Re: [PATCH] kernel/linux: change arch tuple to use -uclinux for uclinux toolchains

[Mike Frysinger <vapier at gentoo dot org>]

On Tuesday 25 September 2012 17:18:31 Esben Haabendal wrote:
> Mike Frysinger <vapier@gentoo.org> writes:
> > On Tuesday 25 September 2012 14:18:38 Esben Haabendal wrote:
> >> What arch tuple should then be used for linux with uClibc?  I don't see
> >> the benefit of not being able to tell it apart from uClinux/FDPIC-ELF
> >> with uClibc.
> > 
> > i don't understand the question.  "uclinux" means you're running Linux
> > with uClibc, as does "linux-uclibc".
> 
> I dare to say "no".  With *-*-uclinux-* you are saying you are running
> Linux without mmu.  With *-*-linux-uclibc or *-*-uclinux-uclibc you are
> saying you are running Linux with uClibc.

Linux is Linux.  "uclinux" is a dead term which has no bearing anymore and 
hasn't for years.  you run Linux w/mmu support turned on or turned off, but 
you're running Linux in either case.  thus saying "Linux with uClibc" is 
meaningless to mmu status.

Blackfin doesn't have a MMU and most likely never will.  bfin-linux-uclibc is 
for running the FDPIC-ELF format with uClibc under Linux.  we build with MMU 
support turned off, but *gcc* does not care at all either way.  uClibc and 
Linux is configured with the MMU turned off.

> With some m68k cpus, you are able to use either Linux with glibc, Linux
> (with mmu) with uClibc, or Linux (without mmu, uCLinux) with uClibc.  It
> would be rather handy to be able to use different arch tuples for all 3
> cases.

running Linux w/mmu support enabled on a processor with a MMU can execute code 
compiled for a system w/mmu disabled.  there's no magic here, just a different 
file format (FLAT) and certain functions disabled (like fork).  similarly, if a 
Blackfin processor was released with a MMU enabled, i could take all the code i 
already have compiled today and run it perfectly fine on that.

> I will rework the patch to set CT_TARGET_KERNEL depending on both
> CT_ARCH_USE_MMU and CT_ARCH.  So "linux" for bfin and "uclinux" for
> m68k.

hard coding one way or the other is wrong.  bfin-uclinux is valid, as is m68k-
uclinux and arm-uclinux and mips-uclinux and many other targets.
-mike

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