linux-kernel - Re: mmotm 2020-05-13-20-30 uploaded (objtool warnings)

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Message-ID: <20200528172005.GP2483@worktop.programming.kicks-ass.net>
Date:   Thu, 28 May 2020 19:20:05 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Randy Dunlap <rdunlap@...radead.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>, broonie@...nel.org,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, linux-next@...r.kernel.org, mhocko@...e.cz,
        mm-commits@...r.kernel.org, sfr@...b.auug.org.au,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        viro@...IV.linux.org.uk, hch@....de, x86@...nel.org
Subject: Re: mmotm 2020-05-13-20-30 uploaded (objtool warnings)

On Thu, May 14, 2020 at 08:32:22AM -0700, Randy Dunlap wrote:
> On 5/13/20 8:31 PM, Andrew Morton wrote:
> > The mm-of-the-moment snapshot 2020-05-13-20-30 has been uploaded to
> > 
> >    http://www.ozlabs.org/~akpm/mmotm/
> > 
> > mmotm-readme.txt says
> > 
> > README for mm-of-the-moment:
> > 
> > http://www.ozlabs.org/~akpm/mmotm/
> > 
> > This is a snapshot of my -mm patch queue.  Uploaded at random hopefully
> > more than once a week.
> > 
> > You will need quilt to apply these patches to the latest Linus release (5.x
> > or 5.x-rcY).  The series file is in broken-out.tar.gz and is duplicated in
> > http://ozlabs.org/~akpm/mmotm/series
> > 
> > The file broken-out.tar.gz contains two datestamp files: .DATE and
> > .DATE-yyyy-mm-dd-hh-mm-ss.  Both contain the string yyyy-mm-dd-hh-mm-ss,
> > followed by the base kernel version against which this patch series is to
> > be applied.
> 
> 
> on x86_64:
> 
> arch/x86/lib/csum-wrappers_64.o: warning: objtool: csum_and_copy_from_user()+0x2a4: call to memset() with UACCESS enabled
> arch/x86/lib/csum-wrappers_64.o: warning: objtool: csum_and_copy_to_user()+0x243: return with UACCESS enabled

Urgh, that's horrible code. That's got plain stac()/clac() calls on
instead of the regular uaccess APIs.

Anybody any clue about what the best way forward here is?

Also, I wonder how we get at memset() with AC set,..