[PATCH 15/38] perf: Add attribute to filter out callchains

[Arnaldo Carvalho de Melo]

From: Frederic Weisbecker <fweisbec@xxxxxxxxx>

Introducing following bits to the the perf_event_attr struct:

  - exclude_callchain_kernel to filter out kernel callchain
    from the sample dump

  - exclude_callchain_user to filter out user callchain
    from the sample dump

We need to be able to disable standard user callchain dump when we use
the dwarf cfi callchain mode, because frame pointer based user
callchains are useless in this mode.

Implementing also exclude_callchain_kernel to have complete set of
options.

Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
[ Added kernel callchains filtering ]
Cc: "Frank Ch. Eigler" <fche@xxxxxxxxxx>
Cc: Arun Sharma <asharma@xxxxxx>
Cc: Benjamin Redelings <benjamin.redelings@xxxxxxxxxxx>
Cc: Corey Ashford <cjashfor@xxxxxxxxxxxxxxxxxx>
Cc: Cyrill Gorcunov <gorcunov@xxxxxxxxxx>
Cc: Frank Ch. Eigler <fche@xxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@xxxxxxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Cc: Robert Richter <robert.richter@xxxxxxx>
Cc: Stephane Eranian <eranian@xxxxxxxxxx>
Cc: Tom Zanussi <tzanussi@xxxxxxxxx>
Cc: Ulrich Drepper <drepper@xxxxxxxxx>
Link: http://lkml.kernel.org/r/1344345647-11536-7-git-send-email-jolsa@xxxxxxxxxx
Signed-off-by: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
---
 include/linux/perf_event.h |    5 ++++-
 kernel/events/callchain.c  |   38 ++++++++++++++++++++++++--------------
 2 files changed, 28 insertions(+), 15 deletions(-)

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index d1d25f6..297ca3d 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -268,7 +268,10 @@ struct perf_event_attr {
 				exclude_host   :  1, /* don't count in host   */
 				exclude_guest  :  1, /* don't count in guest  */
 
-				__reserved_1   : 43;
+				exclude_callchain_kernel : 1, /* exclude kernel callchains */
+				exclude_callchain_user   : 1, /* exclude user callchains */
+
+				__reserved_1   : 41;
 
 	union {
 		__u32		wakeup_events;	  /* wakeup every n events */
diff --git a/kernel/events/callchain.c b/kernel/events/callchain.c
index 98d4597..c772061 100644
--- a/kernel/events/callchain.c
+++ b/kernel/events/callchain.c
@@ -159,6 +159,11 @@ perf_callchain(struct perf_event *event, struct pt_regs *regs)
 	int rctx;
 	struct perf_callchain_entry *entry;
 
+	int kernel = !event->attr.exclude_callchain_kernel;
+	int user   = !event->attr.exclude_callchain_user;
+
+	if (!kernel && !user)
+		return NULL;
 
 	entry = get_callchain_entry(&rctx);
 	if (rctx == -1)
@@ -169,24 +174,29 @@ perf_callchain(struct perf_event *event, struct pt_regs *regs)
 
 	entry->nr = 0;
 
-	if (!user_mode(regs)) {
+	if (kernel && !user_mode(regs)) {
 		perf_callchain_store(entry, PERF_CONTEXT_KERNEL);
 		perf_callchain_kernel(entry, regs);
-		if (current->mm)
-			regs = task_pt_regs(current);
-		else
-			regs = NULL;
 	}
 
-	if (regs) {
-		/*
-		 * Disallow cross-task user callchains.
-		 */
-		if (event->ctx->task && event->ctx->task != current)
-			goto exit_put;
-
-		perf_callchain_store(entry, PERF_CONTEXT_USER);
-		perf_callchain_user(entry, regs);
+	if (user) {
+		if (!user_mode(regs)) {
+			if  (current->mm)
+				regs = task_pt_regs(current);
+			else
+				regs = NULL;
+		}
+
+		if (regs) {
+			/*
+			 * Disallow cross-task user callchains.
+			 */
+			if (event->ctx->task && event->ctx->task != current)
+				goto exit_put;
+
+			perf_callchain_store(entry, PERF_CONTEXT_USER);
+			perf_callchain_user(entry, regs);
+		}
 	}
 
 exit_put:
-- 
1.7.1

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