drivers/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   billm@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 /* Decode the SIB byte. This function assumes mod != 0 */
  44 static void *sib(int mod)
     /*  */
  45 {
  46   unsigned char ss,index,base;
  47   long offset;
  48 
  49   RE_ENTRANT_CHECK_OFF
  50   base = get_fs_byte((char *) FPU_EIP);   /* The SIB byte */
  51   RE_ENTRANT_CHECK_ON
  52   FPU_EIP++;
  53   ss = base >> 6;
  54   index = (base >> 3) & 7;
  55   base &= 7;
  56 
  57   if ((mod == 0) && (base == 5))
  58     offset = 0;              /* No base register */
  59   else
  60     offset = REG_(base);
  61 
  62   if (index == 4)
  63     {
  64       /* No index register */
  65       /* A non-zero ss is illegal */
  66       if ( ss )
  67         EXCEPTION(EX_Invalid);
  68     }
  69   else
  70     {
  71       offset += (REG_(index)) << ss;
  72     }
  73 
  74   if (mod == 1)
  75     {
  76       /* 8 bit signed displacement */
  77       RE_ENTRANT_CHECK_OFF
  78       offset += (signed char) get_fs_byte((char *) FPU_EIP);
  79       RE_ENTRANT_CHECK_ON
  80       FPU_EIP++;
  81     }
  82   else if (mod == 2 || base == 5) /* The second condition also has mod==0 */
  83     {
  84       /* 32 bit displacment */
  85       RE_ENTRANT_CHECK_OFF
  86       offset += (signed) get_fs_long((unsigned long *) FPU_EIP);
  87       RE_ENTRANT_CHECK_ON
  88       FPU_EIP += 4;
  89     }
  90 
  91   return (void *) offset;
  92 }
  93 
  94 
  95 /*
  96        MOD R/M byte:  MOD == 3 has a special use for the FPU
  97                       SIB byte used iff R/M = 100b
  98 
  99        7   6   5   4   3   2   1   0
 100        .....   .........   .........
 101         MOD    OPCODE(2)     R/M
 102 
 103 
 104        SIB byte
 105 
 106        7   6   5   4   3   2   1   0
 107        .....   .........   .........
 108         SS      INDEX        BASE
 109 
 110 */
 111 
 112 void get_address(unsigned char FPU_modrm)
     /*  */
 113 {
 114   unsigned char mod;
 115   long *cpu_reg_ptr;
 116   int offset = 0;     /* Initialized just to stop compiler warnings. */
 117 
 118 #ifndef PECULIAR_486
 119   /* This is a reasonable place to do this */
 120   FPU_data_selector = FPU_DS;
 121 #endif PECULIAR_486
 122 
 123   mod = (FPU_modrm >> 6) & 3;
 124 
 125   if (FPU_rm == 4 && mod != 3)
 126     {
 127       FPU_data_address = sib(mod);
 128       return;
 129     }
 130 
 131   cpu_reg_ptr = & REG_(FPU_rm);
 132   switch (mod)
 133     {
 134     case 0:
 135       if (FPU_rm == 5)
 136         {
 137           /* Special case: disp32 */
 138           RE_ENTRANT_CHECK_OFF
 139           offset = get_fs_long((unsigned long *) FPU_EIP);
 140           RE_ENTRANT_CHECK_ON
 141           FPU_EIP += 4;
 142           FPU_data_address = (void *) offset;
 143           return;
 144         }
 145       else
 146         {
 147           FPU_data_address = (void *)*cpu_reg_ptr;  /* Just return the contents
 148                                                    of the cpu register */
 149           return;
 150         }
 151     case 1:
 152       /* 8 bit signed displacement */
 153       RE_ENTRANT_CHECK_OFF
 154       offset = (signed char) get_fs_byte((char *) FPU_EIP);
 155       RE_ENTRANT_CHECK_ON
 156       FPU_EIP++;
 157       break;
 158     case 2:
 159       /* 32 bit displacement */
 160       RE_ENTRANT_CHECK_OFF
 161       offset = (signed) get_fs_long((unsigned long *) FPU_EIP);
 162       RE_ENTRANT_CHECK_ON
 163       FPU_EIP += 4;
 164       break;
 165     case 3:
 166       /* Not legal for the FPU */
 167       EXCEPTION(EX_Invalid);
 168     }
 169 
 170   FPU_data_address = offset + (char *)*cpu_reg_ptr;
 171 }
/* */
root/drivers/FPU-emu/get_address.c

DEFINITIONS
