errors.c

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/*---------------------------------------------------------------------------+
 |  errors.c                                                                 |
 |                                                                           |
 |  The error handling functions for wm-FPU-emu                              |
 |                                                                           |
 | Copyright (C) 1992,1993,1994,1996                                         |
 |                  W. Metzenthen, 22 Parker St, Ormond, Vic 3163, Australia |
 |                  E-mail   [email protected]                |
 |                                                                           |
 |                                                                           |
 +---------------------------------------------------------------------------*/

/*---------------------------------------------------------------------------+
 | Note:                                                                     |
 |    The file contains code which accesses user memory.                     |
 |    Emulator static data may change when user memory is accessed, due to   |
 |    other processes using the emulator while swapping is in progress.      |
 +---------------------------------------------------------------------------*/

#include <linux/signal.h>

#include <asm/uaccess.h>

#include "fpu_emu.h"
#include "fpu_system.h"
#include "exception.h"
#include "status_w.h"
#include "control_w.h"
#include "reg_constant.h"
#include "version.h"

/* */
#undef PRINT_MESSAGES
/* */

#if 0
void Un_impl(void)
{
    u_char byte1, FPU_modrm;
    unsigned long address = FPU_ORIG_EIP;

    RE_ENTRANT_CHECK_OFF;
    /* No need to check access_ok(), we have previously fetched these bytes. */
    printk("Unimplemented FPU Opcode at eip=%p : ", (void __user *)address);
    if (FPU_CS == __USER_CS) {
        while (1) {
            FPU_get_user(byte1, (u_char __user *) address);
            if ((byte1 & 0xf8) == 0xd8)
                break;
            printk("[%02x]", byte1);
            address++;
        }
        printk("%02x ", byte1);
        FPU_get_user(FPU_modrm, 1 + (u_char __user *) address);

        if (FPU_modrm >= 0300)
            printk("%02x (%02x+%d)\n", FPU_modrm, FPU_modrm & 0xf8,
                   FPU_modrm & 7);
        else
            printk("/%d\n", (FPU_modrm >> 3) & 7);
    } else {
        printk("cs selector = %04x\n", FPU_CS);
    }

    RE_ENTRANT_CHECK_ON;

    EXCEPTION(EX_Invalid);

}
#endif /*  0  */

/*
   Called for opcodes which are illegal and which are known to result in a
   SIGILL with a real 80486.
   */
void FPU_illegal(void)
{
    math_abort(FPU_info, SIGILL);
}

void FPU_printall(void)
{
    int i;
    static const char *tag_desc[] = { "Valid", "Zero", "ERROR", "Empty",
        "DeNorm", "Inf", "NaN"
    };
    u_char byte1, FPU_modrm;
    unsigned long address = FPU_ORIG_EIP;

    RE_ENTRANT_CHECK_OFF;
    /* No need to check access_ok(), we have previously fetched these bytes. */
    printk("At %p:", (void *)address);
    if (FPU_CS == __USER_CS) {
#define MAX_PRINTED_BYTES 20
        for (i = 0; i < MAX_PRINTED_BYTES; i++) {
            FPU_get_user(byte1, (u_char __user *) address);
            if ((byte1 & 0xf8) == 0xd8) {
                printk(" %02x", byte1);
                break;
            }
            printk(" [%02x]", byte1);
            address++;
        }
        if (i == MAX_PRINTED_BYTES)
            printk(" [more..]\n");
        else {
            FPU_get_user(FPU_modrm, 1 + (u_char __user *) address);

            if (FPU_modrm >= 0300)
                printk(" %02x (%02x+%d)\n", FPU_modrm,
                       FPU_modrm & 0xf8, FPU_modrm & 7);
            else
                printk(" /%d, mod=%d rm=%d\n",
                       (FPU_modrm >> 3) & 7,
                       (FPU_modrm >> 6) & 3, FPU_modrm & 7);
        }
    } else {
        printk("%04x\n", FPU_CS);
    }

    partial_status = status_word();

#ifdef DEBUGGING
    if (partial_status & SW_Backward)
        printk("SW: backward compatibility\n");
    if (partial_status & SW_C3)
        printk("SW: condition bit 3\n");
    if (partial_status & SW_C2)
        printk("SW: condition bit 2\n");
    if (partial_status & SW_C1)
        printk("SW: condition bit 1\n");
    if (partial_status & SW_C0)
        printk("SW: condition bit 0\n");
    if (partial_status & SW_Summary)
        printk("SW: exception summary\n");
    if (partial_status & SW_Stack_Fault)
        printk("SW: stack fault\n");
    if (partial_status & SW_Precision)
        printk("SW: loss of precision\n");
    if (partial_status & SW_Underflow)
        printk("SW: underflow\n");
    if (partial_status & SW_Overflow)
        printk("SW: overflow\n");
    if (partial_status & SW_Zero_Div)
        printk("SW: divide by zero\n");
    if (partial_status & SW_Denorm_Op)
        printk("SW: denormalized operand\n");
    if (partial_status & SW_Invalid)
        printk("SW: invalid operation\n");
#endif /* DEBUGGING */

    printk(" SW: b=%d st=%d es=%d sf=%d cc=%d%d%d%d ef=%d%d%d%d%d%d\n", partial_status & 0x8000 ? 1 : 0,    /* busy */
           (partial_status & 0x3800) >> 11, /* stack top pointer */
           partial_status & 0x80 ? 1 : 0,   /* Error summary status */
           partial_status & 0x40 ? 1 : 0,   /* Stack flag */
           partial_status & SW_C3 ? 1 : 0, partial_status & SW_C2 ? 1 : 0,  /* cc */
           partial_status & SW_C1 ? 1 : 0, partial_status & SW_C0 ? 1 : 0,  /* cc */
           partial_status & SW_Precision ? 1 : 0,
           partial_status & SW_Underflow ? 1 : 0,
           partial_status & SW_Overflow ? 1 : 0,
           partial_status & SW_Zero_Div ? 1 : 0,
           partial_status & SW_Denorm_Op ? 1 : 0,
           partial_status & SW_Invalid ? 1 : 0);

    printk(" CW: ic=%d rc=%d%d pc=%d%d iem=%d     ef=%d%d%d%d%d%d\n",
           control_word & 0x1000 ? 1 : 0,
           (control_word & 0x800) >> 11, (control_word & 0x400) >> 10,
           (control_word & 0x200) >> 9, (control_word & 0x100) >> 8,
           control_word & 0x80 ? 1 : 0,
           control_word & SW_Precision ? 1 : 0,
           control_word & SW_Underflow ? 1 : 0,
           control_word & SW_Overflow ? 1 : 0,
           control_word & SW_Zero_Div ? 1 : 0,
           control_word & SW_Denorm_Op ? 1 : 0,
           control_word & SW_Invalid ? 1 : 0);

    for (i = 0; i < 8; i++) {
        FPU_REG *r = &st(i);
        u_char tagi = FPU_gettagi(i);
        switch (tagi) {
        case TAG_Empty:
            continue;
            break;
        case TAG_Zero:
        case TAG_Special:
            tagi = FPU_Special(r);
        case TAG_Valid:
            printk("st(%d)  %c .%04lx %04lx %04lx %04lx e%+-6d ", i,
                   getsign(r) ? '-' : '+',
                   (long)(r->sigh >> 16),
                   (long)(r->sigh & 0xFFFF),
                   (long)(r->sigl >> 16),
                   (long)(r->sigl & 0xFFFF),
                   exponent(r) - EXP_BIAS + 1);
            break;
        default:
            printk("Whoops! Error in errors.c: tag%d is %d ", i,
                   tagi);
            continue;
            break;
        }
        printk("%s\n", tag_desc[(int)(unsigned)tagi]);
    }

    RE_ENTRANT_CHECK_ON;

}

static struct {
    int type;
    const char *name;
} exception_names[] = {
    {
    EX_StackOver, "stack overflow"}, {
    EX_StackUnder, "stack underflow"}, {
    EX_Precision, "loss of precision"}, {
    EX_Underflow, "underflow"}, {
    EX_Overflow, "overflow"}, {
    EX_ZeroDiv, "divide by zero"}, {
    EX_Denormal, "denormalized operand"}, {
    EX_Invalid, "invalid operation"}, {
    EX_INTERNAL, "INTERNAL BUG in " FPU_VERSION}, {
    0, NULL}
};

/*
 EX_INTERNAL is always given with a code which indicates where the
 error was detected.

 Internal error types:
       0x14   in fpu_etc.c
       0x1nn  in a *.c file:
              0x101  in reg_add_sub.c
              0x102  in reg_mul.c
              0x104  in poly_atan.c
              0x105  in reg_mul.c
              0x107  in fpu_trig.c
          0x108  in reg_compare.c
          0x109  in reg_compare.c
          0x110  in reg_add_sub.c
          0x111  in fpe_entry.c
          0x112  in fpu_trig.c
          0x113  in errors.c
          0x115  in fpu_trig.c
          0x116  in fpu_trig.c
          0x117  in fpu_trig.c
          0x118  in fpu_trig.c
          0x119  in fpu_trig.c
          0x120  in poly_atan.c
          0x121  in reg_compare.c
          0x122  in reg_compare.c
          0x123  in reg_compare.c
          0x125  in fpu_trig.c
          0x126  in fpu_entry.c
          0x127  in poly_2xm1.c
          0x128  in fpu_entry.c
          0x129  in fpu_entry.c
          0x130  in get_address.c
          0x131  in get_address.c
          0x132  in get_address.c
          0x133  in get_address.c
          0x140  in load_store.c
          0x141  in load_store.c
              0x150  in poly_sin.c
              0x151  in poly_sin.c
          0x160  in reg_ld_str.c
          0x161  in reg_ld_str.c
          0x162  in reg_ld_str.c
          0x163  in reg_ld_str.c
          0x164  in reg_ld_str.c
          0x170  in fpu_tags.c
          0x171  in fpu_tags.c
          0x172  in fpu_tags.c
          0x180  in reg_convert.c
       0x2nn  in an *.S file:
              0x201  in reg_u_add.S
              0x202  in reg_u_div.S
              0x203  in reg_u_div.S
              0x204  in reg_u_div.S
              0x205  in reg_u_mul.S
              0x206  in reg_u_sub.S
              0x207  in wm_sqrt.S
          0x208  in reg_div.S
              0x209  in reg_u_sub.S
              0x210  in reg_u_sub.S
              0x211  in reg_u_sub.S
              0x212  in reg_u_sub.S
          0x213  in wm_sqrt.S
          0x214  in wm_sqrt.S
          0x215  in wm_sqrt.S
          0x220  in reg_norm.S
          0x221  in reg_norm.S
          0x230  in reg_round.S
          0x231  in reg_round.S
          0x232  in reg_round.S
          0x233  in reg_round.S
          0x234  in reg_round.S
          0x235  in reg_round.S
          0x236  in reg_round.S
          0x240  in div_Xsig.S
          0x241  in div_Xsig.S
          0x242  in div_Xsig.S
 */

asmlinkage void FPU_exception(int n)
{
    int i, int_type;

    int_type = 0;       /* Needed only to stop compiler warnings */
    if (n & EX_INTERNAL) {
        int_type = n - EX_INTERNAL;
        n = EX_INTERNAL;
        /* Set lots of exception bits! */
        partial_status |= (SW_Exc_Mask | SW_Summary | SW_Backward);
    } else {
        /* Extract only the bits which we use to set the status word */
        n &= (SW_Exc_Mask);
        /* Set the corresponding exception bit */
        partial_status |= n;
        /* Set summary bits iff exception isn't masked */
        if (partial_status & ~control_word & CW_Exceptions)
            partial_status |= (SW_Summary | SW_Backward);
        if (n & (SW_Stack_Fault | EX_Precision)) {
            if (!(n & SW_C1))
                /* This bit distinguishes over- from underflow for a stack fault,
                   and roundup from round-down for precision loss. */
                partial_status &= ~SW_C1;
        }
    }

    RE_ENTRANT_CHECK_OFF;
    if ((~control_word & n & CW_Exceptions) || (n == EX_INTERNAL)) {
#ifdef PRINT_MESSAGES
        /* My message from the sponsor */
        printk(FPU_VERSION " " __DATE__ " (C) W. Metzenthen.\n");
#endif /* PRINT_MESSAGES */

        /* Get a name string for error reporting */
        for (i = 0; exception_names[i].type; i++)
            if ((exception_names[i].type & n) ==
                exception_names[i].type)
                break;

        if (exception_names[i].type) {
#ifdef PRINT_MESSAGES
            printk("FP Exception: %s!\n", exception_names[i].name);
#endif /* PRINT_MESSAGES */
        } else
            printk("FPU emulator: Unknown Exception: 0x%04x!\n", n);

        if (n == EX_INTERNAL) {
            printk("FPU emulator: Internal error type 0x%04x\n",
                   int_type);
            FPU_printall();
        }
#ifdef PRINT_MESSAGES
        else
            FPU_printall();
#endif /* PRINT_MESSAGES */

        /*
         * The 80486 generates an interrupt on the next non-control FPU
         * instruction. So we need some means of flagging it.
         * We use the ES (Error Summary) bit for this.
         */
    }
    RE_ENTRANT_CHECK_ON;

#ifdef __DEBUG__
    math_abort(FPU_info, SIGFPE);
#endif /* __DEBUG__ */

}

/* Real operation attempted on a NaN. */
/* Returns < 0 if the exception is unmasked */
int real_1op_NaN(FPU_REG *a)
{
    int signalling, isNaN;

    isNaN = (exponent(a) == EXP_OVER) && (a->sigh & 0x80000000);

    /* The default result for the case of two "equal" NaNs (signs may
       differ) is chosen to reproduce 80486 behaviour */
    signalling = isNaN && !(a->sigh & 0x40000000);

    if (!signalling) {
        if (!isNaN) {   /* pseudo-NaN, or other unsupported? */
            if (control_word & CW_Invalid) {
                /* Masked response */
                reg_copy(&CONST_QNaN, a);
            }
            EXCEPTION(EX_Invalid);
            return (!(control_word & CW_Invalid) ? FPU_Exception :
                0) | TAG_Special;
        }
        return TAG_Special;
    }

    if (control_word & CW_Invalid) {
        /* The masked response */
        if (!(a->sigh & 0x80000000)) {  /* pseudo-NaN ? */
            reg_copy(&CONST_QNaN, a);
        }
        /* ensure a Quiet NaN */
        a->sigh |= 0x40000000;
    }

    EXCEPTION(EX_Invalid);

    return (!(control_word & CW_Invalid) ? FPU_Exception : 0) | TAG_Special;
}

/* Real operation attempted on two operands, one a NaN. */
/* Returns < 0 if the exception is unmasked */
int real_2op_NaN(FPU_REG const *b, u_char tagb,
         int deststnr, FPU_REG const *defaultNaN)
{
    FPU_REG *dest = &st(deststnr);
    FPU_REG const *a = dest;
    u_char taga = FPU_gettagi(deststnr);
    FPU_REG const *x;
    int signalling, unsupported;

    if (taga == TAG_Special)
        taga = FPU_Special(a);
    if (tagb == TAG_Special)
        tagb = FPU_Special(b);

    /* TW_NaN is also used for unsupported data types. */
    unsupported = ((taga == TW_NaN)
               && !((exponent(a) == EXP_OVER)
                && (a->sigh & 0x80000000)))
        || ((tagb == TW_NaN)
        && !((exponent(b) == EXP_OVER) && (b->sigh & 0x80000000)));
    if (unsupported) {
        if (control_word & CW_Invalid) {
            /* Masked response */
            FPU_copy_to_regi(&CONST_QNaN, TAG_Special, deststnr);
        }
        EXCEPTION(EX_Invalid);
        return (!(control_word & CW_Invalid) ? FPU_Exception : 0) |
            TAG_Special;
    }

    if (taga == TW_NaN) {
        x = a;
        if (tagb == TW_NaN) {
            signalling = !(a->sigh & b->sigh & 0x40000000);
            if (significand(b) > significand(a))
                x = b;
            else if (significand(b) == significand(a)) {
                /* The default result for the case of two "equal" NaNs (signs may
                   differ) is chosen to reproduce 80486 behaviour */
                x = defaultNaN;
            }
        } else {
            /* return the quiet version of the NaN in a */
            signalling = !(a->sigh & 0x40000000);
        }
    } else
#ifdef PARANOID
    if (tagb == TW_NaN)
#endif /* PARANOID */
    {
        signalling = !(b->sigh & 0x40000000);
        x = b;
    }
#ifdef PARANOID
    else {
        signalling = 0;
        EXCEPTION(EX_INTERNAL | 0x113);
        x = &CONST_QNaN;
    }
#endif /* PARANOID */

    if ((!signalling) || (control_word & CW_Invalid)) {
        if (!x)
            x = b;

        if (!(x->sigh & 0x80000000))    /* pseudo-NaN ? */
            x = &CONST_QNaN;

        FPU_copy_to_regi(x, TAG_Special, deststnr);

        if (!signalling)
            return TAG_Special;

        /* ensure a Quiet NaN */
        dest->sigh |= 0x40000000;
    }

    EXCEPTION(EX_Invalid);

    return (!(control_word & CW_Invalid) ? FPU_Exception : 0) | TAG_Special;
}

/* Invalid arith operation on Valid registers */
/* Returns < 0 if the exception is unmasked */
asmlinkage int arith_invalid(int deststnr)
{

    EXCEPTION(EX_Invalid);

    if (control_word & CW_Invalid) {
        /* The masked response */
        FPU_copy_to_regi(&CONST_QNaN, TAG_Special, deststnr);
    }

    return (!(control_word & CW_Invalid) ? FPU_Exception : 0) | TAG_Valid;

}

/* Divide a finite number by zero */
asmlinkage int FPU_divide_by_zero(int deststnr, u_char sign)
{
    FPU_REG *dest = &st(deststnr);
    int tag = TAG_Valid;

    if (control_word & CW_ZeroDiv) {
        /* The masked response */
        FPU_copy_to_regi(&CONST_INF, TAG_Special, deststnr);
        setsign(dest, sign);
        tag = TAG_Special;
    }

    EXCEPTION(EX_ZeroDiv);

    return (!(control_word & CW_ZeroDiv) ? FPU_Exception : 0) | tag;

}

/* This may be called often, so keep it lean */
int set_precision_flag(int flags)
{
    if (control_word & CW_Precision) {
        partial_status &= ~(SW_C1 & flags);
        partial_status |= flags;    /* The masked response */
        return 0;
    } else {
        EXCEPTION(flags);
        return 1;
    }
}

/* This may be called often, so keep it lean */
asmlinkage void set_precision_flag_up(void)
{
    if (control_word & CW_Precision)
        partial_status |= (SW_Precision | SW_C1);   /* The masked response */
    else
        EXCEPTION(EX_Precision | SW_C1);
}

/* This may be called often, so keep it lean */
asmlinkage void set_precision_flag_down(void)
{
    if (control_word & CW_Precision) {  /* The masked response */
        partial_status &= ~SW_C1;
        partial_status |= SW_Precision;
    } else
        EXCEPTION(EX_Precision);
}

asmlinkage int denormal_operand(void)
{
    if (control_word & CW_Denormal) {   /* The masked response */
        partial_status |= SW_Denorm_Op;
        return TAG_Special;
    } else {
        EXCEPTION(EX_Denormal);
        return TAG_Special | FPU_Exception;
    }
}

asmlinkage int arith_overflow(FPU_REG *dest)
{
    int tag = TAG_Valid;

    if (control_word & CW_Overflow) {
        /* The masked response */
/* ###### The response here depends upon the rounding mode */
        reg_copy(&CONST_INF, dest);
        tag = TAG_Special;
    } else {
        /* Subtract the magic number from the exponent */
        addexponent(dest, (-3 * (1 << 13)));
    }

    EXCEPTION(EX_Overflow);
    if (control_word & CW_Overflow) {
        /* The overflow exception is masked. */
        /* By definition, precision is lost.
           The roundup bit (C1) is also set because we have
           "rounded" upwards to Infinity. */
        EXCEPTION(EX_Precision | SW_C1);
        return tag;
    }

    return tag;

}

asmlinkage int arith_underflow(FPU_REG *dest)
{
    int tag = TAG_Valid;

    if (control_word & CW_Underflow) {
        /* The masked response */
        if (exponent16(dest) <= EXP_UNDER - 63) {
            reg_copy(&CONST_Z, dest);
            partial_status &= ~SW_C1;   /* Round down. */
            tag = TAG_Zero;
        } else {
            stdexp(dest);
        }
    } else {
        /* Add the magic number to the exponent. */
        addexponent(dest, (3 * (1 << 13)) + EXTENDED_Ebias);
    }

    EXCEPTION(EX_Underflow);
    if (control_word & CW_Underflow) {
        /* The underflow exception is masked. */
        EXCEPTION(EX_Precision);
        return tag;
    }

    return tag;

}

void FPU_stack_overflow(void)
{

    if (control_word & CW_Invalid) {
        /* The masked response */
        top--;
        FPU_copy_to_reg0(&CONST_QNaN, TAG_Special);
    }

    EXCEPTION(EX_StackOver);

    return;

}

void FPU_stack_underflow(void)
{

    if (control_word & CW_Invalid) {
        /* The masked response */
        FPU_copy_to_reg0(&CONST_QNaN, TAG_Special);
    }

    EXCEPTION(EX_StackUnder);

    return;

}

void FPU_stack_underflow_i(int i)
{

    if (control_word & CW_Invalid) {
        /* The masked response */
        FPU_copy_to_regi(&CONST_QNaN, TAG_Special, i);
    }

    EXCEPTION(EX_StackUnder);

    return;

}

void FPU_stack_underflow_pop(int i)
{

    if (control_word & CW_Invalid) {
        /* The masked response */
        FPU_copy_to_regi(&CONST_QNaN, TAG_Special, i);
        FPU_pop();
    }

    EXCEPTION(EX_StackUnder);

    return;

}