2410的linux内核启动地址30008000 由来探讨

内核编译链接过程是依靠vmlinux.lds文件，以arm为例vmlinux.lds文件位于kernel/arch/arm/vmlinux.lds，

vmlinux-armv.lds的生成过程在kernel/arch/arm/Makefile中

ifeq ($(CONFIG_CPU_32),y)
PROCESSOR = armv
TEXTADDR = 0xC0008000
LDSCRIPT = arch/arm/vmlinux-armv.lds.in
endif

arch/arm/vmlinux.lds: $(LDSCRIPT) dummy
@sed 's/TEXTADDR/$(TEXTADDR)/;s/DATAADDR/$(DATAADDR)/' $(LDSCRIPT) >$@

查看arch/arm/vmlinux.lds 中

OUTPUT_ARCH(arm)
ENTRY(stext)
SECTIONS
{
. = 0xC0008000;
.init : { /* Init code and data */
_stext = .;
__init_begin = .;
*(.text.init)
__proc_info_begin = .;
*(.proc.info)
__proc_info_end = .;
__arch_info_begin = .;
*(.arch.info)
__arch_info_end = .;
__tagtable_begin = .;
*(.taglist)
__tagtable_end = .;
*(.data.init)
. = ALIGN(16);
__setup_start = .;
*(.setup.init)
__setup_end = .;
__initcall_start = .;
*(.initcall.init)
__initcall_end = .;
. = ALIGN(4096);
__init_end = .;
}

/DISCARD/ : { /* Exit code and data */
*(.text.exit)
*(.data.exit)
*(.exitcall.exit)
}

.text : { /* Real text segment */
_text = .; /* Text and read-only data */
*(.text)
*(.fixup)
*(.gnu.warning)
*(.rodata)
*(.rodata.*)
*(.glue_7)
*(.glue_7t)
*(.got) /* Global offset table */

_etext = .; /* End of text section */
}

.kstrtab : { *(.kstrtab) }

. = ALIGN(16);
__ex_table : { /* Exception table */
__start___ex_table = .;
*(__ex_table)
__stop___ex_table = .;
}

__ksymtab : { /* Kernel symbol table */
__start___ksymtab = .;
*(__ksymtab)
__stop___ksymtab = .;
}

. = ALIGN(8192);

.data : {
/*
* first, the init task union, aligned
* to an 8192 byte boundary.
*/
*(.init.task)

/*
* then the cacheline aligned data
*/
. = ALIGN(32);
*(.data.cacheline_aligned)

/*
* and the usual data section
*/
*(.data)
CONSTRUCTORS

_edata = .;
}

.bss : {
__bss_start = .; /* BSS */
*(.bss)
*(COMMON)
_end = . ;
}
/* Stabs debugging sections. */
.stab 0 : { *(.stab) }
.stabstr 0 : { *(.stabstr) }
.stab.excl 0 : { *(.stab.excl) }
.stab.exclstr 0 : { *(.stab.exclstr) }
.stab.index 0 : { *(.stab.index) }
.stab.indexstr 0 : { *(.stab.indexstr) }
.comment 0 : { *(.comment) }
}

arch/arm/Makefile中：

vmlinux: arch/arm/vmlinux.lds

arch/arm/vmlinux.lds: $(LDSCRIPT) dummy
@sed 's/TEXTADDR/$(TEXTADDR)/;s/DATAADDR/$(DATAADDR)/' $(LDSCRIPT) >$@

MAKEBOOT = $(MAKE) -C arch/$(ARCH)/boot

bzImage zImage zinstall Image bootpImage install: vmlinux
@$(MAKEBOOT) $@

但在kernel/arch/arm/boot/Makefile

ifeq ($(CONFIG_ARCH_S3C2410),y)
ZTEXTADDR = 0x30008000
ZRELADDR = 0x30008000
endif

zImage: $(CONFIGURE) compressed/vmlinux
$(OBJCOPY) -O binary -R .note -R .comment -S compressed/vmlinux $@

compressed/vmlinux: $(TOPDIR)/vmlinux dep
@$(MAKE) -C compressed vmlinux

在compressed目录下的Makefile中

ZLDFLAGS = -p -X -T vmlinux.lds

SEDFLAGS = s/TEXT_START/$(ZTEXTADDR)/;s/LOAD_ADDR/$(ZRELADDR)/;s/BSS_START/$(ZBSSADDR)/

all: vmlinux

vmlinux: $(HEAD) $(OBJS) piggy.o vmlinux.lds
$(LD) $(ZLDFLAGS) $(HEAD) $(OBJS) piggy.o $(LIBGCC) -o vmlinux

vmlinux.lds: vmlinux.lds.in Makefile $(TOPDIR)/arch/$(ARCH)/boot/Makefile $(TOPDIR)/.config
@sed "$(SEDFLAGS)" vmlinux.lds.in > $@

vmlinux-armv.lds.in文件的内容：

OUTPUT_ARCH(arm)
ENTRY(_start)
SECTIONS
{
. = LOAD_ADDR;
_load_addr = .;

. = TEXT_START;
_text = .;

.text : {
_start = .;
*(.start)
*(.text)
*(.fixup)
*(.gnu.warning)
*(.rodata)
*(.rodata.*)
*(.glue_7)
*(.glue_7t)
input_data = .;
piggy.o
input_data_end = .;
. = ALIGN(4);
}

_etext = .;

_got_start = .;
.got : { *(.got) }
_got_end = .;
.got.plt : { *(.got.plt) }
.data : { *(.data) }
_edata = .;

. = BSS_START;
__bss_start = .;
.bss : { *(.bss) }
_end = .;

.stack (NOLOAD) : { *(.stack) }

.stab 0 : { *(.stab) }
.stabstr 0 : { *(.stabstr) }
.stab.excl 0 : { *(.stab.excl) }
.stab.exclstr 0 : { *(.stab.exclstr) }
.stab.index 0 : { *(.stab.index) }
.stab.indexstr 0 : { *(.stab.indexstr) }
.comment 0 : { *(.comment) }
}