fpu-internal.h revision 9b13a93df267af681a66a6a738bf1af10102da7d 
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 * x86-64 work by Andi Kleen 2002
8 */
9
10#ifndef _FPU_INTERNAL_H
11#define _FPU_INTERNAL_H
12
13#include <linux/kernel_stat.h>
14#include <linux/regset.h>
15#include <linux/compat.h>
16#include <linux/slab.h>
17#include <asm/asm.h>
18#include <asm/cpufeature.h>
19#include <asm/processor.h>
20#include <asm/sigcontext.h>
21#include <asm/user.h>
22#include <asm/uaccess.h>
23#include <asm/xsave.h>
24#include <asm/smap.h>
25
26#ifdef CONFIG_X86_64
27# include <asm/sigcontext32.h>
28# include <asm/user32.h>
29struct ksignal;
30int ia32_setup_rt_frame(int sig, struct ksignal *ksig,
31			compat_sigset_t *set, struct pt_regs *regs);
32int ia32_setup_frame(int sig, struct ksignal *ksig,
33		     compat_sigset_t *set, struct pt_regs *regs);
34#else
35# define user_i387_ia32_struct	user_i387_struct
36# define user32_fxsr_struct	user_fxsr_struct
37# define ia32_setup_frame	__setup_frame
38# define ia32_setup_rt_frame	__setup_rt_frame
39#endif
40
41extern unsigned int mxcsr_feature_mask;
42extern void fpu_init(void);
43extern void eager_fpu_init(void);
44
45DECLARE_PER_CPU(struct task_struct *, fpu_owner_task);
46
47extern void convert_from_fxsr(struct user_i387_ia32_struct *env,
48			      struct task_struct *tsk);
49extern void convert_to_fxsr(struct task_struct *tsk,
50			    const struct user_i387_ia32_struct *env);
51
52extern user_regset_active_fn fpregs_active, xfpregs_active;
53extern user_regset_get_fn fpregs_get, xfpregs_get, fpregs_soft_get,
54				xstateregs_get;
55extern user_regset_set_fn fpregs_set, xfpregs_set, fpregs_soft_set,
56				 xstateregs_set;
57
58/*
59 * xstateregs_active == fpregs_active. Please refer to the comment
60 * at the definition of fpregs_active.
61 */
62#define xstateregs_active	fpregs_active
63
64#ifdef CONFIG_MATH_EMULATION
65extern void finit_soft_fpu(struct i387_soft_struct *soft);
66#else
67static inline void finit_soft_fpu(struct i387_soft_struct *soft) {}
68#endif
69
70static inline int is_ia32_compat_frame(void)
71{
72	return config_enabled(CONFIG_IA32_EMULATION) &&
73	       test_thread_flag(TIF_IA32);
74}
75
76static inline int is_ia32_frame(void)
77{
78	return config_enabled(CONFIG_X86_32) || is_ia32_compat_frame();
79}
80
81static inline int is_x32_frame(void)
82{
83	return config_enabled(CONFIG_X86_X32_ABI) && test_thread_flag(TIF_X32);
84}
85
86#define X87_FSW_ES (1 << 7)	/* Exception Summary */
87
88static __always_inline __pure bool use_eager_fpu(void)
89{
90	return static_cpu_has_safe(X86_FEATURE_EAGER_FPU);
91}
92
93static __always_inline __pure bool use_xsaveopt(void)
94{
95	return static_cpu_has_safe(X86_FEATURE_XSAVEOPT);
96}
97
98static __always_inline __pure bool use_xsave(void)
99{
100	return static_cpu_has_safe(X86_FEATURE_XSAVE);
101}
102
103static __always_inline __pure bool use_fxsr(void)
104{
105	return static_cpu_has_safe(X86_FEATURE_FXSR);
106}
107
108static inline void fx_finit(struct i387_fxsave_struct *fx)
109{
110	memset(fx, 0, xstate_size);
111	fx->cwd = 0x37f;
112	fx->mxcsr = MXCSR_DEFAULT;
113}
114
115extern void __sanitize_i387_state(struct task_struct *);
116
117static inline void sanitize_i387_state(struct task_struct *tsk)
118{
119	if (!use_xsaveopt())
120		return;
121	__sanitize_i387_state(tsk);
122}
123
124#define user_insn(insn, output, input...)				\
125({									\
126	int err;							\
127	asm volatile(ASM_STAC "\n"					\
128		     "1:" #insn "\n\t"					\
129		     "2: " ASM_CLAC "\n"				\
130		     ".section .fixup,\"ax\"\n"				\
131		     "3:  movl $-1,%[err]\n"				\
132		     "    jmp  2b\n"					\
133		     ".previous\n"					\
134		     _ASM_EXTABLE(1b, 3b)				\
135		     : [err] "=r" (err), output				\
136		     : "0"(0), input);					\
137	err;								\
138})
139
140#define check_insn(insn, output, input...)				\
141({									\
142	int err;							\
143	asm volatile("1:" #insn "\n\t"					\
144		     "2:\n"						\
145		     ".section .fixup,\"ax\"\n"				\
146		     "3:  movl $-1,%[err]\n"				\
147		     "    jmp  2b\n"					\
148		     ".previous\n"					\
149		     _ASM_EXTABLE(1b, 3b)				\
150		     : [err] "=r" (err), output				\
151		     : "0"(0), input);					\
152	err;								\
153})
154
155static inline int fsave_user(struct i387_fsave_struct __user *fx)
156{
157	return user_insn(fnsave %[fx]; fwait,  [fx] "=m" (*fx), "m" (*fx));
158}
159
160static inline int fxsave_user(struct i387_fxsave_struct __user *fx)
161{
162	if (config_enabled(CONFIG_X86_32))
163		return user_insn(fxsave %[fx], [fx] "=m" (*fx), "m" (*fx));
164	else if (config_enabled(CONFIG_AS_FXSAVEQ))
165		return user_insn(fxsaveq %[fx], [fx] "=m" (*fx), "m" (*fx));
166
167	/* See comment in fpu_fxsave() below. */
168	return user_insn(rex64/fxsave (%[fx]), "=m" (*fx), [fx] "R" (fx));
169}
170
171static inline int fxrstor_checking(struct i387_fxsave_struct *fx)
172{
173	if (config_enabled(CONFIG_X86_32))
174		return check_insn(fxrstor %[fx], "=m" (*fx), [fx] "m" (*fx));
175	else if (config_enabled(CONFIG_AS_FXSAVEQ))
176		return check_insn(fxrstorq %[fx], "=m" (*fx), [fx] "m" (*fx));
177
178	/* See comment in fpu_fxsave() below. */
179	return check_insn(rex64/fxrstor (%[fx]), "=m" (*fx), [fx] "R" (fx),
180			  "m" (*fx));
181}
182
183static inline int fxrstor_user(struct i387_fxsave_struct __user *fx)
184{
185	if (config_enabled(CONFIG_X86_32))
186		return user_insn(fxrstor %[fx], "=m" (*fx), [fx] "m" (*fx));
187	else if (config_enabled(CONFIG_AS_FXSAVEQ))
188		return user_insn(fxrstorq %[fx], "=m" (*fx), [fx] "m" (*fx));
189
190	/* See comment in fpu_fxsave() below. */
191	return user_insn(rex64/fxrstor (%[fx]), "=m" (*fx), [fx] "R" (fx),
192			  "m" (*fx));
193}
194
195static inline int frstor_checking(struct i387_fsave_struct *fx)
196{
197	return check_insn(frstor %[fx], "=m" (*fx), [fx] "m" (*fx));
198}
199
200static inline int frstor_user(struct i387_fsave_struct __user *fx)
201{
202	return user_insn(frstor %[fx], "=m" (*fx), [fx] "m" (*fx));
203}
204
205static inline void fpu_fxsave(struct fpu *fpu)
206{
207	if (config_enabled(CONFIG_X86_32))
208		asm volatile( "fxsave %[fx]" : [fx] "=m" (fpu->state->fxsave));
209	else if (config_enabled(CONFIG_AS_FXSAVEQ))
210		asm volatile("fxsaveq %0" : "=m" (fpu->state->fxsave));
211	else {
212		/* Using "rex64; fxsave %0" is broken because, if the memory
213		 * operand uses any extended registers for addressing, a second
214		 * REX prefix will be generated (to the assembler, rex64
215		 * followed by semicolon is a separate instruction), and hence
216		 * the 64-bitness is lost.
217		 *
218		 * Using "fxsaveq %0" would be the ideal choice, but is only
219		 * supported starting with gas 2.16.
220		 *
221		 * Using, as a workaround, the properly prefixed form below
222		 * isn't accepted by any binutils version so far released,
223		 * complaining that the same type of prefix is used twice if
224		 * an extended register is needed for addressing (fix submitted
225		 * to mainline 2005-11-21).
226		 *
227		 *  asm volatile("rex64/fxsave %0" : "=m" (fpu->state->fxsave));
228		 *
229		 * This, however, we can work around by forcing the compiler to
230		 * select an addressing mode that doesn't require extended
231		 * registers.
232		 */
233		asm volatile( "rex64/fxsave (%[fx])"
234			     : "=m" (fpu->state->fxsave)
235			     : [fx] "R" (&fpu->state->fxsave));
236	}
237}
238
239/*
240 * These must be called with preempt disabled. Returns
241 * 'true' if the FPU state is still intact.
242 */
243static inline int fpu_save_init(struct fpu *fpu)
244{
245	if (use_xsave()) {
246		fpu_xsave(fpu);
247
248		/*
249		 * xsave header may indicate the init state of the FP.
250		 */
251		if (!(fpu->state->xsave.xsave_hdr.xstate_bv & XSTATE_FP))
252			return 1;
253	} else if (use_fxsr()) {
254		fpu_fxsave(fpu);
255	} else {
256		asm volatile("fnsave %[fx]; fwait"
257			     : [fx] "=m" (fpu->state->fsave));
258		return 0;
259	}
260
261	/*
262	 * If exceptions are pending, we need to clear them so
263	 * that we don't randomly get exceptions later.
264	 *
265	 * FIXME! Is this perhaps only true for the old-style
266	 * irq13 case? Maybe we could leave the x87 state
267	 * intact otherwise?
268	 */
269	if (unlikely(fpu->state->fxsave.swd & X87_FSW_ES)) {
270		asm volatile("fnclex");
271		return 0;
272	}
273	return 1;
274}
275
276static inline int __save_init_fpu(struct task_struct *tsk)
277{
278	return fpu_save_init(&tsk->thread.fpu);
279}
280
281static inline int fpu_restore_checking(struct fpu *fpu)
282{
283	if (use_xsave())
284		return fpu_xrstor_checking(&fpu->state->xsave);
285	else if (use_fxsr())
286		return fxrstor_checking(&fpu->state->fxsave);
287	else
288		return frstor_checking(&fpu->state->fsave);
289}
290
291static inline int restore_fpu_checking(struct task_struct *tsk)
292{
293	/* AMD K7/K8 CPUs don't save/restore FDP/FIP/FOP unless an exception
294	   is pending.  Clear the x87 state here by setting it to fixed
295	   values. "m" is a random variable that should be in L1 */
296	if (unlikely(static_cpu_has_bug_safe(X86_BUG_FXSAVE_LEAK))) {
297		asm volatile(
298			"fnclex\n\t"
299			"emms\n\t"
300			"fildl %P[addr]"	/* set F?P to defined value */
301			: : [addr] "m" (tsk->thread.fpu.has_fpu));
302	}
303
304	return fpu_restore_checking(&tsk->thread.fpu);
305}
306
307/*
308 * Software FPU state helpers. Careful: these need to
309 * be preemption protection *and* they need to be
310 * properly paired with the CR0.TS changes!
311 */
312static inline int __thread_has_fpu(struct task_struct *tsk)
313{
314	return tsk->thread.fpu.has_fpu;
315}
316
317/* Must be paired with an 'stts' after! */
318static inline void __thread_clear_has_fpu(struct task_struct *tsk)
319{
320	tsk->thread.fpu.has_fpu = 0;
321	this_cpu_write(fpu_owner_task, NULL);
322}
323
324/* Must be paired with a 'clts' before! */
325static inline void __thread_set_has_fpu(struct task_struct *tsk)
326{
327	tsk->thread.fpu.has_fpu = 1;
328	this_cpu_write(fpu_owner_task, tsk);
329}
330
331/*
332 * Encapsulate the CR0.TS handling together with the
333 * software flag.
334 *
335 * These generally need preemption protection to work,
336 * do try to avoid using these on their own.
337 */
338static inline void __thread_fpu_end(struct task_struct *tsk)
339{
340	__thread_clear_has_fpu(tsk);
341	if (!use_eager_fpu())
342		stts();
343}
344
345static inline void __thread_fpu_begin(struct task_struct *tsk)
346{
347	if (!static_cpu_has_safe(X86_FEATURE_EAGER_FPU))
348		clts();
349	__thread_set_has_fpu(tsk);
350}
351
352static inline void __drop_fpu(struct task_struct *tsk)
353{
354	if (__thread_has_fpu(tsk)) {
355		/* Ignore delayed exceptions from user space */
356		asm volatile("1: fwait\n"
357			     "2:\n"
358			     _ASM_EXTABLE(1b, 2b));
359		__thread_fpu_end(tsk);
360	}
361}
362
363static inline void drop_fpu(struct task_struct *tsk)
364{
365	/*
366	 * Forget coprocessor state..
367	 */
368	preempt_disable();
369	tsk->thread.fpu_counter = 0;
370	__drop_fpu(tsk);
371	clear_used_math();
372	preempt_enable();
373}
374
375static inline void drop_init_fpu(struct task_struct *tsk)
376{
377	if (!use_eager_fpu())
378		drop_fpu(tsk);
379	else {
380		if (use_xsave())
381			xrstor_state(init_xstate_buf, -1);
382		else
383			fxrstor_checking(&init_xstate_buf->i387);
384	}
385}
386
387/*
388 * FPU state switching for scheduling.
389 *
390 * This is a two-stage process:
391 *
392 *  - switch_fpu_prepare() saves the old state and
393 *    sets the new state of the CR0.TS bit. This is
394 *    done within the context of the old process.
395 *
396 *  - switch_fpu_finish() restores the new state as
397 *    necessary.
398 */
399typedef struct { int preload; } fpu_switch_t;
400
401/*
402 * Must be run with preemption disabled: this clears the fpu_owner_task,
403 * on this CPU.
404 *
405 * This will disable any lazy FPU state restore of the current FPU state,
406 * but if the current thread owns the FPU, it will still be saved by.
407 */
408static inline void __cpu_disable_lazy_restore(unsigned int cpu)
409{
410	per_cpu(fpu_owner_task, cpu) = NULL;
411}
412
413static inline int fpu_lazy_restore(struct task_struct *new, unsigned int cpu)
414{
415	return new == this_cpu_read_stable(fpu_owner_task) &&
416		cpu == new->thread.fpu.last_cpu;
417}
418
419static inline fpu_switch_t switch_fpu_prepare(struct task_struct *old, struct task_struct *new, int cpu)
420{
421	fpu_switch_t fpu;
422
423	/*
424	 * If the task has used the math, pre-load the FPU on xsave processors
425	 * or if the past 5 consecutive context-switches used math.
426	 */
427	fpu.preload = tsk_used_math(new) && (use_eager_fpu() ||
428					     new->thread.fpu_counter > 5);
429	if (__thread_has_fpu(old)) {
430		if (!__save_init_fpu(old))
431			cpu = ~0;
432		old->thread.fpu.last_cpu = cpu;
433		old->thread.fpu.has_fpu = 0;	/* But leave fpu_owner_task! */
434
435		/* Don't change CR0.TS if we just switch! */
436		if (fpu.preload) {
437			new->thread.fpu_counter++;
438			__thread_set_has_fpu(new);
439			prefetch(new->thread.fpu.state);
440		} else if (!use_eager_fpu())
441			stts();
442	} else {
443		old->thread.fpu_counter = 0;
444		old->thread.fpu.last_cpu = ~0;
445		if (fpu.preload) {
446			new->thread.fpu_counter++;
447			if (!use_eager_fpu() && fpu_lazy_restore(new, cpu))
448				fpu.preload = 0;
449			else
450				prefetch(new->thread.fpu.state);
451			__thread_fpu_begin(new);
452		}
453	}
454	return fpu;
455}
456
457/*
458 * By the time this gets called, we've already cleared CR0.TS and
459 * given the process the FPU if we are going to preload the FPU
460 * state - all we need to do is to conditionally restore the register
461 * state itself.
462 */
463static inline void switch_fpu_finish(struct task_struct *new, fpu_switch_t fpu)
464{
465	if (fpu.preload) {
466		if (unlikely(restore_fpu_checking(new)))
467			drop_init_fpu(new);
468	}
469}
470
471/*
472 * Signal frame handlers...
473 */
474extern int save_xstate_sig(void __user *buf, void __user *fx, int size);
475extern int __restore_xstate_sig(void __user *buf, void __user *fx, int size);
476
477static inline int xstate_sigframe_size(void)
478{
479	return use_xsave() ? xstate_size + FP_XSTATE_MAGIC2_SIZE : xstate_size;
480}
481
482static inline int restore_xstate_sig(void __user *buf, int ia32_frame)
483{
484	void __user *buf_fx = buf;
485	int size = xstate_sigframe_size();
486
487	if (ia32_frame && use_fxsr()) {
488		buf_fx = buf + sizeof(struct i387_fsave_struct);
489		size += sizeof(struct i387_fsave_struct);
490	}
491
492	return __restore_xstate_sig(buf, buf_fx, size);
493}
494
495/*
496 * Need to be preemption-safe.
497 *
498 * NOTE! user_fpu_begin() must be used only immediately before restoring
499 * it. This function does not do any save/restore on their own.
500 */
501static inline void user_fpu_begin(void)
502{
503	preempt_disable();
504	if (!user_has_fpu())
505		__thread_fpu_begin(current);
506	preempt_enable();
507}
508
509static inline void __save_fpu(struct task_struct *tsk)
510{
511	if (use_xsave())
512		xsave_state(&tsk->thread.fpu.state->xsave, -1);
513	else
514		fpu_fxsave(&tsk->thread.fpu);
515}
516
517/*
518 * These disable preemption on their own and are safe
519 */
520static inline void save_init_fpu(struct task_struct *tsk)
521{
522	WARN_ON_ONCE(!__thread_has_fpu(tsk));
523
524	if (use_eager_fpu()) {
525		__save_fpu(tsk);
526		return;
527	}
528
529	preempt_disable();
530	__save_init_fpu(tsk);
531	__thread_fpu_end(tsk);
532	preempt_enable();
533}
534
535/*
536 * i387 state interaction
537 */
538static inline unsigned short get_fpu_cwd(struct task_struct *tsk)
539{
540	if (cpu_has_fxsr) {
541		return tsk->thread.fpu.state->fxsave.cwd;
542	} else {
543		return (unsigned short)tsk->thread.fpu.state->fsave.cwd;
544	}
545}
546
547static inline unsigned short get_fpu_swd(struct task_struct *tsk)
548{
549	if (cpu_has_fxsr) {
550		return tsk->thread.fpu.state->fxsave.swd;
551	} else {
552		return (unsigned short)tsk->thread.fpu.state->fsave.swd;
553	}
554}
555
556static inline unsigned short get_fpu_mxcsr(struct task_struct *tsk)
557{
558	if (cpu_has_xmm) {
559		return tsk->thread.fpu.state->fxsave.mxcsr;
560	} else {
561		return MXCSR_DEFAULT;
562	}
563}
564
565static bool fpu_allocated(struct fpu *fpu)
566{
567	return fpu->state != NULL;
568}
569
570static inline int fpu_alloc(struct fpu *fpu)
571{
572	if (fpu_allocated(fpu))
573		return 0;
574	fpu->state = kmem_cache_alloc(task_xstate_cachep, GFP_KERNEL);
575	if (!fpu->state)
576		return -ENOMEM;
577	WARN_ON((unsigned long)fpu->state & 15);
578	return 0;
579}
580
581static inline void fpu_free(struct fpu *fpu)
582{
583	if (fpu->state) {
584		kmem_cache_free(task_xstate_cachep, fpu->state);
585		fpu->state = NULL;
586	}
587}
588
589static inline void fpu_copy(struct task_struct *dst, struct task_struct *src)
590{
591	if (use_eager_fpu()) {
592		memset(&dst->thread.fpu.state->xsave, 0, xstate_size);
593		__save_fpu(dst);
594	} else {
595		struct fpu *dfpu = &dst->thread.fpu;
596		struct fpu *sfpu = &src->thread.fpu;
597
598		unlazy_fpu(src);
599		memcpy(dfpu->state, sfpu->state, xstate_size);
600	}
601}
602
603static inline unsigned long
604alloc_mathframe(unsigned long sp, int ia32_frame, unsigned long *buf_fx,
605		unsigned long *size)
606{
607	unsigned long frame_size = xstate_sigframe_size();
608
609	*buf_fx = sp = round_down(sp - frame_size, 64);
610	if (ia32_frame && use_fxsr()) {
611		frame_size += sizeof(struct i387_fsave_struct);
612		sp -= sizeof(struct i387_fsave_struct);
613	}
614
615	*size = frame_size;
616	return sp;
617}
618
619#endif
620