linux-kernel - Re: [PATCH v2 0/4] Disable compat cruft on ppc64le v2

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Date:   Wed, 28 Aug 2019 20:57:48 +1000
From:   Nicholas Piggin <npiggin@...il.com>
To:     linuxppc-dev@...ts.ozlabs.org, Michal Suchanek <msuchanek@...e.de>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Allison Randal <allison@...utok.net>,
        Andrew Donnellan <andrew.donnellan@....ibm.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Christophe Leroy <christophe.leroy@....fr>,
        David Hildenbrand <david@...hat.com>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Firoz Khan <firoz.khan@...aro.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Hari Bathini <hbathini@...ux.ibm.com>,
        Max Filippov <jcmvbkbc@...il.com>,
        Joel Stanley <joel@....id.au>,
        "Dmitry V. Levin" <ldv@...linux.org>,
        Breno Leitao <leitao@...ian.org>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        Michael Neuling <mikey@...ling.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Paul Mackerras <paulus@...ba.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Alexander Viro <viro@...iv.linux.org.uk>
Subject: Re: [PATCH v2 0/4] Disable compat cruft on ppc64le v2

Michal Suchanek's on August 28, 2019 8:30 pm:
> With endian switch disabled by default the ppc64le compat supports
> ppc32le only which is something next to nobody has binaries for.
> 
> Less code means less bugs so drop the compat stuff.

Interesting patches, thanks for looking into it. I don't know much
about compat and wrong endian userspaces. I think sys_switch_endian
is enabled though, it's just a strange fast endian swap thing that
has been disabled by default.

The first patches look pretty good. Maybe for the last one it could
become a selectable option?


> I am not particularly sure about the best way to resolve the llseek
> situation. I don't see anything in the syscal tables making it
> 32bit-only so I suppose it should be available on 64bit as well.

It's for 32-bit userspace only. Can we just get rid of it, or is
there some old broken 64-bit BE userspace that tries to call it?

Thanks,
Nick