Re: Question howto build a compiler for x86_64 kernel.

On Sun, May 17, 2015 at 10:05:36PM +0200, Stef Bon wrote:
> Hi,
> 
> I've got a LFS/BLFS system, 32-bits, approx 2 years old.
> 
> I've build the chromium browser till december 2014 successfully, but since
> then it failed.
> Contacted the developers, and they told me the browser needs a 64-bits
> kernel:
> 
> https://groups.google.com/a/chromium.org/forum/#!topic/chromium-dev/f3sD6RPKlUM
> 
> My question is: how can I compile a 64-bits kernel on my 32-bits system?
> I've been looking for a cross-compiler, but maybe that's too much. As far as
> I understand I't not required to crosscompile, but only a compiler to create
> 64 bits code. Am I right?
> 
> Stef
> 
Based on my experience with ppc64 (I had a dreadfully slow mac G5,
building userspace as 32-bit allowed me to keep using it for a bit
longer), I would say that a cross-compiler is exactly what you need,
IFF they mean that a 64-bit kernel with only 32-bit libraries will
work - that seems unusual, and excludes all systems which can only
`run 32-bit code such as the netbook on which I'm typing this.  But
the answer from Nico Weber suggests that is the case.

When I've done that (and I might try it again for 32-bit userspace
on x86_64 CPUs, but so far I have not got round to it) I just
replicate the beginning of LFS chapter 5 - binutils pass 1 and gcc
pass 1.  I would put them into somewhere in /opt, such as /opt/kgcc
(kernel gcc - RedHat used to install kgcc for building the kernel in
the days before gcc3) and then fix up the cross-compile stuff in the
kernel config.

Unfortunately, the kernel config options were somewhat different for
i686 and x86_64 when I las looked (a couple of years ago), so
getting an adequate kernel config for x86_64 might take a few
attempts.

ĸen
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