From patchwork Sat Mar 16 02:39:32 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "liuyuntao (F)" X-Patchwork-Id: 13594170 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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 46EE8C54E67 for ; Sat, 16 Mar 2024 02:45:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:Message-ID:Date:Subject:CC :To:From:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:In-Reply-To:References: List-Owner; bh=ccNtsA6TUTmG7B+0DvfWZdfnoksNVP3hLhg4YxstzG8=; b=bPFYH5Hj+aOsOn 5bFctc6kyi3lpbPaE3dgmMxHvcdKklH0tyPyUIeImxg/lRsY5oHjUcWCN5USHKpbvFqjy/LgtWE4B n8oIRivlcgUpq5J8MpJ3p71PSLw1GBgA75305vW0JRmiuUZlRgDg7wTUoJi1vg/xqjY2yXvD8Lj9L 1qVplNvfLNZ0PG/l6nMHvoFHD73CE6r9hoUA0MP5MrIgjS89PWqzDIzjoVOc+4RB7HywXKj528dYq j8iLj9KHaYTdbqE9XPIQ5ge6oPEfrzOHUqxQ1YKxLytAbCghh2bHplFwe+TTtppvtgUjD1JUG7+mB gej/QSoCve8Wdkd/yJzA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1rlK2e-000000028uY-0n7e; Sat, 16 Mar 2024 02:45:00 +0000 Received: from szxga05-in.huawei.com ([45.249.212.191]) by bombadil.infradead.org with esmtps (Exim 4.97.1 #2 (Red Hat Linux)) id 1rlK2W-000000028tU-3XvM for linux-arm-kernel@lists.infradead.org; Sat, 16 Mar 2024 02:44:55 +0000 Received: from mail.maildlp.com (unknown [172.19.88.214]) by szxga05-in.huawei.com (SkyGuard) with ESMTP id 4TxQPc1529z1h2NK; Sat, 16 Mar 2024 10:42:12 +0800 (CST) Received: from dggpemd100004.china.huawei.com (unknown [7.185.36.20]) by mail.maildlp.com (Postfix) with ESMTPS id 8F1DA1A016C; Sat, 16 Mar 2024 10:44:41 +0800 (CST) Received: from huawei.com (10.67.174.76) by dggpemd100004.china.huawei.com (7.185.36.20) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1258.28; Sat, 16 Mar 2024 10:44:41 +0800 From: Yuntao Liu To: , CC: , , , , , , , , , , , , , , Subject: [PATCH-next v4] arm32: enable HAVE_LD_DEAD_CODE_DATA_ELIMINATION Date: Sat, 16 Mar 2024 02:39:32 +0000 Message-ID: <20240316023932.700685-1-liuyuntao12@huawei.com> X-Mailer: git-send-email 2.34.1 MIME-Version: 1.0 X-Originating-IP: [10.67.174.76] X-ClientProxiedBy: dggems706-chm.china.huawei.com (10.3.19.183) To dggpemd100004.china.huawei.com (7.185.36.20) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240315_194453_321501_D36A3CAB X-CRM114-Status: GOOD ( 14.36 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org The current arm32 architecture does not yet support the HAVE_LD_DEAD_CODE_DATA_ELIMINATION feature. arm32 is widely used in embedded scenarios, and enabling this feature would be beneficial for reducing the size of the kernel image. In order to make this work, 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. When using ld.lld for linking, KEEP is not recognized within the OVERLAY command, and Ard proposed a concise method to solve this problem. It boots normally with defconfig, vexpress_defconfig and tinyconfig. The size comparison of zImage is as follows: defconfig vexpress_defconfig tinyconfig 5137712 5138024 424192 no dce 5032560 4997824 298384 dce 2.0% 2.7% 29.7% shrink When using smaller config file, there is a significant reduction in the size of the zImage. We also tested this patch on a commercially available single-board computer, and the comparison is as follows: a15eb_config 2161384 no dce 2092240 dce 3.2% shrink The zImage size has been reduced by approximately 3.2%, which is 70KB on 2.1M. Signed-off-by: Yuntao Liu Tested-by: Arnd Bergmann Reviewed-by: Arnd Bergmann Reviewed-by: Ard Biesheuvel Reviewed-by: Linus Walleij Tested-by: Geert Uytterhoeven --- v4: - remove -fdata-sections flag from KBUILD_CFLAGS_KERNEL in drivers/firmware/efi/libstub/Makefile v3: - A better way to KEEP .vectors section for ld.lld linking. - https://lore.kernel.org/all/20240315063154.696633-1-liuyuntao12@huawei.com/ v2: - Support config XIP_KERNEL. - Support LLVM compilation. - https://lore.kernel.org/all/20240307151231.654025-1-liuyuntao12@huawei.com/ v1: https://lore.kernel.org/all/20240220081527.23408-1-liuyuntao12@huawei.com/ --- arch/arm/Kconfig | 1 + arch/arm/boot/compressed/vmlinux.lds.S | 2 +- arch/arm/include/asm/vmlinux.lds.h | 2 +- arch/arm/kernel/entry-armv.S | 3 +++ arch/arm/kernel/vmlinux-xip.lds.S | 4 ++-- arch/arm/kernel/vmlinux.lds.S | 6 +++--- drivers/firmware/efi/libstub/Makefile | 4 ++++ 7 files changed, 15 insertions(+), 7 deletions(-) diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index b14aed3a17ab..45f25f6e7a62 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -114,6 +114,7 @@ config ARM select HAVE_KERNEL_XZ select HAVE_KPROBES if !XIP_KERNEL && !CPU_ENDIAN_BE32 && !CPU_V7M select HAVE_KRETPROBES if HAVE_KPROBES + select HAVE_LD_DEAD_CODE_DATA_ELIMINATION select HAVE_MOD_ARCH_SPECIFIC select HAVE_NMI select HAVE_OPTPROBES if !THUMB2_KERNEL diff --git a/arch/arm/boot/compressed/vmlinux.lds.S b/arch/arm/boot/compressed/vmlinux.lds.S index 3fcb3e62dc56..d411abd4310e 100644 --- a/arch/arm/boot/compressed/vmlinux.lds.S +++ b/arch/arm/boot/compressed/vmlinux.lds.S @@ -125,7 +125,7 @@ SECTIONS . = BSS_START; __bss_start = .; - .bss : { *(.bss) } + .bss : { *(.bss .bss.*) } _end = .; . = ALIGN(8); /* the stack must be 64-bit aligned */ diff --git a/arch/arm/include/asm/vmlinux.lds.h b/arch/arm/include/asm/vmlinux.lds.h index 4c8632d5c432..d60f6e83a9f7 100644 --- a/arch/arm/include/asm/vmlinux.lds.h +++ b/arch/arm/include/asm/vmlinux.lds.h @@ -42,7 +42,7 @@ #define PROC_INFO \ . = ALIGN(4); \ __proc_info_begin = .; \ - *(.proc.info.init) \ + KEEP(*(.proc.info.init)) \ __proc_info_end = .; #define IDMAP_TEXT \ diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S index 6150a716828c..f01d23a220e6 100644 --- a/arch/arm/kernel/entry-armv.S +++ b/arch/arm/kernel/entry-armv.S @@ -1065,6 +1065,7 @@ vector_addrexcptn: .globl vector_fiq .section .vectors, "ax", %progbits + .reloc .text, R_ARM_NONE, . W(b) vector_rst W(b) vector_und ARM( .reloc ., R_ARM_LDR_PC_G0, .L__vector_swi ) @@ -1078,6 +1079,7 @@ THUMB( .reloc ., R_ARM_THM_PC12, .L__vector_swi ) #ifdef CONFIG_HARDEN_BRANCH_HISTORY .section .vectors.bhb.loop8, "ax", %progbits + .reloc .text, R_ARM_NONE, . W(b) vector_rst W(b) vector_bhb_loop8_und ARM( .reloc ., R_ARM_LDR_PC_G0, .L__vector_bhb_loop8_swi ) @@ -1090,6 +1092,7 @@ THUMB( .reloc ., R_ARM_THM_PC12, .L__vector_bhb_loop8_swi ) W(b) vector_bhb_loop8_fiq .section .vectors.bhb.bpiall, "ax", %progbits + .reloc .text, R_ARM_NONE, . W(b) vector_rst W(b) vector_bhb_bpiall_und ARM( .reloc ., R_ARM_LDR_PC_G0, .L__vector_bhb_bpiall_swi ) diff --git a/arch/arm/kernel/vmlinux-xip.lds.S b/arch/arm/kernel/vmlinux-xip.lds.S index c16d196b5aad..5eddb75a7174 100644 --- a/arch/arm/kernel/vmlinux-xip.lds.S +++ b/arch/arm/kernel/vmlinux-xip.lds.S @@ -63,7 +63,7 @@ SECTIONS . = ALIGN(4); __ex_table : AT(ADDR(__ex_table) - LOAD_OFFSET) { __start___ex_table = .; - ARM_MMU_KEEP(*(__ex_table)) + ARM_MMU_KEEP(KEEP(*(__ex_table))) __stop___ex_table = .; } @@ -83,7 +83,7 @@ SECTIONS } .init.arch.info : { __arch_info_begin = .; - *(.arch.info.init) + KEEP(*(.arch.info.init)) __arch_info_end = .; } .init.tagtable : { diff --git a/arch/arm/kernel/vmlinux.lds.S b/arch/arm/kernel/vmlinux.lds.S index bd9127c4b451..de373c6c2ae8 100644 --- a/arch/arm/kernel/vmlinux.lds.S +++ b/arch/arm/kernel/vmlinux.lds.S @@ -74,7 +74,7 @@ SECTIONS . = ALIGN(4); __ex_table : AT(ADDR(__ex_table) - LOAD_OFFSET) { __start___ex_table = .; - ARM_MMU_KEEP(*(__ex_table)) + ARM_MMU_KEEP(KEEP(*(__ex_table))) __stop___ex_table = .; } @@ -99,7 +99,7 @@ SECTIONS } .init.arch.info : { __arch_info_begin = .; - *(.arch.info.init) + KEEP(*(.arch.info.init)) __arch_info_end = .; } .init.tagtable : { @@ -116,7 +116,7 @@ SECTIONS #endif .init.pv_table : { __pv_table_begin = .; - *(.pv_table) + KEEP(*(.pv_table)) __pv_table_end = .; } diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile index 31eb1e287ce1..619f1f9d9ba9 100644 --- a/drivers/firmware/efi/libstub/Makefile +++ b/drivers/firmware/efi/libstub/Makefile @@ -56,6 +56,10 @@ KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_CFI), $(KBUILD_CFLAGS)) # disable LTO KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_LTO), $(KBUILD_CFLAGS)) +# The .data section would be renamed to .data.efistub, therefore, remove +# `-fdata-sections` flag from KBUILD_CFLAGS_KERNEL +KBUILD_CFLAGS_KERNEL := $(filter-out -fdata-sections, $(KBUILD_CFLAGS_KERNEL)) + GCOV_PROFILE := n # Sanitizer runtimes are unavailable and cannot be linked here. KASAN_SANITIZE := n