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 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 73004C433DB for ; Thu, 18 Feb 2021 18:04:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 37ADE64EB1 for ; Thu, 18 Feb 2021 18:04:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230152AbhBRSEB convert rfc822-to-8bit (ORCPT ); Thu, 18 Feb 2021 13:04:01 -0500 Received: from eu-smtp-delivery-151.mimecast.com ([185.58.85.151]:57350 "EHLO eu-smtp-delivery-151.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232533AbhBRPaV (ORCPT ); Thu, 18 Feb 2021 10:30:21 -0500 Received: from AcuMS.aculab.com (156.67.243.126 [156.67.243.126]) (Using TLS) by relay.mimecast.com with ESMTP id uk-mta-36-PKrX5I6tNO2MkP4XFBpMfg-1; Thu, 18 Feb 2021 15:28:36 +0000 X-MC-Unique: PKrX5I6tNO2MkP4XFBpMfg-1 Received: from AcuMS.Aculab.com (fd9f:af1c:a25b:0:43c:695e:880f:8750) by AcuMS.aculab.com (fd9f:af1c:a25b:0:43c:695e:880f:8750) with Microsoft SMTP Server (TLS) id 15.0.1347.2; Thu, 18 Feb 2021 15:28:35 +0000 Received: from AcuMS.Aculab.com ([fe80::43c:695e:880f:8750]) by AcuMS.aculab.com ([fe80::43c:695e:880f:8750%12]) with mapi id 15.00.1347.000; Thu, 18 Feb 2021 15:28:35 +0000 From: David Laight To: "'Dmitry V. Levin'" , "David S. Miller" CC: "Eric W. Biederman" , Alexey Gladkov , Gleb Fotengauer-Malinovskiy , Anatoly Pugachev , "sparclinux@vger.kernel.org" , "linux-kernel@vger.kernel.org" Subject: RE: [PATCH] sparc: make copy_thread honor pid namespaces Thread-Topic: [PATCH] sparc: make copy_thread honor pid namespaces Thread-Index: AQHXBZd//RPPXGWEKk+rLobcOpszAqpeCBzA Date: Thu, 18 Feb 2021 15:28:35 +0000 Message-ID: <05247c8b0e31420a9e6e7a43831212ff@AcuMS.aculab.com> References: <20210217080000.GA25861@altlinux.org> In-Reply-To: <20210217080000.GA25861@altlinux.org> 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: 8BIT Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Dmitry V. Levin > Sent: 17 February 2021 08:00 > > On sparc, fork and clone syscalls have an unusual semantics of > returning the pid of the parent process to the child process. Isn't that just broken? The application expects fork() to return 0 in the child. libc would have to do horrid things to convert the result. It could be comparing against the saved 'current pid' in order to save a system call for the first ppid() call. But that isn't ever going to work if it is possible to create a child in a different pid namespace. FWIW the test program ought to use syscall() to get the pid and ppid - rather than relying on any optimisations in libc. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)