arch/i386/kernel/i387.c

   1 /*
   2  *  linux/arch/i386/kernel/i387.c
   3  *
   4  *  Copyright (C) 1994 Linus Torvalds
   5  *
   6  *  Pentium III FXSR, SSE support
   7  *  General FPU state handling cleanups
   8  *      Gareth Hughes <gareth@valinux.com>, May 2000
   9  */
  10
  11 #include <linux/config.h>
  12 #include <linux/sched.h>
  13 #include <linux/module.h>
  14 #include <asm/processor.h>
  15 #include <asm/i387.h>
  16 #include <asm/math_emu.h>
  17 #include <asm/sigcontext.h>
  18 #include <asm/user.h>
  19 #include <asm/ptrace.h>
  20 #include <asm/uaccess.h>
  21
  22 #ifdef CONFIG_MATH_EMULATION
  23 #define HAVE_HWFP (boot_cpu_data.hard_math)
  24 #else
  25 #define HAVE_HWFP 1
  26 #endif
  27
  28 static unsigned long mxcsr_feature_mask = 0xffffffff;
  29
  30 void mxcsr_feature_mask_init(void)
  31 {
  32         unsigned long mask = 0;
  33         clts();
  34         if (cpu_has_fxsr) {
  35                 memset(&current->thread.i387.fxsave, 0, sizeof(struct i387_fxsave_struct));
  36                 asm volatile("fxsave %0" : : "m" (current->thread.i387.fxsave));
  37                 mask = current->thread.i387.fxsave.mxcsr_mask;
  38                 if (mask == 0) mask = 0x0000ffbf;
  39         }
  40         mxcsr_feature_mask &= mask;
  41         stts();
  42 }
  43
  44 /*
  45  * The _current_ task is using the FPU for the first time
  46  * so initialize it and set the mxcsr to its default
  47  * value at reset if we support XMM instructions and then
  48  * remeber the current task has used the FPU.
  49  */
  50 void init_fpu(struct task_struct *tsk)
  51 {
  52         if (cpu_has_fxsr) {
  53                 memset(&tsk->thread.i387.fxsave, 0, sizeof(struct i387_fxsave_struct));
  54                 tsk->thread.i387.fxsave.cwd = 0x37f;
  55                 if (cpu_has_xmm)
  56                         tsk->thread.i387.fxsave.mxcsr = 0x1f80;
  57         } else {
  58                 memset(&tsk->thread.i387.fsave, 0, sizeof(struct i387_fsave_struct));
  59                 tsk->thread.i387.fsave.cwd = 0xffff037fu;
  60                 tsk->thread.i387.fsave.swd = 0xffff0000u;
  61                 tsk->thread.i387.fsave.twd = 0xffffffffu;
  62                 tsk->thread.i387.fsave.fos = 0xffff0000u;
  63         }
  64         /* only the device not available exception or ptrace can call init_fpu */
  65         set_stopped_child_used_math(tsk);
  66 }
  67
  68 /*
  69  * FPU lazy state save handling.
  70  */
  71
  72 void kernel_fpu_begin(void)
  73 {
  74         struct thread_info *thread = current_thread_info();
  75
  76         preempt_disable();
  77         if (thread->status & TS_USEDFPU) {
  78                 __save_init_fpu(thread->task);
  79                 return;
  80         }
  81         clts();
  82 }
  83 EXPORT_SYMBOL_GPL(kernel_fpu_begin);
  84
  85 void restore_fpu( struct task_struct *tsk )
  86 {
  87         if ( cpu_has_fxsr ) {
  88                 asm volatile( "fxrstor %0"
  89                               : : "m" (tsk->thread.i387.fxsave) );
  90         } else {
  91                 asm volatile( "frstor %0"
  92                               : : "m" (tsk->thread.i387.fsave) );
  93         }
  94 }
  95
  96 /*
  97  * FPU tag word conversions.
  98  */
  99
 100 static inline unsigned short twd_i387_to_fxsr( unsigned short twd )
 101 {
 102         unsigned int tmp; /* to avoid 16 bit prefixes in the code */
 103
 104         /* Transform each pair of bits into 01 (valid) or 00 (empty) */
 105         tmp = ~twd;
 106         tmp = (tmp | (tmp>>1)) & 0x5555; /* 0V0V0V0V0V0V0V0V */
 107         /* and move the valid bits to the lower byte. */
 108         tmp = (tmp | (tmp >> 1)) & 0x3333; /* 00VV00VV00VV00VV */
 109         tmp = (tmp | (tmp >> 2)) & 0x0f0f; /* 0000VVVV0000VVVV */
 110         tmp = (tmp | (tmp >> 4)) & 0x00ff; /* 00000000VVVVVVVV */
 111         return tmp;
 112 }
 113
 114 static inline unsigned long twd_fxsr_to_i387( struct i387_fxsave_struct *fxsave )
 115 {
 116         struct _fpxreg *st = NULL;
 117         unsigned long tos = (fxsave->swd >> 11) & 7;
 118         unsigned long twd = (unsigned long) fxsave->twd;
 119         unsigned long tag;
 120         unsigned long ret = 0xffff0000u;
 121         int i;
 122
 123 #define FPREG_ADDR(f, n)        ((void *)&(f)->st_space + (n) * 16);
 124
 125         for ( i = 0 ; i < 8 ; i++ ) {
 126                 if ( twd & 0x1 ) {
 127                         st = FPREG_ADDR( fxsave, (i - tos) & 7 );
 128
 129                         switch ( st->exponent & 0x7fff ) {
 130                         case 0x7fff:
 131                                 tag = 2;                /* Special */
 132                                 break;
 133                         case 0x0000:
 134                                 if ( !st->significand[0] &&
 135                                      !st->significand[1] &&
 136                                      !st->significand[2] &&
 137                                      !st->significand[3] ) {
 138                                         tag = 1;        /* Zero */
 139                                 } else {
 140                                         tag = 2;        /* Special */
 141                                 }
 142                                 break;
 143                         default:
 144                                 if ( st->significand[3] & 0x8000 ) {
 145                                         tag = 0;        /* Valid */
 146                                 } else {
 147                                         tag = 2;        /* Special */
 148                                 }
 149                                 break;
 150                         }
 151                 } else {
 152                         tag = 3;                        /* Empty */
 153                 }
 154                 ret |= (tag << (2 * i));
 155                 twd = twd >> 1;
 156         }
 157         return ret;
 158 }
 159
 160 /*
 161  * FPU state interaction.
 162  */
 163
 164 unsigned short get_fpu_cwd( struct task_struct *tsk )
 165 {
 166         if ( cpu_has_fxsr ) {
 167                 return tsk->thread.i387.fxsave.cwd;
 168         } else {
 169                 return (unsigned short)tsk->thread.i387.fsave.cwd;
 170         }
 171 }
 172
 173 unsigned short get_fpu_swd( struct task_struct *tsk )
 174 {
 175         if ( cpu_has_fxsr ) {
 176                 return tsk->thread.i387.fxsave.swd;
 177         } else {
 178                 return (unsigned short)tsk->thread.i387.fsave.swd;
 179         }
 180 }
 181
 182 #if 0
 183 unsigned short get_fpu_twd( struct task_struct *tsk )
 184 {
 185         if ( cpu_has_fxsr ) {
 186                 return tsk->thread.i387.fxsave.twd;
 187         } else {
 188                 return (unsigned short)tsk->thread.i387.fsave.twd;
 189         }
 190 }
 191 #endif  /*  0  */
 192
 193 unsigned short get_fpu_mxcsr( struct task_struct *tsk )
 194 {
 195         if ( cpu_has_xmm ) {
 196                 return tsk->thread.i387.fxsave.mxcsr;
 197         } else {
 198                 return 0x1f80;
 199         }
 200 }
 201
 202 #if 0
 203
 204 void set_fpu_cwd( struct task_struct *tsk, unsigned short cwd )
 205 {
 206         if ( cpu_has_fxsr ) {
 207                 tsk->thread.i387.fxsave.cwd = cwd;
 208         } else {
 209                 tsk->thread.i387.fsave.cwd = ((long)cwd | 0xffff0000u);
 210         }
 211 }
 212
 213 void set_fpu_swd( struct task_struct *tsk, unsigned short swd )
 214 {
 215         if ( cpu_has_fxsr ) {
 216                 tsk->thread.i387.fxsave.swd = swd;
 217         } else {
 218                 tsk->thread.i387.fsave.swd = ((long)swd | 0xffff0000u);
 219         }
 220 }
 221
 222 void set_fpu_twd( struct task_struct *tsk, unsigned short twd )
 223 {
 224         if ( cpu_has_fxsr ) {
 225                 tsk->thread.i387.fxsave.twd = twd_i387_to_fxsr(twd);
 226         } else {
 227                 tsk->thread.i387.fsave.twd = ((long)twd | 0xffff0000u);
 228         }
 229 }
 230
 231 #endif  /*  0  */
 232
 233 /*
 234  * FXSR floating point environment conversions.
 235  */
 236
 237 static int convert_fxsr_to_user( struct _fpstate __user *buf,
 238                                         struct i387_fxsave_struct *fxsave )
 239 {
 240         unsigned long env[7];
 241         struct _fpreg __user *to;
 242         struct _fpxreg *from;
 243         int i;
 244
 245         env[0] = (unsigned long)fxsave->cwd | 0xffff0000ul;
 246         env[1] = (unsigned long)fxsave->swd | 0xffff0000ul;
 247         env[2] = twd_fxsr_to_i387(fxsave);
 248         env[3] = fxsave->fip;
 249         env[4] = fxsave->fcs | ((unsigned long)fxsave->fop << 16);
 250         env[5] = fxsave->foo;
 251         env[6] = fxsave->fos;
 252
 253         if ( __copy_to_user( buf, env, 7 * sizeof(unsigned long) ) )
 254                 return 1;
 255
 256         to = &buf->_st[0];
 257         from = (struct _fpxreg *) &fxsave->st_space[0];
 258         for ( i = 0 ; i < 8 ; i++, to++, from++ ) {
 259                 unsigned long __user *t = (unsigned long __user *)to;
 260                 unsigned long *f = (unsigned long *)from;
 261
 262                 if (__put_user(*f, t) ||
 263                                 __put_user(*(f + 1), t + 1) ||
 264                                 __put_user(from->exponent, &to->exponent))
 265                         return 1;
 266         }
 267         return 0;
 268 }
 269
 270 static int convert_fxsr_from_user( struct i387_fxsave_struct *fxsave,
 271                                           struct _fpstate __user *buf )
 272 {
 273         unsigned long env[7];
 274         struct _fpxreg *to;
 275         struct _fpreg __user *from;
 276         int i;
 277
 278         if ( __copy_from_user( env, buf, 7 * sizeof(long) ) )
 279                 return 1;
 280
 281         fxsave->cwd = (unsigned short)(env[0] & 0xffff);
 282         fxsave->swd = (unsigned short)(env[1] & 0xffff);
 283         fxsave->twd = twd_i387_to_fxsr((unsigned short)(env[2] & 0xffff));
 284         fxsave->fip = env[3];
 285         fxsave->fop = (unsigned short)((env[4] & 0xffff0000ul) >> 16);
 286         fxsave->fcs = (env[4] & 0xffff);
 287         fxsave->foo = env[5];
 288         fxsave->fos = env[6];
 289
 290         to = (struct _fpxreg *) &fxsave->st_space[0];
 291         from = &buf->_st[0];
 292         for ( i = 0 ; i < 8 ; i++, to++, from++ ) {
 293                 unsigned long *t = (unsigned long *)to;
 294                 unsigned long __user *f = (unsigned long __user *)from;
 295
 296                 if (__get_user(*t, f) ||
 297                                 __get_user(*(t + 1), f + 1) ||
 298                                 __get_user(to->exponent, &from->exponent))
 299                         return 1;
 300         }
 301         return 0;
 302 }
 303
 304 /*
 305  * Signal frame handlers.
 306  */
 307
 308 static inline int save_i387_fsave( struct _fpstate __user *buf )
 309 {
 310         struct task_struct *tsk = current;
 311
 312         unlazy_fpu( tsk );
 313         tsk->thread.i387.fsave.status = tsk->thread.i387.fsave.swd;
 314         if ( __copy_to_user( buf, &tsk->thread.i387.fsave,
 315                              sizeof(struct i387_fsave_struct) ) )
 316                 return -1;
 317         return 1;
 318 }
 319
 320 static int save_i387_fxsave( struct _fpstate __user *buf )
 321 {
 322         struct task_struct *tsk = current;
 323         int err = 0;
 324
 325         unlazy_fpu( tsk );
 326
 327         if ( convert_fxsr_to_user( buf, &tsk->thread.i387.fxsave ) )
 328                 return -1;
 329
 330         err |= __put_user( tsk->thread.i387.fxsave.swd, &buf->status );
 331         err |= __put_user( X86_FXSR_MAGIC, &buf->magic );
 332         if ( err )
 333                 return -1;
 334
 335         if ( __copy_to_user( &buf->_fxsr_env[0], &tsk->thread.i387.fxsave,
 336                              sizeof(struct i387_fxsave_struct) ) )
 337                 return -1;
 338         return 1;
 339 }
 340
 341 int save_i387( struct _fpstate __user *buf )
 342 {
 343         if ( !used_math() )
 344                 return 0;
 345
 346         /* This will cause a "finit" to be triggered by the next
 347          * attempted FPU operation by the 'current' process.
 348          */
 349         clear_used_math();
 350
 351         if ( HAVE_HWFP ) {
 352                 if ( cpu_has_fxsr ) {
 353                         return save_i387_fxsave( buf );
 354                 } else {
 355                         return save_i387_fsave( buf );
 356                 }
 357         } else {
 358                 return save_i387_soft( &current->thread.i387.soft, buf );
 359         }
 360 }
 361
 362 static inline int restore_i387_fsave( struct _fpstate __user *buf )
 363 {
 364         struct task_struct *tsk = current;
 365         clear_fpu( tsk );
 366         return __copy_from_user( &tsk->thread.i387.fsave, buf,
 367                                  sizeof(struct i387_fsave_struct) );
 368 }
 369
 370 static int restore_i387_fxsave( struct _fpstate __user *buf )
 371 {
 372         int err;
 373         struct task_struct *tsk = current;
 374         clear_fpu( tsk );
 375         err = __copy_from_user( &tsk->thread.i387.fxsave, &buf->_fxsr_env[0],
 376                                 sizeof(struct i387_fxsave_struct) );
 377         /* mxcsr reserved bits must be masked to zero for security reasons */
 378         tsk->thread.i387.fxsave.mxcsr &= mxcsr_feature_mask;
 379         return err ? 1 : convert_fxsr_from_user( &tsk->thread.i387.fxsave, buf );
 380 }
 381
 382 int restore_i387( struct _fpstate __user *buf )
 383 {
 384         int err;
 385
 386         if ( HAVE_HWFP ) {
 387                 if ( cpu_has_fxsr ) {
 388                         err = restore_i387_fxsave( buf );
 389                 } else {
 390                         err = restore_i387_fsave( buf );
 391                 }
 392         } else {
 393                 err = restore_i387_soft( &current->thread.i387.soft, buf );
 394         }
 395         set_used_math();
 396         return err;
 397 }
 398
 399 /*
 400  * ptrace request handlers.
 401  */
 402
 403 static inline int get_fpregs_fsave( struct user_i387_struct __user *buf,
 404                                     struct task_struct *tsk )
 405 {
 406         return __copy_to_user( buf, &tsk->thread.i387.fsave,
 407                                sizeof(struct user_i387_struct) );
 408 }
 409
 410 static inline int get_fpregs_fxsave( struct user_i387_struct __user *buf,
 411                                      struct task_struct *tsk )
 412 {
 413         return convert_fxsr_to_user( (struct _fpstate __user *)buf,
 414                                      &tsk->thread.i387.fxsave );
 415 }
 416
 417 int get_fpregs( struct user_i387_struct __user *buf, struct task_struct *tsk )
 418 {
 419         if ( HAVE_HWFP ) {
 420                 if ( cpu_has_fxsr ) {
 421                         return get_fpregs_fxsave( buf, tsk );
 422                 } else {
 423                         return get_fpregs_fsave( buf, tsk );
 424                 }
 425         } else {
 426                 return save_i387_soft( &tsk->thread.i387.soft,
 427                                        (struct _fpstate __user *)buf );
 428         }
 429 }
 430
 431 static inline int set_fpregs_fsave( struct task_struct *tsk,
 432                                     struct user_i387_struct __user *buf )
 433 {
 434         return __copy_from_user( &tsk->thread.i387.fsave, buf,
 435                                  sizeof(struct user_i387_struct) );
 436 }
 437
 438 static inline int set_fpregs_fxsave( struct task_struct *tsk,
 439                                      struct user_i387_struct __user *buf )
 440 {
 441         return convert_fxsr_from_user( &tsk->thread.i387.fxsave,
 442                                        (struct _fpstate __user *)buf );
 443 }
 444
 445 int set_fpregs( struct task_struct *tsk, struct user_i387_struct __user *buf )
 446 {
 447         if ( HAVE_HWFP ) {
 448                 if ( cpu_has_fxsr ) {
 449                         return set_fpregs_fxsave( tsk, buf );
 450                 } else {
 451                         return set_fpregs_fsave( tsk, buf );
 452                 }
 453         } else {
 454                 return restore_i387_soft( &tsk->thread.i387.soft,
 455                                           (struct _fpstate __user *)buf );
 456         }
 457 }
 458
 459 int get_fpxregs( struct user_fxsr_struct __user *buf, struct task_struct *tsk )
 460 {
 461         if ( cpu_has_fxsr ) {
 462                 if (__copy_to_user( buf, &tsk->thread.i387.fxsave,
 463                                     sizeof(struct user_fxsr_struct) ))
 464                         return -EFAULT;
 465                 return 0;
 466         } else {
 467                 return -EIO;
 468         }
 469 }
 470
 471 int set_fpxregs( struct task_struct *tsk, struct user_fxsr_struct __user *buf )
 472 {
 473         int ret = 0;
 474
 475         if ( cpu_has_fxsr ) {
 476                 if (__copy_from_user( &tsk->thread.i387.fxsave, buf,
 477                                   sizeof(struct user_fxsr_struct) ))
 478                         ret = -EFAULT;
 479                 /* mxcsr reserved bits must be masked to zero for security reasons */
 480                 tsk->thread.i387.fxsave.mxcsr &= mxcsr_feature_mask;
 481         } else {
 482                 ret = -EIO;
 483         }
 484         return ret;
 485 }
 486
 487 /*
 488  * FPU state for core dumps.
 489  */
 490
 491 static inline void copy_fpu_fsave( struct task_struct *tsk,
 492                                    struct user_i387_struct *fpu )
 493 {
 494         memcpy( fpu, &tsk->thread.i387.fsave,
 495                 sizeof(struct user_i387_struct) );
 496 }
 497
 498 static inline void copy_fpu_fxsave( struct task_struct *tsk,
 499                                    struct user_i387_struct *fpu )
 500 {
 501         unsigned short *to;
 502         unsigned short *from;
 503         int i;
 504
 505         memcpy( fpu, &tsk->thread.i387.fxsave, 7 * sizeof(long) );
 506
 507         to = (unsigned short *)&fpu->st_space[0];
 508         from = (unsigned short *)&tsk->thread.i387.fxsave.st_space[0];
 509         for ( i = 0 ; i < 8 ; i++, to += 5, from += 8 ) {
 510                 memcpy( to, from, 5 * sizeof(unsigned short) );
 511         }
 512 }
 513
 514 int dump_fpu( struct pt_regs *regs, struct user_i387_struct *fpu )
 515 {
 516         int fpvalid;
 517         struct task_struct *tsk = current;
 518
 519         fpvalid = !!used_math();
 520         if ( fpvalid ) {
 521                 unlazy_fpu( tsk );
 522                 if ( cpu_has_fxsr ) {
 523                         copy_fpu_fxsave( tsk, fpu );
 524                 } else {
 525                         copy_fpu_fsave( tsk, fpu );
 526                 }
 527         }
 528
 529         return fpvalid;
 530 }
 531 EXPORT_SYMBOL(dump_fpu);
 532
 533 int dump_task_fpu(struct task_struct *tsk, struct user_i387_struct *fpu)
 534 {
 535         int fpvalid = !!tsk_used_math(tsk);
 536
 537         if (fpvalid) {
 538                 if (tsk == current)
 539                         unlazy_fpu(tsk);
 540                 if (cpu_has_fxsr)
 541                         copy_fpu_fxsave(tsk, fpu);
 542                 else
 543                         copy_fpu_fsave(tsk, fpu);
 544         }
 545         return fpvalid;
 546 }
 547
 548 int dump_task_extended_fpu(struct task_struct *tsk, struct user_fxsr_struct *fpu)
 549 {
 550         int fpvalid = tsk_used_math(tsk) && cpu_has_fxsr;
 551
 552         if (fpvalid) {
 553                 if (tsk == current)
 554                        unlazy_fpu(tsk);
 555                 memcpy(fpu, &tsk->thread.i387.fxsave, sizeof(*fpu));
 556         }
 557         return fpvalid;
 558 }