[linux-block.git] / arch / sh / kernel / kprobes.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Kernel probes (kprobes) for SuperH
 *
 * Copyright (C) 2007 Chris Smith <chris.smith@st.com>
 * Copyright (C) 2006 Lineo Solutions, Inc.
 */
#include <linux/kprobes.h>
#include <linux/extable.h>
#include <linux/ptrace.h>
#include <linux/preempt.h>
#include <linux/kdebug.h>
#include <linux/slab.h>
#include <asm/cacheflush.h>
#include <linux/uaccess.h>

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

static DEFINE_PER_CPU(struct kprobe, saved_current_opcode);
static DEFINE_PER_CPU(struct kprobe, saved_next_opcode);
static DEFINE_PER_CPU(struct kprobe, saved_next_opcode2);

#define OPCODE_JMP(x)	(((x) & 0xF0FF) == 0x402b)
#define OPCODE_JSR(x)	(((x) & 0xF0FF) == 0x400b)
#define OPCODE_BRA(x)	(((x) & 0xF000) == 0xa000)
#define OPCODE_BRAF(x)	(((x) & 0xF0FF) == 0x0023)
#define OPCODE_BSR(x)	(((x) & 0xF000) == 0xb000)
#define OPCODE_BSRF(x)	(((x) & 0xF0FF) == 0x0003)

#define OPCODE_BF_S(x)	(((x) & 0xFF00) == 0x8f00)
#define OPCODE_BT_S(x)	(((x) & 0xFF00) == 0x8d00)

#define OPCODE_BF(x)	(((x) & 0xFF00) == 0x8b00)
#define OPCODE_BT(x)	(((x) & 0xFF00) == 0x8900)

#define OPCODE_RTS(x)	(((x) & 0x000F) == 0x000b)
#define OPCODE_RTE(x)	(((x) & 0xFFFF) == 0x002b)

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

	if (OPCODE_RTE(opcode))
		return -EFAULT;	/* Bad breakpoint */

	memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
	p->opcode = opcode;

	return 0;
}

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));
}

int __kprobes arch_trampoline_kprobe(struct kprobe *p)
{
	if (*p->addr == BREAKPOINT_INSTRUCTION)
		return 1;

	return 0;
}

/**
 * If an illegal slot instruction exception occurs for an address
 * containing a kprobe, remove the probe.
 *
 * Returns 0 if the exception was handled successfully, 1 otherwise.
 */
int __kprobes kprobe_handle_illslot(unsigned long pc)
{
	struct kprobe *p = get_kprobe((kprobe_opcode_t *) pc + 1);

	if (p != NULL) {
		printk("Warning: removing kprobe from delay slot: 0x%.8x\n",
		       (unsigned int)pc + 2);
		unregister_kprobe(p);
		return 0;
	}

	return 1;
}

void __kprobes arch_remove_kprobe(struct kprobe *p)
{
	struct kprobe *saved = this_cpu_ptr(&saved_next_opcode);

	if (saved->addr) {
		arch_disarm_kprobe(p);
		arch_disarm_kprobe(saved);

		saved->addr = NULL;
		saved->opcode = 0;

		saved = this_cpu_ptr(&saved_next_opcode2);
		if (saved->addr) {
			arch_disarm_kprobe(saved);

			saved->addr = NULL;
			saved->opcode = 0;
		}
	}
}

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)
{
	__this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
	kcb->kprobe_status = kcb->prev_kprobe.status;
}

static void __kprobes set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
					 struct kprobe_ctlblk *kcb)
{
	__this_cpu_write(current_kprobe, p);
}

/*
 * Singlestep is implemented by disabling the current kprobe and setting one
 * on the next instruction, following branches. Two probes are set if the
 * branch is conditional.
 */
static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
{
	__this_cpu_write(saved_current_opcode.addr, (kprobe_opcode_t *)regs->pc);

	if (p != NULL) {
		struct kprobe *op1, *op2;

		arch_disarm_kprobe(p);

		op1 = this_cpu_ptr(&saved_next_opcode);
		op2 = this_cpu_ptr(&saved_next_opcode2);

		if (OPCODE_JSR(p->opcode) || OPCODE_JMP(p->opcode)) {
			unsigned int reg_nr = ((p->opcode >> 8) & 0x000F);
			op1->addr = (kprobe_opcode_t *) regs->regs[reg_nr];
		} else if (OPCODE_BRA(p->opcode) || OPCODE_BSR(p->opcode)) {
			unsigned long disp = (p->opcode & 0x0FFF);
			op1->addr =
			    (kprobe_opcode_t *) (regs->pc + 4 + disp * 2);

		} else if (OPCODE_BRAF(p->opcode) || OPCODE_BSRF(p->opcode)) {
			unsigned int reg_nr = ((p->opcode >> 8) & 0x000F);
			op1->addr =
			    (kprobe_opcode_t *) (regs->pc + 4 +
						 regs->regs[reg_nr]);

		} else if (OPCODE_RTS(p->opcode)) {
			op1->addr = (kprobe_opcode_t *) regs->pr;

		} else if (OPCODE_BF(p->opcode) || OPCODE_BT(p->opcode)) {
			unsigned long disp = (p->opcode & 0x00FF);
			/* case 1 */
			op1->addr = p->addr + 1;
			/* case 2 */
			op2->addr =
			    (kprobe_opcode_t *) (regs->pc + 4 + disp * 2);
			op2->opcode = *(op2->addr);
			arch_arm_kprobe(op2);

		} else if (OPCODE_BF_S(p->opcode) || OPCODE_BT_S(p->opcode)) {
			unsigned long disp = (p->opcode & 0x00FF);
			/* case 1 */
			op1->addr = p->addr + 2;
			/* case 2 */
			op2->addr =
			    (kprobe_opcode_t *) (regs->pc + 4 + disp * 2);
			op2->opcode = *(op2->addr);
			arch_arm_kprobe(op2);

		} else {
			op1->addr = p->addr + 1;
		}

		op1->opcode = *(op1->addr);
		arch_arm_kprobe(op1);
	}
}

/* Called with kretprobe_lock held */
void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
				      struct pt_regs *regs)
{
	ri->ret_addr = (kprobe_opcode_t *) regs->pr;
	ri->fp = NULL;

	/* Replace the return addr with trampoline addr */
	regs->pr = (unsigned long)__kretprobe_trampoline;
}

static int __kprobes kprobe_handler(struct pt_regs *regs)
{
	struct kprobe *p;
	int ret = 0;
	kprobe_opcode_t *addr = NULL;
	struct kprobe_ctlblk *kcb;

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

	addr = (kprobe_opcode_t *) (regs->pc);

	/* Check we're not actually recursing */
	if (kprobe_running()) {
		p = get_kprobe(addr);
		if (p) {
			if (kcb->kprobe_status == KPROBE_HIT_SS &&
			    *p->ainsn.insn == BREAKPOINT_INSTRUCTION) {
				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);
			kprobes_inc_nmissed_count(p);
			prepare_singlestep(p, regs);
			kcb->kprobe_status = KPROBE_REENTER;
			return 1;
		}
		goto no_kprobe;
	}

	p = get_kprobe(addr);
	if (!p) {
		/* Not one of ours: let kernel handle it */
		if (*addr != BREAKPOINT_INSTRUCTION) {
			/*
			 * 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;
		}

		goto no_kprobe;
	}

	set_current_kprobe(p, regs, kcb);
	kcb->kprobe_status = KPROBE_HIT_ACTIVE;

	if (p->pre_handler && p->pre_handler(p, regs)) {
		/* handler has already set things up, so skip ss setup */
		reset_current_kprobe();
		preempt_enable_no_resched();
		return 1;
	}

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

no_kprobe:
	preempt_enable_no_resched();
	return ret;
}

/*
 * For function-return probes, init_kprobes() establishes a probepoint
 * here. When a retprobed function returns, this probe is hit and
 * trampoline_probe_handler() runs, calling the kretprobe's handler.
 */
static void __used kretprobe_trampoline_holder(void)
{
	asm volatile (".globl __kretprobe_trampoline\n"
		      "__kretprobe_trampoline:\n\t"
		      "nop\n");
}

/*
 * Called when we hit the probe point at __kretprobe_trampoline
 */
static int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
{
	regs->pc = __kretprobe_trampoline_handler(regs, NULL);

	return 1;
}

static int __kprobes post_kprobe_handler(struct pt_regs *regs)
{
	struct kprobe *cur = kprobe_running();
	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
	kprobe_opcode_t *addr = NULL;
	struct kprobe *p = NULL;

	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);
	}

	p = this_cpu_ptr(&saved_next_opcode);
	if (p->addr) {
		arch_disarm_kprobe(p);
		p->addr = NULL;
		p->opcode = 0;

		addr = __this_cpu_read(saved_current_opcode.addr);
		__this_cpu_write(saved_current_opcode.addr, NULL);

		p = get_kprobe(addr);
		arch_arm_kprobe(p);

		p = this_cpu_ptr(&saved_next_opcode2);
		if (p->addr) {
			arch_disarm_kprobe(p);
			p->addr = NULL;
			p->opcode = 0;
		}
	}

	/* 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();

	return 1;
}

int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
{
	struct kprobe *cur = kprobe_running();
	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
	const struct exception_table_entry *entry;

	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, point the pc back to the probe address
		 * and allow the page fault handler to continue as a
		 * normal page fault.
		 */
		regs->pc = (unsigned long)cur->addr;
		if (kcb->kprobe_status == KPROBE_REENTER)
			restore_previous_kprobe(kcb);
		else
			reset_current_kprobe();
		preempt_enable_no_resched();
		break;
	case KPROBE_HIT_ACTIVE:
	case KPROBE_HIT_SSDONE:
		/*
		 * In case the user-specified fault handler returned
		 * zero, try to fix up.
		 */
		if ((entry = search_exception_tables(regs->pc)) != NULL) {
			regs->pc = entry->fixup;
			return 1;
		}

		/*
		 * fixup_exception() could not handle it,
		 * Let do_page_fault() fix it.
		 */
		break;
	default:
		break;
	}

	return 0;
}

/*
 * Wrapper routine to for handling exceptions.
 */
int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
				       unsigned long val, void *data)
{
	struct kprobe *p = NULL;
	struct die_args *args = (struct die_args *)data;
	int ret = NOTIFY_DONE;
	kprobe_opcode_t *addr = NULL;
	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();

	addr = (kprobe_opcode_t *) (args->regs->pc);
	if (val == DIE_TRAP &&
	    args->trapnr == (BREAKPOINT_INSTRUCTION & 0xff)) {
		if (!kprobe_running()) {
			if (kprobe_handler(args->regs)) {
				ret = NOTIFY_STOP;
			} else {
				/* Not a kprobe trap */
				ret = NOTIFY_DONE;
			}
		} else {
			p = get_kprobe(addr);
			if ((kcb->kprobe_status == KPROBE_HIT_SS) ||
			    (kcb->kprobe_status == KPROBE_REENTER)) {
				if (post_kprobe_handler(args->regs))
					ret = NOTIFY_STOP;
			} else {
				if (kprobe_handler(args->regs))
					ret = NOTIFY_STOP;
			}
		}
	}

	return ret;
}

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
5933f6d2	1	// SPDX-License-Identifier: GPL-2.0
d39f5450 CS	2	/*
	3	* Kernel probes (kprobes) for SuperH
	4	*
	5	* Copyright (C) 2007 Chris Smith <chris.smith@st.com>
	6	* Copyright (C) 2006 Lineo Solutions, Inc.
d39f5450 CS	7	*/
d39f5450 CS	8	#include <linux/kprobes.h>
d92280d1	9	#include <linux/extable.h>
d39f5450 CS	10	#include <linux/ptrace.h>
	11	#include <linux/preempt.h>
	12	#include <linux/kdebug.h>
5a0e3ad6	13	#include <linux/slab.h>
d39f5450	14	#include <asm/cacheflush.h>
7c0f6ba6	15	#include <linux/uaccess.h>
d39f5450 CS	16
	17	DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
	18	DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
	19
57fcfdf9 PM	20	static DEFINE_PER_CPU(struct kprobe, saved_current_opcode);
	21	static DEFINE_PER_CPU(struct kprobe, saved_next_opcode);
	22	static DEFINE_PER_CPU(struct kprobe, saved_next_opcode2);
d39f5450 CS	23
	24	#define OPCODE_JMP(x) (((x) & 0xF0FF) == 0x402b)
	25	#define OPCODE_JSR(x) (((x) & 0xF0FF) == 0x400b)
	26	#define OPCODE_BRA(x) (((x) & 0xF000) == 0xa000)
	27	#define OPCODE_BRAF(x) (((x) & 0xF0FF) == 0x0023)
	28	#define OPCODE_BSR(x) (((x) & 0xF000) == 0xb000)
	29	#define OPCODE_BSRF(x) (((x) & 0xF0FF) == 0x0003)
	30
	31	#define OPCODE_BF_S(x) (((x) & 0xFF00) == 0x8f00)
	32	#define OPCODE_BT_S(x) (((x) & 0xFF00) == 0x8d00)
	33
	34	#define OPCODE_BF(x) (((x) & 0xFF00) == 0x8b00)
	35	#define OPCODE_BT(x) (((x) & 0xFF00) == 0x8900)
	36
	37	#define OPCODE_RTS(x) (((x) & 0x000F) == 0x000b)
	38	#define OPCODE_RTE(x) (((x) & 0xFFFF) == 0x002b)
	39
	40	int __kprobes arch_prepare_kprobe(struct kprobe *p)
	41	{
cb1a55ec	42	kprobe_opcode_t opcode = *p->addr;
d39f5450 CS	43
	44	if (OPCODE_RTE(opcode))
	45	return -EFAULT; /* Bad breakpoint */
	46
1422ae08	47	memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
d39f5450 CS	48	p->opcode = opcode;
	49
	50	return 0;
	51	}
	52
d39f5450 CS	53	void __kprobes arch_arm_kprobe(struct kprobe *p)
	54	{
	55	*p->addr = BREAKPOINT_INSTRUCTION;
	56	flush_icache_range((unsigned long)p->addr,
	57	(unsigned long)p->addr + sizeof(kprobe_opcode_t));
	58	}
	59
	60	void __kprobes arch_disarm_kprobe(struct kprobe *p)
	61	{
	62	*p->addr = p->opcode;
	63	flush_icache_range((unsigned long)p->addr,
	64	(unsigned long)p->addr + sizeof(kprobe_opcode_t));
	65	}
	66
	67	int __kprobes arch_trampoline_kprobe(struct kprobe *p)
	68	{
	69	if (*p->addr == BREAKPOINT_INSTRUCTION)
	70	return 1;
	71
	72	return 0;
	73	}
	74
	75	/**
	76	* If an illegal slot instruction exception occurs for an address
	77	* containing a kprobe, remove the probe.
	78	*
	79	* Returns 0 if the exception was handled successfully, 1 otherwise.
	80	*/
	81	int __kprobes kprobe_handle_illslot(unsigned long pc)
	82	{
	83	struct kprobe p = get_kprobe((kprobe_opcode_t ) pc + 1);
	84
	85	if (p != NULL) {
	86	printk("Warning: removing kprobe from delay slot: 0x%.8x\n",
	87	(unsigned int)pc + 2);
	88	unregister_kprobe(p);
	89	return 0;
	90	}
	91
	92	return 1;
	93	}
	94
	95	void __kprobes arch_remove_kprobe(struct kprobe *p)
	96	{
c473b2c6	97	struct kprobe *saved = this_cpu_ptr(&saved_next_opcode);
57fcfdf9 PM	98
57fcfdf9 PM	99	if (saved->addr) {
d39f5450	100	arch_disarm_kprobe(p);
57fcfdf9 PM	101	arch_disarm_kprobe(saved);
	102
	103	saved->addr = NULL;
	104	saved->opcode = 0;
	105
c473b2c6	106	saved = this_cpu_ptr(&saved_next_opcode2);
57fcfdf9 PM	107	if (saved->addr) {
	108	arch_disarm_kprobe(saved);
	109
	110	saved->addr = NULL;
	111	saved->opcode = 0;
d39f5450 CS	112	}
	113	}
	114	}
	115
4eb5845d	116	static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
d39f5450 CS	117	{
	118	kcb->prev_kprobe.kp = kprobe_running();
	119	kcb->prev_kprobe.status = kcb->kprobe_status;
	120	}
	121
4eb5845d	122	static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
d39f5450	123	{
c473b2c6	124	__this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
d39f5450 CS	125	kcb->kprobe_status = kcb->prev_kprobe.status;
	126	}
	127
4eb5845d PM	128	static void __kprobes set_current_kprobe(struct kprobe p, struct pt_regs regs,
4eb5845d PM	129	struct kprobe_ctlblk *kcb)
d39f5450	130	{
c473b2c6	131	__this_cpu_write(current_kprobe, p);
d39f5450 CS	132	}
	133
	134	/*
	135	* Singlestep is implemented by disabling the current kprobe and setting one
	136	* on the next instruction, following branches. Two probes are set if the
	137	* branch is conditional.
	138	*/
4eb5845d	139	static void __kprobes prepare_singlestep(struct kprobe p, struct pt_regs regs)
d39f5450	140	{
c473b2c6	141	__this_cpu_write(saved_current_opcode.addr, (kprobe_opcode_t *)regs->pc);
d39f5450 CS	142
d39f5450 CS	143	if (p != NULL) {
57fcfdf9 PM	144	struct kprobe op1, op2;
57fcfdf9 PM	145
d39f5450 CS	146	arch_disarm_kprobe(p);
d39f5450 CS	147
c473b2c6 CL	148	op1 = this_cpu_ptr(&saved_next_opcode);
c473b2c6 CL	149	op2 = this_cpu_ptr(&saved_next_opcode2);
57fcfdf9	150
d39f5450 CS	151	if (OPCODE_JSR(p->opcode) \|\| OPCODE_JMP(p->opcode)) {
d39f5450 CS	152	unsigned int reg_nr = ((p->opcode >> 8) & 0x000F);
57fcfdf9	153	op1->addr = (kprobe_opcode_t *) regs->regs[reg_nr];
d39f5450 CS	154	} else if (OPCODE_BRA(p->opcode) \|\| OPCODE_BSR(p->opcode)) {
d39f5450 CS	155	unsigned long disp = (p->opcode & 0x0FFF);
57fcfdf9	156	op1->addr =
d39f5450 CS	157	(kprobe_opcode_t ) (regs->pc + 4 + disp 2);
	158
	159	} else if (OPCODE_BRAF(p->opcode) \|\| OPCODE_BSRF(p->opcode)) {
	160	unsigned int reg_nr = ((p->opcode >> 8) & 0x000F);
57fcfdf9	161	op1->addr =
d39f5450 CS	162	(kprobe_opcode_t *) (regs->pc + 4 +
	163	regs->regs[reg_nr]);
	164
	165	} else if (OPCODE_RTS(p->opcode)) {
57fcfdf9	166	op1->addr = (kprobe_opcode_t *) regs->pr;
d39f5450 CS	167
	168	} else if (OPCODE_BF(p->opcode) \|\| OPCODE_BT(p->opcode)) {
	169	unsigned long disp = (p->opcode & 0x00FF);
	170	/* case 1 */
57fcfdf9	171	op1->addr = p->addr + 1;
d39f5450	172	/* case 2 */
57fcfdf9	173	op2->addr =
d39f5450	174	(kprobe_opcode_t ) (regs->pc + 4 + disp 2);
57fcfdf9 PM	175	op2->opcode = *(op2->addr);
57fcfdf9 PM	176	arch_arm_kprobe(op2);
d39f5450 CS	177
	178	} else if (OPCODE_BF_S(p->opcode) \|\| OPCODE_BT_S(p->opcode)) {
	179	unsigned long disp = (p->opcode & 0x00FF);
	180	/* case 1 */
57fcfdf9	181	op1->addr = p->addr + 2;
d39f5450	182	/* case 2 */
57fcfdf9	183	op2->addr =
d39f5450	184	(kprobe_opcode_t ) (regs->pc + 4 + disp 2);
57fcfdf9 PM	185	op2->opcode = *(op2->addr);
57fcfdf9 PM	186	arch_arm_kprobe(op2);
d39f5450 CS	187
d39f5450 CS	188	} else {
57fcfdf9	189	op1->addr = p->addr + 1;
d39f5450 CS	190	}
d39f5450 CS	191
57fcfdf9 PM	192	op1->opcode = *(op1->addr);
57fcfdf9 PM	193	arch_arm_kprobe(op1);
d39f5450 CS	194	}
	195	}
	196
	197	/* Called with kretprobe_lock held */
	198	void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
	199	struct pt_regs *regs)
	200	{
	201	ri->ret_addr = (kprobe_opcode_t *) regs->pr;
0cf0e2fe	202	ri->fp = NULL;
d39f5450 CS	203
d39f5450 CS	204	/* Replace the return addr with trampoline addr */
adf8a61a	205	regs->pr = (unsigned long)__kretprobe_trampoline;
d39f5450 CS	206	}
	207
	208	static int __kprobes kprobe_handler(struct pt_regs *regs)
	209	{
	210	struct kprobe *p;
	211	int ret = 0;
	212	kprobe_opcode_t *addr = NULL;
	213	struct kprobe_ctlblk *kcb;
	214
	215	/*
	216	* We don't want to be preempted for the entire
	217	* duration of kprobe processing
	218	*/
	219	preempt_disable();
	220	kcb = get_kprobe_ctlblk();
	221
	222	addr = (kprobe_opcode_t *) (regs->pc);
	223
	224	/* Check we're not actually recursing */
	225	if (kprobe_running()) {
	226	p = get_kprobe(addr);
	227	if (p) {
	228	if (kcb->kprobe_status == KPROBE_HIT_SS &&
	229	*p->ainsn.insn == BREAKPOINT_INSTRUCTION) {
	230	goto no_kprobe;
	231	}
	232	/* We have reentered the kprobe_handler(), since
	233	* another probe was hit while within the handler.
	234	* We here save the original kprobes variables and
	235	* just single step on the instruction of the new probe
	236	* without calling any user handlers.
	237	*/
	238	save_previous_kprobe(kcb);
	239	set_current_kprobe(p, regs, kcb);
	240	kprobes_inc_nmissed_count(p);
	241	prepare_singlestep(p, regs);
	242	kcb->kprobe_status = KPROBE_REENTER;
	243	return 1;
d39f5450 CS	244	}
	245	goto no_kprobe;
	246	}
	247
	248	p = get_kprobe(addr);
	249	if (!p) {
	250	/* Not one of ours: let kernel handle it */
cb1a55ec	251	if (*addr != BREAKPOINT_INSTRUCTION) {
734db377 PM	252	/*
	253	* The breakpoint instruction was removed right
	254	* after we hit it. Another cpu has removed
	255	* either a probepoint or a debugger breakpoint
	256	* at this address. In either case, no further
	257	* handling of this interrupt is appropriate.
	258	*/
	259	ret = 1;
	260	}
	261
d39f5450 CS	262	goto no_kprobe;
	263	}
	264
	265	set_current_kprobe(p, regs, kcb);
	266	kcb->kprobe_status = KPROBE_HIT_ACTIVE;
	267
cce188bd	268	if (p->pre_handler && p->pre_handler(p, regs)) {
d39f5450	269	/* handler has already set things up, so skip ss setup */
cce188bd MH	270	reset_current_kprobe();
cce188bd MH	271	preempt_enable_no_resched();
d39f5450	272	return 1;
cce188bd	273	}
d39f5450	274
d39f5450 CS	275	prepare_singlestep(p, regs);
	276	kcb->kprobe_status = KPROBE_HIT_SS;
	277	return 1;
	278
4eb5845d	279	no_kprobe:
d39f5450 CS	280	preempt_enable_no_resched();
	281	return ret;
	282	}
	283
	284	/*
	285	* For function-return probes, init_kprobes() establishes a probepoint
	286	* here. When a retprobed function returns, this probe is hit and
	287	* trampoline_probe_handler() runs, calling the kretprobe's handler.
	288	*/
e7cb016e	289	static void __used kretprobe_trampoline_holder(void)
d39f5450	290	{
adf8a61a MH	291	asm volatile (".globl __kretprobe_trampoline\n"
adf8a61a MH	292	"__kretprobe_trampoline:\n\t"
6eb2139b	293	"nop\n");
d39f5450 CS	294	}
	295
	296	/*
adf8a61a	297	* Called when we hit the probe point at __kretprobe_trampoline
d39f5450	298	*/
f96299b1	299	static int __kprobes trampoline_probe_handler(struct kprobe p, struct pt_regs regs)
d39f5450	300	{
96fed8ac	301	regs->pc = __kretprobe_trampoline_handler(regs, NULL);
d39f5450	302
0cf0e2fe	303	return 1;
d39f5450 CS	304	}
d39f5450 CS	305
4eb5845d	306	static int __kprobes post_kprobe_handler(struct pt_regs *regs)
d39f5450 CS	307	{
	308	struct kprobe *cur = kprobe_running();
	309	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
	310	kprobe_opcode_t *addr = NULL;
	311	struct kprobe *p = NULL;
	312
	313	if (!cur)
	314	return 0;
	315
	316	if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
	317	kcb->kprobe_status = KPROBE_HIT_SSDONE;
	318	cur->post_handler(cur, regs, 0);
	319	}
	320
c473b2c6	321	p = this_cpu_ptr(&saved_next_opcode);
57fcfdf9 PM	322	if (p->addr) {
	323	arch_disarm_kprobe(p);
	324	p->addr = NULL;
	325	p->opcode = 0;
d39f5450	326
c473b2c6 CL	327	addr = __this_cpu_read(saved_current_opcode.addr);
c473b2c6 CL	328	__this_cpu_write(saved_current_opcode.addr, NULL);
d39f5450 CS	329
	330	p = get_kprobe(addr);
	331	arch_arm_kprobe(p);
	332
c473b2c6	333	p = this_cpu_ptr(&saved_next_opcode2);
57fcfdf9 PM	334	if (p->addr) {
	335	arch_disarm_kprobe(p);
	336	p->addr = NULL;
	337	p->opcode = 0;
d39f5450 CS	338	}
	339	}
	340
4eb5845d	341	/* Restore back the original saved kprobes variables and continue. */
d39f5450 CS	342	if (kcb->kprobe_status == KPROBE_REENTER) {
	343	restore_previous_kprobe(kcb);
	344	goto out;
	345	}
4eb5845d	346
d39f5450 CS	347	reset_current_kprobe();
d39f5450 CS	348
4eb5845d	349	out:
d39f5450 CS	350	preempt_enable_no_resched();
	351
	352	return 1;
	353	}
	354
037c10a6	355	int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
d39f5450 CS	356	{
	357	struct kprobe *cur = kprobe_running();
	358	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
	359	const struct exception_table_entry *entry;
	360
	361	switch (kcb->kprobe_status) {
	362	case KPROBE_HIT_SS:
	363	case KPROBE_REENTER:
	364	/*
	365	* We are here because the instruction being single
	366	* stepped caused a page fault. We reset the current
	367	* kprobe, point the pc back to the probe address
	368	* and allow the page fault handler to continue as a
	369	* normal page fault.
	370	*/
	371	regs->pc = (unsigned long)cur->addr;
	372	if (kcb->kprobe_status == KPROBE_REENTER)
	373	restore_previous_kprobe(kcb);
	374	else
	375	reset_current_kprobe();
	376	preempt_enable_no_resched();
	377	break;
	378	case KPROBE_HIT_ACTIVE:
	379	case KPROBE_HIT_SSDONE:
d39f5450 CS	380	/*
	381	* In case the user-specified fault handler returned
	382	* zero, try to fix up.
	383	*/
	384	if ((entry = search_exception_tables(regs->pc)) != NULL) {
	385	regs->pc = entry->fixup;
	386	return 1;
	387	}
	388
	389	/*
	390	* fixup_exception() could not handle it,
	391	* Let do_page_fault() fix it.
	392	*/
	393	break;
	394	default:
	395	break;
	396	}
4eb5845d	397
d39f5450 CS	398	return 0;
	399	}
	400
	401	/*
	402	* Wrapper routine to for handling exceptions.
	403	*/
	404	int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
	405	unsigned long val, void *data)
	406	{
	407	struct kprobe *p = NULL;
	408	struct die_args args = (struct die_args )data;
	409	int ret = NOTIFY_DONE;
	410	kprobe_opcode_t *addr = NULL;
	411	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
	412
	413	addr = (kprobe_opcode_t *) (args->regs->pc);
d3023897 MK	414	if (val == DIE_TRAP &&
d3023897 MK	415	args->trapnr == (BREAKPOINT_INSTRUCTION & 0xff)) {
d39f5450 CS	416	if (!kprobe_running()) {
	417	if (kprobe_handler(args->regs)) {
	418	ret = NOTIFY_STOP;
	419	} else {
	420	/* Not a kprobe trap */
ee386de7	421	ret = NOTIFY_DONE;
d39f5450 CS	422	}
	423	} else {
	424	p = get_kprobe(addr);
	425	if ((kcb->kprobe_status == KPROBE_HIT_SS) \|\|
	426	(kcb->kprobe_status == KPROBE_REENTER)) {
	427	if (post_kprobe_handler(args->regs))
	428	ret = NOTIFY_STOP;
	429	} else {
fa5a24b1	430	if (kprobe_handler(args->regs))
d39f5450	431	ret = NOTIFY_STOP;
d39f5450 CS	432	}
	433	}
	434	}
	435
	436	return ret;
	437	}
	438
d39f5450	439	static struct kprobe trampoline_p = {
adf8a61a	440	.addr = (kprobe_opcode_t *)&__kretprobe_trampoline,
d39f5450 CS	441	.pre_handler = trampoline_probe_handler
	442	};
	443
	444	int __init arch_init_kprobes(void)
	445	{
d39f5450 CS	446	return register_kprobe(&trampoline_p);
d39f5450 CS	447	}