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)))
On Tue, Sep 06, 2005 at 10:13:52PM +0200, Andreas Gruenbacher wrote:
> 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.
I've already included below patch from you.
It was included in -linus last night.
Do we really need more?
Sam
diff-tree d80e22460968ec7986c82fd7d207ebe3de59e03d (from c5f75eca120de6587e67a1951ce3e6912e2c6879)
Author: Sam Ravnborg <sam@mars.(none)>
Date: Thu Jul 14 20:22:39 2005 +0000
kbuild: Don't fail if include/asm symlink exists
From: Andreas Gruenbacher <[email protected]>
We're having the following situation: There are user-space applications
that include kernel headers directly. With a completely unconfigured
/usr/src/linux tree, including most headers fails because essential
files are not there:
include/asm
include/linux/autoconf.h
include/linux/version.h
So we create these files. On the other hand, we want to use
/usr/src/linux as read-only source for building kernels or additional
modules. Now when building a kernel with a separate output directory
(O=), there is a check in the main makefile for the include/asm symlink.
There is no real need for this check: if we ensure that
$(objdir)/include/asm is always created as the patch does,
$(srctree)/include/asm becomes irrelevant.
Signed-off-by: Sam Ravnborg <[email protected]>
diff --git a/Makefile b/Makefile
--- a/Makefile
+++ b/Makefile
@@ -765,11 +765,11 @@ $(vmlinux-dirs): prepare-all scripts
# 2) Create the include2 directory, used for the second asm symlink
prepare2:
ifneq ($(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; \
fi;
$(Q)if [ ! -d include2 ]; then mkdir -p include2; fi;
@@ -777,11 +777,12 @@ ifneq ($(KBUILD_SRC),)
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 include/linux/version.h $(objtree)/include/asm \
+ include/config/MARKER
ifneq ($(KBUILD_MODULES),)
$(Q)rm -rf $(MODVERDIR)
$(Q)mkdir -p $(MODVERDIR)
endif
@@ -816,11 +817,11 @@ export CPPFLAGS_vmlinux.lds += -P -C -U$
# FIXME: The asm symlink changes when $(ARCH) changes. That's
# hard to detect, but I suppose "make mrproper" is a good idea
# before switching between archs anyway.
-include/asm:
+$(objtree)/include/asm:
@echo ' SYMLINK $@ -> include/asm-$(ARCH)'
$(Q)if [ ! -d include ]; then mkdir -p include; fi;
@ln -fsn asm-$(ARCH) $@
# Split autoconf.h into include/linux/config/*
On Tuesday 06 September 2005 22:25, Sam Ravnborg wrote:
> I've already included below patch from you.
> It was included in -linus last night.
That was close.
> Do we really need more?
So it seems I'm afraid: With the version of this patch that just went
in, Jan Beulich <[email protected]> found a bug when building
vmlinux.lds on i386. He triggered it by by putting poisoned version.h and
autoconf.h files in /usr/src/linux.
With the additional changes (rediff against linux-2.6.13-git6
below), things work as expected. There may be a slightly
more minimalistic solution that also works --- I didn't want to risk
strange failures.
(To not confuse people, let me add that this all doesn't matter if the
source tree is distclean.)
Cheers,
Andreas.
Additional fixes for building with O= against a non-distclean tree
Signed-off-by: Andreas Gruenbacher <[email protected]>
Index: linux-2.6.13-git6/Makefile
===================================================================
--- linux-2.6.13-git6.orig/Makefile
+++ linux-2.6.13-git6/Makefile
@@ -462,7 +462,7 @@ ifeq ($(KBUILD_EXTMOD),)
scripts: scripts_basic include/config/MARKER
$(Q)$(MAKE) $(build)=$(@)
-scripts_basic: include/linux/autoconf.h
+scripts_basic: $(objtree)/include/linux/autoconf.h
# Objects we will link into vmlinux / subdirs we need to visit
init-y := init/
@@ -488,11 +488,11 @@ include .config
# If .config is newer than include/linux/autoconf.h, someone tinkered
# with it and forgot to run make oldconfig
-include/linux/autoconf.h: .config
+$(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
@@ -798,7 +798,7 @@ endif
# prepare1 creates a makefile if using a separate output directory
prepare1: prepare2 outputmakefile
-prepare0: prepare1 include/linux/version.h include/asm \
+prepare0: prepare1 $(objtree)/include/linux/version.h $(objtree)/include/asm \
include/config/MARKER
ifneq ($(KBUILD_MODULES),)
$(Q)rm -rf $(MODVERDIR)
@@ -838,14 +838,15 @@ export CPPFLAGS_vmlinux.lds += -P -C -U$
# 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 $@
@@ -869,7 +870,7 @@ 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-git6/scripts/Makefile.lib
===================================================================
--- linux-2.6.13-git6.orig/scripts/Makefile.lib
+++ linux-2.6.13-git6/scripts/Makefile.lib
@@ -98,7 +98,7 @@ __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)),$(o)))
Unfortunately this isn't sufficient, yet. In the architecture-specific
makefiles asm-offsets.s (or however the specific architectures call
this) now need their dependencies on include/linux/version.h changed (I
wonder whether it wouldn't be more efficient to centralize these
dependencies into an architecture-independent file, perhaps at once
applying consistent naming across all architectures), and
arch/um/Makefile additionally has a dangling dependency on
include/linux/autoconf.h now.
greping all Make* across the tree easily shows all locations needing
additional changes.
Jan
>>> Andreas Gruenbacher <[email protected]> 07.09.05 03:03:44 >>>
On Tuesday 06 September 2005 22:25, Sam Ravnborg wrote:
> I've already included below patch from you.
> It was included in -linus last night.
That was close.
> Do we really need more?
So it seems I'm afraid: With the version of this patch that just went
in, Jan Beulich <[email protected]> found a bug when building
vmlinux.lds on i386. He triggered it by by putting poisoned version.h
and
autoconf.h files in /usr/src/linux.
With the additional changes (rediff against linux-2.6.13-git6
below), things work as expected. There may be a slightly
more minimalistic solution that also works --- I didn't want to risk
strange failures.
(To not confuse people, let me add that this all doesn't matter if the
source tree is distclean.)
Cheers,
Andreas.
Additional fixes for building with O= against a non-distclean tree
Signed-off-by: Andreas Gruenbacher <[email protected]>
Index: linux-2.6.13-git6/Makefile
===================================================================
--- linux-2.6.13-git6.orig/Makefile
+++ linux-2.6.13-git6/Makefile
@@ -462,7 +462,7 @@ ifeq ($(KBUILD_EXTMOD),)
scripts: scripts_basic include/config/MARKER
$(Q)$(MAKE) $(build)=$(@)
-scripts_basic: include/linux/autoconf.h
+scripts_basic: $(objtree)/include/linux/autoconf.h
# Objects we will link into vmlinux / subdirs we need to visit
init-y := init/
@@ -488,11 +488,11 @@ include .config
# If .config is newer than include/linux/autoconf.h, someone tinkered
# with it and forgot to run make oldconfig
-include/linux/autoconf.h: .config
+$(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
@@ -798,7 +798,7 @@ endif
# prepare1 creates a makefile if using a separate output directory
prepare1: prepare2 outputmakefile
-prepare0: prepare1 include/linux/version.h include/asm \
+prepare0: prepare1 $(objtree)/include/linux/version.h
$(objtree)/include/asm \
include/config/MARKER
ifneq ($(KBUILD_MODULES),)
$(Q)rm -rf $(MODVERDIR)
@@ -838,14 +838,15 @@ export CPPFLAGS_vmlinux.lds += -P -C -U$
# 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 $@
@@ -869,7 +870,7 @@ 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-git6/scripts/Makefile.lib
===================================================================
--- linux-2.6.13-git6.orig/scripts/Makefile.lib
+++ linux-2.6.13-git6/scripts/Makefile.lib
@@ -98,7 +98,7 @@ __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)),$(o)))
On Wed, Sep 07, 2005 at 09:19:43AM +0200, Jan Beulich wrote:
> Unfortunately this isn't sufficient, yet. In the architecture-specific
> makefiles asm-offsets.s (or however the specific architectures call
> this) now need their dependencies on include/linux/version.h changed (I
> wonder whether it wouldn't be more efficient to centralize these
> dependencies into an architecture-independent file, perhaps at once
> applying consistent naming across all architectures)
This topic has been on my mind to implment over a long time.
So I took a stamp on it and it hit -linus this night.
Dependencies on arch/$(ARCH)/kernel/asm-offsets.s is now tracked
like any other dependency - so we now at last have full dependency
checks for asm-offsets.h.
Take a look at the Kbuild file in the top-level directory.
With respect to the patch posted below I recall I had to zap
two $(objtree) to fix alpha build.
Patch by Jan Dittmer - see 946dc121d7d1c606f6bbeb8ae778963a1e2ff59c
But that may have changed now after introducing generic asm-offsets.h
support.
Sam