From patchwork Wed Aug 25 19:58:20 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Dave Marchevsky X-Patchwork-Id: 502727 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=-24.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER, INCLUDES_PATCH, MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable 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 042B3C432BE for ; Wed, 25 Aug 2021 19:58:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E11A86109E for ; Wed, 25 Aug 2021 19:58:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242519AbhHYT7d (ORCPT ); Wed, 25 Aug 2021 15:59:33 -0400 Received: from mx0a-00082601.pphosted.com ([67.231.145.42]:50028 "EHLO mx0a-00082601.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S242507AbhHYT7a (ORCPT ); Wed, 25 Aug 2021 15:59:30 -0400 Received: from pps.filterd (m0044010.ppops.net [127.0.0.1]) by mx0a-00082601.pphosted.com (8.16.0.43/8.16.0.43) with SMTP id 17PJpONr008913 for ; Wed, 25 Aug 2021 12:58:44 -0700 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=fb.com; h=from : to : cc : subject : date : message-id : in-reply-to : references : content-type : content-transfer-encoding : mime-version; s=facebook; bh=zMLxDb4KnCnHDg/fz+i9Y5/zBLd+vVuW8ncpktLpjm8=; b=F1YW6UXBQFKE8dNc1T0tuAcMnAjDrmC9c0XhP0QtoqmPK0RgLATeciddB7lpvVA2PmP3 ndWONwXUWZCJxtcBSqgqiI6xS/R0d062t3vK5sDKmVNhU48LDXUH9ZMxZfpdP5QSHFrA sR2dr7IATXqahF1nUTOyDSgIT+rScOC0fb0= Received: from mail.thefacebook.com ([163.114.132.120]) by mx0a-00082601.pphosted.com with ESMTP id 3an5sm894f-3 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NOT) for ; Wed, 25 Aug 2021 12:58:44 -0700 Received: from intmgw001.25.frc3.facebook.com (2620:10d:c085:208::11) by mail.thefacebook.com (2620:10d:c085:11d::7) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2176.2; Wed, 25 Aug 2021 12:58:43 -0700 Received: by devbig030.frc3.facebook.com (Postfix, from userid 158236) id 245115A34ED9; Wed, 25 Aug 2021 12:58:37 -0700 (PDT) From: Dave Marchevsky To: CC: Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Yonghong Song , , Dave Marchevsky Subject: [PATCH v2 bpf-next 3/6] libbpf: Modify bpf_printk to choose helper based on arg count Date: Wed, 25 Aug 2021 12:58:20 -0700 Message-ID: <20210825195823.381016-4-davemarchevsky@fb.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210825195823.381016-1-davemarchevsky@fb.com> References: <20210825195823.381016-1-davemarchevsky@fb.com> X-FB-Internal: Safe X-FB-Source: Intern X-Proofpoint-GUID: Lkr36jhIch-SBTEzApAE2bkrzqzZ_iBI X-Proofpoint-ORIG-GUID: Lkr36jhIch-SBTEzApAE2bkrzqzZ_iBI X-Proofpoint-UnRewURL: 0 URL was un-rewritten MIME-Version: 1.0 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391, 18.0.790 definitions=2021-08-25_07:2021-08-25,2021-08-25 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 malwarescore=0 phishscore=0 spamscore=0 mlxlogscore=999 suspectscore=0 lowpriorityscore=0 priorityscore=1501 bulkscore=0 impostorscore=0 clxscore=1015 adultscore=0 mlxscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2107140000 definitions=main-2108250117 X-FB-Internal: deliver Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org Instead of being a thin wrapper which calls into bpf_trace_printk, libbpf's bpf_printk convenience macro now chooses between bpf_trace_printk and bpf_trace_vprintk. If the arg count (excluding format string) is >3, use bpf_trace_vprintk, otherwise use the older helper. The motivation behind this added complexity - instead of migrating entirely to bpf_trace_vprintk - is to maintain good developer experience for users compiling against new libbpf but running on older kernels. Users who are passing <=3 args to bpf_printk will see no change in their bytecode. __bpf_vprintk functions similarly to BPF_SEQ_PRINTF and BPF_SNPRINTF macros elsewhere in the file - it allows use of bpf_trace_vprintk without manual conversion of varargs to u64 array. Previous implementation of bpf_printk macro is moved to __bpf_printk for use by the new implementation. This does change behavior of bpf_printk calls with >3 args in the "new libbpf, old kernels" scenario. On my system, using a clang built from recent upstream sources (14.0.0 https://github.com/llvm/llvm-project.git 50b62731452cb83979bbf3c06e828d26a4698dca), attempting to use 4 args to __bpf_printk (old impl) results in a compile-time error: progs/trace_printk.c:21:21: error: too many args to 0x6cdf4b8: i64 = Constant<6> trace_printk_ret = __bpf_printk("testing,testing %d %d %d %d\n", I was able to replicate this behavior with an older clang as well. When the format string has >3 format specifiers, there is no output to the trace_pipe in either case. After this patch, using bpf_printk with 4 args would result in a trace_vprintk helper call being emitted and a load-time failure on older kernels. Signed-off-by: Dave Marchevsky --- tools/lib/bpf/bpf_helpers.h | 45 ++++++++++++++++++++++++++++++------- 1 file changed, 37 insertions(+), 8 deletions(-) diff --git a/tools/lib/bpf/bpf_helpers.h b/tools/lib/bpf/bpf_helpers.h index b9987c3efa3c..5f087306cdfe 100644 --- a/tools/lib/bpf/bpf_helpers.h +++ b/tools/lib/bpf/bpf_helpers.h @@ -14,14 +14,6 @@ #define __type(name, val) typeof(val) *name #define __array(name, val) typeof(val) *name[] -/* Helper macro to print out debug messages */ -#define bpf_printk(fmt, ...) \ -({ \ - char ____fmt[] = fmt; \ - bpf_trace_printk(____fmt, sizeof(____fmt), \ - ##__VA_ARGS__); \ -}) - /* * Helper macro to place programs, maps, license in * different sections in elf_bpf file. Section names @@ -224,4 +216,41 @@ enum libbpf_tristate { ___param, sizeof(___param)); \ }) +/* Helper macro to print out debug messages */ +#define __bpf_printk(fmt, ...) \ +({ \ + char ____fmt[] = fmt; \ + bpf_trace_printk(____fmt, sizeof(____fmt), \ + ##__VA_ARGS__); \ +}) + +/* + * __bpf_vprintk wraps the bpf_trace_vprintk helper with variadic arguments + * instead of an array of u64. + */ +#define __bpf_vprintk(fmt, args...) \ +({ \ + static const char ___fmt[] = fmt; \ + unsigned long long ___param[___bpf_narg(args)]; \ + \ + _Pragma("GCC diagnostic push") \ + _Pragma("GCC diagnostic ignored \"-Wint-conversion\"") \ + ___bpf_fill(___param, args); \ + _Pragma("GCC diagnostic pop") \ + \ + bpf_trace_vprintk(___fmt, sizeof(___fmt), \ + ___param, sizeof(___param)); \ +}) + +#define ___bpf_pick_printk(...) \ + ___bpf_nth(_, ##__VA_ARGS__, __bpf_vprintk, __bpf_vprintk, __bpf_vprintk, \ + __bpf_vprintk, __bpf_vprintk, __bpf_vprintk, __bpf_vprintk, \ + __bpf_vprintk, __bpf_vprintk, __bpf_printk, __bpf_printk, \ + __bpf_printk, __bpf_printk) + +#define bpf_printk(fmt, args...) \ +({ \ + ___bpf_pick_printk(args)(fmt, args); \ +}) + #endif