linux/arch/arm/kernel/kprobes-common.c

/*
 * arch/arm/kernel/kprobes-common.c
 *
 * Copyright (C) 2011 Jon Medhurst <tixy@yxit.co.uk>.
 *
 * Some contents moved here from arch/arm/include/asm/kprobes-arm.c which is
 * Copyright (C) 2006, 2007 Motorola Inc.
 *
 * 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"


/*
 * For STR and STM instructions, an ARM core may choose to use either
 * a +8 or a +12 displacement from the current instruction's address.
 * Whichever value is chosen for a given core, it must be the same for
 * both instructions and may not change.  This function measures it.
 */

int str_pc_offset;

void __init find_str_pc_offset(void)
{
	int addr, scratch, ret;

	__asm__ (
		"sub	%[ret], pc, #4		\n\t"
		"str	pc, %[addr]		\n\t"
		"ldr	%[scr], %[addr]		\n\t"
		"sub	%[ret], %[scr], %[ret]	\n\t"
		: [ret] "=r" (ret), [scr] "=r" (scratch), [addr] "+m" (addr));

	str_pc_offset = ret;
}


void __init arm_kprobe_decode_init(void)
{
	find_str_pc_offset();
}


static unsigned long __kprobes __check_eq(unsigned long cpsr)
{
	return cpsr & PSR_Z_BIT;
}

static unsigned long __kprobes __check_ne(unsigned long cpsr)
{
	return (~cpsr) & PSR_Z_BIT;
}

static unsigned long __kprobes __check_cs(unsigned long cpsr)
{
	return cpsr & PSR_C_BIT;
}

static unsigned long __kprobes __check_cc(unsigned long cpsr)
{
	return (~cpsr) & PSR_C_BIT;
}

static unsigned long __kprobes __check_mi(unsigned long cpsr)
{
	return cpsr & PSR_N_BIT;
}

static unsigned long __kprobes __check_pl(unsigned long cpsr)
{
	return (~cpsr) & PSR_N_BIT;
}

static unsigned long __kprobes __check_vs(unsigned long cpsr)
{
	return cpsr & PSR_V_BIT;
}

static unsigned long __kprobes __check_vc(unsigned long cpsr)
{
	return (~cpsr) & PSR_V_BIT;
}

static unsigned long __kprobes __check_hi(unsigned long cpsr)
{
	cpsr &= ~(cpsr >> 1); /* PSR_C_BIT &= ~PSR_Z_BIT */
	return cpsr & PSR_C_BIT;
}

static unsigned long __kprobes __check_ls(unsigned long cpsr)
{
	cpsr &= ~(cpsr >> 1); /* PSR_C_BIT &= ~PSR_Z_BIT */
	return (~cpsr) & PSR_C_BIT;
}

static unsigned long __kprobes __check_ge(unsigned long cpsr)
{
	cpsr ^= (cpsr << 3); /* PSR_N_BIT ^= PSR_V_BIT */
	return (~cpsr) & PSR_N_BIT;
}

static unsigned long __kprobes __check_lt(unsigned long cpsr)
{
	cpsr ^= (cpsr << 3); /* PSR_N_BIT ^= PSR_V_BIT */
	return cpsr & PSR_N_BIT;
}

static unsigned long __kprobes __check_gt(unsigned long cpsr)
{
	unsigned long temp = cpsr ^ (cpsr << 3); /* PSR_N_BIT ^= PSR_V_BIT */
	temp |= (cpsr << 1);			 /* PSR_N_BIT |= PSR_Z_BIT */
	return (~temp) & PSR_N_BIT;
}

static unsigned long __kprobes __check_le(unsigned long cpsr)
{
	unsigned long temp = cpsr ^ (cpsr << 3); /* PSR_N_BIT ^= PSR_V_BIT */
	temp |= (cpsr << 1);			 /* PSR_N_BIT |= PSR_Z_BIT */
	return temp & PSR_N_BIT;
}

static unsigned long __kprobes __check_al(unsigned long cpsr)
{
	return true;
}

kprobe_check_cc * const kprobe_condition_checks[16] = {
	&__check_eq, &__check_ne, &__check_cs, &__check_cc,
	&__check_mi, &__check_pl, &__check_vs, &__check_vc,
	&__check_hi, &__check_ls, &__check_ge, &__check_lt,
	&__check_gt, &__check_le, &__check_al, &__check_al
};