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Date:   Mon, 6 Jun 2022 09:25:51 +0100
From:   "Russell King (Oracle)" <linux@armlinux.org.uk>
To:     Masahiro Yamada <masahiroy@kernel.org>
Cc:     "David S . Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>, netdev@vger.kernel.org,
        Eric Dumazet <edumazet@google.com>,
        Paolo Abeni <pabeni@redhat.com>,
        Stephen Rothwell <sfr@canb.auug.org.au>,
        Andrew Lunn <andrew@lunn.ch>,
        Florian Fainelli <f.fainelli@gmail.com>,
        Heiner Kallweit <hkallweit1@gmail.com>,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/3] net: mdio: unexport __init-annotated mdio_bus_init()
Message-ID: <Yp26Dw3f8+XlSx2+@shell.armlinux.org.uk>
References: <20220606045355.4160711-1-masahiroy@kernel.org>
 <20220606045355.4160711-2-masahiroy@kernel.org>
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Sender: Russell King (Oracle) <linux@armlinux.org.uk>
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On Mon, Jun 06, 2022 at 01:53:53PM +0900, 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 the only in-tree call-site,
> drivers/net/phy/phy_device.c is never compiled as modular.
> (CONFIG_PHYLIB is boolean)
> 
> Fixes: 90eff9096c01 ("net: phy: Allow splitting MDIO bus/device support from PHYs")
> Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

Reviewed-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>

Thanks!

-- 
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