kernel-hardening - Re: [PATCH v1 0/2] Introduce the initify gcc plugin

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Message-Id: <20160628134237.910997b2430dfdf4c55b05ee@gmail.com>
Date: Tue, 28 Jun 2016 13:42:37 +0200
From: Emese Revfy <re.emese@...il.com>
To: kernel-hardening@...ts.openwall.com
Cc: pageexec@...email.hu, spender@...ecurity.net, mmarek@...e.com,
 keescook@...omium.org, linux-kernel@...r.kernel.org,
 yamada.masahiro@...ionext.com, linux-kbuild@...r.kernel.org,
 minipli@...linux.so, linux@...linux.org.uk, catalin.marinas@....com,
 linux@...musvillemoes.dk, david.brown@...aro.org, benh@...nel.crashing.org,
 tglx@...utronix.de, akpm@...ux-foundation.org, jlayton@...chiereds.net,
 arnd@...db.de
Subject: Re: [PATCH v1 0/2] Introduce the initify gcc plugin

On Tue, 28 Jun 2016 13:34:07 +0200
Emese Revfy <re.emese@...il.com> wrote:

>  * automatically discover init/exit functions and apply the __init or
>    __exit attributes on them

Hi,

I have a question about this. If a function is called by __init and __exit functions as well then
I move it to the __exit section. I think this is correct because such a function is available to
both __init and __exit functions as well at runtime.
However this generates a section mismatch (from scripts/mod/modpost.c) e.g.,

   WARNING: vmlinux.o(.init.text+0x196849): Section mismatch in reference from the function sctp_init() to the function .exit.text:sctp_v4_del_protocol()
   The function __init sctp_init() references
   a function __exit sctp_v4_del_protocol().
   This is often seen when error handling in the init function
   uses functionality in the exit path.
   The fix is often to remove the __exit annotation of
   sctp_v4_del_protocol() so it may be used outside an exit section.

This check was introduced by this commit (588ccd732ba2d):
kbuild: add verbose option to Section mismatch reporting in modpost

If this move doesn't cause a problem then I would like to keep it because there are a lot of functions that can become __exit and I would like to remove this warning.

Thanks
-- 
Emese

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