arch/x86/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 /* This dummy, gs is not saved on the stack. */
  60 #define ___GS ___ds
  61
  62 static int reg_offset_pm[] = {
  63         offsetof(struct info,___cs),
  64         offsetof(struct info,___ds),
  65         offsetof(struct info,___es),
  66         offsetof(struct info,___fs),
  67         offsetof(struct info,___GS),
  68         offsetof(struct info,___ss),
  69         offsetof(struct info,___ds)
  70       };
  71
  72 #define PM_REG_(x) (*(unsigned short *) \
  73                       (reg_offset_pm[((unsigned)x)]+(u_char *) FPU_info))
  74
  75
  76 /* Decode the SIB byte. This function assumes mod != 0 */
  77 static int sib(int mod, unsigned long *fpu_eip)
  78 {
  79   u_char ss,index,base;
  80   long offset;
  81
  82   RE_ENTRANT_CHECK_OFF;
  83   FPU_code_access_ok(1);
  84   FPU_get_user(base, (u_char __user *) (*fpu_eip));   /* The SIB byte */
  85   RE_ENTRANT_CHECK_ON;
  86   (*fpu_eip)++;
  87   ss = base >> 6;
  88   index = (base >> 3) & 7;
  89   base &= 7;
  90
  91   if ((mod == 0) && (base == 5))
  92     offset = 0;              /* No base register */
  93   else
  94     offset = REG_(base);
  95
  96   if (index == 4)
  97     {
  98       /* No index register */
  99       /* A non-zero ss is illegal */
 100       if ( ss )
 101         EXCEPTION(EX_Invalid);
 102     }
 103   else
 104     {
 105       offset += (REG_(index)) << ss;
 106     }
 107
 108   if (mod == 1)
 109     {
 110       /* 8 bit signed displacement */
 111       long displacement;
 112       RE_ENTRANT_CHECK_OFF;
 113       FPU_code_access_ok(1);
 114       FPU_get_user(displacement, (signed char __user *) (*fpu_eip));
 115       offset += displacement;
 116       RE_ENTRANT_CHECK_ON;
 117       (*fpu_eip)++;
 118     }
 119   else if (mod == 2 || base == 5) /* The second condition also has mod==0 */
 120     {
 121       /* 32 bit displacement */
 122       long displacement;
 123       RE_ENTRANT_CHECK_OFF;
 124       FPU_code_access_ok(4);
 125       FPU_get_user(displacement, (long __user *) (*fpu_eip));
 126       offset += displacement;
 127       RE_ENTRANT_CHECK_ON;
 128       (*fpu_eip) += 4;
 129     }
 130
 131   return offset;
 132 }
 133
 134
 135 static unsigned long vm86_segment(u_char segment,
 136                                   struct address *addr)
 137 {
 138   segment--;
 139 #ifdef PARANOID
 140   if ( segment > PREFIX_SS_ )
 141     {
 142       EXCEPTION(EX_INTERNAL|0x130);
 143       math_abort(FPU_info,SIGSEGV);
 144     }
 145 #endif /* PARANOID */
 146   addr->selector = VM86_REG_(segment);
 147   return (unsigned long)VM86_REG_(segment) << 4;
 148 }
 149
 150
 151 /* This should work for 16 and 32 bit protected mode. */
 152 static long pm_address(u_char FPU_modrm, u_char segment,
 153                        struct address *addr, long offset)
 154 {
 155   struct desc_struct descriptor;
 156   unsigned long base_address, limit, address, seg_top;
 157
 158   segment--;
 159
 160 #ifdef PARANOID
 161   /* segment is unsigned, so this also detects if segment was 0: */
 162   if ( segment > PREFIX_SS_ )
 163     {
 164       EXCEPTION(EX_INTERNAL|0x132);
 165       math_abort(FPU_info,SIGSEGV);
 166     }
 167 #endif /* PARANOID */
 168
 169   switch ( segment )
 170     {
 171       /* gs isn't used by the kernel, so it still has its
 172          user-space value. */
 173     case PREFIX_GS_-1:
 174       /* N.B. - movl %seg, mem is a 2 byte write regardless of prefix */
 175       savesegment(gs, addr->selector);
 176       break;
 177     default:
 178       addr->selector = PM_REG_(segment);
 179     }
 180
 181   descriptor = LDT_DESCRIPTOR(PM_REG_(segment));
 182   base_address = SEG_BASE_ADDR(descriptor);
 183   address = base_address + offset;
 184   limit = base_address
 185         + (SEG_LIMIT(descriptor)+1) * SEG_GRANULARITY(descriptor) - 1;
 186   if ( limit < base_address ) limit = 0xffffffff;
 187
 188   if ( SEG_EXPAND_DOWN(descriptor) )
 189     {
 190       if ( SEG_G_BIT(descriptor) )
 191         seg_top = 0xffffffff;
 192       else
 193         {
 194           seg_top = base_address + (1 << 20);
 195           if ( seg_top < base_address ) seg_top = 0xffffffff;
 196         }
 197       access_limit =
 198         (address <= limit) || (address >= seg_top) ? 0 :
 199           ((seg_top-address) >= 255 ? 255 : seg_top-address);
 200     }
 201   else
 202     {
 203       access_limit =
 204         (address > limit) || (address < base_address) ? 0 :
 205           ((limit-address) >= 254 ? 255 : limit-address+1);
 206     }
 207   if ( SEG_EXECUTE_ONLY(descriptor) ||
 208       (!SEG_WRITE_PERM(descriptor) && (FPU_modrm & FPU_WRITE_BIT)) )
 209     {
 210       access_limit = 0;
 211     }
 212   return address;
 213 }
 214
 215
 216 /*
 217        MOD R/M byte:  MOD == 3 has a special use for the FPU
 218                       SIB byte used iff R/M = 100b
 219
 220        7   6   5   4   3   2   1   0
 221        .....   .........   .........
 222         MOD    OPCODE(2)     R/M
 223
 224
 225        SIB byte
 226
 227        7   6   5   4   3   2   1   0
 228        .....   .........   .........
 229         SS      INDEX        BASE
 230
 231 */
 232
 233 void __user *FPU_get_address(u_char FPU_modrm, unsigned long *fpu_eip,
 234                   struct address *addr,
 235                   fpu_addr_modes addr_modes)
 236 {
 237   u_char mod;
 238   unsigned rm = FPU_modrm & 7;
 239   long *cpu_reg_ptr;
 240   int address = 0;     /* Initialized just to stop compiler warnings. */
 241
 242   /* Memory accessed via the cs selector is write protected
 243      in `non-segmented' 32 bit protected mode. */
 244   if ( !addr_modes.default_mode && (FPU_modrm & FPU_WRITE_BIT)
 245       && (addr_modes.override.segment == PREFIX_CS_) )
 246     {
 247       math_abort(FPU_info,SIGSEGV);
 248     }
 249
 250   addr->selector = FPU_DS;   /* Default, for 32 bit non-segmented mode. */
 251
 252   mod = (FPU_modrm >> 6) & 3;
 253
 254   if (rm == 4 && mod != 3)
 255     {
 256       address = sib(mod, fpu_eip);
 257     }
 258   else
 259     {
 260       cpu_reg_ptr = & REG_(rm);
 261       switch (mod)
 262         {
 263         case 0:
 264           if (rm == 5)
 265             {
 266               /* Special case: disp32 */
 267               RE_ENTRANT_CHECK_OFF;
 268               FPU_code_access_ok(4);
 269               FPU_get_user(address, (unsigned long __user *) (*fpu_eip));
 270               (*fpu_eip) += 4;
 271               RE_ENTRANT_CHECK_ON;
 272               addr->offset = address;
 273               return (void __user *) address;
 274             }
 275           else
 276             {
 277               address = *cpu_reg_ptr;  /* Just return the contents
 278                                           of the cpu register */
 279               addr->offset = address;
 280               return (void __user *) address;
 281             }
 282         case 1:
 283           /* 8 bit signed displacement */
 284           RE_ENTRANT_CHECK_OFF;
 285           FPU_code_access_ok(1);
 286           FPU_get_user(address, (signed char __user *) (*fpu_eip));
 287           RE_ENTRANT_CHECK_ON;
 288           (*fpu_eip)++;
 289           break;
 290         case 2:
 291           /* 32 bit displacement */
 292           RE_ENTRANT_CHECK_OFF;
 293           FPU_code_access_ok(4);
 294           FPU_get_user(address, (long __user *) (*fpu_eip));
 295           (*fpu_eip) += 4;
 296           RE_ENTRANT_CHECK_ON;
 297           break;
 298         case 3:
 299           /* Not legal for the FPU */
 300           EXCEPTION(EX_Invalid);
 301         }
 302       address += *cpu_reg_ptr;
 303     }
 304
 305   addr->offset = address;
 306
 307   switch ( addr_modes.default_mode )
 308     {
 309     case 0:
 310       break;
 311     case VM86:
 312       address += vm86_segment(addr_modes.override.segment, addr);
 313       break;
 314     case PM16:
 315     case SEG32:
 316       address = pm_address(FPU_modrm, addr_modes.override.segment,
 317                            addr, address);
 318       break;
 319     default:
 320       EXCEPTION(EX_INTERNAL|0x133);
 321     }
 322
 323   return (void __user *)address;
 324 }
 325
 326
 327 void __user *FPU_get_address_16(u_char FPU_modrm, unsigned long *fpu_eip,
 328                      struct address *addr,
 329                      fpu_addr_modes addr_modes)
 330 {
 331   u_char mod;
 332   unsigned rm = FPU_modrm & 7;
 333   int address = 0;     /* Default used for mod == 0 */
 334
 335   /* Memory accessed via the cs selector is write protected
 336      in `non-segmented' 32 bit protected mode. */
 337   if ( !addr_modes.default_mode && (FPU_modrm & FPU_WRITE_BIT)
 338       && (addr_modes.override.segment == PREFIX_CS_) )
 339     {
 340       math_abort(FPU_info,SIGSEGV);
 341     }
 342
 343   addr->selector = FPU_DS;   /* Default, for 32 bit non-segmented mode. */
 344
 345   mod = (FPU_modrm >> 6) & 3;
 346
 347   switch (mod)
 348     {
 349     case 0:
 350       if (rm == 6)
 351         {
 352           /* Special case: disp16 */
 353           RE_ENTRANT_CHECK_OFF;
 354           FPU_code_access_ok(2);
 355           FPU_get_user(address, (unsigned short __user *) (*fpu_eip));
 356           (*fpu_eip) += 2;
 357           RE_ENTRANT_CHECK_ON;
 358           goto add_segment;
 359         }
 360       break;
 361     case 1:
 362       /* 8 bit signed displacement */
 363       RE_ENTRANT_CHECK_OFF;
 364       FPU_code_access_ok(1);
 365       FPU_get_user(address, (signed char __user *) (*fpu_eip));
 366       RE_ENTRANT_CHECK_ON;
 367       (*fpu_eip)++;
 368       break;
 369     case 2:
 370       /* 16 bit displacement */
 371       RE_ENTRANT_CHECK_OFF;
 372       FPU_code_access_ok(2);
 373       FPU_get_user(address, (unsigned short __user *) (*fpu_eip));
 374       (*fpu_eip) += 2;
 375       RE_ENTRANT_CHECK_ON;
 376       break;
 377     case 3:
 378       /* Not legal for the FPU */
 379       EXCEPTION(EX_Invalid);
 380       break;
 381     }
 382   switch ( rm )
 383     {
 384     case 0:
 385       address += FPU_info->___ebx + FPU_info->___esi;
 386       break;
 387     case 1:
 388       address += FPU_info->___ebx + FPU_info->___edi;
 389       break;
 390     case 2:
 391       address += FPU_info->___ebp + FPU_info->___esi;
 392       if ( addr_modes.override.segment == PREFIX_DEFAULT )
 393         addr_modes.override.segment = PREFIX_SS_;
 394       break;
 395     case 3:
 396       address += FPU_info->___ebp + FPU_info->___edi;
 397       if ( addr_modes.override.segment == PREFIX_DEFAULT )
 398         addr_modes.override.segment = PREFIX_SS_;
 399       break;
 400     case 4:
 401       address += FPU_info->___esi;
 402       break;
 403     case 5:
 404       address += FPU_info->___edi;
 405       break;
 406     case 6:
 407       address += FPU_info->___ebp;
 408       if ( addr_modes.override.segment == PREFIX_DEFAULT )
 409         addr_modes.override.segment = PREFIX_SS_;
 410       break;
 411     case 7:
 412       address += FPU_info->___ebx;
 413       break;
 414     }
 415
 416  add_segment:
 417   address &= 0xffff;
 418
 419   addr->offset = address;
 420
 421   switch ( addr_modes.default_mode )
 422     {
 423     case 0:
 424       break;
 425     case VM86:
 426       address += vm86_segment(addr_modes.override.segment, addr);
 427       break;
 428     case PM16:
 429     case SEG32:
 430       address = pm_address(FPU_modrm, addr_modes.override.segment,
 431                            addr, address);
 432       break;
 433     default:
 434       EXCEPTION(EX_INTERNAL|0x131);
 435     }
 436
 437   return (void __user *)address ;
 438 }