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Wed, 27 Jan 2021 10:44:15 +0000 Subject: Re: [PATCH v6 0/2] ARM: Implement MODULE_PLT support in FTRACE To: Florian Fainelli , linux-arm-kernel@lists.infradead.org Cc: Ard Biesheuvel , linux-kernel@vger.kernel.org, Steven Rostedt , Russell King , Ingo Molnar References: <20200217140955.211661-1-alexander.sverdlin@nokia.com> <48289cbf-9108-2807-7143-c3ae625bd940@gmail.com> From: Alexander Sverdlin Message-ID: <19e02972-c2e2-0e5f-b9c7-9f750110db77@nokia.com> Date: Wed, 27 Jan 2021 11:43:56 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 In-Reply-To: <48289cbf-9108-2807-7143-c3ae625bd940@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [131.228.32.167] X-ClientProxiedBy: AM0PR02CA0118.eurprd02.prod.outlook.com (2603:10a6:20b:28c::15) To AM0PR07MB4531.eurprd07.prod.outlook.com (2603:10a6:208:6e::15) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from ulegcpsvhp1.emea.nsn-net.net (131.228.32.167) by AM0PR02CA0118.eurprd02.prod.outlook.com (2603:10a6:20b:28c::15) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3805.17 via Frontend Transport; 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X-MS-Exchange-AntiSpam-MessageData: =?utf-8?B?ZUNMTVNXajQ2L2RZMkpuRmlxei9WVWF1V1FmNkh3NlVPRUxPemRnc1pVenBV?= =?utf-8?B?SHFVSGhvRDJ2SXBTZktwSldiMkQ5bjhSUDdObmZRK3RWclo3YlAwUTV1cVNl?= =?utf-8?B?VzJ4UGtIUUhsMHlwYmpQeDRGWkd2OVBieWRyZEE3NVlQZ01FTWY5NE1zaXJK?= =?utf-8?B?ZURZYXc0SnlMaTNEckdnejhhL3NEZmlZd09NVWRuY0NYaHl1SG5MUU40cFRs?= =?utf-8?B?dkUvWTRtQlFadndMcUtGcGx5RXpFOEhPbVVRMWhnRDdSRnV6M1hmaWdJRk5i?= =?utf-8?B?UXcvVmt6RSt3bHlGK1lrRWpOR1NjWjc3ZEV0V2xmYVFVNTFXdFhCd1M1OFZx?= =?utf-8?B?K0lzUU1iODdxTnYrck5JRTZYbldra29lNzVCWkZXeXBXVFNNc1VFbVpjWXE5?= =?utf-8?B?eWdOc24vMzRka1M5UW9qM0xHbTNLUE4vc1E3amFpNU5kcjNsZXJEY0tQU0pR?= =?utf-8?B?VG05QlBaU2t4dWE2VGRKL09LMUlseWdyZ2VDYjFGUUxXZFZNbmpsRDVhR0xn?= =?utf-8?B?QWtpbzFjbjZiVG04U2xQeVl4dGNLdEdPN2RnMXJIL2pTbkI3YVJ3U0I2V2My?= =?utf-8?B?dFdiOUwrNVZsZUJOZ04vZ0pjL3U1TUI3Y1FuSUxqdXVScFd1cE5QRW1uSWRL?= =?utf-8?B?YzF4bERXOGtidjgyL0VpTEkwc0RnKzI4d3ZrWlhRVWF5UmdyNFo2UWtPUldo?= =?utf-8?B?VXpERnhDby9RakNHdjJrNEgxM2w2Q1BNTnZTeDZycyt3MDI4NlZCd0ZHYkpL?= =?utf-8?B?S3EwcVVDTk8rT0ZxdHh5NXl4Y2NsbjdGZkFtZGlnVGRib2ZtcllQc3djUkRN?= =?utf-8?B?SnBJcDRwMTl0am41dlJFb3NLSTBuNFpqcG5jUkpObXZtZkZaQTJMSWJGTnRZ?= =?utf-8?B?YWhic1ZSQmhpTGlJNU9ySDJSYlFPOE0xUmtrQUVkSXFhSTdVYnZsUHBCZURK?= =?utf-8?B?cnRkeFdXdGF5RkppVHhqSkxFTFI0NnFlUktSeXJwQVhreWx1SlYzUmxnaGJY?= =?utf-8?B?ZllFanJ0VnRCMXdqZElQR0NFOGVkWUg0dTZsZjFHcklRckg4c29vM0tyWUl1?= =?utf-8?B?VVYvdW1RZHpGSldsdUYvVTBWejFpRHRrOHlMT1pxNjQ1SUxzT0RTbUxZQ3NQ?= =?utf-8?B?ZUJaNUkzdDNLMW90eFlOQkNMQ25vTWFNd3hyQ0RpQ05henF0ZXNieVNmN2dW?= =?utf-8?B?aVZmNnRhMVpPbW95UG5aSytOTmFuaG11akZDVVlTS29nYmNaV0NQS1pvZEh5?= =?utf-8?B?dC9VVXJaZmhLNGNXNDlUSkJIaFdJcFZZNDEvdUFYVVNLMWtnUHBwckpYUFF4?= =?utf-8?B?d0tFZ2VQckRvVGdLd1R5MjArdmxqT1ZSQ0lGY29TYzJhK3ZTUGJWOXJ1cVFx?= =?utf-8?B?cGtlV3NjWXRkZWhiejR6ZmE1MFFOR3VTZllrMHFTRlora2VzM2taREFISGJO?= =?utf-8?Q?l6mDxqAh?= X-OriginatorOrg: nokia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 798ee174-c672-4e11-939a-08d8c2b07daf X-MS-Exchange-CrossTenant-AuthSource: AM0PR07MB4531.eurprd07.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 27 Jan 2021 10:44:15.3265 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 5d471751-9675-428d-917b-70f44f9630b0 X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: bt2cCiP6Fdue9PizosWYMljRC5DwtaEWwNvBENtz6bVnjE8P0+z9nkaUtphgs4a8zb9hIs9Spr9FZcFw0z2OGuGx/eYHkiLUuqBdx94nsIM= X-MS-Exchange-Transport-CrossTenantHeadersStamped: AM0PR07MB5713 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello Florian, On 27/01/2021 05:48, Florian Fainelli wrote: >> FTRACE's function tracer currently doesn't always work on ARM with >> MODULE_PLT option enabled. If the module is loaded too far, FTRACE's >> code modifier cannot cope with introduced veneers and turns the >> function tracer off globally. >> >> ARM64 already has a solution for the problem, refer to the following >> patches: >> >> arm64: ftrace: emit ftrace-mod.o contents through code >> arm64: module-plts: factor out PLT generation code for ftrace >> arm64: ftrace: fix !CONFIG_ARM64_MODULE_PLTS kernels >> arm64: ftrace: fix building without CONFIG_MODULES >> arm64: ftrace: add support for far branches to dynamic ftrace >> arm64: ftrace: don't validate branch via PLT in ftrace_make_nop() >> >> But the presented ARM variant has just a half of the footprint in terms of >> the changed LoCs. It also retains the code validation-before-modification >> instead of switching it off. > We have been using those patches and I was wondering what happened after > this version since they did not show up upstream nor in Russell's patch > tracker? Would you be willing to resubmit them? it's a pity, but nobody ever showed any interest to take them to fix real problem in FTRACE. A grain of salt would be to remind, that no-one also replied that the series helped him or a Tested-by: tag. This would probably wake more interest from maintainers side. Of course I can re-send them because I personally re-base them regularly. -- Best regards, Alexander Sverdlin.