[PATCH v5 8/9] perf thread: Add helper to get top return address

[Leo Yan]

For the instruction emulation or single step in kernel, when return to
the user space, the return address is not possible to be the same with
the ret_addr in thread stack.

This patch adds a helper to read out the top return address from thread
stack, this can be used for specific calibration in up case.

Signed-off-by: Leo Yan <leo.yan@xxxxxxxxxx>
---
 tools/perf/util/thread-stack.c | 10 ++++++++++
 tools/perf/util/thread-stack.h |  1 +
 2 files changed, 11 insertions(+)

diff --git a/tools/perf/util/thread-stack.c b/tools/perf/util/thread-stack.c
index 0885967d5bc3..60cd6fdca8de 100644
--- a/tools/perf/util/thread-stack.c
+++ b/tools/perf/util/thread-stack.c
@@ -497,6 +497,16 @@ void thread_stack__sample(struct thread *thread, int cpu,
 	chain->nr = i;
 }
 
+u64 thread_stack__get_top_ret_addr(struct thread *thread, int cpu)
+{
+	struct thread_stack *ts = thread__stack(thread, cpu);
+
+	if (!ts || !ts->cnt)
+		return UINT64_MAX;
+
+	return ts->stack[ts->cnt--].ret_addr;
+}
+
 struct call_return_processor *
 call_return_processor__new(int (*process)(struct call_return *cr, u64 *parent_db_id, void *data),
 			   void *data)
diff --git a/tools/perf/util/thread-stack.h b/tools/perf/util/thread-stack.h
index e1ec5a58f1b2..b9d07a3be6c2 100644
--- a/tools/perf/util/thread-stack.h
+++ b/tools/perf/util/thread-stack.h
@@ -88,6 +88,7 @@ void thread_stack__sample(struct thread *thread, int cpu, struct ip_callchain *c
 int thread_stack__flush(struct thread *thread);
 void thread_stack__free(struct thread *thread);
 size_t thread_stack__depth(struct thread *thread, int cpu);
+u64 thread_stack__get_top_ret_addr(struct thread *thread, int cpu);
 
 struct call_return_processor *
 call_return_processor__new(int (*process)(struct call_return *cr, u64 *parent_db_id, void *data),
-- 
2.17.1