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

[ORG 0x1000]
		
pop ax
mov [Bootdrv], ax
jmp		main

;; DATA
%define		TRAM 	 	0x0B8000	; [T]ext[RAM]
%define		VRAM 	 	0x0A0000 	; [V]ideo[RAM] 
Bootdrv     db          0x00
VGA_HEIGHT  dq          0
VIDEO_MODE  dw          0

;; GDT WITH DOC
GDT64:	
		NULL_SELECTOR:	;; null selector within 64 bits		
						dw 	GDT_LENGTH		; limit of GDT 
						dw 	GDT64			; linear address of GDT
						dd 	0x0			
		CODE_SELECTOR:	;; 32-bit code selector (ring 0)
						dw 	0x0FFFF			; Segment Limit 15:00
						db	0x0, 0x0, 0x0	; Base Address 23:00
						db  10011010b		;	|7|6|5|4|3|2|1|0|
											;	 | | | | | | | `----- 1 when segment used. 
											;	 | | | | | | `------ 1 when writable. 
											;	 | | | | | `------- 1 if "conformant". Don't know what is it... spectral ? xD
											;	 | | | | `-------- 1 always
											;	 | | | `--------- 1 for segment descriptor, 0 for system descriptor
											;	 | | `---------- DPL !!! 0 for ring 0 
											;	 | `----------- DPL (2/2)
											;	 `------------ 1 if in physical memory, 0 if page fault 
						db	11001111b		;	|7|6|5|4|3|2|1|0|
											;	 | | | | | | | `----- Limit 16
											;	 | | | | | | `------ Limit 17
											;	 | | | | | `------- Limit 18
											;	 | | | | `-------- Limit 19
											;	 | | | `--------- available for use
											;	 | | `---------- 0 always
											;	 | `----------- size of data. 1 for 32bits
											;	 `------------ 0 if limit is in Bytes, 1 if it's in pages (4ko)
						db	0x0				; Base Address 31:24
						
		DATA_SELECTOR:	;; flat data selector (ring 0)		
						dw 	0x0FFFF			; Segment Limit 15:00
						db	0x0, 0x0, 0x0	; Base Address 23:00
						db  10010010b		;	|7|6|5|4|3|2|1|0| 
											;	 | | | | | | | `----- 1 when segment used.  
											;	 | | | | | | `------ 1 when writable.
											;	 | | | | | `------- expansion direction. 1 for a LIFO
											;	 | | | | `-------- 1 always			
											;	 | | | `--------- 1 for segment descriptor, 0 for system descriptor
											;	 | | `---------- DPL !!! 0 for ring 0 
											;	 | `----------- DPL (2/2)
											;	 `------------ 1 if in physical memory, 0 if page fault  
						db	10001111b		;	|7|6|5|4|3|2|1|0|
											;	 | | | | | | | `----- Limit 16
											;	 | | | | | | `------ Limit 17
											;	 | | | | | `------- Limit 18
											;	 | | | | `-------- Limit 19
											;	 | | | `--------- available for use
											;	 | | `---------- 0 always
											;	 | `----------- size of data. 1 for 32bits
											;	 `------------ 0 if limit is in Bytes, 1 if it's in pages (4ko)
						db	0x0				; Base Address 31:24
						
		LONG_SELECTOR:	;; 64-bit code selector (ring 0)
						dw 	0x0FFFF			;  Segment Limit 15:00
						db	0x0, 0x0, 0x0	; Base Address 23:00
						db  10011010b		;   |7|6|5|4|3|2|1|0|
											;	 | | | | | | | `----- 1 when segment used. 
											;	 | | | | | | `------ 1 when writable. 
											;	 | | | | | `------- 1 if "conformant". Don't know what is it... spectral ? xD
											;	 | | | | `-------- 1 always
											;	 | | | `--------- 1 for segment descriptor, 0 for system descriptor
											;	 | | `---------- DPL !!! 0 for ring 0 
											;	 | `----------- DPL (2/2)
											;	 `------------ 1 if in physical memory, 0 if page fault 
						db	10101111b		;	|7|6|5|4|3|2|1|0|
											;	 | | | | | | | `----- Limit 16
											;	 | | | | | | `------ Limit 17
											;	 | | | | | `------- Limit 18
											;	 | | | | `-------- Limit 19
											;	 | | | `--------- available for use
											;	 | | `---------- 0 always
											;	 | `----------- size of data. 1 for 32bits
											;	 `------------ 0 if limit is in Bytes, 1 if it's in pages (4ko)
						db	0x0				; Base Address 31:24
	GDT_LENGTH:	

[BITS 16]
disable_cursor:
	pushf
	push eax
	push edx
 
	mov dx, 0x3D4
	mov al, 0xA	                            ; low cursor shape register
	out dx, al
 
	inc dx
	mov al, 0x20	                        ; bits 6-7 unused, bit 5 disables the cursor, bits 0-4 control the cursor shape
	out dx, al
 
	pop edx
	pop eax
	popf
	ret
	
get_dimensions:
    push eax
    push ebx
    mov ah, 0x0F
    int 0x10
    mov [VGA_HEIGHT], ah
    mov [VIDEO_MODE], al
    pop ebx
    pop eax
    ret

main:	
	;; 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

[BITS 32]
VIDEO_MODE32 dw 0
VGA_HEIGHT32 dw 0

main32:
    pop dword [VGA_HEIGHT32]
    pop dword [VIDEO_MODE32]
    
    ;; 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]    
;; FUNCTIONS

write:
;-----------------------------------------------------------------------;
; x64/LM Text Printing Functions                                        ;
; bl  : color code                                                      ;
; esi : string address                                                  ;
;-----------------------------------------------------------------------;
    mov  edi, [NextTRAM]                     ;TRAM ADDRESS
    push rsi
    push rdi
.pLoop:
    lodsb
    cmp al, 0                               ; while @al, i.e. while we're not hitting '\0'
    je .pEnd                                
    cmp al, 0x0A                            ; LF
    je .lf
    cmp al, 0x0D                            ; CR
    je .cr
    stosb                                   ; text subpixel
    mov al, bl
    stosb                                   ; color subpixel
    add qword [NextTRAM], 0x2               ; Cursor moving
    add qword  [VGA_X], 0x2                 ; coord + 2 because 2 subpixels
    jmp .pLoop
.pEnd:    
    pop rdi
    pop rsi	
	ret
.lf:
    mov rax, [VGA_HEIGHT64]
    add [NextTRAM], rax                     ; Cursor moving
    add [NextTRAM], rax
    add edi, eax                            ; Address moving
    add edi, eax
    jmp .pLoop
.cr:
    push rax
    mov rax, qword [VGA_X]
    sub qword [NextTRAM], rax               ; pos = X + Y * VGA_HEIGHT64. Donc pos - X = début de ligne
    sub edi, edx
    mov qword [VGA_X], 0
    pop rax
    jmp .pLoop
.scroll:

    jmp .pLoop

;; DATA	
txt             db  0x09, " Switching to Long Mode... OK", 0x0A, 0x0D, 0
NextTRAM        dq  0x0B8AA0                ; Last position of cursor
VIDEO_MODE64    dq  0
VGA_HEIGHT64    dq  0
VGA_X           dq  0x0
msg             db  "The system is now in x64 mode. Is this not beautiful ?", 0x0A, 0x0D, 0

main64:
    pop qword [VGA_HEIGHT64]
    pop qword [VIDEO_MODE64]
    ;; INITIALIZE STACK
    mov rsp, 0x9F000
    
    ;; NOTIFYING
    mov bl, 0x0A
    mov esi, txt
    call write
    
    mov bl, 0x0B
    mov esi, msg
    call write
    
    mov bl, 0x0C
    mov esi, msg
    call write
    
    mov bl, 0x0D
    mov esi, msg
    call write
    
    mov bl, 0x0E
    mov esi, msg
    call write
    
    ;call KERNEL
    jmp $
    
times 1024-($-$$) db 144
KERNEL: