Re: [M68K/ColdFire patch 4/n] Remove kernel headers

[Maxim Kuvyrkov <maxim at codesourcery dot com>]

Andreas Schwab wrote:
> Maxim Kuvyrkov <maxim@codesourcery.com> writes:
>
> > Still, what was the foundation for coldfire-specific changes to
> > fpregset_t, i.e., the use of 8-byte entries instead of 12-byte as for
> > m68k?
>
> The coldfire has 64 bit fpu registers.  The patches were from Richard
> Sandiford.

I did some digging in the archives and found several things I was not 
aware before:

1. Sigcontext ABI of ColdFire is different from M68K's.  It should be 
what the current GLIBC copy is; i.e., struct sigcontext should contain 
%d2-%d7, %a2-%a6 and have fpregs[8][2].

2. A kernel patch was developed by Freescale and CodeSourcery to account 
for the changes in ABI and also to fix various bugs.  This patch is 
against the 2.6.10 kernel and is available at 
http://www.codesourcery.com/archives/coldfire-gnu-discuss/msg00141.html.

3. The kernel changes mentioned above are not included in the latest 
stable LTIBs for ColdFire Linux boards: ltib-m5475-20080808 and 
ltib-mcf5445x-20071214.  This led to great confusion on my part as I 
considered the kernel sources in these LTIBs to represent true ABI.

> > Regarding the sigcontext.h header, there's no competing version in
> > ./sysdeps/m68k/, so this one can be removed in favor of the header
> > installed by the kernel.
>
> Of course, the generic linux version will be used instead, but if the
> kernel header is clean than that will work.

In the light of the above, I think it is too early to fall back to the 
kernel headers.  I will seek to the necessary ABI changes to get to the 
upstream kernel and then will follow up on GLIBC switching to use 
kernel's sigcontext.h.

As things stand, GLIBC contains the true ColdFire sigcontext ABI at the 
moment.

Please consider the patch at the beginning of the thread bogus in 
several different ways :).

Thanks,

--
Maxim K.
CodeSourcery