Commit ef53dae8 authored by Sam Ravnborg's avatar Sam Ravnborg
Browse files

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: default avatarSam Ravnborg <sam@ravnborg.org>
Cc: Tim Abbott <tabbott@mit.edu>
parent eedc9d83

include/asm-generic/vmlinux.lds.h

+224 −7
Original line number Diff line number Diff line 
/*

 * Helper macros to support writing architecture specific

 * linker scripts.

 *

 * A minimal linker scripts has following content:

 * [This is a sample, architectures may have special requiriements]

 *

 * OUTPUT_FORMAT(...)

 * OUTPUT_ARCH(...)

 * ENTRY(...)

 * SECTIONS

 * {

 *	. = START;

 *	__init_begin = .;

 *	HEAD_SECTION

 *	INIT_TEXT_SECTION(PAGE_SIZE)

 *	INIT_DATA_SECTION(...)

 *	PERCPU(PAGE_SIZE)

 *	__init_end = .;

 *

 *	_stext = .;

 *	TEXT_SECTION = 0

 *	_etext = .;

 *

 *      _sdata = .;

 *	RO_DATA_SECTION(PAGE_SIZE)

 *	RW_DATA_SECTION(...)

 *	_edata = .;

 *

 *	EXCEPTION_TABLE(...)

 *	NOTES

 *

 *	__bss_start = .;

 *	BSS_SECTION(0, 0)

 *	__bss_stop = .;

 *	_end = .;

 *

 *	/DISCARD/ : {

 *		EXIT_TEXT

 *		EXIT_DATA

 *		*(.exitcall.exit)

 *	}

 *	STABS_DEBUG

 *	DWARF_DEBUG

 * }

 *

 * [__init_begin, __init_end] is the init section that may be freed after init

 * [_stext, _etext] is the text section

 * [_sdata, _edata] is the data section

 *

 * Some of the included output section have their own set of constants.

 * Examples are: [__initramfs_start, __initramfs_end] for initramfs and

 *               [__nosave_begin, __nosave_end] for the nosave data

 */

 #include <linux/section-names.h>



#ifndef LOAD_OFFSET
@@ -116,7 +170,36 @@ 
	FTRACE_EVENTS()							\

	TRACE_SYSCALLS()



#define RO_DATA(align)							\

/*

 * Data section helpers

 */

#define NOSAVE_DATA							\

	. = ALIGN(PAGE_SIZE);						\

	VMLINUX_SYMBOL(__nosave_begin) = .;				\

	*(.data.nosave)							\

	. = ALIGN(PAGE_SIZE);						\

	VMLINUX_SYMBOL(__nosave_end) = .;



#define PAGE_ALIGNED_DATA(page_align)					\

	. = ALIGN(page_align);						\

	*(.data.page_aligned)



#define READ_MOSTLY_DATA(align)						\

	. = ALIGN(align);						\

	*(.data.read_mostly)



#define CACHELINE_ALIGNED_DATA(align)					\

	. = ALIGN(align);						\

	*(.data.cacheline_aligned)



#define INIT_TASK(align)						\

	. = ALIGN(align);						\

	*(.data.init_task)



/*

 * Read only Data

 */

#define RO_DATA_SECTION(align)						\

	. = ALIGN((align));						\

	.rodata           : AT(ADDR(.rodata) - LOAD_OFFSET) {		\

		VMLINUX_SYMBOL(__start_rodata) = .;			\
@@ -270,9 +353,10 @@ 
	}								\

	. = ALIGN((align));



/* RODATA provided for backward compatibility.

/* RODATA & RO_DATA provided for backward compatibility.

 * All archs are supposed to use RO_DATA() */

#define RODATA RO_DATA(4096)

#define RODATA          RO_DATA_SECTION(4096)

#define RO_DATA(align)  RO_DATA_SECTION(align)



#define SECURITY_INIT							\

	.security_initcall.init : AT(ADDR(.security_initcall.init) - LOAD_OFFSET) { \
@@ -332,6 +416,31 @@ 
/* Section used for early init (in .S files) */

#define HEAD_TEXT  *(HEAD_TEXT_SECTION)



#define HEAD_SECTION							\

	.head.text : AT(ADDR(.head.text) - LOAD_OFFSET) {		\

		HEAD_TEXT						\

	}



/*

 * Exception table

 */

#define EXCEPTION_TABLE(align)						\

	. = ALIGN(align);						\

	__ex_table : AT(ADDR(__ex_table) - LOAD_OFFSET) {		\

		VMLINUX_SYMBOL(__start___ex_table) = .;			\

		*(__ex_table)						\

		VMLINUX_SYMBOL(__stop___ex_table) = .;			\

	}



/*

 * Init task

 */

#define INIT_TASK_DATA(align)						\

	. = ALIGN(align);						\

	.data.init_task : {						\

		INIT_TASK						\

	}



/* init and exit section handling */

#define INIT_DATA							\

	*(.init.data)							\
@@ -364,9 +473,32 @@ 
	CPU_DISCARD(exit.text)						\

	MEM_DISCARD(exit.text)



		/* DWARF debug sections.

		Symbols in the DWARF debugging sections are relative to

		the beginning of the section so we begin them at 0.  */

/*

 * bss (Block Started by Symbol) - uninitialized data

 * zeroed during startup

 */

#define SBSS								\

	.sbss : AT(ADDR(.sbss) - LOAD_OFFSET) {				\

		*(.sbss)						\

		*(.scommon)						\

	}



#define BSS(bss_align)							\

	. = ALIGN(bss_align);						\

	.bss : AT(ADDR(.bss) - LOAD_OFFSET) {				\

		VMLINUX_SYMBOL(__bss_start) = .;			\

		*(.bss.page_aligned)					\

		*(.dynbss)						\

		*(.bss)							\

		*(COMMON)						\

		VMLINUX_SYMBOL(__bss_stop) = .;				\

	}



/*

 * DWARF debug sections.

 * Symbols in the DWARF debugging sections are relative to

 * the beginning of the section so we begin them at 0.

 */

#define DWARF_DEBUG							\

		/* DWARF 1 */						\

		.debug          0 : { *(.debug) }			\
@@ -433,6 +565,12 @@ 
		VMLINUX_SYMBOL(__stop_notes) = .;			\

	}



#define INIT_SETUP(initsetup_align)					\

		. = ALIGN(initsetup_align);				\

		VMLINUX_SYMBOL(__setup_start) = .;			\

		*(.init.setup)						\

		VMLINUX_SYMBOL(__setup_end) = .;



#define INITCALLS							\

	*(.initcallearly.init)						\

	VMLINUX_SYMBOL(__early_initcall_end) = .;			\
@@ -454,6 +592,31 @@ 
  	*(.initcall7.init)						\

  	*(.initcall7s.init)



#define INIT_CALLS							\

		VMLINUX_SYMBOL(__initcall_start) = .;			\

		INITCALLS						\

		VMLINUX_SYMBOL(__initcall_end) = .;



#define CON_INITCALL							\

		VMLINUX_SYMBOL(__con_initcall_start) = .;		\

		*(.con_initcall.init)					\

		VMLINUX_SYMBOL(__con_initcall_end) = .;



#define SECURITY_INITCALL						\

		VMLINUX_SYMBOL(__security_initcall_start) = .;		\

		*(.security_initcall.init)				\

		VMLINUX_SYMBOL(__security_initcall_end) = .;



#ifdef CONFIG_BLK_DEV_INITRD

#define INIT_RAM_FS							\

	. = ALIGN(PAGE_SIZE);						\

	VMLINUX_SYMBOL(__initramfs_start) = .;				\

	*(.init.ramfs)							\

	VMLINUX_SYMBOL(__initramfs_end) = .;

#else

#define INITRAMFS

#endif



/**

 * PERCPU_VADDR - define output section for percpu area

 * @vaddr: explicit base address (optional)
@@ -510,3 +673,57 @@ 
		*(.data.percpu.shared_aligned)				\

		VMLINUX_SYMBOL(__per_cpu_end) = .;			\

	}





/*

 * Definition of the high level *_SECTION macros

 * They will fit only a subset of the architectures

 */





/*

 * Writeable data.

 * All sections are combined in a single .data section.

 * The sections following CONSTRUCTORS are arranged so their

 * typical alignment matches.

 * A cacheline is typical/always less than a PAGE_SIZE so

 * the sections that has this restriction (or similar)

 * is located before the ones requiring PAGE_SIZE alignment.

 * NOSAVE_DATA starts and ends with a PAGE_SIZE alignment which

 * matches the requirment of PAGE_ALIGNED_DATA.

 *

/* use 0 as page_align if page_aligned data is not used */

#define RW_DATA_SECTION(cacheline, nosave, pagealigned, inittask)	\

	. = ALIGN(PAGE_SIZE);						\

	.data : AT(ADDR(.data) - LOAD_OFFSET) {				\

		INIT_TASK(inittask)					\

		CACHELINE_ALIGNED_DATA(cacheline)			\

		READ_MOSTLY_DATA(cacheline)				\

		DATA_DATA						\

		CONSTRUCTORS						\

		NOSAVE_DATA(nosave)					\

		PAGE_ALIGNED_DATA(pagealigned)				\

	}



#define INIT_TEXT_SECTION(inittext_align)				\

	. = ALIGN(inittext_align);					\

	.init.text : AT(ADDR(.init.text) - LOAD_OFFSET) {		\

		VMLINUX_SYMBOL(_sinittext) = .;				\

		INIT_TEXT						\

		VMLINUX_SYMBOL(_einittext) = .;				\

	}



#define INIT_DATA_SECTION(initsetup_align)				\

	.init.data : AT(ADDR(.init.data) - LOAD_OFFSET) {		\

		INIT_DATA						\

		INIT_SETUP(initsetup_align)				\

		INIT_CALLS						\

		CON_INITCALL						\

		SECURITY_INITCALL					\

		INIT_RAM_FS						\

	}



#define BSS_SECTION(sbss_align, bss_align)				\

	SBSS								\

	BSS(bss_align)							\

	. = ALIGN(4);							\

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