From patchwork Thu May 9 14:38:56 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Joe Lawrence X-Patchwork-Id: 10937249 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id A22B91515 for ; Thu, 9 May 2019 14:39:38 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 923F2287E0 for ; Thu, 9 May 2019 14:39:38 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 868F328A29; Thu, 9 May 2019 14:39:38 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id E1A3428A19 for ; Thu, 9 May 2019 14:39:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726895AbfEIOjQ (ORCPT ); Thu, 9 May 2019 10:39:16 -0400 Received: from mx1.redhat.com ([209.132.183.28]:55064 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726787AbfEIOjO (ORCPT ); Thu, 9 May 2019 10:39:14 -0400 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 mx1.redhat.com (Postfix) with ESMTPS id 24BD7308219E; Thu, 9 May 2019 14:39:14 +0000 (UTC) Received: from jlaw-desktop.redhat.com (ovpn-123-90.rdu2.redhat.com [10.10.123.90]) by smtp.corp.redhat.com (Postfix) with ESMTP id 629C617AEA; Thu, 9 May 2019 14:39:13 +0000 (UTC) From: Joe Lawrence To: linux-kernel@vger.kernel.org, live-patching@vger.kernel.org, linux-kbuild@vger.kernel.org Subject: [PATCH v4 07/10] livepatch: Add sample livepatch module Date: Thu, 9 May 2019 10:38:56 -0400 Message-Id: <20190509143859.9050-8-joe.lawrence@redhat.com> In-Reply-To: <20190509143859.9050-1-joe.lawrence@redhat.com> References: <20190509143859.9050-1-joe.lawrence@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.47]); Thu, 09 May 2019 14:39:14 +0000 (UTC) Sender: linux-kbuild-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kbuild@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP From: Josh Poimboeuf Add a new livepatch sample in samples/livepatch/ to make use of symbols that must be post-processed to enable load-time relocation resolution. As the new sample is to be used as an example, it is annotated with KLP_MODULE_RELOC and with KLP_SYMPOS macros. The livepatch sample updates the function cmdline_proc_show to print the string referenced by the symbol saved_command_line appended by the string "livepatch=1". Update livepatch-sample.c to remove livepatch MODULE_INFO statement. Signed-off-by: Josh Poimboeuf Signed-off-by: Joao Moreira Signed-off-by: Joe Lawrence --- samples/livepatch/Makefile | 2 + .../livepatch/livepatch-annotated-sample.c | 102 ++++++++++++++++++ 2 files changed, 104 insertions(+) create mode 100644 samples/livepatch/livepatch-annotated-sample.c diff --git a/samples/livepatch/Makefile b/samples/livepatch/Makefile index 514c8156f979..1a92d6b58f33 100644 --- a/samples/livepatch/Makefile +++ b/samples/livepatch/Makefile @@ -2,6 +2,7 @@ LIVEPATCH_livepatch-sample := y LIVEPATCH_livepatch-shadow-fix1 := y LIVEPATCH_livepatch-shadow-fix2 := y LIVEPATCH_livepatch-callbacks-demo := y +LIVEPATCH_livepatch-annotated-sample := y obj-$(CONFIG_SAMPLE_LIVEPATCH) += livepatch-sample.o obj-$(CONFIG_SAMPLE_LIVEPATCH) += livepatch-shadow-mod.o obj-$(CONFIG_SAMPLE_LIVEPATCH) += livepatch-shadow-fix1.o @@ -9,3 +10,4 @@ obj-$(CONFIG_SAMPLE_LIVEPATCH) += livepatch-shadow-fix2.o obj-$(CONFIG_SAMPLE_LIVEPATCH) += livepatch-callbacks-demo.o obj-$(CONFIG_SAMPLE_LIVEPATCH) += livepatch-callbacks-mod.o obj-$(CONFIG_SAMPLE_LIVEPATCH) += livepatch-callbacks-busymod.o +obj-$(CONFIG_SAMPLE_LIVEPATCH) += livepatch-annotated-sample.o diff --git a/samples/livepatch/livepatch-annotated-sample.c b/samples/livepatch/livepatch-annotated-sample.c new file mode 100644 index 000000000000..556ce7e0bdab --- /dev/null +++ b/samples/livepatch/livepatch-annotated-sample.c @@ -0,0 +1,102 @@ +/* + * livepatch-annotated-sample.c - Kernel Live Patching Sample Module + * + * Copyright (C) 2014 Seth Jennings + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License + * as published by the Free Software Foundation; either version 2 + * of the License, or (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, see . + */ + +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt + +#include +#include +#include + +/* + * This (dumb) live patch overrides the function that prints the + * kernel boot cmdline when /proc/cmdline is read. + * + * This livepatch uses the symbol saved_command_line whose relocation + * must be resolved during load time. To enable that, this module + * must be post-processed by a tool called klp-convert, which embeds + * information to be used by the loader to solve the relocation. + * + * The module is annotated with KLP_MODULE_RELOC/KLP_SYMPOS macros. + * These annotations are used by klp-convert to infer that the symbol + * saved_command_line is in the object vmlinux. + * + * As saved_command_line has no other homonimous symbol across + * kernel objects, this annotation is not a requirement, and can be + * suppressed with no harm to klp-convert. Yet, it is kept here as an + * example on how to annotate livepatch modules that contain symbols + * whose names are used in more than one kernel object. + * + * Example: + * + * $ cat /proc/cmdline + * + * + * $ insmod livepatch-sample.ko + * $ cat /proc/cmdline + * livepatch=1 + * + * $ echo 0 > /sys/kernel/livepatch/livepatch_sample/enabled + * $ cat /proc/cmdline + * + */ + +extern char *saved_command_line; + +#include +static int livepatch_cmdline_proc_show(struct seq_file *m, void *v) +{ + seq_printf(m, "%s livepatch=1\n", saved_command_line); + return 0; +} + +KLP_MODULE_RELOC(vmlinux) vmlinux_relocs[] = { + KLP_SYMPOS(saved_command_line, 0) +}; + +static struct klp_func funcs[] = { + { + .old_name = "cmdline_proc_show", + .new_func = livepatch_cmdline_proc_show, + }, { } +}; + +static struct klp_object objs[] = { + { + /* name being NULL means vmlinux */ + .funcs = funcs, + }, { } +}; + +static struct klp_patch patch = { + .mod = THIS_MODULE, + .objs = objs, +}; + +static int livepatch_init(void) +{ + return klp_enable_patch(&patch); +} + +static void livepatch_exit(void) +{ +} + +module_init(livepatch_init); +module_exit(livepatch_exit); +MODULE_LICENSE("GPL");