summaryrefslogtreecommitdiffstats
path: root/arch/i386/math-emu/fpu_entry.c
blob: 1853524c8b576f5420de5cbd746aecb30f594d50 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
/*---------------------------------------------------------------------------+
 |  fpu_entry.c                                                              |
 |                                                                           |
 | The entry functions for wm-FPU-emu                                        |
 |                                                                           |
 | Copyright (C) 1992,1993,1994,1996,1997                                    |
 |                  W. Metzenthen, 22 Parker St, Ormond, Vic 3163, Australia |
 |                  E-mail   billm@suburbia.net                              |
 |                                                                           |
 | See the files "README" and "COPYING" for further copyright and warranty   |
 | information.                                                              |
 |                                                                           |
 +---------------------------------------------------------------------------*/

/*---------------------------------------------------------------------------+
 | 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.      |
 +---------------------------------------------------------------------------*/

/*---------------------------------------------------------------------------+
 | math_emulate(), restore_i387_soft() and save_i387_soft() are the only     |
 | entry points for wm-FPU-emu.                                              |
 +---------------------------------------------------------------------------*/

#include <linux/signal.h>
#include <linux/ptrace.h>

#include <asm/uaccess.h>
#include <asm/desc.h>

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

#define __BAD__ FPU_illegal   /* Illegal on an 80486, causes SIGILL */

#ifndef NO_UNDOC_CODE    /* Un-documented FPU op-codes supported by default. */

/* WARNING: These codes are not documented by Intel in their 80486 manual
   and may not work on FPU clones or later Intel FPUs. */

/* Changes to support the un-doc codes provided by Linus Torvalds. */

#define _d9_d8_ fstp_i    /* unofficial code (19) */
#define _dc_d0_ fcom_st   /* unofficial code (14) */
#define _dc_d8_ fcompst   /* unofficial code (1c) */
#define _dd_c8_ fxch_i    /* unofficial code (0d) */
#define _de_d0_ fcompst   /* unofficial code (16) */
#define _df_c0_ ffreep    /* unofficial code (07) ffree + pop */
#define _df_c8_ fxch_i    /* unofficial code (0f) */
#define _df_d0_ fstp_i    /* unofficial code (17) */
#define _df_d8_ fstp_i    /* unofficial code (1f) */

static FUNC const st_instr_table[64] = {
  fadd__,   fld_i_,     __BAD__, __BAD__, fadd_i,  ffree_,  faddp_,  _df_c0_,
  fmul__,   fxch_i,     __BAD__, __BAD__, fmul_i,  _dd_c8_, fmulp_,  _df_c8_,
  fcom_st,  fp_nop,     __BAD__, __BAD__, _dc_d0_, fst_i_,  _de_d0_, _df_d0_,
  fcompst,  _d9_d8_,    __BAD__, __BAD__, _dc_d8_, fstp_i,  fcompp,  _df_d8_,
  fsub__,   FPU_etc,    __BAD__, finit_,  fsubri,  fucom_,  fsubrp,  fstsw_,
  fsubr_,   fconst,     fucompp, __BAD__, fsub_i,  fucomp,  fsubp_,  __BAD__,
  fdiv__,   FPU_triga,  __BAD__, __BAD__, fdivri,  __BAD__, fdivrp,  __BAD__,
  fdivr_,   FPU_trigb,  __BAD__, __BAD__, fdiv_i,  __BAD__, fdivp_,  __BAD__,
};

#else     /* Support only documented FPU op-codes */

static FUNC const st_instr_table[64] = {
  fadd__,   fld_i_,     __BAD__, __BAD__, fadd_i,  ffree_,  faddp_,  __BAD__,
  fmul__,   fxch_i,     __BAD__, __BAD__, fmul_i,  __BAD__, fmulp_,  __BAD__,
  fcom_st,  fp_nop,     __BAD__, __BAD__, __BAD__, fst_i_,  __BAD__, __BAD__,
  fcompst,  __BAD__,    __BAD__, __BAD__, __BAD__, fstp_i,  fcompp,  __BAD__,
  fsub__,   FPU_etc,    __BAD__, finit_,  fsubri,  fucom_,  fsubrp,  fstsw_,
  fsubr_,   fconst,     fucompp, __BAD__, fsub_i,  fucomp,  fsubp_,  __BAD__,
  fdiv__,   FPU_triga,  __BAD__, __BAD__, fdivri,  __BAD__, fdivrp,  __BAD__,
  fdivr_,   FPU_trigb,  __BAD__, __BAD__, fdiv_i,  __BAD__, fdivp_,  __BAD__,
};

#endif /* NO_UNDOC_CODE */


#define _NONE_ 0   /* Take no special action */
#define _REG0_ 1   /* Need to check for not empty st(0) */
#define _REGI_ 2   /* Need to check for not empty st(0) and st(rm) */
#define _REGi_ 0   /* Uses st(rm) */
#define _PUSH_ 3   /* Need to check for space to push onto stack */
#define _null_ 4   /* Function illegal or not implemented */
#define _REGIi 5   /* Uses st(0) and st(rm), result to st(rm) */
#define _REGIp 6   /* Uses st(0) and st(rm), result to st(rm) then pop */
#define _REGIc 0   /* Compare st(0) and st(rm) */
#define _REGIn 0   /* Uses st(0) and st(rm), but handle checks later */

#ifndef NO_UNDOC_CODE

/* Un-documented FPU op-codes supported by default. (see above) */

static u_char const type_table[64] = {
  _REGI_, _NONE_, _null_, _null_, _REGIi, _REGi_, _REGIp, _REGi_,
  _REGI_, _REGIn, _null_, _null_, _REGIi, _REGI_, _REGIp, _REGI_,
  _REGIc, _NONE_, _null_, _null_, _REGIc, _REG0_, _REGIc, _REG0_,
  _REGIc, _REG0_, _null_, _null_, _REGIc, _REG0_, _REGIc, _REG0_,
  _REGI_, _NONE_, _null_, _NONE_, _REGIi, _REGIc, _REGIp, _NONE_,
  _REGI_, _NONE_, _REGIc, _null_, _REGIi, _REGIc, _REGIp, _null_,
  _REGI_, _NONE_, _null_, _null_, _REGIi, _null_, _REGIp, _null_,
  _REGI_, _NONE_, _null_, _null_, _REGIi, _null_, _REGIp, _null_
};

#else     /* Support only documented FPU op-codes */

static u_char const type_table[64] = {
  _REGI_, _NONE_, _null_, _null_, _REGIi, _REGi_, _REGIp, _null_,
  _REGI_, _REGIn, _null_, _null_, _REGIi, _null_, _REGIp, _null_,
  _REGIc, _NONE_, _null_, _null_, _null_, _REG0_, _null_, _null_,
  _REGIc, _null_, _null_, _null_, _null_, _REG0_, _REGIc, _null_,
  _REGI_, _NONE_, _null_, _NONE_, _REGIi, _REGIc, _REGIp, _NONE_,
  _REGI_, _NONE_, _REGIc, _null_, _REGIi, _REGIc, _REGIp, _null_,
  _REGI_, _NONE_, _null_, _null_, _REGIi, _null_, _REGIp, _null_,
  _REGI_, _NONE_, _null_, _null_, _REGIi, _null_, _REGIp, _null_
};

#endif /* NO_UNDOC_CODE */


#ifdef RE_ENTRANT_CHECKING
u_char emulating=0;
#endif /* RE_ENTRANT_CHECKING */

static int valid_prefix(u_char *Byte, u_char __user **fpu_eip,
			overrides *override);

asmlinkage void math_emulate(long arg)
{
  u_char  FPU_modrm, byte1;
  unsigned short code;
  fpu_addr_modes addr_modes;
  int unmasked;
  FPU_REG loaded_data;
  FPU_REG *st0_ptr;
  u_char	  loaded_tag, st0_tag;
  void __user *data_address;
  struct address data_sel_off;
  struct address entry_sel_off;
  unsigned long code_base = 0;
  unsigned long code_limit = 0;  /* Initialized to stop compiler warnings */
  struct desc_struct code_descriptor;

#ifdef RE_ENTRANT_CHECKING
  if ( emulating )
    {
      printk("ERROR: wm-FPU-emu is not RE-ENTRANT!\n");
    }
  RE_ENTRANT_CHECK_ON;
#endif /* RE_ENTRANT_CHECKING */

  if (!used_math())
    {
      finit();
      set_used_math();
    }

  SETUP_DATA_AREA(arg);

  FPU_ORIG_EIP = FPU_EIP;

  if ( (FPU_EFLAGS & 0x00020000) != 0 )
    {
      /* Virtual 8086 mode */
      addr_modes.default_mode = VM86;
      FPU_EIP += code_base = FPU_CS << 4;
      code_limit = code_base + 0xffff;  /* Assumes code_base <= 0xffff0000 */
    }
  else if ( FPU_CS == __USER_CS && FPU_DS == __USER_DS )
    {
      addr_modes.default_mode = 0;
    }
  else if ( FPU_CS == __KERNEL_CS )
    {
      printk("math_emulate: %04x:%08lx\n",FPU_CS,FPU_EIP);
      panic("Math emulation needed in kernel");
    }
  else
    {

      if ( (FPU_CS & 4) != 4 )   /* Must be in the LDT */
	{
	  /* Can only handle segmented addressing via the LDT
	     for now, and it must be 16 bit */
	  printk("FPU emulator: Unsupported addressing mode\n");
	  math_abort(FPU_info, SIGILL);
	}

      code_descriptor = LDT_DESCRIPTOR(FPU_CS);
      if ( SEG_D_SIZE(code_descriptor) )
	{
	  /* The above test may be wrong, the book is not clear */
	  /* Segmented 32 bit protected mode */
	  addr_modes.default_mode = SEG32;
	}
      else
	{
	  /* 16 bit protected mode */
	  addr_modes.default_mode = PM16;
	}
      FPU_EIP += code_base = SEG_BASE_ADDR(code_descriptor);
      code_limit = code_base
	+ (SEG_LIMIT(code_descriptor)+1) * SEG_GRANULARITY(code_descriptor)
	  - 1;
      if ( code_limit < code_base ) code_limit = 0xffffffff;
    }

  FPU_lookahead = 1;
  if (current->ptrace & PT_PTRACED)
    FPU_lookahead = 0;

  if ( !valid_prefix(&byte1, (u_char __user **)&FPU_EIP,
		     &addr_modes.override) )
    {
      RE_ENTRANT_CHECK_OFF;
      printk("FPU emulator: Unknown prefix byte 0x%02x, probably due to\n"
	     "FPU emulator: self-modifying code! (emulation impossible)\n",
	     byte1);
      RE_ENTRANT_CHECK_ON;
      EXCEPTION(EX_INTERNAL|0x126);
      math_abort(FPU_info,SIGILL);
    }

do_another_FPU_instruction:

  no_ip_update = 0;

  FPU_EIP++;  /* We have fetched the prefix and first code bytes. */

  if ( addr_modes.default_mode )
    {
      /* This checks for the minimum instruction bytes.
	 We also need to check any extra (address mode) code access. */
      if ( FPU_EIP > code_limit )
	math_abort(FPU_info,SIGSEGV);
    }

  if ( (byte1 & 0xf8) != 0xd8 )
    {
      if ( byte1 == FWAIT_OPCODE )
	{
	  if (partial_status & SW_Summary)
	    goto do_the_FPU_interrupt;
	  else
	    goto FPU_fwait_done;
	}
#ifdef PARANOID
      EXCEPTION(EX_INTERNAL|0x128);
      math_abort(FPU_info,SIGILL);
#endif /* PARANOID */
    }

  RE_ENTRANT_CHECK_OFF;
  FPU_code_access_ok(1);
  FPU_get_user(FPU_modrm, (u_char __user *) FPU_EIP);
  RE_ENTRANT_CHECK_ON;
  FPU_EIP++;

  if (partial_status & SW_Summary)
    {
      /* Ignore the error for now if the current instruction is a no-wait
	 control instruction */
      /* The 80486 manual contradicts itself on this topic,
	 but a real 80486 uses the following instructions:
	 fninit, fnstenv, fnsave, fnstsw, fnstenv, fnclex.
       */
      code = (FPU_modrm << 8) | byte1;
      if ( ! ( (((code & 0xf803) == 0xe003) ||    /* fnclex, fninit, fnstsw */
		(((code & 0x3003) == 0x3001) &&   /* fnsave, fnstcw, fnstenv,
						     fnstsw */
		 ((code & 0xc000) != 0xc000))) ) )
	{
	  /*
	   *  We need to simulate the action of the kernel to FPU
	   *  interrupts here.
	   */
	do_the_FPU_interrupt:

	  FPU_EIP = FPU_ORIG_EIP;	/* Point to current FPU instruction. */

	  RE_ENTRANT_CHECK_OFF;
	  current->thread.trap_no = 16;
	  current->thread.error_code = 0;
	  send_sig(SIGFPE, current, 1);
	  return;
	}
    }

  entry_sel_off.offset = FPU_ORIG_EIP;
  entry_sel_off.selector = FPU_CS;
  entry_sel_off.opcode = (byte1 << 8) | FPU_modrm;

  FPU_rm = FPU_modrm & 7;

  if ( FPU_modrm < 0300 )
    {
      /* All of these instructions use the mod/rm byte to get a data address */

      if ( (addr_modes.default_mode & SIXTEEN)
	  ^ (addr_modes.override.address_size == ADDR_SIZE_PREFIX) )
	data_address = FPU_get_address_16(FPU_modrm, &FPU_EIP, &data_sel_off,
					  addr_modes);
      else
	data_address = FPU_get_address(FPU_modrm, &FPU_EIP, &data_sel_off,
				       addr_modes);

      if ( addr_modes.default_mode )
	{
	  if ( FPU_EIP-1 > code_limit )
	    math_abort(FPU_info,SIGSEGV);
	}

      if ( !(byte1 & 1) )
	{
	  unsigned short status1 = partial_status;

	  st0_ptr = &st(0);
	  st0_tag = FPU_gettag0();

	  /* Stack underflow has priority */
	  if ( NOT_EMPTY_ST0 )
	    {
	      if ( addr_modes.default_mode & PROTECTED )
		{
		  /* This table works for 16 and 32 bit protected mode */
		  if ( access_limit < data_sizes_16[(byte1 >> 1) & 3] )
		    math_abort(FPU_info,SIGSEGV);
		}

	      unmasked = 0;  /* Do this here to stop compiler warnings. */
	      switch ( (byte1 >> 1) & 3 )
		{
		case 0:
		  unmasked = FPU_load_single((float __user *)data_address,
					     &loaded_data);
		  loaded_tag = unmasked & 0xff;
		  unmasked &= ~0xff;
		  break;
		case 1:
		  loaded_tag = FPU_load_int32((long __user *)data_address, &loaded_data);
		  break;
		case 2:
		  unmasked = FPU_load_double((double __user *)data_address,
					     &loaded_data);
		  loaded_tag = unmasked & 0xff;
		  unmasked &= ~0xff;
		  break;
		case 3:
		default:  /* Used here to suppress gcc warnings. */
		  loaded_tag = FPU_load_int16((short __user *)data_address, &loaded_data);
		  break;
		}

	      /* No more access to user memory, it is safe
		 to use static data now */

	      /* NaN operands have the next priority. */
	      /* We have to delay looking at st(0) until after
		 loading the data, because that data might contain an SNaN */
	      if ( ((st0_tag == TAG_Special) && isNaN(st0_ptr)) ||
		  ((loaded_tag == TAG_Special) && isNaN(&loaded_data)) )
		{
		  /* Restore the status word; we might have loaded a
		     denormal. */
		  partial_status = status1;
		  if ( (FPU_modrm & 0x30) == 0x10 )
		    {
		      /* fcom or fcomp */
		      EXCEPTION(EX_Invalid);
		      setcc(SW_C3 | SW_C2 | SW_C0);
		      if ( (FPU_modrm & 0x08) && (control_word & CW_Invalid) )
			FPU_pop();             /* fcomp, masked, so we pop. */
		    }
		  else
		    {
		      if ( loaded_tag == TAG_Special )
			loaded_tag = FPU_Special(&loaded_data);
#ifdef PECULIAR_486
		      /* This is not really needed, but gives behaviour
			 identical to an 80486 */
		      if ( (FPU_modrm & 0x28) == 0x20 )
			/* fdiv or fsub */
			real_2op_NaN(&loaded_data, loaded_tag, 0, &loaded_data);
		      else
#endif /* PECULIAR_486 */ 
			/* fadd, fdivr, fmul, or fsubr */
			real_2op_NaN(&loaded_data, loaded_tag, 0, st0_ptr);
		    }
		  goto reg_mem_instr_done;
		}

	      if ( unmasked && !((FPU_modrm & 0x30) == 0x10) )
		{
		  /* Is not a comparison instruction. */
		  if ( (FPU_modrm & 0x38) == 0x38 )
		    {
		      /* fdivr */
		      if ( (st0_tag == TAG_Zero) &&
			   ((loaded_tag == TAG_Valid)
			    || (loaded_tag == TAG_Special
				&& isdenormal(&loaded_data))) )
			{
			  if ( FPU_divide_by_zero(0, getsign(&loaded_data))
			       < 0 )
			    {
			      /* We use the fact here that the unmasked
				 exception in the loaded data was for a
				 denormal operand */
			      /* Restore the state of the denormal op bit */
			      partial_status &= ~SW_Denorm_Op;
			      partial_status |= status1 & SW_Denorm_Op;
			    }
			  else
			    setsign(st0_ptr, getsign(&loaded_data));
			}
		    }
		  goto reg_mem_instr_done;
		}

	      switch ( (FPU_modrm >> 3) & 7 )
		{
		case 0:         /* fadd */
		  clear_C1();
		  FPU_add(&loaded_data, loaded_tag, 0, control_word);
		  break;
		case 1:         /* fmul */
		  clear_C1();
		  FPU_mul(&loaded_data, loaded_tag, 0, control_word);
		  break;
		case 2:         /* fcom */
		  FPU_compare_st_data(&loaded_data, loaded_tag);
		  break;
		case 3:         /* fcomp */
		  if ( !FPU_compare_st_data(&loaded_data, loaded_tag)
		       && !unmasked )
		    FPU_pop();
		  break;
		case 4:         /* fsub */
		  clear_C1();
		  FPU_sub(LOADED|loaded_tag, (int)&loaded_data, control_word);
		  break;
		case 5:         /* fsubr */
		  clear_C1();
		  FPU_sub(REV|LOADED|loaded_tag, (int)&loaded_data, control_word);
		  break;
		case 6:         /* fdiv */
		  clear_C1();
		  FPU_div(LOADED|loaded_tag, (int)&loaded_data, control_word);
		  break;
		case 7:         /* fdivr */
		  clear_C1();
		  if ( st0_tag == TAG_Zero )
		    partial_status = status1;  /* Undo any denorm tag,
						  zero-divide has priority. */
		  FPU_div(REV|LOADED|loaded_tag, (int)&loaded_data, control_word);
		  break;
		}
	    }
	  else
	    {
	      if ( (FPU_modrm & 0x30) == 0x10 )
		{
		  /* The instruction is fcom or fcomp */
		  EXCEPTION(EX_StackUnder);
		  setcc(SW_C3 | SW_C2 | SW_C0);
		  if ( (FPU_modrm & 0x08) && (control_word & CW_Invalid) )
		    FPU_pop();             /* fcomp */
		}
	      else
		FPU_stack_underflow();
	    }
	reg_mem_instr_done:
	  operand_address = data_sel_off;
	}
      else
	{
	  if ( !(no_ip_update =
		 FPU_load_store(((FPU_modrm & 0x38) | (byte1 & 6)) >> 1,
				addr_modes, data_address)) )
	    {
	      operand_address = data_sel_off;
	    }
	}

    }
  else
    {
      /* None of these instructions access user memory */
      u_char instr_index = (FPU_modrm & 0x38) | (byte1 & 7);

#ifdef PECULIAR_486
      /* This is supposed to be undefined, but a real 80486 seems
	 to do this: */
      operand_address.offset = 0;
      operand_address.selector = FPU_DS;
#endif /* PECULIAR_486 */

      st0_ptr = &st(0);
      st0_tag = FPU_gettag0();
      switch ( type_table[(int) instr_index] )
	{
	case _NONE_:   /* also _REGIc: _REGIn */
	  break;
	case _REG0_:
	  if ( !NOT_EMPTY_ST0 )
	    {
	      FPU_stack_underflow();
	      goto FPU_instruction_done;
	    }
	  break;
	case _REGIi:
	  if ( !NOT_EMPTY_ST0 || !NOT_EMPTY(FPU_rm) )
	    {
	      FPU_stack_underflow_i(FPU_rm);
	      goto FPU_instruction_done;
	    }
	  break;
	case _REGIp:
	  if ( !NOT_EMPTY_ST0 || !NOT_EMPTY(FPU_rm) )
	    {
	      FPU_stack_underflow_pop(FPU_rm);
	      goto FPU_instruction_done;
	    }
	  break;
	case _REGI_:
	  if ( !NOT_EMPTY_ST0 || !NOT_EMPTY(FPU_rm) )
	    {
	      FPU_stack_underflow();
	      goto FPU_instruction_done;
	    }
	  break;
	case _PUSH_:     /* Only used by the fld st(i) instruction */
	  break;
	case _null_:
	  FPU_illegal();
	  goto FPU_instruction_done;
	default:
	  EXCEPTION(EX_INTERNAL|0x111);
	  goto FPU_instruction_done;
	}
      (*st_instr_table[(int) instr_index])();

FPU_instruction_done:
      ;
    }

  if ( ! no_ip_update )
    instruction_address = entry_sel_off;

FPU_fwait_done:

#ifdef DEBUG
  RE_ENTRANT_CHECK_OFF;
  FPU_printall();
  RE_ENTRANT_CHECK_ON;
#endif /* DEBUG */

  if (FPU_lookahead && !need_resched())
    {
      FPU_ORIG_EIP = FPU_EIP - code_base;
      if ( valid_prefix(&byte1, (u_char __user **)&FPU_EIP,
			&addr_modes.override) )
	goto do_another_FPU_instruction;
    }

  if ( addr_modes.default_mode )
    FPU_EIP -= code_base;

  RE_ENTRANT_CHECK_OFF;
}


/* Support for prefix bytes is not yet complete. To properly handle
   all prefix bytes, further changes are needed in the emulator code
   which accesses user address space. Access to separate segments is
   important for msdos emulation. */
static int valid_prefix(u_char *Byte, u_char __user **fpu_eip,
			overrides *override)
{
  u_char byte;
  u_char __user *ip = *fpu_eip;

  *override = (overrides) { 0, 0, PREFIX_DEFAULT };       /* defaults */

  RE_ENTRANT_CHECK_OFF;
  FPU_code_access_ok(1);
  FPU_get_user(byte, ip);
  RE_ENTRANT_CHECK_ON;

  while ( 1 )
    {
      switch ( byte )
	{
	case ADDR_SIZE_PREFIX:
	  override->address_size = ADDR_SIZE_PREFIX;
	  goto do_next_byte;

	case OP_SIZE_PREFIX:
	  override->operand_size = OP_SIZE_PREFIX;
	  goto do_next_byte;

	case PREFIX_CS:
	  override->segment = PREFIX_CS_;
	  goto do_next_byte;
	case PREFIX_ES:
	  override->segment = PREFIX_ES_;
	  goto do_next_byte;
	case PREFIX_SS:
	  override->segment = PREFIX_SS_;
	  goto do_next_byte;
	case PREFIX_FS:
	  override->segment = PREFIX_FS_;
	  goto do_next_byte;
	case PREFIX_GS:
	  override->segment = PREFIX_GS_;
	  goto do_next_byte;
	case PREFIX_DS:
	  override->segment = PREFIX_DS_;
	  goto do_next_byte;

/* lock is not a valid prefix for FPU instructions,
   let the cpu handle it to generate a SIGILL. */
/*	case PREFIX_LOCK: */

	  /* rep.. prefixes have no meaning for FPU instructions */
	case PREFIX_REPE:
	case PREFIX_REPNE:

	do_next_byte:
	  ip++;
	  RE_ENTRANT_CHECK_OFF;
	  FPU_code_access_ok(1);
	  FPU_get_user(byte, ip);
	  RE_ENTRANT_CHECK_ON;
	  break;
	case FWAIT_OPCODE:
	  *Byte = byte;
	  return 1;
	default:
	  if ( (byte & 0xf8) == 0xd8 )
	    {
	      *Byte = byte;
	      *fpu_eip = ip;
	      return 1;
	    }
	  else
	    {
	      /* Not a valid sequence of prefix bytes followed by
		 an FPU instruction. */
	      *Byte = byte;  /* Needed for error message. */
	      return 0;
	    }
	}
    }
}


void math_abort(struct info * info, unsigned int signal)
{
	FPU_EIP = FPU_ORIG_EIP;
	current->thread.trap_no = 16;
	current->thread.error_code = 0;
	send_sig(signal,current,1);
	RE_ENTRANT_CHECK_OFF;
	__asm__("movl %0,%%esp ; ret": :"g" (((long) info)-4));
#ifdef PARANOID
      printk("ERROR: wm-FPU-emu math_abort failed!\n");
#endif /* PARANOID */
}



#define S387 ((struct i387_soft_struct *)s387)
#define sstatus_word() \
  ((S387->swd & ~SW_Top & 0xffff) | ((S387->ftop << SW_Top_Shift) & SW_Top))

int restore_i387_soft(void *s387, struct _fpstate __user *buf)
{
  u_char __user *d = (u_char __user *)buf;
  int offset, other, i, tags, regnr, tag, newtop;

  RE_ENTRANT_CHECK_OFF;
  FPU_access_ok(VERIFY_READ, d, 7*4 + 8*10);
  if (__copy_from_user(&S387->cwd, d, 7*4))
    return -1;
  RE_ENTRANT_CHECK_ON;

  d += 7*4;

  S387->ftop = (S387->swd >> SW_Top_Shift) & 7;
  offset = (S387->ftop & 7) * 10;
  other = 80 - offset;

  RE_ENTRANT_CHECK_OFF;
  /* Copy all registers in stack order. */
  if (__copy_from_user(((u_char *)&S387->st_space)+offset, d, other))
    return -1;
  if ( offset )
    if (__copy_from_user((u_char *)&S387->st_space, d+other, offset))
      return -1;
  RE_ENTRANT_CHECK_ON;

  /* The tags may need to be corrected now. */
  tags = S387->twd;
  newtop = S387->ftop;
  for ( i = 0; i < 8; i++ )
    {
      regnr = (i+newtop) & 7;
      if ( ((tags >> ((regnr & 7)*2)) & 3) != TAG_Empty )
	{
	  /* The loaded data over-rides all other cases. */
	  tag = FPU_tagof((FPU_REG *)((u_char *)S387->st_space + 10*regnr));
	  tags &= ~(3 << (regnr*2));
	  tags |= (tag & 3) << (regnr*2);
	}
    }
  S387->twd = tags;

  return 0;
}


int save_i387_soft(void *s387, struct _fpstate __user * buf)
{
  u_char __user *d = (u_char __user *)buf;
  int offset = (S387->ftop & 7) * 10, other = 80 - offset;

  RE_ENTRANT_CHECK_OFF;
  FPU_access_ok(VERIFY_WRITE, d, 7*4 + 8*10);
#ifdef PECULIAR_486
  S387->cwd &= ~0xe080;
  /* An 80486 sets nearly all of the reserved bits to 1. */
  S387->cwd |= 0xffff0040;
  S387->swd = sstatus_word() | 0xffff0000;
  S387->twd |= 0xffff0000;
  S387->fcs &= ~0xf8000000;
  S387->fos |= 0xffff0000;
#endif /* PECULIAR_486 */
  if (__copy_to_user(d, &S387->cwd, 7*4))
    return -1;
  RE_ENTRANT_CHECK_ON;

  d += 7*4;

  RE_ENTRANT_CHECK_OFF;
  /* Copy all registers in stack order. */
  if (__copy_to_user(d, ((u_char *)&S387->st_space)+offset, other))
    return -1;
  if ( offset )
    if (__copy_to_user(d+other, (u_char *)&S387->st_space, offset))
      return -1;
  RE_ENTRANT_CHECK_ON;

  return 1;
}