dlls/kernel/dosmem.c

   1 /*
   2  * DOS memory emulation
   3  *
   4  * Copyright 1995 Alexandre Julliard
   5  * Copyright 1996 Marcus Meissner
   6  *
   7  * This library is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU Lesser General Public
   9  * License as published by the Free Software Foundation; either
  10  * version 2.1 of the License, or (at your option) any later version.
  11  *
  12  * This library is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15  * Lesser General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU Lesser General Public
  18  * License along with this library; if not, write to the Free Software
  19  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  20  */
  21
  22 #include "config.h"
  23 #include "wine/port.h"
  24
  25 #include <signal.h>
  26 #include <stdarg.h>
  27 #include <stdlib.h>
  28 #include <string.h>
  29 #include <sys/types.h>
  30 #ifdef HAVE_SYS_MMAN_H
  31 # include <sys/mman.h>
  32 #endif
  33
  34 #include <time.h>
  35 #ifdef HAVE_SYS_TIME_H
  36 # include <sys/time.h>
  37 #endif
  38
  39 #include "windef.h"
  40 #include "winbase.h"
  41 #include "wine/winbase16.h"
  42
  43 #include "kernel_private.h"
  44 #include "miscemu.h"
  45 #include "wine/debug.h"
  46
  47 WINE_DEFAULT_DEBUG_CHANNEL(dosmem);
  48 WINE_DECLARE_DEBUG_CHANNEL(selector);
  49
  50 WORD DOSMEM_0000H;        /* segment at 0:0 */
  51 WORD DOSMEM_BiosDataSeg;  /* BIOS data segment at 0x40:0 */
  52 WORD DOSMEM_BiosSysSeg;   /* BIOS ROM segment at 0xf000:0 */
  53
  54 /* use 2 low bits of 'size' for the housekeeping */
  55
  56 #define DM_BLOCK_DEBUG          0xABE00000
  57 #define DM_BLOCK_TERMINAL       0x00000001
  58 #define DM_BLOCK_FREE           0x00000002
  59 #define DM_BLOCK_MASK           0x001FFFFC
  60
  61 /*
  62 #define __DOSMEM_DEBUG__
  63  */
  64
  65 typedef struct {
  66    unsigned     size;
  67 } dosmem_entry;
  68
  69 typedef struct {
  70   unsigned      blocks;
  71   unsigned      free;
  72 } dosmem_info;
  73
  74 #define NEXT_BLOCK(block) \
  75         (dosmem_entry*)(((char*)(block)) + \
  76          sizeof(dosmem_entry) + ((block)->size & DM_BLOCK_MASK))
  77
  78 #define VM_STUB(x) (0x90CF00CD|(x<<8)) /* INT x; IRET; NOP */
  79 #define VM_STUB_SEGMENT 0xf000         /* BIOS segment */
  80
  81 /* DOS memory base */
  82 static char *DOSMEM_dosmem;
  83 /* DOS system base (for interrupt vector table and BIOS data area)
  84  * ...should in theory (i.e. Windows) be equal to DOSMEM_dosmem (NULL),
  85  * but is normally set to 0xf0000 in Wine to allow trapping of NULL pointers,
  86  * and only relocated to NULL when absolutely necessary */
  87 static char *DOSMEM_sysmem;
  88
  89 /* Start of DOS conventional memory */
  90 static char *DOSMEM_membase;
  91
  92 static void DOSMEM_InitMemory(void);
  93
  94 /***********************************************************************
  95  *           DOSMEM_MemoryTop
  96  *
  97  * Gets the DOS memory top.
  98  */
  99 static char *DOSMEM_MemoryTop(void)
 100 {
 101     return DOSMEM_dosmem+0x9FFFC; /* 640K */
 102 }
 103
 104 /***********************************************************************
 105  *           DOSMEM_InfoBlock
 106  *
 107  * Gets the DOS memory info block.
 108  */
 109 static dosmem_info *DOSMEM_InfoBlock(void)
 110 {
 111     if (!DOSMEM_membase)
 112     {
 113         DWORD         reserve;
 114
 115         /*
 116          * Reserve either:
 117          * - lowest 64k for NULL pointer catching (Win16)
 118          * - lowest 1k for interrupt handlers and
 119          *   another 0.5k for BIOS, DOS and intra-application
 120          *   areas (DOS)
 121          */
 122         if (DOSMEM_dosmem != DOSMEM_sysmem)
 123             reserve = 0x10000; /* 64k */
 124         else
 125             reserve = 0x600; /* 1.5k */
 126
 127         /*
 128          * Round to paragraph boundary in order to make
 129          * sure the alignment is correct.
 130          */
 131         reserve = ((reserve + 15) >> 4) << 4;
 132
 133         /*
 134          * Set DOS memory base and initialize conventional memory.
 135          */
 136         DOSMEM_membase = DOSMEM_dosmem + reserve;
 137         DOSMEM_InitMemory();
 138     }
 139
 140     return (dosmem_info*)DOSMEM_membase;
 141 }
 142
 143 /***********************************************************************
 144  *           DOSMEM_RootBlock
 145  *
 146  * Gets the DOS memory root block.
 147  */
 148 static dosmem_entry *DOSMEM_RootBlock(void)
 149 {
 150     /* first block has to be paragraph-aligned */
 151     return (dosmem_entry*)(((char*)DOSMEM_InfoBlock()) +
 152                            ((((sizeof(dosmem_info) + 0xf) & ~0xf) - sizeof(dosmem_entry))));
 153 }
 154
 155 /***********************************************************************
 156  *           DOSMEM_FillIsrTable
 157  *
 158  * Fill the interrupt table with fake BIOS calls to BIOSSEG (0xf000).
 159  *
 160  * NOTES:
 161  * Linux normally only traps INTs performed from or destined to BIOSSEG
 162  * for us to handle, if the int_revectored table is empty. Filling the
 163  * interrupt table with calls to INT stubs in BIOSSEG allows DOS programs
 164  * to hook interrupts, as well as use their familiar retf tricks to call
 165  * them, AND let Wine handle any unhooked interrupts transparently.
 166  */
 167 static void DOSMEM_FillIsrTable(void)
 168 {
 169     SEGPTR *isr = (SEGPTR*)DOSMEM_sysmem;
 170     int x;
 171
 172     for (x=0; x<256; x++) isr[x]=MAKESEGPTR(VM_STUB_SEGMENT,x*4);
 173 }
 174
 175 static void DOSMEM_MakeIsrStubs(void)
 176 {
 177     DWORD *stub = (DWORD*)(DOSMEM_dosmem + (VM_STUB_SEGMENT << 4));
 178     int x;
 179
 180     for (x=0; x<256; x++) stub[x]=VM_STUB(x);
 181 }
 182
 183 static BIOSDATA * DOSMEM_BiosData(void)
 184 {
 185     return (BIOSDATA *)(DOSMEM_sysmem + 0x400);
 186 }
 187
 188 /**********************************************************************
 189  *          DOSMEM_GetTicksSinceMidnight
 190  *
 191  * Return number of clock ticks since midnight.
 192  */
 193 static DWORD DOSMEM_GetTicksSinceMidnight(void)
 194 {
 195     struct tm *bdtime;
 196     struct timeval tvs;
 197     time_t seconds;
 198
 199     /* This should give us the (approximately) correct
 200      * 18.206 clock ticks per second since midnight.
 201      */
 202     gettimeofday( &tvs, NULL );
 203     seconds = tvs.tv_sec;
 204     bdtime = localtime( &seconds );
 205     return (((bdtime->tm_hour * 3600 + bdtime->tm_min * 60 +
 206               bdtime->tm_sec) * 18206) / 1000) +
 207                   (tvs.tv_usec / 54927);
 208 }
 209
 210 /***********************************************************************
 211  *           DOSMEM_FillBiosSegments
 212  *
 213  * Fill the BIOS data segment with dummy values.
 214  */
 215 static void DOSMEM_FillBiosSegments(void)
 216 {
 217     BYTE *pBiosSys = DOSMEM_dosmem + 0xf0000;
 218     BYTE *pBiosROMTable = pBiosSys+0xe6f5;
 219     BIOSDATA *pBiosData = DOSMEM_BiosData();
 220
 221       /* Clear all unused values */
 222     memset( pBiosData, 0, sizeof(*pBiosData) );
 223
 224     /* FIXME: should check the number of configured drives and ports */
 225     pBiosData->Com1Addr             = 0x3f8;
 226     pBiosData->Com2Addr             = 0x2f8;
 227     pBiosData->Lpt1Addr             = 0x378;
 228     pBiosData->Lpt2Addr             = 0x278;
 229     pBiosData->InstalledHardware    = 0x5463;
 230     pBiosData->MemSize              = 640;
 231     pBiosData->NextKbdCharPtr       = 0x1e;
 232     pBiosData->FirstKbdCharPtr      = 0x1e;
 233     pBiosData->VideoMode            = 3;
 234     pBiosData->VideoColumns         = 80;
 235     pBiosData->VideoPageSize        = 80 * 25 * 2;
 236     pBiosData->VideoPageStartAddr   = 0xb800;
 237     pBiosData->VideoCtrlAddr        = 0x3d4;
 238     pBiosData->Ticks                = DOSMEM_GetTicksSinceMidnight();
 239     pBiosData->NbHardDisks          = 2;
 240     pBiosData->KbdBufferStart       = 0x1e;
 241     pBiosData->KbdBufferEnd         = 0x3e;
 242     pBiosData->RowsOnScreenMinus1   = 24;
 243     pBiosData->BytesPerChar         = 0x10;
 244     pBiosData->ModeOptions          = 0x64;
 245     pBiosData->FeatureBitsSwitches  = 0xf9;
 246     pBiosData->VGASettings          = 0x51;
 247     pBiosData->DisplayCombination   = 0x08;
 248     pBiosData->DiskDataRate         = 0;
 249
 250     /* fill ROM configuration table (values from Award) */
 251     *(pBiosROMTable+0x0)        = 0x08; /* number of bytes following LO */
 252     *(pBiosROMTable+0x1)        = 0x00; /* number of bytes following HI */
 253     *(pBiosROMTable+0x2)        = 0xfc; /* model */
 254     *(pBiosROMTable+0x3)        = 0x01; /* submodel */
 255     *(pBiosROMTable+0x4)        = 0x00; /* BIOS revision */
 256     *(pBiosROMTable+0x5)        = 0x74; /* feature byte 1 */
 257     *(pBiosROMTable+0x6)        = 0x00; /* feature byte 2 */
 258     *(pBiosROMTable+0x7)        = 0x00; /* feature byte 3 */
 259     *(pBiosROMTable+0x8)        = 0x00; /* feature byte 4 */
 260     *(pBiosROMTable+0x9)        = 0x00; /* feature byte 5 */
 261
 262     /* BIOS date string */
 263     strcpy((char *)pBiosSys+0xfff5, "13/01/99");
 264
 265     /* BIOS ID */
 266     *(pBiosSys+0xfffe) = 0xfc;
 267
 268     /* Reboot vector (f000:fff0 or ffff:0000) */
 269     *(DWORD*)(pBiosSys + 0xfff0) = VM_STUB(0x19);
 270 }
 271
 272 /***********************************************************************
 273  *           DOSMEM_InitMemory
 274  *
 275  * Initialises the DOS memory structures.
 276  */
 277 static void DOSMEM_InitMemory(void)
 278 {
 279     dosmem_info*        info_block = DOSMEM_InfoBlock();
 280     dosmem_entry*       root_block = DOSMEM_RootBlock();
 281     dosmem_entry*       dm;
 282
 283     root_block->size = DOSMEM_MemoryTop() - (((char*)root_block) + sizeof(dosmem_entry));
 284
 285     info_block->blocks = 0;
 286     info_block->free = root_block->size;
 287
 288     dm = NEXT_BLOCK(root_block);
 289     dm->size = DM_BLOCK_TERMINAL;
 290     root_block->size |= DM_BLOCK_FREE
 291 #ifdef __DOSMEM_DEBUG__
 292                      | DM_BLOCK_DEBUG
 293 #endif
 294                      ;
 295
 296     TRACE( "DOS conventional memory initialized, %d bytes free.\n",
 297            DOSMEM_Available() );
 298 }
 299
 300
 301 /**********************************************************************
 302  *              setup_dos_mem
 303  *
 304  * Setup the first megabyte for DOS memory access
 305  */
 306 static void setup_dos_mem( int dos_init )
 307 {
 308     int sys_offset = 0;
 309     int page_size = getpagesize();
 310     void *addr = wine_anon_mmap( (void *)page_size, 0x110000-page_size,
 311                                  PROT_READ | PROT_WRITE | PROT_EXEC, 0 );
 312     if (addr == (void *)page_size)  /* we got what we wanted */
 313     {
 314         /* now map from address 0 */
 315         addr = wine_anon_mmap( NULL, 0x110000, PROT_READ | PROT_WRITE | PROT_EXEC, MAP_FIXED );
 316         if (addr)
 317         {
 318             ERR("MAP_FIXED failed at address 0 for DOS address space\n" );
 319             ExitProcess(1);
 320         }
 321
 322         /* inform the memory manager that there is a mapping here */
 323         VirtualAlloc( addr, 0x110000, MEM_RESERVE | MEM_SYSTEM, PAGE_EXECUTE_READWRITE );
 324
 325         /* protect the first 64K to catch NULL pointers */
 326         if (!dos_init)
 327         {
 328             VirtualProtect( addr, 0x10000, PAGE_NOACCESS, NULL );
 329             /* move the BIOS and ISR area from 0x00000 to 0xf0000 */
 330             sys_offset += 0xf0000;
 331         }
 332     }
 333     else
 334     {
 335         ERR("Cannot use first megabyte for DOS address space, please report\n" );
 336         if (dos_init) ExitProcess(1);
 337         /* allocate the DOS area somewhere else */
 338         addr = VirtualAlloc( NULL, 0x110000, MEM_COMMIT, PAGE_EXECUTE_READWRITE );
 339         if (!addr)
 340         {
 341             ERR( "Cannot allocate DOS memory\n" );
 342             ExitProcess(1);
 343         }
 344     }
 345     DOSMEM_dosmem = addr;
 346     DOSMEM_sysmem = (char*)addr + sys_offset;
 347 }
 348
 349
 350 /***********************************************************************
 351  *           DOSMEM_Init
 352  *
 353  * Create the dos memory segments, and store them into the KERNEL
 354  * exported values.
 355  */
 356 BOOL DOSMEM_Init(BOOL dos_init)
 357 {
 358     static int already_done, already_mapped;
 359
 360     if (!already_done)
 361     {
 362         setup_dos_mem( dos_init );
 363
 364         DOSMEM_0000H = GLOBAL_CreateBlock( GMEM_FIXED, DOSMEM_sysmem,
 365                                            0x10000, 0, WINE_LDT_FLAGS_DATA );
 366         DOSMEM_BiosDataSeg = GLOBAL_CreateBlock(GMEM_FIXED,DOSMEM_sysmem + 0x400,
 367                                                 0x100, 0, WINE_LDT_FLAGS_DATA );
 368         DOSMEM_BiosSysSeg = GLOBAL_CreateBlock(GMEM_FIXED,DOSMEM_dosmem+0xf0000,
 369                                                0x10000, 0, WINE_LDT_FLAGS_DATA );
 370         DOSMEM_FillBiosSegments();
 371         DOSMEM_FillIsrTable();
 372         already_done = 1;
 373     }
 374     else if (dos_init && !already_mapped)
 375     {
 376         if (DOSMEM_dosmem)
 377         {
 378             ERR( "Needs access to the first megabyte for DOS mode\n" );
 379             ExitProcess(1);
 380         }
 381         MESSAGE( "Warning: unprotecting the first 64KB of memory to allow real-mode calls.\n"
 382                  "         NULL pointer accesses will no longer be caught.\n" );
 383         VirtualProtect( NULL, 0x10000, PAGE_EXECUTE_READWRITE, NULL );
 384         /* copy the BIOS and ISR area down */
 385         memcpy( DOSMEM_dosmem, DOSMEM_sysmem, 0x400 + 0x100 );
 386         DOSMEM_sysmem = DOSMEM_dosmem;
 387         SetSelectorBase( DOSMEM_0000H, 0 );
 388         SetSelectorBase( DOSMEM_BiosDataSeg, 0x400 );
 389         /* we may now need the actual interrupt stubs, and since we've just moved the
 390          * interrupt vector table away, we can fill the area with stubs instead... */
 391         DOSMEM_MakeIsrStubs();
 392         already_mapped = 1;
 393     }
 394     return TRUE;
 395 }
 396
 397
 398 /***********************************************************************
 399  *           DOSMEM_Tick
 400  *
 401  * Increment the BIOS tick counter. Called by timer signal handler.
 402  */
 403 void DOSMEM_Tick( WORD timer )
 404 {
 405     BIOSDATA *pBiosData = DOSMEM_BiosData();
 406     if (pBiosData) pBiosData->Ticks++;
 407 }
 408
 409 /***********************************************************************
 410  *           DOSMEM_GetBlock
 411  *
 412  * Carve a chunk of the DOS memory block (without selector).
 413  */
 414 LPVOID DOSMEM_GetBlock(UINT size, UINT16* pseg)
 415 {
 416    UINT          blocksize;
 417    char         *block = NULL;
 418    dosmem_info  *info_block = DOSMEM_InfoBlock();
 419    dosmem_entry *dm;
 420 #ifdef __DOSMEM_DEBUG_
 421    dosmem_entry *prev = NULL;
 422 #endif
 423
 424    if( size > info_block->free ) return NULL;
 425    dm = DOSMEM_RootBlock();
 426
 427    while (dm && dm->size != DM_BLOCK_TERMINAL)
 428    {
 429 #ifdef __DOSMEM_DEBUG__
 430        if( (dm->size & DM_BLOCK_DEBUG) != DM_BLOCK_DEBUG )
 431        {
 432             WARN("MCB overrun! [prev = 0x%08x]\n", 4 + (UINT)prev);
 433             return NULL;
 434        }
 435        prev = dm;
 436 #endif
 437        if( dm->size & DM_BLOCK_FREE )
 438        {
 439            dosmem_entry  *next = NEXT_BLOCK(dm);
 440
 441            while( next->size & DM_BLOCK_FREE ) /* collapse free blocks */
 442            {
 443                dm->size += sizeof(dosmem_entry) + (next->size & DM_BLOCK_MASK);
 444                next->size = (DM_BLOCK_FREE | DM_BLOCK_TERMINAL);
 445                next = NEXT_BLOCK(dm);
 446            }
 447
 448            blocksize = dm->size & DM_BLOCK_MASK;
 449            if( blocksize >= size )
 450            {
 451                block = ((char*)dm) + sizeof(dosmem_entry);
 452                if( blocksize - size > 0x20 )
 453                {
 454                    /* split dm so that the next one stays
 455                     * paragraph-aligned (and dm loses free bit) */
 456
 457                    dm->size = (((size + 0xf + sizeof(dosmem_entry)) & ~0xf) -
 458                                               sizeof(dosmem_entry));
 459                    next = (dosmem_entry*)(((char*)dm) +
 460                            sizeof(dosmem_entry) + dm->size);
 461                    next->size = (blocksize - (dm->size +
 462                            sizeof(dosmem_entry))) | DM_BLOCK_FREE
 463 #ifdef __DOSMEM_DEBUG__
 464                                                   | DM_BLOCK_DEBUG
 465 #endif
 466                                                   ;
 467                } else dm->size &= DM_BLOCK_MASK;
 468
 469                info_block->blocks++;
 470                info_block->free -= dm->size;
 471                if( pseg ) *pseg = (block - DOSMEM_dosmem) >> 4;
 472 #ifdef __DOSMEM_DEBUG__
 473                dm->size |= DM_BLOCK_DEBUG;
 474 #endif
 475                break;
 476            }
 477            dm = next;
 478        }
 479        else dm = NEXT_BLOCK(dm);
 480    }
 481    return (LPVOID)block;
 482 }
 483
 484 /***********************************************************************
 485  *           DOSMEM_FreeBlock
 486  */
 487 BOOL DOSMEM_FreeBlock(void* ptr)
 488 {
 489    dosmem_info  *info_block = DOSMEM_InfoBlock();
 490
 491    if( ptr >= (void*)(((char*)DOSMEM_RootBlock()) + sizeof(dosmem_entry)) &&
 492        ptr < (void*)DOSMEM_MemoryTop() && !((((char*)ptr)
 493                   - DOSMEM_dosmem) & 0xf) )
 494    {
 495        dosmem_entry  *dm = (dosmem_entry*)(((char*)ptr) - sizeof(dosmem_entry));
 496
 497        if( !(dm->size & (DM_BLOCK_FREE | DM_BLOCK_TERMINAL))
 498 #ifdef __DOSMEM_DEBUG__
 499          && ((dm->size & DM_BLOCK_DEBUG) == DM_BLOCK_DEBUG )
 500 #endif
 501          )
 502        {
 503              info_block->blocks--;
 504              info_block->free += dm->size;
 505
 506              dm->size |= DM_BLOCK_FREE;
 507              return TRUE;
 508        }
 509    }
 510    return FALSE;
 511 }
 512
 513 /***********************************************************************
 514  *           DOSMEM_ResizeBlock
 515  *
 516  * Resize DOS memory block in place. Returns block size or -1 on error.
 517  *
 518  * If exact is TRUE, returned value is either old or requested block
 519  * size. If exact is FALSE, block is expanded even if there is not
 520  * enough space for full requested block size.
 521  */
 522 UINT DOSMEM_ResizeBlock(void *ptr, UINT size, BOOL exact)
 523 {
 524    char         *block = NULL;
 525    dosmem_info  *info_block = DOSMEM_InfoBlock();
 526    dosmem_entry *dm;
 527    dosmem_entry *next;
 528    UINT blocksize;
 529    UINT orgsize;
 530
 531    if( (ptr < (void*)(sizeof(dosmem_entry) + (char*)DOSMEM_RootBlock())) ||
 532        (ptr >= (void*)DOSMEM_MemoryTop()) ||
 533        (((((char*)ptr) - DOSMEM_dosmem) & 0xf) != 0) )
 534      return (UINT)-1;
 535
 536    dm = (dosmem_entry*)(((char*)ptr) - sizeof(dosmem_entry));
 537    if( dm->size & (DM_BLOCK_FREE | DM_BLOCK_TERMINAL) )
 538        return (UINT)-1;
 539
 540    next = NEXT_BLOCK(dm);
 541    orgsize = dm->size & DM_BLOCK_MASK;
 542
 543    /* collapse free blocks */
 544    while( next->size & DM_BLOCK_FREE )
 545    {
 546        dm->size += sizeof(dosmem_entry) + (next->size & DM_BLOCK_MASK);
 547        next->size = (DM_BLOCK_FREE | DM_BLOCK_TERMINAL);
 548        next = NEXT_BLOCK(dm);
 549    }
 550
 551    blocksize = dm->size & DM_BLOCK_MASK;
 552
 553    /*
 554     * If collapse didn't help we either expand block to maximum
 555     * available size (exact == FALSE) or give collapsed blocks
 556     * back to free storage (exact == TRUE).
 557     */
 558    if (blocksize < size)
 559        size = exact ? orgsize : blocksize;
 560
 561    block = ((char*)dm) + sizeof(dosmem_entry);
 562    if( blocksize - size > 0x20 )
 563    {
 564        /*
 565         * split dm so that the next one stays
 566         * paragraph-aligned (and next gains free bit)
 567         */
 568
 569        dm->size = (((size + 0xf + sizeof(dosmem_entry)) & ~0xf) -
 570                    sizeof(dosmem_entry));
 571        next = (dosmem_entry*)(((char*)dm) +
 572                               sizeof(dosmem_entry) + dm->size);
 573        next->size = (blocksize - (dm->size +
 574                                   sizeof(dosmem_entry))) | DM_BLOCK_FREE;
 575    }
 576    else
 577    {
 578        dm->size &= DM_BLOCK_MASK;
 579    }
 580
 581    /*
 582     * Adjust available memory if block size changes.
 583     */
 584    info_block->free += orgsize - dm->size;
 585
 586    return size;
 587 }
 588
 589 /***********************************************************************
 590  *           DOSMEM_Available
 591  */
 592 UINT DOSMEM_Available(void)
 593 {
 594    UINT          blocksize, available = 0;
 595    dosmem_entry *dm;
 596
 597    dm = DOSMEM_RootBlock();
 598
 599    while (dm && dm->size != DM_BLOCK_TERMINAL)
 600    {
 601 #ifdef __DOSMEM_DEBUG__
 602        if( (dm->size & DM_BLOCK_DEBUG) != DM_BLOCK_DEBUG )
 603        {
 604             WARN("MCB overrun! [prev = 0x%08x]\n", 4 + (UINT)prev);
 605             return NULL;
 606        }
 607        prev = dm;
 608 #endif
 609        if( dm->size & DM_BLOCK_FREE )
 610        {
 611            dosmem_entry  *next = NEXT_BLOCK(dm);
 612
 613            while( next->size & DM_BLOCK_FREE ) /* collapse free blocks */
 614            {
 615                dm->size += sizeof(dosmem_entry) + (next->size & DM_BLOCK_MASK);
 616                next->size = (DM_BLOCK_FREE | DM_BLOCK_TERMINAL);
 617                next = NEXT_BLOCK(dm);
 618            }
 619
 620            blocksize = dm->size & DM_BLOCK_MASK;
 621            if ( blocksize > available ) available = blocksize;
 622            dm = next;
 623        }
 624        else dm = NEXT_BLOCK(dm);
 625    }
 626    return available;
 627 }
 628
 629
 630 /***********************************************************************
 631  *           DOSMEM_MapLinearToDos
 632  *
 633  * Linear address to the DOS address space.
 634  */
 635 UINT DOSMEM_MapLinearToDos(LPVOID ptr)
 636 {
 637     if (((char*)ptr >= DOSMEM_dosmem) &&
 638         ((char*)ptr < DOSMEM_dosmem + 0x100000))
 639           return (UINT)ptr - (UINT)DOSMEM_dosmem;
 640     return (UINT)ptr;
 641 }
 642
 643
 644 /***********************************************************************
 645  *           DOSMEM_MapDosToLinear
 646  *
 647  * DOS linear address to the linear address space.
 648  */
 649 LPVOID DOSMEM_MapDosToLinear(UINT ptr)
 650 {
 651     if (ptr < 0x100000) return (LPVOID)(ptr + (UINT)DOSMEM_dosmem);
 652     return (LPVOID)ptr;
 653 }
 654
 655
 656 /***********************************************************************
 657  *           DOSMEM_MapRealToLinear
 658  *
 659  * Real mode DOS address into a linear pointer
 660  */
 661 LPVOID DOSMEM_MapRealToLinear(DWORD x)
 662 {
 663    LPVOID       lin;
 664
 665    lin=DOSMEM_dosmem+(x&0xffff)+(((x&0xffff0000)>>16)*16);
 666    TRACE_(selector)("(0x%08lx) returns %p.\n", x, lin );
 667    return lin;
 668 }
 669
 670 /***********************************************************************
 671  *           DOSMEM_AllocSelector
 672  *
 673  * Allocates a protected mode selector for a realmode segment.
 674  */
 675 WORD DOSMEM_AllocSelector(WORD realsel)
 676 {
 677         HMODULE16 hModule = GetModuleHandle16("KERNEL");
 678         WORD    sel;
 679
 680         sel=GLOBAL_CreateBlock( GMEM_FIXED, DOSMEM_dosmem+realsel*16, 0x10000,
 681                                 hModule, WINE_LDT_FLAGS_DATA );
 682         TRACE_(selector)("(0x%04x) returns 0x%04x.\n", realsel,sel);
 683         return sel;
 684 }