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Date: Thu, 11 Feb 2016 18:00:32 +0000
From: Russell King - ARM Linux <linux@arm.linux.org.uk>
To: Kees Cook <keescook@chromium.org>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>,
        Laura Abbott <labbott@fedoraproject.org>,
        Will Deacon <will.deacon@arm.com>, Nicolas Pitre <nico@linaro.org>,
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Subject: Re: [PATCH v2] ARM: mm: mark section-aligned portion of rodata NX
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On Fri, Jan 22, 2016 at 01:19:03PM -0800, Kees Cook wrote:
> On Tue, Dec 8, 2015 at 10:38 AM, Kees Cook <keescook@chromium.org> wrote:
> > On Mon, Dec 7, 2015 at 11:47 PM, Ard Biesheuvel
> > <ard.biesheuvel@linaro.org> wrote:
> >> On 7 December 2015 at 23:35, Kees Cook <keescook@chromium.org> wrote:
> >>>  /*
> >>> + * Without CONFIG_DEBUG_ALIGN_RODATA, __start_rodata_section_aligned will
> >>> + * be the first section-aligned location after __start_rodata. Otherwise,
> >>> + * it will be equal to __start_rodata.
> >>> + */
> >>> +__start_rodata_section_aligned = ALIGN(__start_rodata, 1 << SECTION_SHIFT);
...

I'm afraid this causes build errors on two configurations:

./arch/arm/kernel/vmlinux.lds:701: undefined symbol `SECTION_SHIFT' referenced in expression

which I think is down to the new __start_rodata_section_aligned line.

Olof's builder errored out with this for both allnoconfig and
lpc18xx_defconfig builds.  Both probably due to CONFIG_MMU being
unset, and hence no definition for SECTION_SHIFT.

I think you need to make this conditional on CONFIG_MMU.

-- 
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