主makefile配置文件config.mk的分析

#
# (C) Copyright 2000-2006
# Wolfgang Denk, DENX Software Engineering, [email protected]
#
# 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
#

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

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))
else
obj :=
src :=
endif

# clean the slate ...
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]

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)

ifeq ($(HOSTOS)-$(HOSTARCH),darwin-ppc)
HOSTCC        = cc
else
HOSTCC        = gcc
endif
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 = $(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...)
#
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

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

# 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  CPU    specific 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)

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
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<format>
# option to the assembler.
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 += -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.

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

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

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

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

ifndef REMOTE_BUILD

%.s:    %.S
    $(CPP) $(AFLAGS) -o [email protected] $<
%.o:    %.S
    $(CC) $(AFLAGS) -c -o [email protected] $<
%.o:    %.c
    $(CC) $(CFLAGS) -c -o [email protected] $<

else

$(obj)%.s:    %.S
    $(CPP) $(AFLAGS) -o [email protected] $<
$(obj)%.o:    %.S
    $(CC) $(AFLAGS) -c -o [email protected] $<
$(obj)%.o:    %.c
    $(CC) $(CFLAGS) -c -o [email protected] $<
endif

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