linux-kernel - Re: Data corruption on i.MX6 IPU in arm_copy_from

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Date:   Wed, 26 May 2021 14:29:07 +0200
From:   Krzysztof Hałasa <khalasa@...p.pl>
To:     "Russell King (Oracle)" <linux@...linux.org.uk>
Cc:     linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        lkml <linux-kernel@...r.kernel.org>
Subject: Re: Data corruption on i.MX6 IPU in arm_copy_from_user()

"Russell King (Oracle)" <linux@...linux.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()).
-- 
Krzysztof Hałasa

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