From nobody Sun Feb 8 13:45:20 2026 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 B0683EB64DC for ; Mon, 17 Jul 2023 08:08:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230313AbjGQIIy (ORCPT ); Mon, 17 Jul 2023 04:08:54 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36096 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229608AbjGQIIw (ORCPT ); Mon, 17 Jul 2023 04:08:52 -0400 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9858A1FDB for ; Mon, 17 Jul 2023 01:08:28 -0700 (PDT) Received: from dggpemm500001.china.huawei.com (unknown [172.30.72.54]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4R4F424VsSzNmQS; Mon, 17 Jul 2023 16:04:50 +0800 (CST) Received: from localhost.localdomain (10.175.112.125) by dggpemm500001.china.huawei.com (7.185.36.107) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.27; Mon, 17 Jul 2023 16:08:09 +0800 From: Kefeng Wang To: Catalin Marinas , Will Deacon CC: , , Kefeng Wang Subject: [PATCH] arm64: enable dead code elimination Date: Mon, 17 Jul 2023 16:07:39 +0800 Message-ID: <20230717080739.1000460-1-wangkefeng.wang@huawei.com> X-Mailer: git-send-email 2.27.0 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Originating-IP: [10.175.112.125] X-ClientProxiedBy: dggems705-chm.china.huawei.com (10.3.19.182) To dggpemm500001.china.huawei.com (7.185.36.107) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Select CONFIG_HAVE_LD_DEAD_CODE_DATA_ELIMINATION for arm64, allowing the user to enable dead code elimination. In order for this to work, ensure that we keep the necessary tables by annotating them with KEEP, also it requires further changes to linker script to KEEP some tables and wildcard compiler generated sections into the right place. The following comparison is based 6.5-rc2 with defconfig, $ ./scripts/bloat-o-meter vmlinux-base vmlinux-new add/remove: 3/1106 grow/shrink: 4102/6964 up/down: 35704/-99980 (-64276) Function old new delta ... Total: Before=3D17888959, After=3D17824683, chg -0.36% add/remove: 0/1 grow/shrink: 0/1 up/down: 0/-44 (-44) Data old new delta ... Total: Before=3D4820808, After=3D4820764, chg -0.00% add/remove: 0/1 grow/shrink: 0/1 up/down: 0/-1096 (-1096) RO Data old new delta ... Total: Before=3D5179123, After=3D5178027, chg -0.02% $ size vmlinux-base vmlinux text data bss dec hex filename 25433734 15385766 630656 41450156 2787aac vmlinux-base 24756738 15360870 629888 40747496 26dc1e8 vmlinux-new Memory available after booting, saving 704k on qemu, base: 8084532K/8388608K new: 8085236K/8388608K Signed-off-by: Kefeng Wang --- arch/arm64/Kconfig | 1 + arch/arm64/kernel/vmlinux.lds.S | 5 +++-- 2 files changed, 4 insertions(+), 2 deletions(-) diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index a2511b30d0f6..73bb908ec62f 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -148,6 +148,7 @@ config ARM64 select GENERIC_VDSO_TIME_NS select HARDIRQS_SW_RESEND select HAS_IOPORT + select HAVE_LD_DEAD_CODE_DATA_ELIMINATION select HAVE_MOVE_PMD select HAVE_MOVE_PUD select HAVE_PCI diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.ld= s.S index 3cd7e76cc562..bb4ce6cd6896 100644 --- a/arch/arm64/kernel/vmlinux.lds.S +++ b/arch/arm64/kernel/vmlinux.lds.S @@ -238,7 +238,7 @@ SECTIONS . =3D ALIGN(4); .altinstructions : { __alt_instructions =3D .; - *(.altinstructions) + KEEP(*(.altinstructions)) __alt_instructions_end =3D .; } =20 @@ -258,8 +258,9 @@ SECTIONS INIT_CALLS CON_INITCALL INIT_RAM_FS - *(.init.altinstructions .init.bss) /* from the EFI stub */ + KEEP(*(.init.altinstructions .init.bss*)) /* from the EFI stub */ } + .exit.data : { EXIT_DATA } --=20 2.27.0