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 (!HAVE_HWFP) {
  60                 xstate_size = sizeof(struct i387_soft_struct);
  61                 return;
  62         }
  63
  64         if (cpu_has_fxsr)
  65                 xstate_size = sizeof(struct i387_fxsave_struct);
  66 #ifdef CONFIG_X86_32
  67         else
  68                 xstate_size = sizeof(struct i387_fsave_struct);
  69 #endif
  70 }
  71
  72 #ifdef CONFIG_X86_64
  73 /*
  74  * Called at bootup to set up the initial FPU state that is later cloned
  75  * into all processes.
  76  */
  77 void __cpuinit fpu_init(void)
  78 {
  79         unsigned long oldcr0 = read_cr0();
  80
  81         set_in_cr4(X86_CR4_OSFXSR);
  82         set_in_cr4(X86_CR4_OSXMMEXCPT);
  83
  84         write_cr0(oldcr0 & ~(X86_CR0_TS|X86_CR0_EM)); /* clear TS and EM */
  85
  86         mxcsr_feature_mask_init();
  87         /* clean state in init */
  88         current_thread_info()->status = 0;
  89         clear_used_math();
  90 }
  91 #endif  /* CONFIG_X86_64 */
  92
  93 /*
  94  * The _current_ task is using the FPU for the first time
  95  * so initialize it and set the mxcsr to its default
  96  * value at reset if we support XMM instructions and then
  97  * remeber the current task has used the FPU.
  98  */
  99 int init_fpu(struct task_struct *tsk)
 100 {
 101         if (tsk_used_math(tsk)) {
 102                 if (HAVE_HWFP && tsk == current)
 103                         unlazy_fpu(tsk);
 104                 return 0;
 105         }
 106
 107         /*
 108          * Memory allocation at the first usage of the FPU and other state.
 109          */
 110         if (!tsk->thread.xstate) {
 111                 tsk->thread.xstate = kmem_cache_alloc(task_xstate_cachep,
 112                                                       GFP_KERNEL);
 113                 if (!tsk->thread.xstate)
 114                         return -ENOMEM;
 115         }
 116
 117 #ifdef CONFIG_X86_32
 118         if (!HAVE_HWFP) {
 119                 memset(tsk->thread.xstate, 0, xstate_size);
 120                 finit();
 121                 set_stopped_child_used_math(tsk);
 122                 return 0;
 123         }
 124 #endif
 125
 126         if (cpu_has_fxsr) {
 127                 struct i387_fxsave_struct *fx = &tsk->thread.xstate->fxsave;
 128
 129                 memset(fx, 0, xstate_size);
 130                 fx->cwd = 0x37f;
 131                 if (cpu_has_xmm)
 132                         fx->mxcsr = MXCSR_DEFAULT;
 133         } else {
 134                 struct i387_fsave_struct *fp = &tsk->thread.xstate->fsave;
 135                 memset(fp, 0, xstate_size);
 136                 fp->cwd = 0xffff037fu;
 137                 fp->swd = 0xffff0000u;
 138                 fp->twd = 0xffffffffu;
 139                 fp->fos = 0xffff0000u;
 140         }
 141         /*
 142          * Only the device not available exception or ptrace can call init_fpu.
 143          */
 144         set_stopped_child_used_math(tsk);
 145         return 0;
 146 }
 147
 148 int fpregs_active(struct task_struct *target, const struct user_regset *regset)
 149 {
 150         return tsk_used_math(target) ? regset->n : 0;
 151 }
 152
 153 int xfpregs_active(struct task_struct *target, const struct user_regset *regset)
 154 {
 155         return (cpu_has_fxsr && tsk_used_math(target)) ? regset->n : 0;
 156 }
 157
 158 int xfpregs_get(struct task_struct *target, const struct user_regset *regset,
 159                 unsigned int pos, unsigned int count,
 160                 void *kbuf, void __user *ubuf)
 161 {
 162         int ret;
 163
 164         if (!cpu_has_fxsr)
 165                 return -ENODEV;
 166
 167         ret = init_fpu(target);
 168         if (ret)
 169                 return ret;
 170
 171         return user_regset_copyout(&pos, &count, &kbuf, &ubuf,
 172                                    &target->thread.xstate->fxsave, 0, -1);
 173 }
 174
 175 int xfpregs_set(struct task_struct *target, const struct user_regset *regset,
 176                 unsigned int pos, unsigned int count,
 177                 const void *kbuf, const void __user *ubuf)
 178 {
 179         int ret;
 180
 181         if (!cpu_has_fxsr)
 182                 return -ENODEV;
 183
 184         ret = init_fpu(target);
 185         if (ret)
 186                 return ret;
 187
 188         set_stopped_child_used_math(target);
 189
 190         ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf,
 191                                  &target->thread.xstate->fxsave, 0, -1);
 192
 193         /*
 194          * mxcsr reserved bits must be masked to zero for security reasons.
 195          */
 196         target->thread.xstate->fxsave.mxcsr &= mxcsr_feature_mask;
 197
 198         return ret;
 199 }
 200
 201 #if defined CONFIG_X86_32 || defined CONFIG_IA32_EMULATION
 202
 203 /*
 204  * FPU tag word conversions.
 205  */
 206
 207 static inline unsigned short twd_i387_to_fxsr(unsigned short twd)
 208 {
 209         unsigned int tmp; /* to avoid 16 bit prefixes in the code */
 210
 211         /* Transform each pair of bits into 01 (valid) or 00 (empty) */
 212         tmp = ~twd;
 213         tmp = (tmp | (tmp>>1)) & 0x5555; /* 0V0V0V0V0V0V0V0V */
 214         /* and move the valid bits to the lower byte. */
 215         tmp = (tmp | (tmp >> 1)) & 0x3333; /* 00VV00VV00VV00VV */
 216         tmp = (tmp | (tmp >> 2)) & 0x0f0f; /* 0000VVVV0000VVVV */
 217         tmp = (tmp | (tmp >> 4)) & 0x00ff; /* 00000000VVVVVVVV */
 218
 219         return tmp;
 220 }
 221
 222 #define FPREG_ADDR(f, n)        ((void *)&(f)->st_space + (n) * 16);
 223 #define FP_EXP_TAG_VALID        0
 224 #define FP_EXP_TAG_ZERO         1
 225 #define FP_EXP_TAG_SPECIAL      2
 226 #define FP_EXP_TAG_EMPTY        3
 227
 228 static inline u32 twd_fxsr_to_i387(struct i387_fxsave_struct *fxsave)
 229 {
 230         struct _fpxreg *st;
 231         u32 tos = (fxsave->swd >> 11) & 7;
 232         u32 twd = (unsigned long) fxsave->twd;
 233         u32 tag;
 234         u32 ret = 0xffff0000u;
 235         int i;
 236
 237         for (i = 0; i < 8; i++, twd >>= 1) {
 238                 if (twd & 0x1) {
 239                         st = FPREG_ADDR(fxsave, (i - tos) & 7);
 240
 241                         switch (st->exponent & 0x7fff) {
 242                         case 0x7fff:
 243                                 tag = FP_EXP_TAG_SPECIAL;
 244                                 break;
 245                         case 0x0000:
 246                                 if (!st->significand[0] &&
 247                                     !st->significand[1] &&
 248                                     !st->significand[2] &&
 249                                     !st->significand[3])
 250                                         tag = FP_EXP_TAG_ZERO;
 251                                 else
 252                                         tag = FP_EXP_TAG_SPECIAL;
 253                                 break;
 254                         default:
 255                                 if (st->significand[3] & 0x8000)
 256                                         tag = FP_EXP_TAG_VALID;
 257                                 else
 258                                         tag = FP_EXP_TAG_SPECIAL;
 259                                 break;
 260                         }
 261                 } else {
 262                         tag = FP_EXP_TAG_EMPTY;
 263                 }
 264                 ret |= tag << (2 * i);
 265         }
 266         return ret;
 267 }
 268
 269 /*
 270  * FXSR floating point environment conversions.
 271  */
 272
 273 static void
 274 convert_from_fxsr(struct user_i387_ia32_struct *env, struct task_struct *tsk)
 275 {
 276         struct i387_fxsave_struct *fxsave = &tsk->thread.xstate->fxsave;
 277         struct _fpreg *to = (struct _fpreg *) &env->st_space[0];
 278         struct _fpxreg *from = (struct _fpxreg *) &fxsave->st_space[0];
 279         int i;
 280
 281         env->cwd = fxsave->cwd | 0xffff0000u;
 282         env->swd = fxsave->swd | 0xffff0000u;
 283         env->twd = twd_fxsr_to_i387(fxsave);
 284
 285 #ifdef CONFIG_X86_64
 286         env->fip = fxsave->rip;
 287         env->foo = fxsave->rdp;
 288         if (tsk == current) {
 289                 /*
 290                  * should be actually ds/cs at fpu exception time, but
 291                  * that information is not available in 64bit mode.
 292                  */
 293                 asm("mov %%ds, %[fos]" : [fos] "=r" (env->fos));
 294                 asm("mov %%cs, %[fcs]" : [fcs] "=r" (env->fcs));
 295         } else {
 296                 struct pt_regs *regs = task_pt_regs(tsk);
 297
 298                 env->fos = 0xffff0000 | tsk->thread.ds;
 299                 env->fcs = regs->cs;
 300         }
 301 #else
 302         env->fip = fxsave->fip;
 303         env->fcs = (u16) fxsave->fcs | ((u32) fxsave->fop << 16);
 304         env->foo = fxsave->foo;
 305         env->fos = fxsave->fos;
 306 #endif
 307
 308         for (i = 0; i < 8; ++i)
 309                 memcpy(&to[i], &from[i], sizeof(to[0]));
 310 }
 311
 312 static void convert_to_fxsr(struct task_struct *tsk,
 313                             const struct user_i387_ia32_struct *env)
 314
 315 {
 316         struct i387_fxsave_struct *fxsave = &tsk->thread.xstate->fxsave;
 317         struct _fpreg *from = (struct _fpreg *) &env->st_space[0];
 318         struct _fpxreg *to = (struct _fpxreg *) &fxsave->st_space[0];
 319         int i;
 320
 321         fxsave->cwd = env->cwd;
 322         fxsave->swd = env->swd;
 323         fxsave->twd = twd_i387_to_fxsr(env->twd);
 324         fxsave->fop = (u16) ((u32) env->fcs >> 16);
 325 #ifdef CONFIG_X86_64
 326         fxsave->rip = env->fip;
 327         fxsave->rdp = env->foo;
 328         /* cs and ds ignored */
 329 #else
 330         fxsave->fip = env->fip;
 331         fxsave->fcs = (env->fcs & 0xffff);
 332         fxsave->foo = env->foo;
 333         fxsave->fos = env->fos;
 334 #endif
 335
 336         for (i = 0; i < 8; ++i)
 337                 memcpy(&to[i], &from[i], sizeof(from[0]));
 338 }
 339
 340 int fpregs_get(struct task_struct *target, const struct user_regset *regset,
 341                unsigned int pos, unsigned int count,
 342                void *kbuf, void __user *ubuf)
 343 {
 344         struct user_i387_ia32_struct env;
 345         int ret;
 346
 347         ret = init_fpu(target);
 348         if (ret)
 349                 return ret;
 350
 351         if (!HAVE_HWFP)
 352                 return fpregs_soft_get(target, regset, pos, count, kbuf, ubuf);
 353
 354         if (!cpu_has_fxsr) {
 355                 return user_regset_copyout(&pos, &count, &kbuf, &ubuf,
 356                                            &target->thread.xstate->fsave, 0,
 357                                            -1);
 358         }
 359
 360         if (kbuf && pos == 0 && count == sizeof(env)) {
 361                 convert_from_fxsr(kbuf, target);
 362                 return 0;
 363         }
 364
 365         convert_from_fxsr(&env, target);
 366
 367         return user_regset_copyout(&pos, &count, &kbuf, &ubuf, &env, 0, -1);
 368 }
 369
 370 int fpregs_set(struct task_struct *target, const struct user_regset *regset,
 371                unsigned int pos, unsigned int count,
 372                const void *kbuf, const void __user *ubuf)
 373 {
 374         struct user_i387_ia32_struct env;
 375         int ret;
 376
 377         ret = init_fpu(target);
 378         if (ret)
 379                 return ret;
 380
 381         set_stopped_child_used_math(target);
 382
 383         if (!HAVE_HWFP)
 384                 return fpregs_soft_set(target, regset, pos, count, kbuf, ubuf);
 385
 386         if (!cpu_has_fxsr) {
 387                 return user_regset_copyin(&pos, &count, &kbuf, &ubuf,
 388                                           &target->thread.xstate->fsave, 0, -1);
 389         }
 390
 391         if (pos > 0 || count < sizeof(env))
 392                 convert_from_fxsr(&env, target);
 393
 394         ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, &env, 0, -1);
 395         if (!ret)
 396                 convert_to_fxsr(target, &env);
 397
 398         return ret;
 399 }
 400
 401 /*
 402  * Signal frame handlers.
 403  */
 404
 405 static inline int save_i387_fsave(struct _fpstate_ia32 __user *buf)
 406 {
 407         struct task_struct *tsk = current;
 408         struct i387_fsave_struct *fp = &tsk->thread.xstate->fsave;
 409
 410         unlazy_fpu(tsk);
 411         fp->status = fp->swd;
 412         if (__copy_to_user(buf, fp, sizeof(struct i387_fsave_struct)))
 413                 return -1;
 414         return 1;
 415 }
 416
 417 static int save_i387_fxsave(struct _fpstate_ia32 __user *buf)
 418 {
 419         struct task_struct *tsk = current;
 420         struct i387_fxsave_struct *fx = &tsk->thread.xstate->fxsave;
 421         struct user_i387_ia32_struct env;
 422         int err = 0;
 423
 424         unlazy_fpu(tsk);
 425
 426         convert_from_fxsr(&env, tsk);
 427         if (__copy_to_user(buf, &env, sizeof(env)))
 428                 return -1;
 429
 430         err |= __put_user(fx->swd, &buf->status);
 431         err |= __put_user(X86_FXSR_MAGIC, &buf->magic);
 432         if (err)
 433                 return -1;
 434
 435         if (__copy_to_user(&buf->_fxsr_env[0], fx,
 436                            sizeof(struct i387_fxsave_struct)))
 437                 return -1;
 438         return 1;
 439 }
 440
 441 int save_i387_ia32(struct _fpstate_ia32 __user *buf)
 442 {
 443         if (!used_math())
 444                 return 0;
 445         /*
 446          * This will cause a "finit" to be triggered by the next
 447          * attempted FPU operation by the 'current' process.
 448          */
 449         clear_used_math();
 450
 451         if (!HAVE_HWFP) {
 452                 return fpregs_soft_get(current, NULL,
 453                                        0, sizeof(struct user_i387_ia32_struct),
 454                                        NULL, buf) ? -1 : 1;
 455         }
 456
 457         if (cpu_has_fxsr)
 458                 return save_i387_fxsave(buf);
 459         else
 460                 return save_i387_fsave(buf);
 461 }
 462
 463 static inline int restore_i387_fsave(struct _fpstate_ia32 __user *buf)
 464 {
 465         struct task_struct *tsk = current;
 466
 467         return __copy_from_user(&tsk->thread.xstate->fsave, buf,
 468                                 sizeof(struct i387_fsave_struct));
 469 }
 470
 471 static int restore_i387_fxsave(struct _fpstate_ia32 __user *buf)
 472 {
 473         struct task_struct *tsk = current;
 474         struct user_i387_ia32_struct env;
 475         int err;
 476
 477         err = __copy_from_user(&tsk->thread.xstate->fxsave, &buf->_fxsr_env[0],
 478                                sizeof(struct i387_fxsave_struct));
 479         /* mxcsr reserved bits must be masked to zero for security reasons */
 480         tsk->thread.xstate->fxsave.mxcsr &= mxcsr_feature_mask;
 481         if (err || __copy_from_user(&env, buf, sizeof(env)))
 482                 return 1;
 483         convert_to_fxsr(tsk, &env);
 484
 485         return 0;
 486 }
 487
 488 int restore_i387_ia32(struct _fpstate_ia32 __user *buf)
 489 {
 490         int err;
 491         struct task_struct *tsk = current;
 492
 493         if (HAVE_HWFP)
 494                 clear_fpu(tsk);
 495
 496         if (!used_math()) {
 497                 err = init_fpu(tsk);
 498                 if (err)
 499                         return err;
 500         }
 501
 502         if (HAVE_HWFP) {
 503                 if (cpu_has_fxsr)
 504                         err = restore_i387_fxsave(buf);
 505                 else
 506                         err = restore_i387_fsave(buf);
 507         } else {
 508                 err = fpregs_soft_set(current, NULL,
 509                                       0, sizeof(struct user_i387_ia32_struct),
 510                                       NULL, buf) != 0;
 511         }
 512         set_used_math();
 513
 514         return err;
 515 }
 516
 517 /*
 518  * FPU state for core dumps.
 519  * This is only used for a.out dumps now.
 520  * It is declared generically using elf_fpregset_t (which is
 521  * struct user_i387_struct) but is in fact only used for 32-bit
 522  * dumps, so on 64-bit it is really struct user_i387_ia32_struct.
 523  */
 524 int dump_fpu(struct pt_regs *regs, struct user_i387_struct *fpu)
 525 {
 526         struct task_struct *tsk = current;
 527         int fpvalid;
 528
 529         fpvalid = !!used_math();
 530         if (fpvalid)
 531                 fpvalid = !fpregs_get(tsk, NULL,
 532                                       0, sizeof(struct user_i387_ia32_struct),
 533                                       fpu, NULL);
 534
 535         return fpvalid;
 536 }
 537 EXPORT_SYMBOL(dump_fpu);
 538
 539 #endif  /* CONFIG_X86_32 || CONFIG_IA32_EMULATION */