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Revert "perf/core: Drop kernel samples even though :u is specified"

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commit 6a8a75f323 upstream.

This reverts commit cc1582c231.

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>
This commit is contained in:
Ingo Molnar
2017-07-11 10:56:54 +02:00
committed by Greg Kroah-Hartman
parent 569da0be82
commit 45c59e792c
1 changed files with 0 additions and 21 deletions
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21
kernel/events/core.c
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@ -6410,21 +6410,6 @@ static void perf_log_itrace_start(struct perf_event *event)
perf_output_end(&handle); perf_output_end(&handle);
} }
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. * Generic event overflow handling, sampling.
*/ */
@ -6471,12 +6456,6 @@ static int __perf_event_overflow(struct perf_event *event,
perf_adjust_period(event, delta, hwc->last_period, true); perf_adjust_period(event, delta, hwc->last_period, true);
} }
/*
* 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 * XXX event_limit might not quite work as expected on inherited
* events * events