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=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 23226C433E0 for ; Thu, 18 Mar 2021 19:32:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E587764F18 for ; Thu, 18 Mar 2021 19:32:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232648AbhCRTbf (ORCPT ); Thu, 18 Mar 2021 15:31:35 -0400 Received: from mail-qk1-f178.google.com ([209.85.222.178]:37469 "EHLO mail-qk1-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232785AbhCRTbZ (ORCPT ); Thu, 18 Mar 2021 15:31:25 -0400 Received: by mail-qk1-f178.google.com with SMTP id g15so429536qkl.4 for ; Thu, 18 Mar 2021 12:31:25 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=vvpNRJKAVW57zXV7q+4Xfj7x19d8NVclr/wTI6p5fZU=; b=ngc5j+IBE0M9Kb/O9QcphqIIcjQawJVRTNTgEnc2f+XsfgdwSwPG5xaxmAKMGjNexs z12EwGzqk9SByLnAtMfAjwE/UOZpvuMnJZZZHIolYrXlSrEaX3RBn01R3XOWOQFRzPIz rx91u60E5paL7SQUaQADEXVScsp1VblgIKr1ZGRAvdGK7tuBzCGZXC6yML1zEhpY1NOr zqT2iMSCAeMbClNmEsAW/7H7CMLYUgYgFAXQynzihLEqYbA3ShKsxtT60IoqN7WM0ost pOG4g5EYAFZK01d7re12fmzxBnZxvkcF0X8PrVdAnsJ/SBoR/+aPNktFxkh+stgN0Oo3 OG6Q== X-Gm-Message-State: AOAM531I+FFZX5PmAYl216jGr7hpBU2n+RrNlDRrq0l9ztDwx/QoEnba aCyuJvo7MW+R4DdZkDSlAg== X-Google-Smtp-Source: ABdhPJzf9VjPAAx2mr1CKAksVeAJEXmCNp1XmLSyeKh47khIAIgiEw6TmakRgfZhK7eB3JZwInnsDQ== X-Received: by 2002:a05:620a:16b1:: with SMTP id s17mr5855452qkj.302.1616095884818; Thu, 18 Mar 2021 12:31:24 -0700 (PDT) Received: from fujitsu.celeiro.cu ([138.204.26.16]) by smtp.gmail.com with ESMTPSA id 73sm2468687qkk.131.2021.03.18.12.31.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 18 Mar 2021 12:31:24 -0700 (PDT) From: Rafael David Tinoco To: rafaeldtinoco@ubuntu.com Cc: andrii.nakryiko@gmail.com, bpf@vger.kernel.org Subject: [PATCH] libbpf: allow bpf object kern_version to be overridden Date: Thu, 18 Mar 2021 16:31:21 -0300 Message-Id: <20210318193121.370561-1-rafaeldtinoco@ubuntu.com> X-Mailer: git-send-email 2.27.0 In-Reply-To: <20210318062520.3838605-1-rafaeldtinoco@ubuntu.com> References: <20210318062520.3838605-1-rafaeldtinoco@ubuntu.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org Unfortunately some distros don't have their accurate kernel version defined correctly in version.h due to long term support decisions. This makes LINUX_VERSION_CODE to be defined as the original upstream version in header, while the running in-kernel version is different. Older kernels might still check kern_version during bpf_prog_load(), making it impossible to load a program that could still be portable. This patch allows one to override bpf objects kern_version attributes, so program can bypass this in-kernel check during load. Example: A kernel 4.15.0-129.132, for example, might have 4.15.18 version defined in its headers, which is the kernel it is based on, but have a 4.15.0 version defined within the kernel due to other factors. $ export LIBBPF_KERN_VERSION=4.15.18 $ sudo -E ./portablebpf -v ... libbpf: bpf object: kernel_version enforced by env variable: 266002 ... This will also help portable binaries within similar older kernels, as long as they have their BTF data converted from DWARVES (for example). Signed-off-by: Rafael David Tinoco --- src/libbpf.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) diff --git a/src/libbpf.c b/src/libbpf.c index 4dc09d3..cbc6e61 100644 --- a/src/libbpf.c +++ b/src/libbpf.c @@ -708,13 +708,19 @@ bpf_object__add_programs(struct bpf_object *obj, Elf_Data *sec_data, static __u32 get_kernel_version(void) { - __u32 major, minor, patch; struct utsname info; + __u32 major, minor, patch, ver; + char *ptr, *e = getenv("LIBBPF_KERN_VERSION"); uname(&info); - if (sscanf(info.release, "%u.%u.%u", &major, &minor, &patch) != 3) + ptr = (e != NULL) ? e : (char *) &info.release; + if (sscanf(ptr, "%u.%u.%u", &major, &minor, &patch) != 3) return 0; - return KERNEL_VERSION(major, minor, patch); + ver = KERNEL_VERSION(major, minor, patch); + if (e) + pr_debug("bpf object: kernel_version enforced by env variable: %u\n", ver); + + return ver; } static const struct btf_member * -- 2.17.1