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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id B7F88C433F5 for ; Fri, 6 May 2022 10:08:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=6Ze6nU4r5rwuyqTzgxlIYA2oqJr9XWrqM01xZwP4uBA=; b=z3CNp19xEuny8t JBT4rNYcTXmJdRMRXzNRT3uF67QiM1kwRnLEpG110U1AstB29zXEsPCNMaou4SGcg3/UDITdEV4UD Hecj4KYgs9+wHy06P6vzfqNODDr13AeWaq/wI9JOlbaLnkqQxRvEDSxZK+UrMPqaTAO/78G0iBVMY hMHxm5wYnHEJ0a3SyPLd4YrI29s5Xqt3Yynl8ITvTWL5GeVI4oPFhHpXvdAmR91DmzP5jNgU4WZC8 jgE23SzG60hvjdg2asBcmd4RF15UIoH5Nonr9DRtbX/9i4h4wj9vxsLoFSoWjd1sDNxjVsu/pPhJE LCLzrKpUH0Cje8S061ag==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1nmurW-002cf5-OX; Fri, 06 May 2022 10:07:02 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1nmurT-002cdy-Fa for linux-arm-kernel@lists.infradead.org; Fri, 06 May 2022 10:07:01 +0000 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 F384C14BF; Fri, 6 May 2022 03:06:57 -0700 (PDT) Received: from FVFF77S0Q05N (unknown [10.57.65.197]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 583A13FA31; Fri, 6 May 2022 03:06:55 -0700 (PDT) Date: Fri, 6 May 2022 11:06:51 +0100 From: Mark Rutland To: Chen Zhongjin Cc: Peter Zijlstra , 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> <51ce37b5-f527-9743-36d3-50247cb0939f@huawei.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <51ce37b5-f527-9743-36d3-50247cb0939f@huawei.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220506_030659_653518_ABC0725D X-CRM114-Status: GOOD ( 24.95 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, May 06, 2022 at 10:18:10AM +0800, Chen Zhongjin wrote: > On 2022/5/5 18:56, Mark Rutland wrote: > > 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. > > . > > However for my build kuser32.o content is in .text We should be able to move that into .rodata; it's never executed in kernel context. > and there is only `vdso` symbol in .rodata without `vdso32`. That means you're not building with CROSS_COMPILE_COMPAT, and so we can't build the 32-bit VDSO. > And for defconfig the CONFIG_KUSER_HELPERS=y is on. Yes. > According to your description, it seems something wrong here? Sorry, I was wrong about how we linked the kuser32 code. I believe we can move that into .rodata by adding: .section .rodata ... to the start of that. I think that'd be a nice cleanup to do regardless of objtool. Thanks, Mark. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel