linux-kernel - [PATCH 4/5] libtraceevent: Add __rel_loc relative location attribute support

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Date:   Mon, 15 Nov 2021 19:20:36 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Steven Rostedt <rostedt@...dmis.org>,
        Beau Belgrave <beaub@...ux.microsoft.com>
Cc:     linux-kernel@...r.kernel.org,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Tom Zanussi <zanussi@...nel.org>
Subject: [PATCH 4/5] libtraceevent: Add __rel_loc relative location attribute support

Add '__rel_loc' new dynamic data location attribute which encodes
the data location from the next to the field itself. This is similar
to the '__data_loc' but the location offset is not from the event
entry but from the next of the field.

This patch adds '__rel_loc' decoding support in the libtraceevent.

Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
---
 tools/lib/traceevent/event-parse.c  |   14 ++++++++++++++
 tools/lib/traceevent/event-parse.h  |    1 +
 tools/lib/traceevent/parse-filter.c |    5 ++++-
 3 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/tools/lib/traceevent/event-parse.c b/tools/lib/traceevent/event-parse.c
index fe58843d047c..170d2c9aa522 100644
--- a/tools/lib/traceevent/event-parse.c
+++ b/tools/lib/traceevent/event-parse.c
@@ -1367,6 +1367,14 @@ static int field_is_dynamic(struct tep_format_field *field)
 	return 0;
 }
 
+static int field_is_relative_dynamic(struct tep_format_field *field)
+{
+	if (strncmp(field->type, "__rel_loc", 9) == 0)
+		return 1;
+
+	return 0;
+}
+
 static int field_is_long(struct tep_format_field *field)
 {
 	/* includes long long */
@@ -1622,6 +1630,8 @@ static int event_read_fields(struct tep_event *event, struct tep_format_field **
 			field->flags |= TEP_FIELD_IS_STRING;
 		if (field_is_dynamic(field))
 			field->flags |= TEP_FIELD_IS_DYNAMIC;
+		if (field_is_relative_dynamic(field))
+			field->flags |= TEP_FIELD_IS_DYNAMIC|TEP_FIELD_IS_REL_DYNAMIC;
 		if (field_is_long(field))
 			field->flags |= TEP_FIELD_IS_LONG;
 
@@ -5109,6 +5119,8 @@ void tep_print_field(struct trace_seq *s, void *data,
 			offset = val;
 			len = offset >> 16;
 			offset &= 0xffff;
+			if (field->flags & TEP_FIELD_IS_REL_DYNAMIC)
+				offset += field->offset + field->size;
 		}
 		if (field->flags & TEP_FIELD_IS_STRING &&
 		    is_printable_array(data + offset, len)) {
@@ -6987,6 +6999,8 @@ void *tep_get_field_raw(struct trace_seq *s, struct tep_event *event,
 					 data + offset, field->size);
 		*len = offset >> 16;
 		offset &= 0xffff;
+		if (field->flags & TEP_FIELD_IS_REL_DYNAMIC)
+			offset += field->offset + field->size;
 	} else
 		*len = field->size;
 
diff --git a/tools/lib/traceevent/event-parse.h b/tools/lib/traceevent/event-parse.h
index a67ad9a5b835..c4138eb72605 100644
--- a/tools/lib/traceevent/event-parse.h
+++ b/tools/lib/traceevent/event-parse.h
@@ -125,6 +125,7 @@ enum tep_format_flags {
 	TEP_FIELD_IS_LONG	= 32,
 	TEP_FIELD_IS_FLAG	= 64,
 	TEP_FIELD_IS_SYMBOLIC	= 128,
+	TEP_FIELD_IS_REL_DYNAMIC = 256,
 };
 
 struct tep_format_field {
diff --git a/tools/lib/traceevent/parse-filter.c b/tools/lib/traceevent/parse-filter.c
index 368826bb5a57..9fcee7012df4 100644
--- a/tools/lib/traceevent/parse-filter.c
+++ b/tools/lib/traceevent/parse-filter.c
@@ -1712,8 +1712,11 @@ static const char *get_field_str(struct tep_filter_arg *arg, struct tep_record *
 
 		if (arg->str.field->flags & TEP_FIELD_IS_DYNAMIC) {
 			addr = *(unsigned int *)val;
-			val = record->data + (addr & 0xffff);
 			size = addr >> 16;
+			addr &= 0xffff;
+			if (arg->str.field->flags & TEP_FIELD_IS_REL_DYNAMIC)
+				addr += arg->str.field->offset + arg->str.field->size;
+			val = record->data + addr;
 		}
 
 		/*