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
 159   segment--;
 160
 161 #ifdef PARANOID
 162   /* segment is unsigned, so this also detects if segment was 0: */
 163   if ( segment > PREFIX_SS_ )
 164     {
 165       EXCEPTION(EX_INTERNAL|0x132);
 166       math_abort(FPU_info,SIGSEGV);
 167     }
 168 #endif /* PARANOID */
 169
 170   switch ( segment )
 171     {
 172       /* fs and gs aren't used by the kernel, so they still have their
 173          user-space values. */
 174     case PREFIX_FS_-1:
 175       /* N.B. - movl %seg, mem is a 2 byte write regardless of prefix */
 176       savesegment(fs, addr->selector);
 177       break;
 178     case PREFIX_GS_-1:
 179       savesegment(gs, addr->selector);
 180       break;
 181     default:
 182       addr->selector = PM_REG_(segment);
 183     }
 184
 185   descriptor = LDT_DESCRIPTOR(PM_REG_(segment));
 186   base_address = SEG_BASE_ADDR(descriptor);
 187   address = base_address + offset;
 188   limit = base_address
 189         + (SEG_LIMIT(descriptor)+1) * SEG_GRANULARITY(descriptor) - 1;
 190   if ( limit < base_address ) limit = 0xffffffff;
 191
 192   if ( SEG_EXPAND_DOWN(descriptor) )
 193     {
 194       if ( SEG_G_BIT(descriptor) )
 195         seg_top = 0xffffffff;
 196       else
 197         {
 198           seg_top = base_address + (1 << 20);
 199           if ( seg_top < base_address ) seg_top = 0xffffffff;
 200         }
 201       access_limit =
 202         (address <= limit) || (address >= seg_top) ? 0 :
 203           ((seg_top-address) >= 255 ? 255 : seg_top-address);
 204     }
 205   else
 206     {
 207       access_limit =
 208         (address > limit) || (address < base_address) ? 0 :
 209           ((limit-address) >= 254 ? 255 : limit-address+1);
 210     }
 211   if ( SEG_EXECUTE_ONLY(descriptor) ||
 212       (!SEG_WRITE_PERM(descriptor) && (FPU_modrm & FPU_WRITE_BIT)) )
 213     {
 214       access_limit = 0;
 215     }
 216   return address;
 217 }
 218
 219
 220 /*
 221        MOD R/M byte:  MOD == 3 has a special use for the FPU
 222                       SIB byte used iff R/M = 100b
 223
 224        7   6   5   4   3   2   1   0
 225        .....   .........   .........
 226         MOD    OPCODE(2)     R/M
 227
 228
 229        SIB byte
 230
 231        7   6   5   4   3   2   1   0
 232        .....   .........   .........
 233         SS      INDEX        BASE
 234
 235 */
 236
 237 void __user *FPU_get_address(u_char FPU_modrm, unsigned long *fpu_eip,
 238                   struct address *addr,
 239                   fpu_addr_modes addr_modes)
 240 {
 241   u_char mod;
 242   unsigned rm = FPU_modrm & 7;
 243   long *cpu_reg_ptr;
 244   int address = 0;     /* Initialized just to stop compiler warnings. */
 245
 246   /* Memory accessed via the cs selector is write protected
 247      in `non-segmented' 32 bit protected mode. */
 248   if ( !addr_modes.default_mode && (FPU_modrm & FPU_WRITE_BIT)
 249       && (addr_modes.override.segment == PREFIX_CS_) )
 250     {
 251       math_abort(FPU_info,SIGSEGV);
 252     }
 253
 254   addr->selector = FPU_DS;   /* Default, for 32 bit non-segmented mode. */
 255
 256   mod = (FPU_modrm >> 6) & 3;
 257
 258   if (rm == 4 && mod != 3)
 259     {
 260       address = sib(mod, fpu_eip);
 261     }
 262   else
 263     {
 264       cpu_reg_ptr = & REG_(rm);
 265       switch (mod)
 266         {
 267         case 0:
 268           if (rm == 5)
 269             {
 270               /* Special case: disp32 */
 271               RE_ENTRANT_CHECK_OFF;
 272               FPU_code_access_ok(4);
 273               FPU_get_user(address, (unsigned long __user *) (*fpu_eip));
 274               (*fpu_eip) += 4;
 275               RE_ENTRANT_CHECK_ON;
 276               addr->offset = address;
 277               return (void __user *) address;
 278             }
 279           else
 280             {
 281               address = *cpu_reg_ptr;  /* Just return the contents
 282                                           of the cpu register */
 283               addr->offset = address;
 284               return (void __user *) address;
 285             }
 286         case 1:
 287           /* 8 bit signed displacement */
 288           RE_ENTRANT_CHECK_OFF;
 289           FPU_code_access_ok(1);
 290           FPU_get_user(address, (signed char __user *) (*fpu_eip));
 291           RE_ENTRANT_CHECK_ON;
 292           (*fpu_eip)++;
 293           break;
 294         case 2:
 295           /* 32 bit displacement */
 296           RE_ENTRANT_CHECK_OFF;
 297           FPU_code_access_ok(4);
 298           FPU_get_user(address, (long __user *) (*fpu_eip));
 299           (*fpu_eip) += 4;
 300           RE_ENTRANT_CHECK_ON;
 301           break;
 302         case 3:
 303           /* Not legal for the FPU */
 304           EXCEPTION(EX_Invalid);
 305         }
 306       address += *cpu_reg_ptr;
 307     }
 308
 309   addr->offset = address;
 310
 311   switch ( addr_modes.default_mode )
 312     {
 313     case 0:
 314       break;
 315     case VM86:
 316       address += vm86_segment(addr_modes.override.segment, addr);
 317       break;
 318     case PM16:
 319     case SEG32:
 320       address = pm_address(FPU_modrm, addr_modes.override.segment,
 321                            addr, address);
 322       break;
 323     default:
 324       EXCEPTION(EX_INTERNAL|0x133);
 325     }
 326
 327   return (void __user *)address;
 328 }
 329
 330
 331 void __user *FPU_get_address_16(u_char FPU_modrm, unsigned long *fpu_eip,
 332                      struct address *addr,
 333                      fpu_addr_modes addr_modes)
 334 {
 335   u_char mod;
 336   unsigned rm = FPU_modrm & 7;
 337   int address = 0;     /* Default used for mod == 0 */
 338
 339   /* Memory accessed via the cs selector is write protected
 340      in `non-segmented' 32 bit protected mode. */
 341   if ( !addr_modes.default_mode && (FPU_modrm & FPU_WRITE_BIT)
 342       && (addr_modes.override.segment == PREFIX_CS_) )
 343     {
 344       math_abort(FPU_info,SIGSEGV);
 345     }
 346
 347   addr->selector = FPU_DS;   /* Default, for 32 bit non-segmented mode. */
 348
 349   mod = (FPU_modrm >> 6) & 3;
 350
 351   switch (mod)
 352     {
 353     case 0:
 354       if (rm == 6)
 355         {
 356           /* Special case: disp16 */
 357           RE_ENTRANT_CHECK_OFF;
 358           FPU_code_access_ok(2);
 359           FPU_get_user(address, (unsigned short __user *) (*fpu_eip));
 360           (*fpu_eip) += 2;
 361           RE_ENTRANT_CHECK_ON;
 362           goto add_segment;
 363         }
 364       break;
 365     case 1:
 366       /* 8 bit signed displacement */
 367       RE_ENTRANT_CHECK_OFF;
 368       FPU_code_access_ok(1);
 369       FPU_get_user(address, (signed char __user *) (*fpu_eip));
 370       RE_ENTRANT_CHECK_ON;
 371       (*fpu_eip)++;
 372       break;
 373     case 2:
 374       /* 16 bit displacement */
 375       RE_ENTRANT_CHECK_OFF;
 376       FPU_code_access_ok(2);
 377       FPU_get_user(address, (unsigned short __user *) (*fpu_eip));
 378       (*fpu_eip) += 2;
 379       RE_ENTRANT_CHECK_ON;
 380       break;
 381     case 3:
 382       /* Not legal for the FPU */
 383       EXCEPTION(EX_Invalid);
 384       break;
 385     }
 386   switch ( rm )
 387     {
 388     case 0:
 389       address += FPU_info->___ebx + FPU_info->___esi;
 390       break;
 391     case 1:
 392       address += FPU_info->___ebx + FPU_info->___edi;
 393       break;
 394     case 2:
 395       address += FPU_info->___ebp + FPU_info->___esi;
 396       if ( addr_modes.override.segment == PREFIX_DEFAULT )
 397         addr_modes.override.segment = PREFIX_SS_;
 398       break;
 399     case 3:
 400       address += FPU_info->___ebp + FPU_info->___edi;
 401       if ( addr_modes.override.segment == PREFIX_DEFAULT )
 402         addr_modes.override.segment = PREFIX_SS_;
 403       break;
 404     case 4:
 405       address += FPU_info->___esi;
 406       break;
 407     case 5:
 408       address += FPU_info->___edi;
 409       break;
 410     case 6:
 411       address += FPU_info->___ebp;
 412       if ( addr_modes.override.segment == PREFIX_DEFAULT )
 413         addr_modes.override.segment = PREFIX_SS_;
 414       break;
 415     case 7:
 416       address += FPU_info->___ebx;
 417       break;
 418     }
 419
 420  add_segment:
 421   address &= 0xffff;
 422
 423   addr->offset = address;
 424
 425   switch ( addr_modes.default_mode )
 426     {
 427     case 0:
 428       break;
 429     case VM86:
 430       address += vm86_segment(addr_modes.override.segment, addr);
 431       break;
 432     case PM16:
 433     case SEG32:
 434       address = pm_address(FPU_modrm, addr_modes.override.segment,
 435                            addr, address);
 436       break;
 437     default:
 438       EXCEPTION(EX_INTERNAL|0x131);
 439     }
 440
 441   return (void __user *)address ;
 442 }