perf/x86/intel/ds: Work around BTS leaking kernel addresses

BTS leaks kernel addresses even in userspace-only mode due to imprecise IP
sampling, so sometimes syscall entry points or page fault handler addresses
end up in a userspace trace.

Since this driver uses a relatively small buffer for BTS records and it has
to iterate through them anyway, it can also take on the additional job of
filtering out the records that contain kernel addresses when kernel space
tracing is not enabled.

This patch changes the bts code to skip the offending records from perf
output. In order to request the exact amount of space on the ring buffer,
we need to do an extra pass through the records to know how many there are
of the valid ones, but considering the small size of the buffer, this extra
pass adds very little overhead to the nmi handler. This way we won't end
up with awkward IP samples with zero IPs in the perf stream.

Signed-off-by: Alexander Shishkin <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Stephane Eranian <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Vince Weaver <[email protected]>
Cc: [email protected]
Link: http://lkml.kernel.org/r/1441030168-6853-2-git-send-email-alexander.shishkin@linux.intel.com
Signed-off-by: Ingo Molnar <[email protected]>

0 files changed, 0 insertions, 0 deletions