linux-kernel - Re: [lkp] [x86] 784d5699ed: kmsg.ip_tables:no_symbol_version_for_copy_from

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Message-ID: <8737k5c0t7.fsf@gmail.com>
Date:   Sun, 09 Oct 2016 11:46:12 +0200
From:   Mathieu OTHACEHE <m.othacehe@...il.com>
To:     Stephen Rothwell <sfr@...b.auug.org.au>
Cc:     Al Viro <viro@...iv.linux.org.uk>,
        LKML <linux-kernel@...r.kernel.org>, lkp@...org,
        Michal Marek <mmarek@...e.cz>
Subject: Re: [lkp] [x86]  784d5699ed: kmsg.ip_tables:no_symbol_version_for_copy_from_user

Hi,

> Do we have any resolution of this?

I got the exact same problem if CONFIG_MODVERSIONS is enabled.
Here is my understanding.

All the symbols exported using assembler macro EXPORT_SYMBOL will need a
__crc_<symbol> to be defined later on (include/asm-generic/export.h).

This is what genksyms should do but it only runs on *.c files. So all the
symbols exported from *.S files won't get crc.

modpost is complaining about missing crc and it will not include those
symbols in *.mod.c modversion_info struct. Then, we got "Unknown
symbol" errors when modules are inserted at runtime.

I fixed it locally by setting __crc_<symbol> to a constant value in
export.h. But it may be a better idea to have genksyms run on *.S files ?

Thanks,

Mathieu