From patchwork Thu Sep 2 17:19:20 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Dave Marchevsky X-Patchwork-Id: 12472189 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=-19.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT 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 CB4BCC8302A for ; Thu, 2 Sep 2021 17:20:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B6F0F60FE6 for ; Thu, 2 Sep 2021 17:20:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242982AbhIBRVD (ORCPT ); Thu, 2 Sep 2021 13:21:03 -0400 Received: from mx0a-00082601.pphosted.com ([67.231.145.42]:21992 "EHLO mx0a-00082601.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1346565AbhIBRVD (ORCPT ); Thu, 2 Sep 2021 13:21:03 -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 182HJ5IC006660 for ; Thu, 2 Sep 2021 10:20:04 -0700 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=fb.com; h=from : to : cc : subject : date : message-id : content-type : content-transfer-encoding : mime-version; s=facebook; bh=33VCdYpStX0Sw+pn5ejIOQKBbirZXE8W/mvrljry0f4=; b=Rh6VhaOtPvPOPw7WG9+d6xCRhGbooigeF5IfnDucM0fB/rfMw7eDyDBwwgoU+5CBhhiP Y16hu38Fct6FkW2CY8YgqA8kdu77+ONGsDSFO0R0W69bjCau2O56bp5kFJo65sjjB8J9 CvCCobgeqHaOxhGWPfxgRCPZt66uWSgVI4o= Received: from mail.thefacebook.com ([163.114.132.120]) by mx0a-00082601.pphosted.com with ESMTP id 3atdxvbbdx-9 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NOT) for ; Thu, 02 Sep 2021 10:20:04 -0700 Received: from intmgw002.25.frc3.facebook.com (2620:10d:c085:208::f) by mail.thefacebook.com (2620:10d:c085:11d::5) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.14; Thu, 2 Sep 2021 10:20:03 -0700 Received: by devbig030.frc3.facebook.com (Postfix, from userid 158236) id E74ED5FE2452; Thu, 2 Sep 2021 10:19:49 -0700 (PDT) From: Dave Marchevsky To: CC: Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Yonghong Song , , Dave Marchevsky Subject: [PATCH v4 bpf-next 0/9] bpf: implement variadic printk helper Date: Thu, 2 Sep 2021 10:19:20 -0700 Message-ID: <20210902171929.3922667-1-davemarchevsky@fb.com> X-Mailer: git-send-email 2.30.2 X-FB-Internal: Safe X-FB-Source: Intern X-Proofpoint-ORIG-GUID: oGkaD0WqXX0BDNJ1M6rmqoU2nXjhxEFw X-Proofpoint-GUID: oGkaD0WqXX0BDNJ1M6rmqoU2nXjhxEFw 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=2021-09-02_04:2021-09-02,2021-09-02 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 clxscore=1015 bulkscore=0 suspectscore=0 phishscore=0 mlxlogscore=999 impostorscore=0 priorityscore=1501 malwarescore=0 mlxscore=0 spamscore=0 adultscore=0 lowpriorityscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2108310000 definitions=main-2109020100 X-FB-Internal: deliver Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org X-Patchwork-Delegate: bpf@iogearbox.net This series introduces a new helper, bpf_trace_vprintk, which functions like bpf_trace_printk but supports > 3 arguments via a pseudo-vararg u64 array. The bpf_printk libbpf convenience macro is modified to use bpf_trace_vprintk when > 3 varargs are passed, otherwise the previous behavior - using bpf_trace_printk - is retained. Helper functions and macros added during the implementation of bpf_seq_printf and bpf_snprintf do most of the heavy lifting for bpf_trace_vprintk. There's no novel format string wrangling here. Usecase here is straightforward: Giving BPF program writers a more powerful printk will ease development of BPF programs, particularly during debugging and testing, where printk tends to be used. This feature was proposed by Andrii in libbpf mirror's issue tracker [1]. [1] https://github.com/libbpf/libbpf/issues/315 v3 -> v4: * Add patch 2, which migrates reference_tracking prog_test away from bpf_program__load. Could be placed a bit later in the series, but wanted to keep the actual vprintk-related patches contiguous * Add patch 9, which adds a program w/ 0 fmt arg bpf_printk to vprintk test * bpf_printk convenience macro isn't multiline anymore, so simplify [Andrii] * Add some comments to ___bpf_pick_printk to make it more obvious when implementation switches from printk to vprintk [Andrii] * BPF_PRINTK_FMT_TYPE -> BPF_PRINTK_FMT_MOD for 'static const' fmt string in printk wrapper macro [Andrii] * checkpatch.pl doesn't like this, says "Macros with complex values should be enclosed in parentheses". Strange that it didn't have similar complaints about v3's BPF_PRINTK_FMT_TYPE. Regardless, IMO the complaint is not highlighting a real issue in the case of this macro. * Fix alignment of __bpf_vprintk and __bpf_pick_printk [Andrii] * rebase v2 -> v3: * Clean up patch 3's commit message [Alexei] * Add patch 4, which modifies __bpf_printk to use 'static const char' to store fmt string with fallback for older kernels [Andrii] * rebase v1 -> v2: * Naming conversation seems to have gone in favor of keeping bpf_trace_vprintk, names are unchanged * Patch 3 now modifies bpf_printk convenience macro to choose between __bpf_printk and __bpf_vprintk 'implementation' macros based on arg count. __bpf_vprintk is a renaming of bpf_vprintk convenience macro from v1, __bpf_printk is the existing bpf_printk implementation. This patch could use some scrutiny as I think current implementation may regress developer experience in a specific case, turning a compile-time error into a load-time error. Unclear to me how common the case is, or whether the macro magic I chose is ideal. * char ___fmt[] to static const char ___fmt[] change was not done, wanted to leave __bpf_printk 'implementation' macro unchanged for v2 to ease discussion of above point * Removed __always_inline from __set_printk_clr_event [Andrii] * Simplified bpf_trace_printk docstring to refer to other functions instead of copy/pasting and avoid specifying 12 vararg limit [Andrii] * Migrated trace_printk selftest to use ASSERT_ instead of CHECK * Adds new patch 5, previous patch 5 is now 6 * Migrated trace_vprintk selftest to use ASSERT_ instead of CHECK, open_and_load instead of separate open, load [Andrii] * Patch 2's commit message now correctly mentions trace_pipe instead of dmesg [Andrii] Dave Marchevsky (9): bpf: merge printk and seq_printf VARARG max macros selftests/bpf: stop using bpf_program__load bpf: add bpf_trace_vprintk helper libbpf: Modify bpf_printk to choose helper based on arg count libbpf: use static const fmt string in __bpf_printk bpftool: only probe trace_vprintk feature in 'full' mode selftests/bpf: Migrate prog_tests/trace_printk CHECKs to ASSERTs selftests/bpf: add trace_vprintk test prog selftests/bpf: Add test for bpf_printk w/ 0 fmt args include/linux/bpf.h | 3 + include/uapi/linux/bpf.h | 9 +++ kernel/bpf/core.c | 5 ++ kernel/bpf/helpers.c | 6 +- kernel/trace/bpf_trace.c | 54 ++++++++++++++- tools/bpf/bpftool/feature.c | 1 + tools/include/uapi/linux/bpf.h | 9 +++ tools/lib/bpf/bpf_helpers.h | 51 ++++++++++++--- tools/testing/selftests/bpf/Makefile | 3 +- .../bpf/prog_tests/reference_tracking.c | 39 ++++++++--- .../selftests/bpf/prog_tests/trace_printk.c | 24 +++---- .../selftests/bpf/prog_tests/trace_vprintk.c | 65 +++++++++++++++++++ .../selftests/bpf/progs/trace_vprintk.c | 32 +++++++++ tools/testing/selftests/bpf/test_bpftool.py | 22 +++---- 14 files changed, 272 insertions(+), 51 deletions(-) create mode 100644 tools/testing/selftests/bpf/prog_tests/trace_vprintk.c create mode 100644 tools/testing/selftests/bpf/progs/trace_vprintk.c