[PATCH RFC 2/2] perf: convert: fix duplicate field names and avoid reserved keywords.

[Wang Nan]

(If Steven Rostedt accept the previous patch which introduce a priv
 field to 'struct format_field', we can use a relative simple method
 for name conversion. If not , perf must track name conversion by
 itself.)

Some parameters of syscall tracepoints named as 'nr', 'event', etc.
When dealing with them, perf convert to ctf meets some problem:

 1. If a parameter with name 'nr', it will duplicate syscall's
    common field 'nr'. One such syscall is io_submit().

 2. If a parameter with name 'event', it is denied to be inserted
    because 'event' is a babeltrace keywork. One such syscall is
    epoll_ctl.

This patch appends '_dupl_X' suffix to avoid problem 1, prepend a '_'
prefix to avoid problem 2.

Signed-off-by: Wang Nan <wangnan0@xxxxxxxxxx>
---
 tools/perf/util/data-convert-bt.c | 94 +++++++++++++++++++++++++++++++++++++--
 1 file changed, 90 insertions(+), 4 deletions(-)

diff --git a/tools/perf/util/data-convert-bt.c b/tools/perf/util/data-convert-bt.c
index ddecce8..a94f3bd 100644
--- a/tools/perf/util/data-convert-bt.c
+++ b/tools/perf/util/data-convert-bt.c
@@ -184,6 +184,7 @@ static int add_tracepoint_field_value(struct ctf_writer *cw,
 	unsigned int len;
 	int ret;
 
+	name = fmtf->priv ? (const char *)fmtf->priv : fmtf->name;
 	offset = fmtf->offset;
 	len = fmtf->size;
 	if (flags & FIELD_IS_STRING)
@@ -567,6 +568,91 @@ static int process_sample_event(struct perf_tool *tool,
 	return cs ? 0 : -1;
 }
 
+/* If dup < 0, add a prefix. Else, add _dupl_X suffix. */
+static char *change_name(char *name, char *orig_name, int dup)
+{
+	char *new_name = NULL;
+	size_t len;
+
+	if (!name)
+		name = orig_name;
+
+	if (dup >= 10)
+		goto out;
+
+	if (dup < 0)
+		len = strlen(name) + sizeof("_");
+	else
+		len = strlen(orig_name) + sizeof("_dupl_X");
+
+	new_name = malloc(len);
+	if (!new_name)
+		goto out;
+
+	if (dup < 0)
+		snprintf(new_name, len, "_%s", name);
+	else
+		snprintf(new_name, len, "%s_dupl_%d", orig_name, dup);
+
+out:
+	if (name != orig_name)
+		free(name);
+	return new_name;
+}
+
+static void destroy_field_priv(struct format_field *field)
+{
+	if (!field->priv)
+		return;
+
+	if (field->priv != field->name)
+		free(field->priv);
+
+	field->priv = NULL;
+	field->destroy_priv = NULL;
+}
+
+static int event_class_add_field(struct bt_ctf_event_class *event_class,
+		struct bt_ctf_field_type *type,
+		struct format_field *field)
+{
+	struct bt_ctf_field_type *t = NULL;
+	char *name;
+	int dup = 1;
+	int ret;
+
+	if (field->priv)
+		return bt_ctf_event_class_add_field(event_class, type,
+				(char *)field->priv);
+
+	name = field->name;
+	while (t = bt_ctf_event_class_get_field_by_name(event_class, name)) {
+		bt_ctf_field_type_put(t);
+		name = change_name(name, field->name, dup++);
+		if (!name) {
+			pr_err("Failed to create dup name for '%s'\n", field->name);
+			return -1;
+		}
+	}
+
+	ret = bt_ctf_event_class_add_field(event_class, type, name);
+
+	/* if failed, we may hit a keywork. try again with a '_' prefix */
+	if (ret) {
+		name = change_name(name, field->name, -1);
+		if (!name) {
+			pr_err("Failed to alloc name for '_%s'\n", field->name);
+			return -1;
+		}
+		ret = bt_ctf_event_class_add_field(event_class, type, name);
+	}
+
+	field->priv = name;
+	field->destroy_priv = destroy_field_priv;
+
+	return ret;
+}
+
 static int add_tracepoint_fields_types(struct ctf_writer *cw,
 				       struct format_field *fields,
 				       struct bt_ctf_event_class *event_class)
@@ -595,14 +681,14 @@ static int add_tracepoint_fields_types(struct ctf_writer *cw,
 		if (flags & FIELD_IS_ARRAY)
 			type = bt_ctf_field_type_array_create(type, field->arraylen);
 
-		ret = bt_ctf_event_class_add_field(event_class, type,
-				field->name);
+		ret = event_class_add_field(event_class, type, field);
 
 		if (flags & FIELD_IS_ARRAY)
 			bt_ctf_field_type_put(type);
 
 		if (ret) {
-			pr_err("Failed to add field '%s\n", field->name);
+			pr_err("Failed to add field '%s': %d\n",
+					field->name, ret);
 			return -1;
 		}
 	}
@@ -646,7 +732,7 @@ static int add_generic_types(struct ctf_writer *cw, struct perf_evsel *evsel,
 	do {								\
 		pr2("  field '%s'\n", n);				\
 		if (bt_ctf_event_class_add_field(cl, t, n)) {		\
-			pr_err("Failed to add field '%s;\n", n);	\
+			pr_err("Failed to add field '%s';\n", n);	\
 			return -1;					\
 		}							\
 	} while (0)
-- 
1.8.4

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