From patchwork Tue Sep 3 15:06:28 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: 11128147 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 984B014F7 for ; Tue, 3 Sep 2019 15:07:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6EE4A23774 for ; Tue, 3 Sep 2019 15:07:31 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="BfHZbHR9" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729727AbfICPHb (ORCPT ); Tue, 3 Sep 2019 11:07:31 -0400 Received: from mail-vs1-f74.google.com ([209.85.217.74]:40171 "EHLO mail-vs1-f74.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729722AbfICPHa (ORCPT ); Tue, 3 Sep 2019 11:07:30 -0400 Received: by mail-vs1-f74.google.com with SMTP id m24so771270vsp.7 for ; Tue, 03 Sep 2019 08:07:30 -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=WpyyM8zjm4wtK5J690VZrM2s4HSiRGUxtkfpxo7zqKI=; b=BfHZbHR97xdAxRIdMmVlOwnyxzrq6JmTVQXv4Fg5l+zyV5iGtr+ffZtaPXCj9UClr2 HBUSLv4AD6uEOTct4s9MJL4qHRMnroaVu+TZIx303DWUAe4bpNCNRpUHhZ9N4Tsfw/Y/ Z6Vl7K0uLitFGrCDhFrtgVbzEuLb86F4SbiR/ZyZL1VWiGNb2INzfCvhjRkamz5g8g9V ZxSOL4PIYiq9rEmw7LakJ4nI5VTYE9x0PyJ1U1mF3bZvU06pcbLkUqx4S7Ipp2030F5D fDto7fdbBtKazVvfo9UtqoXJuWsdHzGzIKJXbV3i6+U+1a/n53z3B7gUU4jhyJb8Msqc F3VQ== 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=WpyyM8zjm4wtK5J690VZrM2s4HSiRGUxtkfpxo7zqKI=; b=K70aDhYKTSmwJQ7/S70TLOwzPAo5/6sD2cvK6g0ohmGo8qROITv66h28MR3evKqU+Z HXhh8As/hQU14Ip4YvA+3J0iQxn+4W67jRLhtKeiR8rO4KHqIJNry1qx9RErwWvSa4Gb J0FmMwHmvAJU35VnG8qEDdMl8ik2dMzHkO/GtcJffupLP8jhHQV91bYv2eOmr7/k5yK6 ENLNfLoOtH4daKaB/ewF+sptQQzyNfpCtY6x7pKU5kjbMRaok3GG1AusbyPBR06KrY3z jJUaEOykw1il4gzod7f9bKLUkokJ7x0h6fUbeoJ2z5y6TE/9g12ZNOqeWohrhs1JSKny VzqA== X-Gm-Message-State: APjAAAUfFutgBRzDMCw0f9HdC7bqn3F7eGFABMVHYXJKL7DsEBpCLYU7 za9ByTE/IOxF2xBLflAhjH95vuTWamYq2Q== X-Google-Smtp-Source: APXvYqyRkq3kWS+md+h91R4aNGpmWOv69BYMd6kwCtRNSe5sfbB/Zp3Ra0kJkrdzunasXK4SgK6CH0kEQqjxxg== X-Received: by 2002:a1f:5c0d:: with SMTP id q13mr3631221vkb.38.1567523249382; Tue, 03 Sep 2019 08:07:29 -0700 (PDT) Date: Tue, 3 Sep 2019 16:06:28 +0100 In-Reply-To: <20190903150638.242049-1-maennich@google.com> Message-Id: <20190903150638.242049-3-maennich@google.com> Mime-Version: 1.0 References: <20180716122125.175792-1-maco@android.com> <20190903150638.242049-1-maennich@google.com> X-Mailer: git-send-email 2.23.0.187.g17f5b7556c-goog Subject: [PATCH v4 02/12] export: explicitly align struct kernel_symbol From: Matthias Maennich To: linux-kernel@vger.kernel.org Cc: kernel-team@android.com, maennich@google.com, arnd@arndb.de, gregkh@linuxfoundation.org, jeyu@kernel.org, joel@joelfernandes.org, lucas.de.marchi@gmail.com, maco@android.com, sspatil@google.com, will@kernel.org, yamada.masahiro@socionext.com, linux-kbuild@vger.kernel.org, linux-modules@vger.kernel.org, linux-usb@vger.kernel.org, usb-storage@lists.one-eyed-alien.net, linux-watchdog@vger.kernel.org Sender: linux-watchdog-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-watchdog@vger.kernel.org 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 Reviewed-by: Greg Kroah-Hartman Signed-off-by: Matthias Maennich --- 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 {