Create instrumentation/ kernel directory

Index: linux-2.6-lttng.stable/instrumentation/kprobes.c
===================================================================
@@ -0,0 +1,1063 @@
+/*
+ *  Kernel Probes (KProbes)
+ *  kernel/kprobes.c
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ *
+ * Copyright (C) IBM Corporation, 2002, 2004
+ *
+ * 2002-Oct	Created by Vamsi Krishna S <[email protected]> Kernel
+ *		Probes initial implementation (includes suggestions from
+ *		Rusty Russell).
+ * 2004-Aug	Updated by Prasanna S Panchamukhi <[email protected]> with
+ *		hlists and exceptions notifier as suggested by Andi Kleen.
+ * 2004-July	Suparna Bhattacharya <[email protected]> added jumper probes
+ *		interface to access function arguments.
+ * 2004-Sep	Prasanna S Panchamukhi <[email protected]> Changed Kprobes
+ *		exceptions notifier to be first on the priority list.
+ * 2005-May	Hien Nguyen <[email protected]>, Jim Keniston
+ *		<[email protected]> and Prasanna S Panchamukhi
+ *		<[email protected]> added function-return probes.
+ */
+#include <linux/kprobes.h>
+#include <linux/hash.h>
+#include <linux/init.h>
+#include <linux/slab.h>
+#include <linux/stddef.h>
+#include <linux/module.h>
+#include <linux/moduleloader.h>
+#include <linux/kallsyms.h>
+#include <linux/freezer.h>
+#include <linux/seq_file.h>
+#include <linux/debugfs.h>
+#include <linux/kdebug.h>
+
+#include <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 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 kprobe_enabled;
+
+DEFINE_MUTEX(kprobe_mutex);		/* Protects kprobe_table */
+DEFINE_SPINLOCK(kretprobe_lock);	/* Protects kretprobe_inst_table */
+static DEFINE_PER_CPU(struct kprobe *, kprobe_instance) = NULL;
+
+#ifdef __ARCH_WANT_KPROBES_INSN_SLOT
+/*
+ * kprobe->ainsn.insn points to the copy of the instruction to be
+ * single-stepped. x86_64, POWER4 and above have no-exec support and
+ * stepping on the instruction on a vmalloced/kmalloced/data page
+ * is a recipe for disaster
+ */
+#define INSNS_PER_PAGE	(PAGE_SIZE/(MAX_INSN_SIZE * sizeof(kprobe_opcode_t)))
+
+struct kprobe_insn_page {
+	struct hlist_node hlist;
+	kprobe_opcode_t *insns;		/* Page of instruction slots */
+	char slot_used[INSNS_PER_PAGE];
+	int nused;
+	int ngarbage;
+};
+
+enum kprobe_slot_state {
+	SLOT_CLEAN = 0,
+	SLOT_DIRTY = 1,
+	SLOT_USED = 2,
+};
+
+static struct hlist_head kprobe_insn_pages;
+static int kprobe_garbage_slots;
+static int collect_garbage_slots(void);
+
+static int __kprobes check_safety(void)
+{
+	int ret = 0;
+#if defined(CONFIG_PREEMPT) && defined(CONFIG_PM)
+	ret = freeze_processes();
+	if (ret == 0) {
+		struct task_struct *p, *q;
+		do_each_thread(p, q) {
+			if (p != current && p->state == TASK_RUNNING &&
+			    p->pid != 0) {
+				printk("Check failed: %s is running\n",p->comm);
+				ret = -1;
+				goto loop_end;
+			}
+		} while_each_thread(p, q);
+	}
+loop_end:
+	thaw_processes();
+#else
+	synchronize_sched();
+#endif
+	return ret;
+}
+
+/**
+ * get_insn_slot() - Find a slot on an executable page for an instruction.
+ * We allocate an executable page if there's no room on existing ones.
+ */
+kprobe_opcode_t __kprobes *get_insn_slot(void)
+{
+	struct kprobe_insn_page *kip;
+	struct hlist_node *pos;
+
+ retry:
+	hlist_for_each_entry(kip, pos, &kprobe_insn_pages, hlist) {
+		if (kip->nused < INSNS_PER_PAGE) {
+			int i;
+			for (i = 0; i < INSNS_PER_PAGE; i++) {
+				if (kip->slot_used[i] == SLOT_CLEAN) {
+					kip->slot_used[i] = SLOT_USED;
+					kip->nused++;
+					return kip->insns + (i * MAX_INSN_SIZE);
+				}
+			}
+			/* Surprise!  No unused slots.  Fix kip->nused. */
+			kip->nused = INSNS_PER_PAGE;
+		}
+	}
+
+	/* If there are any garbage slots, collect it and try again. */
+	if (kprobe_garbage_slots && collect_garbage_slots() == 0) {
+		goto retry;
+	}
+	/* All out of space.  Need to allocate a new page. Use slot 0. */
+	kip = kmalloc(sizeof(struct kprobe_insn_page), GFP_KERNEL);
+	if (!kip)
+		return NULL;
+
+	/*
+	 * Use module_alloc so this page is within +/- 2GB of where the
+	 * kernel image and loaded module images reside. This is required
+	 * so x86_64 can correctly handle the %rip-relative fixups.
+	 */
+	kip->insns = module_alloc(PAGE_SIZE);
+	if (!kip->insns) {
+		kfree(kip);
+		return NULL;
+	}
+	INIT_HLIST_NODE(&kip->hlist);
+	hlist_add_head(&kip->hlist, &kprobe_insn_pages);
+	memset(kip->slot_used, SLOT_CLEAN, INSNS_PER_PAGE);
+	kip->slot_used[0] = SLOT_USED;
+	kip->nused = 1;
+	kip->ngarbage = 0;
+	return kip->insns;
+}
+
+/* Return 1 if all garbages are collected, otherwise 0. */
+static int __kprobes collect_one_slot(struct kprobe_insn_page *kip, int idx)
+{
+	kip->slot_used[idx] = SLOT_CLEAN;
+	kip->nused--;
+	if (kip->nused == 0) {
+		/*
+		 * Page is no longer in use.  Free it unless
+		 * it's the last one.  We keep the last one
+		 * so as not to have to set it up again the
+		 * next time somebody inserts a probe.
+		 */
+		hlist_del(&kip->hlist);
+		if (hlist_empty(&kprobe_insn_pages)) {
+			INIT_HLIST_NODE(&kip->hlist);
+			hlist_add_head(&kip->hlist,
+				       &kprobe_insn_pages);
+		} else {
+			module_free(NULL, kip->insns);
+			kfree(kip);
+		}
+		return 1;
+	}
+	return 0;
+}
+
+static int __kprobes collect_garbage_slots(void)
+{
+	struct kprobe_insn_page *kip;
+	struct hlist_node *pos, *next;
+
+	/* Ensure no-one is preepmted on the garbages */
+	if (check_safety() != 0)
+		return -EAGAIN;
+
+	hlist_for_each_entry_safe(kip, pos, next, &kprobe_insn_pages, hlist) {
+		int i;
+		if (kip->ngarbage == 0)
+			continue;
+		kip->ngarbage = 0;	/* we will collect all garbages */
+		for (i = 0; i < INSNS_PER_PAGE; i++) {
+			if (kip->slot_used[i] == SLOT_DIRTY &&
+			    collect_one_slot(kip, i))
+				break;
+		}
+	}
+	kprobe_garbage_slots = 0;
+	return 0;
+}
+
+void __kprobes free_insn_slot(kprobe_opcode_t * slot, int dirty)
+{
+	struct kprobe_insn_page *kip;
+	struct hlist_node *pos;
+
+	hlist_for_each_entry(kip, pos, &kprobe_insn_pages, hlist) {
+		if (kip->insns <= slot &&
+		    slot < kip->insns + (INSNS_PER_PAGE * MAX_INSN_SIZE)) {
+			int i = (slot - kip->insns) / MAX_INSN_SIZE;
+			if (dirty) {
+				kip->slot_used[i] = SLOT_DIRTY;
+				kip->ngarbage++;
+			} else {
+				collect_one_slot(kip, i);
+			}
+			break;
+		}
+	}
+
+	if (dirty && ++kprobe_garbage_slots > INSNS_PER_PAGE)
+		collect_garbage_slots();
+}
+#endif
+
+/* We have preemption disabled.. so it is safe to use __ versions */
+static inline void set_kprobe_instance(struct kprobe *kp)
+{
+	__get_cpu_var(kprobe_instance) = kp;
+}
+
+static inline void reset_kprobe_instance(void)
+{
+	__get_cpu_var(kprobe_instance) = NULL;
+}
+
+/*
+ * This routine is called either:
+ * 	- under the kprobe_mutex - during kprobe_[un]register()
+ * 				OR
+ * 	- with preemption disabled - from arch/xxx/kernel/kprobes.c
+ */
+struct kprobe __kprobes *get_kprobe(void *addr)
+{
+	struct hlist_head *head;
+	struct hlist_node *node;
+	struct kprobe *p;
+
+	head = &kprobe_table[hash_ptr(addr, KPROBE_HASH_BITS)];
+	hlist_for_each_entry_rcu(p, node, head, hlist) {
+		if (p->addr == addr)
+			return p;
+	}
+	return NULL;
+}
+
+/*
+ * Aggregate handlers for multiple kprobes support - these handlers
+ * take care of invoking the individual kprobe handlers on p->list
+ */
+static int __kprobes aggr_pre_handler(struct kprobe *p, struct pt_regs *regs)
+{
+	struct kprobe *kp;
+
+	list_for_each_entry_rcu(kp, &p->list, list) {
+		if (kp->pre_handler) {
+			set_kprobe_instance(kp);
+			if (kp->pre_handler(kp, regs))
+				return 1;
+		}
+		reset_kprobe_instance();
+	}
+	return 0;
+}
+
+static void __kprobes aggr_post_handler(struct kprobe *p, struct pt_regs *regs,
+					unsigned long flags)
+{
+	struct kprobe *kp;
+
+	list_for_each_entry_rcu(kp, &p->list, list) {
+		if (kp->post_handler) {
+			set_kprobe_instance(kp);
+			kp->post_handler(kp, regs, flags);
+			reset_kprobe_instance();
+		}
+	}
+}
+
+static int __kprobes aggr_fault_handler(struct kprobe *p, struct pt_regs *regs,
+					int trapnr)
+{
+	struct kprobe *cur = __get_cpu_var(kprobe_instance);
+
+	/*
+	 * if we faulted "during" the execution of a user specified
+	 * probe handler, invoke just that probe's fault handler
+	 */
+	if (cur && cur->fault_handler) {
+		if (cur->fault_handler(cur, regs, trapnr))
+			return 1;
+	}
+	return 0;
+}
+
+static int __kprobes aggr_break_handler(struct kprobe *p, struct pt_regs *regs)
+{
+	struct kprobe *cur = __get_cpu_var(kprobe_instance);
+	int ret = 0;
+
+	if (cur && cur->break_handler) {
+		if (cur->break_handler(cur, regs))
+			ret = 1;
+	}
+	reset_kprobe_instance();
+	return ret;
+}
+
+/* Walks the list and increments nmissed count for multiprobe case */
+void __kprobes kprobes_inc_nmissed_count(struct kprobe *p)
+{
+	struct kprobe *kp;
+	if (p->pre_handler != aggr_pre_handler) {
+		p->nmissed++;
+	} else {
+		list_for_each_entry_rcu(kp, &p->list, list)
+			kp->nmissed++;
+	}
+	return;
+}
+
+/* Called with kretprobe_lock held */
+void __kprobes recycle_rp_inst(struct kretprobe_instance *ri,
+				struct hlist_head *head)
+{
+	/* remove rp inst off the rprobe_inst_table */
+	hlist_del(&ri->hlist);
+	if (ri->rp) {
+		/* remove rp inst off the used list */
+		hlist_del(&ri->uflist);
+		/* put rp inst back onto the free list */
+		INIT_HLIST_NODE(&ri->uflist);
+		hlist_add_head(&ri->uflist, &ri->rp->free_instances);
+	} else
+		/* Unregistering */
+		hlist_add_head(&ri->hlist, head);
+}
+
+struct hlist_head __kprobes *kretprobe_inst_table_head(struct task_struct *tsk)
+{
+	return &kretprobe_inst_table[hash_ptr(tsk, KPROBE_HASH_BITS)];
+}
+
+/*
+ * This function is called from finish_task_switch when task tk becomes dead,
+ * so that we can recycle any function-return probe instances associated
+ * with this task. These left over instances represent probed functions
+ * that have been called but will never return.
+ */
+void __kprobes kprobe_flush_task(struct task_struct *tk)
+{
+	struct kretprobe_instance *ri;
+	struct hlist_head *head, empty_rp;
+	struct hlist_node *node, *tmp;
+	unsigned long flags = 0;
+
+	INIT_HLIST_HEAD(&empty_rp);
+	spin_lock_irqsave(&kretprobe_lock, flags);
+	head = kretprobe_inst_table_head(tk);
+	hlist_for_each_entry_safe(ri, node, tmp, head, hlist) {
+		if (ri->task == tk)
+			recycle_rp_inst(ri, &empty_rp);
+	}
+	spin_unlock_irqrestore(&kretprobe_lock, flags);
+
+	hlist_for_each_entry_safe(ri, node, tmp, &empty_rp, hlist) {
+		hlist_del(&ri->hlist);
+		kfree(ri);
+	}
+}
+
+static inline void free_rp_inst(struct kretprobe *rp)
+{
+	struct kretprobe_instance *ri;
+	struct hlist_node *pos, *next;
+
+	hlist_for_each_entry_safe(ri, pos, next, &rp->free_instances, uflist) {
+		hlist_del(&ri->uflist);
+		kfree(ri);
+	}
+}
+
+/*
+ * Keep all fields in the kprobe consistent
+ */
+static inline void copy_kprobe(struct kprobe *old_p, struct kprobe *p)
+{
+	memcpy(&p->opcode, &old_p->opcode, sizeof(kprobe_opcode_t));
+	memcpy(&p->ainsn, &old_p->ainsn, sizeof(struct arch_specific_insn));
+}
+
+/*
+* Add the new probe to old_p->list. Fail if this is the
+* second jprobe at the address - two jprobes can't coexist
+*/
+static int __kprobes add_new_kprobe(struct kprobe *old_p, struct kprobe *p)
+{
+	if (p->break_handler) {
+		if (old_p->break_handler)
+			return -EEXIST;
+		list_add_tail_rcu(&p->list, &old_p->list);
+		old_p->break_handler = aggr_break_handler;
+	} else
+		list_add_rcu(&p->list, &old_p->list);
+	if (p->post_handler && !old_p->post_handler)
+		old_p->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 inline void add_aggr_kprobe(struct kprobe *ap, struct kprobe *p)
+{
+	copy_kprobe(p, ap);
+	flush_insn_slot(ap);
+	ap->addr = p->addr;
+	ap->pre_handler = aggr_pre_handler;
+	ap->fault_handler = aggr_fault_handler;
+	if (p->post_handler)
+		ap->post_handler = aggr_post_handler;
+	if (p->break_handler)
+		ap->break_handler = aggr_break_handler;
+
+	INIT_LIST_HEAD(&ap->list);
+	list_add_rcu(&p->list, &ap->list);
+
+	hlist_replace_rcu(&p->hlist, &ap->hlist);
+}
+
+/*
+ * This is the second or subsequent kprobe at the address - handle
+ * the intricacies
+ */
+static int __kprobes register_aggr_kprobe(struct kprobe *old_p,
+					  struct kprobe *p)
+{
+	int ret = 0;
+	struct kprobe *ap;
+
+	if (old_p->pre_handler == aggr_pre_handler) {
+		copy_kprobe(old_p, p);
+		ret = add_new_kprobe(old_p, p);
+	} else {
+		ap = kzalloc(sizeof(struct kprobe), GFP_KERNEL);
+		if (!ap)
+			return -ENOMEM;
+		add_aggr_kprobe(ap, old_p);
+		copy_kprobe(ap, p);
+		ret = add_new_kprobe(ap, p);
+	}
+	return ret;
+}
+
+static int __kprobes in_kprobes_functions(unsigned long addr)
+{
+	if (addr >= (unsigned long)__kprobes_text_start &&
+	    addr < (unsigned long)__kprobes_text_end)
+		return -EINVAL;
+	return 0;
+}
+
+static int __kprobes __register_kprobe(struct kprobe *p,
+	unsigned long called_from)
+{
+	int ret = 0;
+	struct kprobe *old_p;
+	struct module *probed_mod;
+
+	/*
+	 * If we have a symbol_name argument look it up,
+	 * and add it to the address.  That way the addr
+	 * field can either be global or relative to a symbol.
+	 */
+	if (p->symbol_name) {
+		if (p->addr)
+			return -EINVAL;
+		kprobe_lookup_name(p->symbol_name, p->addr);
+	}
+
+	if (!p->addr)
+		return -EINVAL;
+	p->addr = (kprobe_opcode_t *)(((char *)p->addr)+ p->offset);
+
+	if (!kernel_text_address((unsigned long) p->addr) ||
+	    in_kprobes_functions((unsigned long) p->addr))
+		return -EINVAL;
+
+	p->mod_refcounted = 0;
+
+	/*
+	 * Check if are we probing a module.
+	 */
+	probed_mod = module_text_address((unsigned long) p->addr);
+	if (probed_mod) {
+		struct module *calling_mod = module_text_address(called_from);
+		/*
+		 * We must allow modules to probe themself and in this case
+		 * avoid incrementing the module refcount, so as to allow
+		 * unloading of self probing modules.
+		 */
+		if (calling_mod && calling_mod != probed_mod) {
+			if (unlikely(!try_module_get(probed_mod)))
+				return -EINVAL;
+			p->mod_refcounted = 1;
+		} else
+			probed_mod = NULL;
+	}
+
+	p->nmissed = 0;
+	mutex_lock(&kprobe_mutex);
+	old_p = get_kprobe(p->addr);
+	if (old_p) {
+		ret = register_aggr_kprobe(old_p, p);
+		goto out;
+	}
+
+	ret = arch_prepare_kprobe(p);
+	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 (kprobe_enabled)
+		arch_arm_kprobe(p);
+
+out:
+	mutex_unlock(&kprobe_mutex);
+
+	if (ret && probed_mod)
+		module_put(probed_mod);
+	return ret;
+}
+
+int __kprobes register_kprobe(struct kprobe *p)
+{
+	return __register_kprobe(p, (unsigned long)__builtin_return_address(0));
+}
+
+void __kprobes unregister_kprobe(struct kprobe *p)
+{
+	struct module *mod;
+	struct kprobe *old_p, *list_p;
+	int cleanup_p;
+
+	mutex_lock(&kprobe_mutex);
+	old_p = get_kprobe(p->addr);
+	if (unlikely(!old_p)) {
+		mutex_unlock(&kprobe_mutex);
+		return;
+	}
+	if (p != old_p) {
+		list_for_each_entry_rcu(list_p, &old_p->list, list)
+			if (list_p == p)
+			/* kprobe p is a valid probe */
+				goto valid_p;
+		mutex_unlock(&kprobe_mutex);
+		return;
+	}
+valid_p:
+	if (old_p == p ||
+	    (old_p->pre_handler == aggr_pre_handler &&
+	     p->list.next == &old_p->list && p->list.prev == &old_p->list)) {
+		/*
+		 * Only probe on the hash list. Disarm only if kprobes are
+		 * enabled - otherwise, the breakpoint would already have
+		 * been removed. We save on flushing icache.
+		 */
+		if (kprobe_enabled)
+			arch_disarm_kprobe(p);
+		hlist_del_rcu(&old_p->hlist);
+		cleanup_p = 1;
+	} else {
+		list_del_rcu(&p->list);
+		cleanup_p = 0;
+	}
+
+	mutex_unlock(&kprobe_mutex);
+
+	synchronize_sched();
+	if (p->mod_refcounted) {
+		mod = module_text_address((unsigned long)p->addr);
+		if (mod)
+			module_put(mod);
+	}
+
+	if (cleanup_p) {
+		if (p != old_p) {
+			list_del_rcu(&p->list);
+			kfree(old_p);
+		}
+		arch_remove_kprobe(p);
+	} else {
+		mutex_lock(&kprobe_mutex);
+		if (p->break_handler)
+			old_p->break_handler = NULL;
+		if (p->post_handler){
+			list_for_each_entry_rcu(list_p, &old_p->list, list){
+				if (list_p->post_handler){
+					cleanup_p = 2;
+					break;
+				}
+			}
+			if (cleanup_p == 0)
+				old_p->post_handler = NULL;
+		}
+		mutex_unlock(&kprobe_mutex);
+	}
+}
+
+static struct notifier_block kprobe_exceptions_nb = {
+	.notifier_call = kprobe_exceptions_notify,
+	.priority = 0x7fffffff /* we need to be notified first */
+};
+
+unsigned long __weak arch_deref_entry_point(void *entry)
+{
+	return (unsigned long)entry;
+}
+
+int __kprobes register_jprobe(struct jprobe *jp)
+{
+	unsigned long addr = arch_deref_entry_point(jp->entry);
+
+	if (!kernel_text_address(addr))
+		return -EINVAL;
+
+	/* Todo: Verify probepoint is a function entry point */
+	jp->kp.pre_handler = setjmp_pre_handler;
+	jp->kp.break_handler = longjmp_break_handler;
+
+	return __register_kprobe(&jp->kp,
+		(unsigned long)__builtin_return_address(0));
+}
+
+void __kprobes unregister_jprobe(struct jprobe *jp)
+{
+	unregister_kprobe(&jp->kp);
+}
+
+#ifdef ARCH_SUPPORTS_KRETPROBES
+
+/*
+ * This kprobe pre_handler is registered with every kretprobe. When probe
+ * hits it will set up the return probe.
+ */
+static int __kprobes pre_handler_kretprobe(struct kprobe *p,
+					   struct pt_regs *regs)
+{
+	struct kretprobe *rp = container_of(p, struct kretprobe, kp);
+	unsigned long flags = 0;
+
+	/*TODO: consider to only swap the RA after the last pre_handler fired */
+	spin_lock_irqsave(&kretprobe_lock, flags);
+	if (!hlist_empty(&rp->free_instances)) {
+		struct kretprobe_instance *ri;
+
+		ri = hlist_entry(rp->free_instances.first,
+				 struct kretprobe_instance, uflist);
+		ri->rp = rp;
+		ri->task = current;
+		arch_prepare_kretprobe(ri, regs);
+
+		/* XXX(hch): why is there no hlist_move_head? */
+		hlist_del(&ri->uflist);
+		hlist_add_head(&ri->uflist, &ri->rp->used_instances);
+		hlist_add_head(&ri->hlist, kretprobe_inst_table_head(ri->task));
+	} else
+		rp->nmissed++;
+	spin_unlock_irqrestore(&kretprobe_lock, flags);
+	return 0;
+}
+
+int __kprobes register_kretprobe(struct kretprobe *rp)
+{
+	int ret = 0;
+	struct kretprobe_instance *inst;
+	int i;
+	void *addr = rp->kp.addr;
+
+	if (kretprobe_blacklist_size) {
+		if (addr == NULL)
+			kprobe_lookup_name(rp->kp.symbol_name, addr);
+		addr += rp->kp.offset;
+
+		for (i = 0; kretprobe_blacklist[i].name != NULL; i++) {
+			if (kretprobe_blacklist[i].addr == addr)
+				return -EINVAL;
+		}
+	}
+
+	rp->kp.pre_handler = pre_handler_kretprobe;
+	rp->kp.post_handler = NULL;
+	rp->kp.fault_handler = NULL;
+	rp->kp.break_handler = NULL;
+
+	/* Pre-allocate memory for max kretprobe instances */
+	if (rp->maxactive <= 0) {
+#ifdef CONFIG_PREEMPT
+		rp->maxactive = max(10, 2 * NR_CPUS);
+#else
+		rp->maxactive = NR_CPUS;
+#endif
+	}
+	INIT_HLIST_HEAD(&rp->used_instances);
+	INIT_HLIST_HEAD(&rp->free_instances);
+	for (i = 0; i < rp->maxactive; i++) {
+		inst = kmalloc(sizeof(struct kretprobe_instance), GFP_KERNEL);
+		if (inst == NULL) {
+			free_rp_inst(rp);
+			return -ENOMEM;
+		}
+		INIT_HLIST_NODE(&inst->uflist);
+		hlist_add_head(&inst->uflist, &rp->free_instances);
+	}
+
+	rp->nmissed = 0;
+	/* Establish function entry probe point */
+	if ((ret = __register_kprobe(&rp->kp,
+		(unsigned long)__builtin_return_address(0))) != 0)
+		free_rp_inst(rp);
+	return ret;
+}
+
+#else /* ARCH_SUPPORTS_KRETPROBES */
+
+int __kprobes register_kretprobe(struct kretprobe *rp)
+{
+	return -ENOSYS;
+}
+
+static int __kprobes pre_handler_kretprobe(struct kprobe *p,
+					   struct pt_regs *regs)
+{
+	return 0;
+}
+
+#endif /* ARCH_SUPPORTS_KRETPROBES */
+
+void __kprobes unregister_kretprobe(struct kretprobe *rp)
+{
+	unsigned long flags;
+	struct kretprobe_instance *ri;
+	struct hlist_node *pos, *next;
+
+	unregister_kprobe(&rp->kp);
+
+	/* No race here */
+	spin_lock_irqsave(&kretprobe_lock, flags);
+	hlist_for_each_entry_safe(ri, pos, next, &rp->used_instances, uflist) {
+		ri->rp = NULL;
+		hlist_del(&ri->uflist);
+	}
+	spin_unlock_irqrestore(&kretprobe_lock, flags);
+	free_rp_inst(rp);
+}
+
+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]);
+	}
+
+	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);
+		}
+	}
+
+	/* By default, kprobes are enabled */
+	kprobe_enabled = true;
+
+	err = arch_init_kprobes();
+	if (!err)
+		err = register_die_notifier(&kprobe_exceptions_nb);
+
+	return err;
+}
+
+#ifdef CONFIG_DEBUG_FS
+static void __kprobes report_probe(struct seq_file *pi, struct kprobe *p,
+		const char *sym, int offset,char *modname)
+{
+	char *kprobe_type;
+
+	if (p->pre_handler == pre_handler_kretprobe)
+		kprobe_type = "r";
+	else if (p->pre_handler == setjmp_pre_handler)
+		kprobe_type = "j";
+	else
+		kprobe_type = "k";
+	if (sym)
+		seq_printf(pi, "%p  %s  %s+0x%x  %s\n", p->addr, kprobe_type,
+			sym, offset, (modname ? modname : " "));
+	else
+		seq_printf(pi, "%p  %s  %p\n", p->addr, kprobe_type, p->addr);
+}
+
+static void __kprobes *kprobe_seq_start(struct seq_file *f, loff_t *pos)
+{
+	return (*pos < KPROBE_TABLE_SIZE) ? pos : NULL;
+}
+
+static void __kprobes *kprobe_seq_next(struct seq_file *f, void *v, loff_t *pos)
+{
+	(*pos)++;
+	if (*pos >= KPROBE_TABLE_SIZE)
+		return NULL;
+	return pos;
+}
+
+static void __kprobes kprobe_seq_stop(struct seq_file *f, void *v)
+{
+	/* Nothing to do */
+}
+
+static int __kprobes show_kprobe_addr(struct seq_file *pi, void *v)
+{
+	struct hlist_head *head;
+	struct hlist_node *node;
+	struct kprobe *p, *kp;
+	const char *sym = NULL;
+	unsigned int i = *(loff_t *) v;
+	unsigned long offset = 0;
+	char *modname, namebuf[128];
+
+	head = &kprobe_table[i];
+	preempt_disable();
+	hlist_for_each_entry_rcu(p, node, head, hlist) {
+		sym = kallsyms_lookup((unsigned long)p->addr, NULL,
+					&offset, &modname, namebuf);
+		if (p->pre_handler == aggr_pre_handler) {
+			list_for_each_entry_rcu(kp, &p->list, list)
+				report_probe(pi, kp, sym, offset, modname);
+		} else
+			report_probe(pi, p, sym, offset, modname);
+	}
+	preempt_enable();
+	return 0;
+}
+
+static struct seq_operations kprobes_seq_ops = {
+	.start = kprobe_seq_start,
+	.next  = kprobe_seq_next,
+	.stop  = kprobe_seq_stop,
+	.show  = show_kprobe_addr
+};
+
+static int __kprobes kprobes_open(struct inode *inode, struct file *filp)
+{
+	return seq_open(filp, &kprobes_seq_ops);
+}
+
+static struct file_operations debugfs_kprobes_operations = {
+	.open           = kprobes_open,
+	.read           = seq_read,
+	.llseek         = seq_lseek,
+	.release        = seq_release,
+};
+
+static void __kprobes enable_all_kprobes(void)
+{
+	struct hlist_head *head;
+	struct hlist_node *node;
+	struct kprobe *p;
+	unsigned int i;
+
+	mutex_lock(&kprobe_mutex);
+
+	/* If kprobes are already enabled, just return */
+	if (kprobe_enabled)
+		goto already_enabled;
+
+	for (i = 0; i < KPROBE_TABLE_SIZE; i++) {
+		head = &kprobe_table[i];
+		hlist_for_each_entry_rcu(p, node, head, hlist)
+			arch_arm_kprobe(p);
+	}
+
+	kprobe_enabled = true;
+	printk(KERN_INFO "Kprobes globally enabled\n");
+
+already_enabled:
+	mutex_unlock(&kprobe_mutex);
+	return;
+}
+
+static void __kprobes disable_all_kprobes(void)
+{
+	struct hlist_head *head;
+	struct hlist_node *node;
+	struct kprobe *p;
+	unsigned int i;
+
+	mutex_lock(&kprobe_mutex);
+
+	/* If kprobes are already disabled, just return */
+	if (!kprobe_enabled)
+		goto already_disabled;
+
+	kprobe_enabled = false;
+	printk(KERN_INFO "Kprobes globally disabled\n");
+	for (i = 0; i < KPROBE_TABLE_SIZE; i++) {
+		head = &kprobe_table[i];
+		hlist_for_each_entry_rcu(p, node, head, hlist) {
+			if (!arch_trampoline_kprobe(p))
+				arch_disarm_kprobe(p);
+		}
+	}
+
+	mutex_unlock(&kprobe_mutex);
+	/* Allow all currently running kprobes to complete */
+	synchronize_sched();
+	return;
+
+already_disabled:
+	mutex_unlock(&kprobe_mutex);
+	return;
+}
+
+/*
+ * XXX: The debugfs bool file interface doesn't allow for callbacks
+ * when the bool state is switched. We can reuse that facility when
+ * available
+ */
+static ssize_t read_enabled_file_bool(struct file *file,
+	       char __user *user_buf, size_t count, loff_t *ppos)
+{
+	char buf[3];
+
+	if (kprobe_enabled)
+		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];
+	int buf_size;
+
+	buf_size = min(count, (sizeof(buf)-1));
+	if (copy_from_user(buf, user_buf, buf_size))
+		return -EFAULT;
+
+	switch (buf[0]) {
+	case 'y':
+	case 'Y':
+	case '1':
+		enable_all_kprobes();
+		break;
+	case 'n':
+	case 'N':
+	case '0':
+		disable_all_kprobes();
+		break;
+	}
+
+	return count;
+}
+
+static struct file_operations fops_kp = {
+	.read =         read_enabled_file_bool,
+	.write =        write_enabled_file_bool,
+};
+
+static int __kprobes debugfs_kprobe_init(void)
+{
+	struct dentry *dir, *file;
+	unsigned int value = 1;
+
+	dir = debugfs_create_dir("kprobes", NULL);
+	if (!dir)
+		return -ENOMEM;
+
+	file = debugfs_create_file("list", 0444, dir, NULL,
+				&debugfs_kprobes_operations);
+	if (!file) {
+		debugfs_remove(dir);
+		return -ENOMEM;
+	}
+
+	file = debugfs_create_file("enabled", 0600, dir,
+					&value, &fops_kp);
+	if (!file) {
+		debugfs_remove(dir);
+		return -ENOMEM;
+	}
+
+	return 0;
+}
+
+late_initcall(debugfs_kprobe_init);
+#endif /* CONFIG_DEBUG_FS */
+
+module_init(init_kprobes);
+
+EXPORT_SYMBOL_GPL(register_kprobe);
+EXPORT_SYMBOL_GPL(unregister_kprobe);
+EXPORT_SYMBOL_GPL(register_jprobe);
+EXPORT_SYMBOL_GPL(unregister_jprobe);
+#ifdef CONFIG_KPROBES
+EXPORT_SYMBOL_GPL(jprobe_return);
+#endif
+
+#ifdef CONFIG_KPROBES
+EXPORT_SYMBOL_GPL(register_kretprobe);
+EXPORT_SYMBOL_GPL(unregister_kretprobe);
+#endif

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