Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759333AbcCDPG7 (ORCPT ); Fri, 4 Mar 2016 10:06:59 -0500 Received: from mail-wm0-f41.google.com ([74.125.82.41]:37521 "EHLO mail-wm0-f41.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759179AbcCDPGo convert rfc822-to-8bit (ORCPT ); Fri, 4 Mar 2016 10:06:44 -0500 MIME-Version: 1.0 In-Reply-To: References: <00e9fa7d4adeac2d37a42cf613837e74850d929a.1456504662.git.glider@google.com> <56D471F5.3010202@gmail.com> <56D58398.2010708@gmail.com> Date: Fri, 4 Mar 2016 16:06:42 +0100 Message-ID: Subject: Re: [PATCH v4 5/7] mm, kasan: Stackdepot implementation. Enable stackdepot for SLAB From: Alexander Potapenko To: Andrey Ryabinin Cc: Dmitry Vyukov , Andrey Konovalov , Christoph Lameter , Andrew Morton , Steven Rostedt , Joonsoo Kim , JoonSoo Kim , Kostya Serebryany , kasan-dev , LKML , "linux-mm@kvack.org" Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2889 Lines: 82 On Fri, Mar 4, 2016 at 4:01 PM, Andrey Ryabinin wrote: > 2016-03-04 17:52 GMT+03:00 Alexander Potapenko : >> On Tue, Mar 1, 2016 at 12:57 PM, Andrey Ryabinin wrote: >>> >>> >>> On 02/29/2016 08:12 PM, Dmitry Vyukov wrote: >>> >>>>>> diff --git a/lib/Makefile b/lib/Makefile >>>>>> index a7c26a4..10a4ae3 100644 >>>>>> --- a/lib/Makefile >>>>>> +++ b/lib/Makefile >>>>>> @@ -167,6 +167,13 @@ obj-$(CONFIG_SG_SPLIT) += sg_split.o >>>>>> obj-$(CONFIG_STMP_DEVICE) += stmp_device.o >>>>>> obj-$(CONFIG_IRQ_POLL) += irq_poll.o >>>>>> >>>>>> +ifeq ($(CONFIG_KASAN),y) >>>>>> +ifeq ($(CONFIG_SLAB),y) >>>>> >>>>> Just try to imagine that another subsystem wants to use stackdepot. How this gonna look like? >>>>> >>>>> We have Kconfig to describe dependencies. So, this should be under CONFIG_STACKDEPOT. >>>>> So any user of this feature can just do 'select STACKDEPOT' in Kconfig. >>>>> >>>>>> + obj-y += stackdepot.o >>>>>> + KASAN_SANITIZE_slub.o := n >>> _stackdepot.o >>> >>> >>>>> >>>>>> + >>>>>> + stack->hash = hash; >>>>>> + stack->size = size; >>>>>> + stack->handle.slabindex = depot_index; >>>>>> + stack->handle.offset = depot_offset >> STACK_ALLOC_ALIGN; >>>>>> + __memcpy(stack->entries, entries, size * sizeof(unsigned long)); >>>>> >>>>> s/__memcpy/memcpy/ >>>> >>>> memcpy should be instrumented by asan/tsan, and we would like to avoid >>>> that instrumentation here. >>> >>> KASAN_SANITIZE_* := n already takes care about this. >>> __memcpy() is a special thing solely for kasan internals and some assembly code. >>> And it's not available generally. >> As far as I can see, KASAN_SANITIZE_*:=n does not guarantee it. >> It just removes KASAN flags from GCC command line, it does not >> necessarily replace memcpy() calls with some kind of a >> non-instrumented memcpy(). >> > > With removed kasan cflags '__SANITIZE_ADDRESS__' is not defined, > hence enable the following defines from arch/x86/include/asm/string_64.h: > > #if defined(CONFIG_KASAN) && !defined(__SANITIZE_ADDRESS__) > > /* > * For files that not instrumented (e.g. mm/slub.c) we > * should use not instrumented version of mem* functions. > */ > > #undef memcpy > #define memcpy(dst, src, len) __memcpy(dst, src, len) > #define memmove(dst, src, len) __memmove(dst, src, len) > #define memset(s, c, n) __memset(s, c, n) > #endif Nice! What do you think about providing stub .c files to decouple the shared code used by KASAN runtime from the rest of kernel? (This is a completely different story though and can be done separately). -- Alexander Potapenko Software Engineer Google Germany GmbH Erika-Mann-Straße, 33 80636 München Geschäftsführer: Matthew Scott Sucherman, Paul Terence Manicle Registergericht und -nummer: Hamburg, HRB 86891 Sitz der Gesellschaft: Hamburg