perf tools: Enable LBR call stack support

Currently, there are two call chain recording options, fp and dwarf.

Haswell has a new feature that utilizes the existing LBR facility to
record call chains. Kernel side LBR support code provides this as a
third option to record call chains. This patch enables the lbr call
stack support on the tooling side.

LBR call stack has some limitations:

 - It reuses current LBR facility, so LBR call stack and branch record
   can not be enabled at the same time.

 - It is only available for user-space callchains.

However, it also offers some advantages:

 - LBR call stack can work on user apps which don't have frame-pointers
   or dwarf debug info compiled. It is a good alternative when nothing
   else works.

Tested-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Kan Liang <kan.liang@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Anshuman Khandual <khandual@linux.vnet.ibm.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Cody P Schafer <cody@linux.vnet.ibm.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Jacob Shin <jacob.w.shin@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Masanari Iida <standby24x7@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Rodrigo Campos <rodrigo@sdfg.com.ar>
Cc: Stephane Eranian <eranian@google.com>
Cc: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/1420482185-29830-2-git-send-email-kan.liang@intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 8 insertions, 0 deletions

diff --git a/tools/perf/util/callchain.c b/tools/perf/util/callchain.c
index 14e7a123d43b..9f643ee77001 100644
--- a/tools/perf/util/callchain.c
+++ b/tools/perf/util/callchain.c
@@ -97,6 +97,14 @@ int parse_callchain_record_opt(const char *arg)
 				callchain_param.dump_size = size;
 			}
 #endif /* HAVE_DWARF_UNWIND_SUPPORT */
+		} else if (!strncmp(name, "lbr", sizeof("lbr"))) {
+			if (!strtok_r(NULL, ",", &saveptr)) {
+				callchain_param.record_mode = CALLCHAIN_LBR;
+				ret = 0;
+			} else
+				pr_err("callchain: No more arguments "
+					"needed for --call-graph lbr\n");
+			break;
 		} else {
 			pr_err("callchain: Unknown --call-graph option "
 			       "value: %s\n", arg);