Configuring for bare hw ia32 PC's

duane ellis
Mon May 12 16:26:00 GMT 2008

Luke A. Guest wrote:
> Hi,
> I'm going to be looking into my OS project again and was wondering how
> to configure newlib. Should I be using i386-elf or i386-pc-elf or
> something else?
> I think I'm going to have to do *some* porting work to get newlib to
> compile for bare PC hw access, i.e. getting dummy I/O code working and
> also getting screen I/O to go to the BIOS framebuffer.
> Thanks,
> Luke.
A while back - (April) Jonathan Shapiro was asking about something like 
this for his Cayotie (spelling?) Operating system
I whipped up a simple example for x86 and sent it to him, You might want 
to take a look at this as starting point/example.


(0) My assumption is you load your kernel with something like uboot or 
grub, or
    and that thing can load an "elf" file - because that is what this 

Basically all you need to do is:

(1) figure out your desired memory map - and thus your linker script.

(2) Add appropriate startup code to set registers - establish the stack etc.

    Deal with other 'machine specific stuff'

(3) The attached example - has an example "fake_syscalls.c"

    These functions could make 'bios' calls.
    That is your job, you need to write that.

Two things to note:
    (A) This might be a starting point for you.
    (B) it might not, NEWLIB is more of an application standard C library.
       Not really a "kernel standard c library"

It's a matter of personal preference.  I believe kernels should have a 
stripped down or reduced standard c library  Apps - need the full 
thing.   My reasoning centers around 'syscalls' and the problem of 
kernel code calling functions like 'fopen()' etc.... And - the fact that 
the kernel uses a single language, and does not require things like 
"locale" - the APP does - but not the kernel.

If you look at the makefile - it builds GCC in 2 stages stage 1 - is 
just a straight up C compiler, nothing else. No standard library. That 
should be enough to build your kernel as I describe.


The readme file talks about a "bios library" - if you create one - and 
would like to share it - I'd appreciate it. I'm looking for something 
very simple - at least the PC bios, maybe - timers maybe uart support.

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