From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 74C2BC433B4 for ; Wed, 5 May 2021 10:41:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 32E66613BC for ; Wed, 5 May 2021 10:41:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232789AbhEEKmt (ORCPT ); Wed, 5 May 2021 06:42:49 -0400 Received: from eu-smtp-delivery-151.mimecast.com ([185.58.86.151]:56831 "EHLO eu-smtp-delivery-151.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229524AbhEEKms (ORCPT ); Wed, 5 May 2021 06:42:48 -0400 Received: from AcuMS.aculab.com (156.67.243.121 [156.67.243.121]) (Using TLS) by relay.mimecast.com with ESMTP id uk-mta-51-gJphzZkLOp26gH2Db_oSXQ-1; Wed, 05 May 2021 11:41:45 +0100 X-MC-Unique: gJphzZkLOp26gH2Db_oSXQ-1 Received: from AcuMS.Aculab.com (fd9f:af1c:a25b:0:994c:f5c2:35d6:9b65) by AcuMS.aculab.com (fd9f:af1c:a25b:0:994c:f5c2:35d6:9b65) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Wed, 5 May 2021 11:41:44 +0100 Received: from AcuMS.Aculab.com ([fe80::994c:f5c2:35d6:9b65]) by AcuMS.aculab.com ([fe80::994c:f5c2:35d6:9b65%12]) with mapi id 15.00.1497.015; Wed, 5 May 2021 11:41:44 +0100 From: David Laight To: "'Vladislav K. Valtchev'" , "linux-kernel@vger.kernel.org" , "linux-gcc@vger.kernel.org" Subject: RE: GCC, unaligned access and UB in the Linux kernel Thread-Topic: GCC, unaligned access and UB in the Linux kernel Thread-Index: AQHXQRBnIBNbmTwiK0CwqzjE4VzA6arUr7NQ Date: Wed, 5 May 2021 10:41:44 +0000 Message-ID: References: In-Reply-To: Accept-Language: en-GB, en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.202.205.107] MIME-Version: 1.0 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=C51A453 smtp.mailfrom=david.laight@aculab.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: aculab.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: base64 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org RnJvbTogVmxhZGlzbGF2IEsuIFZhbHRjaGV2DQo+IFNlbnQ6IDA0IE1heSAyMDIxIDE5OjA4DQo+ IA0KPiBIaSBldmVyeW9uZSwNCj4gDQo+IEkgbm90aWNlZCB0aGF0IGluIHRoZSBMaW51eCBrZXJu ZWwgd2UgaGF2ZSBhIGRlZmluZSBjYWxsZWQNCj4gQ09ORklHX0hBVkVfRUZGSUNJRU5UX1VOQUxJ R05FRF9BQ0NFU1MgdGhhdCdzIHVzZWQgaW4gYSBmYWlyIGFtb3VudCBvZiBwbGFjZXMNCj4gd2l0 aCB0aGUgZm9sbG93aW5nIHB1cnBvc2U6IHdoZW4gaXQncyBzZXQsIHVuYWxpZ25lZCBhY2Nlc3Mg aXMgc3VwcG9ydGVkIGJ5IHRoZQ0KPiBDUFUgc28gd2UgY2FuIGRvIGl0IGRpcmVjdGx5LCBvdGhl cndpc2UgZmFsbC1iYWNrIHRvIHNvbWUgbG9naWMgd2hlcmUgYSBieXRlIGF0DQo+IHRoZSB0aW1l IGlzIHJlYWQvd3JpdHRlbi4gRm9yIGV4YW1wbGUsIGNoZWNrIHRoZSBpbXBsZW1lbnRhdGlvbiBv Zg0KPiBkb19zdHJuY3B5X2Zyb21fdXNlcigpOg0KPiBodHRwczovL2VsaXhpci5ib290bGluLmNv bS9saW51eC9sYXRlc3Qvc291cmNlL2xpYi9zdHJuY3B5X2Zyb21fdXNlci5jI0wxNQ0KPiANCj4g DQo+IFRoYXQncyBuaWNlIGFuZCBzZWVtcyB0byB3b3JrIHRvZGF5IGFzIGV4cGVjdGVkLCBidXQg dGhlcmUncyBvbmUgcHJvYmxlbToNCj4gdW5hbGlnbmVkIGFjY2VzcyBpcyBVQiBhY2NvcmRpbmcg dG8gdGhlIElTTyBDIHN0YW5kYXJkLCAuLi4NCg0KVGhlIEMgc3RhbmRhcmQgaXNuJ3QgcmVsZXZh bnQuDQoNCi4uLg0KPiANCj4gTWl0aWdhdGlvbnMNCj4gLS0tLS0tLS0tLS0tDQo+IEluIG15IHVu ZGVyc3RhbmRpbmcsIHRoZSBzaW1wbGVzdCB3YXkgdG8gZm9yY2UgR0NDIHRvIGVtaXQgYSBzaW5n bGUgTU9WDQo+IGluc3RydWN0aW9uIHdpdGggdW5hbGlnbmVkIGFjY2Vzcywgd2l0aG91dCByaXNr aW5nIGFueSBraW5kIG9mIFVCLCBpcyB0byB1c2UNCj4gX19idWlsdGluX21lbWNweSgpLiBJdCB3 b3JrcyBncmVhdCwgYnV0IGl0IHJlcXVpcmVzIGZpeGluZyB0aGUgY29kZSBpbiBtYW55DQo+IHBs YWNlcy4gQWxzbywgbWF5YmUgdXNpbmcgZ2V0X3VuYWxpZ25lZCgpL3B1dF91bmFsaWduZWQoKSBp cyB0aGUgcmlnaHQgdGhpbmcgdG8NCj4gZG8/IFRoZSBwcm9ibGVtIGlzIHRoYXQgdGhlIHB1dF91 bmFsaWduZWRfKiBpbmxpbmUgZnVuY3Rpb25zIGRvbid0IHVzZQ0KPiBfX2J1aWx0aW5fbWVtY3B5 KCkgYW5kIGFyZSBkZWZpbmVkIGxpa2U6DQo+IA0KPiAgICBzdGF0aWMgX19hbHdheXNfaW5saW5l IHZvaWQgcHV0X3VuYWxpZ25lZF9sZTMyKHUzMiB2YWwsIHZvaWQgKnApDQo+ICAgIHsNCj4gICAg CSooKF9fbGUzMiAqKXApID0gY3B1X3RvX2xlMzIodmFsKTsNCj4gICAgfQ0KPiANCj4gU28sIHN0 aWxsIFVCLiBUbyBtYWtlIHRoZSBjb21waWxlciBoYXBweSwgbWF5YmUgd2Ugc2hvdWxkIG1ha2Ug dGhlbSB1c2UNCj4gX19idWlsdGluX21lbWNweSgpPw0KDQpUaGF0IGRvZXNuJ3QgaGVscCB5b3Ug YXQgYWxsLg0KSWYgdGhlIGNvbXBpbGVyIGlzIGdpdmVuIGFueSBoaW50IHRoYXQgdGhlIGFkZHJl c3MgaXMgYWxpZ25lZA0KaXQgd2lsbCB1c2UgcG90ZW50aWFsbHkgbWlzYWxpZ25lZCBtZW1vcnkg YWNjZXNzZXMuDQpTbyBpZiB0aGUgYWJvdmUgd2FzOg0KCSooaW50IF9fYXR0cmlidXRlX18oKHBh Y2tlZCkpICopcCA9IHZhbDsNCmFuZCB0aGUgY2FsbGVyIGhhZDoNCglpbnQgKnAgPSBtYXliZV91 bmFsaWduZWQoKTsNCglwdXRfdW5hbGlnbmVkX2xlMzIoMCwgcCk7DQoNClRoZW4gZ2NjIHdpbGwg Z2VuZXJhdGUgYSAzMmJpdCB3cml0ZSBldmVuIG9uIHNwYXJjLg0KX19idWlsdGluX21lbWNweSgp IHdpbGwgZXhwYW5kIHRvIGV4YWN0bHkgdGhlIHNhbWUgMzJiaXQgd3JpdGUuDQoNClRoaXMgaXMg bm90aGluZyBuZXcgLSBhdCBsZWFzdCAyMCB5ZWFycy4NCg0KQmFzaWNhbGx5LCB0aGUgQyBzdGFu ZGFyZCBvbmx5IGFsbG93cyB5b3UgdG8gY2FzdCBhIHBvaW50ZXINCnRvICd2b2lkIConIGFuZCB0 aGVuIGJhY2sgdG8gaXRzIG9yaWdpbmFsIHR5cGUuDQpHQ0MgbWFrZXMgdXNlIG9mIHRoaXMgZm9y IHZhcmlvdXMgb3B0aW1pc2F0aW9ucyBhbmQgd2lsbA0KdHJhY2sgdGhlIGFsaWdubWVudCB0aHJv dWdoICh2b2lkICopIGNhc3RzLg0KDQpJIGJlbGlldmUgdGhhdCwgZXZlbiBmb3IgdGhlIHNpbWQg aW5zdHJ1Y3Rpb25zLCBnY2Mgd2lsbCBwaWNrDQp0aGUgJ21pc2FsaWduIHN1cHBvcnRpbmcnIHZl cnNpb24gaWYgdGhlIGRhdGEgaXMgbWFya2VkDQp3aXRoIHRoZSByZWxldmFudCBhbGlnbm1lbnQu DQoNCk9oIC0gYW5kIHRoZSBsb29wIHZlY3RvcmlzYXRpb24gY29kZSBpcyBhIHBpbGUgb2YgY3Jh cC4NCllvdSBhbG1vc3QgbmV2ZXIgd2FudCBpdCAtIGxvb2sgYXQgdGhlIGNvZGUgaXQgZ2VuZXJh dGVzDQpmb3IgYSBsb29wIHlvdSBnbyByb3VuZCBhIGZldyB0aW1lcy4NCkl0IHlvdSBhcmUgZG9p bmcgMTAwMDAgaXRlcmFjdGlvbnMgeW91J2xsIG5lZWQgdG8gdW5yb2xsDQppdCB5b3Vyc2VsZiB0 byBnZXQgZGVjZW50IHBlcmZvcm1hbmNlLg0KDQoJRGF2aWQNCg0KLQ0KUmVnaXN0ZXJlZCBBZGRy ZXNzIExha2VzaWRlLCBCcmFtbGV5IFJvYWQsIE1vdW50IEZhcm0sIE1pbHRvbiBLZXluZXMsIE1L MSAxUFQsIFVLDQpSZWdpc3RyYXRpb24gTm86IDEzOTczODYgKFdhbGVzKQ0K