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From:   =?utf-8?Q?Krzysztof_Ha=C5=82asa?= <khalasa@piap.pl>
To:     "Russell King (Oracle)" <linux@armlinux.org.uk>
Cc:     linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
        lkml <linux-kernel@vger.kernel.org>
Subject: Re: Data corruption on i.MX6 IPU in arm_copy_from_user()
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        <20210526100843.GD30436@shell.armlinux.org.uk>
Sender: khalasa@piap.pl
Date:   Wed, 26 May 2021 14:29:07 +0200
In-Reply-To: <20210526100843.GD30436@shell.armlinux.org.uk> (Russell King's
        message of "Wed, 26 May 2021 11:08:44 +0100")
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"Russell King (Oracle)" <linux@armlinux.org.uk> writes:

> Surely someone is not using copy_*_user() to copy data from userspace
> direct to MMIO space... that would be crazy.

No, it's the other way around: reading MMIO mapped to userspace (mmap
on /dev/mem) and copying it to simple kernel buffer (e.g. pipe buffer).
I.e., the MMIO is the userspace here (thus copy_from_user()).
--=20
Krzysztof Ha=C5=82asa

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