From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from CWXP265CU010.outbound.protection.outlook.com (mail-ukwestazon11022101.outbound.protection.outlook.com [52.101.101.101]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 84EE83B0ACB; Sun, 16 Aug 2026 14:05:08 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=fail smtp.client-ip=52.101.101.101 ARC-Seal:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786889109; cv=fail; b=c90IslgRShQa0ruwASWJ8vDqKK09D9BY+Ssva41SxGe4yKTkZdhyawmB8JKRC8zzIk4XUaMTKS5YCZN6PoJxQ9mSxc4vPCiQEabvBbkiPgCsCID8c6BxOLisVoT+z3W10YH0QVt/sFub8UuqBltWn4+J3bp4DMwQGom0b+UIazk= ARC-Message-Signature:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786889109; c=relaxed/simple; bh=aKuVt+6OftjqHHeNF+XxksYJM3UY3I+BUNU11jJcXw0=; h=Content-Type:Date:Message-Id:Cc:Subject:From:To:References: In-Reply-To:MIME-Version; b=YWEcJd9QYkMfOwpaI6SwDfw4+pUcvEeBAx+UlAfVfOIWwmh3GZHxM6u55S6DytOtVxWoy4stejQKb8OWkk5Qp8uDvMHq1yZQNownhQkFbT2NDAqq6ry1HpFEM9mhoqUFc1OfNkUDaCbRmhYtTxZiDEWk5rAyJMHv/0OpmN4WGak= ARC-Authentication-Results:i=2; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=garyguo.net; spf=pass smtp.mailfrom=garyguo.net; dkim=pass (1024-bit key) header.d=garyguo.net header.i=@garyguo.net header.b=KsGkbVuS; arc=fail smtp.client-ip=52.101.101.101 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=garyguo.net Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=garyguo.net Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=garyguo.net header.i=@garyguo.net header.b="KsGkbVuS" ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=OTKnXI6rLnfgCRR0FHRS2UGsMUIs84tddXGHsBE26A15ggm2N15smpe26UgKt7FVoUKLpND8UkltM9+C5pVswaynl4PZSQZbMIaeW6K2FT3IV8zjdkpXyCAS8KdrGV1MYjPps80MADBC/Le6b8qwN3+OnmygCYhyLpnRvjBoJ6OMf7RKTY0RDyPXLJk3fftPqLgoKHpsdyaG0rVkfcOn/gmRdgPb1BHoAT2PVSGPd7iQNCIiSBxiSjY2ro2hSiUxkwN3U72jtjKxv55n0347FTsoKbsCxADBIYVkgxkB5qi9v9mPgtW483gIEywRTh76I6ba2u6wWV7fIHnXZyMGjw== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector10001; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-AntiSpam-MessageData-ChunkCount:X-MS-Exchange-AntiSpam-MessageData-0:X-MS-Exchange-AntiSpam-MessageData-1; bh=jmBS/Xsk8Yk+KhVfcSjYULsidATJy+fvx3untB7uZvM=; b=X7uxVp2ZDsl+BMFayUaC47SuSSKTP5PyDaaEdU60j7QGkG7IqxN/27gfJn3cxCgErmQhrQkDVrK65KRxhJyrHAADA+u0Pl+gmpnLZF5onU0q7pKW1dZpAOqFqArN1QT4uDHNkuqphFvUEzpY6+w0wmczCZtFBgkg9Bby5GhnaoIXIuIgNIdEVLKctEaF0K8jphNVKJu9JDMH4xR0lxMM36+VNBmxZuohZ6oYzEc71Yvp5S9AK7DbhkB+OxPwgWS6TsVdSgb06xJK69SuoMSTDRLkwfpgy8JzBPyRJpeT/3wBvO1A2fQdiX/fvmX7m7l43kKcgMMybiFUM8+ob2s1hA== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=garyguo.net; dmarc=pass action=none header.from=garyguo.net; dkim=pass header.d=garyguo.net; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=garyguo.net; s=selector1; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=jmBS/Xsk8Yk+KhVfcSjYULsidATJy+fvx3untB7uZvM=; b=KsGkbVuST8NpsrbNvywJa4qzsj7QTF3Ema+vx7cV+Ao7A1cVOvSavs7RZvgM/KnG3/bIimFeXMjuLBXAOb1u6NC6vRiN9avBgEAy/Vy8cz0b5taLWVL+s1p5u45cOh8LPnuKq96c0L6bVeYKTJERlHfeUP+RomJKvZoJhodDs+A= Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=garyguo.net; Received: from LOAP265MB8560.GBRP265.PROD.OUTLOOK.COM (2603:10a6:600:4ab::19) by LO8P265MB7753.GBRP265.PROD.OUTLOOK.COM (2603:10a6:600:3ae::5) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.21.315.17; Sun, 16 Aug 2026 14:05:06 +0000 Received: from LOAP265MB8560.GBRP265.PROD.OUTLOOK.COM ([fe80::f60b:1537:68d7:4fc1]) by LOAP265MB8560.GBRP265.PROD.OUTLOOK.COM ([fe80::f60b:1537:68d7:4fc1%4]) with mapi id 15.21.0315.016; Sun, 16 Aug 2026 14:05:06 +0000 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 Date: Sun, 16 Aug 2026 15:05:05 +0100 Message-Id: Cc: , =?utf-8?q?Bj=C3=B6rn_Roy_Baron?= , "Benno Lossin" , "Andreas Hindborg" , "Trevor Gross" , "Danilo Krummrich" , "Daniel Almeida" , "Tamir Duberstein" , "Alexandre Courbot" , =?utf-8?q?Onur_=C3=96zkan?= , , Subject: Re: [PATCH 2/2] kbuild: rust: keep Rust objects out of Clang LTO with inline helpers From: "Gary Guo" To: "Miguel Ojeda" , "Nathan Chancellor" , "Nicolas Schier" , "Boqun Feng" , "Gary Guo" , "Matthew Maurer" , "Alice Ryhl" , "Josh Poimboeuf" , "Peter Zijlstra" X-Mailer: aerc 0.22.0 References: <20260816133233.197500-1-ojeda@kernel.org> <20260816133233.197500-2-ojeda@kernel.org> In-Reply-To: <20260816133233.197500-2-ojeda@kernel.org> X-ClientProxiedBy: LO4P265CA0179.GBRP265.PROD.OUTLOOK.COM (2603:10a6:600:311::7) To LOAP265MB8560.GBRP265.PROD.OUTLOOK.COM (2603:10a6:600:4ab::19) Precedence: bulk X-Mailing-List: linux-kbuild@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: LOAP265MB8560:EE_|LO8P265MB7753:EE_ X-MS-Office365-Filtering-Correlation-Id: f80e2136-eb7d-4d02-7739-08defb9f5fdb X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|376014|7416014|10070799003|1800799024|366016|23010399003|18002099003|22082099003|56012099006|3023799007|6133799003|4143699003|10067099003; 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:LOAP265MB8560.GBRP265.PROD.OUTLOOK.COM;PTR:;CAT:NONE;SFS:(13230040)(376014)(7416014)(10070799003)(1800799024)(366016)(23010399003)(18002099003)(22082099003)(56012099006)(3023799007)(6133799003)(4143699003)(10067099003);DIR:OUT;SFP:1102; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?Mlg0aXFWS0RSaFJaWU8ycXJwZnQrVkorSzRCRytBU3YyZVJpNVhwVGN5ZGVk?= =?utf-8?B?MnNpTUJublVOUk5IeEFPeldBdnluTytaY3RiRnlGM1N5dVhCM1h5RmFQZnp5?= =?utf-8?B?R05HTzJQVFNmSWNJQlY2cGs0V1R4cFlyWnVmeE4xZUpJdVdiMzJFVi84OVRZ?= =?utf-8?B?dkFRL1d3VHdyZHFkOVA5NGo4YWlsVjRSQlR1V0NLc01RQ0p0ZTU3UWs3NjRw?= =?utf-8?B?VmF1UHZKNDB3OW9mYTNPZmFUZWd0NkRsR1FTTkxHWmp5aWZuSGN2QXlBZVlT?= =?utf-8?B?bDNHL2tMVy9OUEhSR2hrZDBtV2JGUGNUSkQ3ZmEyQVN6Q0FKVVVuUGt6L0R3?= =?utf-8?B?dTFXUitFL3hzYVFlMFZsMHlwMHdJNDFHUVl5L0k5aUVvUVBQbHEwTUlRcE5n?= =?utf-8?B?VG83VFg0M2IwdmRwNWd5a2Z6cVhCb1hBVWZqaENHOGpEUGY0VFd4cHpzN1l0?= =?utf-8?B?NHI0b3UrVUs4eEg2VFZyV0gwZllxOVo5QUdQaG1mUEhRMVhMbGc0eVJvZUNF?= =?utf-8?B?Ky94M1d0NnVZU3NZUW5JdUF6NHk1SDhYYzMxejBvZlRGTjdvZEl1ZHJvaktC?= =?utf-8?B?T0kzdlpQNWpJTzIrRUlJOW43VzFoOEpiMjgvSlNIY1ZyR3g0NUFLK2p6SVcv?= =?utf-8?B?ZTk2ZEIrVlFqMEEvOEdseGFwNlBPcGdzS2Z1U3kzMFpaandseWhGT0JFQldv?= =?utf-8?B?cjdEQ1hKQTJlZVpzS3ZvcU0xVVRTaS9Pd3lWOHM2VXg4d2hTWjNRL3dpa3BR?= =?utf-8?B?c3crRFdTQkY5WmptKzkxazZQVWpKUklkaHRzdVQzM0FyY0pWdmduWTFZMnEz?= =?utf-8?B?VDYyWk1saDNtYk04T2xqczJabXF1UTl6bW9wV2dmdVVBNDlLektmTllnVXFD?= =?utf-8?B?aWFDRVV2dU1IaktMUjJSQXZTYkdWUGVIS1VyZTlpTmVDaGhKU0Q3bk1EaHRU?= =?utf-8?B?aDgyWGFSU3R6dDlrTGQ1Wng4SEdPUk9hNWFzWmo5MDcrSklIVXNTOWlWcm1y?= =?utf-8?B?ZFBhZ0hiSjRTZTRGQUI1WURMbkJJcHZmQTR6QlZmaDQ2ckpwNUs0K2J2Y1o1?= =?utf-8?B?ZXg0OVQwYUtRZU9uZC9vUTd3c3pUbDU4T3NTYzdyQWNNTlVhZEVyKzVCTDRy?= =?utf-8?B?am1aeGtZSTZLZTRzN3d3Qm1lZG8wY0xTRDQrZ2pFVGxvLzByelJhVTNmczN5?= =?utf-8?B?WXltekVqSUJpbmlVMlhzcU14cVQxMUU3cFZhZTJKeHFZZldGRVZsdC9oRExS?= =?utf-8?B?UUY1ak4wVjNYR2F0eHAxdWlYcFZCMHZONU4rajJoZ01oN0sxeXRocWlpd2dm?= =?utf-8?B?OFpUSVVSM29sL3JKY3hPbUhSQmpWazBkUTRpOHZkZjVHTkp1cnZYQm15MVRx?= =?utf-8?B?bXpCZWRDa1haYytxMFNxYnV2ZTJIeFBySU1Wa3lhZjMwMTF1SzZzOFhuR0ZE?= =?utf-8?B?bFJ5M0VZaFQvWVd2dExVSFpkOUc5aHY2emZ3alNuRVhNUk9ZQzNPUlMyQktt?= =?utf-8?B?ZkFaRlp0am1vWmlqOWorZFhjUy8vU3FGdXczazhJVC9kY1dBMU9OaHBCMGRP?= =?utf-8?B?RWlZZlA0YW85UDh6MXNmNzlzd2ZRUGhFdHNoQzZaMEpKWE44WUZsaUNaNGpv?= =?utf-8?B?SmZpZTZMUHpjd1oweC9lZi9XZnUyektoRjB1UlJKZTRBdFhqd1NwKzlsOTlO?= =?utf-8?B?ZW9iamp2aGx5SnRkYk5NL3FsTTQwSW1sZTZ0VW1XNU5TTVBhT0h1VGg2Z0RI?= =?utf-8?B?YWdWMXBaNVZQNWFZV3JYOE00UXkzd0RFaUtXY0d0ejQ0Y2hkL2hubjZjQzg4?= =?utf-8?B?UGNwcDNkYWNCNkg5ZzkyWHZBNE5EN2JkZ0kwQTg1dk11eisvK0xybUFWQ1dl?= =?utf-8?B?NWhvS1Q5Mnk2bDBGUDFRVGduUEorVTdwRmVrOHU2NzRvUTJoQkJLeFk1RU5t?= =?utf-8?B?VWhRNGlVLzJoZXdweTcvQ3VJVG16WGxoTUlscCtJMWsxUDNJTXJwSXhFZkxF?= =?utf-8?B?VG1VWlNYWHpERXRyNEF4NkRDaE9lcGpxL0dZUnZKcXpibG5HK1BKMVFUT0wz?= =?utf-8?B?MXB2NEV1NE9LNFYxaHZJREROM1ZHc0UrYXJSSHVUVDlnZnRvTE9IcSt6bERq?= =?utf-8?B?R08vTEdld0dNckpLVEdXdFVveVFJb1NFeTNkS0dPN0ZlN0lCUExDTzNLSkE5?= =?utf-8?B?QTVVczhhdW1hZmk2R2UvSGh5WjVtenpEZm50MDBiSm5rclI1dWQ0b0hTUzBa?= =?utf-8?B?eEZjcGl0aHpLd2JkNnR4TFNBV0plK081dk4zK05jVmp2bFI3Z2FNSmpJNmNI?= =?utf-8?B?OXdDVVZDTkJNSWJiVVJVVm9HZGQweWN1TEhyQTlKOW44dnBuWDlwQT09?= X-OriginatorOrg: garyguo.net X-MS-Exchange-CrossTenant-Network-Message-Id: f80e2136-eb7d-4d02-7739-08defb9f5fdb X-MS-Exchange-CrossTenant-AuthSource: LOAP265MB8560.GBRP265.PROD.OUTLOOK.COM X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 16 Aug 2026 14:05:06.0263 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: bbc898ad-b10f-4e10-8552-d9377b823d45 X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: ovzW75cmTokVvs3f/1MNdyf2qPMJCJdMvKC7BoI9vHdz4wvAcvDgXFWO74FaablShqfyKRDjW4P7M2K7tC/ppA== X-MS-Exchange-Transport-CrossTenantHeadersStamped: LO8P265MB7753 On Sun Aug 16, 2026 at 2:32 PM BST, Miguel Ojeda wrote: > Under `CONFIG_LTO_CLANG` + `CONFIG_RUST_INLINE_HELPERS`, one may hit > `objtool` errors such as: >=20 > vmlinux.o: error: objtool: _R..._3Gsp4boot+0xd6a: > can't find jump dest instruction at .text._R..._3Gsp4boot+0x1dfd >=20 > The reason is that in such builds, the Clang invocation that compiles > the combined Rust plus helpers bitcode emits LLVM bitcode (again) -- > the final code generation happens in the linker's LTO step, which the > `-mllvm` trap options passed to Clang do not reach. >=20 > This, in turn, means that unreachable traps are missing, and the > impossible paths do not merely fallthrough to the next symbol, but past > the end of their own section, since LTO builds place each function in > its own section. >=20 > Thus filter `CC_FLAGS_LTO` out of the Clang invocation, so that it always > emits machine code directly, with the traps in place. >=20 > Assisted-by: LLM > Cc: Gary Guo > Cc: Boqun Feng > Cc: Alice Ryhl > Cc: Matthew Maurer > Cc: stable@vger.kernel.org > Cc: Josh Poimboeuf > Cc: Peter Zijlstra > Fixes: 3a2486cc1da5 ("kbuild: rust: provide an option to inline C helpers= into Rust") > Signed-off-by: Miguel Ojeda Acked-by: Gary Guo > --- > rust/Makefile | 2 +- > scripts/Makefile.build | 2 +- > 2 files changed, 2 insertions(+), 2 deletions(-)