linux-kernel - Re: [PATCH 2/4] ARM: backtrace-clang: add fixup for lr dereference

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Message-ID: <CAKwvOdnDyUw7TZ-ZsWQ=d7ZNPM_ziFnimmbYoVAexWmg2DL36A@mail.gmail.com>
Date:   Wed, 19 Aug 2020 17:13:47 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Nathan Huckleberry <nhuck15@...il.com>
Cc:     Russell King <linux@...linux.org.uk>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Chunyan Zhang <zhang.lyra@...il.com>,
        clang-built-linux <clang-built-linux@...glegroups.com>,
        Dmitry Safonov <0x7f454c46@...il.com>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-mediatek@...ts.infradead.org,
        Lvqiang Huang <lvqiang.huang@...soc.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Miles Chen <miles.chen@...iatek.com>,
        "# 3.4.x" <stable@...r.kernel.org>,
        Nathan Huckleberry <nhuck@...gle.com>
Subject: Re: [PATCH 2/4] ARM: backtrace-clang: add fixup for lr dereference

On Mon, Aug 10, 2020 at 3:33 PM Nick Desaulniers
<ndesaulniers@...gle.com> wrote:
>
> On Thu, Aug 6, 2020 at 3:39 PM Nathan Huckleberry <nhuck15@...il.com> wrote:
> >
> > Mostly looks good to me. Just a minor nit.
> >
> > On Thu, Jul 30, 2020 at 3:51 PM Nick Desaulniers
> > <ndesaulniers@...gle.com> wrote:
> > > +/*
> > > + * Accessing the address pointed to by the link register triggered an
> > > + * exception, don't try to unwind through it.
> > > + */
> > > +bad_lr:                mov     sv_fp, #0
> >
> > It might be nice to emit a warning here since we'll
> > only hit this case if something fishy is going on
> > with the saved lr.
>
> Yeah, something fishy is going on if that ever happens.  Let me create
> a V2 with an additional print.

FWIW, I ran into another bug on -next when trying to update this.

Report:
https://lore.kernel.org/lkml/20200811204729.1116341-1-ndesaulniers@google.com/
Fix:
https://lore.kernel.org/lkml/20200814212525.6118-1-john.ogness@linutronix.de/T/#t

Then I got bogged down in planning for plumbers and other fires. I
hope to revisit the series after plumbers.
-- 
Thanks,
~Nick Desaulniers