[PATCH 06/12] perf header: Reconstruct group relationship by parsing cmdline

[Namhyung Kim <namhyung@kernel.org>]

In order to support the event group viewer, their group relationship
is needed. Since it's not recorded explicitly anywhere in the perf.data
we should parse saved cmdline and apply the result to the evlist. It is
assumed that parsed entries are in a same order with the originals.

I know it's fragile but hard to find other way to do it in the current
condition. :(

Cc: Stephane Eranian <eranian@google.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
---
 tools/perf/util/header.c |  110 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 110 insertions(+)

diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
index 0efbaa3c5a6b..9d9553fed8a6 100644
--- a/tools/perf/util/header.c
+++ b/tools/perf/util/header.c
@@ -1404,6 +1404,40 @@ static int process_version(struct perf_file_section *section __used,
 	return ph->version ? 0 : -ENOMEM;
 }
 
+/*
+ * Reconstruct group relationship using parsed entries. It's assumed that
+ * the parsed entries are in a same order with the original entries.
+ */
+static void reconstruct_group_relation(struct list_head *parsed_head,
+				       struct list_head *orig_head)
+{
+	struct perf_evsel *pos, *orig;
+	struct perf_evsel *leader = NULL;
+
+	/* Fake first entry to use list_for_each_entry_continue */
+	orig = container_of(orig_head, struct perf_evsel, node);
+
+	list_for_each_entry(pos, parsed_head, node) {
+		list_for_each_entry_continue(orig, orig_head, node) {
+			BUG_ON(pos->attr.type != orig->attr.type);
+			BUG_ON(pos->attr.config != orig->attr.config);
+
+			if (pos->leader == NULL) {
+				orig->leader = NULL;
+				if (pos->group_name)
+					orig->group_name = strdup(pos->group_name);
+				orig->nr_children = pos->nr_children;
+
+				leader = orig;
+			} else {
+				orig->leader = leader;
+				orig->group_idx = pos->group_idx;
+			}
+			break;
+		}
+	}
+}
+
 /* Each argv would be separated by a NULL character */
 static int process_cmdline(struct perf_file_section *section __used,
 			   struct perf_header *ph, int fd, void *data __used)
@@ -1413,6 +1447,11 @@ static int process_cmdline(struct perf_file_section *section __used,
 	u32 nr, i;
 	char *cmdline = NULL;
 	size_t len = 0;
+	LIST_HEAD(head);
+	struct perf_evlist *evlist = NULL;
+	int nr_entries = 0;
+	bool found = false;
+	bool regenerated = false;
 
 	ret = read(fd, &nr, sizeof(nr));
 	if (ret != (ssize_t)sizeof(nr))
@@ -1421,6 +1460,25 @@ static int process_cmdline(struct perf_file_section *section __used,
 	if (ph->needs_swap)
 		nr = bswap_32(nr);
 
+	if (symbol_conf.report_group) {
+		struct perf_session *session;
+
+		session = container_of(ph, struct perf_session, header);
+		evlist = session->evlist;
+
+		/*
+		 * The evlist->entries will be regenerated by parsing cmdline
+		 * to track grouping information. However we cannot use the
+		 * generated entries since they lack sample id information.
+		 *
+		 * Save the original entries to 'head' and reconstruct group
+		 * information using parse entries.
+		 */
+		list_splice_init(&evlist->entries, &head);
+		nr_entries = evlist->nr_entries;
+		evlist->nr_entries = 0;
+	}
+
 	ph->cmdline_argc = nr;
 
 	for (i = 0; i < nr; i++) {
@@ -1428,6 +1486,19 @@ static int process_cmdline(struct perf_file_section *section __used,
 		if (!str)
 			goto error;
 
+		if (symbol_conf.report_group) {
+			if (found) {
+				/* Regenerate evlist */
+				if (!parse_events(evlist, str, 0))
+					regenerated = true;
+			}
+
+			if (!strcmp(str, "-e"))
+				found = true;
+			else
+				found = false;
+		}
+
 		tmp = realloc(cmdline, len + strlen(str) + 1);
 		if (!tmp)
 			goto error;
@@ -1439,10 +1510,49 @@ static int process_cmdline(struct perf_file_section *section __used,
 		len += strlen(str) + 1;
 		free(str);
 	}
+
+	if (symbol_conf.report_group) {
+		struct perf_evsel *pos, *orig;
+
+		if (regenerated) {
+			BUG_ON(evlist->nr_entries != nr_entries);
+
+			reconstruct_group_relation(&evlist->entries, &head);
+
+			/* Parsed entries are not needed anymore */
+			list_for_each_entry_safe(pos, orig, &evlist->entries, node) {
+				list_del_init(&pos->node);
+				perf_evsel__delete(pos);
+			}
+
+			/* Restore the original entries */
+			list_splice(&head, &evlist->entries);
+		} else {
+			/*
+			 * Indirect record command doesn't contain events on
+			 * the cmdline. Restore original entries.
+			 */
+			list_splice(&head, &evlist->entries);
+			evlist->nr_entries = nr_entries;
+		}
+	}
 	ph->cmdline = cmdline;
 	return 0;
 
 error:
+	if (symbol_conf.report_group) {
+		struct perf_evsel *pos, *n;
+
+		/* Delete intermediate entries */
+		list_for_each_entry_safe(pos, n, &evlist->entries, node) {
+			list_del_init(&pos->node);
+			perf_evsel__delete(pos);
+		}
+
+		/* Restore original entries */
+		list_splice(&head, &evlist->entries);
+		evlist->nr_entries = nr_entries;
+	}
 	free(cmdline);
 	free(str);
 	return -1;
-- 
1.7.10.4