minor stuff with the A20 line '-'

This commit is contained in:
Adrien Bourmault 2019-01-15 00:23:27 +01:00
parent d3ba9640fc
commit 35c71e4b24
5 changed files with 50 additions and 30 deletions

10
boot/elf/elf.c Normal file
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@ -0,0 +1,10 @@
//----------------------------------------------------------------------------//
// GNU GPL OS/K //
// //
// Authors: spectral` //
// NeoX //
// //
// Desc: ELF64 Parser and Loader //
//----------------------------------------------------------------------------//

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@ -33,13 +33,6 @@
%define volumeLabel bp+0x2b ; Volume Label
%define fatTypeLabel bp+0x36 ; File system type
;; DISK BUFFER "SEGMENT"
%define BUFFER_SEG 0x07c0 ; (BUFFER_SEG << 4) + BUFFER_OFF = 0x07C00
%define BUFFER_OFF 0x0000
;; SECOND STAGE LOADER "SEGMENT"
%define LOAD_SEG LONG_SELECTOR-GDT64 ; (LOAD_SEG << 4) + LOAD_OFF = 0x070000
%define LOAD_OFF Kernel
[BITS 16]
@ -56,13 +49,13 @@ jmp 0x0000:main
;; 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 ;
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
db 0x0, 0x0, 0x0 ; Base Address
dw 0x0000FFFF ; Segment Limit
db 0x0, 0x0, 0x0 ; Base Address
db 10011010b ; |7|6|5|4|3|2|1|0|
; | | | | | | | `----- 1 when segment used.
; | | | | | | `------ 1 when writable.
@ -72,7 +65,7 @@ GDT64:
; | | `---------- 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|
db 11001111b ; |7|6|5|4|3|2|1|0|
; | | | | | | | `----- Limit 16
; | | | | | | `------ Limit 17
; | | | | | `------- Limit 18
@ -81,11 +74,11 @@ GDT64:
; | | `---------- 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
db 0x0 ; Base Address
DATA_SELECTOR: ;; flat data selector (ring 0)
dw 0x0FFFF ; Segment Limit
db 0x0, 0x0, 0x0 ; Base Address
dw 0x0000FFFF ; Segment Limit
db 0x0, 0x0, 0x0 ; Base Address
db 10010010b ; |7|6|5|4|3|2|1|0|
; | | | | | | | `----- 1 when segment used.
; | | | | | | `------ 1 when writable.
@ -95,7 +88,7 @@ GDT64:
; | | `---------- 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|
db 10001111b ; |7|6|5|4|3|2|1|0|
; | | | | | | | `----- Limit 16
; | | | | | | `------ Limit 17
; | | | | | `------- Limit 18
@ -104,11 +97,11 @@ GDT64:
; | | `---------- 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
db 0x0 ; Base Address
LONG_SELECTOR: ;; 64-bit code selector (ring 0)
dw 0x0FFFF ; Segment Limit
db 0x0, 0x0, 0x0 ; Base Address
dw 0x0000FFFF ; Segment Limit
db 0x0, 0x0, 0x0 ; Base Address
db 10011010b ; |7|6|5|4|3|2|1|0|
; | | | | | | | `----- 1 when segment used.
; | | | | | | `------ 1 when writable.
@ -118,7 +111,7 @@ GDT64:
; | | `---------- 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|
db 10101111b ; |7|6|5|4|3|2|1|0|
; | | | | | | | `----- Limit 16
; | | | | | | `------ Limit 17
; | | | | | `------- Limit 18
@ -127,7 +120,7 @@ GDT64:
; | | `---------- 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
db 0x0 ; Base Address
GDT_LENGTH:
%include "boot/loader16.inc"
@ -195,6 +188,21 @@ 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
@ -260,6 +268,7 @@ KernSearch db 0x09, " Loading the Kernel in RAM...", 0
txt db 0x09, " Switching to Long Mode... ", 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
NoLongMode db 0x0A, 0x0D, "ERROR : Your computer is not designed for x64 OS", 0
@ -278,6 +287,7 @@ NextTRAM dq 0x0B8000 ; Last position of cursor
VIDEO_MODE64 dq 0
VGA_HEIGHT64 dq 0
VGA_X dq 0
A20_OK db 0
main64:
pop qword [VGA_HEIGHT64]
@ -304,14 +314,13 @@ main64:
mov esi, EnA20
call write
mov bl, 0x0A
mov esi, Pass
cmp BYTE [A20_OK], 1
je .A20Success
mov bl, 0x0C
mov esi, Fail
call write
mov bl, 0x0F
mov esi, KernSearch
call write
jmp Die
.A20Success:
mov bl, 0x0A
mov esi, Pass
call write
@ -328,6 +337,7 @@ main64:
mov esi, msg
call write
jmp Die
; times 1024 nop

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