Messages in this thread | | | Subject | Re: [PATCH] x86/stacktrace: update kconfig help text for reliable unwinders | From | Joe Lawrence <> | Date | Wed, 6 Nov 2019 18:16:28 -0500 |
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On 11/6/19 6:05 PM, Josh Poimboeuf wrote: > On Wed, Nov 06, 2019 at 05:43:44PM -0500, Joe Lawrence wrote: >> commit 6415b38bae26 ("x86/stacktrace: Enable HAVE_RELIABLE_STACKTRACE >> for the ORC unwinder") marked the ORC unwinder as a "reliable" unwinder. >> Update the help text to reflect that change: the frame pointer unwinder >> is no longer the only one that provides HAVE_RELIABLE_STACKTRACE. >> >> Signed-off-by: Joe Lawrence <joe.lawrence@redhat.com> >> --- >> arch/x86/Kconfig.debug | 8 ++++---- >> 1 file changed, 4 insertions(+), 4 deletions(-) >> >> diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug >> index bf9cd83de777..69cdf0558c13 100644 >> --- a/arch/x86/Kconfig.debug >> +++ b/arch/x86/Kconfig.debug >> @@ -316,10 +316,6 @@ config UNWINDER_FRAME_POINTER >> unwinder, but the kernel text size will grow by ~3% and the kernel's >> overall performance will degrade by roughly 5-10%. >> >> - This option is recommended if you want to use the livepatch >> - consistency model, as this is currently the only way to get a >> - reliable stack trace (CONFIG_HAVE_RELIABLE_STACKTRACE). >> - >> config UNWINDER_GUESS >> bool "Guess unwinder" >> depends on EXPERT >> @@ -333,6 +329,10 @@ config UNWINDER_GUESS >> useful in many cases. Unlike the other unwinders, it has no runtime >> overhead. >> >> + This option is not recommended if you want to use the livepatch >> + consistency model, as this unwinder cannot guarantee reliable stack >> + traces. >> + > > I'm not sure whether this last hunk is helpful. At the very least the > wording of "not recommended" might be confusing because it's not even > possible to combine UNWINDER_GUESS+HAVE_RELIABLE_STACKTRACE. > > arch/x86/Kconfig: select HAVE_RELIABLE_STACKTRACE if X86_64 && (UNWINDER_FRAME_POINTER || UNWINDER_ORC) && STACK_VALIDATION >
Ah good point. The alternative would be to copy the recommended note to both UNWINDER_FRAME_POINTER and UNWINDER_ORC, or at least remove the "only" phrasing. I dunno, nobody has noticed it yet, so maybe the first hunk would be good enough.
-- Joe
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