linux-kernel - [RFC PATCH v4 04/19] dyndbg: accept null site in ddebug_match

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Message-Id: <20210317065412.2890414-5-jim.cromie@gmail.com>
Date:   Wed, 17 Mar 2021 00:53:57 -0600
From:   Jim Cromie <jim.cromie@...il.com>
To:     jbaron@...mai.com, gregkh@...uxfoundation.org,
        linux-kernel@...r.kernel.org
Cc:     Jim Cromie <jim.cromie@...il.com>
Subject: [RFC PATCH v4 04/19] dyndbg: accept null site in ddebug_match_site

basically, reorder the elements to minimize data fetches.

1- move format and line-number check code to the top of the function,
   since they don't use/check site info.

2- test site pointer:
   If its null, we return early, skipping 3:
      If the query tests against missing site info, fail the match.
      otherwize site matches.

3- rest of function (checking site vs query) is unchanged.

ddebug_match_site ignores module, because it's tested already
by the caller, where it is known from debug_tables.

Signed-off-by: Jim Cromie <jim.cromie@...il.com>
---
 lib/dynamic_debug.c | 41 +++++++++++++++++++++++++----------------
 1 file changed, 25 insertions(+), 16 deletions(-)

diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
index 9cff9db15937..da732e0c56e3 100644
--- a/lib/dynamic_debug.c
+++ b/lib/dynamic_debug.c
@@ -145,21 +145,7 @@ static void vpr_info_dq(const struct ddebug_query *query, const char *msg)
 static int ddebug_match_site(const struct ddebug_query *query,
 			     const struct _ddebug *dp)
 {
-	struct _ddebug_site *dc = dp->site;
-
-	/* match against the source filename */
-	if (query->filename &&
-	    !match_wildcard(query->filename, dc->filename) &&
-	    !match_wildcard(query->filename,
-			    kbasename(dc->filename)) &&
-	    !match_wildcard(query->filename,
-			    trim_prefix(dc->filename)))
-		return false;
-
-	/* match against the function */
-	if (query->function &&
-	    !match_wildcard(query->function, dc->function))
-		return false;
+	struct _ddebug_site *dc;
 
 	/* match against the format */
 	if (query->format) {
@@ -181,6 +167,29 @@ static int ddebug_match_site(const struct ddebug_query *query,
 	    dp->lineno > query->last_lineno)
 		return false;
 
+	dc = dp->site;
+	if (!dc) {
+		/* site info has been dropped, so query cannot test these fields */
+		if (query->filename || query->function)
+			return false;
+		else
+			return true;
+	}
+
+	/* match against the source filename */
+	if (query->filename &&
+	    !match_wildcard(query->filename, dc->filename) &&
+	    !match_wildcard(query->filename,
+			    kbasename(dc->filename)) &&
+	    !match_wildcard(query->filename,
+			    trim_prefix(dc->filename)))
+		return false;
+
+	/* match against the function */
+	if (query->function &&
+	    !match_wildcard(query->function, dc->function))
+		return false;
+
 	return true;
 }
 
@@ -210,7 +219,7 @@ static int ddebug_change(const struct ddebug_query *query,
 
 		for (i = 0; i < dt->num_ddebugs; i++) {
 			struct _ddebug *dp = &dt->ddebugs[i];
-			struct _ddebug_site *dc = dp->site;
+			struct _ddebug_site *dc;
 
 			if (!ddebug_match_site(query, dp))
 				continue;
-- 
2.29.2