[POWERPC] ptrace accessors for special regs MSR and TRAP

[deliverable/linux.git] / arch / powerpc / 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@samba.org)
 */

/*
 * 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/delay.h>
#include <linux/kprobes.h>
#include <linux/kexec.h>
#include <linux/backlight.h>
#include <linux/bug.h>
#include <linux/kdebug.h>

#include <asm/pgtable.h>
#include <asm/uaccess.h>
#include <asm/system.h>
#include <asm/io.h>
#include <asm/machdep.h>
#include <asm/rtas.h>
#include <asm/pmc.h>
#ifdef CONFIG_PPC32
#include <asm/reg.h>
#endif
#ifdef CONFIG_PMAC_BACKLIGHT
#include <asm/backlight.h>
#endif
#ifdef CONFIG_PPC64
#include <asm/firmware.h>
#include <asm/processor.h>
#endif
#include <asm/kexec.h>

#if defined(CONFIG_DEBUGGER) || defined(CONFIG_KEXEC)
int (*__debugger)(struct pt_regs *regs);
int (*__debugger_ipi)(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);
int (*__debugger_fault_handler)(struct pt_regs *regs);

EXPORT_SYMBOL(__debugger);
EXPORT_SYMBOL(__debugger_ipi);
EXPORT_SYMBOL(__debugger_bpt);
EXPORT_SYMBOL(__debugger_sstep);
EXPORT_SYMBOL(__debugger_iabr_match);
EXPORT_SYMBOL(__debugger_dabr_match);
EXPORT_SYMBOL(__debugger_fault_handler);
#endif

/*
 * Trap & Exception support
 */

#ifdef CONFIG_PMAC_BACKLIGHT
static void pmac_backlight_unblank(void)
{
        mutex_lock(&pmac_backlight_mutex);
        if (pmac_backlight) {
                struct backlight_properties *props;

                props = &pmac_backlight->props;
                props->brightness = props->max_brightness;
                props->power = FB_BLANK_UNBLANK;
                backlight_update_status(pmac_backlight);
        }
        mutex_unlock(&pmac_backlight_mutex);
}
#else
static inline void pmac_backlight_unblank(void) { }
#endif

int die(const char *str, struct pt_regs *regs, long err)
{
        static struct {
                spinlock_t lock;
                u32 lock_owner;
                int lock_owner_depth;
        } die = {
                .lock =                 __SPIN_LOCK_UNLOCKED(die.lock),
                .lock_owner =           -1,
                .lock_owner_depth =     0
        };
        static int die_counter;
        unsigned long flags;

        if (debugger(regs))
                return 1;

        oops_enter();

        if (die.lock_owner != raw_smp_processor_id()) {
                console_verbose();
                spin_lock_irqsave(&die.lock, flags);
                die.lock_owner = smp_processor_id();
                die.lock_owner_depth = 0;
                bust_spinlocks(1);
                if (machine_is(powermac))
                        pmac_backlight_unblank();
        } else {
                local_save_flags(flags);
        }

        if (++die.lock_owner_depth < 3) {
                printk("Oops: %s, sig: %ld [#%d]\n", str, err, ++die_counter);
#ifdef CONFIG_PREEMPT
                printk("PREEMPT ");
#endif
#ifdef CONFIG_SMP
                printk("SMP NR_CPUS=%d ", NR_CPUS);
#endif
#ifdef CONFIG_DEBUG_PAGEALLOC
                printk("DEBUG_PAGEALLOC ");
#endif
#ifdef CONFIG_NUMA
                printk("NUMA ");
#endif
                printk("%s\n", ppc_md.name ? ppc_md.name : "");

                print_modules();
                show_regs(regs);
        } else {
                printk("Recursive die() failure, output suppressed\n");
        }

        bust_spinlocks(0);
        die.lock_owner = -1;
        add_taint(TAINT_DIE);
        spin_unlock_irqrestore(&die.lock, flags);

        if (kexec_should_crash(current) ||
                kexec_sr_activated(smp_processor_id()))
                crash_kexec(regs);
        crash_kexec_secondary(regs);

        if (in_interrupt())
                panic("Fatal exception in interrupt");

        if (panic_on_oops)
                panic("Fatal exception");

        oops_exit();
        do_exit(err);

        return 0;
}

void _exception(int signr, struct pt_regs *regs, int code, unsigned long addr)
{
        siginfo_t info;
        const char fmt32[] = KERN_INFO "%s[%d]: unhandled signal %d " \
                        "at %08lx nip %08lx lr %08lx code %x\n";
        const char fmt64[] = KERN_INFO "%s[%d]: unhandled signal %d " \
                        "at %016lx nip %016lx lr %016lx code %x\n";

        if (!user_mode(regs)) {
                if (die("Exception in kernel mode", regs, signr))
                        return;
        } else if (show_unhandled_signals &&
                    unhandled_signal(current, signr) &&
                    printk_ratelimit()) {
                        printk(regs->msr & MSR_SF ? fmt64 : fmt32,
                                current->comm, current->pid, signr,
                                addr, regs->nip, regs->link, code);
                }

        memset(&info, 0, sizeof(info));
        info.si_signo = signr;
        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);
                }
        }
}

#ifdef CONFIG_PPC64
void system_reset_exception(struct pt_regs *regs)
{
        /* See if any machine dependent calls */
        if (ppc_md.system_reset_exception) {
                if (ppc_md.system_reset_exception(regs))
                        return;
        }

#ifdef CONFIG_KEXEC
        cpu_set(smp_processor_id(), cpus_in_sr);
#endif

        die("System Reset", regs, SIGABRT);

        /*
         * Some CPUs when released from the debugger will execute this path.
         * These CPUs entered the debugger via a soft-reset. If the CPU was
         * hung before entering the debugger it will return to the hung
         * state when exiting this function.  This causes a problem in
         * kdump since the hung CPU(s) will not respond to the IPI sent
         * from kdump. To prevent the problem we call crash_kexec_secondary()
         * here. If a kdump had not been initiated or we exit the debugger
         * with the "exit and recover" command (x) crash_kexec_secondary()
         * will return after 5ms and the CPU returns to its previous state.
         */
        crash_kexec_secondary(regs);

        /* Must die if the interrupt is not recoverable */
        if (!(regs->msr & MSR_RI))
                panic("Unrecoverable System Reset");

        /* What should we do here? We could issue a shutdown or hard reset. */
}
#endif

/*
 * 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)
{
#ifdef CONFIG_PPC32
        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;
                if (*nip == 0x7c0004ac || (*nip >> 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_PPC32 */
        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)
#ifndef CONFIG_FSL_BOOKE
#define get_mc_reason(regs)     ((regs)->dsisr)
#else
#define get_mc_reason(regs)     (mfspr(SPRN_MCSR) & MCSR_MASK)
#endif
#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

#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;
}
#elif defined(CONFIG_E500)
int machine_check_e500(struct pt_regs *regs)
{
        unsigned long reason = get_mc_reason(regs);

        printk("Machine check in kernel mode.\n");
        printk("Caused by (from MCSR=%lx): ", reason);

        if (reason & MCSR_MCP)
                printk("Machine Check Signal\n");
        if (reason & MCSR_ICPERR)
                printk("Instruction Cache Parity Error\n");
        if (reason & MCSR_DCP_PERR)
                printk("Data Cache Push Parity Error\n");
        if (reason & MCSR_DCPERR)
                printk("Data Cache Parity Error\n");
        if (reason & MCSR_BUS_IAERR)
                printk("Bus - Instruction Address Error\n");
        if (reason & MCSR_BUS_RAERR)
                printk("Bus - Read Address Error\n");
        if (reason & MCSR_BUS_WAERR)
                printk("Bus - Write Address Error\n");
        if (reason & MCSR_BUS_IBERR)
                printk("Bus - Instruction Data Error\n");
        if (reason & MCSR_BUS_RBERR)
                printk("Bus - Read Data Bus Error\n");
        if (reason & MCSR_BUS_WBERR)
                printk("Bus - Read Data Bus Error\n");
        if (reason & MCSR_BUS_IPERR)
                printk("Bus - Instruction Parity Error\n");
        if (reason & MCSR_BUS_RPERR)
                printk("Bus - Read Parity Error\n");

        return 0;
}
#elif defined(CONFIG_E200)
int machine_check_e200(struct pt_regs *regs)
{
        unsigned long reason = get_mc_reason(regs);

        printk("Machine check in kernel mode.\n");
        printk("Caused by (from MCSR=%lx): ", reason);

        if (reason & MCSR_MCP)
                printk("Machine Check Signal\n");
        if (reason & MCSR_CP_PERR)
                printk("Cache Push Parity Error\n");
        if (reason & MCSR_CPERR)
                printk("Cache Parity Error\n");
        if (reason & MCSR_EXCP_ERR)
                printk("ISI, ITLB, or Bus Error on first instruction fetch for an exception handler\n");
        if (reason & MCSR_BUS_IRERR)
                printk("Bus - Read Bus Error on instruction fetch\n");
        if (reason & MCSR_BUS_DRERR)
                printk("Bus - Read Bus Error on data load\n");
        if (reason & MCSR_BUS_WRERR)
                printk("Bus - Write Bus Error on buffered store or cache line push\n");

        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;

        /* See if any machine dependent calls. In theory, we would want
         * to call the CPU first, and call the ppc_md. one if the CPU
         * one returns a positive number. However there is existing code
         * that assumes the board gets a first chance, so let's keep it
         * that way for now and fix things later. --BenH.
         */
        if (ppc_md.machine_check_exception)
                recover = ppc_md.machine_check_exception(regs);
        else 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
         *
         * yuck !!! that totally needs to go away ! There are better ways
         * to deal with that than having a wart in the mcheck handler.
         * -- BenH
         */
        bad_page_fault(regs, regs->dar, SIGBUS);
        return;
#endif

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

        if (check_io_access(regs))
                return;

        if (debugger_fault_handler(regs))
                return;
        die("Machine check", regs, SIGBUS);

        /* Must die if the interrupt is not recoverable */
        if (!(regs->msr & MSR_RI))
                panic("Unrecoverable Machine check");
}

void SMIException(struct pt_regs *regs)
{
        die("System Management Interrupt", regs, SIGABRT);
}

void unknown_exception(struct pt_regs *regs)
{
        printk("Bad trap at PC: %lx, SR: %lx, vector=%lx\n",
               regs->nip, regs->msr, regs->trap);

        _exception(SIGTRAP, regs, 0, 0);
}

void instruction_breakpoint_exception(struct pt_regs *regs)
{
        if (notify_die(DIE_IABR_MATCH, "iabr_match", regs, 5,
                                        5, SIGTRAP) == NOTIFY_STOP)
                return;
        if (debugger_iabr_match(regs))
                return;
        _exception(SIGTRAP, regs, TRAP_BRKPT, regs->nip);
}

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

void __kprobes single_step_exception(struct pt_regs *regs)
{
        regs->msr &= ~(MSR_SE | MSR_BE);  /* Turn off 'trace' bits */

        if (notify_die(DIE_SSTEP, "single_step", regs, 5,
                                        5, SIGTRAP) == NOTIFY_STOP)
                return;
        if (debugger_sstep(regs))
                return;

        _exception(SIGTRAP, regs, TRAP_TRACE, regs->nip);
}

/*
 * 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);
        }
}

static inline int __parse_fpscr(unsigned long fpscr)
{
        int ret = 0;

        /* Invalid operation */
        if ((fpscr & FPSCR_VE) && (fpscr & FPSCR_VX))
                ret = FPE_FLTINV;

        /* Overflow */
        else if ((fpscr & FPSCR_OE) && (fpscr & FPSCR_OX))
                ret = FPE_FLTOVF;

        /* Underflow */
        else if ((fpscr & FPSCR_UE) && (fpscr & FPSCR_UX))
                ret = FPE_FLTUND;

        /* Divide by zero */
        else if ((fpscr & FPSCR_ZE) && (fpscr & FPSCR_ZX))
                ret = FPE_FLTDIV;

        /* Inexact result */
        else if ((fpscr & FPSCR_XE) && (fpscr & FPSCR_XX))
                ret = FPE_FLTRES;

        return ret;
}

static void parse_fpe(struct pt_regs *regs)
{
        int code = 0;

        flush_fp_to_thread(current);

        code = __parse_fpscr(current->thread.fpscr.val);

        _exception(SIGFPE, regs, code, regs->nip);
}

/*
 * 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          0xfc0007fe

#define INST_MCRXR              0x7c000400
#define INST_MCRXR_MASK         0xfc0007fe

#define INST_STRING             0x7c00042a
#define INST_STRING_MASK        0xfc0007fe
#define INST_STRING_GEN_MASK    0xfc00067e
#define INST_LSWI               0x7c0004aa
#define INST_LSWX               0x7c00042a
#define INST_STSWI              0x7c0005aa
#define INST_STSWX              0x7c00052a

#define INST_POPCNTB            0x7c0000f4
#define INST_POPCNTB_MASK       0xfc0007fe

#define INST_ISEL               0x7c00001e
#define INST_ISEL_MASK          0xfc00003e

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_popcntb_inst(struct pt_regs *regs, u32 instword)
{
        u32 ra,rs;
        unsigned long tmp;

        ra = (instword >> 16) & 0x1f;
        rs = (instword >> 21) & 0x1f;

        tmp = regs->gpr[rs];
        tmp = tmp - ((tmp >> 1) & 0x5555555555555555ULL);
        tmp = (tmp & 0x3333333333333333ULL) + ((tmp >> 2) & 0x3333333333333333ULL);
        tmp = (tmp + (tmp >> 4)) & 0x0f0f0f0f0f0f0f0fULL;
        regs->gpr[ra] = tmp;

        return 0;
}

static int emulate_isel(struct pt_regs *regs, u32 instword)
{
        u8 rT = (instword >> 21) & 0x1f;
        u8 rA = (instword >> 16) & 0x1f;
        u8 rB = (instword >> 11) & 0x1f;
        u8 BC = (instword >> 6) & 0x1f;
        u8 bit;
        unsigned long tmp;

        tmp = (rA == 0) ? 0 : regs->gpr[rA];
        bit = (regs->ccr >> (31 - BC)) & 0x1;

        regs->gpr[rT] = bit ? tmp : regs->gpr[rB];

        return 0;
}

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

        if (!user_mode(regs) || (regs->msr & MSR_LE))
                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);

        /* Emulate the popcntb (Population Count Bytes) instruction. */
        if ((instword & INST_POPCNTB_MASK) == INST_POPCNTB) {
                return emulate_popcntb_inst(regs, instword);
        }

        /* Emulate isel (Integer Select) instruction */
        if ((instword & INST_ISEL_MASK) == INST_ISEL) {
                return emulate_isel(regs, instword);
        }

        return -EINVAL;
}

int is_valid_bugaddr(unsigned long addr)
{
        return is_kernel_addr(addr);
}

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

        /* We can now get here via a FP Unavailable exception if the core
         * has no FPU, in that case the reason flags will be 0 */

        if (reason & REASON_FP) {
                /* IEEE FP exception */
                parse_fpe(regs);
                return;
        }
        if (reason & REASON_TRAP) {
                /* trap exception */
                if (notify_die(DIE_BPT, "breakpoint", regs, 5, 5, SIGTRAP)
                                == NOTIFY_STOP)
                        return;
                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, regs->nip);
                return;
        }

        local_irq_enable();

#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 occurences etc. -dgibson 31/Mar/2003 */
        switch (do_mathemu(regs)) {
        case 0:
                emulate_single_step(regs);
                return;
        case 1: {
                        int code = 0;
                        code = __parse_fpscr(current->thread.fpscr.val);
                        _exception(SIGFPE, regs, code, regs->nip);
                        return;
                }
        case -EFAULT:
                _exception(SIGSEGV, regs, SEGV_MAPERR, regs->nip);
                return;
        }
        /* fall through on any other errors */
#endif /* CONFIG_MATH_EMULATION */

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

        /* we don't implement logging of alignment exceptions */
        if (!(current->thread.align_ctl & PR_UNALIGN_SIGBUS))
                fixed = fix_alignment(regs);

        if (fixed == 1) {
                regs->nip += 4; /* skip over emulated instruction */
                emulate_single_step(regs);
                return;
        }

        /* Operand address was bad */
        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, task_pid_nr(current), regs->nip, regs->link, regs->gpr[0],
               regs->ccr&0x10000000?"Error=":"", regs->gpr[3], print_tainted());
}

void kernel_fp_unavailable_exception(struct pt_regs *regs)
{
        printk(KERN_EMERG "Unrecoverable FP Unavailable Exception "
                          "%lx at %lx\n", regs->trap, regs->nip);
        die("Unrecoverable FP Unavailable Exception", regs, SIGABRT);
}

void altivec_unavailable_exception(struct pt_regs *regs)
{
        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;
        }

        printk(KERN_EMERG "Unrecoverable VMX/Altivec Unavailable Exception "
                        "%lx at %lx\n", regs->trap, regs->nip);
        die("Unrecoverable VMX/Altivec Unavailable Exception", regs, SIGABRT);
}

void performance_monitor_exception(struct pt_regs *regs)
{
        perf_irq(regs);
}

#ifdef CONFIG_8xx
void SoftwareEmulation(struct pt_regs *regs)
{
        extern int do_mathemu(struct pt_regs *);
        extern int Soft_emulate_8xx(struct pt_regs *);
#if defined(CONFIG_MATH_EMULATION) || defined(CONFIG_8XX_MINIMAL_FPEMU)
        int errcode;
#endif

        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);

        switch (errcode) {
        case 0:
                emulate_single_step(regs);
                return;
        case 1: {
                        int code = 0;
                        code = __parse_fpscr(current->thread.fpscr.val);
                        _exception(SIGFPE, regs, code, regs->nip);
                        return;
                }
        case -EFAULT:
                _exception(SIGSEGV, regs, SEGV_MAPERR, regs->nip);
                return;
        default:
                _exception(SIGILL, regs, ILL_ILLOPC, regs->nip);
                return;
        }

#elif defined(CONFIG_8XX_MINIMAL_FPEMU)
        errcode = Soft_emulate_8xx(regs);
        switch (errcode) {
        case 0:
                emulate_single_step(regs);
                return;
        case 1:
                _exception(SIGILL, regs, ILL_ILLOPC, regs->nip);
                return;
        case -EFAULT:
                _exception(SIGSEGV, regs, SEGV_MAPERR, regs->nip);
                return;
        }
#else
        _exception(SIGILL, regs, ILL_ILLOPC, regs->nip);
#endif
}
#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 */

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

        if (!user_mode(regs)) {
                printk(KERN_EMERG "VMX/Altivec assist exception in kernel mode"
                       " at %lx\n", regs->nip);
                die("Kernel VMX/Altivec assist exception", regs, SIGILL);
        }

        flush_altivec_to_thread(current);

        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 */
                if (printk_ratelimit())
                        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_FSL_BOOKE
void CacheLockingException(struct pt_regs *regs, unsigned long address,
                           unsigned long error_code)
{
        /* We treat cache locking instructions from the user
         * as priv ops, in the future we could try to do
         * something smarter
         */
        if (error_code & (ESR_DLK|ESR_ILK))
                _exception(SIGILL, regs, ILL_PRVOPC, regs->nip);
        return;
}
#endif /* CONFIG_FSL_BOOKE */

#ifdef CONFIG_SPE
void SPEFloatingPointException(struct pt_regs *regs)
{
        unsigned long spefscr;
        int fpexc_mode;
        int code = 0;

        spefscr = current->thread.spefscr;
        fpexc_mode = current->thread.fpexc_mode;

        /* Hardware does not neccessarily set sticky
         * underflow/overflow/invalid flags */
        if ((spefscr & SPEFSCR_FOVF) && (fpexc_mode & PR_FP_EXC_OVF)) {
                code = FPE_FLTOVF;
                spefscr |= SPEFSCR_FOVFS;
        }
        else if ((spefscr & SPEFSCR_FUNF) && (fpexc_mode & PR_FP_EXC_UND)) {
                code = FPE_FLTUND;
                spefscr |= SPEFSCR_FUNFS;
        }
        else if ((spefscr & SPEFSCR_FDBZ) && (fpexc_mode & PR_FP_EXC_DIV))
                code = FPE_FLTDIV;
        else if ((spefscr & SPEFSCR_FINV) && (fpexc_mode & PR_FP_EXC_INV)) {
                code = FPE_FLTINV;
                spefscr |= SPEFSCR_FINVS;
        }
        else if ((spefscr & (SPEFSCR_FG | SPEFSCR_FX)) && (fpexc_mode & PR_FP_EXC_RES))
                code = FPE_FLTRES;

        current->thread.spefscr = spefscr;

        _exception(SIGFPE, regs, code, regs->nip);
        return;
}
#endif

/*
 * We enter here if we get an unrecoverable exception, that is, one
 * that happened at a point where the RI (recoverable interrupt) bit
 * in the MSR is 0.  This indicates that SRR0/1 are live, and that
 * we therefore lost state by taking this exception.
 */
void unrecoverable_exception(struct pt_regs *regs)
{
        printk(KERN_EMERG "Unrecoverable exception %lx at %lx\n",
               regs->trap, regs->nip);
        die("Unrecoverable exception", regs, SIGABRT);
}

#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

/*
 * We enter here if we discover during exception entry that we are
 * running in supervisor mode with a userspace value in the stack pointer.
 */
void kernel_bad_stack(struct pt_regs *regs)
{
        printk(KERN_EMERG "Bad kernel stack pointer %lx at %lx\n",
               regs->gpr[1], regs->nip);
        die("Bad kernel stack pointer", regs, SIGABRT);
}

void __init trap_init(void)
{
}