linux-kernel - [patch V5 01/32] mm/slab: Remove broken stack trace storage

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Date:   Tue, 16 Apr 2019 16:10:25 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Vlastimil Babka <vbabka@...e.cz>
cc:     Andy Lutomirski <luto@...nel.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>, X86 ML <x86@...nel.org>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Pekka Enberg <penberg@...nel.org>,
        Linux-MM <linux-mm@...ck.org>,
        David Rientjes <rientjes@...gle.com>
Subject: [patch V5 01/32] mm/slab: Remove broken stack trace storage

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

As SLAB seems not to be used much with debugging enabled and might just go
away completely according to:

  https://lkml.kernel.org/r/612f9b99-a75b-6aeb-cf92-7dc5421cd950@suse.cz

just remove the bogus code instead of trying to fix it.

Fixes: 98eb235b7feb ("[PATCH] page unmapping debug") - History tree
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Pekka Enberg <penberg@...nel.org>
Cc: linux-mm@...ck.org
---
V5: Remove the cruft.
V4: Make it actually work
V2: Made the code simpler to understand (Andy)
---
 mm/slab.c |   22 +++-------------------
 1 file changed, 3 insertions(+), 19 deletions(-)

--- a/mm/slab.c
+++ b/mm/slab.c
@@ -1470,33 +1470,17 @@ 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 < 4)
 		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;
+	*addr = 0x87654321;
 }
 
 static void slab_kernel_map(struct kmem_cache *cachep, void *objp,