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i387_32.c

/*
 *  Copyright (C) 1994 Linus Torvalds
 *
 *  Pentium III FXSR, SSE support
 *  General FPU state handling cleanups
 *    Gareth Hughes <gareth@valinux.com>, May 2000
 */

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

#ifdef CONFIG_MATH_EMULATION
#define HAVE_HWFP (boot_cpu_data.hard_math)
#else
#define HAVE_HWFP 1
#endif

static unsigned long mxcsr_feature_mask __read_mostly = 0xffffffff;

void mxcsr_feature_mask_init(void)
{
      unsigned long mask = 0;
      clts();
      if (cpu_has_fxsr) {
            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();
}

/*
 * The _current_ task is using the FPU for the first time
 * so initialize it and set the mxcsr to its default
 * value at reset if we support XMM instructions and then
 * remeber the current task has used the FPU.
 */
void init_fpu(struct task_struct *tsk)
{
      if (cpu_has_fxsr) {
            memset(&tsk->thread.i387.fxsave, 0, sizeof(struct i387_fxsave_struct));
            tsk->thread.i387.fxsave.cwd = 0x37f;
            if (cpu_has_xmm)
                  tsk->thread.i387.fxsave.mxcsr = 0x1f80;
      } else {
            memset(&tsk->thread.i387.fsave, 0, sizeof(struct i387_fsave_struct));
            tsk->thread.i387.fsave.cwd = 0xffff037fu;
            tsk->thread.i387.fsave.swd = 0xffff0000u;
            tsk->thread.i387.fsave.twd = 0xffffffffu;
            tsk->thread.i387.fsave.fos = 0xffff0000u;
      }
      /* only the device not available exception or ptrace can call init_fpu */
      set_stopped_child_used_math(tsk);
}

/*
 * FPU lazy state save handling.
 */

void kernel_fpu_begin(void)
{
      struct thread_info *thread = current_thread_info();

      preempt_disable();
      if (thread->status & TS_USEDFPU) {
            __save_init_fpu(thread->task);
            return;
      }
      clts();
}
EXPORT_SYMBOL_GPL(kernel_fpu_begin);

/*
 * FPU tag word conversions.
 */

static inline unsigned short twd_i387_to_fxsr( unsigned short twd )
{
      unsigned int tmp; /* to avoid 16 bit prefixes in the code */
 
      /* Transform each pair of bits into 01 (valid) or 00 (empty) */
        tmp = ~twd;
        tmp = (tmp | (tmp>>1)) & 0x5555; /* 0V0V0V0V0V0V0V0V */
        /* and move the valid bits to the lower byte. */
        tmp = (tmp | (tmp >> 1)) & 0x3333; /* 00VV00VV00VV00VV */
        tmp = (tmp | (tmp >> 2)) & 0x0f0f; /* 0000VVVV0000VVVV */
        tmp = (tmp | (tmp >> 4)) & 0x00ff; /* 00000000VVVVVVVV */
        return tmp;
}

static inline unsigned long twd_fxsr_to_i387( struct i387_fxsave_struct *fxsave )
{
      struct _fpxreg *st = NULL;
      unsigned long tos = (fxsave->swd >> 11) & 7;
      unsigned long twd = (unsigned long) fxsave->twd;
      unsigned long tag;
      unsigned long ret = 0xffff0000u;
      int i;

#define FPREG_ADDR(f, n)      ((void *)&(f)->st_space + (n) * 16);

      for ( i = 0 ; i < 8 ; i++ ) {
            if ( twd & 0x1 ) {
                  st = FPREG_ADDR( fxsave, (i - tos) & 7 );

                  switch ( st->exponent & 0x7fff ) {
                  case 0x7fff:
                        tag = 2;          /* Special */
                        break;
                  case 0x0000:
                        if ( !st->significand[0] &&
                             !st->significand[1] &&
                             !st->significand[2] &&
                             !st->significand[3] ) {
                              tag = 1;    /* Zero */
                        } else {
                              tag = 2;    /* Special */
                        }
                        break;
                  default:
                        if ( st->significand[3] & 0x8000 ) {
                              tag = 0;    /* Valid */
                        } else {
                              tag = 2;    /* Special */
                        }
                        break;
                  }
            } else {
                  tag = 3;                /* Empty */
            }
            ret |= (tag << (2 * i));
            twd = twd >> 1;
      }
      return ret;
}

/*
 * FPU state interaction.
 */

unsigned short get_fpu_cwd( struct task_struct *tsk )
{
      if ( cpu_has_fxsr ) {
            return tsk->thread.i387.fxsave.cwd;
      } else {
            return (unsigned short)tsk->thread.i387.fsave.cwd;
      }
}

unsigned short get_fpu_swd( struct task_struct *tsk )
{
      if ( cpu_has_fxsr ) {
            return tsk->thread.i387.fxsave.swd;
      } else {
            return (unsigned short)tsk->thread.i387.fsave.swd;
      }
}

#if 0
unsigned short get_fpu_twd( struct task_struct *tsk )
{
      if ( cpu_has_fxsr ) {
            return tsk->thread.i387.fxsave.twd;
      } else {
            return (unsigned short)tsk->thread.i387.fsave.twd;
      }
}
#endif  /*  0  */

unsigned short get_fpu_mxcsr( struct task_struct *tsk )
{
      if ( cpu_has_xmm ) {
            return tsk->thread.i387.fxsave.mxcsr;
      } else {
            return 0x1f80;
      }
}

#if 0

void set_fpu_cwd( struct task_struct *tsk, unsigned short cwd )
{
      if ( cpu_has_fxsr ) {
            tsk->thread.i387.fxsave.cwd = cwd;
      } else {
            tsk->thread.i387.fsave.cwd = ((long)cwd | 0xffff0000u);
      }
}

void set_fpu_swd( struct task_struct *tsk, unsigned short swd )
{
      if ( cpu_has_fxsr ) {
            tsk->thread.i387.fxsave.swd = swd;
      } else {
            tsk->thread.i387.fsave.swd = ((long)swd | 0xffff0000u);
      }
}

void set_fpu_twd( struct task_struct *tsk, unsigned short twd )
{
      if ( cpu_has_fxsr ) {
            tsk->thread.i387.fxsave.twd = twd_i387_to_fxsr(twd);
      } else {
            tsk->thread.i387.fsave.twd = ((long)twd | 0xffff0000u);
      }
}

#endif  /*  0  */

/*
 * FXSR floating point environment conversions.
 */

static int convert_fxsr_to_user( struct _fpstate __user *buf,
                              struct i387_fxsave_struct *fxsave )
{
      unsigned long env[7];
      struct _fpreg __user *to;
      struct _fpxreg *from;
      int i;

      env[0] = (unsigned long)fxsave->cwd | 0xffff0000ul;
      env[1] = (unsigned long)fxsave->swd | 0xffff0000ul;
      env[2] = twd_fxsr_to_i387(fxsave);
      env[3] = fxsave->fip;
      env[4] = fxsave->fcs | ((unsigned long)fxsave->fop << 16);
      env[5] = fxsave->foo;
      env[6] = fxsave->fos;

      if ( __copy_to_user( buf, env, 7 * sizeof(unsigned long) ) )
            return 1;

      to = &buf->_st[0];
      from = (struct _fpxreg *) &fxsave->st_space[0];
      for ( i = 0 ; i < 8 ; i++, to++, from++ ) {
            unsigned long __user *t = (unsigned long __user *)to;
            unsigned long *f = (unsigned long *)from;

            if (__put_user(*f, t) ||
                        __put_user(*(f + 1), t + 1) ||
                        __put_user(from->exponent, &to->exponent))
                  return 1;
      }
      return 0;
}

static int convert_fxsr_from_user( struct i387_fxsave_struct *fxsave,
                                struct _fpstate __user *buf )
{
      unsigned long env[7];
      struct _fpxreg *to;
      struct _fpreg __user *from;
      int i;

      if ( __copy_from_user( env, buf, 7 * sizeof(long) ) )
            return 1;

      fxsave->cwd = (unsigned short)(env[0] & 0xffff);
      fxsave->swd = (unsigned short)(env[1] & 0xffff);
      fxsave->twd = twd_i387_to_fxsr((unsigned short)(env[2] & 0xffff));
      fxsave->fip = env[3];
      fxsave->fop = (unsigned short)((env[4] & 0xffff0000ul) >> 16);
      fxsave->fcs = (env[4] & 0xffff);
      fxsave->foo = env[5];
      fxsave->fos = env[6];

      to = (struct _fpxreg *) &fxsave->st_space[0];
      from = &buf->_st[0];
      for ( i = 0 ; i < 8 ; i++, to++, from++ ) {
            unsigned long *t = (unsigned long *)to;
            unsigned long __user *f = (unsigned long __user *)from;

            if (__get_user(*t, f) ||
                        __get_user(*(t + 1), f + 1) ||
                        __get_user(to->exponent, &from->exponent))
                  return 1;
      }
      return 0;
}

/*
 * Signal frame handlers.
 */

static inline int save_i387_fsave( struct _fpstate __user *buf )
{
      struct task_struct *tsk = current;

      unlazy_fpu( tsk );
      tsk->thread.i387.fsave.status = tsk->thread.i387.fsave.swd;
      if ( __copy_to_user( buf, &tsk->thread.i387.fsave,
                       sizeof(struct i387_fsave_struct) ) )
            return -1;
      return 1;
}

static int save_i387_fxsave( struct _fpstate __user *buf )
{
      struct task_struct *tsk = current;
      int err = 0;

      unlazy_fpu( tsk );

      if ( convert_fxsr_to_user( buf, &tsk->thread.i387.fxsave ) )
            return -1;

      err |= __put_user( tsk->thread.i387.fxsave.swd, &buf->status );
      err |= __put_user( X86_FXSR_MAGIC, &buf->magic );
      if ( err )
            return -1;

      if ( __copy_to_user( &buf->_fxsr_env[0], &tsk->thread.i387.fxsave,
                       sizeof(struct i387_fxsave_struct) ) )
            return -1;
      return 1;
}

int save_i387( struct _fpstate __user *buf )
{
      if ( !used_math() )
            return 0;

      /* This will cause a "finit" to be triggered by the next
       * attempted FPU operation by the 'current' process.
       */
      clear_used_math();

      if ( HAVE_HWFP ) {
            if ( cpu_has_fxsr ) {
                  return save_i387_fxsave( buf );
            } else {
                  return save_i387_fsave( buf );
            }
      } else {
            return save_i387_soft( &current->thread.i387.soft, buf );
      }
}

static inline int restore_i387_fsave( struct _fpstate __user *buf )
{
      struct task_struct *tsk = current;
      clear_fpu( tsk );
      return __copy_from_user( &tsk->thread.i387.fsave, buf,
                         sizeof(struct i387_fsave_struct) );
}

static int restore_i387_fxsave( struct _fpstate __user *buf )
{
      int err;
      struct task_struct *tsk = current;
      clear_fpu( tsk );
      err = __copy_from_user( &tsk->thread.i387.fxsave, &buf->_fxsr_env[0],
                        sizeof(struct i387_fxsave_struct) );
      /* mxcsr reserved bits must be masked to zero for security reasons */
      tsk->thread.i387.fxsave.mxcsr &= mxcsr_feature_mask;
      return err ? 1 : convert_fxsr_from_user( &tsk->thread.i387.fxsave, buf );
}

int restore_i387( struct _fpstate __user *buf )
{
      int err;

      if ( HAVE_HWFP ) {
            if ( cpu_has_fxsr ) {
                  err = restore_i387_fxsave( buf );
            } else {
                  err = restore_i387_fsave( buf );
            }
      } else {
            err = restore_i387_soft( &current->thread.i387.soft, buf );
      }
      set_used_math();
      return err;
}

/*
 * ptrace request handlers.
 */

static inline int get_fpregs_fsave( struct user_i387_struct __user *buf,
                            struct task_struct *tsk )
{
      return __copy_to_user( buf, &tsk->thread.i387.fsave,
                         sizeof(struct user_i387_struct) );
}

static inline int get_fpregs_fxsave( struct user_i387_struct __user *buf,
                             struct task_struct *tsk )
{
      return convert_fxsr_to_user( (struct _fpstate __user *)buf,
                             &tsk->thread.i387.fxsave );
}

int get_fpregs( struct user_i387_struct __user *buf, struct task_struct *tsk )
{
      if ( HAVE_HWFP ) {
            if ( cpu_has_fxsr ) {
                  return get_fpregs_fxsave( buf, tsk );
            } else {
                  return get_fpregs_fsave( buf, tsk );
            }
      } else {
            return save_i387_soft( &tsk->thread.i387.soft,
                               (struct _fpstate __user *)buf );
      }
}

static inline int set_fpregs_fsave( struct task_struct *tsk,
                            struct user_i387_struct __user *buf )
{
      return __copy_from_user( &tsk->thread.i387.fsave, buf,
                         sizeof(struct user_i387_struct) );
}

static inline int set_fpregs_fxsave( struct task_struct *tsk,
                             struct user_i387_struct __user *buf )
{
      return convert_fxsr_from_user( &tsk->thread.i387.fxsave,
                               (struct _fpstate __user *)buf );
}

int set_fpregs( struct task_struct *tsk, struct user_i387_struct __user *buf )
{
      if ( HAVE_HWFP ) {
            if ( cpu_has_fxsr ) {
                  return set_fpregs_fxsave( tsk, buf );
            } else {
                  return set_fpregs_fsave( tsk, buf );
            }
      } else {
            return restore_i387_soft( &tsk->thread.i387.soft,
                                (struct _fpstate __user *)buf );
      }
}

int get_fpxregs( struct user_fxsr_struct __user *buf, struct task_struct *tsk )
{
      if ( cpu_has_fxsr ) {
            if (__copy_to_user( buf, &tsk->thread.i387.fxsave,
                            sizeof(struct user_fxsr_struct) ))
                  return -EFAULT;
            return 0;
      } else {
            return -EIO;
      }
}

int set_fpxregs( struct task_struct *tsk, struct user_fxsr_struct __user *buf )
{
      int ret = 0;

      if ( cpu_has_fxsr ) {
            if (__copy_from_user( &tsk->thread.i387.fxsave, buf,
                          sizeof(struct user_fxsr_struct) ))
                  ret = -EFAULT;
            /* mxcsr reserved bits must be masked to zero for security reasons */
            tsk->thread.i387.fxsave.mxcsr &= mxcsr_feature_mask;
      } else {
            ret = -EIO;
      }
      return ret;
}

/*
 * FPU state for core dumps.
 */

static inline void copy_fpu_fsave( struct task_struct *tsk,
                           struct user_i387_struct *fpu )
{
      memcpy( fpu, &tsk->thread.i387.fsave,
            sizeof(struct user_i387_struct) );
}

static inline void copy_fpu_fxsave( struct task_struct *tsk,
                           struct user_i387_struct *fpu )
{
      unsigned short *to;
      unsigned short *from;
      int i;

      memcpy( fpu, &tsk->thread.i387.fxsave, 7 * sizeof(long) );

      to = (unsigned short *)&fpu->st_space[0];
      from = (unsigned short *)&tsk->thread.i387.fxsave.st_space[0];
      for ( i = 0 ; i < 8 ; i++, to += 5, from += 8 ) {
            memcpy( to, from, 5 * sizeof(unsigned short) );
      }
}

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

      fpvalid = !!used_math();
      if ( fpvalid ) {
            unlazy_fpu( tsk );
            if ( cpu_has_fxsr ) {
                  copy_fpu_fxsave( tsk, fpu );
            } else {
                  copy_fpu_fsave( tsk, fpu );
            }
      }

      return fpvalid;
}
EXPORT_SYMBOL(dump_fpu);

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);
            if (cpu_has_fxsr)
                  copy_fpu_fxsave(tsk, fpu);
            else
                  copy_fpu_fsave(tsk, fpu);
      }
      return fpvalid;
}

int dump_task_extended_fpu(struct task_struct *tsk, struct user_fxsr_struct *fpu)
{
      int fpvalid = tsk_used_math(tsk) && cpu_has_fxsr;

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

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