[deliverable/linux.git] / arch / powerpc / kernel / kprobes.c

/*
 *  Kernel Probes (KProbes)
 *  arch/ppc64/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 contributions from
 *		Rusty Russell).
 * 2004-July	Suparna Bhattacharya <suparna@in.ibm.com> added jumper probes
 *		interface to access function arguments.
 * 2004-Nov	Ananth N Mavinakayanahalli <ananth@in.ibm.com> kprobes port
 *		for PPC64
 */

#include <linux/config.h>
#include <linux/kprobes.h>
#include <linux/ptrace.h>
#include <linux/preempt.h>
#include <asm/cacheflush.h>
#include <asm/kdebug.h>
#include <asm/sstep.h>

static DECLARE_MUTEX(kprobe_mutex);
DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);

int __kprobes arch_prepare_kprobe(struct kprobe *p)
{
	int ret = 0;
	kprobe_opcode_t insn = *p->addr;

	if ((unsigned long)p->addr & 0x03) {
		printk("Attempt to register kprobe at an unaligned address\n");
		ret = -EINVAL;
	} else if (IS_MTMSRD(insn) || IS_RFID(insn)) {
		printk("Cannot register a kprobe on rfid or mtmsrd\n");
		ret = -EINVAL;
	}

	/* insn must be on a special executable page on ppc64 */
	if (!ret) {
		down(&kprobe_mutex);
		p->ainsn.insn = get_insn_slot();
		up(&kprobe_mutex);
		if (!p->ainsn.insn)
			ret = -ENOMEM;
	}
	return ret;
}

void __kprobes arch_copy_kprobe(struct kprobe *p)
{
	memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
	p->opcode = *p->addr;
}

void __kprobes arch_arm_kprobe(struct kprobe *p)
{
	*p->addr = BREAKPOINT_INSTRUCTION;
	flush_icache_range((unsigned long) p->addr,
			   (unsigned long) p->addr + sizeof(kprobe_opcode_t));
}

void __kprobes arch_disarm_kprobe(struct kprobe *p)
{
	*p->addr = p->opcode;
	flush_icache_range((unsigned long) p->addr,
			   (unsigned long) p->addr + sizeof(kprobe_opcode_t));
}

void __kprobes arch_remove_kprobe(struct kprobe *p)
{
	down(&kprobe_mutex);
	free_insn_slot(p->ainsn.insn);
	up(&kprobe_mutex);
}

static inline void prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
{
	kprobe_opcode_t insn = *p->ainsn.insn;

	regs->msr |= MSR_SE;

	/* single step inline if it is a trap variant */
	if (is_trap(insn))
		regs->nip = (unsigned long)p->addr;
	else
		regs->nip = (unsigned long)p->ainsn.insn;
}

static inline void save_previous_kprobe(struct kprobe_ctlblk *kcb)
{
	kcb->prev_kprobe.kp = kprobe_running();
	kcb->prev_kprobe.status = kcb->kprobe_status;
	kcb->prev_kprobe.saved_msr = kcb->kprobe_saved_msr;
}

static inline void restore_previous_kprobe(struct kprobe_ctlblk *kcb)
{
	__get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp;
	kcb->kprobe_status = kcb->prev_kprobe.status;
	kcb->kprobe_saved_msr = kcb->prev_kprobe.saved_msr;
}

static inline void set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
				struct kprobe_ctlblk *kcb)
{
	__get_cpu_var(current_kprobe) = p;
	kcb->kprobe_saved_msr = regs->msr;
}

/* Called with kretprobe_lock held */
void __kprobes arch_prepare_kretprobe(struct kretprobe *rp,
				      struct pt_regs *regs)
{
	struct kretprobe_instance *ri;

	if ((ri = get_free_rp_inst(rp)) != NULL) {
		ri->rp = rp;
		ri->task = current;
		ri->ret_addr = (kprobe_opcode_t *)regs->link;

		/* Replace the return addr with trampoline addr */
		regs->link = (unsigned long)kretprobe_trampoline;
		add_rp_inst(ri);
	} else {
		rp->nmissed++;
	}
}

static inline int kprobe_handler(struct pt_regs *regs)
{
	struct kprobe *p;
	int ret = 0;
	unsigned int *addr = (unsigned int *)regs->nip;
	struct kprobe_ctlblk *kcb;

	/*
	 * We don't want to be preempted for the entire
	 * duration of kprobe processing
	 */
	preempt_disable();
	kcb = get_kprobe_ctlblk();

	/* Check we're not actually recursing */
	if (kprobe_running()) {
		p = get_kprobe(addr);
		if (p) {
			kprobe_opcode_t insn = *p->ainsn.insn;
			if (kcb->kprobe_status == KPROBE_HIT_SS &&
					is_trap(insn)) {
				regs->msr &= ~MSR_SE;
				regs->msr |= kcb->kprobe_saved_msr;
				goto no_kprobe;
			}
			/* We have reentered the kprobe_handler(), since
			 * another probe was hit while within the handler.
			 * We here save the original kprobes variables and
			 * just single step on the instruction of the new probe
			 * without calling any user handlers.
			 */
			save_previous_kprobe(kcb);
			set_current_kprobe(p, regs, kcb);
			kcb->kprobe_saved_msr = regs->msr;
			kprobes_inc_nmissed_count(p);
			prepare_singlestep(p, regs);
			kcb->kprobe_status = KPROBE_REENTER;
			return 1;
		} else {
			p = __get_cpu_var(current_kprobe);
			if (p->break_handler && p->break_handler(p, regs)) {
				goto ss_probe;
			}
		}
		goto no_kprobe;
	}

	p = get_kprobe(addr);
	if (!p) {
		if (*addr != BREAKPOINT_INSTRUCTION) {
			/*
			 * PowerPC has multiple variants of the "trap"
			 * instruction. If the current instruction is a
			 * trap variant, it could belong to someone else
			 */
			kprobe_opcode_t cur_insn = *addr;
			if (is_trap(cur_insn))
		       		goto no_kprobe;
			/*
			 * The breakpoint instruction was removed right
			 * after we hit it.  Another cpu has removed
			 * either a probepoint or a debugger breakpoint
			 * at this address.  In either case, no further
			 * handling of this interrupt is appropriate.
			 */
			ret = 1;
		}
		/* Not one of ours: let kernel handle it */
		goto no_kprobe;
	}

	kcb->kprobe_status = KPROBE_HIT_ACTIVE;
	set_current_kprobe(p, regs, kcb);
	if (p->pre_handler && p->pre_handler(p, regs))
		/* handler has already set things up, so skip ss setup */
		return 1;

ss_probe:
	prepare_singlestep(p, regs);
	kcb->kprobe_status = KPROBE_HIT_SS;
	return 1;

no_kprobe:
	preempt_enable_no_resched();
	return ret;
}

/*
 * Function return probe trampoline:
 * 	- init_kprobes() establishes a probepoint here
 * 	- When the probed function returns, this probe
 * 		causes the handlers to fire
 */
void kretprobe_trampoline_holder(void)
{
	asm volatile(".global kretprobe_trampoline\n"
			"kretprobe_trampoline:\n"
			"nop\n");
}

/*
 * Called when the probe at kretprobe trampoline is hit
 */
int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
{
        struct kretprobe_instance *ri = NULL;
        struct hlist_head *head;
        struct hlist_node *node, *tmp;
	unsigned long flags, orig_ret_address = 0;
	unsigned long trampoline_address =(unsigned long)&kretprobe_trampoline;

	spin_lock_irqsave(&kretprobe_lock, flags);
        head = kretprobe_inst_table_head(current);

	/*
	 * It is possible to have multiple instances associated with a given
	 * task either because an multiple functions in the call path
	 * have a return probe installed on them, and/or more then one return
	 * return probe was registered for a target function.
	 *
	 * We can handle this because:
	 *     - instances are always inserted at the head of the list
	 *     - when multiple return probes are registered for the same
         *       function, the first instance's ret_addr will point to the
	 *       real return address, and all the rest will point to
	 *       kretprobe_trampoline
	 */
	hlist_for_each_entry_safe(ri, node, tmp, head, hlist) {
                if (ri->task != current)
			/* another task is sharing our hash bucket */
                        continue;

		if (ri->rp && ri->rp->handler)
			ri->rp->handler(ri, regs);

		orig_ret_address = (unsigned long)ri->ret_addr;
		recycle_rp_inst(ri);

		if (orig_ret_address != trampoline_address)
			/*
			 * This is the real return address. Any other
			 * instances associated with this task are for
			 * other calls deeper on the call stack
			 */
			break;
	}

	BUG_ON(!orig_ret_address || (orig_ret_address == trampoline_address));
	regs->nip = orig_ret_address;

	reset_current_kprobe();
	spin_unlock_irqrestore(&kretprobe_lock, flags);
	preempt_enable_no_resched();

        /*
         * By returning a non-zero value, we are telling
         * kprobe_handler() that we don't want the post_handler
         * to run (and have re-enabled preemption)
         */
        return 1;
}

/*
 * Called after single-stepping.  p->addr is the address of the
 * instruction whose first byte has been replaced by the "breakpoint"
 * instruction.  To avoid the SMP problems that can occur when we
 * temporarily put back the original opcode to single-step, we
 * single-stepped a copy of the instruction.  The address of this
 * copy is p->ainsn.insn.
 */
static void __kprobes resume_execution(struct kprobe *p, struct pt_regs *regs)
{
	int ret;
	unsigned int insn = *p->ainsn.insn;

	regs->nip = (unsigned long)p->addr;
	ret = emulate_step(regs, insn);
	if (ret == 0)
		regs->nip = (unsigned long)p->addr + 4;
}

static inline int post_kprobe_handler(struct pt_regs *regs)
{
	struct kprobe *cur = kprobe_running();
	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();

	if (!cur)
		return 0;

	if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
		kcb->kprobe_status = KPROBE_HIT_SSDONE;
		cur->post_handler(cur, regs, 0);
	}

	resume_execution(cur, regs);
	regs->msr |= kcb->kprobe_saved_msr;

	/*Restore back the original saved kprobes variables and continue. */
	if (kcb->kprobe_status == KPROBE_REENTER) {
		restore_previous_kprobe(kcb);
		goto out;
	}
	reset_current_kprobe();
out:
	preempt_enable_no_resched();

	/*
	 * if somebody else is singlestepping across a probe point, msr
	 * will have SE set, in which case, continue the remaining processing
	 * of do_debug, as if this is not a probe hit.
	 */
	if (regs->msr & MSR_SE)
		return 0;

	return 1;
}

static inline int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
{
	struct kprobe *cur = kprobe_running();
	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();

	if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
		return 1;

	if (kcb->kprobe_status & KPROBE_HIT_SS) {
		resume_execution(cur, regs);
		regs->msr &= ~MSR_SE;
		regs->msr |= kcb->kprobe_saved_msr;

		reset_current_kprobe();
		preempt_enable_no_resched();
	}
	return 0;
}

/*
 * Wrapper routine to for handling exceptions.
 */
int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
				       unsigned long val, void *data)
{
	struct die_args *args = (struct die_args *)data;
	int ret = NOTIFY_DONE;

	switch (val) {
	case DIE_BPT:
		if (kprobe_handler(args->regs))
			ret = NOTIFY_STOP;
		break;
	case DIE_SSTEP:
		if (post_kprobe_handler(args->regs))
			ret = NOTIFY_STOP;
		break;
	case DIE_PAGE_FAULT:
		/* kprobe_running() needs smp_processor_id() */
		preempt_disable();
		if (kprobe_running() &&
		    kprobe_fault_handler(args->regs, args->trapnr))
			ret = NOTIFY_STOP;
		preempt_enable();
		break;
	default:
		break;
	}
	return ret;
}

int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
{
	struct jprobe *jp = container_of(p, struct jprobe, kp);
	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();

	memcpy(&kcb->jprobe_saved_regs, regs, sizeof(struct pt_regs));

	/* setup return addr to the jprobe handler routine */
	regs->nip = (unsigned long)(((func_descr_t *)jp->entry)->entry);
	regs->gpr[2] = (unsigned long)(((func_descr_t *)jp->entry)->toc);

	return 1;
}

void __kprobes jprobe_return(void)
{
	asm volatile("trap" ::: "memory");
}

void __kprobes jprobe_return_end(void)
{
};

int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
{
	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();

	/*
	 * FIXME - we should ideally be validating that we got here 'cos
	 * of the "trap" in jprobe_return() above, before restoring the
	 * saved regs...
	 */
	memcpy(regs, &kcb->jprobe_saved_regs, sizeof(struct pt_regs));
	preempt_enable_no_resched();
	return 1;
}

static struct kprobe trampoline_p = {
	.addr = (kprobe_opcode_t *) &kretprobe_trampoline,
	.pre_handler = trampoline_probe_handler
};

int __init arch_init_kprobes(void)
{
	return register_kprobe(&trampoline_p);
}
Commit	Line	Data
1da177e4 LT	1	/*
	2	* Kernel Probes (KProbes)
	3	* arch/ppc64/kernel/kprobes.c
	4	*
	5	* This program is free software; you can redistribute it and/or modify
	6	* it under the terms of the GNU General Public License as published by
	7	* the Free Software Foundation; either version 2 of the License, or
	8	* (at your option) any later version.
	9	*
	10	* This program is distributed in the hope that it will be useful,
	11	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	12	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	13	* GNU General Public License for more details.
	14	*
	15	* You should have received a copy of the GNU General Public License
	16	* along with this program; if not, write to the Free Software
	17	* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
	18	*
	19	* Copyright (C) IBM Corporation, 2002, 2004
	20	*
	21	* 2002-Oct Created by Vamsi Krishna S <vamsi_krishna@in.ibm.com> Kernel
	22	* Probes initial implementation ( includes contributions from
	23	* Rusty Russell).
	24	* 2004-July Suparna Bhattacharya <suparna@in.ibm.com> added jumper probes
	25	* interface to access function arguments.
	26	* 2004-Nov Ananth N Mavinakayanahalli <ananth@in.ibm.com> kprobes port
	27	* for PPC64
	28	*/
	29
	30	#include <linux/config.h>
	31	#include <linux/kprobes.h>
	32	#include <linux/ptrace.h>
1da177e4	33	#include <linux/preempt.h>
7e1048b1	34	#include <asm/cacheflush.h>
1da177e4 LT	35	#include <asm/kdebug.h>
	36	#include <asm/sstep.h>
	37
9ec4b1f3	38	static DECLARE_MUTEX(kprobe_mutex);
0dc036c9 AM	39	DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
0dc036c9 AM	40	DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
1da177e4	41
bb144a85	42	int __kprobes arch_prepare_kprobe(struct kprobe *p)
1da177e4	43	{
63224d1e	44	int ret = 0;
1da177e4 LT	45	kprobe_opcode_t insn = *p->addr;
1da177e4 LT	46
63224d1e AM	47	if ((unsigned long)p->addr & 0x03) {
	48	printk("Attempt to register kprobe at an unaligned address\n");
	49	ret = -EINVAL;
	50	} else if (IS_MTMSRD(insn) \|\| IS_RFID(insn)) {
	51	printk("Cannot register a kprobe on rfid or mtmsrd\n");
	52	ret = -EINVAL;
	53	}
9ec4b1f3 AM	54
	55	/* insn must be on a special executable page on ppc64 */
	56	if (!ret) {
9ec4b1f3	57	down(&kprobe_mutex);
2d8ab6ad AM	58	p->ainsn.insn = get_insn_slot();
2d8ab6ad AM	59	up(&kprobe_mutex);
9ec4b1f3 AM	60	if (!p->ainsn.insn)
	61	ret = -ENOMEM;
	62	}
63224d1e	63	return ret;
1da177e4 LT	64	}
1da177e4 LT	65
bb144a85	66	void __kprobes arch_copy_kprobe(struct kprobe *p)
1da177e4 LT	67	{
1da177e4 LT	68	memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
7e1048b1	69	p->opcode = *p->addr;
1da177e4 LT	70	}
1da177e4 LT	71
bb144a85	72	void __kprobes arch_arm_kprobe(struct kprobe *p)
1da177e4	73	{
7e1048b1 RL	74	*p->addr = BREAKPOINT_INSTRUCTION;
	75	flush_icache_range((unsigned long) p->addr,
	76	(unsigned long) p->addr + sizeof(kprobe_opcode_t));
1da177e4 LT	77	}
1da177e4 LT	78
bb144a85	79	void __kprobes arch_disarm_kprobe(struct kprobe *p)
1da177e4 LT	80	{
1da177e4 LT	81	*p->addr = p->opcode;
7e1048b1 RL	82	flush_icache_range((unsigned long) p->addr,
	83	(unsigned long) p->addr + sizeof(kprobe_opcode_t));
	84	}
	85
bb144a85	86	void __kprobes arch_remove_kprobe(struct kprobe *p)
7e1048b1	87	{
9ec4b1f3	88	down(&kprobe_mutex);
2d8ab6ad AM	89	free_insn_slot(p->ainsn.insn);
2d8ab6ad AM	90	up(&kprobe_mutex);
1da177e4 LT	91	}
	92
	93	static inline void prepare_singlestep(struct kprobe p, struct pt_regs regs)
	94	{
9ec4b1f3 AM	95	kprobe_opcode_t insn = *p->ainsn.insn;
9ec4b1f3 AM	96
1da177e4	97	regs->msr \|= MSR_SE;
9ec4b1f3 AM	98
9ec4b1f3 AM	99	/* single step inline if it is a trap variant */
deac66ae	100	if (is_trap(insn))
1da177e4 LT	101	regs->nip = (unsigned long)p->addr;
1da177e4 LT	102	else
9ec4b1f3	103	regs->nip = (unsigned long)p->ainsn.insn;
1da177e4 LT	104	}
1da177e4 LT	105
0dc036c9 AM	106	static inline void save_previous_kprobe(struct kprobe_ctlblk *kcb)
	107	{
	108	kcb->prev_kprobe.kp = kprobe_running();
	109	kcb->prev_kprobe.status = kcb->kprobe_status;
	110	kcb->prev_kprobe.saved_msr = kcb->kprobe_saved_msr;
	111	}
	112
	113	static inline void restore_previous_kprobe(struct kprobe_ctlblk *kcb)
42cc2060	114	{
0dc036c9 AM	115	__get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp;
	116	kcb->kprobe_status = kcb->prev_kprobe.status;
	117	kcb->kprobe_saved_msr = kcb->prev_kprobe.saved_msr;
42cc2060 PP	118	}
42cc2060 PP	119
0dc036c9 AM	120	static inline void set_current_kprobe(struct kprobe p, struct pt_regs regs,
0dc036c9 AM	121	struct kprobe_ctlblk *kcb)
42cc2060	122	{
0dc036c9 AM	123	__get_cpu_var(current_kprobe) = p;
0dc036c9 AM	124	kcb->kprobe_saved_msr = regs->msr;
42cc2060 PP	125	}
42cc2060 PP	126
991a51d8	127	/* Called with kretprobe_lock held */
bb144a85 PP	128	void __kprobes arch_prepare_kretprobe(struct kretprobe *rp,
bb144a85 PP	129	struct pt_regs *regs)
97f7943d RL	130	{
	131	struct kretprobe_instance *ri;
	132
	133	if ((ri = get_free_rp_inst(rp)) != NULL) {
	134	ri->rp = rp;
	135	ri->task = current;
	136	ri->ret_addr = (kprobe_opcode_t *)regs->link;
	137
	138	/* Replace the return addr with trampoline addr */
	139	regs->link = (unsigned long)kretprobe_trampoline;
	140	add_rp_inst(ri);
	141	} else {
	142	rp->nmissed++;
	143	}
	144	}
	145
1da177e4 LT	146	static inline int kprobe_handler(struct pt_regs *regs)
	147	{
	148	struct kprobe *p;
	149	int ret = 0;
	150	unsigned int addr = (unsigned int )regs->nip;
d217d545 AM	151	struct kprobe_ctlblk *kcb;
	152
	153	/*
	154	* We don't want to be preempted for the entire
	155	* duration of kprobe processing
	156	*/
	157	preempt_disable();
	158	kcb = get_kprobe_ctlblk();
1da177e4 LT	159
	160	/* Check we're not actually recursing */
	161	if (kprobe_running()) {
1da177e4 LT	162	p = get_kprobe(addr);
1da177e4 LT	163	if (p) {
deac66ae	164	kprobe_opcode_t insn = *p->ainsn.insn;
0dc036c9	165	if (kcb->kprobe_status == KPROBE_HIT_SS &&
deac66ae	166	is_trap(insn)) {
1da177e4	167	regs->msr &= ~MSR_SE;
0dc036c9	168	regs->msr \|= kcb->kprobe_saved_msr;
1da177e4 LT	169	goto no_kprobe;
1da177e4 LT	170	}
42cc2060 PP	171	/* We have reentered the kprobe_handler(), since
	172	* another probe was hit while within the handler.
	173	* We here save the original kprobes variables and
	174	* just single step on the instruction of the new probe
	175	* without calling any user handlers.
	176	*/
0dc036c9 AM	177	save_previous_kprobe(kcb);
	178	set_current_kprobe(p, regs, kcb);
	179	kcb->kprobe_saved_msr = regs->msr;
bf8d5c52	180	kprobes_inc_nmissed_count(p);
42cc2060	181	prepare_singlestep(p, regs);
0dc036c9	182	kcb->kprobe_status = KPROBE_REENTER;
42cc2060	183	return 1;
1da177e4	184	} else {
0dc036c9	185	p = __get_cpu_var(current_kprobe);
1da177e4 LT	186	if (p->break_handler && p->break_handler(p, regs)) {
	187	goto ss_probe;
	188	}
	189	}
1da177e4 LT	190	goto no_kprobe;
	191	}
	192
1da177e4 LT	193	p = get_kprobe(addr);
1da177e4 LT	194	if (!p) {
1da177e4 LT	195	if (*addr != BREAKPOINT_INSTRUCTION) {
	196	/*
	197	* PowerPC has multiple variants of the "trap"
	198	* instruction. If the current instruction is a
	199	* trap variant, it could belong to someone else
	200	*/
	201	kprobe_opcode_t cur_insn = *addr;
deac66ae	202	if (is_trap(cur_insn))
1da177e4 LT	203	goto no_kprobe;
	204	/*
	205	* The breakpoint instruction was removed right
	206	* after we hit it. Another cpu has removed
	207	* either a probepoint or a debugger breakpoint
	208	* at this address. In either case, no further
	209	* handling of this interrupt is appropriate.
	210	*/
	211	ret = 1;
	212	}
	213	/* Not one of ours: let kernel handle it */
	214	goto no_kprobe;
	215	}
	216
0dc036c9 AM	217	kcb->kprobe_status = KPROBE_HIT_ACTIVE;
0dc036c9 AM	218	set_current_kprobe(p, regs, kcb);
1da177e4 LT	219	if (p->pre_handler && p->pre_handler(p, regs))
	220	/* handler has already set things up, so skip ss setup */
	221	return 1;
	222
	223	ss_probe:
	224	prepare_singlestep(p, regs);
0dc036c9	225	kcb->kprobe_status = KPROBE_HIT_SS;
1da177e4 LT	226	return 1;
	227
	228	no_kprobe:
d217d545	229	preempt_enable_no_resched();
1da177e4 LT	230	return ret;
	231	}
	232
97f7943d RL	233	/*
	234	* Function return probe trampoline:
	235	* - init_kprobes() establishes a probepoint here
	236	* - When the probed function returns, this probe
	237	* causes the handlers to fire
	238	*/
	239	void kretprobe_trampoline_holder(void)
	240	{
	241	asm volatile(".global kretprobe_trampoline\n"
	242	"kretprobe_trampoline:\n"
	243	"nop\n");
	244	}
	245
	246	/*
	247	* Called when the probe at kretprobe trampoline is hit
	248	*/
bb144a85	249	int __kprobes trampoline_probe_handler(struct kprobe p, struct pt_regs regs)
97f7943d RL	250	{
	251	struct kretprobe_instance *ri = NULL;
	252	struct hlist_head *head;
	253	struct hlist_node node, tmp;
991a51d8	254	unsigned long flags, orig_ret_address = 0;
97f7943d RL	255	unsigned long trampoline_address =(unsigned long)&kretprobe_trampoline;
97f7943d RL	256
991a51d8	257	spin_lock_irqsave(&kretprobe_lock, flags);
97f7943d RL	258	head = kretprobe_inst_table_head(current);
	259
	260	/*
	261	* It is possible to have multiple instances associated with a given
	262	* task either because an multiple functions in the call path
	263	* have a return probe installed on them, and/or more then one return
	264	* return probe was registered for a target function.
	265	*
	266	* We can handle this because:
	267	* - instances are always inserted at the head of the list
	268	* - when multiple return probes are registered for the same
	269	* function, the first instance's ret_addr will point to the
	270	* real return address, and all the rest will point to
	271	* kretprobe_trampoline
	272	*/
	273	hlist_for_each_entry_safe(ri, node, tmp, head, hlist) {
	274	if (ri->task != current)
	275	/* another task is sharing our hash bucket */
	276	continue;
	277
	278	if (ri->rp && ri->rp->handler)
	279	ri->rp->handler(ri, regs);
	280
	281	orig_ret_address = (unsigned long)ri->ret_addr;
	282	recycle_rp_inst(ri);
	283
	284	if (orig_ret_address != trampoline_address)
	285	/*
	286	* This is the real return address. Any other
	287	* instances associated with this task are for
	288	* other calls deeper on the call stack
	289	*/
	290	break;
	291	}
	292
	293	BUG_ON(!orig_ret_address \|\| (orig_ret_address == trampoline_address));
	294	regs->nip = orig_ret_address;
	295
0dc036c9	296	reset_current_kprobe();
991a51d8	297	spin_unlock_irqrestore(&kretprobe_lock, flags);
66ff2d06	298	preempt_enable_no_resched();
97f7943d RL	299
	300	/*
	301	* By returning a non-zero value, we are telling
d217d545 AM	302	* kprobe_handler() that we don't want the post_handler
d217d545 AM	303	* to run (and have re-enabled preemption)
97f7943d RL	304	*/
	305	return 1;
	306	}
	307
1da177e4 LT	308	/*
	309	* Called after single-stepping. p->addr is the address of the
	310	* instruction whose first byte has been replaced by the "breakpoint"
	311	* instruction. To avoid the SMP problems that can occur when we
	312	* temporarily put back the original opcode to single-step, we
	313	* single-stepped a copy of the instruction. The address of this
	314	* copy is p->ainsn.insn.
	315	*/
bb144a85	316	static void __kprobes resume_execution(struct kprobe p, struct pt_regs regs)
1da177e4 LT	317	{
1da177e4 LT	318	int ret;
9ec4b1f3	319	unsigned int insn = *p->ainsn.insn;
1da177e4 LT	320
1da177e4 LT	321	regs->nip = (unsigned long)p->addr;
9ec4b1f3	322	ret = emulate_step(regs, insn);
1da177e4 LT	323	if (ret == 0)
1da177e4 LT	324	regs->nip = (unsigned long)p->addr + 4;
1da177e4 LT	325	}
	326
	327	static inline int post_kprobe_handler(struct pt_regs *regs)
	328	{
0dc036c9 AM	329	struct kprobe *cur = kprobe_running();
	330	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
	331
	332	if (!cur)
1da177e4 LT	333	return 0;
1da177e4 LT	334
0dc036c9 AM	335	if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
	336	kcb->kprobe_status = KPROBE_HIT_SSDONE;
	337	cur->post_handler(cur, regs, 0);
42cc2060	338	}
1da177e4	339
0dc036c9 AM	340	resume_execution(cur, regs);
0dc036c9 AM	341	regs->msr \|= kcb->kprobe_saved_msr;
1da177e4	342
42cc2060	343	/Restore back the original saved kprobes variables and continue. /
0dc036c9 AM	344	if (kcb->kprobe_status == KPROBE_REENTER) {
0dc036c9 AM	345	restore_previous_kprobe(kcb);
42cc2060 PP	346	goto out;
42cc2060 PP	347	}
0dc036c9	348	reset_current_kprobe();
42cc2060	349	out:
1da177e4 LT	350	preempt_enable_no_resched();
	351
	352	/*
	353	* if somebody else is singlestepping across a probe point, msr
	354	* will have SE set, in which case, continue the remaining processing
	355	* of do_debug, as if this is not a probe hit.
	356	*/
	357	if (regs->msr & MSR_SE)
	358	return 0;
	359
	360	return 1;
	361	}
	362
1da177e4 LT	363	static inline int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
1da177e4 LT	364	{
0dc036c9 AM	365	struct kprobe *cur = kprobe_running();
	366	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
	367
	368	if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
1da177e4 LT	369	return 1;
1da177e4 LT	370
0dc036c9 AM	371	if (kcb->kprobe_status & KPROBE_HIT_SS) {
0dc036c9 AM	372	resume_execution(cur, regs);
f829fd23	373	regs->msr &= ~MSR_SE;
0dc036c9	374	regs->msr \|= kcb->kprobe_saved_msr;
1da177e4	375
0dc036c9	376	reset_current_kprobe();
1da177e4 LT	377	preempt_enable_no_resched();
	378	}
	379	return 0;
	380	}
	381
	382	/*
	383	* Wrapper routine to for handling exceptions.
	384	*/
bb144a85 PP	385	int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
bb144a85 PP	386	unsigned long val, void *data)
1da177e4 LT	387	{
	388	struct die_args args = (struct die_args )data;
	389	int ret = NOTIFY_DONE;
	390
1da177e4	391	switch (val) {
1da177e4 LT	392	case DIE_BPT:
	393	if (kprobe_handler(args->regs))
	394	ret = NOTIFY_STOP;
	395	break;
	396	case DIE_SSTEP:
	397	if (post_kprobe_handler(args->regs))
	398	ret = NOTIFY_STOP;
	399	break;
1da177e4	400	case DIE_PAGE_FAULT:
d217d545 AM	401	/* kprobe_running() needs smp_processor_id() */
d217d545 AM	402	preempt_disable();
1da177e4 LT	403	if (kprobe_running() &&
	404	kprobe_fault_handler(args->regs, args->trapnr))
	405	ret = NOTIFY_STOP;
d217d545	406	preempt_enable();
1da177e4 LT	407	break;
	408	default:
	409	break;
	410	}
1da177e4 LT	411	return ret;
	412	}
	413
bb144a85	414	int __kprobes setjmp_pre_handler(struct kprobe p, struct pt_regs regs)
1da177e4 LT	415	{
1da177e4 LT	416	struct jprobe *jp = container_of(p, struct jprobe, kp);
0dc036c9	417	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
1da177e4	418
0dc036c9	419	memcpy(&kcb->jprobe_saved_regs, regs, sizeof(struct pt_regs));
1da177e4 LT	420
	421	/* setup return addr to the jprobe handler routine */
	422	regs->nip = (unsigned long)(((func_descr_t *)jp->entry)->entry);
	423	regs->gpr[2] = (unsigned long)(((func_descr_t *)jp->entry)->toc);
	424
	425	return 1;
	426	}
	427
bb144a85	428	void __kprobes jprobe_return(void)
1da177e4 LT	429	{
	430	asm volatile("trap" ::: "memory");
	431	}
	432
bb144a85	433	void __kprobes jprobe_return_end(void)
1da177e4 LT	434	{
	435	};
	436
bb144a85	437	int __kprobes longjmp_break_handler(struct kprobe p, struct pt_regs regs)
1da177e4	438	{
0dc036c9 AM	439	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
0dc036c9 AM	440
1da177e4 LT	441	/*
	442	* FIXME - we should ideally be validating that we got here 'cos
	443	* of the "trap" in jprobe_return() above, before restoring the
	444	* saved regs...
	445	*/
0dc036c9	446	memcpy(regs, &kcb->jprobe_saved_regs, sizeof(struct pt_regs));
d217d545	447	preempt_enable_no_resched();
1da177e4 LT	448	return 1;
1da177e4 LT	449	}
97f7943d RL	450
	451	static struct kprobe trampoline_p = {
	452	.addr = (kprobe_opcode_t *) &kretprobe_trampoline,
	453	.pre_handler = trampoline_probe_handler
	454	};
	455
6772926b	456	int __init arch_init_kprobes(void)
97f7943d RL	457	{
	458	return register_kprobe(&trampoline_p);
	459	}