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>
9 #include <linux/hardirq.h>
12 * Track whether the kernel is using the FPU state
17 * - by IRQ context code to potentially use the FPU
20 * - to debug kernel_fpu_begin()/end() correctness
22 static DEFINE_PER_CPU(bool, in_kernel_fpu);
25 * Track which context is using the FPU on the CPU:
27 DEFINE_PER_CPU(struct fpu *, fpu_fpregs_owner_ctx);
29 static void kernel_fpu_disable(void)
31 WARN_ON(this_cpu_read(in_kernel_fpu));
32 this_cpu_write(in_kernel_fpu, true);
35 static void kernel_fpu_enable(void)
37 WARN_ON_ONCE(!this_cpu_read(in_kernel_fpu));
38 this_cpu_write(in_kernel_fpu, false);
41 static bool kernel_fpu_disabled(void)
43 return this_cpu_read(in_kernel_fpu);
47 * Were we in an interrupt that interrupted kernel mode?
49 * On others, we can do a kernel_fpu_begin/end() pair *ONLY* if that
50 * pair does nothing at all: the thread must not have fpu (so
51 * that we don't try to save the FPU state), and TS must
52 * be set (so that the clts/stts pair does nothing that is
53 * visible in the interrupted kernel thread).
55 * Except for the eagerfpu case when we return true; in the likely case
56 * the thread has FPU but we are not going to set/clear TS.
58 static bool interrupted_kernel_fpu_idle(void)
60 if (kernel_fpu_disabled())
66 return !current->thread.fpu.fpregs_active && (read_cr0() & X86_CR0_TS);
70 * Were we in user mode (or vm86 mode) when we were
73 * Doing kernel_fpu_begin/end() is ok if we are running
74 * in an interrupt context from user mode - we'll just
75 * save the FPU state as required.
77 static bool interrupted_user_mode(void)
79 struct pt_regs *regs = get_irq_regs();
80 return regs && user_mode(regs);
84 * Can we use the FPU in kernel mode with the
85 * whole "kernel_fpu_begin/end()" sequence?
87 * It's always ok in process context (ie "not interrupt")
88 * but it is sometimes ok even from an irq.
90 bool irq_fpu_usable(void)
92 return !in_interrupt() ||
93 interrupted_user_mode() ||
94 interrupted_kernel_fpu_idle();
96 EXPORT_SYMBOL(irq_fpu_usable);
98 void __kernel_fpu_begin(void)
100 struct fpu *fpu = ¤t->thread.fpu;
102 kernel_fpu_disable();
104 if (fpu->fpregs_active) {
105 copy_fpregs_to_fpstate(fpu);
107 this_cpu_write(fpu_fpregs_owner_ctx, NULL);
108 __fpregs_activate_hw();
111 EXPORT_SYMBOL(__kernel_fpu_begin);
113 void __kernel_fpu_end(void)
115 struct fpu *fpu = ¤t->thread.fpu;
117 if (fpu->fpregs_active) {
118 if (WARN_ON(restore_fpu_checking(fpu)))
119 fpu_reset_state(fpu);
121 __fpregs_deactivate_hw();
126 EXPORT_SYMBOL(__kernel_fpu_end);
128 void kernel_fpu_begin(void)
131 WARN_ON_ONCE(!irq_fpu_usable());
132 __kernel_fpu_begin();
134 EXPORT_SYMBOL_GPL(kernel_fpu_begin);
136 void kernel_fpu_end(void)
141 EXPORT_SYMBOL_GPL(kernel_fpu_end);
144 * CR0::TS save/restore functions:
146 int irq_ts_save(void)
149 * If in process context and not atomic, we can take a spurious DNA fault.
150 * Otherwise, doing clts() in process context requires disabling preemption
151 * or some heavy lifting like kernel_fpu_begin()
156 if (read_cr0() & X86_CR0_TS) {
163 EXPORT_SYMBOL_GPL(irq_ts_save);
165 void irq_ts_restore(int TS_state)
170 EXPORT_SYMBOL_GPL(irq_ts_restore);
173 * Save the FPU state (initialize it if necessary):
175 * This only ever gets called for the current task.
177 void fpu__save(struct fpu *fpu)
179 WARN_ON(fpu != ¤t->thread.fpu);
182 if (fpu->fpregs_active) {
183 copy_fpregs_to_fpstate(fpu);
184 if (!use_eager_fpu())
185 fpregs_deactivate(fpu);
189 EXPORT_SYMBOL_GPL(fpu__save);
191 void fpstate_init(struct fpu *fpu)
194 finit_soft_fpu(&fpu->state.soft);
198 memset(&fpu->state, 0, xstate_size);
201 fx_finit(&fpu->state.fxsave);
203 struct i387_fsave_struct *fp = &fpu->state.fsave;
204 fp->cwd = 0xffff037fu;
205 fp->swd = 0xffff0000u;
206 fp->twd = 0xffffffffu;
207 fp->fos = 0xffff0000u;
210 EXPORT_SYMBOL_GPL(fpstate_init);
213 * Copy the current task's FPU state to a new task's FPU context.
215 * In the 'eager' case we just save to the destination context.
217 * In the 'lazy' case we save to the source context, mark the FPU lazy
218 * via stts() and copy the source context into the destination context.
220 static void fpu_copy(struct fpu *dst_fpu, struct fpu *src_fpu)
222 WARN_ON(src_fpu != ¤t->thread.fpu);
224 if (use_eager_fpu()) {
225 memset(&dst_fpu->state.xsave, 0, xstate_size);
226 copy_fpregs_to_fpstate(dst_fpu);
229 memcpy(&dst_fpu->state, &src_fpu->state, xstate_size);
233 int fpu__copy(struct fpu *dst_fpu, struct fpu *src_fpu)
235 dst_fpu->counter = 0;
236 dst_fpu->fpregs_active = 0;
237 dst_fpu->last_cpu = -1;
239 if (src_fpu->fpstate_active)
240 fpu_copy(dst_fpu, src_fpu);
246 * Activate the current task's in-memory FPU context,
247 * if it has not been used before:
249 void fpu__activate_curr(struct fpu *fpu)
251 WARN_ON_ONCE(fpu != ¤t->thread.fpu);
253 if (!fpu->fpstate_active) {
256 /* Safe to do for the current task: */
257 fpu->fpstate_active = 1;
260 EXPORT_SYMBOL_GPL(fpu__activate_curr);
263 * This function must be called before we modify a stopped child's
266 * If the child has not used the FPU before then initialize its
269 * If the child has used the FPU before then unlazy it.
271 * [ After this function call, after registers in the fpstate are
272 * modified and the child task has woken up, the child task will
273 * restore the modified FPU state from the modified context. If we
274 * didn't clear its lazy status here then the lazy in-registers
275 * state pending on its former CPU could be restored, corrupting
276 * the modifications. ]
278 * This function is also called before we read a stopped child's
279 * FPU state - to make sure it's initialized if the child has
280 * no active FPU state.
282 * TODO: A future optimization would be to skip the unlazying in
283 * the read-only case, it's not strictly necessary for
284 * read-only access to the context.
286 static void fpu__activate_stopped(struct fpu *child_fpu)
288 WARN_ON_ONCE(child_fpu == ¤t->thread.fpu);
290 if (child_fpu->fpstate_active) {
291 child_fpu->last_cpu = -1;
293 fpstate_init(child_fpu);
295 /* Safe to do for stopped child tasks: */
296 child_fpu->fpstate_active = 1;
301 * 'fpu__restore()' saves the current math information in the
302 * old math state array, and gets the new ones from the current task
304 * Careful.. There are problems with IBM-designed IRQ13 behaviour.
305 * Don't touch unless you *really* know how it works.
307 * Must be called with kernel preemption disabled (eg with local
308 * local interrupts as in the case of do_device_not_available).
310 void fpu__restore(void)
312 struct task_struct *tsk = current;
313 struct fpu *fpu = &tsk->thread.fpu;
315 fpu__activate_curr(fpu);
317 /* Avoid __kernel_fpu_begin() right after fpregs_activate() */
318 kernel_fpu_disable();
319 fpregs_activate(fpu);
320 if (unlikely(restore_fpu_checking(fpu))) {
321 fpu_reset_state(fpu);
322 force_sig_info(SIGSEGV, SEND_SIG_PRIV, tsk);
324 tsk->thread.fpu.counter++;
328 EXPORT_SYMBOL_GPL(fpu__restore);
330 void fpu__clear(struct task_struct *tsk)
332 struct fpu *fpu = &tsk->thread.fpu;
334 WARN_ON_ONCE(tsk != current); /* Almost certainly an anomaly */
336 if (!use_eager_fpu()) {
337 /* FPU state will be reallocated lazily at the first use. */
340 if (!fpu->fpstate_active) {
341 fpu__activate_curr(fpu);
344 restore_init_xstate();
349 * The xstateregs_active() routine is the same as the regset_fpregs_active() routine,
350 * as the "regset->n" for the xstate regset will be updated based on the feature
351 * capabilites supported by the xsave.
353 int regset_fpregs_active(struct task_struct *target, const struct user_regset *regset)
355 struct fpu *target_fpu = &target->thread.fpu;
357 return target_fpu->fpstate_active ? regset->n : 0;
360 int regset_xregset_fpregs_active(struct task_struct *target, const struct user_regset *regset)
362 struct fpu *target_fpu = &target->thread.fpu;
364 return (cpu_has_fxsr && target_fpu->fpstate_active) ? regset->n : 0;
367 int xfpregs_get(struct task_struct *target, const struct user_regset *regset,
368 unsigned int pos, unsigned int count,
369 void *kbuf, void __user *ubuf)
371 struct fpu *fpu = &target->thread.fpu;
376 fpu__activate_stopped(fpu);
377 sanitize_i387_state(target);
379 return user_regset_copyout(&pos, &count, &kbuf, &ubuf,
380 &fpu->state.fxsave, 0, -1);
383 int xfpregs_set(struct task_struct *target, const struct user_regset *regset,
384 unsigned int pos, unsigned int count,
385 const void *kbuf, const void __user *ubuf)
387 struct fpu *fpu = &target->thread.fpu;
393 fpu__activate_stopped(fpu);
394 sanitize_i387_state(target);
396 ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf,
397 &fpu->state.fxsave, 0, -1);
400 * mxcsr reserved bits must be masked to zero for security reasons.
402 fpu->state.fxsave.mxcsr &= mxcsr_feature_mask;
405 * update the header bits in the xsave header, indicating the
406 * presence of FP and SSE state.
409 fpu->state.xsave.header.xfeatures |= XSTATE_FPSSE;
414 int xstateregs_get(struct task_struct *target, const struct user_regset *regset,
415 unsigned int pos, unsigned int count,
416 void *kbuf, void __user *ubuf)
418 struct fpu *fpu = &target->thread.fpu;
419 struct xsave_struct *xsave;
425 fpu__activate_stopped(fpu);
427 xsave = &fpu->state.xsave;
430 * Copy the 48bytes defined by the software first into the xstate
431 * memory layout in the thread struct, so that we can copy the entire
432 * xstateregs to the user using one user_regset_copyout().
434 memcpy(&xsave->i387.sw_reserved,
435 xstate_fx_sw_bytes, sizeof(xstate_fx_sw_bytes));
437 * Copy the xstate memory layout.
439 ret = user_regset_copyout(&pos, &count, &kbuf, &ubuf, xsave, 0, -1);
443 int xstateregs_set(struct task_struct *target, const struct user_regset *regset,
444 unsigned int pos, unsigned int count,
445 const void *kbuf, const void __user *ubuf)
447 struct fpu *fpu = &target->thread.fpu;
448 struct xsave_struct *xsave;
454 fpu__activate_stopped(fpu);
456 xsave = &fpu->state.xsave;
458 ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, xsave, 0, -1);
460 * mxcsr reserved bits must be masked to zero for security reasons.
462 xsave->i387.mxcsr &= mxcsr_feature_mask;
463 xsave->header.xfeatures &= xfeatures_mask;
465 * These bits must be zero.
467 memset(&xsave->header.reserved, 0, 48);
472 #if defined CONFIG_X86_32 || defined CONFIG_IA32_EMULATION
475 * FPU tag word conversions.
478 static inline unsigned short twd_i387_to_fxsr(unsigned short twd)
480 unsigned int tmp; /* to avoid 16 bit prefixes in the code */
482 /* Transform each pair of bits into 01 (valid) or 00 (empty) */
484 tmp = (tmp | (tmp>>1)) & 0x5555; /* 0V0V0V0V0V0V0V0V */
485 /* and move the valid bits to the lower byte. */
486 tmp = (tmp | (tmp >> 1)) & 0x3333; /* 00VV00VV00VV00VV */
487 tmp = (tmp | (tmp >> 2)) & 0x0f0f; /* 0000VVVV0000VVVV */
488 tmp = (tmp | (tmp >> 4)) & 0x00ff; /* 00000000VVVVVVVV */
493 #define FPREG_ADDR(f, n) ((void *)&(f)->st_space + (n) * 16)
494 #define FP_EXP_TAG_VALID 0
495 #define FP_EXP_TAG_ZERO 1
496 #define FP_EXP_TAG_SPECIAL 2
497 #define FP_EXP_TAG_EMPTY 3
499 static inline u32 twd_fxsr_to_i387(struct i387_fxsave_struct *fxsave)
502 u32 tos = (fxsave->swd >> 11) & 7;
503 u32 twd = (unsigned long) fxsave->twd;
505 u32 ret = 0xffff0000u;
508 for (i = 0; i < 8; i++, twd >>= 1) {
510 st = FPREG_ADDR(fxsave, (i - tos) & 7);
512 switch (st->exponent & 0x7fff) {
514 tag = FP_EXP_TAG_SPECIAL;
517 if (!st->significand[0] &&
518 !st->significand[1] &&
519 !st->significand[2] &&
521 tag = FP_EXP_TAG_ZERO;
523 tag = FP_EXP_TAG_SPECIAL;
526 if (st->significand[3] & 0x8000)
527 tag = FP_EXP_TAG_VALID;
529 tag = FP_EXP_TAG_SPECIAL;
533 tag = FP_EXP_TAG_EMPTY;
535 ret |= tag << (2 * i);
541 * FXSR floating point environment conversions.
545 convert_from_fxsr(struct user_i387_ia32_struct *env, struct task_struct *tsk)
547 struct i387_fxsave_struct *fxsave = &tsk->thread.fpu.state.fxsave;
548 struct _fpreg *to = (struct _fpreg *) &env->st_space[0];
549 struct _fpxreg *from = (struct _fpxreg *) &fxsave->st_space[0];
552 env->cwd = fxsave->cwd | 0xffff0000u;
553 env->swd = fxsave->swd | 0xffff0000u;
554 env->twd = twd_fxsr_to_i387(fxsave);
557 env->fip = fxsave->rip;
558 env->foo = fxsave->rdp;
560 * should be actually ds/cs at fpu exception time, but
561 * that information is not available in 64bit mode.
563 env->fcs = task_pt_regs(tsk)->cs;
564 if (tsk == current) {
565 savesegment(ds, env->fos);
567 env->fos = tsk->thread.ds;
569 env->fos |= 0xffff0000;
571 env->fip = fxsave->fip;
572 env->fcs = (u16) fxsave->fcs | ((u32) fxsave->fop << 16);
573 env->foo = fxsave->foo;
574 env->fos = fxsave->fos;
577 for (i = 0; i < 8; ++i)
578 memcpy(&to[i], &from[i], sizeof(to[0]));
581 void convert_to_fxsr(struct task_struct *tsk,
582 const struct user_i387_ia32_struct *env)
585 struct i387_fxsave_struct *fxsave = &tsk->thread.fpu.state.fxsave;
586 struct _fpreg *from = (struct _fpreg *) &env->st_space[0];
587 struct _fpxreg *to = (struct _fpxreg *) &fxsave->st_space[0];
590 fxsave->cwd = env->cwd;
591 fxsave->swd = env->swd;
592 fxsave->twd = twd_i387_to_fxsr(env->twd);
593 fxsave->fop = (u16) ((u32) env->fcs >> 16);
595 fxsave->rip = env->fip;
596 fxsave->rdp = env->foo;
597 /* cs and ds ignored */
599 fxsave->fip = env->fip;
600 fxsave->fcs = (env->fcs & 0xffff);
601 fxsave->foo = env->foo;
602 fxsave->fos = env->fos;
605 for (i = 0; i < 8; ++i)
606 memcpy(&to[i], &from[i], sizeof(from[0]));
609 int fpregs_get(struct task_struct *target, const struct user_regset *regset,
610 unsigned int pos, unsigned int count,
611 void *kbuf, void __user *ubuf)
613 struct fpu *fpu = &target->thread.fpu;
614 struct user_i387_ia32_struct env;
616 fpu__activate_stopped(fpu);
618 if (!static_cpu_has(X86_FEATURE_FPU))
619 return fpregs_soft_get(target, regset, pos, count, kbuf, ubuf);
622 return user_regset_copyout(&pos, &count, &kbuf, &ubuf,
623 &fpu->state.fsave, 0,
626 sanitize_i387_state(target);
628 if (kbuf && pos == 0 && count == sizeof(env)) {
629 convert_from_fxsr(kbuf, target);
633 convert_from_fxsr(&env, target);
635 return user_regset_copyout(&pos, &count, &kbuf, &ubuf, &env, 0, -1);
638 int fpregs_set(struct task_struct *target, const struct user_regset *regset,
639 unsigned int pos, unsigned int count,
640 const void *kbuf, const void __user *ubuf)
642 struct fpu *fpu = &target->thread.fpu;
643 struct user_i387_ia32_struct env;
646 fpu__activate_stopped(fpu);
648 sanitize_i387_state(target);
650 if (!static_cpu_has(X86_FEATURE_FPU))
651 return fpregs_soft_set(target, regset, pos, count, kbuf, ubuf);
654 return user_regset_copyin(&pos, &count, &kbuf, &ubuf,
655 &fpu->state.fsave, 0,
658 if (pos > 0 || count < sizeof(env))
659 convert_from_fxsr(&env, target);
661 ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, &env, 0, -1);
663 convert_to_fxsr(target, &env);
666 * update the header bit in the xsave header, indicating the
670 fpu->state.xsave.header.xfeatures |= XSTATE_FP;
675 * FPU state for core dumps.
676 * This is only used for a.out dumps now.
677 * It is declared generically using elf_fpregset_t (which is
678 * struct user_i387_struct) but is in fact only used for 32-bit
679 * dumps, so on 64-bit it is really struct user_i387_ia32_struct.
681 int dump_fpu(struct pt_regs *regs, struct user_i387_struct *ufpu)
683 struct task_struct *tsk = current;
684 struct fpu *fpu = &tsk->thread.fpu;
687 fpvalid = fpu->fpstate_active;
689 fpvalid = !fpregs_get(tsk, NULL,
690 0, sizeof(struct user_i387_ia32_struct),
695 EXPORT_SYMBOL(dump_fpu);
697 #endif /* CONFIG_X86_32 || CONFIG_IA32_EMULATION */