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 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 unsigned short get_fpu_twd( struct task_struct *tsk )
 181 {
 182         if ( cpu_has_fxsr ) {
 183                 return tsk->thread.i387.fxsave.twd;
 184         } else {
 185                 return (unsigned short)tsk->thread.i387.fsave.twd;
 186         }
 187 }
 188
 189 unsigned short get_fpu_mxcsr( struct task_struct *tsk )
 190 {
 191         if ( cpu_has_xmm ) {
 192                 return tsk->thread.i387.fxsave.mxcsr;
 193         } else {
 194                 return 0x1f80;
 195         }
 196 }
 197
 198 void set_fpu_cwd( struct task_struct *tsk, unsigned short cwd )
 199 {
 200         if ( cpu_has_fxsr ) {
 201                 tsk->thread.i387.fxsave.cwd = cwd;
 202         } else {
 203                 tsk->thread.i387.fsave.cwd = ((long)cwd | 0xffff0000u);
 204         }
 205 }
 206
 207 void set_fpu_swd( struct task_struct *tsk, unsigned short swd )
 208 {
 209         if ( cpu_has_fxsr ) {
 210                 tsk->thread.i387.fxsave.swd = swd;
 211         } else {
 212                 tsk->thread.i387.fsave.swd = ((long)swd | 0xffff0000u);
 213         }
 214 }
 215
 216 void set_fpu_twd( struct task_struct *tsk, unsigned short twd )
 217 {
 218         if ( cpu_has_fxsr ) {
 219                 tsk->thread.i387.fxsave.twd = twd_i387_to_fxsr(twd);
 220         } else {
 221                 tsk->thread.i387.fsave.twd = ((long)twd | 0xffff0000u);
 222         }
 223 }
 224
 225 /*
 226  * FXSR floating point environment conversions.
 227  */
 228
 229 static int convert_fxsr_to_user( struct _fpstate __user *buf,
 230                                         struct i387_fxsave_struct *fxsave )
 231 {
 232         unsigned long env[7];
 233         struct _fpreg __user *to;
 234         struct _fpxreg *from;
 235         int i;
 236
 237         env[0] = (unsigned long)fxsave->cwd | 0xffff0000ul;
 238         env[1] = (unsigned long)fxsave->swd | 0xffff0000ul;
 239         env[2] = twd_fxsr_to_i387(fxsave);
 240         env[3] = fxsave->fip;
 241         env[4] = fxsave->fcs | ((unsigned long)fxsave->fop << 16);
 242         env[5] = fxsave->foo;
 243         env[6] = fxsave->fos;
 244
 245         if ( __copy_to_user( buf, env, 7 * sizeof(unsigned long) ) )
 246                 return 1;
 247
 248         to = &buf->_st[0];
 249         from = (struct _fpxreg *) &fxsave->st_space[0];
 250         for ( i = 0 ; i < 8 ; i++, to++, from++ ) {
 251                 unsigned long __user *t = (unsigned long __user *)to;
 252                 unsigned long *f = (unsigned long *)from;
 253
 254                 if (__put_user(*f, t) ||
 255                                 __put_user(*(f + 1), t + 1) ||
 256                                 __put_user(from->exponent, &to->exponent))
 257                         return 1;
 258         }
 259         return 0;
 260 }
 261
 262 static int convert_fxsr_from_user( struct i387_fxsave_struct *fxsave,
 263                                           struct _fpstate __user *buf )
 264 {
 265         unsigned long env[7];
 266         struct _fpxreg *to;
 267         struct _fpreg __user *from;
 268         int i;
 269
 270         if ( __copy_from_user( env, buf, 7 * sizeof(long) ) )
 271                 return 1;
 272
 273         fxsave->cwd = (unsigned short)(env[0] & 0xffff);
 274         fxsave->swd = (unsigned short)(env[1] & 0xffff);
 275         fxsave->twd = twd_i387_to_fxsr((unsigned short)(env[2] & 0xffff));
 276         fxsave->fip = env[3];
 277         fxsave->fop = (unsigned short)((env[4] & 0xffff0000ul) >> 16);
 278         fxsave->fcs = (env[4] & 0xffff);
 279         fxsave->foo = env[5];
 280         fxsave->fos = env[6];
 281
 282         to = (struct _fpxreg *) &fxsave->st_space[0];
 283         from = &buf->_st[0];
 284         for ( i = 0 ; i < 8 ; i++, to++, from++ ) {
 285                 unsigned long *t = (unsigned long *)to;
 286                 unsigned long __user *f = (unsigned long __user *)from;
 287
 288                 if (__get_user(*t, f) ||
 289                                 __get_user(*(t + 1), f + 1) ||
 290                                 __get_user(to->exponent, &from->exponent))
 291                         return 1;
 292         }
 293         return 0;
 294 }
 295
 296 /*
 297  * Signal frame handlers.
 298  */
 299
 300 static inline int save_i387_fsave( struct _fpstate __user *buf )
 301 {
 302         struct task_struct *tsk = current;
 303
 304         unlazy_fpu( tsk );
 305         tsk->thread.i387.fsave.status = tsk->thread.i387.fsave.swd;
 306         if ( __copy_to_user( buf, &tsk->thread.i387.fsave,
 307                              sizeof(struct i387_fsave_struct) ) )
 308                 return -1;
 309         return 1;
 310 }
 311
 312 static int save_i387_fxsave( struct _fpstate __user *buf )
 313 {
 314         struct task_struct *tsk = current;
 315         int err = 0;
 316
 317         unlazy_fpu( tsk );
 318
 319         if ( convert_fxsr_to_user( buf, &tsk->thread.i387.fxsave ) )
 320                 return -1;
 321
 322         err |= __put_user( tsk->thread.i387.fxsave.swd, &buf->status );
 323         err |= __put_user( X86_FXSR_MAGIC, &buf->magic );
 324         if ( err )
 325                 return -1;
 326
 327         if ( __copy_to_user( &buf->_fxsr_env[0], &tsk->thread.i387.fxsave,
 328                              sizeof(struct i387_fxsave_struct) ) )
 329                 return -1;
 330         return 1;
 331 }
 332
 333 int save_i387( struct _fpstate __user *buf )
 334 {
 335         if ( !used_math() )
 336                 return 0;
 337
 338         /* This will cause a "finit" to be triggered by the next
 339          * attempted FPU operation by the 'current' process.
 340          */
 341         clear_used_math();
 342
 343         if ( HAVE_HWFP ) {
 344                 if ( cpu_has_fxsr ) {
 345                         return save_i387_fxsave( buf );
 346                 } else {
 347                         return save_i387_fsave( buf );
 348                 }
 349         } else {
 350                 return save_i387_soft( &current->thread.i387.soft, buf );
 351         }
 352 }
 353
 354 static inline int restore_i387_fsave( struct _fpstate __user *buf )
 355 {
 356         struct task_struct *tsk = current;
 357         clear_fpu( tsk );
 358         return __copy_from_user( &tsk->thread.i387.fsave, buf,
 359                                  sizeof(struct i387_fsave_struct) );
 360 }
 361
 362 static int restore_i387_fxsave( struct _fpstate __user *buf )
 363 {
 364         int err;
 365         struct task_struct *tsk = current;
 366         clear_fpu( tsk );
 367         err = __copy_from_user( &tsk->thread.i387.fxsave, &buf->_fxsr_env[0],
 368                                 sizeof(struct i387_fxsave_struct) );
 369         /* mxcsr reserved bits must be masked to zero for security reasons */
 370         tsk->thread.i387.fxsave.mxcsr &= mxcsr_feature_mask;
 371         return err ? 1 : convert_fxsr_from_user( &tsk->thread.i387.fxsave, buf );
 372 }
 373
 374 int restore_i387( struct _fpstate __user *buf )
 375 {
 376         int err;
 377
 378         if ( HAVE_HWFP ) {
 379                 if ( cpu_has_fxsr ) {
 380                         err = restore_i387_fxsave( buf );
 381                 } else {
 382                         err = restore_i387_fsave( buf );
 383                 }
 384         } else {
 385                 err = restore_i387_soft( &current->thread.i387.soft, buf );
 386         }
 387         set_used_math();
 388         return err;
 389 }
 390
 391 /*
 392  * ptrace request handlers.
 393  */
 394
 395 static inline int get_fpregs_fsave( struct user_i387_struct __user *buf,
 396                                     struct task_struct *tsk )
 397 {
 398         return __copy_to_user( buf, &tsk->thread.i387.fsave,
 399                                sizeof(struct user_i387_struct) );
 400 }
 401
 402 static inline int get_fpregs_fxsave( struct user_i387_struct __user *buf,
 403                                      struct task_struct *tsk )
 404 {
 405         return convert_fxsr_to_user( (struct _fpstate __user *)buf,
 406                                      &tsk->thread.i387.fxsave );
 407 }
 408
 409 int get_fpregs( struct user_i387_struct __user *buf, struct task_struct *tsk )
 410 {
 411         if ( HAVE_HWFP ) {
 412                 if ( cpu_has_fxsr ) {
 413                         return get_fpregs_fxsave( buf, tsk );
 414                 } else {
 415                         return get_fpregs_fsave( buf, tsk );
 416                 }
 417         } else {
 418                 return save_i387_soft( &tsk->thread.i387.soft,
 419                                        (struct _fpstate __user *)buf );
 420         }
 421 }
 422
 423 static inline int set_fpregs_fsave( struct task_struct *tsk,
 424                                     struct user_i387_struct __user *buf )
 425 {
 426         return __copy_from_user( &tsk->thread.i387.fsave, buf,
 427                                  sizeof(struct user_i387_struct) );
 428 }
 429
 430 static inline int set_fpregs_fxsave( struct task_struct *tsk,
 431                                      struct user_i387_struct __user *buf )
 432 {
 433         return convert_fxsr_from_user( &tsk->thread.i387.fxsave,
 434                                        (struct _fpstate __user *)buf );
 435 }
 436
 437 int set_fpregs( struct task_struct *tsk, struct user_i387_struct __user *buf )
 438 {
 439         if ( HAVE_HWFP ) {
 440                 if ( cpu_has_fxsr ) {
 441                         return set_fpregs_fxsave( tsk, buf );
 442                 } else {
 443                         return set_fpregs_fsave( tsk, buf );
 444                 }
 445         } else {
 446                 return restore_i387_soft( &tsk->thread.i387.soft,
 447                                           (struct _fpstate __user *)buf );
 448         }
 449 }
 450
 451 int get_fpxregs( struct user_fxsr_struct __user *buf, struct task_struct *tsk )
 452 {
 453         if ( cpu_has_fxsr ) {
 454                 if (__copy_to_user( buf, &tsk->thread.i387.fxsave,
 455                                     sizeof(struct user_fxsr_struct) ))
 456                         return -EFAULT;
 457                 return 0;
 458         } else {
 459                 return -EIO;
 460         }
 461 }
 462
 463 int set_fpxregs( struct task_struct *tsk, struct user_fxsr_struct __user *buf )
 464 {
 465         int ret = 0;
 466
 467         if ( cpu_has_fxsr ) {
 468                 if (__copy_from_user( &tsk->thread.i387.fxsave, buf,
 469                                   sizeof(struct user_fxsr_struct) ))
 470                         ret = -EFAULT;
 471                 /* mxcsr reserved bits must be masked to zero for security reasons */
 472                 tsk->thread.i387.fxsave.mxcsr &= mxcsr_feature_mask;
 473         } else {
 474                 ret = -EIO;
 475         }
 476         return ret;
 477 }
 478
 479 /*
 480  * FPU state for core dumps.
 481  */
 482
 483 static inline void copy_fpu_fsave( struct task_struct *tsk,
 484                                    struct user_i387_struct *fpu )
 485 {
 486         memcpy( fpu, &tsk->thread.i387.fsave,
 487                 sizeof(struct user_i387_struct) );
 488 }
 489
 490 static inline void copy_fpu_fxsave( struct task_struct *tsk,
 491                                    struct user_i387_struct *fpu )
 492 {
 493         unsigned short *to;
 494         unsigned short *from;
 495         int i;
 496
 497         memcpy( fpu, &tsk->thread.i387.fxsave, 7 * sizeof(long) );
 498
 499         to = (unsigned short *)&fpu->st_space[0];
 500         from = (unsigned short *)&tsk->thread.i387.fxsave.st_space[0];
 501         for ( i = 0 ; i < 8 ; i++, to += 5, from += 8 ) {
 502                 memcpy( to, from, 5 * sizeof(unsigned short) );
 503         }
 504 }
 505
 506 int dump_fpu( struct pt_regs *regs, struct user_i387_struct *fpu )
 507 {
 508         int fpvalid;
 509         struct task_struct *tsk = current;
 510
 511         fpvalid = !!used_math();
 512         if ( fpvalid ) {
 513                 unlazy_fpu( tsk );
 514                 if ( cpu_has_fxsr ) {
 515                         copy_fpu_fxsave( tsk, fpu );
 516                 } else {
 517                         copy_fpu_fsave( tsk, fpu );
 518                 }
 519         }
 520
 521         return fpvalid;
 522 }
 523
 524 int dump_task_fpu(struct task_struct *tsk, struct user_i387_struct *fpu)
 525 {
 526         int fpvalid = !!tsk_used_math(tsk);
 527
 528         if (fpvalid) {
 529                 if (tsk == current)
 530                         unlazy_fpu(tsk);
 531                 if (cpu_has_fxsr)
 532                         copy_fpu_fxsave(tsk, fpu);
 533                 else
 534                         copy_fpu_fsave(tsk, fpu);
 535         }
 536         return fpvalid;
 537 }
 538
 539 int dump_task_extended_fpu(struct task_struct *tsk, struct user_fxsr_struct *fpu)
 540 {
 541         int fpvalid = tsk_used_math(tsk) && cpu_has_fxsr;
 542
 543         if (fpvalid) {
 544                 if (tsk == current)
 545                        unlazy_fpu(tsk);
 546                 memcpy(fpu, &tsk->thread.i387.fxsave, sizeof(*fpu));
 547         }
 548         return fpvalid;
 549 }