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