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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Fri, 23 Oct 2020 10:50:55 -0700
Message-ID: <CAHk-=wjyp3Y_vXJwvoieBJpmmTrs46kc4GKbq5x_nvonHvPJBw@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:     Naresh Kamboju <naresh.kamboju@linaro.org>
Cc:     =?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>,
        linux-mm <linux-mm@kvack.org>,
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        Linux-Next Mailing List <linux-next@vger.kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        kasan-dev <kasan-dev@googlegroups.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        Geert Uytterhoeven <geert@linux-m68k.org>,
        Christian Brauner <christian.brauner@ubuntu.com>,
        Ingo Molnar <mingo@redhat.com>, LTP List <ltp@lists.linux.it>,
        Al Viro <viro@zeniv.linux.org.uk>
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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