uboot的编译过程分析——链接脚本u-boot.lds分析

以下内容源于朱有鹏嵌入式的学习与整理，如有侵权，请告知删除。

九鼎uboot的链接脚本u-boot.lds位于uboot//board/samsung/x210目录。

它是本来就写好的，不像其他uboot那样在make的时候才生成。

xjh@ubuntu:~/iot/embedded_basic/uboot/uboot_jiuding-version$ make distclean
xjh@ubuntu:~/iot/embedded_basic/uboot/uboot_jiuding-version$ cd board/samsung/x210/
xjh@ubuntu:~/iot/embedded_basic/uboot/uboot_jiuding-version/board/samsung/x210$ ls
flash.c  lowlevel_init.S  Makefile  smdkc110_val.h  u-boot.lds#这里  x210.c
xjh@ubuntu:~/iot/embedded_basic/uboot/uboot_jiuding-version/board/samsung/x210$ 

九鼎uboot的链接脚本u-boot.lds内容与分析如下。 

/*
 * (C) Copyright 2002
 * Gary Jennejohn, DENX Software Engineering, <[e-mail]>
 *
 * See file CREDITS for list of people who contributed to this
 * project.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of
 * the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
 * MA 02111-1307 USA
 */
//指定输出的可执行文件是32位的ARM指令，小端模式，ELF格式。
OUTPUT_FORMAT("elf32-littlearm", "elf32-littlearm", "elf32-littlearm")
/*OUTPUT_FORMAT("elf32-arm", "elf32-arm", "elf32-arm")*/
OUTPUT_ARCH(arm)    //指定可执行平台是ARM平台
ENTRY(_start)    //指定程序入口是标号_start
SECTIONS
{

//这里指定程序链接地址是0x0，但是会被Makefile文件中的-Ttext $(TEXT_BASE)覆盖掉，
//所以实际的链接地址是$(TEXT_BASE)；“.”代表当前地址
	. = 0x00000000;

//四字节对齐
	. = ALIGN(4);

//代码段（即text段）中将某些文件靠前排列，因为这些文件都是和BL1相关的，负责启动的第一阶段。
	.text      :
	{
	  cpu/s5pc11x/start.o    (.text)  //代码段的第一个.o文件
	  cpu/s5pc11x/s5pc110/cpu_init.o	(.text)
	  board/samsung/x210/lowlevel_init.o	(.text)
          cpu/s5pc11x/onenand_cp.o      (.text)                 
          cpu/s5pc11x/nand_cp.o (.text)                     
          cpu/s5pc11x/movi.o (.text) 
          common/secure_boot.o (.text) 
	  common/ace_sha1.o (.text)
	  cpu/s5pc11x/pmic.o (.text)
	  *(.text) //表示代码段的其余部分
	}

	. = ALIGN(4);
	.rodata : { *(.rodata) } //这是只读数据段
                             //格式其实也是用花括号包围起来，只是这里只有一行

	. = ALIGN(4);
	.data : { *(.data) }//这是数据段

	. = ALIGN(4);
	.got : { *(.got) }

//u_boot_cmd段是一个自定义段，将来uboot的命令结构体都会被赋予这个段属性，集中被链接在一起。
	__u_boot_cmd_start = .;//这个表示__u_boot_cmd_start标号指向u_boot_cmd段起始地址
	.u_boot_cmd : { *(.u_boot_cmd) }
	__u_boot_cmd_end = .;//这个表示__u_boot_cmd_end标号指向u_boot_cmd段结束地址

	. = ALIGN(4);
	.mmudata : { *(.mmudata) }

	. = ALIGN(4);
	__bss_start = .;
	.bss : { *(.bss) }
	_end = .;
}