Merge git://git.kernel.org/pub/scm/linux/kernel/git/sam/fix-kbuild

* git://git.kernel.org/pub/scm/linux/kernel/git/sam/fix-kbuild:
  kbuild: fix building with O=.. options
  kbuild: fix building with redirected output.

Makefile

@@ -108,6 +108,9 @@ endif
 PHONY := _all
 _all:
 
+# Cancel implicit rules on top Makefile
+$(CURDIR)/Makefile Makefile: ;
+
 ifneq ($(KBUILD_OUTPUT),)
 # Invoke a second make in the output directory, passing relevant variables
 # check that the output directory actually exists
@@ -115,13 +118,10 @@ saved-output := $(KBUILD_OUTPUT)
 KBUILD_OUTPUT := $(shell cd $(KBUILD_OUTPUT) && /bin/pwd)
 $(if $(KBUILD_OUTPUT),, \
      $(error output directory "$(saved-output)" does not exist))
-# Check that OUTPUT directory is not the same as where we have kernel src
-$(if $(filter-out $(KBUILD_OUTPUT),$(shell /bin/pwd)),, \
-     $(error Output directory (O=...) specifies kernel src dir))
 
 PHONY += $(MAKECMDGOALS) sub-make
 
-$(filter-out _all sub-make,$(MAKECMDGOALS)) _all: sub-make
+$(filter-out _all sub-make $(CURDIR)/Makefile, $(MAKECMDGOALS)) _all: sub-make
 	$(Q)@:
 
 sub-make: FORCE
@@ -291,7 +291,8 @@ export quiet Q KBUILD_VERBOSE
 # Look for make include files relative to root of kernel src
 MAKEFLAGS += --include-dir=$(srctree)
 
-# We need some generic definitions.
+# We need some generic definitions (do not try to remake the file).
+$(srctree)/scripts/Kbuild.include: ;
 include $(srctree)/scripts/Kbuild.include
 
 # Make variables (CC, etc...)
@@ -1560,9 +1561,6 @@ endif	# skip-makefile
 PHONY += FORCE
 FORCE:
 
-# Cancel implicit rules on top Makefile, `-rR' will apply to sub-makes.
-Makefile: ;
-
 # Declare the contents of the .PHONY variable as phony.  We keep that
 # information in a variable se we can use it in if_changed and friends.
 .PHONY: $(PHONY)

scripts/mkmakefile

@@ -11,6 +11,12 @@
 
 
 test ! -r $2/Makefile -o -O $2/Makefile || exit 0
+# Only overwrite automatically generated Makefiles
+# (so we do not overwrite kernel Makefile)
+if ! grep -q Automatically $2/Makefile
+then
+	exit 0
+fi
 echo "  GEN     $2/Makefile"
 
 cat << EOF > $2/Makefile