[PATCH 3/6] perf script: enable db export to output sampled callchains

[Chris Phlipot <cphlipot0@gmail.com>]

This change enables the db export api to export callchains. This
is accomplished by adding callchains obtained from samples to the
call_path_root structure and exporting them via the current call path
export API.

While the current API does support exporting call paths, this is not
supported when sampling. This commit addresses that missing feature by
allowing the export of call paths when callchains are present in samples.

Summary:
-This feature is activated by initializing the call_path_root member
	inside the db_export structure to a non-null value.
-Callchains are resolved with thread__resolve_callchain() and then stored
	and exported by adding a call path under call path root.
-Symbol and DSO for each callchain node are exported via db_ids_from_al()

This commit puts in place infrastructure to be used by subsequent commits,
and by itself, does not introduce any user-visible changes.

Signed-off-by: Chris Phlipot <cphlipot0@gmail.com>
---
 tools/perf/util/db-export.c | 86 +++++++++++++++++++++++++++++++++++++++++++++
 tools/perf/util/db-export.h |  2 ++
 2 files changed, 88 insertions(+)

diff --git a/tools/perf/util/db-export.c b/tools/perf/util/db-export.c
index 4fc607c..cb96591 100644
--- a/tools/perf/util/db-export.c
+++ b/tools/perf/util/db-export.c
@@ -15,6 +15,8 @@
 
 #include <errno.h>
 
+#include <sys/types.h>
+
 #include "evsel.h"
 #include "machine.h"
 #include "thread.h"
@@ -23,6 +25,7 @@
 #include "event.h"
 #include "util.h"
 #include "thread-stack.h"
+#include "callchain.h"
 #include "call-path.h"
 #include "db-export.h"
 
@@ -277,6 +280,81 @@ static int db_ids_from_al(struct db_export *dbe, struct addr_location *al,
 	return 0;
 }
 
+static struct call_path *call_path_from_sample(struct db_export *dbe,
+					       struct machine *machine,
+					       struct thread *thread,
+					       struct perf_sample *sample,
+					       struct perf_evsel *evsel
+					       )
+{
+	u64 kernel_start = machine__kernel_start(machine);
+
+	struct call_path *current = &dbe->cpr->call_path;
+	enum chain_order saved_order = callchain_param.order;
+
+	int err = 0;
+
+	if (!symbol_conf.use_callchain || !sample->callchain)
+		return NULL;
+
+	/* Since the call path tree must be built starting with the root, we
+	 * must use ORDER_CALL for call chain resolution, in order to process
+	 * the callchain starting with the root node and ending with the leaf.
+	 */
+	callchain_param.order = ORDER_CALLER;
+	err = thread__resolve_callchain(thread, &callchain_cursor, evsel,
+					sample, NULL, NULL,
+					PERF_MAX_STACK_DEPTH);
+	if (err) {
+		callchain_param.order = saved_order;
+		return NULL;
+	}
+	callchain_cursor_commit(&callchain_cursor);
+
+	while (1) {
+		struct callchain_cursor_node *node;
+		struct addr_location al;
+		u64 dso_db_id = 0, sym_db_id = 0, offset = 0;
+
+		memset(&al, 0, sizeof(al));
+
+		node = callchain_cursor_current(&callchain_cursor);
+		if (!node)
+			break;
+
+		/* handle export of symbol and dso for this node by
+		 * constructing an addr_location struct and then passing it to
+		 * db_ids_from_al() to perform the export.
+		 */
+		al.sym = node->sym;
+		al.map = node->map;
+		al.machine = machine;
+		if (al.map)
+			al.addr = al.map->map_ip(al.map, node->ip);
+		else
+			al.addr = node->ip;
+
+		db_ids_from_al(dbe, &al, &dso_db_id, &sym_db_id, &offset);
+
+		/* add node to the call path tree if it doesn't exist */
+		current = call_path__findnew(dbe->cpr, current,
+					     al.sym, node->ip,
+					     kernel_start);
+
+		callchain_cursor_advance(&callchain_cursor);
+	}
+
+	/* Reset the callchain order to its prior value. */
+	callchain_param.order = saved_order;
+
+	if (current == &dbe->cpr->call_path) {
+		/* Bail because the callchain was empty. */
+		return NULL;
+	}
+
+	return current;
+}
+
 int db_export__branch_type(struct db_export *dbe, u32 branch_type,
 			   const char *name)
 {
@@ -330,6 +408,14 @@ int db_export__sample(struct db_export *dbe, union perf_event *event,
 	if (err)
 		goto out_put;
 
+	if (dbe->cpr) {
+		struct call_path *cp = call_path_from_sample(dbe, al->machine,
+							     thread, sample,
+							     evsel);
+		if (cp)
+			db_export__call_path(dbe, cp);
+	}
+
 	if ((evsel->attr.sample_type & PERF_SAMPLE_ADDR) &&
 	    sample_addr_correlates_sym(&evsel->attr)) {
 		struct addr_location addr_al;
diff --git a/tools/perf/util/db-export.h b/tools/perf/util/db-export.h
index 25e22fd..f5daf55 100644
--- a/tools/perf/util/db-export.h
+++ b/tools/perf/util/db-export.h
@@ -27,6 +27,7 @@ struct dso;
 struct perf_sample;
 struct addr_location;
 struct call_return_processor;
+struct call_path_root;
 struct call_path;
 struct call_return;
 
@@ -64,6 +65,7 @@ struct db_export {
 	int (*export_call_return)(struct db_export *dbe,
 				  struct call_return *cr);
 	struct call_return_processor *crp;
+	struct call_path_root *cpr;
 	u64 evsel_last_db_id;
 	u64 machine_last_db_id;
 	u64 thread_last_db_id;
-- 
2.7.4