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Date: Thu, 18 Feb 2016 13:46:38 +0100
From: Ard Biesheuvel <>
To: Arnd Bergmann <>
Cc: PaX Team <>, Laura Abbott <>, 
	Kees Cook <>, Greg Kroah-Hartman <>, 
	Mark Rutland <>, Jeremy Linton <>, 
	"" <>, LKML <>
Subject: Re: [PATCH] lkdtm: add test for executing .rodata

On 18 February 2016 at 13:07, Arnd Bergmann <> wrote:
> On Thursday 18 February 2016 12:34:50 Ard Biesheuvel wrote:
>> We have __section() as an alias for __attribute__((__section__())), so
>> we could use that instead.
>> However, that does not fix the issue Kees is trying to solve, where a
>> .rodata section is emitted with the "x" bit set, which causes the
>> linker to complain:
>> /tmp/cc50ffWw.s: Assembler messages:
>> /tmp/cc50ffWw.s:2: Warning: setting incorrect section attributes for
>> .rodata.text
>> I wonder if we could get away with doing something like
>> AFLAGS_lkdtm.o += -Wa,-W
>> here? This just hides the warnings, but may result in the .rodata
>> section in the vmlinux file to have X permissions as well. I don't
>> think anyone uses an ELF loader to load their kernel, but who knows
>> ...
> Don't we also get a warning when we link objects with conflicting
> section attributes?

I didn't see one

> Maybe a solution would be to define a separate section for this one
> function, and then use a linker script to move it into .rodata?
> Or maybe "objcopy --set-section-flags  --rename-section"?

I think objcopy is the easiest.

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