[PATCH v9 34/39] dyndbg: harden classmap and descriptor validation
From: Jim Cromie via B4 Relay
Date: Tue Sep 08 2026 - 21:06:34 EST
From: Jim Cromie <jim.cromie@xxxxxxxxx>
Dynamic debug classmaps allow modules to _DEFINE and/or _USE multiple
classmaps, but this requires coordination amongst the classmaps.
Previously, class validation done by DYNAMIC_DEBUG_CLASSMAP_DEFINE at
compile-time, and ddebug_class_range_overlap() at modprobe-time, was
incomplete, and DYNAMIC_DEBUG_CLASSMAP_USE_ had no validation. This
could allow broken classmaps, making them harder to use well.
This commit improves classmap and descriptor validation:
- Mirror the compile-time limits of _DEFINE by adding a static_assert
to validate the _offset value passed to DYNAMIC_DEBUG_CLASSMAP_USE_.
- Add run-time overlap checks for _USEd classmaps in ddebug_add_module()
to prevent collisions between private maps and imported APIs.
- Scan module descriptors at load time to print a single warning per
missing class_id, rather than waiting for a user query to trip over it.
- Downgrade the global WARN_ONCE in ddebug_match_desc() to a
pr_warn_ratelimited, since orphaned class IDs are now tracked and
warned about early at module load.
Signed-off-by: Jim Cromie <jim.cromie@xxxxxxxxx>
---
lib/dynamic_debug.c | 68 ++++++++++++++++++++--
lib/test_dynamic_debug.c | 16 +++--
.../selftests/dynamic_debug/dyndbg_selftest.sh | 22 +++----
3 files changed, 84 insertions(+), 22 deletions(-)
diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
index 8c90b1e4cd33..afde13a2121f 100644
--- a/lib/dynamic_debug.c
+++ b/lib/dynamic_debug.c
@@ -316,7 +316,8 @@ static bool ddebug_match_desc(const struct ddebug_query *query,
/* site is class'd */
site_map = ddebug_find_map_by_class_id(di, dp->class_id);
if (!site_map) {
- WARN_ONCE(1, "unknown class_id %d, check %s's CLASSMAP definitions", dp->class_id, di->mod_name);
+ pr_warn_ratelimited("unknown class_id %d, check %s's CLASSMAP definitions\n",
+ dp->class_id, di->mod_name);
return false;
}
/* module(-param) decides protection */
@@ -1483,6 +1484,23 @@ static int ddebug_class_range_overlap(struct ddebug_class_map *cm, u64 *reserved
return 0;
}
+static int ddebug_class_user_overlap(struct ddebug_class_user *cli,
+ u64 *reserved_ids)
+{
+ struct ddebug_class_map *cm = cli->map;
+ int base = cm->base + cli->offset;
+ u64 range = (((1ULL << cm->length) - 1) << base);
+
+ if (range & *reserved_ids) {
+ pr_err("module %s: [%d..%d] (from %s) conflicts with %llx\n",
+ cli->mod_name, base, base + cm->length - 1,
+ cm->class_names[0], *reserved_ids);
+ return -EINVAL;
+ }
+ *reserved_ids |= range;
+ return 0;
+}
+
/*
* Allocate a new ddebug_table for the given module
* and add it to the global list.
@@ -1493,7 +1511,8 @@ static int ddebug_add_module(struct _ddebug_info *di)
struct ddebug_class_map *cm;
struct ddebug_class_user *cli;
u64 reserved_ids = 0;
- int i;
+ u64 bad_ids = 0;
+ int i, err = 0;
if (!di->descs.len)
return 0;
@@ -1524,10 +1543,47 @@ static int ddebug_add_module(struct _ddebug_info *di)
dd_set_module_subrange(i, cm, &dt->info, maps);
dd_set_module_subrange(i, cli, &dt->info, users);
- /* insure 2+ classmaps share the per-module 0..62 class_id space */
+ /* validate the per-module shared 0..62 class_id space */
for_subvec(i, cm, &dt->info, maps)
if (ddebug_class_range_overlap(cm, &reserved_ids))
- goto cleanup;
+ err = -EINVAL;
+
+ for_subvec(i, cli, &dt->info, users) {
+ cm = cli->map;
+ if (!cm) {
+ pr_err("module %s: classmap not found for user\n", di->mod_name);
+ err = -EINVAL;
+ continue;
+ }
+
+ if (cm->base + cm->length + cli->offset > _DPRINTK_CLASS_DFLT) {
+ pr_err("module %s: base:%d + classes.len:%d + cli.offset:%d must be <= %d\n",
+ di->mod_name, cm->base, cm->length,
+ cli->offset, _DPRINTK_CLASS_DFLT);
+ err = -EINVAL;
+ continue;
+ }
+
+ if (ddebug_class_user_overlap(cli, &reserved_ids))
+ err = -EINVAL;
+ }
+ if (err)
+ goto cleanup;
+
+ /* validate all class_ids against module's classmaps/users */
+ for (i = 0; i < dt->info.descs.len; i++) {
+ struct _ddebug *dp = &dt->info.descs.start[i];
+
+ if (dp->class_id == _DPRINTK_CLASS_DFLT)
+ continue;
+ if (bad_ids & (1ULL << dp->class_id))
+ continue;
+ if (!ddebug_find_map_by_class_id(&dt->info, dp->class_id)) {
+ pr_warn("module %s uses unknown class_id %d\n",
+ dt->info.mod_name, dp->class_id);
+ bad_ids |= (1ULL << dp->class_id);
+ }
+ }
mutex_lock(&ddebug_lock);
list_add_tail(&dt->link, &ddebug_tables);
@@ -1539,7 +1595,7 @@ static int ddebug_add_module(struct _ddebug_info *di)
dt->info.descs.len, dt->info.mod_name);
return 0;
cleanup:
- WARN_ONCE(1, "dyndbg multi-classmap conflict in %s\n", di->mod_name);
+ pr_err("dyndbg multi-classmap conflict in %s\n", di->mod_name);
kfree(dt);
return -EINVAL;
}
@@ -1626,7 +1682,7 @@ static int ddebug_module_notify(struct notifier_block *self, unsigned long val,
mod->dyndbg_info.mod_name = mod->name;
ret = ddebug_add_module(&mod->dyndbg_info);
if (ret)
- WARN(1, "Failed to allocate memory: dyndbg may not work properly.\n");
+ pr_err("dyndbg: failed to add module %s: %d\n", mod->name, ret);
break;
case MODULE_STATE_GOING:
ddebug_remove_module(mod->name);
diff --git a/lib/test_dynamic_debug.c b/lib/test_dynamic_debug.c
index 368891075175..97f2c9e1b92b 100644
--- a/lib/test_dynamic_debug.c
+++ b/lib/test_dynamic_debug.c
@@ -161,14 +161,20 @@ DYNAMIC_DEBUG_CLASSMAP_DEFINE(fail_base_len, 0, 60,
#endif
#else /* TEST_DYNAMIC_DEBUG_SUBMOD */
-
/*
- * in submod/drm-drivers, use the classmaps defined in top/parent
- * module above.
+ * In submod (drm-drivers/helpers) use the classmaps defined in
+ * top/parent module above. We _USE_() with offset, to test the
+ * non-zero case.
*/
-
DYNAMIC_DEBUG_CLASSMAP_USE(map_disjoint_bits);
-DYNAMIC_DEBUG_CLASSMAP_USE_(map_level_num, 7);
+/*
+ * maybe force failure of runtime sanity test of classmap.length + offset < 63
+ */
+#if !defined(DD_RUNTIME_CLASS_CHECK)
+DYNAMIC_DEBUG_CLASSMAP_USE_(map_level_num, 8);
+#else
+DYNAMIC_DEBUG_CLASSMAP_USE_(map_level_num, 55);
+#endif
#if defined(DD_MACRO_ARGCHECK)
DYNAMIC_DEBUG_CLASSMAP_USE_(fail_offset_big, 100);
diff --git a/tools/testing/selftests/dynamic_debug/dyndbg_selftest.sh b/tools/testing/selftests/dynamic_debug/dyndbg_selftest.sh
index f10ef7522426..25137663d554 100755
--- a/tools/testing/selftests/dynamic_debug/dyndbg_selftest.sh
+++ b/tools/testing/selftests/dynamic_debug/dyndbg_selftest.sh
@@ -693,12 +693,12 @@ function GOLDEN_RECORDS {
#K= 4542e1e5e7eadcbe8f90a9c934635618 FT_multi_query.4
#K= 8146f6f983c3a76783c89b78b892ed48 FT_test_classes.1
#K= a15ec4843acd721fbdfddc0b512c8032 FT_test_classes.2
-#K= 20d4545f9753e677e72e3adf52527fd3 FT_test_classes.3
-#K= 3a6afd41fadaaf70fad18f8a4632ffec FT_classmap_inheritance.1
-#K= 6f1e347f0a7930814d2e54d589439465 FT_classmap_inheritance.2
+#K= bc074e657d8d7f0bbc960e4dfa8de25d FT_test_classes.3
+#K= 878c5b9b20cbe8b93f2f3e92fc8b77bb FT_classmap_inheritance.1
+#K= 0eb7e891704074434646c2340ddac152 FT_classmap_inheritance.2
#K= a6e6aab5a6cb9a792d4296b1200ba409 FT_classmap_inheritance.3
-#K= 315cc5dad3a775c54a0b60a0276300b7 FT_classmap_inheritance.4
-#K= 7e92245008439ee79fe2460aeaa16a9b FT_classmap_inheritance.5
+#K= 5b6d86bcaa2477699aab655447d780dd FT_classmap_inheritance.4
+#K= f43e0aff8a4b38435b73d90ed8100d1b FT_classmap_inheritance.5
#K= 94610c57ac44bd7011002a654fd78f93 FT_modprobe_w_param.1
#K= 94610c57ac44bd7011002a654fd78f93 FT_modprobe_w_param.2
#K= c1309e18dc9bf2f57184fa13164d917d FT_modprobe_w_param.3
@@ -709,11 +709,11 @@ function GOLDEN_RECORDS {
#K= 13c54ef65e199294fd078ba72c0cd69a FT_modprobe_w_param.8
#K= 591411c42cf52d7c4c46d76bcc345a5f FT_modprobe_w_param.9
#K= 13c54ef65e199294fd078ba72c0cd69a FT_modprobe_w_param.10
-#K= b0435304108118e64529469e59332111 FT_modprobe_w_param.11
+#K= 46d24fecc507a8f9be0bd120e27ff64f FT_modprobe_w_param.11
#K= 13c54ef65e199294fd078ba72c0cd69a FT_modprobe_w_param.12
-#K= 4d036833ce9f661057a4e13d97295c65 FT_modprobe_w_param.13
+#K= 79298a323d3dcca4f74fb9fc0de5a87e FT_modprobe_w_param.13
#K= 13c54ef65e199294fd078ba72c0cd69a FT_modprobe_w_param.14
-#K= 5c3c6ecf6a46f9ccebd60c5ca9ebdbb7 FT_modprobe_w_param.15
+#K= f649752dfb07a68087f04dafc00ed1e8 FT_modprobe_w_param.15
#K= 13c54ef65e199294fd078ba72c0cd69a FT_modprobe_w_param.16
#K= 73a93377a823739e8aae44856a20fa7f FT_modprobe_w_param.17
#K= 13c54ef65e199294fd078ba72c0cd69a FT_modprobe_w_param.18
@@ -727,11 +727,11 @@ function GOLDEN_RECORDS {
#K= 13c54ef65e199294fd078ba72c0cd69a FT_modprobe_w_param.26
#K= 7b91db8e9f160aebb1ee87fab2232404 FT_modprobe_w_param.27
#K= 13c54ef65e199294fd078ba72c0cd69a FT_modprobe_w_param.28
-#K= e393499e02677de414e478f4e710eeb9 FT_modprobe_w_param.29
+#K= d3d111da544dd5cee254e88178823b9d FT_modprobe_w_param.29
#K= 13c54ef65e199294fd078ba72c0cd69a FT_modprobe_w_param.30
-#K= 375e38613af3b49bb7c7689dfecf4177 FT_modprobe_w_param.31
+#K= b5a30ebac06aea6e77a44322667effc7 FT_modprobe_w_param.31
#K= 13c54ef65e199294fd078ba72c0cd69a FT_modprobe_w_param.32
-#K= 745a61d20e26a6a22db0b99420fea80a FT_modprobe_w_param.33
+#K= bbe7b47ed089428429f4264c8cc2a066 FT_modprobe_w_param.33
#K= 13c54ef65e199294fd078ba72c0cd69a FT_modprobe_w_param.34
#K= 3d2538bf868e71bff17c768cf118c352 FT_modprobe_w_param.35
#K= 13c54ef65e199294fd078ba72c0cd69a FT_modprobe_w_param.36
--
2.55.0