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