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Date: Mon, 14 Aug 2017 17:42:27 +0100
From: Russell King - ARM Linux <linux@armlinux.org.uk>
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Sender: Russell King - ARM Linux <linux@armlinux.org.uk>
Subject: [kernel-hardening] Re: [PATCH 02/30] ARM: assembler: introduce adr_l, ldr_l and str_l
 macros
To: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Nicolas Pitre <nicolas.pitre@linaro.org>, Dave Martin <Dave.Martin@arm.com>, Mark Rutland <mark.rutland@arm.com>, Kees Cook <keescook@chromium.org>, Arnd Bergmann <arnd@arndb.de>, Marc Zyngier <marc.zyngier@arm.com>, Kernel Hardening <kernel-hardening@lists.openwall.com>, Tony Lindgren <tony@atomide.com>, "linux-arm-kernel@lists.infradead.org" <linux-arm-kernel@lists.infradead.org>, Thomas Garnier <thgarnie@google.com>, Matt Fleming <matt@codeblueprint.co.uk>
List-ID: <kernel-hardening.lists.openwall.com>

On Mon, Aug 14, 2017 at 05:22:39PM +0100, Ard Biesheuvel wrote:
> On 14 August 2017 at 17:18, Nicolas Pitre <nicolas.pitre@linaro.org> wrote:
> > On Mon, 14 Aug 2017, Dave Martin wrote:
> >
> >> On Mon, Aug 14, 2017 at 04:38:02PM +0100, Ard Biesheuvel wrote:
> >> > That's a trick, actually, which I failed to add a comment for.
> >
> > Shame shame shame !
> >
> >> > We use .arm sections in the thumb2 kernel, and using these macros
> >> > there would result in the wrong offset to be used. Adding the .w
> >> > suffix forces an error in the assembler which even results in a fairly
> >> > meaningful error message complaining about using .w in ARM code.
> >>
> >> Ewww... I think it'd be best to add a comment explaining that.
> >
> > Absolutely!
> >
> 
> Yeah, mea culpa.
> 
> But if people have better ideas how to avoid this situation, I am all ears.

Have you tested building an ARMv7M kernel with your patches - ARMv7M is
Thumb only, so can't contain any ARM code.  If not, please try
mps2_defconfig.

-- 
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
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