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=-0.8 required=3.0 tests=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 016C9C4332B for ; Thu, 19 Mar 2020 16:17:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CFD2E2072C for ; Thu, 19 Mar 2020 16:17:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728207AbgCSQRC convert rfc822-to-8bit (ORCPT ); Thu, 19 Mar 2020 12:17:02 -0400 Received: from albireo.enyo.de ([37.24.231.21]:49206 "EHLO albireo.enyo.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728157AbgCSQRB (ORCPT ); Thu, 19 Mar 2020 12:17:01 -0400 Received: from [172.17.203.2] (helo=deneb.enyo.de) by albireo.enyo.de with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) id 1jExff-0006BE-FU; Thu, 19 Mar 2020 16:05:23 +0000 Received: from fw by deneb.enyo.de with local (Exim 4.92) (envelope-from ) id 1jExdz-0000h9-3G; Thu, 19 Mar 2020 17:03:39 +0100 From: Florian Weimer To: Mathieu Desnoyers Cc: libc-alpha , carlos , Rich Felker , linux-api , Boqun Feng , Will Deacon , linux-kernel , Peter Zijlstra , Ben Maurer , Dave Watson , Thomas Gleixner , Paul , Paul Turner , Joseph Myers Subject: Re: [RFC PATCH glibc 4/8] glibc: Perform rseq(2) registration at C startup and thread creation (v15) References: <20200319144110.3733-1-mathieu.desnoyers@efficios.com> <20200319144110.3733-5-mathieu.desnoyers@efficios.com> <874kukpf9f.fsf@mid.deneb.enyo.de> <2147217200.3240.1584633395285.JavaMail.zimbra@efficios.com> Date: Thu, 19 Mar 2020 17:03:39 +0100 In-Reply-To: <2147217200.3240.1584633395285.JavaMail.zimbra@efficios.com> (Mathieu Desnoyers's message of "Thu, 19 Mar 2020 11:56:35 -0400 (EDT)") Message-ID: <87r1xo5o2s.fsf@mid.deneb.enyo.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8BIT Sender: linux-api-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-api@vger.kernel.org * Mathieu Desnoyers: >> Can you use __has_include in , with a copy of the kernel >> definitions if the kernel header is not available? > > Sure. Should I pull a verbatim copy of uapi linux/rseq.h into glibc ? > If so, where should I put it ? Probably into , perhaps with a construct like this (untested): #ifdef __has_include # if __has_include ("linux/rseq.h") # define __GLIBC_HAVE_KERNEL_RSEQ # endif #else # include # if LINUX_VERSION_CODE >= KERNEL_VERSION (4, 18, 0) # define __GLIBC_HAVE_KERNEL_RSEQ # endif #endif #ifdef __GLIBC_HAVE_KERNEL_RSEQ # include #else … (fallback goes here) #endif We have an ongoing debate whether the fallback definition should use __u64 or uint64_t. You also need to add an assert that the compiler supports __attribute__ ((aligned)) because ignoring it produces an ABI-incompatible header. The struct rseq/struct rseq_cs definitions are broken, they should not try to change the alignment. PS: I have Internet connection trouble. Nobody should be worried if I drop off the net for a while. I understand this is quite a bad time for that. 8-(