linux-kernel - Re: [PATCH 0/4] powerpc/livepatch: reliable stack unwinder fixes

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Date:   Wed, 30 Jan 2019 23:22:22 +1100
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Jiri Kosina <jikos@...nel.org>,
        Joe Lawrence <joe.lawrence@...hat.com>
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        live-patching@...r.kernel.org,
        Balbir Singh <bsingharora@...il.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Nicolai Stange <nstange@...e.de>, Torsten Duwe <duwe@....de>
Subject: Re: [PATCH 0/4] powerpc/livepatch: reliable stack unwinder fixes

Jiri Kosina <jikos@...nel.org> writes:
> On Tue, 22 Jan 2019, Joe Lawrence wrote:
>
>> This patchset fixes a false negative report (ie, unreliable) from the
>> ppc64 reliable stack unwinder, discussed here [1] when it may
>> inadvertently trip over a stale exception marker left on the stack.
>> 
>> The first two patches fix this bug.  Nicolai's change clears the marker
>> from the stack when an exception is finished.  The next patch modifies
>> the unwinder to only look for such on stack elements when the ABI
>> guarantees that they will actually be initialized.
>> 
>> The final two patches consist of code cleanups that Nicolai and I
>> spotted during the development of the fixes.
>> 
>> Testing included re-running the original test scenario (loading a
>> livepatch module on ppc64le) on a 5.0.0-rc2 kernel as well as a RHEL-7
>> backport.  I ran internal tests on the RHEL-7 backport and no new test
>> failures were introduced.  I believe that Nicolai has done the same
>> with respect to the first patch.
>> 
>> [1] https://lore.kernel.org/lkml/7f468285-b149-37e2-e782-c9e538b997a9@redhat.com/
>> 
>> Joe Lawrence (3):
>>   powerpc/livepatch: relax reliable stack tracer checks for first-frame
>>   powerpc/livepatch: small cleanups in save_stack_trace_tsk_reliable()
>>   powerpc/livepatch: return -ERRNO values in
>>     save_stack_trace_tsk_reliable()
>> 
>> Nicolai Stange (1):
>>   powerpc/64s: Clear on-stack exception marker upon exception return
>
> Michael, are you fine with this going through LP tree, or do you plan to 
> take it through yours?

I'm happy to take it, unless there's some reason you'd rather it go via
the LP tree?

I don't have any automated live patch tests, but I assume if it's in
linux-next someone can test it? :)

cheers