msdos/dosmem.c

   1 /*
   2  * DOS memory emulation
   3  *
   4  * Copyright 1995 Alexandre Julliard
   5  * Copyright 1996 Marcus Meissner
   6  */
   7
   8 #include <signal.h>
   9 #include <stdlib.h>
  10 #include <string.h>
  11 #include "windows.h"
  12 #include "winbase.h"
  13 #include "global.h"
  14 #include "ldt.h"
  15 #include "miscemu.h"
  16 #include "module.h"
  17 #include "task.h"
  18 #include "debug.h"
  19
  20 HANDLE16 DOSMEM_BiosSeg;  /* BIOS data segment at 0x40:0 */
  21
  22 #pragma pack(1)
  23
  24 typedef struct
  25 {
  26     WORD  Com1Addr;                  /* 00: COM1 I/O address */
  27     WORD  Com2Addr;                  /* 02: COM2 I/O address */
  28     WORD  Com3Addr;                  /* 04: COM3 I/O address */
  29     WORD  Com4Addr;                  /* 06: COM4 I/O address */
  30     WORD  Lpt1Addr;                  /* 08: LPT1 I/O address */
  31     WORD  Lpt2Addr;                  /* 0a: LPT2 I/O address */
  32     WORD  Lpt3Addr;                  /* 0c: LPT3 I/O address */
  33     WORD  Lpt4Addr;                  /* 0e: LPT4 I/O address */
  34     WORD  InstalledHardware;         /* 10: Installed hardware flags */
  35     BYTE  POSTstatus;                /* 12: Power-On Self Test status */
  36     WORD  MemSize WINE_PACKED;       /* 13: Base memory size in Kb */
  37     WORD  unused1 WINE_PACKED;       /* 15: Manufacturing test scratch pad */
  38     BYTE  KbdFlags1;                 /* 17: Keyboard flags 1 */
  39     BYTE  KbdFlags2;                 /* 18: Keyboard flags 2 */
  40     BYTE  unused2;                   /* 19: Keyboard driver workspace */
  41     WORD  NextKbdCharPtr;            /* 1a: Next character in kbd buffer */
  42     WORD  FirstKbdCharPtr;           /* 1c: First character in kbd buffer */
  43     WORD  KbdBuffer[16];             /* 1e: Keyboard buffer */
  44     BYTE  DisketteStatus1;           /* 3e: Diskette recalibrate status */
  45     BYTE  DisketteStatus2;           /* 3f: Diskette motor status */
  46     BYTE  DisketteStatus3;           /* 40: Diskette motor timeout */
  47     BYTE  DisketteStatus4;           /* 41: Diskette last operation status */
  48     BYTE  DiskStatus[7];             /* 42: Disk status/command bytes */
  49     BYTE  VideoMode;                 /* 49: Video mode */
  50     WORD  VideoColumns;              /* 4a: Number of columns */
  51     WORD  VideoPageSize;             /* 4c: Video page size in bytes */
  52     WORD  VideoPageStartAddr;        /* 4e: Video page start address */
  53     BYTE  VideoCursorPos[16];        /* 50: Cursor position for 8 pages */
  54     WORD  VideoCursorType;           /* 60: Video cursor type */
  55     BYTE  VideoCurPage;              /* 62: Video current page */
  56     WORD  VideoCtrlAddr WINE_PACKED; /* 63: Video controller address */
  57     BYTE  VideoReg1;                 /* 65: Video mode select register */
  58     BYTE  VideoReg2;                 /* 66: Video CGA palette register */
  59     DWORD ResetEntry WINE_PACKED;    /* 67: Warm reset entry point */
  60     BYTE  LastIRQ;                   /* 6b: Last unexpected interrupt */
  61     DWORD Ticks;                     /* 6c: Ticks since midnight */
  62     BYTE  TicksOverflow;             /* 70: Timer overflow if past midnight */
  63     BYTE  CtrlBreakFlag;             /* 71: Ctrl-Break flag */
  64     WORD  ResetFlag;                 /* 72: POST Reset flag */
  65     BYTE  DiskOpStatus;              /* 74: Last hard-disk operation status */
  66     BYTE  NbHardDisks;               /* 75: Number of hard disks */
  67     BYTE  DiskCtrlByte;              /* 76: Disk control byte */
  68     BYTE  DiskIOPort;                /* 77: Disk I/O port offset */
  69     BYTE  LptTimeout[4];             /* 78: Timeouts for parallel ports */
  70     BYTE  ComTimeout[4];             /* 7c: Timeouts for serial ports */
  71     WORD  KbdBufferStart;            /* 80: Keyboard buffer start */
  72     WORD  KbdBufferEnd;              /* 82: Keyboard buffer end */
  73 } BIOSDATA;
  74
  75 #pragma pack(4)
  76
  77 static BIOSDATA *pBiosData = NULL;
  78 static char     *DOSMEM_dosmem;
  79
  80        DWORD     DOSMEM_CollateTable;
  81
  82        DWORD     DOSMEM_ErrorCall;
  83        DWORD     DOSMEM_ErrorBuffer;
  84
  85 /* use 2 low bits of 'size' for the housekeeping */
  86
  87 #define DM_BLOCK_DEBUG          0xABE00000
  88 #define DM_BLOCK_TERMINAL       0x00000001
  89 #define DM_BLOCK_FREE           0x00000002
  90 #define DM_BLOCK_MASK           0x001FFFFC
  91
  92 /*
  93 #define __DOSMEM_DEBUG__
  94  */
  95
  96 typedef struct {
  97    unsigned     size;
  98 } dosmem_entry;
  99
 100 typedef struct {
 101   unsigned      blocks;
 102   unsigned      free;
 103 } dosmem_info;
 104
 105 #define NEXT_BLOCK(block) \
 106         (dosmem_entry*)(((char*)(block)) + \
 107          sizeof(dosmem_entry) + ((block)->size & DM_BLOCK_MASK))
 108
 109 #define VM_STUB(x) (0x90CF00CD|(x<<8)) /* INT x; IRET; NOP */
 110 #define VM_STUB_SEGMENT 0xf000         /* BIOS segment */
 111
 112 /***********************************************************************
 113  *           DOSMEM_MemoryBase
 114  *
 115  * Gets the DOS memory base.
 116  */
 117 char *DOSMEM_MemoryBase(HMODULE16 hModule)
 118 {
 119     TDB *pTask = hModule ? NULL : (TDB *)GlobalLock16( GetCurrentTask() );
 120     NE_MODULE *pModule = (hModule || pTask) ? NE_GetPtr( hModule ? hModule : pTask->hModule ) : NULL;
 121
 122     GlobalUnlock16( GetCurrentTask() );
 123     if (pModule && pModule->dos_image)
 124         return pModule->dos_image;
 125     else
 126         return DOSMEM_dosmem;
 127 }
 128
 129 /***********************************************************************
 130  *           DOSMEM_MemoryTop
 131  *
 132  * Gets the DOS memory top.
 133  */
 134 static char *DOSMEM_MemoryTop(HMODULE16 hModule)
 135 {
 136     return DOSMEM_MemoryBase(hModule)+0x9FFFC; /* 640K */
 137 }
 138
 139 /***********************************************************************
 140  *           DOSMEM_InfoBlock
 141  *
 142  * Gets the DOS memory info block.
 143  */
 144 static dosmem_info *DOSMEM_InfoBlock(HMODULE16 hModule)
 145 {
 146     return (dosmem_info*)(DOSMEM_MemoryBase(hModule)+0x10000); /* 64K */
 147 }
 148
 149 /***********************************************************************
 150  *           DOSMEM_RootBlock
 151  *
 152  * Gets the DOS memory root block.
 153  */
 154 static dosmem_entry *DOSMEM_RootBlock(HMODULE16 hModule)
 155 {
 156     /* first block has to be paragraph-aligned */
 157     return (dosmem_entry*)(((char*)DOSMEM_InfoBlock(hModule)) +
 158                            ((((sizeof(dosmem_info) + 0xf) & ~0xf) - sizeof(dosmem_entry))));
 159 }
 160
 161 /***********************************************************************
 162  *           DOSMEM_FillIsrTable
 163  *
 164  * Fill the interrupt table with fake BIOS calls to BIOSSEG (0xf000).
 165  *
 166  * NOTES:
 167  * Linux normally only traps INTs performed from or destined to BIOSSEG
 168  * for us to handle, if the int_revectored table is empty. Filling the
 169  * interrupt table with calls to INT stubs in BIOSSEG allows DOS programs
 170  * to hook interrupts, as well as use their familiar retf tricks to call
 171  * them, AND let Wine handle any unhooked interrupts transparently.
 172  */
 173 static void DOSMEM_FillIsrTable(HMODULE16 hModule)
 174 {
 175     SEGPTR *isr = (SEGPTR*)DOSMEM_MemoryBase(hModule);
 176     DWORD *stub = (DWORD*)((char*)isr + (VM_STUB_SEGMENT << 4));
 177     int x;
 178
 179     for (x=0; x<256; x++) isr[x]=PTR_SEG_OFF_TO_SEGPTR(VM_STUB_SEGMENT,x*4);
 180     for (x=0; x<256; x++) stub[x]=VM_STUB(x);
 181 }
 182
 183 /***********************************************************************
 184  *           DOSMEM_FillBiosSegment
 185  *
 186  * Fill the BIOS data segment with dummy values.
 187  */
 188 static void DOSMEM_FillBiosSegment(void)
 189 {
 190     pBiosData = (BIOSDATA *)GlobalLock16( DOSMEM_BiosSeg );
 191
 192       /* Clear all unused values */
 193     memset( pBiosData, 0, sizeof(*pBiosData) );
 194
 195     /* FIXME: should check the number of configured drives and ports */
 196
 197     pBiosData->Com1Addr             = 0x3e8;
 198     pBiosData->Com2Addr             = 0x2e8;
 199     pBiosData->Lpt1Addr             = 0x378;
 200     pBiosData->Lpt2Addr             = 0x278;
 201     pBiosData->InstalledHardware    = 0x8443;
 202     pBiosData->MemSize              = 640;
 203     pBiosData->NextKbdCharPtr       = 0x1e;
 204     pBiosData->FirstKbdCharPtr      = 0x1e;
 205     pBiosData->VideoMode            = 0;
 206     pBiosData->VideoColumns         = 80;
 207     pBiosData->VideoPageSize        = 80 * 25 * 2;
 208     pBiosData->VideoPageStartAddr   = 0xb800;
 209     pBiosData->VideoCtrlAddr        = 0x3d4;
 210     pBiosData->Ticks                = INT1A_GetTicksSinceMidnight();
 211     pBiosData->NbHardDisks          = 2;
 212     pBiosData->KbdBufferStart       = 0x1e;
 213     pBiosData->KbdBufferEnd         = 0x3e;
 214 }
 215
 216 /***********************************************************************
 217  *           DOSMEM_InitCollateTable
 218  *
 219  * Initialises the collate table (character sorting, language dependent)
 220  */
 221 static void DOSMEM_InitCollateTable()
 222 {
 223         DWORD           x;
 224         unsigned char   *tbl;
 225         int             i;
 226
 227         x = GlobalDOSAlloc(258);
 228         DOSMEM_CollateTable = MAKELONG(0,(x>>16));
 229         tbl = DOSMEM_MapRealToLinear(DOSMEM_CollateTable);
 230         *(WORD*)tbl     = 0x100;
 231         tbl += 2;
 232         for ( i = 0; i < 0x100; i++) *tbl++ = i;
 233 }
 234
 235 /***********************************************************************
 236  *           DOSMEM_InitErrorTable
 237  *
 238  * Initialises the error tables (DOS 5+)
 239  */
 240 static void DOSMEM_InitErrorTable()
 241 {
 242         DWORD           x;
 243         char            *call;
 244
 245         /* We will use a snippet of real mode code that calls */
 246         /* a WINE-only interrupt to handle moving the requested */
 247         /* message into the buffer... */
 248
 249         /* FIXME - There is still something wrong... */
 250
 251         /* FIXME - Find hex values for opcodes...
 252
 253            (On call, AX contains message number
 254                      DI contains 'offset' (??)
 255             Resturn, ES:DI points to counted string )
 256
 257            PUSH BX
 258            MOV BX, AX
 259            MOV AX, (arbitrary subfunction number)
 260            INT (WINE-only interrupt)
 261            POP BX
 262            RET
 263
 264         */
 265
 266         const int       code = 4;
 267         const int       buffer = 80;
 268         const int       SIZE_TO_ALLOCATE = code + buffer;
 269
 270         /* FIXME - Complete rewrite of the table system to save */
 271         /* precious DOS space. Now, we return the 0001:???? as */
 272         /* DOS 4+ (??, it seems to be the case in MS 7.10) treats that */
 273         /* as a special case and programs will use the alternate */
 274         /* interface (a farcall returned with INT 24 (AX = 0x122e, DL = */
 275         /* 0x08) which lets us have a smaller memory footprint anyway. */
 276
 277         x = GlobalDOSAlloc(SIZE_TO_ALLOCATE);
 278
 279         DOSMEM_ErrorCall = MAKELONG(0,(x>>16));
 280         DOSMEM_ErrorBuffer = DOSMEM_ErrorCall + code;
 281
 282         call = DOSMEM_MapRealToLinear(DOSMEM_ErrorCall);
 283
 284         memset(call, 0, SIZE_TO_ALLOCATE);
 285
 286         /* Fixme - Copy assembly into buffer here */
 287 }
 288
 289 /***********************************************************************
 290  *           DOSMEM_InitMemory
 291  *
 292  * Initialises the DOS memory structures.
 293  */
 294 static void DOSMEM_InitMemory(HMODULE16 hModule)
 295 {
 296    /* Low 64Kb are reserved for DOS/BIOS so the useable area starts at
 297     * 1000:0000 and ends at 9FFF:FFEF. */
 298
 299     dosmem_info*        info_block = DOSMEM_InfoBlock(hModule);
 300     dosmem_entry*       root_block = DOSMEM_RootBlock(hModule);
 301     dosmem_entry*       dm;
 302
 303     root_block->size = DOSMEM_MemoryTop(hModule) - (((char*)root_block) + sizeof(dosmem_entry));
 304
 305     info_block->blocks = 0;
 306     info_block->free = root_block->size;
 307
 308     dm = NEXT_BLOCK(root_block);
 309     dm->size = DM_BLOCK_TERMINAL;
 310     root_block->size |= DM_BLOCK_FREE
 311 #ifdef __DOSMEM_DEBUG__
 312                      | DM_BLOCK_DEBUG;
 313 #endif
 314                      ;
 315 }
 316
 317 /***********************************************************************
 318  *           DOSMEM_Init
 319  *
 320  * Create the dos memory segments, and store them into the KERNEL
 321  * exported values.
 322  */
 323 BOOL32 DOSMEM_Init(HMODULE16 hModule)
 324 {
 325     if (!hModule)
 326     {
 327         /* Allocate 1 MB dosmemory
 328          * - it is mostly wasted but we use can some of it to
 329          *   store internal translation tables, etc...
 330          */
 331         DOSMEM_dosmem = VirtualAlloc( NULL, 0x100000, MEM_COMMIT,
 332                                       PAGE_EXECUTE_READWRITE );
 333         if (!DOSMEM_dosmem)
 334         {
 335             WARN(dosmem, "Could not allocate DOS memory.\n" );
 336             return FALSE;
 337         }
 338         DOSMEM_BiosSeg = GLOBAL_CreateBlock(GMEM_FIXED,DOSMEM_dosmem+0x400,0x100,
 339                                         0, FALSE, FALSE, FALSE, NULL );
 340         DOSMEM_FillIsrTable(0);
 341         DOSMEM_FillBiosSegment();
 342         DOSMEM_InitMemory(0);
 343         DOSMEM_InitCollateTable();
 344         DOSMEM_InitErrorTable();
 345     }
 346     else
 347     {
 348 #if 0
 349         DOSMEM_FillIsrTable(hModule);
 350         DOSMEM_InitMemory(hModule);
 351 #else
 352         /* bootstrap the new V86 task with a copy of the "system" memory */
 353         memcpy(DOSMEM_MemoryBase(hModule), DOSMEM_dosmem, 0x100000);
 354 #endif
 355     }
 356     return TRUE;
 357 }
 358
 359
 360 /***********************************************************************
 361  *           DOSMEM_Tick
 362  *
 363  * Increment the BIOS tick counter. Called by timer signal handler.
 364  */
 365 void DOSMEM_Tick(void)
 366 {
 367     if (pBiosData) pBiosData->Ticks++;
 368 }
 369
 370 /***********************************************************************
 371  *           DOSMEM_GetBlock
 372  *
 373  * Carve a chunk of the DOS memory block (without selector).
 374  */
 375 LPVOID DOSMEM_GetBlock(HMODULE16 hModule, UINT32 size, UINT16* pseg)
 376 {
 377    UINT32        blocksize;
 378    char         *block = NULL;
 379    dosmem_info  *info_block = DOSMEM_InfoBlock(hModule);
 380    dosmem_entry *dm;
 381 #ifdef __DOSMEM_DEBUG_
 382    dosmem_entry *prev = NULL;
 383 #endif
 384
 385    if( size > info_block->free ) return NULL;
 386    dm = DOSMEM_RootBlock(hModule);
 387
 388    while (dm && dm->size != DM_BLOCK_TERMINAL)
 389    {
 390 #ifdef __DOSMEM_DEBUG__
 391        if( (dm->size & DM_BLOCK_DEBUG) != DM_BLOCK_DEBUG )
 392        {
 393             WARN(dosmem,"MCB overrun! [prev = 0x%08x]\n", 4 + (UINT32)prev);
 394             return NULL;
 395        }
 396        prev = dm;
 397 #endif
 398        if( dm->size & DM_BLOCK_FREE )
 399        {
 400            dosmem_entry  *next = NEXT_BLOCK(dm);
 401
 402            while( next->size & DM_BLOCK_FREE ) /* collapse free blocks */
 403            {
 404                dm->size += sizeof(dosmem_entry) + (next->size & DM_BLOCK_MASK);
 405                next->size = (DM_BLOCK_FREE | DM_BLOCK_TERMINAL);
 406                next = NEXT_BLOCK(dm);
 407            }
 408
 409            blocksize = dm->size & DM_BLOCK_MASK;
 410            if( blocksize >= size )
 411            {
 412                block = ((char*)dm) + sizeof(dosmem_entry);
 413                if( blocksize - size > 0x20 )
 414                {
 415                    /* split dm so that the next one stays
 416                     * paragraph-aligned (and dm loses free bit) */
 417
 418                    dm->size = (((size + 0xf + sizeof(dosmem_entry)) & ~0xf) -
 419                                               sizeof(dosmem_entry));
 420                    next = (dosmem_entry*)(((char*)dm) +
 421                            sizeof(dosmem_entry) + dm->size);
 422                    next->size = (blocksize - (dm->size +
 423                            sizeof(dosmem_entry))) | DM_BLOCK_FREE
 424 #ifdef __DOSMEM_DEBUG__
 425                                                   | DM_BLOCK_DEBUG
 426 #endif
 427                                                   ;
 428                } else dm->size &= DM_BLOCK_MASK;
 429
 430                info_block->blocks++;
 431                info_block->free -= dm->size;
 432                if( pseg ) *pseg = (block - DOSMEM_MemoryBase(hModule)) >> 4;
 433 #ifdef __DOSMEM_DEBUG__
 434                dm->size |= DM_BLOCK_DEBUG;
 435 #endif
 436                break;
 437            }
 438            dm = next;
 439        }
 440        else dm = NEXT_BLOCK(dm);
 441    }
 442    return (LPVOID)block;
 443 }
 444
 445 /***********************************************************************
 446  *           DOSMEM_FreeBlock
 447  */
 448 BOOL32 DOSMEM_FreeBlock(HMODULE16 hModule, void* ptr)
 449 {
 450    dosmem_info  *info_block = DOSMEM_InfoBlock(hModule);
 451
 452    if( ptr >= (void*)(((char*)DOSMEM_RootBlock(hModule)) + sizeof(dosmem_entry)) &&
 453        ptr < (void*)DOSMEM_MemoryTop(hModule) && !((((char*)ptr)
 454                   - DOSMEM_MemoryBase(hModule)) & 0xf) )
 455    {
 456        dosmem_entry  *dm = (dosmem_entry*)(((char*)ptr) - sizeof(dosmem_entry));
 457
 458        if( !(dm->size & (DM_BLOCK_FREE | DM_BLOCK_TERMINAL))
 459 #ifdef __DOSMEM_DEBUG__
 460          && ((dm->size & DM_BLOCK_DEBUG) == DM_BLOCK_DEBUG )
 461 #endif
 462          )
 463        {
 464              info_block->blocks--;
 465              info_block->free += dm->size;
 466
 467              dm->size |= DM_BLOCK_FREE;
 468              return TRUE;
 469        }
 470    }
 471    return FALSE;
 472 }
 473
 474 /***********************************************************************
 475  *           DOSMEM_ResizeBlock
 476  */
 477 LPVOID DOSMEM_ResizeBlock(HMODULE16 hModule, void* ptr, UINT32 size, UINT16* pseg)
 478 {
 479    char         *block = NULL;
 480    dosmem_info  *info_block = DOSMEM_InfoBlock(hModule);
 481
 482    if( ptr >= (void*)(((char*)DOSMEM_RootBlock(hModule)) + sizeof(dosmem_entry)) &&
 483        ptr < (void*)DOSMEM_MemoryTop(hModule) && !((((char*)ptr)
 484                   - DOSMEM_MemoryBase(hModule)) & 0xf) )
 485    {
 486        dosmem_entry  *dm = (dosmem_entry*)(((char*)ptr) - sizeof(dosmem_entry));
 487
 488        if( pseg ) *pseg = ((char*)ptr - DOSMEM_MemoryBase(hModule)) >> 4;
 489
 490        if( !(dm->size & (DM_BLOCK_FREE | DM_BLOCK_TERMINAL))
 491          )
 492        {
 493              dosmem_entry  *next = NEXT_BLOCK(dm);
 494              UINT32 blocksize, orgsize = dm->size & DM_BLOCK_MASK;
 495
 496              while( next->size & DM_BLOCK_FREE ) /* collapse free blocks */
 497              {
 498                  dm->size += sizeof(dosmem_entry) + (next->size & DM_BLOCK_MASK);
 499                  next->size = (DM_BLOCK_FREE | DM_BLOCK_TERMINAL);
 500                  next = NEXT_BLOCK(dm);
 501              }
 502
 503              blocksize = dm->size & DM_BLOCK_MASK;
 504              if (blocksize >= size)
 505              {
 506                  block = ((char*)dm) + sizeof(dosmem_entry);
 507                  if( blocksize - size > 0x20 )
 508                  {
 509                      /* split dm so that the next one stays
 510                       * paragraph-aligned (and next gains free bit) */
 511
 512                      dm->size = (((size + 0xf + sizeof(dosmem_entry)) & ~0xf) -
 513                                                 sizeof(dosmem_entry));
 514                      next = (dosmem_entry*)(((char*)dm) +
 515                              sizeof(dosmem_entry) + dm->size);
 516                      next->size = (blocksize - (dm->size +
 517                              sizeof(dosmem_entry))) | DM_BLOCK_FREE
 518                                                     ;
 519                  } else dm->size &= DM_BLOCK_MASK;
 520
 521                  info_block->free += orgsize - dm->size;
 522              } else {
 523                  block = DOSMEM_GetBlock(hModule, size, pseg);
 524                  if (block) {
 525                      info_block->blocks--;
 526                      info_block->free += dm->size;
 527
 528                      dm->size |= DM_BLOCK_FREE;
 529                  }
 530              }
 531        }
 532    }
 533    return (LPVOID)block;
 534 }
 535
 536
 537 /***********************************************************************
 538  *           DOSMEM_Available
 539  */
 540 UINT32 DOSMEM_Available(HMODULE16 hModule)
 541 {
 542    UINT32        blocksize, available = 0;
 543    dosmem_entry *dm;
 544
 545    dm = DOSMEM_RootBlock(hModule);
 546
 547    while (dm && dm->size != DM_BLOCK_TERMINAL)
 548    {
 549 #ifdef __DOSMEM_DEBUG__
 550        if( (dm->size & DM_BLOCK_DEBUG) != DM_BLOCK_DEBUG )
 551        {
 552             WARN(dosmem,"MCB overrun! [prev = 0x%08x]\n", 4 + (UINT32)prev);
 553             return NULL;
 554        }
 555        prev = dm;
 556 #endif
 557        if( dm->size & DM_BLOCK_FREE )
 558        {
 559            dosmem_entry  *next = NEXT_BLOCK(dm);
 560
 561            while( next->size & DM_BLOCK_FREE ) /* collapse free blocks */
 562            {
 563                dm->size += sizeof(dosmem_entry) + (next->size & DM_BLOCK_MASK);
 564                next->size = (DM_BLOCK_FREE | DM_BLOCK_TERMINAL);
 565                next = NEXT_BLOCK(dm);
 566            }
 567
 568            blocksize = dm->size & DM_BLOCK_MASK;
 569            if ( blocksize > available ) available = blocksize;
 570            dm = next;
 571        }
 572        else dm = NEXT_BLOCK(dm);
 573    }
 574    return available;
 575 }
 576
 577
 578 /***********************************************************************
 579  *           DOSMEM_MapLinearToDos
 580  *
 581  * Linear address to the DOS address space.
 582  */
 583 UINT32 DOSMEM_MapLinearToDos(LPVOID ptr)
 584 {
 585     if (((char*)ptr >= DOSMEM_MemoryBase(0)) &&
 586         ((char*)ptr < DOSMEM_MemoryBase(0) + 0x100000))
 587           return (UINT32)ptr - (UINT32)DOSMEM_MemoryBase(0);
 588     return (UINT32)ptr;
 589 }
 590
 591
 592 /***********************************************************************
 593  *           DOSMEM_MapDosToLinear
 594  *
 595  * DOS linear address to the linear address space.
 596  */
 597 LPVOID DOSMEM_MapDosToLinear(UINT32 ptr)
 598 {
 599     if (ptr < 0x100000) return (LPVOID)(ptr + (UINT32)DOSMEM_MemoryBase(0));
 600     return (LPVOID)ptr;
 601 }
 602
 603
 604 /***********************************************************************
 605  *           DOSMEM_MapRealToLinear
 606  *
 607  * Real mode DOS address into a linear pointer
 608  */
 609 LPVOID DOSMEM_MapRealToLinear(DWORD x)
 610 {
 611    LPVOID       lin;
 612
 613    lin=DOSMEM_MemoryBase(0)+(x&0xffff)+(((x&0xffff0000)>>16)*16);
 614    TRACE(selector,"(0x%08lx) returns 0x%p.\n",
 615                     x,lin );
 616    return lin;
 617 }
 618
 619 /***********************************************************************
 620  *           DOSMEM_AllocSelector
 621  *
 622  * Allocates a protected mode selector for a realmode segment.
 623  */
 624 WORD DOSMEM_AllocSelector(WORD realsel)
 625 {
 626         HMODULE16 hModule = GetModuleHandle16("KERNEL");
 627         WORD    sel;
 628
 629         sel=GLOBAL_CreateBlock(
 630                 GMEM_FIXED,DOSMEM_dosmem+realsel*16,0x10000,
 631                 hModule,FALSE,FALSE,FALSE,NULL
 632         );
 633         TRACE(selector,"(0x%04x) returns 0x%04x.\n",
 634                 realsel,sel
 635         );
 636         return sel;
 637 }
 638