text: /*
   * include/asm-i386/i387.h
   *
   * Copyright (C) 1994 Linus Torvalds
   *
   * Pentium III FXSR, SSE support
   * General FPU state handling cleanups
   *	Gareth Hughes <gareth@valinux.com>, May 2000
   */
  
  #ifndef __ASM_I386_I387_H
  #define __ASM_I386_I387_H
  
  #include <linux/sched.h>
  #include <linux/init.h>
  #include <linux/kernel_stat.h>
  #include <asm/processor.h>
  #include <asm/sigcontext.h>
  #include <asm/user.h>
  
  extern void mxcsr_feature_mask_init(void);
  extern void init_fpu(struct task_struct *);
  
  /*
   * FPU lazy state save handling...
   */
  
  /*
   * The "nop" is needed to make the instructions the same
   * length.
   */
  #define restore_fpu(tsk)			\
  	alternative_input(			\
  		"nop ; frstor %1",		\
  		"fxrstor %1",			\
  		X86_FEATURE_FXSR,		\
  		"m" ((tsk)->thread.i387.fxsave))
  
  extern void kernel_fpu_begin(void);
  #define kernel_fpu_end() do { stts(); preempt_enable(); } while(0)
  
  /* We need a safe address that is cheap to find and that is already
     in L1 during context switch. The best choices are unfortunately
     different for UP and SMP */
  #ifdef CONFIG_SMP
  #define safe_address (__per_cpu_offset[0])
  #else
  #define safe_address (kstat_cpu(0).cpustat.user)
  #endif
  
  /*
   * These must be called with preempt disabled
   */
  static inline void __save_init_fpu( struct task_struct *tsk )
  {
  	/* Use more nops than strictly needed in case the compiler
  	   varies code */
  	alternative_input(
  		"fnsave %[fx] ;fwait;" GENERIC_NOP8 GENERIC_NOP4,
  		"fxsave %[fx]\n"
  		"bt $7,%[fsw] ; jnc 1f ; fnclex\n1:",
  		X86_FEATURE_FXSR,
  		[fx] "m" (tsk->thread.i387.fxsave),
  		[fsw] "m" (tsk->thread.i387.fxsave.swd) : "memory");
  	/* AMD K7/K8 CPUs don't save/restore FDP/FIP/FOP unless an exception
  	   is pending.  Clear the x87 state here by setting it to fixed
     	   values. safe_address is a random variable that should be in L1 */
  	alternative_input(
  		GENERIC_NOP8 GENERIC_NOP2,
  		"emms\n\t"	  	/* clear stack tags */
  		"fildl %[addr]", 	/* set F?P to defined value */
  		X86_FEATURE_FXSAVE_LEAK,
  		[addr] "m" (safe_address));
  	task_thread_info(tsk)->status &= ~TS_USEDFPU;
  }
  
  #define __unlazy_fpu( tsk ) do {				\
  	if (task_thread_info(tsk)->status & TS_USEDFPU) {	\
  		__save_init_fpu(tsk);				\
  		stts();						\
  	} else							\
  		tsk->fpu_counter = 0;				\
  } while (0)
  
  #define __clear_fpu( tsk )					\
  do {								\
  	if (task_thread_info(tsk)->status & TS_USEDFPU) {	\
  		asm volatile("fnclex ; fwait");			\
  		task_thread_info(tsk)->status &= ~TS_USEDFPU;	\
  		stts();						\
  	}							\
  } while (0)
  
  
  /*
   * These disable preemption on their own and are safe
   */
  static inline void save_init_fpu( struct task_struct *tsk )
  {
  	preempt_disable();
  	__save_init_fpu(tsk);
  	stts();
  	preempt_enable();
  }
  
  #define unlazy_fpu( tsk ) do {	\
  	preempt_disable();	\
  	__unlazy_fpu(tsk);	\
  	preempt_enable();	\
  } while (0)
  
  #define clear_fpu( tsk ) do {	\
  	preempt_disable();	\
  	__clear_fpu( tsk );	\
  	preempt_enable();	\
  } while (0)
  
  /*
   * FPU state interaction...
   */
  extern unsigned short get_fpu_cwd( struct task_struct *tsk );
  extern unsigned short get_fpu_swd( struct task_struct *tsk );
  extern unsigned short get_fpu_mxcsr( struct task_struct *tsk );
  extern asmlinkage void math_state_restore(void);
  
  /*
   * Signal frame handlers...
   */
  extern int save_i387( struct _fpstate __user *buf );
  extern int restore_i387( struct _fpstate __user *buf );
  
  /*
   * ptrace request handers...
   */
  extern int get_fpregs( struct user_i387_struct __user *buf,
  		       struct task_struct *tsk );
  extern int set_fpregs( struct task_struct *tsk,
  		       struct user_i387_struct __user *buf );
  
  extern int get_fpxregs( struct user_fxsr_struct __user *buf,
  			struct task_struct *tsk );
  extern int set_fpxregs( struct task_struct *tsk,
  			struct user_fxsr_struct __user *buf );
  
  /*
   * FPU state for core dumps...
   */
  extern int dump_fpu( struct pt_regs *regs,
  		     struct user_i387_struct *fpu );
  
  #endif /* __ASM_I386_I387_H */
  