LXR linux/arch/x86/math-emu/get

   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
  32static 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
  45static 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
  58static 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 */
  72static 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
 123static 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. */
 137static 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
 210void __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
 295void __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}
 402