arch/arm/probes/kprobes/actions-arm.c - kernel/common - Git at Google

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * arch/arm/probes/kprobes/actions-arm.c
  *
  * Copyright (C) 2006, 2007 Motorola Inc.
  */

 /*
  * We do not have hardware single-stepping on ARM, This
  * effort is further complicated by the ARM not having a
  * "next PC" register.  Instructions that change the PC
  * can't be safely single-stepped in a MP environment, so
  * we have a lot of work to do:
  *
  * In the prepare phase:
  *   *) If it is an instruction that does anything
  *      with the CPU mode, we reject it for a kprobe.
  *      (This is out of laziness rather than need.  The
  *      instructions could be simulated.)
  *
  *   *) Otherwise, decode the instruction rewriting its
  *      registers to take fixed, ordered registers and
  *      setting a handler for it to run the instruction.
  *
  * In the execution phase by an instruction's handler:
  *
  *   *) If the PC is written to by the instruction, the
  *      instruction must be fully simulated in software.
  *
  *   *) Otherwise, a modified form of the instruction is
  *      directly executed.  Its handler calls the
  *      instruction in insn[0].  In insn[1] is a
  *      "mov pc, lr" to return.
  *
  *      Before calling, load up the reordered registers
  *      from the original instruction's registers.  If one
  *      of the original input registers is the PC, compute
  *      and adjust the appropriate input register.
  *
  *	After call completes, copy the output registers to
  *      the original instruction's original registers.
  *
  * We don't use a real breakpoint instruction since that
  * would have us in the kernel go from SVC mode to SVC
  * mode losing the link register.  Instead we use an
  * undefined instruction.  To simplify processing, the
  * undefined instruction used for kprobes must be reserved
  * exclusively for kprobes use.
  *
  * TODO: ifdef out some instruction decoding based on architecture.
  */

 #include <linux/kernel.h>
 #include <linux/kprobes.h>
 #include <linux/ptrace.h>

 #include "../decode-arm.h"
 #include "core.h"
 #include "checkers.h"

 #if  __LINUX_ARM_ARCH__ >= 6
 #define BLX(reg)	"blx	"reg"		\n\t"
 #else
 #define BLX(reg)	"mov	lr, pc		\n\t"	\
 			"mov	pc, "reg"	\n\t"
 #endif

 static void __kprobes
 emulate_ldrdstrd(probes_opcode_t insn,
 	struct arch_probes_insn *asi, struct pt_regs *regs)
 {
 	unsigned long pc = regs->ARM_pc + 4;
 	int rt = (insn >> 12) & 0xf;
 	int rn = (insn >> 16) & 0xf;
 	int rm = insn & 0xf;

 	register unsigned long rtv asm("r0") = regs->uregs[rt];
 	register unsigned long rt2v asm("r1") = regs->uregs[rt+1];
 	register unsigned long rnv asm("r2") = (rn == 15) ? pc
 							  : regs->uregs[rn];
 	register unsigned long rmv asm("r3") = regs->uregs[rm];

 	__asm__ __volatile__ (
 		BLX("%[fn]")
 		: "=r" (rtv), "=r" (rt2v), "=r" (rnv)
 		: "0" (rtv), "1" (rt2v), "2" (rnv), "r" (rmv),
 		  [fn] "r" (asi->insn_fn)
 		: "lr", "memory", "cc"
 	);

 	regs->uregs[rt] = rtv;
 	regs->uregs[rt+1] = rt2v;
 	if (is_writeback(insn))
 		regs->uregs[rn] = rnv;
 }

 static void __kprobes
 emulate_ldr(probes_opcode_t insn,
 	struct arch_probes_insn *asi, struct pt_regs *regs)
 {
 	unsigned long pc = regs->ARM_pc + 4;
 	int rt = (insn >> 12) & 0xf;
 	int rn = (insn >> 16) & 0xf;
 	int rm = insn & 0xf;

 	register unsigned long rtv asm("r0");
 	register unsigned long rnv asm("r2") = (rn == 15) ? pc
 							  : regs->uregs[rn];
 	register unsigned long rmv asm("r3") = regs->uregs[rm];

 	__asm__ __volatile__ (
 		BLX("%[fn]")
 		: "=r" (rtv), "=r" (rnv)
 		: "1" (rnv), "r" (rmv), [fn] "r" (asi->insn_fn)
 		: "lr", "memory", "cc"
 	);

 	if (rt == 15)
 		load_write_pc(rtv, regs);
 	else
 		regs->uregs[rt] = rtv;

 	if (is_writeback(insn))
 		regs->uregs[rn] = rnv;
 }

 static void __kprobes
 emulate_str(probes_opcode_t insn,
 	struct arch_probes_insn *asi, struct pt_regs *regs)
 {
 	unsigned long rtpc = regs->ARM_pc - 4 + str_pc_offset;
 	unsigned long rnpc = regs->ARM_pc + 4;
 	int rt = (insn >> 12) & 0xf;
 	int rn = (insn >> 16) & 0xf;
 	int rm = insn & 0xf;

 	register unsigned long rtv asm("r0") = (rt == 15) ? rtpc
 							  : regs->uregs[rt];
 	register unsigned long rnv asm("r2") = (rn == 15) ? rnpc
 							  : regs->uregs[rn];
 	register unsigned long rmv asm("r3") = regs->uregs[rm];

 	__asm__ __volatile__ (
 		BLX("%[fn]")
 		: "=r" (rnv)
 		: "r" (rtv), "0" (rnv), "r" (rmv), [fn] "r" (asi->insn_fn)
 		: "lr", "memory", "cc"
 	);

 	if (is_writeback(insn))
 		regs->uregs[rn] = rnv;
 }

 static void __kprobes
 emulate_rd12rn16rm0rs8_rwflags(probes_opcode_t insn,
 	struct arch_probes_insn *asi, struct pt_regs *regs)
 {
 	unsigned long pc = regs->ARM_pc + 4;
 	int rd = (insn >> 12) & 0xf;
 	int rn = (insn >> 16) & 0xf;
 	int rm = insn & 0xf;
 	int rs = (insn >> 8) & 0xf;

 	register unsigned long rdv asm("r0") = regs->uregs[rd];
 	register unsigned long rnv asm("r2") = (rn == 15) ? pc
 							  : regs->uregs[rn];
 	register unsigned long rmv asm("r3") = (rm == 15) ? pc
 							  : regs->uregs[rm];
 	register unsigned long rsv asm("r1") = regs->uregs[rs];
 	unsigned long cpsr = regs->ARM_cpsr;

 	__asm__ __volatile__ (
 		"msr	cpsr_fs, %[cpsr]	\n\t"
 		BLX("%[fn]")
 		"mrs	%[cpsr], cpsr		\n\t"
 		: "=r" (rdv), [cpsr] "=r" (cpsr)
 		: "0" (rdv), "r" (rnv), "r" (rmv), "r" (rsv),
 		  "1" (cpsr), [fn] "r" (asi->insn_fn)
 		: "lr", "memory", "cc"
 	);

 	if (rd == 15)
 		alu_write_pc(rdv, regs);
 	else
 		regs->uregs[rd] = rdv;
 	regs->ARM_cpsr = (regs->ARM_cpsr & ~APSR_MASK) | (cpsr & APSR_MASK);
 }

 static void __kprobes
 emulate_rd12rn16rm0_rwflags_nopc(probes_opcode_t insn,
 	struct arch_probes_insn *asi, struct pt_regs *regs)
 {
 	int rd = (insn >> 12) & 0xf;
 	int rn = (insn >> 16) & 0xf;
 	int rm = insn & 0xf;

 	register unsigned long rdv asm("r0") = regs->uregs[rd];
 	register unsigned long rnv asm("r2") = regs->uregs[rn];
 	register unsigned long rmv asm("r3") = regs->uregs[rm];
 	unsigned long cpsr = regs->ARM_cpsr;

 	__asm__ __volatile__ (
 		"msr	cpsr_fs, %[cpsr]	\n\t"
 		BLX("%[fn]")
 		"mrs	%[cpsr], cpsr		\n\t"
 		: "=r" (rdv), [cpsr] "=r" (cpsr)
 		: "0" (rdv), "r" (rnv), "r" (rmv),
 		  "1" (cpsr), [fn] "r" (asi->insn_fn)
 		: "lr", "memory", "cc"
 	);

 	regs->uregs[rd] = rdv;
 	regs->ARM_cpsr = (regs->ARM_cpsr & ~APSR_MASK) | (cpsr & APSR_MASK);
 }

 static void __kprobes
 emulate_rd16rn12rm0rs8_rwflags_nopc(probes_opcode_t insn,
 	struct arch_probes_insn *asi,
 	struct pt_regs *regs)
 {
 	int rd = (insn >> 16) & 0xf;
 	int rn = (insn >> 12) & 0xf;
 	int rm = insn & 0xf;
 	int rs = (insn >> 8) & 0xf;

 	register unsigned long rdv asm("r2") = regs->uregs[rd];
 	register unsigned long rnv asm("r0") = regs->uregs[rn];
 	register unsigned long rmv asm("r3") = regs->uregs[rm];
 	register unsigned long rsv asm("r1") = regs->uregs[rs];
 	unsigned long cpsr = regs->ARM_cpsr;

 	__asm__ __volatile__ (
 		"msr	cpsr_fs, %[cpsr]	\n\t"
 		BLX("%[fn]")
 		"mrs	%[cpsr], cpsr		\n\t"
 		: "=r" (rdv), [cpsr] "=r" (cpsr)
 		: "0" (rdv), "r" (rnv), "r" (rmv), "r" (rsv),
 		  "1" (cpsr), [fn] "r" (asi->insn_fn)
 		: "lr", "memory", "cc"
 	);

 	regs->uregs[rd] = rdv;
 	regs->ARM_cpsr = (regs->ARM_cpsr & ~APSR_MASK) | (cpsr & APSR_MASK);
 }

 static void __kprobes
 emulate_rd12rm0_noflags_nopc(probes_opcode_t insn,
 	struct arch_probes_insn *asi, struct pt_regs *regs)
 {
 	int rd = (insn >> 12) & 0xf;
 	int rm = insn & 0xf;

 	register unsigned long rdv asm("r0") = regs->uregs[rd];
 	register unsigned long rmv asm("r3") = regs->uregs[rm];

 	__asm__ __volatile__ (
 		BLX("%[fn]")
 		: "=r" (rdv)
 		: "0" (rdv), "r" (rmv), [fn] "r" (asi->insn_fn)
 		: "lr", "memory", "cc"
 	);

 	regs->uregs[rd] = rdv;
 }

 static void __kprobes
 emulate_rdlo12rdhi16rn0rm8_rwflags_nopc(probes_opcode_t insn,
 	struct arch_probes_insn *asi,
 	struct pt_regs *regs)
 {
 	int rdlo = (insn >> 12) & 0xf;
 	int rdhi = (insn >> 16) & 0xf;
 	int rn = insn & 0xf;
 	int rm = (insn >> 8) & 0xf;

 	register unsigned long rdlov asm("r0") = regs->uregs[rdlo];
 	register unsigned long rdhiv asm("r2") = regs->uregs[rdhi];
 	register unsigned long rnv asm("r3") = regs->uregs[rn];
 	register unsigned long rmv asm("r1") = regs->uregs[rm];
 	unsigned long cpsr = regs->ARM_cpsr;

 	__asm__ __volatile__ (
 		"msr	cpsr_fs, %[cpsr]	\n\t"
 		BLX("%[fn]")
 		"mrs	%[cpsr], cpsr		\n\t"
 		: "=r" (rdlov), "=r" (rdhiv), [cpsr] "=r" (cpsr)
 		: "0" (rdlov), "1" (rdhiv), "r" (rnv), "r" (rmv),
 		  "2" (cpsr), [fn] "r" (asi->insn_fn)
 		: "lr", "memory", "cc"
 	);

 	regs->uregs[rdlo] = rdlov;
 	regs->uregs[rdhi] = rdhiv;
 	regs->ARM_cpsr = (regs->ARM_cpsr & ~APSR_MASK) | (cpsr & APSR_MASK);
 }

 const union decode_action kprobes_arm_actions[NUM_PROBES_ARM_ACTIONS] = {
 	[PROBES_PRELOAD_IMM] = {.handler = probes_simulate_nop},
 	[PROBES_PRELOAD_REG] = {.handler = probes_simulate_nop},
 	[PROBES_BRANCH_IMM] = {.handler = simulate_blx1},
 	[PROBES_MRS] = {.handler = simulate_mrs},
 	[PROBES_BRANCH_REG] = {.handler = simulate_blx2bx},
 	[PROBES_CLZ] = {.handler = emulate_rd12rm0_noflags_nopc},
 	[PROBES_SATURATING_ARITHMETIC] = {
 		.handler = emulate_rd12rn16rm0_rwflags_nopc},
 	[PROBES_MUL1] = {.handler = emulate_rdlo12rdhi16rn0rm8_rwflags_nopc},
 	[PROBES_MUL2] = {.handler = emulate_rd16rn12rm0rs8_rwflags_nopc},
 	[PROBES_SWP] = {.handler = emulate_rd12rn16rm0_rwflags_nopc},
 	[PROBES_LDRSTRD] = {.handler = emulate_ldrdstrd},
 	[PROBES_LOAD_EXTRA] = {.handler = emulate_ldr},
 	[PROBES_LOAD] = {.handler = emulate_ldr},
 	[PROBES_STORE_EXTRA] = {.handler = emulate_str},
 	[PROBES_STORE] = {.handler = emulate_str},
 	[PROBES_MOV_IP_SP] = {.handler = simulate_mov_ipsp},
 	[PROBES_DATA_PROCESSING_REG] = {
 		.handler = emulate_rd12rn16rm0rs8_rwflags},
 	[PROBES_DATA_PROCESSING_IMM] = {
 		.handler = emulate_rd12rn16rm0rs8_rwflags},
 	[PROBES_MOV_HALFWORD] = {.handler = emulate_rd12rm0_noflags_nopc},
 	[PROBES_SEV] = {.handler = probes_emulate_none},
 	[PROBES_WFE] = {.handler = probes_simulate_nop},
 	[PROBES_SATURATE] = {.handler = emulate_rd12rn16rm0_rwflags_nopc},
 	[PROBES_REV] = {.handler = emulate_rd12rm0_noflags_nopc},
 	[PROBES_MMI] = {.handler = emulate_rd12rn16rm0_rwflags_nopc},
 	[PROBES_PACK] = {.handler = emulate_rd12rn16rm0_rwflags_nopc},
 	[PROBES_EXTEND] = {.handler = emulate_rd12rm0_noflags_nopc},
 	[PROBES_EXTEND_ADD] = {.handler = emulate_rd12rn16rm0_rwflags_nopc},
 	[PROBES_MUL_ADD_LONG] = {
 		.handler = emulate_rdlo12rdhi16rn0rm8_rwflags_nopc},
 	[PROBES_MUL_ADD] = {.handler = emulate_rd16rn12rm0rs8_rwflags_nopc},
 	[PROBES_BITFIELD] = {.handler = emulate_rd12rm0_noflags_nopc},
 	[PROBES_BRANCH] = {.handler = simulate_bbl},
 	[PROBES_LDMSTM] = {.decoder = kprobe_decode_ldmstm}
 };

 const struct decode_checker *kprobes_arm_checkers[] = {arm_stack_checker, arm_regs_checker, NULL};
	// SPDX-License-Identifier: GPL-2.0-only
	/*
	* arch/arm/probes/kprobes/actions-arm.c
	*
	* Copyright (C) 2006, 2007 Motorola Inc.
	*/

	/*
	* We do not have hardware single-stepping on ARM, This
	* effort is further complicated by the ARM not having a
	* "next PC" register. Instructions that change the PC
	* can't be safely single-stepped in a MP environment, so
	* we have a lot of work to do:
	*
	* In the prepare phase:
	* *) If it is an instruction that does anything
	* with the CPU mode, we reject it for a kprobe.
	* (This is out of laziness rather than need. The
	* instructions could be simulated.)
	*
	* *) Otherwise, decode the instruction rewriting its
	* registers to take fixed, ordered registers and
	* setting a handler for it to run the instruction.
	*
	* In the execution phase by an instruction's handler:
	*
	* *) If the PC is written to by the instruction, the
	* instruction must be fully simulated in software.
	*
	* *) Otherwise, a modified form of the instruction is
	* directly executed. Its handler calls the
	* instruction in insn[0]. In insn[1] is a
	* "mov pc, lr" to return.
	*
	* Before calling, load up the reordered registers
	* from the original instruction's registers. If one
	* of the original input registers is the PC, compute
	* and adjust the appropriate input register.
	*
	* After call completes, copy the output registers to
	* the original instruction's original registers.
	*
	* We don't use a real breakpoint instruction since that
	* would have us in the kernel go from SVC mode to SVC
	* mode losing the link register. Instead we use an
	* undefined instruction. To simplify processing, the
	* undefined instruction used for kprobes must be reserved
	* exclusively for kprobes use.
	*
	* TODO: ifdef out some instruction decoding based on architecture.
	*/

	#include <linux/kernel.h>
	#include <linux/kprobes.h>
	#include <linux/ptrace.h>

	#include "../decode-arm.h"
	#include "core.h"
	#include "checkers.h"

	#if __LINUX_ARM_ARCH__ >= 6
	#define BLX(reg) "blx "reg" \n\t"
	#else
	#define BLX(reg) "mov lr, pc \n\t" \
	"mov pc, "reg" \n\t"
	#endif

	static void __kprobes
	emulate_ldrdstrd(probes_opcode_t insn,
	struct arch_probes_insn asi, struct pt_regs regs)
	{
	unsigned long pc = regs->ARM_pc + 4;
	int rt = (insn >> 12) & 0xf;
	int rn = (insn >> 16) & 0xf;
	int rm = insn & 0xf;

	register unsigned long rtv asm("r0") = regs->uregs[rt];
	register unsigned long rt2v asm("r1") = regs->uregs[rt+1];
	register unsigned long rnv asm("r2") = (rn == 15) ? pc
	: regs->uregs[rn];
	register unsigned long rmv asm("r3") = regs->uregs[rm];

	__asm__ __volatile__ (
	BLX("%[fn]")
	: "=r" (rtv), "=r" (rt2v), "=r" (rnv)
	: "0" (rtv), "1" (rt2v), "2" (rnv), "r" (rmv),
	[fn] "r" (asi->insn_fn)
	: "lr", "memory", "cc"
	);

	regs->uregs[rt] = rtv;
	regs->uregs[rt+1] = rt2v;
	if (is_writeback(insn))
	regs->uregs[rn] = rnv;
	}

	static void __kprobes
	emulate_ldr(probes_opcode_t insn,
	struct arch_probes_insn asi, struct pt_regs regs)
	{
	unsigned long pc = regs->ARM_pc + 4;
	int rt = (insn >> 12) & 0xf;
	int rn = (insn >> 16) & 0xf;
	int rm = insn & 0xf;

	register unsigned long rtv asm("r0");
	register unsigned long rnv asm("r2") = (rn == 15) ? pc
	: regs->uregs[rn];
	register unsigned long rmv asm("r3") = regs->uregs[rm];

	__asm__ __volatile__ (
	BLX("%[fn]")
	: "=r" (rtv), "=r" (rnv)
	: "1" (rnv), "r" (rmv), [fn] "r" (asi->insn_fn)
	: "lr", "memory", "cc"
	);

	if (rt == 15)
	load_write_pc(rtv, regs);
	else
	regs->uregs[rt] = rtv;

	if (is_writeback(insn))
	regs->uregs[rn] = rnv;
	}

	static void __kprobes
	emulate_str(probes_opcode_t insn,
	struct arch_probes_insn asi, struct pt_regs regs)
	{
	unsigned long rtpc = regs->ARM_pc - 4 + str_pc_offset;
	unsigned long rnpc = regs->ARM_pc + 4;
	int rt = (insn >> 12) & 0xf;
	int rn = (insn >> 16) & 0xf;
	int rm = insn & 0xf;

	register unsigned long rtv asm("r0") = (rt == 15) ? rtpc
	: regs->uregs[rt];
	register unsigned long rnv asm("r2") = (rn == 15) ? rnpc
	: regs->uregs[rn];
	register unsigned long rmv asm("r3") = regs->uregs[rm];

	__asm__ __volatile__ (
	BLX("%[fn]")
	: "=r" (rnv)
	: "r" (rtv), "0" (rnv), "r" (rmv), [fn] "r" (asi->insn_fn)
	: "lr", "memory", "cc"
	);

	if (is_writeback(insn))
	regs->uregs[rn] = rnv;
	}

	static void __kprobes
	emulate_rd12rn16rm0rs8_rwflags(probes_opcode_t insn,
	struct arch_probes_insn asi, struct pt_regs regs)
	{
	unsigned long pc = regs->ARM_pc + 4;
	int rd = (insn >> 12) & 0xf;
	int rn = (insn >> 16) & 0xf;
	int rm = insn & 0xf;
	int rs = (insn >> 8) & 0xf;

	register unsigned long rdv asm("r0") = regs->uregs[rd];
	register unsigned long rnv asm("r2") = (rn == 15) ? pc
	: regs->uregs[rn];
	register unsigned long rmv asm("r3") = (rm == 15) ? pc
	: regs->uregs[rm];
	register unsigned long rsv asm("r1") = regs->uregs[rs];
	unsigned long cpsr = regs->ARM_cpsr;

	__asm__ __volatile__ (
	"msr cpsr_fs, %[cpsr] \n\t"
	BLX("%[fn]")
	"mrs %[cpsr], cpsr \n\t"
	: "=r" (rdv), [cpsr] "=r" (cpsr)
	: "0" (rdv), "r" (rnv), "r" (rmv), "r" (rsv),
	"1" (cpsr), [fn] "r" (asi->insn_fn)
	: "lr", "memory", "cc"
	);

	if (rd == 15)
	alu_write_pc(rdv, regs);
	else
	regs->uregs[rd] = rdv;
	regs->ARM_cpsr = (regs->ARM_cpsr & ~APSR_MASK) \| (cpsr & APSR_MASK);
	}

	static void __kprobes
	emulate_rd12rn16rm0_rwflags_nopc(probes_opcode_t insn,
	struct arch_probes_insn asi, struct pt_regs regs)
	{
	int rd = (insn >> 12) & 0xf;
	int rn = (insn >> 16) & 0xf;
	int rm = insn & 0xf;

	register unsigned long rdv asm("r0") = regs->uregs[rd];
	register unsigned long rnv asm("r2") = regs->uregs[rn];
	register unsigned long rmv asm("r3") = regs->uregs[rm];
	unsigned long cpsr = regs->ARM_cpsr;

	__asm__ __volatile__ (
	"msr cpsr_fs, %[cpsr] \n\t"
	BLX("%[fn]")
	"mrs %[cpsr], cpsr \n\t"
	: "=r" (rdv), [cpsr] "=r" (cpsr)
	: "0" (rdv), "r" (rnv), "r" (rmv),
	"1" (cpsr), [fn] "r" (asi->insn_fn)
	: "lr", "memory", "cc"
	);

	regs->uregs[rd] = rdv;
	regs->ARM_cpsr = (regs->ARM_cpsr & ~APSR_MASK) \| (cpsr & APSR_MASK);
	}

	static void __kprobes
	emulate_rd16rn12rm0rs8_rwflags_nopc(probes_opcode_t insn,
	struct arch_probes_insn *asi,
	struct pt_regs *regs)
	{
	int rd = (insn >> 16) & 0xf;
	int rn = (insn >> 12) & 0xf;
	int rm = insn & 0xf;
	int rs = (insn >> 8) & 0xf;

	register unsigned long rdv asm("r2") = regs->uregs[rd];
	register unsigned long rnv asm("r0") = regs->uregs[rn];
	register unsigned long rmv asm("r3") = regs->uregs[rm];
	register unsigned long rsv asm("r1") = regs->uregs[rs];
	unsigned long cpsr = regs->ARM_cpsr;

	__asm__ __volatile__ (
	"msr cpsr_fs, %[cpsr] \n\t"
	BLX("%[fn]")
	"mrs %[cpsr], cpsr \n\t"
	: "=r" (rdv), [cpsr] "=r" (cpsr)
	: "0" (rdv), "r" (rnv), "r" (rmv), "r" (rsv),
	"1" (cpsr), [fn] "r" (asi->insn_fn)
	: "lr", "memory", "cc"
	);

	regs->uregs[rd] = rdv;
	regs->ARM_cpsr = (regs->ARM_cpsr & ~APSR_MASK) \| (cpsr & APSR_MASK);
	}

	static void __kprobes
	emulate_rd12rm0_noflags_nopc(probes_opcode_t insn,
	struct arch_probes_insn asi, struct pt_regs regs)
	{
	int rd = (insn >> 12) & 0xf;
	int rm = insn & 0xf;

	register unsigned long rdv asm("r0") = regs->uregs[rd];
	register unsigned long rmv asm("r3") = regs->uregs[rm];

	__asm__ __volatile__ (
	BLX("%[fn]")
	: "=r" (rdv)
	: "0" (rdv), "r" (rmv), [fn] "r" (asi->insn_fn)
	: "lr", "memory", "cc"
	);

	regs->uregs[rd] = rdv;
	}

	static void __kprobes
	emulate_rdlo12rdhi16rn0rm8_rwflags_nopc(probes_opcode_t insn,
	struct arch_probes_insn *asi,
	struct pt_regs *regs)
	{
	int rdlo = (insn >> 12) & 0xf;
	int rdhi = (insn >> 16) & 0xf;
	int rn = insn & 0xf;
	int rm = (insn >> 8) & 0xf;

	register unsigned long rdlov asm("r0") = regs->uregs[rdlo];
	register unsigned long rdhiv asm("r2") = regs->uregs[rdhi];
	register unsigned long rnv asm("r3") = regs->uregs[rn];
	register unsigned long rmv asm("r1") = regs->uregs[rm];
	unsigned long cpsr = regs->ARM_cpsr;

	__asm__ __volatile__ (
	"msr cpsr_fs, %[cpsr] \n\t"
	BLX("%[fn]")
	"mrs %[cpsr], cpsr \n\t"
	: "=r" (rdlov), "=r" (rdhiv), [cpsr] "=r" (cpsr)
	: "0" (rdlov), "1" (rdhiv), "r" (rnv), "r" (rmv),
	"2" (cpsr), [fn] "r" (asi->insn_fn)
	: "lr", "memory", "cc"
	);

	regs->uregs[rdlo] = rdlov;
	regs->uregs[rdhi] = rdhiv;
	regs->ARM_cpsr = (regs->ARM_cpsr & ~APSR_MASK) \| (cpsr & APSR_MASK);
	}

	const union decode_action kprobes_arm_actions[NUM_PROBES_ARM_ACTIONS] = {
	[PROBES_PRELOAD_IMM] = {.handler = probes_simulate_nop},
	[PROBES_PRELOAD_REG] = {.handler = probes_simulate_nop},
	[PROBES_BRANCH_IMM] = {.handler = simulate_blx1},
	[PROBES_MRS] = {.handler = simulate_mrs},
	[PROBES_BRANCH_REG] = {.handler = simulate_blx2bx},
	[PROBES_CLZ] = {.handler = emulate_rd12rm0_noflags_nopc},
	[PROBES_SATURATING_ARITHMETIC] = {
	.handler = emulate_rd12rn16rm0_rwflags_nopc},
	[PROBES_MUL1] = {.handler = emulate_rdlo12rdhi16rn0rm8_rwflags_nopc},
	[PROBES_MUL2] = {.handler = emulate_rd16rn12rm0rs8_rwflags_nopc},
	[PROBES_SWP] = {.handler = emulate_rd12rn16rm0_rwflags_nopc},
	[PROBES_LDRSTRD] = {.handler = emulate_ldrdstrd},
	[PROBES_LOAD_EXTRA] = {.handler = emulate_ldr},
	[PROBES_LOAD] = {.handler = emulate_ldr},
	[PROBES_STORE_EXTRA] = {.handler = emulate_str},
	[PROBES_STORE] = {.handler = emulate_str},
	[PROBES_MOV_IP_SP] = {.handler = simulate_mov_ipsp},
	[PROBES_DATA_PROCESSING_REG] = {
	.handler = emulate_rd12rn16rm0rs8_rwflags},
	[PROBES_DATA_PROCESSING_IMM] = {
	.handler = emulate_rd12rn16rm0rs8_rwflags},
	[PROBES_MOV_HALFWORD] = {.handler = emulate_rd12rm0_noflags_nopc},
	[PROBES_SEV] = {.handler = probes_emulate_none},
	[PROBES_WFE] = {.handler = probes_simulate_nop},
	[PROBES_SATURATE] = {.handler = emulate_rd12rn16rm0_rwflags_nopc},
	[PROBES_REV] = {.handler = emulate_rd12rm0_noflags_nopc},
	[PROBES_MMI] = {.handler = emulate_rd12rn16rm0_rwflags_nopc},
	[PROBES_PACK] = {.handler = emulate_rd12rn16rm0_rwflags_nopc},
	[PROBES_EXTEND] = {.handler = emulate_rd12rm0_noflags_nopc},
	[PROBES_EXTEND_ADD] = {.handler = emulate_rd12rn16rm0_rwflags_nopc},
	[PROBES_MUL_ADD_LONG] = {
	.handler = emulate_rdlo12rdhi16rn0rm8_rwflags_nopc},
	[PROBES_MUL_ADD] = {.handler = emulate_rd16rn12rm0rs8_rwflags_nopc},
	[PROBES_BITFIELD] = {.handler = emulate_rd12rm0_noflags_nopc},
	[PROBES_BRANCH] = {.handler = simulate_bbl},
	[PROBES_LDMSTM] = {.decoder = kprobe_decode_ldmstm}
	};

	const struct decode_checker *kprobes_arm_checkers[] = {arm_stack_checker, arm_regs_checker, NULL};