tracing: Use seq_buf for building dynevent_cmd string

The dynevent_cmd commands that build up the command string don't need
to do that themselves - there's a seq_buf facility that does pretty
much the same thing those command are doing manually, so use it
instead.

Link: http://lkml.kernel.org/r/eb8a6e835c964d0ab8a38cbf5ffa60746b54a465.1580506712.git.zanussi@kernel.orgReviewed-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Tom Zanussi <zanussi@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

include/linux/trace_events.h

@@ -367,10 +367,8 @@ struct dynevent_cmd;
 typedef int (*dynevent_create_fn_t)(struct dynevent_cmd *cmd);
 
 struct dynevent_cmd {
-	char			*buf;
+	struct seq_buf		seq;
 	const char		*event_name;
-	int			maxlen;
-	int			remaining;
 	unsigned int		n_fields;
 	enum dynevent_type	type;
 	dynevent_create_fn_t	run_command;

kernel/trace/trace_dynevent.c

@@ -247,8 +247,6 @@ int dynevent_arg_add(struct dynevent_cmd *cmd,
 		     dynevent_check_arg_fn_t check_arg)
 {
 	int ret = 0;
-	int delta;
-	char *q;
 
 	if (check_arg) {
 		ret = check_arg(arg);
@@ -256,14 +254,11 @@ int dynevent_arg_add(struct dynevent_cmd *cmd,
 			return ret;
 	}
 
-	q = cmd->buf + (cmd->maxlen - cmd->remaining);
-
-	delta = snprintf(q, cmd->remaining, " %s%c", arg->str, arg->separator);
-	if (delta >= cmd->remaining) {
-		pr_err("String is too long: %s\n", arg->str);
+	ret = seq_buf_printf(&cmd->seq, " %s%c", arg->str, arg->separator);
+	if (ret) {
+		pr_err("String is too long: %s%c\n", arg->str, arg->separator);
 		return -E2BIG;
 	}
-	cmd->remaining -= delta;
 
 	return ret;
 }
@@ -297,8 +292,6 @@ int dynevent_arg_pair_add(struct dynevent_cmd *cmd,
 			  dynevent_check_arg_fn_t check_arg)
 {
 	int ret = 0;
-	int delta;
-	char *q;
 
 	if (check_arg) {
 		ret = check_arg(arg_pair);
@@ -306,23 +299,15 @@ int dynevent_arg_pair_add(struct dynevent_cmd *cmd,
 			return ret;
 	}
 
-	q = cmd->buf + (cmd->maxlen - cmd->remaining);
-
-	delta = snprintf(q, cmd->remaining, " %s%c", arg_pair->lhs,
-			 arg_pair->operator);
-	if (delta >= cmd->remaining) {
-		pr_err("field string is too long: %s\n", arg_pair->lhs);
-		return -E2BIG;
-	}
-	cmd->remaining -= delta; q += delta;
-
-	delta = snprintf(q, cmd->remaining, "%s%c", arg_pair->rhs,
-			 arg_pair->separator);
-	if (delta >= cmd->remaining) {
-		pr_err("field string is too long: %s\n", arg_pair->rhs);
+	ret = seq_buf_printf(&cmd->seq, " %s%c%s%c", arg_pair->lhs,
+			     arg_pair->operator, arg_pair->rhs,
+			     arg_pair->separator);
+	if (ret) {
+		pr_err("field string is too long: %s%c%s%c\n", arg_pair->lhs,
+		       arg_pair->operator, arg_pair->rhs,
+		       arg_pair->separator);
 		return -E2BIG;
 	}
-	cmd->remaining -= delta;
 
 	return ret;
 }
@@ -340,17 +325,12 @@ int dynevent_arg_pair_add(struct dynevent_cmd *cmd,
 int dynevent_str_add(struct dynevent_cmd *cmd, const char *str)
 {
 	int ret = 0;
-	int delta;
-	char *q;
-
-	q = cmd->buf + (cmd->maxlen - cmd->remaining);
 
-	delta = snprintf(q, cmd->remaining, "%s", str);
-	if (delta >= cmd->remaining) {
+	ret = seq_buf_puts(&cmd->seq, str);
+	if (ret) {
 		pr_err("String is too long: %s\n", str);
 		return -E2BIG;
 	}
-	cmd->remaining -= delta;
 
 	return ret;
 }
@@ -381,9 +361,7 @@ void dynevent_cmd_init(struct dynevent_cmd *cmd, char *buf, int maxlen,
 {
 	memset(cmd, '\0', sizeof(*cmd));
 
-	cmd->buf = buf;
-	cmd->maxlen = maxlen;
-	cmd->remaining = cmd->maxlen;
+	seq_buf_init(&cmd->seq, buf, maxlen);
 	cmd->type = type;
 	cmd->run_command = run_command;
 }

kernel/trace/trace_events_hist.c

@@ -1762,7 +1762,7 @@ static int synth_event_run_command(struct dynevent_cmd *cmd)
 	struct synth_event *se;
 	int ret;
 
-	ret = trace_run_command(cmd->buf, create_or_delete_synth_event);
+	ret = trace_run_command(cmd->seq.buffer, create_or_delete_synth_event);
 	if (ret)
 		return ret;
 

kernel/trace/trace_kprobe.c

@@ -903,7 +903,7 @@ static int create_or_delete_trace_kprobe(int argc, char **argv)
 
 static int trace_kprobe_run_command(struct dynevent_cmd *cmd)
 {
-	return trace_run_command(cmd->buf, create_or_delete_trace_kprobe);
+	return trace_run_command(cmd->seq.buffer, create_or_delete_trace_kprobe);
 }
 
 /**