arch/i386/math-emu/get_address.c

   1 /*---------------------------------------------------------------------------+
   2  |  get_address.c                                                            |
   3  |                                                                           |
   4  | Get the effective address from an FPU instruction.                        |
   5  |                                                                           |
   6  | Copyright (C) 1992,1993,1994,1997                                         |
   7  |                       W. Metzenthen, 22 Parker St, Ormond, Vic 3163,      |
   8  |                       Australia.  E-mail   billm@suburbia.net             |
   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/uaccess.h>
  24 #include <asm/desc.h>
  25
  26 #include "fpu_system.h"
  27 #include "exception.h"
  28 #include "fpu_emu.h"
  29
  30
  31 #define FPU_WRITE_BIT 0x10
  32
  33 static int reg_offset[] = {
  34         offsetof(struct info,___eax),
  35         offsetof(struct info,___ecx),
  36         offsetof(struct info,___edx),
  37         offsetof(struct info,___ebx),
  38         offsetof(struct info,___esp),
  39         offsetof(struct info,___ebp),
  40         offsetof(struct info,___esi),
  41         offsetof(struct info,___edi)
  42 };
  43
  44 #define REG_(x) (*(long *)(reg_offset[(x)]+(u_char *) FPU_info))
  45
  46 static int reg_offset_vm86[] = {
  47         offsetof(struct info,___cs),
  48         offsetof(struct info,___vm86_ds),
  49         offsetof(struct info,___vm86_es),
  50         offsetof(struct info,___vm86_fs),
  51         offsetof(struct info,___vm86_gs),
  52         offsetof(struct info,___ss),
  53         offsetof(struct info,___vm86_ds)
  54       };
  55
  56 #define VM86_REG_(x) (*(unsigned short *) \
  57                       (reg_offset_vm86[((unsigned)x)]+(u_char *) FPU_info))
  58
  59 /* These are dummy, fs and gs are not saved on the stack. */
  60 #define ___FS ___ds
  61 #define ___GS ___ds
  62
  63 static int reg_offset_pm[] = {
  64         offsetof(struct info,___cs),
  65         offsetof(struct info,___ds),
  66         offsetof(struct info,___es),
  67         offsetof(struct info,___FS),
  68         offsetof(struct info,___GS),
  69         offsetof(struct info,___ss),
  70         offsetof(struct info,___ds)
  71       };
  72
  73 #define PM_REG_(x) (*(unsigned short *) \
  74                       (reg_offset_pm[((unsigned)x)]+(u_char *) FPU_info))
  75
  76
  77 /* Decode the SIB byte. This function assumes mod != 0 */
  78 static int sib(int mod, unsigned long *fpu_eip)
  79 {
  80   u_char ss,index,base;
  81   long offset;
  82
  83   RE_ENTRANT_CHECK_OFF;
  84   FPU_code_access_ok(1);
  85   FPU_get_user(base, (u_char __user *) (*fpu_eip));   /* The SIB byte */
  86   RE_ENTRANT_CHECK_ON;
  87   (*fpu_eip)++;
  88   ss = base >> 6;
  89   index = (base >> 3) & 7;
  90   base &= 7;
  91
  92   if ((mod == 0) && (base == 5))
  93     offset = 0;              /* No base register */
  94   else
  95     offset = REG_(base);
  96
  97   if (index == 4)
  98     {
  99       /* No index register */
 100       /* A non-zero ss is illegal */
 101       if ( ss )
 102         EXCEPTION(EX_Invalid);
 103     }
 104   else
 105     {
 106       offset += (REG_(index)) << ss;
 107     }
 108
 109   if (mod == 1)
 110     {
 111       /* 8 bit signed displacement */
 112       long displacement;
 113       RE_ENTRANT_CHECK_OFF;
 114       FPU_code_access_ok(1);
 115       FPU_get_user(displacement, (signed char __user *) (*fpu_eip));
 116       offset += displacement;
 117       RE_ENTRANT_CHECK_ON;
 118       (*fpu_eip)++;
 119     }
 120   else if (mod == 2 || base == 5) /* The second condition also has mod==0 */
 121     {
 122       /* 32 bit displacement */
 123       long displacement;
 124       RE_ENTRANT_CHECK_OFF;
 125       FPU_code_access_ok(4);
 126       FPU_get_user(displacement, (long __user *) (*fpu_eip));
 127       offset += displacement;
 128       RE_ENTRANT_CHECK_ON;
 129       (*fpu_eip) += 4;
 130     }
 131
 132   return offset;
 133 }
 134
 135
 136 static unsigned long vm86_segment(u_char segment,
 137                                   struct address *addr)
 138 {
 139   segment--;
 140 #ifdef PARANOID
 141   if ( segment > PREFIX_SS_ )
 142     {
 143       EXCEPTION(EX_INTERNAL|0x130);
 144       math_abort(FPU_info,SIGSEGV);
 145     }
 146 #endif /* PARANOID */
 147   addr->selector = VM86_REG_(segment);
 148   return (unsigned long)VM86_REG_(segment) << 4;
 149 }
 150
 151
 152 /* This should work for 16 and 32 bit protected mode. */
 153 static long pm_address(u_char FPU_modrm, u_char segment,
 154                        struct address *addr, long offset)
 155 {
 156   struct desc_struct descriptor;
 157   unsigned long base_address, limit, address, seg_top;
 158   unsigned short selector;
 159
 160   segment--;
 161
 162 #ifdef PARANOID
 163   /* segment is unsigned, so this also detects if segment was 0: */
 164   if ( segment > PREFIX_SS_ )
 165     {
 166       EXCEPTION(EX_INTERNAL|0x132);
 167       math_abort(FPU_info,SIGSEGV);
 168     }
 169 #endif /* PARANOID */
 170
 171   switch ( segment )
 172     {
 173       /* fs and gs aren't used by the kernel, so they still have their
 174          user-space values. */
 175     case PREFIX_FS_-1:
 176       /* The cast is needed here to get gcc 2.8.0 to use a 16 bit register
 177          in the assembler statement. */
 178
 179       __asm__("mov %%fs,%0":"=r" (selector));
 180       addr->selector = selector;
 181       break;
 182     case PREFIX_GS_-1:
 183       /* The cast is needed here to get gcc 2.8.0 to use a 16 bit register
 184          in the assembler statement. */
 185       __asm__("mov %%gs,%0":"=r" (selector));
 186       addr->selector = selector;
 187       break;
 188     default:
 189       addr->selector = PM_REG_(segment);
 190     }
 191
 192   descriptor = LDT_DESCRIPTOR(PM_REG_(segment));
 193   base_address = SEG_BASE_ADDR(descriptor);
 194   address = base_address + offset;
 195   limit = base_address
 196         + (SEG_LIMIT(descriptor)+1) * SEG_GRANULARITY(descriptor) - 1;
 197   if ( limit < base_address ) limit = 0xffffffff;
 198
 199   if ( SEG_EXPAND_DOWN(descriptor) )
 200     {
 201       if ( SEG_G_BIT(descriptor) )
 202         seg_top = 0xffffffff;
 203       else
 204         {
 205           seg_top = base_address + (1 << 20);
 206           if ( seg_top < base_address ) seg_top = 0xffffffff;
 207         }
 208       access_limit =
 209         (address <= limit) || (address >= seg_top) ? 0 :
 210           ((seg_top-address) >= 255 ? 255 : seg_top-address);
 211     }
 212   else
 213     {
 214       access_limit =
 215         (address > limit) || (address < base_address) ? 0 :
 216           ((limit-address) >= 254 ? 255 : limit-address+1);
 217     }
 218   if ( SEG_EXECUTE_ONLY(descriptor) ||
 219       (!SEG_WRITE_PERM(descriptor) && (FPU_modrm & FPU_WRITE_BIT)) )
 220     {
 221       access_limit = 0;
 222     }
 223   return address;
 224 }
 225
 226
 227 /*
 228        MOD R/M byte:  MOD == 3 has a special use for the FPU
 229                       SIB byte used iff R/M = 100b
 230
 231        7   6   5   4   3   2   1   0
 232        .....   .........   .........
 233         MOD    OPCODE(2)     R/M
 234
 235
 236        SIB byte
 237
 238        7   6   5   4   3   2   1   0
 239        .....   .........   .........
 240         SS      INDEX        BASE
 241
 242 */
 243
 244 void __user *FPU_get_address(u_char FPU_modrm, unsigned long *fpu_eip,
 245                   struct address *addr,
 246                   fpu_addr_modes addr_modes)
 247 {
 248   u_char mod;
 249   unsigned rm = FPU_modrm & 7;
 250   long *cpu_reg_ptr;
 251   int address = 0;     /* Initialized just to stop compiler warnings. */
 252
 253   /* Memory accessed via the cs selector is write protected
 254      in `non-segmented' 32 bit protected mode. */
 255   if ( !addr_modes.default_mode && (FPU_modrm & FPU_WRITE_BIT)
 256       && (addr_modes.override.segment == PREFIX_CS_) )
 257     {
 258       math_abort(FPU_info,SIGSEGV);
 259     }
 260
 261   addr->selector = FPU_DS;   /* Default, for 32 bit non-segmented mode. */
 262
 263   mod = (FPU_modrm >> 6) & 3;
 264
 265   if (rm == 4 && mod != 3)
 266     {
 267       address = sib(mod, fpu_eip);
 268     }
 269   else
 270     {
 271       cpu_reg_ptr = & REG_(rm);
 272       switch (mod)
 273         {
 274         case 0:
 275           if (rm == 5)
 276             {
 277               /* Special case: disp32 */
 278               RE_ENTRANT_CHECK_OFF;
 279               FPU_code_access_ok(4);
 280               FPU_get_user(address, (unsigned long __user *) (*fpu_eip));
 281               (*fpu_eip) += 4;
 282               RE_ENTRANT_CHECK_ON;
 283               addr->offset = address;
 284               return (void __user *) address;
 285             }
 286           else
 287             {
 288               address = *cpu_reg_ptr;  /* Just return the contents
 289                                           of the cpu register */
 290               addr->offset = address;
 291               return (void __user *) address;
 292             }
 293         case 1:
 294           /* 8 bit signed displacement */
 295           RE_ENTRANT_CHECK_OFF;
 296           FPU_code_access_ok(1);
 297           FPU_get_user(address, (signed char __user *) (*fpu_eip));
 298           RE_ENTRANT_CHECK_ON;
 299           (*fpu_eip)++;
 300           break;
 301         case 2:
 302           /* 32 bit displacement */
 303           RE_ENTRANT_CHECK_OFF;
 304           FPU_code_access_ok(4);
 305           FPU_get_user(address, (long __user *) (*fpu_eip));
 306           (*fpu_eip) += 4;
 307           RE_ENTRANT_CHECK_ON;
 308           break;
 309         case 3:
 310           /* Not legal for the FPU */
 311           EXCEPTION(EX_Invalid);
 312         }
 313       address += *cpu_reg_ptr;
 314     }
 315
 316   addr->offset = address;
 317
 318   switch ( addr_modes.default_mode )
 319     {
 320     case 0:
 321       break;
 322     case VM86:
 323       address += vm86_segment(addr_modes.override.segment, addr);
 324       break;
 325     case PM16:
 326     case SEG32:
 327       address = pm_address(FPU_modrm, addr_modes.override.segment,
 328                            addr, address);
 329       break;
 330     default:
 331       EXCEPTION(EX_INTERNAL|0x133);
 332     }
 333
 334   return (void __user *)address;
 335 }
 336
 337
 338 void __user *FPU_get_address_16(u_char FPU_modrm, unsigned long *fpu_eip,
 339                      struct address *addr,
 340                      fpu_addr_modes addr_modes)
 341 {
 342   u_char mod;
 343   unsigned rm = FPU_modrm & 7;
 344   int address = 0;     /* Default used for mod == 0 */
 345
 346   /* Memory accessed via the cs selector is write protected
 347      in `non-segmented' 32 bit protected mode. */
 348   if ( !addr_modes.default_mode && (FPU_modrm & FPU_WRITE_BIT)
 349       && (addr_modes.override.segment == PREFIX_CS_) )
 350     {
 351       math_abort(FPU_info,SIGSEGV);
 352     }
 353
 354   addr->selector = FPU_DS;   /* Default, for 32 bit non-segmented mode. */
 355
 356   mod = (FPU_modrm >> 6) & 3;
 357
 358   switch (mod)
 359     {
 360     case 0:
 361       if (rm == 6)
 362         {
 363           /* Special case: disp16 */
 364           RE_ENTRANT_CHECK_OFF;
 365           FPU_code_access_ok(2);
 366           FPU_get_user(address, (unsigned short __user *) (*fpu_eip));
 367           (*fpu_eip) += 2;
 368           RE_ENTRANT_CHECK_ON;
 369           goto add_segment;
 370         }
 371       break;
 372     case 1:
 373       /* 8 bit signed displacement */
 374       RE_ENTRANT_CHECK_OFF;
 375       FPU_code_access_ok(1);
 376       FPU_get_user(address, (signed char __user *) (*fpu_eip));
 377       RE_ENTRANT_CHECK_ON;
 378       (*fpu_eip)++;
 379       break;
 380     case 2:
 381       /* 16 bit displacement */
 382       RE_ENTRANT_CHECK_OFF;
 383       FPU_code_access_ok(2);
 384       FPU_get_user(address, (unsigned short __user *) (*fpu_eip));
 385       (*fpu_eip) += 2;
 386       RE_ENTRANT_CHECK_ON;
 387       break;
 388     case 3:
 389       /* Not legal for the FPU */
 390       EXCEPTION(EX_Invalid);
 391       break;
 392     }
 393   switch ( rm )
 394     {
 395     case 0:
 396       address += FPU_info->___ebx + FPU_info->___esi;
 397       break;
 398     case 1:
 399       address += FPU_info->___ebx + FPU_info->___edi;
 400       break;
 401     case 2:
 402       address += FPU_info->___ebp + FPU_info->___esi;
 403       if ( addr_modes.override.segment == PREFIX_DEFAULT )
 404         addr_modes.override.segment = PREFIX_SS_;
 405       break;
 406     case 3:
 407       address += FPU_info->___ebp + FPU_info->___edi;
 408       if ( addr_modes.override.segment == PREFIX_DEFAULT )
 409         addr_modes.override.segment = PREFIX_SS_;
 410       break;
 411     case 4:
 412       address += FPU_info->___esi;
 413       break;
 414     case 5:
 415       address += FPU_info->___edi;
 416       break;
 417     case 6:
 418       address += FPU_info->___ebp;
 419       if ( addr_modes.override.segment == PREFIX_DEFAULT )
 420         addr_modes.override.segment = PREFIX_SS_;
 421       break;
 422     case 7:
 423       address += FPU_info->___ebx;
 424       break;
 425     }
 426
 427  add_segment:
 428   address &= 0xffff;
 429
 430   addr->offset = address;
 431
 432   switch ( addr_modes.default_mode )
 433     {
 434     case 0:
 435       break;
 436     case VM86:
 437       address += vm86_segment(addr_modes.override.segment, addr);
 438       break;
 439     case PM16:
 440     case SEG32:
 441       address = pm_address(FPU_modrm, addr_modes.override.segment,
 442                            addr, address);
 443       break;
 444     default:
 445       EXCEPTION(EX_INTERNAL|0x131);
 446     }
 447
 448   return (void __user *)address ;
 449 }