linux-kernel - Re: [PATCH] proc: fix proc-self-map-files selftest for arm

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Date:   Fri, 12 Oct 2018 00:30:06 +0300
From:   Alexey Dobriyan <adobriyan@...il.com>
To:     Cyrill Gorcunov <gorcunov@...il.com>
Cc:     Rafael David Tinoco <rafael.tinoco@...aro.org>,
        linux-kselftest@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
        shuah@...nel.org
Subject: Re: [PATCH] proc: fix proc-self-map-files selftest for arm

On Fri, Oct 12, 2018 at 12:02:56AM +0300, Cyrill Gorcunov wrote:
> On Thu, Oct 11, 2018 at 11:56:01PM +0300, Alexey Dobriyan wrote:
> > 
> > As the comment in the beginning says this test is specifically for addresss 0.
> > Maybe it should be ifdeffed with __arm__ then.
> 
> Is there some other reason than allocating non-mergable VMA?

IIRC the reason is to test address 0 as it is effectively banned
for userspace so if it will be broken, it will be broken silently
for a long time.

As for "unmergeable" libc here doesn't map /dev/zero. I know how to
avoid even theoretical breakage by creating binaries by hand but it
will be probably too much.