DRM has always had /sys/module/drm/parameters/debug (ie drm.debug).
Without dyndbg, this is their only control point. One could presume
they like it - in any case its a system/user interface, ie ABI.
With dyndbg enabled, drm calls DYNAMIC_DEBUG_CLASSMAP_PARAM() to
create the drm.debug kparam, wired to our param-handler, which writes
a "class FOO" query for each bit in the classmap. Since no new
interface was ever contemplated, this is using >control.
Since drm.debug is ABI, we should not allow class-less queries to
alter our implementation of its settings.
This patch provides that protection, *only* when theres a PARAM. This
is the user, expressing their wish for easy control of their entire
classmap. They also wish to trust its settings.
Classes without a PARAM are unprotected, allowing admins their
shortcuts. No such use-cases exist yet.
Anyway, this patch does:
1. adds struct _ddebug_class_map.controlling_param
2. set it in ddebug_match_apply_kparam(), during modprobe/init,
when options like drm.debug are handled.
3. ddebug_class_has_param() checks .controlling_param
4. ddebug_class_wants_protection() macro renames 3.
5. ddebug_change() calls 4 when needed.
IE when applying a class-less query to a class'd pr_debug / drm_dbg_<T>
Historical Summary:
-v0 - before classmaps. no special case keywords
-v1 - "class DEFAULT" is assumed if not mentioned.
this protects classes from class-less queries
-v2.pre-this-patch - protection macro'd to false
-v2.with-this-patch - sysfs knob decides
-v2.speculative - module decides wrt classmap protection
seems unneeded now, TBD
NOTE: protection is only against class-less queries, explicit "class
FOO" adjustments are allowed (that is the mechanism).
Signed-off-by: Jim Cromie <jim.cro...@gmail.com>
---
v3 - new patch
---
include/linux/dynamic_debug.h | 3 +-
lib/dynamic_debug.c | 55 ++++++++++++++++++++++++++---------
2 files changed, 44 insertions(+), 14 deletions(-)
diff --git a/include/linux/dynamic_debug.h b/include/linux/dynamic_debug.h
index 2d87cca27544..d34a44ff961a 100644
--- a/include/linux/dynamic_debug.h
+++ b/include/linux/dynamic_debug.h
@@ -89,8 +89,9 @@ enum ddebug_class_map_type {
* usually by stringifying the enum-vals. Modules with multiple
* classmaps must arrange to share the 0..62 class_id space.
*/
-
+struct _ddebug_class_param;
struct _ddebug_class_map {
+ struct _ddebug_class_param *controlling_param;
const struct module *mod; /* NULL for builtins */
const char *mod_name;
const char **class_names;
diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
index 54f462cf41b0..3eb4a8abeb33 100644
--- a/lib/dynamic_debug.c
+++ b/lib/dynamic_debug.c
@@ -198,16 +198,26 @@ ddebug_find_valid_class(struct _ddebug_info const *di,
const char *query_class,
}
/*
- * classmaps-v1 protected classes from changes by legacy commands
- * (those selecting _DPRINTK_CLASS_DFLT by omission), v2 undoes that
- * special treatment. State so explicitly. Later we could give
- * modules the choice to protect their classes or to keep v2 behavior.
+ * classmaps-V1 protected classes from changes by legacy commands
+ * (those selecting _DPRINTK_CLASS_DFLT by omission). This had the
+ * downside that saying "class FOO" for every change can get tedious.
+ *
+ * V2 is smarter, it protects class-maps if the defining module also
+ * calls DYNAMIC_DEBUG_CLASSMAP_PARAM to create a sysfs parameter.
+ * Since they want the knob, we should assume they intend to use it
+ * (in preference to "class FOO +p" >control), and want to trust its
+ * settings.
+ * This gives protection when its useful, and not when its just tedious.
*/
-static inline bool ddebug_client_module_protects_classes(const struct
ddebug_table *dt)
+static inline bool ddebug_class_has_param(const struct _ddebug_class_map *map)
{
- return false;
+ return !!(map->controlling_param);
}
+/* re-framed as a policy choice */
+#define ddebug_class_wants_protection(map) \
+ ddebug_class_has_param(map)
+
/*
* Search the tables for _ddebug's which match the given `query' and
* apply the `flags' and `mask' to them. Returns number of matching
@@ -250,7 +260,7 @@ static int ddebug_change(const struct ddebug_query *query,
struct flag_settings
/* site.class != given class */
continue;
/* legacy query, class'd site */
- else if
(ddebug_client_module_protects_classes(dt))
+ else if (ddebug_class_wants_protection(map))
continue;
/* allow change on class'd pr_debug */
}
@@ -650,6 +660,7 @@ static int ddebug_exec_queries(char *query, const char
*modname)
}
/* apply a new class-param setting */
+
static int ddebug_apply_class_bitmap(const struct _ddebug_class_param *dcp,
const unsigned long *new_bits,
const unsigned long old_bits,
@@ -1228,25 +1239,36 @@ static void ddebug_sync_classbits(const struct
kernel_param *kp, const char *mod
}
}
-static void ddebug_match_apply_kparam(const struct kernel_param *kp,
- const struct _ddebug_class_map *map,
- const char *mod_name)
+static struct _ddebug_class_param *
+ddebug_get_classmap_kparam(const struct kernel_param *kp,
+ const struct _ddebug_class_map *map)
{
struct _ddebug_class_param *dcp;
if (kp->ops != ¶m_ops_dyndbg_classes)
- return;
+ return false;
dcp = (struct _ddebug_class_param *)kp->arg;
- if (map == dcp->map) {
+ return (map == dcp->map)
+ ? dcp : (struct _ddebug_class_param *)NULL;
+}
+
+static void ddebug_match_apply_kparam(const struct kernel_param *kp,
+ struct _ddebug_class_map *map,
+ const char *mod_name)
+{
+ struct _ddebug_class_param *dcp = ddebug_get_classmap_kparam(kp, map);
+
+ if (dcp) {
+ map->controlling_param = dcp;
v2pr_info(" kp:%s.%s =0x%lx", mod_name, kp->name, *dcp->bits);
vpr_cm_info(map, " %s mapped to: ", mod_name);
ddebug_sync_classbits(kp, mod_name);
}
}
-static void ddebug_apply_params(const struct _ddebug_class_map *cm, const char
*mod_name)
+static void ddebug_apply_params(struct _ddebug_class_map *cm, const char
*mod_name)
{
const struct kernel_param *kp;
#if IS_ENABLED(CONFIG_MODULES)
@@ -1266,6 +1288,13 @@ static void ddebug_apply_params(const struct
_ddebug_class_map *cm, const char *
}
}
+/*
+ * called from add_module, ie early. it can find controlling kparams,
+ * which can/does? enable protection of this classmap from class-less
+ * queries, on the grounds that the user created the kparam, means to
+ * use it, and expects it to reflect reality. We should oblige him,
+ * and protect those classmaps from classless "-p" changes.
+ */
static void ddebug_apply_class_maps(const struct _ddebug_info *di)
{
struct _ddebug_class_map *cm;
--
2.49.0
