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=-2.2 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,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 02C10C433DF for ; Thu, 28 May 2020 09:42:05 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id B361620B80 for ; Thu, 28 May 2020 09:42:04 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="sg4iFrHy" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B361620B80 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject: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=MNDdTbaXUsSPEgDV5mwMOR2E5spfMBILIVdSR2EHgAM=; b=sg4iFrHymZEB/0 0UfrmR0uIA/P5yMkKfTuY8rrMDiHZWGEUU/YKWwDNCwKVZnV0jbzUmJaWpTuQHxaWgIMrR4pn5Fyu Q0BNmZAsr44lT3HuKBC9oF8dvIjj8JwCNPBJZ8TktqpcCDdXNSX+gkLsYVwgoZdyiyOFUkHD7VN7+ UpjsceEggcTxDaAVe9zzFEJ7Jz81uVfv9vqVYsOcadGHNaTlA3qJrg0bG5wfyajf76bvzIcfRpy/4 zh7dlPzXkRGWmj2vqjOq9veZbvil3dcdnFXQx6uqidCrP+1gqsx/RJaV1ZbKrkx/wS/PNqwQj+BYS ODQYl4NWKF/W66ZXapNQ==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jeF35-0000qN-J8; Thu, 28 May 2020 09:42:03 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jeF31-0000pN-P5 for linux-arm-kernel@lists.infradead.org; Thu, 28 May 2020 09:42:01 +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 B72C9D6E; Thu, 28 May 2020 02:41:58 -0700 (PDT) Received: from gaia (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 7DABC3F6C4; Thu, 28 May 2020 02:41:56 -0700 (PDT) Date: Thu, 28 May 2020 10:41:54 +0100 From: Catalin Marinas To: Peter Smith Subject: Re: [PATCH] arm64: vdso32: force vdso32 to be compiled as -marm Message-ID: <20200528094154.GB2961@gaia> References: <20200526173117.155339-1-ndesaulniers@google.com> <2f58c2a4-0f37-d507-7767-00161c6b5d98@arm.com> <34f261f7-c4b5-a628-9a4c-eb97b75fba52@arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200528_024159_856997_0C324E23 X-CRM114-Status: GOOD ( 11.67 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Naohiro Aota , Stephen Boyd , Arnd Bergmann , Will Deacon , Masahiro Yamada , Nick Desaulniers , LKML , "david.spickett@linaro.org" , Manoj Gupta , Kristof Beyls , Luis Lozano , Nathan Chancellor , Vincenzo Frascino , Robin Murphy , Victor Campos , Linux ARM Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thu, May 28, 2020 at 09:05:08AM +0100, Peter Smith wrote: > I suggest using Arm if you need a frame pointer, and disable the > frame pointer if you want/need to use Thumb. My understanding is that > runtime unwinding using the frame pointer in Thumb is already difficult > due to Arm and Thumb functions using different registers for the frame > pointer. IIRC from the Thumb-2 kernel porting days, even in the absence of ARM/Thumb interworking, the Thumb-2 frame pointer was pretty useless for unwinding since it points to the bottom of the current stack frame (the reason I think is that some LDR/STR instructions with negative indexing are not available). So finding the previous frame pointer was not possible and had to rely on the exception unwinding information. -- Catalin _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel