On Tue, Jun 17, 2025 at 12:35:07AM +0900, Masahiro Yamada wrote: > On Wed, Jun 11, 2025 at 4:38 PM Thomas Weißschuh > <thomas.weissschuh@xxxxxxxxxxxxx> wrote: > > > > Userprogs are built with the regular kernel compiler $CC. > > A kernel compiler does not necessarily contain a libc which is required > > for a normal userspace application. > > However the kernel tree does contain a minimal libc implementation > > "nolibc" which can be used to build userspace applications. > > > > Introduce support to build userprogs against nolibc instead of the > > default libc of the compiler, which may not exist. > > > > Signed-off-by: Thomas Weißschuh <thomas.weissschuh@xxxxxxxxxxxxx> > > > > --- > > This could probably be moved out of the generic kbuild makefiles. > > I think the ergonimics would suffer and this functionality could be > > used by other users of userprogs. > > > > Also this does currently not support out-of-tree builds. > > For that tools/include/nolibc/*.h and usr/include/*.h would need to be > > installed into the build directory. <snip> > > --- a/scripts/Makefile.userprogs > > +++ b/scripts/Makefile.userprogs > > @@ -16,10 +16,17 @@ user-csingle := $(addprefix $(obj)/, $(user-csingle)) > > user-cmulti := $(addprefix $(obj)/, $(user-cmulti)) > > user-cobjs := $(addprefix $(obj)/, $(user-cobjs)) > > > > +user_nolibc_ccflags := -nostdlib -nostdinc -static -fno-ident -fno-asynchronous-unwind-tables \ > > + -ffreestanding -fno-stack-protector \ > > + -isystem $(objtree)/usr/include -include $(srctree)/tools/include/nolibc/nolibc.h -isystem $(srctree)/tools/include/nolibc/ > > The tools/ directory is a different world, and Kbuild scripts do not know > anything about it. Ack. How does this statement affect the next patch which creates tools/include/nolibc/Kconfig.nolibc ? Is it fine to create the Kconfig file in tools/ or should I move it? I do want to maintain this file as part of nolibc and not KUnit. The possibilities I see are init/Kconfig.nolibc or lib/Kconfig.nolibc. > And, you do not need to implement this in scripts/Makefile.userprogs > because you can move this to lib/kunit/Makefile.kunit-uapi or somewhere. Understood. This is not unexpected, as hinted in the commit message. > > +user_nolibc_ldflags := -nostdlib -nostdinc -static > > + > > user_ccflags = -Wp,-MMD,$(depfile) $(KBUILD_USERCFLAGS) $(userccflags) \ > > - $($(target-stem)-userccflags) > > -user_ldflags = $(KBUILD_USERLDFLAGS) $(userldflags) $($(target-stem)-userldflags) > > -user_ldlibs = $(userldlibs) $($(target-stem)-userldlibs) > > + $($(target-stem)-userccflags) $(if $($(target-stem)-nolibc),$(user_nolibc_ccflags)) > > +user_ldflags = $(KBUILD_USERLDFLAGS) $(userldflags) $($(target-stem)-userldflags) \ > > + $(if $($(target-stem)-nolibc),$(user_nolibc_ldflags)) > > +user_ldlibs = $(userldlibs) $($(target-stem)-userldlibs) \ > > + $(if $($(target-stem)-nolibc),$(user_nolibc_ldlibs)) > > > > # Create an executable from a single .c file > > quiet_cmd_user_cc_c = CC [U] $@ Thomas
