arch/sh/kernel/kprobes.c - third_party/linux - Git at Google

 /*
  * Kernel probes (kprobes) for SuperH
  *
  * Copyright (C) 2007 Chris Smith <chris.smith@st.com>
  * Copyright (C) 2006 Lineo Solutions, Inc.
  *
  * This file is subject to the terms and conditions of the GNU General Public
  * License.  See the file "COPYING" in the main directory of this archive
  * for more details.
  */
 #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 = *(kprobe_opcode_t *) (p->addr);

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

 	p->opcode = opcode;

 	return 0;
 }

 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));
 }

 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;

 	/* 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 (*(kprobe_opcode_t *)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
  */
 int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
 {
 	struct kretprobe_instance *ri = NULL;
 	struct hlist_head *head, empty_rp;
 	struct hlist_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 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, tmp, head, hlist) {
 		if (ri->task != current)
 			/* another task is sharing our hash bucket */
 			continue;

 		if (ri->rp && ri->rp->handler) {
 			__this_cpu_write(current_kprobe, &ri->rp->kp);
 			ri->rp->handler(ri, regs);
 			__this_cpu_write(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);

 	regs->pc = orig_ret_address;
 	kretprobe_hash_unlock(current, &flags);

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

 	return orig_ret_address;
 }

 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:
 		/*
 		 * 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 first.
 		 */
 		if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
 			return 1;

 		/*
 		 * 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) {
 		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);
 }
	/*
	* Kernel probes (kprobes) for SuperH
	*
	* Copyright (C) 2007 Chris Smith <chris.smith@st.com>
	* Copyright (C) 2006 Lineo Solutions, Inc.
	*
	* This file is subject to the terms and conditions of the GNU General Public
	* License. See the file "COPYING" in the main directory of this archive
	* for more details.
	*/
	#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 = (kprobe_opcode_t ) (p->addr);

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

	p->opcode = opcode;

	return 0;
	}

	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));
	}

	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;

	/* 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 ((kprobe_opcode_t )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
	*/
	int __kprobes trampoline_probe_handler(struct kprobe p, struct pt_regs regs)
	{
	struct kretprobe_instance *ri = NULL;
	struct hlist_head *head, empty_rp;
	struct hlist_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 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, tmp, head, hlist) {
	if (ri->task != current)
	/* another task is sharing our hash bucket */
	continue;

	if (ri->rp && ri->rp->handler) {
	__this_cpu_write(current_kprobe, &ri->rp->kp);
	ri->rp->handler(ri, regs);
	__this_cpu_write(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);

	regs->pc = orig_ret_address;
	kretprobe_hash_unlock(current, &flags);

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

	return orig_ret_address;
	}

	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:
	/*
	* 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 first.
	*/
	if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
	return 1;

	/*
	* 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) {
	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);
	}