x86: clean up i387.c
[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
12 #include <asm/sigcontext.h>
13 #include <asm/processor.h>
14 #include <asm/math_emu.h>
15 #include <asm/uaccess.h>
16 #include <asm/ptrace.h>
17 #include <asm/i387.h>
18 #include <asm/user.h>
19
20 #ifdef CONFIG_X86_64
21 # include <asm/sigcontext32.h>
22 # include <asm/user32.h>
23 #else
24 # define save_i387_ia32         save_i387
25 # define restore_i387_ia32      restore_i387
26 # define _fpstate_ia32          _fpstate
27 # define user_i387_ia32_struct  user_i387_struct
28 # define user32_fxsr_struct     user_fxsr_struct
29 #endif
30
31 #ifdef CONFIG_MATH_EMULATION
32 # define HAVE_HWFP              (boot_cpu_data.hard_math)
33 #else
34 # define HAVE_HWFP              1
35 #endif
36
37 static unsigned int             mxcsr_feature_mask __read_mostly = 0xffffffffu;
38
39 void mxcsr_feature_mask_init(void)
40 {
41         unsigned long mask = 0;
42
43         clts();
44         if (cpu_has_fxsr) {
45                 memset(&current->thread.i387.fxsave, 0,
46                        sizeof(struct i387_fxsave_struct));
47                 asm volatile("fxsave %0" : : "m" (current->thread.i387.fxsave));
48                 mask = current->thread.i387.fxsave.mxcsr_mask;
49                 if (mask == 0)
50                         mask = 0x0000ffbf;
51         }
52         mxcsr_feature_mask &= mask;
53         stts();
54 }
55
56 #ifdef CONFIG_X86_64
57 /*
58  * Called at bootup to set up the initial FPU state that is later cloned
59  * into all processes.
60  */
61 void __cpuinit fpu_init(void)
62 {
63         unsigned long oldcr0 = read_cr0();
64         extern void __bad_fxsave_alignment(void);
65
66         if (offsetof(struct task_struct, thread.i387.fxsave) & 15)
67                 __bad_fxsave_alignment();
68
69         set_in_cr4(X86_CR4_OSFXSR);
70         set_in_cr4(X86_CR4_OSXMMEXCPT);
71
72         write_cr0(oldcr0 & ~(X86_CR0_TS|X86_CR0_EM)); /* clear TS and EM */
73
74         mxcsr_feature_mask_init();
75         /* clean state in init */
76         current_thread_info()->status = 0;
77         clear_used_math();
78 }
79 #endif  /* CONFIG_X86_64 */
80
81 /*
82  * The _current_ task is using the FPU for the first time
83  * so initialize it and set the mxcsr to its default
84  * value at reset if we support XMM instructions and then
85  * remeber the current task has used the FPU.
86  */
87 void init_fpu(struct task_struct *tsk)
88 {
89         if (tsk_used_math(tsk)) {
90                 if (tsk == current)
91                         unlazy_fpu(tsk);
92                 return;
93         }
94
95         if (cpu_has_fxsr) {
96                 memset(&tsk->thread.i387.fxsave, 0,
97                        sizeof(struct i387_fxsave_struct));
98                 tsk->thread.i387.fxsave.cwd = 0x37f;
99                 if (cpu_has_xmm)
100                         tsk->thread.i387.fxsave.mxcsr = MXCSR_DEFAULT;
101         } else {
102                 memset(&tsk->thread.i387.fsave, 0,
103                        sizeof(struct i387_fsave_struct));
104                 tsk->thread.i387.fsave.cwd = 0xffff037fu;
105                 tsk->thread.i387.fsave.swd = 0xffff0000u;
106                 tsk->thread.i387.fsave.twd = 0xffffffffu;
107                 tsk->thread.i387.fsave.fos = 0xffff0000u;
108         }
109         /*
110          * Only the device not available exception or ptrace can call init_fpu.
111          */
112         set_stopped_child_used_math(tsk);
113 }
114
115 int fpregs_active(struct task_struct *target, const struct user_regset *regset)
116 {
117         return tsk_used_math(target) ? regset->n : 0;
118 }
119
120 int xfpregs_active(struct task_struct *target, const struct user_regset *regset)
121 {
122         return (cpu_has_fxsr && tsk_used_math(target)) ? regset->n : 0;
123 }
124
125 int xfpregs_get(struct task_struct *target, const struct user_regset *regset,
126                 unsigned int pos, unsigned int count,
127                 void *kbuf, void __user *ubuf)
128 {
129         if (!cpu_has_fxsr)
130                 return -ENODEV;
131
132         init_fpu(target);
133
134         return user_regset_copyout(&pos, &count, &kbuf, &ubuf,
135                                    &target->thread.i387.fxsave, 0, -1);
136 }
137
138 int xfpregs_set(struct task_struct *target, const struct user_regset *regset,
139                 unsigned int pos, unsigned int count,
140                 const void *kbuf, const void __user *ubuf)
141 {
142         int ret;
143
144         if (!cpu_has_fxsr)
145                 return -ENODEV;
146
147         init_fpu(target);
148         set_stopped_child_used_math(target);
149
150         ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf,
151                                  &target->thread.i387.fxsave, 0, -1);
152
153         /*
154          * mxcsr reserved bits must be masked to zero for security reasons.
155          */
156         target->thread.i387.fxsave.mxcsr &= mxcsr_feature_mask;
157
158         return ret;
159 }
160
161 #if defined CONFIG_X86_32 || defined CONFIG_IA32_EMULATION
162
163 /*
164  * FPU tag word conversions.
165  */
166
167 static inline unsigned short twd_i387_to_fxsr(unsigned short twd)
168 {
169         unsigned int tmp; /* to avoid 16 bit prefixes in the code */
170
171         /* Transform each pair of bits into 01 (valid) or 00 (empty) */
172         tmp = ~twd;
173         tmp = (tmp | (tmp>>1)) & 0x5555; /* 0V0V0V0V0V0V0V0V */
174         /* and move the valid bits to the lower byte. */
175         tmp = (tmp | (tmp >> 1)) & 0x3333; /* 00VV00VV00VV00VV */
176         tmp = (tmp | (tmp >> 2)) & 0x0f0f; /* 0000VVVV0000VVVV */
177         tmp = (tmp | (tmp >> 4)) & 0x00ff; /* 00000000VVVVVVVV */
178
179         return tmp;
180 }
181
182 #define FPREG_ADDR(f, n)        ((void *)&(f)->st_space + (n) * 16);
183 #define FP_EXP_TAG_VALID        0
184 #define FP_EXP_TAG_ZERO         1
185 #define FP_EXP_TAG_SPECIAL      2
186 #define FP_EXP_TAG_EMPTY        3
187
188 static inline u32 twd_fxsr_to_i387(struct i387_fxsave_struct *fxsave)
189 {
190         struct _fpxreg *st;
191         u32 tos = (fxsave->swd >> 11) & 7;
192         u32 twd = (unsigned long) fxsave->twd;
193         u32 tag;
194         u32 ret = 0xffff0000u;
195         int i;
196
197         for (i = 0; i < 8; i++, twd >>= 1) {
198                 if (twd & 0x1) {
199                         st = FPREG_ADDR(fxsave, (i - tos) & 7);
200
201                         switch (st->exponent & 0x7fff) {
202                         case 0x7fff:
203                                 tag = FP_EXP_TAG_SPECIAL;
204                                 break;
205                         case 0x0000:
206                                 if (!st->significand[0] &&
207                                     !st->significand[1] &&
208                                     !st->significand[2] &&
209                                     !st->significand[3])
210                                         tag = FP_EXP_TAG_ZERO;
211                                 else
212                                         tag = FP_EXP_TAG_SPECIAL;
213                                 break;
214                         default:
215                                 if (st->significand[3] & 0x8000)
216                                         tag = FP_EXP_TAG_VALID;
217                                 else
218                                         tag = FP_EXP_TAG_SPECIAL;
219                                 break;
220                         }
221                 } else {
222                         tag = FP_EXP_TAG_EMPTY;
223                 }
224                 ret |= tag << (2 * i);
225         }
226         return ret;
227 }
228
229 /*
230  * FXSR floating point environment conversions.
231  */
232
233 static void
234 convert_from_fxsr(struct user_i387_ia32_struct *env, struct task_struct *tsk)
235 {
236         struct i387_fxsave_struct *fxsave = &tsk->thread.i387.fxsave;
237         struct _fpreg *to = (struct _fpreg *) &env->st_space[0];
238         struct _fpxreg *from = (struct _fpxreg *) &fxsave->st_space[0];
239         int i;
240
241         env->cwd = fxsave->cwd | 0xffff0000u;
242         env->swd = fxsave->swd | 0xffff0000u;
243         env->twd = twd_fxsr_to_i387(fxsave);
244
245 #ifdef CONFIG_X86_64
246         env->fip = fxsave->rip;
247         env->foo = fxsave->rdp;
248         if (tsk == current) {
249                 /*
250                  * should be actually ds/cs at fpu exception time, but
251                  * that information is not available in 64bit mode.
252                  */
253                 asm("mov %%ds, %[fos]" : [fos] "=r" (env->fos));
254                 asm("mov %%cs, %[fcs]" : [fcs] "=r" (env->fcs));
255         } else {
256                 struct pt_regs *regs = task_pt_regs(tsk);
257
258                 env->fos = 0xffff0000 | tsk->thread.ds;
259                 env->fcs = regs->cs;
260         }
261 #else
262         env->fip = fxsave->fip;
263         env->fcs = (u16) fxsave->fcs | ((u32) fxsave->fop << 16);
264         env->foo = fxsave->foo;
265         env->fos = fxsave->fos;
266 #endif
267
268         for (i = 0; i < 8; ++i)
269                 memcpy(&to[i], &from[i], sizeof(to[0]));
270 }
271
272 static void convert_to_fxsr(struct task_struct *tsk,
273                             const struct user_i387_ia32_struct *env)
274
275 {
276         struct i387_fxsave_struct *fxsave = &tsk->thread.i387.fxsave;
277         struct _fpreg *from = (struct _fpreg *) &env->st_space[0];
278         struct _fpxreg *to = (struct _fpxreg *) &fxsave->st_space[0];
279         int i;
280
281         fxsave->cwd = env->cwd;
282         fxsave->swd = env->swd;
283         fxsave->twd = twd_i387_to_fxsr(env->twd);
284         fxsave->fop = (u16) ((u32) env->fcs >> 16);
285 #ifdef CONFIG_X86_64
286         fxsave->rip = env->fip;
287         fxsave->rdp = env->foo;
288         /* cs and ds ignored */
289 #else
290         fxsave->fip = env->fip;
291         fxsave->fcs = (env->fcs & 0xffff);
292         fxsave->foo = env->foo;
293         fxsave->fos = env->fos;
294 #endif
295
296         for (i = 0; i < 8; ++i)
297                 memcpy(&to[i], &from[i], sizeof(from[0]));
298 }
299
300 int fpregs_get(struct task_struct *target, const struct user_regset *regset,
301                unsigned int pos, unsigned int count,
302                void *kbuf, void __user *ubuf)
303 {
304         struct user_i387_ia32_struct env;
305
306         if (!HAVE_HWFP)
307                 return fpregs_soft_get(target, regset, pos, count, kbuf, ubuf);
308
309         init_fpu(target);
310
311         if (!cpu_has_fxsr) {
312                 return user_regset_copyout(&pos, &count, &kbuf, &ubuf,
313                                            &target->thread.i387.fsave, 0, -1);
314         }
315
316         if (kbuf && pos == 0 && count == sizeof(env)) {
317                 convert_from_fxsr(kbuf, target);
318                 return 0;
319         }
320
321         convert_from_fxsr(&env, target);
322
323         return user_regset_copyout(&pos, &count, &kbuf, &ubuf, &env, 0, -1);
324 }
325
326 int fpregs_set(struct task_struct *target, const struct user_regset *regset,
327                unsigned int pos, unsigned int count,
328                const void *kbuf, const void __user *ubuf)
329 {
330         struct user_i387_ia32_struct env;
331         int ret;
332
333         if (!HAVE_HWFP)
334                 return fpregs_soft_set(target, regset, pos, count, kbuf, ubuf);
335
336         init_fpu(target);
337         set_stopped_child_used_math(target);
338
339         if (!cpu_has_fxsr) {
340                 return user_regset_copyin(&pos, &count, &kbuf, &ubuf,
341                                           &target->thread.i387.fsave, 0, -1);
342         }
343
344         if (pos > 0 || count < sizeof(env))
345                 convert_from_fxsr(&env, target);
346
347         ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, &env, 0, -1);
348         if (!ret)
349                 convert_to_fxsr(target, &env);
350
351         return ret;
352 }
353
354 /*
355  * Signal frame handlers.
356  */
357
358 static inline int save_i387_fsave(struct _fpstate_ia32 __user *buf)
359 {
360         struct task_struct *tsk = current;
361
362         unlazy_fpu(tsk);
363         tsk->thread.i387.fsave.status = tsk->thread.i387.fsave.swd;
364         if (__copy_to_user(buf, &tsk->thread.i387.fsave,
365                            sizeof(struct i387_fsave_struct)))
366                 return -1;
367         return 1;
368 }
369
370 static int save_i387_fxsave(struct _fpstate_ia32 __user *buf)
371 {
372         struct task_struct *tsk = current;
373         struct user_i387_ia32_struct env;
374         int err = 0;
375
376         unlazy_fpu(tsk);
377
378         convert_from_fxsr(&env, tsk);
379         if (__copy_to_user(buf, &env, sizeof(env)))
380                 return -1;
381
382         err |= __put_user(tsk->thread.i387.fxsave.swd, &buf->status);
383         err |= __put_user(X86_FXSR_MAGIC, &buf->magic);
384         if (err)
385                 return -1;
386
387         if (__copy_to_user(&buf->_fxsr_env[0], &tsk->thread.i387.fxsave,
388                            sizeof(struct i387_fxsave_struct)))
389                 return -1;
390         return 1;
391 }
392
393 int save_i387_ia32(struct _fpstate_ia32 __user *buf)
394 {
395         if (!used_math())
396                 return 0;
397         /*
398          * This will cause a "finit" to be triggered by the next
399          * attempted FPU operation by the 'current' process.
400          */
401         clear_used_math();
402
403         if (!HAVE_HWFP) {
404                 return fpregs_soft_get(current, NULL,
405                                        0, sizeof(struct user_i387_ia32_struct),
406                                        NULL, buf) ? -1 : 1;
407         }
408
409         if (cpu_has_fxsr)
410                 return save_i387_fxsave(buf);
411         else
412                 return save_i387_fsave(buf);
413 }
414
415 static inline int restore_i387_fsave(struct _fpstate_ia32 __user *buf)
416 {
417         struct task_struct *tsk = current;
418
419         clear_fpu(tsk);
420         return __copy_from_user(&tsk->thread.i387.fsave, buf,
421                                 sizeof(struct i387_fsave_struct));
422 }
423
424 static int restore_i387_fxsave(struct _fpstate_ia32 __user *buf)
425 {
426         struct task_struct *tsk = current;
427         struct user_i387_ia32_struct env;
428         int err;
429
430         clear_fpu(tsk);
431         err = __copy_from_user(&tsk->thread.i387.fxsave, &buf->_fxsr_env[0],
432                                sizeof(struct i387_fxsave_struct));
433         /* mxcsr reserved bits must be masked to zero for security reasons */
434         tsk->thread.i387.fxsave.mxcsr &= mxcsr_feature_mask;
435         if (err || __copy_from_user(&env, buf, sizeof(env)))
436                 return 1;
437         convert_to_fxsr(tsk, &env);
438
439         return 0;
440 }
441
442 int restore_i387_ia32(struct _fpstate_ia32 __user *buf)
443 {
444         int err;
445
446         if (HAVE_HWFP) {
447                 if (cpu_has_fxsr)
448                         err = restore_i387_fxsave(buf);
449                 else
450                         err = restore_i387_fsave(buf);
451         } else {
452                 err = fpregs_soft_set(current, NULL,
453                                       0, sizeof(struct user_i387_ia32_struct),
454                                       NULL, buf) != 0;
455         }
456         set_used_math();
457
458         return err;
459 }
460
461 /*
462  * FPU state for core dumps.
463  * This is only used for a.out dumps now.
464  * It is declared generically using elf_fpregset_t (which is
465  * struct user_i387_struct) but is in fact only used for 32-bit
466  * dumps, so on 64-bit it is really struct user_i387_ia32_struct.
467  */
468 int dump_fpu(struct pt_regs *regs, struct user_i387_struct *fpu)
469 {
470         struct task_struct *tsk = current;
471         int fpvalid;
472
473         fpvalid = !!used_math();
474         if (fpvalid)
475                 fpvalid = !fpregs_get(tsk, NULL,
476                                       0, sizeof(struct user_i387_ia32_struct),
477                                       fpu, NULL);
478
479         return fpvalid;
480 }
481 EXPORT_SYMBOL(dump_fpu);
482
483 #endif  /* CONFIG_X86_32 || CONFIG_IA32_EMULATION */