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 #include <linux/slab.h>
  12
  13 #include <asm/sigcontext.h>
  14 #include <asm/processor.h>
  15 #include <asm/math_emu.h>
  16 #include <asm/uaccess.h>
  17 #include <asm/ptrace.h>
  18 #include <asm/i387.h>
  19 #include <asm/user.h>
  20
  21 #ifdef CONFIG_X86_64
  22 # include <asm/sigcontext32.h>
  23 # include <asm/user32.h>
  24 #else
  25 # define save_i387_xstate_ia32          save_i387_xstate
  26 # define restore_i387_xstate_ia32       restore_i387_xstate
  27 # define _fpstate_ia32          _fpstate
  28 # define _xstate_ia32           _xstate
  29 # define sig_xstate_ia32_size   sig_xstate_size
  30 # define fx_sw_reserved_ia32    fx_sw_reserved
  31 # define user_i387_ia32_struct  user_i387_struct
  32 # define user32_fxsr_struct     user_fxsr_struct
  33 #endif
  34
  35 #ifdef CONFIG_MATH_EMULATION
  36 # define HAVE_HWFP              (boot_cpu_data.hard_math)
  37 #else
  38 # define HAVE_HWFP              1
  39 #endif
  40
  41 static unsigned int             mxcsr_feature_mask __read_mostly = 0xffffffffu;
  42 unsigned int xstate_size;
  43 EXPORT_SYMBOL_GPL(xstate_size);
  44 unsigned int sig_xstate_ia32_size = sizeof(struct _fpstate_ia32);
  45 static struct i387_fxsave_struct fx_scratch __cpuinitdata;
  46
  47 void __cpuinit mxcsr_feature_mask_init(void)
  48 {
  49         unsigned long mask = 0;
  50
  51         clts();
  52         if (cpu_has_fxsr) {
  53                 memset(&fx_scratch, 0, sizeof(struct i387_fxsave_struct));
  54                 asm volatile("fxsave %0" : : "m" (fx_scratch));
  55                 mask = fx_scratch.mxcsr_mask;
  56                 if (mask == 0)
  57                         mask = 0x0000ffbf;
  58         }
  59         mxcsr_feature_mask &= mask;
  60         stts();
  61 }
  62
  63 static void __cpuinit init_thread_xstate(void)
  64 {
  65         /*
  66          * Note that xstate_size might be overwriten later during
  67          * xsave_init().
  68          */
  69
  70         if (!HAVE_HWFP) {
  71                 xstate_size = sizeof(struct i387_soft_struct);
  72                 return;
  73         }
  74
  75         if (cpu_has_fxsr)
  76                 xstate_size = sizeof(struct i387_fxsave_struct);
  77 #ifdef CONFIG_X86_32
  78         else
  79                 xstate_size = sizeof(struct i387_fsave_struct);
  80 #endif
  81 }
  82
  83 #ifdef CONFIG_X86_64
  84 /*
  85  * Called at bootup to set up the initial FPU state that is later cloned
  86  * into all processes.
  87  */
  88
  89 void __cpuinit fpu_init(void)
  90 {
  91         unsigned long oldcr0 = read_cr0();
  92
  93         set_in_cr4(X86_CR4_OSFXSR);
  94         set_in_cr4(X86_CR4_OSXMMEXCPT);
  95
  96         write_cr0(oldcr0 & ~(X86_CR0_TS|X86_CR0_EM)); /* clear TS and EM */
  97
  98         if (!smp_processor_id())
  99                 init_thread_xstate();
 100
 101         mxcsr_feature_mask_init();
 102         /* clean state in init */
 103         current_thread_info()->status = 0;
 104         clear_used_math();
 105 }
 106
 107 #else   /* CONFIG_X86_64 */
 108
 109 void __cpuinit fpu_init(void)
 110 {
 111         if (!smp_processor_id())
 112                 init_thread_xstate();
 113 }
 114
 115 #endif  /* CONFIG_X86_32 */
 116
 117 void fpu_finit(struct fpu *fpu)
 118 {
 119 #ifdef CONFIG_X86_32
 120         if (!HAVE_HWFP) {
 121                 finit_soft_fpu(&fpu->state->soft);
 122                 return;
 123         }
 124 #endif
 125
 126         if (cpu_has_fxsr) {
 127                 struct i387_fxsave_struct *fx = &fpu->state->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 = &fpu->state->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 EXPORT_SYMBOL_GPL(fpu_finit);
 143
 144 /*
 145  * The _current_ task is using the FPU for the first time
 146  * so initialize it and set the mxcsr to its default
 147  * value at reset if we support XMM instructions and then
 148  * remeber the current task has used the FPU.
 149  */
 150 int init_fpu(struct task_struct *tsk)
 151 {
 152         int ret;
 153
 154         if (tsk_used_math(tsk)) {
 155                 if (HAVE_HWFP && tsk == current)
 156                         unlazy_fpu(tsk);
 157                 return 0;
 158         }
 159
 160         /*
 161          * Memory allocation at the first usage of the FPU and other state.
 162          */
 163         ret = fpu_alloc(&tsk->thread.fpu);
 164         if (ret)
 165                 return ret;
 166
 167         fpu_finit(&tsk->thread.fpu);
 168
 169         set_stopped_child_used_math(tsk);
 170         return 0;
 171 }
 172
 173 /*
 174  * The xstateregs_active() routine is the same as the fpregs_active() routine,
 175  * as the "regset->n" for the xstate regset will be updated based on the feature
 176  * capabilites supported by the xsave.
 177  */
 178 int fpregs_active(struct task_struct *target, const struct user_regset *regset)
 179 {
 180         return tsk_used_math(target) ? regset->n : 0;
 181 }
 182
 183 int xfpregs_active(struct task_struct *target, const struct user_regset *regset)
 184 {
 185         return (cpu_has_fxsr && tsk_used_math(target)) ? regset->n : 0;
 186 }
 187
 188 int xfpregs_get(struct task_struct *target, const struct user_regset *regset,
 189                 unsigned int pos, unsigned int count,
 190                 void *kbuf, void __user *ubuf)
 191 {
 192         int ret;
 193
 194         if (!cpu_has_fxsr)
 195                 return -ENODEV;
 196
 197         ret = init_fpu(target);
 198         if (ret)
 199                 return ret;
 200
 201         sanitize_i387_state(target);
 202
 203         return user_regset_copyout(&pos, &count, &kbuf, &ubuf,
 204                                    &target->thread.fpu.state->fxsave, 0, -1);
 205 }
 206
 207 int xfpregs_set(struct task_struct *target, const struct user_regset *regset,
 208                 unsigned int pos, unsigned int count,
 209                 const void *kbuf, const void __user *ubuf)
 210 {
 211         int ret;
 212
 213         if (!cpu_has_fxsr)
 214                 return -ENODEV;
 215
 216         ret = init_fpu(target);
 217         if (ret)
 218                 return ret;
 219
 220         sanitize_i387_state(target);
 221
 222         ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf,
 223                                  &target->thread.fpu.state->fxsave, 0, -1);
 224
 225         /*
 226          * mxcsr reserved bits must be masked to zero for security reasons.
 227          */
 228         target->thread.fpu.state->fxsave.mxcsr &= mxcsr_feature_mask;
 229
 230         /*
 231          * update the header bits in the xsave header, indicating the
 232          * presence of FP and SSE state.
 233          */
 234         if (cpu_has_xsave)
 235                 target->thread.fpu.state->xsave.xsave_hdr.xstate_bv |= XSTATE_FPSSE;
 236
 237         return ret;
 238 }
 239
 240 int xstateregs_get(struct task_struct *target, const struct user_regset *regset,
 241                 unsigned int pos, unsigned int count,
 242                 void *kbuf, void __user *ubuf)
 243 {
 244         int ret;
 245
 246         if (!cpu_has_xsave)
 247                 return -ENODEV;
 248
 249         ret = init_fpu(target);
 250         if (ret)
 251                 return ret;
 252
 253         /*
 254          * Copy the 48bytes defined by the software first into the xstate
 255          * memory layout in the thread struct, so that we can copy the entire
 256          * xstateregs to the user using one user_regset_copyout().
 257          */
 258         memcpy(&target->thread.fpu.state->fxsave.sw_reserved,
 259                xstate_fx_sw_bytes, sizeof(xstate_fx_sw_bytes));
 260
 261         /*
 262          * Copy the xstate memory layout.
 263          */
 264         ret = user_regset_copyout(&pos, &count, &kbuf, &ubuf,
 265                                   &target->thread.fpu.state->xsave, 0, -1);
 266         return ret;
 267 }
 268
 269 int xstateregs_set(struct task_struct *target, const struct user_regset *regset,
 270                   unsigned int pos, unsigned int count,
 271                   const void *kbuf, const void __user *ubuf)
 272 {
 273         int ret;
 274         struct xsave_hdr_struct *xsave_hdr;
 275
 276         if (!cpu_has_xsave)
 277                 return -ENODEV;
 278
 279         ret = init_fpu(target);
 280         if (ret)
 281                 return ret;
 282
 283         ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf,
 284                                  &target->thread.fpu.state->xsave, 0, -1);
 285
 286         /*
 287          * mxcsr reserved bits must be masked to zero for security reasons.
 288          */
 289         target->thread.fpu.state->fxsave.mxcsr &= mxcsr_feature_mask;
 290
 291         xsave_hdr = &target->thread.fpu.state->xsave.xsave_hdr;
 292
 293         xsave_hdr->xstate_bv &= pcntxt_mask;
 294         /*
 295          * These bits must be zero.
 296          */
 297         xsave_hdr->reserved1[0] = xsave_hdr->reserved1[1] = 0;
 298
 299         return ret;
 300 }
 301
 302 #if defined CONFIG_X86_32 || defined CONFIG_IA32_EMULATION
 303
 304 /*
 305  * FPU tag word conversions.
 306  */
 307
 308 static inline unsigned short twd_i387_to_fxsr(unsigned short twd)
 309 {
 310         unsigned int tmp; /* to avoid 16 bit prefixes in the code */
 311
 312         /* Transform each pair of bits into 01 (valid) or 00 (empty) */
 313         tmp = ~twd;
 314         tmp = (tmp | (tmp>>1)) & 0x5555; /* 0V0V0V0V0V0V0V0V */
 315         /* and move the valid bits to the lower byte. */
 316         tmp = (tmp | (tmp >> 1)) & 0x3333; /* 00VV00VV00VV00VV */
 317         tmp = (tmp | (tmp >> 2)) & 0x0f0f; /* 0000VVVV0000VVVV */
 318         tmp = (tmp | (tmp >> 4)) & 0x00ff; /* 00000000VVVVVVVV */
 319
 320         return tmp;
 321 }
 322
 323 #define FPREG_ADDR(f, n)        ((void *)&(f)->st_space + (n) * 16);
 324 #define FP_EXP_TAG_VALID        0
 325 #define FP_EXP_TAG_ZERO         1
 326 #define FP_EXP_TAG_SPECIAL      2
 327 #define FP_EXP_TAG_EMPTY        3
 328
 329 static inline u32 twd_fxsr_to_i387(struct i387_fxsave_struct *fxsave)
 330 {
 331         struct _fpxreg *st;
 332         u32 tos = (fxsave->swd >> 11) & 7;
 333         u32 twd = (unsigned long) fxsave->twd;
 334         u32 tag;
 335         u32 ret = 0xffff0000u;
 336         int i;
 337
 338         for (i = 0; i < 8; i++, twd >>= 1) {
 339                 if (twd & 0x1) {
 340                         st = FPREG_ADDR(fxsave, (i - tos) & 7);
 341
 342                         switch (st->exponent & 0x7fff) {
 343                         case 0x7fff:
 344                                 tag = FP_EXP_TAG_SPECIAL;
 345                                 break;
 346                         case 0x0000:
 347                                 if (!st->significand[0] &&
 348                                     !st->significand[1] &&
 349                                     !st->significand[2] &&
 350                                     !st->significand[3])
 351                                         tag = FP_EXP_TAG_ZERO;
 352                                 else
 353                                         tag = FP_EXP_TAG_SPECIAL;
 354                                 break;
 355                         default:
 356                                 if (st->significand[3] & 0x8000)
 357                                         tag = FP_EXP_TAG_VALID;
 358                                 else
 359                                         tag = FP_EXP_TAG_SPECIAL;
 360                                 break;
 361                         }
 362                 } else {
 363                         tag = FP_EXP_TAG_EMPTY;
 364                 }
 365                 ret |= tag << (2 * i);
 366         }
 367         return ret;
 368 }
 369
 370 /*
 371  * FXSR floating point environment conversions.
 372  */
 373
 374 static void
 375 convert_from_fxsr(struct user_i387_ia32_struct *env, struct task_struct *tsk)
 376 {
 377         struct i387_fxsave_struct *fxsave = &tsk->thread.fpu.state->fxsave;
 378         struct _fpreg *to = (struct _fpreg *) &env->st_space[0];
 379         struct _fpxreg *from = (struct _fpxreg *) &fxsave->st_space[0];
 380         int i;
 381
 382         env->cwd = fxsave->cwd | 0xffff0000u;
 383         env->swd = fxsave->swd | 0xffff0000u;
 384         env->twd = twd_fxsr_to_i387(fxsave);
 385
 386 #ifdef CONFIG_X86_64
 387         env->fip = fxsave->rip;
 388         env->foo = fxsave->rdp;
 389         if (tsk == current) {
 390                 /*
 391                  * should be actually ds/cs at fpu exception time, but
 392                  * that information is not available in 64bit mode.
 393                  */
 394                 asm("mov %%ds, %[fos]" : [fos] "=r" (env->fos));
 395                 asm("mov %%cs, %[fcs]" : [fcs] "=r" (env->fcs));
 396         } else {
 397                 struct pt_regs *regs = task_pt_regs(tsk);
 398
 399                 env->fos = 0xffff0000 | tsk->thread.ds;
 400                 env->fcs = regs->cs;
 401         }
 402 #else
 403         env->fip = fxsave->fip;
 404         env->fcs = (u16) fxsave->fcs | ((u32) fxsave->fop << 16);
 405         env->foo = fxsave->foo;
 406         env->fos = fxsave->fos;
 407 #endif
 408
 409         for (i = 0; i < 8; ++i)
 410                 memcpy(&to[i], &from[i], sizeof(to[0]));
 411 }
 412
 413 static void convert_to_fxsr(struct task_struct *tsk,
 414                             const struct user_i387_ia32_struct *env)
 415
 416 {
 417         struct i387_fxsave_struct *fxsave = &tsk->thread.fpu.state->fxsave;
 418         struct _fpreg *from = (struct _fpreg *) &env->st_space[0];
 419         struct _fpxreg *to = (struct _fpxreg *) &fxsave->st_space[0];
 420         int i;
 421
 422         fxsave->cwd = env->cwd;
 423         fxsave->swd = env->swd;
 424         fxsave->twd = twd_i387_to_fxsr(env->twd);
 425         fxsave->fop = (u16) ((u32) env->fcs >> 16);
 426 #ifdef CONFIG_X86_64
 427         fxsave->rip = env->fip;
 428         fxsave->rdp = env->foo;
 429         /* cs and ds ignored */
 430 #else
 431         fxsave->fip = env->fip;
 432         fxsave->fcs = (env->fcs & 0xffff);
 433         fxsave->foo = env->foo;
 434         fxsave->fos = env->fos;
 435 #endif
 436
 437         for (i = 0; i < 8; ++i)
 438                 memcpy(&to[i], &from[i], sizeof(from[0]));
 439 }
 440
 441 int fpregs_get(struct task_struct *target, const struct user_regset *regset,
 442                unsigned int pos, unsigned int count,
 443                void *kbuf, void __user *ubuf)
 444 {
 445         struct user_i387_ia32_struct env;
 446         int ret;
 447
 448         ret = init_fpu(target);
 449         if (ret)
 450                 return ret;
 451
 452         if (!HAVE_HWFP)
 453                 return fpregs_soft_get(target, regset, pos, count, kbuf, ubuf);
 454
 455         if (!cpu_has_fxsr) {
 456                 return user_regset_copyout(&pos, &count, &kbuf, &ubuf,
 457                                            &target->thread.fpu.state->fsave, 0,
 458                                            -1);
 459         }
 460
 461         sanitize_i387_state(target);
 462
 463         if (kbuf && pos == 0 && count == sizeof(env)) {
 464                 convert_from_fxsr(kbuf, target);
 465                 return 0;
 466         }
 467
 468         convert_from_fxsr(&env, target);
 469
 470         return user_regset_copyout(&pos, &count, &kbuf, &ubuf, &env, 0, -1);
 471 }
 472
 473 int fpregs_set(struct task_struct *target, const struct user_regset *regset,
 474                unsigned int pos, unsigned int count,
 475                const void *kbuf, const void __user *ubuf)
 476 {
 477         struct user_i387_ia32_struct env;
 478         int ret;
 479
 480         ret = init_fpu(target);
 481         if (ret)
 482                 return ret;
 483
 484         sanitize_i387_state(target);
 485
 486         if (!HAVE_HWFP)
 487                 return fpregs_soft_set(target, regset, pos, count, kbuf, ubuf);
 488
 489         if (!cpu_has_fxsr) {
 490                 return user_regset_copyin(&pos, &count, &kbuf, &ubuf,
 491                                           &target->thread.fpu.state->fsave, 0, -1);
 492         }
 493
 494         if (pos > 0 || count < sizeof(env))
 495                 convert_from_fxsr(&env, target);
 496
 497         ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, &env, 0, -1);
 498         if (!ret)
 499                 convert_to_fxsr(target, &env);
 500
 501         /*
 502          * update the header bit in the xsave header, indicating the
 503          * presence of FP.
 504          */
 505         if (cpu_has_xsave)
 506                 target->thread.fpu.state->xsave.xsave_hdr.xstate_bv |= XSTATE_FP;
 507         return ret;
 508 }
 509
 510 /*
 511  * Signal frame handlers.
 512  */
 513
 514 static inline int save_i387_fsave(struct _fpstate_ia32 __user *buf)
 515 {
 516         struct task_struct *tsk = current;
 517         struct i387_fsave_struct *fp = &tsk->thread.fpu.state->fsave;
 518
 519         fp->status = fp->swd;
 520         if (__copy_to_user(buf, fp, sizeof(struct i387_fsave_struct)))
 521                 return -1;
 522         return 1;
 523 }
 524
 525 static int save_i387_fxsave(struct _fpstate_ia32 __user *buf)
 526 {
 527         struct task_struct *tsk = current;
 528         struct i387_fxsave_struct *fx = &tsk->thread.fpu.state->fxsave;
 529         struct user_i387_ia32_struct env;
 530         int err = 0;
 531
 532         convert_from_fxsr(&env, tsk);
 533         if (__copy_to_user(buf, &env, sizeof(env)))
 534                 return -1;
 535
 536         err |= __put_user(fx->swd, &buf->status);
 537         err |= __put_user(X86_FXSR_MAGIC, &buf->magic);
 538         if (err)
 539                 return -1;
 540
 541         if (__copy_to_user(&buf->_fxsr_env[0], fx, xstate_size))
 542                 return -1;
 543         return 1;
 544 }
 545
 546 static int save_i387_xsave(void __user *buf)
 547 {
 548         struct task_struct *tsk = current;
 549         struct _fpstate_ia32 __user *fx = buf;
 550         int err = 0;
 551
 552
 553         sanitize_i387_state(tsk);
 554
 555         /*
 556          * For legacy compatible, we always set FP/SSE bits in the bit
 557          * vector while saving the state to the user context.
 558          * This will enable us capturing any changes(during sigreturn) to
 559          * the FP/SSE bits by the legacy applications which don't touch
 560          * xstate_bv in the xsave header.
 561          *
 562          * xsave aware applications can change the xstate_bv in the xsave
 563          * header as well as change any contents in the memory layout.
 564          * xrestore as part of sigreturn will capture all the changes.
 565          */
 566         tsk->thread.fpu.state->xsave.xsave_hdr.xstate_bv |= XSTATE_FPSSE;
 567
 568         if (save_i387_fxsave(fx) < 0)
 569                 return -1;
 570
 571         err = __copy_to_user(&fx->sw_reserved, &fx_sw_reserved_ia32,
 572                              sizeof(struct _fpx_sw_bytes));
 573         err |= __put_user(FP_XSTATE_MAGIC2,
 574                           (__u32 __user *) (buf + sig_xstate_ia32_size
 575                                             - FP_XSTATE_MAGIC2_SIZE));
 576         if (err)
 577                 return -1;
 578
 579         return 1;
 580 }
 581
 582 int save_i387_xstate_ia32(void __user *buf)
 583 {
 584         struct _fpstate_ia32 __user *fp = (struct _fpstate_ia32 __user *) buf;
 585         struct task_struct *tsk = current;
 586
 587         if (!used_math())
 588                 return 0;
 589
 590         if (!access_ok(VERIFY_WRITE, buf, sig_xstate_ia32_size))
 591                 return -EACCES;
 592         /*
 593          * This will cause a "finit" to be triggered by the next
 594          * attempted FPU operation by the 'current' process.
 595          */
 596         clear_used_math();
 597
 598         if (!HAVE_HWFP) {
 599                 return fpregs_soft_get(current, NULL,
 600                                        0, sizeof(struct user_i387_ia32_struct),
 601                                        NULL, fp) ? -1 : 1;
 602         }
 603
 604         unlazy_fpu(tsk);
 605
 606         if (cpu_has_xsave)
 607                 return save_i387_xsave(fp);
 608         if (cpu_has_fxsr)
 609                 return save_i387_fxsave(fp);
 610         else
 611                 return save_i387_fsave(fp);
 612 }
 613
 614 static inline int restore_i387_fsave(struct _fpstate_ia32 __user *buf)
 615 {
 616         struct task_struct *tsk = current;
 617
 618         return __copy_from_user(&tsk->thread.fpu.state->fsave, buf,
 619                                 sizeof(struct i387_fsave_struct));
 620 }
 621
 622 static int restore_i387_fxsave(struct _fpstate_ia32 __user *buf,
 623                                unsigned int size)
 624 {
 625         struct task_struct *tsk = current;
 626         struct user_i387_ia32_struct env;
 627         int err;
 628
 629         err = __copy_from_user(&tsk->thread.fpu.state->fxsave, &buf->_fxsr_env[0],
 630                                size);
 631         /* mxcsr reserved bits must be masked to zero for security reasons */
 632         tsk->thread.fpu.state->fxsave.mxcsr &= mxcsr_feature_mask;
 633         if (err || __copy_from_user(&env, buf, sizeof(env)))
 634                 return 1;
 635         convert_to_fxsr(tsk, &env);
 636
 637         return 0;
 638 }
 639
 640 static int restore_i387_xsave(void __user *buf)
 641 {
 642         struct _fpx_sw_bytes fx_sw_user;
 643         struct _fpstate_ia32 __user *fx_user =
 644                         ((struct _fpstate_ia32 __user *) buf);
 645         struct i387_fxsave_struct __user *fx =
 646                 (struct i387_fxsave_struct __user *) &fx_user->_fxsr_env[0];
 647         struct xsave_hdr_struct *xsave_hdr =
 648                                 &current->thread.fpu.state->xsave.xsave_hdr;
 649         u64 mask;
 650         int err;
 651
 652         if (check_for_xstate(fx, buf, &fx_sw_user))
 653                 goto fx_only;
 654
 655         mask = fx_sw_user.xstate_bv;
 656
 657         err = restore_i387_fxsave(buf, fx_sw_user.xstate_size);
 658
 659         xsave_hdr->xstate_bv &= pcntxt_mask;
 660         /*
 661          * These bits must be zero.
 662          */
 663         xsave_hdr->reserved1[0] = xsave_hdr->reserved1[1] = 0;
 664
 665         /*
 666          * Init the state that is not present in the memory layout
 667          * and enabled by the OS.
 668          */
 669         mask = ~(pcntxt_mask & ~mask);
 670         xsave_hdr->xstate_bv &= mask;
 671
 672         return err;
 673 fx_only:
 674         /*
 675          * Couldn't find the extended state information in the memory
 676          * layout. Restore the FP/SSE and init the other extended state
 677          * enabled by the OS.
 678          */
 679         xsave_hdr->xstate_bv = XSTATE_FPSSE;
 680         return restore_i387_fxsave(buf, sizeof(struct i387_fxsave_struct));
 681 }
 682
 683 int restore_i387_xstate_ia32(void __user *buf)
 684 {
 685         int err;
 686         struct task_struct *tsk = current;
 687         struct _fpstate_ia32 __user *fp = (struct _fpstate_ia32 __user *) buf;
 688
 689         if (HAVE_HWFP)
 690                 clear_fpu(tsk);
 691
 692         if (!buf) {
 693                 if (used_math()) {
 694                         clear_fpu(tsk);
 695                         clear_used_math();
 696                 }
 697
 698                 return 0;
 699         } else
 700                 if (!access_ok(VERIFY_READ, buf, sig_xstate_ia32_size))
 701                         return -EACCES;
 702
 703         if (!used_math()) {
 704                 err = init_fpu(tsk);
 705                 if (err)
 706                         return err;
 707         }
 708
 709         if (HAVE_HWFP) {
 710                 if (cpu_has_xsave)
 711                         err = restore_i387_xsave(buf);
 712                 else if (cpu_has_fxsr)
 713                         err = restore_i387_fxsave(fp, sizeof(struct
 714                                                            i387_fxsave_struct));
 715                 else
 716                         err = restore_i387_fsave(fp);
 717         } else {
 718                 err = fpregs_soft_set(current, NULL,
 719                                       0, sizeof(struct user_i387_ia32_struct),
 720                                       NULL, fp) != 0;
 721         }
 722         set_used_math();
 723
 724         return err;
 725 }
 726
 727 /*
 728  * FPU state for core dumps.
 729  * This is only used for a.out dumps now.
 730  * It is declared generically using elf_fpregset_t (which is
 731  * struct user_i387_struct) but is in fact only used for 32-bit
 732  * dumps, so on 64-bit it is really struct user_i387_ia32_struct.
 733  */
 734 int dump_fpu(struct pt_regs *regs, struct user_i387_struct *fpu)
 735 {
 736         struct task_struct *tsk = current;
 737         int fpvalid;
 738
 739         fpvalid = !!used_math();
 740         if (fpvalid)
 741                 fpvalid = !fpregs_get(tsk, NULL,
 742                                       0, sizeof(struct user_i387_ia32_struct),
 743                                       fpu, NULL);
 744
 745         return fpvalid;
 746 }
 747 EXPORT_SYMBOL(dump_fpu);
 748
 749 #endif  /* CONFIG_X86_32 || CONFIG_IA32_EMULATION */