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=-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 81ACDC433E0 for ; Wed, 17 Feb 2021 11:10:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5D89264DCF for ; Wed, 17 Feb 2021 11:10:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231578AbhBQLKK (ORCPT ); Wed, 17 Feb 2021 06:10:10 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33902 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231544AbhBQLJz (ORCPT ); Wed, 17 Feb 2021 06:09:55 -0500 Received: from mail-qv1-xf49.google.com (mail-qv1-xf49.google.com [IPv6:2607:f8b0:4864:20::f49]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0F256C0617A7 for ; Wed, 17 Feb 2021 03:08:26 -0800 (PST) Received: by mail-qv1-xf49.google.com with SMTP id h10so9704211qvf.19 for ; Wed, 17 Feb 2021 03:08:26 -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=ICJenGYVVB2UMBJ+iIKGIow1eUvegxgyz46lhETpOEo=; b=PEhEAThsEfNyW5iaB/O495UGeIjmkOQhOja4zRTQcigkQrN0VXhnDEqu5yCsVz8hJt C3RSWAwyrkRcLgJ250YHpCYOhR/d7SbD87sVPf+kQaADqe18hrMxJwgHC3vC3e1r/5hM i6N0SqLKpqT8Yx55U6WIOJhX3XeVVnpUHv4bAJyrcc7RgXMWl7TFjX7EWybymD1i0rE9 fjBEAdbQQpasahkwXL5h00bGF9Z8Z4C9h7a3YEYQMxNDoH1G2jx7Jc6+u1aQqbMwWw85 jHjpHOC+RgJSJPx5UhjMsOnAiVNqt8qFkWUBGOllF96E7qFkPTIe5Pr/lpNKxSCUoeon LYTw== 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=ICJenGYVVB2UMBJ+iIKGIow1eUvegxgyz46lhETpOEo=; b=GdrkUBuBbr+qKZiOQ+qNDqqTeG/9l/kCMtlji3e8FY2yE12VpwxT8g7j5xxm6Mrxdi D7f3y1ZSspSMGpg+57cLr8y58xDNI+/EkeJL1rqSGEZbUnIG7xlAkUlztg6YM92cbsiS C7pCvfwzqJIbbpka7x1cas4Khiysj3Jt6ImtZCFfjjwfUx5FYCUuJBdRdb/smo1UBwhd vj2Pasu4rC9FceTX9EdIEFXcWm5pgERCB/jy/TOg96VRME9xhfV7LqnJjuQE83HiWY4B 0YZL3EW4ynqN3RLj1ThxvV9yn1bDO3Dlc8T+/wytAnZGikv/usErbBE8fI6G25cg73nW aZzg== X-Gm-Message-State: AOAM531CksTcjFzzMSjPGYrozUimK0HIKAS9gKqqo2kpkQNg46tf2PCk 8VBkdEdeI2YGMjCnZ5kuRwpPvgcJHeDtig== X-Google-Smtp-Source: ABdhPJziMOSsIQGNdtJaRQPRS9whDjRhhEU+hGOvIG0l8uCjwtm9jd+lI0E/ouyizbEYfP8GW+SMxFAcBfbP4Q== Sender: "gprocida via sendgmr" X-Received: from tef.lon.corp.google.com ([2a00:79e0:d:110:61b3:1cb2:c180:c3f]) (user=gprocida job=sendgmr) by 2002:a05:6214:16cf:: with SMTP id d15mr23910944qvz.32.1613560105235; Wed, 17 Feb 2021 03:08:25 -0800 (PST) Date: Wed, 17 Feb 2021 11:08:04 +0000 In-Reply-To: <20210217110804.75923-1-gprocida@google.com> Message-Id: <20210217110804.75923-6-gprocida@google.com> Mime-Version: 1.0 References: <20210205134221.2953163-1-gprocida@google.com> <20210217110804.75923-1-gprocida@google.com> X-Mailer: git-send-email 2.30.0.478.g8a0d178c01-goog Subject: [PATCH dwarves v4 5/5] btf_encoder: Align .BTF section to 8 bytes From: Giuliano Procida To: dwarves@vger.kernel.org, acme@kernel.org Cc: andrii@kernel.org, ast@kernel.org, gprocida@google.com, maennich@google.com, kernel-team@android.com, kernel-team@fb.com, bpf@vger.kernel.org Content-Type: text/plain; charset="UTF-8" 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. Acked-by: Andrii Nakryiko Signed-off-by: Giuliano Procida --- libbtf.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/libbtf.c b/libbtf.c index 9ff03ca..ee677fa 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) -- 2.30.0.478.g8a0d178c01-goog