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

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Message-ID: <20190129211001.fsmxhasid4mamlea@treble>
Date:   Tue, 29 Jan 2019 15:10:01 -0600
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     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>,
        Jiri Kosina <jkosina@...e.cz>,
        Michael Ellerman <mpe@...erman.id.au>,
        Nicolai Stange <nstange@...e.de>, Torsten Duwe <duwe@....de>
Subject: Re: [PATCH 0/4] powerpc/livepatch: reliable stack unwinder fixes

On Tue, Jan 22, 2019 at 10:57:20AM -0500, 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
> 
>  arch/powerpc/Kconfig             |  2 +-
>  arch/powerpc/kernel/entry_64.S   |  7 +++
>  arch/powerpc/kernel/stacktrace.c | 74 +++++++++++++++++---------------
>  3 files changed, 47 insertions(+), 36 deletions(-)

Reviewed-by: Josh Poimboeuf <jpoimboe@...hat.com>

-- 
Josh