[mirror_ubuntu-artful-kernel.git] / arch / ppc64 / 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/spinlock.h>
#include <linux/preempt.h>
#include <asm/cacheflush.h>
#include <asm/kdebug.h>
#include <asm/sstep.h>

static DECLARE_MUTEX(kprobe_mutex);

static struct kprobe *current_kprobe;
static unsigned long kprobe_status, kprobe_saved_msr;
static struct kprobe *kprobe_prev;
static unsigned long kprobe_status_prev, kprobe_saved_msr_prev;
static struct pt_regs jprobe_saved_regs;

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) {
		up(&kprobe_mutex);
		p->ainsn.insn = get_insn_slot();
		down(&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)
{
	up(&kprobe_mutex);
	free_insn_slot(p->ainsn.insn);
	down(&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_TW(insn) || IS_TD(insn) || IS_TWI(insn) || IS_TDI(insn))
		regs->nip = (unsigned long)p->addr;
	else
		regs->nip = (unsigned long)p->ainsn.insn;
}

static inline void save_previous_kprobe(void)
{
	kprobe_prev = current_kprobe;
	kprobe_status_prev = kprobe_status;
	kprobe_saved_msr_prev = kprobe_saved_msr;
}

static inline void restore_previous_kprobe(void)
{
	current_kprobe = kprobe_prev;
	kprobe_status = kprobe_status_prev;
	kprobe_saved_msr = kprobe_saved_msr_prev;
}

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;

	/* Check we're not actually recursing */
	if (kprobe_running()) {
		/* We *are* holding lock here, so this is safe.
		   Disarm the probe we just hit, and ignore it. */
		p = get_kprobe(addr);
		if (p) {
			if (kprobe_status == KPROBE_HIT_SS) {
				regs->msr &= ~MSR_SE;
				regs->msr |= kprobe_saved_msr;
				unlock_kprobes();
				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();
			current_kprobe = p;
			kprobe_saved_msr = regs->msr;
			p->nmissed++;
			prepare_singlestep(p, regs);
			kprobe_status = KPROBE_REENTER;
			return 1;
		} else {
			p = current_kprobe;
			if (p->break_handler && p->break_handler(p, regs)) {
				goto ss_probe;
			}
		}
		/* If it's not ours, can't be delete race, (we hold lock). */
		goto no_kprobe;
	}

	lock_kprobes();
	p = get_kprobe(addr);
	if (!p) {
		unlock_kprobes();
		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_TW(cur_insn) || IS_TD(cur_insn) ||
					IS_TWI(cur_insn) || IS_TDI(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;
	}

	kprobe_status = KPROBE_HIT_ACTIVE;
	current_kprobe = p;
	kprobe_saved_msr = regs->msr;
	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);
	kprobe_status = KPROBE_HIT_SS;
	/*
	 * This preempt_disable() matches the preempt_enable_no_resched()
	 * in post_kprobe_handler().
	 */
	preempt_disable();
	return 1;

no_kprobe:
	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 orig_ret_address = 0;
	unsigned long trampoline_address =(unsigned long)&kretprobe_trampoline;

        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;

	unlock_kprobes();

        /*
         * By returning a non-zero value, we are telling
         * kprobe_handler() that we have handled unlocking
         * and re-enabling 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)
{
	if (!kprobe_running())
		return 0;

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

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

	/*Restore back the original saved kprobes variables and continue. */
	if (kprobe_status == KPROBE_REENTER) {
		restore_previous_kprobe();
		goto out;
	}
	unlock_kprobes();
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;
}

/* Interrupts disabled, kprobe_lock held. */
static inline int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
{
	if (current_kprobe->fault_handler
	    && current_kprobe->fault_handler(current_kprobe, regs, trapnr))
		return 1;

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

		unlock_kprobes();
		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;

	/*
	 * Interrupts are not disabled here.  We need to disable
	 * preemption, because kprobe_running() uses smp_processor_id().
	 */
	preempt_disable();
	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_GPF:
	case DIE_PAGE_FAULT:
		if (kprobe_running() &&
		    kprobe_fault_handler(args->regs, args->trapnr))
			ret = NOTIFY_STOP;
		break;
	default:
		break;
	}
	preempt_enable();
	return ret;
}

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

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