path: root/arch/powerpc/lib/sstep.c

/*
 * Single-step support.
 *
 * Copyright (C) 2004 Paul Mackerras <paulus@au.ibm.com>, IBM
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 */
#include <linux/kernel.h>
#include <linux/kprobes.h>
#include <linux/ptrace.h>
#include <linux/prefetch.h>
#include <asm/sstep.h>
#include <asm/processor.h>
#include <asm/uaccess.h>
#include <asm/cputable.h>

extern char system_call_common[];

#ifdef CONFIG_PPC64
/* Bits in SRR1 that are copied from MSR */
#define MSR_MASK	0xffffffff87c0ffffUL
#else
#define MSR_MASK	0x87c0ffff
#endif

/* Bits in XER */
#define XER_SO		0x80000000U
#define XER_OV		0x40000000U
#define XER_CA		0x20000000U

#ifdef CONFIG_PPC_FPU
/*
 * Functions in ldstfp.S
 */
extern int do_lfs(int rn, unsigned long ea);
extern int do_lfd(int rn, unsigned long ea);
extern int do_stfs(int rn, unsigned long ea);
extern int do_stfd(int rn, unsigned long ea);
extern int do_lvx(int rn, unsigned long ea);
extern int do_stvx(int rn, unsigned long ea);
extern int do_lxvd2x(int rn, unsigned long ea);
extern int do_stxvd2x(int rn, unsigned long ea);
#endif

/*
 * Emulate the truncation of 64 bit values in 32-bit mode.
 */
static unsigned long truncate_if_32bit(unsigned long msr, unsigned long val)
{
#ifdef __powerpc64__
	if ((msr & MSR_64BIT) == 0)
		val &= 0xffffffffUL;
#endif
	return val;
}

/*
 * Determine whether a conditional branch instruction would branch.
 */
static int __kprobes branch_taken(unsigned int instr, struct pt_regs *regs)
{
	unsigned int bo = (instr >> 21) & 0x1f;
	unsigned int bi;

	if ((bo & 4) == 0) {
		/* decrement counter */
		--regs->ctr;
		if (((bo >> 1) & 1) ^ (regs->ctr == 0))
			return 0;
	}
	if ((bo & 0x10) == 0) {
		/* check bit from CR */
		bi = (instr >> 16) & 0x1f;
		if (((regs->ccr >> (31 - bi)) & 1) != ((bo >> 3) & 1))
			return 0;
	}
	return 1;
}


static long __kprobes address_ok(struct pt_regs *regs, unsigned long ea, int nb)
{
	if (!user_mode(regs))
		return 1;
	return __access_ok(ea, nb, USER_DS);
}

/*
 * Calculate effective address for a D-form instruction
 */
static unsigned long __kprobes dform_ea(unsigned int instr, struct pt_regs *regs)
{
	int ra;
	unsigned long ea;

	ra = (instr >> 16) & 0x1f;
	ea = (signed short) instr;		/* sign-extend */
	if (ra) {
		ea += regs->gpr[ra];
		if (instr & 0x04000000)		/* update forms */
			regs->gpr[ra] = ea;
	}

	return truncate_if_32bit(regs->msr, ea);
}

#ifdef __powerpc64__
/*
 * Calculate effective address for a DS-form instruction
 */
static unsigned long __kprobes dsform_ea(unsigned int instr, struct pt_regs *regs)
{
	int ra;
	unsigned long ea;

	ra = (instr >> 16) & 0x1f;
	ea = (signed short) (instr & ~3);	/* sign-extend */
	if (ra) {
		ea += regs->gpr[ra];
		if ((instr & 3) == 1)		/* update forms */
			regs->gpr[ra] = ea;
	}

	return truncate_if_32bit(regs->msr, ea);
}
#endif /* __powerpc64 */

/*
 * Calculate effective address for an X-form instruction
 */
static unsigned long __kprobes xform_ea(unsigned int instr, struct pt_regs *regs,
				     int do_update)
{
	int ra, rb;
	unsigned long ea;

	ra = (instr >> 16) & 0x1f;
	rb = (instr >> 11) & 0x1f;
	ea = regs->gpr[rb];
	if (ra) {
		ea += regs->gpr[ra];
		if (do_update)		/* update forms */
			regs->gpr[ra] = ea;
	}

	return truncate_if_32bit(regs->msr, ea);
}

/*
 * Return the largest power of 2, not greater than sizeof(unsigned long),
 * such that x is a multiple of it.
 */
static inline unsigned long max_align(unsigned long x)
{
	x |= sizeof(unsigned long);
	return x & -x;		/* isolates rightmost bit */
}


static inline unsigned long byterev_2(unsigned long x)
{
	return ((x >> 8) & 0xff) | ((x & 0xff) << 8);
}

static inline unsigned long byterev_4(unsigned long x)
{
	return ((x >> 24) & 0xff) | ((x >> 8) & 0xff00) |
		((x & 0xff00) << 8) | ((x & 0xff) << 24);
}

#ifdef __powerpc64__
static inline unsigned long byterev_8(unsigned long x)
{
	return (byterev_4(x) << 32) | b