linux-kernel - Re: [PATCH] zlib: define get_unaligned16() only when used

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]

Message-ID: <CAK8P3a2rVKQ5UHzcycu=0QpjtSQ3Nne4Xre-7+V27vmCe9yfKg@mail.gmail.com>
Date:   Tue, 24 Nov 2020 12:56:30 +0100
From:   Arnd Bergmann <arnd@...nel.org>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     Jann Horn <jannh@...gle.com>,
        Lukas Bulwahn <lukas.bulwahn@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Arnd Bergmann <arnd@...db.de>, Tom Rix <trix@...hat.com>,
        Nathan Chancellor <natechancellor@...il.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        clang-built-linux <clang-built-linux@...glegroups.com>,
        kernel-janitors@...r.kernel.org,
        kernel list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] zlib: define get_unaligned16() only when used

On Tue, Nov 24, 2020 at 12:51 PM Christoph Hellwig <hch@...radead.org> wrote:
> On Tue, Nov 24, 2020 at 12:08:40PM +0100, Jann Horn wrote:
> > > Since commit acaab7335bd6 ("lib/zlib: remove outdated and incorrect
> > > pre-increment optimization"), get_unaligned16() is only used when
> > > !CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS.
> > >
> > > Hence, make CC=clang W=1 warns:
> > >
> > >   lib/zlib_inflate/inffast.c:20:1:
> > >     warning: unused function 'get_unaligned16' [-Wunused-function]
> > >
> > > Define get_unaligned16() only when it is actually used.
> > >
> > > Signed-off-by: Lukas Bulwahn <lukas.bulwahn@...il.com>
> >
> > AFAICS a nicer option would be to "#include <asm/unaligned.h>" and
> > then use "get_unaligned", which should automatically do the right
> > thing everywhere and remove the need for defining get_unaligned16()
> > and checking CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS entirely?
>
> Yes, that is the right thing to do.

It's possible that this didn't work when the code was originally added:
The decompressor functions are called from the compressed boot path,
which is a bit limited regarding which headers it can include, at least
on some architectures.

I would recommend test-building this for all architectures that include
../../../../lib/decompress_inflate.c from their boot code.

     Arnd