linux-kernel - Re: [PATCH 1/7] x86/entry: Fix #UD vs WARN more

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Date:   Wed, 24 Jun 2020 15:37:34 -0700
From:   Andy Lutomirski <luto@...nel.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Andy Lutomirski <luto@...nel.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>, X86 ML <x86@...nel.org>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Marco Elver <elver@...gle.com>,
        Andrey Konovalov <andreyknvl@...gle.com>,
        Mark Rutland <Mark.Rutland@....com>,
        Matthew Helsley <mhelsley@...are.com>,
        Steven Rostedt <rostedt@...dmis.org>, jthierry@...hat.com,
        Miroslav Benes <mbenes@...e.cz>
Subject: Re: [PATCH 1/7] x86/entry: Fix #UD vs WARN more

On Mon, Jun 22, 2020 at 4:47 AM Peter Zijlstra <peterz@...radead.org> wrote:
>
> On Thu, Jun 18, 2020 at 11:18:23PM +0200, Peter Zijlstra wrote:
>
> > > So maybe also do an untraced cond_local_irq_enable()?  After all, if
> > > we’re trying to report a bug from IRQs on, it should be okay to have
> > > IRQs on while reporting it. It might even work better than having IRQs
> > > off.
> >
> > Yes, very good point. Now I want to go look at the old code... I'll frob
> > something tomorrow, brain is pretty fried by now.
>
> How's this then?
>
> ---
> Subject: x86/entry: Fix #UD vs WARN more
> From: Peter Zijlstra <peterz@...radead.org>
> Date: Tue Jun 16 13:28:36 CEST 2020
>
> vmlinux.o: warning: objtool: exc_invalid_op()+0x47: call to probe_kernel_read() leaves .noinstr.text section
>
> Since we use UD2 as a short-cut for 'CALL __WARN', treat it as such.
> Have the bare exception handler do the report_bug() thing.
>
> Fixes: 15a416e8aaa7 ("x86/entry: Treat BUG/WARN as NMI-like entries")

Acked-by: Andy Lutomirski <luto@...nel.org>