[patch V4 01/32] mm/slab: Fix broken stack trace storage

[Thomas Gleixner <tglx@linutronix.de>]

kstack_end() is broken on interrupt stacks as they are not guaranteed to be
sized THREAD_SIZE and THREAD_SIZE aligned.

Use the stack tracer instead. Remove the pointless pointer increment at the
end of the function while at it.

Fixes: 98eb235b7feb ("[PATCH] page unmapping debug") - History tree
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: linux-mm@kvack.org
---
V4: Made the code simpler to understand (Andy) and make it actually compile
---
 mm/slab.c |   30 ++++++++++++++----------------
 1 file changed, 14 insertions(+), 16 deletions(-)

--- a/mm/slab.c
+++ b/mm/slab.c
@@ -1470,33 +1470,31 @@ static bool is_debug_pagealloc_cache(str
 static void store_stackinfo(struct kmem_cache *cachep, unsigned long *addr,
 			    unsigned long caller)
 {
-	int size = cachep->object_size;
+	int size = cachep->object_size / sizeof(unsigned long);
 
 	addr = (unsigned long *)&((char *)addr)[obj_offset(cachep)];
 
-	if (size < 5 * sizeof(unsigned long))
+	if (size < 5)
 		return;
 
 	*addr++ = 0x12345678;
 	*addr++ = caller;
 	*addr++ = smp_processor_id();
-	size -= 3 * sizeof(unsigned long);
+	size -= 3;
+#ifdef CONFIG_STACKTRACE
 	{
-		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;
-			}
-		}
+		struct stack_trace trace = {
+			/* Leave one for the end marker below */
+			.max_entries	= size - 1,
+			.entries	= addr,
+			.skip		= 3,
+		};
 
+		save_stack_trace(&trace);
+		addr += trace.nr_entries;
 	}
-	*addr++ = 0x87654321;
+#endif
+	*addr = 0x87654321;
 }
 
 static void slab_kernel_map(struct kmem_cache *cachep, void *objp,