From patchwork Fri Feb 5 13:42:21 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Giuliano Procida X-Patchwork-Id: 12071213 X-Patchwork-Delegate: bpf@iogearbox.net 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=-26.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT,USER_IN_DEF_DKIM_WL 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 76BDDC433E0 for ; Fri, 5 Feb 2021 22:44:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 428976500E for ; Fri, 5 Feb 2021 22:44:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231189AbhBEWoM (ORCPT ); Fri, 5 Feb 2021 17:44:12 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42956 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231373AbhBENnf (ORCPT ); Fri, 5 Feb 2021 08:43:35 -0500 Received: from mail-qk1-x74a.google.com (mail-qk1-x74a.google.com [IPv6:2607:f8b0:4864:20::74a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B3B1AC061223 for ; Fri, 5 Feb 2021 05:42:48 -0800 (PST) Received: by mail-qk1-x74a.google.com with SMTP id s66so5798913qkh.10 for ; Fri, 05 Feb 2021 05:42:48 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=sender:date:in-reply-to:message-id:mime-version:references:subject :from:to:cc; bh=tAOVQ3G2eN9dGCWyxwwne5gBaM7loqyQjU9wOYpr/6I=; b=OH+gSvlZu8rebHPUVoqKDmTFHlv+/7sQvcchXxOZT1Jn21iONeHO5qh0iOgXDZWX7q jeC17g6FkVEOtLw2JujRlsXjCBYN14uQ/OGcRwPWafs4nX0OA8kWZjC42AjACQRY3E+O 6K/exEZWEsXQ7RObfSoLk6W2LbPGLqRruEHRwzRRiJvTCBgd82+1G8ivxl2sOdOftuJg m2WBkw65oW3/j1LRV1+a1nZkqeU/kLZ7Q1IpGzztRAi0qeh1hjeMjoO8ZWfgx29MYJIa TUwZpYnUIxODrp3LiKHFcqxHFa/CINvN3it27Eev4QLEzWMsmWlQfsjBnm/+Twr7/tdz Qe0w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=tAOVQ3G2eN9dGCWyxwwne5gBaM7loqyQjU9wOYpr/6I=; b=XVFd1WA4SQhlKNzp7ur6qoVmQKUCLBgiC1b3uEUmk8LKKy1TSZT7RMI1jMXhxxz6c4 mYH2nUf3nwiHoyJw1t/8YatzKFysjzMewe1p3ctQXMnKFiRANOknvRGBB0cDCNZC7JRU MWbklzTH5QtJj+sylyHnDPmVwyGa1hueqIALFT2yravF3hC+lZBt6P5Hj6Na9VGlgx2T t1SbW7r94p3PMRnwZbo92MCb2XXb/k6yUwhvrZSX4gBseIEvtPn2a8LXBcR3dT3wrydX GeNZA1dIpMU9YNXFfonCaAPBwQTwhWIGk1PWqjCB9e/8Ck/hPV3rhbcdjcwAfZv3qJ2c s5xA== X-Gm-Message-State: AOAM533IRUaG2Xvi5vitdENyv6/5Llv38ya0BLAbLsT+PdewEYgNSQb3 jUIxCdX6zpIO5urQguj4vtQ8kWWGRu/crg== X-Google-Smtp-Source: ABdhPJz5wihZxlw8hgR5CE0fmzuZmzIXYPXLcOoH3i+RKhajR348e6cGEOGc6mhYA8VGyVScObuVOOKwC0tm4w== Sender: "gprocida via sendgmr" X-Received: from tef.lon.corp.google.com ([2a00:79e0:d:110:656b:9716:1ea:3de6]) (user=gprocida job=sendgmr) by 2002:a05:6214:a54:: with SMTP id ee20mr4390536qvb.16.1612532567845; Fri, 05 Feb 2021 05:42:47 -0800 (PST) Date: Fri, 5 Feb 2021 13:42:21 +0000 In-Reply-To: <20210205134221.2953163-1-gprocida@google.com> Message-Id: <20210205134221.2953163-6-gprocida@google.com> Mime-Version: 1.0 References: <20210201172530.1141087-1-gprocida@google.com> <20210205134221.2953163-1-gprocida@google.com> X-Mailer: git-send-email 2.30.0.478.g8a0d178c01-goog Subject: [PATCH dwarves v3 5/5] btf_encoder: Align .BTF section to 8 bytes From: Giuliano Procida To: dwarves@vger.kernel.org Cc: acme@kernel.org, andrii@kernel.org, ast@kernel.org, gprocida@google.com, maennich@google.com, kernel-team@android.com, kernel-team@fb.com, bpf@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org This is to avoid misaligned access to BTF type structs when memory-mapping ELF objects. Signed-off-by: Giuliano Procida Acked-by: Andrii Nakryiko --- libbtf.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/libbtf.c b/libbtf.c index 9f4abb3..6754a17 100644 --- a/libbtf.c +++ b/libbtf.c @@ -744,6 +744,14 @@ static int btf_elf__write(const char *filename, struct btf *btf) goto out; } + /* + * We'll align .BTF to 8 bytes to cater for all architectures. It'd be + * nice if we could fetch this value from somewhere. The BTF + * specification does not discuss alignment and its trailing string + * table is not currently padded to any particular alignment. + */ + const size_t btf_alignment = 8; + /* * First we check if there is already a .BTF section present. */ @@ -821,6 +829,7 @@ static int btf_elf__write(const char *filename, struct btf *btf) elf_error("elf_getshdr(btf_scn) failed"); goto out; } + btf_shdr.sh_addralign = btf_alignment; btf_shdr.sh_entsize = 0; btf_shdr.sh_flags = 0; if (dot_btf_offset)