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 C4376C32774 for ; Tue, 23 Aug 2022 12:33:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238076AbiHWMdF (ORCPT ); Tue, 23 Aug 2022 08:33:05 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55778 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S243173AbiHWMaf (ORCPT ); Tue, 23 Aug 2022 08:30:35 -0400 Received: from sin.source.kernel.org (sin.source.kernel.org [IPv6:2604:1380:40e1:4800::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8242D1015A5; Tue, 23 Aug 2022 02:45:13 -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 sin.source.kernel.org (Postfix) with ESMTPS id 13B39CE1B58; Tue, 23 Aug 2022 09:43:48 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 29C7DC433C1; Tue, 23 Aug 2022 09:43:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1661247826; bh=/Hs8dKxDq/D/MIDMenQIatozjdVIZmIpupoGHLbXye0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=lK4hfPU2JEphFZ4EVB3hekk7/1yaIDZRxuEtlLkSBoUBXsFNozDu7Pfel/6E1gbFJ wysOyByWontu1VKaV096Qzx8PJvp4MYUDaM9+rVjnTYKj6cAoMuKqE7AyboI6QO9i7 DrurR0QkR3bQGws8wOoe8XI/GD3Zj9skMseyHGTY= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Helge Deller , Luis Chamberlain , Sasha Levin Subject: [PATCH 5.10 136/158] modules: Ensure natural alignment for .altinstructions and __bug_table sections Date: Tue, 23 Aug 2022 10:27:48 +0200 Message-Id: <20220823080051.338255374@linuxfoundation.org> X-Mailer: git-send-email 2.37.2 In-Reply-To: <20220823080046.056825146@linuxfoundation.org> References: <20220823080046.056825146@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@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