From nobody Wed Feb 11 05:07:49 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 B7AA6C77B7F for ; Thu, 11 May 2023 14:24:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238447AbjEKOYB (ORCPT ); Thu, 11 May 2023 10:24:01 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42332 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238169AbjEKOXj (ORCPT ); Thu, 11 May 2023 10:23:39 -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 A8EB6210D; Thu, 11 May 2023 07:23:27 -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 3DBAF63335; Thu, 11 May 2023 14:23:27 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id AEFB6C433EF; Thu, 11 May 2023 14:23:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1683815006; bh=EAl7BYyGkHSJ9u4z4v03MJVzoloTTUlxQ/6IkxdvXp8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=aQAlhdryVtLrijn4plCYeD8GrNC3jkYYQfYYiLdqFuCbLL01xeMxATi5/b0BGkM3s 9pL1vpl41G7btsU04qC3KrO87rvLds7PncrgXtCzI0TzlLyAxUfqxe9l6sJ8pXHMhd yhQTtQsY8s1Rz8rB2ADYYC5lq2GjgG6p1lMoJRviovB4jhO0IgiPOanGPdogFRFGKf M8lKdsRm3s25cOtf3C6WMjn6jdc7/xNC+H3pGs4NafKn5ftut5UIqYwf1d8y4dUyr/ 48sWhQwCzLUjfP7GoO7r/wnUGOitDR2Mu+i737iw2WCUlf+W9v8lzun7HeOBvYMGVS PA6Eg16UdnlTQ== From: Jisheng Zhang To: Paul Walmsley , Palmer Dabbelt , Albert Ou , Arnd Bergmann Cc: linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org Subject: [PATCH 4/4] riscv: enable HAVE_LD_DEAD_CODE_DATA_ELIMINATION Date: Thu, 11 May 2023 22:12:11 +0800 Message-Id: <20230511141211.2418-5-jszhang@kernel.org> X-Mailer: git-send-email 2.40.0 In-Reply-To: <20230511141211.2418-1-jszhang@kernel.org> References: <20230511141211.2418-1-jszhang@kernel.org> 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" When trying to run linux with various opensource riscv core on resource limited FPGA platforms, for example, those FPGAs with less than 16MB SDRAM, I want to save mem as much as possible. One of the major technologies is kernel size optimizations, I found that riscv does not currently support HAVE_LD_DEAD_CODE_DATA_ELIMINATION, which passes -fdata-sections, -ffunction-sections to CFLAGS and passes the --gc-sections flag to the linker. This not only benefits my case on FPGA but also benefits defconfigs. Here are some notable improvements from enabling this with defconfigs: nommu_k210_defconfig: text data bss dec hex 1112009 410288 59837 1582134 182436 before 962838 376656 51285 1390779 1538bb after rv32_defconfig: text data bss dec hex 8804455 2816544 290577 11911576 b5c198 before 8692295 2779872 288977 11761144 b375f8 after defconfig: text data bss dec hex 9438267 3391332 485333 13314932 cb2b74 before 9285914 3350052 483349 13119315 c82f53 after Signed-off-by: Jisheng Zhang --- arch/riscv/Kconfig | 1 + arch/riscv/kernel/vmlinux.lds.S | 6 +++--- 2 files changed, 4 insertions(+), 3 deletions(-) diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig index f0663b52d052..a5feab2c3037 100644 --- a/arch/riscv/Kconfig +++ b/arch/riscv/Kconfig @@ -110,6 +110,7 @@ config RISCV select HAVE_KPROBES if !XIP_KERNEL select HAVE_KPROBES_ON_FTRACE if !XIP_KERNEL select HAVE_KRETPROBES if !XIP_KERNEL + select HAVE_LD_DEAD_CODE_DATA_ELIMINATION select HAVE_MOVE_PMD select HAVE_MOVE_PUD select HAVE_PCI diff --git a/arch/riscv/kernel/vmlinux.lds.S b/arch/riscv/kernel/vmlinux.ld= s.S index e5f9f4677bbf..492dd4b8f3d6 100644 --- a/arch/riscv/kernel/vmlinux.lds.S +++ b/arch/riscv/kernel/vmlinux.lds.S @@ -85,11 +85,11 @@ SECTIONS INIT_DATA_SECTION(16) =20 .init.pi : { - *(.init.pi*) + KEEP(*(.init.pi*)) } =20 .init.bss : { - *(.init.bss) /* from the EFI stub */ + KEEP(*(.init.bss*)) /* from the EFI stub */ } .exit.data : { @@ -112,7 +112,7 @@ SECTIONS . =3D ALIGN(8); .alternative : { __alt_start =3D .; - *(.alternative) + KEEP(*(.alternative)) __alt_end =3D .; } __init_end =3D .; --=20 2.40.1