linux-kernel - Re: [PATCH] powerpc: workaround clang codegen bug in dcbz

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Mon, 29 Jul 2019 13:47:55 -0700
From:   Nathan Chancellor <natechancellor@...il.com>
To:     Nick Desaulniers <ndesaulniers@...gle.com>
Cc:     Michael Ellerman <mpe@...erman.id.au>,
        Christophe Leroy <christophe.leroy@....fr>,
        Segher Boessenkool <segher@...nel.crashing.org>,
        Arnd Bergmann <arnd@...db.de>,
        kbuild test robot <lkp@...el.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        linuxppc-dev@...ts.ozlabs.org, LKML <linux-kernel@...r.kernel.org>,
        clang-built-linux <clang-built-linux@...glegroups.com>
Subject: Re: [PATCH] powerpc: workaround clang codegen bug in dcbz

On Mon, Jul 29, 2019 at 01:45:35PM -0700, Nick Desaulniers wrote:
> On Mon, Jul 29, 2019 at 1:32 PM Nathan Chancellor
> <natechancellor@...il.com> wrote:
> >
> > On Mon, Jul 29, 2019 at 01:25:41PM -0700, Nick Desaulniers wrote:
> > > But I'm not sure how the inlined code generated would be affected.
> >
> > For the record:
> >
> > https://godbolt.org/z/z57VU7
> >
> > This seems consistent with what Michael found so I don't think a revert
> > is entirely unreasonable.
> 
> Thanks for debugging/reporting/testing and the Godbolt link which
> clearly shows that the codegen for out of line versions is no
> different.  The case I can't comment on is what happens when those
> `static inline` functions get inlined (maybe the original patch
> improves those cases?).
> -- 
> Thanks,
> ~Nick Desaulniers

I'll try to build with various versions of GCC and compare the
disassembly of the one problematic location that I found and see
what it looks like.

Cheers,
Nathan