linux-kernel - Re: [PATCH 3/8] powerpc: Mark functions called inside uaccess blocks w/ 'notrace'

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Date:   Fri, 16 Oct 2020 07:56:16 +0100
From:   Christoph Hellwig <hch@...radead.org>
To:     "Christopher M. Riedl" <cmr@...efail.de>
Cc:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        peterz@...radead.org
Subject: Re: [PATCH 3/8] powerpc: Mark functions called inside uaccess blocks
 w/ 'notrace'

On Thu, Oct 15, 2020 at 10:01:54AM -0500, Christopher M. Riedl wrote:
> Functions called between user_*_access_begin() and user_*_access_end()
> should be either inlined or marked 'notrace' to prevent leaving
> userspace access exposed. Mark any such functions relevant to signal
> handling so that subsequent patches can call them inside uaccess blocks.

I don't think running this much code with uaccess enabled is a good
idea.  Please refactor the code to reduce the criticial sections with
uaccess enabled.

Btw, does powerpc already have the objtool validation that we don't
accidentally jump out of unsafe uaccess critical sections?