arch/arm64/kernel/probes/kprobes.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * arch/arm64/kernel/probes/kprobes.c
  *
  * Kprobes support for ARM64
  *
  * Copyright (C) 2013 Linaro Limited.
  * Author: Sandeepa Prabhu <sandeepa.prabhu@linaro.org>
  */

 #define pr_fmt(fmt) "kprobes: " fmt

 #include <linux/extable.h>
 #include <linux/kasan.h>
 #include <linux/kernel.h>
 #include <linux/kprobes.h>
 #include <linux/sched/debug.h>
 #include <linux/set_memory.h>
 #include <linux/slab.h>
 #include <linux/stop_machine.h>
 #include <linux/stringify.h>
 #include <linux/uaccess.h>
 #include <linux/vmalloc.h>

 #include <asm/cacheflush.h>
 #include <asm/daifflags.h>
 #include <asm/debug-monitors.h>
 #include <asm/insn.h>
 #include <asm/irq.h>
 #include <asm/patching.h>
 #include <asm/ptrace.h>
 #include <asm/sections.h>
 #include <asm/system_misc.h>
 #include <asm/traps.h>

 #include "decode-insn.h"

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

 static void __kprobes
 post_kprobe_handler(struct kprobe *, struct kprobe_ctlblk *, struct pt_regs *);

 static void __kprobes arch_prepare_ss_slot(struct kprobe *p)
 {
 	kprobe_opcode_t *addr = p->ainsn.xol_insn;

 	/*
 	 * Prepare insn slot, Mark Rutland points out it depends on a coupe of
 	 * subtleties:
 	 *
 	 * - That the I-cache maintenance for these instructions is complete
 	 *   *before* the kprobe BRK is written (and aarch64_insn_patch_text_nosync()
 	 *   ensures this, but just omits causing a Context-Synchronization-Event
 	 *   on all CPUS).
 	 *
 	 * - That the kprobe BRK results in an exception (and consequently a
 	 *   Context-Synchronoization-Event), which ensures that the CPU will
 	 *   fetch thesingle-step slot instructions *after* this, ensuring that
 	 *   the new instructions are used
 	 *
 	 * It supposes to place ISB after patching to guarantee I-cache maintenance
 	 * is observed on all CPUS, however, single-step slot is installed in
 	 * the BRK exception handler, so it is unnecessary to generate
 	 * Contex-Synchronization-Event via ISB again.
 	 */
 	aarch64_insn_patch_text_nosync(addr, le32_to_cpu(p->opcode));
 	aarch64_insn_patch_text_nosync(addr + 1, BRK64_OPCODE_KPROBES_SS);

 	/*
 	 * Needs restoring of return address after stepping xol.
 	 */
 	p->ainsn.xol_restore = (unsigned long) p->addr +
 	  sizeof(kprobe_opcode_t);
 }

 static void __kprobes arch_prepare_simulate(struct kprobe *p)
 {
 	/* This instructions is not executed xol. No need to adjust the PC */
 	p->ainsn.xol_restore = 0;
 }

 static void __kprobes arch_simulate_insn(struct kprobe *p, struct pt_regs *regs)
 {
 	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();

 	if (p->ainsn.api.handler)
 		p->ainsn.api.handler(le32_to_cpu(p->opcode), (long)p->addr, regs);

 	/* single step simulated, now go for post processing */
 	post_kprobe_handler(p, kcb, regs);
 }

 int __kprobes arch_prepare_kprobe(struct kprobe *p)
 {
 	unsigned long probe_addr = (unsigned long)p->addr;

 	if (probe_addr & 0x3)
 		return -EINVAL;

 	/* copy instruction */
 	p->opcode = *p->addr;

 	if (search_exception_tables(probe_addr))
 		return -EINVAL;

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

 	case INSN_GOOD_NO_SLOT:	/* insn need simulation */
 		p->ainsn.xol_insn = NULL;
 		break;

 	case INSN_GOOD:	/* instruction uses slot */
 		p->ainsn.xol_insn = get_insn_slot();
 		if (!p->ainsn.xol_insn)
 			return -ENOMEM;
 		break;
 	}

 	/* prepare the instruction */
 	if (p->ainsn.xol_insn)
 		arch_prepare_ss_slot(p);
 	else
 		arch_prepare_simulate(p);

 	return 0;
 }

 /* arm kprobe: install breakpoint in text */
 void __kprobes arch_arm_kprobe(struct kprobe *p)
 {
 	void *addr = p->addr;
 	u32 insn = BRK64_OPCODE_KPROBES;

 	aarch64_insn_patch_text(&addr, &insn, 1);
 }

 /* disarm kprobe: remove breakpoint from text */
 void __kprobes arch_disarm_kprobe(struct kprobe *p)
 {
 	void *addr = p->addr;
 	u32 insn = le32_to_cpu(p->opcode);

 	aarch64_insn_patch_text(&addr, &insn, 1);
 }

 void __kprobes arch_remove_kprobe(struct kprobe *p)
 {
 	if (p->ainsn.xol_insn) {
 		free_insn_slot(p->ainsn.xol_insn, 0);
 		p->ainsn.xol_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)
 {
 	__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)
 {
 	__this_cpu_write(current_kprobe, p);
 }

 /*
  * Mask all of DAIF while executing the instruction out-of-line, to keep things
  * simple and avoid nesting exceptions. Interrupts do have to be disabled since
  * the kprobe state is per-CPU and doesn't get migrated.
  */
 static void __kprobes kprobes_save_local_irqflag(struct kprobe_ctlblk *kcb,
 						struct pt_regs *regs)
 {
 	kcb->saved_irqflag = regs->pstate & DAIF_MASK;
 	regs->pstate |= DAIF_MASK;
 }

 static void __kprobes kprobes_restore_local_irqflag(struct kprobe_ctlblk *kcb,
 						struct pt_regs *regs)
 {
 	regs->pstate &= ~DAIF_MASK;
 	regs->pstate |= kcb->saved_irqflag;
 }

 static void __kprobes setup_singlestep(struct kprobe *p,
 				       struct pt_regs *regs,
 				       struct kprobe_ctlblk *kcb, int reenter)
 {
 	unsigned long slot;

 	if (reenter) {
 		save_previous_kprobe(kcb);
 		set_current_kprobe(p);
 		kcb->kprobe_status = KPROBE_REENTER;
 	} else {
 		kcb->kprobe_status = KPROBE_HIT_SS;
 	}


 	if (p->ainsn.xol_insn) {
 		/* prepare for single stepping */
 		slot = (unsigned long)p->ainsn.xol_insn;

 		kprobes_save_local_irqflag(kcb, regs);
 		instruction_pointer_set(regs, slot);
 	} else {
 		/* insn simulation */
 		arch_simulate_insn(p, regs);
 	}
 }

 static int __kprobes reenter_kprobe(struct kprobe *p,
 				    struct pt_regs *regs,
 				    struct kprobe_ctlblk *kcb)
 {
 	switch (kcb->kprobe_status) {
 	case KPROBE_HIT_SSDONE:
 	case KPROBE_HIT_ACTIVE:
 		kprobes_inc_nmissed_count(p);
 		setup_singlestep(p, regs, kcb, 1);
 		break;
 	case KPROBE_HIT_SS:
 	case KPROBE_REENTER:
 		pr_warn("Failed to recover from reentered kprobes.\n");
 		dump_kprobe(p);
 		BUG();
 		break;
 	default:
 		WARN_ON(1);
 		return 0;
 	}

 	return 1;
 }

 static void __kprobes
 post_kprobe_handler(struct kprobe *cur, struct kprobe_ctlblk *kcb, struct pt_regs *regs)
 {
 	/* return addr restore if non-branching insn */
 	if (cur->ainsn.xol_restore != 0)
 		instruction_pointer_set(regs, cur->ainsn.xol_restore);

 	/* restore back original saved kprobe variables and continue */
 	if (kcb->kprobe_status == KPROBE_REENTER) {
 		restore_previous_kprobe(kcb);
 		return;
 	}
 	/* call post handler */
 	kcb->kprobe_status = KPROBE_HIT_SSDONE;
 	if (cur->post_handler)
 		cur->post_handler(cur, regs, 0);

 	reset_current_kprobe();
 }

 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 ip points back to the probe address
 		 * and allow the page fault handler to continue as a
 		 * normal page fault.
 		 */
 		instruction_pointer_set(regs, (unsigned long) cur->addr);
 		BUG_ON(!instruction_pointer(regs));

 		if (kcb->kprobe_status == KPROBE_REENTER) {
 			restore_previous_kprobe(kcb);
 		} else {
 			kprobes_restore_local_irqflag(kcb, regs);
 			reset_current_kprobe();
 		}

 		break;
 	}
 	return 0;
 }

 static int __kprobes
 kprobe_breakpoint_handler(struct pt_regs *regs, unsigned long esr)
 {
 	struct kprobe *p, *cur_kprobe;
 	struct kprobe_ctlblk *kcb;
 	unsigned long addr = instruction_pointer(regs);

 	kcb = get_kprobe_ctlblk();
 	cur_kprobe = kprobe_running();

 	p = get_kprobe((kprobe_opcode_t *) addr);
 	if (WARN_ON_ONCE(!p)) {
 		/*
 		 * Something went wrong. This BRK used an immediate reserved
 		 * for kprobes, but we couldn't find any corresponding probe.
 		 */
 		return DBG_HOOK_ERROR;
 	}

 	if (cur_kprobe) {
 		/* Hit a kprobe inside another kprobe */
 		if (!reenter_kprobe(p, regs, kcb))
 			return DBG_HOOK_ERROR;
 	} else {
 		/* Probe hit */
 		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 will
 		 * modify the execution path and not need to single-step
 		 * Let's just reset current kprobe and exit.
 		 */
 		if (!p->pre_handler || !p->pre_handler(p, regs))
 			setup_singlestep(p, regs, kcb, 0);
 		else
 			reset_current_kprobe();
 	}

 	return DBG_HOOK_HANDLED;
 }

 static struct break_hook kprobes_break_hook = {
 	.imm = KPROBES_BRK_IMM,
 	.fn = kprobe_breakpoint_handler,
 };

 static int __kprobes
 kprobe_breakpoint_ss_handler(struct pt_regs *regs, unsigned long esr)
 {
 	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 	unsigned long addr = instruction_pointer(regs);
 	struct kprobe *cur = kprobe_running();

 	if (cur && (kcb->kprobe_status & (KPROBE_HIT_SS | KPROBE_REENTER)) &&
 	    ((unsigned long)&cur->ainsn.xol_insn[1] == addr)) {
 		kprobes_restore_local_irqflag(kcb, regs);
 		post_kprobe_handler(cur, kcb, regs);

 		return DBG_HOOK_HANDLED;
 	}

 	/* not ours, kprobes should ignore it */
 	return DBG_HOOK_ERROR;
 }

 static struct break_hook kprobes_break_ss_hook = {
 	.imm = KPROBES_BRK_SS_IMM,
 	.fn = kprobe_breakpoint_ss_handler,
 };

 static int __kprobes
 kretprobe_breakpoint_handler(struct pt_regs *regs, unsigned long esr)
 {
 	if (regs->pc != (unsigned long)__kretprobe_trampoline)
 		return DBG_HOOK_ERROR;

 	regs->pc = kretprobe_trampoline_handler(regs, (void *)regs->regs[29]);
 	return DBG_HOOK_HANDLED;
 }

 static struct break_hook kretprobes_break_hook = {
 	.imm = KRETPROBES_BRK_IMM,
 	.fn = kretprobe_breakpoint_handler,
 };

 /*
  * Provide a blacklist of symbols identifying ranges which cannot be kprobed.
  * This blacklist is exposed to userspace via debugfs (kprobes/blacklist).
  */
 int __init arch_populate_kprobe_blacklist(void)
 {
 	int ret;

 	ret = kprobe_add_area_blacklist((unsigned long)__entry_text_start,
 					(unsigned long)__entry_text_end);
 	if (ret)
 		return ret;
 	ret = kprobe_add_area_blacklist((unsigned long)__irqentry_text_start,
 					(unsigned long)__irqentry_text_end);
 	if (ret)
 		return ret;
 	ret = kprobe_add_area_blacklist((unsigned long)__hyp_text_start,
 					(unsigned long)__hyp_text_end);
 	if (ret || is_kernel_in_hyp_mode())
 		return ret;
 	ret = kprobe_add_area_blacklist((unsigned long)__hyp_idmap_text_start,
 					(unsigned long)__hyp_idmap_text_end);
 	return ret;
 }

 void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
 				      struct pt_regs *regs)
 {
 	ri->ret_addr = (kprobe_opcode_t *)regs->regs[30];
 	ri->fp = (void *)regs->regs[29];

 	/* replace return addr (x30) with trampoline */
 	regs->regs[30] = (long)&__kretprobe_trampoline;
 }

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

 int __init arch_init_kprobes(void)
 {
 	register_kernel_break_hook(&kprobes_break_hook);
 	register_kernel_break_hook(&kprobes_break_ss_hook);
 	register_kernel_break_hook(&kretprobes_break_hook);

 	return 0;
 }
	// SPDX-License-Identifier: GPL-2.0-only
	/*
	* arch/arm64/kernel/probes/kprobes.c
	*
	* Kprobes support for ARM64
	*
	* Copyright (C) 2013 Linaro Limited.
	* Author: Sandeepa Prabhu <sandeepa.prabhu@linaro.org>
	*/

	#define pr_fmt(fmt) "kprobes: " fmt

	#include <linux/extable.h>
	#include <linux/kasan.h>
	#include <linux/kernel.h>
	#include <linux/kprobes.h>
	#include <linux/sched/debug.h>
	#include <linux/set_memory.h>
	#include <linux/slab.h>
	#include <linux/stop_machine.h>
	#include <linux/stringify.h>
	#include <linux/uaccess.h>
	#include <linux/vmalloc.h>

	#include <asm/cacheflush.h>
	#include <asm/daifflags.h>
	#include <asm/debug-monitors.h>
	#include <asm/insn.h>
	#include <asm/irq.h>
	#include <asm/patching.h>
	#include <asm/ptrace.h>
	#include <asm/sections.h>
	#include <asm/system_misc.h>
	#include <asm/traps.h>

	#include "decode-insn.h"

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

	static void __kprobes
	post_kprobe_handler(struct kprobe , struct kprobe_ctlblk , struct pt_regs *);

	static void __kprobes arch_prepare_ss_slot(struct kprobe *p)
	{
	kprobe_opcode_t *addr = p->ainsn.xol_insn;

	/*
	* Prepare insn slot, Mark Rutland points out it depends on a coupe of
	* subtleties:
	*
	* - That the I-cache maintenance for these instructions is complete
	* before the kprobe BRK is written (and aarch64_insn_patch_text_nosync()
	* ensures this, but just omits causing a Context-Synchronization-Event
	* on all CPUS).
	*
	* - That the kprobe BRK results in an exception (and consequently a
	* Context-Synchronoization-Event), which ensures that the CPU will
	* fetch thesingle-step slot instructions after this, ensuring that
	* the new instructions are used
	*
	* It supposes to place ISB after patching to guarantee I-cache maintenance
	* is observed on all CPUS, however, single-step slot is installed in
	* the BRK exception handler, so it is unnecessary to generate
	* Contex-Synchronization-Event via ISB again.
	*/
	aarch64_insn_patch_text_nosync(addr, le32_to_cpu(p->opcode));
	aarch64_insn_patch_text_nosync(addr + 1, BRK64_OPCODE_KPROBES_SS);

	/*
	* Needs restoring of return address after stepping xol.
	*/
	p->ainsn.xol_restore = (unsigned long) p->addr +
	sizeof(kprobe_opcode_t);
	}

	static void __kprobes arch_prepare_simulate(struct kprobe *p)
	{
	/* This instructions is not executed xol. No need to adjust the PC */
	p->ainsn.xol_restore = 0;
	}

	static void __kprobes arch_simulate_insn(struct kprobe p, struct pt_regs regs)
	{
	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();

	if (p->ainsn.api.handler)
	p->ainsn.api.handler(le32_to_cpu(p->opcode), (long)p->addr, regs);

	/* single step simulated, now go for post processing */
	post_kprobe_handler(p, kcb, regs);
	}

	int __kprobes arch_prepare_kprobe(struct kprobe *p)
	{
	unsigned long probe_addr = (unsigned long)p->addr;

	if (probe_addr & 0x3)
	return -EINVAL;

	/* copy instruction */
	p->opcode = *p->addr;

	if (search_exception_tables(probe_addr))
	return -EINVAL;

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

	case INSN_GOOD_NO_SLOT: /* insn need simulation */
	p->ainsn.xol_insn = NULL;
	break;

	case INSN_GOOD: /* instruction uses slot */
	p->ainsn.xol_insn = get_insn_slot();
	if (!p->ainsn.xol_insn)
	return -ENOMEM;
	break;
	}

	/* prepare the instruction */
	if (p->ainsn.xol_insn)
	arch_prepare_ss_slot(p);
	else
	arch_prepare_simulate(p);

	return 0;
	}

	/* arm kprobe: install breakpoint in text */
	void __kprobes arch_arm_kprobe(struct kprobe *p)
	{
	void *addr = p->addr;
	u32 insn = BRK64_OPCODE_KPROBES;

	aarch64_insn_patch_text(&addr, &insn, 1);
	}

	/* disarm kprobe: remove breakpoint from text */
	void __kprobes arch_disarm_kprobe(struct kprobe *p)
	{
	void *addr = p->addr;
	u32 insn = le32_to_cpu(p->opcode);

	aarch64_insn_patch_text(&addr, &insn, 1);
	}

	void __kprobes arch_remove_kprobe(struct kprobe *p)
	{
	if (p->ainsn.xol_insn) {
	free_insn_slot(p->ainsn.xol_insn, 0);
	p->ainsn.xol_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)
	{
	__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)
	{
	__this_cpu_write(current_kprobe, p);
	}

	/*
	* Mask all of DAIF while executing the instruction out-of-line, to keep things
	* simple and avoid nesting exceptions. Interrupts do have to be disabled since
	* the kprobe state is per-CPU and doesn't get migrated.
	*/
	static void __kprobes kprobes_save_local_irqflag(struct kprobe_ctlblk *kcb,
	struct pt_regs *regs)
	{
	kcb->saved_irqflag = regs->pstate & DAIF_MASK;
	regs->pstate \|= DAIF_MASK;
	}

	static void __kprobes kprobes_restore_local_irqflag(struct kprobe_ctlblk *kcb,
	struct pt_regs *regs)
	{
	regs->pstate &= ~DAIF_MASK;
	regs->pstate \|= kcb->saved_irqflag;
	}

	static void __kprobes setup_singlestep(struct kprobe *p,
	struct pt_regs *regs,
	struct kprobe_ctlblk *kcb, int reenter)
	{
	unsigned long slot;

	if (reenter) {
	save_previous_kprobe(kcb);
	set_current_kprobe(p);
	kcb->kprobe_status = KPROBE_REENTER;
	} else {
	kcb->kprobe_status = KPROBE_HIT_SS;
	}


	if (p->ainsn.xol_insn) {
	/* prepare for single stepping */
	slot = (unsigned long)p->ainsn.xol_insn;

	kprobes_save_local_irqflag(kcb, regs);
	instruction_pointer_set(regs, slot);
	} else {
	/* insn simulation */
	arch_simulate_insn(p, regs);
	}
	}

	static int __kprobes reenter_kprobe(struct kprobe *p,
	struct pt_regs *regs,
	struct kprobe_ctlblk *kcb)
	{
	switch (kcb->kprobe_status) {
	case KPROBE_HIT_SSDONE:
	case KPROBE_HIT_ACTIVE:
	kprobes_inc_nmissed_count(p);
	setup_singlestep(p, regs, kcb, 1);
	break;
	case KPROBE_HIT_SS:
	case KPROBE_REENTER:
	pr_warn("Failed to recover from reentered kprobes.\n");
	dump_kprobe(p);
	BUG();
	break;
	default:
	WARN_ON(1);
	return 0;
	}

	return 1;
	}

	static void __kprobes
	post_kprobe_handler(struct kprobe cur, struct kprobe_ctlblk kcb, struct pt_regs *regs)
	{
	/* return addr restore if non-branching insn */
	if (cur->ainsn.xol_restore != 0)
	instruction_pointer_set(regs, cur->ainsn.xol_restore);

	/* restore back original saved kprobe variables and continue */
	if (kcb->kprobe_status == KPROBE_REENTER) {
	restore_previous_kprobe(kcb);
	return;
	}
	/* call post handler */
	kcb->kprobe_status = KPROBE_HIT_SSDONE;
	if (cur->post_handler)
	cur->post_handler(cur, regs, 0);

	reset_current_kprobe();
	}

	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 ip points back to the probe address
	* and allow the page fault handler to continue as a
	* normal page fault.
	*/
	instruction_pointer_set(regs, (unsigned long) cur->addr);
	BUG_ON(!instruction_pointer(regs));

	if (kcb->kprobe_status == KPROBE_REENTER) {
	restore_previous_kprobe(kcb);
	} else {
	kprobes_restore_local_irqflag(kcb, regs);
	reset_current_kprobe();
	}

	break;
	}
	return 0;
	}

	static int __kprobes
	kprobe_breakpoint_handler(struct pt_regs *regs, unsigned long esr)
	{
	struct kprobe p, cur_kprobe;
	struct kprobe_ctlblk *kcb;
	unsigned long addr = instruction_pointer(regs);

	kcb = get_kprobe_ctlblk();
	cur_kprobe = kprobe_running();

	p = get_kprobe((kprobe_opcode_t *) addr);
	if (WARN_ON_ONCE(!p)) {
	/*
	* Something went wrong. This BRK used an immediate reserved
	* for kprobes, but we couldn't find any corresponding probe.
	*/
	return DBG_HOOK_ERROR;
	}

	if (cur_kprobe) {
	/* Hit a kprobe inside another kprobe */
	if (!reenter_kprobe(p, regs, kcb))
	return DBG_HOOK_ERROR;
	} else {
	/* Probe hit */
	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 will
	* modify the execution path and not need to single-step
	* Let's just reset current kprobe and exit.
	*/
	if (!p->pre_handler \|\| !p->pre_handler(p, regs))
	setup_singlestep(p, regs, kcb, 0);
	else
	reset_current_kprobe();
	}

	return DBG_HOOK_HANDLED;
	}

	static struct break_hook kprobes_break_hook = {
	.imm = KPROBES_BRK_IMM,
	.fn = kprobe_breakpoint_handler,
	};

	static int __kprobes
	kprobe_breakpoint_ss_handler(struct pt_regs *regs, unsigned long esr)
	{
	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
	unsigned long addr = instruction_pointer(regs);
	struct kprobe *cur = kprobe_running();

	if (cur && (kcb->kprobe_status & (KPROBE_HIT_SS \| KPROBE_REENTER)) &&
	((unsigned long)&cur->ainsn.xol_insn[1] == addr)) {
	kprobes_restore_local_irqflag(kcb, regs);
	post_kprobe_handler(cur, kcb, regs);

	return DBG_HOOK_HANDLED;
	}

	/* not ours, kprobes should ignore it */
	return DBG_HOOK_ERROR;
	}

	static struct break_hook kprobes_break_ss_hook = {
	.imm = KPROBES_BRK_SS_IMM,
	.fn = kprobe_breakpoint_ss_handler,
	};

	static int __kprobes
	kretprobe_breakpoint_handler(struct pt_regs *regs, unsigned long esr)
	{
	if (regs->pc != (unsigned long)__kretprobe_trampoline)
	return DBG_HOOK_ERROR;

	regs->pc = kretprobe_trampoline_handler(regs, (void *)regs->regs[29]);
	return DBG_HOOK_HANDLED;
	}

	static struct break_hook kretprobes_break_hook = {
	.imm = KRETPROBES_BRK_IMM,
	.fn = kretprobe_breakpoint_handler,
	};

	/*
	* Provide a blacklist of symbols identifying ranges which cannot be kprobed.
	* This blacklist is exposed to userspace via debugfs (kprobes/blacklist).
	*/
	int __init arch_populate_kprobe_blacklist(void)
	{
	int ret;

	ret = kprobe_add_area_blacklist((unsigned long)__entry_text_start,
	(unsigned long)__entry_text_end);
	if (ret)
	return ret;
	ret = kprobe_add_area_blacklist((unsigned long)__irqentry_text_start,
	(unsigned long)__irqentry_text_end);
	if (ret)
	return ret;
	ret = kprobe_add_area_blacklist((unsigned long)__hyp_text_start,
	(unsigned long)__hyp_text_end);
	if (ret \|\| is_kernel_in_hyp_mode())
	return ret;
	ret = kprobe_add_area_blacklist((unsigned long)__hyp_idmap_text_start,
	(unsigned long)__hyp_idmap_text_end);
	return ret;
	}

	void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
	struct pt_regs *regs)
	{
	ri->ret_addr = (kprobe_opcode_t *)regs->regs[30];
	ri->fp = (void *)regs->regs[29];

	/* replace return addr (x30) with trampoline */
	regs->regs[30] = (long)&__kretprobe_trampoline;
	}

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

	int __init arch_init_kprobes(void)
	{
	register_kernel_break_hook(&kprobes_break_hook);
	register_kernel_break_hook(&kprobes_break_ss_hook);
	register_kernel_break_hook(&kretprobes_break_hook);

	return 0;
	}