u-boot2010.03 Makefile分析

對於Makefile 由於源碼特別長，所以，我在這裡就一邊摘錄一邊分析

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
8. # load ARCH, BOARD, and CPU configuration
9. # 該文件為配置時生成的
10. include $(obj)include/config.mk
11. export ARCH CPU BOARD VENDOR SOC
13. # set default to nothing for native builds
14. ifeq ($(HOSTARCH),$(ARCH))
15. CROSS_COMPILE ?= arm-linux-
16. endif
18. # load other configuration
19. include $(TOPDIR)/config.mk

這段代碼中，上面的解釋已經很到位了.我這裡就不多說了，直接看一個相對比較重要的文件include $(TOPDIR)/config.mk
不知道怎麼分析好.就挑幾個重點講下.
1:編譯器的變量聲明
2:連接腳本
3:連接選項

1:編譯器的變量聲明

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

這裡就知道為什麼交叉編譯器只需要指定前綴的原因了。

2:連接腳本

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

LDSCRIPT會根據是否啟用nand_boot的選項,來選擇連接腳本,連接腳本可以指定代碼生成的先後位置,比如把nand相關的函數指定到最前面.
uboot就是通過該連接腳本來使start.S這段代碼放到整個程序的最前面,這樣才能保證arm能正常啟動

3:連接選項

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

LDFLAGS指明在連接的時候，指定連接地址,還有連接腳本的參數之類的.

剩下的就自己分析吧....

再回到Makefile,指定要編譯的對象了

1. #########################################################################
2. # U-Boot objects....order is important (i.e. start must be first)
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
16. OBJS := $(addprefix $(obj),$(OBJS))
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
83. LIBS := $(addprefix $(obj),$(LIBS))
84. .PHONY : $(LIBS) $(TIMESTAMP_FILE) $(VERSION_FILE)
86. LIBBOARD = board/$(BOARDDIR)/lib$(BOARD).a
87. LIBBOARD := $(addprefix $(obj),$(LIBBOARD))
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
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')
110. ifeq ($(CONFIG_NAND_U_BOOT),y)
111. NAND_SPL = nand_spl
112. U_BOOT_NAND = $(obj)u-boot-nand.bin
113. endif
115. ifeq ($(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
121. __OBJS := $(subst $(obj),,$(OBJS))
122. __LIBS := $(subst $(obj),,$(LIBS)) $(subst $(obj),,$(LIBBOARD))
124. #########################################################################
125. #########################################################################