[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 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 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;
	}
	return ret;
}

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

void 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 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 arch_remove_kprobe(struct kprobe *p)
{
}

static inline void prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
{
	regs->msr |= MSR_SE;
	/*single step inline if it a breakpoint instruction*/
	if (p->opcode == BREAKPOINT_INSTRUCTION)
		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;
}

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;
}

/*
 * 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 resume_execution(struct kprobe *p, struct pt_regs *regs)
{
	int ret;

	regs->nip = (unsigned long)p->addr;
	ret = emulate_step(regs, p->ainsn.insn[0]);
	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 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 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 jprobe_return(void)
{
	asm volatile("trap" ::: "memory");
}

void jprobe_return_end(void)
{
};

int 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;
}
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
1da177e4 LT	39	static struct kprobe *current_kprobe;
1da177e4 LT	40	static unsigned long kprobe_status, kprobe_saved_msr;
42cc2060 PP	41	static struct kprobe *kprobe_prev;
42cc2060 PP	42	static unsigned long kprobe_status_prev, kprobe_saved_msr_prev;
1da177e4 LT	43	static struct pt_regs jprobe_saved_regs;
	44
	45	int arch_prepare_kprobe(struct kprobe *p)
	46	{
63224d1e	47	int ret = 0;
1da177e4 LT	48	kprobe_opcode_t insn = *p->addr;
1da177e4 LT	49
63224d1e AM	50	if ((unsigned long)p->addr & 0x03) {
	51	printk("Attempt to register kprobe at an unaligned address\n");
	52	ret = -EINVAL;
	53	} else if (IS_MTMSRD(insn) \|\| IS_RFID(insn)) {
	54	printk("Cannot register a kprobe on rfid or mtmsrd\n");
	55	ret = -EINVAL;
	56	}
	57	return ret;
1da177e4 LT	58	}
	59
	60	void arch_copy_kprobe(struct kprobe *p)
	61	{
	62	memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
7e1048b1	63	p->opcode = *p->addr;
1da177e4 LT	64	}
1da177e4 LT	65
7e1048b1	66	void arch_arm_kprobe(struct kprobe *p)
1da177e4	67	{
7e1048b1 RL	68	*p->addr = BREAKPOINT_INSTRUCTION;
	69	flush_icache_range((unsigned long) p->addr,
	70	(unsigned long) p->addr + sizeof(kprobe_opcode_t));
1da177e4 LT	71	}
1da177e4 LT	72
7e1048b1	73	void arch_disarm_kprobe(struct kprobe *p)
1da177e4 LT	74	{
1da177e4 LT	75	*p->addr = p->opcode;
7e1048b1 RL	76	flush_icache_range((unsigned long) p->addr,
	77	(unsigned long) p->addr + sizeof(kprobe_opcode_t));
	78	}
	79
	80	void arch_remove_kprobe(struct kprobe *p)
	81	{
1da177e4 LT	82	}
	83
	84	static inline void prepare_singlestep(struct kprobe p, struct pt_regs regs)
	85	{
	86	regs->msr \|= MSR_SE;
	87	/single step inline if it a breakpoint instruction/
	88	if (p->opcode == BREAKPOINT_INSTRUCTION)
	89	regs->nip = (unsigned long)p->addr;
	90	else
	91	regs->nip = (unsigned long)&p->ainsn.insn;
	92	}
	93
42cc2060 PP	94	static inline void save_previous_kprobe(void)
	95	{
	96	kprobe_prev = current_kprobe;
	97	kprobe_status_prev = kprobe_status;
	98	kprobe_saved_msr_prev = kprobe_saved_msr;
	99	}
	100
	101	static inline void restore_previous_kprobe(void)
	102	{
	103	current_kprobe = kprobe_prev;
	104	kprobe_status = kprobe_status_prev;
	105	kprobe_saved_msr = kprobe_saved_msr_prev;
	106	}
	107
1da177e4 LT	108	static inline int kprobe_handler(struct pt_regs *regs)
	109	{
	110	struct kprobe *p;
	111	int ret = 0;
	112	unsigned int addr = (unsigned int )regs->nip;
	113
	114	/* Check we're not actually recursing */
	115	if (kprobe_running()) {
	116	/* We are holding lock here, so this is safe.
	117	Disarm the probe we just hit, and ignore it. */
	118	p = get_kprobe(addr);
	119	if (p) {
	120	if (kprobe_status == KPROBE_HIT_SS) {
	121	regs->msr &= ~MSR_SE;
	122	regs->msr \|= kprobe_saved_msr;
	123	unlock_kprobes();
	124	goto no_kprobe;
	125	}
42cc2060 PP	126	/* We have reentered the kprobe_handler(), since
	127	* another probe was hit while within the handler.
	128	* We here save the original kprobes variables and
	129	* just single step on the instruction of the new probe
	130	* without calling any user handlers.
	131	*/
	132	save_previous_kprobe();
	133	current_kprobe = p;
	134	kprobe_saved_msr = regs->msr;
	135	p->nmissed++;
	136	prepare_singlestep(p, regs);
	137	kprobe_status = KPROBE_REENTER;
	138	return 1;
1da177e4 LT	139	} else {
	140	p = current_kprobe;
	141	if (p->break_handler && p->break_handler(p, regs)) {
	142	goto ss_probe;
	143	}
	144	}
	145	/* If it's not ours, can't be delete race, (we hold lock). */
	146	goto no_kprobe;
	147	}
	148
	149	lock_kprobes();
	150	p = get_kprobe(addr);
	151	if (!p) {
	152	unlock_kprobes();
	153	if (*addr != BREAKPOINT_INSTRUCTION) {
	154	/*
	155	* PowerPC has multiple variants of the "trap"
	156	* instruction. If the current instruction is a
	157	* trap variant, it could belong to someone else
	158	*/
	159	kprobe_opcode_t cur_insn = *addr;
	160	if (IS_TW(cur_insn) \|\| IS_TD(cur_insn) \|\|
	161	IS_TWI(cur_insn) \|\| IS_TDI(cur_insn))
	162	goto no_kprobe;
	163	/*
	164	* The breakpoint instruction was removed right
	165	* after we hit it. Another cpu has removed
	166	* either a probepoint or a debugger breakpoint
	167	* at this address. In either case, no further
	168	* handling of this interrupt is appropriate.
	169	*/
	170	ret = 1;
	171	}
	172	/* Not one of ours: let kernel handle it */
	173	goto no_kprobe;
	174	}
	175
	176	kprobe_status = KPROBE_HIT_ACTIVE;
	177	current_kprobe = p;
	178	kprobe_saved_msr = regs->msr;
	179	if (p->pre_handler && p->pre_handler(p, regs))
	180	/* handler has already set things up, so skip ss setup */
	181	return 1;
	182
	183	ss_probe:
	184	prepare_singlestep(p, regs);
	185	kprobe_status = KPROBE_HIT_SS;
	186	/*
	187	* This preempt_disable() matches the preempt_enable_no_resched()
	188	* in post_kprobe_handler().
	189	*/
	190	preempt_disable();
	191	return 1;
	192
	193	no_kprobe:
	194	return ret;
	195	}
	196
	197	/*
	198	* Called after single-stepping. p->addr is the address of the
	199	* instruction whose first byte has been replaced by the "breakpoint"
	200	* instruction. To avoid the SMP problems that can occur when we
	201	* temporarily put back the original opcode to single-step, we
	202	* single-stepped a copy of the instruction. The address of this
203	* copy is p->ainsn.insn.
204	*/
205	static void resume_execution(struct kprobe p, struct pt_regs regs)
206	{
207	int ret;
208
209	regs->nip = (unsigned long)p->addr;
210	ret = emulate_step(regs, p->ainsn.insn[0]);
211	if (ret == 0)
212	regs->nip = (unsigned long)p->addr + 4;
1da177e4 LT	213	}
	214
	215	static inline int post_kprobe_handler(struct pt_regs *regs)
	216	{
	217	if (!kprobe_running())
	218	return 0;
	219
42cc2060 PP	220	if ((kprobe_status != KPROBE_REENTER) && current_kprobe->post_handler) {
42cc2060 PP	221	kprobe_status = KPROBE_HIT_SSDONE;
1da177e4	222	current_kprobe->post_handler(current_kprobe, regs, 0);
42cc2060	223	}
1da177e4 LT	224
	225	resume_execution(current_kprobe, regs);
	226	regs->msr \|= kprobe_saved_msr;
	227
42cc2060 PP	228	/Restore back the original saved kprobes variables and continue. /
	229	if (kprobe_status == KPROBE_REENTER) {
	230	restore_previous_kprobe();
	231	goto out;
	232	}
1da177e4	233	unlock_kprobes();
42cc2060	234	out:
1da177e4 LT	235	preempt_enable_no_resched();
	236
	237	/*
	238	* if somebody else is singlestepping across a probe point, msr
	239	* will have SE set, in which case, continue the remaining processing
	240	* of do_debug, as if this is not a probe hit.
	241	*/
	242	if (regs->msr & MSR_SE)
	243	return 0;
	244
	245	return 1;
	246	}
	247
	248	/* Interrupts disabled, kprobe_lock held. */
	249	static inline int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
	250	{
	251	if (current_kprobe->fault_handler
	252	&& current_kprobe->fault_handler(current_kprobe, regs, trapnr))
	253	return 1;
	254
	255	if (kprobe_status & KPROBE_HIT_SS) {
	256	resume_execution(current_kprobe, regs);
f829fd23	257	regs->msr &= ~MSR_SE;
1da177e4 LT	258	regs->msr \|= kprobe_saved_msr;
	259
	260	unlock_kprobes();
	261	preempt_enable_no_resched();
	262	}
	263	return 0;
	264	}
	265
	266	/*
	267	* Wrapper routine to for handling exceptions.
	268	*/
	269	int kprobe_exceptions_notify(struct notifier_block *self, unsigned long val,
	270	void *data)
	271	{
	272	struct die_args args = (struct die_args )data;
	273	int ret = NOTIFY_DONE;
	274
	275	/*
	276	* Interrupts are not disabled here. We need to disable
	277	* preemption, because kprobe_running() uses smp_processor_id().
	278	*/
	279	preempt_disable();
	280	switch (val) {
1da177e4 LT	281	case DIE_BPT:
	282	if (kprobe_handler(args->regs))
	283	ret = NOTIFY_STOP;
	284	break;
	285	case DIE_SSTEP:
	286	if (post_kprobe_handler(args->regs))
	287	ret = NOTIFY_STOP;
	288	break;
	289	case DIE_GPF:
	290	case DIE_PAGE_FAULT:
	291	if (kprobe_running() &&
	292	kprobe_fault_handler(args->regs, args->trapnr))
	293	ret = NOTIFY_STOP;
	294	break;
	295	default:
	296	break;
	297	}
	298	preempt_enable();
	299	return ret;
	300	}
	301
	302	int setjmp_pre_handler(struct kprobe p, struct pt_regs regs)
	303	{
	304	struct jprobe *jp = container_of(p, struct jprobe, kp);
	305
	306	memcpy(&jprobe_saved_regs, regs, sizeof(struct pt_regs));
	307
	308	/* setup return addr to the jprobe handler routine */
	309	regs->nip = (unsigned long)(((func_descr_t *)jp->entry)->entry);
	310	regs->gpr[2] = (unsigned long)(((func_descr_t *)jp->entry)->toc);
	311
	312	return 1;
	313	}
	314
	315	void jprobe_return(void)
	316	{
	317	asm volatile("trap" ::: "memory");
	318	}
	319
	320	void jprobe_return_end(void)
	321	{
	322	};
	323
	324	int longjmp_break_handler(struct kprobe p, struct pt_regs regs)
	325	{
	326	/*
	327	* FIXME - we should ideally be validating that we got here 'cos
	328	* of the "trap" in jprobe_return() above, before restoring the
	329	* saved regs...
	330	*/
	331	memcpy(regs, &jprobe_saved_regs, sizeof(struct pt_regs));
	332	return 1;
	333	}