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(补充)Uboot优美代码赏析1.1:分散加载表u-boot.lds
1.位置：
board\samsung\smdk6410\u-boot.lds

 

2.内容分析：
OUTPUT_FORMAT("elf32-littlearm", "elf32-littlearm", "elf32-littlearm")
OUTPUT_ARCH(arm)
ENTRY(_start)
SECTIONS
{
    . = 0x00000000;

//代码段
    . = ALIGN(4);
    .text      :
    {
      cpu/s3c64xx/start.o    (.text)
      cpu/s3c64xx/s3c6410/cpu_init.o    (.text)
      cpu/s3c64xx/onenand_cp.o    (.text)
      cpu/s3c64xx/nand_cp.o    (.text)
      cpu/s3c64xx/movi.o (.text)
      *(.text)
      lib_arm/div0.o
    }

// const 常量数据段
    . = ALIGN(4);
    .rodata : { *(.rodata) }

// staitc/global 常量段
    . = ALIGN(4);
    .data : { *(.data) }

//这个未使用
    . = ALIGN(4);
    .got : { *(.got) }

//命令定义段
    __u_boot_cmd_start = .;
    .u_boot_cmd : { *(.u_boot_cmd) }
    __u_boot_cmd_end = .;

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

//堆栈段/内部临时变量段
    . = ALIGN(4);
    __bss_start = .;
    .bss : { *(.bss) }
    _end = .;
}

 

下面结合 编译后根目录下生成的u-boot.map和System.map分析：
3  .text 段分析
只分析cpu/s3c64xx/start.o    (.text)
u-boot.map中：
Name             Origin             Length             Attributes
 cpu/s3c64xx/start.o(.text)
 .text          0xc7e00000      0x480 cpu/s3c64xx/start.o
                0xc7e00040                _end_vect
                0xc7e0017c                theLastJump
                0xc7e00460                arm1136_cache_flush
                0xc7e0004c                _bss_start
                0xc7e00050                _bss_end
                0xc7e00048                _armboot_start
                0xc7e00120                copy_from_nand
                0xc7e00000                _start
 cpu/s3c64xx/s3c6410/cpu_init.o(.text)
 .text          0xc7e00480      0x15c cpu/s3c64xx/s3c6410/cpu_init.o
                0xc7e005b0                cleanFlushCache
                0xc7e005a4                cleanFlushDCache
                0xc7e00480                mem_ctrl_asm_init
                0xc7e00598                cleanDCache
 cpu/s3c64xx/onenand_cp.o(.text)
 .text          0xc7e005dc        0x0 cpu/s3c64xx/onenand_cp.o

 

其中cpu_init.o的起始地址0xc7e00480 - start.o的起始地址0xc7e00000 = start.o的长度0x480
start.o的起始地址定义在board\samsung\smdk6410\config.mk的TEXT_BASE

 

System.map中：
c7e00000 T _start
c7e00020 t _undefined_instruction
c7e00024 t _software_interrupt
c7e00028 t _prefetch_abort
c7e0002c t _data_abort
c7e00030 t _not_used
c7e00034 t _irq
c7e00038 t _fiq
c7e0003c t _pad
c7e00040 T _end_vect
c7e00040 t _TEXT_BASE
c7e00044 t _TEXT_PHY_BASE
c7e00048 T _armboot_start
c7e0004c T _bss_start
c7e00050 T _bss_end
c7e00054 t reset
c7e00064 t cpu_init_crit
c7e000b8 t after_copy
c7e000b8 t enable_mmu
c7e000d8 t mmu_on
c7e000f4 t skip_hw_init
c7e000f4 t stack_setup
c7e000f8 t clear_bss
c7e00104 t clbss_l
c7e00118 t _start_armboot
c7e0011c t _mmu_table_base
c7e00120 T copy_from_nand
c7e0016c t copy_failed
c7e00174 t compare_failed
c7e0017c T theLastJump
c7e00198 t phy_last_jump
c7e001c0 t undefined_instruction
c7e00220 t software_interrupt
c7e00280 t prefetch_abort
c7e002e0 t data_abort
c7e00340 t not_used
c7e003a0 t irq
c7e00400 t fiq
c7e00460 T arm1136_cache_flush
c7e00480 T mem_ctrl_asm_init

 

T代表是public的，t代表是local/static的

 

 

4.其他段的定义和生成逻辑同理通过u-boot.map去查

.text 段存放代码.o (.text)的起始地址，长度，与未声明为static的函数符号地址（同上）
.rodata 段存放声明为const的变量及其他预先声明在等号右边的字串数据（.rodata.str1.1 ）

 

 .rodata        0xc7e238a4       0x33 lib_arm/libarm.a(board.o)
                0xc7e238a4                version_string
 .rodata.str1.1
                0xc7e245c8       0x78 lib_arm/libarm.a(board.o)
                                 0x7a (size before relaxing)

 

 

.data 数据存放那些全局定义的变量

 

 

 .data          0xc7e2a5a4       0x34 lib_arm/libarm.a(board.o)
                0xc7e2a5a4                init_sequence

 

 

 

.bss 需要进堆或进栈去申请的数据

 

 

 

 .bss           0xc7e3400c       0x10 lib_arm/libarm.a(board.o)
                0xc7e34018                monitor_flash_len
 .bss           0xc7e3401c     0x25cc net/libnet.a(net.o)
                0xc7e34078                NetArpWaitTry
                0xc7e34054                NetArpWaitPacketMAC
                0xc7e3402c                NetOurEther
                0xc7e34028                NetOurIP
                0xc7e34034                NetPingIP
                0xc7e34060                NetServerIP
                0xc7e3405c                NetArpWaitTxPacketSize
                0xc7e34048                NetArpWaitReplyIP
                0xc7e34058                NetArpWaitTxPacket
                0xc7e35eac                NetRxPackets
                0xc7e364e4                NetOurNISDomain
                0xc7e3403c                NetArpWaitPacketIP
                0xc7e3401c                NetState
                0xc7e36566                BootFile
                0xc7e34064                NetServerEther
                0xc7e34040                NetOurSubnetMask
                0xc7e36564                NetBootFileSize
                0xc7e34024                NetIPID
                0xc7e36504                NetOurHostName
                0xc7e3404c                NetRxPkt
                0xc7e34044                NetOurGatewayIP
                0xc7e34070                NetEtherNullAddr
                0xc7e35ebc                NetArpWaitPacketBuf
                0xc7e34050                NetRxPktLen
                0xc7e34038                NetTxPacket
                0xc7e364dc                NetBootFileXferSize
                0xc7e364e0                NetOurDNSIP
                0xc7e3408c                PktBuf
                0xc7e36524                NetOurRootPath
                0xc7e3407c                NetArpWaitTimerStart

 

 

 

 

 

 

 

5。下面重点说说.u_boot_cmd段：

 先看u-boot.map中生成：

               0xc7e2c980                __u_boot_cmd_start = .

.u_boot_cmd     0xc7e2c980      0x480
 *(.u_boot_cmd)
 .u_boot_cmd    0xc7e2c980       0x18 common/libcommon.a(cmd_bdinfo.o)
                0xc7e2c980                __u_boot_cmd_bdinfo
 .u_boot_cmd    0xc7e2c998       0x30 common/libcommon.a(cmd_boot.o)
                0xc7e2c9b0                __u_boot_cmd_reset
                0xc7e2c998                __u_boot_cmd_go
 .u_boot_cmd    0xc7e2c9c8       0x30 common/libcommon.a(cmd_bootm.o)
                0xc7e2c9c8                __u_boot_cmd_bootm
                0xc7e2c9e0                __u_boot_cmd_imls
 .u_boot_cmd    0xc7e2c9f8       0x48 common/libcommon.a(cmd_cache.o)
                0xc7e2ca10                __u_boot_cmd_dcache
                0xc7e2ca28                __u_boot_cmd_branch
                0xc7e2c9f8                __u_boot_cmd_icache
 .u_boot_cmd    0xc7e2ca40       0x18 common/libcommon.a(cmd_date.o)
                0xc7e2ca40                __u_boot_cmd_date
 .u_boot_cmd    0xc7e2ca58       0x30 common/libcommon.a(cmd_elf.o)
                0xc7e2ca70                __u_boot_cmd_bootvx
                0xc7e2ca58                __u_boot_cmd_bootelf
 .u_boot_cmd    0xc7e2ca88       0x48 common/libcommon.a(cmd_flash.o)
                0xc7e2ca88                __u_boot_cmd_flinfo
                0xc7e2caa0                __u_boot_cmd_erase
                0xc7e2cab8                __u_boot_cmd_protect
 .u_boot_cmd    0xc7e2cad0       0x18 common/libcommon.a(cmd_itest.o)
                0xc7e2cad0                __u_boot_cmd_itest
 .u_boot_cmd    0xc7e2cae8       0x48 common/libcommon.a(cmd_load.o)
                0xc7e2cb18                __u_boot_cmd_loady
                0xc7e2cb00                __u_boot_cmd_loadb
                0xc7e2cae8                __u_boot_cmd_loads
 .u_boot_cmd    0xc7e2cb30       0xf0 common/libcommon.a(cmd_mem.o)
                0xc7e2cb30                __u_boot_cmd_md
                0xc7e2cba8                __u_boot_cmd_cmp
                0xc7e2cb78                __u_boot_cmd_mw
                0xc7e2cbf0                __u_boot_cmd_loop
                0xc7e2cbd8                __u_boot_cmd_base
                0xc7e2cb48                __u_boot_cmd_mm
                0xc7e2cbc0                __u_boot_cmd_crc32
                0xc7e2cb60                __u_boot_cmd_nm
                0xc7e2cc08                __u_boot_cmd_mtest
                0xc7e2cb90                __u_boot_cmd_cp
 .u_boot_cmd    0xc7e2cc20       0x18 common/libcommon.a(cmd_misc.o)
                0xc7e2cc20                __u_boot_cmd_sleep
 .u_boot_cmd    0xc7e2cc38       0x30 common/libcommon.a(cmd_nand.o)
                0xc7e2cc38                __u_boot_cmd_nand
                0xc7e2cc50                __u_boot_cmd_nboot
 .u_boot_cmd    0xc7e2cc68       0x78 common/libcommon.a(cmd_net.o)
                0xc7e2ccb0                __u_boot_cmd_nfs
                0xc7e2ccc8                __u_boot_cmd_ping
                0xc7e2cc98                __u_boot_cmd_rarpboot
                0xc7e2cc80                __u_boot_cmd_tftpboot
                0xc7e2cc68                __u_boot_cmd_bootp
 .u_boot_cmd    0xc7e2cce0       0x48 common/libcommon.a(cmd_nvedit.o)
                0xc7e2cd10                __u_boot_cmd_saveenv
                0xc7e2cce0                __u_boot_cmd_printenv
                0xc7e2ccf8                __u_boot_cmd_setenv
 .u_boot_cmd    0xc7e2cd28       0x30 common/libcommon.a(cmd_usb.o)
                0xc7e2cd28                __u_boot_cmd_usb
                0xc7e2cd40                __u_boot_cmd_usbboot
 .u_boot_cmd    0xc7e2cd58       0x90 common/libcommon.a(command.o)
                0xc7e2cda0                __u_boot_cmd_exit
                0xc7e2cd70                __u_boot_cmd_echo
                0xc7e2cdd0                __u_boot_cmd_question_mark
                0xc7e2cd58                __u_boot_cmd_version
                0xc7e2cdb8                __u_boot_cmd_help
                0xc7e2cd88                __u_boot_cmd_test
 .u_boot_cmd    0xc7e2cde8       0x18 common/libcommon.a(cmd_usbd.o)
                0xc7e2cde8                __u_boot_cmd_dnw
                0xc7e2ce00                __u_boot_cmd_end = .
                0xc7e2ce00                . = ALIGN (0x4)

 

在include/command.h中，

 

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

#ifdef  CFG_LONGHELP

#define U_BOOT_CMD(name,maxargs,rep,cmd,usage,help) \
cmd_tbl_t __u_boot_cmd_##name Struct_Section = {#name, maxargs, rep, cmd, usage, help}

#else    /* no long help info */

#define U_BOOT_CMD(name,maxargs,rep,cmd,usage,help) \
cmd_tbl_t __u_boot_cmd_##name Struct_Section = {#name, maxargs, rep, cmd, usage}

#endif    /* CFG_LONGHELP */

 

所以我们新增指令后直接用U_BOOT_CMD声明，即可将数据放入.u_boot_cmd段，搜索段开始标志符__u_boot_cmd_start和段结束标志符__u_boot_cmd_end，得到此段数据的检测位于：command.c中的find_cmd，执行的入口位于：common/main.c中的run_command函数，此函数的调用位于uboot主循环main_loop的for (;;){……} 代码段内。
作者：Anpher Zhang QQ:275000205 转载请注明出处：http://www.cnblogs.com/zhangsufeng/

 

 

posted on 2011-09-29 01:24  Anpher Zhang  阅读(1863)  评论(0)  编辑  收藏  举报