/*
   *  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/module.h>

  #include <linux/moduleloader.h>

  #include <linux/kallsyms.h>

  #include <linux/freezer.h>

  #include <linux/seq_file.h>
  #include <linux/debugfs.h>

  #include <linux/kdebug.h>

  #include <linux/memory.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;

  static DEFINE_MUTEX(kprobe_mutex);	/* Protects kprobe_table */

  static DEFINE_PER_CPU(struct kprobe *, kprobe_instance) = NULL;

  static struct {

  	spinlock_t lock ____cacheline_aligned_in_smp;

  } kretprobe_table_locks[KPROBE_TABLE_SIZE];
  
  static 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",},
  	{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
   */
  #define INSNS_PER_PAGE	(PAGE_SIZE/(MAX_INSN_SIZE * sizeof(kprobe_opcode_t)))
  
  struct kprobe_insn_page {

  	struct list_head list;

  	kprobe_opcode_t *insns;		/* Page of instruction slots */
  	char slot_used[INSNS_PER_PAGE];
  	int nused;

  	int ngarbage;

  };

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

  static DEFINE_MUTEX(kprobe_insn_mutex);	/* Protects kprobe_insn_pages */

  static LIST_HEAD(kprobe_insn_pages);

  static int kprobe_garbage_slots;
  static int collect_garbage_slots(void);
  
  static int __kprobes check_safety(void)
  {
  	int ret = 0;

  #if defined(CONFIG_PREEMPT) && defined(CONFIG_FREEZER)

  	ret = freeze_processes();
  	if (ret == 0) {
  		struct task_struct *p, *q;
  		do_each_thread(p, q) {
  			if (p != current && p->state == TASK_RUNNING &&
  			    p->pid != 0) {
  				printk("Check failed: %s is running
  ",p->comm);
  				ret = -1;
  				goto loop_end;
  			}
  		} while_each_thread(p, q);
  	}
  loop_end:
  	thaw_processes();
  #else
  	synchronize_sched();
  #endif
  	return ret;
  }

  
  /**

   * __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.
   */

  static kprobe_opcode_t __kprobes *__get_insn_slot(void)

  {
  	struct kprobe_insn_page *kip;

   retry:

  	list_for_each_entry(kip, &kprobe_insn_pages, list) {

  		if (kip->nused < INSNS_PER_PAGE) {
  			int i;
  			for (i = 0; i < INSNS_PER_PAGE; i++) {

  				if (kip->slot_used[i] == SLOT_CLEAN) {
  					kip->slot_used[i] = SLOT_USED;

  					kip->nused++;
  					return kip->insns + (i * MAX_INSN_SIZE);
  				}
  			}
  			/* Surprise!  No unused slots.  Fix kip->nused. */
  			kip->nused = INSNS_PER_PAGE;
  		}
  	}

  	/* If there are any garbage slots, collect it and try again. */
  	if (kprobe_garbage_slots && collect_garbage_slots() == 0) {
  		goto retry;
  	}
  	/* All out of space.  Need to allocate a new page. Use slot 0. */

  	kip = kmalloc(sizeof(struct kprobe_insn_page), 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);
  	list_add(&kip->list, &kprobe_insn_pages);

  	memset(kip->slot_used, SLOT_CLEAN, INSNS_PER_PAGE);
  	kip->slot_used[0] = SLOT_USED;

  	kip->nused = 1;

  	kip->ngarbage = 0;

  	return kip->insns;
  }

  kprobe_opcode_t __kprobes *get_insn_slot(void)
  {
  	kprobe_opcode_t *ret;
  	mutex_lock(&kprobe_insn_mutex);
  	ret = __get_insn_slot();
  	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(&kprobe_insn_pages)) {
  			list_del(&kip->list);

  			module_free(NULL, kip->insns);
  			kfree(kip);
  		}
  		return 1;
  	}
  	return 0;
  }
  
  static int __kprobes collect_garbage_slots(void)
  {

  	struct kprobe_insn_page *kip, *next;

  
  	/* Ensure no-one is preepmted on the garbages */

  	if (check_safety())

  		return -EAGAIN;

  	list_for_each_entry_safe(kip, next, &kprobe_insn_pages, list) {

  		int i;

  		if (kip->ngarbage == 0)
  			continue;
  		kip->ngarbage = 0;	/* we will collect all garbages */
  		for (i = 0; i < INSNS_PER_PAGE; i++) {

  			if (kip->slot_used[i] == SLOT_DIRTY &&

  			    collect_one_slot(kip, i))
  				break;
  		}
  	}
  	kprobe_garbage_slots = 0;
  	return 0;
  }
  
  void __kprobes free_insn_slot(kprobe_opcode_t * slot, int dirty)

  {
  	struct kprobe_insn_page *kip;

  	mutex_lock(&kprobe_insn_mutex);

  	list_for_each_entry(kip, &kprobe_insn_pages, list) {

  		if (kip->insns <= slot &&
  		    slot < kip->insns + (INSNS_PER_PAGE * MAX_INSN_SIZE)) {
  			int i = (slot - kip->insns) / MAX_INSN_SIZE;

  			if (dirty) {

  				kip->slot_used[i] = SLOT_DIRTY;

  				kip->ngarbage++;

  			} else

  				collect_one_slot(kip, i);

  			break;

  		}
  	}

  
  	if (dirty && ++kprobe_garbage_slots > INSNS_PER_PAGE)

  		collect_garbage_slots();

  
  	mutex_unlock(&kprobe_insn_mutex);

  }

  #endif

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

  /* Arm a kprobe with text_mutex */
  static void __kprobes arm_kprobe(struct kprobe *kp)
  {
  	mutex_lock(&text_mutex);
  	arch_arm_kprobe(kp);
  	mutex_unlock(&text_mutex);
  }
  
  /* Disarm a kprobe with text_mutex */
  static void __kprobes disarm_kprobe(struct kprobe *kp)
  {
  	mutex_lock(&text_mutex);
  	arch_disarm_kprobe(kp);
  	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 = __get_cpu_var(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 = __get_cpu_var(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 (p->pre_handler != aggr_pre_handler) {
  		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)) {
  		spin_lock(&rp->lock);
  		hlist_add_head(&ri->hlist, &rp->free_instances);
  		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)
  {
  	unsigned long hash = hash_ptr(tsk, KPROBE_HASH_BITS);
  	spinlock_t *hlist_lock;
  
  	*head = &kretprobe_inst_table[hash];
  	hlist_lock = kretprobe_table_lock_ptr(hash);
  	spin_lock_irqsave(hlist_lock, *flags);
  }

  static void __kprobes kretprobe_table_lock(unsigned long hash,
  	unsigned long *flags)

  {

  	spinlock_t *hlist_lock = kretprobe_table_lock_ptr(hash);
  	spin_lock_irqsave(hlist_lock, *flags);
  }

  void __kprobes kretprobe_hash_unlock(struct task_struct *tsk,
  	unsigned long *flags)

  {
  	unsigned long hash = hash_ptr(tsk, KPROBE_HASH_BITS);
  	spinlock_t *hlist_lock;
  
  	hlist_lock = kretprobe_table_lock_ptr(hash);
  	spin_unlock_irqrestore(hlist_lock, *flags);
  }

  void __kprobes kretprobe_table_unlock(unsigned long hash, unsigned long *flags)

  {
  	spinlock_t *hlist_lock = kretprobe_table_lock_ptr(hash);
  	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;
  
  	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);
  	INIT_HLIST_HEAD(&empty_rp);

  	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);
  }

  /*

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

  * 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) {

  		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;

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

  			arm_kprobe(ap);

  	}

  	return 0;
  }
  
  /*

   * Fill in the required fields of the "manager kprobe". Replace the
   * earlier kprobe in the hlist with the manager kprobe
   */
  static inline void add_aggr_kprobe(struct kprobe *ap, struct kprobe *p)
  {

  	copy_kprobe(p, ap);

  	flush_insn_slot(ap);

  	ap->addr = p->addr;

  	ap->flags = p->flags;

  	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);

  	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 *old_p,
  					  struct kprobe *p)

  {
  	int ret = 0;

  	struct kprobe *ap = old_p;

  	if (old_p->pre_handler != aggr_pre_handler) {
  		/* If old_p is not an aggr_probe, create new aggr_kprobe. */
  		ap = kzalloc(sizeof(struct kprobe), GFP_KERNEL);
  		if (!ap)
  			return -ENOMEM;
  		add_aggr_kprobe(ap, old_p);
  	}
  
  	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.
  			 */

  			return ret;

  		/*

  		 * 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_kprobe(ap, p);
  	return add_new_kprobe(ap, p);

  }

  /* Try to disable aggr_kprobe, and return 1 if succeeded.*/
  static int __kprobes try_to_disable_aggr_kprobe(struct kprobe *p)
  {
  	struct kprobe *kp;
  
  	list_for_each_entry_rcu(kp, &p->list, list) {
  		if (!kprobe_disabled(kp))
  			/*
  			 * There is an active probe on the list.
  			 * We can't disable aggr_kprobe.
  			 */
  			return 0;
  	}
  	p->flags |= KPROBE_FLAG_DISABLED;
  	return 1;
  }

  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.
   */
  static kprobe_opcode_t __kprobes *kprobe_addr(struct kprobe *p)
  {
  	kprobe_opcode_t *addr = p->addr;
  	if (p->symbol_name) {
  		if (addr)
  			return NULL;
  		kprobe_lookup_name(p->symbol_name, addr);
  	}
  
  	if (!addr)
  		return NULL;
  	return (kprobe_opcode_t *)(((char *)addr) + p->offset);
  }

  int __kprobes register_kprobe(struct kprobe *p)

  {
  	int ret = 0;

  	struct kprobe *old_p;

  	struct module *probed_mod;

  	kprobe_opcode_t *addr;

  	addr = kprobe_addr(p);
  	if (!addr)

  		return -EINVAL;

  	p->addr = addr;

  	preempt_disable();

  	if (!kernel_text_address((unsigned long) p->addr) ||

  	    in_kprobes_functions((unsigned long) p->addr)) {
  		preempt_enable();

  		return -EINVAL;

  	}

  	/* User can pass only KPROBE_FLAG_DISABLED to register_kprobe */
  	p->flags &= KPROBE_FLAG_DISABLED;

  	/*
  	 * 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))) {
  			preempt_enable();
  			return -EINVAL;
  		}

  		/*
  		 * 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);
  			preempt_enable();
  			return -EINVAL;
  		}

  	}

  	preempt_enable();

  	p->nmissed = 0;

  	INIT_LIST_HEAD(&p->list);

  	mutex_lock(&kprobe_mutex);

  	old_p = get_kprobe(p->addr);
  	if (old_p) {
  		ret = register_aggr_kprobe(old_p, p);

  		goto out;
  	}

  	mutex_lock(&text_mutex);

  	ret = arch_prepare_kprobe(p);
  	if (ret)

  		goto out_unlock_text;

  	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))

  		arch_arm_kprobe(p);

  out_unlock_text:
  	mutex_unlock(&text_mutex);

  out:

  	mutex_unlock(&kprobe_mutex);

  	if (probed_mod)

  		module_put(probed_mod);

  	return ret;
  }

  EXPORT_SYMBOL_GPL(register_kprobe);

  /* Check passed kprobe is valid and return kprobe in kprobe_table. */
  static struct kprobe * __kprobes __get_valid_kprobe(struct kprobe *p)

  {

  	struct kprobe *old_p, *list_p;

  	old_p = get_kprobe(p->addr);

  	if (unlikely(!old_p))

  		return NULL;

  	if (p != old_p) {
  		list_for_each_entry_rcu(list_p, &old_p->list, list)
  			if (list_p == p)
  			/* kprobe p is a valid probe */

  				goto valid;
  		return NULL;

  	}

  valid:
  	return old_p;
  }
  
  /*
   * Unregister a kprobe without a scheduler synchronization.
   */
  static int __kprobes __unregister_kprobe_top(struct kprobe *p)
  {
  	struct kprobe *old_p, *list_p;
  
  	old_p = __get_valid_kprobe(p);
  	if (old_p == NULL)
  		return -EINVAL;

  	if (old_p == p ||
  	    (old_p->pre_handler == aggr_pre_handler &&

  	     list_is_singular(&old_p->list))) {

  		/*
  		 * Only probe on the hash list. Disarm only if kprobes are

  		 * enabled and not gone - otherwise, the breakpoint would
  		 * already have been removed. We save on flushing icache.

  		 */

  		if (!kprobes_all_disarmed && !kprobe_disabled(old_p))
  			disarm_kprobe(p);

  		hlist_del_rcu(&old_p->hlist);

  	} else {

  		if (p->break_handler && !kprobe_gone(p))

  			old_p->break_handler = NULL;

  		if (p->post_handler && !kprobe_gone(p)) {

  			list_for_each_entry_rcu(list_p, &old_p->list, list) {
  				if ((list_p != p) && (list_p->post_handler))
  					goto noclean;
  			}
  			old_p->post_handler = NULL;
  		}
  noclean:

  		list_del_rcu(&p->list);

  		if (!kprobe_disabled(old_p)) {
  			try_to_disable_aggr_kprobe(old_p);
  			if (!kprobes_all_disarmed && kprobe_disabled(old_p))

  				disarm_kprobe(old_p);

  		}

  	}

  	return 0;
  }

  static void __kprobes __unregister_kprobe_bottom(struct kprobe *p)
  {

  	struct kprobe *old_p;

  	if (list_empty(&p->list))

  		arch_remove_kprobe(p);

  	else if (list_is_singular(&p->list)) {
  		/* "p" is the last child of an aggr_kprobe */
  		old_p = list_entry(p->list.next, struct kprobe, list);
  		list_del(&p->list);
  		arch_remove_kprobe(old_p);
  		kfree(old_p);

  	}
  }

  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;
  		jp = jps[i];
  		addr = arch_deref_entry_point(jp->entry);
  
  		if (!kernel_text_address(addr))
  			ret = -EINVAL;
  		else {
  			/* Todo: Verify probepoint is a function entry point */
  			jp->kp.pre_handler = setjmp_pre_handler;
  			jp->kp.break_handler = longjmp_break_handler;

  			ret = register_kprobe(&jp->kp);

  		}

  		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);
  	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);
  		spin_unlock_irqrestore(&rp->lock, flags);

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

  		if (rp->entry_handler && rp->entry_handler(ri, regs))

  			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++;

  		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 (!addr)
  			return -EINVAL;

  
  		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(10, 2 * NR_CPUS);
  #else
  		rp->maxactive = NR_CPUS;
  #endif
  	}

  	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 (p->pre_handler == aggr_pre_handler) {
  		/*
  		 * 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;
  	}
  	/*
  	 * 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);
  }
  
  /* 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]);

  		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
  ",
  				       kretprobe_blacklist[i].name);
  		}
  	}

  	/* 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)

  {
  	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 %s%s
  ",
  			p->addr, kprobe_type, sym, offset,
  			(modname ? modname : " "),
  			(kprobe_gone(p) ? "[GONE]" : ""),
  			((kprobe_disabled(p) && !kprobe_gone(p)) ?
  			 "[DISABLED]" : ""));

  	else

  		seq_printf(pi, "%p  %s  %p %s%s
  ",
  			p->addr, kprobe_type, p->addr,
  			(kprobe_gone(p) ? "[GONE]" : ""),
  			((kprobe_disabled(p) && !kprobe_gone(p)) ?
  			 "[DISABLED]" : ""));

  }
  
  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 (p->pre_handler == aggr_pre_handler) {
  			list_for_each_entry_rcu(kp, &p->list, list)
  				report_probe(pi, kp, sym, offset, modname);
  		} else
  			report_probe(pi, p, sym, offset, modname);
  	}
  	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,
  };

  /* Disable one kprobe */
  int __kprobes disable_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 the probe is already disabled (or gone), just return */
  	if (kprobe_disabled(kp))
  		goto out;
  
  	kp->flags |= KPROBE_FLAG_DISABLED;
  	if (p != kp)
  		/* When kp != p, p is always enabled. */
  		try_to_disable_aggr_kprobe(p);
  
  	if (!kprobes_all_disarmed && kprobe_disabled(p))

  		disarm_kprobe(p);

  out:
  	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 (!kprobes_all_disarmed && kprobe_disabled(p))

  		arm_kprobe(p);

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

  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;

  	mutex_lock(&text_mutex);

  	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))

  				arch_arm_kprobe(p);

  	}

  	mutex_unlock(&text_mutex);

  	kprobes_all_disarmed = false;

  	printk(KERN_INFO "Kprobes globally enabled
  ");
  
  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)

  		goto already_disabled;

  	kprobes_all_disarmed = true;

  	printk(KERN_INFO "Kprobes globally disabled
  ");

  	mutex_lock(&text_mutex);

  	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))

  				arch_disarm_kprobe(p);
  		}
  	}

  	mutex_unlock(&text_mutex);

  	mutex_unlock(&kprobe_mutex);
  	/* Allow all currently running kprobes to complete */
  	synchronize_sched();

  	return;

  
  already_disabled:
  	mutex_unlock(&kprobe_mutex);
  	return;
  }
  
  /*
   * 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] = '
  ';
  	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];
  	int 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,
  };

  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);