(四)u-boot2013.01.01 for TQ210：《mkconfig分析》

时间：2021-05-07 02:01:16

config.mk主要功能是配置单板信息和编译环境，将会被u-boot的makefile所调用，本文仍然侧重于句法分析。

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

# 脚本所在的目录通常在U-boot源码顶层目录下，所以CURDIR = SRCTREE，所以dir = 空

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

dir :=

else

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

endif

# 不相等的情况下才会建立相应的目录，这里不会被执行

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

# Create object files for SPL in a separate directory

ifeq ($(CONFIG_SPL_BUILD),y)

obj := $(if $(dir),$(SPLTREE)/$(dir)/,$(SPLTREE)/)

else

obj := $(if $(dir),$(OBJTREE)/$(dir)/,$(OBJTREE)/)

endif

src := $(if $(dir),$(SRCTREE)/$(dir)/,$(SRCTREE)/)

$(shell mkdir -p $(obj))

else

# Create object files for SPL in a separate directory

# CONFIG_SPL_BUILD = y的时候才会建立执行的存放编译文件的目录，这里也不执行

ifeq ($(CONFIG_SPL_BUILD),y)

obj := $(if $(dir),$(SPLTREE)/$(dir)/,$(SPLTREE)/)

$(shell mkdir -p $(obj))

else

# 所以最后的结果是obj为空，src也为空

obj :=

endif

src :=

endif

# clean the slate ...

# 清除标志

PLATFORM_RELFLAGS =

PLATFORM_CPPFLAGS =

PLATFORM_LDFLAGS =

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

# HOSTCPPFLAGS的值为空，HOSTCFLAGS = -Wall -Wstrict-prototypes -O2

# -fomit-frame-pointer

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

		  $(HOSTCPPFLAGS)

HOSTSTRIP	= strip

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

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

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

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

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

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

#

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

# multiple symbol definitions are treated as errors, hence the

# -multiply_defined suppress option to turn off this error.

#

# 如果HOSTOS是darwin体系，则做专门处理

ifeq ($(HOSTOS),darwin)

# get major and minor product version (e.g. '10' and '6' for Snow Leopard)

DARWIN_MAJOR_VERSION	= $(shell sw_vers -productVersion | cut -f 1 -d '.')

DARWIN_MINOR_VERSION	= $(shell sw_vers -productVersion | cut -f 2 -d '.')

os_x_before	= $(shell if [ $(DARWIN_MAJOR_VERSION) -le $(1) -a \

	$(DARWIN_MINOR_VERSION) -le $(2) ] ; then echo "$(3)"; else echo "$(4)"; fi ;)

# Snow Leopards build environment has no longer restrictions as described above

HOSTCC		 = $(call os_x_before, 10, 5, "cc", "gcc")

HOSTCFLAGS	+= $(call os_x_before, 10, 4, "-traditional-cpp")

HOSTLDFLAGS	+= $(call os_x_before, 10, 5, "-multiply_defined suppress")

else

# 除了darwin外其他都采用gcc

HOSTCC		= gcc

endif

ifeq ($(HOSTOS),cygwin)

HOSTCFLAGS	+= -ansi

endif

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

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

# exceptions for files that aren't complaint.

# filter-out为反过滤函数，HOSTCFLAGS中的"-pedantic"全部删掉

# HOSTCFLAGS_NOPED = -Wall -Wstrict-prototypes -O2 -fomit-frame-pointer

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

# -pedantic

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

HOSTCFLAGS	+= -pedantic

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

#

# Option checker, gcc version (courtesy linux kernel) to ensure

# only supported compiler options are used

#

# 选项检查器，确保支持编译选项的唯一可用的gcc版本

# cc-option-sys=空  cc-option=空

# strip函数的作用是去掉字符串的空格，call函数作用是把它后面的参数一次赋值给$(1),$(2),...

# findstring函数是从字符串中超找指定内容，$(findstring $1,$(CC_OPTIONS))

# 就是从CC_OPTIONS从查找$(1)的内容，找到则返回$(1)，找不到则返回空

CC_OPTIONS_CACHE_FILE := $(OBJTREE)/include/generated/cc_options.mk

CC_TEST_OFILE := $(OBJTREE)/include/generated/cc_test_file.o

-include $(CC_OPTIONS_CACHE_FILE)

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

# cc-option用于检查编译器CC是否支持某选项。将2个选项作为参数传递给cc-option函数，该函数# 调用CC编译器检查参数1是否支持，若支持则函数返回参数1，否则返回参数2 （因此CC编译器必须支# 持参数1或参数2，若两个都不支持则会编译出错）。可以像下面这样调用cc-option函数，并将支持# 的选项添加到FLAGS中:  FLAGS +=$(call cc-option,option1,option2)

cc-option-sys = $(shell mkdir -p $(dir $(CC_TEST_OFILE)); \

		if $(CC) $(CFLAGS) $(1) -S -xc /dev/null -o $(CC_TEST_OFILE) \

		> /dev/null 2>&1; then \

		echo 'CC_OPTIONS += $(strip $1)' >> $(CC_OPTIONS_CACHE_FILE); \

		echo "$(1)"; fi)

ifeq ($(CONFIG_CC_OPT_CACHE_DISABLE),y)

cc-option = $(strip $(if $(call cc-option-sys,$1),$1,$2))

else

cc-option = $(strip $(if $(findstring $1,$(CC_OPTIONS)),$1,\

		$(if $(call cc-option-sys,$1),$1,$2)))

endif

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

# cc-version       = 0404

# binutils-version = 0221

cc-version = $(shell $(SHELL) $(SRCTREE)/tools/gcc-version.sh $(CC))

binutils-version = $(shell $(SHELL) $(SRCTREE)/tools/binutils-version.sh $(AS))

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

# Include the make variables (CC, etc...)

# AS = as

AS	= $(CROSS_COMPILE)as

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

# 链接器固定使用GNU ld

# LD = ld

LD	= $(shell if $(CROSS_COMPILE)ld.bfd -v > /dev/null 2>&1; \

		then echo "$(CROSS_COMPILE)ld.bfd"; else echo "$(CROSS_COMPILE)ld"; fi;)

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

# 定义交叉工具链集

# CC = gcc

# CPP = gcc -E

# AR = ar

# NM = nm

# LDR = ldr

# STRIP = strip

# OBJCOPY = objcopy

# OBJDUMP = objdump

# RANLIB = RANLIB

# DTC = dtc

CC	= $(CROSS_COMPILE)gcc

CPP	= $(CC) -E

AR	= $(CROSS_COMPILE)ar

NM	= $(CROSS_COMPILE)nm

LDR	= $(CROSS_COMPILE)ldr

STRIP	= $(CROSS_COMPILE)strip

OBJCOPY = $(CROSS_COMPILE)objcopy

OBJDUMP = $(CROSS_COMPILE)objdump

RANLIB	= $(CROSS_COMPILE)RANLIB

DTC	= dtc

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

# 加载产生的单板配置文件autoconf.mk和config.mk，均在include目录下

# config.mk中内容是ARCH CPU BOARD VENDOR SOC5个变量信息

# autoconf.mk为单板配置宏的集合,打开/关闭 用 y/n表示

sinclude $(OBJTREE)/include/autoconf.mk

sinclude $(OBJTREE)/include/config.mk

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

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

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

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

# CPU-specific code.

# 翻译上面这段英文:

# 需要知道CPUDIR的设置来查找一些架构的config.mk文件，所以在加载ARCH/SOC/config.mk和

# ARCH/CPU/config.mk之前要设置好CPUDIR路径。检查目录arch/$ARCH/cpu/$CPU是否存在，

# 否则认为arch/$ARCH/cpu目录下包含有CPU相关的代码。翻译完毕!

# 看看ifneq的执行:

# 首先这里CPUDIR = arch/$(ARCH)/cpu/$(CPU) = arch/arm/cpu/armv7

# wildcard函数用来匹配 arch/arm/cpu/armv7这一目录，意思就是如果不存在这个目录

# 则CPUDIR=arch/$(ARCH)/cpu=arch/arm/cpu，否则就保持采用

# CPUDIR=arch/arm/cpu/armv7

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

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

CPUDIR=arch/$(ARCH)/cpu

endif

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

# 加载 $(TOPDIR)/arch/arm/config.mk

# 加载 $(TOPDIR)/arch/arm/config.mk

sinclude $(TOPDIR)/arch/$(ARCH)/config.mk		  # 加载架构编译选项文件

sinclude $(TOPDIR)/arch/arm/cpu/armv7/config.mk  # 加载CPU相关编译选项文件

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

# 定义有SOC = s5pc1xx，所以加载$(TOPDIR)/arch/arm/cpu/armv7/s5pc1xx/config.mk

ifdef	SOC

sinclude $(TOPDIR)/$(CPUDIR)/$(SOC)/config.mk	# include  SoC	specific rules

endif

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

# 定义有VENDOR = samsung，所以BOARDDIR = samsung/smdkc100

ifdef	VENDOR

BOARDDIR = $(VENDOR)/$(BOARD)

else

BOARDDIR = $(BOARD)

endif

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

# 定义有BOARD = smdkc100,所以加载$(TOPDIR)/board/samsung/smdkc100/config.mk

ifdef	BOARD

sinclude $(TOPDIR)/board/$(BOARDDIR)/config.mk	# 加载单板编译选项文件

endif

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

# 我们不会在任何地方使用ARFLAGS了，所以有人不更新$(AR)就试图处理旧代码的时候就会报错

# ARFLAGS = $(error update your Makefile to use cmd_link_o_target and not AR)

# RELFLAGS=$(PLATFORM_RELFLAGS)=-fno-common -ffixed-r8 -msoft-float

# DBGFLAGS = -g

# OPTFLAGS = -Os

# OBJCFLAGS = --gap-fill=0xff

# gccincdir = $(shell $(CC) -print-file-name=include)=交叉工具链include目录在宿# 主机中的位置CPPFLAGS = -g -Os -fno-common -ffixed-r8 -msoft-float -D__KERNEL__

ARFLAGS = $(error update your Makefile to use cmd_link_o_target and not AR)

RELFLAGS= $(PLATFORM_RELFLAGS)

DBGFLAGS= -g  # -DDEBUG

OPTFLAGS= -Os # -fomit-frame-pointer

OBJCFLAGS += --gap-fill=0xff

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

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

	-D__KERNEL__

# Enable garbage collection of un-used sections for SPL

ifeq ($(CONFIG_SPL_BUILD),y)

CPPFLAGS += -ffunction-sections -fdata-sections

LDFLAGS_FINAL += --gc-sections

endif

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

# U-Boot编译时将使用TEXT_BASE作为代码段连接的起始地址

# CONFIG_SYS_TEXT_BASE不为空，所以CPPFLAGS会多出一项:

# -DCONFIG_SYS_TEXT_BASE=0x34800000

ifneq ($(CONFIG_SYS_TEXT_BASE),)

CPPFLAGS += -DCONFIG_SYS_TEXT_BASE=$(CONFIG_SYS_TEXT_BASE)

endif

ifneq ($(CONFIG_SPL_TEXT_BASE),)

CPPFLAGS += -DCONFIG_SPL_TEXT_BASE=$(CONFIG_SPL_TEXT_BASE)

endif

ifneq ($(CONFIG_SPL_PAD_TO),)

CPPFLAGS += -DCONFIG_SPL_PAD_TO=$(CONFIG_SPL_PAD_TO)

endif

ifeq ($(CONFIG_SPL_BUILD),y)

CPPFLAGS += -DCONFIG_SPL_BUILD

endif

ifneq ($(RESET_VECTOR_ADDRESS),)

CPPFLAGS += -DRESET_VECTOR_ADDRESS=$(RESET_VECTOR_ADDRESS)

endif

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

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

endif

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

# 添加-I$(TOPDIR)/include路径到CPPFLAGS中，还有

# -fno-builtin -ffreestanding -nostdinc	-isystem $(gccincdir)

# -pipe $(PLATFORM_CPPFLAGS)也添加进CPPFLAGS中

CPPFLAGS += -I$(TOPDIR)/include

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

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

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

# 没有定义BUILD_TAG，执行else分支,赋值CFLAGS

ifdef BUILD_TAG

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

	-DBUILD_TAG='"$(BUILD_TAG)"'

else

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

endif

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

# 利用call函数，使得$1=cc-option ,$2=-fno-stack-protector

# CFLAGS_SSP= $1$2 = -fno-stack-protector,然后把CFLAGS_SSP

# 追加给CFLAGS

CFLAGS_SSP := $(call cc-option,-fno-stack-protector)

CFLAGS += $(CFLAGS_SSP)

# Some toolchains enable security related warning flags by default,

# but they don't make much sense in the u-boot world, so disable them.

# 上面英文意思是一些工具链默认使用了一些安全警告选项，但是在U-boot的世界中我们不必要在意

# 太多这些警告，所以禁用它们。

# CFLAGS_WARN = -Wno-format-nonliteral -Wno-format-security，然后追加

# 到编译选项变量CFLAGS中

CFLAGS_WARN := $(call cc-option,-Wno-format-nonliteral) \

	       $(call cc-option,-Wno-format-security)

CFLAGS += $(CFLAGS_WARN)

# Report stack usage if supported

# 如果支持的话开启报告堆栈使用状态，通过参数-fstack-usage开启，追加到CFLAGS中

CFLAGS_STACK := $(call cc-option,-fstack-usage)

CFLAGS += $(CFLAGS_STACK)

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

# option to the assembler.

# CPPFLAGS设置了-g参数，

AFLAGS_DEBUG :=

# turn jbsr into jsr for m68k

ifeq ($(ARCH),m68k)

ifeq ($(findstring 3.4,$(shell $(CC) --version)),3.4)

AFLAGS_DEBUG := -Wa,-gstabs,-S

endif

endif

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

LDFLAGS += $(PLATFORM_LDFLAGS)

LDFLAGS_FINAL += -Bstatic

# 设置U-boot的链接选项

LDFLAGS_u-boot += -T $(obj)u-boot.lds $(LDFLAGS_FINAL)

ifneq ($(CONFIG_SYS_TEXT_BASE),)

LDFLAGS_u-boot += -Ttext $(CONFIG_SYS_TEXT_BASE)

endif

# 设置U-boot的链接选项，当uboot是采用spl时的情况

LDFLAGS_u-boot-spl += -T $(obj)u-boot-spl.lds $(LDFLAGS_FINAL)

ifneq ($(CONFIG_SPL_TEXT_BASE),)

LDFLAGS_u-boot-spl += -Ttext $(CONFIG_SPL_TEXT_BASE)

endif

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

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

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

# - Linux/ppc (native): /usr

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

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

#   files don't like each other)

#

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

# 非arm架构设置，不执行

ifeq ($(HOSTOS),darwin)

BFD_ROOT_DIR =		/usr/local/tools

else

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

# native

BFD_ROOT_DIR =		/usr

else

#BFD_ROOT_DIR =		/LinuxPPC/CDK		# Linux/i386

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

BFD_ROOT_DIR =		/opt/powerpc

endif

endif

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

# 设置各种编译选项的环境变量供Makefile使用

export	HOSTCC HOSTCFLAGS HOSTLDFLAGS PEDCFLAGS HOSTSTRIP CROSS_COMPILE \

	AS LD CC CPP AR NM STRIP OBJCOPY OBJDUMP MAKE

export	CONFIG_SYS_TEXT_BASE PLATFORM_CPPFLAGS PLATFORM_RELFLAGS CPPFLAGS CFLAGS AFLAGS

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

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

# BCURDIR = U-boot源码顶层目录，其他的太长了就不打出来了

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

ALL_AFLAGS = $(AFLAGS) $(AFLAGS_$(BCURDIR)/$(@F)) $(AFLAGS_$(BCURDIR))

ALL_CFLAGS = $(CFLAGS) $(CFLAGS_$(BCURDIR)/$(@F)) $(CFLAGS_$(BCURDIR))

EXTRA_CPPFLAGS = $(CPPFLAGS_$(BCURDIR)/$(@F)) $(CPPFLAGS_$(BCURDIR))

ALL_CFLAGS += $(EXTRA_CPPFLAGS)

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

# The _DEP version uses the $< file target (for dependency generation)

# See rules.mk

# 指定隐含的编译规则，例如：根据以上的定义，以“.s”结尾的目标文件将根据第一条规则由同名但后

# 缀为“.S”的源文件来生成，若不存在“.S”结尾的同名文件则根据最后一条规则由同名的“.c”文件生

# 成。

EXTRA_CPPFLAGS_DEP = $(CPPFLAGS_$(BCURDIR)/$(addsuffix .o,$(basename $<))) \

		$(CPPFLAGS_$(BCURDIR))

$(obj)%.s:	%.S

	$(CPP) $(ALL_AFLAGS) -o $@ $<

$(obj)%.o:	%.S

	$(CC)  $(ALL_AFLAGS) -o $@ $< -c

$(obj)%.o:	%.c

	$(CC)  $(ALL_CFLAGS) -o $@ $< -c

$(obj)%.i:	%.c

	$(CPP) $(ALL_CFLAGS) -o $@ $< -c

$(obj)%.s:	%.c

	$(CC)  $(ALL_CFLAGS) -o $@ $< -c -S

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

# If the list of objects to link is empty, just create an empty built-in.o

# $1为空，if返回空，cmd_link_o_target = rm -f; arm-linux-ar rcs

cmd_link_o_target = $(if $(strip $1),\

		      $(LD) $(LDFLAGS) -r -o $@ $1,\

		      rm -f $@; $(AR) rcs $@ )

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

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