summaryrefslogtreecommitdiffstats
path: root/arch/x86/kernel/i387.c
blob: 8f8102d967b3f4111c58be6dccbd6e4192fc3864 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
/*
 *  Copyright (C) 1994 Linus Torvalds
 *
 *  Pentium III FXSR, SSE support
 *  General FPU state handling cleanups
 *	Gareth Hughes <gareth@valinux.com>, May 2000
 */
#include <linux/module.h>
#include <linux/regset.h>
#include <linux/sched.h>

#include <asm/sigcontext.h>
#include <asm/processor.h>
#include <asm/math_emu.h>
#include <asm/uaccess.h>
#include <asm/ptrace.h>
#include <asm/i387.h>
#include <asm/user.h>

#ifdef CONFIG_X86_64
# include <asm/sigcontext32.h>
# include <asm/user32.h>
#else
# define save_i387_ia32		save_i387
# define restore_i387_ia32	restore_i387
# define _fpstate_ia32		_fpstate
# define user_i387_ia32_struct	user_i387_struct
# define user32_fxsr_struct	user_fxsr_struct
#endif

#ifdef CONFIG_MATH_EMULATION
# define HAVE_HWFP		(boot_cpu_data.hard_math)
#else
# define HAVE_HWFP		1
#endif

static unsigned int		mxcsr_feature_mask __read_mostly = 0xffffffffu;

void mxcsr_feature_mask_init(void)
{
	unsigned long mask = 0;

	clts();
	if (cpu_has_fxsr) {
		memset(&current->thread.i387.fxsave, 0,
		       sizeof(struct i387_fxsave_struct));
		asm volatile("fxsave %0" : : "m" (current->thread.i387.fxsave));
		mask = current->thread.i387.fxsave.mxcsr_mask;
		if (mask == 0)
			mask = 0x0000ffbf;
	}
	mxcsr_feature_mask &= mask;
	stts();
}

#ifdef CONFIG_X86_64
/*
 * Called at bootup to set up the initial FPU state that is later cloned
 * into all processes.
 */
void __cpuinit fpu_init(void)
{
	unsigned long oldcr0 = read_cr0();
	extern void __bad_fxsave_alignment(void);

	if (offsetof(struct task_struct, thread.i387.fxsave) & 15)
		__bad_fxsave_alignment();

	set_in_cr4(X86_CR4_OSFXSR);
	set_in_cr4(X86_CR4_OSXMMEXCPT);

	write_cr0(oldcr0 & ~(X86_CR0_TS|X86_CR0_EM)); /* clear TS and EM */

	mxcsr_feature_mask_init();
	/* clean state in init */
	current_thread_info()->status = 0;
	clear_used_math();
}
#endif	/* CONFIG_X86_64 */

/*
 * The _current_ task is using the FPU for the first time
 * so initialize it and set the mxcsr to its default
 * value at reset if we support XMM instructions and then
 * remeber the current task has used the FPU.
 */
void init_fpu(struct task_struct *tsk)
{
	if (tsk_used_math(tsk)) {
		if (tsk == current)
			unlazy_fpu(tsk);
		return;
	}

	if (cpu_has_fxsr) {
		memset(&tsk->thread.i387.fxsave, 0,
		       sizeof(struct i387_fxsave_struct));
		tsk->thread.i387.fxsave.cwd = 0x37f;
		if (cpu_has_xmm)
			tsk->thread.i387.fxsave.mxcsr = MXCSR_DEFAULT;
	} else {
		memset(&tsk->thread.i387.fsave, 0,
		       sizeof(struct i387_fsave_struct));
		tsk->thread.i387.fsave.cwd = 0xffff037fu;
		tsk->thread.i387.fsave.swd = 0xffff0000u;
		tsk->thread.i387.fsave.twd = 0xffffffffu;
		tsk->thread.i387.fsave.fos = 0xffff0000u;
	}
	/*
	 * Only the device not available exception or ptrace can call init_fpu.
	 */
	set_stopped_child_used_math(tsk);
}

int fpregs_active(struct task_struct *target, const struct user_regset *regset)
{
	return tsk_used_math(target) ? regset->n : 0;
}

int xfpregs_active(struct task_struct *target, const struct user_regset *regset)
{
	return (cpu_has_fxsr && tsk_used_math(target)) ? regset->n : 0;
}

int xfpregs_get(struct task_struct *target, const struct user_regset *regset,
		unsigned int pos, unsigned int count,
		void *kbuf, void __user *ubuf)
{
	if (!cpu_has_fxsr)
		return -ENODEV;

	init_fpu(target);

	return user_regset_copyout(&pos, &count, &kbuf, &ubuf,
				   &target->thread.i387.fxsave, 0, -1);
}

int xfpregs_set(struct task_struct *target, const struct user_regset *regset,
		unsigned int pos, unsigned int count,
		const void *kbuf, const void __user *ubuf)
{
	int ret;

	if (!cpu_has_fxsr)
		return -ENODEV;

	init_fpu(target);
	set_stopped_child_used_math(target);

	ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf,
				 &target->thread.i387.fxsave, 0, -1);

	/*
	 * mxcsr reserved bits must be masked to zero for security reasons.
	 */
	target->thread.i387.fxsave.mxcsr &= mxcsr_feature_mask;

	return ret;
}

#if defined CONFIG_X86_32 || defined CONFIG_IA32_EMULATION

/*
 * FPU tag word conversions.
 */

static inline unsigned short twd_i387_to_fxsr(unsigned short twd)
{
	unsigned int tmp; /* to avoid 16 bit prefixes in the code */

	/* Transform each pair of bits into 01 (valid) or 00 (empty) */
	tmp = ~twd;
	tmp = (tmp | (tmp>>1)) & 0x5555; /* 0V0V0V0V0V0V0V0V */
	/* and move the valid bits to the lower byte. */
	tmp = (tmp | (tmp >> 1)) & 0x3333; /* 00VV00VV00VV00VV */
	tmp = (tmp | (tmp >> 2)) & 0x0f0f; /* 0000VVVV0000VVVV */
	tmp = (tmp | (tmp >> 4)) & 0x00ff; /* 00000000VVVVVVVV */

	return tmp;
}

#define FPREG_ADDR(f, n)	((void *)&(f)->st_space + (n) * 16);
#define FP_EXP_TAG_VALID	0
#define FP_EXP_TAG_ZERO		1
#define FP_EXP_TAG_SPECIAL	2
#define FP_EXP_TAG_EMPTY	3

static inline u32 twd_fxsr_to_i387(struct i387_fxsave_struct *fxsave)
{
	struct _fpxreg *st;
	u32 tos = (fxsave->swd >> 11) & 7;
	u32 twd = (unsigned long) fxsave->twd;
	u32 tag;
	u32 ret = 0xffff0000u;
	int i;

	for (i = 0; i < 8; i++, twd >>= 1) {
		if (twd & 0x1) {
			st = FPREG_ADDR(fxsave, (i - tos) & 7);

			switch (st->exponent & 0x7fff) {
			case 0x7fff:
				tag = FP_EXP_TAG_SPECIAL;
				break;
			case 0x0000:
				if (!st->significand[0] &&
				    !st->significand[1] &&
				    !st->significand[2] &&
				    !st->significand[3])
					tag = FP_EXP_TAG_ZERO;
				else
					tag = FP_EXP_TAG_SPECIAL;
				break;
			default:
				if (st->significand[3] & 0x8000)
					tag = FP_EXP_TAG_VALID;
				else
					tag = FP_EXP_TAG_SPECIAL;
				break;
			}
		} else {
			tag = FP_EXP_TAG_EMPTY;
		}
		ret |= tag << (2 * i);
	}
	return ret;
}

/*
 * FXSR floating point environment conversions.
 */

static void
convert_from_fxsr(struct user_i387_ia32_struct *env, struct task_struct *tsk)
{
	struct i387_fxsave_struct *fxsave = &tsk->thread.i387.fxsave;
	struct _fpreg *to = (struct _fpreg *) &env->st_space[0];
	struct _fpxreg *from = (struct _fpxreg *) &fxsave->st_space[0];
	int i;

	env->cwd = fxsave->cwd | 0xffff0000u;
	env->swd = fxsave->swd | 0xffff0000u;
	env->twd = twd_fxsr_to_i387(fxsave);

#ifdef CONFIG_X86_64
	env->fip = fxsave->rip;
	env->foo = fxsave->rdp;
	if (tsk == current) {
		/*
		 * should be actually ds/cs at fpu exception time, but
		 * that information is not available in 64bit mode.
		 */
		asm("mov %%ds, %[fos]" : [fos] "=r" (env->fos));
		asm("mov %%cs, %[fcs]" : [fcs] "=r" (env->fcs));
	} else {
		struct pt_regs *regs = task_pt_regs(tsk);

		env->fos = 0xffff0000 | tsk->thread.ds;
		env->fcs = regs->cs;
	}
#else
	env->fip = fxsave->fip;
	env->fcs = (u16) fxsave->fcs | ((u32) fxsave->fop << 16);
	env->foo = fxsave->foo;
	env->fos = fxsave->fos;
#endif

	for (i = 0; i < 8; ++i)
		memcpy(&to[i], &from[i], sizeof(to[0]));
}

static void convert_to_fxsr(struct task_struct *tsk,
			    const struct user_i387_ia32_struct *env)

{
	struct i387_fxsave_struct *fxsave = &tsk->thread.i387.fxsave;
	struct _fpreg *from = (struct _fpreg *) &env->st_space[0];
	struct _fpxreg *to = (struct _fpxreg *) &fxsave->st_space[0];
	int i;

	fxsave->cwd = env->cwd;
	fxsave->swd = env->swd;
	fxsave->twd = twd_i387_to_fxsr(env->twd);
	fxsave->fop = (u16) ((u32) env->fcs >> 16);
#ifdef CONFIG_X86_64
	fxsave->rip = env->fip;
	fxsave->rdp = env->foo;
	/* cs and ds ignored */
#else
	fxsave->fip = env->fip;
	fxsave->fcs = (env->fcs & 0xffff);
	fxsave->foo = env->foo;
	fxsave->fos = env->fos;
#endif

	for (i = 0; i < 8; ++i)
		memcpy(&to[i], &from[i], sizeof(from[0]));
}

int fpregs_get(struct task_struct *target, const struct user_regset *regset,
	       unsigned int pos, unsigned int count,
	       void *kbuf, void __user *ubuf)
{
	struct user_i387_ia32_struct env;

	if (!HAVE_HWFP)
		return fpregs_soft_get(target, regset, pos, count, kbuf, ubuf);

	init_fpu(target);

	if (!cpu_has_fxsr) {
		return user_regset_copyout(&pos, &count, &kbuf, &ubuf,
					   &target->thread.i387.fsave, 0, -1);
	}

	if (kbuf && pos == 0 && count == sizeof(env)) {
		convert_from_fxsr(kbuf, target);
		return 0;
	}

	convert_from_fxsr(&env, target);

	return user_regset_copyout(&pos, &count, &kbuf, &ubuf, &env, 0, -1);
}

int fpregs_set(struct task_struct *target, const struct user_regset *regset,
	       unsigned int pos, unsigned int count,
	       const void *kbuf, const void __user *ubuf)
{
	struct user_i387_ia32_struct env;
	int ret;

	if (!HAVE_HWFP)
		return fpregs_soft_set(target, regset, pos, count, kbuf, ubuf);

	init_fpu(target);
	set_stopped_child_used_math(target);

	if (!cpu_has_fxsr) {
		return user_regset_copyin(&pos, &count, &kbuf, &ubuf,
					  &target->thread.i387.fsave, 0, -1);
	}

	if (pos > 0 || count < sizeof(env))
		convert_from_fxsr(&env, target);

	ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, &env, 0, -1);
	if (!ret)
		convert_to_fxsr(target, &env);

	return ret;
}

/*
 * Signal frame handlers.
 */

static inline int save_i387_fsave(struct _fpstate_ia32 __user *buf)
{
	struct task_struct *tsk = current;

	unlazy_fpu(tsk);
	tsk->thread.i387.fsave.status = tsk->thread.i387.fsave.swd;
	if (__copy_to_user(buf, &tsk->thread.i387.fsave,
			   sizeof(struct i387_fsave_struct)))
		return -1;
	return 1;
}

static int save_i387_fxsave(struct _fpstate_ia32 __user *buf)
{
	struct task_struct *tsk = current;
	struct user_i387_ia32_struct env;
	int err = 0;

	unlazy_fpu(tsk);

	convert_from_fxsr(&env, tsk);
	if (__copy_to_user(buf, &env, sizeof(env)))
		return -1;

	err |= __put_user(tsk->thread.i387.fxsave.swd, &buf->status);
	err |= __put_user(X86_FXSR_MAGIC, &buf->magic);
	if (err)
		return -1;

	if (__copy_to_user(&buf->_fxsr_env[0], &tsk->thread.i387.fxsave,
			   sizeof(struct i387_fxsave_struct)))
		return -1;
	return 1;
}

int save_i387_ia32(struct _fpstate_ia32 __user *buf)
{
	if (!used_math())
		return 0;
	/*
	 * This will cause a "finit" to be triggered by the next
	 * attempted FPU operation by the 'current' process.
	 */
	clear_used_math();

	if (!HAVE_HWFP) {
		return fpregs_soft_get(current, NULL,
				       0, sizeof(struct user_i387_ia32_struct),
				       NULL, buf) ? -1 : 1;
	}

	if (cpu_has_fxsr)
		return save_i387_fxsave(buf);
	else
		return save_i387_fsave(buf);
}

static inline int restore_i387_fsave(struct _fpstate_ia32 __user *buf)
{
	struct task_struct *tsk = current;

	clear_fpu(tsk);
	return __copy_from_user(&tsk->thread.i387.fsave, buf,
				sizeof(struct i387_fsave_struct));
}

static int restore_i387_fxsave(struct _fpstate_ia32 __user *buf)
{
	struct task_struct *tsk = current;
	struct user_i387_ia32_struct env;
	int err;

	clear_fpu(tsk);
	err = __copy_from_user(&tsk->thread.i387.fxsave, &buf->_fxsr_env[0],
			       sizeof(struct i387_fxsave_struct));
	/* mxcsr reserved bits must be masked to zero for security reasons */
	tsk->thread.i387.fxsave.mxcsr &= mxcsr_feature_mask;
	if (err || __copy_from_user(&env, buf, sizeof(env)))
		return 1;
	convert_to_fxsr(tsk, &env);

	return 0;
}

int restore_i387_ia32(struct _fpstate_ia32 __user *buf)
{
	int err;

	if (HAVE_HWFP) {
		if (cpu_has_fxsr)
			err = restore_i387_fxsave(buf);
		else
			err = restore_i387_fsave(buf);
	} else {
		err = fpregs_soft_set(current, NULL,
				      0, sizeof(struct user_i387_ia32_struct),
				      NULL, buf) != 0;
	}
	set_used_math();

	return err;
}

/*
 * FPU state for core dumps.
 * This is only used for a.out dumps now.
 * It is declared generically using elf_fpregset_t (which is
 * struct user_i387_struct) but is in fact only used for 32-bit
 * dumps, so on 64-bit it is really struct user_i387_ia32_struct.
 */
int dump_fpu(struct pt_regs *regs, struct user_i387_struct *fpu)
{
	struct task_struct *tsk = current;
	int fpvalid;

	fpvalid = !!used_math();
	if (fpvalid)
		fpvalid = !fpregs_get(tsk, NULL,
				      0, sizeof(struct user_i387_ia32_struct),
				      fpu, NULL);

	return fpvalid;
}
EXPORT_SYMBOL(dump_fpu);

#endif	/* CONFIG_X86_32 || CONFIG_IA32_EMULATION */
OpenPOWER on IntegriCloud