u-boot2010.03 Makefile分析 .

转载自：http://blog.csdn.net/yyttiao/article/details/7899530

 

对于Makefile 由于源码特别长，所以，我在这里就一边摘录一边分析

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1. # Include autoconf.mk before config.mk so that the config options are available  
2. # to all top level build files. We need the dummy all: target to prevent the  
3. # dependency target in autoconf.mk.dep from being the default.  
4. all:  
5. sinclude $(obj)include/autoconf.mk.dep  
6. sinclude $(obj)include/autoconf.mk  
7.   
8. # load ARCH, BOARD, and CPU configuration  
9. # 该文件为配置时生成的   
10. include $(obj)include/config.mk  
11. export  ARCH CPU BOARD VENDOR SOC  
12.   
13. # set default to nothing for native builds  
14. ifeq ($(HOSTARCH),$(ARCH))  
15. CROSS_COMPILE ?= arm-linux-  
16. endif  
17.   
18. # load other configuration   
19. include $(TOPDIR)/config.mk  

# Include autoconf.mk before config.mk so that the config options are available# to all top level build files. We need the dummy all: target to prevent the# dependency target in autoconf.mk.dep from being the default.all:sinclude $(obj)include/autoconf.mk.depsinclude $(obj)include/autoconf.mk# load ARCH, BOARD, and CPU configuration# 该文件为配置时生成的include $(obj)include/config.mkexportARCH CPU BOARD VENDOR SOC# set default to nothing for native buildsifeq ($(HOSTARCH),$(ARCH))CROSS_COMPILE ?= arm-linux-endif# load other configurationinclude $(TOPDIR)/config.mk

这段代码中，上面的解释已经很到位了.我这里就不多说了，直接看一个相对比较重要的文件include $(TOPDIR)/config.mk
不知道怎么分析好.就挑几个重点讲下.
1:编译器的变量声明
2:连接脚本
3:连接选项

1:编译器的变量声明

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1. #   
2. # Include the make variables (CC, etc...)  
3. #   
4. AS       = $(CROSS_COMPILE)as  
5. LD       = $(CROSS_COMPILE)ld  
6. CC       = $(CROSS_COMPILE)gcc  
7. CPP      = $(CC) -E  
8. AR       = $(CROSS_COMPILE)ar  
9. NM       = $(CROSS_COMPILE)nm  
10. LDR      = $(CROSS_COMPILE)ldr  
11. STRIP    = $(CROSS_COMPILE)strip  
12. OBJCOPY  = $(CROSS_COMPILE)objcopy  
13. OBJDUMP  = $(CROSS_COMPILE)objdump  
14. RANLIB   = $(CROSS_COMPILE)RANLIB  

## Include the make variables (CC, etc...)#AS       = $(CROSS_COMPILE)asLD       = $(CROSS_COMPILE)ldCC       = $(CROSS_COMPILE)gccCPP      = $(CC) -EAR       = $(CROSS_COMPILE)arNM       = $(CROSS_COMPILE)nmLDR      = $(CROSS_COMPILE)ldrSTRIP    = $(CROSS_COMPILE)stripOBJCOPY  = $(CROSS_COMPILE)objcopyOBJDUMP  = $(CROSS_COMPILE)objdumpRANLIB   = $(CROSS_COMPILE)RANLIB

这里就知道为什么交叉编译器只需要指定前缀的原因了。

2:连接脚本

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1. ifndef LDSCRIPT  
2.     #LDSCRIPT := $(TOPDIR)/board/$(BOARDDIR)/u-boot.lds.debug  
3. ifeq ($(CONFIG_NAND_U_BOOT),y)  
4.     LDSCRIPT := $(TOPDIR)/board/$(BOARDDIR)/u-boot-nand.lds  
5. else  
6.     LDSCRIPT := $(TOPDIR)/board/$(BOARDDIR)/u-boot.lds  
7. endif  
8. endif  

ifndef LDSCRIPT    #LDSCRIPT := $(TOPDIR)/board/$(BOARDDIR)/u-boot.lds.debugifeq ($(CONFIG_NAND_U_BOOT),y)    LDSCRIPT := $(TOPDIR)/board/$(BOARDDIR)/u-boot-nand.ldselse    LDSCRIPT := $(TOPDIR)/board/$(BOARDDIR)/u-boot.ldsendifendif

LDSCRIPT会根据是否启用nand_boot的选项,来选择连接脚本,连接脚本可以指定代码生成的先后位置,比如把nand相关的函数指定到最前面.
uboot就是通过该连接脚本来使start.S这段代码放到整个程序的最前面,这样才能保证arm能正常启动

3:连接选项

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1. LDFLAGS += -Bstatic -T $(obj)u-boot.lds $(PLATFORM_LDFLAGS)  
2. ifneq ($(TEXT_BASE),)  
3.     LDFLAGS += -Ttext $(TEXT_BASE)  
4. endif  

LDFLAGS += -Bstatic -T $(obj)u-boot.lds $(PLATFORM_LDFLAGS)ifneq ($(TEXT_BASE),)    LDFLAGS += -Ttext $(TEXT_BASE)endif

LDFLAGS指明在连接的时候，指定连接地址,还有连接脚本的参数之类的.
剩下的就自己分析吧....

再回到Makefile,指定要编译的对象了

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1. #########################################################################  
2. # U-Boot objects....order is important (i.e. start must be first)  
3.   
4. OBJS = cpu/$(CPU)/start.o  
5. ifeq ($(CPU),i386)  
6.     OBJS += cpu/$(CPU)/start16.o  
7.     OBJS += cpu/$(CPU)/resetvec.o  
8. endif  
9. ifeq ($(CPU),ppc4xx)  
10.     OBJS += cpu/$(CPU)/resetvec.o  
11. endif  
12. ifeq ($(CPU),mpc85xx)  
13.     OBJS += cpu/$(CPU)/resetvec.o  
14. endif  
15.   
16. OBJS := $(addprefix $(obj),$(OBJS))  
17.   
18. LIBS = lib_generic/libgeneric.a  
19. LIBS += lib_generic/lzma/liblzma.a  
20. LIBS += lib_generic/lzo/liblzo.a  
21. LIBS += $(shell if [ -f board/$(VENDOR)/common/Makefile ]; then echo \  
22. "board/$(VENDOR)/common/lib$(VENDOR).a"; fi)  
23. LIBS += cpu/$(CPU)/lib$(CPU).a  
24. ifdef SOC  
25.     LIBS += cpu/$(CPU)/$(SOC)/lib$(SOC).a  
26. endif  
27. ifeq ($(CPU),ixp)  
28.     LIBS += cpu/ixp/npe/libnpe.a  
29. endif  
30. LIBS += lib_$(ARCH)/lib$(ARCH).a  
31. LIBS += fs/cramfs/libcramfs.a fs/fat/libfat.a fs/fdos/libfdos.a fs/jffs2/libjffs2.a \  
32. fs/reiserfs/libreiserfs.a fs/ext2/libext2fs.a fs/yaffs2/libyaffs2.a \  
33. fs/ubifs/libubifs.a  
34. LIBS += net/libnet.a  
35. LIBS += disk/libdisk.a  
36. LIBS += drivers/bios_emulator/libatibiosemu.a  
37. LIBS += drivers/block/libblock.a  
38. LIBS += drivers/dma/libdma.a  
39. LIBS += drivers/fpga/libfpga.a  
40. LIBS += drivers/gpio/libgpio.a  
41. LIBS += drivers/hwmon/libhwmon.a  
42. LIBS += drivers/i2c/libi2c.a  
43. LIBS += drivers/input/libinput.a  
44. LIBS += drivers/misc/libmisc.a  
45. LIBS += drivers/mmc/libmmc.a  
46. LIBS += drivers/mtd/libmtd.a  
47. LIBS += drivers/mtd/nand/libnand.a  
48. LIBS += drivers/mtd/onenand/libonenand.a  
49. LIBS += drivers/mtd/ubi/libubi.a  
50. LIBS += drivers/mtd/spi/libspi_flash.a  
51. LIBS += drivers/net/libnet.a  
52. LIBS += drivers/net/phy/libphy.a  
53. LIBS += drivers/pci/libpci.a  
54. LIBS += drivers/pcmcia/libpcmcia.a  
55. LIBS += drivers/power/libpower.a  
56. LIBS += drivers/spi/libspi.a  
57. ifeq ($(CPU),mpc83xx)  
58.     LIBS += drivers/qe/qe.a  
59. endif  
60. ifeq ($(CPU),mpc85xx)  
61.     LIBS += drivers/qe/qe.a  
62.     LIBS += cpu/mpc8xxx/ddr/libddr.a  
63.     LIBS += cpu/mpc8xxx/lib8xxx.a  
64. endif  
65. ifeq ($(CPU),mpc86xx)  
66.     LIBS += cpu/mpc8xxx/ddr/libddr.a  
67.     LIBS += cpu/mpc8xxx/lib8xxx.a  
68. endif  
69. LIBS += drivers/rtc/librtc.a  
70. LIBS += drivers/serial/libserial.a  
71. LIBS += drivers/twserial/libtws.a  
72. LIBS += drivers/usb/gadget/libusb_gadget.a  
73. LIBS += drivers/usb/host/libusb_host.a  
74. LIBS += drivers/usb/musb/libusb_musb.a  
75. LIBS += drivers/usb/phy/libusb_phy.a  
76. LIBS += drivers/video/libvideo.a  
77. LIBS += drivers/watchdog/libwatchdog.a  
78. LIBS += common/libcommon.a  
79. LIBS += libfdt/libfdt.a  
80. LIBS += api/libapi.a  
81. LIBS += post/libpost.a  
82.   
83. LIBS := $(addprefix $(obj),$(LIBS))  
84. .PHONY : $(LIBS) $(TIMESTAMP_FILE) $(VERSION_FILE)  
85.   
86. LIBBOARD = board/$(BOARDDIR)/lib$(BOARD).a  
87. LIBBOARD := $(addprefix $(obj),$(LIBBOARD))  
88.   
89. # Add GCC lib   
90. ifdef USE_PRIVATE_LIBGCC  
91. ifeq ("$(USE_PRIVATE_LIBGCC)", "yes")  
92.     PLATFORM_LIBGCC = -L $(OBJTREE)/lib_$(ARCH) -lgcc  
93. else  
94.     PLATFORM_LIBGCC = -L $(USE_PRIVATE_LIBGCC) -lgcc  
95. endif  
96. else  
97.     PLATFORM_LIBGCC = -L $(shell dirname `$(CC) $(CFLAGS) -print-libgcc-file-name`) -lgcc  
98. endif  
99. PLATFORM_LIBS += $(PLATFORM_LIBGCC)  
100. export PLATFORM_LIBS  
101.   
102. # Special flags for CPP when processing the linker script.  
103. # Pass the version down so we can handle backwards compatibility  
104. # on the fly.   
105. LDPPFLAGS += \  
106. -include $(TOPDIR)/include/u-boot/u-boot.lds.h \  
107. $(shell $(LD) --version | \  
108. sed -ne 's/GNU ld version \([0-9][0-9]*\)\.\([0-9][0-9]*\).*/-DLD_MAJOR=\1 -DLD_MINOR=\2/p')  
109.   
110. ifeq ($(CONFIG_NAND_U_BOOT),y)  
111.     NAND_SPL = nand_spl  
112.     U_BOOT_NAND = $(obj)u-boot-nand.bin  
113. endif  
114.   
115. ifeq ($(CONFIG_ONENAND_U_BOOT),y)  
116.     ONENAND_IPL = onenand_ipl  
117.     U_BOOT_ONENAND = $(obj)u-boot-onenand.bin  
118.     ONENAND_BIN ?= $(obj)onenand_ipl/onenand-ipl-2k.bin  
119. endif  
120.   
121. __OBJS := $(subst $(obj),,$(OBJS))  
122. __LIBS := $(subst $(obj),,$(LIBS)) $(subst $(obj),,$(LIBBOARD))  
123.   
124. #########################################################################  
125. #########################################################################  

########################################################################## U-Boot objects....order is important (i.e. start must be first)OBJS = cpu/$(CPU)/start.oifeq ($(CPU),i386)    OBJS += cpu/$(CPU)/start16.o    OBJS += cpu/$(CPU)/resetvec.oendififeq ($(CPU),ppc4xx)    OBJS += cpu/$(CPU)/resetvec.oendififeq ($(CPU),mpc85xx)    OBJS += cpu/$(CPU)/resetvec.oendifOBJS := $(addprefix $(obj),$(OBJS))LIBS = lib_generic/libgeneric.aLIBS += lib_generic/lzma/liblzma.aLIBS += lib_generic/lzo/liblzo.aLIBS += $(shell if [ -f board/$(VENDOR)/common/Makefile ]; then echo \"board/$(VENDOR)/common/lib$(VENDOR).a"; fi)LIBS += cpu/$(CPU)/lib$(CPU).aifdef SOC    LIBS += cpu/$(CPU)/$(SOC)/lib$(SOC).aendififeq ($(CPU),ixp)    LIBS += cpu/ixp/npe/libnpe.aendifLIBS += lib_$(ARCH)/lib$(ARCH).aLIBS += fs/cramfs/libcramfs.a fs/fat/libfat.a fs/fdos/libfdos.a fs/jffs2/libjffs2.a \fs/reiserfs/libreiserfs.a fs/ext2/libext2fs.a fs/yaffs2/libyaffs2.a \fs/ubifs/libubifs.aLIBS += net/libnet.aLIBS += disk/libdisk.aLIBS += drivers/bios_emulator/libatibiosemu.aLIBS += drivers/block/libblock.aLIBS += drivers/dma/libdma.aLIBS += drivers/fpga/libfpga.aLIBS += drivers/gpio/libgpio.aLIBS += drivers/hwmon/libhwmon.aLIBS += drivers/i2c/libi2c.aLIBS += drivers/input/libinput.aLIBS += drivers/misc/libmisc.aLIBS += drivers/mmc/libmmc.aLIBS += drivers/mtd/libmtd.aLIBS += drivers/mtd/nand/libnand.aLIBS += drivers/mtd/onenand/libonenand.aLIBS += drivers/mtd/ubi/libubi.aLIBS += drivers/mtd/spi/libspi_flash.aLIBS += drivers/net/libnet.aLIBS += drivers/net/phy/libphy.aLIBS += drivers/pci/libpci.aLIBS += drivers/pcmcia/libpcmcia.aLIBS += drivers/power/libpower.aLIBS += drivers/spi/libspi.aifeq ($(CPU),mpc83xx)    LIBS += drivers/qe/qe.aendififeq ($(CPU),mpc85xx)    LIBS += drivers/qe/qe.a    LIBS += cpu/mpc8xxx/ddr/libddr.a    LIBS += cpu/mpc8xxx/lib8xxx.aendififeq ($(CPU),mpc86xx)    LIBS += cpu/mpc8xxx/ddr/libddr.a    LIBS += cpu/mpc8xxx/lib8xxx.aendifLIBS += drivers/rtc/librtc.aLIBS += drivers/serial/libserial.aLIBS += drivers/twserial/libtws.aLIBS += drivers/usb/gadget/libusb_gadget.aLIBS += drivers/usb/host/libusb_host.aLIBS += drivers/usb/musb/libusb_musb.aLIBS += drivers/usb/phy/libusb_phy.aLIBS += drivers/video/libvideo.aLIBS += drivers/watchdog/libwatchdog.aLIBS += common/libcommon.aLIBS += libfdt/libfdt.aLIBS += api/libapi.aLIBS += post/libpost.aLIBS := $(addprefix $(obj),$(LIBS)).PHONY : $(LIBS) $(TIMESTAMP_FILE) $(VERSION_FILE)LIBBOARD = board/$(BOARDDIR)/lib$(BOARD).aLIBBOARD := $(addprefix $(obj),$(LIBBOARD))# Add GCC libifdef USE_PRIVATE_LIBGCCifeq ("$(USE_PRIVATE_LIBGCC)", "yes")    PLATFORM_LIBGCC = -L $(OBJTREE)/lib_$(ARCH) -lgccelse    PLATFORM_LIBGCC = -L $(USE_PRIVATE_LIBGCC) -lgccendifelse    PLATFORM_LIBGCC = -L $(shell dirname `$(CC) $(CFLAGS) -print-libgcc-file-name`) -lgccendifPLATFORM_LIBS += $(PLATFORM_LIBGCC)export PLATFORM_LIBS# Special flags for CPP when processing the linker script.# Pass the version down so we can handle backwards compatibility# on the fly.LDPPFLAGS += \-include $(TOPDIR)/include/u-boot/u-boot.lds.h \$(shell $(LD) --version | \sed -ne 's/GNU ld version \([0-9][0-9]*\)\.\([0-9][0-9]*\).*/-DLD_MAJOR=\1 -DLD_MINOR=\2/p')ifeq ($(CONFIG_NAND_U_BOOT),y)    NAND_SPL = nand_spl    U_BOOT_NAND = $(obj)u-boot-nand.binendififeq ($(CONFIG_ONENAND_U_BOOT),y)    ONENAND_IPL = onenand_ipl    U_BOOT_ONENAND = $(obj)u-boot-onenand.bin    ONENAND_BIN ?= $(obj)onenand_ipl/onenand-ipl-2k.binendif__OBJS := $(subst $(obj),,$(OBJS))__LIBS := $(subst $(obj),,$(LIBS)) $(subst $(obj),,$(LIBBOARD))##################################################################################################################################################

由上面的可以看出
OBJS 对应的是 .o文件
LIBS对应的是 .a文件
LIBBOARD 对应的是目录
等等.主要看下这3个是怎么被处理的

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1. $(OBJS):    depend  
2.     $(MAKE) -C cpu/$(CPU) $(if $(REMOTE_BUILD),$@,$(notdir $@))  
3.   
4. $(LIBS):    depend $(SUBDIRS)  
5.     $(MAKE) -C $(dir $(subst $(obj),,$@))  
6.   
7. $(LIBBOARD):    depend $(LIBS)  
8.     $(MAKE) -C $(dir $(subst $(obj),,$@))  

$(OBJS):depend    $(MAKE) -C cpu/$(CPU) $(if $(REMOTE_BUILD),$@,$(notdir $@))$(LIBS):depend $(SUBDIRS)    $(MAKE) -C $(dir $(subst $(obj),,$@))$(LIBBOARD):depend $(LIBS)    $(MAKE) -C $(dir $(subst $(obj),,$@))

由这里可以看出，会逐个的make出来

最后就是连接的过程了.连接会调用

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1. GEN_UBOOT = \  
2.     UNDEF_SYM=`$(OBJDUMP) -x $(LIBBOARD) $(LIBS) | \  
3.     sed -n -e 's/.*\($(SYM_PREFIX)__u_boot_cmd_.*\)/-u\1/p'|sort|uniq`;\  
4.     cd $(LNDIR) && $(LD) $(LDFLAGS) $$UNDEF_SYM $(__OBJS) \  
5.     --start-group $(__LIBS) --end-group $(PLATFORM_LIBS) \  
6.     -Map u-boot.map -o u-boot  
7. $(obj)u-boot:   depend $(SUBDIRS) $(OBJS) $(LIBBOARD) $(LIBS) $(LDSCRIPT) $(obj)u-boot.lds  

GEN_UBOOT = \    UNDEF_SYM=`$(OBJDUMP) -x $(LIBBOARD) $(LIBS) | \    sed -n -e 's/.*\($(SYM_PREFIX)__u_boot_cmd_.*\)/-u\1/p'|sort|uniq`;\    cd $(LNDIR) && $(LD) $(LDFLAGS) $$UNDEF_SYM $(__OBJS) \    --start-group $(__LIBS) --end-group $(PLATFORM_LIBS) \    -Map u-boot.map -o u-boot$(obj)u-boot:depend $(SUBDIRS) $(OBJS) $(LIBBOARD) $(LIBS) $(LDSCRIPT) $(obj)u-boot.lds

最终会连接成功.后面只要通过

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1. $(obj)u-boot.bin:   $(obj)u-boot  
2. $(OBJCOPY) ${OBJCFLAGS} -O binary $< $@  

$(obj)u-boot.bin:$(obj)u-boot$(OBJCOPY) ${OBJCFLAGS} -O binary $< $@

将二进制内容拷贝出来，那么uboot.bin就生成了

来看一下连接脚本吧

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1. OUTPUT_FORMAT("elf32-littlearm", "elf32-littlearm", "elf32-littlearm")  
2. OUTPUT_ARCH(arm)  
3. ENTRY(_start)  
4. SECTIONS  
5. {  
6.     . = 0x00000000;  
7.     . = ALIGN(4);  
8.     .text :  
9.     {  
10.         cpu/arm1176/start.o (.text)  
11.         cpu/arm1176/s3c64xx/cpu_init.o (.text)  
12.        *(.text)  
13.     }  
14.     . = ALIGN(4);  
15.     .rodata :   
16.     {   
17.         *(SORT_BY_ALIGNMENT(SORT_BY_NAME(.rodata*)))   
18.     }  
19.     . = ALIGN(4);  
20.     .data : {  
21.         *(.data)   
22.     }  
23.     . = ALIGN(4);  
24.     .got :   
25.     {  
26.         *(.got)   
27.     }  
28.     __u_boot_cmd_start = .;  
29.     .u_boot_cmd :   
30.     {   
31.         *(.u_boot_cmd)   
32.     }  
33.     __u_boot_cmd_end = .;  
34.     . = ALIGN(4);  
35.     .mmudata :   
36.     {   
37.         *(.mmudata)   
38.     }  
39.     . = ALIGN(4);  
40.     __bss_start = .;  
41.     .bss :   
42.     {   
43.         *(.bss) . = ALIGN(4);   
44.     }  
45.     _end = .;  
46. }  

OUTPUT_FORMAT("elf32-littlearm", "elf32-littlearm", "elf32-littlearm")OUTPUT_ARCH(arm)ENTRY(_start)SECTIONS{    . = 0x00000000;    . = ALIGN(4);    .text :    {        cpu/arm1176/start.o (.text)        cpu/arm1176/s3c64xx/cpu_init.o (.text)       *(.text)    }    . = ALIGN(4);    .rodata :     {         *(SORT_BY_ALIGNMENT(SORT_BY_NAME(.rodata*)))     }    . = ALIGN(4);    .data : {        *(.data)     }    . = ALIGN(4);    .got :     {        *(.got)     }    __u_boot_cmd_start = .;    .u_boot_cmd :     {         *(.u_boot_cmd)     }    __u_boot_cmd_end = .;    . = ALIGN(4);    .mmudata :     {         *(.mmudata)     }    . = ALIGN(4);    __bss_start = .;    .bss :     {         *(.bss) . = ALIGN(4);     }    _end = .;}

从这个链接脚本可以看出，uboot将整个程序进行了如下的布置
.text :
.rodata :
.data :
.got :
.u_boot_cmd :
.mmudata :
.bss :
代码段被首先链接，在代码段内第一个就是start.s 因为这就是uboot启动的第一条代码的地方，看一下map文件
Memory Configuration

Name                  Origin                        Length                Attributes
*default*             0x00000000             0xffffffff

Linker script and memory map

0x00000000  . = 0x0
0x00000000 . = ALIGN (0x4)

.text                 0x57e00000                  0x27b8c
cpu/arm1176/start.o(.text)
.text                 0x57e00000                  0x440              cpu/arm1176/start.o
                        0x57e00040                                           _end_vect
                        0x57e0004c                                           _bss_start
                        0x57e00050                                          _bss_end
                        0x57e00048                                          _armboot_start
                        0x57e00114                                          copy_from_nand
                        0x57e00000                                          _start

从map文件中，可以看到0x57e00000=_start 被放到了一条的位置（0x57e00000就是链接脚本指定的连接地址）
接着打开cpu/arm1176/start.S

[cpp] view plaincopyprint?

1. .globl _start  
2. _start: b   reset  
3. #ifndef CONFIG_NAND_SPL   
4. ldr pc, _undefined_instruction  
5. ldr pc, _software_interrupt  
6. ldr pc, _prefetch_abort  
7. ldr pc, _data_abort  
8. ldr pc, _not_used  
9. ldr pc, _irq  
10. ldr pc, _fiq  

.globl _start_start: breset#ifndef CONFIG_NAND_SPLldrpc, _undefined_instructionldrpc, _software_interruptldrpc, _prefetch_abortldrpc, _data_abortldrpc, _not_usedldrpc, _irqldrpc, _fiq

第一条语句 b reset就被放到了_start的位置，这样uboot启动之后，就会开始执行这条语句，uboot的移植也会从这开始分析了

完。

Thanks a lot！