[PATCH 05/16] perf: Add attribute to filter out user callchains

[Jiri Olsa]

Add the new exclude_user_callchain attribute to filter out
frame pointer based user callchains.

This is something we want to select when we use the dwarf cfi
callchain mode, because frame pointer based user callchains are
useless in this mode.

Signed-off-by: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
---
 include/linux/perf_event.h |    4 +++-
 kernel/events/callchain.c  |    4 ++--
 kernel/events/core.c       |    3 ++-
 kernel/events/internal.h   |    3 ++-
 4 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index dcdc97e..df6ba37 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -275,7 +275,9 @@ struct perf_event_attr {
 				exclude_host   :  1, /* don't count in host   */
 				exclude_guest  :  1, /* don't count in guest  */
 
-				__reserved_1   : 43;
+				exclude_user_callchain : 1, /* only record kernel callchains */
+
+				__reserved_1   : 42;
 
 	union {
 		__u32		wakeup_events;	  /* wakeup every n events */
diff --git a/kernel/events/callchain.c b/kernel/events/callchain.c
index 6581a04..884e997 100644
--- a/kernel/events/callchain.c
+++ b/kernel/events/callchain.c
@@ -153,7 +153,7 @@ put_callchain_entry(int rctx)
 	put_recursion_context(__get_cpu_var(callchain_recursion), rctx);
 }
 
-struct perf_callchain_entry *perf_callchain(struct pt_regs *regs)
+struct perf_callchain_entry *perf_callchain(struct pt_regs *regs, int user)
 {
 	int rctx;
 	struct perf_callchain_entry *entry;
@@ -177,7 +177,7 @@ struct perf_callchain_entry *perf_callchain(struct pt_regs *regs)
 			regs = NULL;
 	}
 
-	if (regs) {
+	if (user && regs) {
 		perf_callchain_store(entry, PERF_CONTEXT_USER);
 		perf_callchain_user(entry, regs);
 	}
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 0ace2c7..8e73a2b 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -4138,8 +4138,9 @@ void perf_prepare_sample(struct perf_event_header *header,
 
 	if (sample_type & PERF_SAMPLE_CALLCHAIN) {
 		int size = 1;
+		int user = !event->attr.exclude_user_callchain;
 
-		data->callchain = perf_callchain(regs);
+		data->callchain = perf_callchain(regs, user);
 
 		if (data->callchain)
 			size += data->callchain->nr;
diff --git a/kernel/events/internal.h b/kernel/events/internal.h
index ed8ab26..b18465b 100644
--- a/kernel/events/internal.h
+++ b/kernel/events/internal.h
@@ -121,7 +121,8 @@ DEFINE_OUTPUT_COPY(__output_copy, memcpy_common)
 DEFINE_OUTPUT_COPY(__output_copy_user, arch_perf_out_copy_user)
 
 /* Callchain handling */
-extern struct perf_callchain_entry *perf_callchain(struct pt_regs *regs);
+extern struct perf_callchain_entry *perf_callchain(struct pt_regs *regs,
+						   int user);
 extern int get_callchain_buffers(void);
 extern void put_callchain_buffers(void);
 
-- 
1.7.7.6

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