subsystems/mvdm/dos/command.S

   1 /*
   2  * PROJECT:     ReactOS Virtual DOS Machine
   3  * LICENSE:     GPL-2.0+ (https://spdx.org/licenses/GPL-2.0+)
   4  * PURPOSE:     DOS32 command.com for NTVDM
   5  * COPYRIGHT:   Copyright 2015-2018 Hermes Belusca-Maito
   6  */
   7
   8 /* INCLUDES *******************************************************************/
   9
  10 #include <asm.inc>
  11 #include "asmxtras.inc"
  12 #include <isvbop.inc>
  13
  14 #define NDEBUG
  15
  16 /* DEFINES ********************************************************************/
  17
  18 #define MAX_PATH            260
  19 #define DOS_CMDLINE_LENGTH  127
  20
  21 #define DOS_VERSION     HEX(0005)   // MAKEWORD(5, 00)
  22 #define NTDOS_VERSION   HEX(3205)   // MAKEWORD(5, 50)
  23
  24 #define SYSTEM_PSP      HEX(08)
  25
  26 #define BOP                 .byte HEX(C4), HEX(C4),
  27 // #define BOP_START_DOS       HEX(2C)
  28 #define BOP_CMD             HEX(54)
  29
  30 /**** PSP MEMBERS ****/
  31 #define PSP_VAR(x)  es:[x]
  32 #define PSP         HEX(0000)
  33 #define ParentPsp   HEX(0016)   // word
  34 #define EnvBlock    HEX(002C)   // word
  35 #define CmdLineLen  HEX(0080)   // byte
  36 #define CmdLineStr  HEX(0081)   // byte[DOS_CMDLINE_LENGTH]
  37
  38 /**** DATA stored inside the stack ****/
  39 #define CmdLine BaseStack   // Command line for the program to be started
  40 #define PgmName [CmdLine + (1 + DOS_CMDLINE_LENGTH)]
  41
  42
  43 // WARNING! Using the VAL(x) macro doesn't work with GCC/GAS (because it inserts
  44 // a spurious space in front of the parameter when the macro is expanded).
  45 // So that: 'VAL(foo)' is expanded to: '\ foo', instead of '\foo' as one would expect.
  46
  47 /* NEXT_CMD structure */
  48 STRUCT(NEXT_CMD, 2)
  49     FIELD_DECL(EnvBlockSeg, word, 0)
  50     FIELD_DECL(EnvBlockLen, word, 0)
  51     FIELD_DECL(CurDrive   , word, 0)
  52     FIELD_DECL(NumDrives  , word, 1)
  53     FIELD_DECL(CmdLineSeg , word, 0)
  54     FIELD_DECL(CmdLineOff , word, 0)
  55     FIELD_DECL(Unknown0   , word, 2)
  56     FIELD_DECL(ExitCode   , word, 3)
  57     FIELD_DECL(Unknown1   , word, 4)
  58     FIELD_DECL(Unknown2   , long, 5)
  59     FIELD_DECL(CodePage   , word, 6)
  60     FIELD_DECL(Unknown3   , word, 7)
  61     FIELD_DECL(Unknown4   , word, 8)
  62     FIELD_DECL(AppNameSeg , word, 0)
  63     FIELD_DECL(AppNameOff , word, 0)
  64     FIELD_DECL(AppNameLen , word, 0)
  65     FIELD_DECL(Flags      , word, 0)
  66 ENDS(NEXT_CMD)
  67
  68 /* DOS_EXEC_PARAM_BLOCK structure */
  69 STRUCT(DOS_EXEC_PARAM_BLOCK, 2)
  70     FIELD_DECL(EnvSeg, word, 0)    // Use parent's environment (ours)
  71     FIELD_DECL(CmdLineOff, word, OFF(CmdLine))
  72     FIELD_DECL(CmdLineSeg, word, 0)
  73     FIELD_DECL(Fcb1Off, word, OFF(Fcb1))
  74     FIELD_DECL(Fcb1Seg, word, 0)
  75     FIELD_DECL(Fcb2Off, word, OFF(Fcb2))
  76     FIELD_DECL(Fcb2Seg, word, 0)
  77 ENDS(DOS_EXEC_PARAM_BLOCK)
  78
  79
  80
  81 /* RESIDENT CODE AND DATA *****************************************************/
  82
  83 .code16
  84 // .org HEX(0100)
  85 ASSUME CS:.text, DS:.text, ES:.text
  86
  87
  88 /* CODE *******************************/
  89
  90 EntryPoint:
  91     jmp Main
  92 .align 2
  93
  94 ResidentMain:
  95     /*
  96      * Relocate our stack.
  97      * Our local stack is big enough for holding the command line and the path
  98      * to the executable to start, plus a full DOS_REGISTER_STATE and for one pusha 16-bit.
  99      *
 100      * FIXME: enlarge it for pushing the needed Load&Exec data.
 101      */
 102     cli
 103     mov ax, ds
 104     mov ss, ax
 105     mov bp, offset BaseStack
 106     lea sp, [bp + (1 + DOS_CMDLINE_LENGTH) + MAX_PATH + 255]
 107     sti
 108
 109     /* Resize ourselves */
 110     mov bx, sp                  // Get size in bytes...
 111 //  sub bx, offset PSP_VAR(PSP)
 112     add bx, HEX(0F)             // (for rounding to the next paragraph)
 113     shr bx, 4                   // ... then the number of paragraphs
 114     mov ah, HEX(4A)
 115     int HEX(21)
 116
 117     /* Check whether we need to start the 32-bit command interpreter */
 118     BOP BOP_CMD, HEX(10)        // Check whether we were started from a new console (SessionId != 0)
 119     test al, al                 // and we are not reentering (32-bit process starting a 16-bit process).
 120     jz Run
 121     cmp word ptr OldParentPsp, SYSTEM_PSP   // Check whether our parent is SYSTEM
 122     je Run
 123
 124 #ifndef NDEBUG
 125 /********************************/
 126     mov dx, offset Msg1
 127     mov ah, HEX(09)
 128     int HEX(21)
 129 /********************************/
 130 #endif
 131
 132     BOP BOP_CMD, HEX(0A)        // Start 32-bit COMSPEC
 133     jnc Quit
 134
 135     /* Loop for new commands to run */
 136 Run:
 137     /* Initialize the NextCmd structure */
 138     mov word ptr FIELD(NextCmd, EnvBlockSeg), ds
 139     mov word ptr FIELD(NextCmd, EnvBlockLen), 0 // FIXME
 140     mov word ptr FIELD(NextCmd, CmdLineSeg), ds
 141     mov word ptr FIELD(NextCmd, CmdLineOff), offset CmdLine
 142     mov word ptr FIELD(NextCmd, AppNameSeg), ds
 143     mov word ptr FIELD(NextCmd, AppNameOff), offset PgmName
 144
 145     /* Wait for the next command */
 146 #ifndef NDEBUG
 147 /********************************/
 148     mov dx, offset Msg2
 149     mov ah, HEX(09)
 150     int HEX(21)
 151 /********************************/
 152 #endif
 153
 154     // FIXME: Initialize memory with structure for holding CmdLine etc...
 155 //  mov ds, seg NextCmd
 156     mov dx, offset NextCmd
 157     BOP BOP_CMD, HEX(01)
 158     /* Quit if we shell-out */
 159     jc Quit
 160
 161     /* Initialize the DosLoadExec structure */
 162 //  mov word ptr FIELD(DosLoadExec, EnvSeg), 0
 163     mov word ptr FIELD(DosLoadExec, CmdLineSeg), ds
 164     mov word ptr FIELD(DosLoadExec, Fcb1Seg), ds
 165     mov word ptr FIELD(DosLoadExec, Fcb2Seg), ds
 166
 167     /* Run the command */
 168     mov ds, word ptr FIELD(NextCmd, AppNameSeg)
 169     mov dx, word ptr FIELD(NextCmd, AppNameOff)
 170 //  mov es, seg DosLoadExec
 171     mov bx, offset DosLoadExec
 172     pusha // Save the registers in case stuff go wrong
 173     // FIXME: Save also SS !!
 174     mov ax, HEX(4B00)
 175     int HEX(21)
 176     popa  // Restore the registers
 177     // FIXME: Restore also SS !!
 178
 179     /* Retrieve and set its exit code. Also detect whether
 180      * we need to continue or whether we need to quit. */
 181     // xor ax, ax
 182     // mov ah, HEX(4D)
 183     mov ax, HEX(4D00)
 184     int HEX(21)
 185     /* Send exit code back to NTVDM */
 186     mov dx, ax
 187     BOP BOP_CMD, HEX(0B)
 188
 189     /* If we don't shell-out, go and get a new app! */
 190     jc Run
 191
 192     mov al, HEX(00) // ERROR_SUCCESS
 193
 194 Quit:
 195     mov bl, al // Save AL in BL
 196
 197 #ifndef NDEBUG
 198 /********************************/
 199     cmp al, HEX(0A)
 200     jne XXXX
 201     mov dx, offset Msg3
 202     mov ah, HEX(09)
 203     int HEX(21)
 204 XXXX:
 205 /********************************/
 206 #endif
 207
 208 #ifndef NDEBUG
 209     /* Say bye-bye */
 210 //  mov ds, seg QuitMsg
 211     mov dx, offset QuitMsg
 212     mov ah, HEX(09)
 213     int HEX(21)
 214 #endif
 215
 216     /* Restore our old parent PSP */
 217     mov ax, word ptr OldParentPsp
 218     mov PSP_VAR(ParentPsp), ax
 219
 220     mov al, bl // Restore AL from BL
 221
 222 Exit:
 223     /* Return to caller (with possible error code in AL) */
 224     mov ah, HEX(4C)
 225     int HEX(21)
 226     int 3
 227
 228     /* Does not return */
 229
 230 /* DATA *******************************/
 231
 232 #ifndef NDEBUG
 233 QuitMsg:
 234     .ascii "Bye bye!", CR, LF, "$"
 235
 236 /********************************/
 237 Msg1: .ascii "Starting COMSPEC...", CR, LF, "$"
 238 Msg2: .ascii "Waiting for new command...", CR, LF, "$"
 239 Msg3: .ascii "Bad environment!", CR, LF, "$"
 240 /********************************/
 241 #endif
 242
 243 OldParentPsp:   .word 0
 244 CurrentPsp:     .word 0
 245
 246 // BOP_CMD, HEX(01) "Get a new app to start" structure
 247 VAR_STRUCT(NextCmd, NEXT_CMD)
 248
 249 // DOS INT 21h, AH=4Bh "Load and Execute" structure
 250 VAR_STRUCT(DosLoadExec, DOS_EXEC_PARAM_BLOCK)
 251
 252 // Blank FCB blocks needed for DOS INT 21h, AH=4Bh
 253 Fcb1:
 254     .byte 0
 255     .space 11, ' '
 256     .space 25, 0
 257 Fcb2:
 258     .byte 0
 259     .space 11, ' '
 260     .space 25, 0
 261
 262 // The stack resides at the end of the resident code+data
 263 // and it overwrites the transient part.
 264 BaseStack:
 265
 266
 267 /* TRANSIENT CODE AND DATA ****************************************************/
 268
 269 /* DATA *******************************/
 270
 271 #ifndef NDEBUG
 272 WelcomeMsg:
 273     .ascii "ReactOS DOS32 Command", CR, LF, \
 274            "Copyright (C) ReactOS Team 2015" , CR, LF, "$"
 275 #endif
 276
 277 VerErrMsg:
 278     .ascii "Incorrect DOS version", CR, LF, "$"
 279
 280 /* CODE *******************************/
 281
 282 .align 2
 283
 284 Main:
 285     /* Setup segment registers */
 286     mov ax, cs  // cs contains the PSP segment on entry
 287     mov ds, ax
 288     mov es, ax
 289 //  mov fs, ax
 290 //  mov gs, ax
 291     /* Stack is set to cs:FFFE down to cs:09xx by the DOS.
 292      * We will need to relocate it before we resize ourselves. */
 293
 294     /*
 295      * Verify DOS version:
 296      * - Check whether we are on DOS 5+ (subject to SETVER);
 297      * - If so, check our real DOS version and see
 298      *   whether we are running on NTVDM (version 5.50).
 299      */
 300     mov ax, HEX(3000)
 301     int HEX(21)
 302     cmp ax, DOS_VERSION     // AH:AL contains minor:major version number
 303     jne VerErr
 304
 305     mov ax, HEX(3306)
 306     int HEX(21)
 307     cmp bx, NTDOS_VERSION   // BH:BL contains minor:major version number
 308     je Continue
 309
 310 VerErr:
 311     /* Display wrong version error message and exit */
 312 //  mov ds, seg VerErrMsg
 313     mov dx, offset VerErrMsg
 314     mov ah, HEX(09)
 315     int HEX(21)
 316     jmp Exit
 317
 318 Continue:
 319     /* Save our PSP */
 320     mov word ptr CurrentPsp, cs
 321 /*
 322  * The DOS way:
 323  *
 324  * mov ah, HEX(51) // DOS 2+ internal, or HEX(62) since DOS 3+
 325  * int HEX(21)
 326  * mov word ptr CurrentPsp, bx
 327  */
 328
 329     /* Save our old parent PSP */
 330     mov ax, PSP_VAR(ParentPsp)
 331     mov word ptr OldParentPsp, ax
 332
 333     /* Give us shell privileges: set our PSP as our new parent */
 334     mov ax, word ptr CurrentPsp
 335     mov PSP_VAR(ParentPsp), ax
 336
 337 #ifndef NDEBUG
 338     /* Say hello */
 339 //  mov ds, seg WelcomeMsg
 340     mov dx, offset WelcomeMsg
 341     mov ah, HEX(09)
 342     int HEX(21)
 343 #endif
 344
 345     /* Jump to resident code */
 346     jmp ResidentMain
 347
 348 .endcode16
 349 END
 350
 351 /* EOF */