/* *  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/module.h>#include <linux/moduleloader.h>#include <asm-generic/sections.h>#include <asm/cacheflush.h>#include <asm/errno.h>#include <asm/kdebug.h> #define KPROBE_HASH_BITS 6#define KPROBE_TABLE_SIZE (1 << KPROBE_HASH_BITS) static struct hlist_head kprobe_table[KPROBE_TABLE_SIZE];static struct hlist_head kretprobe_inst_table[KPROBE_TABLE_SIZE]; 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;}; static struct hlist_head kprobe_insn_pages; /** * 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; 	hlist_for_each(pos, &kprobe_insn_pages) {		kip = hlist_entry(pos, struct kprobe_insn_page, hlist);		if (kip->nused < INSNS_PER_PAGE) {			int i;			for (i = 0; i < INSNS_PER_PAGE; i++) {				if (!kip->slot_used[i]) {					kip->slot_used[i] = 1;					kip->nused++;					return kip->insns + (i * MAX_INSN_SIZE);				}			}			/* Surprise!  No unused slots.  Fix kip->nused. */			kip->nused = INSNS_PER_PAGE;		}	} 	/* 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, 0, INSNS_PER_PAGE);	kip->slot_used[0] = 1;	kip->nused = 1;	return kip->insns;} void __kprobes free_insn_slot(kprobe_opcode_t *slot){	struct kprobe_insn_page *kip;	struct hlist_node *pos; 	hlist_for_each(pos, &kprobe_insn_pages) {		kip = hlist_entry(pos, struct kprobe_insn_page, hlist);		if (kip->insns <= slot &&		    slot < kip->insns + (INSNS_PER_PAGE * MAX_INSN_SIZE)) {			int i = (slot - kip->insns) / MAX_INSN_SIZE;			kip->slot_used[i] = 0;			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;		}	}}#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();		}	}	return;} 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 */struct kretprobe_instance __kprobes *get_free_rp_inst(struct kretprobe *rp){	struct hlist_node *node;	struct kretprobe_instance *ri;	hlist_for_each_entry(ri, node, &rp->free_instances, uflist)		return ri;	return NULL;} /* Called with kretprobe_lock held */static struct kretprobe_instance __kprobes *get_used_rp_inst(struct kretprobe							      *rp){	struct hlist_node *node;	struct kretprobe_instance *ri;	hlist_for_each_entry(ri, node, &rp->used_instances, uflist)		return ri;	return NULL;} /* Called with kretprobe_lock held */void __kprobes add_rp_inst(struct kretprobe_instance *ri){	/*	 * Remove rp inst off the free list -	 * Add it back when probed function returns	 */	hlist_del(&ri->uflist); 	/* Add rp inst onto table */	INIT_HLIST_NODE(&ri->hlist);	hlist_add_head(&ri->hlist,			&kretprobe_inst_table[hash_ptr(ri->task, KPROBE_HASH_BITS)]); 	/* Also add this rp inst to the used list. */	INIT_HLIST_NODE(&ri->uflist);	hlist_add_head(&ri->uflist, &ri->rp->used_instances);} /* Called with kretprobe_lock held */void __kprobes recycle_rp_inst(struct kretprobe_instance *ri){	/* 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 */		kfree(ri);} 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;	struct hlist_node *node, *tmp;	unsigned long flags = 0; 	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);        }	spin_unlock_irqrestore(&kretprobe_lock, flags);} static inline void free_rp_inst(struct kretprobe *rp){	struct kretprobe_instance *ri;	while ((ri = get_free_rp_inst(rp)) != NULL) {		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){        struct kprobe *kp; 	if (p->break_handler) {		list_for_each_entry_rcu(kp, &old_p->list, list) {			if (kp->break_handler)				return -EEXIST;		}		list_add_tail_rcu(&p->list, &old_p->list);	} else		list_add_rcu(&p->list, &old_p->list);	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);	ap->addr = p->addr;	ap->pre_handler = aggr_pre_handler;	ap->post_handler = aggr_post_handler;	ap->fault_handler = aggr_fault_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 ((!kernel_text_address((unsigned long) p->addr)) ||		in_kprobes_functions((unsigned long) p->addr))		return -EINVAL; 	p->mod_refcounted = 0;	/* Check are we probing a module */	if ((probed_mod = module_text_address((unsigned long) p->addr))) {		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;	} 	if ((ret = arch_prepare_kprobe(p)) != 0)		goto out; 	INIT_HLIST_NODE(&p->hlist);	hlist_add_head_rcu(&p->hlist,		       &kprobe_table[hash_ptr(p->addr, KPROBE_HASH_BITS)]);   	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);

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