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 38767C49EC1 for ; Tue, 23 Aug 2022 10:26:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1354882AbiHWK0j (ORCPT ); Tue, 23 Aug 2022 06:26:39 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35642 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1353696AbiHWKLx (ORCPT ); Tue, 23 Aug 2022 06:11:53 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CD168E5C; Tue, 23 Aug 2022 01:58:17 -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 2CF3361561; Tue, 23 Aug 2022 08:58:17 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1571FC433C1; Tue, 23 Aug 2022 08:58:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1661245096; bh=zZLL++bYvl0F92rMoTpAbVJJgVpyIgrqAToCvPmUEYA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Ugn5F5tglJQKSUPwXFIg/zWaZG+8j2aM6IMkXz8o850xcdOHms1Ig4vYjqKQwLMyG +YktQjAfVs/gecCFIVkuyqZ2elsRHTd1ee8lag7+hwe3z62MLxbagepBtQ66yB5zB2 ncqjlVS6yo+xtb5JC+37t2+0BeBDDhhqR+wR4Cxg= 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 5.15 212/244] modules: Ensure natural alignment for .altinstructions and __bug_table sections Date: Tue, 23 Aug 2022 10:26:11 +0200 Message-Id: <20220823080106.579362565@linuxfoundation.org> X-Mailer: git-send-email 2.37.2 In-Reply-To: <20220823080059.091088642@linuxfoundation.org> References: <20220823080059.091088642@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: 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 1d0e1e4dc3d2..3a3aa2354ed8 100644 --- a/scripts/module.lds.S +++ b/scripts/module.lds.S @@ -27,6 +27,8 @@ SECTIONS { .ctors 0 : ALIGN(8) { *(SORT(.ctors.*)) *(.ctors) } .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