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authorIngo Molnar <mingo@kernel.org>2017-07-11 10:56:54 +0200
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-07-27 15:10:21 -0700
commit964b720f3cead6c0947e519bce7e96b17d3ef1ff (patch)
parent371e6d8b85ef23665958d84307bc0fddc5a6a867 (diff)
Revert "perf/core: Drop kernel samples even though :u is specified"
commit 6a8a75f3235724c5941a33e287b2f98966ad14c5 upstream. This reverts commit cc1582c231ea041fbc68861dfaf957eaf902b829. This commit introduced a regression that broke rr-project, which uses sampling events to receive a signal on overflow (but does not care about the contents of the sample). These signals are critical to the correct operation of rr. There's been some back and forth about how to fix it - but to not keep applications in limbo queue up a revert. Reported-by: Kyle Huey <me@kylehuey.com> Acked-by: Kyle Huey <me@kylehuey.com> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Jin Yao <yao.jin@linux.intel.com> Cc: Vince Weaver <vincent.weaver@maine.edu> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Will Deacon <will.deacon@arm.com> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Stephane Eranian <eranian@google.com> Cc: Namhyung Kim <namhyung@kernel.org> Cc: Jiri Olsa <jolsa@redhat.com> Link: http://lkml.kernel.org/r/20170628105600.GC5981@leverpostej Signed-off-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
1 files changed, 0 insertions, 21 deletions
diff --git a/kernel/events/core.c b/kernel/events/core.c
index f389166bc0e0..d7f726747341 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -7323,21 +7323,6 @@ int perf_event_account_interrupt(struct perf_event *event)
return __perf_event_account_interrupt(event, 1);
-static bool sample_is_allowed(struct perf_event *event, struct pt_regs *regs)
- /*
- * Due to interrupt latency (AKA "skid"), we may enter the
- * kernel before taking an overflow, even if the PMU is only
- * counting user events.
- * To avoid leaking information to userspace, we must always
- * reject kernel samples when exclude_kernel is set.
- */
- if (event->attr.exclude_kernel && !user_mode(regs))
- return false;
- return true;
* Generic event overflow handling, sampling.
@@ -7359,12 +7344,6 @@ static int __perf_event_overflow(struct perf_event *event,
ret = __perf_event_account_interrupt(event, throttle);
- * For security, drop the skid kernel samples if necessary.
- */
- if (!sample_is_allowed(event, regs))
- return ret;
- /*
* XXX event_limit might not quite work as expected on inherited
* events