boot loader whit gcc?

[GABOSNAKE]

Hi everyone, I am new in this forum, and i have a question:
I want to write a boot loader, for testing propose, only for display text whit the bios interrupt 0x10, but i don't get it whit GAS&LD, there is a way to do that?
It's posible to compile 16-bit real mode code whit GAS&LD?, i found the .code16 directive, but doesn't work, there is options for ld?...
I am new to os-programming...
Thanks.
Saludos.

[bubach]

You're better off forgetting about realmode, or you'll not learn anything interesting. Do programming under FreeDOS & OpenWatcom C compiler as MZ executables if you want BIOS interrupts, you could even load the program with Alex bootprog if you really want it bootable.

For 32-bit OS-dev in GCC you should take a look at the wiki on how to set up a cross-compiler and read some tutorials on basic kernels and the screen. But remember, real men use assembly.
Haha, even if that's not for you I recommend playing around with bootsectors and second stage loaders a bit before committing to GRUB or anything else, you'll learn valuable stuff.

[Brynet-Inc]

The file generated by the assembler is in whatever object format the toolchain is targeting, ELF, PE.. etc.

You can convert it to a headerless binary with objcopy, or alternatively you'll want to use a linker script with ld.

[GABOSNAKE]

You're better off forgetting about realmode, or you'll not learn anything interesting. Do programming under FreeDOS & OpenWatcom C compiler as MZ executables if you want BIOS interrupts, you could even load the program with Alex bootprog if you really want it bootable.

For 32-bit OS-dev in GCC you should take a look at the wiki on how to set up a cross-compiler and read some tutorials on basic kernels and the screen. But remember, real men use assembly.
Haha, even if that's not for you I recommend playing around with bootsectors and second stage loaders a bit before committing to GRUB or anything else, you'll learn valuable stuff.

Oh, great info!... reading.... thanks

The file generated by the assembler is in whatever object format the toolchain is targeting, ELF, PE.. etc.

You can convert it to a headerless binary with objcopy, or alternatively you'll want to use a linker script with ld.

I will try whit [objdump -O binary...], thanks....

[shikhin]

Hi,

I will try whit [objdump -O binary...], thanks....

You seem to misspell it everywhere. It's with, and not whit.

Regards,
Shikhin

[GABOSNAKE]

Hi,

I will try whit [objdump -O binary...], thanks....

You seem to misspell it everywhere. It's with, and not whit.

Regards,
Shikhin

thank's for the advice

And... I found the way to assembly the bootloader using as&ld
We need to add at top of the source

Code: Select all

.code16 

Next, using ld:

Code: Select all

ld -Ttext 0x7c00 --oformat binary -o $@ $<

With -Ttext we tell to the linker the start address of the text segment, the boot sector is loaded at 0x7c00

At this point we have a flat binary, so the next part is format the bootloader:
512 bytes & and at offset 0x1FE the word 0xAA55
And it work's...