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=-15.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 51C8FC433DB for ; Thu, 4 Mar 2021 07:34:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1E44164EFD for ; Thu, 4 Mar 2021 07:34:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231537AbhCDHdu (ORCPT ); Thu, 4 Mar 2021 02:33:50 -0500 Received: from pegase1.c-s.fr ([93.17.236.30]:12250 "EHLO pegase1.c-s.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230045AbhCDHdm (ORCPT ); Thu, 4 Mar 2021 02:33:42 -0500 Received: from localhost (mailhub1-int [192.168.12.234]) by localhost (Postfix) with ESMTP id 4DrjJW42bKz9v1CH; Thu, 4 Mar 2021 08:32:59 +0100 (CET) X-Virus-Scanned: Debian amavisd-new at c-s.fr Received: from pegase1.c-s.fr ([192.168.12.234]) by localhost (pegase1.c-s.fr [192.168.12.234]) (amavisd-new, port 10024) with ESMTP id Ad7PxQ5yUtUO; Thu, 4 Mar 2021 08:32:59 +0100 (CET) Received: from messagerie.si.c-s.fr (messagerie.si.c-s.fr [192.168.25.192]) by pegase1.c-s.fr (Postfix) with ESMTP id 4DrjJW2W77z9v1DM; Thu, 4 Mar 2021 08:32:59 +0100 (CET) Received: from localhost (localhost [127.0.0.1]) by messagerie.si.c-s.fr (Postfix) with ESMTP id C69468B773; Thu, 4 Mar 2021 08:33:00 +0100 (CET) X-Virus-Scanned: amavisd-new at c-s.fr Received: from messagerie.si.c-s.fr ([127.0.0.1]) by localhost (messagerie.si.c-s.fr [127.0.0.1]) (amavisd-new, port 10023) with ESMTP id iw7dwOrwWfIZ; Thu, 4 Mar 2021 08:33:00 +0100 (CET) Received: from [192.168.4.90] (unknown [192.168.4.90]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 1D9388B7F6; Thu, 4 Mar 2021 08:33:00 +0100 (CET) Subject: Re: [PATCH v3] powerpc/uprobes: Validation for prefixed instruction To: Ravi Bangoria , mpe@ellerman.id.au Cc: jniethe5@gmail.com, oleg@redhat.com, rostedt@goodmis.org, linux-kernel@vger.kernel.org, paulus@samba.org, sandipan@linux.ibm.com, naveen.n.rao@linux.ibm.com, linuxppc-dev@lists.ozlabs.org References: <20210304050529.59391-1-ravi.bangoria@linux.ibm.com> From: Christophe Leroy Message-ID: Date: Thu, 4 Mar 2021 08:32:59 +0100 User-Agent: Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.7.1 MIME-Version: 1.0 In-Reply-To: <20210304050529.59391-1-ravi.bangoria@linux.ibm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: fr Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Le 04/03/2021 à 06:05, Ravi Bangoria a écrit : > As per ISA 3.1, prefixed instruction should not cross 64-byte > boundary. So don't allow Uprobe on such prefixed instruction. > > There are two ways probed instruction is changed in mapped pages. > First, when Uprobe is activated, it searches for all the relevant > pages and replace instruction in them. In this case, if that probe > is on the 64-byte unaligned prefixed instruction, error out > directly. Second, when Uprobe is already active and user maps a > relevant page via mmap(), instruction is replaced via mmap() code > path. But because Uprobe is invalid, entire mmap() operation can > not be stopped. In this case just print an error and continue. > > Signed-off-by: Ravi Bangoria > --- > v2: https://lore.kernel.org/r/20210204104703.273429-1-ravi.bangoria@linux.ibm.com > v2->v3: > - Drop restriction for Uprobe on suffix of prefixed instruction. > It needs lot of code change including generic code but what > we get in return is not worth it. > > arch/powerpc/kernel/uprobes.c | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/arch/powerpc/kernel/uprobes.c b/arch/powerpc/kernel/uprobes.c > index e8a63713e655..c400971ebe70 100644 > --- a/arch/powerpc/kernel/uprobes.c > +++ b/arch/powerpc/kernel/uprobes.c > @@ -41,6 +41,14 @@ int arch_uprobe_analyze_insn(struct arch_uprobe *auprobe, > if (addr & 0x03) > return -EINVAL; > > + if (!IS_ENABLED(CONFIG_PPC64) || !cpu_has_feature(CPU_FTR_ARCH_31)) cpu_has_feature(CPU_FTR_ARCH_31) should return 'false' when CONFIG_PPC64 is not enabled, no need to double check. > + return 0; > + > + if (ppc_inst_prefixed(auprobe->insn) && (addr & 0x3F) == 0x3C) { Maybe 3C instead of 4F ? : (addr & 0x3C) == 0x3C What about (addr & (SZ_64 - 4)) == SZ_64 - 4 to make it more explicit ? Or ALIGN(addr, SZ_64) != ALIGN(addr + 8, SZ_64) > + pr_info_ratelimited("Cannot register a uprobe on 64 byte unaligned prefixed instruction\n"); > + return -EINVAL; > + } > + > return 0; > } > > Christophe