linux-kernel - Re: boot flooded with unwind: Index not found

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Message-ID: <CAMj1kXGRTM99F_Q29Q4G2Q4L6WSHn2YY+_QZCXQGmw=yWPe1mQ@mail.gmail.com>
Date:   Tue, 1 Mar 2022 17:37:59 +0100
From:   Ard Biesheuvel <ardb@...nel.org>
To:     "Russell King (Oracle)" <linux@...linux.org.uk>
Cc:     Corentin Labbe <clabbe.montjoie@...il.com>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: boot flooded with unwind: Index not found

On Tue, 1 Mar 2022 at 16:52, Russell King (Oracle)
<linux@...linux.org.uk> wrote:
>
> On Tue, Mar 01, 2022 at 04:48:25PM +0100, Corentin Labbe wrote:
> > Hello
> >
> > I booted today linux-next (20220301) and my boot is flooded with:
> > [    0.000000] unwind: Index not found c0f0c440
> > [    0.000000] unwind: Index not found 00000000
> > [    0.000000] unwind: Index not found c0f0c440
> > [    0.000000] unwind: Index not found 00000000
> >
> > This happen on a sun8i-a83t-bananapi-m3
>
> Have you enabled vmapped stacks?
>

This is probably related to

538b9265c063 ARM: unwind: track location of LR value in stack frame

which removes a kernel_text_address() check on frame->pc as it is
essentially redundant, given that we won't find unwind data otherwise.
Unfortunately, I failed to realise that the other check carries a
pr_warn(), which may apparently fire spuriously in some cases.

The 0x0 value can easily be filtered out, but i would be interesting
where the other value originates from. We might be able to solve this
with a simple .nounwind directive in a asm routine somewhere.

I'll prepare a patch that disregards the 0x0 value - could you check
in the mean time what the address 0xcf0c440 coincides with in your
build?