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=-2.0 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 3001FFA372A for ; Wed, 16 Oct 2019 12:39:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 09AE621848 for ; Wed, 16 Oct 2019 12:39:24 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="uLYg2csW" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2393126AbfJPMjW (ORCPT ); Wed, 16 Oct 2019 08:39:22 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:55562 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726796AbfJPMjW (ORCPT ); Wed, 16 Oct 2019 08:39:22 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=pkoFAp1KGg4BJ4QfEMtMcBjJr9mldI0trPnE+09Cq5Q=; b=uLYg2csWDUnlpjPXgqJIWxLCJ 2L1Nak/OCP6JcXDxapqqd2+fAnuKHF2Kv5wQdtUjS7HCfmzD+Lo4owUp6hoEyXXTn+c/tZGDMb05o ILCg+IHO50EEypz6L4oPvZWESEga8XaxD1dqeB1GIH9YNUzdMLqOn9RMBHOarbqlggt6r68x5shkD bsav+SlPTRjVTXrGdzEdLVqaVkW/lrWk7J1Ma5olkmZRyyLzhTITKlhRke1o85sovlGQ4bRlavkO8 AlgcOBnmCWB7VZwgeCq1Ajvh97N218dlp/i9TohEPk1iiQwtfeibQIVwkhlxTT0SfbxpX5k4E5omG GRtujYMMg==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1iKia5-0000wv-9J; Wed, 16 Oct 2019 12:39:09 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 73672303C1E; Wed, 16 Oct 2019 14:38:11 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 588562042784E; Wed, 16 Oct 2019 14:39:06 +0200 (CEST) Date: Wed, 16 Oct 2019 14:39:06 +0200 From: Peter Zijlstra To: Miroslav Benes Cc: Joe Lawrence , Jessica Yu , Steven Rostedt , x86@kernel.org, linux-kernel@vger.kernel.org, mhiramat@kernel.org, bristot@redhat.com, jbaron@akamai.com, torvalds@linux-foundation.org, tglx@linutronix.de, mingo@kernel.org, namit@vmware.com, hpa@zytor.com, luto@kernel.org, ard.biesheuvel@linaro.org, jpoimboe@redhat.com, live-patching@vger.kernel.org Subject: Re: [PATCH v3 5/6] x86/ftrace: Use text_poke() Message-ID: <20191016123906.GR2328@hirez.programming.kicks-ass.net> References: <20191010091956.48fbcf42@gandalf.local.home> <20191010140513.GT2311@hirez.programming.kicks-ass.net> <20191010115449.22044b53@gandalf.local.home> <20191010172819.GS2328@hirez.programming.kicks-ass.net> <20191011125903.GN2359@hirez.programming.kicks-ass.net> <20191015130739.GA23565@linux-8ccs> <20191015135634.GK2328@hirez.programming.kicks-ass.net> <88bab814-ea24-ece9-2bc0-7a1e10a62f12@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Oct 16, 2019 at 08:51:27AM +0200, Miroslav Benes wrote: > On Tue, 15 Oct 2019, Joe Lawrence wrote: > > > On 10/15/19 10:13 AM, Miroslav Benes wrote: > > > Yes, it does. klp_module_coming() calls module_disable_ro() on all > > > patching modules which patch the coming module in order to call > > > apply_relocate_add(). New (patching) code for a module can be relocated > > > only when the relevant module is loaded. > > > > FWIW, would the LPC blue-sky2 model (ie, Steve's suggestion @ plumber's where > > livepatches only patch a single object and updates are kept on disk to handle > > coming module updates as they are loaded) eliminate those outstanding > > relocations and the need to perform this late permission flipping? > > Yes, it should, but we don't have to wait for it. PeterZ proposed a > different solution to this specific issue in > https://lore.kernel.org/lkml/20191015141111.GP2359@hirez.programming.kicks-ass.net/ > > It should not be a problem to create a live patch module like that and the > code in kernel/livepatch/ is almost ready. Something like > module_section_disable_ro(mod, section) (and similar for X protection) > should be enough. Module reloads would still require juggling with the > protections, but I think it is all feasible. Something a little like so.. completely fresh of the keyboard. --- --- a/include/linux/module.h +++ b/include/linux/module.h @@ -853,6 +853,18 @@ static inline void module_enable_ro(cons static inline void module_disable_ro(const struct module *mod) { } #endif +#if defined(CONFIG_STRICT_MODULE_RWX) && defined(CONFIG_LIVEPATCH) +extern void module_section_disable_ro(struct module *mod, const char *sec); +extern void module_section_enable_ro(struct module *mod, const char *sec); +extern void module_section_disable_x(struct module *mod, const char *sec); +extern void module_section_enable_x(struct module *mod, const char *sec); +#else +static inline void module_section_disable_ro(struct module *mod, const char *sec) { } +static inline void module_section_enable_ro(struct module *mod, const char *sec) { } +static inline void module_section_disable_x(struct module *mod, const char *sec) { } +static inline void module_section_enable_x(struct module *mod, const char *sec) { } +#endif + #ifdef CONFIG_GENERIC_BUG void module_bug_finalize(const Elf_Ehdr *, const Elf_Shdr *, struct module *); --- a/kernel/module.c +++ b/kernel/module.c @@ -2107,6 +2107,54 @@ static void free_module_elf(struct modul kfree(mod->klp_info->secstrings); kfree(mod->klp_info); } + +#ifdef CONFIG_STRICT_MODULE_RWX + +static void __frob_section(struct Elf_Shdr *sec, int (*set_memory)(unsigned long start, int num_pages)) +{ + BUG_ON((unsigned long)sec->sh_addr & (PAGE_SIZE-1)); + BUG_ON((unsigned long)sec->sh_size & (PAGE_SIZE-1)); + set_memory((unsigned long)sec->sh_addr, sec->sh_size >> PAGE_SHIFT); +} + +static void frob_section(struct module *mod, const char *section, + int (*set_memory)(unsigned long start, int num_pages)) +{ + struct klp_modinfo *info = mod->klp_info; + const char *secname; + Elf_Shdr *s; + + for (s = info->sechdrs; s < info->sechdrs + info->hdr.e_shnum; s++) { + secname = mod->klp_info->secstrings + s->sh_name; + if (strcmp(secname, section)) + continue; + + __frob_section(s, set_memory); + } +} + +void module_section_disable_ro(struct module *mod, const char *section) +{ + frob_section(mod, section, set_memory_rw); +} + +void module_section_enable_ro(struct module *mod, const char *section) +{ + frob_section(mod, section, set_memory_ro); +} + +void module_section_disable_x(struct module *mod, const char *section) +{ + frob_section(mod, section, set_memory_nx); +} + +void module_section_enable_x(struct module *mod, const char *section) +{ + frob_section(mod, section, set_memory_x); +} + +#endif /* ONFIG_STRICT_MODULE_RWX */ + #else /* !CONFIG_LIVEPATCH */ static int copy_module_elf(struct module *mod, struct load_info *info) {