barebox分析

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barebox分析

2012-06-08 11:06 246人阅读评论(0) 收藏举报

cmdcommanddiskstructimagelinker

启动分析

Makefile文件

lds-$(CONFIG_GENERIC_LINKER_SCRIPT) :=arch/arm/lib/barebox.lds

lds-$(CONFIG_BOARD_LINKER_SCRIPT) := $(BOARD)/barebox.lds

配置时使用arch/arm/lib/barebox.lds链接脚本。

OUTPUT_FORMAT("elf32-littlearm", "elf32-littlearm", "elf32-littlearm")

OUTPUT_ARCH(arm)

ENTRY(start)

SECTIONS

{

. = TEXT_BASE;

arch/arm/Makefile:143:TEXT_BASE = $(CONFIG_TEXT_BASE)

CONFIG_TEXT_BASE是在配置文件中配置的

TEXT_BASE

PRE_IMAGE

. = ALIGN(4);

.text :

{

_stext = .;

_text = .;

*(.text_entry*)

__ll_return = .;

*(.text_ll_return*)

#ifdef CONFIG_ARCH_EP93XX

/* the EP93xx expects to find the pattern 'CRUS' at 0x1000 */

. = 0x1000;

LONG(0x53555243) /* 'CRUS' */

#endif

__bare_init_start = .;

*(.text_bare_init*)

__bare_init_end = .;

__exceptions_start = .;

KEEP(*(.text_exceptions*))

__exceptions_stop = .;

*(.text*)

}

BAREBOX_BARE_INIT_SIZE

. = ALIGN(4);

.rodata : { *(.rodata*) }

#ifdef CONFIG_ARM_UNWIND

* Stack unwinding tables

. = ALIGN(8);

.ARM.unwind_idx : {

__start_unwind_idx = .;

*(.ARM.exidx*)

__stop_unwind_idx = .;

}

.ARM.unwind_tab : {

__start_unwind_tab = .;

*(.ARM.extab*)

__stop_unwind_tab = .;

}

#endif

_etext = .; /* End of text and rodata section */

. = ALIGN(4);

.data : { *(.data*) }

. = ALIGN(4);

.got : { *(.got*) }

. = .;

__barebox_cmd_start = .;

.barebox_cmd : { BAREBOX_CMDS }

__barebox_cmd_end = .;

__barebox_magicvar_start = .;

.barebox_magicvar : { BAREBOX_MAGICVARS }

__barebox_magicvar_end = .;

__barebox_initcalls_start = .;

.barebox_initcalls : { INITCALLS }

__barebox_initcalls_end = .;

__usymtab_start = .;

__usymtab : { BAREBOX_SYMS }

__usymtab_end = .;

. = ALIGN(4);

__bss_start = .;

.bss : { *(.bss*) }

__bss_stop = .;

_end = .;

_barebox_image_size = __bss_start - TEXT_BASE;

}

刚开始时.text_entry，

void __naked__section(.text_entry) start(void)

{

barebox_arm_head();

}

进入的函数是barebox_arm_head()，是跳转函数。

staticinlinevoid barebox_arm_head(void)

{

__asm__ __volatile__ (

"b reset\n"

"1: b 1b\n"

".word 0x65726162\n" /* 'bare' */

".word 0x00786f62\n" /* 'box' */

".word _text\n" /* text base. If copied there,

* barebox can skip relocation

".word_barebox_image_size\n" /* image size tocopy */

);

}

这个函数就是一些列跳转函数，正常情况下调转到reset函数。

Reset函数修饰用

#define __bare_init __section(.text_bare_init.text)

__bare_init_start= .;

*(.text_bare_init*)

__bare_init_end= .;

Lds链接脚本有对此的修饰。

void __naked__bare_init reset(void)

{

/* set the cpu to SVC32 mode */

#ifdef CONFIG_ARCH_HAS_LOWLEVEL_INIT

arch_init_lowlevel();

#endif

/* disable MMU stuff and caches */

#ifdef CONFIG_MACH_DO_LOWLEVEL_INIT

board_init_lowlevel(); 这个是特定板子的文件

#endif

board_init_lowlevel_return();

}

lowlevel_init.S (arch\arm\boards\tq2440) 中

.section ".text_bare_init.board_init_lowlevel","ax"

/* ------------------------------------------------------------------------*/

.globl board_init_lowlevel

board_init_lowlevel:

mov r10, lr /* save the link register */

bl s3c24x0_disable_wd

/* skip everything here if we are alreadyrunning from SDRAM */

cmp pc, #S3C_SDRAM_BASE

blo 1f

cmp pc, #S3C_SDRAM_END

bhs 1f

mov pc, r10

/* we are running from NOR or NAND/SRAM memory. Do further initialisation*/

bl s3c24x0_pll_init

bl s3c24x0_sdram_init

#ifdef CONFIG_S3C24XX_NAND_BOOT

mov lr, r10 /* restore the linkregister */

/* up to here we are running from the internal SRAM area */

b s3c24x0_nand_boot /* does return directly to our caller into SDRAM */

#else

mov pc, r10

#endif

执行完函数board_init_lowlevel后，执行board_init_lowlevel_return。

函数board_init_lowlevel中

s3c24x0_disable_wd关闭看门狗

s3c24x0_pll_init PLL初始化

s3c24x0_sdram_init SDRAM初始化，在2440板子上，只初始化了bank6和bank7，其他bank的配置保留。

s3c24x0_nand_boot：如果配置了从nand启动，会将代码从nand中拷贝到SDRAM中的TEXT_BASE地址处。

void __naked__section(.text_ll_return)board_init_lowlevel_return(void)

{

uint32_t r, addr;

* Get runtime address of this function. Do not

* put any code above this.

__asm__ __volatile__("1: adr %0,1b":"=r"(addr));

Adr是当前程序运行的地址

/* Setup the stack */

r = STACK_BASE + STACK_SIZE -16;

__asm__ __volatile__("mov sp,%0"::"r"(r));

/* Get start of binary image */

addr -=(uint32_t)&__ll_return- TEXT_BASE;

TEXT_BASE;这是在arch/XXX/configs/*_defconfig定义的

进行代码重定位

/* relocate to link address ifnecessary */

if(addr != TEXT_BASE)

memcpy((void*)TEXT_BASE,(void*)addr,

(unsignedint)&__bss_start- TEXT_BASE);

__***这些都是在链接脚本中定义的

/* clear bss */

清楚bss段

memset(__bss_start,0, __bss_stop - __bss_start);

/* call start_barebox with itsabsolute address */

r =(unsignedint)&start_barebox; 跳转到函数去

__asm__ __volatile__("mov pc,%0"::"r"(r));

}

__ll_return= .;

*(.text_ll_return*)

void __naked __section(.text_ll_return) board_init_lowlevel_return(void)

这是放在.text_entry之后的函数

函数void __naked __bare_init reset(void)

这是复位函数，其中

1. /* set the cpu to SVC32 mode */

2. #ifdefCONFIG_ARCH_HAS_LOWLEVEL_INIT

arch_init_lowlevel();//对板子硬件中断向量进行了初始化

#endif

3. __mmu_cache_flush

4.disable MMU stuff and caches

5. #ifdefCONFIG_MACH_DO_LOWLEVEL_INIT

board_init_lowlevel();// 板子特定的文件，进行一些板子初始化，板级初始化

#endif

6.board_init_lowlevel_return();// 进行代码重定位

reset函数中清空cache，disable掉mmu后跳去执行board_init_lowlevel（CONFIG_MACH_DO_LOWLEVEL_INIT可以在menuconfig中看到被选中。board_init_lowlevel就是板子特定的文件了

在函数board_init_lowlevel_return中会跳转到start_barebox去接着执行。

voidstart_barebox (void)

{

initcall_t *initcall;

int result;

#ifdef CONFIG_COMMAND_SUPPORT

struct stat s;

#endif

首先执行一系列的初始化函数

for(initcall = __barebox_initcalls_start;

initcall <__barebox_initcalls_end; initcall++){

debug("initcall->%pS\n",*initcall);

result =(*initcall)();

debug("initcall<-%pS (%d)\n",*initcall, result);

}

debug("initcalls done\n");

打印内存信息

display_meminfo();

配置了处理环境信息选项则去读环境变量

首先程序去读取/dev/env0到/env，正常情况下/dev/env0放的是一个（类似）压缩文件，envfs_load会对它做校验。毫无疑问，初始启动时肯定是找不到这个文件的，所以接着读取/dev/defaultenv到/env （loader跑起来后执行saveenv就把/env的东西打包到/dev/env0去了）。然后执行/env/bin/init。

#ifdef CONFIG_ENV_HANDLING

if(envfs_load(default_environment_path,"/env")){

#ifdef CONFIG_DEFAULT_ENVIRONMENT

printf("no validenvironment found on %s. "

"Using defaultenvironment\n",

default_environment_path);

envfs_load("/dev/defaultenv","/env");

#endif

}

#endif

#ifdef CONFIG_COMMAND_SUPPORT

printf("running/env/bin/init...\n");

执行默认的init脚本

if(!stat("/env/bin/init",&s)){

run_command("source/env/bin/init",0);

}else{

printf("notfound\n");

}

#endif

/* main_loop() can return to retry autoboot,if so just run it again. */

for(;;)

run_shell();

/* NOTREACHED - no way out of commandloop except booting */

}

initcall-> 0x33d1e658

initcall<- 0x33d1e658 (0)

initcall-> 0x33d1fd34

initcall<- 0x33d1fd34 (0)

initcall-> 0x33d05368

initcall<- 0x33d05368 (0)

initcall-> 0x33d06480

initcall<- 0x33d06480 (0)

initcall-> 0x33d18088

initcall<- 0x33d18088 (0)

initcall-> 0x33d1a964

initcall<- 0x33d1a964 (0)

initcall-> 0x33d1d62c

initcall<- 0x33d1d62c (0)

initcall-> 0x33d0805c

initcall<- 0x33d0805c (0)

initcall-> 0x33d1e414

barebox 2012.05.0 (Jun 7 2012 - 21:00:25)

Board: TQ 2440

initcall<- 0x33d1e414 (0)

initcall-> 0x33d1e3f0

initcall<- 0x33d1e3f0 (0)

initcall-> 0x33d03780

initcall<- 0x33d03780 (0)

initcall-> 0x33d0dc50

initcall<- 0x33d0dc50 (0)

initcall-> 0x33d1bfb0

initcall<- 0x33d1bfb0 (0)

initcall-> 0x33d1cdcc

initcall<- 0x33d1cdcc (0)

initcall-> 0x33d05e38

initcall<- 0x33d05e38 (0)

initcall-> 0x33d05de8

initcall<- 0x33d05de8 (0)

initcall-> 0x33d071ec

initcall<- 0x33d071ec (0)

initcall-> 0x33d07be8

initcall<- 0x33d07be8 (0)

initcall-> 0x33d0d4d0

initcall<- 0x33d0d4d0 (0)

initcall-> 0x33d0f18c

initcall<- 0x33d0f18c (0)

initcall-> 0x33d1099c

initcall<- 0x33d1099c (0)

initcall-> 0x33d11a88

initcall<- 0x33d11a88 (0)

initcall-> 0x33d125e0

initcall<- 0x33d125e0 (0)

initcall-> 0x33d12618

initcall<- 0x33d12618 (0)

initcall-> 0x33d1e484

NAND device: Manufacturer ID: 0xec, Chip ID: 0xda (Samsung NAND 256MiB 3,3V 8-bit)

Bad block table found at page 131008, version 0x01

Bad block table found at page 130944, version 0x01

nand_read_bbt: Bad block at 0x01b20000

nand_read_bbt: Bad block at 0x02340000

nand_read_bbt: Bad block at 0x08820000

nand_read_bbt: Bad block at 0x09a00000

nand_read_bbt: Bad block at 0x0a6e0000

nand_read_bbt: Bad block at 0x0c840000

dm9000@dm90000: Found DM9000E at i/o: 0x20000300

s3c_mci@mci0: registered as mci0

initcall<- 0x33d1e484 (0)

initcall-> 0x33d04930

initcall<- 0x33d04930 (0)

initcall-> 0x33d1ea80

refclk: 12000 kHz

mpll: 405000 kHz

upll: 48000 kHz

fclk: 405000 kHz

hclk: 101250 kHz

pclk: 50625 kHz

SDRAM1: CL3@101MHz

SDRAM2: CL3@101MHz

initcall<- 0x33d1ea80 (0)

initcall-> 0x33d1f7c0

initcall<- 0x33d1f7c0 (0)

完成了初始化函数

initcalls done

barebox code: 0x33d00000 -> 0x33d285d0

bss segment: 0x33d2a4d8 -> 0x33d2e89c

Malloc space: 0x33900000 -> 0x33cfffff (size 4 MB)

Stack space : 0x338f8000 -> 0x33900000 (size 32 kB)

err -74

envfs: wrong magic on /dev/env0

no valid environment found on /dev/env0. Using default environment

running /env/bin/init...

Hit any key to stop autoboot: 1

tq2440:/

接下去我们分析一下/env/bin/init即/dev/defaultenv/bin/init。打开barebox下的default/bin，找到init文件：

#!/bin/sh

PATH=/env/bin

export PATH

包含config文件

./env/config

判断/dev/nor0是否存在，存在就执行addpart命令，对nor0按照变量nor_parts的设定进行分区。

if[-e/dev/nor0 -a-n"$nor_parts"];then

addpart /dev/nor0 $nor_parts

if[-e/dev/disk0 -a-n"$disk_parts"];then

addpart /dev/disk0 $disk_parts

判断/dev/nand0是否存在，存在就执行对nand0按照变量nand_parts的设定进行分区，并执行source /env/bin/hush_hack

if[-e/dev/nand0 -a-n"$nand_parts"];then

addpart /dev/nand0 $nand_parts

# Uh, oh, hush first expands wildcards and then starts executing

# commands. What a bug!

source /env/bin/hush_hack

如果/env/bin/init_board存在，就执行它。

if[-f/env/bin/init_board ];then

./env/bin/init_board

echo

执行shell timeout，如果timeout不到0的话，就执行update -h，见下面对update文件的分析。如果timeout到0的话，就执行boot

echo -n "Hit any key to stop autoboot: "

timeout -a $autoboot_timeout

if[$?!=0];then

exit

boot

/env/config是barebox下arch/arm/board/{myboard}/env/config的一个复制：

#!/bin/sh

machine=FIXME

#user=

# Enter MAC address here if not retrieved automatically

#eth0.ethaddr=de:ad:be:ef:00:00

# use 'dhcp' to do dhcp in barebox and in kernel

# use 'none' if you want to skip kernel ip autoconfiguration

ip=dhcp

dhcp_vendor_id=barebox

# or set your networking parameters here

#eth0.ipaddr=a.b.c.d

#eth0.netmask=a.b.c.d

#eth0.serverip=a.b.c.d

#eth0.gateway=a.b.c.d

# can be either 'tftp', 'nfs', 'nand', 'nor' or 'disk'

kernel_loc=tftp

# can be either 'net', 'nand', 'nor', 'disk' or 'initrd'

rootfs_loc=net

# for flash based rootfs: 'jffs2' or 'ubifs'

# in case of disk any regular filesystem like 'ext2', 'ext3', 'reiserfs'

rootfs_type=ubifs

# where is the rootfs in case of 'rootfs_loc=disk' (linux name)

rootfs_part_linux_dev=mmcblk0p4

rootfsimage=rootfs-${machine}.$rootfs_type

# where is the kernel image in case of 'kernel_loc=disk'

kernel_part=disk0.2

kernelimage=zImage-$machine

#kernelimage=uImage-$machine

#kernelimage=Image-$machine

#kernelimage=Image-$machine.lzo

bareboximage=barebox-${machine}.bin

bareboxenvimage=barebox-${machine}.bin

if[-n$user];then

bareboximage="$user"-"$bareboximage"

bareboxenvimage="$user"-"$bareboxenvimage"

kernelimage="$user"-"$kernelimage"

rootfsimage="$user"-"$rootfsimage"

nfsroot="/home/$user/nfsroot/$machine"

else

nfsroot="/path/to/nfs/root"

autoboot_timeout=3

bootargs="console=ttyFIXME,115200"

nor_parts="256k(barebox)ro,128k(bareboxenv),3M(kernel),-(root)"

rootfs_mtdblock_nor=3

nand_parts="256k(barebox)ro,128k(bareboxenv),3M(kernel),-(root)"

nand_device="FIXME"

rootfs_mtdblock_nand=7

# set a fancy prompt (if support is compiled in)

PS1="\e[1;32mbarebox@\e[1;31m\h:\w\e[0m "

boot文件建立起bootargs，然后boot系统：

#!/bin/sh

./env/config

if[ x$kernel_loc= xnet ];then

kernel_loc=tftp

whilegetopt"hk:r:i:m:" Option

if[${Option}= k ];then

kernel_loc=${OPTARG}

elif[${Option}= r ];then

rootfs_loc=${OPTARG}

elif[${Option}= i ];then

ip=${OPTARG}

elif[${Option}= m ];then

mode=${OPTARG}

else

./env/bin/_boot_help

exit0

done

if[ x$mode= xnand ];then

rootfs_loc=nand

kernel_loc=nand

elif[ x$mode= xnor ];then

rootfs_loc=nor

kernel_loc=nor

elif[ x$mode= xnfs ];then

rootfs_loc=net

kernel_loc=nfs

elif[ x$mode= xtftp ];then

rootfs_loc=net

kernel_loc=tftp

elif[ x$mode= xdisk ];then

rootfs_loc=disk

kernel_loc=disk

if[ x$ip= xdhcp -o x$ip="xdhcp-barebox"];then

if[ x$kernel_loc= xnfs -o x$kernel_loc= xtftp ];then

dhcp

if[ x$rootpath!= x ];then

nfsroot=$rootpath

if[ x$bootfile!= x ];then

kernelimage=$bootfile

if[ x$ip= xdhcp -o];then

bootargs="$bootargs ip=dhcp"

elif[ x$ip= xnone ];then

bootargs="$bootargs ip=none"

else

bootargs="$bootargs ip=$eth0.ipaddr:$eth0.serverip:$eth0.gateway:$eth0.netmask::eth0:"

if[ x$rootfs_loc= xnet ];then

bootargs="$bootargs root=/dev/nfs nfsroot=$nfsroot,v3,tcp noinitrd"

elif[ x$rootfs_loc= xdisk ];then

bootargs="$bootargs root=/dev/$rootfs_part_linux_dev rootfstype=$rootfs_type noinitrd rootwait"

elif[ x$rootfs_loc= xinitrd ];then

bootargs="$bootargs root=/dev/ram0 rdinit=/sbin/init"

else

if[ x$rootfs_loc= xnand ];then

rootfs_mtdblock=$rootfs_mtdblock_nand

else

rootfs_mtdblock=$rootfs_mtdblock_nor

if[ x$rootfs_type= xubifs ];then

if[-z$ubiroot];then

ubiroot="root"

bootargs="$bootargs root=ubi0:$ubiroot ubi.mtd=$rootfs_mtdblock"

else

bootargs="$bootargs root=/dev/mtdblock$rootfs_mtdblock"

bootargs="$bootargs rootfstype=$rootfs_type noinitrd"

if[-n$nor_parts];then

mtdparts="${mtdparts}physmap-flash.0:${nor_parts}"

if[-n$nand_parts];then

if[-n${mtdparts}];then

mtdparts="${mtdparts};"

mtdparts="${mtdparts}${nand_device}:${nand_parts}"

if[-n$mtdparts];then

bootargs="${bootargs} mtdparts=${mtdparts}"

if[ x$kernel_loc= xnfs -o x$kernel_loc= xtftp ];then

kdev=/image

$kernel_loc$kernelimage$kdev||exit1

elif[ x$kernel_loc= xnor ];then

kdev="/dev/nor0.kernel"

elif[ x$kernel_loc= xnand ];then

kdev="/dev/nand0.kernel.bb"

elif[ x$kernel_loc= xdisk ];then

kdev="/dev/$kernel_part"

else

echo"error: set kernel_loc to one of 'tftp', 'nfs', 'nand', 'nor' or 'disk'"

exit1

echo"booting kernel from $kdev"

bootm $bootm_opt$kdev

Barebox中命令的声明方式

BAREBOX_CMD_START(addpart)

.cmd = do_addpart,

.usage ="adds a partition table to adevice",

BAREBOX_CMD_HELP(cmd_addpart_help)

BAREBOX_CMD_END

我们以addpart命令为例，在commands/partions.c文件中有上面几行，是对命令的声明。

#define Struct_Section __attribute__((unused,section (".barebox_cmd")))

#define BAREBOX_CMD_START(_name) \

extern const struct command __barebox_cmd_##_name; \

const struct command __barebox_cmd_##_name \

__attribute__ ((unused,section(".barebox_cmd_" __stringify(_name)))) = { \

.name = #_name,

#define BAREBOX_CMD_END \

};

#define BAREBOX_CMD_HELP(text) .help= text,

BAREBOX_CMD_HELP_START(addpart)

BAREBOX_CMD_HELP_USAGE("addpart <device><part_desc>\n")

BAREBOX_CMD_HELP_SHORT("Add a partition description to adevice.\n")

BAREBOX_CMD_HELP_OPT ("-n", "no prefix. Do not prepend the device name asprefix before the partition name\n")

BAREBOX_CMD_HELP_OPT ("<device>", "device being worked on\n")

BAREBOX_CMD_HELP_OPT ("<part_desc>", "size1[@offset1](name1)[ro],size2[@offset2](name2)[ro],...\n")

BAREBOX_CMD_HELP_END

上面是对声明了一个字符串cmd_addpart_help

将上面的宏展开

extern const struct command __barebox_cmd_addpart; \

const struct command __barebox_cmd_addpart \

__attribute__ ((unused,section(".barebox_cmd_addpart”)) = { \

.name = addpart,

.cmd = do_addpart,

.usage ="adds a partition table to adevice",

.help = cmd_addpart_help,

}；

命令的段属性是.barebox_cmd_addpart

在lds文件中就有

__barebox_cmd_start = .;

.barebox_cmd : { BAREBOX_CMDS }

__barebox_cmd_end= .;

里面将有关命令的部分都放在了一个地方，用__barebox_cmd_start表示开始，__barebox_cmd_end标记结束。

小结：

现在对后面一部分进行总结，barebox执行完初始化函数后，接着去执行一些环境变量设置，其设置是：

/dev/defaultenv

à/env/bin/init

à. /env/config

àaddpart /dev/nand0 $nand_parts

àsource /env/bin/hush_hack

àtimeout -a $autoboot_timeout

àboot

环境变量的设置，环境变量是在/env/config中设置的。

Nand的分区设置

nand_parts="256k(barebox)ro,128k(bareboxenv),3M(kernel),-(root)"

以上是一部分设置，后面的目标是能够加载内核，能够挂载文件系统。