linux-kernel - [PATCH] tracing user_events: Simplify user_event_parse

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Date: Mon, 8 Jan 2024 13:37:23 -0500
From: Steven Rostedt <rostedt@...dmis.org>
To: LKML <linux-kernel@...r.kernel.org>, Linux Trace Kernel
 <linux-trace-kernel@...r.kernel.org>
Cc: Masami Hiramatsu <mhiramat@...nel.org>, Mathieu Desnoyers
 <mathieu.desnoyers@...icios.com>, Beau Belgrave <beaub@...ux.microsoft.com>
Subject: [PATCH] tracing user_events: Simplify user_event_parse_field()
 parsing

From: "Steven Rostedt (Google)" <rostedt@...dmis.org>

Instead of having a bunch of if statements with:

       len = str_has_prefix(field, "__data_loc unsigned ");
       if (len)
               goto skip_next;

       len = str_has_prefix(field, "__data_loc ");
       if (len)
               goto skip_next;

       len = str_has_prefix(field, "__rel_loc unsigned ");
       if (len)
               goto skip_next;

       len = str_has_prefix(field, "__rel_loc ");
       if (len)
               goto skip_next;

	goto parse;

 skip_next:

Consolidate it into a negative check and jump to parse if all the
str_has_prefix() calls fail. If one succeeds, it will just continue with
len equal to the proper string:

       if (!(len = str_has_prefix(field, "__data_loc unsigned ")) &&
           !(len = str_has_prefix(field, "__data_loc ")) &&
           !(len = str_has_prefix(field, "__rel_loc unsigned ")) &&
           !(len = str_has_prefix(field, "__rel_loc "))) {
               goto parse;
       }

 skip_next:

Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>
---
 kernel/trace/trace_events_user.c | 22 ++++++----------------
 1 file changed, 6 insertions(+), 16 deletions(-)

diff --git a/kernel/trace/trace_events_user.c b/kernel/trace/trace_events_user.c
index 9365ce407426..ce0c5f1ded48 100644
--- a/kernel/trace/trace_events_user.c
+++ b/kernel/trace/trace_events_user.c
@@ -1175,23 +1175,13 @@ static int user_event_parse_field(char *field, struct user_event *user,
 		goto skip_next;
 	}
 
-	len = str_has_prefix(field, "__data_loc unsigned ");
-	if (len)
-		goto skip_next;
-
-	len = str_has_prefix(field, "__data_loc ");
-	if (len)
-		goto skip_next;
-
-	len = str_has_prefix(field, "__rel_loc unsigned ");
-	if (len)
-		goto skip_next;
-
-	len = str_has_prefix(field, "__rel_loc ");
-	if (len)
-		goto skip_next;
+	if (!(len = str_has_prefix(field, "__data_loc unsigned ")) &&
+	    !(len = str_has_prefix(field, "__data_loc ")) &&
+	    !(len = str_has_prefix(field, "__rel_loc unsigned ")) &&
+	    !(len = str_has_prefix(field, "__rel_loc "))) {
+		goto parse;
+	}
 
-	goto parse;
 skip_next:
 	type = field;
 	field = strpbrk(field + len, " ");
-- 
2.43.0