arch/x86/include/asm/i387.h

   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 _ASM_X86_I387_H
  11 #define _ASM_X86_I387_H
  12
  13 #ifndef __ASSEMBLY__
  14
  15 #include <linux/sched.h>
  16 #include <linux/hardirq.h>
  17 #include <asm/system.h>
  18
  19 struct pt_regs;
  20 struct user_i387_struct;
  21
  22 extern int init_fpu(struct task_struct *child);
  23 extern int dump_fpu(struct pt_regs *, struct user_i387_struct *);
  24 extern void math_state_restore(void);
  25
  26 extern bool irq_fpu_usable(void);
  27 extern void kernel_fpu_begin(void);
  28 extern void kernel_fpu_end(void);
  29
  30 /*
  31  * Some instructions like VIA's padlock instructions generate a spurious
  32  * DNA fault but don't modify SSE registers. And these instructions
  33  * get used from interrupt context as well. To prevent these kernel instructions
  34  * in interrupt context interacting wrongly with other user/kernel fpu usage, we
  35  * should use them only in the context of irq_ts_save/restore()
  36  */
  37 static inline int irq_ts_save(void)
  38 {
  39         /*
  40          * If in process context and not atomic, we can take a spurious DNA fault.
  41          * Otherwise, doing clts() in process context requires disabling preemption
  42          * or some heavy lifting like kernel_fpu_begin()
  43          */
  44         if (!in_atomic())
  45                 return 0;
  46
  47         if (read_cr0() & X86_CR0_TS) {
  48                 clts();
  49                 return 1;
  50         }
  51
  52         return 0;
  53 }
  54
  55 static inline void irq_ts_restore(int TS_state)
  56 {
  57         if (TS_state)
  58                 stts();
  59 }
  60
  61 /*
  62  * The question "does this thread have fpu access?"
  63  * is slightly racy, since preemption could come in
  64  * and revoke it immediately after the test.
  65  *
  66  * However, even in that very unlikely scenario,
  67  * we can just assume we have FPU access - typically
  68  * to save the FP state - we'll just take a #NM
  69  * fault and get the FPU access back.
  70  */
  71 static inline int user_has_fpu(void)
  72 {
  73         return current->thread.fpu.has_fpu;
  74 }
  75
  76 extern void unlazy_fpu(struct task_struct *tsk);
  77
  78 #endif /* __ASSEMBLY__ */
  79
  80 #endif /* _ASM_X86_I387_H */