mm/slab: move [__]ksize and slab_ksize() to mm/slub.c

To access SLUB's internal implementation details beyond cache flags in
ksize(), move __ksize(), ksize(), and slab_ksize() to mm/slub.c.

[vbabka@suse.cz: also make __ksize() static and move its kerneldoc to
 ksize() ]

Signed-off-by: Harry Yoo <harry.yoo@oracle.com>
Link: https://patch.msgid.link/20260113061845.159790-9-harry.yoo@oracle.com
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>

Author: hygoni

include/linux/slab.h

@@ -509,7 +509,6 @@ void * __must_check krealloc_node_align_noprof(const void *objp, size_t new_size
 void kfree(const void *objp);
 void kfree_nolock(const void *objp);
 void kfree_sensitive(const void *objp);
-size_t __ksize(const void *objp);
 
 DEFINE_FREE(kfree, void *, if (!IS_ERR_OR_NULL(_T)) kfree(_T))
 DEFINE_FREE(kfree_sensitive, void *, if (_T) kfree_sensitive(_T))

mm/slab.h

@@ -661,33 +661,6 @@ void __memcg_slab_free_hook(struct kmem_cache *s, struct slab *slab,
 
 void kvfree_rcu_cb(struct rcu_head *head);
 
-size_t __ksize(const void *objp);
-
-static inline size_t slab_ksize(const struct kmem_cache *s)
-{
-#ifdef CONFIG_SLUB_DEBUG
-	/*
-	 * Debugging requires use of the padding between object
-	 * and whatever may come after it.
-	 */
-	if (s->flags & (SLAB_RED_ZONE | SLAB_POISON))
-		return s->object_size;
-#endif
-	if (s->flags & SLAB_KASAN)
-		return s->object_size;
-	/*
-	 * If we have the need to store the freelist pointer
-	 * back there or track user information then we can
-	 * only use the space before that information.
-	 */
-	if (s->flags & (SLAB_TYPESAFE_BY_RCU | SLAB_STORE_USER))
-		return s->inuse;
-	/*
-	 * Else we can use all the padding etc for the allocation
-	 */
-	return s->size;
-}
-
 static inline unsigned int large_kmalloc_order(const struct page *page)
 {
 	return page[1].flags.f & 0xff;

mm/slab_common.c

@@ -1021,43 +1021,6 @@ void __init create_kmalloc_caches(void)
 						       0, SLAB_NO_MERGE, NULL);
 }
 
-/**
- * __ksize -- Report full size of underlying allocation
- * @object: pointer to the object
- *
- * This should only be used internally to query the true size of allocations.
- * It is not meant to be a way to discover the usable size of an allocation
- * after the fact. Instead, use kmalloc_size_roundup(). Using memory beyond
- * the originally requested allocation size may trigger KASAN, UBSAN_BOUNDS,
- * and/or FORTIFY_SOURCE.
- *
- * Return: size of the actual memory used by @object in bytes
- */
-size_t __ksize(const void *object)
-{
-	const struct page *page;
-	const struct slab *slab;
-
-	if (unlikely(object == ZERO_SIZE_PTR))
-		return 0;
-
-	page = virt_to_page(object);
-
-	if (unlikely(PageLargeKmalloc(page)))
-		return large_kmalloc_size(page);
-
-	slab = page_slab(page);
-	/* Delete this after we're sure there are no users */
-	if (WARN_ON(!slab))
-		return page_size(page);
-
-#ifdef CONFIG_SLUB_DEBUG
-	skip_orig_size_check(slab->slab_cache, object);
-#endif
-
-	return slab_ksize(slab->slab_cache);
-}
-
 gfp_t kmalloc_fix_flags(gfp_t flags)
 {
 	gfp_t invalid_mask = flags & GFP_SLAB_BUG_MASK;
@@ -1273,30 +1236,6 @@ void kfree_sensitive(const void *p)
 }
 EXPORT_SYMBOL(kfree_sensitive);
 
-size_t ksize(const void *objp)
-{
-	/*
-	 * We need to first check that the pointer to the object is valid.
-	 * The KASAN report printed from ksize() is more useful, then when
-	 * it's printed later when the behaviour could be undefined due to
-	 * a potential use-after-free or double-free.
-	 *
-	 * We use kasan_check_byte(), which is supported for the hardware
-	 * tag-based KASAN mode, unlike kasan_check_read/write().
-	 *
-	 * If the pointed to memory is invalid, we return 0 to avoid users of
-	 * ksize() writing to and potentially corrupting the memory region.
-	 *
-	 * We want to perform the check before __ksize(), to avoid potentially
-	 * crashing in __ksize() due to accessing invalid metadata.
-	 */
-	if (unlikely(ZERO_OR_NULL_PTR(objp)) || !kasan_check_byte(objp))
-		return 0;
-
-	return kfence_ksize(objp) ?: __ksize(objp);
-}
-EXPORT_SYMBOL(ksize);
-
 #ifdef CONFIG_BPF_SYSCALL
 #include <linux/btf.h>
 

mm/slub.c

@@ -7028,6 +7028,92 @@ void kmem_cache_free(struct kmem_cache *s, void *x)
 }
 EXPORT_SYMBOL(kmem_cache_free);
 
+static inline size_t slab_ksize(const struct kmem_cache *s)
+{
+#ifdef CONFIG_SLUB_DEBUG
+	/*
+	 * Debugging requires use of the padding between object
+	 * and whatever may come after it.
+	 */
+	if (s->flags & (SLAB_RED_ZONE | SLAB_POISON))
+		return s->object_size;
+#endif
+	if (s->flags & SLAB_KASAN)
+		return s->object_size;
+	/*
+	 * If we have the need to store the freelist pointer
+	 * back there or track user information then we can
+	 * only use the space before that information.
+	 */
+	if (s->flags & (SLAB_TYPESAFE_BY_RCU | SLAB_STORE_USER))
+		return s->inuse;
+	/*
+	 * Else we can use all the padding etc for the allocation
+	 */
+	return s->size;
+}
+
+static size_t __ksize(const void *object)
+{
+	const struct page *page;
+	const struct slab *slab;
+
+	if (unlikely(object == ZERO_SIZE_PTR))
+		return 0;
+
+	page = virt_to_page(object);
+
+	if (unlikely(PageLargeKmalloc(page)))
+		return large_kmalloc_size(page);
+
+	slab = page_slab(page);
+	/* Delete this after we're sure there are no users */
+	if (WARN_ON(!slab))
+		return page_size(page);
+
+#ifdef CONFIG_SLUB_DEBUG
+	skip_orig_size_check(slab->slab_cache, object);
+#endif
+
+	return slab_ksize(slab->slab_cache);
+}
+
+/**
+ * ksize -- Report full size of underlying allocation
+ * @objp: pointer to the object
+ *
+ * This should only be used internally to query the true size of allocations.
+ * It is not meant to be a way to discover the usable size of an allocation
+ * after the fact. Instead, use kmalloc_size_roundup(). Using memory beyond
+ * the originally requested allocation size may trigger KASAN, UBSAN_BOUNDS,
+ * and/or FORTIFY_SOURCE.
+ *
+ * Return: size of the actual memory used by @objp in bytes
+ */
+size_t ksize(const void *objp)
+{
+	/*
+	 * We need to first check that the pointer to the object is valid.
+	 * The KASAN report printed from ksize() is more useful, then when
+	 * it's printed later when the behaviour could be undefined due to
+	 * a potential use-after-free or double-free.
+	 *
+	 * We use kasan_check_byte(), which is supported for the hardware
+	 * tag-based KASAN mode, unlike kasan_check_read/write().
+	 *
+	 * If the pointed to memory is invalid, we return 0 to avoid users of
+	 * ksize() writing to and potentially corrupting the memory region.
+	 *
+	 * We want to perform the check before __ksize(), to avoid potentially
+	 * crashing in __ksize() due to accessing invalid metadata.
+	 */
+	if (unlikely(ZERO_OR_NULL_PTR(objp)) || !kasan_check_byte(objp))
+		return 0;
+
+	return kfence_ksize(objp) ?: __ksize(objp);
+}
+EXPORT_SYMBOL(ksize);
+
 static void free_large_kmalloc(struct page *page, void *object)
 {
 	unsigned int order = compound_order(page);