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Re: [PATCH] lkdtm: add test for executing .rodata

From Ard Biesheuvel <ard.biesheuvel@linaro.org>
Newsgroups linux.kernel
Subject Re: [PATCH] lkdtm: add test for executing .rodata
Date 2016-02-18 13:50 +0100
Message-ID <r3wbT-5xP-5@gated-at.bofh.it> (permalink)
References <r2VFo-57D-3@gated-at.bofh.it> <r3ua7-49t-37@gated-at.bofh.it> <r3v69-4Nn-5@gated-at.bofh.it> <r3vzc-5gf-15@gated-at.bofh.it>
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On 18 February 2016 at 13:07, Arnd Bergmann <arnd@arndb.de> 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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Thread

[PATCH] lkdtm: add test for executing .rodata Kees Cook <keescook@chromium.org> - 2016-02-16 22:50 +0100
  Re: [PATCH] lkdtm: add test for executing .rodata Laura Abbott <labbott@redhat.com> - 2016-02-17 02:10 +0100
    Re: [PATCH] lkdtm: add test for executing .rodata Kees Cook <keescook@chromium.org> - 2016-02-17 21:30 +0100
      Re: [PATCH] lkdtm: add test for executing .rodata Kees Cook <keescook@chromium.org> - 2016-02-17 22:10 +0100
      Re: [PATCH] lkdtm: add test for executing .rodata "PaX Team" <pageexec@freemail.hu> - 2016-02-18 11:40 +0100
        Re: [PATCH] lkdtm: add test for executing .rodata Ard Biesheuvel <ard.biesheuvel@linaro.org> - 2016-02-18 12:40 +0100
          Re: [PATCH] lkdtm: add test for executing .rodata Ard Biesheuvel <ard.biesheuvel@linaro.org> - 2016-02-18 13:00 +0100
          Re: [PATCH] lkdtm: add test for executing .rodata Arnd Bergmann <arnd@arndb.de> - 2016-02-18 13:10 +0100
            Re: [PATCH] lkdtm: add test for executing .rodata Ard Biesheuvel <ard.biesheuvel@linaro.org> - 2016-02-18 13:50 +0100
              Re: [PATCH] lkdtm: add test for executing .rodata Kees Cook <keescook@chromium.org> - 2016-02-18 21:10 +0100
          Re: [PATCH] lkdtm: add test for executing .rodata "PaX Team" <pageexec@freemail.hu> - 2016-02-18 22:30 +0100
            Re: [PATCH] lkdtm: add test for executing .rodata Kees Cook <keescook@chromium.org> - 2016-02-22 21:50 +0100
  Re: [PATCH] lkdtm: add test for executing .rodata Arnd Bergmann <arnd@arndb.de> - 2016-02-17 22:50 +0100
  Re: [PATCH] lkdtm: add test for executing .rodata Arnd Bergmann <arnd@arndb.de> - 2016-02-17 22:50 +0100

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