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Loading C kernel
Posted: Wed Aug 28, 2002 8:13 pm
by Tom
Hello, my FritzOS has pmode set up, but how do I go to my C kernel? I'm using Linux, and my boot sector is 512 bytes, it jumps to a 2nd loader & sets up Pmode and A20. I also need to know how to use DD to put my C kernel after the asm & 2nd asm loaders.
I'd use ints but ... i'm in PMode :-\ I'm going crazy trying to choose PMode or Real Mode. I'll also doc my os development very [glow=green,2,300]VERY[/glow]( as i've been doing )well so it'll be easy for others to learn, compile, & change FritzOS.
Thank you
Re:Loading C kernel
Posted: Wed Aug 28, 2002 11:31 pm
by roswell
Hi,
I have written a bootloader that seems to work as yours.
1 step : 512b of asm code
Switch to big real mode, check memory, load the second step.
2 step : 512b of asm code
load a multiboot kernel that is stored just the sector after this one.
So I create a big binary image composed of : step1+step2+oskernel.
My disk is no more readable ( no FAT ), but this is not important for me.
This system works fine. I load my C kernel several times every day ( about 900Ko of code ).
If you want me to help you, just send me a mail :
[email protected], or reply to this message.
roswell
Re:Loading C kernel
Posted: Thu Aug 29, 2002 4:25 am
by frank
well,
If you are in pmode, and it jumps to your second sector (your kernel)
than it is not so hard...
Just use this code as basic code:
Code: Select all
asm("jmp start");
void start()
{
while (1) /* hang */
{
}
}
and check if it hangs... if it hangs then you've loaded your kernel.
if it didn't then it'll reboot.
Compile it as binary and put it in the second sector...
I always use an install.sh for that: (which I wrote myself, oufcourse)
Code: Select all
cd boot
nasm boot.asm -f bin
dd if=boot of=/dev/disk # put it onto /dev/disk (change disk into your disk so /dev/hda,/dev/hdb,/dev/hdc)
cd ..
cd kernel
gcc -04 kern.c
ld -o kern -Ttext 0x1000 -e 0x0 kern.o
objcopy -R .note -R .comment -S -O binary kern kern.bin
dd if=kern.bin seek=1 of=/dev/disk # put it on the second sector (change /dev/disk to your disk)
cd ..
Change -Ttext 0x1000 to the place where you loaded it...
I use 0x1000, but perhaps you loaded it into another place...
Also I use int 0x13 for loading the kernel...
Code: Select all
.....
mov bx,0x1000 ; 0x1000:0x0000 :)
......
int 0x13
Then I switch to pmode and jump to the kernel
You can check if it works in an asm kernel too:
Code: Select all
org 0x1000
bits 32
jmp bla
bla: jmp bla ; hang
Best,
Frank Anemaet
Re:Loading C kernel
Posted: Thu Aug 29, 2002 1:29 pm
by Tom
I did that, frank, but it rebooted my computer
Re:Loading C kernel
Posted: Thu Aug 29, 2002 3:39 pm
by frank
I did that, frank, but it rebooted my computer
That has a reason
The reason is one of these
1. you did not switch to pmode correct (that makes the computer reboot)
2. the jumping went wrong or the loading....
Check if it works without the pmode stuff...
so like this:
Code: Select all
org 7c00h
jmp main
main:
mov [drive],dl
; load the kernel of the disk
mov ah,0x02
mov al,4 ; kernel is 4 sectors for now :)
mov ch,0
mov cl,0
mov cl,00000001b ; first sector
mov bx,0x1000 ; memory place
mov dl,[drive]
int 13
; then jump to the kernel
jmp 0x0000:0x10000
drive db 0
times 510-($-$$) db 0
sign dw 0xAA55
The kernel should look like this:
Code: Select all
org 1000h
jmp main
main: jmp main
times 510-($-$$) db 0
Then put it onto the disk:
Code: Select all
nasm bootsector1.asm -f bin
dd if=bootsector1 of=/dev/disk
nasm kernel.asm -f bin
dd if=kernel seek=1 of=/dev/disk
If it hangs, then you jumped to your kernel.
If not, somethings wrong....
If it works, switch to pmode and load the (C?) kernel
uhmmm... did you switch to pmode and then do int 13h?
Re:Loading C kernel
Posted: Thu Aug 29, 2002 5:04 pm
by Tom
; * FritzOS: Fritz Operating System.
; * boot.asm: Boot FritzOS
; * Copyright (C) 2002 Tom Fritz
; *
; * This program is a part of the FritzOS kernel, and may be freely
; * copied under the terms of the GNU General Public License (GPL),
; * version 2, or at your option any later version.
;********************************************************************************
; Not much Kernels are commented very well, so i'll comment this one good.
; This is the Assembly Language source code file for the FritzOS booter.
; This program is run by the BIOS, and this program must end in 0xAA55
; for the BIOS. Also this program must be 512 bytes big.
; You need Linux to compile this.
; This program must be compiled with NASM. You can find it at SourceForge.net
; To compile this boot program look at the 'INSTALLING' file.
; This will put the boot program onto floppy /dev/fd0, or A:
; Make Sure You Have A Blank Floppy In fd0 Or A: Before You Do This!
;
; The .bin part is optional, but it can let you know that file is in the
; plain binary format. The BIOS needs the program in this format.
; This part tells NASM that right here is offset 0 .
; It's not really at offset 0, but it will be after it jumps to "start".
jmp 07C0h:start ; Goto start
;_____________________________________________________________________________________________________________
; Here is where the boot program starts.
start:
; Update the segment registers
mov ax, cs ; Copy cs into ax
mov ds, ax ; cs->ax->ds
mov es, ax ; cs->ax->es
jmp Running ; Go to the running part of the bootsector
;_____________________________________________________________________________________________________________
; This is where the boot program runs.
Running:
; Load the second stage loader.
reset: ; Reset the floppy drive
mov ax, 0 ;
mov dl, 0 ; Drive=0 (=A)
int 13h ;
jc reset
read:
mov ax, 1000h ; ES:BX = 1000:0000
mov es, ax ;
mov bx, 0 ;
mov ah, 2 ; Load disk data to ES:BX
mov al, 5 ; Load 5 sectors
mov ch, 0 ; Cylinder=0
mov cl, 2 ; Sector=2
mov dh, 0 ; Head=0
mov dl, 0 ; Drive=0
int 13h ; Read!
jc read
cli ; Stop BIOS interrups - because PMode can't use them in this manner
; Set Protected Mode ( PMode )
mov eax, CR0
or eax, 0x1
mov CR0, eax
; Start A20
.1: in al, 0x64
test al, 2
jnz .1
mov al, 0xD1
out 0x64, al
.2: in al, 0x64
and ax, byte 2
jnz .2
mov al, 0xDF
out 0x60, al
; PMode needs a jmp, so here it is
jmp pmode
;____________________________________________________________________________________________________________
; We are in protected mode here:
[bits 32]
pmode:
; jmp 1000h:0000 ; Jump to the C kernel
; This part makes sure the bootsector is 512 bytes.
times 510-($-$$) db 0
dw 0xAA55
; End of boot.asm
;_____________________________________________________________________________________________________
/* kernel.c: FritzOS C Kernel
Copyright (C) 2002 Tom Fritz
*/
#define WHITE_TXT 0x07 // white on black text
unsigned int k_printf(char *message, unsigned int line); // the message and then the line #
int _start()
{
k_printf( "HI", 1 );
return 0;
}
unsigned int k_printf(char *message, unsigned int line) // the message and then the line #
{
char *vidmem = (char *) 0xb8000;
unsigned int i=0;
i=(line*80*2);
while(*message!=0)
{
if(*message==0x2F) // check for the next line stuff
{
*message++;
if(*message==0x6e)
{
line++;
i=(line*80*2);
*message++;
if(*message==0)
{
return(1);
};
};
*message--; // got to go back, this is just a forward slash
};
vidmem=*message;
*message++;
i++;
vidmem=WHITE_TXT;
i++;
};
return(1);
};
nasm -f bin -o boot.bin boot.asm
gcc -c kernel.c -o kernel.o
ld -Ttext=0x1000 -o kernel kernel.o -e 0x0
objcopy -R .note -R .comment -S -O binary kernel kernel.bin
dd if=boot.bin of=/dev/fd0
dd if=kernel.bin seek=1 of=/dev/fd0
Re:Loading C kernel
Posted: Fri Aug 30, 2002 4:34 am
by frank
Changes are bold
Code: Select all
[b]org 7c00h[/b]
[b]jmp start[/b] ; Goto start
start:
[b] mov [drive],dl ; (a computer can have 3 floppydisks)[/b]
; Update the segment registers
; mov ax, cs ; Copy cs into ax
; mov ds, ax ; cs->ax->ds
; mov es, ax ; cs->ax->es
[b]; try this instead:[/b]
[b] xor ax,ax [/b]
[b] mov ds,ax [/b]
; (codesegment is already loaded)
jmp Running ; Go to the running part of the bootsector
; This is where the boot program runs.
Running:
; Load the second stage loader.
reset: ; Reset the floppy drive
mov ax, 0x00
[b] mov dl, [drive] ; Drive [/b]
int 13h
jc reset
read:
mov bx, 1000h
mov ah, 0x02 ; Load disk data to ES:BX
mov al, 5 ; Load 5 sectors
mov ch, 0 ; Cylinder=0
mov cl, 2 ; Sector=2
mov dh, 0 ; Head=0
mov dl, [drive] ; Drive=0
int 13h ; Read!
jc read
cli ; Stop BIOS interrups -
; because PMode can't use them
; in this manner
; Load the gdtr
[b] lgdt[gdtr][/b] ; you didn't have a gdt
; Set Protected Mode ( PMode )
mov eax, cr0
or eax, 1
mov cr0, eax
jmp dword codesel:pmode
; Start A20
; a20line is more than this see: ;http://www.mega-tokyo.com/os/os-faq-memory.html
; anyway, I don't know if a20 line is necessary....
; (I just folowed the steps :)))
; We are in protected mode here:
[bits 32]
pmode:
[b]
; load them all with 32bit sel
mov eax,datasel
mov ss,eax
mov ds,eax
mov es,eax
mov fs,eax
mov gs,eax
mov ax,0x10
mov ss,ax
mov esp,0xFFFF ; maxmimum
mov dl,[drive] ; we want to know what drive in
; the kernel :)
jmp dword codesel:0x1000
[/b]
; jmp 1000h:0000 ; Jump to the C kernel
; Global descriptor table
; this tells the comp where
; all the segments (now selectors) are
gdtr
dw gdt_end-1
dd gdt
gdt
nullsel equ $-gdt
gdt0
dd 0
dd 0
codesel equ $-gdt
dw 0ffffh
dw 0
db 0
db 09ah
db 0cfh
db 0h
datasel equ $-gdt
dw 0ffffh
dw 0h
db 0h
db 092h
db 0cfh
db 0
gdt_end
; This part makes sure the bootsector is 512 bytes.
[b] drive db 0 ; store the drive[/b]
times 510-($-$$) db 0
dw 0xAA55
; End of boot.asm
;_____________________________________________________________________________________________________
I haven't test this code, I don't have a floppydrive ::)
Code: Select all
/* kernel.c: FritzOS C Kernel
Copyright (C) 2002 Tom Fritz
*/
asm("jmp start");
void start()
{
while (1){
}
}
should hang
you returned, which means it does not know where
Re:Loading C kernel
Posted: Sat Aug 31, 2002 9:43 pm
by Tom
Thank You ;D FritzOS boots up and sets PMode and loads GCC FritzOS kernel
