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i387_64.c

/*
 *  Copyright (C) 1994 Linus Torvalds
 *  Copyright (C) 2002 Andi Kleen, SuSE Labs
 *
 *  Pentium III FXSR, SSE support
 *  General FPU state handling cleanups
 *    Gareth Hughes <gareth@valinux.com>, May 2000
 * 
 *  x86-64 rework 2002 Andi Kleen. 
 *  Does direct fxsave in and out of user space now for signal handlers.
 *  All the FSAVE<->FXSAVE conversion code has been moved to the 32bit emulation,
 *  the 64bit user space sees a FXSAVE frame directly. 
 */

#include <linux/sched.h>
#include <linux/init.h>
#include <asm/processor.h>
#include <asm/i387.h>
#include <asm/sigcontext.h>
#include <asm/user.h>
#include <asm/ptrace.h>
#include <asm/uaccess.h>

unsigned int mxcsr_feature_mask __read_mostly = 0xffffffff;

void mxcsr_feature_mask_init(void)
{
      unsigned int mask;
      clts();
      memset(&current->thread.i387.fxsave, 0, sizeof(struct i387_fxsave_struct));
      asm volatile("fxsave %0" : : "m" (current->thread.i387.fxsave));
      mask = current->thread.i387.fxsave.mxcsr_mask;
      if (mask == 0) mask = 0x0000ffbf;
      mxcsr_feature_mask &= mask;
      stts();
}

/*
 * Called at bootup to set up the initial FPU state that is later cloned
 * into all processes.
 */
void __cpuinit fpu_init(void)
{
      unsigned long oldcr0 = read_cr0();
      extern void __bad_fxsave_alignment(void);
            
      if (offsetof(struct task_struct, thread.i387.fxsave) & 15)
            __bad_fxsave_alignment();
      set_in_cr4(X86_CR4_OSFXSR);
      set_in_cr4(X86_CR4_OSXMMEXCPT);

      write_cr0(oldcr0 & ~((1UL<<3)|(1UL<<2))); /* clear TS and EM */

      mxcsr_feature_mask_init();
      /* clean state in init */
      current_thread_info()->status = 0;
      clear_used_math();
}

void init_fpu(struct task_struct *child)
{
      if (tsk_used_math(child)) {
            if (child == current)
                  unlazy_fpu(child);
            return;
      }     
      memset(&child->thread.i387.fxsave, 0, sizeof(struct i387_fxsave_struct));
      child->thread.i387.fxsave.cwd = 0x37f;
      child->thread.i387.fxsave.mxcsr = 0x1f80;
      /* only the device not available exception or ptrace can call init_fpu */
      set_stopped_child_used_math(child);
}

/*
 * Signal frame handlers.
 */

int save_i387(struct _fpstate __user *buf)
{
      struct task_struct *tsk = current;
      int err = 0;

      BUILD_BUG_ON(sizeof(struct user_i387_struct) !=
                  sizeof(tsk->thread.i387.fxsave));

      if ((unsigned long)buf % 16) 
            printk("save_i387: bad fpstate %p\n",buf); 

      if (!used_math())
            return 0;
      clear_used_math(); /* trigger finit */
      if (task_thread_info(tsk)->status & TS_USEDFPU) {
            err = save_i387_checking((struct i387_fxsave_struct __user *)buf);
            if (err) return err;
            task_thread_info(tsk)->status &= ~TS_USEDFPU;
            stts();
      } else {
            if (__copy_to_user(buf, &tsk->thread.i387.fxsave,
                           sizeof(struct i387_fxsave_struct)))
                  return -1;
      }
      return 1;
}

/*
 * ptrace request handlers.
 */

int get_fpregs(struct user_i387_struct __user *buf, struct task_struct *tsk)
{
      init_fpu(tsk);
      return __copy_to_user(buf, &tsk->thread.i387.fxsave,
                         sizeof(struct user_i387_struct)) ? -EFAULT : 0;
}

int set_fpregs(struct task_struct *tsk, struct user_i387_struct __user *buf)
{
      if (__copy_from_user(&tsk->thread.i387.fxsave, buf, 
                       sizeof(struct user_i387_struct)))
            return -EFAULT;
            return 0;
}

/*
 * FPU state for core dumps.
 */

int dump_fpu( struct pt_regs *regs, struct user_i387_struct *fpu )
{
      struct task_struct *tsk = current;

      if (!used_math())
            return 0;

      unlazy_fpu(tsk);
      memcpy(fpu, &tsk->thread.i387.fxsave, sizeof(struct user_i387_struct)); 
      return 1; 
}

int dump_task_fpu(struct task_struct *tsk, struct user_i387_struct *fpu)
{
      int fpvalid = !!tsk_used_math(tsk);

      if (fpvalid) {
            if (tsk == current)
                  unlazy_fpu(tsk);
            memcpy(fpu, &tsk->thread.i387.fxsave, sizeof(struct user_i387_struct));       
}
      return fpvalid;
}

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