Bootloader

[seingh]

Hello everyone, I'm new in this forum and in the development of operating systems ^ ^ (XD)
I wanted to ask how to create a custom bootloader ... or better to say how to recognize it from qemu xD.
In short, the boot loader code is this:
Boot.asm:

Code: Select all

global loader
[BITS 32]
extern _kmain
section .text
   LEA SI,[msg]

   MOV AH,0Eh
print:  MOV AL,[SI]         
   CMP AL,0         
   JZ done      
   INT 10h      
        INC SI         
   JMP print

; wait for 'any key':
done:   ;MOV AH,0       
       ;INT 16h     
call _kmain

   MOV  AX,0040h
   MOV  DS,AX
   MOV  word[0072h],0000h.
   JMP  0FFFFh:0000h   

msg    DB  'Benvenuto in patronum OS.',13,10
; end boot1

qemu in windows but does not recognize it ... in ubuntu I need to use "qemu-kernel kernel.bin" instead in windows if I type the same command (with qemu installed) nothing happens ...

Sorry for my **** English, I'm Italian ^ ^

[seingh]

You seem to lack the boot loader signature at the end.

I did not understand what you are saying, please write in another way, I'm sorry.

[seingh]

I assume you have read the Bootloader wiki article, so you know about the BIOS boot signature. There's even an example how to define one.

oh, i haven't read it....

EDIT: After reading the article, I see that do not there is a big difference between that article and "my" ( excepted that the code in the article is in 16 bit and my is in 32 bit, there is also the difference that he does not call any C code, which I will be obliged to do (because I do not know very well asm) )

[b.zaar]

I assume you have read the Bootloader wiki article, so you know about the BIOS boot signature. There's even an example how to define one.

oh, i haven't read it....

EDIT: After reading the article, I see that do not there is a big difference between that article and "my" ( excepted that the code in the article is in 16 bit and my is in 32 bit, there is also the difference that he does not call any C code, which I will be obliged to do (because I do not know very well asm) )

You can't use 32 bit code in a boot sector, the cpu is running in 16 bit mode until you enter protected mode.

[seingh]

I assume you have read the Bootloader wiki article, so you know about the BIOS boot signature. There's even an example how to define one.

oh, i haven't read it....

EDIT: After reading the article, I see that do not there is a big difference between that article and "my" ( excepted that the code in the article is in 16 bit and my is in 32 bit, there is also the difference that he does not call any C code, which I will be obliged to do (because I do not know very well asm) )

You can't use 32 bit code in a boot sector, the cpu is running in 16 bit mode until you enter protected mode.

I solved it this way:

Code: Select all

global loader 
extern kmain
MODULEALIGN equ  1<<0           
MEMINFO     equ  1<<1        
FLAGS       equ  MODULEALIGN | MEMINFO  
MAGIC       equ    0x1BADB002          
CHECKSUM    equ -(MAGIC + FLAGS)    
 
section .text
align 4
MultiBootHeader:
   dd MAGIC
   dd FLAGS
   dd CHECKSUM

STACKSIZE equ 0x4000             
 
loader:
   mov esp, stack+STACKSIZE       
   push eax                        
   push ebx                       
 
   call  kmain                   
 
   cli
hang:
   hlt                            
   jmp   hang
 
section .bss
align 4
stack:
   resb STACKSIZE                 

thank you anyway ^ ^

[Gigasoft]

That isn't a bootloader. It is the entry point and multiboot header for a multiboot executable.

[seingh]

That isn't a bootloader. It is the entry point and multiboot header for a multiboot executable.

What? I tried this code in QEMU with the string "qemu -kernel kernel.bin" (after compiling a "kernel.bin" file ) and it works...
It do what I want: it calls a C function from Assembler in the computer boot. And with this I think it's a bootloader.

[shikhin]

/me shakes his head - this is what happens to people who just aimlessly copy code from some website, without even understanding what it does.

[Chandra]

What? I tried this code in QEMU with the string "qemu -kernel kernel.bin" (after compiling a "kernel.bin" file ) and it works...
It do what I want: it calls a C function from Assembler in the computer boot. And with this I think it's a bootloader.

Do you have any idea what -kernel option does? It's a good practice to examine the water level before diving into this huge sea. Do care to search before complaining.

[seingh]

/me shakes his head - this is what happens to people who just aimlessly copy code from some website, without even understanding what it does.

I already said that I do not know well the assembly, or rather not know anything about assembler.
It is true that I copied that code from a site ... but this does not mean anything.

What? I tried this code in QEMU with the string "qemu -kernel kernel.bin" (after compiling a "kernel.bin" file ) and it works...
It do what I want: it calls a C function from Assembler in the computer boot. And with this I think it's a bootloader.

Do you have any idea what -kernel option does? It's a good practice to examine the water level before diving into this huge sea. Do care to search before complaining.

Yes, it is obvious that I know what are the functions that I say.
It's needless to say ****.

This isn't a bootloader, it's just a multiboot entry point which can be loaded by multiboot-compatible bootloader.

Sorry, but it works without another bootloader ( such as grub ).

[neon]

I wanted to ask how to create a custom bootloader

You asked about creating a bootloader. This isnt a bootloader, stop calling it one.

[seingh]

I wanted to ask how to create a custom bootloader

You asked about creating a bootloader. This isnt a bootloader, stop calling it one.

ok XD

[seingh]

Sorry, but it works without another bootloader ( such as grub ).

Well, you're wrong here. Try to boot it on a real hardware, then we'll talk.

Or you can try booting it in bochs. All the same.

I tried it on my pc and it do not work...
That means that I must use grub -.-

[shikhin]

Accepting that you are wrong is the first step to start learning. And stating that everyone except you is wrong is the first step to damage your reputation.

I warned you.

[seingh]

Accepting that you are wrong is the first step to start learning. And stating that everyone except you is wrong is the first step to damage your reputation.

I warned you.

OK, sorry