| Line 24... |
Line 24... |
| 24 |
; DOS int 21h functions that I use require at least 40 bytes of stack under
|
24 |
; DOS int 21h functions that I use require at least 40 bytes of stack under
|
| 25 |
; DOS-C (FreeDOS) kernel, so here I reserve 64 bytes juste to be sure
|
25 |
; DOS-C (FreeDOS) kernel, so here I reserve 64 bytes juste to be sure
|
| 26 |
STACKBUF db "XXX SVARCOM RMOD BY MATEUSZ VISTE XXXXXXXXXXXXXXXXXXXXXXXXXXXX"
|
26 |
STACKBUF db "XXX SVARCOM RMOD BY MATEUSZ VISTE XXXXXXXXXXXXXXXXXXXXXXXXXXXX"
|
| 27 |
STACKPTR dw 0
|
27 |
STACKPTR dw 0
|
| 28 |
|
28 |
|
| 29 |
; exit code of last application
|
- |
|
| 30 |
LEXCODE dw 0 ; +4Ah
|
- |
|
| 31 |
|
- |
|
| 32 |
; offset of the COMSPEC variable in the environment block, 0 means "use
|
29 |
; offset of the COMSPEC variable in the environment block, 0 means "use
|
| 33 |
; boot drive". this value is patched by the transient part of COMMAND.COM
|
30 |
; boot drive". this value is patched by the transient part of COMMAND.COM
|
| 34 |
COMSPECPTR dw 0 ; +4Ch
|
31 |
COMSPECPTR dw 0 ; +4Ah
|
| 35 |
|
32 |
|
| 36 |
; fallback COMSPEC string used if no COMPSEC is present in the environment
|
33 |
; fallback COMSPEC string used if no COMPSEC is present in the environment
|
| 37 |
; drive. drive is patched by the transient part of COMMAND.COM
|
34 |
; drive. drive is patched by the transient part of COMMAND.COM
|
| 38 |
COMSPECBOOT db "@:\COMMAND.COM", 0 ; +4Eh
|
35 |
COMSPECBOOT db "@:\COMMAND.COM", 0 ; +4Ch
|
| - |
|
36 |
|
| - |
|
37 |
; exit code of last application
|
| - |
|
38 |
LEXCODE db 0 ; +5Bh
|
| 39 |
|
39 |
|
| 40 |
; ExecParamRec used by INT 21h, AX=4b00 (load and execute program), 14 bytes:
|
40 |
; ExecParamRec used by INT 21h, AX=4b00 (load and execute program), 14 bytes:
|
| 41 |
; offset size content
|
41 |
; offset size content
|
| 42 |
; +0 2 segment of environment for child (0 = current)
|
42 |
; +0 2 segment of environment for child (0 = current)
|
| 43 |
; +2 4 address of command line to place at PSP:0080
|
43 |
; +2 4 address of command line to place at PSP:0080
|
| 44 |
; +6 4 address of an FCB to be placed at PSP:005c
|
44 |
; +6 4 address of an FCB to be placed at PSP:005c
|
| 45 |
; +0Ah 4 address of an FCB to be placed at PSP:006c
|
45 |
; +0Ah 4 address of an FCB to be placed at PSP:006c
|
| 46 |
EXEC_PARAM_REC db 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 ; +5Dh
|
46 |
EXEC_PARAM_REC db 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 ; +5Ch
|
| 47 |
|
47 |
|
| 48 |
; Program to execute, preset by SvarCOM (128 bytes, ASCIIZ) ; +6Bh
|
48 |
; Program to execute, preset by SvarCOM (128 bytes, ASCIIZ) ; +6Ah
|
| 49 |
EXECPROG dd 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
|
49 |
EXECPROG dd 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
|
| 50 |
|
50 |
|
| 51 |
; offset within EXECPROG for out and in filenames in case stdin or stdout
|
51 |
; offset within EXECPROG for out and in filenames in case stdin or stdout
|
| 52 |
; needs to be redirected (0xffff=no redirection)
|
52 |
; needs to be redirected (0xffff=no redirection)
|
| 53 |
REDIR_OUTFIL dw 0xffff ; +EBh
|
53 |
REDIR_OUTFIL dw 0xffff ; +EAh
|
| 54 |
REDIR_INFIL dw 0xffff ; +EDh
|
54 |
REDIR_INFIL dw 0xffff ; +ECh
|
| 55 |
REDIR_OUTAPPEND dw 0 ; +EFh
|
55 |
REDIR_OUTAPPEND dw 0 ; +EEh
|
| 56 |
|
56 |
|
| 57 |
skipsig: ; +F1h
|
57 |
skipsig: ; +F0h
|
| 58 |
|
58 |
|
| 59 |
; set up CS=DS=SS and point SP to my private stack buffer
|
59 |
; set up CS=DS=SS and point SP to my private stack buffer
|
| 60 |
mov ax, cs
|
60 |
mov ax, cs
|
| 61 |
mov ds, ax
|
61 |
mov ds, ax
|
| 62 |
mov es, ax
|
62 |
mov es, ax
|
| Line 91... |
Line 91... |
| 91 |
EXEC_COMMAND_COM:
|
91 |
EXEC_COMMAND_COM:
|
| 92 |
|
92 |
|
| 93 |
; collect the exit code of previous application
|
93 |
; collect the exit code of previous application
|
| 94 |
mov ah, 0x4D
|
94 |
mov ah, 0x4D
|
| 95 |
int 0x21
|
95 |
int 0x21
|
| 96 |
xor ah, ah ; clear out termination status, I only want the exit code
|
- |
|
| 97 |
mov [LEXCODE], ax
|
96 |
mov [LEXCODE], al
|
| 98 |
|
97 |
|
| 99 |
; zero out the exec param block (14 bytes)
|
98 |
; zero out the exec param block (14 bytes)
|
| 100 |
mov al, 0 ; byte to write
|
99 |
mov al, 0 ; byte to write
|
| 101 |
mov cx, 14 ; how many times
|
100 |
mov cx, 14 ; how many times
|
| 102 |
mov di, EXEC_PARAM_REC ; ES:DI = destination
|
101 |
mov di, EXEC_PARAM_REC ; ES:DI = destination
|