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From:   Jani Nikula <jani.nikula@linux.intel.com>
To:     Christophe Leroy <christophe.leroy@c-s.fr>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>,
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Subject: Re: [PATCH v3 2/7] uaccess: Tell user_access_begin() if it's for a write or not
In-Reply-To: <e11a8f0670251267f87e3114e0bdbacb1eb72980.1579783936.git.christophe.leroy@c-s.fr>
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References: <fed4f49349913cb6739dac647ba6a61d56b989d2.1579783936.git.christophe.leroy@c-s.fr> <e11a8f0670251267f87e3114e0bdbacb1eb72980.1579783936.git.christophe.leroy@c-s.fr>
Date:   Thu, 23 Jan 2020 15:11:05 +0200
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On Thu, 23 Jan 2020, Christophe Leroy <christophe.leroy@c-s.fr> wrote:
> On 32 bits powerPC (book3s/32), only write accesses to user are
> protected and there is no point spending time on unlocking for reads.
>
> On 64 bits powerpc (book3s/64 at least), access can be granted
> read only, write only or read/write.
>
> Add an argument to user_access_begin() to tell when it's for write and
> return an opaque key that will be used by user_access_end() to know
> what was done by user_access_begin().

IMHO an opaque key is a prime example of a case where the use of an
opaque typedef is warranted. Nobody needs to know or care it's
specifically an unsigned long.

BR,
Jani.


-- 
Jani Nikula, Intel Open Source Graphics Center