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Message-ID: <9b3f635f-9fff-2649-ca1c-01a52b1b8ead@suse.com> Date: Tue, 27 Sep 2022 16:34:06 +0200 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.3.0 Subject: Re: [PATCH] zap linking-only option from EMBEDDED_EXTRA_CFLAGS Content-Language: en-US To: Andrew Cooper Cc: "xen-devel@lists.xenproject.org" , Wei Liu , Julien Grall , Stefano Stabellini , Volodymyr Babchuk , Bertrand Marquis , Anthony Perard , Roger Pau Monne References: <7eab9645-0c7e-e171-870b-814c330fac08@citrix.com> From: Jan Beulich In-Reply-To: <7eab9645-0c7e-e171-870b-814c330fac08@citrix.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-ClientProxiedBy: FR3P281CA0108.DEUP281.PROD.OUTLOOK.COM (2603:10a6:d10:a3::11) To VE1PR04MB6560.eurprd04.prod.outlook.com (2603:10a6:803:122::25) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: VE1PR04MB6560:EE_|DB9PR04MB8219:EE_ X-MS-Office365-Filtering-Correlation-Id: 36e75ef4-7b9f-45c4-04b5-08daa095555f X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; 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(Oddly enough at >>> least older Clang versions complain about the use of '-nopie' now that >>> we actually use '-no-pie'.) Filter out the problematic option in all >>> cases where the variable is consumed for compilation only (which right >>> now is everywhere). >>> >>> Fixes: ecd6b9759919 ("Config.mk: correct PIE-related option(s) in EMBEDDED_EXTRA_CFLAGS") >>> Reported-by: Stefano Stabellini >>> Signed-off-by: Jan Beulich >>> --- >>> Arguably with all users of EMBEDDED_EXTRA_CFLAGS using these just for >>> compiling, the option could be omitted from that variable right away. >>> But if any compile-and-link-in-one-go use appeared, there would be an >>> issue. >> Is it feasible to have compile-and-link-in-one-go in one use feasible >> with what we consider embedded (firmware or kernel like binaries). I >> would expect those to always require a linker script and a separate >> linking step. > > As I've expressed several times previously, the entire variable is bogus. > > Just because we do have several things which are built as > non-freestanding, doesn't mean they share a common CLFLAGS environment. > > PIE is very specific to the intended use, and blindly disabling the > stack protector isn't safe either.  It only works because none of our > freestanding environments have gone to the effort of adding stack > protector support. > > -fno-exceptions is furthermore bogus in CLFLAGS, as its a CXXFLAG only. > > And no, this mess can't plausibly be used for a compile and link in one > go.  Filtering out a non-CFLAG from the collection at every call site is > nonsense. So what do you suggest we do in the short term? Jan