arch/x86/kernel/i387.c

   1 /*
   2  *  Copyright (C) 1994 Linus Torvalds
   3  *
   4  *  Pentium III FXSR, SSE support
   5  *  General FPU state handling cleanups
   6  *      Gareth Hughes <gareth@valinux.com>, May 2000
   7  */
   8 #include <linux/module.h>
   9 #include <linux/regset.h>
  10 #include <linux/sched.h>
  11
  12 #include <asm/sigcontext.h>
  13 #include <asm/processor.h>
  14 #include <asm/math_emu.h>
  15 #include <asm/uaccess.h>
  16 #include <asm/ptrace.h>
  17 #include <asm/i387.h>
  18 #include <asm/user.h>
  19
  20 #ifdef CONFIG_X86_64
  21 # include <asm/sigcontext32.h>
  22 # include <asm/user32.h>
  23 #else
  24 # define save_i387_ia32         save_i387
  25 # define restore_i387_ia32      restore_i387
  26 # define _fpstate_ia32          _fpstate
  27 # define user_i387_ia32_struct  user_i387_struct
  28 # define user32_fxsr_struct     user_fxsr_struct
  29 #endif
  30
  31 #ifdef CONFIG_MATH_EMULATION
  32 # define HAVE_HWFP              (boot_cpu_data.hard_math)
  33 #else
  34 # define HAVE_HWFP              1
  35 #endif
  36
  37 static unsigned int             mxcsr_feature_mask __read_mostly = 0xffffffffu;
  38 unsigned int xstate_size;
  39 static struct i387_fxsave_struct fx_scratch __cpuinitdata;
  40
  41 void __cpuinit mxcsr_feature_mask_init(void)
  42 {
  43         unsigned long mask = 0;
  44
  45         clts();
  46         if (cpu_has_fxsr) {
  47                 memset(&fx_scratch, 0, sizeof(struct i387_fxsave_struct));
  48                 asm volatile("fxsave %0" : : "m" (fx_scratch));
  49                 mask = fx_scratch.mxcsr_mask;
  50                 if (mask == 0)
  51                         mask = 0x0000ffbf;
  52         }
  53         mxcsr_feature_mask &= mask;
  54         stts();
  55 }
  56
  57 void __init init_thread_xstate(void)
  58 {
  59         if (cpu_has_fxsr)
  60                 xstate_size = sizeof(struct i387_fxsave_struct);
  61 #ifdef CONFIG_X86_32
  62         else
  63                 xstate_size = sizeof(struct i387_fsave_struct);
  64 #endif
  65 }
  66
  67 #ifdef CONFIG_X86_64
  68 /*
  69  * Called at bootup to set up the initial FPU state that is later cloned
  70  * into all processes.
  71  */
  72 void __cpuinit fpu_init(void)
  73 {
  74         unsigned long oldcr0 = read_cr0();
  75
  76         set_in_cr4(X86_CR4_OSFXSR);
  77         set_in_cr4(X86_CR4_OSXMMEXCPT);
  78
  79         write_cr0(oldcr0 & ~(X86_CR0_TS|X86_CR0_EM)); /* clear TS and EM */
  80
  81         mxcsr_feature_mask_init();
  82         /* clean state in init */
  83         current_thread_info()->status = 0;
  84         clear_used_math();
  85 }
  86 #endif  /* CONFIG_X86_64 */
  87
  88 /*
  89  * The _current_ task is using the FPU for the first time
  90  * so initialize it and set the mxcsr to its default
  91  * value at reset if we support XMM instructions and then
  92  * remeber the current task has used the FPU.
  93  */
  94 int init_fpu(struct task_struct *tsk)
  95 {
  96         if (tsk_used_math(tsk)) {
  97                 if (tsk == current)
  98                         unlazy_fpu(tsk);
  99                 return 0;
 100         }
 101
 102         /*
 103          * Memory allocation at the first usage of the FPU and other state.
 104          */
 105         if (!tsk->thread.xstate) {
 106                 tsk->thread.xstate = kmem_cache_alloc(task_xstate_cachep,
 107                                                       GFP_KERNEL);
 108                 if (!tsk->thread.xstate)
 109                         return -ENOMEM;
 110         }
 111
 112         if (cpu_has_fxsr) {
 113                 struct i387_fxsave_struct *fx = &tsk->thread.xstate->fxsave;
 114
 115                 memset(fx, 0, xstate_size);
 116                 fx->cwd = 0x37f;
 117                 if (cpu_has_xmm)
 118                         fx->mxcsr = MXCSR_DEFAULT;
 119         } else {
 120                 struct i387_fsave_struct *fp = &tsk->thread.xstate->fsave;
 121                 memset(fp, 0, xstate_size);
 122                 fp->cwd = 0xffff037fu;
 123                 fp->swd = 0xffff0000u;
 124                 fp->twd = 0xffffffffu;
 125                 fp->fos = 0xffff0000u;
 126         }
 127         /*
 128          * Only the device not available exception or ptrace can call init_fpu.
 129          */
 130         set_stopped_child_used_math(tsk);
 131         return 0;
 132 }
 133
 134 int fpregs_active(struct task_struct *target, const struct user_regset *regset)
 135 {
 136         return tsk_used_math(target) ? regset->n : 0;
 137 }
 138
 139 int xfpregs_active(struct task_struct *target, const struct user_regset *regset)
 140 {
 141         return (cpu_has_fxsr && tsk_used_math(target)) ? regset->n : 0;
 142 }
 143
 144 int xfpregs_get(struct task_struct *target, const struct user_regset *regset,
 145                 unsigned int pos, unsigned int count,
 146                 void *kbuf, void __user *ubuf)
 147 {
 148         int ret;
 149
 150         if (!cpu_has_fxsr)
 151                 return -ENODEV;
 152
 153         ret = init_fpu(target);
 154         if (ret)
 155                 return ret;
 156
 157         return user_regset_copyout(&pos, &count, &kbuf, &ubuf,
 158                                    &target->thread.xstate->fxsave, 0, -1);
 159 }
 160
 161 int xfpregs_set(struct task_struct *target, const struct user_regset *regset,
 162                 unsigned int pos, unsigned int count,
 163                 const void *kbuf, const void __user *ubuf)
 164 {
 165         int ret;
 166
 167         if (!cpu_has_fxsr)
 168                 return -ENODEV;
 169
 170         ret = init_fpu(target);
 171         if (ret)
 172                 return ret;
 173
 174         set_stopped_child_used_math(target);
 175
 176         ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf,
 177                                  &target->thread.xstate->fxsave, 0, -1);
 178
 179         /*
 180          * mxcsr reserved bits must be masked to zero for security reasons.
 181          */
 182         target->thread.xstate->fxsave.mxcsr &= mxcsr_feature_mask;
 183
 184         return ret;
 185 }
 186
 187 #if defined CONFIG_X86_32 || defined CONFIG_IA32_EMULATION
 188
 189 /*
 190  * FPU tag word conversions.
 191  */
 192
 193 static inline unsigned short twd_i387_to_fxsr(unsigned short twd)
 194 {
 195         unsigned int tmp; /* to avoid 16 bit prefixes in the code */
 196
 197         /* Transform each pair of bits into 01 (valid) or 00 (empty) */
 198         tmp = ~twd;
 199         tmp = (tmp | (tmp>>1)) & 0x5555; /* 0V0V0V0V0V0V0V0V */
 200         /* and move the valid bits to the lower byte. */
 201         tmp = (tmp | (tmp >> 1)) & 0x3333; /* 00VV00VV00VV00VV */
 202         tmp = (tmp | (tmp >> 2)) & 0x0f0f; /* 0000VVVV0000VVVV */
 203         tmp = (tmp | (tmp >> 4)) & 0x00ff; /* 00000000VVVVVVVV */
 204
 205         return tmp;
 206 }
 207
 208 #define FPREG_ADDR(f, n)        ((void *)&(f)->st_space + (n) * 16);
 209 #define FP_EXP_TAG_VALID        0
 210 #define FP_EXP_TAG_ZERO         1
 211 #define FP_EXP_TAG_SPECIAL      2
 212 #define FP_EXP_TAG_EMPTY        3
 213
 214 static inline u32 twd_fxsr_to_i387(struct i387_fxsave_struct *fxsave)
 215 {
 216         struct _fpxreg *st;
 217         u32 tos = (fxsave->swd >> 11) & 7;
 218         u32 twd = (unsigned long) fxsave->twd;
 219         u32 tag;
 220         u32 ret = 0xffff0000u;
 221         int i;
 222
 223         for (i = 0; i < 8; i++, twd >>= 1) {
 224                 if (twd & 0x1) {
 225                         st = FPREG_ADDR(fxsave, (i - tos) & 7);
 226
 227                         switch (st->exponent & 0x7fff) {
 228                         case 0x7fff:
 229                                 tag = FP_EXP_TAG_SPECIAL;
 230                                 break;
 231                         case 0x0000:
 232                                 if (!st->significand[0] &&
 233                                     !st->significand[1] &&
 234                                     !st->significand[2] &&
 235                                     !st->significand[3])
 236                                         tag = FP_EXP_TAG_ZERO;
 237                                 else
 238                                         tag = FP_EXP_TAG_SPECIAL;
 239                                 break;
 240                         default:
 241                                 if (st->significand[3] & 0x8000)
 242                                         tag = FP_EXP_TAG_VALID;
 243                                 else
 244                                         tag = FP_EXP_TAG_SPECIAL;
 245                                 break;
 246                         }
 247                 } else {
 248                         tag = FP_EXP_TAG_EMPTY;
 249                 }
 250                 ret |= tag << (2 * i);
 251         }
 252         return ret;
 253 }
 254
 255 /*
 256  * FXSR floating point environment conversions.
 257  */
 258
 259 static void
 260 convert_from_fxsr(struct user_i387_ia32_struct *env, struct task_struct *tsk)
 261 {
 262         struct i387_fxsave_struct *fxsave = &tsk->thread.xstate->fxsave;
 263         struct _fpreg *to = (struct _fpreg *) &env->st_space[0];
 264         struct _fpxreg *from = (struct _fpxreg *) &fxsave->st_space[0];
 265         int i;
 266
 267         env->cwd = fxsave->cwd | 0xffff0000u;
 268         env->swd = fxsave->swd | 0xffff0000u;
 269         env->twd = twd_fxsr_to_i387(fxsave);
 270
 271 #ifdef CONFIG_X86_64
 272         env->fip = fxsave->rip;
 273         env->foo = fxsave->rdp;
 274         if (tsk == current) {
 275                 /*
 276                  * should be actually ds/cs at fpu exception time, but
 277                  * that information is not available in 64bit mode.
 278                  */
 279                 asm("mov %%ds, %[fos]" : [fos] "=r" (env->fos));
 280                 asm("mov %%cs, %[fcs]" : [fcs] "=r" (env->fcs));
 281         } else {
 282                 struct pt_regs *regs = task_pt_regs(tsk);
 283
 284                 env->fos = 0xffff0000 | tsk->thread.ds;
 285                 env->fcs = regs->cs;
 286         }
 287 #else
 288         env->fip = fxsave->fip;
 289         env->fcs = (u16) fxsave->fcs | ((u32) fxsave->fop << 16);
 290         env->foo = fxsave->foo;
 291         env->fos = fxsave->fos;
 292 #endif
 293
 294         for (i = 0; i < 8; ++i)
 295                 memcpy(&to[i], &from[i], sizeof(to[0]));
 296 }
 297
 298 static void convert_to_fxsr(struct task_struct *tsk,
 299                             const struct user_i387_ia32_struct *env)
 300
 301 {
 302         struct i387_fxsave_struct *fxsave = &tsk->thread.xstate->fxsave;
 303         struct _fpreg *from = (struct _fpreg *) &env->st_space[0];
 304         struct _fpxreg *to = (struct _fpxreg *) &fxsave->st_space[0];
 305         int i;
 306
 307         fxsave->cwd = env->cwd;
 308         fxsave->swd = env->swd;
 309         fxsave->twd = twd_i387_to_fxsr(env->twd);
 310         fxsave->fop = (u16) ((u32) env->fcs >> 16);
 311 #ifdef CONFIG_X86_64
 312         fxsave->rip = env->fip;
 313         fxsave->rdp = env->foo;
 314         /* cs and ds ignored */
 315 #else
 316         fxsave->fip = env->fip;
 317         fxsave->fcs = (env->fcs & 0xffff);
 318         fxsave->foo = env->foo;
 319         fxsave->fos = env->fos;
 320 #endif
 321
 322         for (i = 0; i < 8; ++i)
 323                 memcpy(&to[i], &from[i], sizeof(from[0]));
 324 }
 325
 326 int fpregs_get(struct task_struct *target, const struct user_regset *regset,
 327                unsigned int pos, unsigned int count,
 328                void *kbuf, void __user *ubuf)
 329 {
 330         struct user_i387_ia32_struct env;
 331         int ret;
 332
 333         if (!HAVE_HWFP)
 334                 return fpregs_soft_get(target, regset, pos, count, kbuf, ubuf);
 335
 336         ret = init_fpu(target);
 337         if (ret)
 338                 return ret;
 339
 340         if (!cpu_has_fxsr) {
 341                 return user_regset_copyout(&pos, &count, &kbuf, &ubuf,
 342                                            &target->thread.xstate->fsave, 0,
 343                                            -1);
 344         }
 345
 346         if (kbuf && pos == 0 && count == sizeof(env)) {
 347                 convert_from_fxsr(kbuf, target);
 348                 return 0;
 349         }
 350
 351         convert_from_fxsr(&env, target);
 352
 353         return user_regset_copyout(&pos, &count, &kbuf, &ubuf, &env, 0, -1);
 354 }
 355
 356 int fpregs_set(struct task_struct *target, const struct user_regset *regset,
 357                unsigned int pos, unsigned int count,
 358                const void *kbuf, const void __user *ubuf)
 359 {
 360         struct user_i387_ia32_struct env;
 361         int ret;
 362
 363         if (!HAVE_HWFP)
 364                 return fpregs_soft_set(target, regset, pos, count, kbuf, ubuf);
 365
 366         ret = init_fpu(target);
 367         if (ret)
 368                 return ret;
 369
 370         set_stopped_child_used_math(target);
 371
 372         if (!cpu_has_fxsr) {
 373                 return user_regset_copyin(&pos, &count, &kbuf, &ubuf,
 374                                           &target->thread.xstate->fsave, 0, -1);
 375         }
 376
 377         if (pos > 0 || count < sizeof(env))
 378                 convert_from_fxsr(&env, target);
 379
 380         ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, &env, 0, -1);
 381         if (!ret)
 382                 convert_to_fxsr(target, &env);
 383
 384         return ret;
 385 }
 386
 387 /*
 388  * Signal frame handlers.
 389  */
 390
 391 static inline int save_i387_fsave(struct _fpstate_ia32 __user *buf)
 392 {
 393         struct task_struct *tsk = current;
 394         struct i387_fsave_struct *fp = &tsk->thread.xstate->fsave;
 395
 396         unlazy_fpu(tsk);
 397         fp->status = fp->swd;
 398         if (__copy_to_user(buf, fp, sizeof(struct i387_fsave_struct)))
 399                 return -1;
 400         return 1;
 401 }
 402
 403 static int save_i387_fxsave(struct _fpstate_ia32 __user *buf)
 404 {
 405         struct task_struct *tsk = current;
 406         struct i387_fxsave_struct *fx = &tsk->thread.xstate->fxsave;
 407         struct user_i387_ia32_struct env;
 408         int err = 0;
 409
 410         unlazy_fpu(tsk);
 411
 412         convert_from_fxsr(&env, tsk);
 413         if (__copy_to_user(buf, &env, sizeof(env)))
 414                 return -1;
 415
 416         err |= __put_user(fx->swd, &buf->status);
 417         err |= __put_user(X86_FXSR_MAGIC, &buf->magic);
 418         if (err)
 419                 return -1;
 420
 421         if (__copy_to_user(&buf->_fxsr_env[0], fx,
 422                            sizeof(struct i387_fxsave_struct)))
 423                 return -1;
 424         return 1;
 425 }
 426
 427 int save_i387_ia32(struct _fpstate_ia32 __user *buf)
 428 {
 429         if (!used_math())
 430                 return 0;
 431         /*
 432          * This will cause a "finit" to be triggered by the next
 433          * attempted FPU operation by the 'current' process.
 434          */
 435         clear_used_math();
 436
 437         if (!HAVE_HWFP) {
 438                 return fpregs_soft_get(current, NULL,
 439                                        0, sizeof(struct user_i387_ia32_struct),
 440                                        NULL, buf) ? -1 : 1;
 441         }
 442
 443         if (cpu_has_fxsr)
 444                 return save_i387_fxsave(buf);
 445         else
 446                 return save_i387_fsave(buf);
 447 }
 448
 449 static inline int restore_i387_fsave(struct _fpstate_ia32 __user *buf)
 450 {
 451         struct task_struct *tsk = current;
 452
 453         return __copy_from_user(&tsk->thread.xstate->fsave, buf,
 454                                 sizeof(struct i387_fsave_struct));
 455 }
 456
 457 static int restore_i387_fxsave(struct _fpstate_ia32 __user *buf)
 458 {
 459         struct task_struct *tsk = current;
 460         struct user_i387_ia32_struct env;
 461         int err;
 462
 463         err = __copy_from_user(&tsk->thread.xstate->fxsave, &buf->_fxsr_env[0],
 464                                sizeof(struct i387_fxsave_struct));
 465         /* mxcsr reserved bits must be masked to zero for security reasons */
 466         tsk->thread.xstate->fxsave.mxcsr &= mxcsr_feature_mask;
 467         if (err || __copy_from_user(&env, buf, sizeof(env)))
 468                 return 1;
 469         convert_to_fxsr(tsk, &env);
 470
 471         return 0;
 472 }
 473
 474 int restore_i387_ia32(struct _fpstate_ia32 __user *buf)
 475 {
 476         int err;
 477
 478         if (HAVE_HWFP) {
 479                 struct task_struct *tsk = current;
 480
 481                 clear_fpu(tsk);
 482
 483                 if (!used_math()) {
 484                         err = init_fpu(tsk);
 485                         if (err)
 486                                 return err;
 487                 }
 488
 489                 if (cpu_has_fxsr)
 490                         err = restore_i387_fxsave(buf);
 491                 else
 492                         err = restore_i387_fsave(buf);
 493         } else {
 494                 err = fpregs_soft_set(current, NULL,
 495                                       0, sizeof(struct user_i387_ia32_struct),
 496                                       NULL, buf) != 0;
 497         }
 498         set_used_math();
 499
 500         return err;
 501 }
 502
 503 /*
 504  * FPU state for core dumps.
 505  * This is only used for a.out dumps now.
 506  * It is declared generically using elf_fpregset_t (which is
 507  * struct user_i387_struct) but is in fact only used for 32-bit
 508  * dumps, so on 64-bit it is really struct user_i387_ia32_struct.
 509  */
 510 int dump_fpu(struct pt_regs *regs, struct user_i387_struct *fpu)
 511 {
 512         struct task_struct *tsk = current;
 513         int fpvalid;
 514
 515         fpvalid = !!used_math();
 516         if (fpvalid)
 517                 fpvalid = !fpregs_get(tsk, NULL,
 518                                       0, sizeof(struct user_i387_ia32_struct),
 519                                       fpu, NULL);
 520
 521         return fpvalid;
 522 }
 523 EXPORT_SYMBOL(dump_fpu);
 524
 525 #endif  /* CONFIG_X86_32 || CONFIG_IA32_EMULATION */