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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>
29 struct ksignal;
30 int ia32_setup_rt_frame(int sig, struct ksignal *ksig,
31 compat_sigset_t *set, struct pt_regs *regs);
32 int 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
41 extern unsigned int mxcsr_feature_mask;
42 extern void fpu_init(void);
43 extern void eager_fpu_init(void);
44
45 DECLARE_PER_CPU(struct task_struct *, fpu_owner_task);
46
47 extern void convert_from_fxsr(struct user_i387_ia32_struct *env,
48 struct task_struct *tsk);
49 extern void convert_to_fxsr(struct task_struct *tsk,
50 const struct user_i387_ia32_struct *env);
51
52 extern user_regset_active_fn fpregs_active, xfpregs_active;
53 extern user_regset_get_fn fpregs_get, xfpregs_get, fpregs_soft_get,
54 xstateregs_get;
55 extern 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
65 extern void finit_soft_fpu(struct i387_soft_struct *soft);
66 #else
67 static inline void finit_soft_fpu(struct i387_soft_struct *soft) {}
68 #endif
69
70 /*
71 * Must be run with preemption disabled: this clears the fpu_owner_task,
72 * on this CPU.
73 *
74 * This will disable any lazy FPU state restore of the current FPU state,
75 * but if the current thread owns the FPU, it will still be saved by.
76 */
77 static inline void __cpu_disable_lazy_restore(unsigned int cpu)
78 {
79 per_cpu(fpu_owner_task, cpu) = NULL;
80 }
81
82 /*
83 * Used to indicate that the FPU state in memory is newer than the FPU
84 * state in registers, and the FPU state should be reloaded next time the
85 * task is run. Only safe on the current task, or non-running tasks.
86 */
87 static inline void task_disable_lazy_fpu_restore(struct task_struct *tsk)
88 {
89 tsk->thread.fpu.last_cpu = ~0;
90 }
91
92 static inline int fpu_lazy_restore(struct task_struct *new, unsigned int cpu)
93 {
94 return new == this_cpu_read_stable(fpu_owner_task) &&
95 cpu == new->thread.fpu.last_cpu;
96 }
97
98 static inline int is_ia32_compat_frame(void)
99 {
100 return config_enabled(CONFIG_IA32_EMULATION) &&
101 test_thread_flag(TIF_IA32);
102 }
103
104 static inline int is_ia32_frame(void)
105 {
106 return config_enabled(CONFIG_X86_32) || is_ia32_compat_frame();
107 }
108
109 static inline int is_x32_frame(void)
110 {
111 return config_enabled(CONFIG_X86_X32_ABI) && test_thread_flag(TIF_X32);
112 }
113
114 #define X87_FSW_ES (1 << 7) /* Exception Summary */
115
116 static __always_inline __pure bool use_eager_fpu(void)
117 {
118 return static_cpu_has_safe(X86_FEATURE_EAGER_FPU);
119 }
120
121 static __always_inline __pure bool use_xsaveopt(void)
122 {
123 return static_cpu_has_safe(X86_FEATURE_XSAVEOPT);
124 }
125
126 static __always_inline __pure bool use_xsave(void)
127 {
128 return static_cpu_has_safe(X86_FEATURE_XSAVE);
129 }
130
131 static __always_inline __pure bool use_fxsr(void)
132 {
133 return static_cpu_has_safe(X86_FEATURE_FXSR);
134 }
135
136 static inline void fx_finit(struct i387_fxsave_struct *fx)
137 {
138 fx->cwd = 0x37f;
139 fx->mxcsr = MXCSR_DEFAULT;
140 }
141
142 extern void __sanitize_i387_state(struct task_struct *);
143
144 static inline void sanitize_i387_state(struct task_struct *tsk)
145 {
146 if (!use_xsaveopt())
147 return;
148 __sanitize_i387_state(tsk);
149 }
150
151 #define user_insn(insn, output, input...) \
152 ({ \
153 int err; \
154 asm volatile(ASM_STAC "\n" \
155 "1:" #insn "\n\t" \
156 "2: " ASM_CLAC "\n" \
157 ".section .fixup,\"ax\"\n" \
158 "3: movl $-1,%[err]\n" \
159 " jmp 2b\n" \
160 ".previous\n" \
161 _ASM_EXTABLE(1b, 3b) \
162 : [err] "=r" (err), output \
163 : "0"(0), input); \
164 err; \
165 })
166
167 #define check_insn(insn, output, input...) \
168 ({ \
169 int err; \
170 asm volatile("1:" #insn "\n\t" \
171 "2:\n" \
172 ".section .fixup,\"ax\"\n" \
173 "3: movl $-1,%[err]\n" \
174 " jmp 2b\n" \
175 ".previous\n" \
176 _ASM_EXTABLE(1b, 3b) \
177 : [err] "=r" (err), output \
178 : "0"(0), input); \
179 err; \
180 })
181
182 static inline int fsave_user(struct i387_fsave_struct __user *fx)
183 {
184 return user_insn(fnsave %[fx]; fwait, [fx] "=m" (*fx), "m" (*fx));
185 }
186
187 static inline int fxsave_user(struct i387_fxsave_struct __user *fx)
188 {
189 if (config_enabled(CONFIG_X86_32))
190 return user_insn(fxsave %[fx], [fx] "=m" (*fx), "m" (*fx));
191 else if (config_enabled(CONFIG_AS_FXSAVEQ))
192 return user_insn(fxsaveq %[fx], [fx] "=m" (*fx), "m" (*fx));
193
194 /* See comment in fpu_fxsave() below. */
195 return user_insn(rex64/fxsave (%[fx]), "=m" (*fx), [fx] "R" (fx));
196 }
197
198 static inline int fxrstor_checking(struct i387_fxsave_struct *fx)
199 {
200 if (config_enabled(CONFIG_X86_32))
201 return check_insn(fxrstor %[fx], "=m" (*fx), [fx] "m" (*fx));
202 else if (config_enabled(CONFIG_AS_FXSAVEQ))
203 return check_insn(fxrstorq %[fx], "=m" (*fx), [fx] "m" (*fx));
204
205 /* See comment in fpu_fxsave() below. */
206 return check_insn(rex64/fxrstor (%[fx]), "=m" (*fx), [fx] "R" (fx),
207 "m" (*fx));
208 }
209
210 static inline int fxrstor_user(struct i387_fxsave_struct __user *fx)
211 {
212 if (config_enabled(CONFIG_X86_32))
213 return user_insn(fxrstor %[fx], "=m" (*fx), [fx] "m" (*fx));
214 else if (config_enabled(CONFIG_AS_FXSAVEQ))
215 return user_insn(fxrstorq %[fx], "=m" (*fx), [fx] "m" (*fx));
216
217 /* See comment in fpu_fxsave() below. */
218 return user_insn(rex64/fxrstor (%[fx]), "=m" (*fx), [fx] "R" (fx),
219 "m" (*fx));
220 }
221
222 static inline int frstor_checking(struct i387_fsave_struct *fx)
223 {
224 return check_insn(frstor %[fx], "=m" (*fx), [fx] "m" (*fx));
225 }
226
227 static inline int frstor_user(struct i387_fsave_struct __user *fx)
228 {
229 return user_insn(frstor %[fx], "=m" (*fx), [fx] "m" (*fx));
230 }
231
232 static inline void fpu_fxsave(struct fpu *fpu)
233 {
234 if (config_enabled(CONFIG_X86_32))
235 asm volatile( "fxsave %[fx]" : [fx] "=m" (fpu->state->fxsave));
236 else if (config_enabled(CONFIG_AS_FXSAVEQ))
237 asm volatile("fxsaveq %[fx]" : [fx] "=m" (fpu->state->fxsave));
238 else {
239 /* Using "rex64; fxsave %0" is broken because, if the memory
240 * operand uses any extended registers for addressing, a second
241 * REX prefix will be generated (to the assembler, rex64
242 * followed by semicolon is a separate instruction), and hence
243 * the 64-bitness is lost.
244 *
245 * Using "fxsaveq %0" would be the ideal choice, but is only
246 * supported starting with gas 2.16.
247 *
248 * Using, as a workaround, the properly prefixed form below
249 * isn't accepted by any binutils version so far released,
250 * complaining that the same type of prefix is used twice if
251 * an extended register is needed for addressing (fix submitted
252 * to mainline 2005-11-21).
253 *
254 * asm volatile("rex64/fxsave %0" : "=m" (fpu->state->fxsave));
255 *
256 * This, however, we can work around by forcing the compiler to
257 * select an addressing mode that doesn't require extended
258 * registers.
259 */
260 asm volatile( "rex64/fxsave (%[fx])"
261 : "=m" (fpu->state->fxsave)
262 : [fx] "R" (&fpu->state->fxsave));
263 }
264 }
265
266 /*
267 * These must be called with preempt disabled. Returns
268 * 'true' if the FPU state is still intact.
269 */
270 static inline int fpu_save_init(struct fpu *fpu)
271 {
272 if (use_xsave()) {
273 fpu_xsave(fpu);
274
275 /*
276 * xsave header may indicate the init state of the FP.
277 */
278 if (!(fpu->state->xsave.xsave_hdr.xstate_bv & XSTATE_FP))
279 return 1;
280 } else if (use_fxsr()) {
281 fpu_fxsave(fpu);
282 } else {
283 asm volatile("fnsave %[fx]; fwait"
284 : [fx] "=m" (fpu->state->fsave));
285 return 0;
286 }
287
288 /*
289 * If exceptions are pending, we need to clear them so
290 * that we don't randomly get exceptions later.
291 *
292 * FIXME! Is this perhaps only true for the old-style
293 * irq13 case? Maybe we could leave the x87 state
294 * intact otherwise?
295 */
296 if (unlikely(fpu->state->fxsave.swd & X87_FSW_ES)) {
297 asm volatile("fnclex");
298 return 0;
299 }
300 return 1;
301 }
302
303 static inline int __save_init_fpu(struct task_struct *tsk)
304 {
305 return fpu_save_init(&tsk->thread.fpu);
306 }
307
308 static inline int fpu_restore_checking(struct fpu *fpu)
309 {
310 if (use_xsave())
311 return fpu_xrstor_checking(&fpu->state->xsave);
312 else if (use_fxsr())
313 return fxrstor_checking(&fpu->state->fxsave);
314 else
315 return frstor_checking(&fpu->state->fsave);
316 }
317
318 static inline int restore_fpu_checking(struct task_struct *tsk)
319 {
320 /*
321 * AMD K7/K8 CPUs don't save/restore FDP/FIP/FOP unless an exception is
322 * pending. Clear the x87 state here by setting it to fixed values.
323 * "m" is a random variable that should be in L1.
324 */
325 if (unlikely(static_cpu_has_bug_safe(X86_BUG_FXSAVE_LEAK))) {
326 asm volatile(
327 "fnclex\n\t"
328 "emms\n\t"
329 "fildl %P[addr]" /* set F?P to defined value */
330 : : [addr] "m" (tsk->thread.fpu.has_fpu));
331 }
332
333 return fpu_restore_checking(&tsk->thread.fpu);
334 }
335
336 /*
337 * Software FPU state helpers. Careful: these need to
338 * be preemption protection *and* they need to be
339 * properly paired with the CR0.TS changes!
340 */
341 static inline int __thread_has_fpu(struct task_struct *tsk)
342 {
343 return tsk->thread.fpu.has_fpu;
344 }
345
346 /* Must be paired with an 'stts' after! */
347 static inline void __thread_clear_has_fpu(struct task_struct *tsk)
348 {
349 tsk->thread.fpu.has_fpu = 0;
350 this_cpu_write(fpu_owner_task, NULL);
351 }
352
353 /* Must be paired with a 'clts' before! */
354 static inline void __thread_set_has_fpu(struct task_struct *tsk)
355 {
356 tsk->thread.fpu.has_fpu = 1;
357 this_cpu_write(fpu_owner_task, tsk);
358 }
359
360 /*
361 * Encapsulate the CR0.TS handling together with the
362 * software flag.
363 *
364 * These generally need preemption protection to work,
365 * do try to avoid using these on their own.
366 */
367 static inline void __thread_fpu_end(struct task_struct *tsk)
368 {
369 __thread_clear_has_fpu(tsk);
370 if (!use_eager_fpu())
371 stts();
372 }
373
374 static inline void __thread_fpu_begin(struct task_struct *tsk)
375 {
376 if (!use_eager_fpu())
377 clts();
378 __thread_set_has_fpu(tsk);
379 }
380
381 static inline void drop_fpu(struct task_struct *tsk)
382 {
383 /*
384 * Forget coprocessor state..
385 */
386 preempt_disable();
387 tsk->thread.fpu_counter = 0;
388
389 if (__thread_has_fpu(tsk)) {
390 /* Ignore delayed exceptions from user space */
391 asm volatile("1: fwait\n"
392 "2:\n"
393 _ASM_EXTABLE(1b, 2b));
394 __thread_fpu_end(tsk);
395 }
396
397 clear_stopped_child_used_math(tsk);
398 preempt_enable();
399 }
400
401 static inline void restore_init_xstate(void)
402 {
403 if (use_xsave())
404 xrstor_state(init_xstate_buf, -1);
405 else
406 fxrstor_checking(&init_xstate_buf->i387);
407 }
408
409 /*
410 * Reset the FPU state in the eager case and drop it in the lazy case (later use
411 * will reinit it).
412 */
413 static inline void fpu_reset_state(struct task_struct *tsk)
414 {
415 if (!use_eager_fpu())
416 drop_fpu(tsk);
417 else
418 restore_init_xstate();
419 }
420
421 /*
422 * FPU state switching for scheduling.
423 *
424 * This is a two-stage process:
425 *
426 * - switch_fpu_prepare() saves the old state and
427 * sets the new state of the CR0.TS bit. This is
428 * done within the context of the old process.
429 *
430 * - switch_fpu_finish() restores the new state as
431 * necessary.
432 */
433 typedef struct { int preload; } fpu_switch_t;
434
435 static inline fpu_switch_t switch_fpu_prepare(struct task_struct *old, struct task_struct *new, int cpu)
436 {
437 fpu_switch_t fpu;
438
439 /*
440 * If the task has used the math, pre-load the FPU on xsave processors
441 * or if the past 5 consecutive context-switches used math.
442 */
443 fpu.preload = tsk_used_math(new) &&
444 (use_eager_fpu() || new->thread.fpu_counter > 5);
445
446 if (__thread_has_fpu(old)) {
447 if (!__save_init_fpu(old))
448 task_disable_lazy_fpu_restore(old);
449 else
450 old->thread.fpu.last_cpu = cpu;
451
452 /* But leave fpu_owner_task! */
453 old->thread.fpu.has_fpu = 0;
454
455 /* Don't change CR0.TS if we just switch! */
456 if (fpu.preload) {
457 new->thread.fpu_counter++;
458 __thread_set_has_fpu(new);
459 prefetch(new->thread.fpu.state);
460 } else if (!use_eager_fpu())
461 stts();
462 } else {
463 old->thread.fpu_counter = 0;
464 task_disable_lazy_fpu_restore(old);
465 if (fpu.preload) {
466 new->thread.fpu_counter++;
467 if (fpu_lazy_restore(new, cpu))
468 fpu.preload = 0;
469 else
470 prefetch(new->thread.fpu.state);
471 __thread_fpu_begin(new);
472 }
473 }
474 return fpu;
475 }
476
477 /*
478 * By the time this gets called, we've already cleared CR0.TS and
479 * given the process the FPU if we are going to preload the FPU
480 * state - all we need to do is to conditionally restore the register
481 * state itself.
482 */
483 static inline void switch_fpu_finish(struct task_struct *new, fpu_switch_t fpu)
484 {
485 if (fpu.preload) {
486 if (unlikely(restore_fpu_checking(new)))
487 fpu_reset_state(new);
488 }
489 }
490
491 /*
492 * Signal frame handlers...
493 */
494 extern int save_xstate_sig(void __user *buf, void __user *fx, int size);
495 extern int __restore_xstate_sig(void __user *buf, void __user *fx, int size);
496
497 static inline int xstate_sigframe_size(void)
498 {
499 return use_xsave() ? xstate_size + FP_XSTATE_MAGIC2_SIZE : xstate_size;
500 }
501
502 static inline int restore_xstate_sig(void __user *buf, int ia32_frame)
503 {
504 void __user *buf_fx = buf;
505 int size = xstate_sigframe_size();
506
507 if (ia32_frame && use_fxsr()) {
508 buf_fx = buf + sizeof(struct i387_fsave_struct);
509 size += sizeof(struct i387_fsave_struct);
510 }
511
512 return __restore_xstate_sig(buf, buf_fx, size);
513 }
514
515 /*
516 * Needs to be preemption-safe.
517 *
518 * NOTE! user_fpu_begin() must be used only immediately before restoring
519 * the save state. It does not do any saving/restoring on its own. In
520 * lazy FPU mode, it is just an optimization to avoid a #NM exception,
521 * the task can lose the FPU right after preempt_enable().
522 */
523 static inline void user_fpu_begin(void)
524 {
525 preempt_disable();
526 if (!user_has_fpu())
527 __thread_fpu_begin(current);
528 preempt_enable();
529 }
530
531 static inline void __save_fpu(struct task_struct *tsk)
532 {
533 if (use_xsave()) {
534 if (unlikely(system_state == SYSTEM_BOOTING))
535 xsave_state_booting(&tsk->thread.fpu.state->xsave, -1);
536 else
537 xsave_state(&tsk->thread.fpu.state->xsave, -1);
538 } else
539 fpu_fxsave(&tsk->thread.fpu);
540 }
541
542 /*
543 * i387 state interaction
544 */
545 static inline unsigned short get_fpu_cwd(struct task_struct *tsk)
546 {
547 if (cpu_has_fxsr) {
548 return tsk->thread.fpu.state->fxsave.cwd;
549 } else {
550 return (unsigned short)tsk->thread.fpu.state->fsave.cwd;
551 }
552 }
553
554 static inline unsigned short get_fpu_swd(struct task_struct *tsk)
555 {
556 if (cpu_has_fxsr) {
557 return tsk->thread.fpu.state->fxsave.swd;
558 } else {
559 return (unsigned short)tsk->thread.fpu.state->fsave.swd;
560 }
561 }
562
563 static inline unsigned short get_fpu_mxcsr(struct task_struct *tsk)
564 {
565 if (cpu_has_xmm) {
566 return tsk->thread.fpu.state->fxsave.mxcsr;
567 } else {
568 return MXCSR_DEFAULT;
569 }
570 }
571
572 static bool fpu_allocated(struct fpu *fpu)
573 {
574 return fpu->state != NULL;
575 }
576
577 static inline int fpu_alloc(struct fpu *fpu)
578 {
579 if (fpu_allocated(fpu))
580 return 0;
581 fpu->state = kmem_cache_alloc(task_xstate_cachep, GFP_KERNEL);
582 if (!fpu->state)
583 return -ENOMEM;
584 WARN_ON((unsigned long)fpu->state & 15);
585 return 0;
586 }
587
588 static inline void fpu_free(struct fpu *fpu)
589 {
590 if (fpu->state) {
591 kmem_cache_free(task_xstate_cachep, fpu->state);
592 fpu->state = NULL;
593 }
594 }
595
596 static inline void fpu_copy(struct task_struct *dst, struct task_struct *src)
597 {
598 if (use_eager_fpu()) {
599 memset(&dst->thread.fpu.state->xsave, 0, xstate_size);
600 __save_fpu(dst);
601 } else {
602 struct fpu *dfpu = &dst->thread.fpu;
603 struct fpu *sfpu = &src->thread.fpu;
604
605 unlazy_fpu(src);
606 memcpy(dfpu->state, sfpu->state, xstate_size);
607 }
608 }
609
610 static inline unsigned long
611 alloc_mathframe(unsigned long sp, int ia32_frame, unsigned long *buf_fx,
612 unsigned long *size)
613 {
614 unsigned long frame_size = xstate_sigframe_size();
615
616 *buf_fx = sp = round_down(sp - frame_size, 64);
617 if (ia32_frame && use_fxsr()) {
618 frame_size += sizeof(struct i387_fsave_struct);
619 sp -= sizeof(struct i387_fsave_struct);
620 }
621
622 *size = frame_size;
623 return sp;
624 }
625
626 #endif