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