2 * Copyright (C) 1994 Linus Torvalds
4 * Pentium III FXSR, SSE support
5 * General FPU state handling cleanups
6 * Gareth Hughes <gareth@valinux.com>, May 2000
8 #include <asm/fpu-internal.h>
11 * Track whether the kernel is using the FPU state
16 * - by IRQ context code to potentially use the FPU
19 * - to debug kernel_fpu_begin()/end() correctness
21 static DEFINE_PER_CPU(bool, in_kernel_fpu);
24 * Track which context is using the FPU on the CPU:
26 DEFINE_PER_CPU(struct fpu *, fpu_fpregs_owner_ctx);
28 static void kernel_fpu_disable(void)
30 WARN_ON(this_cpu_read(in_kernel_fpu));
31 this_cpu_write(in_kernel_fpu, true);
34 static void kernel_fpu_enable(void)
36 WARN_ON_ONCE(!this_cpu_read(in_kernel_fpu));
37 this_cpu_write(in_kernel_fpu, false);
40 static bool kernel_fpu_disabled(void)
42 return this_cpu_read(in_kernel_fpu);
46 * Were we in an interrupt that interrupted kernel mode?
48 * On others, we can do a kernel_fpu_begin/end() pair *ONLY* if that
49 * pair does nothing at all: the thread must not have fpu (so
50 * that we don't try to save the FPU state), and TS must
51 * be set (so that the clts/stts pair does nothing that is
52 * visible in the interrupted kernel thread).
54 * Except for the eagerfpu case when we return true; in the likely case
55 * the thread has FPU but we are not going to set/clear TS.
57 static bool interrupted_kernel_fpu_idle(void)
59 if (kernel_fpu_disabled())
65 return !current->thread.fpu.has_fpu && (read_cr0() & X86_CR0_TS);
69 * Were we in user mode (or vm86 mode) when we were
72 * Doing kernel_fpu_begin/end() is ok if we are running
73 * in an interrupt context from user mode - we'll just
74 * save the FPU state as required.
76 static bool interrupted_user_mode(void)
78 struct pt_regs *regs = get_irq_regs();
79 return regs && user_mode(regs);
83 * Can we use the FPU in kernel mode with the
84 * whole "kernel_fpu_begin/end()" sequence?
86 * It's always ok in process context (ie "not interrupt")
87 * but it is sometimes ok even from an irq.
89 bool irq_fpu_usable(void)
91 return !in_interrupt() ||
92 interrupted_user_mode() ||
93 interrupted_kernel_fpu_idle();
95 EXPORT_SYMBOL(irq_fpu_usable);
97 void __kernel_fpu_begin(void)
99 struct fpu *fpu = ¤t->thread.fpu;
101 kernel_fpu_disable();
106 this_cpu_write(fpu_fpregs_owner_ctx, NULL);
107 if (!use_eager_fpu())
111 EXPORT_SYMBOL(__kernel_fpu_begin);
113 void __kernel_fpu_end(void)
115 struct fpu *fpu = ¤t->thread.fpu;
118 if (WARN_ON(restore_fpu_checking(fpu)))
119 fpu_reset_state(fpu);
120 } else if (!use_eager_fpu()) {
126 EXPORT_SYMBOL(__kernel_fpu_end);
128 static void __save_fpu(struct fpu *fpu)
131 if (unlikely(system_state == SYSTEM_BOOTING))
132 xsave_state_booting(&fpu->state->xsave);
134 xsave_state(&fpu->state->xsave);
141 * Save the FPU state (initialize it if necessary):
143 * This only ever gets called for the current task.
145 void fpu__save(struct fpu *fpu)
147 WARN_ON(fpu != ¤t->thread.fpu);
151 if (use_eager_fpu()) {
155 __thread_fpu_end(fpu);
160 EXPORT_SYMBOL_GPL(fpu__save);
162 void fpstate_init(struct fpu *fpu)
165 finit_soft_fpu(&fpu->state->soft);
169 memset(fpu->state, 0, xstate_size);
172 fx_finit(&fpu->state->fxsave);
174 struct i387_fsave_struct *fp = &fpu->state->fsave;
175 fp->cwd = 0xffff037fu;
176 fp->swd = 0xffff0000u;
177 fp->twd = 0xffffffffu;
178 fp->fos = 0xffff0000u;
181 EXPORT_SYMBOL_GPL(fpstate_init);
184 * FPU state allocation:
186 static struct kmem_cache *task_xstate_cachep;
188 void fpstate_cache_init(void)
191 kmem_cache_create("task_xstate", xstate_size,
192 __alignof__(union thread_xstate),
193 SLAB_PANIC | SLAB_NOTRACK, NULL);
197 int fpstate_alloc(struct fpu *fpu)
202 fpu->state = kmem_cache_alloc(task_xstate_cachep, GFP_KERNEL);
206 /* The CPU requires the FPU state to be aligned to 16 byte boundaries: */
207 WARN_ON((unsigned long)fpu->state & 15);
211 EXPORT_SYMBOL_GPL(fpstate_alloc);
213 void fpstate_free(struct fpu *fpu)
216 kmem_cache_free(task_xstate_cachep, fpu->state);
220 EXPORT_SYMBOL_GPL(fpstate_free);
223 * Copy the current task's FPU state to a new task's FPU context.
225 * In the 'eager' case we just save to the destination context.
227 * In the 'lazy' case we save to the source context, mark the FPU lazy
228 * via stts() and copy the source context into the destination context.
230 static void fpu_copy(struct fpu *dst_fpu, struct fpu *src_fpu)
232 WARN_ON(src_fpu != ¤t->thread.fpu);
234 if (use_eager_fpu()) {
235 memset(&dst_fpu->state->xsave, 0, xstate_size);
239 memcpy(dst_fpu->state, src_fpu->state, xstate_size);
243 int fpu__copy(struct fpu *dst_fpu, struct fpu *src_fpu)
245 dst_fpu->counter = 0;
246 dst_fpu->has_fpu = 0;
247 dst_fpu->state = NULL;
248 dst_fpu->last_cpu = -1;
250 if (src_fpu->fpstate_active) {
251 int err = fpstate_alloc(dst_fpu);
255 fpu_copy(dst_fpu, src_fpu);
261 * Allocate the backing store for the current task's FPU registers
262 * and initialize the registers themselves as well.
266 int fpstate_alloc_init(struct task_struct *curr)
268 struct fpu *fpu = &curr->thread.fpu;
271 if (WARN_ON_ONCE(curr != current))
273 if (WARN_ON_ONCE(fpu->fpstate_active))
277 * Memory allocation at the first usage of the FPU and other state.
279 ret = fpstate_alloc(&curr->thread.fpu);
283 fpstate_init(&curr->thread.fpu);
285 /* Safe to do for the current task: */
286 fpu->fpstate_active = 1;
290 EXPORT_SYMBOL_GPL(fpstate_alloc_init);
293 * This function is called before we modify a stopped child's
296 * If the child has not used the FPU before then initialize its
299 * If the child has used the FPU before then unlazy it.
301 * [ After this function call, after the context is modified and
302 * the child task is woken up, the child task will restore
303 * the modified FPU state from the modified context. If we
304 * didn't clear its lazy status here then the lazy in-registers
305 * state pending on its former CPU could be restored, losing
306 * the modifications. ]
308 * This function is also called before we read a stopped child's
309 * FPU state - to make sure it's modified.
311 * TODO: A future optimization would be to skip the unlazying in
312 * the read-only case, it's not strictly necessary for
313 * read-only access to the context.
315 static int fpu__unlazy_stopped(struct task_struct *child)
317 struct fpu *child_fpu = &child->thread.fpu;
320 if (WARN_ON_ONCE(child == current))
323 if (child_fpu->fpstate_active) {
324 child->thread.fpu.last_cpu = -1;
329 * Memory allocation at the first usage of the FPU and other state.
331 ret = fpstate_alloc(&child->thread.fpu);
335 fpstate_init(&child->thread.fpu);
337 /* Safe to do for stopped child tasks: */
338 child_fpu->fpstate_active = 1;
344 * 'fpu__restore()' saves the current math information in the
345 * old math state array, and gets the new ones from the current task
347 * Careful.. There are problems with IBM-designed IRQ13 behaviour.
348 * Don't touch unless you *really* know how it works.
350 * Must be called with kernel preemption disabled (eg with local
351 * local interrupts as in the case of do_device_not_available).
353 void fpu__restore(void)
355 struct task_struct *tsk = current;
356 struct fpu *fpu = &tsk->thread.fpu;
358 if (!fpu->fpstate_active) {
361 * does a slab alloc which can sleep
363 if (fpstate_alloc_init(tsk)) {
367 do_group_exit(SIGKILL);
373 /* Avoid __kernel_fpu_begin() right after __thread_fpu_begin() */
374 kernel_fpu_disable();
375 __thread_fpu_begin(fpu);
376 if (unlikely(restore_fpu_checking(fpu))) {
377 fpu_reset_state(fpu);
378 force_sig_info(SIGSEGV, SEND_SIG_PRIV, tsk);
380 tsk->thread.fpu.counter++;
384 EXPORT_SYMBOL_GPL(fpu__restore);
386 void fpu__flush_thread(struct task_struct *tsk)
388 struct fpu *fpu = &tsk->thread.fpu;
390 WARN_ON(tsk != current);
392 if (!use_eager_fpu()) {
393 /* FPU state will be reallocated lazily at the first use. */
395 fpstate_free(&tsk->thread.fpu);
397 if (!fpu->fpstate_active) {
398 /* kthread execs. TODO: cleanup this horror. */
399 if (WARN_ON(fpstate_alloc_init(tsk)))
400 force_sig(SIGKILL, tsk);
403 restore_init_xstate();
408 * The xstateregs_active() routine is the same as the fpregs_active() routine,
409 * as the "regset->n" for the xstate regset will be updated based on the feature
410 * capabilites supported by the xsave.
412 int fpregs_active(struct task_struct *target, const struct user_regset *regset)
414 struct fpu *target_fpu = &target->thread.fpu;
416 return target_fpu->fpstate_active ? regset->n : 0;
419 int xfpregs_active(struct task_struct *target, const struct user_regset *regset)
421 struct fpu *target_fpu = &target->thread.fpu;
423 return (cpu_has_fxsr && target_fpu->fpstate_active) ? regset->n : 0;
426 int xfpregs_get(struct task_struct *target, const struct user_regset *regset,
427 unsigned int pos, unsigned int count,
428 void *kbuf, void __user *ubuf)
435 ret = fpu__unlazy_stopped(target);
439 sanitize_i387_state(target);
441 return user_regset_copyout(&pos, &count, &kbuf, &ubuf,
442 &target->thread.fpu.state->fxsave, 0, -1);
445 int xfpregs_set(struct task_struct *target, const struct user_regset *regset,
446 unsigned int pos, unsigned int count,
447 const void *kbuf, const void __user *ubuf)
454 ret = fpu__unlazy_stopped(target);
458 sanitize_i387_state(target);
460 ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf,
461 &target->thread.fpu.state->fxsave, 0, -1);
464 * mxcsr reserved bits must be masked to zero for security reasons.
466 target->thread.fpu.state->fxsave.mxcsr &= mxcsr_feature_mask;
469 * update the header bits in the xsave header, indicating the
470 * presence of FP and SSE state.
473 target->thread.fpu.state->xsave.xsave_hdr.xstate_bv |= XSTATE_FPSSE;
478 int xstateregs_get(struct task_struct *target, const struct user_regset *regset,
479 unsigned int pos, unsigned int count,
480 void *kbuf, void __user *ubuf)
482 struct xsave_struct *xsave;
488 ret = fpu__unlazy_stopped(target);
492 xsave = &target->thread.fpu.state->xsave;
495 * Copy the 48bytes defined by the software first into the xstate
496 * memory layout in the thread struct, so that we can copy the entire
497 * xstateregs to the user using one user_regset_copyout().
499 memcpy(&xsave->i387.sw_reserved,
500 xstate_fx_sw_bytes, sizeof(xstate_fx_sw_bytes));
502 * Copy the xstate memory layout.
504 ret = user_regset_copyout(&pos, &count, &kbuf, &ubuf, xsave, 0, -1);
508 int xstateregs_set(struct task_struct *target, const struct user_regset *regset,
509 unsigned int pos, unsigned int count,
510 const void *kbuf, const void __user *ubuf)
512 struct xsave_struct *xsave;
518 ret = fpu__unlazy_stopped(target);
522 xsave = &target->thread.fpu.state->xsave;
524 ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, xsave, 0, -1);
526 * mxcsr reserved bits must be masked to zero for security reasons.
528 xsave->i387.mxcsr &= mxcsr_feature_mask;
529 xsave->xsave_hdr.xstate_bv &= pcntxt_mask;
531 * These bits must be zero.
533 memset(&xsave->xsave_hdr.reserved, 0, 48);
537 #if defined CONFIG_X86_32 || defined CONFIG_IA32_EMULATION
540 * FPU tag word conversions.
543 static inline unsigned short twd_i387_to_fxsr(unsigned short twd)
545 unsigned int tmp; /* to avoid 16 bit prefixes in the code */
547 /* Transform each pair of bits into 01 (valid) or 00 (empty) */
549 tmp = (tmp | (tmp>>1)) & 0x5555; /* 0V0V0V0V0V0V0V0V */
550 /* and move the valid bits to the lower byte. */
551 tmp = (tmp | (tmp >> 1)) & 0x3333; /* 00VV00VV00VV00VV */
552 tmp = (tmp | (tmp >> 2)) & 0x0f0f; /* 0000VVVV0000VVVV */
553 tmp = (tmp | (tmp >> 4)) & 0x00ff; /* 00000000VVVVVVVV */
558 #define FPREG_ADDR(f, n) ((void *)&(f)->st_space + (n) * 16)
559 #define FP_EXP_TAG_VALID 0
560 #define FP_EXP_TAG_ZERO 1
561 #define FP_EXP_TAG_SPECIAL 2
562 #define FP_EXP_TAG_EMPTY 3
564 static inline u32 twd_fxsr_to_i387(struct i387_fxsave_struct *fxsave)
567 u32 tos = (fxsave->swd >> 11) & 7;
568 u32 twd = (unsigned long) fxsave->twd;
570 u32 ret = 0xffff0000u;
573 for (i = 0; i < 8; i++, twd >>= 1) {
575 st = FPREG_ADDR(fxsave, (i - tos) & 7);
577 switch (st->exponent & 0x7fff) {
579 tag = FP_EXP_TAG_SPECIAL;
582 if (!st->significand[0] &&
583 !st->significand[1] &&
584 !st->significand[2] &&
586 tag = FP_EXP_TAG_ZERO;
588 tag = FP_EXP_TAG_SPECIAL;
591 if (st->significand[3] & 0x8000)
592 tag = FP_EXP_TAG_VALID;
594 tag = FP_EXP_TAG_SPECIAL;
598 tag = FP_EXP_TAG_EMPTY;
600 ret |= tag << (2 * i);
606 * FXSR floating point environment conversions.
610 convert_from_fxsr(struct user_i387_ia32_struct *env, struct task_struct *tsk)
612 struct i387_fxsave_struct *fxsave = &tsk->thread.fpu.state->fxsave;
613 struct _fpreg *to = (struct _fpreg *) &env->st_space[0];
614 struct _fpxreg *from = (struct _fpxreg *) &fxsave->st_space[0];
617 env->cwd = fxsave->cwd | 0xffff0000u;
618 env->swd = fxsave->swd | 0xffff0000u;
619 env->twd = twd_fxsr_to_i387(fxsave);
622 env->fip = fxsave->rip;
623 env->foo = fxsave->rdp;
625 * should be actually ds/cs at fpu exception time, but
626 * that information is not available in 64bit mode.
628 env->fcs = task_pt_regs(tsk)->cs;
629 if (tsk == current) {
630 savesegment(ds, env->fos);
632 env->fos = tsk->thread.ds;
634 env->fos |= 0xffff0000;
636 env->fip = fxsave->fip;
637 env->fcs = (u16) fxsave->fcs | ((u32) fxsave->fop << 16);
638 env->foo = fxsave->foo;
639 env->fos = fxsave->fos;
642 for (i = 0; i < 8; ++i)
643 memcpy(&to[i], &from[i], sizeof(to[0]));
646 void convert_to_fxsr(struct task_struct *tsk,
647 const struct user_i387_ia32_struct *env)
650 struct i387_fxsave_struct *fxsave = &tsk->thread.fpu.state->fxsave;
651 struct _fpreg *from = (struct _fpreg *) &env->st_space[0];
652 struct _fpxreg *to = (struct _fpxreg *) &fxsave->st_space[0];
655 fxsave->cwd = env->cwd;
656 fxsave->swd = env->swd;
657 fxsave->twd = twd_i387_to_fxsr(env->twd);
658 fxsave->fop = (u16) ((u32) env->fcs >> 16);
660 fxsave->rip = env->fip;
661 fxsave->rdp = env->foo;
662 /* cs and ds ignored */
664 fxsave->fip = env->fip;
665 fxsave->fcs = (env->fcs & 0xffff);
666 fxsave->foo = env->foo;
667 fxsave->fos = env->fos;
670 for (i = 0; i < 8; ++i)
671 memcpy(&to[i], &from[i], sizeof(from[0]));
674 int fpregs_get(struct task_struct *target, const struct user_regset *regset,
675 unsigned int pos, unsigned int count,
676 void *kbuf, void __user *ubuf)
678 struct user_i387_ia32_struct env;
681 ret = fpu__unlazy_stopped(target);
685 if (!static_cpu_has(X86_FEATURE_FPU))
686 return fpregs_soft_get(target, regset, pos, count, kbuf, ubuf);
689 return user_regset_copyout(&pos, &count, &kbuf, &ubuf,
690 &target->thread.fpu.state->fsave, 0,
693 sanitize_i387_state(target);
695 if (kbuf && pos == 0 && count == sizeof(env)) {
696 convert_from_fxsr(kbuf, target);
700 convert_from_fxsr(&env, target);
702 return user_regset_copyout(&pos, &count, &kbuf, &ubuf, &env, 0, -1);
705 int fpregs_set(struct task_struct *target, const struct user_regset *regset,
706 unsigned int pos, unsigned int count,
707 const void *kbuf, const void __user *ubuf)
709 struct user_i387_ia32_struct env;
712 ret = fpu__unlazy_stopped(target);
716 sanitize_i387_state(target);
718 if (!static_cpu_has(X86_FEATURE_FPU))
719 return fpregs_soft_set(target, regset, pos, count, kbuf, ubuf);
722 return user_regset_copyin(&pos, &count, &kbuf, &ubuf,
723 &target->thread.fpu.state->fsave, 0,
726 if (pos > 0 || count < sizeof(env))
727 convert_from_fxsr(&env, target);
729 ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, &env, 0, -1);
731 convert_to_fxsr(target, &env);
734 * update the header bit in the xsave header, indicating the
738 target->thread.fpu.state->xsave.xsave_hdr.xstate_bv |= XSTATE_FP;
743 * FPU state for core dumps.
744 * This is only used for a.out dumps now.
745 * It is declared generically using elf_fpregset_t (which is
746 * struct user_i387_struct) but is in fact only used for 32-bit
747 * dumps, so on 64-bit it is really struct user_i387_ia32_struct.
749 int dump_fpu(struct pt_regs *regs, struct user_i387_struct *ufpu)
751 struct task_struct *tsk = current;
752 struct fpu *fpu = &tsk->thread.fpu;
755 fpvalid = fpu->fpstate_active;
757 fpvalid = !fpregs_get(tsk, NULL,
758 0, sizeof(struct user_i387_ia32_struct),
763 EXPORT_SYMBOL(dump_fpu);
765 #endif /* CONFIG_X86_32 || CONFIG_IA32_EMULATION */