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 pt_regs, ax),
  33         offsetof(struct pt_regs, cx),
  34         offsetof(struct pt_regs, dx),
  35         offsetof(struct pt_regs, bx),
  36         offsetof(struct pt_regs, sp),
  37         offsetof(struct pt_regs, bp),
  38         offsetof(struct pt_regs, si),
  39         offsetof(struct pt_regs, di)
  40 };
  41
  42 #define REG_(x) (*(long *)(reg_offset[(x)] + (u_char *)FPU_info->regs))
  43
  44 static int reg_offset_vm86[] = {
  45         offsetof(struct pt_regs, cs),
  46         offsetof(struct kernel_vm86_regs, ds),
  47         offsetof(struct kernel_vm86_regs, es),
  48         offsetof(struct kernel_vm86_regs, fs),
  49         offsetof(struct kernel_vm86_regs, gs),
  50         offsetof(struct pt_regs, ss),
  51         offsetof(struct kernel_vm86_regs, ds)
  52 };
  53
  54 #define VM86_REG_(x) (*(unsigned short *) \
  55                 (reg_offset_vm86[((unsigned)x)] + (u_char *)FPU_info->regs))
  56
  57 static int reg_offset_pm[] = {
  58         offsetof(struct pt_regs, cs),
  59         offsetof(struct pt_regs, ds),
  60         offsetof(struct pt_regs, es),
  61         offsetof(struct pt_regs, fs),
  62         offsetof(struct pt_regs, ds),   /* dummy, not saved on stack */
  63         offsetof(struct pt_regs, ss),
  64         offsetof(struct pt_regs, ds)
  65 };
  66
  67 #define PM_REG_(x) (*(unsigned short *) \
  68                 (reg_offset_pm[((unsigned)x)] + (u_char *)FPU_info->regs))
  69
  70 /* Decode the SIB byte. This function assumes mod != 0 */
  71 static int sib(int mod, unsigned long *fpu_eip)
  72 {
  73         u_char ss, index, base;
  74         long offset;
  75
  76         RE_ENTRANT_CHECK_OFF;
  77         FPU_code_access_ok(1);
  78         FPU_get_user(base, (u_char __user *) (*fpu_eip));       /* The SIB byte */
  79         RE_ENTRANT_CHECK_ON;
  80         (*fpu_eip)++;
  81         ss = base >> 6;
  82         index = (base >> 3) & 7;
  83         base &= 7;
  84
  85         if ((mod == 0) && (base == 5))
  86                 offset = 0;     /* No base register */
  87         else
  88                 offset = REG_(base);
  89
  90         if (index == 4) {
  91                 /* No index register */
  92                 /* A non-zero ss is illegal */
  93                 if (ss)
  94                         EXCEPTION(EX_Invalid);
  95         } else {
  96                 offset += (REG_(index)) << ss;
  97         }
  98
  99         if (mod == 1) {
 100                 /* 8 bit signed displacement */
 101                 long displacement;
 102                 RE_ENTRANT_CHECK_OFF;
 103                 FPU_code_access_ok(1);
 104                 FPU_get_user(displacement, (signed char __user *)(*fpu_eip));
 105                 offset += displacement;
 106                 RE_ENTRANT_CHECK_ON;
 107                 (*fpu_eip)++;
 108         } else if (mod == 2 || base == 5) {     /* The second condition also has mod==0 */
 109                 /* 32 bit displacement */
 110                 long displacement;
 111                 RE_ENTRANT_CHECK_OFF;
 112                 FPU_code_access_ok(4);
 113                 FPU_get_user(displacement, (long __user *)(*fpu_eip));
 114                 offset += displacement;
 115                 RE_ENTRANT_CHECK_ON;
 116                 (*fpu_eip) += 4;
 117         }
 118
 119         return offset;
 120 }
 121
 122 static unsigned long vm86_segment(u_char segment, struct address *addr)
 123 {
 124         segment--;
 125 #ifdef PARANOID
 126         if (segment > PREFIX_SS_) {
 127                 EXCEPTION(EX_INTERNAL | 0x130);
 128                 math_abort(FPU_info, SIGSEGV);
 129         }
 130 #endif /* PARANOID */
 131         addr->selector = VM86_REG_(segment);
 132         return (unsigned long)VM86_REG_(segment) << 4;
 133 }
 134
 135 /* This should work for 16 and 32 bit protected mode. */
 136 static long pm_address(u_char FPU_modrm, u_char segment,
 137                        struct address *addr, long offset)
 138 {
 139         struct desc_struct descriptor;
 140         unsigned long base_address, limit, address, seg_top;
 141
 142         segment--;
 143
 144 #ifdef PARANOID
 145         /* segment is unsigned, so this also detects if segment was 0: */
 146         if (segment > PREFIX_SS_) {
 147                 EXCEPTION(EX_INTERNAL | 0x132);
 148                 math_abort(FPU_info, SIGSEGV);
 149         }
 150 #endif /* PARANOID */
 151
 152         switch (segment) {
 153         case PREFIX_GS_ - 1:
 154                 /* user gs handling can be lazy, use special accessors */
 155                 addr->selector = get_user_gs(FPU_info->regs);
 156                 break;
 157         default:
 158                 addr->selector = PM_REG_(segment);
 159         }
 160
 161         descriptor = LDT_DESCRIPTOR(PM_REG_(segment));
 162         base_address = SEG_BASE_ADDR(descriptor);
 163         address = base_address + offset;
 164         limit = base_address
 165             + (SEG_LIMIT(descriptor) + 1) * SEG_GRANULARITY(descriptor) - 1;
 166         if (limit < base_address)
 167                 limit = 0xffffffff;
 168
 169         if (SEG_EXPAND_DOWN(descriptor)) {
 170                 if (SEG_G_BIT(descriptor))
 171                         seg_top = 0xffffffff;
 172                 else {
 173                         seg_top = base_address + (1 << 20);
 174                         if (seg_top < base_address)
 175                                 seg_top = 0xffffffff;
 176                 }
 177                 access_limit =
 178                     (address <= limit) || (address >= seg_top) ? 0 :
 179                     ((seg_top - address) >= 255 ? 255 : seg_top - address);
 180         } else {
 181                 access_limit =
 182                     (address > limit) || (address < base_address) ? 0 :
 183                     ((limit - address) >= 254 ? 255 : limit - address + 1);
 184         }
 185         if (SEG_EXECUTE_ONLY(descriptor) ||
 186             (!SEG_WRITE_PERM(descriptor) && (FPU_modrm & FPU_WRITE_BIT))) {
 187                 access_limit = 0;
 188         }
 189         return address;
 190 }
 191
 192 /*
 193        MOD R/M byte:  MOD == 3 has a special use for the FPU
 194                       SIB byte used iff R/M = 100b
 195
 196        7   6   5   4   3   2   1   0
 197        .....   .........   .........
 198         MOD    OPCODE(2)     R/M
 199
 200        SIB byte
 201
 202        7   6   5   4   3   2   1   0
 203        .....   .........   .........
 204         SS      INDEX        BASE
 205
 206 */
 207
 208 void __user *FPU_get_address(u_char FPU_modrm, unsigned long *fpu_eip,
 209                              struct address *addr, fpu_addr_modes addr_modes)
 210 {
 211         u_char mod;
 212         unsigned rm = FPU_modrm & 7;
 213         long *cpu_reg_ptr;
 214         int address = 0;        /* Initialized just to stop compiler warnings. */
 215
 216         /* Memory accessed via the cs selector is write protected
 217            in `non-segmented' 32 bit protected mode. */
 218         if (!addr_modes.default_mode && (FPU_modrm & FPU_WRITE_BIT)
 219             && (addr_modes.override.segment == PREFIX_CS_)) {
 220                 math_abort(FPU_info, SIGSEGV);
 221         }
 222
 223         addr->selector = FPU_DS;        /* Default, for 32 bit non-segmented mode. */
 224
 225         mod = (FPU_modrm >> 6) & 3;
 226
 227         if (rm == 4 && mod != 3) {
 228                 address = sib(mod, fpu_eip);
 229         } else {
 230                 cpu_reg_ptr = &REG_(rm);
 231                 switch (mod) {
 232                 case 0:
 233                         if (rm == 5) {
 234                                 /* Special case: disp32 */
 235                                 RE_ENTRANT_CHECK_OFF;
 236                                 FPU_code_access_ok(4);
 237                                 FPU_get_user(address,
 238                                              (unsigned long __user
 239                                               *)(*fpu_eip));
 240                                 (*fpu_eip) += 4;
 241                                 RE_ENTRANT_CHECK_ON;
 242                                 addr->offset = address;
 243                                 return (void __user *)address;
 244                         } else {
 245                                 address = *cpu_reg_ptr; /* Just return the contents
 246                                                            of the cpu register */
 247                                 addr->offset = address;
 248                                 return (void __user *)address;
 249                         }
 250                 case 1:
 251                         /* 8 bit signed displacement */
 252                         RE_ENTRANT_CHECK_OFF;
 253                         FPU_code_access_ok(1);
 254                         FPU_get_user(address, (signed char __user *)(*fpu_eip));
 255                         RE_ENTRANT_CHECK_ON;
 256                         (*fpu_eip)++;
 257                         break;
 258                 case 2:
 259                         /* 32 bit displacement */
 260                         RE_ENTRANT_CHECK_OFF;
 261                         FPU_code_access_ok(4);
 262                         FPU_get_user(address, (long __user *)(*fpu_eip));
 263                         (*fpu_eip) += 4;
 264                         RE_ENTRANT_CHECK_ON;
 265                         break;
 266                 case 3:
 267                         /* Not legal for the FPU */
 268                         EXCEPTION(EX_Invalid);
 269                 }
 270                 address += *cpu_reg_ptr;
 271         }
 272
 273         addr->offset = address;
 274
 275         switch (addr_modes.default_mode) {
 276         case 0:
 277                 break;
 278         case VM86:
 279                 address += vm86_segment(addr_modes.override.segment, addr);
 280                 break;
 281         case PM16:
 282         case SEG32:
 283                 address = pm_address(FPU_modrm, addr_modes.override.segment,
 284                                      addr, address);
 285                 break;
 286         default:
 287                 EXCEPTION(EX_INTERNAL | 0x133);
 288         }
 289
 290         return (void __user *)address;
 291 }
 292
 293 void __user *FPU_get_address_16(u_char FPU_modrm, unsigned long *fpu_eip,
 294                                 struct address *addr, fpu_addr_modes addr_modes)
 295 {
 296         u_char mod;
 297         unsigned rm = FPU_modrm & 7;
 298         int address = 0;        /* Default used for mod == 0 */
 299
 300         /* Memory accessed via the cs selector is write protected
 301            in `non-segmented' 32 bit protected mode. */
 302         if (!addr_modes.default_mode && (FPU_modrm & FPU_WRITE_BIT)
 303             && (addr_modes.override.segment == PREFIX_CS_)) {
 304                 math_abort(FPU_info, SIGSEGV);
 305         }
 306
 307         addr->selector = FPU_DS;        /* Default, for 32 bit non-segmented mode. */
 308
 309         mod = (FPU_modrm >> 6) & 3;
 310
 311         switch (mod) {
 312         case 0:
 313                 if (rm == 6) {
 314                         /* Special case: disp16 */
 315                         RE_ENTRANT_CHECK_OFF;
 316                         FPU_code_access_ok(2);
 317                         FPU_get_user(address,
 318                                      (unsigned short __user *)(*fpu_eip));
 319                         (*fpu_eip) += 2;
 320                         RE_ENTRANT_CHECK_ON;
 321                         goto add_segment;
 322                 }
 323                 break;
 324         case 1:
 325                 /* 8 bit signed displacement */
 326                 RE_ENTRANT_CHECK_OFF;
 327                 FPU_code_access_ok(1);
 328                 FPU_get_user(address, (signed char __user *)(*fpu_eip));
 329                 RE_ENTRANT_CHECK_ON;
 330                 (*fpu_eip)++;
 331                 break;
 332         case 2:
 333                 /* 16 bit displacement */
 334                 RE_ENTRANT_CHECK_OFF;
 335                 FPU_code_access_ok(2);
 336                 FPU_get_user(address, (unsigned short __user *)(*fpu_eip));
 337                 (*fpu_eip) += 2;
 338                 RE_ENTRANT_CHECK_ON;
 339                 break;
 340         case 3:
 341                 /* Not legal for the FPU */
 342                 EXCEPTION(EX_Invalid);
 343                 break;
 344         }
 345         switch (rm) {
 346         case 0:
 347                 address += FPU_info->regs->bx + FPU_info->regs->si;
 348                 break;
 349         case 1:
 350                 address += FPU_info->regs->bx + FPU_info->regs->di;
 351                 break;
 352         case 2:
 353                 address += FPU_info->regs->bp + FPU_info->regs->si;
 354                 if (addr_modes.override.segment == PREFIX_DEFAULT)
 355                         addr_modes.override.segment = PREFIX_SS_;
 356                 break;
 357         case 3:
 358                 address += FPU_info->regs->bp + FPU_info->regs->di;
 359                 if (addr_modes.override.segment == PREFIX_DEFAULT)
 360                         addr_modes.override.segment = PREFIX_SS_;
 361                 break;
 362         case 4:
 363                 address += FPU_info->regs->si;
 364                 break;
 365         case 5:
 366                 address += FPU_info->regs->di;
 367                 break;
 368         case 6:
 369                 address += FPU_info->regs->bp;
 370                 if (addr_modes.override.segment == PREFIX_DEFAULT)
 371                         addr_modes.override.segment = PREFIX_SS_;
 372                 break;
 373         case 7:
 374                 address += FPU_info->regs->bx;
 375                 break;
 376         }
 377
 378       add_segment:
 379         address &= 0xffff;
 380
 381         addr->offset = address;
 382
 383         switch (addr_modes.default_mode) {
 384         case 0:
 385                 break;
 386         case VM86:
 387                 address += vm86_segment(addr_modes.override.segment, addr);
 388                 break;
 389         case PM16:
 390         case SEG32:
 391                 address = pm_address(FPU_modrm, addr_modes.override.segment,
 392                                      addr, address);
 393                 break;
 394         default:
 395                 EXCEPTION(EX_INTERNAL | 0x131);
 396         }
 397
 398         return (void __user *)address;
 399 }