intr.asm: set_intr function

diff --git a/src/intr.asm b/src/intr.asm
index 1bbf319..0c8acf7 100644 (file)
--- 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 (file)
--- a/src/intr.inc
+++ b/src/intr.inc
@@ -43,3 +43,5 @@
 %endif
        out PIC1_CMD, al
 %endmacro
+
+       extern idt