WebSVN – SvarDOS – Diff – /svarcom/tags/svarcom-2022.4/int24.asm


;
; WORK IN PROGRESS TEMPLATE! NOT USED YET
;
; int 24h handler, part of SvarCOM. MIT license.
; Copyright (C) 2022 Mateusz Viste
;
; this is an executable image that can be set up as the critical error handler
; interrupt (int 24h). It displays the usual "Abort, retry, fail" prompt.
;
 
org 0   ; this code does not have a PSP, it is loaded as-is into a memory
        ; segment
 
; === CRIT HANDLER DETAILS ====================================================
;
; *** ON ENTRY ***
;
; upon entry to the INT 24h handler, the registers are as follows:
;  BP:SI = addr of a "device header" that identifies the failing device
;     DI = error code in lower 8 bits (only for non-disk errors)
;     AL = drive number, but only if AH bit 7 is reset
;     AH = error flags
;        0x80 = reset if device is a disk, set otherwise
;           all the following are valid ONLY for disks (0x80 reset):
;        0x20 = set if "ignore" action allowed
;        0x10 = set if "retry" action allowed
;        0x08 = set if "fail" action allowed
;        0x06 = disk area, 0=sys files, 1=fat, 10=directory, 11=data
;        0x01 = set if failure is a write, reset if read
;
; within the int 24h handler, only these DOS functions are allowed:
;   01H-0CH (DOS character I/O)
;   33H (all subfns are OK, including 3306H get DOS version)
;   50H (set PSP address)
;   51H and 62H (query PSP address)
;   59H (get extended error information)
;
;
; *** ON EXIT ***
;
; After handling the error, AL should be set with an action code and get back
; to DOS. Available actions are defined in AH at entry (see above). Possible
; values on exit are:
;   AL=0  ignore error (pretend nothing happenned)
;   AL=1  retry operation
;   AL=2  abort (terminates the failed program via int 23h, like ctrl+break)
;   AL=3  return to application indicating a failure of the DOS function
;
; A very basic "always fail" handler would be as simple as this:
;   mov al, 3
;   iret
; =============================================================================
 
 
; save registers so I can restore them later
push ah
push bx
push cx
push dx
pushf
 
; disk errors product this message:
; CRITICAL ERROR - DRIVE A: - READ|WRITE FAILURE
; (A)bort, (R)etry, (F)ail
;
; non-disk errors produce this:
; CRITICAL ERROR #errno
 
 
; restore registers and quit the handler
popf
pop dx
pop cx
pop bx
pop ah
 
iret
 
 
; write DX string to stderr
write_dx_str_to_stderr:
push ax
push bx
push cx
 
mov ah, 0x40       ; write to file -- am I sure I can use this function safely?
mov bx, 2          ; stderr
mov cx, 1          ; one byte
int 0x21
 
pop cx
pop bx
pop ax
 

Rev 967	Rev 1163
1	`;`	1	`;`
2	`; WORK IN PROGRESS TEMPLATE! NOT USED YET`	2	`; WORK IN PROGRESS TEMPLATE! NOT USED YET`
3	`;`	3	`;`
4	`; int 24h handler, part of SvarCOM. MIT license.`	4	`; int 24h handler, part of SvarCOM. MIT license.`
5	`; Copyright (C) 2022 Mateusz Viste`	5	`; Copyright (C) 2022 Mateusz Viste`
6	`;`	6	`;`
7	`; this is an executable image that can be set up as the critical error handler`	7	`; this is an executable image that can be set up as the critical error handler`
8	`; interrupt (int 24h). It displays the usual "Abort, retry, fail" prompt.`	8	`; interrupt (int 24h). It displays the usual "Abort, retry, fail" prompt.`
9	`;`	9	`;`
10		10
11	`org 0 ; this code does not have a PSP, it is loaded as-is into a memory`	11	`org 0 ; this code does not have a PSP, it is loaded as-is into a memory`
12	`; segment`	12	`; segment`
13		13
14	`; === CRIT HANDLER DETAILS ====================================================`	14	`; === CRIT HANDLER DETAILS ====================================================`
15	`;`	15	`;`
16	`; * ON ENTRY *`	16	`; * ON ENTRY *`
17	`;`	17	`;`
18	`; upon entry to the INT 24h handler, the registers are as follows:`	18	`; upon entry to the INT 24h handler, the registers are as follows:`
19	`; BP:SI = addr of a "device header" that identifies the failing device`	19	`; BP:SI = addr of a "device header" that identifies the failing device`
20	`; DI = error code in lower 8 bits (only for non-disk errors)`	20	`; DI = error code in lower 8 bits (only for non-disk errors)`
21	`; AL = drive number, but only if AH bit 7 is reset`	21	`; AL = drive number, but only if AH bit 7 is reset`
22	`; AH = error flags`	22	`; AH = error flags`
23	`; 0x80 = reset if device is a disk, set otherwise`	23	`; 0x80 = reset if device is a disk, set otherwise`
24	`; all the following are valid ONLY for disks (0x80 reset):`	24	`; all the following are valid ONLY for disks (0x80 reset):`
25	`; 0x20 = set if "ignore" action allowed`	25	`; 0x20 = set if "ignore" action allowed`
26	`; 0x10 = set if "retry" action allowed`	26	`; 0x10 = set if "retry" action allowed`
27	`; 0x08 = set if "fail" action allowed`	27	`; 0x08 = set if "fail" action allowed`
28	`; 0x06 = disk area, 0=sys files, 1=fat, 10=directory, 11=data`	28	`; 0x06 = disk area, 0=sys files, 1=fat, 10=directory, 11=data`
29	`; 0x01 = set if failure is a write, reset if read`	29	`; 0x01 = set if failure is a write, reset if read`
30	`;`	30	`;`
31	`; within the int 24h handler, only these DOS functions are allowed:`	31	`; within the int 24h handler, only these DOS functions are allowed:`
32	`; 01H-0CH (DOS character I/O)`	32	`; 01H-0CH (DOS character I/O)`
33	`; 33H (all subfns are OK, including 3306H get DOS version)`	33	`; 33H (all subfns are OK, including 3306H get DOS version)`
34	`; 50H (set PSP address)`	34	`; 50H (set PSP address)`
35	`; 51H and 62H (query PSP address)`	35	`; 51H and 62H (query PSP address)`
36	`; 59H (get extended error information)`	36	`; 59H (get extended error information)`
37	`;`	37	`;`
38	`;`	38	`;`
39	`; * ON EXIT *`	39	`; * ON EXIT *`
40	`;`	40	`;`
41	`; After handling the error, AL should be set with an action code and get back`	41	`; After handling the error, AL should be set with an action code and get back`
42	`; to DOS. Available actions are defined in AH at entry (see above). Possible`	42	`; to DOS. Available actions are defined in AH at entry (see above). Possible`
43	`; values on exit are:`	43	`; values on exit are:`
44	`; AL=0 ignore error (pretend nothing happenned)`	44	`; AL=0 ignore error (pretend nothing happenned)`
45	`; AL=1 retry operation`	45	`; AL=1 retry operation`
46	`; AL=2 abort (terminates the failed program via int 23h, like ctrl+break)`	46	`; AL=2 abort (terminates the failed program via int 23h, like ctrl+break)`
47	`; AL=3 return to application indicating a failure of the DOS function`	47	`; AL=3 return to application indicating a failure of the DOS function`
48	`;`	48	`;`
49	`; A very basic "always fail" handler would be as simple as this:`	49	`; A very basic "always fail" handler would be as simple as this:`
50	`; mov al, 3`	50	`; mov al, 3`
51	`; iret`	51	`; iret`
52	`; =============================================================================`	52	`; =============================================================================`
53		53
54		54
55	`; save registers so I can restore them later`	55	`; save registers so I can restore them later`
56	`push ah`	56	`push ah`
57	`push bx`	57	`push bx`
58	`push cx`	58	`push cx`
59	`push dx`	59	`push dx`
60	`pushf`	60	`pushf`
61		61
62	`; disk errors product this message:`	62	`; disk errors product this message:`
63	`; CRITICAL ERROR - DRIVE A: - READ\|WRITE FAILURE`	63	`; CRITICAL ERROR - DRIVE A: - READ\|WRITE FAILURE`
64	`; (A)bort, (R)etry, (F)ail`	64	`; (A)bort, (R)etry, (F)ail`
65	`;`	65	`;`
66	`; non-disk errors produce this:`	66	`; non-disk errors produce this:`
67	`; CRITICAL ERROR #errno`	67	`; CRITICAL ERROR #errno`
68		68
69		69
70	`; restore registers and quit the handler`	70	`; restore registers and quit the handler`
71	`popf`	71	`popf`
72	`pop dx`	72	`pop dx`
73	`pop cx`	73	`pop cx`
74	`pop bx`	74	`pop bx`
75	`pop ah`	75	`pop ah`
76		76
77	`iret`	77	`iret`
78		78
79		79
80	`; write DX string to stderr`	80	`; write DX string to stderr`
81	`write_dx_str_to_stderr:`	81	`write_dx_str_to_stderr:`
82	`push ax`	82	`push ax`
83	`push bx`	83	`push bx`
84	`push cx`	84	`push cx`
85		85
86	`mov ah, 0x40 ; write to file -- am I sure I can use this function safely?`	86	`mov ah, 0x40 ; write to file -- am I sure I can use this function safely?`
87	`mov bx, 2 ; stderr`	87	`mov bx, 2 ; stderr`
88	`mov cx, 1 ; one byte`	88	`mov cx, 1 ; one byte`
89	`int 0x21`	89	`int 0x21`
90		90
91	`pop cx`	91	`pop cx`
92	`pop bx`	92	`pop bx`
93	`pop ax`	93	`pop ax`
94		94

Subversion Repositories SvarDOS

(root)/svarcom/tags/svarcom-2022.4/int24.asm – Rev 967 → 1163