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fpu32.c

/* 
 * Copyright 2002 Andi Kleen, SuSE Labs.
 * FXSAVE<->i387 conversion support. Based on code by Gareth Hughes.
 * This is used for ptrace, signals and coredumps in 32bit emulation.
 */ 

#include <linux/sched.h>
#include <asm/sigcontext32.h>
#include <asm/processor.h>
#include <asm/uaccess.h>
#include <asm/i387.h>

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 = 0xffff0000;
      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;
}


static inline int convert_fxsr_from_user(struct i387_fxsave_struct *fxsave,
                               struct _fpstate_ia32 __user *buf)
{
      struct _fpxreg *to;
      struct _fpreg __user *from;
      int i;
      u32 v;
      int err = 0;

#define G(num,val) err |= __get_user(val, num + (u32 __user *)buf)
      G(0, fxsave->cwd);
      G(1, fxsave->swd);
      G(2, fxsave->twd);
      fxsave->twd = twd_i387_to_fxsr(fxsave->twd);
      G(3, fxsave->rip);
      G(4, v);
      fxsave->fop = v>>16;    /* cs ignored */
      G(5, fxsave->rdp);
      /* 6: ds ignored */
#undef G
      if (err) 
            return -1; 

      to = (struct _fpxreg *)&fxsave->st_space[0];
      from = &buf->_st[0];
      for (i = 0 ; i < 8 ; i++, to++, from++) {
            if (__copy_from_user(to, from, sizeof(*from)))
                  return -1;
      }
      return 0;
}


static inline int convert_fxsr_to_user(struct _fpstate_ia32 __user *buf,
                               struct i387_fxsave_struct *fxsave,
                               struct pt_regs *regs,
                               struct task_struct *tsk)
{
      struct _fpreg __user *to;
      struct _fpxreg *from;
      int i;
      u16 cs,ds; 
      int err = 0; 

      if (tsk == current) {
            /* should be actually ds/cs at fpu exception time,
               but that information is not available in 64bit mode. */
            asm("movw %%ds,%0 " : "=r" (ds)); 
            asm("movw %%cs,%0 " : "=r" (cs));         
      } else { /* ptrace. task has stopped. */
            ds = tsk->thread.ds;
            cs = regs->cs;
      } 

#define P(num,val) err |= __put_user(val, num + (u32 __user *)buf)
      P(0, (u32)fxsave->cwd | 0xffff0000);
      P(1, (u32)fxsave->swd | 0xffff0000);
      P(2, twd_fxsr_to_i387(fxsave));
      P(3, (u32)fxsave->rip);
      P(4,  cs | ((u32)fxsave->fop) << 16); 
      P(5, fxsave->rdp);
      P(6, 0xffff0000 | ds);
#undef P

      if (err) 
            return -1; 

      to = &buf->_st[0];
      from = (struct _fpxreg *) &fxsave->st_space[0];
      for ( i = 0 ; i < 8 ; i++, to++, from++ ) {
            if (__copy_to_user(to, from, sizeof(*to)))
                  return -1;
      }
      return 0;
}

int restore_i387_ia32(struct task_struct *tsk, struct _fpstate_ia32 __user *buf, int fsave) 
{ 
      clear_fpu(tsk);
      if (!fsave) { 
            if (__copy_from_user(&tsk->thread.i387.fxsave, 
                             &buf->_fxsr_env[0],
                             sizeof(struct i387_fxsave_struct)))
                  return -1;
            tsk->thread.i387.fxsave.mxcsr &= mxcsr_feature_mask;
            set_stopped_child_used_math(tsk);
      } 
      return convert_fxsr_from_user(&tsk->thread.i387.fxsave, buf);
}  

int save_i387_ia32(struct task_struct *tsk, 
               struct _fpstate_ia32 __user *buf, 
               struct pt_regs *regs,
               int fsave)
{
      int err = 0;

      init_fpu(tsk);
      if (convert_fxsr_to_user(buf, &tsk->thread.i387.fxsave, regs, tsk))
            return -1;
      if (fsave)
            return 0;
      err |= __put_user(tsk->thread.i387.fxsave.swd, &buf->status);
      if (fsave) 
            return err ? -1 : 1;    
      err |= __put_user(X86_FXSR_MAGIC, &buf->magic);
      err |= __copy_to_user(&buf->_fxsr_env[0], &tsk->thread.i387.fxsave,
                        sizeof(struct i387_fxsave_struct));
      return err ? -1 : 1;
}

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