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errors.c

/*---------------------------------------------------------------------------+
 |  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   billm@jacobi.maths.monash.edu.au                |
 |                                                                           |
 |                                                                           |
 +---------------------------------------------------------------------------*/

/*---------------------------------------------------------------------------+
 | 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=%ld 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=%ld%ld pc=%ld%ld 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;

}


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