On Thu, Apr 23, 2020 at 4:40 PM Masahiro Yamada <masahiroy@xxxxxxxxxx> wrote: > > Kbuild supports the infrastructure to build host programs, but there > was no support to build userspace programs for the target architecture > (i.e. the same architecture as the kernel). > > Sam Ravnborg worked on this a long time ago. > > https://lkml.org/lkml/2014/7/13/154 > > But, it was not merged. One problem at that time was, there was no > good way to know whether $(CC) can link standalone programs. In fact, > pre-built kernel.org toolchains [1] do not provide libc. > > Now, we can handle this cleanly because the compiler capability is > evaluated at the Kconfig time. If $(CC) cannot link standalone programs, > the relevant options are hidden by 'depends on CC_CAN_LINK'. > > The implementation just mimics scripts/Makefile.host > > The userspace programs are compiled with the same flags as the host > programs. In addition, it uses -m32 or -m64 if it is found in > $(KBUILD_CFLAGS). > > This new syntax has at least two usecases. > > - Sample programs > > Several userspace programs under samples/ include UAPI headers > installed in usr/include. Most of them were previously built for > the host architecture just to use 'hostprogs' syntax. > > However, 'make headers' always works for the target architecture. > This caused the arch mismatch in cross-compiling. To fix this > distortion, sample code should be built for the target architecture. > > - Bpfilter > > net/bpfilter/Makefile compiles bpfilter_umh as the user mode helper, > and embeds it into the kernel code. Currently, it overrides HOSTCC > with CC to use the 'hostprogs' syntax. This hack should go away. > > [1]: https://mirrors.edge.kernel.org/pub/tools/crosstool/ > Signed-off-by: Masahiro Yamada <masahiroy@xxxxxxxxxx> > --- > > Makefile | 11 +++++++--- > scripts/Makefile.build | 5 +++++ > scripts/Makefile.clean | 2 +- > scripts/Makefile.userprogs | 44 ++++++++++++++++++++++++++++++++++++++ > 4 files changed, 58 insertions(+), 4 deletions(-) > create mode 100644 scripts/Makefile.userprogs > > diff --git a/Makefile b/Makefile > index 49b2709ff44e..f20597820131 100644 > --- a/Makefile > +++ b/Makefile > @@ -406,9 +406,11 @@ else > HOSTCC = gcc > HOSTCXX = g++ > endif > -KBUILD_HOSTCFLAGS := -Wall -Wmissing-prototypes -Wstrict-prototypes -O2 \ > - -fomit-frame-pointer -std=gnu89 $(HOST_LFS_CFLAGS) \ > - $(HOSTCFLAGS) > + > +export KBUILD_USERCFLAGS := -Wall -Wmissing-prototypes -Wstrict-prototypes \ > + -O2 -fomit-frame-pointer -std=gnu89 > + > +KBUILD_HOSTCFLAGS := $(KBUILD_USERCFLAGS) $(HOST_LFS_CFLAGS) $(HOSTCFLAGS) > KBUILD_HOSTCXXFLAGS := -Wall -O2 $(HOST_LFS_CFLAGS) $(HOSTCXXFLAGS) > KBUILD_HOSTLDFLAGS := $(HOST_LFS_LDFLAGS) $(HOSTLDFLAGS) > KBUILD_HOSTLDLIBS := $(HOST_LFS_LIBS) $(HOSTLDLIBS) > @@ -937,6 +939,9 @@ ifeq ($(CONFIG_RELR),y) > LDFLAGS_vmlinux += --pack-dyn-relocs=relr > endif > > +# Align the bit size of userspace programs with the kernel > +KBUILD_USERCFLAGS += $(filter -m32 -m64, $(KBUILD_CFLAGS)) > + > # make the checker run with the right architecture > CHECKFLAGS += --arch=$(ARCH) > > diff --git a/scripts/Makefile.build b/scripts/Makefile.build > index 9fcbfac15d1d..94f2f7016172 100644 > --- a/scripts/Makefile.build > +++ b/scripts/Makefile.build > @@ -50,6 +50,11 @@ ifneq ($(hostprogs)$(hostcxxlibs-y)$(hostcxxlibs-m),) > include scripts/Makefile.host > endif > > +# Do not include userprogs rules unless needed > +ifneq ($(userprogs),) > +include scripts/Makefile.userprogs > +endif > + > ifndef obj > $(warning kbuild: Makefile.build is included improperly) > endif > diff --git a/scripts/Makefile.clean b/scripts/Makefile.clean > index 075f0cc2d8d7..e2c76122319d 100644 > --- a/scripts/Makefile.clean > +++ b/scripts/Makefile.clean > @@ -29,7 +29,7 @@ subdir-ymn := $(addprefix $(obj)/,$(subdir-ymn)) > > __clean-files := $(extra-y) $(extra-m) $(extra-) \ > $(always) $(always-y) $(always-m) $(always-) $(targets) $(clean-files) \ > - $(hostprogs) $(hostprogs-y) $(hostprogs-m) $(hostprogs-) \ > + $(hostprogs) $(hostprogs-y) $(hostprogs-m) $(hostprogs-) $(userprogs) \ > $(hostcxxlibs-y) $(hostcxxlibs-m) > > __clean-files := $(filter-out $(no-clean-files), $(__clean-files)) > diff --git a/scripts/Makefile.userprogs b/scripts/Makefile.userprogs > new file mode 100644 > index 000000000000..0d987085819b > --- /dev/null > +++ b/scripts/Makefile.userprogs > @@ -0,0 +1,44 @@ > +# SPDX-License-Identifier: GPL-2.0-only > +# > +# Build userspace programs for the target system > +# > + > +userprogs := $(sort $(userprogs)) > + > +# Executables compiled from a single .c file > +user-csingle := $(foreach m, $(userprogs), $(if $($(m)-objs),,$(m))) > + > +# C executables linked based on several .o files > +user-cmulti := $(foreach m, $(userprogs), $(if $($(m)-objs),$(m))) > + > +# Object (.o) files compiled from .c files > +user-cobjs := $(foreach m, $(userprogs), $($(m)-objs)) > + > +user-csingle := $(addprefix $(obj)/, $(user-csingle)) > +user-cmulti := $(addprefix $(obj)/, $(user-cmulti)) > +user-cobjs := $(addprefix $(obj)/, $(user-cobjs)) > + > +user_c_flags = -Wp,-MMD,$(depfile) $(KBUILD_USERCFLAGS) $(user-ccflags) \ > + $($(target-stem)-ccflags) > + > +# Create an executable from a single .c file > +quiet_cmd_user_cc_c = CC [U] $@ > + cmd_user_cc_c = $(CC) $(user_c_flags) -o $@ $< $($(target-stem)-ldlibs) is needed here too. > +$(user-csingle): $(obj)/%: $(src)/%.c FORCE > + $(call if_changed_dep,user_cc_c) > + > +# Link an executable based on list of .o files > +quiet_cmd_user_ld = LD [U] $@ > + cmd_user_ld = $(CC) -o $@ $(addprefix $(obj)/, $($(target-stem)-objs)) \ > + $($(target-stem)-ldlibs) > +$(user-cmulti): FORCE > + $(call if_changed,user_ld) > +$(call multi_depend, $(user-cmulti), , -objs) > + > +# Create .o file from a .c file > +quiet_cmd_user_cc_o_c = CC [U] $@ > + cmd_user_cc_o_c = $(CC) $(user_c_flags) -c -o $@ $< > +$(user-cobjs): $(obj)/%.o: $(src)/%.c FORCE > + $(call if_changed_dep,user_cc_o_c) > + > +targets += $(user-csingle) $(user-cmulti) $(user-cobjs) > -- > 2.25.1 > -- Best Regards Masahiro Yamada
