| 21,8 → 21,10 |
|---|
| SIG3 dw 0x2017 ; +4 |
| SIG4 dw 0x2019 ; +6 |
| |
| ; environment segment - this is updated by SvarCOM at init time |
| ENVSEG dw 0 ; +8 |
| ; offset where a program name to be executed is awaiting (0=none) |
| ; this is set by SvarCOM, after it presets the ExecParamRec struct and |
| ; stores the command to be executed somewhere within rmod's segment. |
| EXECPROG dw 0 ; +8 |
| |
| ; exit code of last application |
| LEXCODE dw 0 ; +0Ah |
| 35,8 → 37,16 |
|---|
| ; drive. drive is patched by the transient part of COMMAND.COM |
| COMSPECBOOT db "@:\COMMAND.COM", 0 ; +0Eh |
| |
| skipsig: ; +1Dh |
| ; ExecParamRec used by INT 21h, AX=4b00 (load and execute program), 14 bytes: |
| ; offset size content |
| ; +0 2 segment of environment for child (0 = current) |
| ; +2 4 address of command line to place at PSP:0080 |
| ; +6 4 address of an FCB to be placed at PSP:005c |
| ; +0Ah 4 address of an FCB to be placed at PSP:006c |
| EXEC_PARAM_REC db 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 ; +1Dh |
| |
| skipsig: ; +2Bh |
| |
| ; set up CS=DS=SS and point SP to my private stack buffer |
| mov ax, cs |
| mov ds, ax |
| 44,6 → 54,21 |
|---|
| mov ss, ax |
| mov sp, STACKPTR |
| |
| ; should I executed command.com or a pre-set application? |
| or [EXECPROG], byte 0 |
| jz EXEC_COMMAND_COM |
| |
| ; TODO: most probably I should call the DOS SetPSP function here |
| |
| ; exec an application preset (by SvarCOM) in the ExecParamRec |
| mov [EXECPROG], byte 0 ; make sure to spawn command.com after app exits |
| mov ax, 0x4B00 ; DOS 2+ - load & execute program |
| mov dx, [EXECPROG] ; DS:DX - ASCIZ program name (preset at PSP[already) |
| mov bx, EXEC_PARAM_REC ; ES:BX - parameter block pointer |
| int 0x21 |
| |
| EXEC_COMMAND_COM: |
| |
| ; collect the exit code of previous application |
| mov ah, 0x4D |
| int 0x21 |
| 50,6 → 75,13 |
|---|
| xor ah, ah ; clear out termination status, I only want the exit code |
| mov [LEXCODE], ax |
| |
| ; zero out the exec param block (14 bytes) |
| mov al, 0 ; byte to write |
| mov cx, 14 ; how many times |
| mov di, EXEC_PARAM_REC ; ES:DI = destination |
| cld ; stosb must move forward |
| rep stosb ; repeat cx times |
| |
| ; preset the default COMSPEC pointer to ES:DX (ES is already set to DS) |
| mov dx, COMSPECBOOT |
| |
| 101,17 → 133,10 |
|---|
| ; back to program start |
| jmp skipsig |
| |
| ; command.com tail arguments, in PSP format (length byte followed by arg) |
| CMDTAIL db 0 |
| ; command.com tail arguments, in PSP format: length byte followed by args and |
| ; terminated with \r) |
| CMDTAIL db 0x00, 0x0D |
| |
| ; ExecParamRec used by INT 21h, AX=4b00 (load and execute program), 14 bytes: |
| ; offset size content |
| ; +0 2 segment of environment for child (0 = current) |
| ; +2 4 address of command line to place at PSP:0080 |
| ; +6 4 address of an FCB to be placed at PSP:005c |
| ; +0Ah 4 address of an FCB to be placed at PSP:006c |
| EXEC_PARAM_REC db 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 |
| |
| ERRLOAD db "ERR x, FAILED TO LOAD COMMAND.COM", 13, 10, '$' |
| |
| ; DOS int 21h functions that I use require at least 32 bytes of stack, here I |