kbuild: change kbuild to not rely on incorrect GNU make behavior

The kbuild system takes advantage of an incorrect behavior in GNU make.
Once this behavior is fixed, all files in the kernel rebuild every time,
even if nothing has changed.  This patch ensures kbuild works with both
the incorrect and correct behaviors of GNU make.

For more details on the incorrect behavior, see:

http://lists.gnu.org/archive/html/bug-make/2006-03/msg00003.html

Changes in this patch:
  - Keep all targets that are to be marked .PHONY in a variable, PHONY.
  - Add .PHONY: $(PHONY) to mark them properly.
  - Remove any $(PHONY) files from the $? list when determining whether
    targets are up-to-date or not.

Signed-off-by: Paul Smith <psmith@gnu.org>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>

15 files changed, 50 insertions, 20 deletions

diff --git a/arch/arm/Makefile b/arch/arm/Makefile
index fbfc14a..585d334 100644
--- a/arch/arm/Makefile
+++ b/arch/arm/Makefile
@@ -1,6 +1,9 @@
 #
 # arch/arm/Makefile
 #
+# This file is included by the global makefile so that you can add your own
+# architecture-specific flags and dependencies.
+#
 # This file is subject to the terms and conditions of the GNU General Public
 # License.  See the file "COPYING" in the main directory of this archive
 # for more details.
@@ -176,7 +179,7 @@ endif
 
 archprepare: maketools
 
-.PHONY: maketools FORCE
+PHONY += maketools FORCE
 maketools: include/linux/version.h include/asm-arm/.arch FORCE
 	$(Q)$(MAKE) $(build)=arch/arm/tools include/asm-arm/mach-types.h
 
diff --git a/arch/arm/boot/Makefile b/arch/arm/boot/Makefile
index a174d63..ec9c400c 100644
--- a/arch/arm/boot/Makefile
+++ b/arch/arm/boot/Makefile
@@ -1,6 +1,9 @@
 #
 # arch/arm/boot/Makefile
 #
+# This file is included by the global makefile so that you can add your own
+# architecture-specific flags and dependencies.
+#
 # This file is subject to the terms and conditions of the GNU General Public
 # License.  See the file "COPYING" in the main directory of this archive
 # for more details.
@@ -73,7 +76,7 @@ $(obj)/bootpImage: $(obj)/bootp/bootp FORCE
 	$(call if_changed,objcopy)
 	@echo '  Kernel: $@ is ready'
 
-.PHONY: initrd FORCE
+PHONY += initrd FORCE
 initrd:
 	@test "$(INITRD_PHYS)" != "" || \
 	(echo This machine does not support INITRD; exit -1)
diff --git a/arch/arm/boot/bootp/Makefile b/arch/arm/boot/bootp/Makefile
index 8e8879b..c394e30 100644
--- a/arch/arm/boot/bootp/Makefile
+++ b/arch/arm/boot/bootp/Makefile
@@ -1,6 +1,9 @@
 #
 # linux/arch/arm/boot/bootp/Makefile
 #
+# This file is included by the global makefile so that you can add your own
+# architecture-specific flags and dependencies.
+#
 
 LDFLAGS_bootp	:=-p --no-undefined -X \
 		 --defsym initrd_phys=$(INITRD_PHYS) \
@@ -21,4 +24,4 @@ $(obj)/kernel.o: arch/arm/boot/zImage FORCE
 
 $(obj)/initrd.o: $(INITRD) FORCE
 
-.PHONY:	$(INITRD) FORCE
+PHONY += $(INITRD) FORCE
diff --git a/arch/arm26/Makefile b/arch/arm26/Makefile
index 844a9e4..fe91eda 100644
--- a/arch/arm26/Makefile
+++ b/arch/arm26/Makefile
@@ -1,6 +1,9 @@
 #
 # arch/arm26/Makefile
 #
+# This file is included by the global makefile so that you can add your own
+# architecture-specific flags and dependencies.
+#
 # This file is subject to the terms and conditions of the GNU General Public
 # License.  See the file "COPYING" in the main directory of this archive
 # for more details.
@@ -49,9 +52,9 @@ all: zImage
 
 boot := arch/arm26/boot
 
-.PHONY: maketools FORCE
+PHONY += maketools FORCE
 maketools: FORCE
-	
+
 
 # Convert bzImage to zImage
 bzImage: vmlinux
diff --git a/arch/arm26/boot/Makefile b/arch/arm26/boot/Makefile
index b5c2277..68acb7b 100644
--- a/arch/arm26/boot/Makefile
+++ b/arch/arm26/boot/Makefile
@@ -1,6 +1,9 @@
 #
 # arch/arm26/boot/Makefile
 #
+# This file is included by the global makefile so that you can add your own
+# architecture-specific flags and dependencies.
+#
 # This file is subject to the terms and conditions of the GNU General Public
 # License.  See the file "COPYING" in the main directory of this archive
 # for more details.
@@ -60,7 +63,7 @@ $(obj)/xipImage: vmlinux FORCE
 	@echo '  Kernel: $@ is ready'
 endif
 
-.PHONY: initrd
+PHONY += initrd
 initrd:
 	@test "$(INITRD_PHYS)" != "" || \
 	(echo This machine does not support INITRD; exit -1)
diff --git a/arch/i386/Makefile b/arch/i386/Makefile
index 36bef65..ff6973a 100644
--- a/arch/i386/Makefile
+++ b/arch/i386/Makefile
@@ -99,8 +99,8 @@ AFLAGS += $(mflags-y)
 
 boot := arch/i386/boot
 
-.PHONY: zImage bzImage compressed zlilo bzlilo \
-	zdisk bzdisk fdimage fdimage144 fdimage288 install
+PHONY += zImage bzImage compressed zlilo bzlilo \
+         zdisk bzdisk fdimage fdimage144 fdimage288 install
 
 all: bzImage
 
diff --git a/arch/ia64/Makefile b/arch/ia64/Makefile
index f722e1a..80ea750 100644
--- a/arch/ia64/Makefile
+++ b/arch/ia64/Makefile
@@ -1,6 +1,9 @@
 #
 # ia64/Makefile
 #
+# This file is included by the global makefile so that you can add your own
+# architecture-specific flags and dependencies.
+#
 # This file is subject to the terms and conditions of the GNU General Public
 # License.  See the file "COPYING" in the main directory of this archive
 # for more details.
@@ -62,7 +65,7 @@ drivers-$(CONFIG_OPROFILE)	+= arch/ia64/oprofile/
 
 boot := arch/ia64/hp/sim/boot
 
-.PHONY: boot compressed check
+PHONY += boot compressed check
 
 all: compressed unwcheck
 
diff --git a/arch/m32r/Makefile b/arch/m32r/Makefile
index 983d438..229f66f 100644
--- a/arch/m32r/Makefile
+++ b/arch/m32r/Makefile
@@ -1,6 +1,9 @@
 #
 # m32r/Makefile
 #
+# This file is included by the global makefile so that you can add your own
+# architecture-specific flags and dependencies.
+#
 
 LDFLAGS		:=
 OBJCOPYFLAGS	:= -O binary -R .note -R .comment -S
@@ -39,7 +42,7 @@ drivers-$(CONFIG_OPROFILE)	+= arch/m32r/oprofile/
 
 boot := arch/m32r/boot
 
-.PHONY: zImage
+PHONY += zImage
 
 all: zImage
 
diff --git a/arch/powerpc/Makefile b/arch/powerpc/Makefile
index 5500ab5..5787d55 100644
--- a/arch/powerpc/Makefile
+++ b/arch/powerpc/Makefile
@@ -150,7 +150,7 @@ CPPFLAGS_vmlinux.lds	:= -Upowerpc
 
 BOOT_TARGETS = zImage zImage.initrd znetboot znetboot.initrd vmlinux.sm uImage
 
-.PHONY: $(BOOT_TARGETS)
+PHONY += $(BOOT_TARGETS)
 
 boot := arch/$(ARCH)/boot
 
diff --git a/arch/ppc/Makefile b/arch/ppc/Makefile
index 98e940b..9fbdf54 100644
--- a/arch/ppc/Makefile
+++ b/arch/ppc/Makefile
@@ -82,7 +82,7 @@ drivers-$(CONFIG_OPROFILE)	+= arch/powerpc/oprofile/
 
 BOOT_TARGETS = zImage zImage.initrd znetboot znetboot.initrd vmlinux.sm
 
-.PHONY: $(BOOT_TARGETS)
+PHONY += $(BOOT_TARGETS)
 
 all: uImage zImage
 
diff --git a/arch/ppc/boot/Makefile b/arch/ppc/boot/Makefile
index efd8ce5..84eec0b 100644
--- a/arch/ppc/boot/Makefile
+++ b/arch/ppc/boot/Makefile
@@ -1,6 +1,9 @@
 #
 # arch/ppc/boot/Makefile
 #
+# This file is included by the global makefile so that you can add your own
+# architecture-specific flags and dependencies.
+#
 # This file is subject to the terms and conditions of the GNU General Public
 # License.  See the file "COPYING" in the main directory of this archive
 # for more details.
@@ -25,7 +28,7 @@ subdir-				+= simple openfirmware
 
 hostprogs-y := $(addprefix utils/, addnote mknote hack-coff mkprep mkbugboot mktree)
 
-.PHONY: $(BOOT_TARGETS) $(bootdir-y)
+PHONY += $(BOOT_TARGETS) $(bootdir-y)
 
 $(BOOT_TARGETS): $(bootdir-y)
 
diff --git a/arch/ppc/boot/openfirmware/Makefile b/arch/ppc/boot/openfirmware/Makefile
index 2a411ec..66b7397 100644
--- a/arch/ppc/boot/openfirmware/Makefile
+++ b/arch/ppc/boot/openfirmware/Makefile
@@ -1,5 +1,8 @@
 # Makefile for making bootable images on various OpenFirmware machines.
 #
+# This file is included by the global makefile so that you can add your own
+# architecture-specific flags and dependencies.
+#
 # Paul Mackerras	January 1997
 #	XCOFF bootable images for PowerMacs
 # Geert Uytterhoeven	September 1997
@@ -86,7 +89,7 @@ $(images)/zImage.chrp-rs6k $(images)/zImage.initrd.chrp-rs6k: \
 
 # The targets used on the make command-line
 
-.PHONY: zImage zImage.initrd
+PHONY += zImage zImage.initrd
 zImage:		 $(images)/zImage.chrp		\
 		 $(images)/zImage.chrp-rs6k
 	@echo '  kernel: $@ is ready ($<)'
@@ -96,7 +99,7 @@ zImage.initrd:	 $(images)/zImage.initrd.chrp		\
 
 TFTPIMAGE	:= /tftpboot/zImage
 
-.PHONY: znetboot znetboot.initrd
+PHONY += znetboot znetboot.initrd
 znetboot:	$(images)/zImage.chrp
 	cp $(images)/zImage.chrp      $(TFTPIMAGE).chrp$(END)
 	@echo '  kernel: $@ is ready ($<)'
diff --git a/arch/sh/Makefile b/arch/sh/Makefile
index 08c9515..c72e17a 100644
--- a/arch/sh/Makefile
+++ b/arch/sh/Makefile
@@ -172,7 +172,7 @@ include/asm-sh/.mach: $(wildcard include/config/sh/*.h) include/config/MARKER
 
 archprepare: maketools include/asm-sh/.cpu include/asm-sh/.mach
 
-.PHONY: maketools FORCE
+PHONY += maketools FORCE
 maketools:  include/linux/version.h FORCE
 	$(Q)$(MAKE) $(build)=arch/sh/tools include/asm-sh/machtypes.h
 
diff --git a/arch/um/Makefile b/arch/um/Makefile
index c58b657..8d14c7a 100644
--- a/arch/um/Makefile
+++ b/arch/um/Makefile
@@ -1,4 +1,7 @@
-# 
+#
+# This file is included by the global makefile so that you can add your own
+# architecture-specific flags and dependencies.
+#
 # Copyright (C) 2002 Jeff Dike (jdike@karaya.com)
 # Licensed under the GPL
 #
@@ -88,7 +91,7 @@ CONFIG_KERNEL_HALF_GIGS ?= 0
 
 SIZE = (($(CONFIG_NEST_LEVEL) + $(CONFIG_KERNEL_HALF_GIGS)) * 0x20000000)
 
-.PHONY: linux
+PHONY += linux
 
 all: linux
 
diff --git a/arch/x86_64/Makefile b/arch/x86_64/Makefile
index d7fd464..7405dfd 100644
--- a/arch/x86_64/Makefile
+++ b/arch/x86_64/Makefile
@@ -67,8 +67,8 @@ drivers-$(CONFIG_OPROFILE)		+= arch/x86_64/oprofile/
 
 boot := arch/x86_64/boot
 
-.PHONY: bzImage bzlilo install archmrproper \
-	fdimage fdimage144 fdimage288 archclean
+PHONY += bzImage bzlilo install archmrproper \
+	 fdimage fdimage144 fdimage288 archclean
 
 #Default target when executing "make"
 all: bzImage