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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7AA7EC433F5 for ; Thu, 5 May 2022 10:57:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1356518AbiEELBa (ORCPT ); Thu, 5 May 2022 07:01:30 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36986 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1356365AbiEELAz (ORCPT ); Thu, 5 May 2022 07:00:55 -0400 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 852754EA0F; Thu, 5 May 2022 03:56:54 -0700 (PDT) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 5544A106F; Thu, 5 May 2022 03:56:54 -0700 (PDT) Received: from FVFF77S0Q05N.cambridge.arm.com (FVFF77S0Q05N.cambridge.arm.com [10.1.29.132]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 1F9233FA27; Thu, 5 May 2022 03:56:52 -0700 (PDT) Date: Thu, 5 May 2022 11:56:45 +0100 From: Mark Rutland To: Peter Zijlstra Cc: Chen Zhongjin , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-arch@vger.kernel.org, jthierry@redhat.com, catalin.marinas@arm.com, will@kernel.org, masahiroy@kernel.org, jpoimboe@redhat.com, ycote@redhat.com, herbert@gondor.apana.org.au, davem@davemloft.net, ardb@kernel.org, maz@kernel.org, tglx@linutronix.de, luc.vanoostenryck@gmail.com Subject: Re: [RFC PATCH v4 22/37] arm64: kernel: Skip validation of kuser32.o Message-ID: References: <20220429094355.122389-1-chenzhongjin@huawei.com> <20220429094355.122389-23-chenzhongjin@huawei.com> <20220505092448.GE2501@worktop.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220505092448.GE2501@worktop.programming.kicks-ass.net> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, May 05, 2022 at 11:24:48AM +0200, Peter Zijlstra wrote: > On Thu, May 05, 2022 at 11:36:12AM +0800, Chen Zhongjin wrote: > > Hi Peter, > > > > IIRC now the blacklist mechanisms all run on check stage, which after > > decoding, but the problem of kuser32.S happens in decoding stage. Other > > than that the assembly symbols in kuser32 is STT_NOTYPE and > > STACK_FRAME_NON_STANDARD will throw an error for this. > > > > OBJECT_FILES_NON_STANDARD works for the single file but as you said > > after LTO it's invalid. However STACK_FRAME_NON_STANDARD doesn't work > > for kuser32 case at all. > > > > Now my strategy for undecodable instructions is: show an error message > > and mark insn->ignore = true, but do not stop anything so decoding work > > can going on. > > > > To totally solve this my idea is that applying blacklist before decode. > > However for this part objtool doesn't have any insn or func info, so we > > should add a new blacklist just for this case... > > OK, so Mark explained that this is 32bit userspace (VDSO) code. > > And as such there's really no point in running objtool on it. Does all > that live in it's own section? Should it? It's placed in .rodata by a linker script: * The 32-bit vdso + kuser code is placed in .rodata, between the `vdso32_start` and `vdso32_end` symbols, as raw bytes (via .incbin). See arch/arm64/kernel/vdso32-wrap.S. * The 64-bit vdso code is placed in .rodata, between the `vdso_start` and `vdso32` symbols, as raw bytes (via .incbin). See arch/arm64/kernel/vdso-wrap.S. The objects under arch/arm64/kernel/{vdso,vdso32}/ are all userspace objects, and from userspace's PoV the existing secrtions within those objects are correct, so I don't think those should change. How does x86 deal with its vdso objects? Thanks, Mark.