kbuild: Don't cd into subdirs during build

Instead of using make -C <subdir>, just use make -f <subdir>/Makefile.
This means we now call gcc/ld/... always from the topdir.

Advantages are:
o We don't need to use -I$(TOPDIR)/include and the like, just 
  -Iinclude works.
o __FILE__ gives the correct relative path from the topdir instead
  of an absolute path, as it did before for included headers
o gcc errors/warnings give the correct relative path from the topdir
o takes us a step closer to a non-recursive build (though that's probably
  as close as it gets)

The changes to Rules.make were done in a way which only uses the new way
for the standard recursive build (which remains recursive, just without
cd), all the archs do make -C arch/$(ARCH)/boot ..., which should keep
working as before. However, of course this should be converted eventually,
it's possible to do so piecemeal arch by arch.

It seems to work fine for most of the standard kernel. Potential places
which need changing are added -I flags to the command line, which now
need to have the path relative to the topdir and explicit rules for
generating files, which need to properly use $(obj) / $(src) to work
correctly.

Rules.make

@@ -25,22 +25,20 @@ ifdef list-multi
 $(warning kbuild: list-multi ($(list-multi)) is obsolete in 2.5. Please fix!)
 endif
 
-# Figure out paths
+# Some paths for the Makefiles to use
 # ---------------------------------------------------------------------------
-# Find the path relative to the toplevel dir, $(RELDIR), and express
-# the toplevel dir as a relative path from this dir, $(TOPDIR_REL)
 
-ifeq ($(findstring $(TOPDIR),$(CURDIR)),)
-  # Can only happen when something is built out of tree
-  RELDIR := $(CURDIR)
-  TOPDIR_REL := $(TOPDIR)
-else
-  RELDIR := $(subst $(TOPDIR)/,,$(CURDIR))
-  TOPDIR_REL := $(subst $(space),,$(foreach d,$(subst /, ,$(RELDIR)),../))
+# FIXME. For now, we leave it possible to use make -C or make -f
+# to do work in subdirs.
+
+ifndef obj
+obj = .
+CFLAGS := $(patsubst -I%,-I$(TOPDIR)/%,$(patsubst -I$(TOPDIR)/%,-I%,$(CFLAGS)))
+AFLAGS := $(patsubst -I%,-I$(TOPDIR)/%,$(patsubst -I$(TOPDIR)/%,-I%,$(AFLAGS)))
 endif
 
-# Some paths for the Makefiles to use
-# ---------------------------------------------------------------------------
+# For use in the quiet output
+echo_target = $@
 
 # Usage:
 #
@@ -58,12 +56,7 @@ endif
 # We don't support separate source / object yet, so these are just
 # placeholders for now
 
-obj := .
-src := .
-
-# For use in the quiet output
-
-echo_target = $(RELDIR)/$@
+src := $(obj)
 
 # Figure out what we need to build from the various variables
 # ===========================================================================
@@ -120,6 +113,21 @@ real-objs-m := $(foreach m, $(obj-m), $(if $($(m:.o=-objs)),$($(m:.o=-objs)),$(m
 # Only build module versions for files which are selected to be built
 export-objs := $(filter $(export-objs),$(real-objs-y) $(real-objs-m))
 
+# Add subdir path
+
+EXTRA_TARGETS	:= $(addprefix $(obj)/,$(EXTRA_TARGETS))
+obj-y		:= $(addprefix $(obj)/,$(obj-y))
+obj-m		:= $(addprefix $(obj)/,$(obj-m))
+export-objs	:= $(addprefix $(obj)/,$(export-objs))
+subdir-obj-y	:= $(addprefix $(obj)/,$(subdir-obj-y))
+real-objs-y	:= $(addprefix $(obj)/,$(real-objs-y))
+real-objs-m	:= $(addprefix $(obj)/,$(real-objs-m))
+multi-used-y	:= $(addprefix $(obj)/,$(multi-used-y))
+multi-used-m	:= $(addprefix $(obj)/,$(multi-used-m))
+multi-objs-y	:= $(addprefix $(obj)/,$(multi-objs-y))
+multi-objs-m	:= $(addprefix $(obj)/,$(multi-objs-m))
+subdir-ym	:= $(addprefix $(obj)/,$(subdir-ym))
+
 # The temporary file to save gcc -MD generated dependencies must not
 # contain a comma
 depfile = $(subst $(comma),_,$(@D)/.$(@F).d)
@@ -153,7 +161,7 @@ else
 # This sets version suffixes on exported symbols
 # ---------------------------------------------------------------------------
 
-MODVERDIR := $(TOPDIR)/include/linux/modules/$(RELDIR)
+MODVERDIR := include/linux/modules/$(obj)
 
 #
 # Added the SMP separator to stop module accidents between uniprocessor
@@ -183,7 +191,7 @@ c_flags = -Wp,-MD,$(depfile) $(CFLAGS) $(NOSTDINC_FLAGS) \
 # files (fix-dep filters them), so touch modversions.h if any of the .ver
 # files changes
 
-quiet_cmd_cc_ver_c = MKVER   include/linux/modules/$(RELDIR)/$*.ver
+quiet_cmd_cc_ver_c = MKVER   include/linux/modules/$(obj)/$*.ver
 cmd_cc_ver_c = $(CPP) $(c_flags) $< | $(GENKSYMS) $(genksyms_smp_prefix) \
 		 -k $(VERSION).$(PATCHLEVEL).$(SUBLEVEL) > $@.tmp
 
@@ -216,8 +224,8 @@ $(MODVERDIR)/%.ver: %.c FORCE
 targets := $(addprefix $(MODVERDIR)/,$(export-objs:.o=.ver))
 
 fastdep: $(targets) $(subdir-ym)
-	@mkdir -p $(dir $(addprefix $(TOPDIR)/.tmp_export-objs/modules/$(RELDIR),$(export-objs:.o=.ver)))
-	@touch $(addprefix $(TOPDIR)/.tmp_export-objs/modules/$(RELDIR)/,$(export-objs:.o=.ver))
+	@mkdir -p $(dir $(addprefix .tmp_export-objs/modules/,$(export-objs:.o=.ver)))
+	@touch $(addprefix .tmp_export-objs/modules/,$(export-objs:.o=.ver))
 
 endif # export-objs 
 
@@ -228,13 +236,15 @@ ifeq ($(MAKECMDGOALS),modules_install)
 # Installing modules
 # ==========================================================================
 
+quiet_cmd_modules_install = INSTALL $(obj-m)
+cmd_modules_install = mkdir -p $(MODLIB)/kernel/$(obj); \
+		      cp $(obj-m) $(MODLIB)/kernel/$(obj)
+
 .PHONY: modules_install
 
 modules_install: $(subdir-ym)
 ifneq ($(obj-m),)
-	@echo Installing modules in $(MODLIB)/kernel/$(RELDIR)
-	@mkdir -p $(MODLIB)/kernel/$(RELDIR)
-	@cp $(obj-m) $(MODLIB)/kernel/$(RELDIR)
+	$(call cmd,modules_install)
 else
 	@/bin/true
 endif
@@ -250,8 +260,12 @@ else # ! modules_install
 
 ifndef O_TARGET
 ifndef L_TARGET
-O_TARGET := built-in.o
+O_TARGET := $(obj)/built-in.o
+endif
 endif
+
+ifdef L_TARGET
+L_TARGET := $(obj)/$(L_TARGET)
 endif
 
 first_rule: $(if $(KBUILD_BUILTIN),$(O_TARGET) $(L_TARGET) $(EXTRA_TARGETS)) \
@@ -368,7 +382,7 @@ endif
 #
 
 quiet_cmd_link_multi = LD      $(echo_target)
-cmd_link_multi = $(LD) $(LDFLAGS) $(EXTRA_LDFLAGS) -r -o $@ $(filter $($(basename $@)-objs),$^)
+cmd_link_multi = $(LD) $(LDFLAGS) $(EXTRA_LDFLAGS) -r -o $@ $(filter $(addprefix $(obj)/,$($(subst $(obj)/,,$(@:.o=-objs)))),$^)
 
 # We would rather have a list of rules like
 # 	foo.o: $(foo-objs)
@@ -388,6 +402,9 @@ targets += $(multi-used-y) $(multi-used-m)
 host-progs-single     := $(foreach m,$(host-progs),$(if $($(m)-objs),,$(m)))
 host-progs-multi      := $(foreach m,$(host-progs),$(if $($(m)-objs),$(m)))
 host-progs-multi-objs := $(foreach m,$(host-progs-multi),$($(m)-objs))
+host-progs-single     := $(addprefix $(obj)/,$(host-progs-single))
+host-progs-multi      := $(addprefix $(obj)/,$(host-progs-multi))
+host-progs-multi-objs := $(addprefix $(obj)/,$(host-progs-multi-objs))
 
 quiet_cmd_host_cc__c  = HOSTCC  $(echo_target)
 cmd_host_cc__c        = $(HOSTCC) -Wp,-MD,$(depfile) \
@@ -405,7 +422,7 @@ $(host-progs-multi-objs): %.o: %.c FORCE
 	$(call if_changed_dep,host_cc_o_c)
 
 quiet_cmd_host_cc__o  = HOSTLD  $(echo_target)
-cmd_host_cc__o        = $(HOSTCC) $(HOSTLDFLAGS) -o $@ $($@-objs) \
+cmd_host_cc__o        = $(HOSTCC) $(HOSTLDFLAGS) -o $@ $(addprefix $(obj)/,$($(subst $(obj)/,,$@)-objs)) \
 			$(HOST_LOADLIBES)
 
 $(host-progs-multi): %: $(host-progs-multi-objs) FORCE
@@ -583,5 +600,7 @@ endef
 #	$(call descend,<dir>,<target>)
 #	Recursively call a sub-make in <dir> with target <target> 
 
-descend = $(MAKE) -C $(1) $(2)
-
+ifeq ($(KBUILD_VERBOSE),1)
+descend = echo '$(MAKE) -f $(1)/Makefile $(2)';
+endif
+descend += $(MAKE) -f $(1)/Makefile obj=$(1) $(2)

arch/i386/Makefile

@@ -98,8 +98,8 @@ core-y					+= arch/i386/kernel/ arch/i386/mm/ arch/i386/$(MACHINE)/
 drivers-$(CONFIG_MATH_EMULATION)	+= arch/i386/math-emu/
 drivers-$(CONFIG_PCI)			+= arch/i386/pci/
 
-CFLAGS += -I$(TOPDIR)/arch/i386/$(MACHINE)
-AFLAGS += -I$(TOPDIR)/arch/i386/$(MACHINE)
+CFLAGS += -Iarch/i386/$(MACHINE)
+AFLAGS += -Iarch/i386/$(MACHINE)
 
 MAKEBOOT = +$(MAKE) -C arch/$(ARCH)/boot
 

arch/i386/boot/Makefile

@@ -44,7 +44,7 @@ bzImage: IMAGE_OFFSET := 0x100000
 bzImage: EXTRA_AFLAGS := -traditional $(SVGA_MODE) $(RAMDISK) -D__BIG_KERNEL__
 bzImage: BUILDFLAGS   := -b
 
-quiet_cmd_image = BUILD  $(RELDIR)/$@
+quiet_cmd_image = BUILD   $(echo_target)
 cmd_image = tools/build $(BUILDFLAGS) bootsect setup vmlinux.bin \
 			$(ROOT_DEV) > $@
 

drivers/acpi/Makefile

@@ -4,7 +4,7 @@
 
 export ACPI_CFLAGS
 
-ACPI_CFLAGS	:= -D_LINUX -I$(CURDIR)/include
+ACPI_CFLAGS	:= -D_LINUX -Idrivers/acpi/include
 
 ifdef CONFIG_ACPI_DEBUG
   ACPI_CFLAGS	+= -DACPI_DEBUG_OUTPUT

drivers/ide/arm/Makefile

@@ -2,6 +2,6 @@
 obj-$(CONFIG_BLK_DEV_IDE_ICSIDE)	+= icside.o
 obj-$(CONFIG_BLK_DEV_IDE_RAPIDE)	+= rapide.o
 
-EXTRA_CFLAGS	:= -I../
+EXTRA_CFLAGS	:= -Idrivers/ide
 
 include $(TOPDIR)/Rules.make

drivers/ide/legacy/Makefile

@@ -17,6 +17,6 @@ obj-$(CONFIG_BLK_DEV_IDECS)		+= ide-cs.o
 # Last of all
 obj-$(CONFIG_BLK_DEV_HD)		+= hd.o
 
-EXTRA_CFLAGS	:= -I../
+EXTRA_CFLAGS	:= -Idrivers/ide
 
 include $(TOPDIR)/Rules.make

drivers/ide/pci/Makefile

@@ -31,6 +31,6 @@ obj-$(CONFIG_BLK_DEV_VIA82CXXX)		+= via82cxxx.o
 # Must appear at the end of the block
 obj-$(CONFIG_BLK_DEV_GENERIC)          += generic.o
 
-EXTRA_CFLAGS	:= -I../
+EXTRA_CFLAGS	:= -Idrivers/ide
 
 include $(TOPDIR)/Rules.make

drivers/ide/ppc/Makefile

@@ -3,6 +3,6 @@ obj-$(CONFIG_BLK_DEV_MPC8xx_IDE)	+= mpc8xx.o
 obj-$(CONFIG_BLK_DEV_IDE_PMAC)		+= pmac.o
 obj-$(CONFIG_BLK_DEV_IDE_SWARM)		+= swarm.o
 
-EXTRA_CFLAGS	:= -I../
+EXTRA_CFLAGS	:= -Idrivers/ide
 
 include $(TOPDIR)/Rules.make

drivers/message/fusion/Makefile

@@ -13,7 +13,7 @@
 #			# sparc64
 #EXTRA_CFLAGS += -gstabs+
 
-EXTRA_CFLAGS += -I. ${MPT_CFLAGS}
+EXTRA_CFLAGS += ${MPT_CFLAGS}
 
 # Fusion MPT drivers; recognized debug defines...
 #  MPT general:

drivers/net/sk98lin/Makefile

@@ -55,7 +55,7 @@ endif
 # SK_DBGCAT_DRV_INT_SRC         0x04000000      interrupts sources
 # SK_DBGCAT_DRV_EVENT           0x08000000      driver events
 
-EXTRA_CFLAGS += -I. -DSK_USE_CSUM $(DBGDEF)
+EXTRA_CFLAGS += -Idrivers/net/sk98lin -DSK_USE_CSUM $(DBGDEF)
 
 include $(TOPDIR)/Rules.make
 

drivers/net/skfp/Makefile

@@ -17,7 +17,7 @@ skfp-objs :=  skfddi.o    hwmtm.o    fplustm.o  smt.o      cfm.o     \
 #   projects. To keep the source common for all those drivers (and
 #   thus simplify fixes to it), please do not clean it up!
 
-EXTRA_CFLAGS += -I. -DPCI -DMEM_MAPPED_IO -Wno-strict-prototypes 
+EXTRA_CFLAGS += -Idrivers/net/skfp -DPCI -DMEM_MAPPED_IO -Wno-strict-prototypes 
 
 include $(TOPDIR)/Rules.make
 

drivers/scsi/sym53c8xx_2/Makefile

@@ -3,7 +3,5 @@
 sym53c8xx-objs := sym_fw.o sym_glue.o sym_hipd.o sym_malloc.o sym_misc.o sym_nvram.o
 obj-$(CONFIG_SCSI_SYM53C8XX_2) := sym53c8xx.o
 
-EXTRA_CFLAGS += -I.
-
 include $(TOPDIR)/Rules.make
 

drivers/usb/storage/Makefile

@@ -5,7 +5,7 @@
 # Rewritten to use lists instead of if-statements.
 #
 
-EXTRA_CFLAGS	:= -I../../scsi/
+EXTRA_CFLAGS	:= -Idrivers/scsi
 
 obj-$(CONFIG_USB_STORAGE)	+= usb-storage.o
 

fs/xfs/Makefile

@@ -32,10 +32,10 @@
 # Makefile for XFS on Linux.
 #
 
-# This needs -I. because everything does #include <xfs.h> instead of "xfs.h".
+# This needs -I because everything does #include <xfs.h> instead of "xfs.h".
 # The code is wrong, local files should be included using "xfs.h", not <xfs.h>
 # but I am not going to change every file at the moment.
-EXTRA_CFLAGS +=	 -I. -funsigned-char
+EXTRA_CFLAGS +=	 -Ifs/xfs -funsigned-char
 
 ifeq ($(CONFIG_XFS_DEBUG),y)
 	EXTRA_CFLAGS += -g -DSTATIC="" -DDEBUG -DXFSDEBUG
@@ -154,6 +154,6 @@ ifneq ($(CONFIG_KDB_MODULES),)
   endif
 endif
 
-CFLAGS_xfsidbg.o += -I $(TOPDIR)/arch/$(ARCH)/kdb
+CFLAGS_xfsidbg.o += -Iarch/$(ARCH)/kdb
 
 include $(TOPDIR)/Rules.make