From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qa0-f45.google.com (mail-qa0-f45.google.com [209.85.216.45]) by kanga.kvack.org (Postfix) with ESMTP id 9779C6B0035 for ; Fri, 26 Sep 2014 13:29:56 -0400 (EDT) Received: by mail-qa0-f45.google.com with SMTP id k15so6366678qaq.4 for ; Fri, 26 Sep 2014 10:29:56 -0700 (PDT) Received: from mail-qg0-x22b.google.com (mail-qg0-x22b.google.com [2607:f8b0:400d:c04::22b]) by mx.google.com with ESMTPS id u98si6528349qge.88.2014.09.26.10.29.55 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Fri, 26 Sep 2014 10:29:55 -0700 (PDT) Received: by mail-qg0-f43.google.com with SMTP id j107so626635qga.16 for ; Fri, 26 Sep 2014 10:29:55 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: References: <1404905415-9046-1-git-send-email-a.ryabinin@samsung.com> <1411562649-28231-1-git-send-email-a.ryabinin@samsung.com> <54259BD4.8090508@oracle.com> From: Dmitry Vyukov Date: Fri, 26 Sep 2014 10:29:34 -0700 Message-ID: Subject: Re: [PATCH v3 00/13] Kernel address sanitizer - runtime memory debugger. Content-Type: text/plain; charset=UTF-8 Sender: owner-linux-mm@kvack.org List-ID: To: Andrey Ryabinin Cc: Sasha Levin , Andrey Ryabinin , LKML , Konstantin Serebryany , Dmitry Chernenkov , Andrey Konovalov , Yuri Gribov , Konstantin Khlebnikov , Michal Marek , Thomas Gleixner , Ingo Molnar , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Andrew Morton , Dave Hansen , Andi Kleen , Vegard Nossum , "H. Peter Anvin" , linux-kbuild@vger.kernel.org, x86@kernel.org, "linux-mm@kvack.org" , Randy Dunlap , Peter Zijlstra , Alexander Viro , Dave Jones On Fri, Sep 26, 2014 at 10:22 AM, Andrey Ryabinin wrote: > 2014-09-26 21:07 GMT+04:00 Dmitry Vyukov : >> On Fri, Sep 26, 2014 at 10:01 AM, Sasha Levin wrote: >>> On 09/24/2014 08:43 AM, Andrey Ryabinin wrote: >>>> Hi. >>>> >>>> This is a third iteration of kerenel address sanitizer (KASan). >>>> >>>> KASan is a runtime memory debugger designed to find use-after-free >>>> and out-of-bounds bugs. >>>> >>>> Currently KASAN supported only for x86_64 architecture and requires kernel >>>> to be build with SLUB allocator. >>>> KASAN uses compile-time instrumentation for checking every memory access, therefore you >>>> will need a fresh GCC >= v5.0.0. >>> >>> Hi Andrey, >>> >>> I tried this patchset, with the latest gcc, and I'm seeing the following: >>> >>> arch/x86/kernel/head.o: In function `_GLOBAL__sub_I_00099_0_reserve_ebda_region': >>> /home/sasha/linux-next/arch/x86/kernel/head.c:71: undefined reference to `__asan_init_v4' >>> init/built-in.o: In function `_GLOBAL__sub_I_00099_0___ksymtab_system_state': >>> /home/sasha/linux-next/init/main.c:1034: undefined reference to `__asan_init_v4' >>> init/built-in.o: In function `_GLOBAL__sub_I_00099_0_init_uts_ns': >>> /home/sasha/linux-next/init/version.c:50: undefined reference to `__asan_init_v4' >>> init/built-in.o: In function `_GLOBAL__sub_I_00099_0_root_mountflags': >>> /home/sasha/linux-next/init/do_mounts.c:638: undefined reference to `__asan_init_v4' >>> init/built-in.o: In function `_GLOBAL__sub_I_00099_0_rd_prompt': >>> /home/sasha/linux-next/init/do_mounts_rd.c:361: undefined reference to `__asan_init_v4' >>> init/built-in.o:/home/sasha/linux-next/init/do_mounts_md.c:312: more undefined references to `__asan_init_v4' follow >>> >>> >>> What am I missing? >> >> >> Emission of __asan_init_vx needs to be disabled when >> -fsanitize=kernel-address. Our kernel does not boot with them at all. >> It probably hits some limit for something that can be increased. But I >> don't want to investigate what that limit is, as __asan_init is not >> needed for kasan at all. >> > > __asan_init_vx maybe not needed for kernel, but we still need somehow > to identify > compiler's asan version (e.g. for globals). > We could add some define to GCC or just something like this in kernel: > #if __GNUC__ == 5 > #define ASAN_V4 > .... This looks good to me. The versioning won't work the same way it works for clang/compiler-rt and gcc/libgcc. Because clang/compiler-rt are both part of the same repo and always versioned simultaneously. While kernel and gcc are versioned independently, so once you bump API version you break all users who use old gcc. So in kernel we will need to support all API versions, and the following looks like a much simpler way to identify current API version: > #if __GNUC__ == 5 > #define ASAN_V4 Note that in user-space asan the other important purpose of __asan_init is to trigger asan runtime initialization as early as possible. This is not needed for kernel. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org