arch/arm/kernel/kprobes-thumb.c

/*
 * arch/arm/kernel/kprobes-thumb.c
 *
 * Copyright (C) 2011 Jon Medhurst <tixy@yxit.co.uk>.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

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

#include "kprobes.h"


/*
 * True if current instruction is in an IT block.
 */
#define in_it_block(cpsr)	((cpsr & 0x06000c00) != 0x00000000)

/*
 * Return the condition code to check for the currently executing instruction.
 * This is in ITSTATE<7:4> which is in CPSR<15:12> but is only valid if
 * in_it_block returns true.
 */
#define current_cond(cpsr)	((cpsr >> 12) & 0xf)

static unsigned long __kprobes thumb_check_cc(unsigned long cpsr)
{
	if (unlikely(in_it_block(cpsr)))
		return kprobe_condition_checks[current_cond(cpsr)](cpsr);
	return true;
}

static void __kprobes thumb16_singlestep(struct kprobe *p, struct pt_regs *regs)
{
	regs->ARM_pc += 2;
	p->ainsn.insn_handler(p, regs);
	regs->ARM_cpsr = it_advance(regs->ARM_cpsr);
}

static void __kprobes thumb32_singlestep(struct kprobe *p, struct pt_regs *regs)
{
	regs->ARM_pc += 4;
	p->ainsn.insn_handler(p, regs);
	regs->ARM_cpsr = it_advance(regs->ARM_cpsr);
}

enum kprobe_insn __kprobes
thumb16_kprobe_decode_insn(kprobe_opcode_t insn, struct arch_specific_insn *asi)
{
	asi->insn_singlestep = thumb16_singlestep;
	asi->insn_check_cc = thumb_check_cc;
	return INSN_REJECTED;
}

enum kprobe_insn __kprobes
thumb32_kprobe_decode_insn(kprobe_opcode_t insn, struct arch_specific_insn *asi)
{
	asi->insn_singlestep = thumb32_singlestep;
	asi->insn_check_cc = thumb_check_cc;
	return INSN_REJECTED;
}