;=----------------------------------------------------------------------------=;
;                            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:main                     ; 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 main
    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 ----------------------------------------------------------------- ;;
main:
    call MB_check

    call Check_cpuid
    call Is64Bits

    call Setup_paging

    ;; Registering paging
    mov eax, PML4_table
    mov cr3, eax                    ; Load PML4 to cr3

    mov eax, cr4
    or eax, 1 << 5
    mov cr4, eax                    ; Enable PAE

    ;; Activate long mode
    mov ecx, 0xC0000080             ; address of MSR
    rdmsr                           ; read MSR
    or eax, 1 << 8                  ; LME = 1. (Long Mode Enable)
    wrmsr                           ; write MSR

    ;; Enable paging
    mov eax, cr0
    or eax, 1 << 31                 ; make MSR bit 31 (PG = Paging) to 1 :
                                    ;    |1|000000000000000000000000000000
                                    ;     |
                                    ;     `------ Paging bit
    mov cr0, eax

    mov dword [0xb8000], 0x2f4b2f4f
    ret

;; INCLUDES ----------------------------------------------------------------- ;;
%include "boot/loader/cpu/cpuid.inc"
%include "boot/loader/multiboot/check.inc"
%include "boot/loader/mem/structures.inc"
%include "boot/loader/mem/management.inc"