linux-kernel - Re: [PATCH] x86/orc: Don't bail on stack overflow

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Date:   Mon, 27 Nov 2017 10:38:42 +0100
From:   Ingo Molnar <mingo@...nel.org>
To:     Josh Poimboeuf <jpoimboe@...hat.com>
Cc:     Andy Lutomirski <luto@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>, X86 ML <x86@...nel.org>,
        Borislav Petkov <bpetkov@...e.de>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Brian Gerst <brgerst@...il.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH] x86/orc: Don't bail on stack overflow


* Josh Poimboeuf <jpoimboe@...hat.com> wrote:

> On Sat, Nov 25, 2017 at 04:16:23PM -0800, Andy Lutomirski wrote:
> > Can you send me whatever config and exact commit hash generated this?
> > I can try to figure out why it failed.
> 
> Sorry, I've been traveling.  I just got some time to take a look at
> this.  I think there are at least two unwinder issues here:
> 
> - It doesn't deal gracefully with the case where the stack overflows and
>   the stack pointer itself isn't on a valid stack but the
>   to-be-dereferenced data *is*.
> 
> - The oops dump code doesn't know how to print partial pt_regs, for the
>   case where if we get an interrupt/exception in *early* entry code
>   before the full pt_regs have been saved.
> 
> (Andy, I'm not quite sure about your patch, and whether it's still
> needed after these patches.  I'll need to look at it later when I have
> more time.)
> 
> I attempted to fix both of the issues with the below patch.  Thomas or
> Ingo, can you test to see if this gets rid of the question marks?
> 
> I can split it up into proper patches next week.  I'm assuming this
> isn't holding up the KAISER merge?

It's not holding up the Kaiser merge, but good debuggability of weird crashes is a 
really good thing, so I constructed a changelog and picked up this patch as a 
single commit, and added your Signed-off-by, if that's OK with you.

Will only push it out if it passes testing.

Thanks,

	Ingo