From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1070212AACC for ; Thu, 7 Mar 2024 15:17:52 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.249.212.188 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709824678; cv=none; b=ky553s2qFGGQl6rMTsQnkg2c+Ya8geQaZg0rmO0Loh8+GY04ZdigPKNgMmnrvg+73tk/DWI34f3st5s9algy4pjHBRtCoYkfAmbWFKpJoDwVKNkAsjFGNTKnQdRsMByeWXf9iZS0rNTiPuzty7bW4hTMMl4/N2S+R1Hq12CpMo4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709824678; c=relaxed/simple; bh=5DWssUIGR3KV6TRdXCF5ssSzXxz005yYj66HEPTdEps=; h=From:To:CC:Subject:Date:Message-ID:MIME-Version:Content-Type; b=Uep1etoP5oaP5vbBSACYih+ky/xvC7dH1y04cEXDZ6+NA0/B/5+9YV7L0tXr0Pfbb/enxQjRTt46XsavrcLcuMVN/4ILrwRQ/qLLzZpJhTL2B5T158ucMFTn46Nks7VTdJ2cf7QLEbMNC4W8JchVHtJqqk/SOJWDfG5sjm996m0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com; spf=pass smtp.mailfrom=huawei.com; arc=none smtp.client-ip=45.249.212.188 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huawei.com Received: from mail.maildlp.com (unknown [172.19.163.174]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4TrCZj13sbzbcdY; Thu, 7 Mar 2024 23:17:01 +0800 (CST) Received: from dggpemd100004.china.huawei.com (unknown [7.185.36.20]) by mail.maildlp.com (Postfix) with ESMTPS id 155A5140134; Thu, 7 Mar 2024 23:17:44 +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; Thu, 7 Mar 2024 23:17:43 +0800 From: Yuntao Liu To: , CC: , , , , , , , , , , , Subject: [PATCH-next v2] arm32: enable HAVE_LD_DEAD_CODE_DATA_ELIMINATION Date: Thu, 7 Mar 2024 15:12:31 +0000 Message-ID: <20240307151231.654025-1-liuyuntao12@huawei.com> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-ClientProxiedBy: dggems702-chm.china.huawei.com (10.3.19.179) To dggpemd100004.china.huawei.com (7.185.36.20) 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. 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 --- v2: - Support config XIP_KERNEL. - Support LLVM compilation. v1: https://lore.kernel.org/all/20240220081527.23408-1-liuyuntao12@huawei.com/ --- arch/arm/Kconfig | 1 + arch/arm/boot/compressed/vmlinux.lds.S | 4 ++-- arch/arm/include/asm/vmlinux.lds.h | 18 +++++++++++++++++- arch/arm/kernel/vmlinux-xip.lds.S | 8 ++++++-- arch/arm/kernel/vmlinux.lds.S | 10 +++++++--- 5 files changed, 33 insertions(+), 8 deletions(-) diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index 0af6709570d1..de78ceb821df 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -113,6 +113,7 @@ 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..da21244aa892 100644 --- a/arch/arm/boot/compressed/vmlinux.lds.S +++ b/arch/arm/boot/compressed/vmlinux.lds.S @@ -89,7 +89,7 @@ SECTIONS * The EFI stub always executes from RAM, and runs strictly before the * decompressor, so we can make an exception for its r/w data, and keep it */ - *(.data.efistub .bss.efistub) + *(.data.* .bss.*) __pecoff_data_end = .; /* @@ -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..dfe2b6ad6b51 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 \ @@ -87,6 +87,22 @@ *(.vfp11_veneer) \ *(.v4_bx) +/* +When CONFIG_LD_DEAD_CODE_DATA_ELIMINATION is enabled, it is important to +annotate .vectors sections with KEEP. While linking with ld, it is +acceptable to directly use KEEP with .vectors sections in ARM_VECTORS. +However, when using ld.lld for linking, KEEP is not recognized within the +OVERLAY command; it is treated as a regular string. Hence, it is advisable +to define a distinct section here that explicitly retains the .vectors +sections when CONFIG_LD_DEAD_CODE_DATA_ELIMINATION is turned on. +*/ +#define ARM_VECTORS_TEXT \ + .vectors.text : { \ + KEEP(*(.vectors)) \ + KEEP(*(.vectors.bhb.loop8)) \ + KEEP(*(.vectors.bhb.bpiall)) \ + } + #define ARM_TEXT \ IDMAP_TEXT \ __entry_text_start = .; \ diff --git a/arch/arm/kernel/vmlinux-xip.lds.S b/arch/arm/kernel/vmlinux-xip.lds.S index c16d196b5aad..035fa18060b3 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 : { @@ -135,6 +135,10 @@ SECTIONS ARM_TCM #endif +#ifdef LD_DEAD_CODE_DATA_ELIMINATION + ARM_VECTORS_TEXT +#endif + /* * End of copied data. We need a dummy section to get its LMA. * Also located before final ALIGN() as trailing padding is not stored diff --git a/arch/arm/kernel/vmlinux.lds.S b/arch/arm/kernel/vmlinux.lds.S index bd9127c4b451..2cfb890c93fb 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 = .; } @@ -134,6 +134,10 @@ SECTIONS ARM_TCM #endif +#ifdef LD_DEAD_CODE_DATA_ELIMINATION + ARM_VECTORS_TEXT +#endif + #ifdef CONFIG_STRICT_KERNEL_RWX . = ALIGN(1< 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 AA654C54798 for ; Thu, 7 Mar 2024 15:18:18 +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=oqLTCk1eFfXYMHNtVXWHrF/qfiyhh5qVJcOeFdYB7XI=; b=uRz90GNMOV8gVE dpVIMntCSKi6+jrxRiKojt4BOg6drTTxW2s1pwkjBczL5ejiJ4nNroYWO9ptUjD5zwFK2DtC6UQfE 97HtetCbuHEXXGSpMiwC4OEPfa8TNDTsVsRiFVRTYLFWLgHP/y4vQafoAUE5+l07L1LpMfFpq7uVn 6YkZrN2Ixxf4FSu1t7C4hFCndH8hrsoa3Pmj0BGaEzmSlA+T9Veu7CGrnYdF7iRS+AC/XfVMWCyuo zlRdfrf3fT3Xkq0XrJMTOpXP83CUWgq+ayq7LLHAIUGhQED6BYN9ewIRi2BujeVZ6hET6qj/2yl7U u9oVCxh/IX60+XdQXodQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1riFVP-00000005FNh-3xTN; Thu, 07 Mar 2024 15:17:59 +0000 Received: from szxga02-in.huawei.com ([45.249.212.188]) by bombadil.infradead.org with esmtps (Exim 4.97.1 #2 (Red Hat Linux)) id 1riFVM-00000005FMl-1vi2 for linux-arm-kernel@lists.infradead.org; Thu, 07 Mar 2024 15:17:59 +0000 Received: from mail.maildlp.com (unknown [172.19.163.174]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4TrCZj13sbzbcdY; Thu, 7 Mar 2024 23:17:01 +0800 (CST) Received: from dggpemd100004.china.huawei.com (unknown [7.185.36.20]) by mail.maildlp.com (Postfix) with ESMTPS id 155A5140134; Thu, 7 Mar 2024 23:17:44 +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; Thu, 7 Mar 2024 23:17:43 +0800 From: Yuntao Liu To: , CC: , , , , , , , , , , , Subject: [PATCH-next v2] arm32: enable HAVE_LD_DEAD_CODE_DATA_ELIMINATION Date: Thu, 7 Mar 2024 15:12:31 +0000 Message-ID: <20240307151231.654025-1-liuyuntao12@huawei.com> X-Mailer: git-send-email 2.34.1 MIME-Version: 1.0 X-Originating-IP: [10.67.174.76] X-ClientProxiedBy: dggems702-chm.china.huawei.com (10.3.19.179) 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-20240307_071756_994189_9B5D5B52 X-CRM114-Status: GOOD ( 16.52 ) 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: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit 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. 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 --- v2: - Support config XIP_KERNEL. - Support LLVM compilation. v1: https://lore.kernel.org/all/20240220081527.23408-1-liuyuntao12@huawei.com/ --- arch/arm/Kconfig | 1 + arch/arm/boot/compressed/vmlinux.lds.S | 4 ++-- arch/arm/include/asm/vmlinux.lds.h | 18 +++++++++++++++++- arch/arm/kernel/vmlinux-xip.lds.S | 8 ++++++-- arch/arm/kernel/vmlinux.lds.S | 10 +++++++--- 5 files changed, 33 insertions(+), 8 deletions(-) diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index 0af6709570d1..de78ceb821df 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -113,6 +113,7 @@ 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..da21244aa892 100644 --- a/arch/arm/boot/compressed/vmlinux.lds.S +++ b/arch/arm/boot/compressed/vmlinux.lds.S @@ -89,7 +89,7 @@ SECTIONS * The EFI stub always executes from RAM, and runs strictly before the * decompressor, so we can make an exception for its r/w data, and keep it */ - *(.data.efistub .bss.efistub) + *(.data.* .bss.*) __pecoff_data_end = .; /* @@ -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..dfe2b6ad6b51 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 \ @@ -87,6 +87,22 @@ *(.vfp11_veneer) \ *(.v4_bx) +/* +When CONFIG_LD_DEAD_CODE_DATA_ELIMINATION is enabled, it is important to +annotate .vectors sections with KEEP. While linking with ld, it is +acceptable to directly use KEEP with .vectors sections in ARM_VECTORS. +However, when using ld.lld for linking, KEEP is not recognized within the +OVERLAY command; it is treated as a regular string. Hence, it is advisable +to define a distinct section here that explicitly retains the .vectors +sections when CONFIG_LD_DEAD_CODE_DATA_ELIMINATION is turned on. +*/ +#define ARM_VECTORS_TEXT \ + .vectors.text : { \ + KEEP(*(.vectors)) \ + KEEP(*(.vectors.bhb.loop8)) \ + KEEP(*(.vectors.bhb.bpiall)) \ + } + #define ARM_TEXT \ IDMAP_TEXT \ __entry_text_start = .; \ diff --git a/arch/arm/kernel/vmlinux-xip.lds.S b/arch/arm/kernel/vmlinux-xip.lds.S index c16d196b5aad..035fa18060b3 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 : { @@ -135,6 +135,10 @@ SECTIONS ARM_TCM #endif +#ifdef LD_DEAD_CODE_DATA_ELIMINATION + ARM_VECTORS_TEXT +#endif + /* * End of copied data. We need a dummy section to get its LMA. * Also located before final ALIGN() as trailing padding is not stored diff --git a/arch/arm/kernel/vmlinux.lds.S b/arch/arm/kernel/vmlinux.lds.S index bd9127c4b451..2cfb890c93fb 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 = .; } @@ -134,6 +134,10 @@ SECTIONS ARM_TCM #endif +#ifdef LD_DEAD_CODE_DATA_ELIMINATION + ARM_VECTORS_TEXT +#endif + #ifdef CONFIG_STRICT_KERNEL_RWX . = ALIGN(1<