[Crash-utility] [PATCH 03/12] crash-trace-command: use special functions to load event type

[Lai Jiangshan]

The struct ftrace_event_call in linux kernel are changes frequently,
We use special functions to load the fields.

It is just cleanup patch, it just moves the old code into the special
functions, and the late patches will changed these functions for suiting
different kernels.

Signed-off-by: Lai Jiangshan <laijs at cn.fujitsu.com>
---
diff --git a/extensions/trace.c b/extensions/trace.c
index 4247bfa..3697108 100755
--- a/extensions/trace.c
+++ b/extensions/trace.c
@@ -51,11 +51,6 @@ static int koffset(buffer_page, page);
 static int koffset(list_head, next);
 
 static int koffset(ftrace_event_call, list);
-static int koffset(ftrace_event_call, name);
-static int koffset(ftrace_event_call, system);
-static int koffset(ftrace_event_call, print_fmt);
-static int koffset(ftrace_event_call, id);
-static int koffset(ftrace_event_call, fields);
 
 static int koffset(ftrace_event_field, link);
 static int koffset(ftrace_event_field, name);
@@ -178,11 +173,6 @@ static int init_offsets(void)
 	init_offset(list_head, next);
 
 	init_offset(ftrace_event_call, list);
-	init_offset(ftrace_event_call, name);
-	init_offset(ftrace_event_call, system);
-	init_offset(ftrace_event_call, print_fmt);
-	init_offset(ftrace_event_call, id);
-	init_offset(ftrace_event_call, fields);
 
 	init_offset(ftrace_event_field, link);
 	init_offset(ftrace_event_field, name);
@@ -227,11 +217,6 @@ static void print_offsets(void)
 	print_offset(list_head, next);
 
 	print_offset(ftrace_event_call, list);
-	print_offset(ftrace_event_call, name);
-	print_offset(ftrace_event_call, system);
-	print_offset(ftrace_event_call, print_fmt);
-	print_offset(ftrace_event_call, id);
-	print_offset(ftrace_event_call, fields);
 
 	print_offset(ftrace_event_field, link);
 	print_offset(ftrace_event_field, name);
@@ -677,6 +662,25 @@ static void event_generic_print_fmt_print(struct event_type *t,
 static void event_default_print(struct event_type *t,
 		struct format_context *fc);
 
+static
+int ftrace_get_event_type_fields(ulong call, ulong *fields)
+{
+	static int inited;
+	static int fields_offset;
+
+	if (!inited) {
+		inited = 1;
+		fields_offset = MEMBER_OFFSET("ftrace_event_call", "fields");
+	}
+
+	if (fields_offset < 0)
+		return -1;
+
+	*fields = call + fields_offset;
+
+	return 0;
+}
+
 static int ftrace_init_event_type(ulong call, struct event_type *aevent_type)
 {
 	ulong fields_addr, pos;
@@ -684,7 +688,8 @@ static int ftrace_init_event_type(ulong call, struct event_type *aevent_type)
 	int nfields = 0, max_fields = 16;
 	struct ftrace_field *fields = NULL;
 
-	fields_addr = call + koffset(ftrace_event_call, fields);
+	if (ftrace_get_event_type_fields(call, &fields_addr) < 0)
+		return -1;
 	read_value(pos, fields_addr, list_head, next);
 
 	if (pos == 0) {
@@ -786,6 +791,105 @@ static void ftrace_destroy_event_types(void)
 	free(event_types);
 }
 
+static
+int ftrace_get_event_type_name(ulong call, char *name, int len)
+{
+	static int inited;
+	static int name_offset;
+
+	ulong name_addr;
+
+	if (!inited) {
+		inited = 1;
+		name_offset = MEMBER_OFFSET("ftrace_event_call", "name");
+	}
+
+	if (name_offset < 0)
+		return -1;
+
+	if (!readmem(call + name_offset, KVADDR, &name_addr, sizeof(name_addr),
+			"read ftrace_event_call name_addr", RETURN_ON_ERROR))
+		return -1;
+
+	if (!read_string(name_addr, name, len))
+		return -1;
+
+	return 0;
+}
+
+static
+int ftrace_get_event_type_system(ulong call, char *system, int len)
+{
+	static int inited;
+	static int sys_offset;
+
+	ulong sys_addr;
+
+	if (!inited) {
+		inited = 1;
+		sys_offset = MEMBER_OFFSET("ftrace_event_call", "system");
+	}
+
+	if (sys_offset < 0)
+		return -1;
+
+	if (!readmem(call + sys_offset, KVADDR, &sys_addr, sizeof(sys_addr),
+			"read ftrace_event_call sys_addr", RETURN_ON_ERROR))
+		return -1;
+
+	if (!read_string(sys_addr, system, len))
+		return -1;
+
+	return 0;
+}
+
+static
+int ftrace_get_event_type_print_fmt(ulong call, char *print_fmt, int len)
+{
+	static int inited;
+	static int fmt_offset;
+
+	ulong fmt_addr;
+
+	if (!inited) {
+		inited = 1;
+		fmt_offset = MEMBER_OFFSET("ftrace_event_call", "print_fmt");
+	}
+
+	if (fmt_offset < 0)
+		return -1;
+
+	if (!readmem(call + fmt_offset, KVADDR, &fmt_addr, sizeof(fmt_addr),
+			"read ftrace_event_call fmt_addr", RETURN_ON_ERROR))
+		return -1;
+
+	if (!read_string(fmt_addr, print_fmt, len))
+		return -1;
+
+	return 0;
+}
+
+static
+int ftrace_get_event_type_id(ulong call, int *id)
+{
+	static int inited;
+	static int id_offset;
+
+	if (!inited) {
+		inited = 1;
+		id_offset = MEMBER_OFFSET("ftrace_event_call", "id");
+	}
+
+	if (id_offset < 0)
+		return -1;
+
+	if (!readmem(call + id_offset, KVADDR, id, sizeof(*id),
+			"read ftrace_event_call id", RETURN_ON_ERROR))
+		return -1;
+
+	return 0;
+}
+
 static int ftrace_init_event_types(void)
 {
 	ulong event;
@@ -799,23 +903,16 @@ static int ftrace_init_event_types(void)
 	read_value(event, ftrace_events, list_head, next);
 	while (event != ftrace_events) {
 		ulong call;
-		ulong name_addr, system_addr, print_fmt_addr;
 		char name[128], system[128], print_fmt[4096];
 		int id;
 
 		call = event - koffset(ftrace_event_call, list);
 
 		/* Read a event type from the core */
-		read_value(id, call, ftrace_event_call, id);
-		read_value(name_addr, call, ftrace_event_call, name);
-		read_value(system_addr, call, ftrace_event_call, system);
-		read_value(print_fmt_addr, call, ftrace_event_call, print_fmt);
-
-		if (!read_string(name_addr, name, 128))
-			goto out_fail;
-		if (!read_string(system_addr, system, 128))
-			goto out_fail;
-		if (!read_string(print_fmt_addr, print_fmt, 4096))
+		if (ftrace_get_event_type_id(call, &id) < 0 ||
+		    ftrace_get_event_type_name(call, name, 128) < 0 ||
+		    ftrace_get_event_type_system(call, system, 128) < 0 ||
+		    ftrace_get_event_type_print_fmt(call, print_fmt, 4096) < 0)
 			goto out_fail;
 
 		/* Enlarge event types array when need */