From cf50c9c2e4481cde39ffd419ee6dc5a73a1c502a Mon Sep 17 00:00:00 2001 From: Yuntao Liu Date: Mon, 3 Jun 2024 16:37:50 +0100 Subject: [PATCH] BACKPORT: ARM: 9404/1: arm32: enable HAVE_LD_DEAD_CODE_DATA_ELIMINATION 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. Change-Id: Id2c136f7c992c6699c6c576ada46bfb025378f78 Signed-off-by: Yuntao Liu Tested-by: Arnd Bergmann Reviewed-by: Arnd Bergmann Reviewed-by: Linus Walleij Signed-off-by: Russell King (Oracle) Signed-off-by: Tao Huang (cherry picked from commit ed0f941022515ff40473ea5335769a5dc2524a3f) --- 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 773770c47e37..dd68422c2aa1 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -108,6 +108,7 @@ 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 fad45c884e98..fa031135710f 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 c39303e5c234..fe3a24fe6a00 100644 --- a/arch/arm/kernel/entry-armv.S +++ b/arch/arm/kernel/entry-armv.S @@ -1297,6 +1297,7 @@ 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 ) @@ -1310,6 +1311,7 @@ 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 ) @@ -1322,6 +1324,7 @@ 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 76678732c60d..8ab517f26c22 100644 --- a/arch/arm/kernel/vmlinux-xip.lds.S +++ b/arch/arm/kernel/vmlinux-xip.lds.S @@ -64,7 +64,7 @@ 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 = .; } @@ -84,7 +84,7 @@ 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 aa12b65a7fd6..392cb962a40c 100644 --- a/arch/arm/kernel/vmlinux.lds.S +++ b/arch/arm/kernel/vmlinux.lds.S @@ -75,7 +75,7 @@ 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 = .; } @@ -100,7 +100,7 @@ SECTIONS } .init.arch.info : { __arch_info_begin = .; - *(.arch.info.init) + KEEP(*(.arch.info.init)) __arch_info_end = .; } .init.tagtable : { @@ -117,7 +117,7 @@ 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 473ef18421db..850fcf1a5b88 100644 --- a/drivers/firmware/efi/libstub/Makefile +++ b/drivers/firmware/efi/libstub/Makefile @@ -53,6 +53,10 @@ 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