/* *  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/spinlock.h>#include <linux/hash.h>#include <linux/init.h>#include <linux/module.h>#include <linux/moduleloader.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]; unsigned int kprobe_cpu = NR_CPUS;static DEFINE_SPINLOCK(kprobe_lock);static struct kprobe *curr_kprobe; /* * 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 *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 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;		}	}} /* Locks kprobe: irqs must be disabled */void lock_kprobes(void){	spin_lock(&kprobe_lock);	kprobe_cpu = smp_processor_id();} void unlock_kprobes(void){	kprobe_cpu = NR_CPUS;	spin_unlock(&kprobe_lock);} /* You have to be holding the kprobe_lock */struct kprobe *get_kprobe(void *addr){	struct hlist_head *head;	struct hlist_node *node; 	head = &kprobe_table[hash_ptr(addr, KPROBE_HASH_BITS)];	hlist_for_each(node, head) {		struct kprobe *p = hlist_entry(node, struct kprobe, 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 aggr_pre_handler(struct kprobe *p, struct pt_regs *regs){	struct kprobe *kp; 	list_for_each_entry(kp, &p->list, list) {		if (kp->pre_handler) {			curr_kprobe = kp;			if (kp->pre_handler(kp, regs))				return 1;		}		curr_kprobe = NULL;	}	return 0;} static void aggr_post_handler(struct kprobe *p, struct pt_regs *regs,			      unsigned long flags){	struct kprobe *kp; 	list_for_each_entry(kp, &p->list, list) {		if (kp->post_handler) {			curr_kprobe = kp;			kp->post_handler(kp, regs, flags);			curr_kprobe = NULL;		}	}	return;} static int aggr_fault_handler(struct kprobe *p, struct pt_regs *regs,			      int trapnr){	/*	 * if we faulted "during" the execution of a user specified	 * probe handler, invoke just that probe's fault handler	 */	if (curr_kprobe && curr_kprobe->fault_handler) {		if (curr_kprobe->fault_handler(curr_kprobe, regs, trapnr))			return 1;	}	return 0;} static int aggr_break_handler(struct kprobe *p, struct pt_regs *regs){	struct kprobe *kp = curr_kprobe;	if (curr_kprobe && kp->break_handler) {		if (kp->break_handler(kp, regs)) {			curr_kprobe = NULL;			return 1;		}	}	curr_kprobe = NULL;	return 0;} struct kretprobe_instance *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;} static struct kretprobe_instance *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;} void 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);} void 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 * kretprobe_inst_table_head(struct task_struct *tsk){	return &kretprobe_inst_table[hash_ptr(tsk, KPROBE_HASH_BITS)];} /* * This function is called from exit_thread or flush_thread when task tk's * stack is being recycled 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;	struct hlist_node *node, *tmp;	unsigned long flags = 0; 	spin_lock_irqsave(&kprobe_lock, flags);        head = kretprobe_inst_table_head(current);        hlist_for_each_entry_safe(ri, node, tmp, head, hlist) {                if (ri->task == tk)                        recycle_rp_inst(ri);        }	spin_unlock_irqrestore(&kprobe_lock, flags);} /* * 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); 	/*TODO: consider to only swap the RA after the last pre_handler fired */	arch_prepare_kretprobe(rp, regs);	return 0;} 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 add_new_kprobe(struct kprobe *old_p, struct kprobe *p){        struct kprobe *kp; 	if (p->break_handler) {		list_for_each_entry(kp, &old_p->list, list) {			if (kp->break_handler)				return -EEXIST;		}		list_add_tail(&p->list, &old_p->list);	} else		list_add(&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(&p->list, &ap->list); 	INIT_HLIST_NODE(&ap->hlist);	hlist_del(&p->hlist);	hlist_add_head(&ap->hlist,		&kprobe_table[hash_ptr(ap->addr, KPROBE_HASH_BITS)]);} /* * This is the second or subsequent kprobe at the address - handle * the intricacies * TODO: Move kcalloc outside the spinlock */static int 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 = kcalloc(1, sizeof(struct kprobe), GFP_ATOMIC);		if (!ap)			return -ENOMEM;		add_aggr_kprobe(ap, old_p);		copy_kprobe(ap, p);		ret = add_new_kprobe(ap, p);	}	return ret;} /* kprobe removal house-keeping routines */static inline void cleanup_kprobe(struct kprobe *p, unsigned long flags){	arch_disarm_kprobe(p);	hlist_del(&p->hlist);	spin_unlock_irqrestore(&kprobe_lock, flags);	arch_remove_kprobe(p);} static inline void cleanup_aggr_kprobe(struct kprobe *old_p,		struct kprobe *p, unsigned long flags){	list_del(&p->list);	if (list_empty(&old_p->list)) {		cleanup_kprobe(old_p, flags);		kfree(old_p);	} else		spin_unlock_irqrestore(&kprobe_lock, flags);} int register_kprobe(struct kprobe *p){	int ret = 0;	unsigned long flags = 0;	struct kprobe *old_p; 	if ((ret = arch_prepare_kprobe(p)) != 0) {		goto rm_kprobe;	}	spin_lock_irqsave(&kprobe_lock, flags);	old_p = get_kprobe(p->addr);	p->nmissed = 0;	if (old_p) {		ret = register_aggr_kprobe(old_p, p);		goto out;	} 	arch_copy_kprobe(p);	INIT_HLIST_NODE(&p->hlist);	hlist_add_head(&p->hlist,		       &kprobe_table[hash_ptr(p->addr, KPROBE_HASH_BITS)]);   	arch_arm_kprobe(p); out:	spin_unlock_irqrestore(&kprobe_lock, flags);rm_kprobe:	if (ret == -EEXIST)		arch_remove_kprobe(p);	return ret;} void unregister_kprobe(struct kprobe *p){	unsigned long flags;	struct kprobe *old_p; 	spin_lock_irqsave(&kprobe_lock, flags);	old_p = get_kprobe(p->addr);	if (old_p) {		if (old_p->pre_handler == aggr_pre_handler)			cleanup_aggr_kprobe(old_p, p, flags);		else			cleanup_kprobe(p, flags);	} else		spin_unlock_irqrestore(&kprobe_lock, flags);} static struct notifier_block kprobe_exceptions_nb = {	.notifier_call = kprobe_exceptions_notify,	.priority = 0x7fffffff /* we need to notified first */}; int register_jprobe(struct jprobe *jp){	/* 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);} void unregister_jprobe(struct jprobe *jp){

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