Create releng/7.2 from stable/7 in preparation for 7.2-RELEASE.

[FreeBSD/releng/7.2.git] / sys / i386 / isa / npx.c

/*-
 * Copyright (c) 1990 William Jolitz.
 * Copyright (c) 1991 The Regents of the University of California.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *      from: @(#)npx.c 7.2 (Berkeley) 5/12/91
 */

#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");

#include "opt_cpu.h"
#include "opt_isa.h"
#include "opt_npx.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/bus.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/module.h>
#include <sys/mutex.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/smp.h>
#include <sys/sysctl.h>
#include <machine/bus.h>
#include <sys/rman.h>
#ifdef NPX_DEBUG
#include <sys/syslog.h>
#endif
#include <sys/signalvar.h>

#include <machine/asmacros.h>
#include <machine/cputypes.h>
#include <machine/frame.h>
#include <machine/md_var.h>
#include <machine/pcb.h>
#include <machine/psl.h>
#include <machine/resource.h>
#include <machine/specialreg.h>
#include <machine/segments.h>
#include <machine/ucontext.h>

#include <machine/intr_machdep.h>
#ifdef DEV_ISA
#include <isa/isavar.h>
#endif

#if !defined(CPU_DISABLE_SSE) && defined(I686_CPU)
#define CPU_ENABLE_SSE
#endif

/*
 * 387 and 287 Numeric Coprocessor Extension (NPX) Driver.
 */

/* Configuration flags. */
#define NPX_DISABLE_I586_OPTIMIZED_BCOPY        (1 << 0)
#define NPX_DISABLE_I586_OPTIMIZED_BZERO        (1 << 1)
#define NPX_DISABLE_I586_OPTIMIZED_COPYIO       (1 << 2)

#if defined(__GNUCLIKE_ASM) && !defined(lint)

#define fldcw(addr)             __asm("fldcw %0" : : "m" (*(addr)))
#define fnclex()                __asm("fnclex")
#define fninit()                __asm("fninit")
#define fnsave(addr)            __asm __volatile("fnsave %0" : "=m" (*(addr)))
#define fnstcw(addr)            __asm __volatile("fnstcw %0" : "=m" (*(addr)))
#define fnstsw(addr)            __asm __volatile("fnstsw %0" : "=m" (*(addr)))
#define fp_divide_by_0()        __asm("fldz; fld1; fdiv %st,%st(1); fnop")
#define frstor(addr)            __asm("frstor %0" : : "m" (*(addr)))
#ifdef CPU_ENABLE_SSE
#define fxrstor(addr)           __asm("fxrstor %0" : : "m" (*(addr)))
#define fxsave(addr)            __asm __volatile("fxsave %0" : "=m" (*(addr)))
#define ldmxcsr(__csr)          __asm __volatile("ldmxcsr %0" : : "m" (__csr))
#endif
#define start_emulating()       __asm("smsw %%ax; orb %0,%%al; lmsw %%ax" \
                                      : : "n" (CR0_TS) : "ax")
#define stop_emulating()        __asm("clts")

#else   /* !(__GNUCLIKE_ASM && !lint) */

void    fldcw(caddr_t addr);
void    fnclex(void);
void    fninit(void);
void    fnsave(caddr_t addr);
void    fnstcw(caddr_t addr);
void    fnstsw(caddr_t addr);
void    fp_divide_by_0(void);
void    frstor(caddr_t addr);
#ifdef CPU_ENABLE_SSE
void    fxsave(caddr_t addr);
void    fxrstor(caddr_t addr);
#endif
void    start_emulating(void);
void    stop_emulating(void);

#endif  /* __GNUCLIKE_ASM && !lint */

#ifdef CPU_ENABLE_SSE
#define GET_FPU_CW(thread) \
        (cpu_fxsr ? \
                (thread)->td_pcb->pcb_save.sv_xmm.sv_env.en_cw : \
                (thread)->td_pcb->pcb_save.sv_87.sv_env.en_cw)
#define GET_FPU_SW(thread) \
        (cpu_fxsr ? \
                (thread)->td_pcb->pcb_save.sv_xmm.sv_env.en_sw : \
                (thread)->td_pcb->pcb_save.sv_87.sv_env.en_sw)
#define SET_FPU_CW(savefpu, value) do { \
        if (cpu_fxsr) \
                (savefpu)->sv_xmm.sv_env.en_cw = (value); \
        else \
                (savefpu)->sv_87.sv_env.en_cw = (value); \
} while (0)
#else /* CPU_ENABLE_SSE */
#define GET_FPU_CW(thread) \
        (thread->td_pcb->pcb_save.sv_87.sv_env.en_cw)
#define GET_FPU_SW(thread) \
        (thread->td_pcb->pcb_save.sv_87.sv_env.en_sw)
#define SET_FPU_CW(savefpu, value) \
        (savefpu)->sv_87.sv_env.en_cw = (value)
#endif /* CPU_ENABLE_SSE */

typedef u_char bool_t;

#ifdef CPU_ENABLE_SSE
static  void    fpu_clean_state(void);
#endif

static  void    fpusave(union savefpu *);
static  void    fpurstor(union savefpu *);
static  int     npx_attach(device_t dev);
static  void    npx_identify(driver_t *driver, device_t parent);
static  int     npx_intr(void *);
static  int     npx_probe(device_t dev);
#ifdef I586_CPU_XXX
static  long    timezero(const char *funcname,
                    void (*func)(void *buf, size_t len));
#endif /* I586_CPU */

int     hw_float;               /* XXX currently just alias for npx_exists */

SYSCTL_INT(_hw, HW_FLOATINGPT, floatingpoint, CTLFLAG_RD,
    &hw_float, 0, "Floating point instructions executed in hardware");

static  volatile u_int          npx_intrs_while_probing;
static  volatile u_int          npx_traps_while_probing;

static  union savefpu           npx_cleanstate;
static  bool_t                  npx_ex16;
static  bool_t                  npx_exists;
static  bool_t                  npx_irq13;

alias_for_inthand_t probetrap;
__asm("                                                         \n\
        .text                                                   \n\
        .p2align 2,0x90                                         \n\
        .type   " __XSTRING(CNAME(probetrap)) ",@function       \n\
" __XSTRING(CNAME(probetrap)) ":                                \n\
        ss                                                      \n\
        incl    " __XSTRING(CNAME(npx_traps_while_probing)) "   \n\
        fnclex                                                  \n\
        iret                                                    \n\
");

/*
 * Identify routine.  Create a connection point on our parent for probing.
 */
static void
npx_identify(driver, parent)
        driver_t *driver;
        device_t parent;
{
        device_t child;

        child = BUS_ADD_CHILD(parent, 0, "npx", 0);
        if (child == NULL)
                panic("npx_identify");
}

/*
 * Do minimal handling of npx interrupts to convert them to traps.
 */
static int
npx_intr(dummy)
        void *dummy;
{
        struct thread *td;

        npx_intrs_while_probing++;

        /*
         * The BUSY# latch must be cleared in all cases so that the next
         * unmasked npx exception causes an interrupt.
         */
        outb(IO_NPX, 0);

        /*
         * fpcurthread is normally non-null here.  In that case, schedule an
         * AST to finish the exception handling in the correct context
         * (this interrupt may occur after the thread has entered the
         * kernel via a syscall or an interrupt).  Otherwise, the npx
         * state of the thread that caused this interrupt must have been
         * pushed to the thread's pcb, and clearing of the busy latch
         * above has finished the (essentially null) handling of this
         * interrupt.  Control will eventually return to the instruction
         * that caused it and it will repeat.  We will eventually (usually
         * soon) win the race to handle the interrupt properly.
         */
        td = PCPU_GET(fpcurthread);
        if (td != NULL) {
                td->td_pcb->pcb_flags |= PCB_NPXTRAP;
                thread_lock(td);
                td->td_flags |= TDF_ASTPENDING;
                thread_unlock(td);
        }
        return (FILTER_HANDLED);
}

/*
 * Probe routine.  Set flags to tell npxattach() what to do.  Set up an
 * interrupt handler if npx needs to use interrupts.
 */
static int
npx_probe(dev)
        device_t dev;
{
        struct gate_descriptor save_idt_npxtrap;
        struct resource *ioport_res, *irq_res;
        void *irq_cookie;
        int ioport_rid, irq_num, irq_rid;
        u_short control;
        u_short status;

        device_set_desc(dev, "math processor");

        /*
         * Modern CPUs all have an FPU that uses the INT16 interface
         * and provide a simple way to verify that, so handle the
         * common case right away.
         */
        if (cpu_feature & CPUID_FPU) {
                hw_float = npx_exists = 1;
                npx_ex16 = 1;
                device_quiet(dev);
                return (0);
        }

        save_idt_npxtrap = idt[IDT_MF];
        setidt(IDT_MF, probetrap, SDT_SYS386TGT, SEL_KPL,
            GSEL(GCODE_SEL, SEL_KPL));
        ioport_rid = 0;
        ioport_res = bus_alloc_resource(dev, SYS_RES_IOPORT, &ioport_rid,
            IO_NPX, IO_NPX + IO_NPXSIZE - 1, IO_NPXSIZE, RF_ACTIVE);
        if (ioport_res == NULL)
                panic("npx: can't get ports");
        if (resource_int_value("npx", 0, "irq", &irq_num) != 0)
                irq_num = IRQ_NPX;
        irq_rid = 0;
        irq_res = bus_alloc_resource(dev, SYS_RES_IRQ, &irq_rid, irq_num,
            irq_num, 1, RF_ACTIVE);
        if (irq_res != NULL) {
                if (bus_setup_intr(dev, irq_res, INTR_TYPE_MISC,
                        npx_intr, NULL, NULL, &irq_cookie) != 0)
                        panic("npx: can't create intr");
        }

        /*
         * Partially reset the coprocessor, if any.  Some BIOS's don't reset
         * it after a warm boot.
         */
        npx_full_reset();
        outb(IO_NPX, 0);

        /*
         * Don't trap while we're probing.
         */
        stop_emulating();

        /*
         * Finish resetting the coprocessor, if any.  If there is an error
         * pending, then we may get a bogus IRQ13, but npx_intr() will handle
         * it OK.  Bogus halts have never been observed, but we enabled
         * IRQ13 and cleared the BUSY# latch early to handle them anyway.
         */
        fninit();

        /*
         * Don't use fwait here because it might hang.
         * Don't use fnop here because it usually hangs if there is no FPU.
         */
        DELAY(1000);            /* wait for any IRQ13 */
#ifdef DIAGNOSTIC
        if (npx_intrs_while_probing != 0)
                printf("fninit caused %u bogus npx interrupt(s)\n",
                       npx_intrs_while_probing);
        if (npx_traps_while_probing != 0)
                printf("fninit caused %u bogus npx trap(s)\n",
                       npx_traps_while_probing);
#endif
        /*
         * Check for a status of mostly zero.
         */
        status = 0x5a5a;
        fnstsw(&status);
        if ((status & 0xb8ff) == 0) {
                /*
                 * Good, now check for a proper control word.
                 */
                control = 0x5a5a;
                fnstcw(&control);
                if ((control & 0x1f3f) == 0x033f) {
                        hw_float = npx_exists = 1;
                        /*
                         * We have an npx, now divide by 0 to see if exception
                         * 16 works.
                         */
                        control &= ~(1 << 2);   /* enable divide by 0 trap */
                        fldcw(&control);
#ifdef FPU_ERROR_BROKEN
                        /*
                         * FPU error signal doesn't work on some CPU
                         * accelerator board.
                         */
                        npx_ex16 = 1;
                        return (0);
#endif
                        npx_traps_while_probing = npx_intrs_while_probing = 0;
                        fp_divide_by_0();
                        DELAY(1000);    /* wait for any IRQ13 */
                        if (npx_traps_while_probing != 0) {
                                /*
                                 * Good, exception 16 works.
                                 */
                                npx_ex16 = 1;
                                goto no_irq13;
                        }
                        if (npx_intrs_while_probing != 0) {
                                /*
                                 * Bad, we are stuck with IRQ13.
                                 */
                                npx_irq13 = 1;
                                idt[IDT_MF] = save_idt_npxtrap;
#ifdef SMP
                                if (mp_ncpus > 1)
                                        panic("npx0 cannot use IRQ 13 on an SMP system");
#endif
                                return (0);
                        }
                        /*
                         * Worse, even IRQ13 is broken.
                         */
                }
        }

        /* Probe failed.  Floating point simply won't work. */
        device_printf(dev, "WARNING: no FPU!\n");

        /* FALLTHROUGH */
no_irq13:
        idt[IDT_MF] = save_idt_npxtrap;
        if (irq_res != NULL) {
                bus_teardown_intr(dev, irq_res, irq_cookie);
                bus_release_resource(dev, SYS_RES_IRQ, irq_rid, irq_res);
        }
        bus_release_resource(dev, SYS_RES_IOPORT, ioport_rid, ioport_res);
        return (npx_exists ? 0 : ENXIO);
}

/*
 * Attach routine - announce which it is, and wire into system
 */
static int
npx_attach(dev)
        device_t dev;
{
        int flags;
        register_t s;

        flags = device_get_flags(dev);

        if (npx_irq13)
                device_printf(dev, "IRQ 13 interface\n");
        else if (!device_is_quiet(dev) || bootverbose)
                device_printf(dev, "INT 16 interface\n");

        npxinit();

        s = intr_disable();
        stop_emulating();
        fpusave(&npx_cleanstate);
        start_emulating();
#ifdef CPU_ENABLE_SSE
        if (cpu_fxsr) {
                if (npx_cleanstate.sv_xmm.sv_env.en_mxcsr_mask)
                        cpu_mxcsr_mask = 
                            npx_cleanstate.sv_xmm.sv_env.en_mxcsr_mask;
                else
                        cpu_mxcsr_mask = 0xFFBF;
                bzero(npx_cleanstate.sv_xmm.sv_fp,
                    sizeof(npx_cleanstate.sv_xmm.sv_fp));
                bzero(npx_cleanstate.sv_xmm.sv_xmm,
                    sizeof(npx_cleanstate.sv_xmm.sv_xmm));
                /* XXX might need even more zeroing. */
        } else
#endif
                bzero(npx_cleanstate.sv_87.sv_ac,
                    sizeof(npx_cleanstate.sv_87.sv_ac));
        intr_restore(s);
#ifdef I586_CPU_XXX
        if (cpu_class == CPUCLASS_586 && npx_ex16 &&
            timezero("i586_bzero()", i586_bzero) <
            timezero("bzero()", bzero) * 4 / 5) {
                if (!(flags & NPX_DISABLE_I586_OPTIMIZED_BCOPY))
                        bcopy_vector = i586_bcopy;
                if (!(flags & NPX_DISABLE_I586_OPTIMIZED_BZERO))
                        bzero_vector = i586_bzero;
                if (!(flags & NPX_DISABLE_I586_OPTIMIZED_COPYIO)) {
                        copyin_vector = i586_copyin;
                        copyout_vector = i586_copyout;
                }
        }
#endif

        return (0);             /* XXX unused */
}

/*
 * Initialize floating point unit.
 */
void
npxinit(void)
{
        static union savefpu dummy;
        register_t savecrit;
        u_short control;

        if (!npx_exists)
                return;
        /*
         * fninit has the same h/w bugs as fnsave.  Use the detoxified
         * fnsave to throw away any junk in the fpu.  npxsave() initializes
         * the fpu and sets fpcurthread = NULL as important side effects.
         */
        savecrit = intr_disable();
        npxsave(&dummy);
        stop_emulating();
#ifdef CPU_ENABLE_SSE
        /* XXX npxsave() doesn't actually initialize the fpu in the SSE case. */
        if (cpu_fxsr)
                fninit();
#endif
        control = __INITIAL_NPXCW__;
        fldcw(&control);
        start_emulating();
        intr_restore(savecrit);
}

/*
 * Free coprocessor (if we have it).
 */
void
npxexit(td)
        struct thread *td;
{
        register_t savecrit;

        savecrit = intr_disable();
        if (curthread == PCPU_GET(fpcurthread))
                npxsave(&PCPU_GET(curpcb)->pcb_save);
        intr_restore(savecrit);
#ifdef NPX_DEBUG
        if (npx_exists) {
                u_int   masked_exceptions;

                masked_exceptions = GET_FPU_CW(td) & GET_FPU_SW(td) & 0x7f;
                /*
                 * Log exceptions that would have trapped with the old
                 * control word (overflow, divide by 0, and invalid operand).
                 */
                if (masked_exceptions & 0x0d)
                        log(LOG_ERR,
        "pid %d (%s) exited with masked floating point exceptions 0x%02x\n",
                            td->td_proc->p_pid, td->td_proc->p_comm,
                            masked_exceptions);
        }
#endif
}

int
npxformat()
{

        if (!npx_exists)
                return (_MC_FPFMT_NODEV);
#ifdef  CPU_ENABLE_SSE
        if (cpu_fxsr)
                return (_MC_FPFMT_XMM);
#endif
        return (_MC_FPFMT_387);
}

/* 
 * The following mechanism is used to ensure that the FPE_... value
 * that is passed as a trapcode to the signal handler of the user
 * process does not have more than one bit set.
 * 
 * Multiple bits may be set if the user process modifies the control
 * word while a status word bit is already set.  While this is a sign
 * of bad coding, we have no choise than to narrow them down to one
 * bit, since we must not send a trapcode that is not exactly one of
 * the FPE_ macros.
 *
 * The mechanism has a static table with 127 entries.  Each combination
 * of the 7 FPU status word exception bits directly translates to a
 * position in this table, where a single FPE_... value is stored.
 * This FPE_... value stored there is considered the "most important"
 * of the exception bits and will be sent as the signal code.  The
 * precedence of the bits is based upon Intel Document "Numerical
 * Applications", Chapter "Special Computational Situations".
 *
 * The macro to choose one of these values does these steps: 1) Throw
 * away status word bits that cannot be masked.  2) Throw away the bits
 * currently masked in the control word, assuming the user isn't
 * interested in them anymore.  3) Reinsert status word bit 7 (stack
 * fault) if it is set, which cannot be masked but must be presered.
 * 4) Use the remaining bits to point into the trapcode table.
 *
 * The 6 maskable bits in order of their preference, as stated in the
 * above referenced Intel manual:
 * 1  Invalid operation (FP_X_INV)
 * 1a   Stack underflow
 * 1b   Stack overflow
 * 1c   Operand of unsupported format
 * 1d   SNaN operand.
 * 2  QNaN operand (not an exception, irrelavant here)
 * 3  Any other invalid-operation not mentioned above or zero divide
 *      (FP_X_INV, FP_X_DZ)
 * 4  Denormal operand (FP_X_DNML)
 * 5  Numeric over/underflow (FP_X_OFL, FP_X_UFL)
 * 6  Inexact result (FP_X_IMP) 
 */
static char fpetable[128] = {
        0,
        FPE_FLTINV,     /*  1 - INV */
        FPE_FLTUND,     /*  2 - DNML */
        FPE_FLTINV,     /*  3 - INV | DNML */
        FPE_FLTDIV,     /*  4 - DZ */
        FPE_FLTINV,     /*  5 - INV | DZ */
        FPE_FLTDIV,     /*  6 - DNML | DZ */
        FPE_FLTINV,     /*  7 - INV | DNML | DZ */
        FPE_FLTOVF,     /*  8 - OFL */
        FPE_FLTINV,     /*  9 - INV | OFL */
        FPE_FLTUND,     /*  A - DNML | OFL */
        FPE_FLTINV,     /*  B - INV | DNML | OFL */
        FPE_FLTDIV,     /*  C - DZ | OFL */
        FPE_FLTINV,     /*  D - INV | DZ | OFL */
        FPE_FLTDIV,     /*  E - DNML | DZ | OFL */
        FPE_FLTINV,     /*  F - INV | DNML | DZ | OFL */
        FPE_FLTUND,     /* 10 - UFL */
        FPE_FLTINV,     /* 11 - INV | UFL */
        FPE_FLTUND,     /* 12 - DNML | UFL */
        FPE_FLTINV,     /* 13 - INV | DNML | UFL */
        FPE_FLTDIV,     /* 14 - DZ | UFL */
        FPE_FLTINV,     /* 15 - INV | DZ | UFL */
        FPE_FLTDIV,     /* 16 - DNML | DZ | UFL */
        FPE_FLTINV,     /* 17 - INV | DNML | DZ | UFL */
        FPE_FLTOVF,     /* 18 - OFL | UFL */
        FPE_FLTINV,     /* 19 - INV | OFL | UFL */
        FPE_FLTUND,     /* 1A - DNML | OFL | UFL */
        FPE_FLTINV,     /* 1B - INV | DNML | OFL | UFL */
        FPE_FLTDIV,     /* 1C - DZ | OFL | UFL */
        FPE_FLTINV,     /* 1D - INV | DZ | OFL | UFL */
        FPE_FLTDIV,     /* 1E - DNML | DZ | OFL | UFL */
        FPE_FLTINV,     /* 1F - INV | DNML | DZ | OFL | UFL */
        FPE_FLTRES,     /* 20 - IMP */
        FPE_FLTINV,     /* 21 - INV | IMP */
        FPE_FLTUND,     /* 22 - DNML | IMP */
        FPE_FLTINV,     /* 23 - INV | DNML | IMP */
        FPE_FLTDIV,     /* 24 - DZ | IMP */
        FPE_FLTINV,     /* 25 - INV | DZ | IMP */
        FPE_FLTDIV,     /* 26 - DNML | DZ | IMP */
        FPE_FLTINV,     /* 27 - INV | DNML | DZ | IMP */
        FPE_FLTOVF,     /* 28 - OFL | IMP */
        FPE_FLTINV,     /* 29 - INV | OFL | IMP */
        FPE_FLTUND,     /* 2A - DNML | OFL | IMP */
        FPE_FLTINV,     /* 2B - INV | DNML | OFL | IMP */
        FPE_FLTDIV,     /* 2C - DZ | OFL | IMP */
        FPE_FLTINV,     /* 2D - INV | DZ | OFL | IMP */
        FPE_FLTDIV,     /* 2E - DNML | DZ | OFL | IMP */
        FPE_FLTINV,     /* 2F - INV | DNML | DZ | OFL | IMP */
        FPE_FLTUND,     /* 30 - UFL | IMP */
        FPE_FLTINV,     /* 31 - INV | UFL | IMP */
        FPE_FLTUND,     /* 32 - DNML | UFL | IMP */
        FPE_FLTINV,     /* 33 - INV | DNML | UFL | IMP */
        FPE_FLTDIV,     /* 34 - DZ | UFL | IMP */
        FPE_FLTINV,     /* 35 - INV | DZ | UFL | IMP */
        FPE_FLTDIV,     /* 36 - DNML | DZ | UFL | IMP */
        FPE_FLTINV,     /* 37 - INV | DNML | DZ | UFL | IMP */
        FPE_FLTOVF,     /* 38 - OFL | UFL | IMP */
        FPE_FLTINV,     /* 39 - INV | OFL | UFL | IMP */
        FPE_FLTUND,     /* 3A - DNML | OFL | UFL | IMP */
        FPE_FLTINV,     /* 3B - INV | DNML | OFL | UFL | IMP */
        FPE_FLTDIV,     /* 3C - DZ | OFL | UFL | IMP */
        FPE_FLTINV,     /* 3D - INV | DZ | OFL | UFL | IMP */
        FPE_FLTDIV,     /* 3E - DNML | DZ | OFL | UFL | IMP */
        FPE_FLTINV,     /* 3F - INV | DNML | DZ | OFL | UFL | IMP */
        FPE_FLTSUB,     /* 40 - STK */
        FPE_FLTSUB,     /* 41 - INV | STK */
        FPE_FLTUND,     /* 42 - DNML | STK */
        FPE_FLTSUB,     /* 43 - INV | DNML | STK */
        FPE_FLTDIV,     /* 44 - DZ | STK */
        FPE_FLTSUB,     /* 45 - INV | DZ | STK */
        FPE_FLTDIV,     /* 46 - DNML | DZ | STK */
        FPE_FLTSUB,     /* 47 - INV | DNML | DZ | STK */
        FPE_FLTOVF,     /* 48 - OFL | STK */
        FPE_FLTSUB,     /* 49 - INV | OFL | STK */
        FPE_FLTUND,     /* 4A - DNML | OFL | STK */
        FPE_FLTSUB,     /* 4B - INV | DNML | OFL | STK */
        FPE_FLTDIV,     /* 4C - DZ | OFL | STK */
        FPE_FLTSUB,     /* 4D - INV | DZ | OFL | STK */
        FPE_FLTDIV,     /* 4E - DNML | DZ | OFL | STK */
        FPE_FLTSUB,     /* 4F - INV | DNML | DZ | OFL | STK */
        FPE_FLTUND,     /* 50 - UFL | STK */
        FPE_FLTSUB,     /* 51 - INV | UFL | STK */
        FPE_FLTUND,     /* 52 - DNML | UFL | STK */
        FPE_FLTSUB,     /* 53 - INV | DNML | UFL | STK */
        FPE_FLTDIV,     /* 54 - DZ | UFL | STK */
        FPE_FLTSUB,     /* 55 - INV | DZ | UFL | STK */
        FPE_FLTDIV,     /* 56 - DNML | DZ | UFL | STK */
        FPE_FLTSUB,     /* 57 - INV | DNML | DZ | UFL | STK */
        FPE_FLTOVF,     /* 58 - OFL | UFL | STK */
        FPE_FLTSUB,     /* 59 - INV | OFL | UFL | STK */
        FPE_FLTUND,     /* 5A - DNML | OFL | UFL | STK */
        FPE_FLTSUB,     /* 5B - INV | DNML | OFL | UFL | STK */
        FPE_FLTDIV,     /* 5C - DZ | OFL | UFL | STK */
        FPE_FLTSUB,     /* 5D - INV | DZ | OFL | UFL | STK */
        FPE_FLTDIV,     /* 5E - DNML | DZ | OFL | UFL | STK */
        FPE_FLTSUB,     /* 5F - INV | DNML | DZ | OFL | UFL | STK */
        FPE_FLTRES,     /* 60 - IMP | STK */
        FPE_FLTSUB,     /* 61 - INV | IMP | STK */
        FPE_FLTUND,     /* 62 - DNML | IMP | STK */
        FPE_FLTSUB,     /* 63 - INV | DNML | IMP | STK */
        FPE_FLTDIV,     /* 64 - DZ | IMP | STK */
        FPE_FLTSUB,     /* 65 - INV | DZ | IMP | STK */
        FPE_FLTDIV,     /* 66 - DNML | DZ | IMP | STK */
        FPE_FLTSUB,     /* 67 - INV | DNML | DZ | IMP | STK */
        FPE_FLTOVF,     /* 68 - OFL | IMP | STK */
        FPE_FLTSUB,     /* 69 - INV | OFL | IMP | STK */
        FPE_FLTUND,     /* 6A - DNML | OFL | IMP | STK */
        FPE_FLTSUB,     /* 6B - INV | DNML | OFL | IMP | STK */
        FPE_FLTDIV,     /* 6C - DZ | OFL | IMP | STK */
        FPE_FLTSUB,     /* 6D - INV | DZ | OFL | IMP | STK */
        FPE_FLTDIV,     /* 6E - DNML | DZ | OFL | IMP | STK */
        FPE_FLTSUB,     /* 6F - INV | DNML | DZ | OFL | IMP | STK */
        FPE_FLTUND,     /* 70 - UFL | IMP | STK */
        FPE_FLTSUB,     /* 71 - INV | UFL | IMP | STK */
        FPE_FLTUND,     /* 72 - DNML | UFL | IMP | STK */
        FPE_FLTSUB,     /* 73 - INV | DNML | UFL | IMP | STK */
        FPE_FLTDIV,     /* 74 - DZ | UFL | IMP | STK */
        FPE_FLTSUB,     /* 75 - INV | DZ | UFL | IMP | STK */
        FPE_FLTDIV,     /* 76 - DNML | DZ | UFL | IMP | STK */
        FPE_FLTSUB,     /* 77 - INV | DNML | DZ | UFL | IMP | STK */
        FPE_FLTOVF,     /* 78 - OFL | UFL | IMP | STK */
        FPE_FLTSUB,     /* 79 - INV | OFL | UFL | IMP | STK */
        FPE_FLTUND,     /* 7A - DNML | OFL | UFL | IMP | STK */
        FPE_FLTSUB,     /* 7B - INV | DNML | OFL | UFL | IMP | STK */
        FPE_FLTDIV,     /* 7C - DZ | OFL | UFL | IMP | STK */
        FPE_FLTSUB,     /* 7D - INV | DZ | OFL | UFL | IMP | STK */
        FPE_FLTDIV,     /* 7E - DNML | DZ | OFL | UFL | IMP | STK */
        FPE_FLTSUB,     /* 7F - INV | DNML | DZ | OFL | UFL | IMP | STK */
};

/*
 * Preserve the FP status word, clear FP exceptions, then generate a SIGFPE.
 *
 * Clearing exceptions is necessary mainly to avoid IRQ13 bugs.  We now
 * depend on longjmp() restoring a usable state.  Restoring the state
 * or examining it might fail if we didn't clear exceptions.
 *
 * The error code chosen will be one of the FPE_... macros. It will be
 * sent as the second argument to old BSD-style signal handlers and as
 * "siginfo_t->si_code" (second argument) to SA_SIGINFO signal handlers.
 *
 * XXX the FP state is not preserved across signal handlers.  So signal
 * handlers cannot afford to do FP unless they preserve the state or
 * longjmp() out.  Both preserving the state and longjmp()ing may be
 * destroyed by IRQ13 bugs.  Clearing FP exceptions is not an acceptable
 * solution for signals other than SIGFPE.
 */
int
npxtrap()
{
        register_t savecrit;
        u_short control, status;

        if (!npx_exists) {
                printf("npxtrap: fpcurthread = %p, curthread = %p, npx_exists = %d\n",
                       PCPU_GET(fpcurthread), curthread, npx_exists);
                panic("npxtrap from nowhere");
        }
        savecrit = intr_disable();

        /*
         * Interrupt handling (for another interrupt) may have pushed the
         * state to memory.  Fetch the relevant parts of the state from
         * wherever they are.
         */
        if (PCPU_GET(fpcurthread) != curthread) {
                control = GET_FPU_CW(curthread);
                status = GET_FPU_SW(curthread);
        } else {
                fnstcw(&control);
                fnstsw(&status);
        }

        if (PCPU_GET(fpcurthread) == curthread)
                fnclex();
        intr_restore(savecrit);
        return (fpetable[status & ((~control & 0x3f) | 0x40)]);
}

/*
 * Implement device not available (DNA) exception
 *
 * It would be better to switch FP context here (if curthread != fpcurthread)
 * and not necessarily for every context switch, but it is too hard to
 * access foreign pcb's.
 */

static int err_count = 0;

int
npxdna(void)
{
        struct pcb *pcb;
        register_t s;

        if (!npx_exists)
                return (0);
        if (PCPU_GET(fpcurthread) == curthread) {
                printf("npxdna: fpcurthread == curthread %d times\n",
                    ++err_count);
                stop_emulating();
                return (1);
        }
        if (PCPU_GET(fpcurthread) != NULL) {
                printf("npxdna: fpcurthread = %p (%d), curthread = %p (%d)\n",
                       PCPU_GET(fpcurthread),
                       PCPU_GET(fpcurthread)->td_proc->p_pid,
                       curthread, curthread->td_proc->p_pid);
                panic("npxdna");
        }
        s = intr_disable();
        stop_emulating();
        /*
         * Record new context early in case frstor causes an IRQ13.
         */
        PCPU_SET(fpcurthread, curthread);
        pcb = PCPU_GET(curpcb);

        if ((pcb->pcb_flags & PCB_NPXINITDONE) == 0) {
                /*
                 * This is the first time this thread has used the FPU or
                 * the PCB doesn't contain a clean FPU state.  Explicitly
                 * load sanitized registers.
                 */
                fpurstor(&npx_cleanstate);
                if (pcb->pcb_initial_npxcw != __INITIAL_NPXCW__)
                        fldcw(&pcb->pcb_initial_npxcw);
                pcb->pcb_flags |= PCB_NPXINITDONE;
        } else {
                /*
                 * The following fpurstor() may cause an IRQ13 when the
                 * state being restored has a pending error.  The error will
                 * appear to have been triggered by the current (npx) user
                 * instruction even when that instruction is a no-wait
                 * instruction that should not trigger an error (e.g.,
                 * fnclex).  On at least one 486 system all of the no-wait
                 * instructions are broken the same as frstor, so our
                 * treatment does not amplify the breakage.  On at least
                 * one 386/Cyrix 387 system, fnclex works correctly while
                 * frstor and fnsave are broken, so our treatment breaks
                 * fnclex if it is the first FPU instruction after a context
                 * switch.
                 */
                fpurstor(&pcb->pcb_save);
        }
        intr_restore(s);

        return (1);
}

/*
 * Wrapper for fnsave instruction, partly to handle hardware bugs.  When npx
 * exceptions are reported via IRQ13, spurious IRQ13's may be triggered by
 * no-wait npx instructions.  See the Intel application note AP-578 for
 * details.  This doesn't cause any additional complications here.  IRQ13's
 * are inherently asynchronous unless the CPU is frozen to deliver them --
 * one that started in userland may be delivered many instructions later,
 * after the process has entered the kernel.  It may even be delivered after
 * the fnsave here completes.  A spurious IRQ13 for the fnsave is handled in
 * the same way as a very-late-arriving non-spurious IRQ13 from user mode:
 * it is normally ignored at first because we set fpcurthread to NULL; it is
 * normally retriggered in npxdna() after return to user mode.
 *
 * npxsave() must be called with interrupts disabled, so that it clears
 * fpcurthread atomically with saving the state.  We require callers to do the
 * disabling, since most callers need to disable interrupts anyway to call
 * npxsave() atomically with checking fpcurthread.
 *
 * A previous version of npxsave() went to great lengths to excecute fnsave
 * with interrupts enabled in case executing it froze the CPU.  This case
 * can't happen, at least for Intel CPU/NPX's.  Spurious IRQ13's don't imply
 * spurious freezes.
 */
void
npxsave(addr)
        union savefpu *addr;
{

        stop_emulating();
        fpusave(addr);

        start_emulating();
        PCPU_SET(fpcurthread, NULL);
}

/*
 * This should be called with interrupts disabled and only when the owning
 * FPU thread is non-null.
 */
void
npxdrop()
{
        struct thread *td;

        /*
         * Discard pending exceptions in the !cpu_fxsr case so that unmasked
         * ones don't cause a panic on the next frstor.
         */
#ifdef CPU_ENABLE_SSE
        if (!cpu_fxsr)
#endif
                fnclex();

        td = PCPU_GET(fpcurthread);
        PCPU_SET(fpcurthread, NULL);
        td->td_pcb->pcb_flags &= ~PCB_NPXINITDONE;
        start_emulating();
}

/*
 * Get the state of the FPU without dropping ownership (if possible).
 * It returns the FPU ownership status.
 */
int
npxgetregs(td, addr)
        struct thread *td;
        union savefpu *addr;
{
        register_t s;

        if (!npx_exists)
                return (_MC_FPOWNED_NONE);

        if ((td->td_pcb->pcb_flags & PCB_NPXINITDONE) == 0) {
                bcopy(&npx_cleanstate, addr, sizeof(npx_cleanstate));
                SET_FPU_CW(addr, td->td_pcb->pcb_initial_npxcw);
                return (_MC_FPOWNED_NONE);
        }
        s = intr_disable();
        if (td == PCPU_GET(fpcurthread)) {
                fpusave(addr);
#ifdef CPU_ENABLE_SSE
                if (!cpu_fxsr)
#endif
                        /*
                         * fnsave initializes the FPU and destroys whatever
                         * context it contains.  Make sure the FPU owner
                         * starts with a clean state next time.
                         */
                        npxdrop();
                intr_restore(s);
                return (_MC_FPOWNED_FPU);
        } else {
                intr_restore(s);
                bcopy(&td->td_pcb->pcb_save, addr, sizeof(*addr));
                return (_MC_FPOWNED_PCB);
        }
}

/*
 * Set the state of the FPU.
 */
void
npxsetregs(td, addr)
        struct thread *td;
        union savefpu *addr;
{
        register_t s;

        if (!npx_exists)
                return;

        s = intr_disable();
        if (td == PCPU_GET(fpcurthread)) {
#ifdef CPU_ENABLE_SSE
                if (!cpu_fxsr)
#endif
                        fnclex();       /* As in npxdrop(). */
                fpurstor(addr);
                intr_restore(s);
        } else {
                intr_restore(s);
                bcopy(addr, &td->td_pcb->pcb_save, sizeof(*addr));
        }
        curthread->td_pcb->pcb_flags |= PCB_NPXINITDONE;
}

static void
fpusave(addr)
        union savefpu *addr;
{
        
#ifdef CPU_ENABLE_SSE
        if (cpu_fxsr)
                fxsave(addr);
        else
#endif
                fnsave(addr);
}

#ifdef CPU_ENABLE_SSE
/*
 * On AuthenticAMD processors, the fxrstor instruction does not restore
 * the x87's stored last instruction pointer, last data pointer, and last
 * opcode values, except in the rare case in which the exception summary
 * (ES) bit in the x87 status word is set to 1.
 *
 * In order to avoid leaking this information across processes, we clean
 * these values by performing a dummy load before executing fxrstor().
 */
static  double  dummy_variable = 0.0;
static void
fpu_clean_state(void)
{
        u_short status;

        /*
         * Clear the ES bit in the x87 status word if it is currently
         * set, in order to avoid causing a fault in the upcoming load.
         */
        fnstsw(&status);
        if (status & 0x80)
                fnclex();

        /*
         * Load the dummy variable into the x87 stack.  This mangles
         * the x87 stack, but we don't care since we're about to call
         * fxrstor() anyway.
         */
        __asm __volatile("ffree %%st(7); fld %0" : : "m" (dummy_variable));
}
#endif /* CPU_ENABLE_SSE */

static void
fpurstor(addr)
        union savefpu *addr;
{

#ifdef CPU_ENABLE_SSE
        if (cpu_fxsr) {
                fpu_clean_state();
                fxrstor(addr);
        } else
#endif
                frstor(addr);
}

#ifdef I586_CPU_XXX
static long
timezero(funcname, func)
        const char *funcname;
        void (*func)(void *buf, size_t len);

{
        void *buf;
#define BUFSIZE         1048576
        long usec;
        struct timeval finish, start;

        buf = malloc(BUFSIZE, M_TEMP, M_NOWAIT);
        if (buf == NULL)
                return (BUFSIZE);
        microtime(&start);
        (*func)(buf, BUFSIZE);
        microtime(&finish);
        usec = 1000000 * (finish.tv_sec - start.tv_sec) +
            finish.tv_usec - start.tv_usec;
        if (usec <= 0)
                usec = 1;
        if (bootverbose)
                printf("%s bandwidth = %u kBps\n", funcname,
                    (u_int32_t)(((BUFSIZE >> 10) * 1000000) / usec));
        free(buf, M_TEMP);
        return (usec);
}
#endif /* I586_CPU */

static device_method_t npx_methods[] = {
        /* Device interface */
        DEVMETHOD(device_identify,      npx_identify),
        DEVMETHOD(device_probe,         npx_probe),
        DEVMETHOD(device_attach,        npx_attach),
        DEVMETHOD(device_detach,        bus_generic_detach),
        DEVMETHOD(device_shutdown,      bus_generic_shutdown),
        DEVMETHOD(device_suspend,       bus_generic_suspend),
        DEVMETHOD(device_resume,        bus_generic_resume),
        
        { 0, 0 }
};

static driver_t npx_driver = {
        "npx",
        npx_methods,
        1,                      /* no softc */
};

static devclass_t npx_devclass;

/*
 * We prefer to attach to the root nexus so that the usual case (exception 16)
 * doesn't describe the processor as being `on isa'.
 */
DRIVER_MODULE(npx, nexus, npx_driver, npx_devclass, 0, 0);

#ifdef DEV_ISA
/*
 * This sucks up the legacy ISA support assignments from PNPBIOS/ACPI.
 */
static struct isa_pnp_id npxisa_ids[] = {
        { 0x040cd041, "Legacy ISA coprocessor support" }, /* PNP0C04 */
        { 0 }
};

static int
npxisa_probe(device_t dev)
{
        int result;
        if ((result = ISA_PNP_PROBE(device_get_parent(dev), dev, npxisa_ids)) <= 0) {
                device_quiet(dev);
        }
        return(result);
}

static int
npxisa_attach(device_t dev)
{
        return (0);
}

static device_method_t npxisa_methods[] = {
        /* Device interface */
        DEVMETHOD(device_probe,         npxisa_probe),
        DEVMETHOD(device_attach,        npxisa_attach),
        DEVMETHOD(device_detach,        bus_generic_detach),
        DEVMETHOD(device_shutdown,      bus_generic_shutdown),
        DEVMETHOD(device_suspend,       bus_generic_suspend),
        DEVMETHOD(device_resume,        bus_generic_resume),
        
        { 0, 0 }
};

static driver_t npxisa_driver = {
        "npxisa",
        npxisa_methods,
        1,                      /* no softc */
};

static devclass_t npxisa_devclass;

DRIVER_MODULE(npxisa, isa, npxisa_driver, npxisa_devclass, 0, 0);
#ifndef PC98
DRIVER_MODULE(npxisa, acpi, npxisa_driver, npxisa_devclass, 0, 0);
#endif
#endif /* DEV_ISA */