From nobody Thu Dec 18 12:44:49 2025 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 5F7A1C32772 for ; Tue, 23 Aug 2022 09:48:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1344258AbiHWJsU (ORCPT ); Tue, 23 Aug 2022 05:48:20 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55342 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1352164AbiHWJqA (ORCPT ); Tue, 23 Aug 2022 05:46:00 -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 1CDFE60509; Tue, 23 Aug 2022 01:43:47 -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 3E964CE1B39; Tue, 23 Aug 2022 08:33:23 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 529CDC433D7; Tue, 23 Aug 2022 08:33:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1661243601; bh=zZLL++bYvl0F92rMoTpAbVJJgVpyIgrqAToCvPmUEYA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=VmRSCqBn//LUADhOOiNW8oEzqoLeoGhx5UdtPDY5pUsSKn+hge+eReoH6I1cd+fdF KavDY1+klCUGk+x8A5i8+Ya4FOkomML2tZktmrM51mfdsE/irMv5F9lmezcgeuP2t2 6xu5LXEqr+Z6oRqGSFr8UAaY9aLWK4Df2lXMToYg= 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 5.19 327/365] modules: Ensure natural alignment for .altinstructions and __bug_table sections Date: Tue, 23 Aug 2022 10:03:48 +0200 Message-Id: <20220823080131.868020705@linuxfoundation.org> X-Mailer: git-send-email 2.37.2 In-Reply-To: <20220823080118.128342613@linuxfoundation.org> References: <20220823080118.128342613@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" 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) } =20 + .altinstructions 0 : ALIGN(8) { KEEP(*(.altinstructions)) } + __bug_table 0 : ALIGN(8) { KEEP(*(__bug_table)) } __jump_table 0 : ALIGN(8) { KEEP(*(__jump_table)) } =20 __patchable_function_entries : { *(__patchable_function_entries) } --=20 2.35.1