arch/x86/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  */
   6
   7 #include <linux/sched.h>
   8 #include <asm/sigcontext32.h>
   9 #include <asm/processor.h>
  10 #include <asm/uaccess.h>
  11 #include <asm/i387.h>
  12
  13 static inline unsigned short twd_i387_to_fxsr(unsigned short twd)
  14 {
  15         unsigned int tmp; /* to avoid 16 bit prefixes in the code */
  16
  17         /* Transform each pair of bits into 01 (valid) or 00 (empty) */
  18         tmp = ~twd;
  19         tmp = (tmp | (tmp>>1)) & 0x5555; /* 0V0V0V0V0V0V0V0V */
  20         /* and move the valid bits to the lower byte. */
  21         tmp = (tmp | (tmp >> 1)) & 0x3333; /* 00VV00VV00VV00VV */
  22         tmp = (tmp | (tmp >> 2)) & 0x0f0f; /* 0000VVVV0000VVVV */
  23         tmp = (tmp | (tmp >> 4)) & 0x00ff; /* 00000000VVVVVVVV */
  24         return tmp;
  25 }
  26
  27 #define FPREG_ADDR(f, n)        ((void *)&(f)->st_space + (n) * 16);
  28 #define FP_EXP_TAG_VALID        0
  29 #define FP_EXP_TAG_ZERO         1
  30 #define FP_EXP_TAG_SPECIAL      2
  31 #define FP_EXP_TAG_EMPTY        3
  32
  33 static inline unsigned long twd_fxsr_to_i387(struct i387_fxsave_struct *fxsave)
  34 {
  35         struct _fpxreg *st;
  36         unsigned long tos = (fxsave->swd >> 11) & 7;
  37         unsigned long twd = (unsigned long) fxsave->twd;
  38         unsigned long tag;
  39         unsigned long ret = 0xffff0000;
  40         int i;
  41
  42         for (i = 0; i < 8; i++, twd >>= 1) {
  43                 if (twd & 0x1) {
  44                         st = FPREG_ADDR(fxsave, (i - tos) & 7);
  45
  46                         switch (st->exponent & 0x7fff) {
  47                         case 0x7fff:
  48                                 tag = FP_EXP_TAG_SPECIAL;
  49                                 break;
  50                         case 0x0000:
  51                                 if (!st->significand[0] &&
  52                                     !st->significand[1] &&
  53                                     !st->significand[2] &&
  54                                     !st->significand[3])
  55                                         tag = FP_EXP_TAG_ZERO;
  56                                 else
  57                                         tag = FP_EXP_TAG_SPECIAL;
  58                                 break;
  59                         default:
  60                                 if (st->significand[3] & 0x8000)
  61                                         tag = FP_EXP_TAG_VALID;
  62                                 else
  63                                         tag = FP_EXP_TAG_SPECIAL;
  64                                 break;
  65                         }
  66                 } else {
  67                         tag = FP_EXP_TAG_EMPTY;
  68                 }
  69                 ret |= tag << (2 * i);
  70         }
  71         return ret;
  72 }
  73
  74 #define G(num, val) err |= __get_user(val, num + (u32 __user *)buf)
  75
  76 static inline int convert_fxsr_from_user(struct i387_fxsave_struct *fxsave,
  77                                          struct _fpstate_ia32 __user *buf)
  78 {
  79         struct _fpxreg *to;
  80         struct _fpreg __user *from;
  81         int i, err = 0;
  82         u32 v;
  83
  84         G(0, fxsave->cwd);
  85         G(1, fxsave->swd);
  86         G(2, fxsave->twd);
  87         fxsave->twd = twd_i387_to_fxsr(fxsave->twd);
  88         G(3, fxsave->rip);
  89         G(4, v);
  90         /* cs ignored */
  91         fxsave->fop = v>>16;
  92         G(5, fxsave->rdp);
  93         /* 6: ds ignored */
  94         if (err)
  95                 return -1;
  96
  97         to = (struct _fpxreg *)&fxsave->st_space[0];
  98         from = &buf->_st[0];
  99         for (i = 0; i < 8; i++, to++, from++) {
 100                 if (__copy_from_user(to, from, sizeof(*from)))
 101                         return -1;
 102         }
 103         return 0;
 104 }
 105
 106 #define P(num, val) err |= __put_user(val, num + (u32 __user *)buf)
 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, err = 0;
 116         u16 cs, ds;
 117
 118         if (tsk == current) {
 119                 /*
 120                  * should be actually ds/cs at fpu exception time, but
 121                  * that information is not available in 64bit mode.
 122                  */
 123                 asm("movw %%ds,%0 " : "=r" (ds));
 124                 asm("movw %%cs,%0 " : "=r" (cs));
 125         } else {
 126                  /* ptrace. task has stopped. */
 127                 ds = tsk->thread.ds;
 128                 cs = regs->cs;
 129         }
 130
 131         P(0, (u32)fxsave->cwd | 0xffff0000);
 132         P(1, (u32)fxsave->swd | 0xffff0000);
 133         P(2, twd_fxsr_to_i387(fxsave));
 134         P(3, (u32)fxsave->rip);
 135         P(4,  cs | ((u32)fxsave->fop) << 16);
 136         P(5, fxsave->rdp);
 137         P(6, 0xffff0000 | ds);
 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,
 152                       struct _fpstate_ia32 __user *buf, int fsave)
 153 {
 154         clear_fpu(tsk);
 155         if (!fsave) {
 156                 if (__copy_from_user(&tsk->thread.i387.fxsave,
 157                                      &buf->_fxsr_env[0],
 158                                      sizeof(struct i387_fxsave_struct)))
 159                         return -1;
 160                 tsk->thread.i387.fxsave.mxcsr &= mxcsr_feature_mask;
 161                 set_stopped_child_used_math(tsk);
 162         }
 163         return convert_fxsr_from_user(&tsk->thread.i387.fxsave, buf);
 164 }
 165
 166 int save_i387_ia32(struct task_struct *tsk, struct _fpstate_ia32 __user *buf,
 167                    struct pt_regs *regs, int fsave)
 168 {
 169         int err = 0;
 170
 171         init_fpu(tsk);
 172         if (convert_fxsr_to_user(buf, &tsk->thread.i387.fxsave, regs, tsk))
 173                 return -1;
 174         if (fsave)
 175                 return 0;
 176         err |= __put_user(tsk->thread.i387.fxsave.swd, &buf->status);
 177         err |= __put_user(X86_FXSR_MAGIC, &buf->magic);
 178         err |= __copy_to_user(&buf->_fxsr_env[0], &tsk->thread.i387.fxsave,
 179                               sizeof(struct i387_fxsave_struct));
 180         return err ? -1 : 1;
 181 }