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=-13.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham 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 AA700C433E0 for ; Sat, 27 Feb 2021 05:14:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5F1F864E99 for ; Sat, 27 Feb 2021 05:14:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229915AbhB0FOR (ORCPT ); Sat, 27 Feb 2021 00:14:17 -0500 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:28264 "EHLO mx0b-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229846AbhB0FOQ (ORCPT ); Sat, 27 Feb 2021 00:14:16 -0500 Received: from pps.filterd (m0098417.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.43/8.16.0.43) with SMTP id 11R54LuZ096415; Sat, 27 Feb 2021 00:13:23 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=message-id : subject : from : to : cc : date : in-reply-to : references : content-type : mime-version : content-transfer-encoding; s=pp1; bh=bRtw7DpQs0NwtjAiBX1UphIOJfHzmzPillNmd05vu3I=; b=eDDxhxfiIWpgX1juXofIeRkFEfJIeixuBtMDe0UCclIJaXF2wBAPp4EX6LcAw2I7GqGU wuBCCWjSv3tRIcbvKCA13weWArhJkxw1+BFQy9zQXqW7dXLKfNX+gablVcZGaP+Vr/GF bCqgf7edFDFrHeJndneaM4eJ2d7k2HG8gQH/NKzkL7SFkMbeA7Jp7sAbLc8hizXtY7fc hP4mtf46yNVJ1yOptxzpXvLnTKF91ofqfPf61r5wvRMUu6jyzgH7Sji9lSnb2g+pJzNi dmYX6zS1vasKMgFkPYJYn6AI4uXE1V1tJrx3lRmvpDV1CJL04D/QY0w2/XOEWs9wiJmh 1Q== Received: from ppma06fra.de.ibm.com (48.49.7a9f.ip4.static.sl-reverse.com [159.122.73.72]) by mx0a-001b2d01.pphosted.com with ESMTP id 36ycenur3k-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Sat, 27 Feb 2021 00:13:23 -0500 Received: from pps.filterd (ppma06fra.de.ibm.com [127.0.0.1]) by ppma06fra.de.ibm.com (8.16.0.42/8.16.0.42) with SMTP id 11R5Clxa005859; Sat, 27 Feb 2021 05:13:21 GMT Received: from b06avi18626390.portsmouth.uk.ibm.com (b06avi18626390.portsmouth.uk.ibm.com [9.149.26.192]) by ppma06fra.de.ibm.com with ESMTP id 36ydbh818b-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Sat, 27 Feb 2021 05:13:21 +0000 Received: from d06av23.portsmouth.uk.ibm.com (d06av23.portsmouth.uk.ibm.com [9.149.105.59]) by b06avi18626390.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 11R5D50530343560 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Sat, 27 Feb 2021 05:13:05 GMT Received: from d06av23.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id B79FCA4051; Sat, 27 Feb 2021 05:13:18 +0000 (GMT) Received: from d06av23.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 5CA77A404D; Sat, 27 Feb 2021 05:13:18 +0000 (GMT) Received: from sig-9-145-151-190.de.ibm.com (unknown [9.145.151.190]) by d06av23.portsmouth.uk.ibm.com (Postfix) with ESMTP; Sat, 27 Feb 2021 05:13:18 +0000 (GMT) Message-ID: <5493032612904e8aeeb0622146a14f0a4254016a.camel@linux.ibm.com> Subject: Re: [PATCH v3 bpf-next] selftests/bpf: Use the last page in test_snprintf_btf on s390 From: Ilya Leoshkevich To: Yonghong Song , Alexei Starovoitov , Daniel Borkmann , Heiko Carstens Cc: bpf@vger.kernel.org, Vasily Gorbik Date: Sat, 27 Feb 2021 06:13:18 +0100 In-Reply-To: <21c13c15-0dbc-8430-9e04-0932f6f913f0@fb.com> References: <20210226190908.115706-1-iii@linux.ibm.com> <21c13c15-0dbc-8430-9e04-0932f6f913f0@fb.com> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.38.4 (3.38.4-1.fc33) MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.369,18.0.761 definitions=2021-02-27_03:2021-02-26,2021-02-27 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1015 priorityscore=1501 spamscore=0 phishscore=0 adultscore=0 bulkscore=0 mlxscore=0 lowpriorityscore=0 malwarescore=0 mlxlogscore=999 suspectscore=0 impostorscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2102270034 Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Fri, 2021-02-26 at 19:47 -0800, Yonghong Song wrote: > > > On 2/26/21 11:09 AM, Ilya Leoshkevich wrote: > > test_snprintf_btf fails on s390, because NULL points to a readable > > struct lowcore there. Fix by using the last page instead. > > > > Error message example: > > > >      printing 0000000000000000 should generate error, got (361) > > > > Signed-off-by: Ilya Leoshkevich > > --- > > > > v1: > > https://lore.kernel.org/bpf/20210226135923.114211-1-iii@linux.ibm.com/ > > v1 -> v2: Yonghong suggested to add the pointer value to the error > >            message. > >            I've noticed that I've been passing BADPTR as flags, > > therefore > >            the fix worked only by accident. Put it into p.ptr where > > it > >            belongs. > > > > v2: > > https://lore.kernel.org/bpf/20210226182014.115347-1-iii@linux.ibm.com/ > > v2 -> v3: Heiko mentioned that using _REGION1_SIZE is not future- > > proof. > >            We had a private discussion and came to the conclusion > > that > >            the the last page is good enough. > > Heiko, could you ack the patch if it is okay? Thanks! > > > > >   .../testing/selftests/bpf/progs/netif_receive_skb.c | 13 > > ++++++++++--- > >   1 file changed, 10 insertions(+), 3 deletions(-) > > > > diff --git a/tools/testing/selftests/bpf/progs/netif_receive_skb.c > > b/tools/testing/selftests/bpf/progs/netif_receive_skb.c > > index 6b670039ea67..c3669967067e 100644 > > --- a/tools/testing/selftests/bpf/progs/netif_receive_skb.c > > +++ b/tools/testing/selftests/bpf/progs/netif_receive_skb.c > > @@ -16,6 +16,13 @@ bool skip = false; > >   #define STRSIZE                       2048 > >   #define EXPECTED_STRSIZE      256 > >   > > +#if defined(bpf_target_s390) > > +/* NULL points to a readable struct lowcore on s390, so take the > > last page */ > > +#define BADPTR                 ((void *)0xFFFFFFFFFFFFF000ULL) > > +#else > > +#define BADPTR                 0 > > +#endif > > + > >   #ifndef ARRAY_SIZE > >   #define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0])) > >   #endif > > @@ -113,11 +120,11 @@ int BPF_PROG(trace_netif_receive_skb, struct > > sk_buff *skb) > >         } > >   > >         /* Check invalid ptr value */ > > -       p.ptr = 0; > > +       p.ptr = BADPTR; > >         __ret = bpf_snprintf_btf(str, STRSIZE, &p, sizeof(p), 0); > >         if (__ret >= 0) { > > -               bpf_printk("printing NULL should generate error, > > got (%d)", > > -                          __ret); > > +               bpf_printk("printing %p should generate error, got > > (%d)", > > +                          BADPTR, __ret); > >  From https://www.kernel.org/doc/Documentation/printk-formats.txt: > > Pointers printed without a specifier extension (i.e unadorned %p) are > hashed to give a unique identifier without leaking kernel addresses > to user > space. On 64 bit machines the first 32 bits are zeroed. If you > _really_ > want the address see %px below. > > I think it is okay to use %px here. I don't think bpf_trace_printk supports it, but I'll use %llx instead. [...]