arch/x86/kernel/fpu/core.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 <asm/fpu/internal.h>
   9 #include <linux/hardirq.h>
  10
  11 /*
  12  * Track whether the kernel is using the FPU state
  13  * currently.
  14  *
  15  * This flag is used:
  16  *
  17  *   - by IRQ context code to potentially use the FPU
  18  *     if it's unused.
  19  *
  20  *   - to debug kernel_fpu_begin()/end() correctness
  21  */
  22 static DEFINE_PER_CPU(bool, in_kernel_fpu);
  23
  24 /*
  25  * Track which context is using the FPU on the CPU:
  26  */
  27 DEFINE_PER_CPU(struct fpu *, fpu_fpregs_owner_ctx);
  28
  29 static void kernel_fpu_disable(void)
  30 {
  31         WARN_ON(this_cpu_read(in_kernel_fpu));
  32         this_cpu_write(in_kernel_fpu, true);
  33 }
  34
  35 static void kernel_fpu_enable(void)
  36 {
  37         WARN_ON_ONCE(!this_cpu_read(in_kernel_fpu));
  38         this_cpu_write(in_kernel_fpu, false);
  39 }
  40
  41 static bool kernel_fpu_disabled(void)
  42 {
  43         return this_cpu_read(in_kernel_fpu);
  44 }
  45
  46 /*
  47  * Were we in an interrupt that interrupted kernel mode?
  48  *
  49  * On others, we can do a kernel_fpu_begin/end() pair *ONLY* if that
  50  * pair does nothing at all: the thread must not have fpu (so
  51  * that we don't try to save the FPU state), and TS must
  52  * be set (so that the clts/stts pair does nothing that is
  53  * visible in the interrupted kernel thread).
  54  *
  55  * Except for the eagerfpu case when we return true; in the likely case
  56  * the thread has FPU but we are not going to set/clear TS.
  57  */
  58 static bool interrupted_kernel_fpu_idle(void)
  59 {
  60         if (kernel_fpu_disabled())
  61                 return false;
  62
  63         if (use_eager_fpu())
  64                 return true;
  65
  66         return !current->thread.fpu.fpregs_active && (read_cr0() & X86_CR0_TS);
  67 }
  68
  69 /*
  70  * Were we in user mode (or vm86 mode) when we were
  71  * interrupted?
  72  *
  73  * Doing kernel_fpu_begin/end() is ok if we are running
  74  * in an interrupt context from user mode - we'll just
  75  * save the FPU state as required.
  76  */
  77 static bool interrupted_user_mode(void)
  78 {
  79         struct pt_regs *regs = get_irq_regs();
  80         return regs && user_mode(regs);
  81 }
  82
  83 /*
  84  * Can we use the FPU in kernel mode with the
  85  * whole "kernel_fpu_begin/end()" sequence?
  86  *
  87  * It's always ok in process context (ie "not interrupt")
  88  * but it is sometimes ok even from an irq.
  89  */
  90 bool irq_fpu_usable(void)
  91 {
  92         return !in_interrupt() ||
  93                 interrupted_user_mode() ||
  94                 interrupted_kernel_fpu_idle();
  95 }
  96 EXPORT_SYMBOL(irq_fpu_usable);
  97
  98 void __kernel_fpu_begin(void)
  99 {
 100         struct fpu *fpu = &current->thread.fpu;
 101
 102         kernel_fpu_disable();
 103
 104         if (fpu->fpregs_active) {
 105                 copy_fpregs_to_fpstate(fpu);
 106         } else {
 107                 this_cpu_write(fpu_fpregs_owner_ctx, NULL);
 108                 __fpregs_activate_hw();
 109         }
 110 }
 111 EXPORT_SYMBOL(__kernel_fpu_begin);
 112
 113 void __kernel_fpu_end(void)
 114 {
 115         struct fpu *fpu = &current->thread.fpu;
 116
 117         if (fpu->fpregs_active) {
 118                 if (WARN_ON(restore_fpu_checking(fpu)))
 119                         fpu_reset_state(fpu);
 120         } else {
 121                 __fpregs_deactivate_hw();
 122         }
 123
 124         kernel_fpu_enable();
 125 }
 126 EXPORT_SYMBOL(__kernel_fpu_end);
 127
 128 void kernel_fpu_begin(void)
 129 {
 130         preempt_disable();
 131         WARN_ON_ONCE(!irq_fpu_usable());
 132         __kernel_fpu_begin();
 133 }
 134 EXPORT_SYMBOL_GPL(kernel_fpu_begin);
 135
 136 void kernel_fpu_end(void)
 137 {
 138         __kernel_fpu_end();
 139         preempt_enable();
 140 }
 141 EXPORT_SYMBOL_GPL(kernel_fpu_end);
 142
 143 /*
 144  * CR0::TS save/restore functions:
 145  */
 146 int irq_ts_save(void)
 147 {
 148         /*
 149          * If in process context and not atomic, we can take a spurious DNA fault.
 150          * Otherwise, doing clts() in process context requires disabling preemption
 151          * or some heavy lifting like kernel_fpu_begin()
 152          */
 153         if (!in_atomic())
 154                 return 0;
 155
 156         if (read_cr0() & X86_CR0_TS) {
 157                 clts();
 158                 return 1;
 159         }
 160
 161         return 0;
 162 }
 163 EXPORT_SYMBOL_GPL(irq_ts_save);
 164
 165 void irq_ts_restore(int TS_state)
 166 {
 167         if (TS_state)
 168                 stts();
 169 }
 170 EXPORT_SYMBOL_GPL(irq_ts_restore);
 171
 172 /*
 173  * Save the FPU state (mark it for reload if necessary):
 174  *
 175  * This only ever gets called for the current task.
 176  */
 177 void fpu__save(struct fpu *fpu)
 178 {
 179         WARN_ON(fpu != &current->thread.fpu);
 180
 181         preempt_disable();
 182         if (fpu->fpregs_active) {
 183                 if (!copy_fpregs_to_fpstate(fpu))
 184                         fpregs_deactivate(fpu);
 185         }
 186         preempt_enable();
 187 }
 188 EXPORT_SYMBOL_GPL(fpu__save);
 189
 190 void fpstate_init(struct fpu *fpu)
 191 {
 192         if (!cpu_has_fpu) {
 193                 finit_soft_fpu(&fpu->state.soft);
 194                 return;
 195         }
 196
 197         memset(&fpu->state, 0, xstate_size);
 198
 199         if (cpu_has_fxsr) {
 200                 fx_finit(&fpu->state.fxsave);
 201         } else {
 202                 struct i387_fsave_struct *fp = &fpu->state.fsave;
 203                 fp->cwd = 0xffff037fu;
 204                 fp->swd = 0xffff0000u;
 205                 fp->twd = 0xffffffffu;
 206                 fp->fos = 0xffff0000u;
 207         }
 208 }
 209 EXPORT_SYMBOL_GPL(fpstate_init);
 210
 211 /*
 212  * Copy the current task's FPU state to a new task's FPU context.
 213  *
 214  * In the 'eager' case we just save to the destination context.
 215  *
 216  * In the 'lazy' case we save to the source context, mark the FPU lazy
 217  * via stts() and copy the source context into the destination context.
 218  */
 219 static void fpu_copy(struct fpu *dst_fpu, struct fpu *src_fpu)
 220 {
 221         WARN_ON(src_fpu != &current->thread.fpu);
 222
 223         /*
 224          * Don't let 'init optimized' areas of the XSAVE area
 225          * leak into the child task:
 226          */
 227         if (use_eager_fpu())
 228                 memset(&dst_fpu->state.xsave, 0, xstate_size);
 229
 230         /*
 231          * Save current FPU registers directly into the child
 232          * FPU context, without any memory-to-memory copying.
 233          *
 234          * If the FPU context got destroyed in the process (FNSAVE
 235          * done on old CPUs) then copy it back into the source
 236          * context and mark the current task for lazy restore.
 237          *
 238          * We have to do all this with preemption disabled,
 239          * mostly because of the FNSAVE case, because in that
 240          * case we must not allow preemption in the window
 241          * between the FNSAVE and us marking the context lazy.
 242          *
 243          * It shouldn't be an issue as even FNSAVE is plenty
 244          * fast in terms of critical section length.
 245          */
 246         preempt_disable();
 247         if (!copy_fpregs_to_fpstate(dst_fpu)) {
 248                 memcpy(&src_fpu->state, &dst_fpu->state, xstate_size);
 249                 fpregs_deactivate(src_fpu);
 250         }
 251         preempt_enable();
 252 }
 253
 254 int fpu__copy(struct fpu *dst_fpu, struct fpu *src_fpu)
 255 {
 256         dst_fpu->counter = 0;
 257         dst_fpu->fpregs_active = 0;
 258         dst_fpu->last_cpu = -1;
 259
 260         if (src_fpu->fpstate_active)
 261                 fpu_copy(dst_fpu, src_fpu);
 262
 263         return 0;
 264 }
 265
 266 /*
 267  * Activate the current task's in-memory FPU context,
 268  * if it has not been used before:
 269  */
 270 void fpu__activate_curr(struct fpu *fpu)
 271 {
 272         WARN_ON_ONCE(fpu != &current->thread.fpu);
 273
 274         if (!fpu->fpstate_active) {
 275                 fpstate_init(fpu);
 276
 277                 /* Safe to do for the current task: */
 278                 fpu->fpstate_active = 1;
 279         }
 280 }
 281 EXPORT_SYMBOL_GPL(fpu__activate_curr);
 282
 283 /*
 284  * This function must be called before we modify a stopped child's
 285  * fpstate.
 286  *
 287  * If the child has not used the FPU before then initialize its
 288  * fpstate.
 289  *
 290  * If the child has used the FPU before then unlazy it.
 291  *
 292  * [ After this function call, after registers in the fpstate are
 293  *   modified and the child task has woken up, the child task will
 294  *   restore the modified FPU state from the modified context. If we
 295  *   didn't clear its lazy status here then the lazy in-registers
 296  *   state pending on its former CPU could be restored, corrupting
 297  *   the modifications. ]
 298  *
 299  * This function is also called before we read a stopped child's
 300  * FPU state - to make sure it's initialized if the child has
 301  * no active FPU state.
 302  *
 303  * TODO: A future optimization would be to skip the unlazying in
 304  *       the read-only case, it's not strictly necessary for
 305  *       read-only access to the context.
 306  */
 307 static void fpu__activate_stopped(struct fpu *child_fpu)
 308 {
 309         WARN_ON_ONCE(child_fpu == &current->thread.fpu);
 310
 311         if (child_fpu->fpstate_active) {
 312                 child_fpu->last_cpu = -1;
 313         } else {
 314                 fpstate_init(child_fpu);
 315
 316                 /* Safe to do for stopped child tasks: */
 317                 child_fpu->fpstate_active = 1;
 318         }
 319 }
 320
 321 /*
 322  * 'fpu__restore()' saves the current math information in the
 323  * old math state array, and gets the new ones from the current task
 324  *
 325  * Careful.. There are problems with IBM-designed IRQ13 behaviour.
 326  * Don't touch unless you *really* know how it works.
 327  *
 328  * Must be called with kernel preemption disabled (eg with local
 329  * local interrupts as in the case of do_device_not_available).
 330  */
 331 void fpu__restore(void)
 332 {
 333         struct task_struct *tsk = current;
 334         struct fpu *fpu = &tsk->thread.fpu;
 335
 336         fpu__activate_curr(fpu);
 337
 338         /* Avoid __kernel_fpu_begin() right after fpregs_activate() */
 339         kernel_fpu_disable();
 340         fpregs_activate(fpu);
 341         if (unlikely(restore_fpu_checking(fpu))) {
 342                 fpu_reset_state(fpu);
 343                 force_sig_info(SIGSEGV, SEND_SIG_PRIV, tsk);
 344         } else {
 345                 tsk->thread.fpu.counter++;
 346         }
 347         kernel_fpu_enable();
 348 }
 349 EXPORT_SYMBOL_GPL(fpu__restore);
 350
 351 void fpu__clear(struct task_struct *tsk)
 352 {
 353         struct fpu *fpu = &tsk->thread.fpu;
 354
 355         WARN_ON_ONCE(tsk != current); /* Almost certainly an anomaly */
 356
 357         if (!use_eager_fpu()) {
 358                 /* FPU state will be reallocated lazily at the first use. */
 359                 drop_fpu(fpu);
 360         } else {
 361                 if (!fpu->fpstate_active) {
 362                         fpu__activate_curr(fpu);
 363                         user_fpu_begin();
 364                 }
 365                 restore_init_xstate();
 366         }
 367 }
 368
 369 /*
 370  * The xstateregs_active() routine is the same as the regset_fpregs_active() routine,
 371  * as the "regset->n" for the xstate regset will be updated based on the feature
 372  * capabilites supported by the xsave.
 373  */
 374 int regset_fpregs_active(struct task_struct *target, const struct user_regset *regset)
 375 {
 376         struct fpu *target_fpu = &target->thread.fpu;
 377
 378         return target_fpu->fpstate_active ? regset->n : 0;
 379 }
 380
 381 int regset_xregset_fpregs_active(struct task_struct *target, const struct user_regset *regset)
 382 {
 383         struct fpu *target_fpu = &target->thread.fpu;
 384
 385         return (cpu_has_fxsr && target_fpu->fpstate_active) ? regset->n : 0;
 386 }
 387
 388 int xfpregs_get(struct task_struct *target, const struct user_regset *regset,
 389                 unsigned int pos, unsigned int count,
 390                 void *kbuf, void __user *ubuf)
 391 {
 392         struct fpu *fpu = &target->thread.fpu;
 393
 394         if (!cpu_has_fxsr)
 395                 return -ENODEV;
 396
 397         fpu__activate_stopped(fpu);
 398         sanitize_i387_state(target);
 399
 400         return user_regset_copyout(&pos, &count, &kbuf, &ubuf,
 401                                    &fpu->state.fxsave, 0, -1);
 402 }
 403
 404 int xfpregs_set(struct task_struct *target, const struct user_regset *regset,
 405                 unsigned int pos, unsigned int count,
 406                 const void *kbuf, const void __user *ubuf)
 407 {
 408         struct fpu *fpu = &target->thread.fpu;
 409         int ret;
 410
 411         if (!cpu_has_fxsr)
 412                 return -ENODEV;
 413
 414         fpu__activate_stopped(fpu);
 415         sanitize_i387_state(target);
 416
 417         ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf,
 418                                  &fpu->state.fxsave, 0, -1);
 419
 420         /*
 421          * mxcsr reserved bits must be masked to zero for security reasons.
 422          */
 423         fpu->state.fxsave.mxcsr &= mxcsr_feature_mask;
 424
 425         /*
 426          * update the header bits in the xsave header, indicating the
 427          * presence of FP and SSE state.
 428          */
 429         if (cpu_has_xsave)
 430                 fpu->state.xsave.header.xfeatures |= XSTATE_FPSSE;
 431
 432         return ret;
 433 }
 434
 435 int xstateregs_get(struct task_struct *target, const struct user_regset *regset,
 436                 unsigned int pos, unsigned int count,
 437                 void *kbuf, void __user *ubuf)
 438 {
 439         struct fpu *fpu = &target->thread.fpu;
 440         struct xsave_struct *xsave;
 441         int ret;
 442
 443         if (!cpu_has_xsave)
 444                 return -ENODEV;
 445
 446         fpu__activate_stopped(fpu);
 447
 448         xsave = &fpu->state.xsave;
 449
 450         /*
 451          * Copy the 48bytes defined by the software first into the xstate
 452          * memory layout in the thread struct, so that we can copy the entire
 453          * xstateregs to the user using one user_regset_copyout().
 454          */
 455         memcpy(&xsave->i387.sw_reserved,
 456                 xstate_fx_sw_bytes, sizeof(xstate_fx_sw_bytes));
 457         /*
 458          * Copy the xstate memory layout.
 459          */
 460         ret = user_regset_copyout(&pos, &count, &kbuf, &ubuf, xsave, 0, -1);
 461         return ret;
 462 }
 463
 464 int xstateregs_set(struct task_struct *target, const struct user_regset *regset,
 465                   unsigned int pos, unsigned int count,
 466                   const void *kbuf, const void __user *ubuf)
 467 {
 468         struct fpu *fpu = &target->thread.fpu;
 469         struct xsave_struct *xsave;
 470         int ret;
 471
 472         if (!cpu_has_xsave)
 473                 return -ENODEV;
 474
 475         fpu__activate_stopped(fpu);
 476
 477         xsave = &fpu->state.xsave;
 478
 479         ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, xsave, 0, -1);
 480         /*
 481          * mxcsr reserved bits must be masked to zero for security reasons.
 482          */
 483         xsave->i387.mxcsr &= mxcsr_feature_mask;
 484         xsave->header.xfeatures &= xfeatures_mask;
 485         /*
 486          * These bits must be zero.
 487          */
 488         memset(&xsave->header.reserved, 0, 48);
 489
 490         return ret;
 491 }
 492
 493 #if defined CONFIG_X86_32 || defined CONFIG_IA32_EMULATION
 494
 495 /*
 496  * FPU tag word conversions.
 497  */
 498
 499 static inline unsigned short twd_i387_to_fxsr(unsigned short twd)
 500 {
 501         unsigned int tmp; /* to avoid 16 bit prefixes in the code */
 502
 503         /* Transform each pair of bits into 01 (valid) or 00 (empty) */
 504         tmp = ~twd;
 505         tmp = (tmp | (tmp>>1)) & 0x5555; /* 0V0V0V0V0V0V0V0V */
 506         /* and move the valid bits to the lower byte. */
 507         tmp = (tmp | (tmp >> 1)) & 0x3333; /* 00VV00VV00VV00VV */
 508         tmp = (tmp | (tmp >> 2)) & 0x0f0f; /* 0000VVVV0000VVVV */
 509         tmp = (tmp | (tmp >> 4)) & 0x00ff; /* 00000000VVVVVVVV */
 510
 511         return tmp;
 512 }
 513
 514 #define FPREG_ADDR(f, n)        ((void *)&(f)->st_space + (n) * 16)
 515 #define FP_EXP_TAG_VALID        0
 516 #define FP_EXP_TAG_ZERO         1
 517 #define FP_EXP_TAG_SPECIAL      2
 518 #define FP_EXP_TAG_EMPTY        3
 519
 520 static inline u32 twd_fxsr_to_i387(struct i387_fxsave_struct *fxsave)
 521 {
 522         struct _fpxreg *st;
 523         u32 tos = (fxsave->swd >> 11) & 7;
 524         u32 twd = (unsigned long) fxsave->twd;
 525         u32 tag;
 526         u32 ret = 0xffff0000u;
 527         int i;
 528
 529         for (i = 0; i < 8; i++, twd >>= 1) {
 530                 if (twd & 0x1) {
 531                         st = FPREG_ADDR(fxsave, (i - tos) & 7);
 532
 533                         switch (st->exponent & 0x7fff) {
 534                         case 0x7fff:
 535                                 tag = FP_EXP_TAG_SPECIAL;
 536                                 break;
 537                         case 0x0000:
 538                                 if (!st->significand[0] &&
 539                                     !st->significand[1] &&
 540                                     !st->significand[2] &&
 541                                     !st->significand[3])
 542                                         tag = FP_EXP_TAG_ZERO;
 543                                 else
 544                                         tag = FP_EXP_TAG_SPECIAL;
 545                                 break;
 546                         default:
 547                                 if (st->significand[3] & 0x8000)
 548                                         tag = FP_EXP_TAG_VALID;
 549                                 else
 550                                         tag = FP_EXP_TAG_SPECIAL;
 551                                 break;
 552                         }
 553                 } else {
 554                         tag = FP_EXP_TAG_EMPTY;
 555                 }
 556                 ret |= tag << (2 * i);
 557         }
 558         return ret;
 559 }
 560
 561 /*
 562  * FXSR floating point environment conversions.
 563  */
 564
 565 void
 566 convert_from_fxsr(struct user_i387_ia32_struct *env, struct task_struct *tsk)
 567 {
 568         struct i387_fxsave_struct *fxsave = &tsk->thread.fpu.state.fxsave;
 569         struct _fpreg *to = (struct _fpreg *) &env->st_space[0];
 570         struct _fpxreg *from = (struct _fpxreg *) &fxsave->st_space[0];
 571         int i;
 572
 573         env->cwd = fxsave->cwd | 0xffff0000u;
 574         env->swd = fxsave->swd | 0xffff0000u;
 575         env->twd = twd_fxsr_to_i387(fxsave);
 576
 577 #ifdef CONFIG_X86_64
 578         env->fip = fxsave->rip;
 579         env->foo = fxsave->rdp;
 580         /*
 581          * should be actually ds/cs at fpu exception time, but
 582          * that information is not available in 64bit mode.
 583          */
 584         env->fcs = task_pt_regs(tsk)->cs;
 585         if (tsk == current) {
 586                 savesegment(ds, env->fos);
 587         } else {
 588                 env->fos = tsk->thread.ds;
 589         }
 590         env->fos |= 0xffff0000;
 591 #else
 592         env->fip = fxsave->fip;
 593         env->fcs = (u16) fxsave->fcs | ((u32) fxsave->fop << 16);
 594         env->foo = fxsave->foo;
 595         env->fos = fxsave->fos;
 596 #endif
 597
 598         for (i = 0; i < 8; ++i)
 599                 memcpy(&to[i], &from[i], sizeof(to[0]));
 600 }
 601
 602 void convert_to_fxsr(struct task_struct *tsk,
 603                      const struct user_i387_ia32_struct *env)
 604
 605 {
 606         struct i387_fxsave_struct *fxsave = &tsk->thread.fpu.state.fxsave;
 607         struct _fpreg *from = (struct _fpreg *) &env->st_space[0];
 608         struct _fpxreg *to = (struct _fpxreg *) &fxsave->st_space[0];
 609         int i;
 610
 611         fxsave->cwd = env->cwd;
 612         fxsave->swd = env->swd;
 613         fxsave->twd = twd_i387_to_fxsr(env->twd);
 614         fxsave->fop = (u16) ((u32) env->fcs >> 16);
 615 #ifdef CONFIG_X86_64
 616         fxsave->rip = env->fip;
 617         fxsave->rdp = env->foo;
 618         /* cs and ds ignored */
 619 #else
 620         fxsave->fip = env->fip;
 621         fxsave->fcs = (env->fcs & 0xffff);
 622         fxsave->foo = env->foo;
 623         fxsave->fos = env->fos;
 624 #endif
 625
 626         for (i = 0; i < 8; ++i)
 627                 memcpy(&to[i], &from[i], sizeof(from[0]));
 628 }
 629
 630 int fpregs_get(struct task_struct *target, const struct user_regset *regset,
 631                unsigned int pos, unsigned int count,
 632                void *kbuf, void __user *ubuf)
 633 {
 634         struct fpu *fpu = &target->thread.fpu;
 635         struct user_i387_ia32_struct env;
 636
 637         fpu__activate_stopped(fpu);
 638
 639         if (!static_cpu_has(X86_FEATURE_FPU))
 640                 return fpregs_soft_get(target, regset, pos, count, kbuf, ubuf);
 641
 642         if (!cpu_has_fxsr)
 643                 return user_regset_copyout(&pos, &count, &kbuf, &ubuf,
 644                                            &fpu->state.fsave, 0,
 645                                            -1);
 646
 647         sanitize_i387_state(target);
 648
 649         if (kbuf && pos == 0 && count == sizeof(env)) {
 650                 convert_from_fxsr(kbuf, target);
 651                 return 0;
 652         }
 653
 654         convert_from_fxsr(&env, target);
 655
 656         return user_regset_copyout(&pos, &count, &kbuf, &ubuf, &env, 0, -1);
 657 }
 658
 659 int fpregs_set(struct task_struct *target, const struct user_regset *regset,
 660                unsigned int pos, unsigned int count,
 661                const void *kbuf, const void __user *ubuf)
 662 {
 663         struct fpu *fpu = &target->thread.fpu;
 664         struct user_i387_ia32_struct env;
 665         int ret;
 666
 667         fpu__activate_stopped(fpu);
 668
 669         sanitize_i387_state(target);
 670
 671         if (!static_cpu_has(X86_FEATURE_FPU))
 672                 return fpregs_soft_set(target, regset, pos, count, kbuf, ubuf);
 673
 674         if (!cpu_has_fxsr)
 675                 return user_regset_copyin(&pos, &count, &kbuf, &ubuf,
 676                                           &fpu->state.fsave, 0,
 677                                           -1);
 678
 679         if (pos > 0 || count < sizeof(env))
 680                 convert_from_fxsr(&env, target);
 681
 682         ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, &env, 0, -1);
 683         if (!ret)
 684                 convert_to_fxsr(target, &env);
 685
 686         /*
 687          * update the header bit in the xsave header, indicating the
 688          * presence of FP.
 689          */
 690         if (cpu_has_xsave)
 691                 fpu->state.xsave.header.xfeatures |= XSTATE_FP;
 692         return ret;
 693 }
 694
 695 /*
 696  * FPU state for core dumps.
 697  * This is only used for a.out dumps now.
 698  * It is declared generically using elf_fpregset_t (which is
 699  * struct user_i387_struct) but is in fact only used for 32-bit
 700  * dumps, so on 64-bit it is really struct user_i387_ia32_struct.
 701  */
 702 int dump_fpu(struct pt_regs *regs, struct user_i387_struct *ufpu)
 703 {
 704         struct task_struct *tsk = current;
 705         struct fpu *fpu = &tsk->thread.fpu;
 706         int fpvalid;
 707
 708         fpvalid = fpu->fpstate_active;
 709         if (fpvalid)
 710                 fpvalid = !fpregs_get(tsk, NULL,
 711                                       0, sizeof(struct user_i387_ia32_struct),
 712                                       ufpu, NULL);
 713
 714         return fpvalid;
 715 }
 716 EXPORT_SYMBOL(dump_fpu);
 717
 718 #endif  /* CONFIG_X86_32 || CONFIG_IA32_EMULATION */