arch/ppc/kernel/traps.c

/*
 *  Copyright (C) 1995-1996  Gary Thomas (gdt@linuxppc.org)
 *
 *  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.
 *
 *  Modified by Cort Dougan (cort@cs.nmt.edu)
 *  and Paul Mackerras (paulus@cs.anu.edu.au)
 */

/*
 * This file handles the architecture-dependent parts of hardware exceptions
 */

#include <linux/errno.h>
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/stddef.h>
#include <linux/unistd.h>
#include <linux/ptrace.h>
#include <linux/slab.h>
#include <linux/user.h>
#include <linux/a.out.h>
#include <linux/interrupt.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/prctl.h>
#include <linux/bug.h>

#include <asm/pgtable.h>
#include <asm/uaccess.h>
#include <asm/system.h>
#include <asm/io.h>
#include <asm/reg.h>
#include <asm/xmon.h>
#include <asm/pmc.h>

#ifdef CONFIG_XMON
extern int xmon_bpt(struct pt_regs *regs);
extern int xmon_sstep(struct pt_regs *regs);
extern int xmon_iabr_match(struct pt_regs *regs);
extern int xmon_dabr_match(struct pt_regs *regs);

int (*debugger)(struct pt_regs *regs) = xmon;
int (*debugger_bpt)(struct pt_regs *regs) = xmon_bpt;
int (*debugger_sstep)(struct pt_regs *regs) = xmon_sstep;
int (*debugger_iabr_match)(struct pt_regs *regs) = xmon_iabr_match;
int (*debugger_dabr_match)(struct pt_regs *regs) = xmon_dabr_match;
void (*debugger_fault_handler)(struct pt_regs *regs);
#else
#ifdef CONFIG_KGDB
int (*debugger)(struct pt_regs *regs);
int (*debugger_bpt)(struct pt_regs *regs);
int (*debugger_sstep)(struct pt_regs *regs);
int (*debugger_iabr_match)(struct pt_regs *regs);
int (*debugger_dabr_match)(struct pt_regs *regs);
void (*debugger_fault_handler)(struct pt_regs *regs);
#else
#define debugger(regs)			do { } while (0)
#define debugger_bpt(regs)		0
#define debugger_sstep(regs)		0
#define debugger_iabr_match(regs)	0
#define debugger_dabr_match(regs)	0
#define debugger_fault_handler		((void (*)(struct pt_regs *))0)
#endif
#endif

/*
 * Trap & Exception support
 */

DEFINE_SPINLOCK(die_lock);

int die(const char * str, struct pt_regs * fp, long err)
{
	static int die_counter;
	int nl = 0;
	console_verbose();
	spin_lock_irq(&die_lock);
	printk("Oops: %s, sig: %ld [#%d]\n", str, err, ++die_counter);
#ifdef CONFIG_PREEMPT
	printk("PREEMPT ");
	nl = 1;
#endif
#ifdef CONFIG_SMP
	printk("SMP NR_CPUS=%d ", NR_CPUS);
	nl = 1;
#endif
	if (nl)
		printk("\n");
	show_regs(fp);
	add_taint(TAINT_DIE);
	spin_unlock_irq(&die_lock);
	/* do_exit() should take care of panic'ing from an interrupt
	 * context so we don't handle it here
	 */
	do_exit(err);
}

void _exception(int signr, struct pt_regs *regs, int code, unsigned long addr)
{
	siginfo_t info;

	if (!user_mode(regs)) {
		debugger(regs);
		die("Exception in kernel mode", regs, signr);
	}
	info.si_signo = signr;
	info.si_errno = 0;
	info.si_code = code;
	info.si_addr = (void __user *) addr;
	force_sig_info(signr, &info, current);

	/*
	 * Init gets no signals that it doesn't have a handler for.
	 * That's all very well, but if it has caused a synchronous
	 * exception and we ignore the resulting signal, it will just
	 * generate the same exception over and over again and we get
	 * nowhere.  Better to kill it and let the kernel panic.
	 */
	if (is_global_init(current)) {
		__sighandler_t handler;

		spin_lock_irq(&current->sighand->siglock);
		handler = current->sighand->action[signr-1].sa.sa_handler;
		spin_unlock_irq(&current->sighand->siglock);
		if (handler == SIG_DFL) {
			/* init has generated a synchronous exception
			   and it doesn't have a handler for the signal */
			printk(KERN_CRIT "init has generated signal %d "
			       "but has no handler for it\n", signr);
			do_exit(signr);
		}
	}
}

/*
 * I/O accesses can cause machine checks on powermacs.
 * Check if the NIP corresponds to the address of a sync
 * instruction for which there is an entry in the exception
 * table.
 * Note that the 601 only takes a machine check on TEA
 * (transfer error ack) signal assertion, and does not
 * set any of the top 16 bits of SRR1.
 *  -- paulus.
 */
static inline int check_io_access(struct pt_regs *regs)
{
#if defined CONFIG_8xx
	unsigned long msr = regs->msr;
	const struct exception_table_entry *entry;
	unsigned int *nip = (unsigned int *)regs->nip;

	if (((msr & 0xffff0000) == 0 || (msr & (0x80000 | 0x40000)))
	    && (entry = search_exception_tables(regs->nip)) != NULL) {
		/*
		 * Check that it's a sync instruction, or somewhere
		 * in the twi; isync; nop sequence that inb/inw/inl uses.
		 * As the address is in the exception table
		 * we should be able to read the instr there.
		 * For the debug message, we look at the preceding
		 * load or store.
		 */
		if (*nip == 0x60000000)		/* nop */
			nip -= 2;
		else if (*nip == 0x4c00012c)	/* isync */
			--nip;
		/* eieio from I/O string functions */
		else if ((*nip) == 0x7c0006ac || *(nip+1) == 0x7c0006ac)
			nip += 2;
		if (*nip == 0x7c0004ac || (*nip >> 26) == 3 ||
			(*(nip+1) >> 26) == 3) {
			/* sync or twi */
			unsigned int rb;

			--nip;
			rb = (*nip >> 11) & 0x1f;
			printk(KERN_DEBUG "%s bad port %lx at %p\n",
			       (*nip & 0x100)? "OUT to": "IN from",
			       regs->gpr[rb] - _IO_BASE, nip);
			regs->msr |= MSR_RI;
			regs->nip = entry->fixup;
			return 1;
		}
	}
#endif /* CONFIG_8xx */
	return 0;
}

#if defined(CONFIG_4xx) || defined(CONFIG_BOOKE)
/* On 4xx, the reason for the machine check or program exception
   is in the ESR. */
#define get_reason(regs)	((regs)->dsisr)
#define get_mc_reason(regs)	((regs)->dsisr)
#define REASON_FP		ESR_FP
#define REASON_ILLEGAL		(ESR_PIL | ESR_PUO)
#define REASON_PRIVILEGED	ESR_PPR
#define REASON_TRAP		ESR_PTR

/* single-step stuff */
#define single_stepping(regs)	(current->thread.dbcr0 & DBCR0_IC)
#define clear_single_step(regs)	(current->thread.dbcr0 &= ~DBCR0_IC)

#else
/* On non-4xx, the reason for the machine check or program
   exception is in the MSR. */
#define get_reason(regs)	((regs)->msr)
#define get_mc_reason(regs)	((regs)->msr)
#define REASON_FP		0x100000
#define REASON_ILLEGAL		0x80000
#define REASON_PRIVILEGED	0x40000
#define REASON_TRAP		0x20000

#define single_stepping(regs)	((regs)->msr & MSR_SE)
#define clear_single_step(regs)	((regs)->msr &= ~MSR_SE)
#endif

/*
 * This is "fall-back" implementation for configurations
 * which don't provide platform-specific machine check info
 */
void __attribute__ ((weak))
platform_machine_check(struct pt_regs *regs)
{
}

#if defined(CONFIG_4xx)
int machine_check_4xx(struct pt_regs *regs)
{
	unsigned long reason = get_mc_reason(regs);

	if (reason & ESR_IMCP) {
		printk("Instruction");
		mtspr(SPRN_ESR, reason & ~ESR_IMCP);
	} else
		printk("Data");
	printk(" machine check in kernel mode.\n");

	return 0;
}

int machine_check_440A(struct pt_regs *regs)
{
	unsigned long reason = get_mc_reason(regs);

	printk("Machine check in kernel mode.\n");
	if (reason & ESR_IMCP){
		printk("Instruction Synchronous Machine Check exception\n");
		mtspr(SPRN_ESR, reason & ~ESR_IMCP);
	}
	else {
		u32 mcsr = mfspr(SPRN_MCSR);
		if (mcsr & MCSR_IB)
			printk("Instruction Read PLB Error\n");
		if (mcsr & MCSR_DRB)
			printk("Data Read PLB Error\n");
		if (mcsr & MCSR_DWB)
			printk("Data Write PLB Error\n");
		if (mcsr & MCSR_TLBP)
			printk("TLB Parity Error\n");
		if (mcsr & MCSR_ICP){
			flush_instruction_cache();
			printk("I-Cache Parity Error\n");
		}
		if (mcsr & MCSR_DCSP)
			printk("D-Cache Search Parity Error\n");
		if (mcsr & MCSR_DCFP)
			printk("D-Cache Flush Parity Error\n");
		if (mcsr & MCSR_IMPE)
			printk("Machine Check exception is imprecise\n");

		/* Clear MCSR */
		mtspr(SPRN_MCSR, mcsr);
	}
	return 0;
}
#else
int machine_check_generic(struct pt_regs *regs)
{
	unsigned long reason = get_mc_reason(regs);

	printk("Machine check in kernel mode.\n");
	printk("Caused by (from SRR1=%lx): ", reason);
	switch (reason & 0x601F0000) {
	case 0x80000:
		printk("Machine check signal\n");
		break;
	case 0:		/* for 601 */
	case 0x40000:
	case 0x140000:	/* 7450 MSS error and TEA */
		printk("Transfer error ack signal\n");
		break;
	case 0x20000:
		printk("Data parity error signal\n");
		break;
	case 0x10000:
		printk("Address parity error signal\n");
		break;
	case 0x20000000:
		printk("L1 Data Cache error\n");
		break;
	case 0x40000000:
		printk("L1 Instruction Cache error\n");
		break;
	case 0x00100000:
		printk("L2 data cache parity error\n");
		break;
	default:
		printk("Unknown values in msr\n");
	}
	return 0;
}
#endif /* everything else */

void machine_check_exception(struct pt_regs *regs)
{
	int recover = 0;

	if (cur_cpu_spec->machine_check)
		recover = cur_cpu_spec->machine_check(regs);
	if (recover > 0)
		return;

	if (user_mode(regs)) {
		regs->msr |= MSR_RI;
		_exception(SIGBUS, regs, BUS_ADRERR, regs->nip);
		return;
	}

#if defined(CONFIG_8xx) && defined(CONFIG_PCI)
	/* the qspan pci read routines can cause machine checks -- Cort */
	bad_page_fault(regs, regs->dar, SIGBUS);
	return;
#endif

	if (debugger_fault_handler) {
		debugger_fault_handler(regs);
		regs->msr |= MSR_RI;
		return;
	}

	if (check_io_access(regs))
		return;

	/*
	 * Optional platform-provided routine to print out
	 * additional info, e.g. bus error registers.
	 */
	platform_machine_check(regs);

	debugger(regs);
	die("machine check", regs, SIGBUS);
}

void SMIException(struct pt_regs *regs)
{
	debugger(regs);
#if !(defined(CONFIG_XMON) || defined(CONFIG_KGDB))
	show_regs(regs);
	panic("System Management Interrupt");
#endif
}

void unknown_exception(struct pt_regs *regs)
{
	printk("Bad trap at PC: %lx, MSR: %lx, vector=%lx    %s\n",
	       regs->nip, regs->msr, regs->trap, print_tainted());
	_exception(SIGTRAP, regs, 0, 0);
}

void instruction_breakpoint_exception(struct pt_regs *regs)
{
	if (debugger_iabr_match(regs))
		return;
	_exception(SIGTRAP, regs, TRAP_BRKPT, 0);
}

void RunModeException(struct pt_regs *regs)
{
	_exception(SIGTRAP, regs, 0, 0);
}

/* Illegal instruction emulation support.  Originally written to
 * provide the PVR to user applications using the mfspr rd, PVR.
 * Return non-zero if we can't emulate, or -EFAULT if the associated
 * memory access caused an access fault.  Return zero on success.
 *
 * There are a couple of ways to do this, either "decode" the instruction
 * or directly match lots of bits.  In this case, matching lots of
 * bits is faster and easier.
 *
 */
#define INST_MFSPR_PVR		0x7c1f42a6
#define INST_MFSPR_PVR_MASK	0xfc1fffff

#define INST_DCBA		0x7c0005ec
#define INST_DCBA_MASK		0x7c0007fe

#define INST_MCRXR		0x7c000400
#define INST_MCRXR_MASK		0x7c0007fe

#define INST_STRING		0x7c00042a
#define INST_STRING_MASK	0x7c0007fe
#define INST_STRING_GEN_MASK	0x7c00067e
#define INST_LSWI		0x7c0004aa
#define INST_LSWX		0x7c00042a
#define INST_STSWI		0x7c0005aa
#define INST_STSWX		0x7c00052a

static int emulate_string_inst(struct pt_regs *regs, u32 instword)
{
	u8 rT = (instword >> 21) & 0x1f;
	u8 rA = (instword >> 16) & 0x1f;
	u8 NB_RB = (instword >> 11) & 0x1f;
	u32 num_bytes;
	unsigned long EA;
	int pos = 0;

	/* Early out if we are an invalid form of lswx */
	if ((instword & INST_STRING_MASK) == INST_LSWX)
		if ((rT == rA) || (rT == NB_RB))
			return -EINVAL;

	EA = (rA == 0) ? 0 : regs->gpr[rA];

	switch (instword & INST_STRING_MASK) {
		case INST_LSWX:
		case INST_STSWX:
			EA += NB_RB;
			num_bytes = regs->xer & 0x7f;
			break;
		case INST_LSWI:
		case INST_STSWI:
			num_bytes = (NB_RB == 0) ? 32 : NB_RB;
			break;
		default:
			return -EINVAL;
	}

	while (num_bytes != 0)
	{
		u8 val;
		u32 shift = 8 * (3 - (pos & 0x3));

		switch ((instword & INST_STRING_MASK)) {
			case INST_LSWX:
			case INST_LSWI:
				if (get_user(val, (u8 __user *)EA))
					return -EFAULT;
				/* first time updating this reg,
				 * zero it out */
				if (pos == 0)
					regs->gpr[rT] = 0;
				regs->gpr[rT] |= val << shift;
				break;
			case INST_STSWI:
			case INST_STSWX:
				val = regs->gpr[rT] >> shift;
				if (put_user(val, (u8 __user *)EA))
					return -EFAULT;
				break;
		}
		/* move EA to next address */
		EA += 1;
		num_bytes--;

		/* manage our position within the register */
		if (++pos == 4) {
			pos = 0;
			if (++rT == 32)
				rT = 0;
		}
	}

	return 0;
}

static int emulate_instruction(struct pt_regs *regs)
{
	u32 instword;
	u32 rd;

	if (!user_mode(regs))
		return -EINVAL;
	CHECK_FULL_REGS(regs);

	if (get_user(instword, (u32 __user *)(regs->nip)))
		return -EFAULT;

	/* Emulate the mfspr rD, PVR.
	 */
	if ((instword & INST_MFSPR_PVR_MASK) == INST_MFSPR_PVR) {
		rd = (instword >> 21) & 0x1f;
		regs->gpr[rd] = mfspr(SPRN_PVR);
		return 0;
	}

	/* Emulating the dcba insn is just a no-op.  */
	if ((instword & INST_DCBA_MASK) == INST_DCBA)
		return 0;

	/* Emulate the mcrxr insn.  */
	if ((instword & INST_MCRXR_MASK) == INST_MCRXR) {
		int shift = (instword >> 21) & 0x1c;
		unsigned long msk = 0xf0000000UL >> shift;

		regs->ccr = (regs->ccr & ~msk) | ((regs->xer >> shift) & msk);
		regs->xer &= ~0xf0000000UL;
		return 0;
	}

	/* Emulate load/store string insn. */
	if ((instword & INST_STRING_GEN_MASK) == INST_STRING)
		return emulate_string_inst(regs, instword);

	return -EINVAL;
}

/*
 * After we have successfully emulated an instruction, we have to
 * check if the instruction was being single-stepped, and if so,
 * pretend we got a single-step exception.  This was pointed out
 * by Kumar Gala.  -- paulus
 */
static void emulate_single_step(struct pt_regs *regs)
{
	if (single_stepping(regs)) {
		clear_single_step(regs);
		_exception(SIGTRAP, regs, TRAP_TRACE, 0);
	}
}

int is_valid_bugaddr(unsigned long addr)
{
	return addr >= PAGE_OFFSET;
}

void program_check_exception(struct pt_regs *regs)
{
	unsigned int reason = get_reason(regs);
	extern int do_mathemu(struct pt_regs *regs);

#ifdef CONFIG_MATH_EMULATION
	/* (reason & REASON_ILLEGAL) would be the obvious thing here,
	 * but there seems to be a hardware bug on the 405GP (RevD)
	 * that means ESR is sometimes set incorrectly - either to
	 * ESR_DST (!?) or 0.  In the process of chasing this with the
	 * hardware people - not sure if it can happen on any illegal
	 * instruction or only on FP instructions, whether there is a
	 * pattern to occurrences etc. -dgibson 31/Mar/2003 */
	if (!(reason & REASON_TRAP) && do_mathemu(regs) == 0) {
		emulate_single_step(regs);
		return;
	}
#endif /* CONFIG_MATH_EMULATION */

	if (reason & REASON_FP) {
		/* IEEE FP exception */
		int code = 0;
		u32 fpscr;

		/* We must make sure the FP state is consistent with
		 * our MSR_FP in regs
		 */
		preempt_disable();
		if (regs->msr & MSR_FP)
			giveup_fpu(current);
		preempt_enable();

		fpscr = current->thread.fpscr.val;
		fpscr &= fpscr << 22;	/* mask summary bits with enables */
		if (fpscr & FPSCR_VX)
			code = FPE_FLTINV;
		else if (fpscr & FPSCR_OX)
			code = FPE_FLTOVF;
		else if (fpscr & FPSCR_UX)
			code = FPE_FLTUND;
		else if (fpscr & FPSCR_ZX)
			code = FPE_FLTDIV;
		else if (fpscr & FPSCR_XX)
			code = FPE_FLTRES;
		_exception(SIGFPE, regs, code, regs->nip);
		return;
	}

	if (reason & REASON_TRAP) {
		/* trap exception */
		if (debugger_bpt(regs))
			return;

		if (!(regs->msr & MSR_PR) &&  /* not user-mode */
		    report_bug(regs->nip, regs) == BUG_TRAP_TYPE_WARN) {
			regs->nip += 4;
			return;
		}
		_exception(SIGTRAP, regs, TRAP_BRKPT, 0);
		return;
	}

	/* Try to emulate it if we should. */
	if (reason & (REASON_ILLEGAL | REASON_PRIVILEGED)) {
		switch (emulate_instruction(regs)) {
		case 0:
			regs->nip += 4;
			emulate_single_step(regs);
			return;
		case -EFAULT:
			_exception(SIGSEGV, regs, SEGV_MAPERR, regs->nip);
			return;
		}
	}

	if (reason & REASON_PRIVILEGED)
		_exception(SIGILL, regs, ILL_PRVOPC, regs->nip);
	else
		_exception(SIGILL, regs, ILL_ILLOPC, regs->nip);
}

void single_step_exception(struct pt_regs *regs)
{
	regs->msr &= ~(MSR_SE | MSR_BE);  /* Turn off 'trace' bits */
	if (debugger_sstep(regs))
		return;
	_exception(SIGTRAP, regs, TRAP_TRACE, 0);
}

void alignment_exception(struct pt_regs *regs)
{
	int sig, code, fixed = 0;

	fixed = fix_alignment(regs);
	if (fixed == 1) {
		regs->nip += 4;	/* skip over emulated instruction */
		emulate_single_step(regs);
		return;
	}
	if (fixed == -EFAULT) {
		sig = SIGSEGV;
		code = SEGV_ACCERR;
	} else {
		sig = SIGBUS;
		code = BUS_ADRALN;
	}
	if (user_mode(regs))
		_exception(sig, regs, code, regs->dar);
	else
		bad_page_fault(regs, regs->dar, sig);
}

void StackOverflow(struct pt_regs *regs)
{
	printk(KERN_CRIT "Kernel stack overflow in process %p, r1=%lx\n",
	       current, regs->gpr[1]);
	debugger(regs);
	show_regs(regs);
	panic("kernel stack overflow");
}

void nonrecoverable_exception(struct pt_regs *regs)
{
	printk(KERN_ERR "Non-recoverable exception at PC=%lx MSR=%lx\n",
	       regs->nip, regs->msr);
	debugger(regs);
	die("nonrecoverable exception", regs, SIGKILL);
}

void trace_syscall(struct pt_regs *regs)
{
	printk("Task: %p(%d), PC: %08lX/%08lX, Syscall: %3ld, Result: %s%ld    %s\n",
	       current, current->pid, regs->nip, regs->link, regs->gpr[0],
	       regs->ccr&0x10000000?"Error=":"", regs->gpr[3], print_tainted());
}

#ifdef CONFIG_8xx
void SoftwareEmulation(struct pt_regs *regs)
{
	extern int do_mathemu(struct pt_regs *);
	extern int Soft_emulate_8xx(struct pt_regs *);
	int errcode;

	CHECK_FULL_REGS(regs);

	if (!user_mode(regs)) {
		debugger(regs);
		die("Kernel Mode Software FPU Emulation", regs, SIGFPE);
	}

#ifdef CONFIG_MATH_EMULATION
	errcode = do_mathemu(regs);
#else
	errcode = Soft_emulate_8xx(regs);
#endif
	if (errcode) {
		if (errcode > 0)
			_exception(SIGFPE, regs, 0, 0);
		else if (errcode == -EFAULT)
			_exception(SIGSEGV, regs, 0, 0);
		else
			_exception(SIGILL, regs, ILL_ILLOPC, regs->nip);
	} else
		emulate_single_step(regs);
}
#endif /* CONFIG_8xx */

#if defined(CONFIG_40x) || defined(CONFIG_BOOKE)

void DebugException(struct pt_regs *regs, unsigned long debug_status)
{
	if (debug_status & DBSR_IC) {	/* instruction completion */
		regs->msr &= ~MSR_DE;
		if (user_mode(regs)) {
			current->thread.dbcr0 &= ~DBCR0_IC;
		} else {
			/* Disable instruction completion */
			mtspr(SPRN_DBCR0, mfspr(SPRN_DBCR0) & ~DBCR0_IC);
			/* Clear the instruction completion event */
			mtspr(SPRN_DBSR, DBSR_IC);
			if (debugger_sstep(regs))
				return;
		}
		_exception(SIGTRAP, regs, TRAP_TRACE, 0);
	}
}
#endif /* CONFIG_4xx || CONFIG_BOOKE */

#if !defined(CONFIG_TAU_INT)
void TAUException(struct pt_regs *regs)
{
	printk("TAU trap at PC: %lx, MSR: %lx, vector=%lx    %s\n",
	       regs->nip, regs->msr, regs->trap, print_tainted());
}
#endif /* CONFIG_INT_TAU */

/*
 * FP unavailable trap from kernel - print a message, but let
 * the task use FP in the kernel until it returns to user mode.
 */
void kernel_fp_unavailable_exception(struct pt_regs *regs)
{
	regs->msr |= MSR_FP;
	printk(KERN_ERR "floating point used in kernel (task=%p, pc=%lx)\n",
	       current, regs->nip);
}

void altivec_unavailable_exception(struct pt_regs *regs)
{
	static int kernel_altivec_count;

#ifndef CONFIG_ALTIVEC
	if (user_mode(regs)) {
		/* A user program has executed an altivec instruction,
		   but this kernel doesn't support altivec. */
		_exception(SIGILL, regs, ILL_ILLOPC, regs->nip);
		return;
	}
#endif
	/* The kernel has executed an altivec instruction without
	   first enabling altivec.  Whinge but let it do it. */
	if (++kernel_altivec_count < 10)
		printk(KERN_ERR "AltiVec used in kernel (task=%p, pc=%lx)\n",
		       current, regs->nip);
	regs->msr |= MSR_VEC;
}

#ifdef CONFIG_ALTIVEC
void altivec_assist_exception(struct pt_regs *regs)
{
	int err;

	preempt_disable();
	if (regs->msr & MSR_VEC)
		giveup_altivec(current);
	preempt_enable();
	if (!user_mode(regs)) {
		printk(KERN_ERR "altivec assist exception in kernel mode"
		       " at %lx\n", regs->nip);
		debugger(regs);
		die("altivec assist exception", regs, SIGFPE);
		return;
	}

	err = emulate_altivec(regs);
	if (err == 0) {
		regs->nip += 4;		/* skip emulated instruction */
		emulate_single_step(regs);
		return;
	}

	if (err == -EFAULT) {
		/* got an error reading the instruction */
		_exception(SIGSEGV, regs, SEGV_ACCERR, regs->nip);
	} else {
		/* didn't recognize the instruction */
		/* XXX quick hack for now: set the non-Java bit in the VSCR */
		printk(KERN_ERR "unrecognized altivec instruction "
		       "in %s at %lx\n", current->comm, regs->nip);
		current->thread.vscr.u[3] |= 0x10000;
	}
}
#endif /* CONFIG_ALTIVEC */

#ifdef CONFIG_BOOKE_WDT
/*
 * Default handler for a Watchdog exception,
 * spins until a reboot occurs
 */
void __attribute__ ((weak)) WatchdogHandler(struct pt_regs *regs)
{
	/* Generic WatchdogHandler, implement your own */
	mtspr(SPRN_TCR, mfspr(SPRN_TCR)&(~TCR_WIE));
	return;
}

void WatchdogException(struct pt_regs *regs)
{
	printk (KERN_EMERG "PowerPC Book-E Watchdog Exception\n");
	WatchdogHandler(regs);
}
#endif

void __init trap_init(void)
{
}