mm, kfence: support kmem_dump_obj() for KFENCE objects

Calling kmem_obj_info() via kmem_dump_obj() on KFENCE objects has been
producing garbage data due to the object not actually being maintained
by SLAB or SLUB.

Fix this by implementing __kfence_obj_info() that copies relevant
information to struct kmem_obj_info when the object was allocated by
KFENCE; this is called by a common kmem_obj_info(), which also calls the
slab/slub/slob specific variant now called __kmem_obj_info().

For completeness, kmem_dump_obj() now displays if the object was
allocated by KFENCE.

Link: https://lore.kernel.org/all/20220323090520.GG16885@xsang-OptiPlex-9020/
Link: https://lkml.kernel.org/r/20220406131558.3558585-1-elver@google.com
Fixes: b89fb5ef0ce6 ("mm, kfence: insert KFENCE hooks for SLUB")
Fixes: d3fb45f370d9 ("mm, kfence: insert KFENCE hooks for SLAB")
Signed-off-by: Marco Elver <elver@google.com>
Reviewed-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Reported-by: kernel test robot <oliver.sang@intel.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>	[slab]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 0 insertions, 21 deletions

diff --git a/mm/kfence/core.c b/mm/kfence/core.c
index a203747ad2c0..9b2b5f56f4ae 100644
--- a/mm/kfence/core.c
+++ b/mm/kfence/core.c
@@ -231,27 +231,6 @@ static bool kfence_unprotect(unsigned long addr)
 	return !KFENCE_WARN_ON(!kfence_protect_page(ALIGN_DOWN(addr, PAGE_SIZE), false));
 }
 
-static inline struct kfence_metadata *addr_to_metadata(unsigned long addr)
-{
-	long index;
-
-	/* The checks do not affect performance; only called from slow-paths. */
-
-	if (!is_kfence_address((void *)addr))
-		return NULL;
-
-	/*
-	 * May be an invalid index if called with an address at the edge of
-	 * __kfence_pool, in which case we would report an "invalid access"
-	 * error.
-	 */
-	index = (addr - (unsigned long)__kfence_pool) / (PAGE_SIZE * 2) - 1;
-	if (index < 0 || index >= CONFIG_KFENCE_NUM_OBJECTS)
-		return NULL;
-
-	return &kfence_metadata[index];
-}
-
 static inline unsigned long metadata_to_pageaddr(const struct kfence_metadata *meta)
 {
 	unsigned long offset = (meta - kfence_metadata + 1) * PAGE_SIZE * 2;