From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5411FC433EF for ; Wed, 16 Feb 2022 20:33:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231319AbiBPUd1 (ORCPT ); Wed, 16 Feb 2022 15:33:27 -0500 Received: from mxb-00190b01.gslb.pphosted.com ([23.128.96.19]:52198 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229832AbiBPUdX (ORCPT ); Wed, 16 Feb 2022 15:33:23 -0500 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id E3F5018E10D for ; Wed, 16 Feb 2022 12:33:10 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1645043590; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=esrjKhqDjQRh/iEBpaxk9ksIYgz7Irgaj2mX7UxyKYA=; b=SXth4u3usvEkSNfzXkJZwNffggJSjuwJCkRr3PrthipaFWKrc9nbv32QUHjrlBVKUp7PZA M2OLzN3cAJKEDagkfwo6woPR45AcLcMPe1i9nxd5dofklfDRwHVjs5gxCR9LJVg5OCWxNJ KjhTZ4kg493e8t9DkCM3/BE7RkRgkzk= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-561-Vy3cQXvAM8KFOvE-Jg-Pqw-1; Wed, 16 Feb 2022 15:33:06 -0500 X-MC-Unique: Vy3cQXvAM8KFOvE-Jg-Pqw-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 423DB1091DA0; Wed, 16 Feb 2022 20:33:01 +0000 (UTC) Received: from redhat.com (unknown [10.22.8.49]) by smtp.corp.redhat.com (Postfix) with ESMTPS id C152C12E39; Wed, 16 Feb 2022 20:32:43 +0000 (UTC) Date: Wed, 16 Feb 2022 15:32:41 -0500 From: Joe Lawrence To: Josh Poimboeuf Cc: Alexander Lobakin , =?utf-8?B?RsSBbmctcnXDrCBTw7JuZw==?= , linux-hardening@vger.kernel.org, x86@kernel.org, Borislav Petkov , Jesse Brandeburg , Kristen Carlson Accardi , Kees Cook , Miklos Szeredi , Ard Biesheuvel , Tony Luck , Bruce Schlobohm , Jessica Yu , kernel test robot , Miroslav Benes , Evgenii Shatokhin , Jonathan Corbet , Masahiro Yamada , Michal Marek , Nick Desaulniers , Herbert Xu , "David S. Miller" , Thomas Gleixner , Will Deacon , Ingo Molnar , Christoph Hellwig , Dave Hansen , "H. Peter Anvin" , Andy Lutomirski , Peter Zijlstra , Arnd Bergmann , Nathan Chancellor , Masami Hiramatsu , Marios Pomonis , Sami Tolvanen , "H.J. Lu" , Nicolas Pitre , linux-kernel@vger.kernel.org, linux-kbuild@vger.kernel.org, linux-arch@vger.kernel.org, live-patching@vger.kernel.org, llvm@lists.linux.dev Subject: Re: [PATCH v10 02/15] livepatch: avoid position-based search if `-z unique-symbol` is available Message-ID: References: <20220209185752.1226407-1-alexandr.lobakin@intel.com> <20220209185752.1226407-3-alexandr.lobakin@intel.com> <20220211174130.xxgjoqr2vidotvyw@treble> <20220211183529.q7qi2qmlyuscxyto@treble> <20220214122433.288910-1-alexandr.lobakin@intel.com> <20220214181000.xln2qgyzgswjxwcz@treble> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220214181000.xln2qgyzgswjxwcz@treble> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 Precedence: bulk List-ID: X-Mailing-List: linux-hardening@vger.kernel.org On Mon, Feb 14, 2022 at 10:10:00AM -0800, Josh Poimboeuf wrote: > On Mon, Feb 14, 2022 at 01:24:33PM +0100, Alexander Lobakin wrote: > > > One idea I mentioned before, it may be worth exploring changing the "F" > > > in FGKASLR to "File" instead of "Function". In other words, only > > > shuffle at an object-file granularity. Then, even with duplicates, the > > > symbol pair doesn't change in the symbol table. And as > > > a bonus, it should help FGKASLR i-cache performance, significantly. > > > > Yeah, I keep that in mind. However, this wouldn't solve the > > duplicate static function names problem, right? > > Let's say you have a static function f() in file1 and f() in file2, > > then the layout each boot can be > > > > .text.file1 or .text.file2 > > f() f() > > .text.file2 .text.file1 > > f() f() > > > > and position-based search won't work anyway, right? > > Right, so we'd have to abandon position-based search in favor of > file+func based search. > > It's not perfect because there are still a few file+func duplicates. > But it might be good enough. We would presumably just refuse to patch a > duplicate. Or we could remove them (and enforce their continued removal > with tooling-based warnings). > You're talking about duplicate file+func combinations as stored in the symbol table? >From a recent rhel-9 development kernel: $ readelf --wide --symbols vmlinux | \ awk '$4=="FILE" { f=$NF } $4=="OBJECT" || $4=="FUNC" { print $4 " " f "::" $NF }' | \ sort | uniq -c | sort -n | awk '$1 != 1' 2 FUNC bus.c::new_id_store 2 FUNC core.c::native_read_msr 2 FUNC core.c::type_show 2 FUNC diag.c::sk_diag_fill.constprop.0 2 FUNC hid-core.c::hid_exit 2 FUNC hid-core.c::hid_init 2 FUNC inode.c::remove_one 2 FUNC iommu.c::__list_del_entry 2 FUNC msr.c::msr_init 2 FUNC msr.c::msr_read 2 FUNC proc.c::c_next 2 FUNC proc.c::c_start 2 FUNC proc.c::c_stop 2 FUNC raw.c::copy_overflow 2 FUNC raw.c::dst_output 2 FUNC route.c::dst_discard 2 FUNC sysfs.c::name_show 2 FUNC udp.c::copy_overflow 2 FUNC udp.c::udp_lib_close 2 FUNC udp.c::udp_lib_hash 2 FUNC udp.c::udplite_getfrag 2 FUNC udplite.c::udp_lib_close 2 FUNC udplite.c::udp_lib_hash 2 FUNC udplite.c::udplite_sk_init 2 OBJECT acpi.c::__func__.0 2 OBJECT amd.c::__already_done.10 2 OBJECT amd.c::__func__.4 2 OBJECT amd.c::__func__.5 2 OBJECT bus.c::driver_attr_new_id 2 OBJECT bus.c::__func__.1 2 OBJECT bus.c::__func__.2 2 OBJECT bus.c::__func__.3 2 OBJECT bus.c::__func__.4 2 OBJECT bus.c::__func__.5 2 OBJECT bus.c::__func__.6 2 OBJECT bus.c::__func__.7 2 OBJECT bus.c::__func__.8 2 OBJECT bus.c::__func__.9 2 OBJECT cgroup.c::__func__.0 2 OBJECT class.c::__func__.0 2 OBJECT class.c::__func__.1 2 OBJECT class.c::__func__.3 2 OBJECT class.c::__func__.5 2 OBJECT class.c::__key.0 2 OBJECT class.c::__key.1 2 OBJECT class.c::__key.4 2 OBJECT core.c::__already_done.18 2 OBJECT core.c::__already_done.19 2 OBJECT core.c::__already_done.3 2 OBJECT core.c::dev_attr_size 2 OBJECT core.c::dev_attr_start 2 OBJECT core.c::dev_attr_type 2 OBJECT core.c::empty_attrs 2 OBJECT core.c::__func__.10 2 OBJECT core.c::__func__.14 2 OBJECT core.c::__func__.7 2 OBJECT core.c::__func__.9 2 OBJECT core.c::__key.0 2 OBJECT core.c::__key.2 2 OBJECT core.c::__key.3 2 OBJECT dev.c::__func__.0 2 OBJECT dir.c::__func__.3 2 OBJECT driver.c::__func__.0 2 OBJECT fib_rules.c::__msg.0 2 OBJECT file.c::__func__.2 2 OBJECT file.c::__key.1 2 OBJECT file.c::__key.2 2 OBJECT hpet.c::__func__.4 2 OBJECT icmp.c::__func__.1 2 OBJECT inode.c::__func__.1 2 OBJECT inode.c::__func__.3 2 OBJECT intel.c::__already_done.10 2 OBJECT intel.c::__already_done.11 2 OBJECT intel.c::__already_done.13 2 OBJECT ioctl.c::__func__.0 2 OBJECT iommu.c::__already_done.15 2 OBJECT iommu.c::__func__.10 2 OBJECT iommu.c::__func__.2 2 OBJECT iommu.c::_rs.13 2 OBJECT iommu.c::_rs.5 2 OBJECT iommu.c::_rs.9 2 OBJECT irq.c::__func__.0 2 OBJECT irq.c::__func__.2 2 OBJECT irqdomain.c::__func__.0 2 OBJECT irqdomain.c::__func__.1 2 OBJECT irqdomain.c::__func__.3 2 OBJECT main.c::__func__.10 2 OBJECT main.c::__func__.11 2 OBJECT main.c::__func__.3 2 OBJECT main.c::__func__.4 2 OBJECT main.c::__func__.5 2 OBJECT manage.c::__func__.1 2 OBJECT mount.c::__func__.0 2 OBJECT msr.c::__func__.0 2 OBJECT ping.c::__func__.1 2 OBJECT property.c::__func__.3 2 OBJECT qos.c::__func__.0 2 OBJECT qos.c::__func__.2 2 OBJECT resource.c::__func__.1 2 OBJECT route.c::__key.0 2 OBJECT route.c::__msg.1 2 OBJECT route.c::__msg.2 2 OBJECT route.c::__msg.3 2 OBJECT route.c::__msg.4 2 OBJECT route.c::__msg.5 2 OBJECT route.c::__msg.6 2 OBJECT swap.c::__func__.0 2 OBJECT syncookies.c::___done.1 2 OBJECT syncookies.c::msstab 2 OBJECT syncookies.c::___once_key.2 2 OBJECT sysfs.c::dev_attr_name 2 OBJECT sysfs.c::__key.1 2 OBJECT sysfs.c::power_attrs 2 OBJECT udp.c::descriptor.12 2 OBJECT udp.c::descriptor.13 2 OBJECT udp.c::__func__.2 2 OBJECT udp.c::__func__.3 2 OBJECT udp.c::__func__.4 2 OBJECT utils.c::__func__.5 3 FUNC core.c::cmask_show 3 FUNC core.c::edge_show 3 FUNC core.c::event_show 3 FUNC core.c::inv_show 3 FUNC core.c::umask_show 3 FUNC inode.c::init_once 3 OBJECT acpi.c::__func__.1 3 OBJECT core.c::format_attr_cmask 3 OBJECT core.c::format_attr_edge 3 OBJECT core.c::format_attr_event 3 OBJECT core.c::format_attr_inv 3 OBJECT core.c::format_attr_umask 3 OBJECT core.c::__func__.6 3 OBJECT core.c::__func__.8 3 OBJECT file.c::__key.3 3 OBJECT generic.c::__func__.0 3 OBJECT iommu.c::__func__.0 3 OBJECT iommu.c::__func__.1 3 OBJECT iommu.c::__func__.8 3 OBJECT main.c::__func__.0 3 OBJECT main.c::__func__.1 3 OBJECT main.c::__func__.6 3 OBJECT quirks.c::__func__.0 3 OBJECT sysfs.c::__func__.0 4 OBJECT core.c::__func__.4 5 OBJECT inode.c::tokens 6 OBJECT core.c::__func__.3 6 OBJECT core.c::__func__.5 7 OBJECT core.c::__func__.1 8 OBJECT core.c::__func__.0 8 OBJECT core.c::__func__.2 We could probably minimize the FUNC duplicates with unique names, but I'm not as optimistic about the OBJECTs as most are created via macros like __already_done.X. Unless clever macro magic? Next question: what are the odds that these entries, at least the ones we can't easily rename, need disambiguity for livepatching? or kpatch-build for related purposes? -- Joe