[PATCH v8 18/43] kbuild, dyndbg: clean up builtin module-name ambiguities
From: Jim Cromie via B4 Relay
Date: Sat Sep 05 2026 - 14:26:03 EST
From: Jim Cromie <jim.cromie@xxxxxxxxx>
Currently, dyndbg gets its module name from KBUILD_MODNAME. This works
well for loadable modules, because the loader requires that the names
are unique. For builtins theres no such guarantee, KBUILD_MODNAME
gives us several unrelated builtin modules named "main".
So we adapt DEFINE_DYNAMIC_DEBUG_METADATA_CLS to get its .modname from
DDEBUG_MODNAME instead, and derive that from either KBUILD_MODNAME for
loadable modules, or KBUILD_DD_MODNAME.
KBUILD_DD_MODNAME derives from KBUILD_MODFILE, which worked (and was
unique), but it appends the module target to the directory path,
producing redundant tails for subsystem-dedicated directories (e.g.,
"arch/x86/kvm/kvm", "drivers/gpu/drm/i915/i915").
Finally, we land upon:
0. Check for per-target override: DD_MODNAME_<target>.o
1. Check for directory-level override: DD_MODNAME in local Makefile
2. Fall back to automatic clean heuristic: strip leading "drivers/" and
deduplicate the tail if the directory name matches the module target.
This gives us nice clean subsystem namespaces ("arch/x86/kvm",
"gpu/drm/i915") without altering existing KBUILD_* symbols.
Adjust documentation and selftests for unique subsystem module names.
NB: maybe KBUILD_MODNAME is malleable for builtins ?
Signed-off-by: Jim Cromie <jim.cromie@xxxxxxxxx>
---
Documentation/admin-guide/dynamic-debug-howto.rst | 42 ++++++++++++----------
include/linux/dynamic_debug.h | 17 +++++++--
lib/dynamic_debug.c | 3 +-
scripts/Makefile.lib | 9 +++++
.../selftests/dynamic_debug/dyndbg_selftest.sh | 7 ++--
5 files changed, 54 insertions(+), 24 deletions(-)
diff --git a/Documentation/admin-guide/dynamic-debug-howto.rst b/Documentation/admin-guide/dynamic-debug-howto.rst
index 9c2f096ed1d8..99bbae37d34e 100644
--- a/Documentation/admin-guide/dynamic-debug-howto.rst
+++ b/Documentation/admin-guide/dynamic-debug-howto.rst
@@ -38,12 +38,12 @@ You can view the currently configured behaviour in the *prdbg* catalog::
:#> head -n7 /proc/dynamic_debug/control
# filename:lineno [module]function flags format
- init/main.c:1179 [main]initcall_blacklist =_ "blacklisting initcall %s\n"
- init/main.c:1218 [main]initcall_blacklisted =_ "initcall %s blacklisted\n"
- init/main.c:1424 [main]run_init_process =_ " with arguments:\n"
- init/main.c:1426 [main]run_init_process =_ " %s\n"
- init/main.c:1427 [main]run_init_process =_ " with environment:\n"
- init/main.c:1429 [main]run_init_process =_ " %s\n"
+ init/main.c:1179 [init/main]initcall_blacklist =_ "blacklisting initcall %s\n"
+ init/main.c:1218 [init/main]initcall_blacklisted =_ "initcall %s blacklisted\n"
+ init/main.c:1424 [init/main]run_init_process =_ " with arguments:\n"
+ init/main.c:1426 [init/main]run_init_process =_ " %s\n"
+ init/main.c:1427 [init/main]run_init_process =_ " with environment:\n"
+ init/main.c:1429 [init/main]run_init_process =_ " %s\n"
The 3rd space-delimited column shows the current flags, preceded by
a ``=`` for easy use with grep/cut. ``=p`` shows enabled callsites.
@@ -59,10 +59,10 @@ query/commands to the control file. Example::
:#> ddcmd '-p; module main func run* +p'
:#> grep =p /proc/dynamic_debug/control
- init/main.c:1424 [main]run_init_process =p " with arguments:\n"
- init/main.c:1426 [main]run_init_process =p " %s\n"
- init/main.c:1427 [main]run_init_process =p " with environment:\n"
- init/main.c:1429 [main]run_init_process =p " %s\n"
+ init/main.c:1424 [init/main]run_init_process =p " with arguments:\n"
+ init/main.c:1426 [init/main]run_init_process =p " %s\n"
+ init/main.c:1427 [init/main]run_init_process =p " with environment:\n"
+ init/main.c:1429 [init/main]run_init_process =p " %s\n"
Error messages go to console/syslog::
@@ -161,17 +161,21 @@ file
file kernel/freezer.c # ie column 1 of control file
file drivers/usb/* # all callsites under it
file inode.c:start_* # parse :tail as a func (above)
- file inode.c:1-100 # parse :tail as a line-range (above)
+ file inode.c:1-100 # parse :tail as a line-range (below)
module
- The given string is compared against the module name
- of each callsite. The module name is the string as
- seen in ``lsmod``, i.e. without the directory or the ``.ko``
- suffix and with ``-`` changed to ``_``. Examples::
-
- module sunrpc
- module nfsd
- module drm* # both drm, drm_kms_helper
+ The query string is compared against the subsystem module name of
+ each callsite, as shown in the control file, or its simple name.
+ The simple module name is the string as seen in ``lsmod``,
+ i.e. without the directory or the ``.ko`` suffix and with ``-``
+ changed to ``_``.
+ Examples::
+
+ module nfsd # simple modname (as from lsmod)
+ module init/main # subsystem modname (as in control file)
+ module */main # any subsystem ending in main
+ module main # simple modname, selects same as above
+ module drm* # both drm, drm_kms_helper
format
The given string is searched for in the dynamic debug format
diff --git a/include/linux/dynamic_debug.h b/include/linux/dynamic_debug.h
index baf5c0853f45..1a8848670fcf 100644
--- a/include/linux/dynamic_debug.h
+++ b/include/linux/dynamic_debug.h
@@ -10,6 +10,19 @@
#define __DDEBUG_ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0]))
+/*
+ * Pick the best name for the module:
+ * KBUILD_MODFILE includes the path (e.g., drivers/usb/core/usbcore) for built-ins.
+ * Fall back to KBUILD_MODNAME for modules (loader requires unique names).
+ */
+#ifdef KBUILD_DD_MODNAME
+# define DDEBUG_MODNAME KBUILD_DD_MODNAME
+#elif defined(KBUILD_MODFILE)
+# define DDEBUG_MODNAME KBUILD_MODFILE
+#else
+# define DDEBUG_MODNAME KBUILD_MODNAME
+#endif
+
/*
* An instance of this structure is created in a special
* ELF section at every dynamic debug callsite. At runtime,
@@ -121,7 +134,7 @@ struct ddebug_class_param {
static struct ddebug_class_map __aligned(8) __used \
__section("__dyndbg_classes") _var = { \
.mod = THIS_MODULE, \
- .mod_name = KBUILD_MODNAME, \
+ .mod_name = DDEBUG_MODNAME, \
.base = _base, \
.map_type = _maptype, \
.class_names = _var##_classnames, \
@@ -160,7 +173,7 @@ void __dynamic_ibdev_dbg(struct _ddebug *descriptor,
#define DEFINE_DYNAMIC_DEBUG_METADATA_CLS(name, cls, fmt) \
static struct _ddebug __aligned(8) \
__section("__dyndbg") name = { \
- .modname = KBUILD_MODNAME, \
+ .modname = DDEBUG_MODNAME, \
.function = __func__, \
.filename = __FILE__, \
.format = (fmt), \
diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
index b2892be2de36..2f18d2970aa6 100644
--- a/lib/dynamic_debug.c
+++ b/lib/dynamic_debug.c
@@ -242,7 +242,8 @@ static int ddebug_change(const struct ddebug_query *query,
/* match against the module name */
if (query->module &&
- !match_wildcard(query->module, dt->mod_name))
+ !match_wildcard_hyphen(query->module, dt->mod_name) &&
+ !match_wildcard_hyphen(query->module, kbasename(dt->mod_name)))
continue;
if (query->class_string) {
diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index 0a4fdd8bd975..2d1544b30185 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -23,6 +23,15 @@ modname_flags = -DKBUILD_MODNAME=$(call name-fix,$(modname)) \
-D__KBUILD_MODNAME=$(call name-fix-token,$(modname))
modfile_flags = -DKBUILD_MODFILE=$(call stringify,$(modfile))
+# Dynamic debug subsystem modname with clean heuristic and Makefile override support
+dd_modname_override = $(firstword $(DD_MODNAME_$(target-stem).o) $(DD_MODNAME))
+dd_obj := $(patsubst drivers/%,%,$(obj))
+dd_modname_default = $(if $(filter $(notdir $(dd_obj)),$(__modname)),$(dd_obj),$(addprefix $(dd_obj)/,$(__modname)))
+dd_modname = $(if $(dd_modname_override),$(dd_modname_override),$(dd_modname_default))
+dd_modname_flags = -DKBUILD_DD_MODNAME=$(call stringify,$(dd_modname))
+
+modfile_flags += $(dd_modname_flags)
+
_c_flags = $(filter-out $(CFLAGS_REMOVE_$(target-stem).o), \
$(filter-out $(ccflags-remove-y), \
$(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS) $(ccflags-y)) \
diff --git a/tools/testing/selftests/dynamic_debug/dyndbg_selftest.sh b/tools/testing/selftests/dynamic_debug/dyndbg_selftest.sh
index 8e881b5c860c..fac5a0eab32d 100755
--- a/tools/testing/selftests/dynamic_debug/dyndbg_selftest.sh
+++ b/tools/testing/selftests/dynamic_debug/dyndbg_selftest.sh
@@ -462,7 +462,6 @@ function FT_hyphen_underscore {
ddcmd =_
}
-
# testing classmap-based query enablers and class configurations
function FT_test_classes {
v_echo "${GREEN}# TEST_CLASSES - classmap-based query enablers and class configs ${NC}"
@@ -592,7 +591,7 @@ builtin_tests=(
FT_grammar_ok
FT_grammar_errs
FT_basic_queries
- #FT_path_module_queries
+ FT_path_module_queries
FT_hyphen_underscore
)
@@ -666,6 +665,10 @@ function GOLDEN_RECORDS {
#K= de950a3e60669fdd58d0a8c2867a056d FT_basic_queries.5
#K= 2ff49f0c4d18ec99bcb1c30840fe8afc FT_basic_queries.6
#K= 9a1b13c32a15363dcf93913308edeea5 FT_basic_queries.7
+#K= 4b902c159d7f08f91377bf0a353e0051 FT_path_module_queries.1
+#K= bede904b02278e5648bb7a8243be8d98 FT_path_module_queries.2
+#K= 4b902c159d7f08f91377bf0a353e0051 FT_path_module_queries.3
+#K= bede904b02278e5648bb7a8243be8d98 FT_path_module_queries.4
EOF
# Read the K-recs and skip those for tests that can't run
while read -r line; do
--
2.55.0