uboot的Makefile分析之顶层config.mk

顶层目录下的config.mk文件主要完成如下功能的配置：

1、确定生成可执行文件过程中需要的各种工具，如编译器(arm-linux-gcc)、连接器(arm-linux-ld)、反汇编器(arm-linux-objdump)等

2、确定CPU、板相关的配置文件，存在于各个目录下的config.mk

3、确定编译、链接、转换等过程的操作选项

4、根据步骤3确定的编译连接选项生成需要的文件

config.mk完整内容及必要注释如下

注：config.mk文件注释符改为/* 注释内容 */

view
sourceprint?

001.

ifneq
($(OBJTREE),$(SRCTREE))

002.

ifeq
($(CURDIR),$(SRCTREE))

003.

dir
:=

004.

else

005.

dir
:= $(subst $(SRCTREE)/,,$(CURDIR))

006.

endif

007.

008.

obj
:= $(

if

$(dir),$(OBJTREE)/$(dir)/,$(OBJTREE)/)

009.

src
:= $(

if

$(dir),$(SRCTREE)/$(dir)/,$(SRCTREE)/)

010.

011.

$(shell
mkdir -p $(obj))

012.

else

013.

obj
:=

014.

src
:=

015.

endif

016.

/*
obj = 空，src = 空

017.

*
dir = 空

018.

*/

019.

020.

/*
clean the slate ... */

021.

PLATFORM_RELFLAGS
=

022.

PLATFORM_CPPFLAGS
=

023.

PLATFORM_LDFLAGS
=

024.

025.

/*
HOSTCFLAGS = -Wall -Wstrict-prototypes -O2 -fomit-frame-pointer

026.

*
-Wall: 打印出编译时所有的错误或警告信息

027.

*
-Wstrict-prototypes: 编译时，若产生与数据类型不相符的问题，打印出提示或警告信息。当在不同体系结构间移植时，加上该选项可避免很多错误

028.

*
-O: 编译代码时的优化等级，共有五种：-O0、-O1、-O2、-O3和-Os

029.

*
-fomit-frame-pointer: 对于不需要帧指针的函数,不要在寄存器中保存帧指针

030.

*
代码优化时打开-fomit-frame-pointer，函数调用时不保存frame指针，也就不能用backtrace()来查看函数栈调用

031.

*
backtrace()系列函数见[http://blog.csdn.net/u013686019/article/details/42128771](Linux中backtrace()系列函数的应用实例)

032.

*/

033.

HOSTCFLAGS
= -Wall -Wstrict-prototypes -O2 -fomit-frame-pointer \

034.

$(HOSTCPPFLAGS)

035.

/*
HOSTSTRIP = strip

036.

*
strip能清除执行文件中不必要的标示符及调试信息，可减小文件大小而不影响正常使用，、

037.

*
与压缩不同的是，文件一旦strip后就不能恢复原样

038.

*
strip后的文件不包含调试信息

039.

*/

040.

HOSTSTRIP
= strip

041.

042.

/*

043.

*
Mac OS X / Darwin's C preprocessor is Apple specific.  It

044.

*
generates numerous errors and warnings.  We want to bypass it

045.

*
and use GNU C's cpp.  To do this we pass the -traditional-cpp

046.

*
option to the compiler.  Note that the -traditional-cpp flag

047.

*
DOES NOT have the same semantics as GNU C's flag, all it does

048.

*
is invoke the GNU preprocessor in stock ANSI/ISO C fashion.

049.

*

050.

*
Apple's linker is similar, thanks to the new 2 stage linking

051.

*
multiple symbol definitions are treated as errors, hence the

052.

*
-multiply_defined suppress option to turn off this error.

053.

*/

054.

ifeq
($(HOSTOS),darwin)

055.

......

056.

else

057.

HOSTCC
= gcc

058.

endif

059.

060.

ifeq
($(HOSTOS),cygwin)

061.

......

062.

endif

063.

064.

/*
We build some files with extra pedantic flags to try to minimize things

065.

*
that won't build on some weird host compiler -- though there are lots of

066.

*
exceptions for files that aren't complaint.

067.

*/

068.

HOSTCFLAGS_NOPED
= $(filter-out -pedantic,$(HOSTCFLAGS))

069.

/*
-pedantic: 当GCC在编译不符合ANSI/ISO C语言标准的源代码时，如果在编译指令中加上了-pedantic选项

070.

*
那么源程序中使用了扩展语法的地方将产生相应的警告信息

071.

*/

072.

HOSTCFLAGS
+= -pedantic

073.

074.

#########################################################################

075.

/*
Option checker (courtesy linux kernel) to ensure

076.

*
only supported compiler options are used

077.

*
cc-option变量保存了一个测试编译选项的命令，其他地方会经常用call函数来调用它，测试编译选项

078.

*
if $(CC) $(CFLAGS) $(1) -S -o /dev/null -xc /dev/null >/dev/null 2>&1;then

079.

echo
"$(1)";

080.

else

081.

echo
"$(2)";

082.

fi;

083.

*
-S：编译后立即结束，不进行<a href="http://www.it165.net/pro/yysam/"
target="_blank" class="keylink">汇编</a>等操作

084.

*
-o /dev/null : 生成文件到/dev/null，即不生成任何编译结果,要编译的文件也为空

085.

*
-xc: 指定按c语言编译

086.

*
用此语句如：call cc-option,-a,-b 则如果支持-a选项则返回-a否则返回-b

087.

*/

088.

cc-option
= $(shell

if

$(CC)
$(CFLAGS) $(

1

)
-S -o /dev/

null

-xc
/dev/

null

\

089.

>
/dev/

null

2

>&

1

;
then echo

"$(1)"

;

else

echo

"$(2)"

;
fi ;)

090.

091.

/*
Include the make variables (CC, etc...) */

092.

AS
= $(CROSS_COMPILE)as

/*
汇编工具 */

093.

LD
= $(CROSS_COMPILE)ld

/*
链接工具 */

094.

CC
= $(CROSS_COMPILE)gcc

/*
编译工具 */

095.

CPP
= $(CC) -E

/*
预处理   */

096.

AR
= $(CROSS_COMPILE)ar

/*
归档工具 */

097.

NM
= $(CROSS_COMPILE)nm

/*
列出object文件中的符号 */

098.

LDR
= $(CROSS_COMPILE)ldr

099.

STRIP
= $(CROSS_COMPILE)strip

100.

OBJCOPY
= $(CROSS_COMPILE)objcopy

/*
转换可执行文件格式工具 */

101.

OBJDUMP
= $(CROSS_COMPILE)objdump

/*
反汇编工具 */

102.

RANLIB
= $(CROSS_COMPILE)RANLIB

/*
产生归档文件索引 */

103.

104.

#########################################################################

105.

/*
Load generated board configuration */

106.

/*
sinclude:

107.

*
在Makefile中可使用"sinclude"代替"include"，用来忽略由于包含文件不存在或者无法创建时的错误

108.

*/

109.

sinclude
$(OBJTREE)/include/autoconf.mk

110.

111.

/*
Some architecture config.mk files need to know what CPUDIR is set to,

112.

*
so calculate CPUDIR before including ARCH/SOC/CPU config.mk files.

113.

*
Check if arch/$ARCH/cpu/$CPU exists, otherwise assume arch/$ARCH/cpu contains

114.

*
CPU-specific code.

115.

*/

116.

CPUDIR=arch/$(ARCH)/cpu/$(CPU)

117.

ifneq
($(SRCTREE)/$(CPUDIR),$(wildcard $(SRCTREE)/$(CPUDIR)))

118.

CPUDIR=arch/$(ARCH)/cpu

119.

endif

120.

/*
CPUDIR=arch/arm/cpu/arm920t */

121.

122.

/*
include architecture dependend rules: arch/arm/config.mk */

123.

sinclude
$(TOPDIR)/arch/$(ARCH)/config.mk

124.

/*
include  CPU specific rules: arch/arm/cpu/arm920t/config.mk */

125.

sinclude
$(TOPDIR)/$(CPUDIR)/config.mk

126.

ifdef
SOC

127.

/*
include  SoC specific rules: arch/arm/cpu/arm920t/s3c24x0/config.mk */

128.

sinclude
$(TOPDIR)/$(CPUDIR)/$(SOC)/config.mk

129.

endif

130.

ifdef
VENDOR

131.

BOARDDIR
= $(VENDOR)/$(BOARD)

132.

else

133.

BOARDDIR
= $(BOARD)

134.

endif

135.

/*
BOARDDIR = samsung/smdk2410 */

136.

137.

ifdef
BOARD

138.

/*
include board specific rules: board/samsung/smdk2410/config.mk */

139.

sinclude
$(TOPDIR)/board/$(BOARDDIR)/config.mk

140.

endif

141.

142.

#########################################################################

143.

ifneq
(,$(findstring s,$(MAKEFLAGS)))

144.

ARFLAGS
= cr

145.

else

146.

ARFLAGS
= crv

147.

endif

148.

RELFLAGS=
$(PLATFORM_RELFLAGS)

149.

DBGFLAGS=
-g # -DDEBUG

150.

OPTFLAGS=
-Os #-fomit-frame-pointer

151.

152.

/*
LDSCRIPT = arch/arm/cpu/arm920t/u-boot.lds，在在文件arch/arm/config.mk中赋值*/

153.

ifndef
LDSCRIPT

154.

#LDSCRIPT
:= $(TOPDIR)/board/$(BOARDDIR)/u-boot.lds.debug

155.

ifeq
($(CONFIG_NAND_U_BOOT),y)

156.

LDSCRIPT
:= $(TOPDIR)/board/$(BOARDDIR)/u-boot-nand.lds

157.

else

158.

LDSCRIPT
:= $(TOPDIR)/board/$(BOARDDIR)/u-boot.lds

159.

endif

160.

endif

161.

/*
段之间的空隙用0xff填充 */

162.

OBJCFLAGS
+= --gap-fill=

0xff

163.

164.

gccincdir
:= $(shell $(CC) -print-file-name=include)

165.

166.

/*
CPPFLAGS变量综合了DBGFLAGS，OPTFLAGS，RELFLAGS编译选项，并定义了__KERBEL__

167.

*
-D: 设置宏定义__KERNEL__

168.

*/

169.

CPPFLAGS
:= $(DBGFLAGS) $(OPTFLAGS) $(RELFLAGS)     \

170.

-D__KERNEL__

171.

ifneq
($(TEXT_BASE),)

172.

CPPFLAGS
+= -DTEXT_BASE=$(TEXT_BASE)

173.

endif

174.

175.

ifneq
($(RESET_VECTOR_ADDRESS),)

176.

CPPFLAGS
+= -DRESET_VECTOR_ADDRESS=$(RESET_VECTOR_ADDRESS)

177.

endif

178.

179.

ifneq
($(OBJTREE),$(SRCTREE))

180.

CPPFLAGS
+= -I$(OBJTREE)/include2 -I$(OBJTREE)/include

181.

endif

182.

183.

CPPFLAGS
+= -I$(TOPDIR)/include

184.

CPPFLAGS
+= -fno-builtin -ffreestanding -nostdinc   \

185.

-isystem
$(gccincdir) -pipe $(PLATFORM_CPPFLAGS)

186.

187.

ifdef
BUILD_TAG

188.

CFLAGS
:= $(CPPFLAGS) -Wall -Wstrict-prototypes \

189.

-DBUILD_TAG=

'"$(BUILD_TAG)"'

190.

else

191.

CFLAGS
:= $(CPPFLAGS) -Wall -Wstrict-prototypes

192.

endif

193.

194.

CFLAGS
+= $(call cc-option,-fno-stack-protector)

195.

196.

/*
$(CPPFLAGS) sets -g, which causes gcc to pass a suitable -g<format>*/

197.

/*
option to the assembler. */

198.

AFLAGS_DEBUG
:=

199.

200.

AFLAGS
:= $(AFLAGS_DEBUG) -D__ASSEMBLY__ $(CPPFLAGS)

201.

202.

LDFLAGS
+= -Bstatic -T $(obj)u-boot.lds $(PLATFORM_LDFLAGS)

203.

ifneq
($(TEXT_BASE),)

204.

LDFLAGS
+= -Ttext $(TEXT_BASE)

205.

endif

206.

/*
LDFLAGS = -Bstatic -T u-boot.lds -Ttext 0x33F80000 */

207.

/*
CFLAGS = -g  -Os   -fno-common -ffixed-r8 -msoft-float  -D__KERNEL__ -DTEXT_BASE=0x33F80000 -I/u-boot-2010.06/include -fno-builtin -ffreestanding -nostdinc -isystem /usr/local/arm/4.2.2-eabi/usr/bin-ccache/../lib/gcc/arm-unknown-linux-gnueabi/4.2.2/include
-pipe  -DCONFIG_ARM -D__ARM__ -marm  -mabi=aapcs-linux -mno-thumb-interwork -march=armv4 -Wall -Wstrict-prototypes -fno-stack-protector */

208.

209.

/*
Location of a usable BFD library, where we define "usable" as

210.

*
"built for ${HOST}, supports ${TARGET}".  Sensible values are

211.

*
- When cross-compiling: the root of the cross-environment

212.

*
- Linux/ppc (native): /usr

213.

*
- NetBSD/ppc (native): you lose ... (must extract these from the

214.

*
binutils build directory, plus the native and U-Boot include

215.

*
files don't like each other)

216.

*

217.

*
So far, this is used only by tools/gdb/Makefile.

218.

*/

219.

ifeq
($(HOSTOS),darwin)

220.

BFD_ROOT_DIR
=      /usr/local/tools

221.

else

222.

ifeq
($(HOSTARCH),$(ARCH))

223.

/*
native */

224.

BFD_ROOT_DIR
=      /usr

225.

else

226.

/*
BFD_ROOT_DIR =       /LinuxPPC/CDK       # Linux/i386 */

227.

/*
BFD_ROOT_DIR =       /usr/pkg/cross      # NetBSD/i386 */

228.

BFD_ROOT_DIR
=      /opt/powerpc

229.

endif

230.

endif

231.

232.

#########################################################################

233.

export
HOSTCC HOSTCFLAGS HO<a href=

"http://www.it165.net/pro/"

target=

"_blank"

class

=

"keylink"

>STL</a>DFLAGS
PEDCFLAGS HOSTSTRIP CROSS_COMPILE \

234.

AS
LD CC CPP AR NM STRIP OBJCOPY OBJDUMP MAKE

235.

export
TEXT_BASE PLATFORM_CPPFLAGS PLATFORM_RELFLAGS CPPFLAGS CFLAGS AFLAGS

236.

237.

#########################################################################

238.

/*
下面几行规定了各种文件的编译时用到的编译选项 */

239.

/*
Allow boards to use custom optimize flags on a per dir/file basis */

240.

BCURDIR
= $(subst $(SRCTREE)/,,$(CURDIR:$(obj)%=%))

241.

/*
BCURDIR = 顶层目录 */

242.

$(obj)%.s:
%.S

243.

$(CPP)
$(AFLAGS) $(AFLAGS_$(BCURDIR)/$(

@F

))
$(AFLAGS_$(BCURDIR)) \

244.

-o
$@ $<

245.

$(obj)%.o:
%.S

246.

$(CC)
$(AFLAGS) $(AFLAGS_$(BCURDIR)/$(

@F

))
$(AFLAGS_$(BCURDIR)) \

247.

-o
$@ $<-c

248.

$(obj)%.o:
%.c

249.

$(CC)
$(CFLAGS) $(CFLAGS_$(BCURDIR)/$(

@F

))
$(CFLAGS_$(BCURDIR)) \

250.

-o
$@ $<-c

251.

$(obj)%.i:
%.c

252.

$(CPP)
$(CFLAGS) $(CFLAGS_$(BCURDIR)/$(

@F

))
$(CFLAGS_$(BCURDIR)) \

253.

-o
$@ $<-c

254.

$(obj)%.s:
%.c

255.

$(CC)
$(CFLAGS) $(CFLAGS_$(BCURDIR)/$(

@F

))
$(CFLAGS_$(BCURDIR)) \

256.

-o
$@ $<-c -S