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 (initialize it 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 (use_eager_fpu()) {
 184                         copy_fpregs_to_fpstate(fpu);
 185                 } else {
 186                         copy_fpregs_to_fpstate(fpu);
 187                         fpregs_deactivate(fpu);
 188                 }
 189         }
 190         preempt_enable();
 191 }
 192 EXPORT_SYMBOL_GPL(fpu__save);
 193
 194 void fpstate_init(struct fpu *fpu)
 195 {
 196         if (!cpu_has_fpu) {
 197                 finit_soft_fpu(&fpu->state.soft);
 198                 return;
 199         }
 200
 201         memset(&fpu->state, 0, xstate_size);
 202
 203         if (cpu_has_fxsr) {
 204                 fx_finit(&fpu->state.fxsave);
 205         } else {
 206                 struct i387_fsave_struct *fp = &fpu->state.fsave;
 207                 fp->cwd = 0xffff037fu;
 208                 fp->swd = 0xffff0000u;
 209                 fp->twd = 0xffffffffu;
 210                 fp->fos = 0xffff0000u;
 211         }
 212 }
 213 EXPORT_SYMBOL_GPL(fpstate_init);
 214
 215 /*
 216  * Copy the current task's FPU state to a new task's FPU context.
 217  *
 218  * In the 'eager' case we just save to the destination context.
 219  *
 220  * In the 'lazy' case we save to the source context, mark the FPU lazy
 221  * via stts() and copy the source context into the destination context.
 222  */
 223 static void fpu_copy(struct fpu *dst_fpu, struct fpu *src_fpu)
 224 {
 225         WARN_ON(src_fpu != &current->thread.fpu);
 226
 227         if (use_eager_fpu()) {
 228                 memset(&dst_fpu->state.xsave, 0, xstate_size);
 229                 copy_fpregs_to_fpstate(dst_fpu);
 230         } else {
 231                 fpu__save(src_fpu);
 232                 memcpy(&dst_fpu->state, &src_fpu->state, xstate_size);
 233         }
 234 }
 235
 236 int fpu__copy(struct fpu *dst_fpu, struct fpu *src_fpu)
 237 {
 238         dst_fpu->counter = 0;
 239         dst_fpu->fpregs_active = 0;
 240         dst_fpu->last_cpu = -1;
 241
 242         if (src_fpu->fpstate_active)
 243                 fpu_copy(dst_fpu, src_fpu);
 244
 245         return 0;
 246 }
 247
 248 /*
 249  * Activate the current task's in-memory FPU context,
 250  * if it has not been used before:
 251  */
 252 void fpu__activate_curr(struct fpu *fpu)
 253 {
 254         WARN_ON_ONCE(fpu != &current->thread.fpu);
 255
 256         if (!fpu->fpstate_active) {
 257                 fpstate_init(fpu);
 258
 259                 /* Safe to do for the current task: */
 260                 fpu->fpstate_active = 1;
 261         }
 262 }
 263 EXPORT_SYMBOL_GPL(fpu__activate_curr);
 264
 265 /*
 266  * This function must be called before we modify a stopped child's
 267  * fpstate.
 268  *
 269  * If the child has not used the FPU before then initialize its
 270  * fpstate.
 271  *
 272  * If the child has used the FPU before then unlazy it.
 273  *
 274  * [ After this function call, after registers in the fpstate are
 275  *   modified and the child task has woken up, the child task will
 276  *   restore the modified FPU state from the modified context. If we
 277  *   didn't clear its lazy status here then the lazy in-registers
 278  *   state pending on its former CPU could be restored, corrupting
 279  *   the modifications. ]
 280  *
 281  * This function is also called before we read a stopped child's
 282  * FPU state - to make sure it's initialized if the child has
 283  * no active FPU state.
 284  *
 285  * TODO: A future optimization would be to skip the unlazying in
 286  *       the read-only case, it's not strictly necessary for
 287  *       read-only access to the context.
 288  */
 289 static void fpu__activate_stopped(struct fpu *child_fpu)
 290 {
 291         WARN_ON_ONCE(child_fpu == &current->thread.fpu);
 292
 293         if (child_fpu->fpstate_active) {
 294                 child_fpu->last_cpu = -1;
 295         } else {
 296                 fpstate_init(child_fpu);
 297
 298                 /* Safe to do for stopped child tasks: */
 299                 child_fpu->fpstate_active = 1;
 300         }
 301 }
 302
 303 /*
 304  * 'fpu__restore()' saves the current math information in the
 305  * old math state array, and gets the new ones from the current task
 306  *
 307  * Careful.. There are problems with IBM-designed IRQ13 behaviour.
 308  * Don't touch unless you *really* know how it works.
 309  *
 310  * Must be called with kernel preemption disabled (eg with local
 311  * local interrupts as in the case of do_device_not_available).
 312  */
 313 void fpu__restore(void)
 314 {
 315         struct task_struct *tsk = current;
 316         struct fpu *fpu = &tsk->thread.fpu;
 317
 318         fpu__activate_curr(fpu);
 319
 320         /* Avoid __kernel_fpu_begin() right after fpregs_activate() */
 321         kernel_fpu_disable();
 322         fpregs_activate(fpu);
 323         if (unlikely(restore_fpu_checking(fpu))) {
 324                 fpu_reset_state(fpu);
 325                 force_sig_info(SIGSEGV, SEND_SIG_PRIV, tsk);
 326         } else {
 327                 tsk->thread.fpu.counter++;
 328         }
 329         kernel_fpu_enable();
 330 }
 331 EXPORT_SYMBOL_GPL(fpu__restore);
 332
 333 void fpu__clear(struct task_struct *tsk)
 334 {
 335         struct fpu *fpu = &tsk->thread.fpu;
 336
 337         WARN_ON_ONCE(tsk != current); /* Almost certainly an anomaly */
 338
 339         if (!use_eager_fpu()) {
 340                 /* FPU state will be reallocated lazily at the first use. */
 341                 drop_fpu(fpu);
 342         } else {
 343                 if (!fpu->fpstate_active) {
 344                         fpu__activate_curr(fpu);
 345                         user_fpu_begin();
 346                 }
 347                 restore_init_xstate();
 348         }
 349 }
 350
 351 /*
 352  * The xstateregs_active() routine is the same as the regset_fpregs_active() routine,
 353  * as the "regset->n" for the xstate regset will be updated based on the feature
 354  * capabilites supported by the xsave.
 355  */
 356 int regset_fpregs_active(struct task_struct *target, const struct user_regset *regset)
 357 {
 358         struct fpu *target_fpu = &target->thread.fpu;
 359
 360         return target_fpu->fpstate_active ? regset->n : 0;
 361 }
 362
 363 int regset_xregset_fpregs_active(struct task_struct *target, const struct user_regset *regset)
 364 {
 365         struct fpu *target_fpu = &target->thread.fpu;
 366
 367         return (cpu_has_fxsr && target_fpu->fpstate_active) ? regset->n : 0;
 368 }
 369
 370 int xfpregs_get(struct task_struct *target, const struct user_regset *regset,
 371                 unsigned int pos, unsigned int count,
 372                 void *kbuf, void __user *ubuf)
 373 {
 374         struct fpu *fpu = &target->thread.fpu;
 375
 376         if (!cpu_has_fxsr)
 377                 return -ENODEV;
 378
 379         fpu__activate_stopped(fpu);
 380         sanitize_i387_state(target);
 381
 382         return user_regset_copyout(&pos, &count, &kbuf, &ubuf,
 383                                    &fpu->state.fxsave, 0, -1);
 384 }
 385
 386 int xfpregs_set(struct task_struct *target, const struct user_regset *regset,
 387                 unsigned int pos, unsigned int count,
 388                 const void *kbuf, const void __user *ubuf)
 389 {
 390         struct fpu *fpu = &target->thread.fpu;
 391         int ret;
 392
 393         if (!cpu_has_fxsr)
 394                 return -ENODEV;
 395
 396         fpu__activate_stopped(fpu);
 397         sanitize_i387_state(target);
 398
 399         ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf,
 400                                  &fpu->state.fxsave, 0, -1);
 401
 402         /*
 403          * mxcsr reserved bits must be masked to zero for security reasons.
 404          */
 405         fpu->state.fxsave.mxcsr &= mxcsr_feature_mask;
 406
 407         /*
 408          * update the header bits in the xsave header, indicating the
 409          * presence of FP and SSE state.
 410          */
 411         if (cpu_has_xsave)
 412                 fpu->state.xsave.header.xfeatures |= XSTATE_FPSSE;
 413
 414         return ret;
 415 }
 416
 417 int xstateregs_get(struct task_struct *target, const struct user_regset *regset,
 418                 unsigned int pos, unsigned int count,
 419                 void *kbuf, void __user *ubuf)
 420 {
 421         struct fpu *fpu = &target->thread.fpu;
 422         struct xsave_struct *xsave;
 423         int ret;
 424
 425         if (!cpu_has_xsave)
 426                 return -ENODEV;
 427
 428         fpu__activate_stopped(fpu);
 429
 430         xsave = &fpu->state.xsave;
 431
 432         /*
 433          * Copy the 48bytes defined by the software first into the xstate
 434          * memory layout in the thread struct, so that we can copy the entire
 435          * xstateregs to the user using one user_regset_copyout().
 436          */
 437         memcpy(&xsave->i387.sw_reserved,
 438                 xstate_fx_sw_bytes, sizeof(xstate_fx_sw_bytes));
 439         /*
 440          * Copy the xstate memory layout.
 441          */
 442         ret = user_regset_copyout(&pos, &count, &kbuf, &ubuf, xsave, 0, -1);
 443         return ret;
 444 }
 445
 446 int xstateregs_set(struct task_struct *target, const struct user_regset *regset,
 447                   unsigned int pos, unsigned int count,
 448                   const void *kbuf, const void __user *ubuf)
 449 {
 450         struct fpu *fpu = &target->thread.fpu;
 451         struct xsave_struct *xsave;
 452         int ret;
 453
 454         if (!cpu_has_xsave)
 455                 return -ENODEV;
 456
 457         fpu__activate_stopped(fpu);
 458
 459         xsave = &fpu->state.xsave;
 460
 461         ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, xsave, 0, -1);
 462         /*
 463          * mxcsr reserved bits must be masked to zero for security reasons.
 464          */
 465         xsave->i387.mxcsr &= mxcsr_feature_mask;
 466         xsave->header.xfeatures &= xfeatures_mask;
 467         /*
 468          * These bits must be zero.
 469          */
 470         memset(&xsave->header.reserved, 0, 48);
 471
 472         return ret;
 473 }
 474
 475 #if defined CONFIG_X86_32 || defined CONFIG_IA32_EMULATION
 476
 477 /*
 478  * FPU tag word conversions.
 479  */
 480
 481 static inline unsigned short twd_i387_to_fxsr(unsigned short twd)
 482 {
 483         unsigned int tmp; /* to avoid 16 bit prefixes in the code */
 484
 485         /* Transform each pair of bits into 01 (valid) or 00 (empty) */
 486         tmp = ~twd;
 487         tmp = (tmp | (tmp>>1)) & 0x5555; /* 0V0V0V0V0V0V0V0V */
 488         /* and move the valid bits to the lower byte. */
 489         tmp = (tmp | (tmp >> 1)) & 0x3333; /* 00VV00VV00VV00VV */
 490         tmp = (tmp | (tmp >> 2)) & 0x0f0f; /* 0000VVVV0000VVVV */
 491         tmp = (tmp | (tmp >> 4)) & 0x00ff; /* 00000000VVVVVVVV */
 492
 493         return tmp;
 494 }
 495
 496 #define FPREG_ADDR(f, n)        ((void *)&(f)->st_space + (n) * 16)
 497 #define FP_EXP_TAG_VALID        0
 498 #define FP_EXP_TAG_ZERO         1
 499 #define FP_EXP_TAG_SPECIAL      2
 500 #define FP_EXP_TAG_EMPTY        3
 501
 502 static inline u32 twd_fxsr_to_i387(struct i387_fxsave_struct *fxsave)
 503 {
 504         struct _fpxreg *st;
 505         u32 tos = (fxsave->swd >> 11) & 7;
 506         u32 twd = (unsigned long) fxsave->twd;
 507         u32 tag;
 508         u32 ret = 0xffff0000u;
 509         int i;
 510
 511         for (i = 0; i < 8; i++, twd >>= 1) {
 512                 if (twd & 0x1) {
 513                         st = FPREG_ADDR(fxsave, (i - tos) & 7);
 514
 515                         switch (st->exponent & 0x7fff) {
 516                         case 0x7fff:
 517                                 tag = FP_EXP_TAG_SPECIAL;
 518                                 break;
 519                         case 0x0000:
 520                                 if (!st->significand[0] &&
 521                                     !st->significand[1] &&
 522                                     !st->significand[2] &&
 523                                     !st->significand[3])
 524                                         tag = FP_EXP_TAG_ZERO;
 525                                 else
 526                                         tag = FP_EXP_TAG_SPECIAL;
 527                                 break;
 528                         default:
 529                                 if (st->significand[3] & 0x8000)
 530                                         tag = FP_EXP_TAG_VALID;
 531                                 else
 532                                         tag = FP_EXP_TAG_SPECIAL;
 533                                 break;
 534                         }
 535                 } else {
 536                         tag = FP_EXP_TAG_EMPTY;
 537                 }
 538                 ret |= tag << (2 * i);
 539         }
 540         return ret;
 541 }
 542
 543 /*
 544  * FXSR floating point environment conversions.
 545  */
 546
 547 void
 548 convert_from_fxsr(struct user_i387_ia32_struct *env, struct task_struct *tsk)
 549 {
 550         struct i387_fxsave_struct *fxsave = &tsk->thread.fpu.state.fxsave;
 551         struct _fpreg *to = (struct _fpreg *) &env->st_space[0];
 552         struct _fpxreg *from = (struct _fpxreg *) &fxsave->st_space[0];
 553         int i;
 554
 555         env->cwd = fxsave->cwd | 0xffff0000u;
 556         env->swd = fxsave->swd | 0xffff0000u;
 557         env->twd = twd_fxsr_to_i387(fxsave);
 558
 559 #ifdef CONFIG_X86_64
 560         env->fip = fxsave->rip;
 561         env->foo = fxsave->rdp;
 562         /*
 563          * should be actually ds/cs at fpu exception time, but
 564          * that information is not available in 64bit mode.
 565          */
 566         env->fcs = task_pt_regs(tsk)->cs;
 567         if (tsk == current) {
 568                 savesegment(ds, env->fos);
 569         } else {
 570                 env->fos = tsk->thread.ds;
 571         }
 572         env->fos |= 0xffff0000;
 573 #else
 574         env->fip = fxsave->fip;
 575         env->fcs = (u16) fxsave->fcs | ((u32) fxsave->fop << 16);
 576         env->foo = fxsave->foo;
 577         env->fos = fxsave->fos;
 578 #endif
 579
 580         for (i = 0; i < 8; ++i)
 581                 memcpy(&to[i], &from[i], sizeof(to[0]));
 582 }
 583
 584 void convert_to_fxsr(struct task_struct *tsk,
 585                      const struct user_i387_ia32_struct *env)
 586
 587 {
 588         struct i387_fxsave_struct *fxsave = &tsk->thread.fpu.state.fxsave;
 589         struct _fpreg *from = (struct _fpreg *) &env->st_space[0];
 590         struct _fpxreg *to = (struct _fpxreg *) &fxsave->st_space[0];
 591         int i;
 592
 593         fxsave->cwd = env->cwd;
 594         fxsave->swd = env->swd;
 595         fxsave->twd = twd_i387_to_fxsr(env->twd);
 596         fxsave->fop = (u16) ((u32) env->fcs >> 16);
 597 #ifdef CONFIG_X86_64
 598         fxsave->rip = env->fip;
 599         fxsave->rdp = env->foo;
 600         /* cs and ds ignored */
 601 #else
 602         fxsave->fip = env->fip;
 603         fxsave->fcs = (env->fcs & 0xffff);
 604         fxsave->foo = env->foo;
 605         fxsave->fos = env->fos;
 606 #endif
 607
 608         for (i = 0; i < 8; ++i)
 609                 memcpy(&to[i], &from[i], sizeof(from[0]));
 610 }
 611
 612 int fpregs_get(struct task_struct *target, const struct user_regset *regset,
 613                unsigned int pos, unsigned int count,
 614                void *kbuf, void __user *ubuf)
 615 {
 616         struct fpu *fpu = &target->thread.fpu;
 617         struct user_i387_ia32_struct env;
 618
 619         fpu__activate_stopped(fpu);
 620
 621         if (!static_cpu_has(X86_FEATURE_FPU))
 622                 return fpregs_soft_get(target, regset, pos, count, kbuf, ubuf);
 623
 624         if (!cpu_has_fxsr)
 625                 return user_regset_copyout(&pos, &count, &kbuf, &ubuf,
 626                                            &fpu->state.fsave, 0,
 627                                            -1);
 628
 629         sanitize_i387_state(target);
 630
 631         if (kbuf && pos == 0 && count == sizeof(env)) {
 632                 convert_from_fxsr(kbuf, target);
 633                 return 0;
 634         }
 635
 636         convert_from_fxsr(&env, target);
 637
 638         return user_regset_copyout(&pos, &count, &kbuf, &ubuf, &env, 0, -1);
 639 }
 640
 641 int fpregs_set(struct task_struct *target, const struct user_regset *regset,
 642                unsigned int pos, unsigned int count,
 643                const void *kbuf, const void __user *ubuf)
 644 {
 645         struct fpu *fpu = &target->thread.fpu;
 646         struct user_i387_ia32_struct env;
 647         int ret;
 648
 649         fpu__activate_stopped(fpu);
 650
 651         sanitize_i387_state(target);
 652
 653         if (!static_cpu_has(X86_FEATURE_FPU))
 654                 return fpregs_soft_set(target, regset, pos, count, kbuf, ubuf);
 655
 656         if (!cpu_has_fxsr)
 657                 return user_regset_copyin(&pos, &count, &kbuf, &ubuf,
 658                                           &fpu->state.fsave, 0,
 659                                           -1);
 660
 661         if (pos > 0 || count < sizeof(env))
 662                 convert_from_fxsr(&env, target);
 663
 664         ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, &env, 0, -1);
 665         if (!ret)
 666                 convert_to_fxsr(target, &env);
 667
 668         /*
 669          * update the header bit in the xsave header, indicating the
 670          * presence of FP.
 671          */
 672         if (cpu_has_xsave)
 673                 fpu->state.xsave.header.xfeatures |= XSTATE_FP;
 674         return ret;
 675 }
 676
 677 /*
 678  * FPU state for core dumps.
 679  * This is only used for a.out dumps now.
 680  * It is declared generically using elf_fpregset_t (which is
 681  * struct user_i387_struct) but is in fact only used for 32-bit
 682  * dumps, so on 64-bit it is really struct user_i387_ia32_struct.
 683  */
 684 int dump_fpu(struct pt_regs *regs, struct user_i387_struct *ufpu)
 685 {
 686         struct task_struct *tsk = current;
 687         struct fpu *fpu = &tsk->thread.fpu;
 688         int fpvalid;
 689
 690         fpvalid = fpu->fpstate_active;
 691         if (fpvalid)
 692                 fpvalid = !fpregs_get(tsk, NULL,
 693                                       0, sizeof(struct user_i387_ia32_struct),
 694                                       ufpu, NULL);
 695
 696         return fpvalid;
 697 }
 698 EXPORT_SYMBOL(dump_fpu);
 699
 700 #endif  /* CONFIG_X86_32 || CONFIG_IA32_EMULATION */