From: Felix Fietkau use -ffunction-sections, -fdata-sections and --gc-sections In combination with kernel symbol export stripping this significantly reduces the kernel image size. Used on both ARM and MIPS architectures. Signed-off-by: Felix Fietkau Signed-off-by: Jonas Gorski Signed-off-by: Gabor Juhos --- --- a/arch/mips/Makefile +++ b/arch/mips/Makefile @@ -89,10 +89,14 @@ all-$(CONFIG_SYS_SUPPORTS_ZBOOT)+= vmlin # cflags-y += -G 0 -mno-abicalls -fno-pic -pipe cflags-y += -msoft-float -LDFLAGS_vmlinux += -G 0 -static -n -nostdlib +LDFLAGS_vmlinux += -G 0 -static -n -nostdlib --gc-sections KBUILD_AFLAGS_MODULE += -mlong-calls KBUILD_CFLAGS_MODULE += -mlong-calls +ifndef CONFIG_FUNCTION_TRACER +KBUILD_CFLAGS_KERNEL += -ffunction-sections -fdata-sections +endif + cflags-y += -ffreestanding # --- a/arch/mips/kernel/vmlinux.lds.S +++ b/arch/mips/kernel/vmlinux.lds.S @@ -67,7 +67,7 @@ SECTIONS /* Exception table for data bus errors */ __dbe_table : { __start___dbe_table = .; - *(__dbe_table) + KEEP(*(__dbe_table)) __stop___dbe_table = .; } @@ -112,7 +112,7 @@ SECTIONS . = ALIGN(4); .mips.machines.init : AT(ADDR(.mips.machines.init) - LOAD_OFFSET) { __mips_machines_start = .; - *(.mips.machines.init) + KEEP(*(.mips.machines.init)) __mips_machines_end = .; } --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -87,7 +87,7 @@ #ifdef CONFIG_FTRACE_MCOUNT_RECORD #define MCOUNT_REC() . = ALIGN(8); \ VMLINUX_SYMBOL(__start_mcount_loc) = .; \ - *(__mcount_loc) \ + KEEP(*(__mcount_loc)) \ VMLINUX_SYMBOL(__stop_mcount_loc) = .; #else #define MCOUNT_REC() @@ -95,7 +95,7 @@ #ifdef CONFIG_TRACE_BRANCH_PROFILING #define LIKELY_PROFILE() VMLINUX_SYMBOL(__start_annotated_branch_profile) = .; \ - *(_ftrace_annotated_branch) \ + KEEP(*(_ftrace_annotated_branch)) \ VMLINUX_SYMBOL(__stop_annotated_branch_profile) = .; #else #define LIKELY_PROFILE() @@ -103,7 +103,7 @@ #ifdef CONFIG_PROFILE_ALL_BRANCHES #define BRANCH_PROFILE() VMLINUX_SYMBOL(__start_branch_profile) = .; \ - *(_ftrace_branch) \ + KEEP(*(_ftrace_branch)) \ VMLINUX_SYMBOL(__stop_branch_profile) = .; #else #define BRANCH_PROFILE() @@ -112,7 +112,7 @@ #ifdef CONFIG_EVENT_TRACING #define FTRACE_EVENTS() . = ALIGN(8); \ VMLINUX_SYMBOL(__start_ftrace_events) = .; \ - *(_ftrace_events) \ + KEEP(*(_ftrace_events)) \ VMLINUX_SYMBOL(__stop_ftrace_events) = .; #else #define FTRACE_EVENTS() @@ -120,7 +120,7 @@ #ifdef CONFIG_TRACING #define TRACE_PRINTKS() VMLINUX_SYMBOL(__start___trace_bprintk_fmt) = .; \ - *(__trace_printk_fmt) /* Trace_printk fmt' pointer */ \ + KEEP(*(__trace_printk_fmt)) /* Trace_printk fmt' pointer */ \ VMLINUX_SYMBOL(__stop___trace_bprintk_fmt) = .; #define TRACEPOINT_STR() VMLINUX_SYMBOL(__start___tracepoint_str) = .; \ *(__tracepoint_str) /* Trace_printk fmt' pointer */ \ @@ -133,7 +133,7 @@ #ifdef CONFIG_FTRACE_SYSCALLS #define TRACE_SYSCALLS() . = ALIGN(8); \ VMLINUX_SYMBOL(__start_syscalls_metadata) = .; \ - *(__syscalls_metadata) \ + KEEP(*(__syscalls_metadata)) \ VMLINUX_SYMBOL(__stop_syscalls_metadata) = .; #else #define TRACE_SYSCALLS() @@ -142,8 +142,8 @@ #ifdef CONFIG_CLKSRC_OF #define CLKSRC_OF_TABLES() . = ALIGN(8); \ VMLINUX_SYMBOL(__clksrc_of_table) = .; \ - *(__clksrc_of_table) \ - *(__clksrc_of_table_end) + KEEP(*(__clksrc_of_table)) \ + KEEP(*(__clksrc_of_table_end)) #else #define CLKSRC_OF_TABLES() #endif @@ -152,8 +152,8 @@ #define IRQCHIP_OF_MATCH_TABLE() \ . = ALIGN(8); \ VMLINUX_SYMBOL(__irqchip_begin) = .; \ - *(__irqchip_of_table) \ - *(__irqchip_of_end) + KEEP(*(__irqchip_of_table)) \ + KEEP(*(__irqchip_of_end)) #else #define IRQCHIP_OF_MATCH_TABLE() #endif @@ -161,8 +161,8 @@ #ifdef CONFIG_COMMON_CLK #define CLK_OF_TABLES() . = ALIGN(8); \ VMLINUX_SYMBOL(__clk_of_table) = .; \ - *(__clk_of_table) \ - *(__clk_of_table_end) + KEEP(*(__clk_of_table)) \ + KEEP(*(__clk_of_table_end)) #else #define CLK_OF_TABLES() #endif @@ -170,7 +170,7 @@ #define KERNEL_DTB() \ STRUCT_ALIGN(); \ VMLINUX_SYMBOL(__dtb_start) = .; \ - *(.dtb.init.rodata) \ + KEEP(*(.dtb.init.rodata)) \ VMLINUX_SYMBOL(__dtb_end) = .; /* .data section */ @@ -186,16 +186,17 @@ /* implement dynamic printk debug */ \ . = ALIGN(8); \ VMLINUX_SYMBOL(__start___jump_table) = .; \ - *(__jump_table) \ + KEEP(*(__jump_table)) \ VMLINUX_SYMBOL(__stop___jump_table) = .; \ . = ALIGN(8); \ VMLINUX_SYMBOL(__start___verbose) = .; \ - *(__verbose) \ + KEEP(*(__verbose)) \ VMLINUX_SYMBOL(__stop___verbose) = .; \ LIKELY_PROFILE() \ BRANCH_PROFILE() \ TRACE_PRINTKS() \ - TRACEPOINT_STR() + TRACEPOINT_STR() \ + *(.data.[a-zA-Z_]*) /* * Data section helpers @@ -249,32 +250,32 @@ /* PCI quirks */ \ .pci_fixup : AT(ADDR(.pci_fixup) - LOAD_OFFSET) { \ VMLINUX_SYMBOL(__start_pci_fixups_early) = .; \ - *(.pci_fixup_early) \ + KEEP(*(.pci_fixup_early)) \ VMLINUX_SYMBOL(__end_pci_fixups_early) = .; \ VMLINUX_SYMBOL(__start_pci_fixups_header) = .; \ - *(.pci_fixup_header) \ + KEEP(*(.pci_fixup_header)) \ VMLINUX_SYMBOL(__end_pci_fixups_header) = .; \ VMLINUX_SYMBOL(__start_pci_fixups_final) = .; \ - *(.pci_fixup_final) \ + KEEP(*(.pci_fixup_final)) \ VMLINUX_SYMBOL(__end_pci_fixups_final) = .; \ VMLINUX_SYMBOL(__start_pci_fixups_enable) = .; \ - *(.pci_fixup_enable) \ + KEEP(*(.pci_fixup_enable)) \ VMLINUX_SYMBOL(__end_pci_fixups_enable) = .; \ VMLINUX_SYMBOL(__start_pci_fixups_resume) = .; \ - *(.pci_fixup_resume) \ + KEEP(*(.pci_fixup_resume)) \ VMLINUX_SYMBOL(__end_pci_fixups_resume) = .; \ VMLINUX_SYMBOL(__start_pci_fixups_resume_early) = .; \ - *(.pci_fixup_resume_early) \ + KEEP(*(.pci_fixup_resume_early)) \ VMLINUX_SYMBOL(__end_pci_fixups_resume_early) = .; \ VMLINUX_SYMBOL(__start_pci_fixups_suspend) = .; \ - *(.pci_fixup_suspend) \ + KEEP(*(.pci_fixup_suspend)) \ VMLINUX_SYMBOL(__end_pci_fixups_suspend) = .; \ } \ \ /* Built-in firmware blobs */ \ .builtin_fw : AT(ADDR(.builtin_fw) - LOAD_OFFSET) { \ VMLINUX_SYMBOL(__start_builtin_fw) = .; \ - *(.builtin_fw) \ + KEEP(*(.builtin_fw)) \ VMLINUX_SYMBOL(__end_builtin_fw) = .; \ } \ \ @@ -283,49 +284,49 @@ /* Kernel symbol table: Normal symbols */ \ __ksymtab : AT(ADDR(__ksymtab) - LOAD_OFFSET) { \ VMLINUX_SYMBOL(__start___ksymtab) = .; \ - *(SORT(___ksymtab+*)) \ + KEEP(*(SORT(___ksymtab+*))) \ VMLINUX_SYMBOL(__stop___ksymtab) = .; \ } \ \ /* Kernel symbol table: GPL-only symbols */ \ __ksymtab_gpl : AT(ADDR(__ksymtab_gpl) - LOAD_OFFSET) { \ VMLINUX_SYMBOL(__start___ksymtab_gpl) = .; \ - *(SORT(___ksymtab_gpl+*)) \ + KEEP(*(SORT(___ksymtab_gpl+*))) \ VMLINUX_SYMBOL(__stop___ksymtab_gpl) = .; \ } \ \ /* Kernel symbol table: Normal unused symbols */ \ __ksymtab_unused : AT(ADDR(__ksymtab_unused) - LOAD_OFFSET) { \ VMLINUX_SYMBOL(__start___ksymtab_unused) = .; \ - *(SORT(___ksymtab_unused+*)) \ + KEEP(*(SORT(___ksymtab_unused+*))) \ VMLINUX_SYMBOL(__stop___ksymtab_unused) = .; \ } \ \ /* Kernel symbol table: GPL-only unused symbols */ \ __ksymtab_unused_gpl : AT(ADDR(__ksymtab_unused_gpl) - LOAD_OFFSET) { \ VMLINUX_SYMBOL(__start___ksymtab_unused_gpl) = .; \ - *(SORT(___ksymtab_unused_gpl+*)) \ + KEEP(*(SORT(___ksymtab_unused_gpl+*))) \ VMLINUX_SYMBOL(__stop___ksymtab_unused_gpl) = .; \ } \ \ /* Kernel symbol table: GPL-future-only symbols */ \ __ksymtab_gpl_future : AT(ADDR(__ksymtab_gpl_future) - LOAD_OFFSET) { \ VMLINUX_SYMBOL(__start___ksymtab_gpl_future) = .; \ - *(SORT(___ksymtab_gpl_future+*)) \ + KEEP(*(SORT(___ksymtab_gpl_future+*))) \ VMLINUX_SYMBOL(__stop___ksymtab_gpl_future) = .; \ } \ \ /* Kernel symbol table: Normal symbols */ \ __kcrctab : AT(ADDR(__kcrctab) - LOAD_OFFSET) { \ VMLINUX_SYMBOL(__start___kcrctab) = .; \ - *(SORT(___kcrctab+*)) \ + KEEP(*(SORT(___kcrctab+*))) \ VMLINUX_SYMBOL(__stop___kcrctab) = .; \ } \ \ /* Kernel symbol table: GPL-only symbols */ \ __kcrctab_gpl : AT(ADDR(__kcrctab_gpl) - LOAD_OFFSET) { \ VMLINUX_SYMBOL(__start___kcrctab_gpl) = .; \ - *(SORT(___kcrctab_gpl+*)) \ + KEEP(*(SORT(___kcrctab_gpl+*))) \ VMLINUX_SYMBOL(__stop___kcrctab_gpl) = .; \ } \ \ @@ -339,14 +340,14 @@ /* Kernel symbol table: GPL-only unused symbols */ \ __kcrctab_unused_gpl : AT(ADDR(__kcrctab_unused_gpl) - LOAD_OFFSET) { \ VMLINUX_SYMBOL(__start___kcrctab_unused_gpl) = .; \ - *(SORT(___kcrctab_unused_gpl+*)) \ + KEEP(*(SORT(___kcrctab_unused_gpl+*))) \ VMLINUX_SYMBOL(__stop___kcrctab_unused_gpl) = .; \ } \ \ /* Kernel symbol table: GPL-future-only symbols */ \ __kcrctab_gpl_future : AT(ADDR(__kcrctab_gpl_future) - LOAD_OFFSET) { \ VMLINUX_SYMBOL(__start___kcrctab_gpl_future) = .; \ - *(SORT(___kcrctab_gpl_future+*)) \ + KEEP(*(SORT(___kcrctab_gpl_future+*))) \ VMLINUX_SYMBOL(__stop___kcrctab_gpl_future) = .; \ } \ \ @@ -365,14 +366,14 @@ /* Built-in module parameters. */ \ __param : AT(ADDR(__param) - LOAD_OFFSET) { \ VMLINUX_SYMBOL(__start___param) = .; \ - *(__param) \ + KEEP(*(__param)) \ VMLINUX_SYMBOL(__stop___param) = .; \ } \ \ /* Built-in module versions. */ \ __modver : AT(ADDR(__modver) - LOAD_OFFSET) { \ VMLINUX_SYMBOL(__start___modver) = .; \ - *(__modver) \ + KEEP(*(__modver)) \ VMLINUX_SYMBOL(__stop___modver) = .; \ . = ALIGN((align)); \ VMLINUX_SYMBOL(__end_rodata) = .; \ @@ -428,7 +429,7 @@ #define ENTRY_TEXT \ ALIGN_FUNCTION(); \ VMLINUX_SYMBOL(__entry_text_start) = .; \ - *(.entry.text) \ + KEEP(*(.entry.text)) \ VMLINUX_SYMBOL(__entry_text_end) = .; #ifdef CONFIG_FUNCTION_GRAPH_TRACER @@ -456,7 +457,7 @@ . = ALIGN(align); \ __ex_table : AT(ADDR(__ex_table) - LOAD_OFFSET) { \ VMLINUX_SYMBOL(__start___ex_table) = .; \ - *(__ex_table) \ + KEEP(*(__ex_table)) \ VMLINUX_SYMBOL(__stop___ex_table) = .; \ } @@ -472,8 +473,8 @@ #ifdef CONFIG_CONSTRUCTORS #define KERNEL_CTORS() . = ALIGN(8); \ VMLINUX_SYMBOL(__ctors_start) = .; \ - *(.ctors) \ - *(.init_array) \ + KEEP(*(.ctors)) \ + KEEP(*(.init_array)) \ VMLINUX_SYMBOL(__ctors_end) = .; #else #define KERNEL_CTORS() --- a/arch/arm/Makefile +++ b/arch/arm/Makefile @@ -18,11 +18,16 @@ ifeq ($(CONFIG_CPU_ENDIAN_BE8),y) LDFLAGS_vmlinux += --be8 LDFLAGS_MODULE += --be8 endif +LDFLAGS_vmlinux += --gc-sections OBJCOPYFLAGS :=-O binary -R .comment -S GZFLAGS :=-9 #KBUILD_CFLAGS +=-pipe +ifndef CONFIG_FUNCTION_TRACER +KBUILD_CFLAGS_KERNEL += -ffunction-sections -fdata-sections +endif + # Never generate .eh_frame KBUILD_CFLAGS += $(call cc-option,-fno-dwarf2-cfi-asm) --- a/arch/arm/kernel/vmlinux.lds.S +++ b/arch/arm/kernel/vmlinux.lds.S @@ -12,13 +12,13 @@ #define PROC_INFO \ . = ALIGN(4); \ VMLINUX_SYMBOL(__proc_info_begin) = .; \ - *(.proc.info.init) \ + KEEP(*(.proc.info.init)) \ VMLINUX_SYMBOL(__proc_info_end) = .; #define IDMAP_TEXT \ ALIGN_FUNCTION(); \ VMLINUX_SYMBOL(__idmap_text_start) = .; \ - *(.idmap.text) \ + KEEP(*(.idmap.text)) \ VMLINUX_SYMBOL(__idmap_text_end) = .; \ . = ALIGN(32); \ VMLINUX_SYMBOL(__hyp_idmap_text_start) = .; \ @@ -93,7 +93,7 @@ SECTIONS .text : { /* Real text segment */ _stext = .; /* Text and read-only data */ __exception_text_start = .; - *(.exception.text) + KEEP(*(.exception.text)) __exception_text_end = .; IRQENTRY_TEXT TEXT_TEXT @@ -118,7 +118,7 @@ SECTIONS __ex_table : AT(ADDR(__ex_table) - LOAD_OFFSET) { __start___ex_table = .; #ifdef CONFIG_MMU - *(__ex_table) + KEEP(*(__ex_table)) #endif __stop___ex_table = .; } @@ -130,12 +130,12 @@ SECTIONS . = ALIGN(8); .ARM.unwind_idx : { __start_unwind_idx = .; - *(.ARM.exidx*) + KEEP(*(.ARM.exidx*)) __stop_unwind_idx = .; } .ARM.unwind_tab : { __start_unwind_tab = .; - *(.ARM.extab*) + KEEP(*(.ARM.extab*)) __stop_unwind_tab = .; } #endif @@ -154,14 +154,14 @@ SECTIONS */ __vectors_start = .; .vectors 0 : AT(__vectors_start) { - *(.vectors) + KEEP(*(.vectors)) } . = __vectors_start + SIZEOF(.vectors); __vectors_end = .; __stubs_start = .; .stubs 0x1000 : AT(__stubs_start) { - *(.stubs) + KEEP(*(.stubs)) } . = __stubs_start + SIZEOF(.stubs); __stubs_end = .; @@ -175,24 +175,24 @@ SECTIONS } .init.arch.info : { __arch_info_begin = .; - *(.arch.info.init) + KEEP(*(.arch.info.init)) __arch_info_end = .; } .init.tagtable : { __tagtable_begin = .; - *(.taglist.init) + KEEP(*(.taglist.init)) __tagtable_end = .; } #ifdef CONFIG_SMP_ON_UP .init.smpalt : { __smpalt_begin = .; - *(.alt.smp.init) + KEEP(*(.alt.smp.init)) __smpalt_end = .; } #endif .init.pv_table : { __pv_table_begin = .; - *(.pv_table) + KEEP(*(.pv_table)) __pv_table_end = .; } .init.data : { --- a/arch/arm/boot/compressed/Makefile +++ b/arch/arm/boot/compressed/Makefile @@ -120,6 +120,7 @@ ifeq ($(CONFIG_FUNCTION_TRACER),y) ORIG_CFLAGS := $(KBUILD_CFLAGS) KBUILD_CFLAGS = $(subst -pg, , $(ORIG_CFLAGS)) endif +KBUILD_CFLAGS_KERNEL := $(patsubst -f%-sections,,$(KBUILD_CFLAGS_KERNEL)) ccflags-y := -fpic -mno-single-pic-base -fno-builtin -I$(obj) asflags-y := -DZIMAGE