From 877e9bfe8e7d9e93536f4cb4af36aac65805be11 Mon Sep 17 00:00:00 2001
From: Joseph Hunkeler <jhunkeler@gmail.com>
Date: Wed, 4 Jul 2018 20:55:53 -0400
Subject: Begin refactoring ISR code

---
 constants.asm |  3 +++
 isr.asm       | 19 ++++++++++++++++++-
 kernel.asm    | 39 ++++++++++++++++++++++++++++-----------
 3 files changed, 49 insertions(+), 12 deletions(-)

diff --git a/constants.asm b/constants.asm
index ac6438a..16f7510 100644
--- a/constants.asm
+++ b/constants.asm
@@ -7,6 +7,9 @@ MAX_COLS equ 80
 LENGTH_ROW equ 0A0h	; NOTE: length in bytes (80 * 2 = 160)
 LENGTH_COL equ 02h	; NOTE: length in bytes (1 * 2 = 2)
 
+ISR_TEST equ 20h
+ISR_MINOS equ 21h
+
 %include "colors.asm"
 %include "ascii.asm"		; ASCII control codes
 %include "scancodes.asm"	; Keyboard scancodes
diff --git a/isr.asm b/isr.asm
index 9ac6bb6..9bab410 100644
--- a/isr.asm
+++ b/isr.asm
@@ -1,5 +1,22 @@
 int21:
-	nop
+	cmp al, .fn_table_size
+	jg .return
+
+	push bx
+	push di
+	movsx bx, al
+	mov di, .fn_table
+	call [di+bx]
+	pop di
+	pop bx
+
+	.return:
+		iret
+
+	.fn_table:
+		dw memset
+		dw memcpy
+	.fn_table_size dw $-.fn_table
 int22:
 	nop
 int20:
diff --git a/kernel.asm b/kernel.asm
index f92b294..5ef64f0 100644
--- a/kernel.asm
+++ b/kernel.asm
@@ -88,6 +88,14 @@ kmain:
 		jle .info_disk_loop		; continue
 
 .preload:
+	push ISR_TEST
+	push int20
+	call isr_inject
+
+	int 20h					; test routine
+
+	push ISR_MINOS
+	push int21
 	call isr_inject
 
 .mainloop:
@@ -105,31 +113,40 @@ isr_inject:
 	push es
 	push ax
 	push bx
-	push bp
+	push cx
+	push di
+	push ds
 
-	mov ax, 0000h		; set ES to Interrupt Vector Table
+	mov ax, 0000h		; set DS/ES to Interrupt Vector Table
 				; (start of RAM)
 	mov es, ax
+	mov ds, ax
 
-	mov bp, 20h * 4		; Set vector (v = es:offset * 4))
-	lea bx, [int22]		; Load address of ISR routine
-	mov ax, cs		; Load code segment into AX
+	;mov bp, 20h * 4		; Set vector (v = es:offset * 4))
+	;lea bx, [int22]		; Load address of ISR routine
+	mov bx, [bp + 4]		; ISR routine
+	mov di, [bp + 6]		; IVT offset
+	shl di, 2			; IVT * 4
 
-	mov word [es:bp], bx	; Store address of ISR routine
-	mov word [es:bp+2], ax	; Store code segment of ISR routine
+	mov ax, cs		; Load code segment into AX
+	mov word [ds:di], bx	; Store address of ISR routine
+	mov word [ds:di+2], ax	; Store code segment of ISR routine
 
+	pop ds			; Restore DS so we can print
 	push bx
 	push ax
+	push word [bp + 6]
 	push msg_isr_fmt
 	call printf		; print injected ISR address
-	add sp, 2 * 3		; cleanup stack
+	add sp, 2 * 4		; cleanup stack
 
-	pop bp
+	pop di
+	pop cx
 	pop bx
 	pop ax
 	pop es
 
-	int 20h			; test new ISR
+	;int 20h			; test new ISR
 
 	mov sp, bp
 	pop bp
@@ -164,7 +181,7 @@ msg_entry_point_fmt:
 	db 'Kernel address:	%5x:%4x - %5x:%4x (%d:%d - %d:%d)\n'
         db 'Stack address :	%5x:%4x (%d:%d)\n'
         db 'Boot device   :    %2x\n\n', 0
-msg_isr_fmt: db "ISR %5x:%4x\n", 0
+msg_isr_fmt: db "ISR %2xh, %5x:%4x\n", 0
 
 ; Error messages
 error_msg_panic: db "PANIC: ", 0
-- 
cgit