[syslinux] Booting Embedded x86 - Looking for Information

H. Peter Anvin hpa at zytor.com
Mon Feb 1 09:09:52 PST 2010


On 01/31/2010 08:58 PM, Graeme Russ wrote:
> 
> Hmm, true - But not trivial. My only output is raw writes to the
> serial port using outb.
> 
> And how does the bzImage boot process work in a 100% disk less
> environment? The kernel image I have will be loaded into NOR Flash
> and copied directly into RAM by the bootloader. I assume the whole
> Boot Sector bootstrap is skipped in this scenario?
> 

The Boot Sector in the bzImage is a vestigial piece of history.  It's
not relevant.

> I assume this would be the same scenario as something like Loadlin/
> GRUB. I have looked at the Loadlin source but must admit I was
> completely dumbfounded by it. Haven't looked at GRUB yet, but by the
> sounds of it, they don't do things 'the right way'(tm)

Don't look at Loadlin.  It's much worse than Grub.  It's severely
weirdified by the fact that it has to run under DOS.

What you want to do is read Documentation/x86/boot.txt.  You might also
look at com32/lib/syslinux/load_linux.c in the Syslinux sources if you
want a code example.

> Should I look at putting some outb's in arch/x86/boot/compressed/head_32.S
> i.e. is this the earliest point that I can check that control has
> passed into Linux kernel source or is there an even earlier point?

arch/x86/boot/main.c gets invoked first (in 16-bit mode).

> And lastly, is there a more appropriate mailing list for me to ask
> these questions on?

linux-kernel at vger.kernel.org would be much more appropriate.

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.




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