arch/x86/math-emu/get_address.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*---------------------------------------------------------------------------+
   3  |  get_address.c                                                            |
   4  |                                                                           |
   5  | Get the effective address from an FPU instruction.                        |
   6  |                                                                           |
   7  | Copyright (C) 1992,1993,1994,1997                                         |
   8  |                       W. Metzenthen, 22 Parker St, Ormond, Vic 3163,      |
   9  |                       Australia.  E-mail   billm@suburbia.net             |
  10  |                                                                           |
  11  |                                                                           |
  12  +---------------------------------------------------------------------------*/
  13
  14 /*---------------------------------------------------------------------------+
  15  | Note:                                                                     |
  16  |    The file contains code which accesses user memory.                     |
  17  |    Emulator static data may change when user memory is accessed, due to   |
  18  |    other processes using the emulator while swapping is in progress.      |
  19  +---------------------------------------------------------------------------*/
  20
  21 #include <linux/stddef.h>
  22
  23 #include <linux/uaccess.h>
  24 #include <asm/vm86.h>
  25
  26 #include "fpu_system.h"
  27 #include "exception.h"
  28 #include "fpu_emu.h"
  29
  30 #define FPU_WRITE_BIT 0x10
  31
  32 static int reg_offset[] = {
  33         offsetof(struct pt_regs, ax),
  34         offsetof(struct pt_regs, cx),
  35         offsetof(struct pt_regs, dx),
  36         offsetof(struct pt_regs, bx),
  37         offsetof(struct pt_regs, sp),
  38         offsetof(struct pt_regs, bp),
  39         offsetof(struct pt_regs, si),
  40         offsetof(struct pt_regs, di)
  41 };
  42
  43 #define REG_(x) (*(long *)(reg_offset[(x)] + (u_char *)FPU_info->regs))
  44
  45 static int reg_offset_vm86[] = {
  46         offsetof(struct pt_regs, cs),
  47         offsetof(struct kernel_vm86_regs, ds),
  48         offsetof(struct kernel_vm86_regs, es),
  49         offsetof(struct kernel_vm86_regs, fs),
  50         offsetof(struct kernel_vm86_regs, gs),
  51         offsetof(struct pt_regs, ss),
  52         offsetof(struct kernel_vm86_regs, ds)
  53 };
  54
  55 #define VM86_REG_(x) (*(unsigned short *) \
  56                 (reg_offset_vm86[((unsigned)x)] + (u_char *)FPU_info->regs))
  57
  58 static int reg_offset_pm[] = {
  59         offsetof(struct pt_regs, cs),
  60         offsetof(struct pt_regs, ds),
  61         offsetof(struct pt_regs, es),
  62         offsetof(struct pt_regs, fs),
  63         offsetof(struct pt_regs, ds),   /* dummy, not saved on stack */
  64         offsetof(struct pt_regs, ss),
  65         offsetof(struct pt_regs, ds)
  66 };
  67
  68 #define PM_REG_(x) (*(unsigned short *) \
  69                 (reg_offset_pm[((unsigned)x)] + (u_char *)FPU_info->regs))
  70
  71 /* Decode the SIB byte. This function assumes mod != 0 */
  72 static int sib(int mod, unsigned long *fpu_eip)
  73 {
  74         u_char ss, index, base;
  75         long offset;
  76
  77         RE_ENTRANT_CHECK_OFF;
  78         FPU_code_access_ok(1);
  79         FPU_get_user(base, (u_char __user *) (*fpu_eip));       /* The SIB byte */
  80         RE_ENTRANT_CHECK_ON;
  81         (*fpu_eip)++;
  82         ss = base >> 6;
  83         index = (base >> 3) & 7;
  84         base &= 7;
  85
  86         if ((mod == 0) && (base == 5))
  87                 offset = 0;     /* No base register */
  88         else
  89                 offset = REG_(base);
  90
  91         if (index == 4) {
  92                 /* No index register */
  93                 /* A non-zero ss is illegal */
  94                 if (ss)
  95                         EXCEPTION(EX_Invalid);
  96         } else {
  97                 offset += (REG_(index)) << ss;
  98         }
  99
 100         if (mod == 1) {
 101                 /* 8 bit signed displacement */
 102                 long displacement;
 103                 RE_ENTRANT_CHECK_OFF;
 104                 FPU_code_access_ok(1);
 105                 FPU_get_user(displacement, (signed char __user *)(*fpu_eip));
 106                 offset += displacement;
 107                 RE_ENTRANT_CHECK_ON;
 108                 (*fpu_eip)++;
 109         } else if (mod == 2 || base == 5) {     /* The second condition also has mod==0 */
 110                 /* 32 bit displacement */
 111                 long displacement;
 112                 RE_ENTRANT_CHECK_OFF;
 113                 FPU_code_access_ok(4);
 114                 FPU_get_user(displacement, (long __user *)(*fpu_eip));
 115                 offset += displacement;
 116                 RE_ENTRANT_CHECK_ON;
 117                 (*fpu_eip) += 4;
 118         }
 119
 120         return offset;
 121 }
 122
 123 static unsigned long vm86_segment(u_char segment, struct address *addr)
 124 {
 125         segment--;
 126 #ifdef PARANOID
 127         if (segment > PREFIX_SS_) {
 128                 EXCEPTION(EX_INTERNAL | 0x130);
 129                 math_abort(FPU_info, SIGSEGV);
 130         }
 131 #endif /* PARANOID */
 132         addr->selector = VM86_REG_(segment);
 133         return (unsigned long)VM86_REG_(segment) << 4;
 134 }
 135
 136 /* This should work for 16 and 32 bit protected mode. */
 137 static long pm_address(u_char FPU_modrm, u_char segment,
 138                        struct address *addr, long offset)
 139 {
 140         struct desc_struct descriptor;
 141         unsigned long base_address, limit, address, seg_top;
 142
 143         segment--;
 144
 145 #ifdef PARANOID
 146         /* segment is unsigned, so this also detects if segment was 0: */
 147         if (segment > PREFIX_SS_) {
 148                 EXCEPTION(EX_INTERNAL | 0x132);
 149                 math_abort(FPU_info, SIGSEGV);
 150         }
 151 #endif /* PARANOID */
 152
 153         switch (segment) {
 154         case PREFIX_GS_ - 1:
 155                 /* user gs handling can be lazy, use special accessors */
 156                 addr->selector = get_user_gs(FPU_info->regs);
 157                 break;
 158         default:
 159                 addr->selector = PM_REG_(segment);
 160         }
 161
 162         descriptor = FPU_get_ldt_descriptor(addr->selector);
 163         base_address = seg_get_base(&descriptor);
 164         address = base_address + offset;
 165         limit = seg_get_limit(&descriptor) + 1;
 166         limit *= seg_get_granularity(&descriptor);
 167         limit += base_address - 1;
 168         if (limit < base_address)
 169                 limit = 0xffffffff;
 170
 171         if (seg_expands_down(&descriptor)) {
 172                 if (descriptor.g) {
 173                         seg_top = 0xffffffff;
 174                 } else {
 175                         seg_top = base_address + (1 << 20);
 176                         if (seg_top < base_address)
 177                                 seg_top = 0xffffffff;
 178                 }
 179                 access_limit =
 180                     (address <= limit) || (address >= seg_top) ? 0 :
 181                     ((seg_top - address) >= 255 ? 255 : seg_top - address);
 182         } else {
 183                 access_limit =
 184                     (address > limit) || (address < base_address) ? 0 :
 185                     ((limit - address) >= 254 ? 255 : limit - address + 1);
 186         }
 187         if (seg_execute_only(&descriptor) ||
 188             (!seg_writable(&descriptor) && (FPU_modrm & FPU_WRITE_BIT))) {
 189                 access_limit = 0;
 190         }
 191         return address;
 192 }
 193
 194 /*
 195        MOD R/M byte:  MOD == 3 has a special use for the FPU
 196                       SIB byte used iff R/M = 100b
 197
 198        7   6   5   4   3   2   1   0
 199        .....   .........   .........
 200         MOD    OPCODE(2)     R/M
 201
 202        SIB byte
 203
 204        7   6   5   4   3   2   1   0
 205        .....   .........   .........
 206         SS      INDEX        BASE
 207
 208 */
 209
 210 void __user *FPU_get_address(u_char FPU_modrm, unsigned long *fpu_eip,
 211                              struct address *addr, fpu_addr_modes addr_modes)
 212 {
 213         u_char mod;
 214         unsigned rm = FPU_modrm & 7;
 215         long *cpu_reg_ptr;
 216         int address = 0;        /* Initialized just to stop compiler warnings. */
 217
 218         /* Memory accessed via the cs selector is write protected
 219            in `non-segmented' 32 bit protected mode. */
 220         if (!addr_modes.default_mode && (FPU_modrm & FPU_WRITE_BIT)
 221             && (addr_modes.override.segment == PREFIX_CS_)) {
 222                 math_abort(FPU_info, SIGSEGV);
 223         }
 224
 225         addr->selector = FPU_DS;        /* Default, for 32 bit non-segmented mode. */
 226
 227         mod = (FPU_modrm >> 6) & 3;
 228
 229         if (rm == 4 && mod != 3) {
 230                 address = sib(mod, fpu_eip);
 231         } else {
 232                 cpu_reg_ptr = &REG_(rm);
 233                 switch (mod) {
 234                 case 0:
 235                         if (rm == 5) {
 236                                 /* Special case: disp32 */
 237                                 RE_ENTRANT_CHECK_OFF;
 238                                 FPU_code_access_ok(4);
 239                                 FPU_get_user(address,
 240                                              (unsigned long __user
 241                                               *)(*fpu_eip));
 242                                 (*fpu_eip) += 4;
 243                                 RE_ENTRANT_CHECK_ON;
 244                                 addr->offset = address;
 245                                 return (void __user *)address;
 246                         } else {
 247                                 address = *cpu_reg_ptr; /* Just return the contents
 248                                                            of the cpu register */
 249                                 addr->offset = address;
 250                                 return (void __user *)address;
 251                         }
 252                 case 1:
 253                         /* 8 bit signed displacement */
 254                         RE_ENTRANT_CHECK_OFF;
 255                         FPU_code_access_ok(1);
 256                         FPU_get_user(address, (signed char __user *)(*fpu_eip));
 257                         RE_ENTRANT_CHECK_ON;
 258                         (*fpu_eip)++;
 259                         break;
 260                 case 2:
 261                         /* 32 bit displacement */
 262                         RE_ENTRANT_CHECK_OFF;
 263                         FPU_code_access_ok(4);
 264                         FPU_get_user(address, (long __user *)(*fpu_eip));
 265                         (*fpu_eip) += 4;
 266                         RE_ENTRANT_CHECK_ON;
 267                         break;
 268                 case 3:
 269                         /* Not legal for the FPU */
 270                         EXCEPTION(EX_Invalid);
 271                 }
 272                 address += *cpu_reg_ptr;
 273         }
 274
 275         addr->offset = address;
 276
 277         switch (addr_modes.default_mode) {
 278         case 0:
 279                 break;
 280         case VM86:
 281                 address += vm86_segment(addr_modes.override.segment, addr);
 282                 break;
 283         case PM16:
 284         case SEG32:
 285                 address = pm_address(FPU_modrm, addr_modes.override.segment,
 286                                      addr, address);
 287                 break;
 288         default:
 289                 EXCEPTION(EX_INTERNAL | 0x133);
 290         }
 291
 292         return (void __user *)address;
 293 }
 294
 295 void __user *FPU_get_address_16(u_char FPU_modrm, unsigned long *fpu_eip,
 296                                 struct address *addr, fpu_addr_modes addr_modes)
 297 {
 298         u_char mod;
 299         unsigned rm = FPU_modrm & 7;
 300         int address = 0;        /* Default used for mod == 0 */
 301
 302         /* Memory accessed via the cs selector is write protected
 303            in `non-segmented' 32 bit protected mode. */
 304         if (!addr_modes.default_mode && (FPU_modrm & FPU_WRITE_BIT)
 305             && (addr_modes.override.segment == PREFIX_CS_)) {
 306                 math_abort(FPU_info, SIGSEGV);
 307         }
 308
 309         addr->selector = FPU_DS;        /* Default, for 32 bit non-segmented mode. */
 310
 311         mod = (FPU_modrm >> 6) & 3;
 312
 313         switch (mod) {
 314         case 0:
 315                 if (rm == 6) {
 316                         /* Special case: disp16 */
 317                         RE_ENTRANT_CHECK_OFF;
 318                         FPU_code_access_ok(2);
 319                         FPU_get_user(address,
 320                                      (unsigned short __user *)(*fpu_eip));
 321                         (*fpu_eip) += 2;
 322                         RE_ENTRANT_CHECK_ON;
 323                         goto add_segment;
 324                 }
 325                 break;
 326         case 1:
 327                 /* 8 bit signed displacement */
 328                 RE_ENTRANT_CHECK_OFF;
 329                 FPU_code_access_ok(1);
 330                 FPU_get_user(address, (signed char __user *)(*fpu_eip));
 331                 RE_ENTRANT_CHECK_ON;
 332                 (*fpu_eip)++;
 333                 break;
 334         case 2:
 335                 /* 16 bit displacement */
 336                 RE_ENTRANT_CHECK_OFF;
 337                 FPU_code_access_ok(2);
 338                 FPU_get_user(address, (unsigned short __user *)(*fpu_eip));
 339                 (*fpu_eip) += 2;
 340                 RE_ENTRANT_CHECK_ON;
 341                 break;
 342         case 3:
 343                 /* Not legal for the FPU */
 344                 EXCEPTION(EX_Invalid);
 345                 break;
 346         }
 347         switch (rm) {
 348         case 0:
 349                 address += FPU_info->regs->bx + FPU_info->regs->si;
 350                 break;
 351         case 1:
 352                 address += FPU_info->regs->bx + FPU_info->regs->di;
 353                 break;
 354         case 2:
 355                 address += FPU_info->regs->bp + FPU_info->regs->si;
 356                 if (addr_modes.override.segment == PREFIX_DEFAULT)
 357                         addr_modes.override.segment = PREFIX_SS_;
 358                 break;
 359         case 3:
 360                 address += FPU_info->regs->bp + FPU_info->regs->di;
 361                 if (addr_modes.override.segment == PREFIX_DEFAULT)
 362                         addr_modes.override.segment = PREFIX_SS_;
 363                 break;
 364         case 4:
 365                 address += FPU_info->regs->si;
 366                 break;
 367         case 5:
 368                 address += FPU_info->regs->di;
 369                 break;
 370         case 6:
 371                 address += FPU_info->regs->bp;
 372                 if (addr_modes.override.segment == PREFIX_DEFAULT)
 373                         addr_modes.override.segment = PREFIX_SS_;
 374                 break;
 375         case 7:
 376                 address += FPU_info->regs->bx;
 377                 break;
 378         }
 379
 380       add_segment:
 381         address &= 0xffff;
 382
 383         addr->offset = address;
 384
 385         switch (addr_modes.default_mode) {
 386         case 0:
 387                 break;
 388         case VM86:
 389                 address += vm86_segment(addr_modes.override.segment, addr);
 390                 break;
 391         case PM16:
 392         case SEG32:
 393                 address = pm_address(FPU_modrm, addr_modes.override.segment,
 394                                      addr, address);
 395                 break;
 396         default:
 397                 EXCEPTION(EX_INTERNAL | 0x131);
 398         }
 399
 400         return (void __user *)address;
 401 }