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Message-ID: <20251118201842.1447666-31-jim.cromie@gmail.com>
Date: Tue, 18 Nov 2025 13:18:40 -0700
From: Jim Cromie <jim.cromie@...il.com>
To: linux-kernel@...r.kernel.org,
dri-devel@...ts.freedesktop.org,
gregkh@...uxfoundation.org,
jbaron@...mai.com
Cc: ukaszb@...omium.org,
louis.chauvet@...tlin.com,
Jim Cromie <jim.cromie@...il.com>
Subject: [PATCH v6 30/31] 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 drm-driver does:
DYNAMIC_DEBUG_CLASSMAP_USE(drm_debug_classes);
DYNAMIC_DEBUG_CLASSMAP_USE(drm_accel_xfer_debug);
And (for some reason) drm-accel will not define their constants to
avoid DRM's 0..10 reservations (seems a long stretch).
So I dont think this potential conflict would become an issue until we
have at least a 3-X-3 of classmap-defns X classmap-users
So drop this if its too speculative, knowing theres at least a
notional solution should the situation arise.
Signed-off-by: Jim Cromie <jim.cromie@...il.com>
---
re-ref of an lvalue is fine.
CHECK: Macro argument reuse '_var' - possible side-effects?
-v5+ less hand-wavy
---
include/linux/dynamic_debug.h | 30 +++++++++++++++++++++++-------
lib/dynamic_debug.c | 19 ++++++++++++-------
2 files changed, 35 insertions(+), 14 deletions(-)
diff --git a/include/linux/dynamic_debug.h b/include/linux/dynamic_debug.h
index b22da40e2583..5307be8da5c1 100644
--- a/include/linux/dynamic_debug.h
+++ b/include/linux/dynamic_debug.h
@@ -87,7 +87,7 @@ struct _ddebug_class_map {
struct _ddebug_class_user {
char *mod_name;
struct _ddebug_class_map *map;
- const int base; /* user offset to re-number the used map */
+ const int offset; /* offset from map->base */
};
/*
@@ -235,21 +235,37 @@ struct _ddebug_class_param {
/**
* DYNAMIC_DEBUG_CLASSMAP_USE - refer to a classmap, DEFINEd elsewhere.
* @_var: name of the exported classmap var
- * @_not_yet: _base-like, but applies only to this USEr. (if needed)
*
* 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.
+ * 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, __UNIQUE_ID(_ddebug_class_user))
-#define DYNAMIC_DEBUG_CLASSMAP_USE_(_var, _base, _uname) \
+#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 + @_base.
+ */
+#define DYNAMIC_DEBUG_CLASSMAP_USE_(_var, _offset) \
+ __DYNAMIC_DEBUG_CLASSMAP_USE(_var, _offset, __UNIQUE_ID(_ddebug_class_user))
+
+#define __DYNAMIC_DEBUG_CLASSMAP_USE(_var, _offset, _uname) \
extern struct _ddebug_class_map _var; \
static struct _ddebug_class_user __aligned(8) __used \
__section("__dyndbg_class_users") _uname = { \
.mod_name = KBUILD_MODNAME, \
.map = &(_var), \
- .base = _base \
+ .offset = _offset \
}
/**
diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
index 1082e0273f0e..bf1ff29cca95 100644
--- a/lib/dynamic_debug.c
+++ b/lib/dynamic_debug.c
@@ -198,7 +198,7 @@ ddebug_find_valid_class(struct _ddebug_info const *di, const char *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;
+ *class_id = idx + cli->map->base - cli->offset;
return cli->map;
}
}
@@ -206,12 +206,17 @@ ddebug_find_valid_class(struct _ddebug_info const *di, const char *query_class,
return NULL;
}
-static bool ddebug_class_in_range(const int class_id, const struct _ddebug_class_map *map)
+static bool ddebug_class_map_in_range(const int class_id, const struct _ddebug_class_map *map)
{
return (class_id >= map->base &&
class_id < map->base + map->length);
}
+static bool ddebug_class_user_in_range(const int class_id, const struct _ddebug_class_user *user)
+{
+ return ddebug_class_map_in_range(class_id - user->offset, user->map);
+}
+
static struct _ddebug_class_map *
ddebug_find_map_by_class_id(struct _ddebug_info *di, int class_id)
{
@@ -220,11 +225,11 @@ ddebug_find_map_by_class_id(struct _ddebug_info *di, int class_id)
int i;
for_subvec(i, map, di, maps)
- if (ddebug_class_in_range(class_id, map))
+ if (ddebug_class_map_in_range(class_id, map))
return map;
for_subvec(i, cli, di, users)
- if (ddebug_class_in_range(class_id, cli->map))
+ if (ddebug_class_user_in_range(class_id, cli))
return cli->map;
return NULL;
@@ -1177,12 +1182,12 @@ static const char *ddebug_class_name(struct _ddebug_info *di, struct _ddebug *dp
int i;
for_subvec(i, map, di, maps)
- if (ddebug_class_in_range(dp->class_id, map))
+ if (ddebug_class_map_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];
+ if (ddebug_class_user_in_range(dp->class_id, cli))
+ return cli->map->class_names[dp->class_id - cli->map->base - cli->offset];
return NULL;
}
--
2.51.1
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