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 16BA6C433F5 for ; Mon, 3 Jan 2022 13:46:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233208AbiACNo7 (ORCPT ); Mon, 3 Jan 2022 08:44:59 -0500 Received: from smtp-out2.suse.de ([195.135.220.29]:38308 "EHLO smtp-out2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229992AbiACNo6 (ORCPT ); Mon, 3 Jan 2022 08:44:58 -0500 Received: from relay2.suse.de (relay2.suse.de [149.44.160.134]) by smtp-out2.suse.de (Postfix) with ESMTP id 9DB211F38B; Mon, 3 Jan 2022 13:44:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1641217496; h=from:from:reply-to: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=fTJ1dFgK+e5nEjMCy1hx4JFFE95pm729J/0lTIXNYPQ=; b=mj/DmFRpnAQn6IsHlOFXXObU9OcYXvK0jsyh+ZGcLL1aRwhrlgcwlyqpLesy26E7TcXv2r C2FsSdeaVOAAG0b+6tEscjs264JEFqMhWjZu7GVZsBpjyOwQWx25m9Dc2eOAFtYFG/uLFO GUGIzHt3y/sAqQ9s1xoPs9kLRHm0Fyc= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1641217496; h=from:from:reply-to: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=fTJ1dFgK+e5nEjMCy1hx4JFFE95pm729J/0lTIXNYPQ=; b=d/FL6e2yBkq7hBqztokwqPKphOccyHc7hm6myfbJoGFBNUPn0kCU/krfro7FkpPomzr8nD QZ5nL5sD+G3EvJBA== Received: from pobox.suse.cz (pobox.suse.cz [10.100.2.14]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by relay2.suse.de (Postfix) with ESMTPS id 3E6D3A3B8D; Mon, 3 Jan 2022 13:44:54 +0000 (UTC) Date: Mon, 3 Jan 2022 14:44:09 +0100 (CET) From: Miroslav Benes To: Alexander Lobakin cc: linux-hardening@vger.kernel.org, x86@kernel.org, Jesse Brandeburg , Kristen Carlson Accardi , Kees Cook , Miklos Szeredi , Ard Biesheuvel , Tony Luck , Bruce Schlobohm , Jessica Yu , kernel test robot , Evgenii Shatokhin , Jonathan Corbet , Masahiro Yamada , Michal Marek , Nick Desaulniers , Herbert Xu , "David S. Miller" , Thomas Gleixner , Will Deacon , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , Andy Lutomirski , Peter Zijlstra , Arnd Bergmann , Josh Poimboeuf , 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 v9 02/15] livepatch: use `-z unique-symbol` if available to nuke pos-based search In-Reply-To: <20211223002209.1092165-3-alexandr.lobakin@intel.com> Message-ID: References: <20211223002209.1092165-1-alexandr.lobakin@intel.com> <20211223002209.1092165-3-alexandr.lobakin@intel.com> User-Agent: Alpine 2.21 (LSU 202 2017-01-01) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > --- a/kernel/livepatch/core.c > +++ b/kernel/livepatch/core.c > @@ -143,11 +143,13 @@ static int klp_find_callback(void *data, const char *name, > args->count++; > > /* > - * Finish the search when the symbol is found for the desired position > - * or the position is not defined for a non-unique symbol. > + * Finish the search when unique symbol names are enabled > + * or the symbol is found for the desired position or the > + * position is not defined for a non-unique symbol. > */ > - if ((args->pos && (args->count == args->pos)) || > - (!args->pos && (args->count > 1))) > + if (IS_ENABLED(CONFIG_LD_HAS_Z_UNIQUE_SYMBOL) || > + (args->pos && args->count == args->pos) || > + (!args->pos && args->count > 1)) > return 1; > > return 0; > @@ -171,17 +173,21 @@ static int klp_find_object_symbol(const char *objname, const char *name, > > /* > * Ensure an address was found. If sympos is 0, ensure symbol is unique; > - * otherwise ensure the symbol position count matches sympos. > + * otherwise ensure the symbol position count matches sympos. If the LD > + * `-z unique` flag is enabled, sympos checks are not relevant. > */ > - if (args.addr == 0) > + if (args.addr == 0) { > pr_err("symbol '%s' not found in symbol table\n", name); > - else if (args.count > 1 && sympos == 0) { > + } else if (IS_ENABLED(CONFIG_LD_HAS_Z_UNIQUE_SYMBOL)) { > + goto out_ok; > + } else if (args.count > 1 && sympos == 0) { > pr_err("unresolvable ambiguity for symbol '%s' in object '%s'\n", > name, objname); > } else if (sympos != args.count && sympos > 0) { > pr_err("symbol position %lu for symbol '%s' in object '%s' not found\n", > sympos, name, objname ? objname : "vmlinux"); > } else { > +out_ok: > *addr = args.addr; > return 0; > } I think it would be better to return to something like if (IS_ENABLED(CONFIG_LD_HAS_Z_UNIQUE_SYMBOL)) sympos = 0; in klp_find_object_symbol() just after kallsyms search is performed. You would not need the above changes at all. I did not like it before when sympos clearing was proposed, but the situation was different back then. '-z unique-symbol' was not available. It has changed and we have a guarantee that symbols are unique now. There would not be any impact on the user. What do you think? Miroslav