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Wed, 25 Sep 2024 16:10:59 -0500 Message-ID: <81fb3f6b-4ded-41d1-be66-d86af4f22171@amd.com> Date: Wed, 25 Sep 2024 17:10:56 -0400 Precedence: bulk X-Mailing-List: linux-efi@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH 11/28] x86/pvh: Avoid absolute symbol references in .head.text To: Ard Biesheuvel , CC: Ard Biesheuvel , , "H. Peter Anvin" , Andy Lutomirski , Peter Zijlstra , Uros Bizjak , Dennis Zhou , Tejun Heo , Christoph Lameter , Mathieu Desnoyers , "Paolo Bonzini" , Vitaly Kuznetsov , Juergen Gross , Boris Ostrovsky , Greg Kroah-Hartman , Arnd Bergmann , Masahiro Yamada , Kees Cook , Nathan Chancellor , Keith Packard , Justin Stitt , Josh Poimboeuf , "Arnaldo Carvalho de Melo" , Namhyung Kim , "Jiri Olsa" , Ian Rogers , Adrian Hunter , Kan Liang , , , , , , , , , , , References: <20240925150059.3955569-30-ardb+git@google.com> <20240925150059.3955569-41-ardb+git@google.com> Content-Language: en-US From: Jason Andryuk In-Reply-To: <20240925150059.3955569-41-ardb+git@google.com> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit Received-SPF: None (SATLEXMB05.amd.com: jason.andryuk@amd.com does not designate permitted sender hosts) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: BN2PEPF000055DC:EE_|SA0PR12MB4430:EE_ X-MS-Office365-Filtering-Correlation-Id: 2a8b3ce5-d2b6-407b-9a44-08dcdda69057 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|82310400026|36860700013|7416014|376014; X-Microsoft-Antispam-Message-Info: =?utf-8?B?OEJwb29wcWhNT2x0SDFYTTlrdFNpeXNaNG1QcnFKM2hsMDlQS2RMOHNXSWNw?= =?utf-8?B?QTZrKzVTaytRaWk2WFU0Z1RHWjJxNkJ3ZGNoeTNtYVBGQXU5TkxNZDJPZWtO?= =?utf-8?B?ZXFSNm5xQm50blV0UGpWaUlXQy9XZC9wZXAzL3Avd09mdHZ5MjFGTEZ5czlU?= =?utf-8?B?Tmtidk93YjdEc0xScG1qYXJtcUNTNjI5NDlCbmZZWHM2TUxZVE9NK3ZmWFZk?= =?utf-8?B?b2crQlBOOFdJa3VUWkZXQkd6T2Yyb2wzTThLbDUxVTJMN205azNmWEQzUzlS?= =?utf-8?B?UVluRmtYNXp5eEYwL0c1TXVJb2RXSDAvdjNmTC8ramFpVmVNZGdqY1Nma2RT?= =?utf-8?B?WFB5ZExVdDdYd0pJTGtGNGdra2lJMkE4emxBdk9HZTNRR3BwQk5pdk83L1Rl?= =?utf-8?B?UVNTNE9Nakc0SDZQZ3crVFNoZjFKZkhjRVoydStBQmQxeDl3RnN3MDFQVXlP?= =?utf-8?B?ZEpxbndkZDlqMjY0VzBhUENpQWFlMTlGcTFxNzV4aEJHV1Jnai9jelpOMGRR?= =?utf-8?B?eFk2WWh5c3pOTmpYN2ZhVVg5aWhoTVV4Sm5BcWhod3RVOEROWVcwaHcrYWxQ?= =?utf-8?B?WGdLZEovZFRjSWx2NFlRdlorclQwdUg5TG9KS3pxTEhkbUFPMGFNeUhhb3d3?= =?utf-8?B?bkxxYUpZbkMxcnpJby9hTGpkNnRyVEdHSDczeUlYNUgwYU9HYnF1OHE2emZU?= =?utf-8?B?OXpNMEZnVXJjNmpKY3hQbVhMT3Awc3lzVmE0andMbVU4Sld1d2Rqa3VSZGp3?= =?utf-8?B?MS9jTk8yVW5NbGVkZU1yZ1BIVTE1UVZ2UlRlL0EwN0VwZ2lySEdqbktHK2M2?= =?utf-8?B?bExaZ0pIcHR1OTlIcGNDYTE4ZnFoTGFiR2dqOW1JWXVhdWl3YVNJZDJTeWpR?= =?utf-8?B?YzlpaEk3UEszMWw5cUd0RmpOb1ZuMU41N3pHQ28zRVdDNVhaTGFFeS9MbVI1?= =?utf-8?B?Z2ZyVTJsYU43cUlkT21scHN5OHVFWUlraSs4OHVFWnRLVzhNL1lxVEJDNTZm?= =?utf-8?B?OEdKTmk1dmw0eHM1U0c3QzkxT0ZRL0Y4Uks0T21mc1RsNXB0WjMxdCtnN2ZN?= =?utf-8?B?OEpxZU43c2F0UVhnSXlaSGYwZjFrWkNzQ0tOMzFCQnhZYnJYY1VqVmVsN2Ex?= =?utf-8?B?ZG9xajlZU0ZpNndCWHI5Z2gyOFF6M3pNODNKcGE4blgrYzA4Wk55eFViN1RT?= =?utf-8?B?WndIZ3RGTDhDSWNBYnM3S0toOVd5OWdzY3JlODhFdTFHaGF0RUp5RkcwWVk5?= =?utf-8?B?NTNjL3laaFNBUDVFd3hPYVZTajZ2Ykk3OUJBM1I2aHl4bzdYZGlieUp0NDdi?= =?utf-8?B?T3dTT25XNHBZbnBsTlMwNzZzWFdUNkVkWWxrTWJCbDFvUkZ4VVNtTzc4cXB4?= =?utf-8?B?VUFuVmh0b2FsbzY5dlhXWTBCMS9IMzY4TjVZSTNpZjU1c2NFRVNBUC9OdTFQ?= =?utf-8?B?NzFvRjYrTDlrbjFRWWIrTzFvYTVvN2pBOEJacnQ0UkYrQUczUWRONVc1eVp0?= =?utf-8?B?aHVwQW5sOU9uWWtJeExZSFlKQU9hVE8rT2dxbUVuRCt4bVFjNmF5VHlGTEhZ?= =?utf-8?B?bjQxY0tadnlMb0hYVUlBOG5PZTBMSEdCdDdmTUVSRmRDRXVqamNxRVpjYkRp?= =?utf-8?B?aC9BQ0RuUWJ1VzRwTmpmamtNWVJocUxnRkxGajQyZ3M4THl0cUJOQVhtaEFI?= =?utf-8?B?UHJ0bWs1bkluR0xVOWJMUnJBMDRibXcwVFN5S05kajZJdE43aWtQS1Qwa2J5?= =?utf-8?B?c2JsblY3Um5TY1g3SUgrTWN5bStOdkVpSmxjK3RRaStBUS9XL3ArR3NVcndr?= =?utf-8?B?cVp5S0pZTHNBd0lZM2oxOHVRVkFiS2FUWXY1YzFJVnkvOFRCUmhhZjhNdXpJ?= =?utf-8?Q?quEuBNmFiQ/hN?= X-Forefront-Antispam-Report: CIP:165.204.84.17;CTRY:US;LANG:en;SCL:1;SRV:;IPV:CAL;SFV:NSPM;H:SATLEXMB04.amd.com;PTR:InfoDomainNonexistent;CAT:NONE;SFS:(13230040)(1800799024)(82310400026)(36860700013)(7416014)(376014);DIR:OUT;SFP:1101; X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 25 Sep 2024 21:11:03.4956 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 2a8b3ce5-d2b6-407b-9a44-08dcdda69057 X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[165.204.84.17];Helo=[SATLEXMB04.amd.com] X-MS-Exchange-CrossTenant-AuthSource: BN2PEPF000055DC.namprd21.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: SA0PR12MB4430 Hi Ard, On 2024-09-25 11:01, Ard Biesheuvel wrote: > From: Ard Biesheuvel > > The .head.text section contains code that may execute from a different > address than it was linked at. This is fragile, given that the x86 ABI > can refer to global symbols via absolute or relative references, and the > toolchain assumes that these are interchangeable, which they are not in > this particular case. > > In the case of the PVH code, there are some additional complications: > - the absolute references are in 32-bit code, which get emitted with > R_X86_64_32 relocations, and these are not permitted in PIE code; > - the code in question is not actually relocatable: it can only run > correctly from the physical load address specified in the ELF note. > > So rewrite the code to only rely on relative symbol references: these > are always 32-bits wide, even in 64-bit code, and are resolved by the > linker at build time. > > Signed-off-by: Ard Biesheuvel Juergen queued up my patches to make the PVH entry point position independent (5 commits): https://git.kernel.org/pub/scm/linux/kernel/git/xen/tip.git/log/?h=linux-next My commit that corresponds to this patch of yours is: https://git.kernel.org/pub/scm/linux/kernel/git/xen/tip.git/commit/?h=linux-next&id=1db29f99edb056d8445876292f53a63459142309 (There are more changes to handle adjusting the page tables.) Regards, Jason