Improve vmlinux.lds.h support for arch specific linker scripts
To support alingment of the individual architecture specific linker scripts provide a set of general definitions in vmlinux.lds.h With these definitions applied the diverse linekr scripts can be reduced in line count and their readability are improved - IMO. A sample linker script is included to give the preferred order of the sections for the architectures that do not have any special requirments. These definitions are also a first step towards eventual support for -ffunction-sections. The definitions makes it much easier to do a global renaming of section names - but the main purpose is to clean up the linker scripts. Tim Aboot has provided a lot of inputs to improve the definitions - all faults are mine. Signed-off-by: Sam Ravnborg <sam@ravnborg.org> Cc: Tim Abbott <tabbott@mit.edu>
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Sam Ravnborg
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eedc9d83ea
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ef53dae865
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@ -1,4 +1,58 @@
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#include <linux/section-names.h>
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/*
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* Helper macros to support writing architecture specific
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* linker scripts.
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*
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* A minimal linker scripts has following content:
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* [This is a sample, architectures may have special requiriements]
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*
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* OUTPUT_FORMAT(...)
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* OUTPUT_ARCH(...)
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* ENTRY(...)
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* SECTIONS
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* {
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* . = START;
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* __init_begin = .;
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* HEAD_SECTION
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* INIT_TEXT_SECTION(PAGE_SIZE)
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* INIT_DATA_SECTION(...)
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* PERCPU(PAGE_SIZE)
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* __init_end = .;
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*
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* _stext = .;
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* TEXT_SECTION = 0
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* _etext = .;
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*
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* _sdata = .;
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* RO_DATA_SECTION(PAGE_SIZE)
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* RW_DATA_SECTION(...)
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* _edata = .;
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*
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* EXCEPTION_TABLE(...)
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* NOTES
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*
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* __bss_start = .;
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* BSS_SECTION(0, 0)
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* __bss_stop = .;
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* _end = .;
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*
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* /DISCARD/ : {
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* EXIT_TEXT
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* EXIT_DATA
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* *(.exitcall.exit)
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* }
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* STABS_DEBUG
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* DWARF_DEBUG
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* }
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*
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* [__init_begin, __init_end] is the init section that may be freed after init
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* [_stext, _etext] is the text section
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* [_sdata, _edata] is the data section
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*
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* Some of the included output section have their own set of constants.
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* Examples are: [__initramfs_start, __initramfs_end] for initramfs and
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* [__nosave_begin, __nosave_end] for the nosave data
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*/
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#include <linux/section-names.h>
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#ifndef LOAD_OFFSET
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#define LOAD_OFFSET 0
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@ -116,7 +170,36 @@
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FTRACE_EVENTS() \
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TRACE_SYSCALLS()
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#define RO_DATA(align) \
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/*
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* Data section helpers
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*/
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#define NOSAVE_DATA \
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. = ALIGN(PAGE_SIZE); \
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VMLINUX_SYMBOL(__nosave_begin) = .; \
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*(.data.nosave) \
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. = ALIGN(PAGE_SIZE); \
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VMLINUX_SYMBOL(__nosave_end) = .;
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#define PAGE_ALIGNED_DATA(page_align) \
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. = ALIGN(page_align); \
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*(.data.page_aligned)
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#define READ_MOSTLY_DATA(align) \
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. = ALIGN(align); \
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*(.data.read_mostly)
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#define CACHELINE_ALIGNED_DATA(align) \
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. = ALIGN(align); \
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*(.data.cacheline_aligned)
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#define INIT_TASK(align) \
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. = ALIGN(align); \
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*(.data.init_task)
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/*
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* Read only Data
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*/
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#define RO_DATA_SECTION(align) \
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. = ALIGN((align)); \
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.rodata : AT(ADDR(.rodata) - LOAD_OFFSET) { \
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VMLINUX_SYMBOL(__start_rodata) = .; \
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@ -270,9 +353,10 @@
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} \
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. = ALIGN((align));
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/* RODATA provided for backward compatibility.
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/* RODATA & RO_DATA provided for backward compatibility.
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* All archs are supposed to use RO_DATA() */
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#define RODATA RO_DATA(4096)
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#define RODATA RO_DATA_SECTION(4096)
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#define RO_DATA(align) RO_DATA_SECTION(align)
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#define SECURITY_INIT \
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.security_initcall.init : AT(ADDR(.security_initcall.init) - LOAD_OFFSET) { \
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@ -332,6 +416,31 @@
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/* Section used for early init (in .S files) */
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#define HEAD_TEXT *(HEAD_TEXT_SECTION)
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#define HEAD_SECTION \
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.head.text : AT(ADDR(.head.text) - LOAD_OFFSET) { \
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HEAD_TEXT \
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}
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/*
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* Exception table
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*/
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#define EXCEPTION_TABLE(align) \
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. = ALIGN(align); \
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__ex_table : AT(ADDR(__ex_table) - LOAD_OFFSET) { \
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VMLINUX_SYMBOL(__start___ex_table) = .; \
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*(__ex_table) \
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VMLINUX_SYMBOL(__stop___ex_table) = .; \
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}
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/*
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* Init task
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*/
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#define INIT_TASK_DATA(align) \
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. = ALIGN(align); \
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.data.init_task : { \
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INIT_TASK \
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}
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/* init and exit section handling */
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#define INIT_DATA \
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*(.init.data) \
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@ -364,9 +473,32 @@
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CPU_DISCARD(exit.text) \
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MEM_DISCARD(exit.text)
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/* DWARF debug sections.
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Symbols in the DWARF debugging sections are relative to
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the beginning of the section so we begin them at 0. */
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/*
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* bss (Block Started by Symbol) - uninitialized data
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* zeroed during startup
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*/
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#define SBSS \
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.sbss : AT(ADDR(.sbss) - LOAD_OFFSET) { \
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*(.sbss) \
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*(.scommon) \
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}
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#define BSS(bss_align) \
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. = ALIGN(bss_align); \
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.bss : AT(ADDR(.bss) - LOAD_OFFSET) { \
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VMLINUX_SYMBOL(__bss_start) = .; \
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*(.bss.page_aligned) \
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*(.dynbss) \
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*(.bss) \
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*(COMMON) \
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VMLINUX_SYMBOL(__bss_stop) = .; \
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}
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/*
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* DWARF debug sections.
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* Symbols in the DWARF debugging sections are relative to
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* the beginning of the section so we begin them at 0.
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*/
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#define DWARF_DEBUG \
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/* DWARF 1 */ \
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.debug 0 : { *(.debug) } \
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@ -433,6 +565,12 @@
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VMLINUX_SYMBOL(__stop_notes) = .; \
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}
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#define INIT_SETUP(initsetup_align) \
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. = ALIGN(initsetup_align); \
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VMLINUX_SYMBOL(__setup_start) = .; \
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*(.init.setup) \
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VMLINUX_SYMBOL(__setup_end) = .;
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#define INITCALLS \
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*(.initcallearly.init) \
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VMLINUX_SYMBOL(__early_initcall_end) = .; \
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@ -454,6 +592,31 @@
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*(.initcall7.init) \
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*(.initcall7s.init)
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#define INIT_CALLS \
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VMLINUX_SYMBOL(__initcall_start) = .; \
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INITCALLS \
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VMLINUX_SYMBOL(__initcall_end) = .;
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#define CON_INITCALL \
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VMLINUX_SYMBOL(__con_initcall_start) = .; \
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*(.con_initcall.init) \
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VMLINUX_SYMBOL(__con_initcall_end) = .;
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#define SECURITY_INITCALL \
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VMLINUX_SYMBOL(__security_initcall_start) = .; \
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*(.security_initcall.init) \
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VMLINUX_SYMBOL(__security_initcall_end) = .;
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#ifdef CONFIG_BLK_DEV_INITRD
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#define INIT_RAM_FS \
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. = ALIGN(PAGE_SIZE); \
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VMLINUX_SYMBOL(__initramfs_start) = .; \
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*(.init.ramfs) \
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VMLINUX_SYMBOL(__initramfs_end) = .;
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#else
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#define INITRAMFS
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#endif
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/**
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* PERCPU_VADDR - define output section for percpu area
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* @vaddr: explicit base address (optional)
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@ -510,3 +673,57 @@
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*(.data.percpu.shared_aligned) \
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VMLINUX_SYMBOL(__per_cpu_end) = .; \
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}
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/*
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* Definition of the high level *_SECTION macros
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* They will fit only a subset of the architectures
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*/
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/*
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* Writeable data.
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* All sections are combined in a single .data section.
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* The sections following CONSTRUCTORS are arranged so their
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* typical alignment matches.
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* A cacheline is typical/always less than a PAGE_SIZE so
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* the sections that has this restriction (or similar)
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* is located before the ones requiring PAGE_SIZE alignment.
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* NOSAVE_DATA starts and ends with a PAGE_SIZE alignment which
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* matches the requirment of PAGE_ALIGNED_DATA.
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*
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/* use 0 as page_align if page_aligned data is not used */
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#define RW_DATA_SECTION(cacheline, nosave, pagealigned, inittask) \
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. = ALIGN(PAGE_SIZE); \
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.data : AT(ADDR(.data) - LOAD_OFFSET) { \
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INIT_TASK(inittask) \
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CACHELINE_ALIGNED_DATA(cacheline) \
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READ_MOSTLY_DATA(cacheline) \
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DATA_DATA \
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CONSTRUCTORS \
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NOSAVE_DATA(nosave) \
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PAGE_ALIGNED_DATA(pagealigned) \
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}
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#define INIT_TEXT_SECTION(inittext_align) \
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. = ALIGN(inittext_align); \
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.init.text : AT(ADDR(.init.text) - LOAD_OFFSET) { \
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VMLINUX_SYMBOL(_sinittext) = .; \
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INIT_TEXT \
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VMLINUX_SYMBOL(_einittext) = .; \
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}
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#define INIT_DATA_SECTION(initsetup_align) \
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.init.data : AT(ADDR(.init.data) - LOAD_OFFSET) { \
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INIT_DATA \
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INIT_SETUP(initsetup_align) \
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INIT_CALLS \
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CON_INITCALL \
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SECURITY_INITCALL \
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INIT_RAM_FS \
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}
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#define BSS_SECTION(sbss_align, bss_align) \
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SBSS \
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BSS(bss_align) \
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. = ALIGN(4); \
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