From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com [148.163.156.1]) by sourceware.org (Postfix) with ESMTPS id E70203858D39 for ; Tue, 3 Oct 2023 22:12:58 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.2 sourceware.org E70203858D39 Authentication-Results: sourceware.org; dmarc=none (p=none dis=none) header.from=linux.ibm.com Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=linux.ibm.com Received: from pps.filterd (m0353726.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.17.1.19/8.17.1.19) with ESMTP id 393M841h017578; Tue, 3 Oct 2023 22:12:44 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=message-id : date : mime-version : subject : to : cc : references : from : in-reply-to : content-type : content-transfer-encoding; s=pp1; bh=YP5wAVIPc/j/VuI7EZ2emXZX/mLoB2rjvhdkiLByvlM=; b=HCirntTjn/QkQiFBB4hOlGZfTF3baZd3CuljLrtOMexdxPWXvTzZA04BXAMxIayANAGA DrtZ/hcr09JrM/RaY3/jgdaOIXP7DH81nNrMQci1aGZL4eVG8vq6Ni+nZxyhjjEur0Md gYOyr6qPbJFFq2mojj+T9DS6M1E3zx2ZxfLYXIH46Ux4CPMFZ0JSHNHIAZF2ySxrp7jr wDWM7ohlpLE27ZsyUx1D8lLAQFELpouHm7SRlquW9gKKVqLNr4SWS/kwuCOt5vu+mvon zlmAuaPEobbR/rh3JV/OaO83OczxWR4Z3s4iZDPh+vH/LITJnfKEBL3uQwHa+U3RYWW6 cw== Received: from pps.reinject (localhost [127.0.0.1]) by mx0a-001b2d01.pphosted.com (PPS) with ESMTPS id 3tgu8909kk-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Tue, 03 Oct 2023 22:12:43 +0000 Received: from m0353726.ppops.net (m0353726.ppops.net [127.0.0.1]) by pps.reinject (8.17.1.5/8.17.1.5) with ESMTP id 393M90vj020103; Tue, 3 Oct 2023 22:12:43 GMT Received: from ppma11.dal12v.mail.ibm.com (db.9e.1632.ip4.static.sl-reverse.com [50.22.158.219]) by mx0a-001b2d01.pphosted.com (PPS) with ESMTPS id 3tgu8909k9-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Tue, 03 Oct 2023 22:12:43 +0000 Received: from pps.filterd (ppma11.dal12v.mail.ibm.com [127.0.0.1]) by ppma11.dal12v.mail.ibm.com (8.17.1.19/8.17.1.19) with ESMTP id 393KhBFR010898; Tue, 3 Oct 2023 22:12:42 GMT Received: from smtprelay02.dal12v.mail.ibm.com ([172.16.1.4]) by ppma11.dal12v.mail.ibm.com (PPS) with ESMTPS id 3tf0q1nmd3-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Tue, 03 Oct 2023 22:12:42 +0000 Received: from smtpav01.dal12v.mail.ibm.com (smtpav01.dal12v.mail.ibm.com [10.241.53.100]) by smtprelay02.dal12v.mail.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 393MCfbj26673772 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 3 Oct 2023 22:12:41 GMT Received: from smtpav01.dal12v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id BA40858058; Tue, 3 Oct 2023 22:12:41 +0000 (GMT) Received: from smtpav01.dal12v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 1E05D58057; Tue, 3 Oct 2023 22:12:41 +0000 (GMT) Received: from [9.61.61.107] (unknown [9.61.61.107]) by smtpav01.dal12v.mail.ibm.com (Postfix) with ESMTP; Tue, 3 Oct 2023 22:12:41 +0000 (GMT) Message-ID: Date: Tue, 3 Oct 2023 17:12:40 -0500 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] uapi/auxvec: Define AT_HWCAP3 and AT_HWCAP4 aux vector, entries Content-Language: en-US To: Adhemerval Zanella Netto , linux-api@vger.kernel.org, linux-arch@vger.kernel.org, "linuxppc-dev@lists.ozlabs.org" Cc: Nicholas Piggin , Michael Ellerman , Segher Boessenkool , GNU C Library References: <97eb2099-23c2-4921-89ac-9523226ad221@linaro.org> <891957ad-453e-4c68-9c5a-7a979667543d@linux.ibm.com> <057366c2-ee65-441d-b2ac-f40e1d94b44e@linaro.org> From: Peter Bergner In-Reply-To: <057366c2-ee65-441d-b2ac-f40e1d94b44e@linaro.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: QBv_-BKDIIjD6Ym1H1PQ2Xb6PFMUBl_I X-Proofpoint-GUID: Tb47txw3PRJ5F1pBchWwQ_ZiRAOEEZ1e X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.267,Aquarius:18.0.980,Hydra:6.0.619,FMLib:17.11.176.26 definitions=2023-10-03_18,2023-10-02_01,2023-05-22_02 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 bulkscore=0 priorityscore=1501 lowpriorityscore=0 phishscore=0 clxscore=1015 malwarescore=0 mlxscore=0 adultscore=0 suspectscore=0 mlxlogscore=598 spamscore=0 impostorscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2309180000 definitions=main-2310030167 X-Spam-Status: No, score=-3.1 required=5.0 tests=BAYES_00,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_EF,RCVD_IN_MSPIKE_H4,RCVD_IN_MSPIKE_WL,SPF_HELO_NONE,SPF_PASS,TXREP autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org List-Id: On 10/3/23 9:08 AM, Adhemerval Zanella Netto wrote: > What it is not clear to me is what kind of ABI boundary you are trying to > preemptively add support here. The TCB ABI for __builtin_cpu_supports is > userland only, so if your intention is just to allow gcc to work on older > glibcs, it should be a matter to just reserve the space on tcbhead_t. Yes, extending tcbhead_t to contain the slots for hwcap3 and hwcap4 are the ABI extensions we are interested in, and not something that can be backported into a distro point release. Yes, we don't strictly need the AT_HWCAP3 and AT_HWCAP4 kernel defines to reserve (and clear) that space in glibc, but.... > If your intention is to also add support on glibc, it makes more sense to > already reserve it. For __builtin_cpu_supports it should work, although > for glibc itself some backporting would be required (to correctly showing > the bits with LD_SHOW_AUXV). Our intention is to also add the glibc support too once we have the AT_HWCAP3 and AT_HWCAP4 kernel macros defined. 1) Once the defines are there, adding the support should be pretty straight forward, so why wait? And 2) part of the glibc and compiler support introduces a new symbol that is exported by glibc and referenced by the compilers to ensure the compilers *never* access the hwcap* fields in the TCB unless the glibc supports them. See the symbol __parse_hwcap_and_convert_at_platform used for HWCAP/HWCAP2. We'll need a similar one for HWCAP3/HWCAP4 and I'm doubtful whether the distros will allow the backport of a patch that introduces a new exported symbol from glibc in a distro point release. Peter