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 |