[Intel-gfx] [PATCH v6 17/57] dyndbg: validate class FOO by checking with module

Jim Cromie
2022-09-04T21:46:07Z

Add module-to-class validation:

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

If a query has "class FOO", then ddebug_find_valid_class(), called
from ddebug_change(), requires that FOO is known to module X,
otherwize the query is skipped entirely for X. This protects each
module's class-space, other than the default:31.

The authors' 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).

Notes:

For all "class FOO" queries, ddebug_find_valid_class() is called, it
returns the map matching the query, and sets valid_class via an
*outvar).

If no "class FOO" is supplied, valid_class = _CLASS_DFLT. This
insures that legacy queries do not trample on new class'd callsites,
as they get added.

Also add a new column to control-file output, displaying non-default
class-name (when found) or the "unknown _id:", if it has not been
(correctly) declared with one of the declarator macros.

Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
---
lib/dynamic_debug.c | 76 ++++++++++++++++++++++++++++++++++++++++-----
1 file changed, 68 insertions(+), 8 deletions(-)

diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
index b71efd0b491d..db96ded78c3f 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;
};

@@ -136,15 +137,33 @@ 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);
}

+static struct ddebug_class_map *ddebug_find_valid_class(struct ddebug_table const *dt,
+ const char *class_string, int *class_id)
+{
+ struct ddebug_class_map *map;
+ int idx;
+
+ list_for_each_entry(map, &dt->maps, link) {
+ idx = match_string(map->class_names, map->length, class_string);
+ if (idx >= 0) {
+ *class_id = idx + map->base;
+ return map;
+ }
+ }
+ *class_id = -ENOENT;
+ return NULL;
+}
+
+#define __outvar /* filled by callee */
/*
* Search the tables for _ddebug's which match the given `query' and
* apply the `flags' and `mask' to them. Returns number of matching
@@ -159,6 +178,8 @@ static int ddebug_change(const struct ddebug_query *query,
unsigned int newflags;
unsigned int nfound = 0;
struct flagsbuf fbuf, nbuf;
+ struct ddebug_class_map *map = NULL;
+ int __outvar valid_class;

/* search for matching ddebugs */
mutex_lock(&ddebug_lock);
@@ -169,9 +190,22 @@ static int ddebug_change(const struct ddebug_query *query,
!match_wildcard(query->module, dt->mod_name))
continue;

+ if (query->class_string) {
+ map = ddebug_find_valid_class(dt, query->class_string, &valid_class);
+ if (!map)
+ continue;
+ } else {
+ /* constrain query, do not touch class'd callsites */
+ valid_class = _DPRINTK_CLASS_DFLT;
+ }
+
for (i = 0; i < dt->num_ddebugs; i++) {
struct _ddebug *dp = &dt->ddebugs[i];

+ /* match site against query-class */
+ if (dp->class_id != valid_class)
+ continue;
+
/* match against the source filename */
if (query->filename &&
!match_wildcard(query->filename, dp->filename) &&
@@ -420,6 +454,8 @@ 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;
@@ -854,6 +890,20 @@ static void *ddebug_proc_next(struct seq_file *m, void *p, loff_t *pos)
return dp;
}

+#define class_in_range(class_id, map) \
+ (class_id >= map->base && class_id < map->base + map->length)
+
+static const char *ddebug_class_name(struct ddebug_iter *iter, struct _ddebug *dp)
+{
+ struct ddebug_class_map *map;
+
+ list_for_each_entry(map, &iter->table->maps, link)
+ if (class_in_range(dp->class_id, map))
+ return map->class_names[dp->class_id - map->base];
+
+ return NULL;
+}
+
/*
* Seq_ops show method. Called several times within a read()
* call from userspace, with ddebug_lock held. Formats the
@@ -865,6 +915,7 @@ 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,
@@ -877,7 +928,16 @@ 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_str(m, dp->format, ESCAPE_SPACE, "\t\r\n\"");
- seq_puts(m, "\"\n");
+ seq_puts(m, "\"");
+
+ if (dp->class_id != _DPRINTK_CLASS_DFLT) {
+ class = ddebug_class_name(iter, dp);
+ if (class)
+ seq_printf(m, " class:%s", class);
+ else
+ seq_printf(m, " class unknown, _id:%d", dp->class_id);
+ }
+ seq_puts(m, "\n");

return 0;
}
--
2.37.2