From 72eec372bc82e28afee824b440fc76aad177d66b Mon Sep 17 00:00:00 2001
From: John Tsiombikas <nuclear@member.fsf.org>
Date: Sat, 12 Oct 2019 13:00:31 +0300
Subject: [PATCH] intr.asm: set_intr function

---
 src/intr.asm |   32 ++++++++++++++++++++++++++++++++
 src/intr.inc |    2 ++
 2 files changed, 34 insertions(+)

diff --git a/src/intr.asm b/src/intr.asm
index 1bbf319..0c8acf7 100644
--- a/src/intr.asm
+++ b/src/intr.asm
@@ -1,8 +1,14 @@
 ; vi:filetype=nasm ts=8 sts=8 sw=8:
 	section .text
 
+%define INTR_ASM_
 %include "intr.inc"
 
+GATE_INTR equ 0600h
+GATE_TRAP equ 0700h
+GATE_DEFAULT equ 0800h
+GATE_PRESENT equ 8000h
+
 	global init_intr
 init_intr:
 	call init_pic
@@ -10,6 +16,32 @@ init_intr:
 
 	global set_intr
 set_intr:
+	push ebp
+	mov ebp, esp
+	push ebx
+
+	mov ebx, [ebp + 8]
+	mov eax, GATE_TRAP
+	cmp ebx, 32	; determine if it's an IRQ or an exception (trap)
+	jb .notirq
+	mov eax, GATE_INTR
+.notirq:
+	shl ebx, 1
+	lea ebx, [ebx * 8 + idt] ; ebx <- pointer to gate descriptor
+	; type|dpl goes to the 3rd dword of the descriptor (dpl is 0)
+	or eax, (GATE_DEFAULT | GATE_PRESENT)
+	mov [ebx + 8], eax
+	; address low 16bits go to the first dword of the descriptor
+	mov eax, [ebp + 12]
+	mov [ebx], ax
+	; address high 16bits go to the last dword of the descriptor
+	shr eax, 16
+	mov [ebx + 12], eax
+	; selector (kcode:1) goes to the second dword of the descriptor
+	mov dword [ebx + 4], 08h
+
+	pop ebx
+	pop ebp
 	ret
 
 PIC1_CMD equ 20h
diff --git a/src/intr.inc b/src/intr.inc
index 95b18d6..55a1c9d 100644
--- a/src/intr.inc
+++ b/src/intr.inc
@@ -43,3 +43,5 @@
 %endif
 	out PIC1_CMD, al
 %endmacro
+
+	extern idt
-- 
1.7.10.4