Commit 239d6c96 authored by Suren Baghdasaryan's avatar Suren Baghdasaryan Committed by Andrew Morton
Browse files

codetag: debug: skip objext checking when it's for objext itself 

objext objects are created with __GFP_NO_OBJ_EXT flag and therefore have
no corresponding objext themselves (otherwise we would get an infinite
recursion). When freeing these objects their codetag will be empty and
when CONFIG_MEM_ALLOC_PROFILING_DEBUG is enabled this will lead to false
warnings. Introduce CODETAG_EMPTY special codetag value to mark
allocations which intentionally lack codetag to avoid these warnings.
Set objext codetags to CODETAG_EMPTY before freeing to indicate that
the codetag is expected to be empty.

Link: https://lkml.kernel.org/r/20240321163705.3067592-34-surenb@google.com


Signed-off-by: default avatarSuren Baghdasaryan <surenb@google.com>
Tested-by: default avatarKees Cook <keescook@chromium.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Alex Gaynor <alex.gaynor@gmail.com>
Cc: Alice Ryhl <aliceryhl@google.com>
Cc: Andreas Hindborg <a.hindborg@samsung.com>
Cc: Benno Lossin <benno.lossin@proton.me>
Cc: "Björn Roy Baron" <bjorn3_gh@protonmail.com>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Dennis Zhou <dennis@kernel.org>
Cc: Gary Guo <gary@garyguo.net>
Cc: Kent Overstreet <kent.overstreet@linux.dev>
Cc: Miguel Ojeda <ojeda@kernel.org>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Wedson Almeida Filho <wedsonaf@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 1438d349

include/linux/alloc_tag.h

+26 −0
Original line number Diff line number Diff line
@@ -29,6 +29,27 @@ struct alloc_tag { 
	struct alloc_tag_counters __percpu	*counters;

} __aligned(8);



#ifdef CONFIG_MEM_ALLOC_PROFILING_DEBUG



#define CODETAG_EMPTY	((void *)1)



static inline bool is_codetag_empty(union codetag_ref *ref)

{

	return ref->ct == CODETAG_EMPTY;

}



static inline void set_codetag_empty(union codetag_ref *ref)

{

	if (ref)

		ref->ct = CODETAG_EMPTY;

}



#else /* CONFIG_MEM_ALLOC_PROFILING_DEBUG */



static inline bool is_codetag_empty(union codetag_ref *ref) { return false; }



#endif /* CONFIG_MEM_ALLOC_PROFILING_DEBUG */



#ifdef CONFIG_MEM_ALLOC_PROFILING



struct codetag_bytes {
@@ -151,6 +172,11 @@ static inline void alloc_tag_sub(union codetag_ref *ref, size_t bytes) 
	if (!ref || !ref->ct)

		return;



	if (is_codetag_empty(ref)) {

		ref->ct = NULL;

		return;

	}



	tag = ct_to_alloc_tag(ref->ct);



	this_cpu_sub(tag->counters->bytes, bytes);

mm/slub.c

+33 −0
Original line number Diff line number Diff line
@@ -1873,6 +1873,30 @@ static inline enum node_stat_item cache_vmstat_idx(struct kmem_cache *s) 


#ifdef CONFIG_SLAB_OBJ_EXT



#ifdef CONFIG_MEM_ALLOC_PROFILING_DEBUG



static inline void mark_objexts_empty(struct slabobj_ext *obj_exts)

{

	struct slabobj_ext *slab_exts;

	struct slab *obj_exts_slab;



	obj_exts_slab = virt_to_slab(obj_exts);

	slab_exts = slab_obj_exts(obj_exts_slab);

	if (slab_exts) {

		unsigned int offs = obj_to_index(obj_exts_slab->slab_cache,

						 obj_exts_slab, obj_exts);

		/* codetag should be NULL */

		WARN_ON(slab_exts[offs].ref.ct);

		set_codetag_empty(&slab_exts[offs].ref);

	}

}



#else /* CONFIG_MEM_ALLOC_PROFILING_DEBUG */



static inline void mark_objexts_empty(struct slabobj_ext *obj_exts) {}



#endif /* CONFIG_MEM_ALLOC_PROFILING_DEBUG */



/*

 * The allocated objcg pointers array is not accounted directly.

 * Moreover, it should not come from DMA buffer and is not readily
@@ -1913,6 +1937,7 @@ static int alloc_slab_obj_exts(struct slab *slab, struct kmem_cache *s, 
		 * assign slabobj_exts in parallel. In this case the existing

		 * objcg vector should be reused.

		 */

		mark_objexts_empty(vec);

		kfree(vec);

		return 0;

	}
@@ -1929,6 +1954,14 @@ static inline void free_slab_obj_exts(struct slab *slab) 
	if (!obj_exts)

		return;



	/*

	 * obj_exts was created with __GFP_NO_OBJ_EXT flag, therefore its

	 * corresponding extension will be NULL. alloc_tag_sub() will throw a

	 * warning if slab has extensions but the extension of an object is

	 * NULL, therefore replace NULL with CODETAG_EMPTY to indicate that

	 * the extension for obj_exts is expected to be NULL.

	 */

	mark_objexts_empty(obj_exts);

	kfree(obj_exts);

	slab->obj_exts = 0;

}