v4.0/src/DOS/DISP.ASM

   1 ;       SCCSID = @(#)disp.asm   1.1 85/04/10
   2 ;       SCCSID = @(#)disp.asm   1.1 85/04/10
   3 ;
   4 ; Dispatcher code
   5 ;
   6
   7 .xlist
   8 .xcref
   9 INCLUDE DOSSYM.INC
  10 include dosseg.asm
  11 .cref
  12 .list
  13
  14 AsmVars <Kanji, Debug>
  15
  16 BREAK   <Copyright notice and version>
  17 CODE    SEGMENT BYTE PUBLIC 'CODE'
  18
  19
  20         I_need  CurrentPDB,WORD
  21         I_need  CntCFlag,BYTE
  22         I_need  User_SS,WORD
  23         I_need  User_SP,WORD
  24         I_need  NSS,WORD
  25         I_need  NSP,WORD
  26         I_need  MaxCall,BYTE
  27         I_need  MaxCom,BYTE
  28         I_need  SaveDS,WORD
  29         I_need  SaveBX,WORD
  30         I_need  INDOS,BYTE
  31         I_need  User_ID,WORD
  32         I_need  Proc_ID,WORD
  33         I_need  AuxStack,BYTE
  34         I_need  IOSTACK,BYTE
  35         I_need  DSKSTACK,BYTE
  36         I_need  fsharing,BYTE
  37         I_need  NoSetDir,BYTE
  38         I_need  FailERR,BYTE
  39         I_need  Errormode,BYTE
  40         I_need  restore_tmp,WORD
  41         I_need  WPERR,BYTE
  42         I_need  Dispatch,WORD
  43         I_need  ConSwap,BYTE
  44         I_need  User_In_AX,WORD
  45         I_need  EXTERR_LOCUS,BYTE
  46         I_need  IdleInt,BYTE
  47         I_need  Printer_Flag,BYTE
  48         I_need  CPSWFLAG,BYTE              ;AN000;
  49         I_need  CPSWSAVE,BYTE              ;AN000;
  50         I_need  DISK_FULL,BYTE             ;AN000;
  51         I_need  InterCon,BYTE              ;AN000;
  52         I_need  BOOTDRIVE,BYTE             ;AN000;
  53         I_need  EXTOPEN_ON,BYTE            ;AN000;
  54         I_need  DOS34_FLAG,WORD            ;AN000;
  55         I_need  ACT_PAGE,WORD              ;AN000;
  56
  57         IF      NOT IBM
  58         I_need  OEM_HANDLER,DWORD
  59         ENDIF
  60
  61         IF      BUFFERFLAG
  62         I_am    SETVECTFLAG,BYTE,<0>
  63         i_need  BUF_EMS_SEG_CNT,WORD         ; DOS 4.00 EMS seg count           ;AN000;
  64         i_need  BUF_EMS_MODE,BYTE            ; DOS 4.00 EMS mode                ;AN000;
  65         i_am    BUF_EMS_MAP_USER,12,<0,0,0,0,0,0,0,0,0,0,0,0>
  66         ENDIF
  67
  68 ASSUME  CS:DOSGROUP,DS:NOTHING,ES:NOTHING,SS:NOTHING
  69
  70 BREAK   <System call entry points and dispatcher>
  71 ASSUME  CS:DOSGROUP,DS:NOTHING,ES:NOTHING,SS:NOTHING
  72
  73 BREAK <$Set_CTRL_C_Trapping -- En/Disable ^C check in dispatcher>
  74
  75 ; Inputs:
  76 ;       AL = 0 read ^C status
  77 ;       AL = 1 Set ^C status, DL = 0/1 for ^C off/on
  78 ;       AL = 2 Set ^C status to contents of DL.  Output is old state.
  79 ;       AL = 3 Get CPSW state to DL        DOS 3.4
  80 ;       AL = 4 Set CPSW state from DL      DOS 3.4
  81 ;       AL = 5 get DOS boot drive
  82 ; Function:
  83 ;       Enable disable ^C checking in dispatcher
  84 ; Outputs:
  85 ;       If AL = 0 then DL = 0/1 for ^C off/on
  86
  87         procedure   $SET_CTRL_C_TRAPPING,NEAR
  88 ASSUME  DS:NOTHING,ES:NOTHING,SS:NOTHING
  89         OR      AL,AL
  90         JNZ     Check1
  91         MOV     DL,CntCFlag
  92         IRET
  93 Check1:
  94         CMP     AL,2
  95         JA      CPSWchk                        ;AN000;
  96         JZ      SetAndRet
  97         PUSH    DX
  98         AND     DL,01h
  99         MOV     [CNTCFLAG],DL
 100         POP     DX
 101         IRET
 102 SetAndRet:
 103         AND     DL,01h
 104         XCHG    CntCFlag,DL
 105         IRET
 106 BadVal:
 107         MOV     AL,0FFH
 108         IRET
 109 ;; DOS 4.00 File Tagging
 110
 111 CPSWchk:                                ;AN000;
 112 ;       PUSH    AX                      ;AN000;;FT.
 113 ;       MOV     AL,[CPSWSAVE]           ;AN000;;FT. DOS 3.4
 114 ;       MOV     [CPSWFLAG],AL           ;AN000;;FT. DOS 3.4 in case ABORT
 115 ;       POP     AX                      ;AN000;;FT.
 116         CMP     AL,3                    ;AN000;;FT get CPSW state ?
 117         JNZ     CPSWset                 ;AN000;;FT. no
 118 ;       MOV     DL,CPSWFLAG             ;AN000;;FT. return CPSW state
 119         IRET                            ;AN000;
 120 CPSWset:                                ;AN000;
 121         CMP     AL,4                     ;AN000;;FT. set CPSW state ?
 122         JA      QueryDOSboot             ;AN000;;FT. check query dos boot drive
 123 ;       PUSH    AX                       ;AN000;;FT.
 124 ;       CallInstall NLSInstall,NLSFUNC,0 ;AN000;;FT. NLSFUNC installed ?
 125 ;       CMP     AL,0FFH                  ;AN000;;FT.
 126 ;       POP     AX                       ;AN000;;FT.
 127 ;       JNZ     BadVal                   ;AN000;;FT. not loaded, therefore ignore
 128 ;;;;    AND     DL,01H                   ;AN000;;FT. only 0 or 1
 129 ;;;;    MOV     [CPSWFLAG],DL            ;AN000;;FT. set the flag
 130 ;;;;    MOV     [CPSWSAVE],DL            ;AN000;;FT. save one copy
 131         IRET                             ;AN000;;FT.
 132 QueryDOSboot:                            ;AN000;
 133         CMP     AL,5                ;AN000;MS.
 134         JA      BadVal              ;AN000;MS.
 135         MOV     DL,[BOOTDRIVE]      ;AN000;;MS. put boot drive in DL
 136         IRET                        ;AN000;;MS.
 137
 138
 139 ;; DOS 4.00 File Tagging
 140
 141 EndProc $SET_CTRL_C_TRAPPING
 142
 143 BREAK <$Get_current_PDB -- Set/Get PDB value>
 144 ;----+----+----+----+----+----+----+----+----+----+----+----+----+----+----;
 145 ;            C  A  V  E  A  T     P  R  O  G  R  A  M  M  E  R             ;
 146 ;                                                                          ;
 147 ; The following two routines are dispatched to directly with ints disabled
 148 ; immediately after the int 21h entry.  no DIS state is set.
 149 ;
 150 ; $Set_current_PDB takes BX and sets it to be the current process
 151 ;   *** THIS FUNCTION CALL IS SUBJECT TO CHANGE!!! ***
 152 ;
 153         procedure   $SET_CURRENT_PDB,NEAR
 154         ASSUME  DS:NOTHING,ES:NOTHING,SS:NOTHING
 155         MOV     [CurrentPDB],BX
 156         IRET
 157 EndProc $SET_CURRENT_PDB
 158
 159 ;
 160 ; $get_current_PDB returns in BX the current process
 161 ;   *** THIS FUNCTION CALL IS SUBJECT TO CHANGE!!! ***
 162 ;
 163 procedure   $GET_CURRENT_PDB,NEAR
 164         ASSUME  DS:NOTHING,ES:NOTHING,SS:NOTHING
 165         MOV     BX,[CurrentPDB]
 166         IRET
 167 EndProc $GET_CURRENT_PDB
 168 ;            C  A  V  E  A  T     P  R  O  G  R  A  M  M  E  R             ;
 169 ;                                                                          ;
 170 ;----+----+----+----+----+----+----+----+----+----+----+----+----+----+----;
 171
 172 ;
 173 ; Sets the Printer Flag to whatever is in AL.
 174 ; NOTE: THIS PROCEDURE IS SUBJECT TO CHANGE!!!
 175 ;
 176 Procedure $Set_Printer_Flag
 177 ASSUME DS:NOTHING, ES:NOTHING, SS:NOTHING
 178         mov     [Printer_Flag],al
 179         IRET
 180 EndProc $Set_Printer_Flag
 181
 182         procedure   SYSTEM_CALL,NEAR
 183 ;
 184 ; The Quit entry point is where all INT 20h's come from.  These are old- style
 185 ; exit system calls.  The CS of the caller indicates which Process is dying.
 186 ; The error code is presumed to be 0.  We simulate an ABORT system call.
 187 ;
 188         entry   QUIT
 189         MOV     AH,0
 190         JMP     SHORT SAVREGS
 191 ;
 192 ; The system call in AH is out of the range that we know how to handle.  We
 193 ; arbitrarily set the contents of AL to 0 and IRET.  Note that we CANNOT set
 194 ; the carry flag to indicate an error as this may break some programs
 195 ; compatability.
 196 ;
 197 BADCALL:
 198         MOV     AL,0
 199         entry   IRETT
 200         IRET
 201 ;
 202 ; An alternative method of entering the system is to perform a CALL 5 in the
 203 ; program segment prefix with the contents of CL indicating what system call
 204 ; the user would like.  A subset of the possible system calls is allowed here;
 205 ; only the CPM-compatible calls may get dispatched.
 206 ;
 207         entry   CALL_ENTRY              ; System call entry point and dispatcher
 208         POP     AX                      ; IP from the long call at 5
 209         POP     AX                      ; Segment from the long call at 5
 210         POP     [User_SP]               ; IP from the CALL 5
 211 ;
 212 ; Re order the stack to simulate an interrupt 21.
 213 ;
 214         PUSHF                           ; Start re-ordering the stack
 215         CLI
 216         PUSH    AX                      ; Save segment
 217         PUSH    [User_SP]               ; Stack now ordered as if INT had been used
 218         CMP     CL,MAXCALL              ; This entry point doesn't get as many calls
 219         JA      BADCALL
 220         MOV     AH,CL
 221         JMP     SHORT SavRegs
 222 ;
 223 ; This is the normal INT 21 entry point.  We first perform a quick test to see
 224 ; if we need to perform expensive DOS-entry functions.  Certain system calls
 225 ; are done without interrupts being enabled.
 226 ;
 227
 228 entry   COMMAND                         ; Interrupt call entry point (INT 21H)
 229
 230         IF      NOT IBM
 231         CMP     AH,SET_OEM_HANDLER
 232         JB      NOTOEM
 233         JMP     $SET_OEM_HANDLER
 234 NOTOEM:
 235         ENDIF
 236
 237         CMP     AH,MAXCOM
 238         JA      BadCall
 239
 240 ;
 241 ; The following set of calls are issued by the server at *arbitrary* times
 242 ; and, therefore, must be executed on the user's entry stack and executed with
 243 ; interrupts off.
 244 ;
 245 SAVREGS:
 246         CMP     AH,GET_CURRENT_PDB
 247         JZ      $GET_CURRENT_PDB
 248         CMP     AH,GetCurrentPSP
 249         JZ      $GET_CURRENT_PDB
 250         CMP     AH,SET_CURRENT_PDB
 251         JZ      $SET_CURRENT_PDB
 252         CMP     AH,Set_CTRL_C_Trapping
 253         JNZ     chkprt
 254         JMP     $Set_CTRL_C_Trapping
 255 chkprt:
 256         CMP     AH,SET_PRINTER_FLAG
 257         JZ      $Set_Printer_Flag
 258 ;
 259 ; Preserve all user's registers on his own stack.
 260 ;
 261         CALL    save_world
 262         MOV     [SaveDS],DS
 263         MOV     [SaveBX],BX
 264         MOV     BX,CS
 265         MOV     DS,BX
 266         ASSUME  DS:DOSGROUP
 267         INC     [INDOS]                 ; Flag that we're in the DOS
 268         XOR     AX,AX
 269         MOV     [USER_ID],AX
 270         MOV     AX,CurrentPDB           ; current process
 271         MOV     [PROC_ID],AX            ; Assume local machine for the moment
 272 ;
 273 ; Provide one level of reentrancy for INT 24 recallability.
 274 ;
 275         MOV     AX,[user_SP]
 276         MOV     [NSP],AX
 277         MOV     AX,[user_SS]
 278         MOV     [NSS],AX
 279         POP     AX
 280         PUSH    AX
 281         MOV     [user_SP],SP
 282         MOV     [user_SS],SS
 283 ;
 284 ; save user stack in his area for later returns (possibly from EXEC)
 285 ;
 286         MOV     DS,[CurrentPDB]
 287 ASSUME  DS:NOTHING
 288         MOV     WORD PTR DS:[PDB_User_stack],SP
 289         MOV     WORD PTR DS:[PDB_User_stack+2],SS
 290
 291         MOV     fSharing,0              ; allow redirection
 292
 293         MOV     BX,CS                   ; no holes here.
 294         MOV     SS,BX
 295 ASSUME  SS:DOSGROUP
 296
 297 entry   REDISP
 298         MOV     SP,OFFSET DOSGROUP:AUXSTACK ; Enough stack for interrupts
 299         STI                             ; stack is in our space now...
 300  IF  DBCS                                       ;AN000;
 301         MOV     BH, BYTE PTR DS:[PDB_InterCon]  ;AN000;; get interim mode  2/13/KK
 302         MOV     SS:[InterCon], BH               ;AN000;; 2/13/KK
 303  ENDIF                                          ;AN000;
 304         MOV     BX,CS
 305         MOV     DS,BX
 306         DOSAssume   CS,<DS>,"MSCODE/ReDisp"
 307 ;; DOS 3.4 INIT
 308 ;       MOV     BL,[CPSWSAVE]           ;AN000;;FT. DOS 3.4
 309 ;       MOV     [CPSWFLAG],BL           ;AN000;;FT. DOS 3.4 in case ABORT
 310         MOV     [DISK_FULL],0           ;AN000;;MS. no disk full
 311         MOV     [EXTOPEN_ON],0          ;AN000;;EO. clear extended open flag
 312         MOV     [DOS34_FLAG],0          ;AN000;;MS. clear common flag
 313         MOV     [ACT_PAGE],-1           ;BN000;BL;AN000;;LB. invalidate active page
 314 ;; DOS 4.00 INIT
 315         XOR     BH,BH
 316         MOV     [CONSWAP],BH            ; random clean up of possibly mis-set flags
 317         MOV     [IDLEINT],1             ; presume that we can issue INT 28
 318         MOV     BYTE PTR [NoSetDir],BH  ; set directories on search
 319         MOV     BYTE PTR [FAILERR],BH   ; FAIL not in progress
 320         MOV     BL,AH
 321         SHL     BX,1                    ; 2 bytes per call in table
 322         CLD
 323 ;
 324 ; Since the DOS maintains mucho state information across system calls, we
 325 ; must be very careful about which stack we use.
 326 ;
 327 ; First, all abort operations must be on the disk stack.  THis is due to the
 328 ; fact that we may be hitting the disk (close operations, flushing) and may
 329 ; need to report an INT 24.
 330 ;
 331         OR      AH,AH
 332         JZ      DSKROUT                 ; ABORT
 333 ;
 334 ; Second, PRINT and PSPRINT and the server issue GetExtendedError calls at
 335 ; INT 28 and INT 24 time.  This call MUST, therefore, use the AUXSTACK.
 336 ;
 337         CMP     AH,GetExtendedError
 338         JZ      DISPCALL
 339 ;
 340 ; Old 1-12 system calls may be either on the IOSTACK (normal operation) or
 341 ; on the AUXSTACK (at INT 24 time).
 342 ;
 343         CMP     AH,12
 344         JA      DSKROUT
 345         CMP     [ERRORMODE],0           ; Are we in an INT 24?
 346         JNZ     DISPCALL                ; Stay on AUXSTACK if INT 24.
 347         MOV     SP,OFFSET DOSGROUP:IOSTACK
 348         JMP     SHORT DISPCALL
 349 ;
 350 ; We are on a system call that is classified as "the rest".  We place
 351 ; ourselves onto the DSKSTACK and away we go.  We know at this point:
 352 ;
 353 ;   o   An INT 24 cannot be in progress.  Therefore we reset errormode and
 354 ;       wperr
 355 ;   o   That there can be no critical sections in effect.  We signal the
 356 ;       server to remove all the resources.
 357 ;
 358 DSKROUT:
 359         MOV     [USER_IN_AX],AX         ; Remember what user is doing
 360         MOV     [EXTERR_LOCUS],errLOC_Unk ; Default
 361         MOV     [ERRORMODE],0           ; Cannot make non 1-12 calls in
 362         MOV     [WPERR],-1              ; error mode, so good place to make
 363 ;
 364 ; Release all resource information
 365 ;
 366         PUSH    AX
 367         MOV     AH,82h
 368         INT     int_IBM
 369         POP     AX
 370
 371 ;
 372 ; Since we are going to be running on the DSKStack and since INT 28 people
 373 ; will use the DSKStack, we must turn OFF the generation of INT 28's.
 374 ;
 375         MOV     IdleInt,0
 376         MOV     SP,OFFSET DOSGROUP:DSKSTACK
 377         TEST    [CNTCFLAG],-1
 378         JZ      DISPCALL                ; Extra ^C checking is disabled
 379         PUSH    AX
 380         invoke  DSKSTATCHK
 381         POP     AX
 382 DISPCALL:
 383         MOV     BX,CS:Dispatch[BX]
 384         XCHG    BX,SaveBX
 385         MOV     DS,SaveDS
 386
 387 IF      BUFFERFLAG
 388         mov     cs:[SETVECTFLAG], 0
 389         cmp     ah, 25h
 390         jne     saveuser
 391         cmp     ah, 35h
 392         jne     saveuser
 393         mov     cs:[SETVECTFLAG], 1
 394 saveuser:
 395         invoke  SAVE_USER_MAP               ;AN000;LB.  save EMS map
 396 ENDIF
 397
 398         ASSUME  DS:NOTHING
 399         CALL    SaveBX
 400
 401 IF      BUFFERFLAG
 402       invoke  RESTORE_USER_MAP            ;AN000;LB.  retsore EMS map
 403 ENDIF
 404
 405         entry   LEAVEDOS
 406 ASSUME  SS:NOTHING                      ; User routines may misbehave
 407         CLI
 408         DEC     [INDOS]
 409         MOV     SS,[user_SS]
 410         MOV     SP,[user_SP]
 411         MOV     BP,SP
 412         MOV     BYTE PTR [BP.user_AX],AL
 413         MOV     AX,[NSP]
 414         MOV     [user_SP],AX
 415         MOV     AX,[NSS]
 416         MOV     [user_SS],AX
 417         CALL    restore_world
 418         IRET
 419 EndProc SYSTEM_CALL
 420
 421 ;
 422 ; restore_world restores all registers ('cept SS:SP, CS:IP, flags) from
 423 ; the stack prior to giving the user control
 424 ;
 425         ASSUME  DS:NOTHING,ES:NOTHING,SS:NOTHING
 426         procedure   restore_world,NEAR
 427         POP     restore_tmp             ; POP     restore_tmp
 428         POP     AX                      ; PUSH    ES
 429         POP     BX                      ; PUSH    DS
 430         POP     CX                      ; PUSH    BP
 431         POP     DX                      ; PUSH    DI
 432         POP     SI                      ; PUSH    SI
 433         POP     DI                      ; PUSH    DX
 434         POP     BP                      ; PUSH    CX
 435         POP     DS                      ; PUSH    BX
 436         POP     ES                      ; PUSH    AX
 437         JMP     restore_tmp             ; PUSH    restore_tmp
 438 EndProc restore_world
 439
 440 ;
 441 ; save_world saves complete registers on the stack
 442 ;
 443         ASSUME  DS:NOTHING,ES:NOTHING,SS:NOTHING
 444         procedure   save_world,NEAR
 445         POP     restore_tmp
 446         PUSH    ES
 447         PUSH    DS
 448         PUSH    BP
 449         PUSH    DI
 450         PUSH    SI
 451         PUSH    DX
 452         PUSH    CX
 453         PUSH    BX
 454         PUSH    AX
 455         JMP     restore_tmp             ; PUSH    restore_tmp
 456 EndProc save_world
 457
 458 IF BUFFERFLAG
 459
 460 Break   <SAVE_USER_MAP - save map >                                                     ;AN000;
 461 ; Inputs:                                                                       ;AN000;
 462 ;       none                                                                    ;AN000;
 463 ; Function:                                                                     ;AN000;
 464 ;       save map                                                                ;AN000;
 465 ; Outputs:                                                                      ;AN000;
 466 ;       none                                                                    ;AN000;
 467 ; No other registers altered                                                    ;AN000;
 468                                                                                 ;AN000;
 469 Procedure   SAVE_USER_MAP,NEAR                                                   ;AN000;
 470         ASSUME  DS:NOTHING,ES:NOTHING                                           ;AN000;
 471                                                                                 ;AN000;
 472         CMP     cs:[BUF_EMS_MODE],-1      ;LB. EMS support                      ;AN000;
 473         JZ      No_user_save              ;LB. no                               ;AN000;
 474         CMP     cs:[SETVECTFLAG], 1
 475         jz      No_user_save
 476 ;       MOV     [ACT_PAGE],-1             ;LB. invalidate active page           ;AN000;
 477 ;       MOV     WORD PTR [LASTBUFFER],-1  ;LB.  and last buffer pointer         ;AN000;
 478         PUSH    AX                        ;LB. save regs                        ;AN000;
 479         PUSH    DS                        ;LB. save regs                        ;AN000;
 480         PUSH    ES                        ;LB.                                  ;AN000;
 481         PUSH    SI                        ;LB.                                  ;AN000;
 482         PUSH    DI                        ;LB.                                  ;AN000;
 483         MOV     SI,OFFSET DOSGROUP:BUF_EMS_SEG_CNT     ;LB.                     ;AN000;
 484         MOV     DI,OFFSET DOSGROUP:BUF_EMS_MAP_USER     ;LB.                    ;AN000;
 485
 486         PUSH    CS
 487         POP     ES
 488         PUSH    CS                        ;LB. ds:si -> ems seg cnt             ;AN000;
 489         POP     DS                        ;LB.                                  ;AN000;
 490
 491         MOV     AX,4F00H                  ;LB. save map                         ;AN000;
 492         EnterCrit  critDisk               ;LB. enter critical section           ;AN000;
 493         INT     67H                       ;LB.                                  ;AN000;
 494         LeaveCrit  critDisk               ;LB. leave critical section           ;AN000;
 495         POP     DI                        ;LB.                                  ;AN000;
 496         POP     SI                        ;LB. restore regs                     ;AN000;
 497         POP     ES                        ;LB.                                  ;AN000;
 498         POP     DS                        ;LB.                                  ;AN000;
 499         POP     AX                        ;LB. restore                          ;AN000;
 500 No_user_save:                                                                    ;AN000;
 501         return                                                                  ;AN000;
 502 EndProc SAVE_USER_MAP                                                            ;AN000;
 503                                                                                 ;AN000;
 504
 505 Break   <RESTORE_USER_MAP- retore map >                                         ;AN000;
 506 ; Inputs:                                                                       ;AN000;
 507 ;       none                                                                    ;AN000;
 508 ; Function:                                                                     ;AN000;
 509 ;       restore_map                                                             ;AN000;
 510 ; Outputs:                                                                      ;AN000;
 511 ;       none                                                                    ;AN000;
 512 ; No other registers altered                                                    ;AN000;
 513                                                                                 ;AN000;
 514 Procedure   RESTORE_USER_MAP,NEAR                                                        ;AN000;
 515         ASSUME  DS:NOTHING,ES:NOTHING                                           ;AN000;
 516
 517         CMP     cs:[BUF_EMS_MODE],-1      ;LB. EMS support                      ;AN000;
 518         JZ      No_user_restore           ;LB. no                               ;AN000;
 519         CMP     cs:[SETVECTFLAG], 1
 520         jz      No_user_restore
 521         PUSH    AX                        ;LB. save regs                        ;AN000;
 522         PUSH    DS                        ;LB. save regs                        ;AN000;
 523         PUSH    SI                        ;LB.                                  ;AN000;
 524         MOV     SI,OFFSET DOSGROUP:BUF_EMS_MAP_USER     ;LB.                    ;AN000;
 525
 526         PUSH    CS
 527         POP     DS
 528
 529         MOV     AX,4F01H                  ;LB. restore map                      ;AN000;
 530         EnterCrit  critDisk               ;LB. enter critical section           ;AN000;
 531         INT     67H                       ;LB.                                  ;AN000;
 532         LeaveCrit  critDisk               ;LB. leave critical section           ;AN000;
 533         POP     SI                        ;LB. restore regs                     ;AN000;
 534         POP     DS                        ;LB.                                  ;AN000;
 535         POP     AX                        ;LB.                                  ;AN000;
 536 No_user_restore:                                                                         ;AN000;
 537         return                                                                  ;AN000;
 538 EndProc RESTORE_USER_MAP
 539
 540 ENDIF
 541
 542 ;
 543 ; get_user_stack returns the user's stack (and hence registers) in DS:SI
 544 ;
 545         procedure   get_user_stack,NEAR
 546         LDS     SI,DWORD PTR [user_SP]
 547         return
 548 EndProc get_user_stack
 549
 550         IF      NOT IBM
 551 BREAK <Set_OEM_Handler -- Set OEM sys call address and handle OEM Calls
 552
 553 $SET_OEM_HANDLER:
 554 ASSUME  DS:NOTHING,ES:NOTHING,SS:NOTHING
 555
 556 ; Inputs:
 557 ;       User registers, User Stack, INTS disabled
 558 ;       If CALL F8, DS:DX is new handler address
 559 ; Function:
 560 ;       Process OEM INT 21 extensions
 561 ; Outputs:
 562 ;       Jumps to OEM_HANDLER if appropriate
 563
 564         JNE     DO_OEM_FUNC             ; If above F8 try to jump to handler
 565         MOV     WORD PTR [OEM_HANDLER],DX   ; Set Handler
 566         MOV     WORD PTR [OEM_HANDLER+2],DS
 567         IRET                            ; Quick return, Have altered no registers
 568
 569 DO_OEM_FUNC:
 570         CMP     WORD PTR [OEM_HANDLER],-1
 571         JNZ     OEM_JMP
 572         JMP     BADCALL                 ; Handler not initialized
 573
 574 OEM_JMP:
 575         JMP     [OEM_HANDLER]
 576         ENDIF
 577
 578
 579 CODE    ENDS