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

/*
 * arch/arm/kernel/kprobes.c
 *
 * Kprobes on ARM
 *
 * Abhishek Sagar <sagar.abhishek@gmail.com>
 * Copyright (C) 2006, 2007 Motorola Inc.
 *
 * Nicolas Pitre <nico@marvell.com>
 * Copyright (C) 2007 Marvell Ltd.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * 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.
 */

#include <linux/kernel.h>
#include <linux/kprobes.h>
#include <linux/module.h>
#include <linux/stop_machine.h>
#include <linux/stringify.h>
#include <asm/traps.h>
#include <asm/cacheflush.h>

#define MIN_STACK_SIZE(addr) 				\
	min((unsigned long)MAX_STACK_SIZE,		\
	    (unsigned long)current_thread_info() + THREAD_START_SP - (addr))

#define flush_insns(addr, cnt) 				\
	flush_icache_range((unsigned long)(addr),	\
			   (unsigned long)(addr) +	\
			   sizeof(kprobe_opcode_t) * (cnt))

/* Used as a marker in ARM_pc to note when we're in a jprobe. */
#define JPROBE_MAGIC_ADDR		0xffffffff

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


int __kprobes arch_prepare_kprobe(struct kprobe *p)
{
	kprobe_opcode_t insn;
	kprobe_opcode_t tmp_insn[MAX_INSN_SIZE];
	unsigned long addr = (unsigned long)p->addr;
	int is;

	if (addr & 0x3 || in_exception_text(addr))
		return -EINVAL;

	insn = *p->addr;
	p->opcode = insn;
	p->ainsn.insn = tmp_insn;

	switch (arm_kprobe_decode_insn(insn, &p->ainsn)) {
	case INSN_REJECTED:	/* not supported */
		return -EINVAL;

	case INSN_GOOD:		/* instruction uses slot */
		p->ainsn.insn = get_insn_slot();
		if (!p->ainsn.insn)
			return -ENOMEM;
		for (is = 0; is < MAX_INSN_SIZE; ++is)
			p->ainsn.insn[is] = tmp_insn[is];
		flush_insns(p->ainsn.insn, MAX_INSN_SIZE);
		break;

	case INSN_GOOD_NO_SLOT:	/* instruction doesn't need insn slot */
		p->ainsn.insn = NULL;
		break;
	}

	return 0;
}

void __kprobes arch_arm_kprobe(struct kprobe *p)
{
	*p->addr = KPROBE_BREAKPOINT_INSTRUCTION;
	flush_insns(p->addr, 1);
}

/*
 * The actual disarming is done here on each CPU and synchronized using
 * stop_machine. This synchronization is necessary on SMP to avoid removing
 * a probe between the moment the 'Undefined Instruction' exception is raised
 * and the moment the exception handler reads the faulting instruction from
 * memory.
 */
int __kprobes __arch_disarm_kprobe(void *p)
{
	struct kprobe *kp = p;
	*kp->addr = kp->opcode;
	flush_insns(kp->addr, 1);
	return 0;
}

void __kprobes arch_disarm_kprobe(struct kprobe *p)
{
	stop_machine(__arch_disarm_kprobe, p, &cpu_online_map);
}

void __kprobes arch_remove_kprobe(struct kprobe *p)
{
	if (p->ainsn.insn) {
		free_insn_slot(p->ainsn.insn, 0);
		p->ainsn.insn = NULL;
	}
}

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

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

static void __kprobes set_current_kprobe(struct kprobe *p)
{
	__get_cpu_var(current_kprobe) = p;
}

static void __kprobes singlestep(struct kprobe *p, struct pt_regs *regs,
				 struct kprobe_ctlblk *kcb)
{
	regs->ARM_pc += 4;
	p->ainsn.insn_handler(p, regs);
}

/*
 * Called with IRQs disabled. IRQs must remain disabled from that point
 * all the way until processing this kprobe is complete.  The current
 * kprobes implementation cannot process more than one nested level of
 * kprobe, and that level is reserved for user kprobe handlers, so we can't
 * risk encountering a new kprobe in an interrupt handler.
 */
void __kprobes kprobe_handler(struct pt_regs *regs)
{
	struct kprobe *p, *cur;
	struct kprobe_ctlblk *kcb;
	kprobe_opcode_t	*addr = (kprobe_opcode_t *)regs->ARM_pc;

	kcb = get_kprobe_ctlblk();
	cur = kprobe_running();
	p = get_kprobe(addr);

	if (p) {
		if (cur) {
			/* Kprobe is pending, so we're recursing. */
			switch (kcb->kprobe_status) {
			case KPROBE_HIT_ACTIVE:
			case KPROBE_HIT_SSDONE:
				/* A pre- or post-handler probe got us here. */
				kprobes_inc_nmissed_count(p);
				save_previous_kprobe(kcb);
				set_current_kprobe(p);
				kcb->kprobe_status = KPROBE_REENTER;
				singlestep(p, regs, kcb);
				restore_previous_kprobe(kcb);
				break;
			default:
				/* impossible cases */
				BUG();
			}
		} else {
			set_current_kprobe(p);
			kcb->kprobe_status = KPROBE_HIT_ACTIVE;

			/*
			 * If we have no pre-handler or it returned 0, we
			 * continue with normal processing.  If we have a
			 * pre-handler and it returned non-zero, it prepped
			 * for calling the break_handler below on re-entry,
			 * so get out doing nothing more here.
			 */
			if (!p->pre_handler || !p->pre_handler(p, regs)) {
				kcb->kprobe_status = KPROBE_HIT_SS;
				singlestep(p, regs, kcb);
				if (p->post_handler) {
					kcb->kprobe_status = KPROBE_HIT_SSDONE;
					p->post_handler(p, regs, 0);
				}
				reset_current_kprobe();
			}
		}
	} else if (cur) {
		/* We probably hit a jprobe.  Call its break handler. */
		if (cur->break_handler && cur->break_handler(cur, regs)) {
			kcb->kprobe_status = KPROBE_HIT_SS;
			singlestep(cur, regs, kcb);
			if (cur->post_handler) {
				kcb->kprobe_status = KPROBE_HIT_SSDONE;
				cur->post_handler(cur, regs, 0);
			}
		}
		reset_current_kprobe();
	} else {
		/*
		 * The probe was removed and a race is in progress.
		 * There is nothing we can do about it.  Let's restart
		 * the instruction.  By the time we can restart, the
		 * real instruction will be there.
		 */
	}
}

static int __kprobes kprobe_trap_handler(struct pt_regs *regs, unsigned int instr)
{
	unsigned long flags;
	local_irq_save(flags);
	kprobe_handler(regs);
	local_irq_restore(flags);
	return 0;
}

int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned int fsr)
{
	struct kprobe *cur = kprobe_running();
	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();

	switch (kcb->kprobe_status) {
	case KPROBE_HIT_SS:
	case KPROBE_REENTER:
		/*
		 * We are here because the instruction being single
		 * stepped caused a page fault. We reset the current
		 * kprobe and the PC to point back to the probe address
		 * and allow the page fault handler to continue as a
		 * normal page fault.
		 */
		regs->ARM_pc = (long)cur->addr;
		if (kcb->kprobe_status == KPROBE_REENTER) {
			restore_previous_kprobe(kcb);
		} else {
			reset_current_kprobe();
		}
		break;

	case KPROBE_HIT_ACTIVE:
	case KPROBE_HIT_SSDONE:
		/*
		 * We increment the nmissed count for accounting,
		 * we can also use npre/npostfault count for accounting
		 * these specific fault cases.
		 */
		kprobes_inc_nmissed_count(cur);

		/*
		 * We come here because instructions in the pre/post
		 * handler caused the page_fault, this could happen
		 * if handler tries to access user space by
		 * copy_from_user(), get_user() etc. Let the
		 * user-specified handler try to fix it.
		 */
		if (cur->fault_handler && cur->fault_handler(cur, regs, fsr))
			return 1;
		break;

	default:
		break;
	}

	return 0;
}

int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
				       unsigned long val, void *data)
{
	/*
	 * notify_die() is currently never called on ARM,
	 * so this callback is currently empty.
	 */
	return NOTIFY_DONE;
}

/*
 * When a retprobed function returns, trampoline_handler() is called,
 * calling the kretprobe's handler. We construct a struct pt_regs to
 * give a view of registers r0-r11 to the user return-handler.  This is
 * not a complete pt_regs structure, but that should be plenty sufficient
 * for kretprobe handlers which should normally be interested in r0 only
 * anyway.
 */
void __naked __kprobes kretprobe_trampoline(void)
{
	__asm__ __volatile__ (
		"stmdb	sp!, {r0 - r11}		\n\t"
		"mov	r0, sp			\n\t"
		"bl	trampoline_handler	\n\t"
		"mov	lr, r0			\n\t"
		"ldmia	sp!, {r0 - r11}		\n\t"
		"mov	pc, lr			\n\t"
		: : : "memory");
}

/* Called from kretprobe_trampoline */
static __used __kprobes void *trampoline_handler(struct pt_regs *regs)
{
	struct kretprobe_instance *ri = NULL;
	struct hlist_head *head, empty_rp;
	struct hlist_node *node, *tmp;
	unsigned long flags, orig_ret_address = 0;
	unsigned long trampoline_address = (unsigned long)&kretprobe_trampoline;

	INIT_HLIST_HEAD(&empty_rp);
	kretprobe_hash_lock(current, &head, &flags);

	/*
	 * It is possible to have multiple instances associated with a given
	 * task either because multiple functions in the call path have
	 * a return probe installed on them, and/or more than one 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) {
			__get_cpu_var(current_kprobe) = &ri->rp->kp;
			get_kprobe_ctlblk()->kprobe_status = KPROBE_HIT_ACTIVE;
			ri->rp->handler(ri, regs);
			__get_cpu_var(current_kprobe) = NULL;
		}

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

		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;
	}

	kretprobe_assert(ri, orig_ret_address, trampoline_address);
	kretprobe_hash_unlock(current, &flags);

	hlist_for_each_entry_safe(ri, node, tmp, &empty_rp, hlist) {
		hlist_del(&ri->hlist);
		kfree(ri);
	}

	return (void *)orig_ret_address;
}

void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
				      struct pt_regs *regs)
{
	ri->ret_addr = (kprobe_opcode_t *)regs->ARM_lr;

	/* Replace the return addr with trampoline addr. */
	regs->ARM_lr = (unsigned long)&kretprobe_trampoline;
}

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();
	long sp_addr = regs->ARM_sp;

	kcb->jprobe_saved_regs = *regs;
	memcpy(kcb->jprobes_stack, (void *)sp_addr, MIN_STACK_SIZE(sp_addr));
	regs->ARM_pc = (long)jp->entry;
	regs->ARM_cpsr |= PSR_I_BIT;
	preempt_disable();
	return 1;
}

void __kprobes jprobe_return(void)
{
	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();

	__asm__ __volatile__ (
		/*
		 * Setup an empty pt_regs. Fill SP and PC fields as
		 * they're needed by longjmp_break_handler.
		 */
		"sub    sp, %0, %1		\n\t"
		"ldr    r0, ="__stringify(JPROBE_MAGIC_ADDR)"\n\t"
		"str    %0, [sp, %2]		\n\t"
		"str    r0, [sp, %3]		\n\t"
		"mov    r0, sp			\n\t"
		"bl     kprobe_handler		\n\t"

		/*
		 * Return to the context saved by setjmp_pre_handler
		 * and restored by longjmp_break_handler.
		 */
		"ldr	r0, [sp, %4]		\n\t"
		"msr	cpsr_cxsf, r0		\n\t"
		"ldmia	sp, {r0 - pc}		\n\t"
		:
		: "r" (kcb->jprobe_saved_regs.ARM_sp),
		  "I" (sizeof(struct pt_regs)),
		  "J" (offsetof(struct pt_regs, ARM_sp)),
		  "J" (offsetof(struct pt_regs, ARM_pc)),
		  "J" (offsetof(struct pt_regs, ARM_cpsr))
		: "memory", "cc");
}

int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
{
	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
	long stack_addr = kcb->jprobe_saved_regs.ARM_sp;
	long orig_sp = regs->ARM_sp;
	struct jprobe *jp = container_of(p, struct jprobe, kp);

	if (regs->ARM_pc == JPROBE_MAGIC_ADDR) {
		if (orig_sp != stack_addr) {
			struct pt_regs *saved_regs =
				(struct pt_regs *)kcb->jprobe_saved_regs.ARM_sp;
			printk("current sp %lx does not match saved sp %lx\n",
			       orig_sp, stack_addr);
			printk("Saved registers for jprobe %p\n", jp);
			show_regs(saved_regs);
			printk("Current registers\n");
			show_regs(regs);
			BUG();
		}
		*regs = kcb->jprobe_saved_regs;
		memcpy((void *)stack_addr, kcb->jprobes_stack,
		       MIN_STACK_SIZE(stack_addr));
		preempt_enable_no_resched();
		return 1;
	}
	return 0;
}

int __kprobes arch_trampoline_kprobe(struct kprobe *p)
{
	return 0;
}

static struct undef_hook kprobes_break_hook = {
	.instr_mask	= 0xffffffff,
	.instr_val	= KPROBE_BREAKPOINT_INSTRUCTION,
	.cpsr_mask	= MODE_MASK,
	.cpsr_val	= SVC_MODE,
	.fn		= kprobe_trap_handler,
};

int __init arch_init_kprobes()
{
	arm_kprobe_decode_init();
	register_undef_hook(&kprobes_break_hook);
	return 0;
}
Commit	Line	Data
24ba613c AS	1	/*
	2	* arch/arm/kernel/kprobes.c
	3	*
	4	* Kprobes on ARM
	5	*
	6	* Abhishek Sagar <sagar.abhishek@gmail.com>
	7	* Copyright (C) 2006, 2007 Motorola Inc.
	8	*
	9	* Nicolas Pitre <nico@marvell.com>
	10	* Copyright (C) 2007 Marvell Ltd.
	11	*
	12	* This program is free software; you can redistribute it and/or modify
	13	* it under the terms of the GNU General Public License version 2 as
	14	* published by the Free Software Foundation.
	15	*
	16	* This program is distributed in the hope that it will be useful,
	17	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	18	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	19	* General Public License for more details.
	20	*/
	21
	22	#include <linux/kernel.h>
	23	#include <linux/kprobes.h>
	24	#include <linux/module.h>
2003b7af	25	#include <linux/stop_machine.h>
24ba613c AS	26	#include <linux/stringify.h>
	27	#include <asm/traps.h>
	28	#include <asm/cacheflush.h>
	29
24ba613c AS	30	#define MIN_STACK_SIZE(addr) \
	31	min((unsigned long)MAX_STACK_SIZE, \
	32	(unsigned long)current_thread_info() + THREAD_START_SP - (addr))
	33
	34	#define flush_insns(addr, cnt) \
	35	flush_icache_range((unsigned long)(addr), \
	36	(unsigned long)(addr) + \
	37	sizeof(kprobe_opcode_t) * (cnt))
	38
	39	/* Used as a marker in ARM_pc to note when we're in a jprobe. */
	40	#define JPROBE_MAGIC_ADDR 0xffffffff
	41
	42	DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
	43	DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
	44
	45
	46	int __kprobes arch_prepare_kprobe(struct kprobe *p)
	47	{
	48	kprobe_opcode_t insn;
	49	kprobe_opcode_t tmp_insn[MAX_INSN_SIZE];
	50	unsigned long addr = (unsigned long)p->addr;
	51	int is;
	52
785d3cd2	53	if (addr & 0x3 \|\| in_exception_text(addr))
24ba613c AS	54	return -EINVAL;
	55
	56	insn = *p->addr;
	57	p->opcode = insn;
	58	p->ainsn.insn = tmp_insn;
	59
	60	switch (arm_kprobe_decode_insn(insn, &p->ainsn)) {
	61	case INSN_REJECTED: /* not supported */
	62	return -EINVAL;
	63
	64	case INSN_GOOD: /* instruction uses slot */
	65	p->ainsn.insn = get_insn_slot();
	66	if (!p->ainsn.insn)
	67	return -ENOMEM;
	68	for (is = 0; is < MAX_INSN_SIZE; ++is)
	69	p->ainsn.insn[is] = tmp_insn[is];
8f79ff0c	70	flush_insns(p->ainsn.insn, MAX_INSN_SIZE);
24ba613c AS	71	break;
	72
	73	case INSN_GOOD_NO_SLOT: /* instruction doesn't need insn slot */
	74	p->ainsn.insn = NULL;
	75	break;
	76	}
	77
	78	return 0;
	79	}
	80
	81	void __kprobes arch_arm_kprobe(struct kprobe *p)
	82	{
	83	*p->addr = KPROBE_BREAKPOINT_INSTRUCTION;
	84	flush_insns(p->addr, 1);
	85	}
	86
2003b7af FR	87	/*
	88	* The actual disarming is done here on each CPU and synchronized using
	89	* stop_machine. This synchronization is necessary on SMP to avoid removing
	90	* a probe between the moment the 'Undefined Instruction' exception is raised
	91	* and the moment the exception handler reads the faulting instruction from
	92	* memory.
	93	*/
	94	int __kprobes __arch_disarm_kprobe(void *p)
	95	{
	96	struct kprobe *kp = p;
	97	*kp->addr = kp->opcode;
	98	flush_insns(kp->addr, 1);
	99	return 0;
	100	}
	101
24ba613c AS	102	void __kprobes arch_disarm_kprobe(struct kprobe *p)
24ba613c AS	103	{
2003b7af	104	stop_machine(__arch_disarm_kprobe, p, &cpu_online_map);
24ba613c AS	105	}
	106
	107	void __kprobes arch_remove_kprobe(struct kprobe *p)
	108	{
	109	if (p->ainsn.insn) {
24ba613c	110	free_insn_slot(p->ainsn.insn, 0);
24ba613c AS	111	p->ainsn.insn = NULL;
	112	}
	113	}
	114
	115	static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
	116	{
	117	kcb->prev_kprobe.kp = kprobe_running();
	118	kcb->prev_kprobe.status = kcb->kprobe_status;
	119	}
	120
	121	static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
	122	{
	123	__get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp;
	124	kcb->kprobe_status = kcb->prev_kprobe.status;
	125	}
	126
	127	static void __kprobes set_current_kprobe(struct kprobe *p)
	128	{
	129	__get_cpu_var(current_kprobe) = p;
	130	}
	131
	132	static void __kprobes singlestep(struct kprobe p, struct pt_regs regs,
	133	struct kprobe_ctlblk *kcb)
	134	{
	135	regs->ARM_pc += 4;
	136	p->ainsn.insn_handler(p, regs);
	137	}
	138
	139	/*
	140	* Called with IRQs disabled. IRQs must remain disabled from that point
	141	* all the way until processing this kprobe is complete. The current
	142	* kprobes implementation cannot process more than one nested level of
	143	* kprobe, and that level is reserved for user kprobe handlers, so we can't
	144	* risk encountering a new kprobe in an interrupt handler.
	145	*/
	146	void __kprobes kprobe_handler(struct pt_regs *regs)
	147	{
	148	struct kprobe p, cur;
	149	struct kprobe_ctlblk *kcb;
	150	kprobe_opcode_t addr = (kprobe_opcode_t )regs->ARM_pc;
	151
	152	kcb = get_kprobe_ctlblk();
	153	cur = kprobe_running();
	154	p = get_kprobe(addr);
	155
	156	if (p) {
	157	if (cur) {
	158	/* Kprobe is pending, so we're recursing. */
	159	switch (kcb->kprobe_status) {
	160	case KPROBE_HIT_ACTIVE:
	161	case KPROBE_HIT_SSDONE:
	162	/* A pre- or post-handler probe got us here. */
	163	kprobes_inc_nmissed_count(p);
	164	save_previous_kprobe(kcb);
	165	set_current_kprobe(p);
	166	kcb->kprobe_status = KPROBE_REENTER;
	167	singlestep(p, regs, kcb);
	168	restore_previous_kprobe(kcb);
	169	break;
	170	default:
	171	/* impossible cases */
	172	BUG();
	173	}
	174	} else {
175	set_current_kprobe(p);
176	kcb->kprobe_status = KPROBE_HIT_ACTIVE;
177
178	/*
179	* If we have no pre-handler or it returned 0, we
180	* continue with normal processing. If we have a
181	* pre-handler and it returned non-zero, it prepped
182	* for calling the break_handler below on re-entry,
183	* so get out doing nothing more here.
184	*/
185	if (!p->pre_handler \|\| !p->pre_handler(p, regs)) {
186	kcb->kprobe_status = KPROBE_HIT_SS;
187	singlestep(p, regs, kcb);
188	if (p->post_handler) {
189	kcb->kprobe_status = KPROBE_HIT_SSDONE;
190	p->post_handler(p, regs, 0);
191	}
192	reset_current_kprobe();
193	}
194	}
195	} else if (cur) {
196	/* We probably hit a jprobe. Call its break handler. */
197	if (cur->break_handler && cur->break_handler(cur, regs)) {
198	kcb->kprobe_status = KPROBE_HIT_SS;
199	singlestep(cur, regs, kcb);
200	if (cur->post_handler) {
201	kcb->kprobe_status = KPROBE_HIT_SSDONE;
202	cur->post_handler(cur, regs, 0);
203	}
204	}
205	reset_current_kprobe();
206	} else {
207	/*
208	* The probe was removed and a race is in progress.
209	* There is nothing we can do about it. Let's restart
210	* the instruction. By the time we can restart, the
211	* real instruction will be there.
212	*/
213	}
214	}
215
3305a607	216	static int __kprobes kprobe_trap_handler(struct pt_regs *regs, unsigned int instr)
24ba613c	217	{
3305a607 NP	218	unsigned long flags;
3305a607 NP	219	local_irq_save(flags);
24ba613c	220	kprobe_handler(regs);
3305a607	221	local_irq_restore(flags);
24ba613c AS	222	return 0;
	223	}
	224
	225	int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned int fsr)
	226	{
	227	struct kprobe *cur = kprobe_running();
	228	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
	229
	230	switch (kcb->kprobe_status) {
	231	case KPROBE_HIT_SS:
	232	case KPROBE_REENTER:
	233	/*
	234	* We are here because the instruction being single
	235	* stepped caused a page fault. We reset the current
	236	* kprobe and the PC to point back to the probe address
	237	* and allow the page fault handler to continue as a
	238	* normal page fault.
	239	*/
	240	regs->ARM_pc = (long)cur->addr;
	241	if (kcb->kprobe_status == KPROBE_REENTER) {
	242	restore_previous_kprobe(kcb);
	243	} else {
	244	reset_current_kprobe();
	245	}
	246	break;
	247
	248	case KPROBE_HIT_ACTIVE:
	249	case KPROBE_HIT_SSDONE:
	250	/*
	251	* We increment the nmissed count for accounting,
	252	* we can also use npre/npostfault count for accounting
	253	* these specific fault cases.
	254	*/
	255	kprobes_inc_nmissed_count(cur);
	256
	257	/*
	258	* We come here because instructions in the pre/post
	259	* handler caused the page_fault, this could happen
	260	* if handler tries to access user space by
	261	* copy_from_user(), get_user() etc. Let the
	262	* user-specified handler try to fix it.
	263	*/
	264	if (cur->fault_handler && cur->fault_handler(cur, regs, fsr))
	265	return 1;
	266	break;
	267
	268	default:
	269	break;
	270	}
	271
	272	return 0;
	273	}
	274
	275	int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
	276	unsigned long val, void *data)
	277	{
	278	/*
	279	* notify_die() is currently never called on ARM,
	280	* so this callback is currently empty.
	281	*/
	282	return NOTIFY_DONE;
	283	}
	284
	285	/*
286	* When a retprobed function returns, trampoline_handler() is called,
287	* calling the kretprobe's handler. We construct a struct pt_regs to
288	* give a view of registers r0-r11 to the user return-handler. This is
289	* not a complete pt_regs structure, but that should be plenty sufficient
290	* for kretprobe handlers which should normally be interested in r0 only
291	* anyway.
292	*/
e0773410	293	void __naked __kprobes kretprobe_trampoline(void)
24ba613c AS	294	{
	295	__asm__ __volatile__ (
	296	"stmdb sp!, {r0 - r11} \n\t"
	297	"mov r0, sp \n\t"
	298	"bl trampoline_handler \n\t"
	299	"mov lr, r0 \n\t"
	300	"ldmia sp!, {r0 - r11} \n\t"
	301	"mov pc, lr \n\t"
	302	: : : "memory");
	303	}
	304
	305	/* Called from kretprobe_trampoline */
	306	static __used __kprobes void trampoline_handler(struct pt_regs regs)
	307	{
	308	struct kretprobe_instance *ri = NULL;
	309	struct hlist_head *head, empty_rp;
	310	struct hlist_node node, tmp;
	311	unsigned long flags, orig_ret_address = 0;
	312	unsigned long trampoline_address = (unsigned long)&kretprobe_trampoline;
	313
	314	INIT_HLIST_HEAD(&empty_rp);
ef53d9c5	315	kretprobe_hash_lock(current, &head, &flags);
24ba613c AS	316
	317	/*
	318	* It is possible to have multiple instances associated with a given
	319	* task either because multiple functions in the call path have
	320	* a return probe installed on them, and/or more than one return
	321	* probe was registered for a target function.
	322	*
	323	* We can handle this because:
	324	* - instances are always inserted at the head of the list
	325	* - when multiple return probes are registered for the same
	326	* function, the first instance's ret_addr will point to the
	327	* real return address, and all the rest will point to
	328	* kretprobe_trampoline
	329	*/
	330	hlist_for_each_entry_safe(ri, node, tmp, head, hlist) {
	331	if (ri->task != current)
	332	/* another task is sharing our hash bucket */
	333	continue;
	334
	335	if (ri->rp && ri->rp->handler) {
	336	__get_cpu_var(current_kprobe) = &ri->rp->kp;
	337	get_kprobe_ctlblk()->kprobe_status = KPROBE_HIT_ACTIVE;
	338	ri->rp->handler(ri, regs);
	339	__get_cpu_var(current_kprobe) = NULL;
	340	}
	341
	342	orig_ret_address = (unsigned long)ri->ret_addr;
	343	recycle_rp_inst(ri, &empty_rp);
	344
	345	if (orig_ret_address != trampoline_address)
	346	/*
	347	* This is the real return address. Any other
	348	* instances associated with this task are for
	349	* other calls deeper on the call stack
	350	*/
	351	break;
	352	}
	353
	354	kretprobe_assert(ri, orig_ret_address, trampoline_address);
ef53d9c5	355	kretprobe_hash_unlock(current, &flags);
24ba613c AS	356
	357	hlist_for_each_entry_safe(ri, node, tmp, &empty_rp, hlist) {
	358	hlist_del(&ri->hlist);
	359	kfree(ri);
	360	}
	361
	362	return (void *)orig_ret_address;
	363	}
	364
24ba613c AS	365	void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
	366	struct pt_regs *regs)
	367	{
	368	ri->ret_addr = (kprobe_opcode_t *)regs->ARM_lr;
	369
	370	/* Replace the return addr with trampoline addr. */
	371	regs->ARM_lr = (unsigned long)&kretprobe_trampoline;
	372	}
	373
	374	int __kprobes setjmp_pre_handler(struct kprobe p, struct pt_regs regs)
	375	{
	376	struct jprobe *jp = container_of(p, struct jprobe, kp);
	377	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
	378	long sp_addr = regs->ARM_sp;
	379
	380	kcb->jprobe_saved_regs = *regs;
	381	memcpy(kcb->jprobes_stack, (void *)sp_addr, MIN_STACK_SIZE(sp_addr));
	382	regs->ARM_pc = (long)jp->entry;
	383	regs->ARM_cpsr \|= PSR_I_BIT;
	384	preempt_disable();
	385	return 1;
	386	}
	387
	388	void __kprobes jprobe_return(void)
	389	{
	390	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
	391
	392	__asm__ __volatile__ (
	393	/*
	394	* Setup an empty pt_regs. Fill SP and PC fields as
	395	* they're needed by longjmp_break_handler.
	396	*/
	397	"sub sp, %0, %1 \n\t"
	398	"ldr r0, ="__stringify(JPROBE_MAGIC_ADDR)"\n\t"
	399	"str %0, [sp, %2] \n\t"
	400	"str r0, [sp, %3] \n\t"
	401	"mov r0, sp \n\t"
	402	"bl kprobe_handler \n\t"
	403
	404	/*
	405	* Return to the context saved by setjmp_pre_handler
	406	* and restored by longjmp_break_handler.
	407	*/
	408	"ldr r0, [sp, %4] \n\t"
	409	"msr cpsr_cxsf, r0 \n\t"
	410	"ldmia sp, {r0 - pc} \n\t"
	411	:
	412	: "r" (kcb->jprobe_saved_regs.ARM_sp),
	413	"I" (sizeof(struct pt_regs)),
	414	"J" (offsetof(struct pt_regs, ARM_sp)),
	415	"J" (offsetof(struct pt_regs, ARM_pc)),
	416	"J" (offsetof(struct pt_regs, ARM_cpsr))
	417	: "memory", "cc");
	418	}
	419
	420	int __kprobes longjmp_break_handler(struct kprobe p, struct pt_regs regs)
	421	{
	422	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
	423	long stack_addr = kcb->jprobe_saved_regs.ARM_sp;
	424	long orig_sp = regs->ARM_sp;
	425	struct jprobe *jp = container_of(p, struct jprobe, kp);
	426
	427	if (regs->ARM_pc == JPROBE_MAGIC_ADDR) {
	428	if (orig_sp != stack_addr) {
429	struct pt_regs *saved_regs =
430	(struct pt_regs *)kcb->jprobe_saved_regs.ARM_sp;
431	printk("current sp %lx does not match saved sp %lx\n",
432	orig_sp, stack_addr);
433	printk("Saved registers for jprobe %p\n", jp);
434	show_regs(saved_regs);
435	printk("Current registers\n");
436	show_regs(regs);
437	BUG();
438	}
439	*regs = kcb->jprobe_saved_regs;
440	memcpy((void *)stack_addr, kcb->jprobes_stack,
441	MIN_STACK_SIZE(stack_addr));
442	preempt_enable_no_resched();
443	return 1;
444	}
445	return 0;
446	}
447
b24061fa NP	448	int __kprobes arch_trampoline_kprobe(struct kprobe *p)
	449	{
	450	return 0;
	451	}
	452
24ba613c AS	453	static struct undef_hook kprobes_break_hook = {
	454	.instr_mask = 0xffffffff,
	455	.instr_val = KPROBE_BREAKPOINT_INSTRUCTION,
	456	.cpsr_mask = MODE_MASK,
	457	.cpsr_val = SVC_MODE,
	458	.fn = kprobe_trap_handler,
	459	};
	460
	461	int __init arch_init_kprobes()
	462	{
	463	arm_kprobe_decode_init();
	464	register_undef_hook(&kprobes_break_hook);
	465	return 0;
	466	}