When compiling a kernel with a separate output directory,
/var/tmp/kernel-obj> cp $CONFIG_FILE .config
/var/tmp/kernel-obj> make -C /usr/src/linux O=`pwd`
the main kernel Makefile first tries to make sure that /usr/src/linux
is a clean source tree by checking if /usr/src/linux contains .config
or the include/asm symlink. This test is more restrictive than
necessary, and can be relaxed with a few additional changes so that
/usr/src/linux may contain a few additional critical files, and may
still be used as the kernel compilation source.
The additional files I have in mind are include/asm,
include/linux/version.h, include/linux/autoconf.h, and perhaps also
include/asm/offset.h. With these files present, it's possible to use
kernel headers from user-space. I know that's evil and frowned upon,
but it's still done once in a while, and sometimes it's the least
painful path compared to the alternatives. The kbuild changes required
to allow this IMHO are harmless; please consider for inclusion.
Thanks,
Andreas.
Signed-off-by: Andreas Gruenbacher <[email protected]>
Index: linux-2.6.13-kbuild/Makefile
===================================================================
--- linux-2.6.13-kbuild.orig/Makefile
+++ linux-2.6.13-kbuild/Makefile
@@ -465,7 +465,7 @@ ifeq ($(KBUILD_EXTMOD),)
scripts: scripts_basic include/config/MARKER
$(Q)$(MAKE) $(build)=$(@)
-scripts_basic: include/linux/autoconf.h
+scripts_basic: $(objtree)/include/linux/autoconf.h
# Objects we will link into vmlinux / subdirs we need to visit
init-y := init/
@@ -491,11 +491,11 @@ include .config
# If .config is newer than include/linux/autoconf.h, someone tinkered
# with it and forgot to run make oldconfig
-include/linux/autoconf.h: .config
+$(objtree)/include/linux/autoconf.h: .config
$(Q)$(MAKE) -f $(srctree)/Makefile silentoldconfig
else
# Dummy target needed, because used as prerequisite
-include/linux/autoconf.h: ;
+$(objtree)/include/linux/autoconf.h: ;
endif
# The all: target is the default when no target is given on the
@@ -757,7 +757,7 @@ $(vmlinux-dirs): prepare-all scripts
prepare2:
ifneq ($(KBUILD_SRC),)
@echo ' Using $(srctree) as source for kernel'
- $(Q)if [ -h $(srctree)/include/asm -o -f $(srctree)/.config ]; then \
+ $(Q)if [ -f $(srctree)/.config ]; then \
echo " $(srctree) is not clean, please run 'make mrproper'";\
echo " in the '$(srctree)' directory.";\
/bin/false; \
@@ -769,7 +769,7 @@ endif
# prepare1 creates a makefile if using a separate output directory
prepare1: prepare2 outputmakefile
-prepare0: prepare1 include/linux/version.h include/asm include/config/MARKER
+prepare0: prepare1 $(objtree)/include/linux/version.h $(objtree)/include/asm include/config/MARKER
ifneq ($(KBUILD_MODULES),)
$(Q)rm -rf $(MODVERDIR)
$(Q)mkdir -p $(MODVERDIR)
@@ -808,14 +808,15 @@ export CPPFLAGS_vmlinux.lds += -P -C -U$
# hard to detect, but I suppose "make mrproper" is a good idea
# before switching between archs anyway.
-include/asm:
+include/asm: $(objtree)/include/asm
+$(objtree)/include/asm:
@echo ' SYMLINK $@ -> include/asm-$(ARCH)'
$(Q)if [ ! -d include ]; then mkdir -p include; fi;
@ln -fsn asm-$(ARCH) $@
# Split autoconf.h into include/linux/config/*
-include/config/MARKER: include/linux/autoconf.h
+include/config/MARKER: $(objtree)/include/linux/autoconf.h
@echo ' SPLIT include/linux/autoconf.h -> include/config/*'
@scripts/basic/split-include include/linux/autoconf.h include/config
@touch $@
@@ -839,7 +840,7 @@ define filechk_version.h
)
endef
-include/linux/version.h: $(srctree)/Makefile FORCE
+$(objtree)/include/linux/version.h: $(srctree)/Makefile FORCE
$(call filechk,version.h)
# ---------------------------------------------------------------------------
Index: linux-2.6.13-kbuild/scripts/Makefile.lib
===================================================================
--- linux-2.6.13-kbuild.orig/scripts/Makefile.lib
+++ linux-2.6.13-kbuild/scripts/Makefile.lib
@@ -112,7 +112,7 @@ __cpp_flags = $(_cpp_flags)
else
# Prefix -I with $(srctree) if it is not an absolute path
-addtree = $(if $(filter-out -I/%,$(1)),$(patsubst -I%,-I$(srctree)/%,$(1))) $(1)
+addtree = $(1) $(if $(filter-out -I/%,$(1)),$(patsubst -I%,-I$(srctree)/%,$(1)))
# Find all -I options and call addtree
flags = $(foreach o,$($(1)),$(if $(filter -I%,$(o)),$(call addtree,$(o)),$(o)))
-
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