kernel/FPU-emu/get

/* */
This source file includes following definitions.
sib
get_address
   1 /*---------------------------------------------------------------------------+
   2  |  get_address.c                                                            |
   3  |                                                                           |
   4  | Get the effective address from an FPU instruction.                        |
   5  |                                                                           |
   6  | Copyright (C) 1992,1993                                                   |
   7  |                       W. Metzenthen, 22 Parker St, Ormond, Vic 3163,      |
   8  |                       Australia.  E-mail apm233m@vaxc.cc.monash.edu.au    |
   9  |                                                                           |
  10  |                                                                           |
  11  +---------------------------------------------------------------------------*/
  12 
  13 /*---------------------------------------------------------------------------+
  14  | Note:                                                                     |
  15  |    The file contains code which accesses user memory.                     |
  16  |    Emulator static data may change when user memory is accessed, due to   |
  17  |    other processes using the emulator while swapping is in progress.      |
  18  +---------------------------------------------------------------------------*/
  19 
  20 
  21 #include <linux/stddef.h>
  22 
  23 #include <asm/segment.h>
  24 
  25 #include "fpu_system.h"
  26 #include "exception.h"
  27 #include "fpu_emu.h"
  28 
  29 static int reg_offset[] = {
  30         offsetof(struct info,___eax),
  31         offsetof(struct info,___ecx),
  32         offsetof(struct info,___edx),
  33         offsetof(struct info,___ebx),
  34         offsetof(struct info,___esp),
  35         offsetof(struct info,___ebp),
  36         offsetof(struct info,___esi),
  37         offsetof(struct info,___edi)
  38 };
  39 
  40 #define REG_(x) (*(long *)(reg_offset[(x)]+(char *) FPU_info))
  41 
  42 
  43 void  *FPU_data_address;
  44 
  45 
  46 /* Decode the SIB byte. This function assumes mod != 0 */
  47 static void *sib(int mod)
     /*  */
  48 {
  49   unsigned char ss,index,base;
  50   long offset;
  51 
  52   RE_ENTRANT_CHECK_OFF
  53   base = get_fs_byte((char *) FPU_EIP);   /* The SIB byte */
  54   RE_ENTRANT_CHECK_ON
  55   FPU_EIP++;
  56   ss = base >> 6;
  57   index = (base >> 3) & 7;
  58   base &= 7;
  59 
  60   if ((mod == 0) && (base == 5))
  61     offset = 0;              /* No base register */
  62   else
  63     offset = REG_(base);
  64 
  65   if (index == 4)
  66     {
  67       /* No index register */
  68       /* A non-zero ss is illegal */
  69       if ( ss )
  70         EXCEPTION(EX_Invalid);
  71     }
  72   else
  73     {
  74       offset += (REG_(index)) << ss;
  75     }
  76 
  77   if (mod == 1)
  78     {
  79       /* 8 bit signed displacement */
  80       RE_ENTRANT_CHECK_OFF
  81       offset += (signed char) get_fs_byte((char *) FPU_EIP);
  82       RE_ENTRANT_CHECK_ON
  83       FPU_EIP++;
  84     }
  85   else if (mod == 2 || base == 5) /* The second condition also has mod==0 */
  86     {
  87       /* 32 bit displacment */
  88       RE_ENTRANT_CHECK_OFF
  89       offset += (signed) get_fs_long((unsigned long *) FPU_EIP);
  90       RE_ENTRANT_CHECK_ON
  91       FPU_EIP += 4;
  92     }
  93 
  94   return (void *) offset;
  95 }
  96 
  97 
  98 /*
  99        MOD R/M byte:  MOD == 3 has a special use for the FPU
 100                       SIB byte used iff R/M = 100b
 101 
 102        7   6   5   4   3   2   1   0
 103        .....   .........   .........
 104         MOD    OPCODE(2)     R/M
 105 
 106 
 107        SIB byte
 108 
 109        7   6   5   4   3   2   1   0
 110        .....   .........   .........
 111         SS      INDEX        BASE
 112 
 113 */
 114 
 115 void get_address(unsigned char FPU_modrm)
     /*  */
 116 {
 117   unsigned char mod;
 118   long *cpu_reg_ptr;
 119   int offset = 0;     /* Initialized just to stop compiler warnings. */
 120   
 121   mod = (FPU_modrm >> 6) & 3;
 122 
 123   if (FPU_rm == 4 && mod != 3)
 124     {
 125       FPU_data_address = sib(mod);
 126       return;
 127     }
 128 
 129   cpu_reg_ptr = & REG_(FPU_rm);
 130   switch (mod)
 131     {
 132     case 0:
 133       if (FPU_rm == 5)
 134         {
 135           /* Special case: disp32 */
 136           RE_ENTRANT_CHECK_OFF
 137           offset = get_fs_long((unsigned long *) FPU_EIP);
 138           RE_ENTRANT_CHECK_ON
 139           FPU_EIP += 4;
 140           FPU_data_address = (void *) offset;
 141           return;
 142         }
 143       else
 144         {
 145           FPU_data_address = (void *)*cpu_reg_ptr;  /* Just return the contents
 146                                                    of the cpu register */
 147           return;
 148         }
 149     case 1:
 150       /* 8 bit signed displacement */
 151       RE_ENTRANT_CHECK_OFF
 152       offset = (signed char) get_fs_byte((char *) FPU_EIP);
 153       RE_ENTRANT_CHECK_ON
 154       FPU_EIP++;
 155       break;
 156     case 2:
 157       /* 32 bit displacement */
 158       RE_ENTRANT_CHECK_OFF
 159       offset = (signed) get_fs_long((unsigned long *) FPU_EIP);
 160       RE_ENTRANT_CHECK_ON
 161       FPU_EIP += 4;
 162       break;
 163     case 3:
 164       /* Not legal for the FPU */
 165       EXCEPTION(EX_Invalid);
 166     }
 167 
 168   FPU_data_address = offset + (char *)*cpu_reg_ptr;
 169 }
/* */
root/kernel/FPU-emu/get_address.c

DEFINITIONS
