linux-kernel - Re: [PATCH 1/3] Makefile: Include arch Makefiles as late as possible

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Date:	Mon, 16 Feb 2009 21:04:15 +0100
From:	Sam Ravnborg <sam@...nborg.org>
To:	Anton Vorontsov <avorontsov@...mvista.com>
Cc:	Ingo Molnar <mingo@...e.hu>, Steven Rostedt <srostedt@...hat.com>,
	Paul Mackerras <paulus@...ba.org>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	linuxppc-dev@...abs.org, linux-kernel@...r.kernel.org,
	linux-rt-users@...r.kernel.org, Ralf Baechle <ralf@...ux-mips.org>
Subject: Re: [PATCH 1/3] Makefile: Include arch Makefiles as late as possible

> 
> There are few arches that have "auto detection" of CROSS_COMPILE
> variable: mips, m68k, parisc, xtensa, h8300 and blackfin.
> 
> So `normal' arches don't have any chance to overwrite the flags
> because of the few offenders above. ;-)

We also have archs where we add options to gcc that may
impact for example -fno-stack-protector.
We had a bug in x86 in this area for a while.

So the only sane thing is to only add the most generic options to
KBUILD_CFLAGS before we include the arch specific part.
And we can then add the conditional options later - like
the KBUILD_CFLAGS += $(call cc-option, -fno-stack-protector)
in this case.

We learned a few lessons in this area over time as your
history digging also showed.

	Sam
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