (kb->start_addr) {
1065            if (addr >= kb->start_addr &&
1066                addr < (kb->start_addr + kb->range))
1067                return -EINVAL;
1068        }
1069    }
1070    return 0;
1071}
1072
1073/*
1074 * If we have a symbol_name argument, look it up and add the offset field
1075 * to it. This way, we can specify a relative address to a symbol.
1076 */
1077static kprobe_opcode_t __kprobes *kprobe_addr(struct kprobe *p)
1078{
1079    kprobe_opcode_t *addr = p->addr;
1080    if (p->symbol_name) {
1081        if (addr)
1082            return NULL;
1083        kprobe_lookup_name(p->symbol_name, addr);
1084    }
1085
1086    if (!addr)
1087        return NULL;
1088    return (kprobe_opcode_t *)(((char *)addr) + p->offset);
1089}
1090
1091/* Check passed kprobe is valid and return kprobe in kprobe_table. */
1092static struct kprobe * __kprobes __get_valid_kprobe(struct kprobe *p)
1093{
1094    struct kprobe *old_p, *list_p;
1095
1096    old_p = get_kprobe(p->addr);
1097    if (unlikely(!old_p))
1098        return NULL;
1099
1100    if (p != old_p) {
1101        list_for_each_entry_rcu(list_p, &old_p->list, list)
1102            if (list_p == p)
1103            /* kprobe p is a valid probe */
1104                goto valid;
1105        return NULL;
1106    }
1107valid:
1108    return old_p;
1109}
1110
1111/* Return error if the kprobe is being re-registered */
1112static inline int check_kprobe_rereg(struct kprobe *p)
1113{
1114    int ret = 0;
1115    struct kprobe *old_p;
1116
1117    mutex_lock(&kprobe_mutex);
1118    old_p = __get_valid_kprobe(p);
1119    if (old_p)
1120        ret = -EINVAL;
1121    mutex_unlock(&kprobe_mutex);
1122    return ret;
1123}
1124
1125int __kprobes register_kprobe(struct kprobe *p)
1126{
1127    int ret = 0;
1128    struct kprobe *old_p;
1129    struct module *probed_mod;
1130    kprobe_opcode_t *addr;
1131
1132    addr = kprobe_addr(p);
1133    if (!addr)
1134        return -EINVAL;
1135    p->addr = addr;
1136
1137    ret = check_kprobe_rereg(p);
1138    if (ret)
1139        return ret;
1140
1141    preempt_disable();
1142    if (!kernel_text_address((unsigned long) p->addr) ||
1143        in_kprobes_functions((unsigned long) p->addr) ||
1144        ftrace_text_reserved(p->addr, p->addr)) {
1145        preempt_enable();
1146        return -EINVAL;
1147    }
1148
1149    /* User can pass only KPROBE_FLAG_DISABLED to register_kprobe */
1150    p->flags &= KPROBE_FLAG_DISABLED;
1151
1152    /*
1153     * Check if are we probing a module.
1154     */
1155    probed_mod = __module_text_address((unsigned long) p->addr);
1156    if (probed_mod) {
1157        /*
1158         * We must hold a refcount of the probed module while updating
1159         * its code to prohibit unexpected unloading.
1160         */
1161        if (unlikely(!try_module_get(probed_mod))) {
1162            preempt_enable();
1163            return -EINVAL;
1164        }
1165        /*
1166         * If the module freed .init.text, we couldn't insert
1167         * kprobes in there.
1168         */
1169        if (within_module_init((unsigned long)p->addr, probed_mod) &&
1170            probed_mod->state != MODULE_STATE_COMING) {
1171            module_put(probed_mod);
1172            preempt_enable();
1173            return -EINVAL;
1174        }
1175    }
1176    preempt_enable();
1177
1178    p->nmissed = 0;
1179    INIT_LIST_HEAD(&p->list);
1180    mutex_lock(&kprobe_mutex);
1181
1182    get_online_cpus(); /* For avoiding text_mutex deadlock. */
1183    mutex_lock(&text_mutex);
1184
1185    old_p = get_kprobe(p->addr);
1186    if (old_p) {
1187        /* Since this may unoptimize old_p, locking text_mutex. */
1188        ret = register_aggr_kprobe(old_p, p);
1189        goto out;
1190    }
1191
1192    ret = arch_prepare_kprobe(p);
1193    if (ret)
1194        goto out;
1195
1196    INIT_HLIST_NODE(&p->hlist);
1197    hlist_add_head_rcu(&p->hlist,
1198               &kprobe_table[hash_ptr(p->addr, KPROBE_HASH_BITS)]);
1199
1200    if (!kprobes_all_disarmed && !kprobe_disabled(p))
1201        __arm_kprobe(p);
1202
1203    /* Try to optimize kprobe */
1204    try_to_optimize_kprobe(p);
1205
1206out:
1207    mutex_unlock(&text_mutex);
1208    put_online_cpus();
1209    mutex_unlock(&kprobe_mutex);
1210
1211    if (probed_mod)
1212        module_put(probed_mod);
1213
1214    return ret;
1215}
1216EXPORT_SYMBOL_GPL(register_kprobe);
1217
1218/*
1219 * Unregister a kprobe without a scheduler synchronization.
1220 */
1221static int __kprobes __unregister_kprobe_top(struct kprobe *p)
1222{
1223    struct kprobe *old_p, *list_p;
1224
1225    old_p = __get_valid_kprobe(p);
1226    if (old_p == NULL)
1227        return -EINVAL;
1228
1229    if (old_p == p ||
1230        (kprobe_aggrprobe(old_p) &&
1231         list_is_singular(&old_p->list))) {
1232        /*
1233         * Only probe on the hash list. Disarm only if kprobes are
1234         * enabled and not gone - otherwise, the breakpoint would
1235         * already have been removed. We save on flushing icache.
1236         */
1237        if (!kprobes_all_disarmed && !kprobe_disabled(old_p))
1238            disarm_kprobe(old_p);
1239        hlist_del_rcu(&old_p->hlist);
1240    } else {
1241        if (p->break_handler && !kprobe_gone(p))
1242            old_p->break_handler = NULL;
1243        if (p->post_handler && !kprobe_gone(p)) {
1244            list_for_each_entry_rcu(list_p, &old_p->list, list) {
1245                if ((list_p != p) && (list_p->post_handler))
1246                    goto noclean;
1247            }
1248            old_p->post_handler = NULL;
1249        }
1250noclean:
1251        list_del_rcu(&p->list);
1252        if (!kprobe_disabled(old_p)) {
1253            try_to_disable_aggr_kprobe(old_p);
1254            if (!kprobes_all_disarmed) {
1255                if (kprobe_disabled(old_p))
1256                    disarm_kprobe(old_p);
1257                else
1258                    /* Try to optimize this probe again */
1259                    optimize_kprobe(old_p);
1260            }
1261        }
1262    }
1263    return 0;
1264}
1265
1266static void __kprobes __unregister_kprobe_bottom(struct kprobe *p)
1267{
1268    struct kprobe *old_p;
1269
1270    if (list_empty(&p->list))
1271        arch_remove_kprobe(p);
1272    else if (list_is_singular(&p->list)) {
1273        /* "p" is the last child of an aggr_kprobe */
1274        old_p = list_entry(p->list.next, struct kprobe, list);
1275        list_del(&p->list);
1276        arch_remove_kprobe(old_p);
1277        free_aggr_kprobe(old_p);
1278    }
1279}
1280
1281int __kprobes register_kprobes(struct kprobe **kps, int num)
1282{
1283    int i, ret = 0;
1284
1285    if (num <= 0)
1286        return -EINVAL;
1287    for (i = 0; i < num; i++) {
1288        ret = register_kprobe(kps[i]);
1289        if (ret < 0) {
1290            if (i > 0)
1291                unregister_kprobes(kps, i);
1292            break;
1293        }
1294    }
1295    return ret;
1296}
1297EXPORT_SYMBOL_GPL(register_kprobes);
1298
1299void __kprobes unregister_kprobe(struct kprobe *p)
1300{
1301    unregister_kprobes(&p, 1);
1302}
1303EXPORT_SYMBOL_GPL(unregister_kprobe);
1304
1305void __kprobes unregister_kprobes(struct kprobe **kps, int num)
1306{
1307    int i;
1308
1309    if (num <= 0)
1310        return;
1311    mutex_lock(&kprobe_mutex);
1312    for (i = 0; i < num; i++)
1313        if (__unregister_kprobe_top(kps[i]) < 0)
1314            kps[i]->addr = NULL;
1315    mutex_unlock(&kprobe_mutex);
1316
1317    synchronize_sched();
1318    for (i = 0; i < num; i++)
1319        if (kps[i]->addr)
1320            __unregister_kprobe_bottom(kps[i]);
1321}
1322EXPORT_SYMBOL_GPL(unregister_kprobes);
1323
1324static struct notifier_block kprobe_exceptions_nb = {
1325    .notifier_call = kprobe_exceptions_notify,
1326    .priority = 0x7fffffff /* we need to be notified first */
1327};
1328
1329unsigned long __weak arch_deref_entry_point(void *entry)
1330{
1331    return (unsigned long)entry;
1332}
1333
1334int __kprobes register_jprobes(struct jprobe **jps, int num)
1335{
1336    struct jprobe *jp;
1337    int ret = 0, i;
1338
1339    if (num <= 0)
1340        return -EINVAL;
1341    for (i = 0; i < num; i++) {
1342        unsigned long addr;
1343        jp = jps[i];
1344        addr = arch_deref_entry_point(jp->entry);
1345
1346        if (!kernel_text_address(addr))
1347            ret = -EINVAL;
1348        else {
1349            /* Todo: Verify probepoint is a function entry point */
1350            jp->kp.pre_handler = setjmp_pre_handler;
1351            jp->kp.break_handler = longjmp_break_handler;
1352            ret = register_kprobe(&jp->kp);
1353        }
1354        if (ret < 0) {
1355            if (i > 0)
1356                unregister_jprobes(jps, i);
1357            break;
1358        }
1359    }
1360    return ret;
1361}
1362EXPORT_SYMBOL_GPL(register_jprobes);
1363
1364int __kprobes register_jprobe(struct jprobe *jp)
1365{
1366    return register_jprobes(&jp, 1);
1367}
1368EXPORT_SYMBOL_GPL(register_jprobe);
1369
1370void __kprobes unregister_jprobe(struct jprobe *jp)
1371{
1372    unregister_jprobes(&jp, 1);
1373}
1374EXPORT_SYMBOL_GPL(unregister_jprobe);
1375
1376void __kprobes unregister_jprobes(struct jprobe **jps, int num)
1377{
1378    int i;
1379
1380    if (num <= 0)
1381        return;
1382    mutex_lock(&kprobe_mutex);
1383    for (i = 0; i < num; i++)
1384        if (__unregister_kprobe_top(&jps[i]->kp) < 0)
1385            jps[i]->kp.addr = NULL;
1386    mutex_unlock(&kprobe_mutex);
1387
1388    synchronize_sched();
1389    for (i = 0; i < num; i++) {
1390        if (jps[i]->kp.addr)
1391            __unregister_kprobe_bottom(&jps[i]->kp);
1392    }
1393}
1394EXPORT_SYMBOL_GPL(unregister_jprobes);
1395
1396#ifdef CONFIG_KRETPROBES
1397/*
1398 * This kprobe pre_handler is registered with every kretprobe. When probe
1399 * hits it will set up the return probe.
1400 */
1401static int __kprobes pre_handler_kretprobe(struct kprobe *p,
1402                       struct pt_regs *regs)
1403{
1404    struct kretprobe *rp = container_of(p, struct kretprobe, kp);
1405    unsigned long hash, flags = 0;
1406    struct kretprobe_instance *ri;
1407
1408    /*TODO: consider to only swap the RA after the last pre_handler fired */
1409    hash = hash_ptr(current, KPROBE_HASH_BITS);
1410    spin_lock_irqsave(&rp->lock, flags);
1411    if (!hlist_empty(&rp->free_instances)) {
1412        ri = hlist_entry(rp->free_instances.first,
1413                struct kretprobe_instance, hlist);
1414        hlist_del(&ri->hlist);
1415        spin_unlock_irqrestore(&rp->lock, flags);
1416
1417        ri->rp = rp;
1418        ri->task = current;
1419
1420        if (rp->entry_handler && rp->entry_handler(ri, regs))
1421            return 0;
1422
1423        arch_prepare_kretprobe(ri, regs);
1424
1425        /* XXX(hch): why is there no hlist_move_head? */
1426        INIT_HLIST_NODE(&ri->hlist);
1427        kretprobe_table_lock(hash, &flags);
1428        hlist_add_head(&ri->hlist, &kretprobe_inst_table[hash]);
1429        kretprobe_table_unlock(hash, &flags);
1430    } else {
1431        rp->nmissed++;
1432        spin_unlock_irqrestore(&rp->lock, flags);
1433    }
1434    return 0;
1435}
1436
1437int __kprobes register_kretprobe(struct kretprobe *rp)
1438{
1439    int ret = 0;
1440    struct kretprobe_instance *inst;
1441    int i;
1442    void *addr;
1443
1444    if (kretprobe_blacklist_size) {
1445        addr = kprobe_addr(&rp->kp);
1446        if (!addr)
1447            return -EINVAL;
1448
1449        for (i = 0; kretprobe_blacklist[i].name != NULL; i++) {
1450            if (kretprobe_blacklist[i].addr == addr)
1451                return -EINVAL;
1452        }
1453    }
1454
1455    rp->kp.pre_handler = pre_handler_kretprobe;
1456    rp->kp.post_handler = NULL;
1457    rp->kp.fault_handler = NULL;
1458    rp->kp.break_handler = NULL;
1459
1460    /* Pre-allocate memory for max kretprobe instances */
1461    if (rp->maxactive <= 0) {
1462#ifdef CONFIG_PREEMPT
1463        rp->maxactive = max_t(unsigned int, 10, 2*num_possible_cpus());
1464#else
1465        rp->maxactive = num_possible_cpus();
1466#endif
1467    }
1468    spin_lock_init(&rp->lock);
1469    INIT_HLIST_HEAD(&rp->free_instances);
1470    for (i = 0; i < rp->maxactive; i++) {
1471        inst = kmalloc(sizeof(struct kretprobe_instance) +
1472                   rp->data_size, GFP_KERNEL);
1473        if (inst == NULL) {
1474            free_rp_inst(rp);
1475            return -ENOMEM;
1476        }
1477        INIT_HLIST_NODE(&inst->hlist);
1478        hlist_add_head(&inst->hlist, &rp->free_instances);
1479    }
1480
1481    rp->nmissed = 0;
1482    /* Establish function entry probe point */
1483    ret = register_kprobe(&rp->kp);
1484    if (ret != 0)
1485        free_rp_inst(rp);
1486    return ret;
1487}
1488EXPORT_SYMBOL_GPL(register_kretprobe);
1489
1490int __kprobes register_kretprobes(struct kretprobe **rps, int num)
1491{
1492    int ret = 0, i;
1493
1494    if (num <= 0)
1495        return -EINVAL;
1496    for (i = 0; i < num; i++) {
1497        ret = register_kretprobe(rps[i]);
1498        if (ret < 0) {
1499            if (i > 0)
1500                unregister_kretprobes(rps, i);
1501            break;
1502        }
1503    }
1504    return ret;
1505}
1506EXPORT_SYMBOL_GPL(register_kretprobes);
1507
1508void __kprobes unregister_kretprobe(struct kretprobe *rp)
1509{
1510    unregister_kretprobes(&rp, 1);
1511}
1512EXPORT_SYMBOL_GPL(unregister_kretprobe);
1513
1514void __kprobes unregister_kretprobes(struct kretprobe **rps, int num)
1515{
1516    int i;
1517
1518    if (num <= 0)
1519        return;
1520    mutex_lock(&kprobe_mutex);
1521    for (i = 0; i < num; i++)
1522        if (__unregister_kprobe_top(&rps[i]->kp) < 0)
1523            rps[i]->kp.addr = NULL;
1524    mutex_unlock(&kprobe_mutex);
1525
1526    synchronize_sched();
1527    for (i = 0; i < num; i++) {
1528        if (rps[i]->kp.addr) {
1529            __unregister_kprobe_bottom(&rps[i]->kp);
1530            cleanup_rp_inst(rps[i]);
1531        }
1532    }
1533}
1534EXPORT_SYMBOL_GPL(unregister_kretprobes);
1535
1536#else /* CONFIG_KRETPROBES */
1537int __kprobes register_kretprobe(struct kretprobe *rp)
1538{
1539    return -ENOSYS;
1540}
1541EXPORT_SYMBOL_GPL(register_kretprobe);
1542
1543int __kprobes register_kretprobes(struct kretprobe **rps, int num)
1544{
1545    return -ENOSYS;
1546}
1547EXPORT_SYMBOL_GPL(register_kretprobes);
1548
1549void __kprobes unregister_kretprobe(struct kretprobe *rp)
1550{
1551}
1552EXPORT_SYMBOL_GPL(unregister_kretprobe);
1553
1554void __kprobes unregister_kretprobes(struct kretprobe **rps, int num)
1555{
1556}
1557EXPORT_SYMBOL_GPL(unregister_kretprobes);
1558
1559static int __kprobes pre_handler_kretprobe(struct kprobe *p,
1560                       struct pt_regs *regs)
1561{
1562    return 0;
1563}
1564
1565#endif /* CONFIG_KRETPROBES */
1566
1567/* Set the kprobe gone and remove its instruction buffer. */
1568static void __kprobes kill_kprobe(struct kprobe *p)
1569{
1570    struct kprobe *kp;
1571
1572    p->flags |= KPROBE_FLAG_GONE;
1573    if (kprobe_aggrprobe(p)) {
1574        /*
1575         * If this is an aggr_kprobe, we have to list all the
1576         * chained probes and mark them GONE.
1577         */
1578        list_for_each_entry_rcu(kp, &p->list, list)
1579            kp->flags |= KPROBE_FLAG_GONE;
1580        p->post_handler = NULL;
1581        p->break_handler = NULL;
1582        kill_optimized_kprobe(p);
1583    }
1584    /*
1585     * Here, we can remove insn_slot safely, because no thread calls
1586     * the original probed function (which will be freed soon) any more.
1587     */
1588    arch_remove_kprobe(p);
1589}
1590
1591/* Disable one kprobe */
1592int __kprobes disable_kprobe(struct kprobe *kp)
1593{
1594    int ret = 0;
1595    struct kprobe *p;
1596
1597    mutex_lock(&kprobe_mutex);
1598
1599    /* Check whether specified probe is valid. */
1600    p = __get_valid_kprobe(kp);
1601    if (unlikely(p == NULL)) {
1602        ret = -EINVAL;
1603        goto out;
1604    }
1605
1606    /* If the probe is already disabled (or gone), just return */
1607    if (kprobe_disabled(kp))
1608        goto out;
1609
1610    kp->flags |= KPROBE_FLAG_DISABLED;
1611    if (p != kp)
1612        /* When kp != p, p is always enabled. */
1613        try_to_disable_aggr_kprobe(p);
1614
1615    if (!kprobes_all_disarmed && kprobe_disabled(p))
1616        disarm_kprobe(p);
1617out:
1618    mutex_unlock(&kprobe_mutex);
1619    return ret;
1620}
1621EXPORT_SYMBOL_GPL(disable_kprobe);
1622
1623/* Enable one kprobe */
1624int __kprobes enable_kprobe(struct kprobe *kp)
1625{
1626    int ret = 0;
1627    struct kprobe *p;
1628
1629    mutex_lock(&kprobe_mutex);
1630
1631    /* Check whether specified probe is valid. */
1632    p = __get_valid_kprobe(kp);
1633    if (unlikely(p == NULL)) {
1634        ret = -EINVAL;
1635        goto out;
1636    }
1637
1638    if (kprobe_gone(kp)) {
1639        /* This kprobe has gone, we couldn't enable it. */
1640        ret = -EINVAL;
1641        goto out;
1642    }
1643
1644    if (p != kp)
1645        kp->flags &= ~KPROBE_FLAG_DISABLED;
1646
1647    if (!kprobes_all_disarmed && kprobe_disabled(p)) {
1648        p->flags &= ~KPROBE_FLAG_DISABLED;
1649        arm_kprobe(p);
1650    }
1651out:
1652    mutex_unlock(&kprobe_mutex);
1653    return ret;
1654}
1655EXPORT_SYMBOL_GPL(enable_kprobe);
1656
1657void __kprobes dump_kprobe(struct kprobe *kp)
1658{
1659    printk(KERN_WARNING "Dumping kprobe:\n");
1660    printk(KERN_WARNING "Name: %s\nAddress: %p\nOffset: %x\n",
1661           kp->symbol_name, kp->addr, kp->offset);
1662}
1663
1664/* Module notifier call back, checking kprobes on the module */
1665static int __kprobes kprobes_module_callback(struct notifier_block *nb,
1666                         unsigned long val, void *data)
1667{
1668    struct module *mod = data;
1669    struct hlist_head *head;
1670    struct hlist_node *node;
1671    struct kprobe *p;
1672    unsigned int i;
1673    int checkcore = (val == MODULE_STATE_GOING);
1674
1675    if (val != MODULE_STATE_GOING && val != MODULE_STATE_LIVE)
1676        return NOTIFY_DONE;
1677
1678    /*
1679     * When MODULE_STATE_GOING was notified, both of module .text and
1680     * .init.text sections would be freed. When MODULE_STATE_LIVE was
1681     * notified, only .init.text section would be freed. We need to
1682     * disable kprobes which have been inserted in the sections.
1683     */
1684    mutex_lock(&kprobe_mutex);
1685    for (i = 0; i < KPROBE_TABLE_SIZE; i++) {
1686        head = &kprobe_table[i];
1687        hlist_for_each_entry_rcu(p, node, head, hlist)
1688            if (within_module_init((unsigned long)p->addr, mod) ||
1689                (checkcore &&
1690                 within_module_core((unsigned long)p->addr, mod))) {
1691                /*
1692                 * The vaddr this probe is installed will soon
1693                 * be vfreed buy not synced to disk. Hence,
1694                 * disarming the breakpoint isn't needed.
1695                 */
1696                kill_kprobe(p);
1697            }
1698    }
1699    mutex_unlock(&kprobe_mutex);
1700    return NOTIFY_DONE;
1701}
1702
1703static struct notifier_block kprobe_module_nb = {
1704    .notifier_call = kprobes_module_callback,
1705    .priority = 0
1706};
1707
1708static int __init init_kprobes(void)
1709{
1710    int i, err = 0;
1711    unsigned long offset = 0, size = 0;
1712    char *modname, namebuf[128];
1713    const char *symbol_name;
1714    void *addr;
1715    struct kprobe_blackpoint *kb;
1716
1717    /* FIXME allocate the probe table, currently defined statically */
1718    /* initialize all list heads */
1719    for (i = 0; i < KPROBE_TABLE_SIZE; i++) {
1720        INIT_HLIST_HEAD(&kprobe_table[i]);
1721        INIT_HLIST_HEAD(&kretprobe_inst_table[i]);
1722        spin_lock_init(&(kretprobe_table_locks[i].lock));
1723    }
1724
1725    /*
1726     * Lookup and populate the kprobe_blacklist.
1727     *
1728     * Unlike the kretprobe blacklist, we'll need to determine
1729     * the range of addresses that belong to the said functions,
1730     * since a kprobe need not necessarily be at the beginning
1731     * of a function.
1732     */
1733    for (kb = kprobe_blacklist; kb->name != NULL; kb++) {
1734        kprobe_lookup_name(kb->name, addr);
1735        if (!addr)
1736            continue;
1737
1738        kb->start_addr = (unsigned long)addr;
1739        symbol_name = kallsyms_lookup(kb->start_addr,
1740                &size, &offset, &modname, namebuf);
1741        if (!symbol_name)
1742            kb->range = 0;
1743        else
1744            kb->range = size;
1745    }
1746
1747    if (kretprobe_blacklist_size) {
1748        /* lookup the function address from its name */
1749        for (i = 0; kretprobe_blacklist[i].name != NULL; i++) {
1750            kprobe_lookup_name(kretprobe_blacklist[i].name,
1751                       kretprobe_blacklist[i].addr);
1752            if (!kretprobe_blacklist[i].addr)
1753                printk("kretprobe: lookup failed: %s\n",
1754                       kretprobe_blacklist[i].name);
1755        }
1756    }
1757
1758#if defined(CONFIG_OPTPROBES)
1759#if defined(__ARCH_WANT_KPROBES_INSN_SLOT)
1760    /* Init kprobe_optinsn_slots */
1761    kprobe_optinsn_slots.insn_size = MAX_OPTINSN_SIZE;
1762#endif
1763    /* By default, kprobes can be optimized */
1764    kprobes_allow_optimization = true;
1765#endif
1766
1767    /* By default, kprobes are armed */
1768    kprobes_all_disarmed = false;
1769
1770    err = arch_init_kprobes();
1771    if (!err)
1772        err = register_die_notifier(&kprobe_exceptions_nb);
1773    if (!err)
1774        err = register_module_notifier(&kprobe_module_nb);
1775
1776    kprobes_initialized = (err == 0);
1777
1778    if (!err)
1779        init_test_probes();
1780    return err;
1781}
1782
1783#ifdef CONFIG_DEBUG_FS
1784static void __kprobes report_probe(struct seq_file *pi, struct kprobe *p,
1785        const char *sym, int offset, char *modname, struct kprobe *pp)
1786{
1787    char *kprobe_type;
1788
1789    if (p->pre_handler == pre_handler_kretprobe)
1790        kprobe_type = "r";
1791    else if (p->pre_handler == setjmp_pre_handler)
1792        kprobe_type = "j";
1793    else
1794        kprobe_type = "k";
1795
1796    if (sym)
1797        seq_printf(pi, "%p %s %s+0x%x %s ",
1798            p->addr, kprobe_type, sym, offset,
1799            (modname ? modname : " "));
1800    else
1801        seq_printf(pi, "%p %s %p ",
1802            p->addr, kprobe_type, p->addr);
1803
1804    if (!pp)
1805        pp = p;
1806    seq_printf(pi, "%s%s%s\n",
1807        (kprobe_gone(p) ? "[GONE]" : ""),
1808        ((kprobe_disabled(p) && !kprobe_gone(p)) ? "[DISABLED]" : ""),
1809        (kprobe_optimized(pp) ? "[OPTIMIZED]" : ""));
1810}
1811
1812static void __kprobes *kprobe_seq_start(struct seq_file *f, loff_t *pos)
1813{
1814    return (*pos < KPROBE_TABLE_SIZE) ? pos : NULL;
1815}
1816
1817static void __kprobes *kprobe_seq_next(struct seq_file *f, void *v, loff_t *pos)
1818{
1819    (*pos)++;
1820    if (*pos >= KPROBE_TABLE_SIZE)
1821        return NULL;
1822    return pos;
1823}
1824
1825static void __kprobes kprobe_seq_stop(struct seq_file *f, void *v)
1826{
1827    /* Nothing to do */
1828}
1829
1830static int __kprobes show_kprobe_addr(struct seq_file *pi, void *v)
1831{
1832    struct hlist_head *head;
1833    struct hlist_node *node;
1834    struct kprobe *p, *kp;
1835    const char *sym = NULL;
1836    unsigned int i = *(loff_t *) v;
1837    unsigned long offset = 0;
1838    char *modname, namebuf[128];
1839
1840    head = &kprobe_table[i];
1841    preempt_disable();
1842    hlist_for_each_entry_rcu(p, node, head, hlist) {
1843        sym = kallsyms_lookup((unsigned long)p->addr, NULL,
1844                    &offset, &modname, namebuf);
1845        if (kprobe_aggrprobe(p)) {
1846            list_for_each_entry_rcu(kp, &p->list, list)
1847                report_probe(pi, kp, sym, offset, modname, p);
1848        } else
1849            report_probe(pi, p, sym, offset, modname, NULL);
1850    }
1851    preempt_enable();
1852    return 0;
1853}
1854
1855static const struct seq_operations kprobes_seq_ops = {
1856    .start = kprobe_seq_start,
1857    .next = kprobe_seq_next,
1858    .stop = kprobe_seq_stop,
1859    .show = show_kprobe_addr
1860};
1861
1862static int __kprobes kprobes_open(struct inode *inode, struct file *filp)
1863{
1864    return seq_open(filp, &kprobes_seq_ops);
1865}
1866
1867static const struct file_operations debugfs_kprobes_operations = {
1868    .open = kprobes_open,
1869    .read = seq_read,
1870    .llseek = seq_lseek,
1871    .release = seq_release,
1872};
1873
1874static void __kprobes arm_all_kprobes(void)
1875{
1876    struct hlist_head *head;
1877    struct hlist_node *node;
1878    struct kprobe *p;
1879    unsigned int i;
1880
1881    mutex_lock(&kprobe_mutex);
1882
1883    /* If kprobes are armed, just return */
1884    if (!kprobes_all_disarmed)
1885        goto already_enabled;
1886
1887    /* Arming kprobes doesn't optimize kprobe itself */
1888    mutex_lock(&text_mutex);
1889    for (i = 0; i < KPROBE_TABLE_SIZE; i++) {
1890        head = &kprobe_table[i];
1891        hlist_for_each_entry_rcu(p, node, head, hlist)
1892            if (!kprobe_disabled(p))
1893                __arm_kprobe(p);
1894    }
1895    mutex_unlock(&text_mutex);
1896
1897    kprobes_all_disarmed = false;
1898    printk(KERN_INFO "Kprobes globally enabled\n");
1899
1900already_enabled:
1901    mutex_unlock(&kprobe_mutex);
1902    return;
1903}
1904
1905static void __kprobes disarm_all_kprobes(void)
1906{
1907    struct hlist_head *head;
1908    struct hlist_node *node;
1909    struct kprobe *p;
1910    unsigned int i;
1911
1912    mutex_lock(&kprobe_mutex);
1913
1914    /* If kprobes are already disarmed, just return */
1915    if (kprobes_all_disarmed)
1916        goto already_disabled;
1917
1918    kprobes_all_disarmed = true;
1919    printk(KERN_INFO "Kprobes globally disabled\n");
1920
1921    /*
1922     * Here we call get_online_cpus() for avoiding text_mutex deadlock,
1923     * because disarming may also unoptimize kprobes.
1924     */
1925    get_online_cpus();
1926    mutex_lock(&text_mutex);
1927    for (i = 0; i < KPROBE_TABLE_SIZE; i++) {
1928        head = &kprobe_table[i];
1929        hlist_for_each_entry_rcu(p, node, head, hlist) {
1930            if (!arch_trampoline_kprobe(p) && !kprobe_disabled(p))
1931                __disarm_kprobe(p);
1932        }
1933    }
1934
1935    mutex_unlock(&text_mutex);
1936    put_online_cpus();
1937    mutex_unlock(&kprobe_mutex);
1938    /* Allow all currently running kprobes to complete */
1939    synchronize_sched();
1940    return;
1941
1942already_disabled:
1943    mutex_unlock(&kprobe_mutex);
1944    return;
1945}
1946
1947/*
1948 * XXX: The debugfs bool file interface doesn't allow for callbacks
1949 * when the bool state is switched. We can reuse that facility when
1950 * available
1951 */
1952static ssize_t read_enabled_file_bool(struct file *file,
1953           char __user *user_buf, size_t count, loff_t *ppos)
1954{
1955    char buf[3];
1956
1957    if (!kprobes_all_disarmed)
1958        buf[0] = '1';
1959    else
1960        buf[0] = '0';
1961    buf[1] = '\n';
1962    buf[2] = 0x00;
1963    return simple_read_from_buffer(user_buf, count, ppos, buf, 2);
1964}
1965
1966static ssize_t write_enabled_file_bool(struct file *file,
1967           const char __user *user_buf, size_t count, loff_t *ppos)
1968{
1969    char buf[32];
1970    int buf_size;
1971
1972    buf_size = min(count, (sizeof(buf)-1));
1973    if (copy_from_user(buf, user_buf, buf_size))
1974        return -EFAULT;
1975
1976    switch (buf[0]) {
1977    case 'y':
1978    case 'Y':
1979    case '1':
1980        arm_all_kprobes();
1981        break;
1982    case 'n':
1983    case 'N':
1984    case '0':
1985        disarm_all_kprobes();
1986        break;
1987    }
1988
1989    return count;
1990}
1991
1992static const struct file_operations fops_kp = {
1993    .read = read_enabled_file_bool,
1994    .write = write_enabled_file_bool,
1995};
1996
1997static int __kprobes debugfs_kprobe_init(void)
1998{
1999    struct dentry *dir, *file;
2000    unsigned int value = 1;
2001
2002    dir = debugfs_create_dir("kprobes", NULL);
2003    if (!dir)
2004        return -ENOMEM;
2005
2006    file = debugfs_create_file("list", 0444, dir, NULL,
2007                &debugfs_kprobes_operations);
2008    if (!file) {
2009        debugfs_remove(dir);
2010        return -ENOMEM;
2011    }
2012
2013    file = debugfs_create_file("enabled", 0600, dir,
2014                    &value, &fops_kp);
2015    if (!file) {
2016        debugfs_remove(dir);
2017        return -ENOMEM;
2018    }
2019
2020    return 0;
2021}
2022
2023late_initcall(debugfs_kprobe_init);
2024#endif /* CONFIG_DEBUG_FS */
2025
2026module_init(init_kprobes);
2027
2028/* defined in arch/.../kernel/kprobes.c */
2029EXPORT_SYMBOL_GPL(jprobe_return);
2030

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