linux-kernel - Re: [PATCH] ARM: tegra: remove board_init

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Message-ID: <20160622133457.GM26943@ulmo.ba.sec>
Date:	Wed, 22 Jun 2016 15:34:57 +0200
From:	Thierry Reding <thierry.reding@...il.com>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	linux-arm-kernel@...ts.infradead.org, linux-tegra@...r.kernel.org,
	Alexandre Courbot <gnurou@...il.com>,
	linux-kernel@...r.kernel.org,
	Stephen Warren <swarren@...dotorg.org>
Subject: Re: [PATCH] ARM: tegra: remove board_init_funcs array

On Wed, Jun 22, 2016 at 03:05:35PM +0200, Arnd Bergmann wrote:
> On Wednesday, June 22, 2016 2:50:13 PM CEST Thierry Reding wrote:
> > 
> > Not enough information to check signature validity.
> > On Wed, Jun 22, 2016 at 02:39:41PM +0200, Arnd Bergmann wrote:
> > > In a configuration that enables CONFIG_UBSAN_SANITIZE_ALL, I am getting
> > > a section mismatch warning for tegra20:
> > > 
> > > WARNING: arch/arm/mach-tegra/built-in.o(.data+0x6e0): Section mismatch in reference from the variable board_init_funcs to the function .init.text:paz00_init()
> > > 
> > > The array is no longer useful here since there is only one entry,
> > > so we can simply call the function directly after checking
> > > of_machine_is_compatible(). This fixes the section mismatch
> > > and is easier to read.
> > > 
> > > Signed-off-by: Arnd Bergmann <arnd@...db.de>
> > > ---
> > >  arch/arm/mach-tegra/tegra.c | 24 +++---------------------
> > >  1 file changed, 3 insertions(+), 21 deletions(-)
> > 
> > Shouldn't these section mismatches show up with default builds? I
> > haven't seen any when building Tegra configurations.
> > 
> > I'm going to apply this patch because I think it's useful, but it sure
> > would be nice to know why I need to enable this new UBSAN stuff to get
> > these warnings now.
> 
> It depends on the how aggressive the inlining works. Without UBSAN,
> gcc seems to completely optimze away the loop and just the function
> directly, which it can do because 'board_init_funcs' is static.
> 
> I assume that the UBSAN object overflow check has the effect of
> not dropping the symbol so it can check the size.

Ah, I see. Thanks.

Thierry

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