linux-kernel - Re: [PATCH] s390/livepatch: Implement reliable stack tracing for the consistency model

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Message-ID: <20190728203053.q3pafkwnzm5j3ccs@treble>
Date:   Sun, 28 Jul 2019 15:30:53 -0500
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Miroslav Benes <mbenes@...e.cz>
Cc:     Joe Lawrence <joe.lawrence@...hat.com>, heiko.carstens@...ibm.com,
        gor@...ux.ibm.com, borntraeger@...ibm.com,
        linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org,
        jikos@...nel.org, pmladek@...e.com, nstange@...e.de,
        live-patching@...r.kernel.org
Subject: Re: [PATCH] s390/livepatch: Implement reliable stack tracing for the
 consistency model

On Wed, Jul 17, 2019 at 01:01:27PM +0200, Miroslav Benes wrote:
> > On a related note, do you think it would be feasible to extend (in
> > another patchset) the reliable stack unwinding code a bit so that we
> > could feed it pre-baked stacks ... then we could verify that the code
> > was finding interesting scenarios.  That was a passing thought I had
> > back when Nicolai and I were debugging the ppc64le exception frame
> > marker bug, but didn't think it worth the time/effort at the time.
> 
> That is an interesting thought. It would help the testing a lot. I will 
> make a note in my todo list.

Another idea I had for reliable unwinder testing: add a
CONFIG_RELIABLE_STACKTRACE_DEBUG option which does a periodic stack
trace and warns if it doesn't reach the end.  It could triggered from a
periodic NMI, or from schedule().

-- 
Josh