linux-kernel - Re: [PATCH] libkmod-elf: resolve CRC if module is built with MODULE_REL

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Date:   Wed, 19 Jul 2017 20:10:17 +0100
From:   Ard Biesheuvel <ard.biesheuvel@...aro.org>
To:     Yauheni Kaliuta <yauheni.kaliuta@...hat.com>
Cc:     Lucas De Marchi <lucas.de.marchi@...il.com>,
        linux-modules <linux-modules@...r.kernel.org>,
        lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] libkmod-elf: resolve CRC if module is built with MODULE_REL_CRCS

On 19 July 2017 at 20:04, Yauheni Kaliuta <yauheni.kaliuta@...hat.com> wrote:
> Hi, Lucas!
>
>>>>>> On Wed, 19 Jul 2017 10:51:44 -0700, Lucas De Marchi  wrote:
>  > On Wed, Jul 19, 2017 at 7:56 AM, Yauheni Kaliuta
>  > <yauheni.kaliuta@...hat.com> wrote:
>  >> Normally exported symbol's crc is stored as absolute (SHN_ABS)
>  >> value of special named symbol __crc_<symbol name>.
>  >>
>  >> When the kernel and modules are built with the config option
>  >> CONFIG_MODULE_REL_CRCS, all the CRCs are put in a special section
>  >> and the __crc_<symbol name> symbols values are offsets in the
>  >> section. See patch description of the commit:
>  >>
>  >> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=56067812d5b0e737ac2063e94a50f76b810d6ca3
>  >>
>  >> Add kmod support of this configuration.
>
> [...]
>
>  > LGTM. I'll give this a try and apply.
>
> Thanks! I would also like to get some feedback from the kernel feature
> author, Ard Biesheuvel, that this does not miss other usecases.
>

Hi all,

The patch looks correct to me. My only comment is that
kmod_elf_resolve_crc() should probably return a uint32_t instead,
given the size of a CRC32.

In any case,

Reviewed-by: Ard Biesheuvel <ard.biesheuvel@...aro.org>

Thanks,
Ard.


>  > Do you think it's possible to build an out-of-tree module with this
>  > option so we can add one to the testsuite?
>
> I'll check what I can do.
>
> The problem is seen if you run depmod with -e -E, which I guess is not used
> too often.
>
> --
> WBR,
> Yauheni Kaliuta