Skip to content
Snippets Groups Projects
Select Git revision
  • bf5eb3de3847ebcfd1fea7bc14072ef9f21d4e8d
  • vme-testing default
  • ci-test
  • master
  • remoteproc
  • am625-sk-ov5640
  • pcal6534-upstreaming
  • lps22df-upstreaming
  • msc-upstreaming
  • imx8mp
  • iio/noa1305
  • vme-next
  • vme-next-4.14-rc4
  • v4.14-rc4
  • v4.14-rc3
  • v4.14-rc2
  • v4.14-rc1
  • v4.13
  • vme-next-4.13-rc7
  • v4.13-rc7
  • v4.13-rc6
  • v4.13-rc5
  • v4.13-rc4
  • v4.13-rc3
  • v4.13-rc2
  • v4.13-rc1
  • v4.12
  • v4.12-rc7
  • v4.12-rc6
  • v4.12-rc5
  • v4.12-rc4
  • v4.12-rc3
32 results

slab_common.c

Blame
  • kprobes.c 60.54 KiB
    /*
     *  Kernel Probes (KProbes)
     *  kernel/kprobes.c
     *
     * This program is free software; you can redistribute it and/or modify
     * it under the terms of the GNU General Public License as published by
     * the Free Software Foundation; either version 2 of the License, or
     * (at your option) any later version.
     *
     * This program is distributed in the hope that it will be useful,
     * but WITHOUT ANY WARRANTY; without even the implied warranty of
     * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
     * GNU General Public License for more details.
     *
     * You should have received a copy of the GNU General Public License
     * along with this program; if not, write to the Free Software
     * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
     *
     * Copyright (C) IBM Corporation, 2002, 2004
     *
     * 2002-Oct	Created by Vamsi Krishna S <vamsi_krishna@in.ibm.com> Kernel
     *		Probes initial implementation (includes suggestions from
     *		Rusty Russell).
     * 2004-Aug	Updated by Prasanna S Panchamukhi <prasanna@in.ibm.com> with
     *		hlists and exceptions notifier as suggested by Andi Kleen.
     * 2004-July	Suparna Bhattacharya <suparna@in.ibm.com> added jumper probes
     *		interface to access function arguments.
     * 2004-Sep	Prasanna S Panchamukhi <prasanna@in.ibm.com> Changed Kprobes
     *		exceptions notifier to be first on the priority list.
     * 2005-May	Hien Nguyen <hien@us.ibm.com>, Jim Keniston
     *		<jkenisto@us.ibm.com> and Prasanna S Panchamukhi
     *		<prasanna@in.ibm.com> added function-return probes.
     */
    #include <linux/kprobes.h>
    #include <linux/hash.h>
    #include <linux/init.h>
    #include <linux/slab.h>
    #include <linux/stddef.h>
    #include <linux/export.h>
    #include <linux/moduleloader.h>
    #include <linux/kallsyms.h>
    #include <linux/freezer.h>
    #include <linux/seq_file.h>
    #include <linux/debugfs.h>
    #include <linux/sysctl.h>
    #include <linux/kdebug.h>
    #include <linux/memory.h>
    #include <linux/ftrace.h>
    #include <linux/cpu.h>
    #include <linux/jump_label.h>
    
    #include <asm-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);
    }
    
    /* Blacklist -- list of struct kprobe_blacklist_entry */
    static LIST_HEAD(kprobe_blacklist);
    
    #ifdef __ARCH_WANT_KPROBES_INSN_SLOT
    /*
     * kprobe->ainsn.insn points to the copy of the instruction to be
     * single-stepped. x86_64, POWER4 and above have no-exec support and
     * stepping on the instruction on a vmalloced/kmalloced/data page
     * is a recipe for disaster
     */
    struct kprobe_insn_page {
    	struct list_head list;
    	kprobe_opcode_t *insns;		/* Page of instruction slots */
    	struct kprobe_insn_cache *cache;
    	int nused;
    	int ngarbage;
    	char slot_used[];
    };
    
    #define KPROBE_INSN_PAGE_SIZE(slots)			\
    	(offsetof(struct kprobe_insn_page, slot_used) +	\
    	 (sizeof(char) * (slots)))
    
    static int slots_per_page(struct kprobe_insn_cache *c)
    {
    	return PAGE_SIZE/(c->insn_size * sizeof(kprobe_opcode_t));
    }
    
    enum kprobe_slot_state {
    	SLOT_CLEAN = 0,
    	SLOT_DIRTY = 1,
    	SLOT_USED = 2,
    };
    
    static void *alloc_insn_page(void)
    {
    	return module_alloc(PAGE_SIZE);
    }
    
    static void free_insn_page(void *page)
    {
    	module_memfree(page);
    }
    
    struct kprobe_insn_cache kprobe_insn_slots = {
    	.mutex = __MUTEX_INITIALIZER(kprobe_insn_slots.mutex),
    	.alloc = alloc_insn_page,
    	.free = free_insn_page,
    	.pages = LIST_HEAD_INIT(kprobe_insn_slots.pages),
    	.insn_size = MAX_INSN_SIZE,
    	.nr_garbage = 0,
    };
    static int collect_garbage_slots(struct kprobe_insn_cache *c);
    
    /**
     * __get_insn_slot() - Find a slot on an executable page for an instruction.
     * We allocate an executable page if there's no room on existing ones.
     */
    kprobe_opcode_t *__get_insn_slot(struct kprobe_insn_cache *c)
    {
    	struct kprobe_insn_page *kip;
    	kprobe_opcode_t *slot = NULL;
    
    	mutex_lock(&c->mutex);
     retry:
    	list_for_each_entry(kip, &c->pages, list) {
    		if (kip->nused < slots_per_page(c)) {
    			int i;
    			for (i = 0; i < slots_per_page(c); i++) {
    				if (kip->slot_used[i] == SLOT_CLEAN) {
    					kip->slot_used[i] = SLOT_USED;
    					kip->nused++;
    					slot = kip->insns + (i * c->insn_size);
    					goto out;
    				}
    			}
    			/* kip->nused is broken. Fix it. */
    			kip->nused = slots_per_page(c);
    			WARN_ON(1);
    		}
    	}
    
    	/* If there are any garbage slots, collect it and try again. */
    	if (c->nr_garbage && collect_garbage_slots(c) == 0)
    		goto retry;
    
    	/* All out of space.  Need to allocate a new page. */
    	kip = kmalloc(KPROBE_INSN_PAGE_SIZE(slots_per_page(c)), GFP_KERNEL);
    	if (!kip)
    		goto out;
    
    	/*
    	 * Use module_alloc so this page is within +/- 2GB of where the
    	 * kernel image and loaded module images reside. This is required
    	 * so x86_64 can correctly handle the %rip-relative fixups.
    	 */
    	kip->insns = c->alloc();
    	if (!kip->insns) {
    		kfree(kip);
    		goto out;
    	}
    	INIT_LIST_HEAD(&kip->list);
    	memset(kip->slot_used, SLOT_CLEAN, slots_per_page(c));
    	kip->slot_used[0] = SLOT_USED;
    	kip->nused = 1;
    	kip->ngarbage = 0;
    	kip->cache = c;
    	list_add(&kip->list, &c->pages);
    	slot = kip->insns;
    out:
    	mutex_unlock(&c->mutex);
    	return slot;
    }
    
    /* Return 1 if all garbages are collected, otherwise 0. */
    static int collect_one_slot(struct kprobe_insn_page *kip, int idx)
    {
    	kip->slot_used[idx] = SLOT_CLEAN;
    	kip->nused--;
    	if (kip->nused == 0) {
    		/*
    		 * Page is no longer in use.  Free it unless
    		 * it's the last one.  We keep the last one
    		 * so as not to have to set it up again the
    		 * next time somebody inserts a probe.
    		 */
    		if (!list_is_singular(&kip->list)) {
    			list_del(&kip->list);
    			kip->cache->free(kip->insns);
    			kfree(kip);
    		}
    		return 1;
    	}
    	return 0;
    }
    
    static int collect_garbage_slots(struct kprobe_insn_cache *c)
    {
    	struct kprobe_insn_page *kip, *next;
    
    	/* Ensure no-one is interrupted on the garbages */
    	synchronize_sched();
    
    	list_for_each_entry_safe(kip, next, &c->pages, list) {
    		int i;
    		if (kip->ngarbage == 0)
    			continue;
    		kip->ngarbage = 0;	/* we will collect all garbages */
    		for (i = 0; i < slots_per_page(c); i++) {
    			if (kip->slot_used[i] == SLOT_DIRTY &&
    			    collect_one_slot(kip, i))
    				break;
    		}
    	}
    	c->nr_garbage = 0;
    	return 0;
    }
    
    void __free_insn_slot(struct kprobe_insn_cache *c,
    		      kprobe_opcode_t *slot, int dirty)
    {
    	struct kprobe_insn_page *kip;
    
    	mutex_lock(&c->mutex);
    	list_for_each_entry(kip, &c->pages, list) {
    		long idx = ((long)slot - (long)kip->insns) /
    				(c->insn_size * sizeof(kprobe_opcode_t));
    		if (idx >= 0 && idx < slots_per_page(c)) {
    			WARN_ON(kip->slot_used[idx] != SLOT_USED);
    			if (dirty) {
    				kip->slot_used[idx] = SLOT_DIRTY;
    				kip->ngarbage++;
    				if (++c->nr_garbage > slots_per_page(c))
    					collect_garbage_slots(c);
    			} else
    				collect_one_slot(kip, idx);
    			goto out;
    		}
    	}
    	/* Could not free this slot. */
    	WARN_ON(1);
    out:
    	mutex_unlock(&c->mutex);
    }
    
    #ifdef CONFIG_OPTPROBES
    /* For optimized_kprobe buffer */
    struct kprobe_insn_cache kprobe_optinsn_slots = {
    	.mutex = __MUTEX_INITIALIZER(kprobe_optinsn_slots.mutex),
    	.alloc = alloc_insn_page,
    	.free = free_insn_page,
    	.pages = LIST_HEAD_INIT(kprobe_optinsn_slots.pages),
    	/* .insn_size is initialized later */
    	.nr_garbage = 0,
    };
    #endif
    #endif
    
    /* We have preemption disabled.. so it is safe to use __ versions */
    static inline void set_kprobe_instance(struct kprobe *kp)
    {
    	__this_cpu_write(kprobe_instance, kp);
    }
    
    static inline void reset_kprobe_instance(void)
    {
    	__this_cpu_write(kprobe_instance, NULL);
    }
    
    /*
     * This routine is called either:
     * 	- under the kprobe_mutex - during kprobe_[un]register()
     * 				OR
     * 	- with preemption disabled - from arch/xxx/kernel/kprobes.c
     */
    struct kprobe *get_kprobe(void *addr)
    {
    	struct hlist_head *head;
    	struct kprobe *p;
    
    	head = &kprobe_table[hash_ptr(addr, KPROBE_HASH_BITS)];
    	hlist_for_each_entry_rcu(p, head, hlist) {
    		if (p->addr == addr)
    			return p;
    	}
    
    	return NULL;
    }
    NOKPROBE_SYMBOL(get_kprobe);
    
    static int aggr_pre_handler(struct kprobe *p, struct pt_regs *regs);
    
    /* Return true if the kprobe is an aggregator */
    static inline int kprobe_aggrprobe(struct kprobe *p)
    {
    	return p->pre_handler == aggr_pre_handler;
    }
    
    /* Return true(!0) if the kprobe is unused */
    static inline int kprobe_unused(struct kprobe *p)
    {
    	return kprobe_aggrprobe(p) && kprobe_disabled(p) &&
    	       list_empty(&p->list);
    }
    
    /*
     * Keep all fields in the kprobe consistent
     */
    static inline void copy_kprobe(struct kprobe *ap, struct kprobe *p)
    {
    	memcpy(&p->opcode, &ap->opcode, sizeof(kprobe_opcode_t));
    	memcpy(&p->ainsn, &ap->ainsn, sizeof(struct arch_specific_insn));
    }
    
    #ifdef CONFIG_OPTPROBES
    /* NOTE: change this value only with kprobe_mutex held */
    static bool kprobes_allow_optimization;
    
    /*
     * Call all pre_handler on the list, but ignores its return value.
     * This must be called from arch-dep optimized caller.
     */
    void opt_pre_handler(struct kprobe *p, struct pt_regs *regs)
    {
    	struct kprobe *kp;
    
    	list_for_each_entry_rcu(kp, &p->list, list) {
    		if (kp->pre_handler && likely(!kprobe_disabled(kp))) {
    			set_kprobe_instance(kp);
    			kp->pre_handler(kp, regs);
    		}
    		reset_kprobe_instance();
    	}
    }
    NOKPROBE_SYMBOL(opt_pre_handler);
    
    /* Free optimized instructions and optimized_kprobe */
    static void free_aggr_kprobe(struct kprobe *p)
    {
    	struct optimized_kprobe *op;
    
    	op = container_of(p, struct optimized_kprobe, kp);
    	arch_remove_optimized_kprobe(op);
    	arch_remove_kprobe(p);
    	kfree(op);
    }
    
    /* Return true(!0) if the kprobe is ready for optimization. */
    static inline int kprobe_optready(struct kprobe *p)
    {
    	struct optimized_kprobe *op;
    
    	if (kprobe_aggrprobe(p)) {
    		op = container_of(p, struct optimized_kprobe, kp);
    		return arch_prepared_optinsn(&op->optinsn);
    	}
    
    	return 0;
    }
    
    /* Return true(!0) if the kprobe is disarmed. Note: p must be on hash list */
    static inline int kprobe_disarmed(struct kprobe *p)
    {
    	struct optimized_kprobe *op;
    
    	/* If kprobe is not aggr/opt probe, just return kprobe is disabled */
    	if (!kprobe_aggrprobe(p))
    		return kprobe_disabled(p);
    
    	op = container_of(p, struct optimized_kprobe, kp);
    
    	return kprobe_disabled(p) && list_empty(&op->list);
    }
    
    /* Return true(!0) if the probe is queued on (un)optimizing lists */
    static int kprobe_queued(struct kprobe *p)
    {
    	struct optimized_kprobe *op;
    
    	if (kprobe_aggrprobe(p)) {
    		op = container_of(p, struct optimized_kprobe, kp);
    		if (!list_empty(&op->list))
    			return 1;
    	}
    	return 0;
    }
    
    /*
     * Return an optimized kprobe whose optimizing code replaces
     * instructions including addr (exclude breakpoint).
     */
    static struct kprobe *get_optimized_kprobe(unsigned long addr)
    {
    	int i;
    	struct kprobe *p = NULL;
    	struct optimized_kprobe *op;
    
    	/* Don't check i == 0, since that is a breakpoint case. */
    	for (i = 1; !p && i < MAX_OPTIMIZED_LENGTH; i++)
    		p = get_kprobe((void *)(addr - i));
    
    	if (p && kprobe_optready(p)) {
    		op = container_of(p, struct optimized_kprobe, kp);
    		if (arch_within_optimized_kprobe(op, addr))
    			return p;
    	}
    
    	return NULL;
    }
    
    /* Optimization staging list, protected by kprobe_mutex */
    static LIST_HEAD(optimizing_list);
    static LIST_HEAD(unoptimizing_list);
    static LIST_HEAD(freeing_list);
    
    static void kprobe_optimizer(struct work_struct *work);
    static DECLARE_DELAYED_WORK(optimizing_work, kprobe_optimizer);
    #define OPTIMIZE_DELAY 5
    
    /*
     * Optimize (replace a breakpoint with a jump) kprobes listed on
     * optimizing_list.
     */
    static void do_optimize_kprobes(void)
    {
    	/* Optimization never be done when disarmed */
    	if (kprobes_all_disarmed || !kprobes_allow_optimization ||
    	    list_empty(&optimizing_list))
    		return;
    
    	/*
    	 * The optimization/unoptimization refers online_cpus via
    	 * stop_machine() and cpu-hotplug modifies online_cpus.
    	 * And same time, text_mutex will be held in cpu-hotplug and here.
    	 * This combination can cause a deadlock (cpu-hotplug try to lock
    	 * text_mutex but stop_machine can not be done because online_cpus
    	 * has been changed)
    	 * To avoid this deadlock, we need to call get_online_cpus()
    	 * for preventing cpu-hotplug outside of text_mutex locking.
    	 */
    	get_online_cpus();
    	mutex_lock(&text_mutex);
    	arch_optimize_kprobes(&optimizing_list);
    	mutex_unlock(&text_mutex);
    	put_online_cpus();
    }
    
    /*
     * Unoptimize (replace a jump with a breakpoint and remove the breakpoint
     * if need) kprobes listed on unoptimizing_list.
     */
    static void do_unoptimize_kprobes(void)
    {
    	struct optimized_kprobe *op, *tmp;
    
    	/* Unoptimization must be done anytime */
    	if (list_empty(&unoptimizing_list))
    		return;
    
    	/* Ditto to do_optimize_kprobes */
    	get_online_cpus();
    	mutex_lock(&text_mutex);
    	arch_unoptimize_kprobes(&unoptimizing_list, &freeing_list);
    	/* Loop free_list for disarming */
    	list_for_each_entry_safe(op, tmp, &freeing_list, list) {
    		/* Disarm probes if marked disabled */
    		if (kprobe_disabled(&op->kp))
    			arch_disarm_kprobe(&op->kp);
    		if (kprobe_unused(&op->kp)) {
    			/*
    			 * Remove unused probes from hash list. After waiting
    			 * for synchronization, these probes are reclaimed.
    			 * (reclaiming is done by do_free_cleaned_kprobes.)
    			 */
    			hlist_del_rcu(&op->kp.hlist);
    		} else
    			list_del_init(&op->list);
    	}
    	mutex_unlock(&text_mutex);
    	put_online_cpus();
    }
    
    /* Reclaim all kprobes on the free_list */
    static void do_free_cleaned_kprobes(void)
    {
    	struct optimized_kprobe *op, *tmp;
    
    	list_for_each_entry_safe(op, tmp, &freeing_list, list) {
    		BUG_ON(!kprobe_unused(&op->kp));
    		list_del_init(&op->list);
    		free_aggr_kprobe(&op->kp);
    	}
    }
    
    /* Start optimizer after OPTIMIZE_DELAY passed */
    static void kick_kprobe_optimizer(void)
    {
    	schedule_delayed_work(&optimizing_work, OPTIMIZE_DELAY);
    }
    
    /* Kprobe jump optimizer */
    static void kprobe_optimizer(struct work_struct *work)
    {
    	mutex_lock(&kprobe_mutex);
    	/* Lock modules while optimizing kprobes */
    	mutex_lock(&module_mutex);
    
    	/*
    	 * Step 1: Unoptimize kprobes and collect cleaned (unused and disarmed)
    	 * kprobes before waiting for quiesence period.
    	 */
    	do_unoptimize_kprobes();
    
    	/*
    	 * Step 2: Wait for quiesence period to ensure all running interrupts
    	 * are done. Because optprobe may modify multiple instructions
    	 * there is a chance that Nth instruction is interrupted. In that
    	 * case, running interrupt can return to 2nd-Nth byte of jump
    	 * instruction. This wait is for avoiding it.
    	 */
    	synchronize_sched();
    
    	/* Step 3: Optimize kprobes after quiesence period */
    	do_optimize_kprobes();
    
    	/* Step 4: Free cleaned kprobes after quiesence period */
    	do_free_cleaned_kprobes();
    
    	mutex_unlock(&module_mutex);
    	mutex_unlock(&kprobe_mutex);
    
    	/* Step 5: Kick optimizer again if needed */
    	if (!list_empty(&optimizing_list) || !list_empty(&unoptimizing_list))
    		kick_kprobe_optimizer();
    }
    
    /* Wait for completing optimization and unoptimization */
    static void wait_for_kprobe_optimizer(void)
    {
    	mutex_lock(&kprobe_mutex);
    
    	while (!list_empty(&optimizing_list) || !list_empty(&unoptimizing_list)) {
    		mutex_unlock(&kprobe_mutex);
    
    		/* this will also make optimizing_work execute immmediately */
    		flush_delayed_work(&optimizing_work);
    		/* @optimizing_work might not have been queued yet, relax */
    		cpu_relax();
    
    		mutex_lock(&kprobe_mutex);
    	}
    
    	mutex_unlock(&kprobe_mutex);
    }
    
    /* Optimize kprobe if p is ready to be optimized */
    static void optimize_kprobe(struct kprobe *p)
    {
    	struct optimized_kprobe *op;
    
    	/* Check if the kprobe is disabled or not ready for optimization. */
    	if (!kprobe_optready(p) || !kprobes_allow_optimization ||
    	    (kprobe_disabled(p) || kprobes_all_disarmed))
    		return;
    
    	/* Both of break_handler and post_handler are not supported. */
    	if (p->break_handler || p->post_handler)
    		return;
    
    	op = container_of(p, struct optimized_kprobe, kp);
    
    	/* Check there is no other kprobes at the optimized instructions */
    	if (arch_check_optimized_kprobe(op) < 0)
    		return;
    
    	/* Check if it is already optimized. */
    	if (op->kp.flags & KPROBE_FLAG_OPTIMIZED)
    		return;
    	op->kp.flags |= KPROBE_FLAG_OPTIMIZED;
    
    	if (!list_empty(&op->list))
    		/* This is under unoptimizing. Just dequeue the probe */
    		list_del_init(&op->list);
    	else {
    		list_add(&op->list, &optimizing_list);
    		kick_kprobe_optimizer();
    	}
    }
    
    /* Short cut to direct unoptimizing */
    static void force_unoptimize_kprobe(struct optimized_kprobe *op)
    {
    	get_online_cpus();
    	arch_unoptimize_kprobe(op);
    	put_online_cpus();
    	if (kprobe_disabled(&op->kp))
    		arch_disarm_kprobe(&op->kp);
    }
    
    /* Unoptimize a kprobe if p is optimized */
    static void unoptimize_kprobe(struct kprobe *p, bool force)
    {
    	struct optimized_kprobe *op;
    
    	if (!kprobe_aggrprobe(p) || kprobe_disarmed(p))
    		return; /* This is not an optprobe nor optimized */
    
    	op = container_of(p, struct optimized_kprobe, kp);
    	if (!kprobe_optimized(p)) {
    		/* Unoptimized or unoptimizing case */
    		if (force && !list_empty(&op->list)) {
    			/*
    			 * Only if this is unoptimizing kprobe and forced,
    			 * forcibly unoptimize it. (No need to unoptimize
    			 * unoptimized kprobe again :)
    			 */
    			list_del_init(&op->list);
    			force_unoptimize_kprobe(op);
    		}
    		return;
    	}
    
    	op->kp.flags &= ~KPROBE_FLAG_OPTIMIZED;
    	if (!list_empty(&op->list)) {
    		/* Dequeue from the optimization queue */
    		list_del_init(&op->list);
    		return;
    	}
    	/* Optimized kprobe case */
    	if (force)
    		/* Forcibly update the code: this is a special case */
    		force_unoptimize_kprobe(op);
    	else {
    		list_add(&op->list, &unoptimizing_list);
    		kick_kprobe_optimizer();
    	}
    }
    
    /* Cancel unoptimizing for reusing */
    static 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 kill_optimized_kprobe(struct kprobe *p)
    {
    	struct optimized_kprobe *op;
    
    	op = container_of(p, struct optimized_kprobe, kp);
    	if (!list_empty(&op->list))
    		/* Dequeue from the (un)optimization queue */
    		list_del_init(&op->list);
    	op->kp.flags &= ~KPROBE_FLAG_OPTIMIZED;
    
    	if (kprobe_unused(p)) {
    		/* Enqueue if it is unused */
    		list_add(&op->list, &freeing_list);
    		/*
    		 * Remove unused probes from the hash list. After waiting
    		 * for synchronization, this probe is reclaimed.
    		 * (reclaiming is done by do_free_cleaned_kprobes().)
    		 */
    		hlist_del_rcu(&op->kp.hlist);
    	}
    
    	/* Don't touch the code, because it is already freed. */
    	arch_remove_optimized_kprobe(op);
    }
    
    /* Try to prepare optimized instructions */
    static void prepare_optimized_kprobe(struct kprobe *p)
    {
    	struct optimized_kprobe *op;
    
    	op = container_of(p, struct optimized_kprobe, kp);
    	arch_prepare_optimized_kprobe(op, p);
    }
    
    /* Allocate new optimized_kprobe and try to prepare optimized instructions */
    static struct kprobe *alloc_aggr_kprobe(struct kprobe *p)
    {
    	struct optimized_kprobe *op;
    
    	op = kzalloc(sizeof(struct optimized_kprobe), GFP_KERNEL);
    	if (!op)
    		return NULL;
    
    	INIT_LIST_HEAD(&op->list);
    	op->kp.addr = p->addr;
    	arch_prepare_optimized_kprobe(op, p);
    
    	return &op->kp;
    }
    
    static void init_aggr_kprobe(struct kprobe *ap, struct kprobe *p);
    
    /*
     * Prepare an optimized_kprobe and optimize it
     * NOTE: p must be a normal registered kprobe
     */
    static void try_to_optimize_kprobe(struct kprobe *p)
    {
    	struct kprobe *ap;
    	struct optimized_kprobe *op;
    
    	/* Impossible to optimize ftrace-based kprobe */
    	if (kprobe_ftrace(p))
    		return;
    
    	/* For preparing optimization, jump_label_text_reserved() is called */
    	jump_label_lock();
    	mutex_lock(&text_mutex);
    
    	ap = alloc_aggr_kprobe(p);
    	if (!ap)
    		goto out;
    
    	op = container_of(ap, struct optimized_kprobe, kp);
    	if (!arch_prepared_optinsn(&op->optinsn)) {
    		/* If failed to setup optimizing, fallback to kprobe */
    		arch_remove_optimized_kprobe(op);
    		kfree(op);
    		goto out;
    	}
    
    	init_aggr_kprobe(ap, p);
    	optimize_kprobe(ap);	/* This just kicks optimizer thread */
    
    out:
    	mutex_unlock(&text_mutex);
    	jump_label_unlock();
    }
    
    #ifdef CONFIG_SYSCTL
    static void optimize_all_kprobes(void)
    {
    	struct hlist_head *head;
    	struct kprobe *p;
    	unsigned int i;
    
    	mutex_lock(&kprobe_mutex);
    	/* If optimization is already allowed, just return */
    	if (kprobes_allow_optimization)
    		goto out;
    
    	kprobes_allow_optimization = true;
    	for (i = 0; i < KPROBE_TABLE_SIZE; i++) {
    		head = &kprobe_table[i];
    		hlist_for_each_entry_rcu(p, head, hlist)
    			if (!kprobe_disabled(p))
    				optimize_kprobe(p);
    	}
    	printk(KERN_INFO "Kprobes globally optimized\n");
    out:
    	mutex_unlock(&kprobe_mutex);
    }
    
    static void unoptimize_all_kprobes(void)
    {
    	struct hlist_head *head;
    	struct kprobe *p;
    	unsigned int i;
    
    	mutex_lock(&kprobe_mutex);
    	/* If optimization is already prohibited, just return */
    	if (!kprobes_allow_optimization) {
    		mutex_unlock(&kprobe_mutex);
    		return;
    	}
    
    	kprobes_allow_optimization = false;
    	for (i = 0; i < KPROBE_TABLE_SIZE; i++) {
    		head = &kprobe_table[i];
    		hlist_for_each_entry_rcu(p, head, hlist) {
    			if (!kprobe_disabled(p))
    				unoptimize_kprobe(p, false);
    		}
    	}
    	mutex_unlock(&kprobe_mutex);
    
    	/* Wait for unoptimizing completion */
    	wait_for_kprobe_optimizer();
    	printk(KERN_INFO "Kprobes globally unoptimized\n");
    }
    
    static DEFINE_MUTEX(kprobe_sysctl_mutex);
    int sysctl_kprobes_optimization;
    int proc_kprobes_optimization_handler(struct ctl_table *table, int write,
    				      void __user *buffer, size_t *length,
    				      loff_t *ppos)
    {
    	int ret;
    
    	mutex_lock(&kprobe_sysctl_mutex);
    	sysctl_kprobes_optimization = kprobes_allow_optimization ? 1 : 0;
    	ret = proc_dointvec_minmax(table, write, buffer, length, ppos);
    
    	if (sysctl_kprobes_optimization)
    		optimize_all_kprobes();
    	else
    		unoptimize_all_kprobes();
    	mutex_unlock(&kprobe_sysctl_mutex);
    
    	return ret;
    }
    #endif /* CONFIG_SYSCTL */
    
    /* Put a breakpoint for a probe. Must be called with text_mutex locked */
    static void __arm_kprobe(struct kprobe *p)
    {
    	struct kprobe *_p;
    
    	/* Check collision with other optimized kprobes */
    	_p = get_optimized_kprobe((unsigned long)p->addr);
    	if (unlikely(_p))
    		/* Fallback to unoptimized kprobe */
    		unoptimize_kprobe(_p, true);
    
    	arch_arm_kprobe(p);
    	optimize_kprobe(p);	/* Try to optimize (add kprobe to a list) */
    }
    
    /* Remove the breakpoint of a probe. Must be called with text_mutex locked */
    static void __disarm_kprobe(struct kprobe *p, bool reopt)
    {
    	struct kprobe *_p;
    
    	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 void free_aggr_kprobe(struct kprobe *p)
    {
    	arch_remove_kprobe(p);
    	kfree(p);
    }
    
    static struct kprobe *alloc_aggr_kprobe(struct kprobe *p)
    {
    	return kzalloc(sizeof(struct kprobe), GFP_KERNEL);
    }
    #endif /* CONFIG_OPTPROBES */
    
    #ifdef CONFIG_KPROBES_ON_FTRACE
    static struct ftrace_ops kprobe_ftrace_ops __read_mostly = {
    	.func = kprobe_ftrace_handler,
    	.flags = FTRACE_OPS_FL_SAVE_REGS | FTRACE_OPS_FL_IPMODIFY,
    };
    static int kprobe_ftrace_enabled;
    
    /* Must ensure p->addr is really on ftrace */
    static int prepare_kprobe(struct kprobe *p)
    {
    	if (!kprobe_ftrace(p))
    		return arch_prepare_kprobe(p);
    
    	return arch_prepare_kprobe_ftrace(p);
    }
    
    /* Caller must lock kprobe_mutex */
    static void arm_kprobe_ftrace(struct kprobe *p)
    {
    	int ret;
    
    	ret = ftrace_set_filter_ip(&kprobe_ftrace_ops,
    				   (unsigned long)p->addr, 0, 0);
    	WARN(ret < 0, "Failed to arm kprobe-ftrace at %p (%d)\n", p->addr, ret);
    	kprobe_ftrace_enabled++;
    	if (kprobe_ftrace_enabled == 1) {
    		ret = register_ftrace_function(&kprobe_ftrace_ops);
    		WARN(ret < 0, "Failed to init kprobe-ftrace (%d)\n", ret);
    	}
    }
    
    /* Caller must lock kprobe_mutex */
    static void disarm_kprobe_ftrace(struct kprobe *p)
    {
    	int ret;
    
    	kprobe_ftrace_enabled--;
    	if (kprobe_ftrace_enabled == 0) {
    		ret = unregister_ftrace_function(&kprobe_ftrace_ops);
    		WARN(ret < 0, "Failed to init kprobe-ftrace (%d)\n", ret);
    	}
    	ret = ftrace_set_filter_ip(&kprobe_ftrace_ops,
    			   (unsigned long)p->addr, 1, 0);
    	WARN(ret < 0, "Failed to disarm kprobe-ftrace at %p (%d)\n", p->addr, ret);
    }
    #else	/* !CONFIG_KPROBES_ON_FTRACE */
    #define prepare_kprobe(p)	arch_prepare_kprobe(p)
    #define arm_kprobe_ftrace(p)	do {} while (0)
    #define disarm_kprobe_ftrace(p)	do {} while (0)
    #endif
    
    /* Arm a kprobe with text_mutex */
    static void arm_kprobe(struct kprobe *kp)
    {
    	if (unlikely(kprobe_ftrace(kp))) {
    		arm_kprobe_ftrace(kp);
    		return;
    	}
    	/*
    	 * Here, since __arm_kprobe() doesn't use stop_machine(),
    	 * this doesn't cause deadlock on text_mutex. So, we don't
    	 * need get_online_cpus().
    	 */
    	mutex_lock(&text_mutex);
    	__arm_kprobe(kp);
    	mutex_unlock(&text_mutex);
    }
    
    /* Disarm a kprobe with text_mutex */
    static void disarm_kprobe(struct kprobe *kp, bool reopt)
    {
    	if (unlikely(kprobe_ftrace(kp))) {
    		disarm_kprobe_ftrace(kp);
    		return;
    	}
    	/* Ditto */
    	mutex_lock(&text_mutex);
    	__disarm_kprobe(kp, reopt);
    	mutex_unlock(&text_mutex);
    }
    
    /*
     * Aggregate handlers for multiple kprobes support - these handlers
     * take care of invoking the individual kprobe handlers on p->list
     */
    static int aggr_pre_handler(struct kprobe *p, struct pt_regs *regs)
    {
    	struct kprobe *kp;
    
    	list_for_each_entry_rcu(kp, &p->list, list) {
    		if (kp->pre_handler && likely(!kprobe_disabled(kp))) {
    			set_kprobe_instance(kp);
    			if (kp->pre_handler(kp, regs))
    				return 1;
    		}
    		reset_kprobe_instance();
    	}
    	return 0;
    }
    NOKPROBE_SYMBOL(aggr_pre_handler);
    
    static void aggr_post_handler(struct kprobe *p, struct pt_regs *regs,
    			      unsigned long flags)
    {
    	struct kprobe *kp;
    
    	list_for_each_entry_rcu(kp, &p->list, list) {
    		if (kp->post_handler && likely(!kprobe_disabled(kp))) {
    			set_kprobe_instance(kp);
    			kp->post_handler(kp, regs, flags);
    			reset_kprobe_instance();
    		}
    	}
    }
    NOKPROBE_SYMBOL(aggr_post_handler);
    
    static int aggr_fault_handler(struct kprobe *p, struct pt_regs *regs,
    			      int trapnr)
    {
    	struct kprobe *cur = __this_cpu_read(kprobe_instance);
    
    	/*
    	 * if we faulted "during" the execution of a user specified
    	 * probe handler, invoke just that probe's fault handler
    	 */
    	if (cur && cur->fault_handler) {
    		if (cur->fault_handler(cur, regs, trapnr))
    			return 1;
    	}
    	return 0;
    }
    NOKPROBE_SYMBOL(aggr_fault_handler);
    
    static int aggr_break_handler(struct kprobe *p, struct pt_regs *regs)
    {
    	struct kprobe *cur = __this_cpu_read(kprobe_instance);
    	int ret = 0;
    
    	if (cur && cur->break_handler) {
    		if (cur->break_handler(cur, regs))
    			ret = 1;
    	}
    	reset_kprobe_instance();
    	return ret;
    }
    NOKPROBE_SYMBOL(aggr_break_handler);
    
    /* Walks the list and increments nmissed count for multiprobe case */
    void kprobes_inc_nmissed_count(struct kprobe *p)
    {
    	struct kprobe *kp;
    	if (!kprobe_aggrprobe(p)) {
    		p->nmissed++;
    	} else {
    		list_for_each_entry_rcu(kp, &p->list, list)
    			kp->nmissed++;
    	}
    	return;
    }
    NOKPROBE_SYMBOL(kprobes_inc_nmissed_count);
    
    void recycle_rp_inst(struct kretprobe_instance *ri,
    		     struct hlist_head *head)
    {
    	struct kretprobe *rp = ri->rp;
    
    	/* remove rp inst off the rprobe_inst_table */
    	hlist_del(&ri->hlist);
    	INIT_HLIST_NODE(&ri->hlist);
    	if (likely(rp)) {
    		raw_spin_lock(&rp->lock);
    		hlist_add_head(&ri->hlist, &rp->free_instances);
    		raw_spin_unlock(&rp->lock);
    	} else
    		/* Unregistering */
    		hlist_add_head(&ri->hlist, head);
    }
    NOKPROBE_SYMBOL(recycle_rp_inst);
    
    void kretprobe_hash_lock(struct task_struct *tsk,
    			 struct hlist_head **head, unsigned long *flags)
    __acquires(hlist_lock)
    {
    	unsigned long hash = hash_ptr(tsk, KPROBE_HASH_BITS);
    	raw_spinlock_t *hlist_lock;
    
    	*head = &kretprobe_inst_table[hash];
    	hlist_lock = kretprobe_table_lock_ptr(hash);
    	raw_spin_lock_irqsave(hlist_lock, *flags);
    }
    NOKPROBE_SYMBOL(kretprobe_hash_lock);
    
    static void kretprobe_table_lock(unsigned long hash,
    				 unsigned long *flags)
    __acquires(hlist_lock)
    {
    	raw_spinlock_t *hlist_lock = kretprobe_table_lock_ptr(hash);
    	raw_spin_lock_irqsave(hlist_lock, *flags);
    }
    NOKPROBE_SYMBOL(kretprobe_table_lock);
    
    void kretprobe_hash_unlock(struct task_struct *tsk,
    			   unsigned long *flags)
    __releases(hlist_lock)
    {
    	unsigned long hash = hash_ptr(tsk, KPROBE_HASH_BITS);
    	raw_spinlock_t *hlist_lock;
    
    	hlist_lock = kretprobe_table_lock_ptr(hash);
    	raw_spin_unlock_irqrestore(hlist_lock, *flags);
    }
    NOKPROBE_SYMBOL(kretprobe_hash_unlock);
    
    static void kretprobe_table_unlock(unsigned long hash,
    				   unsigned long *flags)
    __releases(hlist_lock)
    {
    	raw_spinlock_t *hlist_lock = kretprobe_table_lock_ptr(hash);
    	raw_spin_unlock_irqrestore(hlist_lock, *flags);
    }
    NOKPROBE_SYMBOL(kretprobe_table_unlock);
    
    /*
     * This function is called from finish_task_switch when task tk becomes dead,
     * so that we can recycle any function-return probe instances associated
     * with this task. These left over instances represent probed functions
     * that have been called but will never return.
     */
    void kprobe_flush_task(struct task_struct *tk)
    {
    	struct kretprobe_instance *ri;
    	struct hlist_head *head, empty_rp;
    	struct hlist_node *tmp;
    	unsigned long hash, flags = 0;
    
    	if (unlikely(!kprobes_initialized))
    		/* Early boot.  kretprobe_table_locks not yet initialized. */
    		return;
    
    	INIT_HLIST_HEAD(&empty_rp);
    	hash = hash_ptr(tk, KPROBE_HASH_BITS);
    	head = &kretprobe_inst_table[hash];
    	kretprobe_table_lock(hash, &flags);
    	hlist_for_each_entry_safe(ri, tmp, head, hlist) {
    		if (ri->task == tk)
    			recycle_rp_inst(ri, &empty_rp);
    	}
    	kretprobe_table_unlock(hash, &flags);
    	hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {
    		hlist_del(&ri->hlist);
    		kfree(ri);
    	}
    }
    NOKPROBE_SYMBOL(kprobe_flush_task);
    
    static inline void free_rp_inst(struct kretprobe *rp)
    {
    	struct kretprobe_instance *ri;
    	struct hlist_node *next;
    
    	hlist_for_each_entry_safe(ri, next, &rp->free_instances, hlist) {
    		hlist_del(&ri->hlist);
    		kfree(ri);
    	}
    }
    
    static void cleanup_rp_inst(struct kretprobe *rp)
    {
    	unsigned long flags, hash;
    	struct kretprobe_instance *ri;
    	struct hlist_node *next;
    	struct hlist_head *head;
    
    	/* No race here */
    	for (hash = 0; hash < KPROBE_TABLE_SIZE; hash++) {
    		kretprobe_table_lock(hash, &flags);
    		head = &kretprobe_inst_table[hash];
    		hlist_for_each_entry_safe(ri, next, head, hlist) {
    			if (ri->rp == rp)
    				ri->rp = NULL;
    		}
    		kretprobe_table_unlock(hash, &flags);
    	}
    	free_rp_inst(rp);
    }
    NOKPROBE_SYMBOL(cleanup_rp_inst);
    
    /*
    * Add the new probe to ap->list. Fail if this is the
    * second jprobe at the address - two jprobes can't coexist
    */
    static int add_new_kprobe(struct kprobe *ap, struct kprobe *p)
    {
    	BUG_ON(kprobe_gone(ap) || kprobe_gone(p));
    
    	if (p->break_handler || p->post_handler)
    		unoptimize_kprobe(ap, true);	/* Fall back to normal kprobe */
    
    	if (p->break_handler) {
    		if (ap->break_handler)
    			return -EEXIST;
    		list_add_tail_rcu(&p->list, &ap->list);
    		ap->break_handler = aggr_break_handler;
    	} else
    		list_add_rcu(&p->list, &ap->list);
    	if (p->post_handler && !ap->post_handler)
    		ap->post_handler = aggr_post_handler;
    
    	return 0;
    }
    
    /*
     * Fill in the required fields of the "manager kprobe". Replace the
     * earlier kprobe in the hlist with the manager kprobe
     */
    static void init_aggr_kprobe(struct kprobe *ap, struct kprobe *p)
    {
    	/* Copy p's insn slot to ap */
    	copy_kprobe(p, ap);
    	flush_insn_slot(ap);
    	ap->addr = p->addr;
    	ap->flags = p->flags & ~KPROBE_FLAG_OPTIMIZED;
    	ap->pre_handler = aggr_pre_handler;
    	ap->fault_handler = aggr_fault_handler;
    	/* We don't care the kprobe which has gone. */
    	if (p->post_handler && !kprobe_gone(p))
    		ap->post_handler = aggr_post_handler;
    	if (p->break_handler && !kprobe_gone(p))
    		ap->break_handler = aggr_break_handler;
    
    	INIT_LIST_HEAD(&ap->list);
    	INIT_HLIST_NODE(&ap->hlist);
    
    	list_add_rcu(&p->list, &ap->list);
    	hlist_replace_rcu(&p->hlist, &ap->hlist);
    }
    
    /*
     * This is the second or subsequent kprobe at the address - handle
     * the intricacies
     */
    static int register_aggr_kprobe(struct kprobe *orig_p, struct kprobe *p)
    {
    	int ret = 0;
    	struct kprobe *ap = orig_p;
    
    	/* For preparing optimization, jump_label_text_reserved() is called */
    	jump_label_lock();
    	/*
    	 * Get online CPUs to avoid text_mutex deadlock.with stop machine,
    	 * which is invoked by unoptimize_kprobe() in add_new_kprobe()
    	 */
    	get_online_cpus();
    	mutex_lock(&text_mutex);
    
    	if (!kprobe_aggrprobe(orig_p)) {
    		/* If orig_p is not an aggr_kprobe, create new aggr_kprobe. */
    		ap = alloc_aggr_kprobe(orig_p);
    		if (!ap) {
    			ret = -ENOMEM;
    			goto out;
    		}
    		init_aggr_kprobe(ap, orig_p);
    	} else if (kprobe_unused(ap))
    		/* This probe is going to die. Rescue it */
    		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;
    }
    
    bool __weak arch_within_kprobe_blacklist(unsigned long addr)
    {
    	/* The __kprobes marked functions and entry code must not be probed */
    	return addr >= (unsigned long)__kprobes_text_start &&
    	       addr < (unsigned long)__kprobes_text_end;
    }
    
    static bool within_kprobe_blacklist(unsigned long addr)
    {
    	struct kprobe_blacklist_entry *ent;
    
    	if (arch_within_kprobe_blacklist(addr))
    		return true;
    	/*
    	 * If there exists a kprobe_blacklist, verify and
    	 * fail any probe registration in the prohibited area
    	 */
    	list_for_each_entry(ent, &kprobe_blacklist, list) {
    		if (addr >= ent->start_addr && addr < ent->end_addr)
    			return true;
    	}
    
    	return false;
    }
    
    /*
     * If we have a symbol_name argument, look it up and add the offset field
     * to it. This way, we can specify a relative address to a symbol.
     * This returns encoded errors if it fails to look up symbol or invalid
     * combination of parameters.
     */
    static kprobe_opcode_t *kprobe_addr(struct kprobe *p)
    {
    	kprobe_opcode_t *addr = p->addr;
    
    	if ((p->symbol_name && p->addr) ||
    	    (!p->symbol_name && !p->addr))
    		goto invalid;
    
    	if (p->symbol_name) {
    		kprobe_lookup_name(p->symbol_name, addr);
    		if (!addr)
    			return ERR_PTR(-ENOENT);
    	}
    
    	addr = (kprobe_opcode_t *)(((char *)addr) + p->offset);
    	if (addr)
    		return addr;
    
    invalid:
    	return ERR_PTR(-EINVAL);
    }
    
    /* Check passed kprobe is valid and return kprobe in kprobe_table. */
    static struct kprobe *__get_valid_kprobe(struct kprobe *p)
    {
    	struct kprobe *ap, *list_p;
    
    	ap = get_kprobe(p->addr);
    	if (unlikely(!ap))
    		return NULL;
    
    	if (p != ap) {
    		list_for_each_entry_rcu(list_p, &ap->list, list)
    			if (list_p == p)
    			/* kprobe p is a valid probe */
    				goto valid;
    		return NULL;
    	}
    valid:
    	return ap;
    }
    
    /* Return error if the kprobe is being re-registered */
    static inline int check_kprobe_rereg(struct kprobe *p)
    {
    	int ret = 0;
    
    	mutex_lock(&kprobe_mutex);
    	if (__get_valid_kprobe(p))
    		ret = -EINVAL;
    	mutex_unlock(&kprobe_mutex);
    
    	return ret;
    }
    
    int __weak arch_check_ftrace_location(struct kprobe *p)
    {
    	unsigned long ftrace_addr;
    
    	ftrace_addr = ftrace_location((unsigned long)p->addr);
    	if (ftrace_addr) {
    #ifdef CONFIG_KPROBES_ON_FTRACE
    		/* Given address is not on the instruction boundary */
    		if ((unsigned long)p->addr != ftrace_addr)
    			return -EILSEQ;
    		p->flags |= KPROBE_FLAG_FTRACE;
    #else	/* !CONFIG_KPROBES_ON_FTRACE */
    		return -EINVAL;
    #endif
    	}
    	return 0;
    }
    
    static int check_kprobe_address_safe(struct kprobe *p,
    				     struct module **probed_mod)
    {
    	int ret;
    
    	ret = arch_check_ftrace_location(p);
    	if (ret)
    		return ret;
    	jump_label_lock();
    	preempt_disable();
    
    	/* Ensure it is not in reserved area nor out of text */
    	if (!kernel_text_address((unsigned long) p->addr) ||
    	    within_kprobe_blacklist((unsigned long) p->addr) ||
    	    jump_label_text_reserved(p->addr, p->addr)) {
    		ret = -EINVAL;
    		goto out;
    	}
    
    	/* Check if are we probing a module */
    	*probed_mod = __module_text_address((unsigned long) p->addr);
    	if (*probed_mod) {
    		/*
    		 * We must hold a refcount of the probed module while updating
    		 * its code to prohibit unexpected unloading.
    		 */
    		if (unlikely(!try_module_get(*probed_mod))) {
    			ret = -ENOENT;
    			goto out;
    		}
    
    		/*
    		 * If the module freed .init.text, we couldn't insert
    		 * kprobes in there.
    		 */
    		if (within_module_init((unsigned long)p->addr, *probed_mod) &&
    		    (*probed_mod)->state != MODULE_STATE_COMING) {
    			module_put(*probed_mod);
    			*probed_mod = NULL;
    			ret = -ENOENT;
    		}
    	}
    out:
    	preempt_enable();
    	jump_label_unlock();
    
    	return ret;
    }
    
    int register_kprobe(struct kprobe *p)
    {
    	int ret;
    	struct kprobe *old_p;
    	struct module *probed_mod;
    	kprobe_opcode_t *addr;
    
    	/* Adjust probe address from symbol */
    	addr = kprobe_addr(p);
    	if (IS_ERR(addr))
    		return PTR_ERR(addr);
    	p->addr = addr;
    
    	ret = check_kprobe_rereg(p);
    	if (ret)
    		return ret;
    
    	/* User can pass only KPROBE_FLAG_DISABLED to register_kprobe */
    	p->flags &= KPROBE_FLAG_DISABLED;
    	p->nmissed = 0;
    	INIT_LIST_HEAD(&p->list);
    
    	ret = check_kprobe_address_safe(p, &probed_mod);
    	if (ret)
    		return ret;
    
    	mutex_lock(&kprobe_mutex);
    
    	old_p = get_kprobe(p->addr);
    	if (old_p) {
    		/* Since this may unoptimize old_p, locking text_mutex. */
    		ret = register_aggr_kprobe(old_p, p);
    		goto out;
    	}
    
    	mutex_lock(&text_mutex);	/* Avoiding text modification */
    	ret = prepare_kprobe(p);
    	mutex_unlock(&text_mutex);
    	if (ret)
    		goto out;
    
    	INIT_HLIST_NODE(&p->hlist);
    	hlist_add_head_rcu(&p->hlist,
    		       &kprobe_table[hash_ptr(p->addr, KPROBE_HASH_BITS)]);
    
    	if (!kprobes_all_disarmed && !kprobe_disabled(p))
    		arm_kprobe(p);
    
    	/* Try to optimize kprobe */
    	try_to_optimize_kprobe(p);
    
    out:
    	mutex_unlock(&kprobe_mutex);
    
    	if (probed_mod)
    		module_put(probed_mod);
    
    	return ret;
    }
    EXPORT_SYMBOL_GPL(register_kprobe);
    
    /* Check if all probes on the aggrprobe are disabled */
    static int aggr_kprobe_disabled(struct kprobe *ap)
    {
    	struct kprobe *kp;
    
    	list_for_each_entry_rcu(kp, &ap->list, list)
    		if (!kprobe_disabled(kp))
    			/*
    			 * There is an active probe on the list.
    			 * We can't disable this ap.
    			 */
    			return 0;
    
    	return 1;
    }
    
    /* Disable one kprobe: Make sure called under kprobe_mutex is locked */
    static struct kprobe *__disable_kprobe(struct kprobe *p)
    {
    	struct kprobe *orig_p;
    
    	/* Get an original kprobe for return */
    	orig_p = __get_valid_kprobe(p);
    	if (unlikely(orig_p == NULL))
    		return NULL;
    
    	if (!kprobe_disabled(p)) {
    		/* Disable probe if it is a child probe */
    		if (p != orig_p)
    			p->flags |= KPROBE_FLAG_DISABLED;
    
    		/* Try to disarm and disable this/parent probe */
    		if (p == orig_p || aggr_kprobe_disabled(orig_p)) {
    			disarm_kprobe(orig_p, true);
    			orig_p->flags |= KPROBE_FLAG_DISABLED;
    		}
    	}
    
    	return orig_p;
    }
    
    /*
     * Unregister a kprobe without a scheduler synchronization.
     */
    static int __unregister_kprobe_top(struct kprobe *p)
    {
    	struct kprobe *ap, *list_p;
    
    	/* Disable kprobe. This will disarm it if needed. */
    	ap = __disable_kprobe(p);
    	if (ap == NULL)
    		return -EINVAL;
    
    	if (ap == p)
    		/*
    		 * This probe is an independent(and non-optimized) kprobe
    		 * (not an aggrprobe). Remove from the hash list.
    		 */
    		goto disarmed;
    
    	/* Following process expects this probe is an aggrprobe */
    	WARN_ON(!kprobe_aggrprobe(ap));
    
    	if (list_is_singular(&ap->list) && kprobe_disarmed(ap))
    		/*
    		 * !disarmed could be happen if the probe is under delayed
    		 * unoptimizing.
    		 */
    		goto disarmed;
    	else {
    		/* If disabling probe has special handlers, update aggrprobe */
    		if (p->break_handler && !kprobe_gone(p))
    			ap->break_handler = NULL;
    		if (p->post_handler && !kprobe_gone(p)) {
    			list_for_each_entry_rcu(list_p, &ap->list, list) {
    				if ((list_p != p) && (list_p->post_handler))
    					goto noclean;
    			}
    			ap->post_handler = NULL;
    		}
    noclean:
    		/*
    		 * Remove from the aggrprobe: this path will do nothing in
    		 * __unregister_kprobe_bottom().
    		 */
    		list_del_rcu(&p->list);
    		if (!kprobe_disabled(ap) && !kprobes_all_disarmed)
    			/*
    			 * Try to optimize this probe again, because post
    			 * handler may have been changed.
    			 */
    			optimize_kprobe(ap);
    	}
    	return 0;
    
    disarmed:
    	BUG_ON(!kprobe_disarmed(ap));
    	hlist_del_rcu(&ap->hlist);
    	return 0;
    }
    
    static void __unregister_kprobe_bottom(struct kprobe *p)
    {
    	struct kprobe *ap;
    
    	if (list_empty(&p->list))
    		/* This is an independent kprobe */
    		arch_remove_kprobe(p);
    	else if (list_is_singular(&p->list)) {
    		/* This is the last child of an aggrprobe */
    		ap = list_entry(p->list.next, struct kprobe, list);
    		list_del(&p->list);
    		free_aggr_kprobe(ap);
    	}
    	/* Otherwise, do nothing. */
    }
    
    int register_kprobes(struct kprobe **kps, int num)
    {
    	int i, ret = 0;
    
    	if (num <= 0)
    		return -EINVAL;
    	for (i = 0; i < num; i++) {
    		ret = register_kprobe(kps[i]);
    		if (ret < 0) {
    			if (i > 0)
    				unregister_kprobes(kps, i);
    			break;
    		}
    	}
    	return ret;
    }
    EXPORT_SYMBOL_GPL(register_kprobes);
    
    void unregister_kprobe(struct kprobe *p)
    {
    	unregister_kprobes(&p, 1);
    }
    EXPORT_SYMBOL_GPL(unregister_kprobe);
    
    void unregister_kprobes(struct kprobe **kps, int num)
    {
    	int i;
    
    	if (num <= 0)
    		return;
    	mutex_lock(&kprobe_mutex);
    	for (i = 0; i < num; i++)
    		if (__unregister_kprobe_top(kps[i]) < 0)
    			kps[i]->addr = NULL;
    	mutex_unlock(&kprobe_mutex);
    
    	synchronize_sched();
    	for (i = 0; i < num; i++)
    		if (kps[i]->addr)
    			__unregister_kprobe_bottom(kps[i]);
    }
    EXPORT_SYMBOL_GPL(unregister_kprobes);
    
    static struct notifier_block kprobe_exceptions_nb = {
    	.notifier_call = kprobe_exceptions_notify,
    	.priority = 0x7fffffff /* we need to be notified first */
    };
    
    unsigned long __weak arch_deref_entry_point(void *entry)
    {
    	return (unsigned long)entry;
    }
    
    int register_jprobes(struct jprobe **jps, int num)
    {
    	struct jprobe *jp;
    	int ret = 0, i;
    
    	if (num <= 0)
    		return -EINVAL;
    	for (i = 0; i < num; i++) {
    		unsigned long addr, offset;
    		jp = jps[i];
    		addr = arch_deref_entry_point(jp->entry);
    
    		/* Verify probepoint is a function entry point */
    		if (kallsyms_lookup_size_offset(addr, NULL, &offset) &&
    		    offset == 0) {
    			jp->kp.pre_handler = setjmp_pre_handler;
    			jp->kp.break_handler = longjmp_break_handler;
    			ret = register_kprobe(&jp->kp);
    		} else
    			ret = -EINVAL;
    
    		if (ret < 0) {
    			if (i > 0)
    				unregister_jprobes(jps, i);
    			break;
    		}
    	}
    	return ret;
    }
    EXPORT_SYMBOL_GPL(register_jprobes);
    
    int register_jprobe(struct jprobe *jp)
    {
    	return register_jprobes(&jp, 1);
    }
    EXPORT_SYMBOL_GPL(register_jprobe);
    
    void unregister_jprobe(struct jprobe *jp)
    {
    	unregister_jprobes(&jp, 1);
    }
    EXPORT_SYMBOL_GPL(unregister_jprobe);
    
    void unregister_jprobes(struct jprobe **jps, int num)
    {
    	int i;
    
    	if (num <= 0)
    		return;
    	mutex_lock(&kprobe_mutex);
    	for (i = 0; i < num; i++)
    		if (__unregister_kprobe_top(&jps[i]->kp) < 0)
    			jps[i]->kp.addr = NULL;
    	mutex_unlock(&kprobe_mutex);
    
    	synchronize_sched();
    	for (i = 0; i < num; i++) {
    		if (jps[i]->kp.addr)
    			__unregister_kprobe_bottom(&jps[i]->kp);
    	}
    }
    EXPORT_SYMBOL_GPL(unregister_jprobes);
    
    #ifdef CONFIG_KRETPROBES
    /*
     * This kprobe pre_handler is registered with every kretprobe. When probe
     * hits it will set up the return probe.
     */
    static int pre_handler_kretprobe(struct kprobe *p, struct pt_regs *regs)
    {
    	struct kretprobe *rp = container_of(p, struct kretprobe, kp);
    	unsigned long hash, flags = 0;
    	struct kretprobe_instance *ri;
    
    	/*
    	 * To avoid deadlocks, prohibit return probing in NMI contexts,
    	 * just skip the probe and increase the (inexact) 'nmissed'
    	 * statistical counter, so that the user is informed that
    	 * something happened:
    	 */
    	if (unlikely(in_nmi())) {
    		rp->nmissed++;
    		return 0;
    	}
    
    	/* TODO: consider to only swap the RA after the last pre_handler fired */
    	hash = hash_ptr(current, KPROBE_HASH_BITS);
    	raw_spin_lock_irqsave(&rp->lock, flags);
    	if (!hlist_empty(&rp->free_instances)) {
    		ri = hlist_entry(rp->free_instances.first,
    				struct kretprobe_instance, hlist);
    		hlist_del(&ri->hlist);
    		raw_spin_unlock_irqrestore(&rp->lock, flags);
    
    		ri->rp = rp;
    		ri->task = current;
    
    		if (rp->entry_handler && rp->entry_handler(ri, regs)) {
    			raw_spin_lock_irqsave(&rp->lock, flags);
    			hlist_add_head(&ri->hlist, &rp->free_instances);
    			raw_spin_unlock_irqrestore(&rp->lock, flags);
    			return 0;
    		}
    
    		arch_prepare_kretprobe(ri, regs);
    
    		/* XXX(hch): why is there no hlist_move_head? */
    		INIT_HLIST_NODE(&ri->hlist);
    		kretprobe_table_lock(hash, &flags);
    		hlist_add_head(&ri->hlist, &kretprobe_inst_table[hash]);
    		kretprobe_table_unlock(hash, &flags);
    	} else {
    		rp->nmissed++;
    		raw_spin_unlock_irqrestore(&rp->lock, flags);
    	}
    	return 0;
    }
    NOKPROBE_SYMBOL(pre_handler_kretprobe);
    
    int register_kretprobe(struct kretprobe *rp)
    {
    	int ret = 0;
    	struct kretprobe_instance *inst;
    	int i;
    	void *addr;
    
    	if (kretprobe_blacklist_size) {
    		addr = kprobe_addr(&rp->kp);
    		if (IS_ERR(addr))
    			return PTR_ERR(addr);
    
    		for (i = 0; kretprobe_blacklist[i].name != NULL; i++) {
    			if (kretprobe_blacklist[i].addr == addr)
    				return -EINVAL;
    		}
    	}
    
    	rp->kp.pre_handler = pre_handler_kretprobe;
    	rp->kp.post_handler = NULL;
    	rp->kp.fault_handler = NULL;
    	rp->kp.break_handler = NULL;
    
    	/* Pre-allocate memory for max kretprobe instances */
    	if (rp->maxactive <= 0) {
    #ifdef CONFIG_PREEMPT
    		rp->maxactive = max_t(unsigned int, 10, 2*num_possible_cpus());
    #else
    		rp->maxactive = num_possible_cpus();
    #endif
    	}
    	raw_spin_lock_init(&rp->lock);
    	INIT_HLIST_HEAD(&rp->free_instances);
    	for (i = 0; i < rp->maxactive; i++) {
    		inst = kmalloc(sizeof(struct kretprobe_instance) +
    			       rp->data_size, GFP_KERNEL);
    		if (inst == NULL) {
    			free_rp_inst(rp);
    			return -ENOMEM;
    		}
    		INIT_HLIST_NODE(&inst->hlist);
    		hlist_add_head(&inst->hlist, &rp->free_instances);
    	}
    
    	rp->nmissed = 0;
    	/* Establish function entry probe point */
    	ret = register_kprobe(&rp->kp);
    	if (ret != 0)
    		free_rp_inst(rp);
    	return ret;
    }
    EXPORT_SYMBOL_GPL(register_kretprobe);
    
    int register_kretprobes(struct kretprobe **rps, int num)
    {
    	int ret = 0, i;
    
    	if (num <= 0)
    		return -EINVAL;
    	for (i = 0; i < num; i++) {
    		ret = register_kretprobe(rps[i]);
    		if (ret < 0) {
    			if (i > 0)
    				unregister_kretprobes(rps, i);
    			break;
    		}
    	}
    	return ret;
    }
    EXPORT_SYMBOL_GPL(register_kretprobes);
    
    void unregister_kretprobe(struct kretprobe *rp)
    {
    	unregister_kretprobes(&rp, 1);
    }
    EXPORT_SYMBOL_GPL(unregister_kretprobe);
    
    void unregister_kretprobes(struct kretprobe **rps, int num)
    {
    	int i;
    
    	if (num <= 0)
    		return;
    	mutex_lock(&kprobe_mutex);
    	for (i = 0; i < num; i++)
    		if (__unregister_kprobe_top(&rps[i]->kp) < 0)
    			rps[i]->kp.addr = NULL;
    	mutex_unlock(&kprobe_mutex);
    
    	synchronize_sched();
    	for (i = 0; i < num; i++) {
    		if (rps[i]->kp.addr) {
    			__unregister_kprobe_bottom(&rps[i]->kp);
    			cleanup_rp_inst(rps[i]);
    		}
    	}
    }
    EXPORT_SYMBOL_GPL(unregister_kretprobes);
    
    #else /* CONFIG_KRETPROBES */
    int register_kretprobe(struct kretprobe *rp)
    {
    	return -ENOSYS;
    }
    EXPORT_SYMBOL_GPL(register_kretprobe);
    
    int register_kretprobes(struct kretprobe **rps, int num)
    {
    	return -ENOSYS;
    }
    EXPORT_SYMBOL_GPL(register_kretprobes);
    
    void unregister_kretprobe(struct kretprobe *rp)
    {
    }
    EXPORT_SYMBOL_GPL(unregister_kretprobe);
    
    void unregister_kretprobes(struct kretprobe **rps, int num)
    {
    }
    EXPORT_SYMBOL_GPL(unregister_kretprobes);
    
    static int pre_handler_kretprobe(struct kprobe *p, struct pt_regs *regs)
    {
    	return 0;
    }
    NOKPROBE_SYMBOL(pre_handler_kretprobe);
    
    #endif /* CONFIG_KRETPROBES */
    
    /* Set the kprobe gone and remove its instruction buffer. */
    static void kill_kprobe(struct kprobe *p)
    {
    	struct kprobe *kp;
    
    	p->flags |= KPROBE_FLAG_GONE;
    	if (kprobe_aggrprobe(p)) {
    		/*
    		 * If this is an aggr_kprobe, we have to list all the
    		 * chained probes and mark them GONE.
    		 */
    		list_for_each_entry_rcu(kp, &p->list, list)
    			kp->flags |= KPROBE_FLAG_GONE;
    		p->post_handler = NULL;
    		p->break_handler = NULL;
    		kill_optimized_kprobe(p);
    	}
    	/*
    	 * Here, we can remove insn_slot safely, because no thread calls
    	 * the original probed function (which will be freed soon) any more.
    	 */
    	arch_remove_kprobe(p);
    }
    
    /* Disable one kprobe */
    int disable_kprobe(struct kprobe *kp)
    {
    	int ret = 0;
    
    	mutex_lock(&kprobe_mutex);
    
    	/* Disable this kprobe */
    	if (__disable_kprobe(kp) == NULL)
    		ret = -EINVAL;
    
    	mutex_unlock(&kprobe_mutex);
    	return ret;
    }
    EXPORT_SYMBOL_GPL(disable_kprobe);
    
    /* Enable one kprobe */
    int enable_kprobe(struct kprobe *kp)
    {
    	int ret = 0;
    	struct kprobe *p;
    
    	mutex_lock(&kprobe_mutex);
    
    	/* Check whether specified probe is valid. */
    	p = __get_valid_kprobe(kp);
    	if (unlikely(p == NULL)) {
    		ret = -EINVAL;
    		goto out;
    	}
    
    	if (kprobe_gone(kp)) {
    		/* This kprobe has gone, we couldn't enable it. */
    		ret = -EINVAL;
    		goto out;
    	}
    
    	if (p != kp)
    		kp->flags &= ~KPROBE_FLAG_DISABLED;
    
    	if (!kprobes_all_disarmed && kprobe_disabled(p)) {
    		p->flags &= ~KPROBE_FLAG_DISABLED;
    		arm_kprobe(p);
    	}
    out:
    	mutex_unlock(&kprobe_mutex);
    	return ret;
    }
    EXPORT_SYMBOL_GPL(enable_kprobe);
    
    void dump_kprobe(struct kprobe *kp)
    {
    	printk(KERN_WARNING "Dumping kprobe:\n");
    	printk(KERN_WARNING "Name: %s\nAddress: %p\nOffset: %x\n",
    	       kp->symbol_name, kp->addr, kp->offset);
    }
    NOKPROBE_SYMBOL(dump_kprobe);
    
    /*
     * Lookup and populate the kprobe_blacklist.
     *
     * Unlike the kretprobe blacklist, we'll need to determine
     * the range of addresses that belong to the said functions,
     * since a kprobe need not necessarily be at the beginning
     * of a function.
     */
    static int __init populate_kprobe_blacklist(unsigned long *start,
    					     unsigned long *end)
    {
    	unsigned long *iter;
    	struct kprobe_blacklist_entry *ent;
    	unsigned long entry, offset = 0, size = 0;
    
    	for (iter = start; iter < end; iter++) {
    		entry = arch_deref_entry_point((void *)*iter);
    
    		if (!kernel_text_address(entry) ||
    		    !kallsyms_lookup_size_offset(entry, &size, &offset)) {
    			pr_err("Failed to find blacklist at %p\n",
    				(void *)entry);
    			continue;
    		}
    
    		ent = kmalloc(sizeof(*ent), GFP_KERNEL);
    		if (!ent)
    			return -ENOMEM;
    		ent->start_addr = entry;
    		ent->end_addr = entry + size;
    		INIT_LIST_HEAD(&ent->list);
    		list_add_tail(&ent->list, &kprobe_blacklist);
    	}
    	return 0;
    }
    
    /* Module notifier call back, checking kprobes on the module */
    static int kprobes_module_callback(struct notifier_block *nb,
    				   unsigned long val, void *data)
    {
    	struct module *mod = data;
    	struct hlist_head *head;
    	struct kprobe *p;
    	unsigned int i;
    	int checkcore = (val == MODULE_STATE_GOING);
    
    	if (val != MODULE_STATE_GOING && val != MODULE_STATE_LIVE)
    		return NOTIFY_DONE;
    
    	/*
    	 * When MODULE_STATE_GOING was notified, both of module .text and
    	 * .init.text sections would be freed. When MODULE_STATE_LIVE was
    	 * notified, only .init.text section would be freed. We need to
    	 * disable kprobes which have been inserted in the sections.
    	 */
    	mutex_lock(&kprobe_mutex);
    	for (i = 0; i < KPROBE_TABLE_SIZE; i++) {
    		head = &kprobe_table[i];
    		hlist_for_each_entry_rcu(p, head, hlist)
    			if (within_module_init((unsigned long)p->addr, mod) ||
    			    (checkcore &&
    			     within_module_core((unsigned long)p->addr, mod))) {
    				/*
    				 * The vaddr this probe is installed will soon
    				 * be vfreed buy not synced to disk. Hence,
    				 * disarming the breakpoint isn't needed.
    				 */
    				kill_kprobe(p);
    			}
    	}
    	mutex_unlock(&kprobe_mutex);
    	return NOTIFY_DONE;
    }
    
    static struct notifier_block kprobe_module_nb = {
    	.notifier_call = kprobes_module_callback,
    	.priority = 0
    };
    
    /* Markers of _kprobe_blacklist section */
    extern unsigned long __start_kprobe_blacklist[];
    extern unsigned long __stop_kprobe_blacklist[];
    
    static int __init init_kprobes(void)
    {
    	int i, err = 0;
    
    	/* FIXME allocate the probe table, currently defined statically */
    	/* initialize all list heads */
    	for (i = 0; i < KPROBE_TABLE_SIZE; i++) {
    		INIT_HLIST_HEAD(&kprobe_table[i]);
    		INIT_HLIST_HEAD(&kretprobe_inst_table[i]);
    		raw_spin_lock_init(&(kretprobe_table_locks[i].lock));
    	}
    
    	err = populate_kprobe_blacklist(__start_kprobe_blacklist,
    					__stop_kprobe_blacklist);
    	if (err) {
    		pr_err("kprobes: failed to populate blacklist: %d\n", err);
    		pr_err("Please take care of using kprobes.\n");
    	}
    
    	if (kretprobe_blacklist_size) {
    		/* lookup the function address from its name */
    		for (i = 0; kretprobe_blacklist[i].name != NULL; i++) {
    			kprobe_lookup_name(kretprobe_blacklist[i].name,
    					   kretprobe_blacklist[i].addr);
    			if (!kretprobe_blacklist[i].addr)
    				printk("kretprobe: lookup failed: %s\n",
    				       kretprobe_blacklist[i].name);
    		}
    	}
    
    #if defined(CONFIG_OPTPROBES)
    #if defined(__ARCH_WANT_KPROBES_INSN_SLOT)
    	/* Init kprobe_optinsn_slots */
    	kprobe_optinsn_slots.insn_size = MAX_OPTINSN_SIZE;
    #endif
    	/* By default, kprobes can be optimized */
    	kprobes_allow_optimization = true;
    #endif
    
    	/* By default, kprobes are armed */
    	kprobes_all_disarmed = false;
    
    	err = arch_init_kprobes();
    	if (!err)
    		err = register_die_notifier(&kprobe_exceptions_nb);
    	if (!err)
    		err = register_module_notifier(&kprobe_module_nb);
    
    	kprobes_initialized = (err == 0);
    
    	if (!err)
    		init_test_probes();
    	return err;
    }
    
    #ifdef CONFIG_DEBUG_FS
    static void report_probe(struct seq_file *pi, struct kprobe *p,
    		const char *sym, int offset, char *modname, struct kprobe *pp)
    {
    	char *kprobe_type;
    
    	if (p->pre_handler == pre_handler_kretprobe)
    		kprobe_type = "r";
    	else if (p->pre_handler == setjmp_pre_handler)
    		kprobe_type = "j";
    	else
    		kprobe_type = "k";
    
    	if (sym)
    		seq_printf(pi, "%p  %s  %s+0x%x  %s ",
    			p->addr, kprobe_type, sym, offset,
    			(modname ? modname : " "));
    	else
    		seq_printf(pi, "%p  %s  %p ",
    			p->addr, kprobe_type, p->addr);
    
    	if (!pp)
    		pp = p;
    	seq_printf(pi, "%s%s%s%s\n",
    		(kprobe_gone(p) ? "[GONE]" : ""),
    		((kprobe_disabled(p) && !kprobe_gone(p)) ?  "[DISABLED]" : ""),
    		(kprobe_optimized(pp) ? "[OPTIMIZED]" : ""),
    		(kprobe_ftrace(pp) ? "[FTRACE]" : ""));
    }
    
    static void *kprobe_seq_start(struct seq_file *f, loff_t *pos)
    {
    	return (*pos < KPROBE_TABLE_SIZE) ? pos : NULL;
    }
    
    static void *kprobe_seq_next(struct seq_file *f, void *v, loff_t *pos)
    {
    	(*pos)++;
    	if (*pos >= KPROBE_TABLE_SIZE)
    		return NULL;
    	return pos;
    }
    
    static void kprobe_seq_stop(struct seq_file *f, void *v)
    {
    	/* Nothing to do */
    }
    
    static int show_kprobe_addr(struct seq_file *pi, void *v)
    {
    	struct hlist_head *head;
    	struct kprobe *p, *kp;
    	const char *sym = NULL;
    	unsigned int i = *(loff_t *) v;
    	unsigned long offset = 0;
    	char *modname, namebuf[KSYM_NAME_LEN];
    
    	head = &kprobe_table[i];
    	preempt_disable();
    	hlist_for_each_entry_rcu(p, head, hlist) {
    		sym = kallsyms_lookup((unsigned long)p->addr, NULL,
    					&offset, &modname, namebuf);
    		if (kprobe_aggrprobe(p)) {
    			list_for_each_entry_rcu(kp, &p->list, list)
    				report_probe(pi, kp, sym, offset, modname, p);
    		} else
    			report_probe(pi, p, sym, offset, modname, NULL);
    	}
    	preempt_enable();
    	return 0;
    }
    
    static const struct seq_operations kprobes_seq_ops = {
    	.start = kprobe_seq_start,
    	.next  = kprobe_seq_next,
    	.stop  = kprobe_seq_stop,
    	.show  = show_kprobe_addr
    };
    
    static int kprobes_open(struct inode *inode, struct file *filp)
    {
    	return seq_open(filp, &kprobes_seq_ops);
    }
    
    static const struct file_operations debugfs_kprobes_operations = {
    	.open           = kprobes_open,
    	.read           = seq_read,
    	.llseek         = seq_lseek,
    	.release        = seq_release,
    };
    
    /* kprobes/blacklist -- shows which functions can not be probed */
    static void *kprobe_blacklist_seq_start(struct seq_file *m, loff_t *pos)
    {
    	return seq_list_start(&kprobe_blacklist, *pos);
    }
    
    static void *kprobe_blacklist_seq_next(struct seq_file *m, void *v, loff_t *pos)
    {
    	return seq_list_next(v, &kprobe_blacklist, pos);
    }
    
    static int kprobe_blacklist_seq_show(struct seq_file *m, void *v)
    {
    	struct kprobe_blacklist_entry *ent =
    		list_entry(v, struct kprobe_blacklist_entry, list);
    
    	seq_printf(m, "0x%p-0x%p\t%ps\n", (void *)ent->start_addr,
    		   (void *)ent->end_addr, (void *)ent->start_addr);
    	return 0;
    }
    
    static const struct seq_operations kprobe_blacklist_seq_ops = {
    	.start = kprobe_blacklist_seq_start,
    	.next  = kprobe_blacklist_seq_next,
    	.stop  = kprobe_seq_stop,	/* Reuse void function */
    	.show  = kprobe_blacklist_seq_show,
    };
    
    static int kprobe_blacklist_open(struct inode *inode, struct file *filp)
    {
    	return seq_open(filp, &kprobe_blacklist_seq_ops);
    }
    
    static const struct file_operations debugfs_kprobe_blacklist_ops = {
    	.open           = kprobe_blacklist_open,
    	.read           = seq_read,
    	.llseek         = seq_lseek,
    	.release        = seq_release,
    };
    
    static void arm_all_kprobes(void)
    {
    	struct hlist_head *head;
    	struct kprobe *p;
    	unsigned int i;
    
    	mutex_lock(&kprobe_mutex);
    
    	/* If kprobes are armed, just return */
    	if (!kprobes_all_disarmed)
    		goto already_enabled;
    
    	/*
    	 * optimize_kprobe() called by arm_kprobe() checks
    	 * kprobes_all_disarmed, so set kprobes_all_disarmed before
    	 * arm_kprobe.
    	 */
    	kprobes_all_disarmed = false;
    	/* Arming kprobes doesn't optimize kprobe itself */
    	for (i = 0; i < KPROBE_TABLE_SIZE; i++) {
    		head = &kprobe_table[i];
    		hlist_for_each_entry_rcu(p, head, hlist)
    			if (!kprobe_disabled(p))
    				arm_kprobe(p);
    	}
    
    	printk(KERN_INFO "Kprobes globally enabled\n");
    
    already_enabled:
    	mutex_unlock(&kprobe_mutex);
    	return;
    }
    
    static void disarm_all_kprobes(void)
    {
    	struct hlist_head *head;
    	struct kprobe *p;
    	unsigned int i;
    
    	mutex_lock(&kprobe_mutex);
    
    	/* If kprobes are already disarmed, just return */
    	if (kprobes_all_disarmed) {
    		mutex_unlock(&kprobe_mutex);
    		return;
    	}
    
    	kprobes_all_disarmed = true;
    	printk(KERN_INFO "Kprobes globally disabled\n");
    
    	for (i = 0; i < KPROBE_TABLE_SIZE; i++) {
    		head = &kprobe_table[i];
    		hlist_for_each_entry_rcu(p, head, hlist) {
    			if (!arch_trampoline_kprobe(p) && !kprobe_disabled(p))
    				disarm_kprobe(p, false);
    		}
    	}
    	mutex_unlock(&kprobe_mutex);
    
    	/* Wait for disarming all kprobes by optimizer */
    	wait_for_kprobe_optimizer();
    }
    
    /*
     * XXX: The debugfs bool file interface doesn't allow for callbacks
     * when the bool state is switched. We can reuse that facility when
     * available
     */
    static ssize_t read_enabled_file_bool(struct file *file,
    	       char __user *user_buf, size_t count, loff_t *ppos)
    {
    	char buf[3];
    
    	if (!kprobes_all_disarmed)
    		buf[0] = '1';
    	else
    		buf[0] = '0';
    	buf[1] = '\n';
    	buf[2] = 0x00;
    	return simple_read_from_buffer(user_buf, count, ppos, buf, 2);
    }
    
    static ssize_t write_enabled_file_bool(struct file *file,
    	       const char __user *user_buf, size_t count, loff_t *ppos)
    {
    	char buf[32];
    	size_t buf_size;
    
    	buf_size = min(count, (sizeof(buf)-1));
    	if (copy_from_user(buf, user_buf, buf_size))
    		return -EFAULT;
    
    	buf[buf_size] = '\0';
    	switch (buf[0]) {
    	case 'y':
    	case 'Y':
    	case '1':
    		arm_all_kprobes();
    		break;
    	case 'n':
    	case 'N':
    	case '0':
    		disarm_all_kprobes();
    		break;
    	default:
    		return -EINVAL;
    	}
    
    	return count;
    }
    
    static const struct file_operations fops_kp = {
    	.read =         read_enabled_file_bool,
    	.write =        write_enabled_file_bool,
    	.llseek =	default_llseek,
    };
    
    static int __init debugfs_kprobe_init(void)
    {
    	struct dentry *dir, *file;
    	unsigned int value = 1;
    
    	dir = debugfs_create_dir("kprobes", NULL);
    	if (!dir)
    		return -ENOMEM;
    
    	file = debugfs_create_file("list", 0444, dir, NULL,
    				&debugfs_kprobes_operations);
    	if (!file)
    		goto error;
    
    	file = debugfs_create_file("enabled", 0600, dir,
    					&value, &fops_kp);
    	if (!file)
    		goto error;
    
    	file = debugfs_create_file("blacklist", 0444, dir, NULL,
    				&debugfs_kprobe_blacklist_ops);
    	if (!file)
    		goto error;
    
    	return 0;
    
    error:
    	debugfs_remove(dir);
    	return -ENOMEM;
    }
    
    late_initcall(debugfs_kprobe_init);
    #endif /* CONFIG_DEBUG_FS */
    
    module_init(init_kprobes);
    
    /* defined in arch/.../kernel/kprobes.c */
    EXPORT_SYMBOL_GPL(jprobe_return);