2020年12月16日 | TQ210——S5PV210 uboot顶层config.mk分析

#

# (C) Copyright 2000-2006

# Wolfgang Denk, DENX Software Engineering, wd@denx.de.

#

# See file CREDITS for list of people who contributed to this

# project.

#

# This program is free software; you can redistribute it and/or

# modify it under the terms of the GNU General Public License as

# published by the Free Software Foundation; either version 2 of

# the License, or (at your option) any later version.

#

# This program is distributed in the hope that it will be useful,

# but WITHOUT ANY WARRANTY; without even the implied warranty of

# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

# GNU General Public License for more details.

#

# You should have received a copy of the GNU General Public License

# along with this program; if not, write to the Free Software

# Foundation, Inc., 59 Temple Place, Suite 330, Boston,

# MA 02111-1307 USA

#

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

# $@  表示目标文件

# $^  表示所有的依赖文件

# $<  表示第一个依赖文件

# $?  表示比目标还要新的依赖文件列表

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

# config.mk功能是配置单板信息和编译环境，被Makefile调用

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

# 此脚本在uboot顶层目录。如果目标存放目录不等于源码目录（这里不会执行）

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

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

dir :=

else

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

endif

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

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

$(shell mkdir -p $(obj))

# 所以上面的几行都不会执行，会执行下面这个，obj和src为空

else

obj :=

src :=

endif

# clean the slate ...

# 清楚标志

PLATFORM_RELFLAGS =

PLATFORM_CPPFLAGS =

PLATFORM_LDFLAGS =

#

# When cross-compiling on NetBSD, we have to define __PPC__ or else we

# will pick up a va_list declaration that is incompatible with the

# actual argument lists emitted by the compiler.

#

# [Tested on NetBSD/i386 1.5 + cross-powerpc-netbsd-1.3]

# ARCH=arm，这段不会执行

ifeq ($(ARCH),ppc)

ifeq ($(CROSS_COMPILE),powerpc-netbsd-)

PLATFORM_CPPFLAGS+= -D__PPC__

endif

ifeq ($(CROSS_COMPILE),powerpc-openbsd-)

PLATFORM_CPPFLAGS+= -D__PPC__

endif

endif

# 

ifeq ($(ARCH),arm)

ifeq ($(CROSS_COMPILE),powerpc-netbsd-)

PLATFORM_CPPFLAGS+= -D__ARM__

endif

ifeq ($(CROSS_COMPILE),powerpc-openbsd-)

PLATFORM_CPPFLAGS+= -D__ARM__

endif

endif

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

CONFIG_SHELL := $(shell if [ -x "$$BASH" ]; then echo $$BASH;

   else if [ -x /bin/bash ]; then echo /bin/bash;

   else echo sh; fi ; fi)

# 除了darwin-pcc外其他都采用gcc编译器

ifeq ($(HOSTOS)-$(HOSTARCH),darwin-ppc)

HOSTCC = cc

else

HOSTCC = gcc

endif

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

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

# -fomit-frame-pointer  

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

HOSTSTRIP = strip

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

#

# Option checker (courtesy linux kernel) to ensure

# only supported compiler options are used

#

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

# 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 = $(shell if $(CC) $(CFLAGS) $(1) -S -o /dev/null -xc /dev/null

> /dev/null 2>&1; then echo "$(1)"; else echo "$(2)"; fi ;)

#

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

# 下面一些是定义交叉工具链的集合

AS = $(CROSS_COMPILE)as

LD = $(CROSS_COMPILE)ld

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

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

# 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  

# Load generated board configuration

sinclude $(OBJTREE)/include/autoconf.mk

ifdef ARCH

sinclude $(TOPDIR)/$(ARCH)_config.mk # include architecture dependend rules

endif

ifdef CPU

sinclude $(TOPDIR)/cpu/$(CPU)/config.mk # include  CPUspecific rules

endif

ifdef SOC

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

endif

ifdef VENDOR

BOARDDIR = $(VENDOR)/$(BOARD)

else

BOARDDIR = $(BOARD)

endif

ifdef BOARD

sinclude $(TOPDIR)/board/$(BOARDDIR)/config.mk # include board specific rules

endif

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

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

ARFLAGS = cr

else

ARFLAGS = crv

endif

RELFLAGS= $(PLATFORM_RELFLAGS)

DBGFLAGS= -g # -DDEBUG

OPTFLAGS= -Os #-fomit-frame-pointer

ifndef LDSCRIPT

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

ifeq ($(CONFIG_NAND_U_BOOT),y)

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

else

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

endif

endif

OBJCFLAGS += --gap-fill=0xff

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

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

-D__KERNEL__

ifneq ($(TEXT_BASE),)

CPPFLAGS += -DTEXT_BASE=$(TEXT_BASE)

endif

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

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

endif

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

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

# avoid trigraph warnings while parsing pci.h (produced by NIOS gcc-2.9)

# this option have to be placed behind -Wall -- that's why it is here

# 不执行

ifeq ($(ARCH),nios)

ifeq ($(findstring 2.9,$(shell $(CC) --version)),2.9)

CFLAGS := $(CPPFLAGS) -Wall -Wno-trigraphs

endif

endif

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

# 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)

# 设置uboot的链接选项

LDFLAGS += -Bstatic -T $(LDSCRIPT) $(PLATFORM_LDFLAGS)

ifneq ($(TEXT_BASE),)

LDFLAGS += -Ttext $(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.

# 不是arm架构，不执行

ifeq ($(HOSTOS)-$(HOSTARCH),darwin-ppc)

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

ifeq ($(PCI_CLOCK),PCI_66M)

CFLAGS := $(CFLAGS) -DPCI_66M

endif

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

# 输出这些信息为环境变量

export CONFIG_SHELL HPATH HOSTCC HOSTCFLAGS CROSS_COMPILE

AS LD CC CPP AR NM STRIP OBJCOPY OBJDUMP

MAKE

export TEXT_BASE PLATFORM_CPPFLAGS PLATFORM_RELFLAGS CPPFLAGS CFLAGS AFLAGS

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

# 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。  

ifndef REMOTE_BUILD

%.s: %.S

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

%.o: %.S

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

%.o: %.c

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

else

$(obj)%.s: %.S

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

$(obj)%.o: %.S

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

$(obj)%.o: %.c

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

endif

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