Commit ef53dae8 authored by Sam Ravnborg's avatar Sam Ravnborg
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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 <linux/section-names.h>
/*
* 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
#define LOAD_OFFSET 0
......@@ -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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