[PATCH v13 08/36] docs/dyndbg: explain flags parse 1st

[PATCH v13 08/36] docs/dyndbg: explain flags parse 1st

[Jim Cromie]

When writing queries to >control, flags are parsed 1st, since they are
the only required field, and they require specific compositions.  So
if the flags draw an error (on those specifics), then keyword errors
aren't reported.  This can be mildly confusing/annoying, so explain it
instead.

cc: linux-doc@vger.kernel.org
Reviewed-by: Louis Chauvet <louis.chauvet@bootlin.com>
Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
---
 .../admin-guide/dynamic-debug-howto.rst         | 17 +++++++++++++----
 1 file changed, 13 insertions(+), 4 deletions(-)

diff --git a/Documentation/admin-guide/dynamic-debug-howto.rst b/Documentation/admin-guide/dynamic-debug-howto.rst
index 4b14d9fd0300..9c2f096ed1d8 100644
--- a/Documentation/admin-guide/dynamic-debug-howto.rst
+++ b/Documentation/admin-guide/dynamic-debug-howto.rst
@@ -109,10 +109,19 @@ The match-spec's select *prdbgs* from the catalog, upon which to apply
 the flags-spec, all constraints are ANDed together.  An absent keyword
 is the same as keyword "*".
 
-
-A match specification is a keyword, which selects the attribute of
-the callsite to be compared, and a value to compare against.  Possible
-keywords are:::
+Note that since the match-spec can be empty, the flags are checked 1st,
+then the pairs of keyword and value.  Flag errs will hide keyword errs::
+
+  bash-5.2# ddcmd mod bar +foo
+  dyndbg: read 13 bytes from userspace
+  dyndbg: query 0: "mod bar +foo" mod:*
+  dyndbg: unknown flag 'o'
+  dyndbg: flags parse failed
+  dyndbg: processed 1 queries, with 0 matches, 1 errs
+
+So a match-spec is a keyword, which selects the attribute of the
+callsite to be compared, and a value to compare against.  Possible
+keywords are::
 
   match-spec ::= 'func' string |
 		 'file' string |
-- 
2.53.0

[PATCH v13 25/36] dyndbg-API: replace DECLARE_DYNDBG_CLASSMAP

[Jim Cromie]

commit aad0214f3026 ("dyndbg: add DECLARE_DYNDBG_CLASSMAP macro")

DECLARE_DYNDBG_CLASSMAP() has a design error; its usage fails a
basic K&R rule: "define once, refer many times".

When CONFIG_DRM_USE_DYNAMIC_DEBUG=y, it is used across DRM core &
drivers; each invocation allocates/inits the classmap understood by
that module.  They *all* must match for the DRM modules to respond
consistently when drm.debug categories are enabled.  This is at least
a maintenance hassle.

Worse, its the root-cause of the CONFIG_DRM_USE_DYNAMIC_DEBUG=Y
regression; its use in both core & drivers obfuscates the 2 roles,
muddling the design, yielding an incomplete initialization when
modprobing drivers:

1st drm.ko loads, and dyndbg initializes its drm.debug callsites, then
a drm-driver loads, but too late for the drm.debug enablement.

And that led to:
commit bb2ff6c27bc9 ("drm: Disable dynamic debug as broken")

So retire it, replace with 2 macros:
  DYNAMIC_DEBUG_CLASSMAP_DEFINE - invoked once from core - drm.ko
  DYNAMIC_DEBUG_CLASSMAP_USE*   - from all drm drivers and helpers.
  NB: name-space de-noise

DYNAMIC_DEBUG_CLASSMAP_DEFINE: this reworks DECLARE_DYNDBG_CLASSMAP,
basically by dropping the static qualifier on the classmap, and
exporting it instead.

DYNAMIC_DEBUG_CLASSMAP_USE: then refers to the exported var by name:
  used from drivers, helper-mods
  lets us drop the repetitive "classname" declarations
  fixes 2nd-defn problem
  creates a ddebug_class_user record in new __dyndbg_class_users section
  new section is scanned "differently"

DECLARE_DYNDBG_CLASSMAP is preserved temporarily, to decouple DRM
adaptation work and avoid compile-errs before its done.

The DEFINE,USE distinction, and the separate classmap-use record,
allows dyndbg to initialize the driver's & helper's drm.debug
callsites separately after each is modprobed.

Basically, the classmap initial scan is repeated for classmap-users.

dyndbg's existing __dyndbg_classes[] section does:

. catalogs the module's classmaps
. tells dyndbg about them, allowing >control
. DYNAMIC_DEBUG_CLASSMAP_DEFINE creates section records.
. we rename it to: __dyndbg_class_maps[]

this patch adds __dyndbg_class_users[] section:

. catalogs users of classmap definitions from elsewhere
. authorizes dyndbg to >control user's class'd prdbgs
. DYNAMIC_DEBUG_CLASSMAP_USE() creates section records.

Now ddebug_add_module(etal) can handle classmap-uses similar to (and
after) classmaps; when a dependent module is loaded, if it has
classmap-uses (to a classmap-def in another module), that module's
kernel params are scanned to find if it has a kparam that is wired to
dyndbg's param-ops, and whose classmap is the one being ref'd.

To support this, theres a few data/header changes:

new struct ddebug_class_user
  contains: user-module-name, &classmap-defn
  it records drm-driver's use of a classmap in the section, allowing lookup

struct ddebug_info gets 2 new fields for the new sections:
  class_users, num_class_users.
  set by dynamic_debug_init() for builtins.
  or by kernel/module/main:load_info() for loadable modules.

vmlinux.lds.h: Add a new BOUNDED_SECTION for __dyndbg_class_users.
this creates start,stop C symbol-names for the section.

TLDR ?

dynamic_debug.c: 2 changes from ddebug_add_module() & ddebug_change():

ddebug_add_module():

ddebug_attach_module_classes() is reworked/renamed/split into
debug_apply_class_maps(), ddebug_apply_class_users(), which both call
ddebug_apply_params().

ddebug_apply_params(new fn):

It scans module's/builtin kernel-params, calls ddebug_match_apply_kparam
for each to find any params/sysfs-nodes which may be wired to a classmap.

ddebug_match_apply_kparam(new fn):

1st, it tests the kernel-param.ops is dyndbg's; this guarantees that
the attached arg is a struct ddebug_class_param, which has a ref to
the param's state, and to the classmap defining the param's handling.

2nd, it requires that the classmap ref'd by the kparam is the one
we've been called for; modules can use many separate classmaps (as
test_dynamic_debug does).

Then apply the "parent" kparam's setting to the dependent module,
using ddebug_apply_class_bitmap().

ddebug_change(and callees) also gets adjustments:

ddebug_find_valid_class(): This does a search over the module's
classmaps, looking for the class FOO echo'd to >control.  So now it
searches over __dyndbg_class_users[] after __dyndbg_classes[].

ddebug_class_name(): return class-names for defined OR used classes.

test_dynamic_debug.c, test_dynamic_debug_submod.c:

This demonstrates the 2 types of classmaps & sysfs-params, following
the 4-part recipe:

0. define an enum for the classmap's class_ids
   drm.debug gives us DRM_UT_<*> (aka <T>)
   multiple classmaps in a module(s) must share 0-62 classid space.

1. DYNAMIC_DEBUG_CLASSMAP_DEFINE(classmap_name, .. "<T>")
   names the classes, maps them to consecutive class-ids.
   convention here is stringified ENUM_SYMBOLS
   these become API/ABI if 2 is done.

2. DYNAMIC_DEBUG_CLASSMAP_PARAM* (classmap_name)
   adds a controlling kparam to the class

3. DYNAMIC_DEBUG_CLASSMAP_USE(classmap_name)
   for subsystem/group/drivers to use extern created by 1.

Move all the enum declarations together, to better explain how they
share the 0..62 class-id space available to a module (non-overlapping
subranges).

reorg macros 2,3 by name.  This gives a tabular format, making it easy
to see the pattern of repetition, and the points of change.

And extend the test to replicate the 2-module (parent & dependent)
scenario which caused the CONFIG_DRM_USE_DYNAMIC_DEBUG=y regression
seen in drm & drivers.

The _submod.c is a 2-line file: #define _SUBMOD, #include parent.

This gives identical complements of prdbgs in parent & _submod, and
thus identical print behavior when all of: >control, >params, and
parent->_submod propagation are working correctly.

It also puts all the parent/_submod declarations together in the same
source; the new ifdef _SUBMOD block invokes DYNAMIC_DEBUG_CLASSMAP_USE
for the 2 test-interfaces.  I think this is clearer.

These 2 modules are both tristate, allowing 3 super/sub combos: Y/Y,
Y/M, M/M (not N/Y, since this is disallowed by dependence).

Y/Y, Y/M testing once exposed a missing __align(8) in the _METADATA
macro, which M/M didn't see, probably because the module-loader memory
placement constrained it from misalignment.

Fixes: aad0214f3026 ("dyndbg: add DECLARE_DYNDBG_CLASSMAP macro")
cc: linux-doc@vger.kernel.org
Reviewed-by: Louis Chauvet <louis.chauvet@bootlin.com>
Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
---
-v?
replace di with &dt->info, since di becomes stale
fix dd_mark_vector_subrange macro param ordering to match kdoc
s/base/offset/ in _ddebug_class_user, to reduce later churn

-v12 - squash in _USE_ and refinements.

A: dyndbg: add DYNAMIC_DEBUG_CLASSMAP_USE_(dd_class_name, offset)

Allow a module to use 2 classmaps together that would otherwise have a
class_id range conflict.

Suppose a drm-driver does:

  DYNAMIC_DEBUG_CLASSMAP_USE(drm_debug_classes);
  DYNAMIC_DEBUG_CLASSMAP_USE(drm_accel_xfer_debug);

If (for some reason) drm-accel cannot define their constants to avoid
DRM's drm_debug_category 0..10 reservations, we would have a conflict
with reserved-ids.

In this case a driver needing to use both would _USE_ one of them with
an offset to avoid the conflict.  This will handle most forseeable
cases; perhaps a 3-X-3 of classmap-defns X classmap-users would get
too awkward and fiddly.

B: dyndbg: refine DYNAMIC_DEBUG_CLASSMAP_USE_ macro

The struct _ddebug_class_user _varname construct is needlessly
permissive; it has a static qualifier, and a unique name.  Together,
these allow a module to have 2 or more _USE(foo)s, which is contrary
to its purpose, and therefore potentially confusing.

So drop the unique name, and the static qualifier, and replace it with
an extern pre-declaration.  Construct the name by pasting together the
_var (which is the name of the exported ddebug_class_map), and
__KBUILD_MODNAME (which is the user module name).  This allows only a
single USE() reference to the exported record, which is all that is
required.

Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
---
 MAINTAINERS                      |   2 +-
 include/asm-generic/dyndbg.lds.h |   7 +-
 include/linux/dynamic_debug.h    | 159 +++++++++++++++++++++++---
 kernel/module/main.c             |   3 +
 lib/Kconfig.debug                |  24 +++-
 lib/Makefile                     |   5 +
 lib/dynamic_debug.c              | 185 ++++++++++++++++++++++++-------
 lib/test_dynamic_debug.c         | 132 ++++++++++++++++------
 lib/test_dynamic_debug_submod.c  |  14 +++
 9 files changed, 433 insertions(+), 98 deletions(-)
 create mode 100644 lib/test_dynamic_debug_submod.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 0f4c2f182d63..31c945228fab 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -9034,7 +9034,7 @@ M:	Jim Cromie <jim.cromie@gmail.com>
 S:	Maintained
 F:	include/linux/dynamic_debug.h
 F:	lib/dynamic_debug.c
-F:	lib/test_dynamic_debug.c
+F:	lib/test_dynamic_debug*.c
 F:	tools/testing/selftests/dynamic_debug/*
 
 DYNAMIC INTERRUPT MODERATION
diff --git a/include/asm-generic/dyndbg.lds.h b/include/asm-generic/dyndbg.lds.h
index 8345ac6c52b7..6e38d0f1d00b 100644
--- a/include/asm-generic/dyndbg.lds.h
+++ b/include/asm-generic/dyndbg.lds.h
@@ -6,7 +6,8 @@
 #define DYNDBG_SECTIONS()						\
 	. = ALIGN(8);							\
 	BOUNDED_SECTION_BY(__dyndbg_descriptors, ___dyndbg_descs)	\
-	BOUNDED_SECTION_BY(__dyndbg_class_maps, ___dyndbg_class_maps)
+	BOUNDED_SECTION_BY(__dyndbg_class_maps, ___dyndbg_class_maps)	\
+	BOUNDED_SECTION_BY(__dyndbg_class_users, ___dyndbg_class_users)
 
 #define MOD_DYNDBG_SECTIONS()                                           \
 	__dyndbg_descriptors : {					\
@@ -16,6 +17,10 @@
 	__dyndbg_class_maps : {						\
 		BOUNDED_SECTION_BY(__dyndbg_class_maps,			\
 				   ___dyndbg_class_maps)		\
+	}								\
+	__dyndbg_class_users : {					\
+		BOUNDED_SECTION_BY(__dyndbg_class_users,		\
+				   ___dyndbg_class_users)		\
 	}
 
 #endif /* __ASM_GENERIC_DYNDBG_LDS_H */
diff --git a/include/linux/dynamic_debug.h b/include/linux/dynamic_debug.h
index 33291abd8971..71c91bc8d3a6 100644
--- a/include/linux/dynamic_debug.h
+++ b/include/linux/dynamic_debug.h
@@ -72,19 +72,30 @@ enum ddebug_class_map_type {
 	 */
 };
 
+/*
+ * map @class_names 0..N to consecutive constants starting at @base.
+ */
 struct _ddebug_class_map {
-	struct module *mod;	/* NULL for builtins */
-	const char *mod_name;	/* needed for builtins */
+	const struct module *mod;	/* NULL for builtins */
+	const char *mod_name;		/* needed for builtins */
 	const char **class_names;
 	const int length;
 	const int base;		/* index of 1st .class_id, allows split/shared space */
 	enum ddebug_class_map_type map_type;
 };
 
+struct _ddebug_class_user {
+	char *mod_name;
+	struct _ddebug_class_map *map;
+	const int offset;	/* offset from map->base */
+};
+
 /*
- * @_ddebug_info: gathers module/builtin dyndbg_* __sections together.
+ * @_ddebug_info: gathers module/builtin __dyndbg_<T> __sections
+ * together, each is a vec_<T>: a struct { struct T start[], int len }.
+ *
  * For builtins, it is used as a cursor, with the inner structs
- * marking sub-vectors of the builtin __sections in DATA.
+ * marking sub-vectors of the builtin __sections in DATA_DATA
  */
 struct _ddebug_descs {
 	struct _ddebug *start;
@@ -96,10 +107,16 @@ struct _ddebug_class_maps {
 	int len;
 };
 
+struct _ddebug_class_users {
+	struct _ddebug_class_user *start;
+	int len;
+};
+
 struct _ddebug_info {
 	const char *mod_name;
 	struct _ddebug_descs descs;
 	struct _ddebug_class_maps maps;
+	struct _ddebug_class_users users;
 };
 
 struct _ddebug_class_param {
@@ -118,12 +135,81 @@ struct _ddebug_class_param {
 #if defined(CONFIG_DYNAMIC_DEBUG) || \
 	(defined(CONFIG_DYNAMIC_DEBUG_CORE) && defined(DYNAMIC_DEBUG_MODULE))
 
+/*
+ * dyndbg classmaps is modelled closely upon drm.debug:
+ *
+ *  1. run-time control via sysfs node (api/abi)
+ *  2. each bit 0..N controls a single "category"
+ *  3. a pr_debug can have only 1 category, not several.
+ *  4. "kind" is a compile-time constant: 0..N or BIT() thereof
+ *  5. macro impls - give compile-time resolution or fail.
+ *
+ * dyndbg classmaps design axioms/constraints:
+ *
+ *  . optimizing compilers use 1-5 above, so preserve them.
+ *  . classmaps.class_id *is* the category.
+ *  . classmap definers/users are modules.
+ *  . every user wants 0..N
+ *  . 0..N exposes as ABI
+ *  . no 1 use-case wants N > 32, 16 is more usable
+ *  . N <= 64 in *all* cases
+ *  . modules/subsystems make category/classmap decisions
+ *  . ie an enum: DRM has DRM_UT_CORE..DRM_UT_DRMRES
+ *  . some categories are exposed to user: ABI
+ *  . making modules change their numbering is bogus, avoid if possible
+ *
+ * We can solve for all these at once:
+ *  A: map class-names to a .class_id range at compile-time
+ *  B: allow only "class NAME" changes to class'd callsites at run-time
+ *  C: users/modules must manage 0..62 hardcoded .class_id range limit.
+ *  D: existing pr_debugs get CLASS_DFLT=63
+ *
+ * By mapping class-names at >control to class-ids underneath, and
+ * responding only to class-names DEFINEd or USEd by the module, we
+ * can private-ize the class-id, and adjust class'd pr_debugs only by
+ * their names.
+ *
+ * This give us:
+ *  E: class_ids without classnames are unreachable
+ *  F: user modules opt-in by DEFINEing a classmap and/or USEing another
+ *
+ * Multi-classmap modules/groups are supported, if the classmaps share
+ * the class_id space [0..62] without overlap/conflict.
+ *
+ * NOTE: Due to the integer class_id, this api cannot disallow these:
+ * __pr_debug_cls(0, "fake CORE msg");  works only if a classmap maps 0.
+ * __pr_debug_cls(22, "no such class"); compiles but is not reachable
+ */
+
 /**
- * DECLARE_DYNDBG_CLASSMAP - declare classnames known by a module
- * @_var:   a struct ddebug_class_map, passed to module_param_cb
- * @_type:  enum class_map_type, chooses bits/verbose, numeric/symbolic
- * @_base:  offset of 1st class-name. splits .class_id space
- * @classes: class-names used to control class'd prdbgs
+ * DYNAMIC_DEBUG_CLASSMAP_DEFINE - define debug classes used by a module.
+ * @_var:   name of the classmap, exported for other modules coordinated use.
+ * @_mapty: enum ddebug_class_map_type: 0:DISJOINT - independent, 1:LEVEL - v2>v1
+ * @_base:  reserve N classids starting at _base, to split 0..62 classid space
+ * @classes: names of the N classes.
+ *
+ * This tells dyndbg what class_ids the module is using: _base..+N, by
+ * mapping names onto them.  This qualifies "class NAME" >controls on
+ * the defining module, ignoring unknown names.
+ */
+#define DYNAMIC_DEBUG_CLASSMAP_DEFINE(_var, _mapty, _base, ...)		\
+	static const char *_var##_classnames[] = { __VA_ARGS__ };	\
+	extern struct _ddebug_class_map _var;				\
+	struct _ddebug_class_map __aligned(8) __used			\
+		__section("__dyndbg_class_maps") _var = {		\
+		.mod = THIS_MODULE,					\
+		.mod_name = KBUILD_MODNAME,				\
+		.base = (_base),					\
+		.map_type = (_mapty),					\
+		.length = ARRAY_SIZE(_var##_classnames),		\
+		.class_names = _var##_classnames,			\
+	};								\
+	EXPORT_SYMBOL(_var)
+
+/*
+ * XXX: keep this until DRM adapts to use the DEFINE/USE api, it
+ * differs from DYNAMIC_DEBUG_CLASSMAP_DEFINE by the lack of the
+ * extern/EXPORT on the struct init, and cascading thinkos.
  */
 #define DECLARE_DYNDBG_CLASSMAP(_var, _maptype, _base, ...)		\
 	static const char *_var##_classnames[] = { __VA_ARGS__ };	\
@@ -137,6 +223,44 @@ struct _ddebug_class_param {
 		.class_names = _var##_classnames,			\
 	}
 
+/**
+ * DYNAMIC_DEBUG_CLASSMAP_USE - refer to a classmap, DEFINEd elsewhere.
+ * @_var: name of the exported classmap var
+ *
+ * This tells dyndbg that the module has prdbgs with classids defined
+ * in the named classmap.  This qualifies "class NAME" >controls on
+ * the user module, and ignores unknown names. This is a wrapper for
+ * DYNAMIC_DEBUG_CLASSMAP_USE_() with a base offset of 0.
+ */
+#define DYNAMIC_DEBUG_CLASSMAP_USE(_var) \
+	DYNAMIC_DEBUG_CLASSMAP_USE_(_var, 0)
+
+/**
+ * DYNAMIC_DEBUG_CLASSMAP_USE_ - refer to a classmap with a manual offset.
+ * @_var:   name of the exported classmap var to use.
+ * @_offset:  an integer offset to add to the class IDs of the used map.
+ *
+ * This is an extended version of DYNAMIC_DEBUG_CLASSMAP_USE(). It should
+ * only be used to resolve class ID conflicts when a module uses multiple
+ * classmaps that have overlapping ID ranges.
+ *
+ * The final class IDs for the used map will be calculated as:
+ * original_map_base + class_index + @_offset.
+ */
+#define DYNAMIC_DEBUG_CLASSMAP_USE_(_var, _offset)			\
+	extern struct _ddebug_class_map _var;				\
+	static_assert((_offset) >= 0 && (_offset) < _DPRINTK_CLASS_DFLT, \
+		      "classmap use offset must be in 0..62");          \
+	extern struct _ddebug_class_user __aligned(8)			\
+		__PASTE(_var ## _, __KBUILD_MODNAME);			\
+	struct _ddebug_class_user __aligned(8) __used			\
+		__section("__dyndbg_class_users")			\
+		__PASTE(_var ## _, __KBUILD_MODNAME) = {		\
+		.mod_name = KBUILD_MODNAME,				\
+		.map = &(_var),						\
+		.offset = _offset					\
+	}
+
 extern __printf(2, 3)
 void __dynamic_pr_debug(struct _ddebug *descriptor, const char *fmt, ...);
 
@@ -298,12 +422,18 @@ void __dynamic_ibdev_dbg(struct _ddebug *descriptor,
 				   KERN_DEBUG, prefix_str, prefix_type,	\
 				   rowsize, groupsize, buf, len, ascii)
 
-/* for test only, generally expect drm.debug style macro wrappers */
-#define __pr_debug_cls(cls, fmt, ...) do {			\
+/*
+ * This is the "model" class variant of pr_debug.  It is not really
+ * intended for direct use; I'd encourage DRM-style drm_dbg_<T>
+ * macros for the interface, along with an enum for the <T>
+ *
+ * __printf(2, 3) would apply.
+ */
+#define __pr_debug_cls(cls, fmt, ...) ({			\
 	BUILD_BUG_ON_MSG(!__builtin_constant_p(cls),		\
 			 "expecting constant class int/enum");	\
 	dynamic_pr_debug_cls(cls, fmt, ##__VA_ARGS__);		\
-	} while (0)
+})
 
 #else /* !(CONFIG_DYNAMIC_DEBUG || (CONFIG_DYNAMIC_DEBUG_CORE && DYNAMIC_DEBUG_MODULE)) */
 
@@ -311,6 +441,8 @@ void __dynamic_ibdev_dbg(struct _ddebug *descriptor,
 #include <linux/errno.h>
 #include <linux/printk.h>
 
+#define DYNAMIC_DEBUG_CLASSMAP_DEFINE(_var, _mapty, _base, ...)
+#define DYNAMIC_DEBUG_CLASSMAP_USE(_var)
 #define DEFINE_DYNAMIC_DEBUG_METADATA(name, fmt)
 #define DYNAMIC_DEBUG_BRANCH(descriptor) false
 #define DECLARE_DYNDBG_CLASSMAP(...)
@@ -357,8 +489,7 @@ static inline int param_set_dyndbg_classes(const char *instr, const struct kerne
 static inline int param_get_dyndbg_classes(char *buffer, const struct kernel_param *kp)
 { return 0; }
 
-#endif
-
+#endif /* !CONFIG_DYNAMIC_DEBUG_CORE */
 
 extern const struct kernel_param_ops param_ops_dyndbg_classes;
 
diff --git a/kernel/module/main.c b/kernel/module/main.c
index a0fe6c7aab75..8a3fc98d8a4c 100644
--- a/kernel/module/main.c
+++ b/kernel/module/main.c
@@ -2723,6 +2723,9 @@ static int find_module_sections(struct module *mod, struct load_info *info)
 	mod->dyndbg_info.maps.start = section_objs(info, "__dyndbg_class_maps",
 						   sizeof(*mod->dyndbg_info.maps.start),
 						   &mod->dyndbg_info.maps.len);
+	mod->dyndbg_info.users.start = section_objs(info, "__dyndbg_class_users",
+						   sizeof(*mod->dyndbg_info.users.start),
+						   &mod->dyndbg_info.users.len);
 #endif
 
 	return 0;
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 93f356d2b3d9..302bb2656682 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -3106,12 +3106,26 @@ config TEST_STATIC_KEYS
 	  If unsure, say N.
 
 config TEST_DYNAMIC_DEBUG
-	tristate "Test DYNAMIC_DEBUG"
-	depends on DYNAMIC_DEBUG
+	tristate "Build test-dynamic-debug module"
+	depends on DYNAMIC_DEBUG || DYNAMIC_DEBUG_CORE
 	help
-	  This module registers a tracer callback to count enabled
-	  pr_debugs in a 'do_debugging' function, then alters their
-	  enablements, calls the function, and compares counts.
+	  This module exercises/demonstrates dyndbg's classmap API, by
+	  creating 2 classes: a DISJOINT classmap (supporting DRM.debug)
+	  and a LEVELS/VERBOSE classmap (like verbose2 > verbose1).
+
+	  If unsure, say N.
+
+config TEST_DYNAMIC_DEBUG_SUBMOD
+	tristate "Build test-dynamic-debug submodule"
+	default m
+	depends on DYNAMIC_DEBUG || DYNAMIC_DEBUG_CORE
+	depends on TEST_DYNAMIC_DEBUG
+	help
+	  This sub-module uses a classmap defined and exported by the
+	  parent module, recapitulating drm & driver's shared use of
+	  drm.debug to control enabled debug-categories.
+	  It is tristate, independent of parent, to allow testing all
+	  proper combinations of parent=y/m submod=y/m.
 
 	  If unsure, say N.
 
diff --git a/lib/Makefile b/lib/Makefile
index 1b9ee167517f..19ab40903436 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -83,6 +83,9 @@ obj-$(CONFIG_TEST_RHASHTABLE) += test_rhashtable.o
 obj-$(CONFIG_TEST_STATIC_KEYS) += test_static_keys.o
 obj-$(CONFIG_TEST_STATIC_KEYS) += test_static_key_base.o
 obj-$(CONFIG_TEST_DYNAMIC_DEBUG) += test_dynamic_debug.o
+obj-$(CONFIG_TEST_DYNAMIC_DEBUG_SUBMOD) += test_dynamic_debug_submod.o
+obj-$(CONFIG_TEST_PRINTF) += test_printf.o
+obj-$(CONFIG_TEST_SCANF) += test_scanf.o
 
 obj-$(CONFIG_TEST_BITMAP) += test_bitmap.o
 ifeq ($(CONFIG_CC_IS_CLANG)$(CONFIG_KASAN),yy)
@@ -206,6 +209,8 @@ obj-$(CONFIG_ARCH_NEED_CMPXCHG_1_EMU) += cmpxchg-emu.o
 obj-$(CONFIG_DYNAMIC_DEBUG_CORE) += dynamic_debug.o
 #ensure exported functions have prototypes
 CFLAGS_dynamic_debug.o := -DDYNAMIC_DEBUG_MODULE
+CFLAGS_test_dynamic_debug.o := -DDYNAMIC_DEBUG_MODULE
+CFLAGS_test_dynamic_debug_submod.o := -DDYNAMIC_DEBUG_MODULE
 
 obj-$(CONFIG_SYMBOLIC_ERRNAME) += errname.o
 
diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
index b8983e095e60..ce512efaeffd 100644
--- a/lib/dynamic_debug.c
+++ b/lib/dynamic_debug.c
@@ -29,6 +29,7 @@
 #include <linux/string_helpers.h>
 #include <linux/uaccess.h>
 #include <linux/dynamic_debug.h>
+
 #include <linux/debugfs.h>
 #include <linux/slab.h>
 #include <linux/jump_label.h>
@@ -43,6 +44,8 @@ extern struct _ddebug __start___dyndbg_descs[];
 extern struct _ddebug __stop___dyndbg_descs[];
 extern struct _ddebug_class_map __start___dyndbg_class_maps[];
 extern struct _ddebug_class_map __stop___dyndbg_class_maps[];
+extern struct _ddebug_class_user __start___dyndbg_class_users[];
+extern struct _ddebug_class_user __stop___dyndbg_class_users[];
 
 struct ddebug_table {
 	struct list_head link;
@@ -168,20 +171,37 @@ static void vpr_info_dq(const struct ddebug_query *query, const char *msg)
 		  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)
+#define vpr_di_info(di_p, msg_p, ...) ({				\
+	struct _ddebug_info const *_di = di_p;				\
+	v2pr_info(msg_p "module:%s nd:%d nc:%d nu:%d\n", ##__VA_ARGS__, \
+		  _di->mod_name, _di->descs.len, _di->maps.len,		\
+		  _di->users.len);					\
+	})
+
+static struct _ddebug_class_map *
+ddebug_find_valid_class(struct _ddebug_info const *di, const char *query_class, int *class_id)
 {
 	struct _ddebug_class_map *map;
+	struct _ddebug_class_user *cli;
 	int i, idx;
 
-	for_subvec(i, map, &dt->info, maps) {
-		idx = match_string(map->class_names, map->length, class_string);
+	for_subvec(i, map, di, maps) {
+		idx = match_string(map->class_names, map->length, query_class);
 		if (idx >= 0) {
+			vpr_di_info(di, "good-class: %s.%s ", map->mod_name, query_class);
 			*class_id = idx + map->base;
 			return map;
 		}
 	}
+	for_subvec(i, cli, di, users) {
+		idx = match_string(cli->map->class_names, cli->map->length, query_class);
+		if (idx >= 0) {
+			vpr_di_info(di, "class-ref: %s -> %s.%s ",
+				    cli->mod_name, cli->map->mod_name, query_class);
+			*class_id = idx + cli->map->base - cli->offset;
+			return cli->map;
+		}
+	}
 	*class_id = -ENOENT;
 	return NULL;
 }
@@ -238,8 +258,7 @@ static bool ddebug_match_desc(const struct ddebug_query *query,
 	return true;
 }
 
-static int ddebug_change(const struct ddebug_query *query,
-			 struct flag_settings *modifiers)
+static int ddebug_change(const struct ddebug_query *query, struct flag_settings *modifiers)
 {
 	int i;
 	struct ddebug_table *dt;
@@ -260,7 +279,8 @@ static int ddebug_change(const struct ddebug_query *query,
 			continue;
 
 		if (query->class_string) {
-			map = ddebug_find_valid_class(dt, query->class_string, &valid_class);
+			map = ddebug_find_valid_class(&dt->info, query->class_string,
+						      &valid_class);
 			if (!map)
 				continue;
 		} else {
@@ -590,7 +610,7 @@ static int ddebug_exec_query(char *query_string, const char *modname)
 
 /* handle multiple queries in query string, continue on error, return
    last error or number of matching callsites.  Module name is either
-   in param (for boot arg) or perhaps in query string.
+   in the modname arg (for boot args) or perhaps in query string.
 */
 static int ddebug_exec_queries(char *query, const char *modname)
 {
@@ -721,7 +741,7 @@ static int param_set_dyndbg_module_classes(const char *instr,
 /**
  * param_set_dyndbg_classes - classmap kparam setter
  * @instr: string echo>d to sysfs, input depends on map_type
- * @kp:    kp->arg has state: bits/lvl, map, map_type
+ * @kp:    kp->arg has state: bits/lvl, classmap, map_type
  *
  * enable/disable all class'd pr_debugs in the classmap. For LEVEL
  * map-types, enforce * relative levels by bitpos.
@@ -758,6 +778,7 @@ int param_get_dyndbg_classes(char *buffer, const struct kernel_param *kp)
 	default:
 		return -1;
 	}
+	return 0;
 }
 EXPORT_SYMBOL(param_get_dyndbg_classes);
 
@@ -1073,12 +1094,17 @@ static bool ddebug_class_in_range(const int class_id, const struct _ddebug_class
 static const char *ddebug_class_name(struct _ddebug_info *di, struct _ddebug *dp)
 {
 	struct _ddebug_class_map *map;
+	struct _ddebug_class_user *cli;
 	int i;
 
 	for_subvec(i, map, di, maps)
 		if (ddebug_class_in_range(dp->class_id, map))
 			return map->class_names[dp->class_id - map->base];
 
+	for_subvec(i, cli, di, users)
+		if (ddebug_class_in_range(dp->class_id, cli->map))
+			return cli->map->class_names[dp->class_id - cli->map->base - cli->offset];
+
 	return NULL;
 }
 
@@ -1159,32 +1185,87 @@ static const struct proc_ops proc_fops = {
 	.proc_write = ddebug_proc_write
 };
 
-static void ddebug_attach_module_classes(struct ddebug_table *dt, struct _ddebug_info *di)
+#define vpr_cm_info(cm_p, msg_fmt, ...) ({				\
+	struct _ddebug_class_map const *_cm = cm_p;			\
+	v2pr_info(msg_fmt "%s [%d..%d] %s..%s\n", ##__VA_ARGS__,	\
+		  _cm->mod_name, _cm->base, _cm->base + _cm->length,	\
+		  _cm->class_names[0], _cm->class_names[_cm->length - 1]); \
+	})
+
+static void ddebug_sync_classbits(const struct kernel_param *kp, const char *modname)
 {
-	struct _ddebug_class_map *cm;
-	int i, nc = 0;
+	const struct _ddebug_class_param *dcp = kp->arg;
 
-	/*
-	 * Find this module's classmaps in a subrange/wholerange of
-	 * the builtin/modular classmap vector/section.  Save the start
-	 * and length of the subrange at its edges.
-	 */
-	for_subvec(i, cm, di, maps) {
-		if (!strcmp(cm->mod_name, dt->info.mod_name)) {
-			if (!nc) {
-				v2pr_info("start subrange, class[%d]: module:%s base:%d len:%d ty:%d\n",
-					  i, cm->mod_name, cm->base, cm->length, cm->map_type);
-				dt->info.maps.start = cm;
-			}
-			nc++;
-		}
+	/* clamp initial bitvec, mask off hi-bits */
+	if (*dcp->bits & ~CLASSMAP_BITMASK(dcp->map->length)) {
+		*dcp->bits &= CLASSMAP_BITMASK(dcp->map->length);
+		v2pr_info("preset classbits: %lx\n", *dcp->bits);
+	}
+	/* force class'd prdbgs (in USEr module) to match (DEFINEr module) class-param */
+	ddebug_apply_class_bitmap(dcp, dcp->bits, ~0, modname);
+	ddebug_apply_class_bitmap(dcp, dcp->bits, 0, modname);
+}
+
+static void ddebug_match_apply_kparam(const struct kernel_param *kp,
+				      const struct _ddebug_class_map *map,
+				      const char *mod_name)
+{
+	struct _ddebug_class_param *dcp;
+
+	if (kp->ops != &param_ops_dyndbg_classes)
+		return;
+
+	dcp = (struct _ddebug_class_param *)kp->arg;
+
+	if (map == dcp->map) {
+		v2pr_info(" kp:%s.%s =0x%lx", mod_name, kp->name, *dcp->bits);
+		vpr_cm_info(map, " %s maps ", mod_name);
+		ddebug_sync_classbits(kp, mod_name);
+	}
+}
+
+static void ddebug_apply_params(const struct _ddebug_class_map *cm, const char *mod_name)
+{
+	const struct kernel_param *kp;
+#if IS_ENABLED(CONFIG_MODULES)
+	int i;
+
+	if (cm->mod) {
+		vpr_cm_info(cm, "loaded classmap: %s ", mod_name);
+		/* ifdef protects the cm->mod->kp deref */
+		for (i = 0, kp = cm->mod->kp; i < cm->mod->num_kp; i++, kp++)
+			ddebug_match_apply_kparam(kp, cm, mod_name);
 	}
-	if (nc) {
-		dt->info.maps.len = nc;
-		vpr_info("module:%s attached %d classes\n", dt->info.mod_name, nc);
+#endif
+	if (!cm->mod) {
+		vpr_cm_info(cm, "builtin classmap: %s ", mod_name);
+		for (kp = __start___param; kp < __stop___param; kp++)
+			ddebug_match_apply_kparam(kp, cm, mod_name);
 	}
 }
 
+static void ddebug_apply_class_maps(const struct _ddebug_info *di)
+{
+	struct _ddebug_class_map *cm;
+	int i;
+
+	for_subvec(i, cm, di, maps)
+		ddebug_apply_params(cm, cm->mod_name);
+
+	vpr_di_info(di, "attached %d class-maps to ", i);
+}
+
+static void ddebug_apply_class_users(const struct _ddebug_info *di)
+{
+	struct _ddebug_class_user *cli;
+	int i;
+
+	for_subvec(i, cli, di, users)
+		ddebug_apply_params(cli->map, cli->mod_name);
+
+	vpr_di_info(di, "attached %d class-users to ", i);
+}
+
 /*
  * Narrow a _ddebug_info's vector (@_vec) to the contiguous subrange
  * of elements where ->mod_name matches @__di->mod_name.
@@ -1214,6 +1295,22 @@ static void ddebug_attach_module_classes(struct ddebug_table *dt, struct _ddebug
 	__di->_vec.len = __nc;						\
 })
 
+static int __maybe_unused
+ddebug_class_range_overlap(struct _ddebug_class_map *cm,
+			   u64 *reserved_ids)
+{
+	u64 range = (((1ULL << cm->length) - 1) << cm->base);
+
+	if (range & *reserved_ids) {
+		pr_err("[%d..%d] on %s conflicts with %llx\n", cm->base,
+		       cm->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.
@@ -1222,6 +1319,7 @@ static int ddebug_add_module(struct _ddebug_info *di)
 {
 	struct ddebug_table *dt;
 	struct _ddebug_class_map *cm;
+	struct _ddebug_class_user *cli;
 	int i;
 
 	if (!di->descs.len)
@@ -1234,26 +1332,29 @@ static int ddebug_add_module(struct _ddebug_info *di)
 		pr_err("error adding module: %s\n", di->mod_name);
 		return -ENOMEM;
 	}
+	INIT_LIST_HEAD(&dt->link);
 	/*
-	 * For built-in modules, name (as supplied in di by its
-	 * callers) lives in .rodata and is immortal. For loaded
-	 * modules, name points at the name[] member of struct module,
-	 * which lives at least as long as this struct ddebug_table.
+	 * For built-in modules, di-> referents live in .*data and are
+	 * immortal. For loaded modules, di points at the dyndbg_info
+	 * member of its struct module, which lives at least as
+	 * long as this struct ddebug_table.
 	 */
 	dt->info = *di;
-
-	INIT_LIST_HEAD(&dt->link);
-
 	dd_set_module_subrange(i, cm, &dt->info, maps);
-
-	if (di->maps.len)
-		ddebug_attach_module_classes(dt, di);
+	dd_set_module_subrange(i, cli, &dt->info, users);
+	/* now di is stale */
 
 	mutex_lock(&ddebug_lock);
 	list_add_tail(&dt->link, &ddebug_tables);
 	mutex_unlock(&ddebug_lock);
 
-	vpr_info("%3u debug prints in module %s\n", di->descs.len, di->mod_name);
+	if (dt->info.maps.len)
+		ddebug_apply_class_maps(&dt->info);
+	if (dt->info.users.len)
+		ddebug_apply_class_users(&dt->info);
+
+	vpr_info("%3u debug prints in module %s\n",
+		 dt->info.descs.len, dt->info.mod_name);
 	return 0;
 }
 
@@ -1403,8 +1504,10 @@ static int __init dynamic_debug_init(void)
 	struct _ddebug_info di = {
 		.descs.start = __start___dyndbg_descs,
 		.maps.start  = __start___dyndbg_class_maps,
+		.users.start = __start___dyndbg_class_users,
 		.descs.len = __stop___dyndbg_descs - __start___dyndbg_descs,
 		.maps.len  = __stop___dyndbg_class_maps - __start___dyndbg_class_maps,
+		.users.len = __stop___dyndbg_class_users - __start___dyndbg_class_users,
 	};
 
 #ifdef CONFIG_MODULES
diff --git a/lib/test_dynamic_debug.c b/lib/test_dynamic_debug.c
index 9c3e53cd26bd..6c4548f63512 100644
--- a/lib/test_dynamic_debug.c
+++ b/lib/test_dynamic_debug.c
@@ -6,11 +6,30 @@
  *      Jim Cromie	<jim.cromie@gmail.com>
  */
 
-#define pr_fmt(fmt) "test_dd: " fmt
+/*
+ * This file is built 2x, also making test_dynamic_debug_submod.ko,
+ * whose 2-line src file #includes this file.  This gives us a _submod
+ * clone with identical pr_debugs, without further maintenance.
+ *
+ * If things are working properly, they should operate identically
+ * when printed or adjusted by >control.  This eases visual perusal of
+ * the logs, and simplifies testing, by easing the proper accounting
+ * of expectations.
+ *
+ * It also puts both halves of the subsystem _DEFINE & _USE use case
+ * together, and integrates the common ENUM providing both class_ids
+ * and class-names to both _DEFINErs and _USERs.  I think this makes
+ * the usage clearer.
+ */
+#if defined(TEST_DYNAMIC_DEBUG_SUBMOD)
+  #define pr_fmt(fmt) "test_dd_submod: " fmt
+#else
+  #define pr_fmt(fmt) "test_dd: " fmt
+#endif
 
 #include <linux/module.h>
 
-/* run tests by reading or writing sysfs node: do_prints */
+/* re-gen output by reading or writing sysfs node: do_prints */
 
 static void do_prints(void); /* device under test */
 static int param_set_do_prints(const char *instr, const struct kernel_param *kp)
@@ -29,24 +48,39 @@ static const struct kernel_param_ops param_ops_do_prints = {
 };
 module_param_cb(do_prints, &param_ops_do_prints, NULL, 0600);
 
-/*
- * Using the CLASSMAP api:
- * - classmaps must have corresponding enum
- * - enum symbols must match/correlate with class-name strings in the map.
- * - base must equal enum's 1st value
- * - multiple maps must set their base to share the 0-30 class_id space !!
- *   (build-bug-on tips welcome)
- * Additionally, here:
- * - tie together sysname, mapname, bitsname, flagsname
- */
-#define DD_SYS_WRAP(_model, _flags)					\
-	static unsigned long bits_##_model;				\
-	static struct _ddebug_class_param _flags##_model = {		\
+#define CLASSMAP_BITMASK(width, base) (((1UL << (width)) - 1) << (base))
+
+/* sysfs param wrapper, proto-API */
+#define DYNAMIC_DEBUG_CLASSMAP_PARAM_(_model, _flags, _init)		\
+	static unsigned long bits_##_model = _init;			\
+	static struct _ddebug_class_param _flags##_##_model = {		\
 		.bits = &bits_##_model,					\
 		.flags = #_flags,					\
 		.map = &map_##_model,					\
 	};								\
-	module_param_cb(_flags##_##_model, &param_ops_dyndbg_classes, &_flags##_model, 0600)
+	module_param_cb(_flags##_##_model, &param_ops_dyndbg_classes,	\
+			&_flags##_##_model, 0600)
+#ifdef DEBUG
+#define DYNAMIC_DEBUG_CLASSMAP_PARAM(_model, _flags)		\
+	DYNAMIC_DEBUG_CLASSMAP_PARAM_(_model, _flags, ~0)
+#else
+#define DYNAMIC_DEBUG_CLASSMAP_PARAM(_model, _flags)		\
+	DYNAMIC_DEBUG_CLASSMAP_PARAM_(_model, _flags, 0)
+#endif
+
+/*
+ * Demonstrate/test DISJOINT & LEVEL typed classmaps with a sys-param.
+ *
+ * To comport with DRM debug-category (an int), classmaps map names to
+ * ids (also an int).  So a classmap starts with an enum; DRM has enum
+ * debug_category: with DRM_UT_<CORE,DRIVER,KMS,etc>.  We use the enum
+ * values as class-ids, and stringified enum-symbols as classnames.
+ *
+ * Modules with multiple CLASSMAPS must have enums with distinct
+ * value-ranges, as arranged below with explicit enum_sym = X inits.
+ * To clarify this sharing, declare the 2 enums now, for the 2
+ * different classmap types
+ */
 
 /* numeric input, independent bits */
 enum cat_disjoint_bits {
@@ -60,26 +94,51 @@ enum cat_disjoint_bits {
 	D2_LEASE,
 	D2_DP,
 	D2_DRMRES };
-DECLARE_DYNDBG_CLASSMAP(map_disjoint_bits, DD_CLASS_TYPE_DISJOINT_BITS, 0,
-			"D2_CORE",
-			"D2_DRIVER",
-			"D2_KMS",
-			"D2_PRIME",
-			"D2_ATOMIC",
-			"D2_VBL",
-			"D2_STATE",
-			"D2_LEASE",
-			"D2_DP",
-			"D2_DRMRES");
-DD_SYS_WRAP(disjoint_bits, p);
-DD_SYS_WRAP(disjoint_bits, T);
-
-/* numeric verbosity, V2 > V1 related */
-enum cat_level_num { V0 = 14, V1, V2, V3, V4, V5, V6, V7 };
-DECLARE_DYNDBG_CLASSMAP(map_level_num, DD_CLASS_TYPE_LEVEL_NUM, 14,
-		       "V0", "V1", "V2", "V3", "V4", "V5", "V6", "V7");
-DD_SYS_WRAP(level_num, p);
-DD_SYS_WRAP(level_num, T);
+
+/* numeric verbosity, V2 > V1 related.  V0 is > D2_DRMRES */
+enum cat_level_num { V0 = 16, V1, V2, V3, V4, V5, V6, V7 };
+
+/* recapitulate DRM's multi-classmap setup */
+#if !defined(TEST_DYNAMIC_DEBUG_SUBMOD)
+/*
+ * In single user, or parent / coordinator (drm.ko) modules, define
+ * classmaps on the client enums above, and then declares the PARAMS
+ * ref'g the classmaps.  Each is exported.
+ */
+DYNAMIC_DEBUG_CLASSMAP_DEFINE(map_disjoint_bits, DD_CLASS_TYPE_DISJOINT_BITS,
+			      D2_CORE,
+			      "D2_CORE",
+			      "D2_DRIVER",
+			      "D2_KMS",
+			      "D2_PRIME",
+			      "D2_ATOMIC",
+			      "D2_VBL",
+			      "D2_STATE",
+			      "D2_LEASE",
+			      "D2_DP",
+			      "D2_DRMRES");
+
+DYNAMIC_DEBUG_CLASSMAP_DEFINE(map_level_num, DD_CLASS_TYPE_LEVEL_NUM,
+			      V0, "V0", "V1", "V2", "V3", "V4", "V5", "V6", "V7");
+
+/*
+ * now add the sysfs-params
+ */
+
+DYNAMIC_DEBUG_CLASSMAP_PARAM(disjoint_bits, p);
+DYNAMIC_DEBUG_CLASSMAP_PARAM(level_num, p);
+
+#else /* TEST_DYNAMIC_DEBUG_SUBMOD */
+
+/*
+ * in submod/drm-drivers, use the classmaps defined in top/parent
+ * module above.
+ */
+
+DYNAMIC_DEBUG_CLASSMAP_USE(map_disjoint_bits);
+DYNAMIC_DEBUG_CLASSMAP_USE(map_level_num);
+
+#endif
 
 /* stand-in for all pr_debug etc */
 #define prdbg(SYM) __pr_debug_cls(SYM, #SYM " msg\n")
@@ -115,6 +174,7 @@ static void do_levels(void)
 
 static void do_prints(void)
 {
+	pr_debug("do_prints:\n");
 	do_cats();
 	do_levels();
 }
diff --git a/lib/test_dynamic_debug_submod.c b/lib/test_dynamic_debug_submod.c
new file mode 100644
index 000000000000..672aabf40160
--- /dev/null
+++ b/lib/test_dynamic_debug_submod.c
@@ -0,0 +1,14 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Kernel module for testing dynamic_debug
+ *
+ * Authors:
+ *      Jim Cromie	<jim.cromie@gmail.com>
+ */
+
+/*
+ * clone the parent, inherit all the properties, for consistency and
+ * simpler accounting in test expectations.
+ */
+#define TEST_DYNAMIC_DEBUG_SUBMOD
+#include "test_dynamic_debug.c"
-- 
2.53.0

[PATCH v13 29/36] dyndbg-API: promote DYNAMIC_DEBUG_CLASSMAP_PARAM to API

[Jim Cromie]

move the DYNAMIC_DEBUG_CLASSMAP_PARAM macro from test-dynamic-debug.c into
the header, and refine it, by distinguishing the 2 use cases:

1.DYNAMIC_DEBUG_CLASSMAP_PARAM_REF
    for DRM, to pass in extern __drm_debug by name.
    dyndbg keeps bits in it, so drm can still use it as before

2.DYNAMIC_DEBUG_CLASSMAP_PARAM
    new user (test_dynamic_debug) doesn't need to share state,
    decls a static long unsigned int to store the bitvec.

__DYNAMIC_DEBUG_CLASSMAP_PARAM
   bottom layer - allocate,init a ddebug-class-param, module-param-cb.

Modify ddebug_sync_classbits() argtype deref inside the fn, to give
access to all kp members.

Also add stub macros, clean up and improve comments in test-code, and
add MODULE_DESCRIPTIONs.

cc: linux-doc@vger.kernel.org
Reviewed-by: Louis Chauvet <louis.chauvet@bootlin.com>
Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
---
 include/linux/dynamic_debug.h   | 40 ++++++++++++++++++++++
 lib/dynamic_debug.c             | 60 ++++++++++++++++++++++-----------
 lib/test_dynamic_debug.c        | 47 ++++++++++----------------
 lib/test_dynamic_debug_submod.c |  9 ++++-
 4 files changed, 106 insertions(+), 50 deletions(-)

diff --git a/include/linux/dynamic_debug.h b/include/linux/dynamic_debug.h
index a1c75237abaa..1cae9a2f32d7 100644
--- a/include/linux/dynamic_debug.h
+++ b/include/linux/dynamic_debug.h
@@ -273,6 +273,44 @@ struct _ddebug_class_param {
 		.offset = _offset					\
 	}
 
+/**
+ * DYNAMIC_DEBUG_CLASSMAP_PARAM - control a ddebug-classmap from a sys-param
+ * @_name:  sysfs node name
+ * @_var:   name of the classmap var defining the controlled classes/bits
+ * @_flags: flags to be toggled, typically just 'p'
+ *
+ * Creates a sysfs-param to control the classes defined by the
+ * exported classmap, with bits 0..N-1 mapped to the classes named.
+ * This version keeps class-state in a private long int.
+ */
+#define DYNAMIC_DEBUG_CLASSMAP_PARAM(_name, _var, _flags)		\
+	static unsigned long _name##_bvec;				\
+	__DYNAMIC_DEBUG_CLASSMAP_PARAM(_name, _name##_bvec, _var, _flags)
+
+/**
+ * DYNAMIC_DEBUG_CLASSMAP_PARAM_REF - wrap a classmap with a controlling sys-param
+ * @_name:  sysfs node name
+ * @_bits:  name of the module's unsigned long bit-vector, ex: __drm_debug
+ * @_var:   name of the (exported) classmap var defining the classes/bits
+ * @_flags: flags to be toggled, typically just 'p'
+ *
+ * Creates a sysfs-param to control the classes defined by the
+ * exported clasmap, with bits 0..N-1 mapped to the classes named.
+ * This version keeps class-state in user @_bits.  This lets drm check
+ * __drm_debug elsewhere too.
+ */
+#define DYNAMIC_DEBUG_CLASSMAP_PARAM_REF(_name, _bits, _var, _flags)	\
+	__DYNAMIC_DEBUG_CLASSMAP_PARAM(_name, _bits, _var, _flags)
+
+#define __DYNAMIC_DEBUG_CLASSMAP_PARAM(_name, _bits, _var, _flags)	\
+	static struct _ddebug_class_param _name##_##_flags = {		\
+		.bits = &(_bits),					\
+		.flags = #_flags,					\
+		.map = &(_var),						\
+	};								\
+	module_param_cb(_name, &param_ops_dyndbg_classes,		\
+			&_name##_##_flags, 0600)
+
 extern __printf(2, 3)
 void __dynamic_pr_debug(struct _ddebug *descriptor, const char *fmt, ...);
 
@@ -455,6 +493,8 @@ void __dynamic_ibdev_dbg(struct _ddebug *descriptor,
 
 #define DYNAMIC_DEBUG_CLASSMAP_DEFINE(_var, _mapty, _base, ...)
 #define DYNAMIC_DEBUG_CLASSMAP_USE(_var)
+#define DYNAMIC_DEBUG_CLASSMAP_PARAM(_name, _var, _flags)
+#define DYNAMIC_DEBUG_CLASSMAP_PARAM_REF(_name, _var, _flags)
 #define DEFINE_DYNAMIC_DEBUG_METADATA(name, fmt)
 #define DYNAMIC_DEBUG_BRANCH(descriptor) false
 #define DECLARE_DYNDBG_CLASSMAP(...)
diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
index a7f67ecbc4d7..c6f3b0452dfa 100644
--- a/lib/dynamic_debug.c
+++ b/lib/dynamic_debug.c
@@ -687,6 +687,30 @@ static int ddebug_apply_class_bitmap(const struct _ddebug_class_param *dcp,
 
 #define CLASSMAP_BITMASK(width) ((1UL << (width)) - 1)
 
+static void ddebug_class_param_clamp_input(unsigned long *inrep, const struct kernel_param *kp)
+{
+	const struct _ddebug_class_param *dcp = kp->arg;
+	const struct _ddebug_class_map *map = dcp->map;
+
+	switch (map->map_type) {
+	case DD_CLASS_TYPE_DISJOINT_BITS:
+		/* expect bits. mask and warn if too many */
+		if (*inrep & ~CLASSMAP_BITMASK(map->length)) {
+			pr_warn("%s: input: 0x%lx exceeds mask: 0x%lx, masking\n",
+				KP_NAME(kp), *inrep, CLASSMAP_BITMASK(map->length));
+			*inrep &= CLASSMAP_BITMASK(map->length);
+		}
+		break;
+	case DD_CLASS_TYPE_LEVEL_NUM:
+		/* input is bitpos, of highest verbosity to be enabled */
+		if (*inrep > map->length) {
+			pr_warn("%s: level:%ld exceeds max:%d, clamping\n",
+				KP_NAME(kp), *inrep, map->length);
+			*inrep = map->length;
+		}
+		break;
+	}
+}
 static int param_set_dyndbg_module_classes(const char *instr,
 					   const struct kernel_param *kp,
 					   const char *mod_name)
@@ -705,26 +729,15 @@ static int param_set_dyndbg_module_classes(const char *instr,
 		pr_err("expecting numeric input, not: %s > %s\n", instr, KP_NAME(kp));
 		return -EINVAL;
 	}
+	ddebug_class_param_clamp_input(&inrep, kp);
 
 	switch (map->map_type) {
 	case DD_CLASS_TYPE_DISJOINT_BITS:
-		/* expect bits. mask and warn if too many */
-		if (inrep & ~CLASSMAP_BITMASK(map->length)) {
-			pr_warn("%s: input: 0x%lx exceeds mask: 0x%lx, masking\n",
-				KP_NAME(kp), inrep, CLASSMAP_BITMASK(map->length));
-			inrep &= CLASSMAP_BITMASK(map->length);
-		}
 		v2pr_info("bits:0x%lx > %s.%s\n", inrep, mod_name ?: "*", KP_NAME(kp));
 		totct += ddebug_apply_class_bitmap(dcp, &inrep, *dcp->bits, mod_name);
 		*dcp->bits = inrep;
 		break;
 	case DD_CLASS_TYPE_LEVEL_NUM:
-		/* input is bitpos, of highest verbosity to be enabled */
-		if (inrep > map->length) {
-			pr_warn("%s: level:%ld exceeds max:%d, clamping\n",
-				KP_NAME(kp), inrep, map->length);
-			inrep = map->length;
-		}
 		old_bits = CLASSMAP_BITMASK(*dcp->lvl);
 		new_bits = CLASSMAP_BITMASK(inrep);
 		v2pr_info("lvl:%ld bits:0x%lx > %s\n", inrep, new_bits, KP_NAME(kp));
@@ -1200,15 +1213,24 @@ static const struct proc_ops proc_fops = {
 static void ddebug_sync_classbits(const struct kernel_param *kp, const char *modname)
 {
 	const struct _ddebug_class_param *dcp = kp->arg;
+	unsigned long new_bits;
 
-	/* clamp initial bitvec, mask off hi-bits */
-	if (*dcp->bits & ~CLASSMAP_BITMASK(dcp->map->length)) {
-		*dcp->bits &= CLASSMAP_BITMASK(dcp->map->length);
-		v2pr_info("preset classbits: %lx\n", *dcp->bits);
+	ddebug_class_param_clamp_input(dcp->bits, kp);
+
+	switch (dcp->map->map_type) {
+	case DD_CLASS_TYPE_DISJOINT_BITS:
+		v2pr_info("  %s: classbits: 0x%lx\n", KP_NAME(kp), *dcp->bits);
+		ddebug_apply_class_bitmap(dcp, dcp->bits, 0UL, modname);
+		break;
+	case DD_CLASS_TYPE_LEVEL_NUM:
+		new_bits = CLASSMAP_BITMASK(*dcp->lvl);
+		v2pr_info("  %s: lvl:%ld bits:0x%lx\n", KP_NAME(kp), *dcp->lvl, new_bits);
+		ddebug_apply_class_bitmap(dcp, &new_bits, 0UL, modname);
+		break;
+	default:
+		pr_err("bad map type %d\n", dcp->map->map_type);
+		return;
 	}
-	/* force class'd prdbgs (in USEr module) to match (DEFINEr module) class-param */
-	ddebug_apply_class_bitmap(dcp, dcp->bits, ~0, modname);
-	ddebug_apply_class_bitmap(dcp, dcp->bits, 0, modname);
 }
 
 static void ddebug_match_apply_kparam(const struct kernel_param *kp,
diff --git a/lib/test_dynamic_debug.c b/lib/test_dynamic_debug.c
index 5de839f13c8b..d65fa3f3ef9e 100644
--- a/lib/test_dynamic_debug.c
+++ b/lib/test_dynamic_debug.c
@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0-only
 /*
- * Kernel module for testing dynamic_debug
+ * Kernel module to test/demonstrate dynamic_debug features,
+ * particularly classmaps and their support for subsystems like DRM.
  *
  * Authors:
  *      Jim Cromie	<jim.cromie@gmail.com>
@@ -57,24 +58,6 @@ module_param_cb(do_prints, &param_ops_do_prints, NULL, 0600);
 
 #define CLASSMAP_BITMASK(width, base) (((1UL << (width)) - 1) << (base))
 
-/* sysfs param wrapper, proto-API */
-#define DYNAMIC_DEBUG_CLASSMAP_PARAM_(_model, _flags, _init)		\
-	static unsigned long bits_##_model = _init;			\
-	static struct _ddebug_class_param _flags##_##_model = {		\
-		.bits = &bits_##_model,					\
-		.flags = #_flags,					\
-		.map = &map_##_model,					\
-	};								\
-	module_param_cb(_flags##_##_model, &param_ops_dyndbg_classes,	\
-			&_flags##_##_model, 0600)
-#ifdef DEBUG
-#define DYNAMIC_DEBUG_CLASSMAP_PARAM(_model, _flags)		\
-	DYNAMIC_DEBUG_CLASSMAP_PARAM_(_model, _flags, ~0)
-#else
-#define DYNAMIC_DEBUG_CLASSMAP_PARAM(_model, _flags)		\
-	DYNAMIC_DEBUG_CLASSMAP_PARAM_(_model, _flags, 0)
-#endif
-
 /*
  * Demonstrate/test DISJOINT & LEVEL typed classmaps with a sys-param.
  *
@@ -105,12 +88,15 @@ enum cat_disjoint_bits {
 /* numeric verbosity, V2 > V1 related.  V0 is > D2_DRMRES */
 enum cat_level_num { V0 = 16, V1, V2, V3, V4, V5, V6, V7 };
 
-/* recapitulate DRM's multi-classmap setup */
+/*
+ * use/demonstrate multi-module-group classmaps, as for DRM
+ */
 #if !defined(TEST_DYNAMIC_DEBUG_SUBMOD)
 /*
- * In single user, or parent / coordinator (drm.ko) modules, define
- * classmaps on the client enums above, and then declares the PARAMS
- * ref'g the classmaps.  Each is exported.
+ * For module-groups of 1+, define classmaps with names (stringified
+ * enum-symbols) copied from above. 1-to-1 mapping is recommended.
+ * The classmap is exported, so that other modules in the group can
+ * link to it and control their prdbgs.
  */
 DYNAMIC_DEBUG_CLASSMAP_DEFINE(map_disjoint_bits, DD_CLASS_TYPE_DISJOINT_BITS,
 			      D2_CORE,
@@ -129,11 +115,13 @@ DYNAMIC_DEBUG_CLASSMAP_DEFINE(map_level_num, DD_CLASS_TYPE_LEVEL_NUM,
 			      V0, "V0", "V1", "V2", "V3", "V4", "V5", "V6", "V7");
 
 /*
- * now add the sysfs-params
+ * for use-cases that want it, provide a sysfs-param to set the
+ * classes in the classmap.  It is at this interface where the
+ * "v3>v2" property is applied to DD_CLASS_TYPE_LEVEL_NUM inputs.
  */
 
-DYNAMIC_DEBUG_CLASSMAP_PARAM(disjoint_bits, p);
-DYNAMIC_DEBUG_CLASSMAP_PARAM(level_num, p);
+DYNAMIC_DEBUG_CLASSMAP_PARAM(p_disjoint_bits,	map_disjoint_bits, p);
+DYNAMIC_DEBUG_CLASSMAP_PARAM(p_level_num,	map_level_num, p);
 
 #ifdef FORCE_CLASSID_CONFLICT
 /*
@@ -144,12 +132,10 @@ DYNAMIC_DEBUG_CLASSMAP_DEFINE(classid_range_conflict, 0, D2_CORE + 1, "D3_CORE")
 #endif
 
 #else /* TEST_DYNAMIC_DEBUG_SUBMOD */
-
 /*
- * in submod/drm-drivers, use the classmaps defined in top/parent
- * module above.
+ * the +1 members of a multi-module group refer to the classmap
+ * DEFINEd (and exported) above.
  */
-
 DYNAMIC_DEBUG_CLASSMAP_USE(map_disjoint_bits);
 DYNAMIC_DEBUG_CLASSMAP_USE(map_level_num);
 
@@ -228,6 +214,7 @@ static void __exit test_dynamic_debug_exit(void)
 module_init(test_dynamic_debug_init);
 module_exit(test_dynamic_debug_exit);
 
+MODULE_DESCRIPTION("test/demonstrate dynamic-debug features");
 MODULE_AUTHOR("Jim Cromie <jim.cromie@gmail.com>");
 MODULE_DESCRIPTION("Kernel module for testing dynamic_debug");
 MODULE_LICENSE("GPL");
diff --git a/lib/test_dynamic_debug_submod.c b/lib/test_dynamic_debug_submod.c
index 672aabf40160..3adf3925fb86 100644
--- a/lib/test_dynamic_debug_submod.c
+++ b/lib/test_dynamic_debug_submod.c
@@ -1,6 +1,9 @@
 // SPDX-License-Identifier: GPL-2.0
 /*
- * Kernel module for testing dynamic_debug
+ * Kernel module to test/demonstrate dynamic_debug features,
+ * particularly classmaps and their support for subsystems, like DRM,
+ * which defines its drm_debug classmap in drm module, and uses it in
+ * helpers & drivers.
  *
  * Authors:
  *      Jim Cromie	<jim.cromie@gmail.com>
@@ -12,3 +15,7 @@
  */
 #define TEST_DYNAMIC_DEBUG_SUBMOD
 #include "test_dynamic_debug.c"
+
+MODULE_DESCRIPTION("test/demonstrate dynamic-debug subsystem support");
+MODULE_AUTHOR("Jim Cromie <jim.cromie@gmail.com>");
+MODULE_LICENSE("GPL");
-- 
2.53.0

[PATCH v13 35/36] docs/dyndbg: add classmap info to howto

[Jim Cromie]

Describe the 3 API macros providing dynamic_debug's classmaps

DYNAMIC_DEBUG_CLASSMAP_DEFINE - create & export a classmap
DYNAMIC_DEBUG_CLASSMAP_USE    - refer to exported map
DYNAMIC_DEBUG_CLASSMAP_PARAM  - bind control param to the classmap
DYNAMIC_DEBUG_CLASSMAP_PARAM_REF + use module's storage - __drm_debug

NB: The _DEFINE & _USE model makes the user dependent on the definer,
just like EXPORT_SYMBOL(__drm_debug) already does.

cc: linux-doc@vger.kernel.org
Reviewed-by: Louis Chauvet <louis.chauvet@bootlin.com>
Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
---
 .../admin-guide/dynamic-debug-howto.rst       | 132 ++++++++++++++++--
 1 file changed, 122 insertions(+), 10 deletions(-)

diff --git a/Documentation/admin-guide/dynamic-debug-howto.rst b/Documentation/admin-guide/dynamic-debug-howto.rst
index 0a42b9de55ac..734be0b5fe9a 100644
--- a/Documentation/admin-guide/dynamic-debug-howto.rst
+++ b/Documentation/admin-guide/dynamic-debug-howto.rst
@@ -146,6 +146,9 @@ keywords are::
   "1-30" is valid range but "1 - 30" is not.
 
 
+Keywords
+--------
+
 The meanings of each keyword are:
 
 func
@@ -194,16 +197,6 @@ format
 	format "nfsd: SETATTR"  // a neater way to match a format with whitespace
 	format 'nfsd: SETATTR'  // yet another way to match a format with whitespace
 
-class
-    The given class_name is validated against each module, which may
-    have declared a list of known class_names.  If the class_name is
-    found for a module, callsite & class matching and adjustment
-    proceeds.  Examples::
-
-	class DRM_UT_KMS	# a DRM.debug category
-	class JUNK		# silent non-match
-	// class TLD_*		# NOTICE: no wildcard in class names
-
 line
     The given line number or range of line numbers is compared
     against the line number of each ``pr_debug()`` callsite.  A single
@@ -218,6 +211,25 @@ line
 	line -1605          // the 1605 lines from line 1 to line 1605
 	line 1600-          // all lines from line 1600 to the end of the file
 
+class
+
+    The given class_name is validated against each module, which may
+    have declared a list of class_names it accepts.  If the class_name
+    accepted by a module, callsite & class matching and adjustment
+    proceeds.  Examples::
+
+	class DRM_UT_KMS	# a drm.debug category
+	class JUNK		# silent non-match
+	// class TLD_*		# NOTICE: no wildcard in class names
+
+.. note::
+
+    Unlike other keywords, classes are "name-to-change", not
+    "omitting-constraint-allows-change".  See Dynamic Debug Classmaps
+
+Flags
+-----
+
 The flags specification comprises a change operation followed
 by one or more flag characters.  The change operation is one
 of the characters::
@@ -239,6 +251,11 @@ The flags are::
   l    Include line number
   d    Include call trace
 
+.. note::
+
+   * To query without changing	``+_`` or ``-_``.
+   * To clear all flags		``=_`` or ``-fslmpt``.
+
 For ``print_hex_dump_debug()`` and ``print_hex_dump_bytes()``, only
 the ``p`` flag has meaning, other flags are ignored.
 
@@ -395,3 +412,98 @@ just a shortcut for ``print_hex_dump(KERN_DEBUG)``.
 For ``print_hex_dump_debug()``/``print_hex_dump_bytes()``, format string is
 its ``prefix_str`` argument, if it is constant string; or ``hexdump``
 in case ``prefix_str`` is built dynamically.
+
+.. _dyndbg-classmaps:
+
+Dynamic Debug Classmaps
+=======================
+
+The "class" keyword selects prdbgs based on author supplied,
+domain-oriented names.  This complements the nested-scope keywords:
+module, file, function, line.
+
+The main difference from the others: classes must be named to be
+changed.  This protects them from unintended overwrite::
+
+  # IOW this cannot undo any drm.debug settings
+  :#> ddcmd -p
+
+This protection is needed; /sys/module/drm/parameters/debug is ABI.
+drm.debug is authoritative when dyndbg is not used, dyndbg-under-DRM
+is an implementation detail, and must not behave erratically, just
+because another admin fed >control something unrelated.
+
+So each class must be enabled individually (no wildcards)::
+
+  :#> ddcmd class DRM_UT_CORE +p
+  :#> ddcmd class DRM_UT_KMS +p
+  # or more selectively
+  :#> ddcmd class DRM_UT_CORE module drm +p
+
+That makes direct >control wordy and annoying, but it is a secondary
+interface; it is not intended to replace the ABI, just slide in
+underneath and reimplement the guaranteed behavior.  So DRM would keep
+using the convenient way, and be able to trust it::
+
+  :#> echo 0x1ff > /sys/module/drm/parameters/debug
+
+That said, since the sysfs/kparam is the ABI, if the author omits the
+CLASSMAP_PARAM, theres no ABI to guard, and he probably wants a less
+pedantic >control interface.  In this case, protection is dropped.
+
+Dynamic Debug Classmap API
+==========================
+
+DYNAMIC_DEBUG_CLASSMAP_DEFINE(clname,type,_base,classnames) - this maps
+classnames (a list of strings) onto class-ids consecutively, starting
+at _base.
+
+DYNAMIC_DEBUG_CLASSMAP_USE(clname) & _USE_(clname,_base) - modules
+call this to refer to the var _DEFINEd elsewhere (and exported).
+
+DYNAMIC_DEBUG_CLASSMAP_PARAM(clname) - creates the sysfs/kparam,
+maps/exposes bits 0..N as class-names.
+
+Classmaps are opt-in: modules invoke _DEFINE or _USE to authorize
+dyndbg to update those named classes.  "class FOO" queries are
+validated against the classes defined or used by the module, this
+finds the classid to alter; classes are not directly selectable by
+their classid.
+
+Classnames are global in scope, so subsystems (module-groups) should
+prepend a subsystem name; unqualified names like "CORE" are discouraged.
+
+NB: It is an inherent API limitation (due to class_id's int type) that
+the following are possible:
+
+  // these errors should be caught in review
+  __pr_debug_cls(0, "fake DRM_UT_CORE msg");  // this works
+  __pr_debug_cls(62, "un-known classid msg"); // this compiles, does nothing
+
+There are 2 types of classmaps:
+
+* DD_CLASS_TYPE_DISJOINT_BITS: classes are independent, like drm.debug
+* DD_CLASS_TYPE_LEVEL_NUM: classes are relative, ordered (V3 > V2)
+
+DYNAMIC_DEBUG_CLASSMAP_PARAM - modelled after module_param_cb, it
+refers to a DEFINEd classmap, and associates it to the param's
+data-store.  This state is then applied to DEFINEr and USEr modules
+when they're modprobed.
+
+The PARAM interface also enforces the DD_CLASS_TYPE_LEVEL_NUM relation
+amongst the contained classnames; all classes are independent in the
+control parser itself.  There is no implied meaning in names like "V4"
+or "PL_ERROR" vs "PL_WARNING".
+
+Modules or subsystems (drm & drivers) can define multiple classmaps,
+as long as they (all the classmaps) share the limited 0..62
+per-module-group _class_id range, without overlap.
+
+If a module encounters a conflict between 2 classmaps it is _USEing or
+_DEFINEing, it can invoke the extended _USE_(name,_base) macro to
+de-conflict the respective ranges.
+
+``#define DEBUG`` will enable all pr_debugs in scope, including any
+class'd ones.  This won't be reflected in the PARAM readback value,
+but the class'd pr_debug callsites can be forced off by toggling the
+classmap-kparam all-on then all-off.
-- 
2.53.0