linux-kernel - [PATCH 1/3] debugobjects: Add ODEBUG_FLAG_NO

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Message-ID: <20250604220926.870760-2-longman@redhat.com>
Date: Wed,  4 Jun 2025 18:09:24 -0400
From: Waiman Long <longman@...hat.com>
To: Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Anna-Maria Behnsen <anna-maria@...utronix.de>,
	Frederic Weisbecker <frederic@...nel.org>
Cc: linux-kernel@...r.kernel.org,
	Waiman Long <longman@...hat.com>
Subject: [PATCH 1/3] debugobjects: Add ODEBUG_FLAG_NO_ALLOC to disable memory allocation

Some of the objects associated with debug_obj may be handled
in a sensitive context that allowing debug_obj pre-allocation
in debug_objects_fill_pool() may casue deadlock. Add a new flags
parameter to the debug_obj_descr structure as well as adding the new
ODEBUG_FLAG_NO_ALLOC flag to enable us to disallow memory allocation
for those types of objects.

Signed-off-by: Waiman Long <longman@...hat.com>
---
 include/linux/debugobjects.h |  6 ++++++
 lib/debugobjects.c           | 10 +++++-----
 2 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/include/linux/debugobjects.h b/include/linux/debugobjects.h
index 8b95545e7924..a058c7dba898 100644
--- a/include/linux/debugobjects.h
+++ b/include/linux/debugobjects.h
@@ -41,6 +41,7 @@ struct debug_obj {
  * struct debug_obj_descr - object type specific debug description structure
  *
  * @name:		name of the object typee
+ * @flags:		debug object flags
  * @debug_hint:		function returning address, which have associated
  *			kernel symbol, to allow identify the object
  * @is_static_object:	return true if the obj is static, otherwise return false
@@ -58,6 +59,7 @@ struct debug_obj {
  */
 struct debug_obj_descr {
 	const char		*name;
+	unsigned long		 flags;
 	void *(*debug_hint)(void *addr);
 	bool (*is_static_object)(void *addr);
 	bool (*fixup_init)(void *addr, enum debug_obj_state state);
@@ -67,6 +69,10 @@ struct debug_obj_descr {
 	bool (*fixup_assert_init)(void *addr, enum debug_obj_state state);
 };
 
+enum debug_obj_flags {
+	ODEBUG_FLAG_NO_ALLOC = 0x1,	/* Disallow debug object pre-allocation */
+};
+
 #ifdef CONFIG_DEBUG_OBJECTS
 extern void debug_object_init      (void *addr, const struct debug_obj_descr *descr);
 extern void
diff --git a/lib/debugobjects.c b/lib/debugobjects.c
index 7f50c4480a4e..52bc77b41f48 100644
--- a/lib/debugobjects.c
+++ b/lib/debugobjects.c
@@ -694,7 +694,7 @@ static struct debug_obj *lookup_object_or_alloc(void *addr, struct debug_bucket
 	return NULL;
 }
 
-static void debug_objects_fill_pool(void)
+static void debug_objects_fill_pool(bool no_alloc)
 {
 	if (!static_branch_likely(&obj_cache_enabled))
 		return;
@@ -705,7 +705,7 @@ static void debug_objects_fill_pool(void)
 	/* Try reusing objects from obj_to_free_list */
 	fill_pool_from_freelist();
 
-	if (likely(!pool_should_refill(&pool_global)))
+	if (likely(!pool_should_refill(&pool_global) || no_alloc))
 		return;
 
 	/*
@@ -734,7 +734,7 @@ __debug_object_init(void *addr, const struct debug_obj_descr *descr, int onstack
 	struct debug_bucket *db;
 	unsigned long flags;
 
-	debug_objects_fill_pool();
+	debug_objects_fill_pool(descr->flags & ODEBUG_FLAG_NO_ALLOC);
 
 	db = get_bucket((unsigned long) addr);
 
@@ -811,7 +811,7 @@ int debug_object_activate(void *addr, const struct debug_obj_descr *descr)
 	if (!debug_objects_enabled)
 		return 0;
 
-	debug_objects_fill_pool();
+	debug_objects_fill_pool(descr->flags & ODEBUG_FLAG_NO_ALLOC);
 
 	db = get_bucket((unsigned long) addr);
 
@@ -1000,7 +1000,7 @@ void debug_object_assert_init(void *addr, const struct debug_obj_descr *descr)
 	if (!debug_objects_enabled)
 		return;
 
-	debug_objects_fill_pool();
+	debug_objects_fill_pool(descr->flags & ODEBUG_FLAG_NO_ALLOC);
 
 	db = get_bucket((unsigned long) addr);
 
-- 
2.49.0