Linux 4.9.151

[linux/fpc-iii.git] / kernel / kprobes.c

/*
 *  Kernel Probes (KProbes)
 *  kernel/kprobes.c
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 *
 * Copyright (C) IBM Corporation, 2002, 2004
 *
 * 2002-Oct     Created by Vamsi Krishna S <vamsi_krishna@in.ibm.com> Kernel
 *              Probes initial implementation (includes suggestions from
 *              Rusty Russell).
 * 2004-Aug     Updated by Prasanna S Panchamukhi <prasanna@in.ibm.com> with
 *              hlists and exceptions notifier as suggested by Andi Kleen.
 * 2004-July    Suparna Bhattacharya <suparna@in.ibm.com> added jumper probes
 *              interface to access function arguments.
 * 2004-Sep     Prasanna S Panchamukhi <prasanna@in.ibm.com> Changed Kprobes
 *              exceptions notifier to be first on the priority list.
 * 2005-May     Hien Nguyen <hien@us.ibm.com>, Jim Keniston
 *              <jkenisto@us.ibm.com> and Prasanna S Panchamukhi
 *              <prasanna@in.ibm.com> added function-return probes.
 */
#include <linux/kprobes.h>
#include <linux/hash.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/stddef.h>
#include <linux/export.h>
#include <linux/moduleloader.h>
#include <linux/kallsyms.h>
#include <linux/freezer.h>
#include <linux/seq_file.h>
#include <linux/debugfs.h>
#include <linux/sysctl.h>
#include <linux/kdebug.h>
#include <linux/memory.h>
#include <linux/ftrace.h>
#include <linux/cpu.h>
#include <linux/jump_label.h>

#include <asm/sections.h>
#include <asm/cacheflush.h>
#include <asm/errno.h>
#include <asm/uaccess.h>

#define KPROBE_HASH_BITS 6
#define KPROBE_TABLE_SIZE (1 << KPROBE_HASH_BITS)


/*
 * Some oddball architectures like 64bit powerpc have function descriptors
 * so this must be overridable.
 */
#ifndef kprobe_lookup_name
#define kprobe_lookup_name(name, addr) \
        addr = ((kprobe_opcode_t *)(kallsyms_lookup_name(name)))
#endif

static int kprobes_initialized;
static struct hlist_head kprobe_table[KPROBE_TABLE_SIZE];
static struct hlist_head kretprobe_inst_table[KPROBE_TABLE_SIZE];

/* NOTE: change this value only with kprobe_mutex held */
static bool kprobes_all_disarmed;

/* This protects kprobe_table and optimizing_list */
static DEFINE_MUTEX(kprobe_mutex);
static DEFINE_PER_CPU(struct kprobe *, kprobe_instance) = NULL;
static struct {
        raw_spinlock_t lock ____cacheline_aligned_in_smp;
} kretprobe_table_locks[KPROBE_TABLE_SIZE];

static raw_spinlock_t *kretprobe_table_lock_ptr(unsigned long hash)
{
        return &(kretprobe_table_locks[hash].lock);
}

/* Blacklist -- list of struct kprobe_blacklist_entry */
static LIST_HEAD(kprobe_blacklist);

#ifdef __ARCH_WANT_KPROBES_INSN_SLOT
/*
 * kprobe->ainsn.insn points to the copy of the instruction to be
 * single-stepped. x86_64, POWER4 and above have no-exec support and
 * stepping on the instruction on a vmalloced/kmalloced/data page
 * is a recipe for disaster
 */
struct kprobe_insn_page {
        struct list_head list;
        kprobe_opcode_t *insns;         /* Page of instruction slots */
        struct kprobe_insn_cache *cache;
        int nused;
        int ngarbage;
        char slot_used[];
};

#define KPROBE_INSN_PAGE_SIZE(slots)                    \
        (offsetof(struct kprobe_insn_page, slot_used) + \
         (sizeof(char) * (slots)))

static int slots_per_page(struct kprobe_insn_cache *c)
{
        return PAGE_SIZE/(c->insn_size * sizeof(kprobe_opcode_t));
}

enum kprobe_slot_state {
        SLOT_CLEAN = 0,
        SLOT_DIRTY = 1,
        SLOT_USED = 2,
};

static void *alloc_insn_page(void)
{
        return module_alloc(PAGE_SIZE);
}

void __weak free_insn_page(void *page)
{
        module_memfree(page);
}

struct kprobe_insn_cache kprobe_insn_slots = {
        .mutex = __MUTEX_INITIALIZER(kprobe_insn_slots.mutex),
        .alloc = alloc_insn_page,
        .free = free_insn_page,
        .pages = LIST_HEAD_INIT(kprobe_insn_slots.pages),
        .insn_size = MAX_INSN_SIZE,
        .nr_garbage = 0,
};
static int collect_garbage_slots(struct kprobe_insn_cache *c);

/**
 * __get_insn_slot() - Find a slot on an executable page for an instruction.
 * We allocate an executable page if there's no room on existing ones.
 */
kprobe_opcode_t *__get_insn_slot(struct kprobe_insn_cache *c)
{
        struct kprobe_insn_page *kip;
        kprobe_opcode_t *slot = NULL;

        mutex_lock(&c->mutex);
 retry:
        list_for_each_entry(kip, &c->pages, list) {
                if (kip->nused < slots_per_page(c)) {
                        int i;
                        for (i = 0; i < slots_per_page(c); i++) {
                                if (kip->slot_used[i] == SLOT_CLEAN) {
                                        kip->slot_used[i] = SLOT_USED;
                                        kip->nused++;
                                        slot = kip->insns + (i * c->insn_size);
                                        goto out;
                                }
                        }
                        /* kip->nused is broken. Fix it. */
                        kip->nused = slots_per_page(c);
                        WARN_ON(1);
                }
        }

        /* If there are any garbage slots, collect it and try again. */
        if (c->nr_garbage && collect_garbage_slots(c) == 0)
                goto retry;

        /* All out of space.  Need to allocate a new page. */
        kip = kmalloc(KPROBE_INSN_PAGE_SIZE(slots_per_page(c)), GFP_KERNEL);
        if (!kip)
                goto out;

        /*
         * Use module_alloc so this page is within +/- 2GB of where the
         * kernel image and loaded module images reside. This is required
         * so x86_64 can correctly handle the %rip-relative fixups.
         */
        kip->insns = c->alloc();
        if (!kip->insns) {
                kfree(kip);
                goto out;
        }
        INIT_LIST_HEAD(&kip->list);
        memset(kip->slot_used, SLOT_CLEAN, slots_per_page(c));
        kip->slot_used[0] = SLOT_USED;
        kip->nused = 1;
        kip->ngarbage = 0;
        kip->cache = c;
        list_add(&kip->list, &c->pages);
        slot = kip->insns;
out:
        mutex_unlock(&c->mutex);
        return slot;
}

/* Return 1 if all garbages are collected, otherwise 0. */
static int collect_one_slot(struct kprobe_insn_page *kip, int idx)
{
        kip->slot_used[idx] = SLOT_CLEAN;
        kip->nused--;
        if (kip->nused == 0) {
                /*
                 * Page is no longer in use.  Free it unless
                 * it's the last one.  We keep the last one
                 * so as not to have to set it up again the
                 * next time somebody inserts a probe.
                 */
                if (!list_is_singular(&kip->list)) {
                        list_del(&kip->list);
                        kip->cache->free(kip->insns);
                        kfree(kip);
                }
                return 1;
        }
        return 0;
}

static int collect_garbage_slots(struct kprobe_insn_cache *c)
{
        struct kprobe_insn_page *kip, *next;

        /* Ensure no-one is interrupted on the garbages */
        synchronize_sched();

        list_for_each_entry_safe(kip, next, &c->pages, list) {
                int i;
                if (kip->ngarbage == 0)
                        continue;
                kip->ngarbage = 0;      /* we will collect all garbages */
                for (i = 0; i < slots_per_page(c); i++) {
                        if (kip->slot_used[i] == SLOT_DIRTY &&
                            collect_one_slot(kip, i))
                                break;
                }
        }
        c->nr_garbage = 0;
        return 0;
}

void __free_insn_slot(struct kprobe_insn_cache *c,
                      kprobe_opcode_t *slot, int dirty)
{
        struct kprobe_insn_page *kip;

        mutex_lock(&c->mutex);
        list_for_each_entry(kip, &c->pages, list) {
                long idx = ((long)slot - (long)kip->insns) /
                                (c->insn_size * sizeof(kprobe_opcode_t));
                if (idx >= 0 && idx < slots_per_page(c)) {
                        WARN_ON(kip->slot_used[idx] != SLOT_USED);
                        if (dirty) {
                                kip->slot_used[idx] = SLOT_DIRTY;
                                kip->ngarbage++;
                                if (++c->nr_garbage > slots_per_page(c))
                                        collect_garbage_slots(c);
                        } else
                                collect_one_slot(kip, idx);
                        goto out;
                }
        }
        /* Could not free this slot. */
        WARN_ON(1);
out:
        mutex_unlock(&c->mutex);
}

#ifdef CONFIG_OPTPROBES
/* For optimized_kprobe buffer */
struct kprobe_insn_cache kprobe_optinsn_slots = {
        .mutex = __MUTEX_INITIALIZER(kprobe_optinsn_slots.mutex),
        .alloc = alloc_insn_page,
        .free = free_insn_page,
        .pages = LIST_HEAD_INIT(kprobe_optinsn_slots.pages),
        /* .insn_size is initialized later */
        .nr_garbage = 0,
};
#endif
#endif

/* We have preemption disabled.. so it is safe to use __ versions */
static inline void set_kprobe_instance(struct kprobe *kp)
{
        __this_cpu_write(kprobe_instance, kp);
}

static inline void reset_kprobe_instance(void)
{
        __this_cpu_write(kprobe_instance, NULL);
}

/*
 * This routine is called either:
 *      - under the kprobe_mutex - during kprobe_[un]register()
 *                              OR
 *      - with preemption disabled - from arch/xxx/kernel/kprobes.c
 */
struct kprobe *get_kprobe(void *addr)
{
        struct hlist_head *head;
        struct kprobe *p;

        head = &kprobe_table[hash_ptr(addr, KPROBE_HASH_BITS)];
        hlist_for_each_entry_rcu(p, head, hlist) {
                if (p->addr == addr)
                        return p;
        }

        return NULL;
}
NOKPROBE_SYMBOL(get_kprobe);

static int aggr_pre_handler(struct kprobe *p, struct pt_regs *regs);

/* Return true if the kprobe is an aggregator */
static inline int kprobe_aggrprobe(struct kprobe *p)
{
        return p->pre_handler == aggr_pre_handler;
}

/* Return true(!0) if the kprobe is unused */
static inline int kprobe_unused(struct kprobe *p)
{
        return kprobe_aggrprobe(p) && kprobe_disabled(p) &&
               list_empty(&p->list);
}

/*
 * Keep all fields in the kprobe consistent
 */
static inline void copy_kprobe(struct kprobe *ap, struct kprobe *p)
{
        memcpy(&p->opcode, &ap->opcode, sizeof(kprobe_opcode_t));
        memcpy(&p->ainsn, &ap->ainsn, sizeof(struct arch_specific_insn));
}

#ifdef CONFIG_OPTPROBES
/* NOTE: change this value only with kprobe_mutex held */
static bool kprobes_allow_optimization;

/*
 * Call all pre_handler on the list, but ignores its return value.
 * This must be called from arch-dep optimized caller.
 */
void opt_pre_handler(struct kprobe *p, struct pt_regs *regs)
{
        struct kprobe *kp;

        list_for_each_entry_rcu(kp, &p->list, list) {
                if (kp->pre_handler && likely(!kprobe_disabled(kp))) {
                        set_kprobe_instance(kp);
                        kp->pre_handler(kp, regs);
                }
                reset_kprobe_instance();
        }
}
NOKPROBE_SYMBOL(opt_pre_handler);

/* Free optimized instructions and optimized_kprobe */
static void free_aggr_kprobe(struct kprobe *p)
{
        struct optimized_kprobe *op;

        op = container_of(p, struct optimized_kprobe, kp);
        arch_remove_optimized_kprobe(op);
        arch_remove_kprobe(p);
        kfree(op);
}

/* Return true(!0) if the kprobe is ready for optimization. */
static inline int kprobe_optready(struct kprobe *p)
{
        struct optimized_kprobe *op;

        if (kprobe_aggrprobe(p)) {
                op = container_of(p, struct optimized_kprobe, kp);
                return arch_prepared_optinsn(&op->optinsn);
        }

        return 0;
}

/* Return true(!0) if the kprobe is disarmed. Note: p must be on hash list */
static inline int kprobe_disarmed(struct kprobe *p)
{
        struct optimized_kprobe *op;

        /* If kprobe is not aggr/opt probe, just return kprobe is disabled */
        if (!kprobe_aggrprobe(p))
                return kprobe_disabled(p);

        op = container_of(p, struct optimized_kprobe, kp);

        return kprobe_disabled(p) && list_empty(&op->list);
}

/* Return true(!0) if the probe is queued on (un)optimizing lists */
static int kprobe_queued(struct kprobe *p)
{
        struct optimized_kprobe *op;

        if (kprobe_aggrprobe(p)) {
                op = container_of(p, struct optimized_kprobe, kp);
                if (!list_empty(&op->list))
                        return 1;
        }
        return 0;
}

/*
 * Return an optimized kprobe whose optimizing code replaces
 * instructions including addr (exclude breakpoint).
 */
static struct kprobe *get_optimized_kprobe(unsigned long addr)
{
        int i;
        struct kprobe *p = NULL;
        struct optimized_kprobe *op;

        /* Don't check i == 0, since that is a breakpoint case. */
        for (i = 1; !p && i < MAX_OPTIMIZED_LENGTH; i++)
                p = get_kprobe((void *)(addr - i));

        if (p && kprobe_optready(p)) {
                op = container_of(p, struct optimized_kprobe, kp);
                if (arch_within_optimized_kprobe(op, addr))
                        return p;
        }

        return NULL;
}

/* Optimization staging list, protected by kprobe_mutex */
static LIST_HEAD(optimizing_list);
static LIST_HEAD(unoptimizing_list);
static LIST_HEAD(freeing_list);

static void kprobe_optimizer(struct work_struct *work);
static DECLARE_DELAYED_WORK(optimizing_work, kprobe_optimizer);
#define OPTIMIZE_DELAY 5

/*
 * Optimize (replace a breakpoint with a jump) kprobes listed on
 * optimizing_list.
 */
static void do_optimize_kprobes(void)
{
        /* Optimization never be done when disarmed */
        if (kprobes_all_disarmed || !kprobes_allow_optimization ||
            list_empty(&optimizing_list))
                return;

        /*
         * The optimization/unoptimization refers online_cpus via
         * stop_machine() and cpu-hotplug modifies online_cpus.
         * And same time, text_mutex will be held in cpu-hotplug and here.
         * This combination can cause a deadlock (cpu-hotplug try to lock
         * text_mutex but stop_machine can not be done because online_cpus
         * has been changed)
         * To avoid this deadlock, we need to call get_online_cpus()
         * for preventing cpu-hotplug outside of text_mutex locking.
         */
        get_online_cpus();
        mutex_lock(&text_mutex);
        arch_optimize_kprobes(&optimizing_list);
        mutex_unlock(&text_mutex);
        put_online_cpus();
}

/*
 * Unoptimize (replace a jump with a breakpoint and remove the breakpoint
 * if need) kprobes listed on unoptimizing_list.
 */
static void do_unoptimize_kprobes(void)
{
        struct optimized_kprobe *op, *tmp;

        /* Unoptimization must be done anytime */
        if (list_empty(&unoptimizing_list))
                return;

        /* Ditto to do_optimize_kprobes */
        get_online_cpus();
        mutex_lock(&text_mutex);
        arch_unoptimize_kprobes(&unoptimizing_list, &freeing_list);
        /* Loop free_list for disarming */
        list_for_each_entry_safe(op, tmp, &freeing_list, list) {
                /* Disarm probes if marked disabled */
                if (kprobe_disabled(&op->kp))
                        arch_disarm_kprobe(&op->kp);
                if (kprobe_unused(&op->kp)) {
                        /*
                         * Remove unused probes from hash list. After waiting
                         * for synchronization, these probes are reclaimed.
                         * (reclaiming is done by do_free_cleaned_kprobes.)
                         */
                        hlist_del_rcu(&op->kp.hlist);
                } else
                        list_del_init(&op->list);
        }
        mutex_unlock(&text_mutex);
        put_online_cpus();
}

/* Reclaim all kprobes on the free_list */
static void do_free_cleaned_kprobes(void)
{
        struct optimized_kprobe *op, *tmp;

        list_for_each_entry_safe(op, tmp, &freeing_list, list) {
                BUG_ON(!kprobe_unused(&op->kp));
                list_del_init(&op->list);
                free_aggr_kprobe(&op->kp);
        }
}

/* Start optimizer after OPTIMIZE_DELAY passed */
static void kick_kprobe_optimizer(void)
{
        schedule_delayed_work(&optimizing_work, OPTIMIZE_DELAY);
}

/* Kprobe jump optimizer */
static void kprobe_optimizer(struct work_struct *work)
{
        mutex_lock(&kprobe_mutex);
        /* Lock modules while optimizing kprobes */
        mutex_lock(&module_mutex);

        /*
         * Step 1: Unoptimize kprobes and collect cleaned (unused and disarmed)
         * kprobes before waiting for quiesence period.
         */
        do_unoptimize_kprobes();

        /*
         * Step 2: Wait for quiesence period to ensure all running interrupts
         * are done. Because optprobe may modify multiple instructions
         * there is a chance that Nth instruction is interrupted. In that
         * case, running interrupt can return to 2nd-Nth byte of jump
         * instruction. This wait is for avoiding it.
         */
        synchronize_sched();

        /* Step 3: Optimize kprobes after quiesence period */
        do_optimize_kprobes();

        /* Step 4: Free cleaned kprobes after quiesence period */
        do_free_cleaned_kprobes();

        mutex_unlock(&module_mutex);
        mutex_unlock(&kprobe_mutex);

        /* Step 5: Kick optimizer again if needed */
        if (!list_empty(&optimizing_list) || !list_empty(&unoptimizing_list))
                kick_kprobe_optimizer();
}

/* Wait for completing optimization and unoptimization */
void wait_for_kprobe_optimizer(void)
{
        mutex_lock(&kprobe_mutex);

        while (!list_empty(&optimizing_list) || !list_empty(&unoptimizing_list)) {
                mutex_unlock(&kprobe_mutex);

                /* this will also make optimizing_work execute immmediately */
                flush_delayed_work(&optimizing_work);
                /* @optimizing_work might not have been queued yet, relax */
                cpu_relax();

                mutex_lock(&kprobe_mutex);
        }

        mutex_unlock(&kprobe_mutex);
}

/* Optimize kprobe if p is ready to be optimized */
static void optimize_kprobe(struct kprobe *p)
{
        struct optimized_kprobe *op;

        /* Check if the kprobe is disabled or not ready for optimization. */
        if (!kprobe_optready(p) || !kprobes_allow_optimization ||
            (kprobe_disabled(p) || kprobes_all_disarmed))
                return;

        /* Both of break_handler and post_handler are not supported. */
        if (p->break_handler || p->post_handler)
                return;

        op = container_of(p, struct optimized_kprobe, kp);

        /* Check there is no other kprobes at the optimized instructions */
        if (arch_check_optimized_kprobe(op) < 0)
                return;

        /* Check if it is already optimized. */
        if (op->kp.flags & KPROBE_FLAG_OPTIMIZED)
                return;
        op->kp.flags |= KPROBE_FLAG_OPTIMIZED;

        if (!list_empty(&op->list))
                /* This is under unoptimizing. Just dequeue the probe */
                list_del_init(&op->list);
        else {
                list_add(&op->list, &optimizing_list);
                kick_kprobe_optimizer();
        }
}

/* Short cut to direct unoptimizing */
static void force_unoptimize_kprobe(struct optimized_kprobe *op)
{
        get_online_cpus();
        arch_unoptimize_kprobe(op);
        put_online_cpus();
        if (kprobe_disabled(&op->kp))
                arch_disarm_kprobe(&op->kp);
}

/* Unoptimize a kprobe if p is optimized */
static void unoptimize_kprobe(struct kprobe *p, bool force)
{
        struct optimized_kprobe *op;

        if (!kprobe_aggrprobe(p) || kprobe_disarmed(p))
                return; /* This is not an optprobe nor optimized */

        op = container_of(p, struct optimized_kprobe, kp);
        if (!kprobe_optimized(p)) {
                /* Unoptimized or unoptimizing case */
                if (force && !list_empty(&op->list)) {
                        /*
                         * Only if this is unoptimizing kprobe and forced,
                         * forcibly unoptimize it. (No need to unoptimize
                         * unoptimized kprobe again :)
                         */
                        list_del_init(&op->list);
                        force_unoptimize_kprobe(op);
                }
                return;
        }

        op->kp.flags &= ~KPROBE_FLAG_OPTIMIZED;
        if (!list_empty(&op->list)) {
                /* Dequeue from the optimization queue */
                list_del_init(&op->list);
                return;
        }
        /* Optimized kprobe case */
        if (force)
                /* Forcibly update the code: this is a special case */
                force_unoptimize_kprobe(op);
        else {
                list_add(&op->list, &unoptimizing_list);
                kick_kprobe_optimizer();
        }
}

/* Cancel unoptimizing for reusing */
static int reuse_unused_kprobe(struct kprobe *ap)
{
        struct optimized_kprobe *op;
        int ret;

        BUG_ON(!kprobe_unused(ap));
        /*
         * Unused kprobe MUST be on the way of delayed unoptimizing (means
         * there is still a relative jump) and disabled.
         */
        op = container_of(ap, struct optimized_kprobe, kp);
        if (unlikely(list_empty(&op->list)))
                printk(KERN_WARNING "Warning: found a stray unused "
                        "aggrprobe@%p\n", ap->addr);
        /* Enable the probe again */
        ap->flags &= ~KPROBE_FLAG_DISABLED;
        /* Optimize it again (remove from op->list) */
        ret = kprobe_optready(ap);
        if (ret)
                return ret;

        optimize_kprobe(ap);
        return 0;
}

/* Remove optimized instructions */
static void kill_optimized_kprobe(struct kprobe *p)
{
        struct optimized_kprobe *op;

        op = container_of(p, struct optimized_kprobe, kp);
        if (!list_empty(&op->list))
                /* Dequeue from the (un)optimization queue */
                list_del_init(&op->list);
        op->kp.flags &= ~KPROBE_FLAG_OPTIMIZED;

        if (kprobe_unused(p)) {
                /* Enqueue if it is unused */
                list_add(&op->list, &freeing_list);
                /*
                 * Remove unused probes from the hash list. After waiting
                 * for synchronization, this probe is reclaimed.
                 * (reclaiming is done by do_free_cleaned_kprobes().)
                 */
                hlist_del_rcu(&op->kp.hlist);
        }

        /* Don't touch the code, because it is already freed. */
        arch_remove_optimized_kprobe(op);
}

/* Try to prepare optimized instructions */
static void prepare_optimized_kprobe(struct kprobe *p)
{
        struct optimized_kprobe *op;

        op = container_of(p, struct optimized_kprobe, kp);
        arch_prepare_optimized_kprobe(op, p);
}

/* Allocate new optimized_kprobe and try to prepare optimized instructions */
static struct kprobe *alloc_aggr_kprobe(struct kprobe *p)
{
        struct optimized_kprobe *op;

        op = kzalloc(sizeof(struct optimized_kprobe), GFP_KERNEL);
        if (!op)
                return NULL;

        INIT_LIST_HEAD(&op->list);
        op->kp.addr = p->addr;
        arch_prepare_optimized_kprobe(op, p);

        return &op->kp;
}

static void init_aggr_kprobe(struct kprobe *ap, struct kprobe *p);

/*
 * Prepare an optimized_kprobe and optimize it
 * NOTE: p must be a normal registered kprobe
 */
static void try_to_optimize_kprobe(struct kprobe *p)
{
        struct kprobe *ap;
        struct optimized_kprobe *op;

        /* Impossible to optimize ftrace-based kprobe */
        if (kprobe_ftrace(p))
                return;

        /* For preparing optimization, jump_label_text_reserved() is called */
        jump_label_lock();
        mutex_lock(&text_mutex);

        ap = alloc_aggr_kprobe(p);
        if (!ap)
                goto out;

        op = container_of(ap, struct optimized_kprobe, kp);
        if (!arch_prepared_optinsn(&op->optinsn)) {
                /* If failed to setup optimizing, fallback to kprobe */
                arch_remove_optimized_kprobe(op);
                kfree(op);
                goto out;
        }

        init_aggr_kprobe(ap, p);
        optimize_kprobe(ap);    /* This just kicks optimizer thread */

out:
        mutex_unlock(&text_mutex);
        jump_label_unlock();
}

#ifdef CONFIG_SYSCTL
static void optimize_all_kprobes(void)
{
        struct hlist_head *head;
        struct kprobe *p;
        unsigned int i;

        mutex_lock(&kprobe_mutex);
        /* If optimization is already allowed, just return */
        if (kprobes_allow_optimization)
                goto out;

        kprobes_allow_optimization = true;
        for (i = 0; i < KPROBE_TABLE_SIZE; i++) {
                head = &kprobe_table[i];
                hlist_for_each_entry_rcu(p, head, hlist)
                        if (!kprobe_disabled(p))
                                optimize_kprobe(p);
        }
        printk(KERN_INFO "Kprobes globally optimized\n");
out:
        mutex_unlock(&kprobe_mutex);
}

static void unoptimize_all_kprobes(void)
{
        struct hlist_head *head;
        struct kprobe *p;
        unsigned int i;

        mutex_lock(&kprobe_mutex);
        /* If optimization is already prohibited, just return */
        if (!kprobes_allow_optimization) {
                mutex_unlock(&kprobe_mutex);
                return;
        }

        kprobes_allow_optimization = false;
        for (i = 0; i < KPROBE_TABLE_SIZE; i++) {
                head = &kprobe_table[i];
                hlist_for_each_entry_rcu(p, head, hlist) {
                        if (!kprobe_disabled(p))
                                unoptimize_kprobe(p, false);
                }
        }
        mutex_unlock(&kprobe_mutex);

        /* Wait for unoptimizing completion */
        wait_for_kprobe_optimizer();
        printk(KERN_INFO "Kprobes globally unoptimized\n");
}

static DEFINE_MUTEX(kprobe_sysctl_mutex);
int sysctl_kprobes_optimization;
int proc_kprobes_optimization_handler(struct ctl_table *table, int write,
                                      void __user *buffer, size_t *length,
                                      loff_t *ppos)
{
        int ret;

        mutex_lock(&kprobe_sysctl_mutex);
        sysctl_kprobes_optimization = kprobes_allow_optimization ? 1 : 0;
        ret = proc_dointvec_minmax(table, write, buffer, length, ppos);

        if (sysctl_kprobes_optimization)
                optimize_all_kprobes();
        else
                unoptimize_all_kprobes();
        mutex_unlock(&kprobe_sysctl_mutex);

        return ret;
}
#endif /* CONFIG_SYSCTL */

/* Put a breakpoint for a probe. Must be called with text_mutex locked */
static void __arm_kprobe(struct kprobe *p)
{
        struct kprobe *_p;

        /* Check collision with other optimized kprobes */
        _p = get_optimized_kprobe((unsigned long)p->addr);
        if (unlikely(_p))
                /* Fallback to unoptimized kprobe */
                unoptimize_kprobe(_p, true);

        arch_arm_kprobe(p);
        optimize_kprobe(p);     /* Try to optimize (add kprobe to a list) */
}

/* Remove the breakpoint of a probe. Must be called with text_mutex locked */
static void __disarm_kprobe(struct kprobe *p, bool reopt)
{
        struct kprobe *_p;

        /* Try to unoptimize */
        unoptimize_kprobe(p, kprobes_all_disarmed);

        if (!kprobe_queued(p)) {
                arch_disarm_kprobe(p);
                /* If another kprobe was blocked, optimize it. */
                _p = get_optimized_kprobe((unsigned long)p->addr);
                if (unlikely(_p) && reopt)
                        optimize_kprobe(_p);
        }
        /* TODO: reoptimize others after unoptimized this probe */
}

#else /* !CONFIG_OPTPROBES */

#define optimize_kprobe(p)                      do {} while (0)
#define unoptimize_kprobe(p, f)                 do {} while (0)
#define kill_optimized_kprobe(p)                do {} while (0)
#define prepare_optimized_kprobe(p)             do {} while (0)
#define try_to_optimize_kprobe(p)               do {} while (0)
#define __arm_kprobe(p)                         arch_arm_kprobe(p)
#define __disarm_kprobe(p, o)                   arch_disarm_kprobe(p)
#define kprobe_disarmed(p)                      kprobe_disabled(p)
#define wait_for_kprobe_optimizer()             do {} while (0)

static int reuse_unused_kprobe(struct kprobe *ap)
{
        /*
         * If the optimized kprobe is NOT supported, the aggr kprobe is
         * released at the same time that the last aggregated kprobe is
         * unregistered.
         * Thus there should be no chance to reuse unused kprobe.
         */
        printk(KERN_ERR "Error: There should be no unused kprobe here.\n");
        return -EINVAL;
}

static void free_aggr_kprobe(struct kprobe *p)
{
        arch_remove_kprobe(p);
        kfree(p);
}

static struct kprobe *alloc_aggr_kprobe(struct kprobe *p)
{
        return kzalloc(sizeof(struct kprobe), GFP_KERNEL);
}
#endif /* CONFIG_OPTPROBES */

#ifdef CONFIG_KPROBES_ON_FTRACE
static struct ftrace_ops kprobe_ftrace_ops __read_mostly = {
        .func = kprobe_ftrace_handler,
        .flags = FTRACE_OPS_FL_SAVE_REGS | FTRACE_OPS_FL_IPMODIFY,
};
static int kprobe_ftrace_enabled;

/* Must ensure p->addr is really on ftrace */
static int prepare_kprobe(struct kprobe *p)
{
        if (!kprobe_ftrace(p))
                return arch_prepare_kprobe(p);

        return arch_prepare_kprobe_ftrace(p);
}

/* Caller must lock kprobe_mutex */
static void arm_kprobe_ftrace(struct kprobe *p)
{
        int ret;

        ret = ftrace_set_filter_ip(&kprobe_ftrace_ops,
                                   (unsigned long)p->addr, 0, 0);
        WARN(ret < 0, "Failed to arm kprobe-ftrace at %p (%d)\n", p->addr, ret);
        kprobe_ftrace_enabled++;
        if (kprobe_ftrace_enabled == 1) {
                ret = register_ftrace_function(&kprobe_ftrace_ops);
                WARN(ret < 0, "Failed to init kprobe-ftrace (%d)\n", ret);
        }
}

/* Caller must lock kprobe_mutex */
static void disarm_kprobe_ftrace(struct kprobe *p)
{
        int ret;

        kprobe_ftrace_enabled--;
        if (kprobe_ftrace_enabled == 0) {
                ret = unregister_ftrace_function(&kprobe_ftrace_ops);
                WARN(ret < 0, "Failed to init kprobe-ftrace (%d)\n", ret);
        }
        ret = ftrace_set_filter_ip(&kprobe_ftrace_ops,
                           (unsigned long)p->addr, 1, 0);
        WARN(ret < 0, "Failed to disarm kprobe-ftrace at %p (%d)\n", p->addr, ret);
}
#else   /* !CONFIG_KPROBES_ON_FTRACE */
#define prepare_kprobe(p)       arch_prepare_kprobe(p)
#define arm_kprobe_ftrace(p)    do {} while (0)
#define disarm_kprobe_ftrace(p) do {} while (0)
#endif

/* Arm a kprobe with text_mutex */
static void arm_kprobe(struct kprobe *kp)
{
        if (unlikely(kprobe_ftrace(kp))) {
                arm_kprobe_ftrace(kp);
                return;
        }
        /*
         * Here, since __arm_kprobe() doesn't use stop_machine(),
         * this doesn't cause deadlock on text_mutex. So, we don't
         * need get_online_cpus().
         */
        mutex_lock(&text_mutex);
        __arm_kprobe(kp);
        mutex_unlock(&text_mutex);
}

/* Disarm a kprobe with text_mutex */
static void disarm_kprobe(struct kprobe *kp, bool reopt)
{
        if (unlikely(kprobe_ftrace(kp))) {
                disarm_kprobe_ftrace(kp);
                return;
        }
        /* Ditto */
        mutex_lock(&text_mutex);
        __disarm_kprobe(kp, reopt);
        mutex_unlock(&text_mutex);
}

/*
 * Aggregate handlers for multiple kprobes support - these handlers
 * take care of invoking the individual kprobe handlers on p->list
 */
static int aggr_pre_handler(struct kprobe *p, struct pt_regs *regs)
{
        struct kprobe *kp;

        list_for_each_entry_rcu(kp, &p->list, list) {
                if (kp->pre_handler && likely(!kprobe_disabled(kp))) {
                        set_kprobe_instance(kp);
                        if (kp->pre_handler(kp, regs))
                                return 1;
                }
                reset_kprobe_instance();
        }
        return 0;
}
NOKPROBE_SYMBOL(aggr_pre_handler);

static void aggr_post_handler(struct kprobe *p, struct pt_regs *regs,
                              unsigned long flags)
{
        struct kprobe *kp;

        list_for_each_entry_rcu(kp, &p->list, list) {
                if (kp->post_handler && likely(!kprobe_disabled(kp))) {
                        set_kprobe_instance(kp);
                        kp->post_handler(kp, regs, flags);
                        reset_kprobe_instance();
                }
        }
}
NOKPROBE_SYMBOL(aggr_post_handler);

static int aggr_fault_handler(struct kprobe *p, struct pt_regs *regs,
                              int trapnr)
{
        struct kprobe *cur = __this_cpu_read(kprobe_instance);

        /*
         * if we faulted "during" the execution of a user specified
         * probe handler, invoke just that probe's fault handler
         */
        if (cur && cur->fault_handler) {
                if (cur->fault_handler(cur, regs, trapnr))
                        return 1;
        }
        return 0;
}
NOKPROBE_SYMBOL(aggr_fault_handler);

static int aggr_break_handler(struct kprobe *p, struct pt_regs *regs)
{
        struct kprobe *cur = __this_cpu_read(kprobe_instance);
        int ret = 0;

        if (cur && cur->break_handler) {
                if (cur->break_handler(cur, regs))
                        ret = 1;
        }
        reset_kprobe_instance();
        return ret;
}
NOKPROBE_SYMBOL(aggr_break_handler);

/* Walks the list and increments nmissed count for multiprobe case */
void kprobes_inc_nmissed_count(struct kprobe *p)
{
        struct kprobe *kp;
        if (!kprobe_aggrprobe(p)) {
                p->nmissed++;
        } else {
                list_for_each_entry_rcu(kp, &p->list, list)
                        kp->nmissed++;
        }
        return;
}
NOKPROBE_SYMBOL(kprobes_inc_nmissed_count);

void recycle_rp_inst(struct kretprobe_instance *ri,
                     struct hlist_head *head)
{
        struct kretprobe *rp = ri->rp;

        /* remove rp inst off the rprobe_inst_table */
        hlist_del(&ri->hlist);
        INIT_HLIST_NODE(&ri->hlist);
        if (likely(rp)) {
                raw_spin_lock(&rp->lock);
                hlist_add_head(&ri->hlist, &rp->free_instances);
                raw_spin_unlock(&rp->lock);
        } else
                /* Unregistering */
                hlist_add_head(&ri->hlist, head);
}
NOKPROBE_SYMBOL(recycle_rp_inst);

void kretprobe_hash_lock(struct task_struct *tsk,
                         struct hlist_head **head, unsigned long *flags)
__acquires(hlist_lock)
{
        unsigned long hash = hash_ptr(tsk, KPROBE_HASH_BITS);
        raw_spinlock_t *hlist_lock;

        *head = &kretprobe_inst_table[hash];
        hlist_lock = kretprobe_table_lock_ptr(hash);
        raw_spin_lock_irqsave(hlist_lock, *flags);
}
NOKPROBE_SYMBOL(kretprobe_hash_lock);

static void kretprobe_table_lock(unsigned long hash,
                                 unsigned long *flags)
__acquires(hlist_lock)
{
        raw_spinlock_t *hlist_lock = kretprobe_table_lock_ptr(hash);
        raw_spin_lock_irqsave(hlist_lock, *flags);
}
NOKPROBE_SYMBOL(kretprobe_table_lock);

void kretprobe_hash_unlock(struct task_struct *tsk,
                           unsigned long *flags)
__releases(hlist_lock)
{
        unsigned long hash = hash_ptr(tsk, KPROBE_HASH_BITS);
        raw_spinlock_t *hlist_lock;

        hlist_lock = kretprobe_table_lock_ptr(hash);
        raw_spin_unlock_irqrestore(hlist_lock, *flags);
}
NOKPROBE_SYMBOL(kretprobe_hash_unlock);

static void kretprobe_table_unlock(unsigned long hash,
                                   unsigned long *flags)
__releases(hlist_lock)
{
        raw_spinlock_t *hlist_lock = kretprobe_table_lock_ptr(hash);
        raw_spin_unlock_irqrestore(hlist_lock, *flags);
}
NOKPROBE_SYMBOL(kretprobe_table_unlock);

/*
 * This function is called from finish_task_switch when task tk becomes dead,
 * so that we can recycle any function-return probe instances associated
 * with this task. These left over instances represent probed functions
 * that have been called but will never return.
 */
void kprobe_flush_task(struct task_struct *tk)
{
        struct kretprobe_instance *ri;
        struct hlist_head *head, empty_rp;
        struct hlist_node *tmp;
        unsigned long hash, flags = 0;

        if (unlikely(!kprobes_initialized))
                /* Early boot.  kretprobe_table_locks not yet initialized. */
                return;

        INIT_HLIST_HEAD(&empty_rp);
        hash = hash_ptr(tk, KPROBE_HASH_BITS);
        head = &kretprobe_inst_table[hash];
        kretprobe_table_lock(hash, &flags);
        hlist_for_each_entry_safe(ri, tmp, head, hlist) {
                if (ri->task == tk)
                        recycle_rp_inst(ri, &empty_rp);
        }
        kretprobe_table_unlock(hash, &flags);
        hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {
                hlist_del(&ri->hlist);
                kfree(ri);
        }
}
NOKPROBE_SYMBOL(kprobe_flush_task);

static inline void free_rp_inst(struct kretprobe *rp)
{
        struct kretprobe_instance *ri;
        struct hlist_node *next;

        hlist_for_each_entry_safe(ri, next, &rp->free_instances, hlist) {
                hlist_del(&ri->hlist);
                kfree(ri);
        }
}

static void cleanup_rp_inst(struct kretprobe *rp)
{
        unsigned long flags, hash;
        struct kretprobe_instance *ri;
        struct hlist_node *next;
        struct hlist_head *head;

        /* No race here */
        for (hash = 0; hash < KPROBE_TABLE_SIZE; hash++) {
                kretprobe_table_lock(hash, &flags);
                head = &kretprobe_inst_table[hash];
                hlist_for_each_entry_safe(ri, next, head, hlist) {
                        if (ri->rp == rp)
                                ri->rp = NULL;
                }
                kretprobe_table_unlock(hash, &flags);
        }
        free_rp_inst(rp);
}
NOKPROBE_SYMBOL(cleanup_rp_inst);

/*
* Add the new probe to ap->list. Fail if this is the
* second jprobe at the address - two jprobes can't coexist
*/
static int add_new_kprobe(struct kprobe *ap, struct kprobe *p)
{
        BUG_ON(kprobe_gone(ap) || kprobe_gone(p));

        if (p->break_handler || p->post_handler)
                unoptimize_kprobe(ap, true);    /* Fall back to normal kprobe */

        if (p->break_handler) {
                if (ap->break_handler)
                        return -EEXIST;
                list_add_tail_rcu(&p->list, &ap->list);
                ap->break_handler = aggr_break_handler;
        } else
                list_add_rcu(&p->list, &ap->list);
        if (p->post_handler && !ap->post_handler)
                ap->post_handler = aggr_post_handler;

        return 0;
}

/*
 * Fill in the required fields of the "manager kprobe". Replace the
 * earlier kprobe in the hlist with the manager kprobe
 */
static void init_aggr_kprobe(struct kprobe *ap, struct kprobe *p)
{
        /* Copy p's insn slot to ap */
        copy_kprobe(p, ap);
        flush_insn_slot(ap);
        ap->addr = p->addr;
        ap->flags = p->flags & ~KPROBE_FLAG_OPTIMIZED;
        ap->pre_handler = aggr_pre_handler;
        ap->fault_handler = aggr_fault_handler;
        /* We don't care the kprobe which has gone. */
        if (p->post_handler && !kprobe_gone(p))
                ap->post_handler = aggr_post_handler;
        if (p->break_handler && !kprobe_gone(p))
                ap->break_handler = aggr_break_handler;

        INIT_LIST_HEAD(&ap->list);
        INIT_HLIST_NODE(&ap->hlist);

        list_add_rcu(&p->list, &ap->list);
        hlist_replace_rcu(&p->hlist, &ap->hlist);
}

/*
 * This is the second or subsequent kprobe at the address - handle
 * the intricacies
 */
static int register_aggr_kprobe(struct kprobe *orig_p, struct kprobe *p)
{
        int ret = 0;
        struct kprobe *ap = orig_p;

        /* For preparing optimization, jump_label_text_reserved() is called */
        jump_label_lock();
        /*
         * Get online CPUs to avoid text_mutex deadlock.with stop machine,
         * which is invoked by unoptimize_kprobe() in add_new_kprobe()
         */
        get_online_cpus();
        mutex_lock(&text_mutex);

        if (!kprobe_aggrprobe(orig_p)) {
                /* If orig_p is not an aggr_kprobe, create new aggr_kprobe. */
                ap = alloc_aggr_kprobe(orig_p);
                if (!ap) {
                        ret = -ENOMEM;
                        goto out;
                }
                init_aggr_kprobe(ap, orig_p);
        } else if (kprobe_unused(ap)) {
                /* This probe is going to die. Rescue it */
                ret = reuse_unused_kprobe(ap);
                if (ret)
                        goto out;
        }

        if (kprobe_gone(ap)) {
                /*
                 * Attempting to insert new probe at the same location that
                 * had a probe in the module vaddr area which already
                 * freed. So, the instruction slot has already been
                 * released. We need a new slot for the new probe.
                 */
                ret = arch_prepare_kprobe(ap);
                if (ret)
                        /*
                         * Even if fail to allocate new slot, don't need to
                         * free aggr_probe. It will be used next time, or
                         * freed by unregister_kprobe.
                         */
                        goto out;

                /* Prepare optimized instructions if possible. */
                prepare_optimized_kprobe(ap);

                /*
                 * Clear gone flag to prevent allocating new slot again, and
                 * set disabled flag because it is not armed yet.
                 */
                ap->flags = (ap->flags & ~KPROBE_FLAG_GONE)
                            | KPROBE_FLAG_DISABLED;
        }

        /* Copy ap's insn slot to p */
        copy_kprobe(ap, p);
        ret = add_new_kprobe(ap, p);

out:
        mutex_unlock(&text_mutex);
        put_online_cpus();
        jump_label_unlock();

        if (ret == 0 && kprobe_disabled(ap) && !kprobe_disabled(p)) {
                ap->flags &= ~KPROBE_FLAG_DISABLED;
                if (!kprobes_all_disarmed)
                        /* Arm the breakpoint again. */
                        arm_kprobe(ap);
        }
        return ret;
}

bool __weak arch_within_kprobe_blacklist(unsigned long addr)
{
        /* The __kprobes marked functions and entry code must not be probed */
        return addr >= (unsigned long)__kprobes_text_start &&
               addr < (unsigned long)__kprobes_text_end;
}

bool within_kprobe_blacklist(unsigned long addr)
{
        struct kprobe_blacklist_entry *ent;

        if (arch_within_kprobe_blacklist(addr))
                return true;
        /*
         * If there exists a kprobe_blacklist, verify and
         * fail any probe registration in the prohibited area
         */
        list_for_each_entry(ent, &kprobe_blacklist, list) {
                if (addr >= ent->start_addr && addr < ent->end_addr)
                        return true;
        }

        return false;
}

/*
 * If we have a symbol_name argument, look it up and add the offset field
 * to it. This way, we can specify a relative address to a symbol.
 * This returns encoded errors if it fails to look up symbol or invalid
 * combination of parameters.
 */
static kprobe_opcode_t *kprobe_addr(struct kprobe *p)
{
        kprobe_opcode_t *addr = p->addr;

        if ((p->symbol_name && p->addr) ||
            (!p->symbol_name && !p->addr))
                goto invalid;

        if (p->symbol_name) {
                kprobe_lookup_name(p->symbol_name, addr);
                if (!addr)
                        return ERR_PTR(-ENOENT);
        }

        addr = (kprobe_opcode_t *)(((char *)addr) + p->offset);
        if (addr)
                return addr;

invalid:
        return ERR_PTR(-EINVAL);
}

/* Check passed kprobe is valid and return kprobe in kprobe_table. */
static struct kprobe *__get_valid_kprobe(struct kprobe *p)
{
        struct kprobe *ap, *list_p;

        ap = get_kprobe(p->addr);
        if (unlikely(!ap))
                return NULL;

        if (p != ap) {
                list_for_each_entry_rcu(list_p, &ap->list, list)
                        if (list_p == p)
                        /* kprobe p is a valid probe */
                                goto valid;
                return NULL;
        }
valid:
        return ap;
}

/* Return error if the kprobe is being re-registered */
static inline int check_kprobe_rereg(struct kprobe *p)
{
        int ret = 0;

        mutex_lock(&kprobe_mutex);
        if (__get_valid_kprobe(p))
                ret = -EINVAL;
        mutex_unlock(&kprobe_mutex);

        return ret;
}

int __weak arch_check_ftrace_location(struct kprobe *p)
{
        unsigned long ftrace_addr;

        ftrace_addr = ftrace_location((unsigned long)p->addr);
        if (ftrace_addr) {
#ifdef CONFIG_KPROBES_ON_FTRACE
                /* Given address is not on the instruction boundary */
                if ((unsigned long)p->addr != ftrace_addr)
                        return -EILSEQ;
                p->flags |= KPROBE_FLAG_FTRACE;
#else   /* !CONFIG_KPROBES_ON_FTRACE */
                return -EINVAL;
#endif
        }
        return 0;
}

static int check_kprobe_address_safe(struct kprobe *p,
                                     struct module **probed_mod)
{
        int ret;

        ret = arch_check_ftrace_location(p);
        if (ret)
                return ret;
        jump_label_lock();
        preempt_disable();

        /* Ensure it is not in reserved area nor out of text */
        if (!kernel_text_address((unsigned long) p->addr) ||
            within_kprobe_blacklist((unsigned long) p->addr) ||
            jump_label_text_reserved(p->addr, p->addr)) {
                ret = -EINVAL;
                goto out;
        }

        /* Check if are we probing a module */
        *probed_mod = __module_text_address((unsigned long) p->addr);
        if (*probed_mod) {
                /*
                 * We must hold a refcount of the probed module while updating
                 * its code to prohibit unexpected unloading.
                 */
                if (unlikely(!try_module_get(*probed_mod))) {
                        ret = -ENOENT;
                        goto out;
                }

                /*
                 * If the module freed .init.text, we couldn't insert
                 * kprobes in there.
                 */
                if (within_module_init((unsigned long)p->addr, *probed_mod) &&
                    (*probed_mod)->state != MODULE_STATE_COMING) {
                        module_put(*probed_mod);
                        *probed_mod = NULL;
                        ret = -ENOENT;
                }
        }
out:
        preempt_enable();
        jump_label_unlock();

        return ret;
}

int register_kprobe(struct kprobe *p)
{
        int ret;
        struct kprobe *old_p;
        struct module *probed_mod;
        kprobe_opcode_t *addr;

        /* Adjust probe address from symbol */
        addr = kprobe_addr(p);
        if (IS_ERR(addr))
                return PTR_ERR(addr);
        p->addr = addr;

        ret = check_kprobe_rereg(p);
        if (ret)
                return ret;

        /* User can pass only KPROBE_FLAG_DISABLED to register_kprobe */
        p->flags &= KPROBE_FLAG_DISABLED;
        p->nmissed = 0;
        INIT_LIST_HEAD(&p->list);

        ret = check_kprobe_address_safe(p, &probed_mod);
        if (ret)
                return ret;

        mutex_lock(&kprobe_mutex);

        old_p = get_kprobe(p->addr);
        if (old_p) {
                /* Since this may unoptimize old_p, locking text_mutex. */
                ret = register_aggr_kprobe(old_p, p);
                goto out;
        }

        mutex_lock(&text_mutex);        /* Avoiding text modification */
        ret = prepare_kprobe(p);
        mutex_unlock(&text_mutex);
        if (ret)
                goto out;

        INIT_HLIST_NODE(&p->hlist);
        hlist_add_head_rcu(&p->hlist,
                       &kprobe_table[hash_ptr(p->addr, KPROBE_HASH_BITS)]);

        if (!kprobes_all_disarmed && !kprobe_disabled(p))
                arm_kprobe(p);

        /* Try to optimize kprobe */
        try_to_optimize_kprobe(p);

out:
        mutex_unlock(&kprobe_mutex);

        if (probed_mod)
                module_put(probed_mod);

        return ret;
}
EXPORT_SYMBOL_GPL(register_kprobe);

/* Check if all probes on the aggrprobe are disabled */
static int aggr_kprobe_disabled(struct kprobe *ap)
{
        struct kprobe *kp;

        list_for_each_entry_rcu(kp, &ap->list, list)
                if (!kprobe_disabled(kp))
                        /*
                         * There is an active probe on the list.
                         * We can't disable this ap.
                         */
                        return 0;

        return 1;
}

/* Disable one kprobe: Make sure called under kprobe_mutex is locked */
static struct kprobe *__disable_kprobe(struct kprobe *p)
{
        struct kprobe *orig_p;

        /* Get an original kprobe for return */
        orig_p = __get_valid_kprobe(p);
        if (unlikely(orig_p == NULL))
                return NULL;

        if (!kprobe_disabled(p)) {
                /* Disable probe if it is a child probe */
                if (p != orig_p)
                        p->flags |= KPROBE_FLAG_DISABLED;

                /* Try to disarm and disable this/parent probe */
                if (p == orig_p || aggr_kprobe_disabled(orig_p)) {
                        /*
                         * If kprobes_all_disarmed is set, orig_p
                         * should have already been disarmed, so
                         * skip unneed disarming process.
                         */
                        if (!kprobes_all_disarmed)
                                disarm_kprobe(orig_p, true);
                        orig_p->flags |= KPROBE_FLAG_DISABLED;
                }
        }

        return orig_p;
}

/*
 * Unregister a kprobe without a scheduler synchronization.
 */
static int __unregister_kprobe_top(struct kprobe *p)
{
        struct kprobe *ap, *list_p;

        /* Disable kprobe. This will disarm it if needed. */
        ap = __disable_kprobe(p);
        if (ap == NULL)
                return -EINVAL;

        if (ap == p)
                /*
                 * This probe is an independent(and non-optimized) kprobe
                 * (not an aggrprobe). Remove from the hash list.
                 */
                goto disarmed;

        /* Following process expects this probe is an aggrprobe */
        WARN_ON(!kprobe_aggrprobe(ap));

        if (list_is_singular(&ap->list) && kprobe_disarmed(ap))
                /*
                 * !disarmed could be happen if the probe is under delayed
                 * unoptimizing.
                 */
                goto disarmed;
        else {
                /* If disabling probe has special handlers, update aggrprobe */
                if (p->break_handler && !kprobe_gone(p))
                        ap->break_handler = NULL;
                if (p->post_handler && !kprobe_gone(p)) {
                        list_for_each_entry_rcu(list_p, &ap->list, list) {
                                if ((list_p != p) && (list_p->post_handler))
                                        goto noclean;
                        }
                        ap->post_handler = NULL;
                }
noclean:
                /*
                 * Remove from the aggrprobe: this path will do nothing in
                 * __unregister_kprobe_bottom().
                 */
                list_del_rcu(&p->list);
                if (!kprobe_disabled(ap) && !kprobes_all_disarmed)
                        /*
                         * Try to optimize this probe again, because post
                         * handler may have been changed.
                         */
                        optimize_kprobe(ap);
        }
        return 0;

disarmed:
        BUG_ON(!kprobe_disarmed(ap));
        hlist_del_rcu(&ap->hlist);
        return 0;
}

static void __unregister_kprobe_bottom(struct kprobe *p)
{
        struct kprobe *ap;

        if (list_empty(&p->list))
                /* This is an independent kprobe */
                arch_remove_kprobe(p);
        else if (list_is_singular(&p->list)) {
                /* This is the last child of an aggrprobe */
                ap = list_entry(p->list.next, struct kprobe, list);
                list_del(&p->list);
                free_aggr_kprobe(ap);
        }
        /* Otherwise, do nothing. */
}

int register_kprobes(struct kprobe **kps, int num)
{
        int i, ret = 0;

        if (num <= 0)
                return -EINVAL;
        for (i = 0; i < num; i++) {
                ret = register_kprobe(kps[i]);
                if (ret < 0) {
                        if (i > 0)
                                unregister_kprobes(kps, i);
                        break;
                }
        }
        return ret;
}
EXPORT_SYMBOL_GPL(register_kprobes);

void unregister_kprobe(struct kprobe *p)
{
        unregister_kprobes(&p, 1);
}
EXPORT_SYMBOL_GPL(unregister_kprobe);

void unregister_kprobes(struct kprobe **kps, int num)
{
        int i;

        if (num <= 0)
                return;
        mutex_lock(&kprobe_mutex);
        for (i = 0; i < num; i++)
                if (__unregister_kprobe_top(kps[i]) < 0)
                        kps[i]->addr = NULL;
        mutex_unlock(&kprobe_mutex);

        synchronize_sched();
        for (i = 0; i < num; i++)
                if (kps[i]->addr)
                        __unregister_kprobe_bottom(kps[i]);
}
EXPORT_SYMBOL_GPL(unregister_kprobes);

static struct notifier_block kprobe_exceptions_nb = {
        .notifier_call = kprobe_exceptions_notify,
        .priority = 0x7fffffff /* we need to be notified first */
};

unsigned long __weak arch_deref_entry_point(void *entry)
{
        return (unsigned long)entry;
}

int register_jprobes(struct jprobe **jps, int num)
{
        struct jprobe *jp;
        int ret = 0, i;

        if (num <= 0)
                return -EINVAL;
        for (i = 0; i < num; i++) {
                unsigned long addr, offset;
                jp = jps[i];
                addr = arch_deref_entry_point(jp->entry);

                /* Verify probepoint is a function entry point */
                if (kallsyms_lookup_size_offset(addr, NULL, &offset) &&
                    offset == 0) {
                        jp->kp.pre_handler = setjmp_pre_handler;
                        jp->kp.break_handler = longjmp_break_handler;
                        ret = register_kprobe(&jp->kp);
                } else
                        ret = -EINVAL;

                if (ret < 0) {
                        if (i > 0)
                                unregister_jprobes(jps, i);
                        break;
                }
        }
        return ret;
}
EXPORT_SYMBOL_GPL(register_jprobes);

int register_jprobe(struct jprobe *jp)
{
        return register_jprobes(&jp, 1);
}
EXPORT_SYMBOL_GPL(register_jprobe);

void unregister_jprobe(struct jprobe *jp)
{
        unregister_jprobes(&jp, 1);
}
EXPORT_SYMBOL_GPL(unregister_jprobe);

void unregister_jprobes(struct jprobe **jps, int num)
{
        int i;

        if (num <= 0)
                return;
        mutex_lock(&kprobe_mutex);
        for (i = 0; i < num; i++)
                if (__unregister_kprobe_top(&jps[i]->kp) < 0)
                        jps[i]->kp.addr = NULL;
        mutex_unlock(&kprobe_mutex);

        synchronize_sched();
        for (i = 0; i < num; i++) {
                if (jps[i]->kp.addr)
                        __unregister_kprobe_bottom(&jps[i]->kp);
        }
}
EXPORT_SYMBOL_GPL(unregister_jprobes);

#ifdef CONFIG_KRETPROBES
/*
 * This kprobe pre_handler is registered with every kretprobe. When probe
 * hits it will set up the return probe.
 */
static int pre_handler_kretprobe(struct kprobe *p, struct pt_regs *regs)
{
        struct kretprobe *rp = container_of(p, struct kretprobe, kp);
        unsigned long hash, flags = 0;
        struct kretprobe_instance *ri;

        /*
         * To avoid deadlocks, prohibit return probing in NMI contexts,
         * just skip the probe and increase the (inexact) 'nmissed'
         * statistical counter, so that the user is informed that
         * something happened:
         */
        if (unlikely(in_nmi())) {
                rp->nmissed++;
                return 0;
        }

        /* TODO: consider to only swap the RA after the last pre_handler fired */
        hash = hash_ptr(current, KPROBE_HASH_BITS);
        raw_spin_lock_irqsave(&rp->lock, flags);
        if (!hlist_empty(&rp->free_instances)) {
                ri = hlist_entry(rp->free_instances.first,
                                struct kretprobe_instance, hlist);
                hlist_del(&ri->hlist);
                raw_spin_unlock_irqrestore(&rp->lock, flags);

                ri->rp = rp;
                ri->task = current;

                if (rp->entry_handler && rp->entry_handler(ri, regs)) {
                        raw_spin_lock_irqsave(&rp->lock, flags);
                        hlist_add_head(&ri->hlist, &rp->free_instances);
                        raw_spin_unlock_irqrestore(&rp->lock, flags);
                        return 0;
                }

                arch_prepare_kretprobe(ri, regs);

                /* XXX(hch): why is there no hlist_move_head? */
                INIT_HLIST_NODE(&ri->hlist);
                kretprobe_table_lock(hash, &flags);
                hlist_add_head(&ri->hlist, &kretprobe_inst_table[hash]);
                kretprobe_table_unlock(hash, &flags);
        } else {
                rp->nmissed++;
                raw_spin_unlock_irqrestore(&rp->lock, flags);
        }
        return 0;
}
NOKPROBE_SYMBOL(pre_handler_kretprobe);

int register_kretprobe(struct kretprobe *rp)
{
        int ret = 0;
        struct kretprobe_instance *inst;
        int i;
        void *addr;

        if (kretprobe_blacklist_size) {
                addr = kprobe_addr(&rp->kp);
                if (IS_ERR(addr))
                        return PTR_ERR(addr);

                for (i = 0; kretprobe_blacklist[i].name != NULL; i++) {
                        if (kretprobe_blacklist[i].addr == addr)
                                return -EINVAL;
                }
        }

        rp->kp.pre_handler = pre_handler_kretprobe;
        rp->kp.post_handler = NULL;
        rp->kp.fault_handler = NULL;
        rp->kp.break_handler = NULL;

        /* Pre-allocate memory for max kretprobe instances */
        if (rp->maxactive <= 0) {
#ifdef CONFIG_PREEMPT
                rp->maxactive = max_t(unsigned int, 10, 2*num_possible_cpus());
#else
                rp->maxactive = num_possible_cpus();
#endif
        }
        raw_spin_lock_init(&rp->lock);
        INIT_HLIST_HEAD(&rp->free_instances);
        for (i = 0; i < rp->maxactive; i++) {
                inst = kmalloc(sizeof(struct kretprobe_instance) +
                               rp->data_size, GFP_KERNEL);
                if (inst == NULL) {
                        free_rp_inst(rp);
                        return -ENOMEM;
                }
                INIT_HLIST_NODE(&inst->hlist);
                hlist_add_head(&inst->hlist, &rp->free_instances);
        }

        rp->nmissed = 0;
        /* Establish function entry probe point */
        ret = register_kprobe(&rp->kp);
        if (ret != 0)
                free_rp_inst(rp);
        return ret;
}
EXPORT_SYMBOL_GPL(register_kretprobe);

int register_kretprobes(struct kretprobe **rps, int num)
{
        int ret = 0, i;

        if (num <= 0)
                return -EINVAL;
        for (i = 0; i < num; i++) {
                ret = register_kretprobe(rps[i]);
                if (ret < 0) {
                        if (i > 0)
                                unregister_kretprobes(rps, i);
                        break;
                }
        }
        return ret;
}
EXPORT_SYMBOL_GPL(register_kretprobes);

void unregister_kretprobe(struct kretprobe *rp)
{
        unregister_kretprobes(&rp, 1);
}
EXPORT_SYMBOL_GPL(unregister_kretprobe);

void unregister_kretprobes(struct kretprobe **rps, int num)
{
        int i;

        if (num <= 0)
                return;
        mutex_lock(&kprobe_mutex);
        for (i = 0; i < num; i++)
                if (__unregister_kprobe_top(&rps[i]->kp) < 0)
                        rps[i]->kp.addr = NULL;
        mutex_unlock(&kprobe_mutex);

        synchronize_sched();
        for (i = 0; i < num; i++) {
                if (rps[i]->kp.addr) {
                        __unregister_kprobe_bottom(&rps[i]->kp);
                        cleanup_rp_inst(rps[i]);
                }
        }
}
EXPORT_SYMBOL_GPL(unregister_kretprobes);

#else /* CONFIG_KRETPROBES */
int register_kretprobe(struct kretprobe *rp)
{
        return -ENOSYS;
}
EXPORT_SYMBOL_GPL(register_kretprobe);

int register_kretprobes(struct kretprobe **rps, int num)
{
        return -ENOSYS;
}
EXPORT_SYMBOL_GPL(register_kretprobes);

void unregister_kretprobe(struct kretprobe *rp)
{
}
EXPORT_SYMBOL_GPL(unregister_kretprobe);

void unregister_kretprobes(struct kretprobe **rps, int num)
{
}
EXPORT_SYMBOL_GPL(unregister_kretprobes);

static int pre_handler_kretprobe(struct kprobe *p, struct pt_regs *regs)
{
        return 0;
}
NOKPROBE_SYMBOL(pre_handler_kretprobe);

#endif /* CONFIG_KRETPROBES */

/* Set the kprobe gone and remove its instruction buffer. */
static void kill_kprobe(struct kprobe *p)
{
        struct kprobe *kp;

        p->flags |= KPROBE_FLAG_GONE;
        if (kprobe_aggrprobe(p)) {
                /*
                 * If this is an aggr_kprobe, we have to list all the
                 * chained probes and mark them GONE.
                 */
                list_for_each_entry_rcu(kp, &p->list, list)
                        kp->flags |= KPROBE_FLAG_GONE;
                p->post_handler = NULL;
                p->break_handler = NULL;
                kill_optimized_kprobe(p);
        }
        /*
         * Here, we can remove insn_slot safely, because no thread calls
         * the original probed function (which will be freed soon) any more.
         */
        arch_remove_kprobe(p);
}

/* Disable one kprobe */
int disable_kprobe(struct kprobe *kp)
{
        int ret = 0;

        mutex_lock(&kprobe_mutex);

        /* Disable this kprobe */
        if (__disable_kprobe(kp) == NULL)
                ret = -EINVAL;

        mutex_unlock(&kprobe_mutex);
        return ret;
}
EXPORT_SYMBOL_GPL(disable_kprobe);

/* Enable one kprobe */
int enable_kprobe(struct kprobe *kp)
{
        int ret = 0;
        struct kprobe *p;

        mutex_lock(&kprobe_mutex);

        /* Check whether specified probe is valid. */
        p = __get_valid_kprobe(kp);
        if (unlikely(p == NULL)) {
                ret = -EINVAL;
                goto out;
        }

        if (kprobe_gone(kp)) {
                /* This kprobe has gone, we couldn't enable it. */
                ret = -EINVAL;
                goto out;
        }

        if (p != kp)
                kp->flags &= ~KPROBE_FLAG_DISABLED;

        if (!kprobes_all_disarmed && kprobe_disabled(p)) {
                p->flags &= ~KPROBE_FLAG_DISABLED;
                arm_kprobe(p);
        }
out:
        mutex_unlock(&kprobe_mutex);
        return ret;
}
EXPORT_SYMBOL_GPL(enable_kprobe);

void dump_kprobe(struct kprobe *kp)
{
        printk(KERN_WARNING "Dumping kprobe:\n");
        printk(KERN_WARNING "Name: %s\nAddress: %p\nOffset: %x\n",
               kp->symbol_name, kp->addr, kp->offset);
}
NOKPROBE_SYMBOL(dump_kprobe);

/*
 * Lookup and populate the kprobe_blacklist.
 *
 * Unlike the kretprobe blacklist, we'll need to determine
 * the range of addresses that belong to the said functions,
 * since a kprobe need not necessarily be at the beginning
 * of a function.
 */
static int __init populate_kprobe_blacklist(unsigned long *start,
                                             unsigned long *end)
{
        unsigned long *iter;
        struct kprobe_blacklist_entry *ent;
        unsigned long entry, offset = 0, size = 0;

        for (iter = start; iter < end; iter++) {
                entry = arch_deref_entry_point((void *)*iter);

                if (!kernel_text_address(entry) ||
                    !kallsyms_lookup_size_offset(entry, &size, &offset)) {
                        pr_err("Failed to find blacklist at %p\n",
                                (void *)entry);
                        continue;
                }

                ent = kmalloc(sizeof(*ent), GFP_KERNEL);
                if (!ent)
                        return -ENOMEM;
                ent->start_addr = entry;
                ent->end_addr = entry + size;
                INIT_LIST_HEAD(&ent->list);
                list_add_tail(&ent->list, &kprobe_blacklist);
        }
        return 0;
}

/* Module notifier call back, checking kprobes on the module */
static int kprobes_module_callback(struct notifier_block *nb,
                                   unsigned long val, void *data)
{
        struct module *mod = data;
        struct hlist_head *head;
        struct kprobe *p;
        unsigned int i;
        int checkcore = (val == MODULE_STATE_GOING);

        if (val != MODULE_STATE_GOING && val != MODULE_STATE_LIVE)
                return NOTIFY_DONE;

        /*
         * When MODULE_STATE_GOING was notified, both of module .text and
         * .init.text sections would be freed. When MODULE_STATE_LIVE was
         * notified, only .init.text section would be freed. We need to
         * disable kprobes which have been inserted in the sections.
         */
        mutex_lock(&kprobe_mutex);
        for (i = 0; i < KPROBE_TABLE_SIZE; i++) {
                head = &kprobe_table[i];
                hlist_for_each_entry_rcu(p, head, hlist)
                        if (within_module_init((unsigned long)p->addr, mod) ||
                            (checkcore &&
                             within_module_core((unsigned long)p->addr, mod))) {
                                /*
                                 * The vaddr this probe is installed will soon
                                 * be vfreed buy not synced to disk. Hence,
                                 * disarming the breakpoint isn't needed.
                                 */
                                kill_kprobe(p);
                        }
        }
        mutex_unlock(&kprobe_mutex);
        return NOTIFY_DONE;
}

static struct notifier_block kprobe_module_nb = {
        .notifier_call = kprobes_module_callback,
        .priority = 0
};

/* Markers of _kprobe_blacklist section */
extern unsigned long __start_kprobe_blacklist[];
extern unsigned long __stop_kprobe_blacklist[];

static int __init init_kprobes(void)
{
        int i, err = 0;

        /* FIXME allocate the probe table, currently defined statically */
        /* initialize all list heads */
        for (i = 0; i < KPROBE_TABLE_SIZE; i++) {
                INIT_HLIST_HEAD(&kprobe_table[i]);
                INIT_HLIST_HEAD(&kretprobe_inst_table[i]);
                raw_spin_lock_init(&(kretprobe_table_locks[i].lock));
        }

        err = populate_kprobe_blacklist(__start_kprobe_blacklist,
                                        __stop_kprobe_blacklist);
        if (err) {
                pr_err("kprobes: failed to populate blacklist: %d\n", err);
                pr_err("Please take care of using kprobes.\n");
        }

        if (kretprobe_blacklist_size) {
                /* lookup the function address from its name */
                for (i = 0; kretprobe_blacklist[i].name != NULL; i++) {
                        kprobe_lookup_name(kretprobe_blacklist[i].name,
                                           kretprobe_blacklist[i].addr);
                        if (!kretprobe_blacklist[i].addr)
                                printk("kretprobe: lookup failed: %s\n",
                                       kretprobe_blacklist[i].name);
                }
        }

#if defined(CONFIG_OPTPROBES)
#if defined(__ARCH_WANT_KPROBES_INSN_SLOT)
        /* Init kprobe_optinsn_slots */
        kprobe_optinsn_slots.insn_size = MAX_OPTINSN_SIZE;
#endif
        /* By default, kprobes can be optimized */
        kprobes_allow_optimization = true;
#endif

        /* By default, kprobes are armed */
        kprobes_all_disarmed = false;

        err = arch_init_kprobes();
        if (!err)
                err = register_die_notifier(&kprobe_exceptions_nb);
        if (!err)
                err = register_module_notifier(&kprobe_module_nb);

        kprobes_initialized = (err == 0);

        if (!err)
                init_test_probes();
        return err;
}

#ifdef CONFIG_DEBUG_FS
static void report_probe(struct seq_file *pi, struct kprobe *p,
                const char *sym, int offset, char *modname, struct kprobe *pp)
{
        char *kprobe_type;

        if (p->pre_handler == pre_handler_kretprobe)
                kprobe_type = "r";
        else if (p->pre_handler == setjmp_pre_handler)
                kprobe_type = "j";
        else
                kprobe_type = "k";

        if (sym)
                seq_printf(pi, "%p  %s  %s+0x%x  %s ",
                        p->addr, kprobe_type, sym, offset,
                        (modname ? modname : " "));
        else
                seq_printf(pi, "%p  %s  %p ",
                        p->addr, kprobe_type, p->addr);

        if (!pp)
                pp = p;
        seq_printf(pi, "%s%s%s%s\n",
                (kprobe_gone(p) ? "[GONE]" : ""),
                ((kprobe_disabled(p) && !kprobe_gone(p)) ?  "[DISABLED]" : ""),
                (kprobe_optimized(pp) ? "[OPTIMIZED]" : ""),
                (kprobe_ftrace(pp) ? "[FTRACE]" : ""));
}

static void *kprobe_seq_start(struct seq_file *f, loff_t *pos)
{
        return (*pos < KPROBE_TABLE_SIZE) ? pos : NULL;
}

static void *kprobe_seq_next(struct seq_file *f, void *v, loff_t *pos)
{
        (*pos)++;
        if (*pos >= KPROBE_TABLE_SIZE)
                return NULL;
        return pos;
}

static void kprobe_seq_stop(struct seq_file *f, void *v)
{
        /* Nothing to do */
}

static int show_kprobe_addr(struct seq_file *pi, void *v)
{
        struct hlist_head *head;
        struct kprobe *p, *kp;
        const char *sym = NULL;
        unsigned int i = *(loff_t *) v;
        unsigned long offset = 0;
        char *modname, namebuf[KSYM_NAME_LEN];

        head = &kprobe_table[i];
        preempt_disable();
        hlist_for_each_entry_rcu(p, head, hlist) {
                sym = kallsyms_lookup((unsigned long)p->addr, NULL,
                                        &offset, &modname, namebuf);
                if (kprobe_aggrprobe(p)) {
                        list_for_each_entry_rcu(kp, &p->list, list)
                                report_probe(pi, kp, sym, offset, modname, p);
                } else
                        report_probe(pi, p, sym, offset, modname, NULL);
        }
        preempt_enable();
        return 0;
}

static const struct seq_operations kprobes_seq_ops = {
        .start = kprobe_seq_start,
        .next  = kprobe_seq_next,
        .stop  = kprobe_seq_stop,
        .show  = show_kprobe_addr
};

static int kprobes_open(struct inode *inode, struct file *filp)
{
        return seq_open(filp, &kprobes_seq_ops);
}

static const struct file_operations debugfs_kprobes_operations = {
        .open           = kprobes_open,
        .read           = seq_read,
        .llseek         = seq_lseek,
        .release        = seq_release,
};

/* kprobes/blacklist -- shows which functions can not be probed */
static void *kprobe_blacklist_seq_start(struct seq_file *m, loff_t *pos)
{
        return seq_list_start(&kprobe_blacklist, *pos);
}

static void *kprobe_blacklist_seq_next(struct seq_file *m, void *v, loff_t *pos)
{
        return seq_list_next(v, &kprobe_blacklist, pos);
}

static int kprobe_blacklist_seq_show(struct seq_file *m, void *v)
{
        struct kprobe_blacklist_entry *ent =
                list_entry(v, struct kprobe_blacklist_entry, list);

        seq_printf(m, "0x%p-0x%p\t%ps\n", (void *)ent->start_addr,
                   (void *)ent->end_addr, (void *)ent->start_addr);
        return 0;
}

static const struct seq_operations kprobe_blacklist_seq_ops = {
        .start = kprobe_blacklist_seq_start,
        .next  = kprobe_blacklist_seq_next,
        .stop  = kprobe_seq_stop,       /* Reuse void function */
        .show  = kprobe_blacklist_seq_show,
};

static int kprobe_blacklist_open(struct inode *inode, struct file *filp)
{
        return seq_open(filp, &kprobe_blacklist_seq_ops);
}

static const struct file_operations debugfs_kprobe_blacklist_ops = {
        .open           = kprobe_blacklist_open,
        .read           = seq_read,
        .llseek         = seq_lseek,
        .release        = seq_release,
};

static void arm_all_kprobes(void)
{
        struct hlist_head *head;
        struct kprobe *p;
        unsigned int i;

        mutex_lock(&kprobe_mutex);

        /* If kprobes are armed, just return */
        if (!kprobes_all_disarmed)
                goto already_enabled;

        /*
         * optimize_kprobe() called by arm_kprobe() checks
         * kprobes_all_disarmed, so set kprobes_all_disarmed before
         * arm_kprobe.
         */
        kprobes_all_disarmed = false;
        /* Arming kprobes doesn't optimize kprobe itself */
        for (i = 0; i < KPROBE_TABLE_SIZE; i++) {
                head = &kprobe_table[i];
                hlist_for_each_entry_rcu(p, head, hlist)
                        if (!kprobe_disabled(p))
                                arm_kprobe(p);
        }

        printk(KERN_INFO "Kprobes globally enabled\n");

already_enabled:
        mutex_unlock(&kprobe_mutex);
        return;
}

static void disarm_all_kprobes(void)
{
        struct hlist_head *head;
        struct kprobe *p;
        unsigned int i;

        mutex_lock(&kprobe_mutex);

        /* If kprobes are already disarmed, just return */
        if (kprobes_all_disarmed) {
                mutex_unlock(&kprobe_mutex);
                return;
        }

        kprobes_all_disarmed = true;
        printk(KERN_INFO "Kprobes globally disabled\n");

        for (i = 0; i < KPROBE_TABLE_SIZE; i++) {
                head = &kprobe_table[i];
                hlist_for_each_entry_rcu(p, head, hlist) {
                        if (!arch_trampoline_kprobe(p) && !kprobe_disabled(p))
                                disarm_kprobe(p, false);
                }
        }
        mutex_unlock(&kprobe_mutex);

        /* Wait for disarming all kprobes by optimizer */
        wait_for_kprobe_optimizer();
}

/*
 * XXX: The debugfs bool file interface doesn't allow for callbacks
 * when the bool state is switched. We can reuse that facility when
 * available
 */
static ssize_t read_enabled_file_bool(struct file *file,
               char __user *user_buf, size_t count, loff_t *ppos)
{
        char buf[3];

        if (!kprobes_all_disarmed)
                buf[0] = '1';
        else
                buf[0] = '0';
        buf[1] = '\n';
        buf[2] = 0x00;
        return simple_read_from_buffer(user_buf, count, ppos, buf, 2);
}

static ssize_t write_enabled_file_bool(struct file *file,
               const char __user *user_buf, size_t count, loff_t *ppos)
{
        char buf[32];
        size_t buf_size;

        buf_size = min(count, (sizeof(buf)-1));
        if (copy_from_user(buf, user_buf, buf_size))
                return -EFAULT;

        buf[buf_size] = '\0';
        switch (buf[0]) {
        case 'y':
        case 'Y':
        case '1':
                arm_all_kprobes();
                break;
        case 'n':
        case 'N':
        case '0':
                disarm_all_kprobes();
                break;
        default:
                return -EINVAL;
        }

        return count;
}

static const struct file_operations fops_kp = {
        .read =         read_enabled_file_bool,
        .write =        write_enabled_file_bool,
        .llseek =       default_llseek,
};

static int __init debugfs_kprobe_init(void)
{
        struct dentry *dir, *file;
        unsigned int value = 1;

        dir = debugfs_create_dir("kprobes", NULL);
        if (!dir)
                return -ENOMEM;

        file = debugfs_create_file("list", 0400, dir, NULL,
                                &debugfs_kprobes_operations);
        if (!file)
                goto error;

        file = debugfs_create_file("enabled", 0600, dir,
                                        &value, &fops_kp);
        if (!file)
                goto error;

        file = debugfs_create_file("blacklist", 0400, dir, NULL,
                                &debugfs_kprobe_blacklist_ops);
        if (!file)
                goto error;

        return 0;

error:
        debugfs_remove(dir);
        return -ENOMEM;
}

late_initcall(debugfs_kprobe_init);
#endif /* CONFIG_DEBUG_FS */

module_init(init_kprobes);

/* defined in arch/.../kernel/kprobes.c */
EXPORT_SYMBOL_GPL(jprobe_return);