%if 0

IRQ trace flag test
 2026 by E. C. Masloch

Usage of the works is permitted provided that this
instrument is retained with the works, so that any entity
that uses the works is notified of this instrument.

DISCLAIMER: THE WORKS ARE WITHOUT WARRANTY.

%endif

	cpu 8086
	org 256
start:
	mov si, 81h
.skip:
	lodsb
	cmp al, 32
	je .skip
	cmp al, 9
	je .skip
	cmp al, '0'
	jb error
	cmp al, '9'
	ja error
	xor di, di
	jmp .digit
.loop:
	lodsb
.digit:
	sub al, '0'
	jb .end
	cmp al, 10
	jae .end
	cbw
	add di, di	; times 2
	mov bx, di
	add di, di	; times 4
	add di, di	; times 8
	add di, bx	; times 10
	add di, ax
	jmp .loop

.end:

hook:
	mov ax, 3508h
	int 21h
	mov word [i08.next], bx
	mov word [i08.next + 2], es
	mov dx, i08
	mov ax, 2508h
	int 21h
	mov ax, 3501h
	int 21h
	mov word [i01.next], bx
	mov word [i01.next + 2], es
	mov dx, i01
	mov ax, 2501h
	int 21h

test:
	mov dx, msg.header
	mov ah, 09h
	int 21h
	mov si, 4
.si:
	mov cx, di
	cli
.outer:
	push cx
	mov cx, -1
.inner:
	mov ax, 16661
	mul ax
	add ax, ax
	loop .inner
	pop cx
	loop .outer
	xchg ax, cx
	mov word [timer.1], ax
	mov word [timer.2], ax
	mov word [timer.3], ax
	mov ax, 100h | 200h	; set TF and IF
	push ax
	push cs
	call iret_inst
addr1: equ $
	mov ax, [timer.1]
addr2: equ $
	mov bx, [timer.2]
addr3: equ $
	mov cx, [timer.3]
	sti
	call disp_ax_hex
	mov dx, msg.sep
	mov ah, 09h
	int 21h
	xchg ax, bx
	call disp_ax_hex
	mov dx, msg.sep
	mov ah, 09h
	int 21h
	xchg ax, cx
	call disp_ax_hex
	mov bx, [match]
	mov dx, [bx - 2]
	mov ah, 09h
	int 21h
	dec si
	jnz .si

	lds dx, [cs:i08.next]
	mov ax, 2508h
	int 21h
	lds dx, [cs:i01.next]
	mov ax, 2501h
	int 21h
	mov ax, 4C00h
	int 21h

error:
	mov dx, msg.error
	mov ah, 09h
	int 21h
	mov ax, 4C01h
	int 21h


iret_inst:
	iret


i08:
addr4 equ $
	jmp strict short .enter
.next:
	dd 0
	dw "KB"
	db 0
	jmp strict short iret_inst
	times 7 db 0
.enter:
addr5 equ $
	nop
	inc word [cs:timer.1]
	inc word [cs:timer.2]
	inc word [cs:timer.3]
	jmp far [cs:.next]

i01:
	jmp strict short .enter
.next:
	dd 0
	dw "KB"
	db 0
	jmp strict short iret_inst
	times 7 db 0
.enter:
	push bp
	mov bp, sp
	push ds
	push si
	push ax
	mov ax, cs
	mov ds, ax
	cld
	mov si, table
	mov word [match], si
	cmp word [bp + 4], ax
	jne .none
.loop:
	lodsw
	test ax, ax
	jz .none
	cmp word [bp + 2], ax
	lodsw
	jne .loop
	mov word [match], si
	jmp .done
.none:
	stc
.done:
	pop ax
	pop si
	pop ds
	jc .chain
	and byte [bp + 7], ~1
	pop bp
	iret

.chain:
	pop bp
	jmp far [cs:.next]

disp_ax_hex:
	xchg al, ah
	call disp_al_hex
	xchg al, ah
disp_al_hex:
	push cx
	mov cl, 4
	rol al, cl
	call disp_al_nybble_hex
	rol al, cl
	pop cx
disp_al_nybble_hex:
	push ax
	push dx
	and al, 15
	add al, '0'
	cmp al, '9'
	jbe .got
	add al, 7
.got:
	xchg dx, ax
	mov ah, 02h
	int 21h
	pop dx
	pop ax
	retn


	align 2
timer:
.1:		dw 0
.2:		dw 0
.3:		dw 0
match:		dw 0
pre:	dw 0, msg.pre	; pre+4 = table
table:
	dw addr1, msg.addr1
	dw addr2, msg.addr2
	dw addr3, msg.addr3
	dw addr4, msg.addr4
	dw addr5, msg.addr5
	dw 0
msg:
.error:		db "Error!",13,10,36
.header:	db "Traced Next   Double",13,10,36
.sep:		db "h, ",36
.addr1:		db "h, Iret points to inst traced",13,10,36
.addr2:		db "h, Iret points to next inst traced",13,10,36
.addr3:		db "h, Iret points to double next inst traced",13,10,36
.addr4:		db "h, Iret points to i08",13,10,36
.addr5:		db "h, Iret points to i08.enter",13,10,36
.pre:		db "h, Iret points to unknown",13,10,36