Added GDT.

Unfortunately I can't do it in C, but whatever.
This commit is contained in:
Nicolás Ortega Froysa 2018-03-14 17:10:51 +01:00
parent ea6b0f69d2
commit 9703f2484c
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GPG Key ID: FEC70E3BAE2E69BF
4 changed files with 85 additions and 2 deletions

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@ -20,7 +20,7 @@ ARCH=$(shell echo $(TARGET) | sed s/i.86/x86/)
CROSSFLAGS=--target=$(TARGET)-pc-none-elf -march=$(TARGET)
# Assembly options
AS=nasm
AFLAGS=-felf32
AFLAGS=-felf32 -Isrc/kernel/arch/$(ARCH)/ -Isrc/
# C options
CC=clang
CFLAGS?=-O0 -g

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@ -32,12 +32,27 @@ stack_bottom:
resb 16384 ; 16KiB
stack_top:
section .data
%include "gdt.s"
section .text
global _start:function (_start.end - _start)
_start:
; setup the stack
mov esp, stack_top
; TODO: setup GDT, IDT, paging, etc. here
cli
lgdt [gdtr]
jmp 0x08:.reload_segs
.reload_segs:
mov ax, 0x10
mov ds, ax
mov es, ax
mov fs, ax
mov gs, ax
mov ss, ax
; call the kernel
extern kernel_main
call kernel_main

68
src/kernel/arch/x86/gdt.s Normal file
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@ -0,0 +1,68 @@
; Copyright (C) 2018 Ortega Froysa, Nicolás <nortega@themusicinnoise.net>
; Author: Ortega Froysa, Nicolás <nortega@themusicinnoise.net>
;
; This program is free software: you can redistribute it and/or modify
; it under the terms of the GNU General Public License as published by
; the Free Software Foundation, either version 3 of the License, or
; (at your option) any later version.
;
; This program is distributed in the hope that it will be useful,
; but WITHOUT ANY WARRANTY; without even the implied warranty of
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
; GNU General Public License for more details.
;
; You should have received a copy of the GNU General Public License
; along with this program. If not, see <http://www.gnu.org/licenses/>.
gdt_start:
gdt_null:
dd 0x0
dd 0x0
gdt_kcode:
dw 0xFFFF ; limit (bits 0-15)
dw 0x0 ; base (bits 0-15)
db 0x0 ; base (bits 16-23)
db 10011010b ; 1st flags | type flags
db 11001111b ; 2nd flags | limit (bits 16-19)
db 0x0 ; base (bits 24-31)
gdt_kdata:
dw 0xFFFF
dw 0x0
db 0x0
db 10010010b
db 11001111b
db 0x0
gdt_ucode:
dw 0xFFFF
dw 0x0
db 0x0
db 11111010b
db 11001111b
db 0x0
gdt_udata:
dw 0xFFFF
dw 0x0
db 0x0
db 11110010b
db 11001111b
db 0x0
; TODO: fill this in later
gdt_tss:
dd 0x0
dd 0x0
gdt_end:
gdtr:
dw gdt_end - gdt_start - 1
dd gdt_start

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@ -18,7 +18,7 @@
#pragma once
volatile struct tss {
struct tss {
uint16_t link;
uint16_t link_r; // reserved