WebSVN – SvarDOS – Diff – /svarcom/rmod.asm


;
; rmod - resident module of the SvarCOM command interpreter
;
; Copyright (C) 2021 Mateusz Viste
; MIT license
;
; this is installed in memory by the transient part of SvarCOM. it has only
; two jobs: providing a resident buffer for command history, environment, etc
; and respawning COMMAND.COM whenever necessary.
 
CPU 8086
org 0h           ; this is meant to be executed without a PSP
 
section .text    ; all goes into code segment
 
                 ; offset
SIG1 dw 0x1983   ;  +0
SIG2 dw 0x1985   ;  +2
SIG3 dw 0x2017   ;  +4
SIG4 dw 0x2019   ;  +6
 
; environment segment - this is updated by SvarCOM at init time
ENVSEG   dw 0    ;  +8
 
; exit code of last application
LEXCODE  dw 0    ; +0Ah
 
; input buffer used for the "previous command" history
BUF000 db 128, 0 ; +0Ch
BUF064 db "0123456789ABCDEF0123456789ABCDEF0123456789ABCDEF0123456789ABCDEF"
BUF128 db "0123456789ABCDEF0123456789ABCDEF0123456789ABCDEF0123456789ABCDEF"
 
 
skipsig:         ; +8Eh
 
; set up CS=DS=SS and point SP to my private stack buffer
mov ax, cs
mov ds, ax
mov es, ax
mov ss, ax
mov sp, STACKPTR
 
; collect the exit code of previous application
mov ah, 0x4D
int 0x21
xor ah, ah          ; clear out termination status, I only want the exit code
mov [LEXCODE], ax
 
; prepare the exec param block
mov ax, [ENVSEG]
mov [EXEC_PARAM_REC], ax
mov ax, COMSPEC
mov [EXEC_PARAM_REC+2], ax
mov [EXEC_PARAM_REC+4], ds
 
; execute command.com
mov ax, 0x4B00         ; DOS 2+ - load & execute program
mov dx, COMSPEC        ; DS:DX  - ASCIZ program name TODO: use real COMSPEC...
mov bx, EXEC_PARAM_REC ; ES:BX  - parameter block pointer
int 0x21
 
; if all went well, jump back to start
jnc skipsig
 
; update error string so it contains the error number
add al, '0'
mov [ERRLOAD + 4], al
 
; display error message (with trailing COMSPEC)
mov ah, 0x09
mov dx, ERRLOAD
mov [COMSPCZ], byte '$' ; patch comspec terminator to be $
int 0x21
mov [COMSPCZ], byte 0   ; restore initial (NULL) compsec terminator
 
; wait for keypress
mov ah, 0x08
int 0x21
 
; back to program start
jmp skipsig
 
; 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 FROM:", 13, 10
 
COMSPEC db "C:\SVN\SVARDOS\SVARCOM\COMMAND.COM"
COMSPCZ db 0
 
; FreeDOS int 21h functions that I use require at least 32 bytes of stack,
; here I allocate 64 bytes to be sure
STACKBUF db "0123456789ABCDEF0123456789ABCDEF0123456789ABCDEF0123456789ABCDEF"
STACKPTR db "xx"
 

Rev 350	Rev 353
1	`;`	1	`;`
2	`; rmod - resident module of the SvarCOM command interpreter`	2	`; rmod - resident module of the SvarCOM command interpreter`
3	`;`	3	`;`
4	`; Copyright (C) 2021 Mateusz Viste`	4	`; Copyright (C) 2021 Mateusz Viste`
5	`; MIT license`	5	`; MIT license`
6	`;`	6	`;`
7	`; this is installed in memory by the transient part of SvarCOM. it has only`	7	`; this is installed in memory by the transient part of SvarCOM. it has only`
8	`; two jobs: providing a resident buffer for command history, environment, etc`	8	`; two jobs: providing a resident buffer for command history, environment, etc`
9	`; and respawning COMMAND.COM whenever necessary.`	9	`; and respawning COMMAND.COM whenever necessary.`
10		10
11	`CPU 8086`	11	`CPU 8086`
12	`org 0h ; this is meant to be executed without a PSP`	12	`org 0h ; this is meant to be executed without a PSP`
13		13
14	`section .text ; all goes into code segment`	14	`section .text ; all goes into code segment`
15		15
16	`; offset`	16	`; offset`
17	`SIG1 dw 0x1983 ; +0`	17	`SIG1 dw 0x1983 ; +0`
18	`SIG2 dw 0x1985 ; +2`	18	`SIG2 dw 0x1985 ; +2`
19	`SIG3 dw 0x2017 ; +4`	19	`SIG3 dw 0x2017 ; +4`
20	`SIG4 dw 0x2019 ; +6`	20	`SIG4 dw 0x2019 ; +6`
21		21
22	`; environment segment - this is updated by SvarCOM at init time`	22	`; environment segment - this is updated by SvarCOM at init time`
23	`ENVSEG dw 0 ; +8`	23	`ENVSEG dw 0 ; +8`
24		24
-		25	`; exit code of last application`
-		26	`LEXCODE dw 0 ; +0Ah`
-		27
25	`; input buffer used for the "previous command" history`	28	`; input buffer used for the "previous command" history`
26	`BUF000 db 128, 0 ; +0Ah`	29	`BUF000 db 128, 0 ; +0Ch`
27	`BUF064 db "0123456789ABCDEF0123456789ABCDEF0123456789ABCDEF0123456789ABCDEF"`	30	`BUF064 db "0123456789ABCDEF0123456789ABCDEF0123456789ABCDEF0123456789ABCDEF"`
28	`BUF128 db "0123456789ABCDEF0123456789ABCDEF0123456789ABCDEF0123456789ABCDEF"`	31	`BUF128 db "0123456789ABCDEF0123456789ABCDEF0123456789ABCDEF0123456789ABCDEF"`
29		32
30		33
31	`skipsig: ; +8Ch`	34	`skipsig: ; +8Eh`
32		35
33	`; set up CS=DS=SS and point SP to my private stack buffer`	36	`; set up CS=DS=SS and point SP to my private stack buffer`
34	`mov ax, cs`	37	`mov ax, cs`
35	`mov ds, ax`	38	`mov ds, ax`
36	`mov es, ax`	39	`mov es, ax`
37	`mov ss, ax`	40	`mov ss, ax`
38	`mov sp, STACKPTR`	41	`mov sp, STACKPTR`
39		42
-		43	`; collect the exit code of previous application`
-		44	`mov ah, 0x4D`
-		45	`int 0x21`
-		46	`xor ah, ah ; clear out termination status, I only want the exit code`
-		47	`mov [LEXCODE], ax`
-		48
40	`; prepare the exec param block`	49	`; prepare the exec param block`
41	`mov ax, [ENVSEG]`	50	`mov ax, [ENVSEG]`
42	`mov [EXEC_PARAM_REC], ax`	51	`mov [EXEC_PARAM_REC], ax`
43	`mov ax, COMSPEC`	52	`mov ax, COMSPEC`
44	`mov [EXEC_PARAM_REC+2], ax`	53	`mov [EXEC_PARAM_REC+2], ax`
45	`mov [EXEC_PARAM_REC+4], ds`	54	`mov [EXEC_PARAM_REC+4], ds`
46		55
47	`; execute command.com`	56	`; execute command.com`
48	`mov ax, 0x4B00 ; DOS 2+ - load & execute program`	57	`mov ax, 0x4B00 ; DOS 2+ - load & execute program`
49	`mov dx, COMSPEC ; DS:DX - ASCIZ program name TODO: use real COMSPEC...`	58	`mov dx, COMSPEC ; DS:DX - ASCIZ program name TODO: use real COMSPEC...`
50	`mov bx, EXEC_PARAM_REC ; ES:BX - parameter block pointer`	59	`mov bx, EXEC_PARAM_REC ; ES:BX - parameter block pointer`
51	`int 0x21`	60	`int 0x21`
52		61
53	`; if all went well, jump back to start`	62	`; if all went well, jump back to start`
54	`jnc skipsig`	63	`jnc skipsig`
55		64
56	`; update error string so it contains the error number`	65	`; update error string so it contains the error number`
57	`add al, '0'`	66	`add al, '0'`
58	`mov [ERRLOAD + 4], al`	67	`mov [ERRLOAD + 4], al`
59		68
60	`; display error message (with trailing COMSPEC)`	69	`; display error message (with trailing COMSPEC)`
61	`mov ah, 0x09`	70	`mov ah, 0x09`
62	`mov dx, ERRLOAD`	71	`mov dx, ERRLOAD`
63	`mov [COMSPCZ], byte '$' ; patch comspec terminator to be $`	72	`mov [COMSPCZ], byte '$' ; patch comspec terminator to be $`
64	`int 0x21`	73	`int 0x21`
65	`mov [COMSPCZ], byte 0 ; restore initial (NULL) compsec terminator`	74	`mov [COMSPCZ], byte 0 ; restore initial (NULL) compsec terminator`
66		75
67	`; wait for keypress`	76	`; wait for keypress`
68	`mov ah, 0x08`	77	`mov ah, 0x08`
69	`int 0x21`	78	`int 0x21`
70		79
71	`; back to program start`	80	`; back to program start`
72	`jmp skipsig`	81	`jmp skipsig`
73		82
74	`; ExecParamRec used by INT 21h, AX=4b00 (load and execute program), 14 bytes:`	83	`; ExecParamRec used by INT 21h, AX=4b00 (load and execute program), 14 bytes:`
75	`; offset size content`	84	`; offset size content`
76	`; +0 2 segment of environment for child (0 = current)`	85	`; +0 2 segment of environment for child (0 = current)`
77	`; +2 4 address of command line to place at PSP:0080`	86	`; +2 4 address of command line to place at PSP:0080`
78	`; +6 4 address of an FCB to be placed at PSP:005c`	87	`; +6 4 address of an FCB to be placed at PSP:005c`
79	`; +0Ah 4 address of an FCB to be placed at PSP:006c`	88	`; +0Ah 4 address of an FCB to be placed at PSP:006c`
80	`EXEC_PARAM_REC db 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0`	89	`EXEC_PARAM_REC db 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0`
81		90
82	`ERRLOAD db "ERR x, FAILED TO LOAD COMMAND.COM FROM:", 13, 10`	91	`ERRLOAD db "ERR x, FAILED TO LOAD COMMAND.COM FROM:", 13, 10`
83		92
84	`COMSPEC db "C:\SVN\SVARDOS\SVARCOM\COMMAND.COM"`	93	`COMSPEC db "C:\SVN\SVARDOS\SVARCOM\COMMAND.COM"`
85	`COMSPCZ db 0`	94	`COMSPCZ db 0`
86		95
87	`; FreeDOS int 21h functions that I use require at least 32 bytes of stack,`	96	`; FreeDOS int 21h functions that I use require at least 32 bytes of stack,`
88	`; here I allocate 64 bytes to be sure`	97	`; here I allocate 64 bytes to be sure`
89	`STACKBUF db "0123456789ABCDEF0123456789ABCDEF0123456789ABCDEF0123456789ABCDEF"`	98	`STACKBUF db "0123456789ABCDEF0123456789ABCDEF0123456789ABCDEF0123456789ABCDEF"`
90	`STACKPTR db "xx"`	99	`STACKPTR db "xx"`
91		100

Subversion Repositories SvarDOS

(root)/svarcom/rmod.asm @ 362 – Rev 350 → 353