kprobes.c

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/*
 *  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 <[email protected]> Kernel
 *      Probes initial implementation (includes suggestions from
 *      Rusty Russell).
 * 2004-Aug Updated by Prasanna S Panchamukhi <[email protected]> with
 *      hlists and exceptions notifier as suggested by Andi Kleen.
 * 2004-July    Suparna Bhattacharya <[email protected]> added jumper probes
 *      interface to access function arguments.
 * 2004-Sep Prasanna S Panchamukhi <[email protected]> Changed Kprobes
 *      exceptions notifier to be first on the priority list.
 * 2005-May Hien Nguyen <[email protected]>, Jim Keniston
 *      <[email protected]> and Prasanna S Panchamukhi
 *      <[email protected]> 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-generic/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);
}

/*
 * Normally, functions that we'd want to prohibit kprobes in, are marked
 * __kprobes. But, there are cases where such functions already belong to
 * a different section (__sched for preempt_schedule)
 *
 * For such cases, we now have a blacklist
 */
static struct kprobe_blackpoint kprobe_blacklist[] = {
    {"preempt_schedule",},
    {"native_get_debugreg",},
    {"irq_entries_start",},
    {"common_interrupt",},
    {"mcount",},    /* mcount can be called from everywhere */
    {NULL}    /* Terminator */
};

#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 */
    int nused;
    int ngarbage;
    char slot_used[];
};

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

struct kprobe_insn_cache {
    struct list_head pages; /* list of kprobe_insn_page */
    size_t insn_size;   /* size of instruction slot */
    int nr_garbage;
};

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 DEFINE_MUTEX(kprobe_insn_mutex); /* Protects kprobe_insn_slots */
static struct kprobe_insn_cache kprobe_insn_slots = {
    .pages = LIST_HEAD_INIT(kprobe_insn_slots.pages),
    .insn_size = MAX_INSN_SIZE,
    .nr_garbage = 0,
};
static int __kprobes collect_garbage_slots(struct kprobe_insn_cache *c);

static kprobe_opcode_t __kprobes *__get_insn_slot(struct kprobe_insn_cache *c)
{
    struct kprobe_insn_page *kip;

 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++;
                    return kip->insns + (i * c->insn_size);
                }
            }
            /* 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)
        return NULL;

    /*
     * 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 = module_alloc(PAGE_SIZE);
    if (!kip->insns) {
        kfree(kip);
        return NULL;
    }
    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;
    list_add(&kip->list, &c->pages);
    return kip->insns;
}


kprobe_opcode_t __kprobes *get_insn_slot(void)
{
    kprobe_opcode_t *ret = NULL;

    mutex_lock(&kprobe_insn_mutex);
    ret = __get_insn_slot(&kprobe_insn_slots);
    mutex_unlock(&kprobe_insn_mutex);

    return ret;
}

/* Return 1 if all garbages are collected, otherwise 0. */
static int __kprobes 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);
            module_free(NULL, kip->insns);
            kfree(kip);
        }
        return 1;
    }
    return 0;
}

static int __kprobes 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;
}

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

    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);
            return;
        }
    }
    /* Could not free this slot. */
    WARN_ON(1);
}

void __kprobes free_insn_slot(kprobe_opcode_t * slot, int dirty)
{
    mutex_lock(&kprobe_insn_mutex);
    __free_insn_slot(&kprobe_insn_slots, slot, dirty);
    mutex_unlock(&kprobe_insn_mutex);
}
#ifdef CONFIG_OPTPROBES
/* For optimized_kprobe buffer */
static DEFINE_MUTEX(kprobe_optinsn_mutex); /* Protects kprobe_optinsn_slots */
static struct kprobe_insn_cache kprobe_optinsn_slots = {
    .pages = LIST_HEAD_INIT(kprobe_optinsn_slots.pages),
    /* .insn_size is initialized later */
    .nr_garbage = 0,
};
/* Get a slot for optimized_kprobe buffer */
kprobe_opcode_t __kprobes *get_optinsn_slot(void)
{
    kprobe_opcode_t *ret = NULL;

    mutex_lock(&kprobe_optinsn_mutex);
    ret = __get_insn_slot(&kprobe_optinsn_slots);
    mutex_unlock(&kprobe_optinsn_mutex);

    return ret;
}

void __kprobes free_optinsn_slot(kprobe_opcode_t * slot, int dirty)
{
    mutex_lock(&kprobe_optinsn_mutex);
    __free_insn_slot(&kprobe_optinsn_slots, slot, dirty);
    mutex_unlock(&kprobe_optinsn_mutex);
}
#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 __kprobes *get_kprobe(void *addr)
{
    struct hlist_head *head;
    struct hlist_node *node;
    struct kprobe *p;

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

    return NULL;
}

static int __kprobes 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 __kprobes 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();
    }
}

/* Free optimized instructions and optimized_kprobe */
static __kprobes 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 __kprobes 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 *__kprobes 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 void kprobe_optimizer(struct work_struct *work);
static DECLARE_DELAYED_WORK(optimizing_work, kprobe_optimizer);
static DECLARE_COMPLETION(optimizer_comp);
#define OPTIMIZE_DELAY 5

/*
 * Optimize (replace a breakpoint with a jump) kprobes listed on
 * optimizing_list.
 */
static __kprobes 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 __kprobes void do_unoptimize_kprobes(struct list_head *free_list)
{
    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, free_list);
    /* Loop free_list for disarming */
    list_for_each_entry_safe(op, tmp, free_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 __kprobes void do_free_cleaned_kprobes(struct list_head *free_list)
{
    struct optimized_kprobe *op, *tmp;

    list_for_each_entry_safe(op, tmp, free_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 __kprobes void kick_kprobe_optimizer(void)
{
    if (!delayed_work_pending(&optimizing_work))
        schedule_delayed_work(&optimizing_work, OPTIMIZE_DELAY);
}

/* Kprobe jump optimizer */
static __kprobes void kprobe_optimizer(struct work_struct *work)
{
    LIST_HEAD(free_list);

    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(&free_list);

    /*
     * 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(&free_list);

    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();
    else
        /* Wake up all waiters */
        complete_all(&optimizer_comp);
}

/* Wait for completing optimization and unoptimization */
static __kprobes void wait_for_kprobe_optimizer(void)
{
    if (delayed_work_pending(&optimizing_work))
        wait_for_completion(&optimizer_comp);
}

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

    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) */
    BUG_ON(!kprobe_optready(ap));
    optimize_kprobe(ap);
}

/* Remove optimized instructions */
static void __kprobes 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;
    /* Don't touch the code, because it is already freed. */
    arch_remove_optimized_kprobe(op);
}

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

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

/* Allocate new optimized_kprobe and try to prepare optimized instructions */
static __kprobes 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);

    return &op->kp;
}

static void __kprobes 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 __kprobes 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
/* This should be called with kprobe_mutex locked */
static void __kprobes optimize_all_kprobes(void)
{
    struct hlist_head *head;
    struct hlist_node *node;
    struct kprobe *p;
    unsigned int i;

    /* If optimization is already allowed, just return */
    if (kprobes_allow_optimization)
        return;

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

/* This should be called with kprobe_mutex locked */
static void __kprobes unoptimize_all_kprobes(void)
{
    struct hlist_head *head;
    struct hlist_node *node;
    struct kprobe *p;
    unsigned int i;

    /* If optimization is already prohibited, just return */
    if (!kprobes_allow_optimization)
        return;

    kprobes_allow_optimization = false;
    for (i = 0; i < KPROBE_TABLE_SIZE; i++) {
        head = &kprobe_table[i];
        hlist_for_each_entry_rcu(p, node, head, hlist) {
            if (!kprobe_disabled(p))
                unoptimize_kprobe(p, false);
        }
    }
    /* Wait for unoptimizing completion */
    wait_for_kprobe_optimizer();
    printk(KERN_INFO "Kprobes globally unoptimized\n");
}

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_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_mutex);

    return ret;
}
#endif /* CONFIG_SYSCTL */

/* Put a breakpoint for a probe. Must be called with text_mutex locked */
static void __kprobes __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 __kprobes __disarm_kprobe(struct kprobe *p, bool reopt)
{
    struct kprobe *_p;

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

    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)

/* There should be no unused kprobes can be reused without optimization */
static void reuse_unused_kprobe(struct kprobe *ap)
{
    printk(KERN_ERR "Error: There should be no unused kprobe here.\n");
    BUG_ON(kprobe_unused(ap));
}

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

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

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

/* Must ensure p->addr is really on ftrace */
static int __kprobes 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 __kprobes 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 __kprobes 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   /* !KPROBES_CAN_USE_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 __kprobes 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 __kprobes 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 __kprobes 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;
}

static void __kprobes 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();
        }
    }
}

static int __kprobes 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;
}

static int __kprobes 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;
}

/* Walks the list and increments nmissed count for multiprobe case */
void __kprobes 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;
}

void __kprobes 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);
}

void __kprobes 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);
}

static void __kprobes 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);
}

void __kprobes 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);
}

static void __kprobes 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);
}

/*
 * 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 __kprobes kprobe_flush_task(struct task_struct *tk)
{
    struct kretprobe_instance *ri;
    struct hlist_head *head, empty_rp;
    struct hlist_node *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, node, tmp, head, hlist) {
        if (ri->task == tk)
            recycle_rp_inst(ri, &empty_rp);
    }
    kretprobe_table_unlock(hash, &flags);
    hlist_for_each_entry_safe(ri, node, tmp, &empty_rp, hlist) {
        hlist_del(&ri->hlist);
        kfree(ri);
    }
}

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

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

static void __kprobes cleanup_rp_inst(struct kretprobe *rp)
{
    unsigned long flags, hash;
    struct kretprobe_instance *ri;
    struct hlist_node *pos, *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, pos, next, head, hlist) {
            if (ri->rp == rp)
                ri->rp = NULL;
        }
        kretprobe_table_unlock(hash, &flags);
    }
    free_rp_inst(rp);
}

/*
* Add the new probe to ap->list. Fail if this is the
* second jprobe at the address - two jprobes can't coexist
*/
static int __kprobes 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 __kprobes 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 __kprobes 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 */
        reuse_unused_kprobe(ap);

    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;
}

static int __kprobes in_kprobes_functions(unsigned long addr)
{
    struct kprobe_blackpoint *kb;

    if (addr >= (unsigned long)__kprobes_text_start &&
        addr < (unsigned long)__kprobes_text_end)
        return -EINVAL;
    /*
     * If there exists a kprobe_blacklist, verify and
     * fail any probe registration in the prohibited area
     */
    for (kb = kprobe_blacklist; kb->name != NULL; kb++) {
        if (kb->start_addr) {
            if (addr >= kb->start_addr &&
                addr < (kb->start_addr + kb->range))
                return -EINVAL;
        }
    }
    return 0;
}

/*
 * 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 __kprobes *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 * __kprobes __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;
}

static __kprobes int check_kprobe_address_safe(struct kprobe *p,
                           struct module **probed_mod)
{
    int ret = 0;
    unsigned long ftrace_addr;

    /*
     * If the address is located on a ftrace nop, set the
     * breakpoint to the following instruction.
     */
    ftrace_addr = ftrace_location((unsigned long)p->addr);
    if (ftrace_addr) {
#ifdef KPROBES_CAN_USE_FTRACE
        /* Given address is not on the instruction boundary */
        if ((unsigned long)p->addr != ftrace_addr)
            return -EILSEQ;
        p->flags |= KPROBE_FLAG_FTRACE;
#else   /* !KPROBES_CAN_USE_FTRACE */
        return -EINVAL;
#endif
    }

    jump_label_lock();
    preempt_disable();

    /* Ensure it is not in reserved area nor out of text */
    if (!kernel_text_address((unsigned long) p->addr) ||
        in_kprobes_functions((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 __kprobes 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 __kprobes 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 *__kprobes __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)) {
            disarm_kprobe(orig_p, true);
            orig_p->flags |= KPROBE_FLAG_DISABLED;
        }
    }

    return orig_p;
}

/*
 * Unregister a kprobe without a scheduler synchronization.
 */
static int __kprobes __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 __kprobes __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 __kprobes 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 __kprobes unregister_kprobe(struct kprobe *p)
{
    unregister_kprobes(&p, 1);
}
EXPORT_SYMBOL_GPL(unregister_kprobe);

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

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

void __kprobes 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 __kprobes 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;

    /*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;
}

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

void __kprobes 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 __kprobes register_kretprobe(struct kretprobe *rp)
{
    return -ENOSYS;
}
EXPORT_SYMBOL_GPL(register_kretprobe);

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

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

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

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

#endif /* CONFIG_KRETPROBES */

/* Set the kprobe gone and remove its instruction buffer. */
static void __kprobes 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 __kprobes 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 __kprobes 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 __kprobes 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);
}

/* Module notifier call back, checking kprobes on the module */
static int __kprobes kprobes_module_callback(struct notifier_block *nb,
                         unsigned long val, void *data)
{
    struct module *mod = data;
    struct hlist_head *head;
    struct hlist_node *node;
    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, node, 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
};

static int __init init_kprobes(void)
{
    int i, err = 0;
    unsigned long offset = 0, size = 0;
    char *modname, namebuf[128];
    const char *symbol_name;
    void *addr;
    struct kprobe_blackpoint *kb;

    /* 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));
    }

    /*
     * 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.
     */
    for (kb = kprobe_blacklist; kb->name != NULL; kb++) {
        kprobe_lookup_name(kb->name, addr);
        if (!addr)
            continue;

        kb->start_addr = (unsigned long)addr;
        symbol_name = kallsyms_lookup(kb->start_addr,
                &size, &offset, &modname, namebuf);
        if (!symbol_name)
            kb->range = 0;
        else
            kb->range = size;
    }

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

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

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

static int __kprobes show_kprobe_addr(struct seq_file *pi, void *v)
{
    struct hlist_head *head;
    struct hlist_node *node;
    struct kprobe *p, *kp;
    const char *sym = NULL;
    unsigned int i = *(loff_t *) v;
    unsigned long offset = 0;
    char *modname, namebuf[128];

    head = &kprobe_table[i];
    preempt_disable();
    hlist_for_each_entry_rcu(p, node, 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 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,
};

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

    mutex_lock(&kprobe_mutex);

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

    /* 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, node, head, hlist)
            if (!kprobe_disabled(p))
                arm_kprobe(p);
    }

    kprobes_all_disarmed = false;
    printk(KERN_INFO "Kprobes globally enabled\n");

already_enabled:
    mutex_unlock(&kprobe_mutex);
    return;
}

static void __kprobes disarm_all_kprobes(void)
{
    struct hlist_head *head;
    struct hlist_node *node;
    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, node, 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;

    switch (buf[0]) {
    case 'y':
    case 'Y':
    case '1':
        arm_all_kprobes();
        break;
    case 'n':
    case 'N':
    case '0':
        disarm_all_kprobes();
        break;
    }

    return count;
}

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

static int __kprobes 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", 0444, dir, NULL,
                &debugfs_kprobes_operations);
    if (!file) {
        debugfs_remove(dir);
        return -ENOMEM;
    }

    file = debugfs_create_file("enabled", 0600, dir,
                    &value, &fops_kp);
    if (!file) {
        debugfs_remove(dir);
        return -ENOMEM;
    }

    return 0;
}

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

module_init(init_kprobes);

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