mm/slab: Remove store_stackinfo()

store_stackinfo() does not seem used in actual SLAB debugging.
Potentially, it could be added to check_poison_obj() to provide more
information but this seems like an overkill due to the declining
popularity of SLAB, so just remove it instead.
Signed-off-by: Qian Cai <cai@lca.pw>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: linux-mm <linux-mm@kvack.org>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: rientjes@google.com
Cc: sean.j.christopherson@intel.com
Link: https://lkml.kernel.org/r/20190416142258.18694-1-cai@lca.pw

mm/slab.c

@@ -1467,53 +1467,17 @@ static bool is_debug_pagealloc_cache(struct kmem_cache *cachep)
 }
 
 #ifdef CONFIG_DEBUG_PAGEALLOC
-static void store_stackinfo(struct kmem_cache *cachep, unsigned long *addr,
-			    unsigned long caller)
-{
-	int size = cachep->object_size;
-
-	addr = (unsigned long *)&((char *)addr)[obj_offset(cachep)];
-
-	if (size < 5 * sizeof(unsigned long))
-		return;
-
-	*addr++ = 0x12345678;
-	*addr++ = caller;
-	*addr++ = smp_processor_id();
-	size -= 3 * sizeof(unsigned long);
-	{
-		unsigned long *sptr = &caller;
-		unsigned long svalue;
-
-		while (!kstack_end(sptr)) {
-			svalue = *sptr++;
-			if (kernel_text_address(svalue)) {
-				*addr++ = svalue;
-				size -= sizeof(unsigned long);
-				if (size <= sizeof(unsigned long))
-					break;
-			}
-		}
-
-	}
-	*addr++ = 0x87654321;
-}
-
-static void slab_kernel_map(struct kmem_cache *cachep, void *objp,
-				int map, unsigned long caller)
+static void slab_kernel_map(struct kmem_cache *cachep, void *objp, int map)
 {
 	if (!is_debug_pagealloc_cache(cachep))
 		return;
 
-	if (caller)
-		store_stackinfo(cachep, objp, caller);
-
 	kernel_map_pages(virt_to_page(objp), cachep->size / PAGE_SIZE, map);
 }
 
 #else
 static inline void slab_kernel_map(struct kmem_cache *cachep, void *objp,
-				int map, unsigned long caller) {}
+				int map) {}
 
 #endif
 
@@ -1661,7 +1625,7 @@ static void slab_destroy_debugcheck(struct kmem_cache *cachep,
 
 		if (cachep->flags & SLAB_POISON) {
 			check_poison_obj(cachep, objp);
-			slab_kernel_map(cachep, objp, 1, 0);
+			slab_kernel_map(cachep, objp, 1);
 		}
 		if (cachep->flags & SLAB_RED_ZONE) {
 			if (*dbg_redzone1(cachep, objp) != RED_INACTIVE)
@@ -2434,7 +2398,7 @@ static void cache_init_objs_debug(struct kmem_cache *cachep, struct page *page)
 		/* need to poison the objs? */
 		if (cachep->flags & SLAB_POISON) {
 			poison_obj(cachep, objp, POISON_FREE);
-			slab_kernel_map(cachep, objp, 0, 0);
+			slab_kernel_map(cachep, objp, 0);
 		}
 	}
 #endif
@@ -2813,7 +2777,7 @@ static void *cache_free_debugcheck(struct kmem_cache *cachep, void *objp,
 
 	if (cachep->flags & SLAB_POISON) {
 		poison_obj(cachep, objp, POISON_FREE);
-		slab_kernel_map(cachep, objp, 0, caller);
+		slab_kernel_map(cachep, objp, 0);
 	}
 	return objp;
 }
@@ -3077,7 +3041,7 @@ static void *cache_alloc_debugcheck_after(struct kmem_cache *cachep,
 		return objp;
 	if (cachep->flags & SLAB_POISON) {
 		check_poison_obj(cachep, objp);
-		slab_kernel_map(cachep, objp, 1, 0);
+		slab_kernel_map(cachep, objp, 1);
 		poison_obj(cachep, objp, POISON_INUSE);
 	}
 	if (cachep->flags & SLAB_STORE_USER)