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SubjectRe: [PATCH 0/4] powerpc/livepatch: reliable stack unwinder fixes
Jiri Kosina <> 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]
>> 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? :)


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