linux-kernel - Re: [PATCH] xen: unexport __init-annotated xen_xlate_map_ballooned

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Message-ID: <d7ab14e9-2411-774e-21f1-2ecf3cffd2e9@suse.com>
Date:   Wed, 8 Jun 2022 07:37:09 +0200
From:   Juergen Gross <jgross@...e.com>
To:     Masahiro Yamada <masahiroy@...nel.org>,
        Stefano Stabellini <sstabellini@...nel.org>,
        Oleksandr Tyshchenko <oleksandr_tyshchenko@...m.com>,
        moderated for non-subscribers <xen-devel@...ts.xenproject.org>
Cc:     Stephen Rothwell <sfr@...b.auug.org.au>,
        Julien Grall <julien.grall@....com>,
        Shannon Zhao <shannon.zhao@...aro.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] xen: unexport __init-annotated
 xen_xlate_map_ballooned_pages()

On 06.06.22 06:59, Masahiro Yamada wrote:
> EXPORT_SYMBOL and __init is a bad combination because the .init.text
> section is freed up after the initialization. Hence, modules cannot
> use symbols annotated __init. The access to a freed symbol may end up
> with kernel panic.
> 
> modpost used to detect it, but it has been broken for a decade.
> 
> Recently, I fixed modpost so it started to warn it again, then this
> showed up in linux-next builds.
> 
> There are two ways to fix it:
> 
>    - Remove __init
>    - Remove EXPORT_SYMBOL
> 
> I chose the latter for this case because none of the in-tree call-sites
> (arch/arm/xen/enlighten.c, arch/x86/xen/grant-table.c) is compiled as
> modular.
> 
> Fixes: 243848fc018c ("xen/grant-table: Move xlated_setup_gnttab_pages to common place")
> Reported-by: Stephen Rothwell <sfr@...b.auug.org.au>
> Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>

Pushed to xen/tip.git for-linus-5.19a


Juergen

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