;=----------------------------------------------------------------------------=;
;                            GNU GPL OS/K                                      ;
;                                                                              ;
;   Desc:   Kernel 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/>.             ;
;=----------------------------------------------------------------------------=;

%include "boot/loader/multiboot/header.inc"
%include "boot/loader/multiboot/check.inc"
%include "boot/loader/cpu/cpu32.inc"
%include "boot/loader/mem/management.inc"
%include "boot/loader/io/terminal.inc"
%include "boot/loader/cpu/cpu.inc"
%include "boot/loader/mem/structures.inc"

global MB_start
global MB_header
extern BtStartKern

[BITS 32]
[section .multiboot]

;; MAGNIFICENT MULTIBOOT HEADER FOR GRUB ------------------------------------ ;;
MB_header:
    ALIGN 4
    dd MB_HEADER_MAGIC
    dd MB_HEADER_FLAGS
    dd CHECKSUM
    times 5 dd 0x0                      ; The unused section (provided for a.out)
    dd MB_VIDEO_MODE
    dd MB_VIDEO_WIDTH
    dd MB_VIDEO_HEIGHT
    dd MB_VIDEO_DEPTH

[section .text]

;;MULTIBOOT POINT ENTRY FOR GRUB -------------------------------------------- ;;
MB_start:
    mov esp, KERNEL_STACK               ; Setup the stack
    push 0                              ; Reset EFLAGS
    popf
    mov [mbInfo], ebx
    mov [mbMagic], eax
    mov ecx, eax                        ; For debug
    call _loader
    add esp, 8                          ; Cleanup arguments "A la MIPS"
    jmp Die                             ; Aufwiedersehen, but never used

;; THE HOLES ---------------------------------------------------------------- ;;
; ---------------------------------------------------------------------------- ;
; Prints 'ERR:XX' where 'XX' is the str in AX                                  ;
; ---------------------------------------------------------------------------- ;
Error:
    mov word [.code], ax
    push esi
    mov bl, 0x0c
    mov esi, .ergo
    call write32
    pop esi
    jmp Die
.ergo : db 219, 219, 219, " OS/K Loader Error "
.code : db "00"
        db 0x0
; ---------------------------------------------------------------------------- ;
; Kills the mind of your computer to get it prostrated                         ;
; ---------------------------------------------------------------------------- ;
Die:
    cli
    hlt                                 ; die nooooow
    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

LOGO    db 219, 219, 219, " OS/K", 0
mbInfo  dq 0
mbMagic dq 0

lbegin:
    call clear                          ; Clear the screen

    push esi                            ; Print the logo
    mov bl, 0x0E
    mov esi, LOGO
    call write32
    pop esi

    ;; BEGIN OF CHECKLIST
    call MB_check                       ; Check Multiboot State, ERR 01

    call Check_cpuid                    ; Check if cpuid supported, ERR 02
    call Is64Bits                       ; Check if long mode available, ERR 03
    call CheckA20                       ; Check if A20 is correctly enable, ERR 04

    ;; BEGIN OF WORK
    call Setup_paging                   ; Enable paging
    call Go64                           ; Prepare switch into long mode

    ;call disable_cursor

    lgdt [GDT64.pointer]
    jmp GDT64.code:_loader64            ; SWITCH

[BITS 64]

x64_K           db "64 bits long mode activated !", 0x0A, 0x0D, 0x0
GoKernel        db "Launching Kernel...", 0
GoStack         db "Initializing the stack...", 0x0A, 0x0D, 0x0
nokernel        db 219, 219, 219, " Error 05 : Kernel returns",0

_loader64:
    ;; Some cleanup
    mov ax, 0
    mov ss, ax
    mov ds, ax
    mov es, ax
    mov fs, ax
    mov gs, ax

    call bitemporize

    mov qword [NextTRAM], TRAM+80*4     ; Because we don't want to overwrite

    ;; Hello world
    mov bl, 0x0A
    mov esi, x64_K
    call write

    ;; Initialize the stack
    mov bl, 0x0F
    mov esi, GoStack
    call write

    call temporize                      ; clear the pipeline
    call InitStack

    ;; Launch the kernel !
    mov bl, 0x0F
    mov esi, GoKernel
    call write

    mov qword [newKernelEnd], KERNEL_STACK
    mov qword [realKernelEnd], realKernelEnd
    mov rdi, [mbInfo]
    mov rsi, [mbMagic]
    mov rdx, GDT64.code
    call BtStartKern

;; We must never reach this point ------------------------------------------- ;;
    call tritemporize                   ; Let time to see
    call clear
    mov bl, 0x0c
    mov esi, nokernel                   ; Error 05
    call write
    jmp Die