linux-kernel - Re: WARNING: can't access registers at asm_common

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Message-ID: <20201119120122.GJ3121392@hirez.programming.kicks-ass.net>
Date:   Thu, 19 Nov 2020 13:01:22 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Shinichiro Kawasaki <shinichiro.kawasaki@....com>
Cc:     Jürgen Groß <jgross@...e.com>,
        Andy Lutomirski <luto@...nel.org>,
        Andrew Cooper <andrew.cooper3@...rix.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Nicholas Piggin <npiggin@...il.com>,
        Damien Le Moal <Damien.LeMoal@....com>,
        X86 ML <x86@...nel.org>
Subject: Re: WARNING: can't access registers at asm_common_interrupt

On Thu, Nov 19, 2020 at 11:51:00AM +0000, Shinichiro Kawasaki wrote:
> I tried Peter's patch in my test system and result looks good. The warning is
> still observed with 5.10-rc4. With the patch on top of 5.10-rc4, the warning
> disappeared.

The patch on its own is not sufficient to fix things; there needs to be
an accompanying objtool patch to generate the correct unwind
information.

This patch only ensures objtool has enough information to be able to
dtrt, but as it stands it shouldn't even compile, it should complain
about an alternative trying to modify the stack and bail.