From patchwork Tue Aug 13 12:16:59 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: =?utf-8?q?Matthias_M=C3=A4nnich?= X-Patchwork-Id: 11092059 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 92D1C14D5 for ; Tue, 13 Aug 2019 12:19:54 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 839772849D for ; Tue, 13 Aug 2019 12:19:54 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 76974284AA; Tue, 13 Aug 2019 12:19:54 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.5 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI, USER_IN_DEF_DKIM_WL autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id C0DD1284A3 for ; Tue, 13 Aug 2019 12:19:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727869AbfHMMTQ (ORCPT ); Tue, 13 Aug 2019 08:19:16 -0400 Received: from mail-qt1-f201.google.com ([209.85.160.201]:50464 "EHLO mail-qt1-f201.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727348AbfHMMTP (ORCPT ); Tue, 13 Aug 2019 08:19:15 -0400 Received: by mail-qt1-f201.google.com with SMTP id c14so6318222qtn.17 for ; Tue, 13 Aug 2019 05:19:14 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=52i5W7bwo5L4NKPi/t621ZC4mfXuxf76PQ3XmRwW6HM=; b=X/pgFG/TYnO3wKM8nw/G0c4v0tOMmQdSnN8sjbDmuSgMHWrl6X+89yGWfc1zRmqGBm 2psEodSKm+/2j3izZcJSwh+do0lxOJ4IdJ919zTrnssGXYKHj74o5LYYGq9C8uPDHY5q g2LiVJBFkP/CGURRmfNZIany5JG8mi2TMrG0Bd6uXJ7oNOJoL/pnInv0Qzjz7lymxdtT GJKYSZXUWMP5I8obvV1nxyk8xIUK02USI2/gUQVi95NnK73bsBva9KSzKlQ5r01eUJZC vFkcc1Qu8HnPfg8KB//WUh0W5FcntqIdFm+4BfszHkaidZELeMy4MwnDiZUvpNyAafnm niNw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=52i5W7bwo5L4NKPi/t621ZC4mfXuxf76PQ3XmRwW6HM=; b=DdYCTwNyZA6jACVRPuJ0fMtRv5efKN3WVcHT58Zk5vY+1/OsQqBPG5K6K4ZX+jste5 t0fyXPe5jztGKxoIGVb2iwaFQ+H7JQ8utq0ue0QAgTd9y8M19wY/+BOMpTGwRKzQst/x P3jzrZ1msScemRvHwzrpYXxWFgY+7obmmZEvJdfD8dHzJQ91+J9GiDlJZqtKDi/Kkhbw pxbOmLajk7W8W1AmqvZ/nJeWMjqPOUMou4xAQ0gsJUozzgbaW4V9BwsMEM7nEFdTyDLA xEmZ69lzUQ9XUby/50fSjMuMfTph3ir4GtYWAbAQq+OsZz/SoqVDyauZT2tmu9He+AT4 MUog== X-Gm-Message-State: APjAAAV6LPUDDl5IRv+JZh+szAqkdKVq2JdLlH7YP0v45fMQ87hzQpJL HATQnL5icGzJrTnvsImlg4zKLVayMQmPnA== X-Google-Smtp-Source: APXvYqx4tXl8kJyrgPk73kSdFDxtYVeFJ3ZKPrk2o0B9NEEoRmlA/4IcV5D6ufbujg8Fb+w0iwWYKEEibfHjFw== X-Received: by 2002:a37:e306:: with SMTP id y6mr9040041qki.174.1565698753802; Tue, 13 Aug 2019 05:19:13 -0700 (PDT) Date: Tue, 13 Aug 2019 13:16:59 +0100 In-Reply-To: <20190813121733.52480-1-maennich@google.com> Message-Id: <20190813121733.52480-3-maennich@google.com> Mime-Version: 1.0 References: <20180716122125.175792-1-maco@android.com> <20190813121733.52480-1-maennich@google.com> X-Mailer: git-send-email 2.23.0.rc1.153.gdeed80330f-goog Subject: [PATCH v2 02/10] export: explicitly align struct kernel_symbol From: Matthias Maennich To: linux-kernel@vger.kernel.org, maco@android.com Cc: kernel-team@android.com, maennich@google.com, arnd@arndb.de, geert@linux-m68k.org, gregkh@linuxfoundation.org, hpa@zytor.com, jeyu@kernel.org, joel@joelfernandes.org, kstewart@linuxfoundation.org, linux-arch@vger.kernel.org, linux-kbuild@vger.kernel.org, linux-m68k@lists.linux-m68k.org, linux-modules@vger.kernel.org, linux-scsi@vger.kernel.org, linux-usb@vger.kernel.org, lucas.de.marchi@gmail.com, maco@google.com, michal.lkml@markovi.net, mingo@redhat.com, oneukum@suse.com, pombredanne@nexb.com, sam@ravnborg.org, sboyd@codeaurora.org, sspatil@google.com, stern@rowland.harvard.edu, tglx@linutronix.de, usb-storage@lists.one-eyed-alien.net, x86@kernel.org, yamada.masahiro@socionext.com, Andrew Morton , Nicolas Pitre , Michael Ellerman , Ard Biesheuvel Sender: linux-kbuild-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kbuild@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP This change allows growing struct kernel_symbol without wasting bytes to alignment. It also concretized the alignment of ksymtab entries if relative references are used for ksymtab entries. struct kernel_symbol was already implicitly being aligned to the word size, except on x86_64 and m68k, where it is aligned to 16 and 2 bytes, respectively. As far as I can tell there is no requirement for aligning struct kernel_symbol to 16 bytes on x86_64, but gcc aligns structs to their size, and the linker aligns the custom __ksymtab sections to the largest data type contained within, so setting KSYM_ALIGN to 16 was necessary to stay consistent with the code generated for non-ASM EXPORT_SYMBOL(). Now that non-ASM EXPORT_SYMBOL() explicitly aligns to word size (8), KSYM_ALIGN is no longer necessary. In case of relative references, the alignment has been changed accordingly to not waste space when adding new struct members. As for m68k, struct kernel_symbol is aligned to 2 bytes even though the structure itself is 8 bytes; using a 4-byte alignment shouldn't hurt. I manually verified the output of the __ksymtab sections didn't change on x86, x86_64, arm, arm64 and m68k. As expected, the section contents didn't change, and the ELF section alignment only changed on x86_64 and m68k. Feedback from other archs more than welcome. Co-developed-by: Martijn Coenen Signed-off-by: Martijn Coenen Signed-off-by: Matthias Maennich Reviewed-by: Greg Kroah-Hartman --- arch/m68k/include/asm/export.h | 1 - include/asm-generic/export.h | 8 +++----- include/linux/export.h | 3 ++- 3 files changed, 5 insertions(+), 7 deletions(-) diff --git a/arch/m68k/include/asm/export.h b/arch/m68k/include/asm/export.h index 0af20f48bd07..b53008b67ce1 100644 --- a/arch/m68k/include/asm/export.h +++ b/arch/m68k/include/asm/export.h @@ -1,3 +1,2 @@ -#define KSYM_ALIGN 2 #define KCRC_ALIGN 2 #include diff --git a/include/asm-generic/export.h b/include/asm-generic/export.h index 294d6ae785d4..63f54907317b 100644 --- a/include/asm-generic/export.h +++ b/include/asm-generic/export.h @@ -4,15 +4,13 @@ #ifndef KSYM_FUNC #define KSYM_FUNC(x) x #endif -#ifdef CONFIG_64BIT -#ifndef KSYM_ALIGN +#ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS +#define KSYM_ALIGN 4 +#elif defined(CONFIG_64BIT) #define KSYM_ALIGN 8 -#endif #else -#ifndef KSYM_ALIGN #define KSYM_ALIGN 4 #endif -#endif #ifndef KCRC_ALIGN #define KCRC_ALIGN 4 #endif diff --git a/include/linux/export.h b/include/linux/export.h index fd8711ed9ac4..28a4d2150689 100644 --- a/include/linux/export.h +++ b/include/linux/export.h @@ -52,7 +52,7 @@ extern struct module __this_module; #define __KSYMTAB_ENTRY(sym, sec) \ __ADDRESSABLE(sym) \ asm(" .section \"___ksymtab" sec "+" #sym "\", \"a\" \n" \ - " .balign 8 \n" \ + " .balign 4 \n" \ "__ksymtab_" #sym ": \n" \ " .long " #sym "- . \n" \ " .long __kstrtab_" #sym "- . \n" \ @@ -66,6 +66,7 @@ struct kernel_symbol { #define __KSYMTAB_ENTRY(sym, sec) \ static const struct kernel_symbol __ksymtab_##sym \ __attribute__((section("___ksymtab" sec "+" #sym), used)) \ + __aligned(sizeof(void *)) \ = { (unsigned long)&sym, __kstrtab_##sym } struct kernel_symbol {