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From:   Florian Weimer <fweimer@redhat.com>
To:     Mark Wielaard <mark@klomp.org>
Cc:     Christian Brauner <christian.brauner@ubuntu.com>,
        linux-api@vger.kernel.org, linux-doc@vger.kernel.org,
        linux-kernel@vger.kernel.org, dev@opencontainers.org,
        corbet@lwn.net, Carlos O'Donell <carlos@redhat.com>
Subject: Re: [PATCH] syscalls: Document OCI seccomp filter interactions &
 workaround
References: <87lfer2c0b.fsf@oldenburg2.str.redhat.com>
        <20201124122639.x4zqtxwlpnvw7ycx@wittgenstein>
        <878saq3ofx.fsf@oldenburg2.str.redhat.com>
        <dcffcbacbc75086582ea3f073c9e6a981a6dd27f.camel@klomp.org>
Date:   Tue, 24 Nov 2020 19:09:44 +0100
In-Reply-To: <dcffcbacbc75086582ea3f073c9e6a981a6dd27f.camel@klomp.org> (Mark
        Wielaard's message of "Tue, 24 Nov 2020 15:08:05 +0100")
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* Mark Wielaard:

> For valgrind the issue is statx which we try to use before falling back
> to stat64, fstatat or stat (depending on architecture, not all define
> all of these). The problem with these fallbacks is that under some
> containers (libseccomp versions) they might return EPERM instead of
> ENOSYS. This causes really obscure errors that are really hard to
> diagnose.

The probing sequence I proposed should also work for statx. 8-p

> Don't you have the same issue with glibc for those architectures that
> don't have fstatat or 32bit arches that need 64-bit time_t? And if so,
> how are you working around containers possibly returning EPERM instead
> of ENOSYS?

That's a good point.  I don't think many people run 32-bit containers in
the cloud.  The Y2038 changes in glibc impact 64-bit ports a little, but
mostly on the fringes (e.g., clock_nanosleep vs nanosleep).

Thanks,
Florian
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