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 X-Spam-Level: X-Spam-Status: No, score=-3.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8EE1CC3A5A0 for ; Mon, 20 Apr 2020 18:25:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 708E1206D9 for ; Mon, 20 Apr 2020 18:25:30 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="LJsWIQBQ" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726845AbgDTSZa (ORCPT ); Mon, 20 Apr 2020 14:25:30 -0400 Received: from us-smtp-2.mimecast.com ([205.139.110.61]:33202 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726838AbgDTSZ3 (ORCPT ); Mon, 20 Apr 2020 14:25:29 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1587407127; 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=VHKvl33Abr0fTYth11HDGBq8eZzlB7XRZhJAHr6xvHU=; b=LJsWIQBQmTK06z3btnxxkFTZ2gvL1/WrBFnk9+vpkuUfGRnpwwSS3AyjxH8feoEJK27nNu 9djSXsAQB34c1n+y210NkmgpgpV1LdPn+xtvmHb+dg1yEd3zHOe1kLqd4yHgBDxAQSF7o7 MQxMcWNDFgbtbQ+fL9fAKGm0Q4NHewU= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-290-x0b4Iy8sNiq2TcpjLUSREA-1; Mon, 20 Apr 2020 14:25:23 -0400 X-MC-Unique: x0b4Iy8sNiq2TcpjLUSREA-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 952C910753F5; Mon, 20 Apr 2020 18:25:22 +0000 (UTC) Received: from treble (ovpn-118-158.rdu2.redhat.com [10.10.118.158]) by smtp.corp.redhat.com (Postfix) with ESMTPS id C58535D9E5; Mon, 20 Apr 2020 18:25:19 +0000 (UTC) Date: Mon, 20 Apr 2020 13:25:16 -0500 From: Josh Poimboeuf To: Joe Lawrence Cc: live-patching@vger.kernel.org, linux-kernel@vger.kernel.org, Peter Zijlstra , Jessica Yu Subject: Re: [PATCH v2 2/9] livepatch: Apply vmlinux-specific KLP relocations early Message-ID: <20200420182516.6awwwbvoen62gwbr@treble> References: <83eb0be61671eab05e2d7bcd0aa848f6e20087b0.1587131959.git.jpoimboe@redhat.com> <20200420175751.GA13807@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20200420175751.GA13807@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Sender: live-patching-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: live-patching@vger.kernel.org On Mon, Apr 20, 2020 at 01:57:51PM -0400, Joe Lawrence wrote: > On Fri, Apr 17, 2020 at 09:04:27AM -0500, Josh Poimboeuf wrote: > > > > [ ... snip ... ] > > > > diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c > > index 40cfac8156fd..5fda3afc0285 100644 > > --- a/kernel/livepatch/core.c > > +++ b/kernel/livepatch/core.c > > > > [ ... snip ... ] > > > > +int klp_write_relocations(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs, > > + const char *shstrtab, const char *strtab, > > + unsigned int symndx, struct module *pmod, > > + const char *objname) > > { > > int i, cnt, ret = 0; > > - const char *objname, *secname; > > char sec_objname[MODULE_NAME_LEN]; > > Elf_Shdr *sec; > > > > - if (WARN_ON(!klp_is_object_loaded(obj))) > > - return -EINVAL; > > - > > - objname = klp_is_module(obj) ? obj->name : "vmlinux"; > > - > > /* For each klp relocation section */ > > - for (i = 1; i < pmod->klp_info->hdr.e_shnum; i++) { > > - sec = pmod->klp_info->sechdrs + i; > > - secname = pmod->klp_info->secstrings + sec->sh_name; > > + for (i = 1; i < ehdr->e_shnum; i++) { > > + sec = sechdrs + i; > > Hi Josh, minor bug: > > Note the for loop through the section headers in > klp_write_relocations(), but its calling function ... > > > [ ... snip ... ] > > > > diff --git a/kernel/module.c b/kernel/module.c > > index 646f1e2330d2..d36ea8a8c3ec 100644 > > --- a/kernel/module.c > > +++ b/kernel/module.c > > @@ -2334,11 +2334,12 @@ static int apply_relocations(struct module *mod, const struct load_info *info) > > if (!(info->sechdrs[infosec].sh_flags & SHF_ALLOC)) > > continue; > > > > - /* Livepatch relocation sections are applied by livepatch */ > > if (info->sechdrs[i].sh_flags & SHF_RELA_LIVEPATCH) > > - continue; > > - > > - if (info->sechdrs[i].sh_type == SHT_REL) > > + err = klp_write_relocations(info->hdr, info->sechdrs, > > + info->secstrings, > > + info->strtab, > > + info->index.sym, mod, NULL); > > + else if (info->sechdrs[i].sh_type == SHT_REL) > > err = apply_relocate(info->sechdrs, info->strtab, > > info->index.sym, i, mod); > > else if (info->sechdrs[i].sh_type == SHT_RELA) > > ... apply_relocations() is also iterating over the section headers (the > diff context doesn't show it here, but i is an incrementing index over > sechdrs[]). > > So if there is more than one KLP relocation section, we'll process them > multiple times. At least the x86 relocation code will detect this and > fail the module load with an invalid relocation (existing value not > zero). Ah, yes, good catch! -- Josh