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Message-ID: Date: Tue, 27 Sep 2022 17:21:48 +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: =?UTF-8?Q?Roger_Pau_Monn=c3=a9?= Cc: "xen-devel@lists.xenproject.org" , Andrew Cooper , Wei Liu , Julien Grall , Stefano Stabellini , Volodymyr Babchuk , Bertrand Marquis , Anthony Perard References: From: Jan Beulich In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-ClientProxiedBy: AS9PR06CA0175.eurprd06.prod.outlook.com (2603:10a6:20b:45c::25) To VE1PR04MB6560.eurprd04.prod.outlook.com (2603:10a6:803:122::25) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: VE1PR04MB6560:EE_|PAXPR04MB9665:EE_ X-MS-Office365-Filtering-Correlation-Id: e558ed5a-ac12-4d6b-3419-08daa09c0033 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:VE1PR04MB6560.eurprd04.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230022)(366004)(136003)(396003)(376002)(346002)(39860400002)(451199015)(83380400001)(6486002)(2616005)(86362001)(31696002)(186003)(38100700002)(6666004)(8936002)(316002)(66556008)(2906002)(4326008)(5660300002)(66476007)(41300700001)(66946007)(54906003)(8676002)(478600001)(6512007)(6506007)(6916009)(26005)(53546011)(31686004)(36756003)(45980500001)(43740500002);DIR:OUT;SFP:1101; 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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. >> >> A separate linking step doesn't mean this needs doing via $(LD) - it >> could also be done via $(CC). There's also no connection between using >> a separate linking step and using a linker script - aiui the linker >> script could also be handed to $(CC) for it to pass on the option to >> the linker. > > There's one thing that puzzles me, if we already pass -fno-pie for > code generation, do we also need the -no-pie linker option explicitly > added? I would expect the compiler to be clever enough to > automatically pass -no-pie to the linker if -fno-pie is used, > otherwise the code won't be correctly linked? For -pie gcc doc states: "For predictable results, you must also specify the same set of options used for compilation (‘-fpie’, ‘-fPIE’, or model suboptions) when you specify this linker option." I infer there's no deriving along the lines of what you suggest. I'm also unconvinced of there necessarily being issues with correct linking. I can see there being executables where mismatched options simply don't matter. > I would rather prefer to remove the -no-pie option from > EMBEDDED_EXTRA_CFLAGS and just add a note that users wanting to > link-in-place need to review the set of options used. Which then raises the question why it was added there (in a mis-spelled manner) in the first place, years ago. That uncertainty was the only reason why in the earlier change I didn't go and remove the option altogether. Jan