54c31c285488e4d0db84826dcd697878e20fc953
[linux-2.6.git] / 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 unsigned int sig_xstate_ia32_size = sizeof(struct _fpstate_ia32);
44 static struct i387_fxsave_struct fx_scratch __cpuinitdata;
45
46 void __cpuinit mxcsr_feature_mask_init(void)
47 {
48         unsigned long mask = 0;
49
50         clts();
51         if (cpu_has_fxsr) {
52                 memset(&fx_scratch, 0, sizeof(struct i387_fxsave_struct));
53                 asm volatile("fxsave %0" : : "m" (fx_scratch));
54                 mask = fx_scratch.mxcsr_mask;
55                 if (mask == 0)
56                         mask = 0x0000ffbf;
57         }
58         mxcsr_feature_mask &= mask;
59         stts();
60 }
61
62 void __cpuinit init_thread_xstate(void)
63 {
64         if (!HAVE_HWFP) {
65                 xstate_size = sizeof(struct i387_soft_struct);
66                 return;
67         }
68
69         if (cpu_has_xsave) {
70                 xsave_cntxt_init();
71                 return;
72         }
73
74         if (cpu_has_fxsr)
75                 xstate_size = sizeof(struct i387_fxsave_struct);
76 #ifdef CONFIG_X86_32
77         else
78                 xstate_size = sizeof(struct i387_fsave_struct);
79 #endif
80 }
81
82 #ifdef CONFIG_X86_64
83 /*
84  * Called at bootup to set up the initial FPU state that is later cloned
85  * into all processes.
86  */
87 void __cpuinit fpu_init(void)
88 {
89         unsigned long oldcr0 = read_cr0();
90
91         set_in_cr4(X86_CR4_OSFXSR);
92         set_in_cr4(X86_CR4_OSXMMEXCPT);
93
94         write_cr0(oldcr0 & ~(X86_CR0_TS|X86_CR0_EM)); /* clear TS and EM */
95
96         /*
97          * Boot processor to setup the FP and extended state context info.
98          */
99         if (!smp_processor_id())
100                 init_thread_xstate();
101         xsave_init();
102
103         mxcsr_feature_mask_init();
104         /* clean state in init */
105         if (cpu_has_xsave)
106                 current_thread_info()->status = TS_XSAVE;
107         else
108                 current_thread_info()->status = 0;
109         clear_used_math();
110 }
111 #endif  /* CONFIG_X86_64 */
112
113 /*
114  * The _current_ task is using the FPU for the first time
115  * so initialize it and set the mxcsr to its default
116  * value at reset if we support XMM instructions and then
117  * remeber the current task has used the FPU.
118  */
119 int init_fpu(struct task_struct *tsk)
120 {
121         if (tsk_used_math(tsk)) {
122                 if (HAVE_HWFP && tsk == current)
123                         unlazy_fpu(tsk);
124                 return 0;
125         }
126
127         /*
128          * Memory allocation at the first usage of the FPU and other state.
129          */
130         if (!tsk->thread.xstate) {
131                 tsk->thread.xstate = kmem_cache_alloc(task_xstate_cachep,
132                                                       GFP_KERNEL);
133                 if (!tsk->thread.xstate)
134                         return -ENOMEM;
135         }
136
137 #ifdef CONFIG_X86_32
138         if (!HAVE_HWFP) {
139                 memset(tsk->thread.xstate, 0, xstate_size);
140                 finit_task(tsk);
141                 set_stopped_child_used_math(tsk);
142                 return 0;
143         }
144 #endif
145
146         if (cpu_has_fxsr) {
147                 struct i387_fxsave_struct *fx = &tsk->thread.xstate->fxsave;
148
149                 memset(fx, 0, xstate_size);
150                 fx->cwd = 0x37f;
151                 if (cpu_has_xmm)
152                         fx->mxcsr = MXCSR_DEFAULT;
153         } else {
154                 struct i387_fsave_struct *fp = &tsk->thread.xstate->fsave;
155                 memset(fp, 0, xstate_size);
156                 fp->cwd = 0xffff037fu;
157                 fp->swd = 0xffff0000u;
158                 fp->twd = 0xffffffffu;
159                 fp->fos = 0xffff0000u;
160         }
161         /*
162          * Only the device not available exception or ptrace can call init_fpu.
163          */
164         set_stopped_child_used_math(tsk);
165         return 0;
166 }
167
168 /*
169  * The xstateregs_active() routine is the same as the fpregs_active() routine,
170  * as the "regset->n" for the xstate regset will be updated based on the feature
171  * capabilites supported by the xsave.
172  */
173 int fpregs_active(struct task_struct *target, const struct user_regset *regset)
174 {
175         return tsk_used_math(target) ? regset->n : 0;
176 }
177
178 int xfpregs_active(struct task_struct *target, const struct user_regset *regset)
179 {
180         return (cpu_has_fxsr && tsk_used_math(target)) ? regset->n : 0;
181 }
182
183 int xfpregs_get(struct task_struct *target, const struct user_regset *regset,
184                 unsigned int pos, unsigned int count,
185                 void *kbuf, void __user *ubuf)
186 {
187         int ret;
188
189         if (!cpu_has_fxsr)
190                 return -ENODEV;
191
192         ret = init_fpu(target);
193         if (ret)
194                 return ret;
195
196         return user_regset_copyout(&pos, &count, &kbuf, &ubuf,
197                                    &target->thread.xstate->fxsave, 0, -1);
198 }
199
200 int xfpregs_set(struct task_struct *target, const struct user_regset *regset,
201                 unsigned int pos, unsigned int count,
202                 const void *kbuf, const void __user *ubuf)
203 {
204         int ret;
205
206         if (!cpu_has_fxsr)
207                 return -ENODEV;
208
209         ret = init_fpu(target);
210         if (ret)
211                 return ret;
212
213         ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf,
214                                  &target->thread.xstate->fxsave, 0, -1);
215
216         /*
217          * mxcsr reserved bits must be masked to zero for security reasons.
218          */
219         target->thread.xstate->fxsave.mxcsr &= mxcsr_feature_mask;
220
221         /*
222          * update the header bits in the xsave header, indicating the
223          * presence of FP and SSE state.
224          */
225         if (cpu_has_xsave)
226                 target->thread.xstate->xsave.xsave_hdr.xstate_bv |= XSTATE_FPSSE;
227
228         return ret;
229 }
230
231 int xstateregs_get(struct task_struct *target, const struct user_regset *regset,
232                 unsigned int pos, unsigned int count,
233                 void *kbuf, void __user *ubuf)
234 {
235         int ret;
236
237         if (!cpu_has_xsave)
238                 return -ENODEV;
239
240         ret = init_fpu(target);
241         if (ret)
242                 return ret;
243
244         /*
245          * Copy the 48bytes defined by the software first into the xstate
246          * memory layout in the thread struct, so that we can copy the entire
247          * xstateregs to the user using one user_regset_copyout().
248          */
249         memcpy(&target->thread.xstate->fxsave.sw_reserved,
250                xstate_fx_sw_bytes, sizeof(xstate_fx_sw_bytes));
251
252         /*
253          * Copy the xstate memory layout.
254          */
255         ret = user_regset_copyout(&pos, &count, &kbuf, &ubuf,
256                                   &target->thread.xstate->xsave, 0, -1);
257         return ret;
258 }
259
260 int xstateregs_set(struct task_struct *target, const struct user_regset *regset,
261                   unsigned int pos, unsigned int count,
262                   const void *kbuf, const void __user *ubuf)
263 {
264         int ret;
265         struct xsave_hdr_struct *xsave_hdr;
266
267         if (!cpu_has_xsave)
268                 return -ENODEV;
269
270         ret = init_fpu(target);
271         if (ret)
272                 return ret;
273
274         ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf,
275                                  &target->thread.xstate->xsave, 0, -1);
276
277         /*
278          * mxcsr reserved bits must be masked to zero for security reasons.
279          */
280         target->thread.xstate->fxsave.mxcsr &= mxcsr_feature_mask;
281
282         xsave_hdr = &target->thread.xstate->xsave.xsave_hdr;
283
284         xsave_hdr->xstate_bv &= pcntxt_mask;
285         /*
286          * These bits must be zero.
287          */
288         xsave_hdr->reserved1[0] = xsave_hdr->reserved1[1] = 0;
289
290         return ret;
291 }
292
293 #if defined CONFIG_X86_32 || defined CONFIG_IA32_EMULATION
294
295 /*
296  * FPU tag word conversions.
297  */
298
299 static inline unsigned short twd_i387_to_fxsr(unsigned short twd)
300 {
301         unsigned int tmp; /* to avoid 16 bit prefixes in the code */
302
303         /* Transform each pair of bits into 01 (valid) or 00 (empty) */
304         tmp = ~twd;
305         tmp = (tmp | (tmp>>1)) & 0x5555; /* 0V0V0V0V0V0V0V0V */
306         /* and move the valid bits to the lower byte. */
307         tmp = (tmp | (tmp >> 1)) & 0x3333; /* 00VV00VV00VV00VV */
308         tmp = (tmp | (tmp >> 2)) & 0x0f0f; /* 0000VVVV0000VVVV */
309         tmp = (tmp | (tmp >> 4)) & 0x00ff; /* 00000000VVVVVVVV */
310
311         return tmp;
312 }
313
314 #define FPREG_ADDR(f, n)        ((void *)&(f)->st_space + (n) * 16);
315 #define FP_EXP_TAG_VALID        0
316 #define FP_EXP_TAG_ZERO         1
317 #define FP_EXP_TAG_SPECIAL      2
318 #define FP_EXP_TAG_EMPTY        3
319
320 static inline u32 twd_fxsr_to_i387(struct i387_fxsave_struct *fxsave)
321 {
322         struct _fpxreg *st;
323         u32 tos = (fxsave->swd >> 11) & 7;
324         u32 twd = (unsigned long) fxsave->twd;
325         u32 tag;
326         u32 ret = 0xffff0000u;
327         int i;
328
329         for (i = 0; i < 8; i++, twd >>= 1) {
330                 if (twd & 0x1) {
331                         st = FPREG_ADDR(fxsave, (i - tos) & 7);
332
333                         switch (st->exponent & 0x7fff) {
334                         case 0x7fff:
335                                 tag = FP_EXP_TAG_SPECIAL;
336                                 break;
337                         case 0x0000:
338                                 if (!st->significand[0] &&
339                                     !st->significand[1] &&
340                                     !st->significand[2] &&
341                                     !st->significand[3])
342                                         tag = FP_EXP_TAG_ZERO;
343                                 else
344                                         tag = FP_EXP_TAG_SPECIAL;
345                                 break;
346                         default:
347                                 if (st->significand[3] & 0x8000)
348                                         tag = FP_EXP_TAG_VALID;
349                                 else
350                                         tag = FP_EXP_TAG_SPECIAL;
351                                 break;
352                         }
353                 } else {
354                         tag = FP_EXP_TAG_EMPTY;
355                 }
356                 ret |= tag << (2 * i);
357         }
358         return ret;
359 }
360
361 /*
362  * FXSR floating point environment conversions.
363  */
364
365 static void
366 convert_from_fxsr(struct user_i387_ia32_struct *env, struct task_struct *tsk)
367 {
368         struct i387_fxsave_struct *fxsave = &tsk->thread.xstate->fxsave;
369         struct _fpreg *to = (struct _fpreg *) &env->st_space[0];
370         struct _fpxreg *from = (struct _fpxreg *) &fxsave->st_space[0];
371         int i;
372
373         env->cwd = fxsave->cwd | 0xffff0000u;
374         env->swd = fxsave->swd | 0xffff0000u;
375         env->twd = twd_fxsr_to_i387(fxsave);
376
377 #ifdef CONFIG_X86_64
378         env->fip = fxsave->rip;
379         env->foo = fxsave->rdp;
380         if (tsk == current) {
381                 /*
382                  * should be actually ds/cs at fpu exception time, but
383                  * that information is not available in 64bit mode.
384                  */
385                 asm("mov %%ds, %[fos]" : [fos] "=r" (env->fos));
386                 asm("mov %%cs, %[fcs]" : [fcs] "=r" (env->fcs));
387         } else {
388                 struct pt_regs *regs = task_pt_regs(tsk);
389
390                 env->fos = 0xffff0000 | tsk->thread.ds;
391                 env->fcs = regs->cs;
392         }
393 #else
394         env->fip = fxsave->fip;
395         env->fcs = (u16) fxsave->fcs | ((u32) fxsave->fop << 16);
396         env->foo = fxsave->foo;
397         env->fos = fxsave->fos;
398 #endif
399
400         for (i = 0; i < 8; ++i)
401                 memcpy(&to[i], &from[i], sizeof(to[0]));
402 }
403
404 static void convert_to_fxsr(struct task_struct *tsk,
405                             const struct user_i387_ia32_struct *env)
406
407 {
408         struct i387_fxsave_struct *fxsave = &tsk->thread.xstate->fxsave;
409         struct _fpreg *from = (struct _fpreg *) &env->st_space[0];
410         struct _fpxreg *to = (struct _fpxreg *) &fxsave->st_space[0];
411         int i;
412
413         fxsave->cwd = env->cwd;
414         fxsave->swd = env->swd;
415         fxsave->twd = twd_i387_to_fxsr(env->twd);
416         fxsave->fop = (u16) ((u32) env->fcs >> 16);
417 #ifdef CONFIG_X86_64
418         fxsave->rip = env->fip;
419         fxsave->rdp = env->foo;
420         /* cs and ds ignored */
421 #else
422         fxsave->fip = env->fip;
423         fxsave->fcs = (env->fcs & 0xffff);
424         fxsave->foo = env->foo;
425         fxsave->fos = env->fos;
426 #endif
427
428         for (i = 0; i < 8; ++i)
429                 memcpy(&to[i], &from[i], sizeof(from[0]));
430 }
431
432 int fpregs_get(struct task_struct *target, const struct user_regset *regset,
433                unsigned int pos, unsigned int count,
434                void *kbuf, void __user *ubuf)
435 {
436         struct user_i387_ia32_struct env;
437         int ret;
438
439         ret = init_fpu(target);
440         if (ret)
441                 return ret;
442
443         if (!HAVE_HWFP)
444                 return fpregs_soft_get(target, regset, pos, count, kbuf, ubuf);
445
446         if (!cpu_has_fxsr) {
447                 return user_regset_copyout(&pos, &count, &kbuf, &ubuf,
448                                            &target->thread.xstate->fsave, 0,
449                                            -1);
450         }
451
452         if (kbuf && pos == 0 && count == sizeof(env)) {
453                 convert_from_fxsr(kbuf, target);
454                 return 0;
455         }
456
457         convert_from_fxsr(&env, target);
458
459         return user_regset_copyout(&pos, &count, &kbuf, &ubuf, &env, 0, -1);
460 }
461
462 int fpregs_set(struct task_struct *target, const struct user_regset *regset,
463                unsigned int pos, unsigned int count,
464                const void *kbuf, const void __user *ubuf)
465 {
466         struct user_i387_ia32_struct env;
467         int ret;
468
469         ret = init_fpu(target);
470         if (ret)
471                 return ret;
472
473         if (!HAVE_HWFP)
474                 return fpregs_soft_set(target, regset, pos, count, kbuf, ubuf);
475
476         if (!cpu_has_fxsr) {
477                 return user_regset_copyin(&pos, &count, &kbuf, &ubuf,
478                                           &target->thread.xstate->fsave, 0, -1);
479         }
480
481         if (pos > 0 || count < sizeof(env))
482                 convert_from_fxsr(&env, target);
483
484         ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, &env, 0, -1);
485         if (!ret)
486                 convert_to_fxsr(target, &env);
487
488         /*
489          * update the header bit in the xsave header, indicating the
490          * presence of FP.
491          */
492         if (cpu_has_xsave)
493                 target->thread.xstate->xsave.xsave_hdr.xstate_bv |= XSTATE_FP;
494         return ret;
495 }
496
497 /*
498  * Signal frame handlers.
499  */
500
501 static inline int save_i387_fsave(struct _fpstate_ia32 __user *buf)
502 {
503         struct task_struct *tsk = current;
504         struct i387_fsave_struct *fp = &tsk->thread.xstate->fsave;
505
506         fp->status = fp->swd;
507         if (__copy_to_user(buf, fp, sizeof(struct i387_fsave_struct)))
508                 return -1;
509         return 1;
510 }
511
512 static int save_i387_fxsave(struct _fpstate_ia32 __user *buf)
513 {
514         struct task_struct *tsk = current;
515         struct i387_fxsave_struct *fx = &tsk->thread.xstate->fxsave;
516         struct user_i387_ia32_struct env;
517         int err = 0;
518
519         convert_from_fxsr(&env, tsk);
520         if (__copy_to_user(buf, &env, sizeof(env)))
521                 return -1;
522
523         err |= __put_user(fx->swd, &buf->status);
524         err |= __put_user(X86_FXSR_MAGIC, &buf->magic);
525         if (err)
526                 return -1;
527
528         if (__copy_to_user(&buf->_fxsr_env[0], fx, xstate_size))
529                 return -1;
530         return 1;
531 }
532
533 static int save_i387_xsave(void __user *buf)
534 {
535         struct task_struct *tsk = current;
536         struct _fpstate_ia32 __user *fx = buf;
537         int err = 0;
538
539         /*
540          * For legacy compatible, we always set FP/SSE bits in the bit
541          * vector while saving the state to the user context.
542          * This will enable us capturing any changes(during sigreturn) to
543          * the FP/SSE bits by the legacy applications which don't touch
544          * xstate_bv in the xsave header.
545          *
546          * xsave aware applications can change the xstate_bv in the xsave
547          * header as well as change any contents in the memory layout.
548          * xrestore as part of sigreturn will capture all the changes.
549          */
550         tsk->thread.xstate->xsave.xsave_hdr.xstate_bv |= XSTATE_FPSSE;
551
552         if (save_i387_fxsave(fx) < 0)
553                 return -1;
554
555         err = __copy_to_user(&fx->sw_reserved, &fx_sw_reserved_ia32,
556                              sizeof(struct _fpx_sw_bytes));
557         err |= __put_user(FP_XSTATE_MAGIC2,
558                           (__u32 __user *) (buf + sig_xstate_ia32_size
559                                             - FP_XSTATE_MAGIC2_SIZE));
560         if (err)
561                 return -1;
562
563         return 1;
564 }
565
566 int save_i387_xstate_ia32(void __user *buf)
567 {
568         struct _fpstate_ia32 __user *fp = (struct _fpstate_ia32 __user *) buf;
569         struct task_struct *tsk = current;
570
571         if (!used_math())
572                 return 0;
573
574         if (!access_ok(VERIFY_WRITE, buf, sig_xstate_ia32_size))
575                 return -EACCES;
576         /*
577          * This will cause a "finit" to be triggered by the next
578          * attempted FPU operation by the 'current' process.
579          */
580         clear_used_math();
581
582         if (!HAVE_HWFP) {
583                 return fpregs_soft_get(current, NULL,
584                                        0, sizeof(struct user_i387_ia32_struct),
585                                        NULL, fp) ? -1 : 1;
586         }
587
588         unlazy_fpu(tsk);
589
590         if (cpu_has_xsave)
591                 return save_i387_xsave(fp);
592         if (cpu_has_fxsr)
593                 return save_i387_fxsave(fp);
594         else
595                 return save_i387_fsave(fp);
596 }
597
598 static inline int restore_i387_fsave(struct _fpstate_ia32 __user *buf)
599 {
600         struct task_struct *tsk = current;
601
602         return __copy_from_user(&tsk->thread.xstate->fsave, buf,
603                                 sizeof(struct i387_fsave_struct));
604 }
605
606 static int restore_i387_fxsave(struct _fpstate_ia32 __user *buf,
607                                unsigned int size)
608 {
609         struct task_struct *tsk = current;
610         struct user_i387_ia32_struct env;
611         int err;
612
613         err = __copy_from_user(&tsk->thread.xstate->fxsave, &buf->_fxsr_env[0],
614                                size);
615         /* mxcsr reserved bits must be masked to zero for security reasons */
616         tsk->thread.xstate->fxsave.mxcsr &= mxcsr_feature_mask;
617         if (err || __copy_from_user(&env, buf, sizeof(env)))
618                 return 1;
619         convert_to_fxsr(tsk, &env);
620
621         return 0;
622 }
623
624 static int restore_i387_xsave(void __user *buf)
625 {
626         struct _fpx_sw_bytes fx_sw_user;
627         struct _fpstate_ia32 __user *fx_user =
628                         ((struct _fpstate_ia32 __user *) buf);
629         struct i387_fxsave_struct __user *fx =
630                 (struct i387_fxsave_struct __user *) &fx_user->_fxsr_env[0];
631         struct xsave_hdr_struct *xsave_hdr =
632                                 &current->thread.xstate->xsave.xsave_hdr;
633         u64 mask;
634         int err;
635
636         if (check_for_xstate(fx, buf, &fx_sw_user))
637                 goto fx_only;
638
639         mask = fx_sw_user.xstate_bv;
640
641         err = restore_i387_fxsave(buf, fx_sw_user.xstate_size);
642
643         xsave_hdr->xstate_bv &= pcntxt_mask;
644         /*
645          * These bits must be zero.
646          */
647         xsave_hdr->reserved1[0] = xsave_hdr->reserved1[1] = 0;
648
649         /*
650          * Init the state that is not present in the memory layout
651          * and enabled by the OS.
652          */
653         mask = ~(pcntxt_mask & ~mask);
654         xsave_hdr->xstate_bv &= mask;
655
656         return err;
657 fx_only:
658         /*
659          * Couldn't find the extended state information in the memory
660          * layout. Restore the FP/SSE and init the other extended state
661          * enabled by the OS.
662          */
663         xsave_hdr->xstate_bv = XSTATE_FPSSE;
664         return restore_i387_fxsave(buf, sizeof(struct i387_fxsave_struct));
665 }
666
667 int restore_i387_xstate_ia32(void __user *buf)
668 {
669         int err;
670         struct task_struct *tsk = current;
671         struct _fpstate_ia32 __user *fp = (struct _fpstate_ia32 __user *) buf;
672
673         if (HAVE_HWFP)
674                 clear_fpu(tsk);
675
676         if (!buf) {
677                 if (used_math()) {
678                         clear_fpu(tsk);
679                         clear_used_math();
680                 }
681
682                 return 0;
683         } else
684                 if (!access_ok(VERIFY_READ, buf, sig_xstate_ia32_size))
685                         return -EACCES;
686
687         if (!used_math()) {
688                 err = init_fpu(tsk);
689                 if (err)
690                         return err;
691         }
692
693         if (HAVE_HWFP) {
694                 if (cpu_has_xsave)
695                         err = restore_i387_xsave(buf);
696                 else if (cpu_has_fxsr)
697                         err = restore_i387_fxsave(fp, sizeof(struct
698                                                            i387_fxsave_struct));
699                 else
700                         err = restore_i387_fsave(fp);
701         } else {
702                 err = fpregs_soft_set(current, NULL,
703                                       0, sizeof(struct user_i387_ia32_struct),
704                                       NULL, fp) != 0;
705         }
706         set_used_math();
707
708         return err;
709 }
710
711 /*
712  * FPU state for core dumps.
713  * This is only used for a.out dumps now.
714  * It is declared generically using elf_fpregset_t (which is
715  * struct user_i387_struct) but is in fact only used for 32-bit
716  * dumps, so on 64-bit it is really struct user_i387_ia32_struct.
717  */
718 int dump_fpu(struct pt_regs *regs, struct user_i387_struct *fpu)
719 {
720         struct task_struct *tsk = current;
721         int fpvalid;
722
723         fpvalid = !!used_math();
724         if (fpvalid)
725                 fpvalid = !fpregs_get(tsk, NULL,
726                                       0, sizeof(struct user_i387_ia32_struct),
727                                       fpu, NULL);
728
729         return fpvalid;
730 }
731 EXPORT_SYMBOL(dump_fpu);
732
733 #endif  /* CONFIG_X86_32 || CONFIG_IA32_EMULATION */