[PATCH v2 07/27] dyndbg: validate class FOO on module

[Jim Cromie <jim.cromie@gmail.com>]

Add module-to-class validation, in

  #> echo class DRM_UT_KMS +p > /proc/dynamic_debug/control

If a query has "class FOO", ddebug_validate_classname (called from
ddebug_change) requires that FOO is known to module X, otherwize X is
skipped entirely.

The choice of FOO is highly selective, giving isolation and/or
coordinated sharing of FOOs.  For example, only DRM modules should
know and respond to DRM_UT_KMS.

So this, combined with module's opt-in declaration of known classes,
effectively privatizes the .class_id space for each module (or
coordinated set of modules).

Ignoring a bad query, with dynamic_debug.verbose=3:
(lots of modules will not know other module's classes)

bash-5.1# echo module drm class FOO +p > /proc/dynamic_debug/control
[   54.507983] dyndbg: read 24 bytes from userspace
[   54.509549] dyndbg: query 0: "module drm class FOO +p" mod:*
[   54.511502] dyndbg: split into words: "module" "drm" "class" "FOO" "+p"
[   54.513672] dyndbg: op='+'
[   54.514575] dyndbg: flags=0x1
[   54.515547] dyndbg: *flagsp=0x1 *maskp=0xffffffff
[   54.517112] dyndbg: parsed: func="" file="" module="drm" format="" lineno=0-0 class=FOO
[   54.519707] dyndbg: class: drm.FOO unknown
[   54.521302] dyndbg: no matches for query
[   54.522581] dyndbg: no-match: func="" file="" module="drm" format="" lineno=0-0 class=FOO
[   54.525236] dyndbg: processed 1 queries, with 0 matches, 0 errs

Also add a new column to control-file output, displaying the
class-name when its not default.  If a module has pr_debugs with
non-default .class_id's, and has not registered them, "<unregistered>"
is issued.

Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
---
. split out validate_classnames()
---
 lib/dynamic_debug.c | 70 +++++++++++++++++++++++++++++++++++++++------
 1 file changed, 62 insertions(+), 8 deletions(-)

diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
index 8f600c13048a..b1aaf8893cdf 100644
--- a/lib/dynamic_debug.c
+++ b/lib/dynamic_debug.c
@@ -56,6 +56,7 @@ struct ddebug_query {
 	const char *module;
 	const char *function;
 	const char *format;
+	const char *class_string;
 	unsigned int first_lineno, last_lineno;
 };
 
@@ -136,13 +137,40 @@ static void vpr_info_dq(const struct ddebug_query *query, const char *msg)
 			fmtlen--;
 	}
 
-	v3pr_info("%s: func=\"%s\" file=\"%s\" module=\"%s\" format=\"%.*s\" lineno=%u-%u\n",
-		 msg,
-		 query->function ?: "",
-		 query->filename ?: "",
-		 query->module ?: "",
-		 fmtlen, query->format ?: "",
-		 query->first_lineno, query->last_lineno);
+	v3pr_info("%s: func=\"%s\" file=\"%s\" module=\"%s\" format=\"%.*s\" lineno=%u-%u class=%s\n",
+		  msg,
+		  query->function ?: "",
+		  query->filename ?: "",
+		  query->module ?: "",
+		  fmtlen, query->format ?: "",
+		  query->first_lineno, query->last_lineno, query->class_string);
+}
+
+/* return <0 if class-name is unknown/invalid, 0..CLASS_DFLT otherwise */
+static int ddebug_validate_classname(struct ddebug_table *dt, const char *class_string)
+{
+	int query_class = -ENOENT;
+	int idx;
+
+	if (!class_string)
+		/* all queries w/o class given work only on default class */
+		return _DPRINTK_CLASS_DFLT;
+
+	/*
+	 * XXX single list will need to be a for-list
+	 * so that modules can have 2 sets of class-decls
+	 */
+	if (!dt->map)
+		return -ENOENT;
+
+	idx = match_string(dt->map->classes, dt->map->length, class_string);
+	if (idx < 0) {
+		v3pr_info("class: %s.%s unknown\n", dt->mod_name, class_string);
+		return -ENOENT;
+	}
+	query_class = idx + dt->map->base;
+
+	return query_class;
 }
 
 /*
@@ -159,6 +187,7 @@ static int ddebug_change(const struct ddebug_query *query,
 	unsigned int newflags;
 	unsigned int nfound = 0;
 	struct flagsbuf fbuf, nbuf;
+	int query_class;
 
 	/* search for matching ddebugs */
 	mutex_lock(&ddebug_lock);
@@ -169,9 +198,18 @@ static int ddebug_change(const struct ddebug_query *query,
 		    !match_wildcard(query->module, dt->mod_name))
 			continue;
 
+		/* validate class-string against module's known classes */
+		query_class = ddebug_validate_classname(dt, query->class_string);
+		if (query_class < 0)
+			continue;
+
 		for (i = 0; i < dt->num_ddebugs; i++) {
 			struct _ddebug *dp = &dt->ddebugs[i];
 
+			/* match against query-class, either valid input or default */
+			if (query_class != dp->class_id)
+				continue;
+
 			/* match against the source filename */
 			if (query->filename &&
 			    !match_wildcard(query->filename, dp->filename) &&
@@ -424,6 +462,8 @@ static int ddebug_parse_query(char *words[], int nwords,
 		} else if (!strcmp(keyword, "line")) {
 			if (parse_linerange(query, arg))
 				return -EINVAL;
+		} else if (!strcmp(keyword, "class")) {
+			rc = check_set(&query->class_string, arg, "class");
 		} else {
 			pr_err("unknown keyword \"%s\"\n", keyword);
 			return -EINVAL;
@@ -851,6 +891,13 @@ static void *ddebug_proc_next(struct seq_file *m, void *p, loff_t *pos)
 	return dp;
 }
 
+static const char *ddebug_class_name(struct ddebug_iter *iter, struct _ddebug *dp)
+{
+	if (iter->table->map)
+		return iter->table->map->classes[dp->class_id];
+	return NULL;
+}
+
 /*
  * Seq_ops show method.  Called several times within a read()
  * call from userspace, with ddebug_lock held.  Formats the
@@ -862,6 +909,7 @@ static int ddebug_proc_show(struct seq_file *m, void *p)
 	struct ddebug_iter *iter = m->private;
 	struct _ddebug *dp = p;
 	struct flagsbuf flags;
+	char const *class;
 
 	if (p == SEQ_START_TOKEN) {
 		seq_puts(m,
@@ -874,7 +922,13 @@ static int ddebug_proc_show(struct seq_file *m, void *p)
 		   iter->table->mod_name, dp->function,
 		   ddebug_describe_flags(dp->flags, &flags));
 	seq_escape(m, dp->format, "\t\r\n\"");
-	seq_puts(m, "\"\n");
+	seq_puts(m, "\"");
+
+	if (dp->class_id != _DPRINTK_CLASS_DFLT) {
+		class = ddebug_class_name(iter, dp);
+		seq_printf(m, " class:%s", class ?: "<unregistered>");
+	}
+	seq_puts(m, "\n");
 
 	return 0;
 }
-- 
2.35.3


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