Adding upstream version 4.19.249.upstream/4.19.249

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 2699 insertions, 0 deletions

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
new file mode 100644
index 000000000..993b84cc1
--- /dev/null
+++ b/kernel/kprobes.c
@@ -0,0 +1,2699 @@
+/*
+ *  Kernel Probes (KProbes)
+ *  kernel/kprobes.c
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ *
+ * Copyright (C) IBM Corporation, 2002, 2004
+ *
+ * 2002-Oct	Created by Vamsi Krishna S <vamsi_krishna@in.ibm.com> Kernel
+ *		Probes initial implementation (includes suggestions from
+ *		Rusty Russell).
+ * 2004-Aug	Updated by Prasanna S Panchamukhi <prasanna@in.ibm.com> with
+ *		hlists and exceptions notifier as suggested by Andi Kleen.
+ * 2004-July	Suparna Bhattacharya <suparna@in.ibm.com> added jumper probes
+ *		interface to access function arguments.
+ * 2004-Sep	Prasanna S Panchamukhi <prasanna@in.ibm.com> Changed Kprobes
+ *		exceptions notifier to be first on the priority list.
+ * 2005-May	Hien Nguyen <hien@us.ibm.com>, Jim Keniston
+ *		<jkenisto@us.ibm.com> and Prasanna S Panchamukhi
+ *		<prasanna@in.ibm.com> added function-return probes.
+ */
+#include <linux/kprobes.h>
+#include <linux/hash.h>
+#include <linux/init.h>
+#include <linux/slab.h>
+#include <linux/stddef.h>
+#include <linux/export.h>
+#include <linux/moduleloader.h>
+#include <linux/kallsyms.h>
+#include <linux/freezer.h>
+#include <linux/seq_file.h>
+#include <linux/debugfs.h>
+#include <linux/sysctl.h>
+#include <linux/kdebug.h>
+#include <linux/memory.h>
+#include <linux/ftrace.h>
+#include <linux/cpu.h>
+#include <linux/jump_label.h>
+
+#include <asm/sections.h>
+#include <asm/cacheflush.h>
+#include <asm/errno.h>
+#include <linux/uaccess.h>
+
+#define KPROBE_HASH_BITS 6
+#define KPROBE_TABLE_SIZE (1 << KPROBE_HASH_BITS)
+
+
+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];
+
+kprobe_opcode_t * __weak kprobe_lookup_name(const char *name,
+					unsigned int __unused)
+{
+	return ((kprobe_opcode_t *)(kallsyms_lookup_name(name)));
+}
+
+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,
+};
+
+void __weak *alloc_insn_page(void)
+{
+	return module_alloc(PAGE_SIZE);
+}
+
+void __weak free_insn_page(void *page)
+{
+	module_memfree(page);
+}
+
+struct kprobe_insn_cache kprobe_insn_slots = {
+	.mutex = __MUTEX_INITIALIZER(kprobe_insn_slots.mutex),
+	.alloc = alloc_insn_page,
+	.free = free_insn_page,
+	.pages = LIST_HEAD_INIT(kprobe_insn_slots.pages),
+	.insn_size = MAX_INSN_SIZE,
+	.nr_garbage = 0,
+};
+static int collect_garbage_slots(struct kprobe_insn_cache *c);
+
+/**
+ * __get_insn_slot() - Find a slot on an executable page for an instruction.
+ * We allocate an executable page if there's no room on existing ones.
+ */
+kprobe_opcode_t *__get_insn_slot(struct kprobe_insn_cache *c)
+{
+	struct kprobe_insn_page *kip;
+	kprobe_opcode_t *slot = NULL;
+
+	/* Since the slot array is not protected by rcu, we need a mutex */
+	mutex_lock(&c->mutex);
+ retry:
+	rcu_read_lock();
+	list_for_each_entry_rcu(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);
+					rcu_read_unlock();
+					goto out;
+				}
+			}
+			/* kip->nused is broken. Fix it. */
+			kip->nused = slots_per_page(c);
+			WARN_ON(1);
+		}
+	}
+	rcu_read_unlock();
+
+	/* 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_rcu(&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_rcu(&kip->list);
+			synchronize_rcu();
+			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;
+	long idx;
+
+	mutex_lock(&c->mutex);
+	rcu_read_lock();
+	list_for_each_entry_rcu(kip, &c->pages, list) {
+		idx = ((long)slot - (long)kip->insns) /
+			(c->insn_size * sizeof(kprobe_opcode_t));
+		if (idx >= 0 && idx < slots_per_page(c))
+			goto out;
+	}
+	/* Could not find this slot. */
+	WARN_ON(1);
+	kip = NULL;
+out:
+	rcu_read_unlock();
+	/* Mark and sweep: this may sleep */
+	if (kip) {
+		/* Check double free */
+		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);
+		}
+	}
+	mutex_unlock(&c->mutex);
+}
+
+/*
+ * Check given address is on the page of kprobe instruction slots.
+ * This will be used for checking whether the address on a stack
+ * is on a text area or not.
+ */
+bool __is_insn_slot_addr(struct kprobe_insn_cache *c, unsigned long addr)
+{
+	struct kprobe_insn_page *kip;
+	bool ret = false;
+
+	rcu_read_lock();
+	list_for_each_entry_rcu(kip, &c->pages, list) {
+		if (addr >= (unsigned long)kip->insns &&
+		    addr < (unsigned long)kip->insns + PAGE_SIZE) {
+			ret = true;
+			break;
+		}
+	}
+	rcu_read_unlock();
+
+	return ret;
+}
+
+#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)
+{
+	lockdep_assert_held(&text_mutex);
+	/*
+	 * 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, caller must have locked cpu hotplug
+	 * for preventing cpu-hotplug outside of text_mutex locking.
+	 */
+	lockdep_assert_cpus_held();
+
+	/* Optimization never be done when disarmed */
+	if (kprobes_all_disarmed || !kprobes_allow_optimization ||
+	    list_empty(&optimizing_list))
+		return;
+
+	arch_optimize_kprobes(&optimizing_list);
+}
+
+/*
+ * 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;
+
+	lockdep_assert_held(&text_mutex);
+	/* See comment in do_optimize_kprobes() */
+	lockdep_assert_cpus_held();
+
+	/* Unoptimization must be done anytime */
+	if (list_empty(&unoptimizing_list))
+		return;
+
+	arch_unoptimize_kprobes(&unoptimizing_list, &freeing_list);
+	/* Loop free_list for disarming */
+	list_for_each_entry_safe(op, tmp, &freeing_list, list) {
+		/* Switching from detour code to origin */
+		op->kp.flags &= ~KPROBE_FLAG_OPTIMIZED;
+		/* 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);
+	}
+}
+
+/* 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) {
+		list_del_init(&op->list);
+		if (WARN_ON_ONCE(!kprobe_unused(&op->kp))) {
+			/*
+			 * This must not happen, but if there is a kprobe
+			 * still in use, keep it on kprobes hash list.
+			 */
+			continue;
+		}
+		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);
+	cpus_read_lock();
+	mutex_lock(&text_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 potentially
+	 * preempted tasks to have normally scheduled. Because optprobe
+	 * may modify multiple instructions, there is a chance that Nth
+	 * instruction is preempted. In that case, such tasks can return
+	 * to 2nd-Nth byte of jump instruction. This wait is for avoiding it.
+	 * Note that on non-preemptive kernel, this is transparently converted
+	 * to synchronoze_sched() to wait for all interrupts to have completed.
+	 */
+	synchronize_rcu_tasks();
+
+	/* 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(&text_mutex);
+	cpus_read_unlock();
+
+	/* Step 5: Kick optimizer again if needed */
+	if (!list_empty(&optimizing_list) || !list_empty(&unoptimizing_list))
+		kick_kprobe_optimizer();
+
+	mutex_unlock(&kprobe_mutex);
+}
+
+/* Wait for completing optimization and unoptimization */
+void wait_for_kprobe_optimizer(void)
+{
+	mutex_lock(&kprobe_mutex);
+
+	while (!list_empty(&optimizing_list) || !list_empty(&unoptimizing_list)) {
+		mutex_unlock(&kprobe_mutex);
+
+		/* this will also make optimizing_work execute immmediately */
+		flush_delayed_work(&optimizing_work);
+		/* @optimizing_work might not have been queued yet, relax */
+		cpu_relax();
+
+		mutex_lock(&kprobe_mutex);
+	}
+
+	mutex_unlock(&kprobe_mutex);
+}
+
+static bool optprobe_queued_unopt(struct optimized_kprobe *op)
+{
+	struct optimized_kprobe *_op;
+
+	list_for_each_entry(_op, &unoptimizing_list, list) {
+		if (op == _op)
+			return true;
+	}
+
+	return false;
+}
+
+/* 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;
+
+	/* kprobes with post_handler can not be optimized */
+	if (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) {
+		if (optprobe_queued_unopt(op)) {
+			/* This is under unoptimizing. Just dequeue the probe */
+			list_del_init(&op->list);
+		}
+		return;
+	}
+	op->kp.flags |= KPROBE_FLAG_OPTIMIZED;
+
+	/* On unoptimizing/optimizing_list, op must have OPTIMIZED flag */
+	if (WARN_ON_ONCE(!list_empty(&op->list)))
+		return;
+
+	list_add(&op->list, &optimizing_list);
+	kick_kprobe_optimizer();
+}
+
+/* Short cut to direct unoptimizing */
+static void force_unoptimize_kprobe(struct optimized_kprobe *op)
+{
+	lockdep_assert_cpus_held();
+	arch_unoptimize_kprobe(op);
+	op->kp.flags &= ~KPROBE_FLAG_OPTIMIZED;
+	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))
+		return;
+
+	if (!list_empty(&op->list)) {
+		if (optprobe_queued_unopt(op)) {
+			/* Queued in unoptimizing queue */
+			if (force) {
+				/*
+				 * Forcibly unoptimize the kprobe here, and queue it
+				 * in the freeing list for release afterwards.
+				 */
+				force_unoptimize_kprobe(op);
+				list_move(&op->list, &freeing_list);
+			}
+		} else {
+			/* Dequeue from the optimizing queue */
+			list_del_init(&op->list);
+			op->kp.flags &= ~KPROBE_FLAG_OPTIMIZED;
+		}
+		return;
+	}
+
+	/* Optimized kprobe case */
+	if (force) {
+		/* Forcibly update the code: this is a special case */
+		force_unoptimize_kprobe(op);
+	} else {
+		list_add(&op->list, &unoptimizing_list);
+		kick_kprobe_optimizer();
+	}
+}
+
+/* Cancel unoptimizing for reusing */
+static int reuse_unused_kprobe(struct kprobe *ap)
+{
+	struct optimized_kprobe *op;
+
+	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);
+	WARN_ON_ONCE(list_empty(&op->list));
+	/* Enable the probe again */
+	ap->flags &= ~KPROBE_FLAG_DISABLED;
+	/* Optimize it again (remove from op->list) */
+	if (!kprobe_optready(ap))
+		return -EINVAL;
+
+	optimize_kprobe(ap);
+	return 0;
+}
+
+/* Remove optimized instructions */
+static void kill_optimized_kprobe(struct kprobe *p)
+{
+	struct optimized_kprobe *op;
+
+	op = container_of(p, struct optimized_kprobe, kp);
+	if (!list_empty(&op->list))
+		/* Dequeue from the (un)optimization queue */
+		list_del_init(&op->list);
+	op->kp.flags &= ~KPROBE_FLAG_OPTIMIZED;
+
+	if (kprobe_unused(p)) {
+		/* Enqueue if it is unused */
+		list_add(&op->list, &freeing_list);
+		/*
+		 * Remove unused probes from the hash list. After waiting
+		 * for synchronization, this probe is reclaimed.
+		 * (reclaiming is done by do_free_cleaned_kprobes().)
+		 */
+		hlist_del_rcu(&op->kp.hlist);
+	}
+
+	/* Don't touch the code, because it is already freed. */
+	arch_remove_optimized_kprobe(op);
+}
+
+static inline
+void __prepare_optimized_kprobe(struct optimized_kprobe *op, struct kprobe *p)
+{
+	if (!kprobe_ftrace(p))
+		arch_prepare_optimized_kprobe(op, p);
+}
+
+/* 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);
+	__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;
+	__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 */
+	cpus_read_lock();
+	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();
+	cpus_read_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;
+
+	cpus_read_lock();
+	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);
+	}
+	cpus_read_unlock();
+	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;
+	}
+
+	cpus_read_lock();
+	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);
+		}
+	}
+	cpus_read_unlock();
+	mutex_unlock(&kprobe_mutex);
+
+	/* Wait for unoptimizing completion */
+	wait_for_kprobe_optimizer();
+	printk(KERN_INFO "Kprobes globally unoptimized\n");
+}
+
+static DEFINE_MUTEX(kprobe_sysctl_mutex);
+int sysctl_kprobes_optimization;
+int proc_kprobes_optimization_handler(struct ctl_table *table, int write,
+				      void __user *buffer, size_t *length,
+				      loff_t *ppos)
+{
+	int ret;
+
+	mutex_lock(&kprobe_sysctl_mutex);
+	sysctl_kprobes_optimization = kprobes_allow_optimization ? 1 : 0;
+	ret = proc_dointvec_minmax(table, write, buffer, length, ppos);
+
+	if (sysctl_kprobes_optimization)
+		optimize_all_kprobes();
+	else
+		unoptimize_all_kprobes();
+	mutex_unlock(&kprobe_sysctl_mutex);
+
+	return ret;
+}
+#endif /* CONFIG_SYSCTL */
+
+/* Put a breakpoint for a probe. Must be called with text_mutex locked */
+static void __arm_kprobe(struct kprobe *p)
+{
+	struct kprobe *_p;
+
+	/* Check collision with other optimized kprobes */
+	_p = get_optimized_kprobe((unsigned long)p->addr);
+	if (unlikely(_p))
+		/* Fallback to unoptimized kprobe */
+		unoptimize_kprobe(_p, true);
+
+	arch_arm_kprobe(p);
+	optimize_kprobe(p);	/* Try to optimize (add kprobe to a list) */
+}
+
+/* Remove the breakpoint of a probe. Must be called with text_mutex locked */
+static void __disarm_kprobe(struct kprobe *p, bool reopt)
+{
+	struct kprobe *_p;
+
+	/* Try to unoptimize */
+	unoptimize_kprobe(p, kprobes_all_disarmed);
+
+	if (!kprobe_queued(p)) {
+		arch_disarm_kprobe(p);
+		/* If another kprobe was blocked, optimize it. */
+		_p = get_optimized_kprobe((unsigned long)p->addr);
+		if (unlikely(_p) && reopt)
+			optimize_kprobe(_p);
+	}
+	/* TODO: reoptimize others after unoptimized this probe */
+}
+
+#else /* !CONFIG_OPTPROBES */
+
+#define optimize_kprobe(p)			do {} while (0)
+#define unoptimize_kprobe(p, f)			do {} while (0)
+#define kill_optimized_kprobe(p)		do {} while (0)
+#define prepare_optimized_kprobe(p)		do {} while (0)
+#define try_to_optimize_kprobe(p)		do {} while (0)
+#define __arm_kprobe(p)				arch_arm_kprobe(p)
+#define __disarm_kprobe(p, o)			arch_disarm_kprobe(p)
+#define kprobe_disarmed(p)			kprobe_disabled(p)
+#define wait_for_kprobe_optimizer()		do {} while (0)
+
+static int reuse_unused_kprobe(struct kprobe *ap)
+{
+	/*
+	 * If the optimized kprobe is NOT supported, the aggr kprobe is
+	 * released at the same time that the last aggregated kprobe is
+	 * unregistered.
+	 * Thus there should be no chance to reuse unused kprobe.
+	 */
+	printk(KERN_ERR "Error: There should be no unused kprobe here.\n");
+	return -EINVAL;
+}
+
+static void free_aggr_kprobe(struct kprobe *p)
+{
+	arch_remove_kprobe(p);
+	kfree(p);
+}
+
+static struct kprobe *alloc_aggr_kprobe(struct kprobe *p)
+{
+	return kzalloc(sizeof(struct kprobe), GFP_KERNEL);
+}
+#endif /* CONFIG_OPTPROBES */
+
+#ifdef CONFIG_KPROBES_ON_FTRACE
+static struct ftrace_ops kprobe_ftrace_ops __read_mostly = {
+	.func = kprobe_ftrace_handler,
+	.flags = FTRACE_OPS_FL_SAVE_REGS | FTRACE_OPS_FL_IPMODIFY,
+};
+static int kprobe_ftrace_enabled;
+
+/* Must ensure p->addr is really on ftrace */
+static int prepare_kprobe(struct kprobe *p)
+{
+	if (!kprobe_ftrace(p))
+		return arch_prepare_kprobe(p);
+
+	return arch_prepare_kprobe_ftrace(p);
+}
+
+/* Caller must lock kprobe_mutex */
+static int arm_kprobe_ftrace(struct kprobe *p)
+{
+	int ret = 0;
+
+	ret = ftrace_set_filter_ip(&kprobe_ftrace_ops,
+				   (unsigned long)p->addr, 0, 0);
+	if (ret) {
+		pr_debug("Failed to arm kprobe-ftrace at %pS (%d)\n",
+			 p->addr, ret);
+		return ret;
+	}
+
+	if (kprobe_ftrace_enabled == 0) {
+		ret = register_ftrace_function(&kprobe_ftrace_ops);
+		if (ret) {
+			pr_debug("Failed to init kprobe-ftrace (%d)\n", ret);
+			goto err_ftrace;
+		}
+	}
+
+	kprobe_ftrace_enabled++;
+	return ret;
+
+err_ftrace:
+	/*
+	 * Note: Since kprobe_ftrace_ops has IPMODIFY set, and ftrace requires a
+	 * non-empty filter_hash for IPMODIFY ops, we're safe from an accidental
+	 * empty filter_hash which would undesirably trace all functions.
+	 */
+	ftrace_set_filter_ip(&kprobe_ftrace_ops, (unsigned long)p->addr, 1, 0);
+	return ret;
+}
+
+/* Caller must lock kprobe_mutex */
+static int disarm_kprobe_ftrace(struct kprobe *p)
+{
+	int ret = 0;
+
+	if (kprobe_ftrace_enabled == 1) {
+		ret = unregister_ftrace_function(&kprobe_ftrace_ops);
+		if (WARN(ret < 0, "Failed to unregister kprobe-ftrace (%d)\n", ret))
+			return ret;
+	}
+
+	kprobe_ftrace_enabled--;
+
+	ret = ftrace_set_filter_ip(&kprobe_ftrace_ops,
+			   (unsigned long)p->addr, 1, 0);
+	WARN_ONCE(ret < 0, "Failed to disarm kprobe-ftrace at %pS (%d)\n",
+		  p->addr, ret);
+	return ret;
+}
+#else	/* !CONFIG_KPROBES_ON_FTRACE */
+static inline int prepare_kprobe(struct kprobe *p)
+{
+	return arch_prepare_kprobe(p);
+}
+
+static inline int arm_kprobe_ftrace(struct kprobe *p)
+{
+	return -ENODEV;
+}
+
+static inline int disarm_kprobe_ftrace(struct kprobe *p)
+{
+	return -ENODEV;
+}
+#endif
+
+/* Arm a kprobe with text_mutex */
+static int arm_kprobe(struct kprobe *kp)
+{
+	if (unlikely(kprobe_ftrace(kp)))
+		return arm_kprobe_ftrace(kp);
+
+	cpus_read_lock();
+	mutex_lock(&text_mutex);
+	__arm_kprobe(kp);
+	mutex_unlock(&text_mutex);
+	cpus_read_unlock();
+
+	return 0;
+}
+
+/* Disarm a kprobe with text_mutex */
+static int disarm_kprobe(struct kprobe *kp, bool reopt)
+{
+	if (unlikely(kprobe_ftrace(kp)))
+		return disarm_kprobe_ftrace(kp);
+
+	cpus_read_lock();
+	mutex_lock(&text_mutex);
+	__disarm_kprobe(kp, reopt);
+	mutex_unlock(&text_mutex);
+	cpus_read_unlock();
+
+	return 0;
+}
+
+/*
+ * 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);
+
+/* 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);
+
+struct kprobe kprobe_busy = {
+	.addr = (void *) get_kprobe,
+};
+
+void kprobe_busy_begin(void)
+{
+	struct kprobe_ctlblk *kcb;
+
+	preempt_disable();
+	__this_cpu_write(current_kprobe, &kprobe_busy);
+	kcb = get_kprobe_ctlblk();
+	kcb->kprobe_status = KPROBE_HIT_ACTIVE;
+}
+
+void kprobe_busy_end(void)
+{
+	__this_cpu_write(current_kprobe, NULL);
+	preempt_enable();
+}
+
+/*
+ * 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;
+
+	kprobe_busy_begin();
+
+	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);
+	}
+
+	kprobe_busy_end();
+}
+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 */
+static int add_new_kprobe(struct kprobe *ap, struct kprobe *p)
+{
+	BUG_ON(kprobe_gone(ap) || kprobe_gone(p));
+
+	if (p->post_handler)
+		unoptimize_kprobe(ap, true);	/* Fall back to normal kprobe */
+
+	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;
+
+	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;
+
+	cpus_read_lock();
+
+	/* For preparing optimization, jump_label_text_reserved() is called */
+	jump_label_lock();
+	mutex_lock(&text_mutex);
+
+	if (!kprobe_aggrprobe(orig_p)) {
+		/* If orig_p is not an aggr_kprobe, create new aggr_kprobe. */
+		ap = alloc_aggr_kprobe(orig_p);
+		if (!ap) {
+			ret = -ENOMEM;
+			goto out;
+		}
+		init_aggr_kprobe(ap, orig_p);
+	} else if (kprobe_unused(ap)) {
+		/* This probe is going to die. Rescue it */
+		ret = reuse_unused_kprobe(ap);
+		if (ret)
+			goto out;
+	}
+
+	if (kprobe_gone(ap)) {
+		/*
+		 * Attempting to insert new probe at the same location that
+		 * had a probe in the module vaddr area which already
+		 * freed. So, the instruction slot has already been
+		 * released. We need a new slot for the new probe.
+		 */
+		ret = arch_prepare_kprobe(ap);
+		if (ret)
+			/*
+			 * Even if fail to allocate new slot, don't need to
+			 * free aggr_probe. It will be used next time, or
+			 * freed by unregister_kprobe.
+			 */
+			goto out;
+
+		/* Prepare optimized instructions if possible. */
+		prepare_optimized_kprobe(ap);
+
+		/*
+		 * Clear gone flag to prevent allocating new slot again, and
+		 * set disabled flag because it is not armed yet.
+		 */
+		ap->flags = (ap->flags & ~KPROBE_FLAG_GONE)
+			    | KPROBE_FLAG_DISABLED;
+	}
+
+	/* Copy ap's insn slot to p */
+	copy_kprobe(ap, p);
+	ret = add_new_kprobe(ap, p);
+
+out:
+	mutex_unlock(&text_mutex);
+	jump_label_unlock();
+	cpus_read_unlock();
+
+	if (ret == 0 && kprobe_disabled(ap) && !kprobe_disabled(p)) {
+		ap->flags &= ~KPROBE_FLAG_DISABLED;
+		if (!kprobes_all_disarmed) {
+			/* Arm the breakpoint again. */
+			ret = arm_kprobe(ap);
+			if (ret) {
+				ap->flags |= KPROBE_FLAG_DISABLED;
+				list_del_rcu(&p->list);
+				synchronize_sched();
+			}
+		}
+	}
+	return ret;
+}
+
+bool __weak arch_within_kprobe_blacklist(unsigned long addr)
+{
+	/* The __kprobes marked functions and entry code must not be probed */
+	return addr >= (unsigned long)__kprobes_text_start &&
+	       addr < (unsigned long)__kprobes_text_end;
+}
+
+bool within_kprobe_blacklist(unsigned long addr)
+{
+	struct kprobe_blacklist_entry *ent;
+
+	if (arch_within_kprobe_blacklist(addr))
+		return true;
+	/*
+	 * If there exists a kprobe_blacklist, verify and
+	 * fail any probe registration in the prohibited area
+	 */
+	list_for_each_entry(ent, &kprobe_blacklist, list) {
+		if (addr >= ent->start_addr && addr < ent->end_addr)
+			return true;
+	}
+
+	return false;
+}
+
+/*
+ * If we have a symbol_name argument, look it up and add the offset field
+ * to it. This way, we can specify a relative address to a symbol.
+ * This returns encoded errors if it fails to look up symbol or invalid
+ * combination of parameters.
+ */
+static kprobe_opcode_t *_kprobe_addr(kprobe_opcode_t *addr,
+			const char *symbol_name, unsigned int offset)
+{
+	if ((symbol_name && addr) || (!symbol_name && !addr))
+		goto invalid;
+
+	if (symbol_name) {
+		addr = kprobe_lookup_name(symbol_name, offset);
+		if (!addr)
+			return ERR_PTR(-ENOENT);
+	}
+
+	addr = (kprobe_opcode_t *)(((char *)addr) + offset);
+	if (addr)
+		return addr;
+
+invalid:
+	return ERR_PTR(-EINVAL);
+}
+
+static kprobe_opcode_t *kprobe_addr(struct kprobe *p)
+{
+	return _kprobe_addr(p->addr, p->symbol_name, p->offset);
+}
+
+/* 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) ||
+	    find_bug((unsigned long)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;
+	}
+
+	cpus_read_lock();
+	/* Prevent text modification */
+	mutex_lock(&text_mutex);
+	ret = prepare_kprobe(p);
+	mutex_unlock(&text_mutex);
+	cpus_read_unlock();
+	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)) {
+		ret = arm_kprobe(p);
+		if (ret) {
+			hlist_del_rcu(&p->hlist);
+			synchronize_sched();
+			goto out;
+		}
+	}
+
+	/* 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;
+	int ret;
+
+	/* Get an original kprobe for return */
+	orig_p = __get_valid_kprobe(p);
+	if (unlikely(orig_p == NULL))
+		return ERR_PTR(-EINVAL);
+
+	if (!kprobe_disabled(p)) {
+		/* Disable probe if it is a child probe */
+		if (p != orig_p)
+			p->flags |= KPROBE_FLAG_DISABLED;
+
+		/* Try to disarm and disable this/parent probe */
+		if (p == orig_p || aggr_kprobe_disabled(orig_p)) {
+			/*
+			 * If kprobes_all_disarmed is set, orig_p
+			 * should have already been disarmed, so
+			 * skip unneed disarming process.
+			 */
+			if (!kprobes_all_disarmed) {
+				ret = disarm_kprobe(orig_p, true);
+				if (ret) {
+					p->flags &= ~KPROBE_FLAG_DISABLED;
+					return ERR_PTR(ret);
+				}
+			}
+			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 (IS_ERR(ap))
+		return PTR_ERR(ap);
+
+	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->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);
+
+int __weak kprobe_exceptions_notify(struct notifier_block *self,
+					unsigned long val, void *data)
+{
+	return NOTIFY_DONE;
+}
+NOKPROBE_SYMBOL(kprobe_exceptions_notify);
+
+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;
+}
+
+#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);
+
+bool __weak arch_kprobe_on_func_entry(unsigned long offset)
+{
+	return !offset;
+}
+
+/**
+ * kprobe_on_func_entry() -- check whether given address is function entry
+ * @addr: Target address
+ * @sym:  Target symbol name
+ * @offset: The offset from the symbol or the address
+ *
+ * This checks whether the given @addr+@offset or @sym+@offset is on the
+ * function entry address or not.
+ * This returns 0 if it is the function entry, or -EINVAL if it is not.
+ * And also it returns -ENOENT if it fails the symbol or address lookup.
+ * Caller must pass @addr or @sym (either one must be NULL), or this
+ * returns -EINVAL.
+ */
+int kprobe_on_func_entry(kprobe_opcode_t *addr, const char *sym, unsigned long offset)
+{
+	kprobe_opcode_t *kp_addr = _kprobe_addr(addr, sym, offset);
+
+	if (IS_ERR(kp_addr))
+		return PTR_ERR(kp_addr);
+
+	if (!kallsyms_lookup_size_offset((unsigned long)kp_addr, NULL, &offset))
+		return -ENOENT;
+
+	if (!arch_kprobe_on_func_entry(offset))
+		return -EINVAL;
+
+	return 0;
+}
+
+int register_kretprobe(struct kretprobe *rp)
+{
+	int ret;
+	struct kretprobe_instance *inst;
+	int i;
+	void *addr;
+
+	ret = kprobe_on_func_entry(rp->kp.addr, rp->kp.symbol_name, rp->kp.offset);
+	if (ret)
+		return ret;
+
+	/* If only rp->kp.addr is specified, check reregistering kprobes */
+	if (rp->kp.addr && check_kprobe_rereg(&rp->kp))
+		return -EINVAL;
+
+	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;
+		}
+	}
+
+	if (rp->data_size > KRETPROBE_MAX_DATA_SIZE)
+		return -E2BIG;
+
+	rp->kp.pre_handler = pre_handler_kretprobe;
+	rp->kp.post_handler = NULL;
+	rp->kp.fault_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;
+
+	if (WARN_ON_ONCE(kprobe_gone(p)))
+		return;
+
+	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;
+		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);
+
+	/*
+	 * The module is going away. We should disarm the kprobe which
+	 * is using ftrace, because ftrace framework is still available at
+	 * MODULE_STATE_GOING notification.
+	 */
+	if (kprobe_ftrace(p) && !kprobe_disabled(p) && !kprobes_all_disarmed)
+		disarm_kprobe_ftrace(p);
+}
+
+/* Disable one kprobe */
+int disable_kprobe(struct kprobe *kp)
+{
+	int ret = 0;
+	struct kprobe *p;
+
+	mutex_lock(&kprobe_mutex);
+
+	/* Disable this kprobe */
+	p = __disable_kprobe(kp);
+	if (IS_ERR(p))
+		ret = PTR_ERR(p);
+
+	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;
+		ret = arm_kprobe(p);
+		if (ret)
+			p->flags |= KPROBE_FLAG_DISABLED;
+	}
+out:
+	mutex_unlock(&kprobe_mutex);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(enable_kprobe);
+
+/* Caller must NOT call this in usual path. This is only for critical case */
+void dump_kprobe(struct kprobe *kp)
+{
+	pr_err("Dumping kprobe:\n");
+	pr_err("Name: %s\nOffset: %x\nAddress: %pS\n",
+	       kp->symbol_name, kp->offset, kp->addr);
+}
+NOKPROBE_SYMBOL(dump_kprobe);
+
+int kprobe_add_ksym_blacklist(unsigned long entry)
+{
+	struct kprobe_blacklist_entry *ent;
+	unsigned long offset = 0, size = 0;
+
+	if (!kernel_text_address(entry) ||
+	    !kallsyms_lookup_size_offset(entry, &size, &offset))
+		return -EINVAL;
+
+	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 (int)size;
+}
+
+/* Add all symbols in given area into kprobe blacklist */
+int kprobe_add_area_blacklist(unsigned long start, unsigned long end)
+{
+	unsigned long entry;
+	int ret = 0;
+
+	for (entry = start; entry < end; entry += ret) {
+		ret = kprobe_add_ksym_blacklist(entry);
+		if (ret < 0)
+			return ret;
+		if (ret == 0)	/* In case of alias symbol */
+			ret = 1;
+	}
+	return 0;
+}
+
+int __init __weak arch_populate_kprobe_blacklist(void)
+{
+	return 0;
+}
+
+/*
+ * 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 entry;
+	unsigned long *iter;
+	int ret;
+
+	for (iter = start; iter < end; iter++) {
+		entry = arch_deref_entry_point((void *)*iter);
+		ret = kprobe_add_ksym_blacklist(entry);
+		if (ret == -EINVAL)
+			continue;
+		if (ret < 0)
+			return ret;
+	}
+
+	/* Symbols in __kprobes_text are blacklisted */
+	ret = kprobe_add_area_blacklist((unsigned long)__kprobes_text_start,
+					(unsigned long)__kprobes_text_end);
+
+	return ret ? : arch_populate_kprobe_blacklist();
+}
+
+/* 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 (kprobe_gone(p))
+				continue;
+
+			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.
+				 *
+				 * Note, this will also move any optimized probes
+				 * that are pending to be removed from their
+				 * corresponding lists to the freeing_list and
+				 * will not be touched by the delayed
+				 * kprobe_optimizer work handler.
+				 */
+				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++) {
+			kretprobe_blacklist[i].addr =
+				kprobe_lookup_name(kretprobe_blacklist[i].name, 0);
+			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;
+	void *addr = p->addr;
+
+	if (p->pre_handler == pre_handler_kretprobe)
+		kprobe_type = "r";
+	else
+		kprobe_type = "k";
+
+	if (!kallsyms_show_value(pi->file->f_cred))
+		addr = NULL;
+
+	if (sym)
+		seq_printf(pi, "%px  %s  %s+0x%x  %s ",
+			addr, kprobe_type, sym, offset,
+			(modname ? modname : " "));
+	else	/* try to use %pS */
+		seq_printf(pi, "%px  %s  %pS ",
+			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);
+
+	/*
+	 * If /proc/kallsyms is not showing kernel address, we won't
+	 * show them here either.
+	 */
+	if (!kallsyms_show_value(m->file->f_cred))
+		seq_printf(m, "0x%px-0x%px\t%ps\n", NULL, NULL,
+			   (void *)ent->start_addr);
+	else
+		seq_printf(m, "0x%px-0x%px\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 int arm_all_kprobes(void)
+{
+	struct hlist_head *head;
+	struct kprobe *p;
+	unsigned int i, total = 0, errors = 0;
+	int err, ret = 0;
+
+	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];
+		/* Arm all kprobes on a best-effort basis */
+		hlist_for_each_entry_rcu(p, head, hlist) {
+			if (!kprobe_disabled(p)) {
+				err = arm_kprobe(p);
+				if (err)  {
+					errors++;
+					ret = err;
+				}
+				total++;
+			}
+		}
+	}
+
+	if (errors)
+		pr_warn("Kprobes globally enabled, but failed to arm %d out of %d probes\n",
+			errors, total);
+	else
+		pr_info("Kprobes globally enabled\n");
+
+already_enabled:
+	mutex_unlock(&kprobe_mutex);
+	return ret;
+}
+
+static int disarm_all_kprobes(void)
+{
+	struct hlist_head *head;
+	struct kprobe *p;
+	unsigned int i, total = 0, errors = 0;
+	int err, ret = 0;
+
+	mutex_lock(&kprobe_mutex);
+
+	/* If kprobes are already disarmed, just return */
+	if (kprobes_all_disarmed) {
+		mutex_unlock(&kprobe_mutex);
+		return 0;
+	}
+
+	kprobes_all_disarmed = true;
+
+	for (i = 0; i < KPROBE_TABLE_SIZE; i++) {
+		head = &kprobe_table[i];
+		/* Disarm all kprobes on a best-effort basis */
+		hlist_for_each_entry_rcu(p, head, hlist) {
+			if (!arch_trampoline_kprobe(p) && !kprobe_disabled(p)) {
+				err = disarm_kprobe(p, false);
+				if (err) {
+					errors++;
+					ret = err;
+				}
+				total++;
+			}
+		}
+	}
+
+	if (errors)
+		pr_warn("Kprobes globally disabled, but failed to disarm %d out of %d probes\n",
+			errors, total);
+	else
+		pr_info("Kprobes globally disabled\n");
+
+	mutex_unlock(&kprobe_mutex);
+
+	/* Wait for disarming all kprobes by optimizer */
+	wait_for_kprobe_optimizer();
+
+	return ret;
+}
+
+/*
+ * 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;
+	int ret = 0;
+
+	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':
+		ret = arm_all_kprobes();
+		break;
+	case 'n':
+	case 'N':
+	case '0':
+		ret = disarm_all_kprobes();
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	if (ret)
+		return ret;
+
+	return count;
+}
+
+static const struct file_operations fops_kp = {
+	.read =         read_enabled_file_bool,
+	.write =        write_enabled_file_bool,
+	.llseek =	default_llseek,
+};
+
+static int __init debugfs_kprobe_init(void)
+{
+	struct dentry *dir, *file;
+	unsigned int value = 1;
+
+	dir = debugfs_create_dir("kprobes", NULL);
+	if (!dir)
+		return -ENOMEM;
+
+	file = debugfs_create_file("list", 0400, dir, NULL,
+				&debugfs_kprobes_operations);
+	if (!file)
+		goto error;
+
+	file = debugfs_create_file("enabled", 0600, dir,
+					&value, &fops_kp);
+	if (!file)
+		goto error;
+
+	file = debugfs_create_file("blacklist", 0400, dir, NULL,
+				&debugfs_kprobe_blacklist_ops);
+	if (!file)
+		goto error;
+
+	return 0;
+
+error:
+	debugfs_remove(dir);
+	return -ENOMEM;
+}
+
+late_initcall(debugfs_kprobe_init);
+#endif /* CONFIG_DEBUG_FS */
+
+module_init(init_kprobes);