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 static inline unsigned long twd_fxsr_to_i387(struct i387_fxsave_struct *fxsave)
  28 {
  29         struct _fpxreg *st = NULL;
  30         unsigned long tos = (fxsave->swd >> 11) & 7;
  31         unsigned long twd = (unsigned long) fxsave->twd;
  32         unsigned long tag;
  33         unsigned long ret = 0xffff0000;
  34         int i;
  35
  36 #define FPREG_ADDR(f, n)        ((void *)&(f)->st_space + (n) * 16);
  37
  38         for (i = 0 ; i < 8 ; i++) {
  39                 if (twd & 0x1) {
  40                         st = FPREG_ADDR( fxsave, (i - tos) & 7 );
  41
  42                         switch (st->exponent & 0x7fff) {
  43                         case 0x7fff:
  44                                 tag = 2;                /* Special */
  45                                 break;
  46                         case 0x0000:
  47                                 if ( !st->significand[0] &&
  48                                      !st->significand[1] &&
  49                                      !st->significand[2] &&
  50                                      !st->significand[3] ) {
  51                                         tag = 1;        /* Zero */
  52                                 } else {
  53                                         tag = 2;        /* Special */
  54                                 }
  55                                 break;
  56                         default:
  57                                 if (st->significand[3] & 0x8000) {
  58                                         tag = 0;        /* Valid */
  59                                 } else {
  60                                         tag = 2;        /* Special */
  61                                 }
  62                                 break;
  63                         }
  64                 } else {
  65                         tag = 3;                        /* Empty */
  66                 }
  67                 ret |= (tag << (2 * i));
  68                 twd = twd >> 1;
  69         }
  70         return ret;
  71 }
  72
  73
  74 static inline int convert_fxsr_from_user(struct i387_fxsave_struct *fxsave,
  75                                          struct _fpstate_ia32 __user *buf)
  76 {
  77         struct _fpxreg *to;
  78         struct _fpreg __user *from;
  79         int i;
  80         u32 v;
  81         int err = 0;
  82
  83 #define G(num,val) err |= __get_user(val, num + (u32 __user *)buf)
  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         fxsave->fop = v>>16;    /* cs ignored */
  91         G(5, fxsave->rdp);
  92         /* 6: ds ignored */
  93 #undef G
  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
 107 static inline int convert_fxsr_to_user(struct _fpstate_ia32 __user *buf,
 108                                        struct i387_fxsave_struct *fxsave,
 109                                        struct pt_regs *regs,
 110                                        struct task_struct *tsk)
 111 {
 112         struct _fpreg __user *to;
 113         struct _fpxreg *from;
 114         int i;
 115         u16 cs,ds;
 116         int err = 0;
 117
 118         if (tsk == current) {
 119                 /* should be actually ds/cs at fpu exception time,
 120                    but that information is not available in 64bit mode. */
 121                 asm("movw %%ds,%0 " : "=r" (ds));
 122                 asm("movw %%cs,%0 " : "=r" (cs));
 123         } else { /* ptrace. task has stopped. */
 124                 ds = tsk->thread.ds;
 125                 cs = regs->cs;
 126         }
 127
 128 #define P(num,val) err |= __put_user(val, num + (u32 __user *)buf)
 129         P(0, (u32)fxsave->cwd | 0xffff0000);
 130         P(1, (u32)fxsave->swd | 0xffff0000);
 131         P(2, twd_fxsr_to_i387(fxsave));
 132         P(3, (u32)fxsave->rip);
 133         P(4,  cs | ((u32)fxsave->fop) << 16);
 134         P(5, fxsave->rdp);
 135         P(6, 0xffff0000 | ds);
 136 #undef P
 137
 138         if (err)
 139                 return -1;
 140
 141         to = &buf->_st[0];
 142         from = (struct _fpxreg *) &fxsave->st_space[0];
 143         for ( i = 0 ; i < 8 ; i++, to++, from++ ) {
 144                 if (__copy_to_user(to, from, sizeof(*to)))
 145                         return -1;
 146         }
 147         return 0;
 148 }
 149
 150 int restore_i387_ia32(struct task_struct *tsk, struct _fpstate_ia32 __user *buf, int fsave)
 151 {
 152         clear_fpu(tsk);
 153         if (!fsave) {
 154                 if (__copy_from_user(&tsk->thread.i387.fxsave,
 155                                      &buf->_fxsr_env[0],
 156                                      sizeof(struct i387_fxsave_struct)))
 157                         return -1;
 158                 tsk->thread.i387.fxsave.mxcsr &= mxcsr_feature_mask;
 159                 set_stopped_child_used_math(tsk);
 160         }
 161         return convert_fxsr_from_user(&tsk->thread.i387.fxsave, buf);
 162 }
 163
 164 int save_i387_ia32(struct task_struct *tsk,
 165                    struct _fpstate_ia32 __user *buf,
 166                    struct pt_regs *regs,
 167                    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         if (fsave)
 178                 return err ? -1 : 1;
 179         err |= __put_user(X86_FXSR_MAGIC, &buf->magic);
 180         err |= __copy_to_user(&buf->_fxsr_env[0], &tsk->thread.i387.fxsave,
 181                               sizeof(struct i387_fxsave_struct));
 182         return err ? -1 : 1;
 183 }