;=----------------------------------------------------------------------------=;
;                            GNU GPL OS/K                                      ;
;                                                                              ;
;   Authors: spectral`                                                         ;
;            NeoX                                                              ;
;                                                                              ;
;   Desc:   Kernel (second stage) Loader for OS/K                              ;
;                   (x86_64 architecture only)                                 ;
;=----------------------------------------------------------------------------=;

%define DEBUG

[BITS 16]
[ORG 0x1000]

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

%include "boot/loader/cpu/cpuid.asm"
%include "boot/loader/io/rmterm.asm"
%include "boot/loader/io/rmmem.asm"

main:

    ;; compatibility check
    push si
    mov si, Init
    call PrintB
    pop si

    call Is64bits

    jc ErrorNo64
    push si
    mov si, Pass
    call PrintB
    pop si

    ;; Enabling A20
    push si
    mov si, EnA20
    call PrintB
    pop si

    call set_a20

    push si
    mov si, Pass
    call PrintB
    pop si

    ;; DISABLING CURSOR BLINKING AND GETTING INFOS
    call get_dimensions
    call disable_cursor

    ;;GO GDT64
    cli                                     ; disable interrupts
    lgdt [GDT64]
    ;; ACTIVATE PROTECTED MODE
    mov eax, cr0
    or al, 1b                               ; PE = 1
    mov cr0, eax
    ;; DISABLE PAGING
    mov eax, cr0
    and eax, 0x7FFFFFFF                     ; PG = 0
                                            ;   |0|111111111111111111111111111111
                                            ;    |
                                            ;    `------ Paging bit
    mov cr0, eax

    push dword [VIDEO_MODE]
    push dword [VGA_HEIGHT]
    jmp (CODE_SELECTOR-GDT64):main32

;; THE HOLE ----------------------------------------------------------------- ;;
ErrorNo64:
    mov si, NoLongMode
    call PrintB
Die:
    cli
    hlt                                     ; die nooooow
    jmp 0xF000:0xFFF0
;; END OF THE HOLE ---------------------------------------------------------- ;;

[BITS 32]
main32:
    pop dword [VGA_HEIGHT32]
    pop dword [VIDEO_MODE32]

    ;; VERIFY A20
    pushad
    mov edi,0x112345                        ;odd megabyte address.
    mov esi,0x012345                        ;even megabyte address.
    mov [esi],esi                           ;making sure that both addresses contain diffrent values.
    mov [edi],edi                           ;(if A20 line is cleared the two pointers would point to the address 0x012345 that would contain 0x112345 (edi))
    cmpsd                                   ;compare addresses to see if the're equivalent.
    popad
    jne .A20_on                             ;if not equivalent , A20 line is set.
    mov WORD [A20_OK], 0
    jmp .A20_end
.A20_on:
    mov BYTE [A20_OK], 1
.A20_end:

    ;; INITIALIZE PROTECTED MODE SEGMENT REGISTERS
    mov ax, DATA_SELECTOR-GDT64
    mov ds, ax
    mov es, ax
    mov fs, ax
    mov gs, ax
    mov ss, ax

    ;; ACTIVATE PHYSICAL ADRESS EXTENSION
    mov eax, cr4
    or eax, 100000b                         ; PAE = 1 = 4 Mo / page.  0 = 4 Ko
    mov cr4, eax

    ;;cleanup
    mov edi, 0x70000
    mov ecx, 0x10000
    xor eax, eax
    rep stosd
    ;;formatting
    mov dword [0x70000], 0x71000 + 7        ; first PDP table
    mov dword [0x71000], 0x72000 + 7        ; first page directory
    mov dword [0x72000], 0x73000 + 7        ; first page table
    mov edi, 0x73000                        ; address of first page table
    mov eax, 7
    mov ecx, 256                            ; number of pages to map (1 MB)
.make_page_entries:
    stosd
    add edi, 4
    add    eax, 0x1000
    loop .make_page_entries
    ;; pointing pml4
    mov eax, 0x70000                        ; Bass address of PML4
    mov    cr3, eax                            ; load page-map level-4 base

    ;; ACTIVATE LONG MODE
    mov ecx, 0xC0000080                     ; address of MSR
    rdmsr                                   ; read MSR
    or eax, 100000000b                      ; LME = 1. (Long Mode Enable)
    wrmsr                                   ; write MSR

    ;; ACTIVATE PAGING
    mov    eax, cr0
    or eax, 0x80000000                      ; make bit 31 (PG = Paging) to 1 :
                                            ;    |1|000000000000000000000000000000
                                            ;     |
                                            ;     `------ Paging bit
    mov cr0, eax
    push dword 0
    push dword [VIDEO_MODE]
    push dword 0
    push dword [VGA_HEIGHT]
    jmp (LONG_SELECTOR-GDT64):main64

[BITS 64]

;; DATA
    Init            db  "Booting OS/K !", 0x0D, 0x0A, 0x0D, 0x0A, 0x09, " Checking CPUID...",0
    CPUIDD          db  0x09, " Checking CPUID...", 0
    EnA20           db  0x09, " Enabling A20 line...", 0
%ifdef DEBUG
    ReadAttempt     db  0x09, " Attempt to read a sector with ATA commands...", 0x0A, 0x0D, 0x0A, 0x0D, 0
%else
    ReadAttempt     db  0x09, " Attempt to read a sector with ATA commands...", 0
%endif
    txt             db  0x09, " Switching to Long Mode... ", 0
    EndOfLoader     db  "End of loader.bin. System will halt !", 0x0A, 0x0D, 0
    Reinit          db  "Booting OS/K !", 0x0D, 0x0A, 0x0D, 0x0A, 0
    Pass            db  " OK", 0x0A, 0x0D, 0
    Fail            db  " FAIL!", 0x0A, 0x0D, 0
    msg             db  "The system is now in x64 mode. Is this not beautiful ?", 0x0A, 0x0D, 0
    FileNotFound    db  "Second Stage Error : The Kernel was not found.", 0x0A, 0x0D, 0
    DiskError       db  "Second Stage Error : The Disk has crashed.", 0x0A, 0x0D, 0
    filename        db  "KERNEL  BIN"

%include "boot/loader/io/lmmem.asm"
%include "boot/loader/io/lmterm.asm"
%include "boot/loader/io/ata.asm"
%include "boot/loader/cpu/cpu.asm"
%include "boot/loader/fs/fat.asm"

main64:
    pop qword [VGA_HEIGHT64]
    pop qword [VIDEO_MODE64]
    ;; INITIALIZE STACK
    mov rsp, 0x9F000

    call clear

    ;; Printing
    mov bl, 0x0B
    mov esi, Reinit
    call write

    mov bl, 0x0F
    mov esi, CPUIDD
    call write

    mov bl, 0x0A
    mov esi, Pass
    call write

    mov bl, 0x0F
    mov esi, EnA20
    call write

    call check_a20

    mov bl, 0x0F
    mov esi, txt
    call write

    mov bl, 0x0A
    mov esi, Pass
    call write

    mov bl, 0x0D
    mov esi, msg
    call write

    mov bl, 0x0F
    mov esi, ReadAttempt
    call write

    call temporize                           ; Temporized because the ATA drive must be ready

    mov bl, 1
    mov bh, 1
    call ata_read

    mov bl, 0x0D
    mov esi, EndOfLoader
    call write

    jmp Die

times 20 db 0