arch/x86_64/ia32/fpu32.c

   1 /*
   2  * Copyright 2002 Andi Kleen, SuSE Labs.
   3  * FXSAVE<->i387 conversion support. Based on code by Gareth Hughes.
   4  * This is used for ptrace, signals and coredumps in 32bit emulation.
   5  * $Id: fpu32.c,v 1.1 2002/03/21 14:16:32 ak Exp $
   6  */
   7
   8 #include <linux/sched.h>
   9 #include <asm/sigcontext32.h>
  10 #include <asm/processor.h>
  11 #include <asm/uaccess.h>
  12 #include <asm/i387.h>
  13
  14 static inline unsigned short twd_i387_to_fxsr(unsigned short twd)
  15 {
  16         unsigned int tmp; /* to avoid 16 bit prefixes in the code */
  17
  18         /* Transform each pair of bits into 01 (valid) or 00 (empty) */
  19         tmp = ~twd;
  20         tmp = (tmp | (tmp>>1)) & 0x5555; /* 0V0V0V0V0V0V0V0V */
  21         /* and move the valid bits to the lower byte. */
  22         tmp = (tmp | (tmp >> 1)) & 0x3333; /* 00VV00VV00VV00VV */
  23         tmp = (tmp | (tmp >> 2)) & 0x0f0f; /* 0000VVVV0000VVVV */
  24         tmp = (tmp | (tmp >> 4)) & 0x00ff; /* 00000000VVVVVVVV */
  25         return tmp;
  26 }
  27
  28 static inline unsigned long twd_fxsr_to_i387(struct i387_fxsave_struct *fxsave)
  29 {
  30         struct _fpxreg *st = NULL;
  31         unsigned long tos = (fxsave->swd >> 11) & 7;
  32         unsigned long twd = (unsigned long) fxsave->twd;
  33         unsigned long tag;
  34         unsigned long ret = 0xffff0000;
  35         int i;
  36
  37 #define FPREG_ADDR(f, n)        ((void *)&(f)->st_space + (n) * 16);
  38
  39         for (i = 0 ; i < 8 ; i++) {
  40                 if (twd & 0x1) {
  41                         st = FPREG_ADDR( fxsave, (i - tos) & 7 );
  42
  43                         switch (st->exponent & 0x7fff) {
  44                         case 0x7fff:
  45                                 tag = 2;                /* Special */
  46                                 break;
  47                         case 0x0000:
  48                                 if ( !st->significand[0] &&
  49                                      !st->significand[1] &&
  50                                      !st->significand[2] &&
  51                                      !st->significand[3] ) {
  52                                         tag = 1;        /* Zero */
  53                                 } else {
  54                                         tag = 2;        /* Special */
  55                                 }
  56                                 break;
  57                         default:
  58                                 if (st->significand[3] & 0x8000) {
  59                                         tag = 0;        /* Valid */
  60                                 } else {
  61                                         tag = 2;        /* Special */
  62                                 }
  63                                 break;
  64                         }
  65                 } else {
  66                         tag = 3;                        /* Empty */
  67                 }
  68                 ret |= (tag << (2 * i));
  69                 twd = twd >> 1;
  70         }
  71         return ret;
  72 }
  73
  74
  75 static inline int convert_fxsr_from_user(struct i387_fxsave_struct *fxsave,
  76                                          struct _fpstate_ia32 __user *buf)
  77 {
  78         struct _fpxreg *to;
  79         struct _fpreg __user *from;
  80         int i;
  81         u32 v;
  82         int err = 0;
  83
  84 #define G(num,val) err |= __get_user(val, num + (u32 __user *)buf)
  85         G(0, fxsave->cwd);
  86         G(1, fxsave->swd);
  87         G(2, fxsave->twd);
  88         fxsave->twd = twd_i387_to_fxsr(fxsave->twd);
  89         G(3, fxsave->rip);
  90         G(4, v);
  91         fxsave->fop = v>>16;    /* cs ignored */
  92         G(5, fxsave->rdp);
  93         /* 6: ds ignored */
  94 #undef G
  95         if (err)
  96                 return -1;
  97
  98         to = (struct _fpxreg *)&fxsave->st_space[0];
  99         from = &buf->_st[0];
 100         for (i = 0 ; i < 8 ; i++, to++, from++) {
 101                 if (__copy_from_user(to, from, sizeof(*from)))
 102                         return -1;
 103         }
 104         return 0;
 105 }
 106
 107
 108 static inline int convert_fxsr_to_user(struct _fpstate_ia32 __user *buf,
 109                                        struct i387_fxsave_struct *fxsave,
 110                                        struct pt_regs *regs,
 111                                        struct task_struct *tsk)
 112 {
 113         struct _fpreg __user *to;
 114         struct _fpxreg *from;
 115         int i;
 116         u16 cs,ds;
 117         int err = 0;
 118
 119         if (tsk == current) {
 120                 /* should be actually ds/cs at fpu exception time,
 121                    but that information is not available in 64bit mode. */
 122                 asm("movw %%ds,%0 " : "=r" (ds));
 123                 asm("movw %%cs,%0 " : "=r" (cs));
 124         } else { /* ptrace. task has stopped. */
 125                 ds = tsk->thread.ds;
 126                 cs = regs->cs;
 127         }
 128
 129 #define P(num,val) err |= __put_user(val, num + (u32 __user *)buf)
 130         P(0, (u32)fxsave->cwd | 0xffff0000);
 131         P(1, (u32)fxsave->swd | 0xffff0000);
 132         P(2, twd_fxsr_to_i387(fxsave));
 133         P(3, (u32)fxsave->rip);
 134         P(4,  cs | ((u32)fxsave->fop) << 16);
 135         P(5, fxsave->rdp);
 136         P(6, 0xffff0000 | ds);
 137 #undef P
 138
 139         if (err)
 140                 return -1;
 141
 142         to = &buf->_st[0];
 143         from = (struct _fpxreg *) &fxsave->st_space[0];
 144         for ( i = 0 ; i < 8 ; i++, to++, from++ ) {
 145                 if (__copy_to_user(to, from, sizeof(*to)))
 146                         return -1;
 147         }
 148         return 0;
 149 }
 150
 151 int restore_i387_ia32(struct task_struct *tsk, struct _fpstate_ia32 __user *buf, int fsave)
 152 {
 153         clear_fpu(tsk);
 154         if (!fsave) {
 155                 if (__copy_from_user(&tsk->thread.i387.fxsave,
 156                                      &buf->_fxsr_env[0],
 157                                      sizeof(struct i387_fxsave_struct)))
 158                         return -1;
 159                 tsk->thread.i387.fxsave.mxcsr &= mxcsr_feature_mask;
 160                 set_stopped_child_used_math(tsk);
 161         }
 162         return convert_fxsr_from_user(&tsk->thread.i387.fxsave, buf);
 163 }
 164
 165 int save_i387_ia32(struct task_struct *tsk,
 166                    struct _fpstate_ia32 __user *buf,
 167                    struct pt_regs *regs,
 168                    int fsave)
 169 {
 170         int err = 0;
 171
 172         init_fpu(tsk);
 173         if (convert_fxsr_to_user(buf, &tsk->thread.i387.fxsave, regs, tsk))
 174                 return -1;
 175         if (fsave)
 176                 return 0;
 177         err |= __put_user(tsk->thread.i387.fxsave.swd, &buf->status);
 178         if (fsave)
 179                 return err ? -1 : 1;
 180         err |= __put_user(X86_FXSR_MAGIC, &buf->magic);
 181         err |= __copy_to_user(&buf->_fxsr_env[0], &tsk->thread.i387.fxsave,
 182                               sizeof(struct i387_fxsave_struct));
 183         return err ? -1 : 1;
 184 }