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Wysocki" , Len Brown , Pavel Machek References: <5017a6c5-55fa-0767-b1ed-2bd9e2a5efc1@citrix.com> <20210114234737.xpltgdu3vpa6spgb@treble> From: Andrew Cooper Message-ID: <70343174-b9cd-d80b-7be0-5d3e3e609ca2@citrix.com> Date: Fri, 15 Jan 2021 00:54:41 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.6.1 In-Reply-To: <20210114234737.xpltgdu3vpa6spgb@treble> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Content-Language: en-GB X-ClientProxiedBy: LO4P123CA0045.GBRP123.PROD.OUTLOOK.COM (2603:10a6:600:152::14) To BYAPR03MB4728.namprd03.prod.outlook.com (2603:10b6:a03:13a::24) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: a96ec3bb-15ff-40b9-7184-08d8b8f02973 X-MS-TrafficTypeDiagnostic: BYAPR03MB4341: X-Microsoft-Antispam-PRVS: X-MS-Oob-TLC-OOBClassifiers: OLM:9508; X-MS-Exchange-SenderADCheck: 1 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: e/6yOAj8YTIx+2zEuAzq0v/+MlNS+AvCNmyMc35Ry7iS/6pUKe8NEY7Oo99kowczxxDKrID+tIgGR97y5w4kKtq7yHV3RBSK0HWz6SwvUpNJGK4W/y/7d2A5egixBsuELKDUyBWlf/jxmAaUWYNalMcOrA0suhuuQKtopM0fIgyyAM7Fds+Y/ZiSxSz013OIOrpD6JneId3js34rE0XCPhNcVk3+A0zNnNCWKOyeVr/TQyrk9j/IiL3kRSdJA2A1BE2FAfdSn5QPT7M3/CzEn42EqCdwTK7vlAjRgSA3iYrBd6KjtrXkPnCwXEHBs+Jy5DmCWYa/8JcvoB28gv50dvmFJpt8KeHnNJhu8IFIMZFCg3RCeyW4sPB4HZH5BnYkuCVhnjJFhw5alY8qDK/0t5GYEnd8LDgutq2XmoP5qYTOKgg2Z+IZ/GMxJkk91BnvC/S6NlRBmxh0cBm+F2HCmMy9uNpRfp9U03kWPLqaMFU= X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:BYAPR03MB4728.namprd03.prod.outlook.com;PTR:;CAT:NONE;SFS:(4636009)(376002)(346002)(136003)(396003)(366004)(39860400002)(7416002)(478600001)(2616005)(31686004)(316002)(16576012)(6666004)(16526019)(956004)(54906003)(186003)(66946007)(36756003)(53546011)(31696002)(4326008)(6916009)(86362001)(2906002)(66476007)(5660300002)(66556008)(6486002)(8936002)(26005)(83380400001)(8676002)(45980500001)(43740500002);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData: =?utf-8?B?RlQ1V1luN3NrMnBobGVlZG9Kbm1VQ1N2WkdOSzF4ZUptU2x2aXhobEhuS2Na?= =?utf-8?B?OU5QcVNTYnpidUkzdkhyclY3MERmSEoxNG1UVkZpUjVVK2FrRjd3bEZ3MEFU?= =?utf-8?B?aCtJcDZZbENMZ3lURzZSeVpxVnFqU0tRSTU1NzhKY1NFMHJJa1Y1OW8yL2JE?= =?utf-8?B?WkoxT1cxUEdsZWIvVEZUWnV5SlpvTUhiaG84SG9DZXVQNklXVlVPcHlVUm5o?= =?utf-8?B?QktsWmZvcVlhT0orbnhiT0hNVVIzQXRHT21MUmZwVERZRzBHZ21nYkRUakQr?= =?utf-8?B?SE9TMFoyeEE3L1d4MEZvSmMydllHaDMxWnpBN2xKT283aFhEcEpFZnNiTWRS?= =?utf-8?B?Nlk3TnhCcjlveVREWnRMWjI2NGNMNFkyckhZVzNoanF3dlRmUjlXM0xiVDg0?= =?utf-8?B?QzBOdGtZcUtwbFlXa1JXOXB3cS8rQTdjYWIzeDhyNklQdm5XOFk2Qk5NMmV2?= =?utf-8?B?Mk5XdlA4a3M5dGl4Mkt0TktZaXVNbXlFcVlvRlh0dDluL09PdFVzbno5c2JV?= =?utf-8?B?OTFkRVdiLy9FTlVyQVNSM1VrdFp4Z3paQnV3QzhCMkhVd2dxazRjc0xTUzIz?= =?utf-8?B?ZE1WK1haa3oyZ1lxVkZYWGVtOWRkQUJLcHo4SGF1WGpnRmltVU1nb2hPRTEz?= =?utf-8?B?S3dSUkVFdlRsb3RjdFV1QWhidE9QVlEvTlA1Y1BpUmhCckpsYTBHODJ1MW9K?= =?utf-8?B?aXZwRXlkcEpqZ3dSYzFBcG9MVk5ZT1o1Mkl6KzlmZ2lsWS9IRWtrcnBHT3h6?= =?utf-8?B?L0hRZUx4UU8yMmpYMTNmQkdsN21DbW1vd2RCMG9UaGVmTW5YcmR3SkNLMnp4?= =?utf-8?B?WW5IVzJjcDh0ei9nOXQ1WnZiQ2F5NHJMT0M5Y2hwejJFays0L3ByZExpRTFT?= =?utf-8?B?YUNOYkswOTVaeHg4UW52Qlk3Ymw3VXM3NUh0Ujltc0JCUE1mYjU5V2dUcVky?= =?utf-8?B?TUYvVjd6U2J6M1NINVB1eDl5MHhnKzdnTWhiQnA3NnpCL3pBQ1BUMFdxN3ox?= =?utf-8?B?VjdOVHI5bnZuSkw4NVFzNzcydDZEYkpsVko2UlE4cTJaVFBGTkw0ZVM4YmlQ?= =?utf-8?B?bUsvYm5SSzhidnhGbFNzeHp6Y1RSRlJsdStZb3ZXL1NJZWlxUTg0VGxOb0gz?= =?utf-8?B?bTBQeXVKdDdiZzRHRWYrVnZGS3lSSEluaTUxVTVXL1c4NkUrakNFQXJmMitV?= =?utf-8?B?WGtnR3RPUnJNRm1tbnFtS2JGSk1lRThTdzdmQU1wbUdhc1JVMUpBWkcrK09J?= =?utf-8?B?R0NQSkYra01iZmRXemdOZlpLWjZnQ2tMZWZqeEtzZlppRmZIeDRicjdxNWtU?= =?utf-8?Q?MQ/0AWkn7C3fb18o3FUpzR9ohZt/0UWld5?= X-MS-Exchange-CrossTenant-AuthSource: BYAPR03MB4728.namprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 15 Jan 2021 00:54:49.9159 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 335836de-42ef-43a2-b145-348c2ee9ca5b X-MS-Exchange-CrossTenant-Network-Message-Id: a96ec3bb-15ff-40b9-7184-08d8b8f02973 X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: 2W5lGpzmd5TzrumTRUEjxSf+ghW7TH2RKWecfMkBS4JCzbsfiMewIBktClOYMxgf65vNlLVseRZnBvC47YgvQ9xX6mWmgkUUDYk1p4GwYcU= X-MS-Exchange-Transport-CrossTenantHeadersStamped: BYAPR03MB4341 X-OriginatorOrg: citrix.com Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 14/01/2021 23:47, Josh Poimboeuf wrote: > On Thu, Jan 14, 2021 at 10:59:39PM +0000, Andrew Cooper wrote: >> On 14/01/2021 19:40, Josh Poimboeuf wrote: >>> It's kernel policy to not have (unannotated) indirect jumps because of >>> Spectre v2. This one's probably harmless, but better safe than sorry. >>> Convert it to a retpoline. >>> >>> Cc: "Rafael J. Wysocki" >>> Cc: Len Brown >>> Cc: Pavel Machek >>> Signed-off-by: Josh Poimboeuf >>> --- >>> arch/x86/kernel/acpi/wakeup_64.S | 3 ++- >>> 1 file changed, 2 insertions(+), 1 deletion(-) >>> >>> diff --git a/arch/x86/kernel/acpi/wakeup_64.S b/arch/x86/kernel/acpi/wakeup_64.S >>> index 5d3a0b8fd379..0b371580e620 100644 >>> --- a/arch/x86/kernel/acpi/wakeup_64.S >>> +++ b/arch/x86/kernel/acpi/wakeup_64.S >>> @@ -7,6 +7,7 @@ >>> #include >>> #include >>> #include >>> +#include >>> >>> # Copyright 2003 Pavel Machek >> >>> @@ -39,7 +40,7 @@ SYM_FUNC_START(wakeup_long64) >>> movq saved_rbp, %rbp >>> >>> movq saved_rip, %rax >>> - jmp *%rax >>> + JMP_NOSPEC rax >>> SYM_FUNC_END(wakeup_long64) >> I suspect this won't work as you intend. >> >> wakeup_long64() still executes on the low mappings, not the high >> mappings, so the `jmp __x86_indirect_thunk_rax` under this JMP_NOSPEC >> will wander off into the weeds. >> >> This is why none of the startup "jmps from weird contexts onto the high >> mappings" have been retpolined-up. > D'oh. Of course it wouldn't be that easy. I suppose the other two > retpoline patches (15 and 21) are bogus as well. If by 21 you mean 19, then most likely, yes.  They're all low=>high jumps in weird contexts. ~Andrew