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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6981BC25B06 for ; Sun, 14 Aug 2022 16:37:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242867AbiHNQg6 (ORCPT ); Sun, 14 Aug 2022 12:36:58 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52252 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S242846AbiHNQff (ORCPT ); Sun, 14 Aug 2022 12:35:35 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C6C8432BAE; Sun, 14 Aug 2022 09:27:50 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 2D67960F49; Sun, 14 Aug 2022 16:27:50 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0D2F7C433D6; Sun, 14 Aug 2022 16:27:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1660494469; bh=/Hs8dKxDq/D/MIDMenQIatozjdVIZmIpupoGHLbXye0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=AWAOxcfkmXuY1kxUAhqaHdyiY3bCAbuyvtuL1tYhaPVZXuIPL66XFaSBQuCh0RNJ6 Rm01Nyh21jERJF30SgP4XwdDWsdrUXoCf50abxjgVstdnnRut0anPiegtUxMub9kyP 3SgurmFrvX/v4ahEp7Mkmy3lW85M83IiZUyVrYnCmJ8hZ1LB+91UlWXeJ2mN0NQmfg kDyFqRt10tOfQAfMCAesaORRxAFPqR7y+Zg/tg1IolJ2S7cNZQepAmcpABwF89xsLS eia9qr/5LxDRBs/c18yfqA40azdbEqAOGNiBQVDwmEnf8J0DURZeXSDTTi9YJP9YFS Xj10vE0D83qFw== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Helge Deller , Luis Chamberlain , Sasha Levin Subject: [PATCH AUTOSEL 5.10 05/19] modules: Ensure natural alignment for .altinstructions and __bug_table sections Date: Sun, 14 Aug 2022 12:27:24 -0400 Message-Id: <20220814162739.2398217-5-sashal@kernel.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220814162739.2398217-1-sashal@kernel.org> References: <20220814162739.2398217-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Helge Deller [ Upstream commit 87c482bdfa79f378297d92af49cdf265be199df5 ] In the kernel image vmlinux.lds.S linker scripts the .altinstructions and __bug_table sections are 4- or 8-byte aligned because they hold 32- and/or 64-bit values. Most architectures use altinstructions and BUG() or WARN() in modules as well, but in the module linker script (module.lds.S) those sections are currently missing. As consequence the linker will store their content byte-aligned by default, which then can lead to unnecessary unaligned memory accesses by the CPU when those tables are processed at runtime. Usually unaligned memory accesses are unnoticed, because either the hardware (as on x86 CPUs) or in-kernel exception handlers (e.g. on parisc or sparc) emulate and fix them up at runtime. Nevertheless, such unaligned accesses introduce a performance penalty and can even crash the kernel if there is a bug in the unalignment exception handlers (which happened once to me on the parisc architecture and which is why I noticed that issue at all). This patch fixes a non-critical issue and might be backported at any time. It's trivial and shouldn't introduce any regression because it simply tells the linker to use a different (8-byte alignment) for those sections by default. Signed-off-by: Helge Deller Link: https://lore.kernel.org/all/Yr8%2Fgr8e8I7tVX4d@p100/ Signed-off-by: Luis Chamberlain Signed-off-by: Sasha Levin --- scripts/module.lds.S | 2 ++ 1 file changed, 2 insertions(+) diff --git a/scripts/module.lds.S b/scripts/module.lds.S index c5f12195817b..2c510db6c2ed 100644 --- a/scripts/module.lds.S +++ b/scripts/module.lds.S @@ -22,6 +22,8 @@ SECTIONS { .init_array 0 : ALIGN(8) { *(SORT(.init_array.*)) *(.init_array) } + .altinstructions 0 : ALIGN(8) { KEEP(*(.altinstructions)) } + __bug_table 0 : ALIGN(8) { KEEP(*(__bug_table)) } __jump_table 0 : ALIGN(8) { KEEP(*(__jump_table)) } __patchable_function_entries : { *(__patchable_function_entries) } -- 2.35.1