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 #include <linux/stddef.h>
  21
  22 #include <asm/uaccess.h>
  23 #include <asm/desc.h>
  24
  25 #include "fpu_system.h"
  26 #include "exception.h"
  27 #include "fpu_emu.h"
  28
  29 #define FPU_WRITE_BIT 0x10
  30
  31 static int reg_offset[] = {
  32         offsetof(struct info, ___eax),
  33         offsetof(struct info, ___ecx),
  34         offsetof(struct info, ___edx),
  35         offsetof(struct info, ___ebx),
  36         offsetof(struct info, ___esp),
  37         offsetof(struct info, ___ebp),
  38         offsetof(struct info, ___esi),
  39         offsetof(struct info, ___edi)
  40 };
  41
  42 #define REG_(x) (*(long *)(reg_offset[(x)]+(u_char *) FPU_info))
  43
  44 static int reg_offset_vm86[] = {
  45         offsetof(struct info, ___cs),
  46         offsetof(struct info, ___vm86_ds),
  47         offsetof(struct info, ___vm86_es),
  48         offsetof(struct info, ___vm86_fs),
  49         offsetof(struct info, ___vm86_gs),
  50         offsetof(struct info, ___ss),
  51         offsetof(struct info, ___vm86_ds)
  52 };
  53
  54 #define VM86_REG_(x) (*(unsigned short *) \
  55                       (reg_offset_vm86[((unsigned)x)]+(u_char *) FPU_info))
  56
  57 /* This dummy, gs is not saved on the stack. */
  58 #define ___GS ___ds
  59
  60 static int reg_offset_pm[] = {
  61         offsetof(struct info, ___cs),
  62         offsetof(struct info, ___ds),
  63         offsetof(struct info, ___es),
  64         offsetof(struct info, ___fs),
  65         offsetof(struct info, ___GS),
  66         offsetof(struct info, ___ss),
  67         offsetof(struct info, ___ds)
  68 };
  69
  70 #define PM_REG_(x) (*(unsigned short *) \
  71                       (reg_offset_pm[((unsigned)x)]+(u_char *) FPU_info))
  72
  73 /* Decode the SIB byte. This function assumes mod != 0 */
  74 static int sib(int mod, unsigned long *fpu_eip)
  75 {
  76         u_char ss, index, base;
  77         long offset;
  78
  79         RE_ENTRANT_CHECK_OFF;
  80         FPU_code_access_ok(1);
  81         FPU_get_user(base, (u_char __user *) (*fpu_eip));       /* The SIB byte */
  82         RE_ENTRANT_CHECK_ON;
  83         (*fpu_eip)++;
  84         ss = base >> 6;
  85         index = (base >> 3) & 7;
  86         base &= 7;
  87
  88         if ((mod == 0) && (base == 5))
  89                 offset = 0;     /* No base register */
  90         else
  91                 offset = REG_(base);
  92
  93         if (index == 4) {
  94                 /* No index register */
  95                 /* A non-zero ss is illegal */
  96                 if (ss)
  97                         EXCEPTION(EX_Invalid);
  98         } else {
  99                 offset += (REG_(index)) << ss;
 100         }
 101
 102         if (mod == 1) {
 103                 /* 8 bit signed displacement */
 104                 long displacement;
 105                 RE_ENTRANT_CHECK_OFF;
 106                 FPU_code_access_ok(1);
 107                 FPU_get_user(displacement, (signed char __user *)(*fpu_eip));
 108                 offset += displacement;
 109                 RE_ENTRANT_CHECK_ON;
 110                 (*fpu_eip)++;
 111         } else if (mod == 2 || base == 5) {     /* The second condition also has mod==0 */
 112                 /* 32 bit displacement */
 113                 long displacement;
 114                 RE_ENTRANT_CHECK_OFF;
 115                 FPU_code_access_ok(4);
 116                 FPU_get_user(displacement, (long __user *)(*fpu_eip));
 117                 offset += displacement;
 118                 RE_ENTRANT_CHECK_ON;
 119                 (*fpu_eip) += 4;
 120         }
 121
 122         return offset;
 123 }
 124
 125 static unsigned long vm86_segment(u_char segment, struct address *addr)
 126 {
 127         segment--;
 128 #ifdef PARANOID
 129         if (segment > PREFIX_SS_) {
 130                 EXCEPTION(EX_INTERNAL | 0x130);
 131                 math_abort(FPU_info, SIGSEGV);
 132         }
 133 #endif /* PARANOID */
 134         addr->selector = VM86_REG_(segment);
 135         return (unsigned long)VM86_REG_(segment) << 4;
 136 }
 137
 138 /* This should work for 16 and 32 bit protected mode. */
 139 static long pm_address(u_char FPU_modrm, u_char segment,
 140                        struct address *addr, long offset)
 141 {
 142         struct desc_struct descriptor;
 143         unsigned long base_address, limit, address, seg_top;
 144
 145         segment--;
 146
 147 #ifdef PARANOID
 148         /* segment is unsigned, so this also detects if segment was 0: */
 149         if (segment > PREFIX_SS_) {
 150                 EXCEPTION(EX_INTERNAL | 0x132);
 151                 math_abort(FPU_info, SIGSEGV);
 152         }
 153 #endif /* PARANOID */
 154
 155         switch (segment) {
 156                 /* gs isn't used by the kernel, so it still has its
 157                    user-space value. */
 158         case PREFIX_GS_ - 1:
 159                 /* N.B. - movl %seg, mem is a 2 byte write regardless of prefix */
 160                 savesegment(gs, addr->selector);
 161                 break;
 162         default:
 163                 addr->selector = PM_REG_(segment);
 164         }
 165
 166         descriptor = LDT_DESCRIPTOR(PM_REG_(segment));
 167         base_address = SEG_BASE_ADDR(descriptor);
 168         address = base_address + offset;
 169         limit = base_address
 170             + (SEG_LIMIT(descriptor) + 1) * SEG_GRANULARITY(descriptor) - 1;
 171         if (limit < base_address)
 172                 limit = 0xffffffff;
 173
 174         if (SEG_EXPAND_DOWN(descriptor)) {
 175                 if (SEG_G_BIT(descriptor))
 176                         seg_top = 0xffffffff;
 177                 else {
 178                         seg_top = base_address + (1 << 20);
 179                         if (seg_top < base_address)
 180                                 seg_top = 0xffffffff;
 181                 }
 182                 access_limit =
 183                     (address <= limit) || (address >= seg_top) ? 0 :
 184                     ((seg_top - address) >= 255 ? 255 : seg_top - address);
 185         } else {
 186                 access_limit =
 187                     (address > limit) || (address < base_address) ? 0 :
 188                     ((limit - address) >= 254 ? 255 : limit - address + 1);
 189         }
 190         if (SEG_EXECUTE_ONLY(descriptor) ||
 191             (!SEG_WRITE_PERM(descriptor) && (FPU_modrm & FPU_WRITE_BIT))) {
 192                 access_limit = 0;
 193         }
 194         return address;
 195 }
 196
 197 /*
 198        MOD R/M byte:  MOD == 3 has a special use for the FPU
 199                       SIB byte used iff R/M = 100b
 200
 201        7   6   5   4   3   2   1   0
 202        .....   .........   .........
 203         MOD    OPCODE(2)     R/M
 204
 205        SIB byte
 206
 207        7   6   5   4   3   2   1   0
 208        .....   .........   .........
 209         SS      INDEX        BASE
 210
 211 */
 212
 213 void __user *FPU_get_address(u_char FPU_modrm, unsigned long *fpu_eip,
 214                              struct address *addr, fpu_addr_modes addr_modes)
 215 {
 216         u_char mod;
 217         unsigned rm = FPU_modrm & 7;
 218         long *cpu_reg_ptr;
 219         int address = 0;        /* Initialized just to stop compiler warnings. */
 220
 221         /* Memory accessed via the cs selector is write protected
 222            in `non-segmented' 32 bit protected mode. */
 223         if (!addr_modes.default_mode && (FPU_modrm & FPU_WRITE_BIT)
 224             && (addr_modes.override.segment == PREFIX_CS_)) {
 225                 math_abort(FPU_info, SIGSEGV);
 226         }
 227
 228         addr->selector = FPU_DS;        /* Default, for 32 bit non-segmented mode. */
 229
 230         mod = (FPU_modrm >> 6) & 3;
 231
 232         if (rm == 4 && mod != 3) {
 233                 address = sib(mod, fpu_eip);
 234         } else {
 235                 cpu_reg_ptr = &REG_(rm);
 236                 switch (mod) {
 237                 case 0:
 238                         if (rm == 5) {
 239                                 /* Special case: disp32 */
 240                                 RE_ENTRANT_CHECK_OFF;
 241                                 FPU_code_access_ok(4);
 242                                 FPU_get_user(address,
 243                                              (unsigned long __user
 244                                               *)(*fpu_eip));
 245                                 (*fpu_eip) += 4;
 246                                 RE_ENTRANT_CHECK_ON;
 247                                 addr->offset = address;
 248                                 return (void __user *)address;
 249                         } else {
 250                                 address = *cpu_reg_ptr; /* Just return the contents
 251                                                            of the cpu register */
 252                                 addr->offset = address;
 253                                 return (void __user *)address;
 254                         }
 255                 case 1:
 256                         /* 8 bit signed displacement */
 257                         RE_ENTRANT_CHECK_OFF;
 258                         FPU_code_access_ok(1);
 259                         FPU_get_user(address, (signed char __user *)(*fpu_eip));
 260                         RE_ENTRANT_CHECK_ON;
 261                         (*fpu_eip)++;
 262                         break;
 263                 case 2:
 264                         /* 32 bit displacement */
 265                         RE_ENTRANT_CHECK_OFF;
 266                         FPU_code_access_ok(4);
 267                         FPU_get_user(address, (long __user *)(*fpu_eip));
 268                         (*fpu_eip) += 4;
 269                         RE_ENTRANT_CHECK_ON;
 270                         break;
 271                 case 3:
 272                         /* Not legal for the FPU */
 273                         EXCEPTION(EX_Invalid);
 274                 }
 275                 address += *cpu_reg_ptr;
 276         }
 277
 278         addr->offset = address;
 279
 280         switch (addr_modes.default_mode) {
 281         case 0:
 282                 break;
 283         case VM86:
 284                 address += vm86_segment(addr_modes.override.segment, addr);
 285                 break;
 286         case PM16:
 287         case SEG32:
 288                 address = pm_address(FPU_modrm, addr_modes.override.segment,
 289                                      addr, address);
 290                 break;
 291         default:
 292                 EXCEPTION(EX_INTERNAL | 0x133);
 293         }
 294
 295         return (void __user *)address;
 296 }
 297
 298 void __user *FPU_get_address_16(u_char FPU_modrm, unsigned long *fpu_eip,
 299                                 struct address *addr, fpu_addr_modes addr_modes)
 300 {
 301         u_char mod;
 302         unsigned rm = FPU_modrm & 7;
 303         int address = 0;        /* Default used for mod == 0 */
 304
 305         /* Memory accessed via the cs selector is write protected
 306            in `non-segmented' 32 bit protected mode. */
 307         if (!addr_modes.default_mode && (FPU_modrm & FPU_WRITE_BIT)
 308             && (addr_modes.override.segment == PREFIX_CS_)) {
 309                 math_abort(FPU_info, SIGSEGV);
 310         }
 311
 312         addr->selector = FPU_DS;        /* Default, for 32 bit non-segmented mode. */
 313
 314         mod = (FPU_modrm >> 6) & 3;
 315
 316         switch (mod) {
 317         case 0:
 318                 if (rm == 6) {
 319                         /* Special case: disp16 */
 320                         RE_ENTRANT_CHECK_OFF;
 321                         FPU_code_access_ok(2);
 322                         FPU_get_user(address,
 323                                      (unsigned short __user *)(*fpu_eip));
 324                         (*fpu_eip) += 2;
 325                         RE_ENTRANT_CHECK_ON;
 326                         goto add_segment;
 327                 }
 328                 break;
 329         case 1:
 330                 /* 8 bit signed displacement */
 331                 RE_ENTRANT_CHECK_OFF;
 332                 FPU_code_access_ok(1);
 333                 FPU_get_user(address, (signed char __user *)(*fpu_eip));
 334                 RE_ENTRANT_CHECK_ON;
 335                 (*fpu_eip)++;
 336                 break;
 337         case 2:
 338                 /* 16 bit displacement */
 339                 RE_ENTRANT_CHECK_OFF;
 340                 FPU_code_access_ok(2);
 341                 FPU_get_user(address, (unsigned short __user *)(*fpu_eip));
 342                 (*fpu_eip) += 2;
 343                 RE_ENTRANT_CHECK_ON;
 344                 break;
 345         case 3:
 346                 /* Not legal for the FPU */
 347                 EXCEPTION(EX_Invalid);
 348                 break;
 349         }
 350         switch (rm) {
 351         case 0:
 352                 address += FPU_info->___ebx + FPU_info->___esi;
 353                 break;
 354         case 1:
 355                 address += FPU_info->___ebx + FPU_info->___edi;
 356                 break;
 357         case 2:
 358                 address += FPU_info->___ebp + FPU_info->___esi;
 359                 if (addr_modes.override.segment == PREFIX_DEFAULT)
 360                         addr_modes.override.segment = PREFIX_SS_;
 361                 break;
 362         case 3:
 363                 address += FPU_info->___ebp + FPU_info->___edi;
 364                 if (addr_modes.override.segment == PREFIX_DEFAULT)
 365                         addr_modes.override.segment = PREFIX_SS_;
 366                 break;
 367         case 4:
 368                 address += FPU_info->___esi;
 369                 break;
 370         case 5:
 371                 address += FPU_info->___edi;
 372                 break;
 373         case 6:
 374                 address += FPU_info->___ebp;
 375                 if (addr_modes.override.segment == PREFIX_DEFAULT)
 376                         addr_modes.override.segment = PREFIX_SS_;
 377                 break;
 378         case 7:
 379                 address += FPU_info->___ebx;
 380                 break;
 381         }
 382
 383       add_segment:
 384         address &= 0xffff;
 385
 386         addr->offset = address;
 387
 388         switch (addr_modes.default_mode) {
 389         case 0:
 390                 break;
 391         case VM86:
 392                 address += vm86_segment(addr_modes.override.segment, addr);
 393                 break;
 394         case PM16:
 395         case SEG32:
 396                 address = pm_address(FPU_modrm, addr_modes.override.segment,
 397                                      addr, address);
 398                 break;
 399         default:
 400                 EXCEPTION(EX_INTERNAL | 0x131);
 401         }
 402
 403         return (void __user *)address;
 404 }