[PATCH v9 37/39] dyndbg: add epilogue to dynamic_debug/control file

[Jim Cromie via B4 Relay]

From: Jim Cromie <jim.cromie@xxxxxxxxx>

Add an epilogue to the control-file, to allow display of statistics
etc, without disturbing the header.

NB: epilogue lines should start with "#: " to distinguish them from
lines describing pr_debugs (and from the header line).  No new lines
are added here, only the place to do so.

Signed-off-by: Jim Cromie <jim.cromie@xxxxxxxxx>
---
v9:
. update ddebug_proc_start() to return EPILOGUE_TOKEN when seeking directly to epilogue.
---
 lib/dynamic_debug.c | 23 ++++++++++++++++++++---
 1 file changed, 20 insertions(+), 3 deletions(-)

diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
index afde13a2121f..77976e7b264c 100644
--- a/lib/dynamic_debug.c
+++ b/lib/dynamic_debug.c
@@ -1159,6 +1159,9 @@ static struct _ddebug *ddebug_iter_next(struct ddebug_iter *iter)
  * read() call from userspace.  Takes the ddebug_lock and
  * seeks the seq_file's iterator to the given position.
  */
+static char ddebug_epilogue_token;
+#define EPILOGUE_TOKEN (&ddebug_epilogue_token)
+
 static void *ddebug_proc_start(struct seq_file *m, loff_t *pos)
 {
 	struct ddebug_iter *iter = m->private;
@@ -1174,7 +1177,9 @@ static void *ddebug_proc_start(struct seq_file *m, loff_t *pos)
 	dp = ddebug_iter_first(iter);
 	while (dp != NULL && --n > 0)
 		dp = ddebug_iter_next(iter);
-	return dp;
+	if (dp)
+		return dp;
+	return n == 0 ? EPILOGUE_TOKEN : NULL;
 }
 
 /*
@@ -1187,12 +1192,20 @@ static void *ddebug_proc_next(struct seq_file *m, void *p, loff_t *pos)
 	struct ddebug_iter *iter = m->private;
 	struct _ddebug *dp;
 
+	(*pos)++;
+
+	if (p == EPILOGUE_TOKEN)
+		return NULL;
+
 	if (p == SEQ_START_TOKEN)
 		dp = ddebug_iter_first(iter);
 	else
 		dp = ddebug_iter_next(iter);
-	++*pos;
-	return dp;
+
+	if (dp)
+		return dp;
+
+	return EPILOGUE_TOKEN;
 }
 
 static bool ddebug_class_map_in_range(const int class_id, const struct ddebug_class_map *map)
@@ -1244,6 +1257,10 @@ static int ddebug_proc_show(struct seq_file *m, void *p)
 			 "# filename:lineno [module]function flags format\n");
 		return 0;
 	}
+	if (p == EPILOGUE_TOKEN) {
+		/* use this soon */
+		return 0;
+	}
 
 	seq_printf(m, "%s:%u [%s]%s =%s \"",
 		   trim_prefix(dp->filename), dp->lineno,

-- 
2.55.0