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From:   Song Liu <song@kernel.org>
Date:   Fri, 23 Oct 2020 14:15:53 -0700
Message-ID: <CAPhsuW6wZRVoT3Bu6YBVjWVm6JBz9n6_RoZKGM7KrVAXx89SFQ@mail.gmail.com>
Subject: Re: [LTP] mmstress[1309]: segfault at 7f3d71a36ee8 ip
 00007f3d77132bdf sp 00007f3d71a36ee8 error 4 in libc-2.27.so[7f3d77058000+1aa000]
To:     Linus Torvalds <torvalds@linux-foundation.org>
Cc:     Naresh Kamboju <naresh.kamboju@linaro.org>,
        =?UTF-8?B?RGFuaWVsIETDrWF6?= <daniel.diaz@linaro.org>,
        Stephen Rothwell <sfr@canb.auug.org.au>,
        "Matthew Wilcox (Oracle)" <willy@infradead.org>,
        "Peter Zijlstra (Intel)" <peterz@infradead.org>,
        Viresh Kumar <viresh.kumar@linaro.org>,
        X86 ML <x86@kernel.org>,
        open list <linux-kernel@vger.kernel.org>,
        lkft-triage@lists.linaro.org,
        "Eric W. Biederman" <ebiederm@xmission.com>,
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        Dmitry Vyukov <dvyukov@google.com>,
        Geert Uytterhoeven <geert@linux-m68k.org>,
        Christian Brauner <christian.brauner@ubuntu.com>,
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On Fri, Oct 23, 2020 at 10:51 AM Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>
> On Fri, Oct 23, 2020 at 10:00 AM Naresh Kamboju
> <naresh.kamboju@linaro.org> wrote:
> >
> > [Old patch from yesterday]
> >
> > After applying your patch on top on linux next tag 20201015
> > there are two observations,
> >   1) i386 build failed. please find build error build
>
> Yes, this was expected. That patch explicitly only works on x86-64,
> because 32-bit needs the double register handling for 64-bit values
> (mainly loff_t).
>
> >   2) x86_64 kasan test PASS and the reported error not found.
>
> Ok, good. That confirms that the problem you reported is indeed the
> register allocation.
>
> The patch I sent an hour ago (the one based on Rasmus' one from
> yesterday) should fix things too, and - unlike yesterday's - work on
> 32-bit.
>
> But I'll wait for confirmation (and hopefully a sign-off from Rasmus
> so that I can give him authorship) before actually committing it.
>
>               Linus

My test vm failed to boot since

commit d55564cfc222326e944893eff0c4118353e349ec
x86: Make __put_user() generate an out-of-line call

The patch also fixed it.

Thanks!
Song