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Message-ID: <89b27c44-5287-ab31-1fa2-46b9762da272@suse.com> Date: Tue, 28 Feb 2023 17:36:08 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.8.0 Subject: Re: [PATCH v3 4/4] xen/x86: switch x86 to use generic implemetation of bug.h Content-Language: en-US To: Oleksii Cc: Andrew Cooper , Stefano Stabellini , Gianluca Guida , =?UTF-8?Q?Roger_Pau_Monn=c3=a9?= , Wei Liu , xen-devel@lists.xenproject.org References: <38bb75b9add8655288347aa4df1394450e4e10c9.1677233393.git.oleksii.kurochko@gmail.com> <90ec98cc-e416-05c3-f507-5e4b2b7f937d@suse.com> <48e16f406cd85fea531c736f1f213038f8282613.camel@gmail.com> From: Jan Beulich In-Reply-To: <48e16f406cd85fea531c736f1f213038f8282613.camel@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-ClientProxiedBy: FR3P281CA0041.DEUP281.PROD.OUTLOOK.COM (2603:10a6:d10:4a::17) To VE1PR04MB6560.eurprd04.prod.outlook.com (2603:10a6:803:122::25) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: VE1PR04MB6560:EE_|AM8PR04MB7844:EE_ X-MS-Office365-Filtering-Correlation-Id: 8e5a8276-7916-4fbf-7997-08db19a9e61f X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; 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>>> +    int rc = __trap_to_gdb((struct cpu_user_regs *)regs, vector); >> >> I view casts in general as risky and hence preferable to avoid. >> Casting >> away const-ness is particularly problematic. I guess the least bad >> option is to drop const from the do_bug_frame()'s parameter again in >> patch 1. However, for a fatal trap (assuming that really _is_ fatal, >> i.e. execution cannot continue), not allowing register state to be >> altered makes kind of sense. So I wonder whether we couldn't push the >> casting into the gdbstub functions. But quite likely that's going to >> be too intrusive for re-work like you do here. > I am not sure that casting inside the gdbstub functions will help as > do_bug_frame() calls debugger_trap_fatal() which has define regs > without const. So it will still be compile issue as in do_bug_frame() > regs are declared as const. Well, the idea was of course to propagate const further down, to cast it away only in restricted cases. But ... > So it looks like the best one issue now will be drop const from the > do_bug_frame()... ... looks like we're in agreement then about this being the better route for the time being. Jan