linux-kernel - Re: [PATCH] ARM: two possible fixes for the KALLSYMS build problem

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Message-ID: <20120612182036.GE7918@n2100.arm.linux.org.uk>
Date:	Tue, 12 Jun 2012 19:20:36 +0100
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	David Brown <davidb@...eaurora.org>
Cc:	Kukjin Kim <kgene.kim@...sung.com>,
	Eric Miao <eric.y.miao@...il.com>,
	Arnd Bergmann <arnd@...db.de>, linux-arm-msm@...r.kernel.org,
	linux-kernel@...r.kernel.org, Tomasz Figa <tomasz.figa@...il.com>,
	Paul Gortmaker <paul.gortmaker@...driver.com>,
	Paulo Marques <pmarques@...popie.com>,
	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>,
	Jon Masters <jonathan@...masters.org>,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] ARM: two possible fixes for the KALLSYMS build problem

On Tue, Jun 12, 2012 at 09:02:29AM -0700, David Brown wrote:
> On Tue, Jun 12, 2012 at 03:32:49PM +0100, Russell King - ARM Linux wrote:
> > On Mon, Jun 11, 2012 at 01:37:48PM -0700, David Brown wrote:
> > > On Fri, Jun 01, 2012 at 09:21:59AM -0700, David Brown wrote:
> > > 
> > > > David Brown (1):
> > > >   ARM: Prevent KALLSYM size mismatch on ARM.
> > > > 
> > > >  arch/arm/kernel/vmlinux.lds.S |    3 +++
> > > >  1 file changed, 3 insertions(+)
> > > 
> > > Just wondering if anyone has had a chance to look at either of these,
> > > or try them.  I haven't seen any KALLSYMS mismatch build errors with
> > > either of these patches applied.
> > 
> > I think variant 2 is the better approach out of either as it doesn't add
> > to the size of the resulting kernel image.
> 
> The first variant doesn't ever increase the size of the kernel,
> either.  Variant two actually makes it a little smaller, since a few
> symbols are eliminated.

Ok.

> The second variant is cleaner, though as long as it is safe in every
> configuration.

Well, we don't have any per-CPU data unless we're building for SMP.
See:

#ifndef PER_CPU_BASE_SECTION
#ifdef CONFIG_SMP
#define PER_CPU_BASE_SECTION ".data..percpu"
#else
#define PER_CPU_BASE_SECTION ".data"
#endif
#endif

in include/asm-generic/percpu.h.
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