cos2000v2/boot/loader.asm

859 lines
18 KiB
NASM
Executable File

;/*******************************************************************************/
;/* COS2000 - Compatible Operating System - LGPL v3 - Hordé Nicolas */
;/* */
[BITS 16]
[ORG 0x0]
SECTION .text
push cs
push cs
pop ds
pop es
mov si,msg0
call showstr
;Projection de la FAT12 en mémoire
mov si,msg1
call showstr
call initfat
call ok
;Recherche du système
mov si,msg2
call showstr
mov si,System_File
call search
call ok
;Activation du BUS A20
mov si,msg3
call showstr
call EnableA20
call ok
;Chargement d'une GDT pour le mode FLAT REAL
mov si,msg4
call showstr
mov eax,cs
shl eax,4
mov [GDT.Entry1+2],ax
mov [GDT.Entry2+2],ax
shr eax,16
mov [GDT.Entry1+4],al
mov [GDT.Entry2+4],al
mov eax,cs
shl eax,4
add eax,gdt0
mov [GDTR.Address],eax
lgdt [GDTR]
call ok
;Passage en mode FLAT REAL
mov si,msg5
call showstr
cli
mov eax,cr0
or al,1
mov cr0,eax
jmp short $+2
mov bx,SYS_DATA_SEL
mov fs,bx
mov ds,bx
mov es,bx
mov gs,bx
and al,0FEh
mov cr0,eax
jmp short $+2
mov bx,cs
mov fs,bx
mov ds,bx
mov es,bx
mov gs,bx
sti
call ok
;Chargement du noyau en 0x30000
mov si,msg6
call showstr
mov ebx,0x300000
call load
call ok
;Chargement du fichier PE
mov si,msg7
call showstr
call initpe
call ok
;suite:
;mov cx,suite
;call debug
mov si,msg8
call showstr
cli
;Passage en mode protégé
mov al,0x80
out 0x70,al
mov eax,cr0
or al,1
mov cr0,eax
;Exécution du code 32 bits
jmp SYS_CODE_SEL:GoPMode32
Boot_Error:
mov si,error
call showstr
xor ax,ax
int 16h
jmp 0xFFFF:0x0
ok:
push si
push cx
mov cl,67
call eol
mov si,okay
call showstr
pop cx
pop si
ret
;======================INITPE========================
;Initialise le PE de l'adresse EBX
;->
;<- Flag Carry si erreur
;=====================================================
initpe:
pusha
push es
xor ax,ax
mov es,ax
mov [begin],ebx
cmp word [es:ebx+ELFheader.Magic],0x457F ; bien l'entete .elf ?
jne near errorelf
cmp word [es:ebx+ELFheader.Magic+2],"LF" ; bien l'entete .elf ?
jne near errorelf
cmp byte [es:ebx+ELFheader.Computertype],0x1 ; type ok ?
jne near errorelf
cmp byte [es:ebx+ELFheader.Endianness],0x1 ; type ok ?
jne near errorelf
cmp byte [es:ebx+ELFheader.Original],0x1 ; type ok ?
jne near errorelf
cmp byte [es:ebx+ELFheader.OS],0x0 ; type ok ?
jne near errorelf
cmp byte [es:ebx+ELFheader.ABI],0x0 ; type ok ?
jne near errorelf
cmp byte [es:ebx+ELFheader.Dummy],0x0 ; type ok ?
jne near errorelf
mov si,info1
call showstr
mov esi,[es:ebx+ELFheader.Entrypoint]
mov [entriepoint],esi
mov esi,[es:ebx+ELFheader.Offsetprogram]
add esi,ebx
mov [offsetheader],esi
mov esi,[es:ebx+ELFheader.Offsetsection]
add esi,ebx
mov [offsetsection],esi
mov cx,[es:ebx+ELFheader.Nbprogram]
mov [cs:nbprogram],cx
mov cx,[es:ebx+ELFheader.Nbsection]
mov [cs:nbsection],cx
xor eax,eax
mov ax,[es:ebx+ELFheader.Index]
xor edx,edx
mov dx,[es:ebx+ELFheader.Sizesection]
mul edx
add eax,esi
mov eax,[es:eax+Sections.Offset]
add eax,ebx
mov [cs:symbol],eax
xor eax,eax
add ax,[es:ebx+ELFheader.Sizesection]
add esi,eax
sections:
mov edi,esi
cmp dword [es:edi+Sections.Type],0x00
jz nothing
mov esi,info2
call showstr
push ds
push es
pop ds
mov esi,[es:edi+Sections.Name]
add esi,[cs:symbol]
call showstr
pop ds
mov esi,info3
call showstr
mov edx,[es:edi+Sections.Offset]
push cx
mov cx,32
call ShowHex
pop cx
mov esi,info4
call showstr
mov edx,[es:edi+Sections.Size]
push cx
mov cx,32
call ShowHex
pop cx
mov esi,info5
call showstr
mov edx,[es:edi+Sections.Vadress]
push cx
mov cx,32
call ShowHex
pop cx
and dword [es:edi+Sections.Flags],SF_ALLOC
jne itsok
mov esi,info6
call showstr
jmp itsok2
itsok:
mov esi,info10
call showstr
call copy2mem
cmp dword [es:edi+Sections.Type],ST_NOBITS
jne itsok2
mov esi,info9
call showstr
mov esi,info10
call showstr
call zero2mem
itsok2:
push cx
xor cx,cx
mov edx,[es:edi+Sections.Align]
mov esi,info8
call showstr
nextpower:
cmp edx,0
je powerok
cmp edx,1
je powerok
cmp cx,32
je powerok
inc cx
shr edx,1
jnc nextpower
powerok:
mov edx,ecx
mov cx,4
call ShowHex
pop cx
call showrtn
mov esi,edi
nothing:
add esi,eax
dec cx
jnz sections
mov esi,info7
call showstr
mov edx,[cs:entriepoint]
mov cx,32
call ShowHex
clc
pop es
popa
ret
errorelf:
stc
pop es
popa
ret
;==========DEBUG===========
;CX adresse
;->CX
;<-
;==========================
debug:
mov esi,info11
call showstr
xor edx,edx
mov dx,cs
shl edx,4
add edx,ecx
mov cx,32
call ShowHex
infini:
jmp infini
;==========COPY2MEM===========
;Copie de es:esi vers es:edi
;->ES:ESI ES:EDI CX
;<- Flag
;=============================
copy2mem:
push eax
push esi
push edi
push ecx
mov esi,[es:edi+Sections.Offset]
add esi,[cs:begin]
mov ecx,[es:edi+Sections.Size]
shr ecx,2
inc ecx
mov edi,[es:edi+Sections.Vadress]
copietomem:
mov eax,[es:esi]
mov [es:edi],eax
add edi,4
add esi,4
dec ecx
jnz copietomem
pop ecx
pop edi
pop esi
pop eax
ret
;==========ZERO2MEM===========
;Remise à zero de es:edi
;->ES:EDI CX
;<- Flag
;=============================
zero2mem:
push eax
push esi
push edi
push ecx
mov esi,[es:edi+Sections.Offset]
add esi,[cs:begin]
mov ecx,[es:edi+Sections.Size]
shr ecx,2
inc ecx
mov edi,[es:edi+Sections.Vadress]
mov eax,0
zerotomem:
mov [es:edi],eax
add edi,4
dec ecx
jnz zerotomem
pop ecx
pop edi
pop esi
pop eax
ret
begin dd 0
entriepoint dd 0
offsetheader dd 0
offsetsection dd 0
nbprogram dw 0
nbsection dw 0
symbol dd 0
;==========SHOWHEX===========
;Affiche un nombre hexadécimal EDX de taille CX aprés le curseur
;-> EDX un entier, CX la taille
;<-
;============================
ShowHex:
push ax
push bx
push cx
push edx
push si
mov ax,cx
shr ax,2
sub cx,32
neg cx
shl edx,cl
xor cx,cx
inc cx
Hexaize:
rol edx,4
mov bx,dx
and bx,0fh
mov si,ax
mov al,[cs:bx+Tab]
xor bx,bx
mov ah,0x09
mov bl,[cs:thecolor]
int 0x10
mov ah,0x0E
int 0x10
mov ax,si
dec al
jnz Hexaize
pop si
pop edx
pop cx
pop bx
pop ax
ret
Tab db '0123456789ABCDEF'
;============EOL=============
;Va en colonne CX
;->
;<- Flag Carry si erreur
;============================
eol:
pusha
mov bp,cx
mov ah,03
xor bx,bx
int 10h
mov ah,02
mov cx,bp
mov dl,cl
int 10h
popa
ret
;============LOAD==============
;Charge le groupe en mémoire en EBX pour le groupe CX
;-> CX
;<- Flag Carry si erreur
;==============================
load:
push ax
push ebx
push ecx
push edx
push esi
push edi
push fs
xor edx,edx
xor ax,ax
mov fs,ax
mov si,The_Dot
mov dx,[Sectors_Size]
Resume_Loading:
cmp cx,0x0FF0
jae Finish_Loading
push cx
add cx,word [data]
mov edi,Buffer
call ReadSector
pop cx
jc near Boot_Error
call showstr
push esi
push ebx
push cx
mov esi,Buffer
mov cx,dx
shr cx,2
copie:
mov eax,[ds:esi]
mov [fs:ebx],eax
add ebx,4
add esi,4
dec cx
jnz copie
pop cx
pop ebx
pop esi
add ebx,edx
call NextFatGroup
jc near Boot_Error
jmp Resume_Loading
Finish_Loading:
pop fs
pop edi
pop esi
pop edx
pop ecx
pop ebx
pop ax
ret
;===========INITFAT=============
;Initialise les variables de la fat
;->
;<- Flag Carry si erreur
;===============================
initfat:
pusha
push ds
xor ax,ax
mov ds,ax
mov si,0x7C0B
mov di,bootsector
mov cx, 512
rep movsb
pop ds
mov cx,[Reserved_Sectors]
add cx,[Sectors_Hidden]
adc cx,[Sectors_Hidden+2]
mov bx,[Sectors_Per_Fat]
mov di,Fat_Buffer
push bx
push cx
readfat:
call ReadSector
jc Boot_Error
inc cx
add di,[Sectors_Size]
dec bx
jnz readfat
pop cx
pop bx
xor ax,ax
mov al,[Fats_Number]
mul bx
add cx,ax
mov [entries],cx
mov ax,32
mul word [Fits_Number]
div word [Sectors_Size]
add cx,ax
sub cx,2
mov word [data],cx
popa
ret
;===========SEARCH============
;Recherche le groupe d'un fichier
;-> si nom du fichier
;<- Flag Carry si erreur CX
;=============================
search:
push bx
push dx
push di
mov cx,[entries]
mov di,Buffer
call ReadSector
jc Boot_Error
xor bx,bx
Next_Root_Entrie:
cmp byte [di],0
je Boot_Error
push si
push di
push cx
mov cx,32
rep cmpsb
pop cx
pop di
pop si
je Found
add di,32
add bx,32
inc dx
cmp dx,[Fits_Number]
ja Boot_Error
cmp bx,[Sectors_Size]
jb Next_Root_Entrie
inc cx
Found:
mov cx,[di+26+32]
pop di
pop dx
pop bx
ret
;============SHOWRTN============
;Affiche la chaine de caractère return
;->
;<- Flag Carry si erreur
;===============================
showrtn:
push ds
push ax
push esi
mov esi,return
mov ax,cs
mov ds,ax
call showstr
pop esi
pop ax
pop ds
ret
;==============SHOWSTR=============
;Affiche la chaine de caractère pointé par ds:esi à l'écran
;-> DS, ESI
;<- Flag Carry si erreur
;==================================
showstr:
pushad
xor bh,bh
nextchar:
mov al,[ds:esi]
inc esi
or al,al
jz endshow
cmp al,' '
jb justchar
cmp al,'#'
jne nocolor
mov al,[ds:esi]
inc esi
sub al,'0'
shl al,3
mov [cs:thecolor],al
shr al,2
add [cs:thecolor],al
mov al,[ds:esi]
inc esi
sub al,'0'
add [cs:thecolor],al
jmp nextchar
nocolor:
cmp al,'@'
jne nocolor2
mov al,[ds:esi]
inc esi
sub al,'0'
shl al,3
mov cl,al
shr al,2
add cl,al
mov al,[ds:esi]
inc esi
sub cl,'0'
add cl,al
call eol
jmp nextchar
nocolor2:
xor bx,bx
mov ah,0x09
mov bl,[cs:thecolor]
xor cx,cx
inc cx
int 0x10
justchar:
mov ah,0x0E
int 0x10
jmp nextchar
endshow:
popad
ret
;==========READSECTOR============
;Lit le secteur logique LBA CX et le met en es:di
;-> CX (limité à 65536 secteurs, soit 32 Mo avec secteur 512 octets)
;<- Flag Carry si erreur
;================================
ReadSector:
pusha
mov ax,cx
xor dx,dx
div word [Sectors_Per_Track]
inc dl
mov bl,dl
xor dx,dx
div word [Heads_Number]
mov dh, [Boot_Drive]
xchg dl,dh
mov cx,ax
xchg cl,ch
shl cl,6
or cl, bl
mov bx,di
mov si, 4
mov al, 1
Read_Again:
mov ah, 2
int 0x13
jnc Read_Done
dec si
jnz Read_Again
Read_Done:
popa
ret
;============NEXTFATGROUP===========
;Renvoie en CX le groupe qui succède dans la FAT le groupe CX
;-> CX
;<- CX
;===================================
NextFatGroup:
push bx
push dx
push di
mov ax,cx
mov bx,ax
and bx,0000000000000001b
shr ax,1
mov cx,3
mul cx
mov di,Fat_Buffer
add di,ax
cmp bx,0
jnz Even_Group
Odd_Group:
mov dx,[di]
and dx,0x0FFF
mov cx,dx
jmp Next_Group_Found
Even_Group:
mov dx,[di+1]
and dx,0xFFF0
shr dx,4
mov cx,dx
Next_Group_Found:
pop di
pop dx
pop bx
ret
;============EnableA20============
;->
;<-
;Ouvre l'autoroute A20
;=================================
EnableA20:
cli
call ClearKeybBuffer
call WaitKeybCommand
mov al,0xd1
out 0x64,al
call WaitKeybCommand
mov al,0xdf
out 0x60,al
call WaitKeybCommand
jmp A20Enabled
WaitKeybCommand:
in al,0x64
test al,0x02
jnz WaitKeybCommand
ret
ClearKeybBuffer:
in al,0x64
test al,0x01
jnz ReadKeyb
ret
ReadKeyb:
in al,0x60
jmp ClearKeybBuffer
A20Enabled:
sti
ret
;=================================
;CODE 32 bits mode protégé
;=================================
GoPMode32:
[BITS 32]
;Initialisation des selecteurs
mov ax,ALL_DATA_SEL
mov es,ax
mov gs,ax
mov fs,ax
mov ss,ax
mov ds,ax
mov esp,0x3fffff
push KERNEL_SEL
push dword [cs:entriepoint]
;Execution du système
retf
section .data
thecolor db 0x07
msg0 db '#12@20-=< Lancement du Chargeur ELF >=-',0x0A,0x0D,0x0A,0x0D,0
msg1 db '#07Initialisation de la FAT',0
msg2 db '#07Recherche du systeme',0
msg3 db '#07Activation adressage 24 bits',0
msg4 db '#07Chargement des descripteurs',0
msg5 db '#07Passage en mode Flat real',0
msg6 db '#07Chargement du systeme',0
msg7 db '#07Mise en place format ELF',0
msg8 db '#07Passage en mode protege',0
info1 db 0x0A,0x0D,'Format ELF i386 reconnu, #08Sections :',0x0A,0x0D,0
info2 db ' ',0
info3 db '@12 | ',0
info4 db ' - ',0
info5 db ' -> ',0
info6 db '@35#12NON ALLOUE #08',0
info7 db 'Point entree en ',0
info8 db '@48 2**',0
info9 db '@15#12 VIDE #08',0
info10 db '@70MEM',0
info11 db 0x0A,0x0D,'#12Arret debug en ',0
return db 0x0A,0x0D,0
okay db ' #15[ #10OK #15]',0x0A,0x0D,0
error db ' #15[#12Erreur#15]',0x0A,0x0D,0x0A,0x0D,' <Appuyez une touche pour redemarrer>',0
The_Dot db '.',0
System_File db "As",0,"y",0,"s",0,"t",0,"e",0,0x0F,0,0xB8,"m",0,".",0,"s",0,"y",0,"s",0,0,0,0,0,0xFF,0xFF,0xFF,0xFF
entries dw 0
data dw 0
xy dw 0
GDTR:
.Size: dw GDT_END
.Address: dd 0
gdt0 equ $ ; null entry
GDT:
.Entry0: dw 0 ; limit 15:0
dw 0 ; base 15:0
db 0 ; base 23:16
db 0 ; type
db 0 ; limit 19:16, flags
db 0 ; base 31:24
SYS_CODE_SEL equ $-gdt0 ; code segment descriptor
.Entry1: dw 0xFFFF
dw 0x0 ; base
db 0x0 ; base
db 0x9A ; present, ring 0, code, non-conforming, readable
db 0xCF ; 32 bit
db 0
SYS_DATA_SEL equ $-gdt0 ; data segment descriptor
.Entry2: dw 0xFFFF
dw 0x0 ; base
db 0x0 ; base
db 0x92 ; present, ring 0, data, expand-up, writable
db 0xCF ; 32 bit
db 0
ALL_DATA_SEL equ $-gdt0 ; 4meg data segment descriptor
.Entry3: dw 0xFFFF
dw 0x0 ; base
db 0x0 ; base
db 0x92 ; present, ring 0, data, expand-up, writable
db 0xCF ; 4k pages, 32 bit
db 0
KERNEL_SEL equ $-gdt0 ; 4g code segment descriptor
.Entry4: dw 0xffff
dw 0x0 ; base
db 0x0 ; base
db 0x9A ; present, ring 0, code, non-conforming, readable
db 0xCF ; 4k pages, 32 bit
db 0
GDT_END equ $-gdt0 -1
bootsector equ $
Sectors_Size dw 0 ;Nombre d'octets/secteur
Sectors_Per_Cluster db 0 ;Nombre de secteurs/cluster
Reserved_Sectors dw 0 ;Nombre de secteurs réservé
Fats_Number db 0 ;Nombre de copies de la FAT
Fits_Number dw 0 ;Taille du répertoire racine
Sectors_Per_Disk dw 0 ;Nombre secteurs du volume si < 32 Mo
Media_Descriptor db 0 ;Descripteur de média
Sectors_Per_Fat dw 0 ;Nombre secteurs/FAT
Sectors_Per_Track dw 0 ;Nombre secteurs/piste
Heads_Number dw 0 ;Nombre de tete de lecture/écriture
Sectors_Hidden dd 0 ;Nombre de secteurs cachés
Sectors_Per_Disk2 dd 0 ;Nombre secteurs du volume si > 32 Mo
Boot_Drive db 0 ;Lecteur de démarrage
Reserved db 0 ;NA (pour NT seulement)
Extended_Boot_ID db 0 ;Signature Boot étendu 29h
Buffer equ $
Fat_Buffer equ $+512
SECTION .bss
%include "elf.h"