os-k/boot/loader/loader.asm

;=----------------------------------------------------------------------------=;
;                            GNU GPL OS/K                                      ;
;                                                                              ;
;   Desc:   Kernel (second stage) Loader for OS/K                              ;
;                   (x86_64 architecture only)                                 ;
;                                                                              ;
;                                                                              ;
;   Copyright © 2018-2019 The OS/K Team                                        ;
;                                                                              ;
;   This file is part of OS/K.                                                 ;
;                                                                              ;
;   OS/K 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.                                        ;
;                                                                              ;
;   OS/K 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 OS/K.  If not, see <https://www.gnu.org/licenses/>.             ;
;=----------------------------------------------------------------------------=;

%define DEBUG

[BITS 32]
[global _start]
[ORG 0x100000]                          ; Where GRUB loads us.

%include "boot/loader/multiboot/header.inc"

;; Normal entry point, but a little bit unused since we never use it because...
_start:
    mov ax, cs                          ; correcting cs after the horrible far jump
    mov ds, ax                          ; hm... And ds too
    mov es, ax                          ; And es because it is jealous
    ;mov [Bootdrv], dl
    xor dl, dl
    jmp 0x0000:_loader                  ; pas sûr

;; Magnificent multiboot header for GRUB ------------------------------------ ;;
MB_header:
    align 4
    dd MB_HEADER_MAGIC
    dd MB_HEADER_FLAGS
    dd CHECKSUM
    dd MB_header                        ; Header address
    dd _start                           ; Address of code entry point
    dd 00                               ; (end of code) not necessary
    dd 00                               ; (bss) not necessary
    dd MB_start                         ; entry address GRUB will start at

;; Multiboot entry point for Grub ------------------------------------------- ;;
MB_start:
    mov esp, KERNEL_STACK               ; Setup the stack
    push 0                              ; Reset EFLAGS
    popf
    push eax                            ; 2nd argument is magic number
    push ebx                            ; 1st argument multiboot info pointer
    mov ecx, eax
    call _loader
    add esp, 8                          ; Cleanup arguments "A la MIPS"
    jmp Die                             ; Aufwiedersehen

;; THE HOLES ---------------------------------------------------------------- ;;
Error:
    mov dword [0xb8000], 0x4f524f45
    mov dword [0xb8004], 0x4f3a4f52
    mov dword [0xb8008], 0x4f204f20
    mov byte  [0xb800a], al
    jmp Die

Die:
    cli
    hlt                                 ; die nooooow
    ;jmp 0xF000:0xFFF0
    jmp $

;; THE CODE ----------------------------------------------------------------- ;;

; ---------------------------------------------------------------------------- ;
;  _loader                                                                     ;
;                                                                              ;
;  This is the function that initiates the launch of OS/K. It verifies that    ;
;  Grub has properly loaded this loader and makes the appropriate setup so     ;
;  that the kernel will work properly                                          ;
;                                                                              ;
;  Why this original design ? Because it works well and prevent us to cause    ;
;  triple faults by aligment error or too long jumps (yup, it can be a problem);
;                                                                              ;
; ---------------------------------------------------------------------------- ;
_loader:
    jmp lbegin

%include "boot/loader/multiboot/check.inc"
lbegin:
    call MB_check
    jmp lnext

%include "boot/loader/cpu/cpuid.inc"
lnext:
    call Check_cpuid
    call Is64Bits
    jmp lnext2

%include "boot/loader/mem/structures.inc"
lnext2:
    call Setup_paging
    call Go64
    jmp lnext3
%include "boot/loader/mem/management.inc"

lnext3:
    mov dword [0xb8000], 0x2f4b2f4f
    ret