arch/powerpc/kernel/align.c

/* align.c - handle alignment exceptions for the Power PC.
 *
 * Copyright (c) 1996 Paul Mackerras <paulus@cs.anu.edu.au>
 * Copyright (c) 1998-1999 TiVo, Inc.
 *   PowerPC 403GCX modifications.
 * Copyright (c) 1999 Grant Erickson <grant@lcse.umn.edu>
 *   PowerPC 403GCX/405GP modifications.
 * Copyright (c) 2001-2002 PPC64 team, IBM Corp
 *   64-bit and Power4 support
 * Copyright (c) 2005 Benjamin Herrenschmidt, IBM Corp
 *                    <benh@kernel.crashing.org>
 *   Merge ppc32 and ppc64 implementations
 *
 * 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/mm.h>
#include <asm/processor.h>
#include <asm/uaccess.h>
#include <asm/system.h>
#include <asm/cache.h>
#include <asm/cputable.h>

struct aligninfo {
	unsigned char len;
	unsigned char flags;
};

#define IS_XFORM(inst)	(((inst) >> 26) == 31)
#define IS_DSFORM(inst)	(((inst) >> 26) >= 56)

#define INVALID	{ 0, 0 }

#define LD	1	/* load */
#define ST	2	/* store */
#define	SE	4	/* sign-extend value */
#define F	8	/* to/from fp regs */
#define U	0x10	/* update index register */
#define M	0x20	/* multiple load/store */
#define SW	0x40	/* byte swap int or ... */
#define S	0x40	/* ... single-precision fp */
#define SX	0x40	/* byte count in XER */
#define HARD	0x80	/* string, stwcx. */

#define DCBZ	0x5f	/* 8xx/82xx dcbz faults when cache not enabled */

#define SWAP(a, b)	(t = (a), (a) = (b), (b) = t)

/*
 * The PowerPC stores certain bits of the instruction that caused the
 * alignment exception in the DSISR register.  This array maps those
 * bits to information about the operand length and what the
 * instruction would do.
 */
static struct aligninfo aligninfo[128] = {
	{ 4, LD },		/* 00 0 0000: lwz / lwarx */
	INVALID,		/* 00 0 0001 */
	{ 4, ST },		/* 00 0 0010: stw */
	INVALID,		/* 00 0 0011 */
	{ 2, LD },		/* 00 0 0100: lhz */
	{ 2, LD+SE },		/* 00 0 0101: lha */
	{ 2, ST },		/* 00 0 0110: sth */
	{ 4, LD+M },		/* 00 0 0111: lmw */
	{ 4, LD+F+S },		/* 00 0 1000: lfs */
	{ 8, LD+F },		/* 00 0 1001: lfd */
	{ 4, ST+F+S },		/* 00 0 1010: stfs */
	{ 8, ST+F },		/* 00 0 1011: stfd */
	INVALID,		/* 00 0 1100 */
	{ 8, LD },		/* 00 0 1101: ld/ldu/lwa */
	INVALID,		/* 00 0 1110 */
	{ 8, ST },		/* 00 0 1111: std/stdu */
	{ 4, LD+U },		/* 00 1 0000: lwzu */
	INVALID,		/* 00 1 0001 */
	{ 4, ST+U },		/* 00 1 0010: stwu */
	INVALID,		/* 00 1 0011 */
	{ 2, LD+U },		/* 00 1 0100: lhzu */
	{ 2, LD+SE+U },		/* 00 1 0101: lhau */
	{ 2, ST+U },		/* 00 1 0110: sthu */
	{ 4, ST+M },		/* 00 1 0111: stmw */
	{ 4, LD+F+S+U },	/* 00 1 1000: lfsu */
	{ 8, LD+F+U },		/* 00 1 1001: lfdu */
	{ 4, ST+F+S+U },	/* 00 1 1010: stfsu */
	{ 8, ST+F+U },		/* 00 1 1011: stfdu */
	INVALID,		/* 00 1 1100 */
	INVALID,		/* 00 1 1101 */
	INVALID,		/* 00 1 1110 */
	INVALID,		/* 00 1 1111 */
	{ 8, LD },		/* 01 0 0000: ldx */
	INVALID,		/* 01 0 0001 */
	{ 8, ST },		/* 01 0 0010: stdx */
	INVALID,		/* 01 0 0011 */
	INVALID,		/* 01 0 0100 */
	{ 4, LD+SE },		/* 01 0 0101: lwax */
	INVALID,		/* 01 0 0110 */
	INVALID,		/* 01 0 0111 */
	{ 4, LD+M+HARD+SX },	/* 01 0 1000: lswx */
	{ 4, LD+M+HARD },	/* 01 0 1001: lswi */
	{ 4, ST+M+HARD+SX },	/* 01 0 1010: stswx */
	{ 4, ST+M+HARD },	/* 01 0 1011: stswi */
	INVALID,		/* 01 0 1100 */
	{ 8, LD+U },		/* 01 0 1101: ldu */
	INVALID,		/* 01 0 1110 */
	{ 8, ST+U },		/* 01 0 1111: stdu */
	{ 8, LD+U },		/* 01 1 0000: ldux */
	INVALID,		/* 01 1 0001 */
	{ 8, ST+U },		/* 01 1 0010: stdux */
	INVALID,		/* 01 1 0011 */
	INVALID,		/* 01 1 0100 */
	{ 4, LD+SE+U },		/* 01 1 0101: lwaux */
	INVALID,		/* 01 1 0110 */
	INVALID,		/* 01 1 0111 */
	INVALID,		/* 01 1 1000 */
	INVALID,		/* 01 1 1001 */
	INVALID,		/* 01 1 1010 */
	INVALID,		/* 01 1 1011 */
	INVALID,		/* 01 1 1100 */
	INVALID,		/* 01 1 1101 */
	INVALID,		/* 01 1 1110 */
	INVALID,		/* 01 1 1111 */
	INVALID,		/* 10 0 0000 */
	INVALID,		/* 10 0 0001 */
	INVALID,		/* 10 0 0010: stwcx. */
	INVALID,		/* 10 0 0011 */
	INVALID,		/* 10 0 0100 */
	INVALID,		/* 10 0 0101 */
	INVALID,		/* 10 0 0110 */
	INVALID,		/* 10 0 0111 */
	{ 4, LD+SW },		/* 10 0 1000: lwbrx */
	INVALID,		/* 10 0 1001 */
	{ 4, ST+SW },		/* 10 0 1010: stwbrx */
	INVALID,		/* 10 0 1011 */
	{ 2, LD+SW },		/* 10 0 1100: lhbrx */
	{ 4, LD+SE },		/* 10 0 1101  lwa */
	{ 2, ST+SW },		/* 10 0 1110: sthbrx */
	INVALID,		/* 10 0 1111 */
	INVALID,		/* 10 1 0000 */
	INVALID,		/* 10 1 0001 */
	INVALID,		/* 10 1 0010 */
	INVALID,		/* 10 1 0011 */
	INVALID,		/* 10 1 0100 */
	INVALID,		/* 10 1 0101 */
	INVALID,		/* 10 1 0110 */
	INVALID,		/* 10 1 0111 */
	INVALID,		/* 10 1 1000 */
	INVALID,		/* 10 1 1001 */
	INVALID,		/* 10 1 1010 */
	INVALID,		/* 10 1 1011 */
	INVALID,		/* 10 1 1100 */
	INVALID,		/* 10 1 1101 */
	INVALID,		/* 10 1 1110 */
	{ 0, ST+HARD },		/* 10 1 1111: dcbz */
	{ 4, LD },		/* 11 0 0000: lwzx */
	INVALID,		/* 11 0 0001 */
	{ 4, ST },		/* 11 0 0010: stwx */
	INVALID,		/* 11 0 0011 */
	{ 2, LD },		/* 11 0 0100: lhzx */
	{ 2, LD+SE },		/* 11 0 0101: lhax */
	{ 2, ST },		/* 11 0 0110: sthx */
	INVALID,		/* 11 0 0111 */
	{ 4, LD+F+S },		/* 11 0 1000: lfsx */
	{ 8, LD+F },		/* 11 0 1001: lfdx */
	{ 4, ST+F+S },		/* 11 0 1010: stfsx */
	{ 8, ST+F },		/* 11 0 1011: stfdx */
	INVALID,		/* 11 0 1100 */
	{ 8, LD+M },		/* 11 0 1101: lmd */
	INVALID,		/* 11 0 1110 */
	{ 8, ST+M },		/* 11 0 1111: stmd */
	{ 4, LD+U },		/* 11 1 0000: lwzux */
	INVALID,		/* 11 1 0001 */
	{ 4, ST+U },		/* 11 1 0010: stwux */
	INVALID,		/* 11 1 0011 */
	{ 2, LD+U },		/* 11 1 0100: lhzux */
	{ 2, LD+SE+U },		/* 11 1 0101: lhaux */
	{ 2, ST+U },		/* 11 1 0110: sthux */
	INVALID,		/* 11 1 0111 */
	{ 4, LD+F+S+U },	/* 11 1 1000: lfsux */
	{ 8, LD+F+U },		/* 11 1 1001: lfdux */
	{ 4, ST+F+S+U },	/* 11 1 1010: stfsux */
	{ 8, ST+F+U },		/* 11 1 1011: stfdux */
	INVALID,		/* 11 1 1100 */
	INVALID,		/* 11 1 1101 */
	INVALID,		/* 11 1 1110 */
	INVALID,		/* 11 1 1111 */
};

/*
 * Create a DSISR value from the instruction
 */
static inline unsigned make_dsisr(unsigned instr)
{
	unsigned dsisr;


	/* bits  6:15 --> 22:31 */
	dsisr = (instr & 0x03ff0000) >> 16;

	if (IS_XFORM(instr)) {
		/* bits 29:30 --> 15:16 */
		dsisr |= (instr & 0x00000006) << 14;
		/* bit     25 -->    17 */
		dsisr |= (instr & 0x00000040) << 8;
		/* bits 21:24 --> 18:21 */
		dsisr |= (instr & 0x00000780) << 3;
	} else {
		/* bit      5 -->    17 */
		dsisr |= (instr & 0x04000000) >> 12;
		/* bits  1: 4 --> 18:21 */
		dsisr |= (instr & 0x78000000) >> 17;
		/* bits 30:31 --> 12:13 */
		if (IS_DSFORM(instr))
			dsisr |= (instr & 0x00000003) << 18;
	}

	return dsisr;
}

/*
 * The dcbz (data cache block zero) instruction
 * gives an alignment fault if used on non-cacheable
 * memory.  We handle the fault mainly for the
 * case when we are running with the cache disabled
 * for debugging.
 */
static int emulate_dcbz(struct pt_regs *regs, unsigned char __user *addr)
{
	long __user *p;
	int i, size;

#ifdef __powerpc64__
	size = ppc64_caches.dline_size;
#else
	size = L1_CACHE_BYTES;
#endif
	p = (long __user *) (regs->dar & -size);
	if (user_mode(regs) && !access_ok(VERIFY_WRITE, p, size))
		return -EFAULT;
	for (i = 0; i < size / sizeof(long); ++i)
		if (__put_user(0, p+i))
			return -EFAULT;
	return 1;
}

/*
 * Emulate load & store multiple instructions
 * On 64-bit machines, these instructions only affect/use the
 * bottom 4 bytes of each register, and the loads clear the
 * top 4 bytes of the affected register.
 */
#ifdef CONFIG_PPC64
#define REG_BYTE(rp, i)		*((u8 *)((rp) + ((i) >> 2)) + ((i) & 3) + 4)
#else
#define REG_BYTE(rp, i)		*((u8 *)(rp) + (i))
#endif

static int emulate_multiple(struct pt_regs *regs, unsigned char __user *addr,
			    unsigned int reg, unsigned int nb,
			    unsigned int flags, unsigned int instr)
{
	unsigned long *rptr;
	unsigned int nb0, i;

	/*
	 * We do not try to emulate 8 bytes multiple as they aren't really
	 * available in our operating environments and we don't try to
	 * emulate multiples operations in kernel land as they should never
	 * be used/generated there at least not on unaligned boundaries
	 */
	if (unlikely((nb > 4) || !user_mode(regs)))
		return 0;

	/* lmw, stmw, lswi/x, stswi/x */
	nb0 = 0;
	if (flags & HARD) {
		if (flags & SX) {
			nb = regs->xer & 127;
			if (nb == 0)
				return 1;
		} else {
			if (__get_user(instr,
				       (unsigned int __user *)regs->nip))
				return -EFAULT;
			nb = (instr >> 11) & 0x1f;
			if (nb == 0)
				nb = 32;
		}
		if (nb + reg * 4 > 128) {
			nb0 = nb + reg * 4 - 128;
			nb = 128 - reg * 4;
		}
	} else {
		/* lwm, stmw */
		nb = (32 - reg) * 4;
	}

	if (!access_ok((flags & ST ? VERIFY_WRITE: VERIFY_READ), addr, nb+nb0))
		return -EFAULT;	/* bad address */

	rptr = &regs->gpr[reg];
	if (flags & LD) {
		/*
		 * This zeroes the top 4 bytes of the affected registers
		 * in 64-bit mode, and also zeroes out any remaining
		 * bytes of the last register for lsw*.
		 */
		memset(rptr, 0, ((nb + 3) / 4) * sizeof(unsigned long));
		if (nb0 > 0)
			memset(&regs->gpr[0], 0,
			       ((nb0 + 3) / 4) * sizeof(unsigned long));

		for (i = 0; i < nb; ++i)
			if (__get_user(REG_BYTE(rptr, i), addr + i))
				return -EFAULT;
		if (nb0 > 0) {
			rptr = &regs->gpr[0];
			addr += nb;
			for (i = 0; i < nb0; ++i)
				if (__get_user(REG_BYTE(rptr, i), addr + i))
					return -EFAULT;
		}

	} else {
		for (i = 0; i < nb; ++i)
			if (__put_user(REG_BYTE(rptr, i), addr + i))
				return -EFAULT;
		if (nb0 > 0) {
			rptr = &regs->gpr[0];
			addr += nb;
			for (i = 0; i < nb0; ++i)
				if (__put_user(REG_BYTE(rptr, i), addr + i))
					return -EFAULT;
		}
	}
	return 1;
}


/*
 * Called on alignment exception. Attempts to fixup
 *
 * Return 1 on success
 * Return 0 if unable to handle the interrupt
 * Return -EFAULT if data address is bad
 */

int fix_alignment(struct pt_regs *regs)
{
	unsigned int instr, nb, flags;
	unsigned int reg, areg;
	unsigned int dsisr;
	unsigned char __user *addr;
	unsigned char __user *p;
	int ret, t;
	union {
		u64 ll;
		double dd;
		unsigned char v[8];
		struct {
			unsigned hi32;
			int	 low32;
		} x32;
		struct {
			unsigned char hi48[6];
			short	      low16;
		} x16;
	} data;

	/*
	 * We require a complete register set, if not, then our assembly
	 * is broken
	 */
	CHECK_FULL_REGS(regs);

	dsisr = regs->dsisr;

	/* Some processors don't provide us with a DSISR we can use here,
	 * let's make one up from the instruction
	 */
	if (cpu_has_feature(CPU_FTR_NODSISRALIGN)) {
		unsigned int real_instr;
		if (unlikely(__get_user(real_instr,
					(unsigned int __user *)regs->nip)))
			return -EFAULT;
		dsisr = make_dsisr(real_instr);
	}

	/* extract the operation and registers from the dsisr */
	reg = (dsisr >> 5) & 0x1f;	/* source/dest register */
	areg = dsisr & 0x1f;		/* register to update */
	instr = (dsisr >> 10) & 0x7f;
	instr |= (dsisr >> 13) & 0x60;

	/* Lookup the operation in our table */
	nb = aligninfo[instr].len;
	flags = aligninfo[instr].flags;

	/* DAR has the operand effective address */
	addr = (unsigned char __user *)regs->dar;

	/* A size of 0 indicates an instruction we don't support, with
	 * the exception of DCBZ which is handled as a special case here
	 */
	if (instr == DCBZ)
		return emulate_dcbz(regs, addr);
	if (unlikely(nb == 0))
		return 0;

	/* Load/Store Multiple instructions are handled in their own
	 * function
	 */
	if (flags & M)
		return emulate_multiple(regs, addr, reg, nb, flags, instr);

	/* Verify the address of the operand */
	if (unlikely(user_mode(regs) &&
		     !access_ok((flags & ST ? VERIFY_WRITE : VERIFY_READ),
				addr, nb)))
		return -EFAULT;

	/* Force the fprs into the save area so we can reference them */
	if (flags & F) {
		/* userland only */
		if (unlikely(!user_mode(regs)))
			return 0;
		flush_fp_to_thread(current);
	}

	/* If we are loading, get the data from user space, else
	 * get it from register values
	 */
	if (flags & LD) {
		data.ll = 0;
		ret = 0;
		p = addr;
		switch (nb) {
		case 8:
			ret |= __get_user(data.v[0], p++);
			ret |= __get_user(data.v[1], p++);
			ret |= __get_user(data.v[2], p++);
			ret |= __get_user(data.v[3], p++);
		case 4:
			ret |= __get_user(data.v[4], p++);
			ret |= __get_user(data.v[5], p++);
		case 2:
			ret |= __get_user(data.v[6], p++);
			ret |= __get_user(data.v[7], p++);
			if (unlikely(ret))
				return -EFAULT;
		}
	} else if (flags & F)
		data.dd = current->thread.fpr[reg];
	else
		data.ll = regs->gpr[reg];

	/* Perform other misc operations like sign extension, byteswap,
	 * or floating point single precision conversion
	 */
	switch (flags & ~U) {
	case LD+SE:	/* sign extend */
		if ( nb == 2 )
			data.ll = data.x16.low16;
		else	/* nb must be 4 */
			data.ll = data.x32.low32;
		break;
	case LD+S:	/* byte-swap */
	case ST+S:
		if (nb == 2) {
			SWAP(data.v[6], data.v[7]);
		} else {
			SWAP(data.v[4], data.v[7]);
			SWAP(data.v[5], data.v[6]);
		}
		break;

	/* Single-precision FP load and store require conversions... */
	case LD+F+S:
#ifdef CONFIG_PPC_FPU
		preempt_disable();
		enable_kernel_fp();
		cvt_fd((float *)&data.v[4], &data.dd, &current->thread);
		preempt_enable();
#else
		return 0;
#endif
		break;
	case ST+F+S:
#ifdef CONFIG_PPC_FPU
		preempt_disable();
		enable_kernel_fp();
		cvt_df(&data.dd, (float *)&data.v[4], &current->thread);
		preempt_enable();
#else
		return 0;
#endif
		break;
	}

	/* Store result to memory or update registers */
	if (flags & ST) {
		ret = 0;
		p = addr;
		switch (nb) {
		case 8:
			ret |= __put_user(data.v[0], p++);
			ret |= __put_user(data.v[1], p++);
			ret |= __put_user(data.v[2], p++);
			ret |= __put_user(data.v[3], p++);
		case 4:
			ret |= __put_user(data.v[4], p++);
			ret |= __put_user(data.v[5], p++);
		case 2:
			ret |= __put_user(data.v[6], p++);
			ret |= __put_user(data.v[7], p++);
		}
		if (unlikely(ret))
			return -EFAULT;
	} else if (flags & F)
		current->thread.fpr[reg] = data.dd;
	else
		regs->gpr[reg] = data.ll;

	/* Update RA as needed */
	if (flags & U)
		regs->gpr[areg] = regs->dar;

	return 1;
}