On 2025-09-24 16:20:55+0200, Benjamin Berg wrote:
From: Benjamin Berg benjamin.berg@intel.com
Add NOLIBC_CFLAGS and NOLIBC_OBJS to build files against nolibc rather than libc. With this it is possible to move to nolibc in smaller steps.
Set NOLIBC_IGNORE_ERRNO, as the nolibc errno implementation is overly simple and cannot handle threading. nolibc provides sys_* functions that do not emulate the libc errno behaviour and can be used instead.
Leave the syscall definition for kernel code for now, but guard it as it is a macro in nolibc.
Signed-off-by: Benjamin Berg benjamin.berg@intel.com
v3:
- Change the syscall guard to use __KERNEL__
v2:
- Do not include nolibc.h via CFLAGS
- Make syscall guard more explicit
- Remove __UM_NOLIBC__ define, it is not needed
- Fix out-of-tree building
arch/um/Makefile | 20 +++++++++++++++++++- arch/um/include/shared/os.h | 2 ++ arch/um/include/shared/user.h | 1 - arch/um/scripts/Makefile.rules | 8 +++++++- 4 files changed, 28 insertions(+), 3 deletions(-)
diff --git a/arch/um/Makefile b/arch/um/Makefile index f7c509262568..c3a81df50911 100644 --- a/arch/um/Makefile +++ b/arch/um/Makefile @@ -78,6 +78,24 @@ USER_CFLAGS = $(patsubst $(KERNEL_DEFINES),,$(patsubst -I%,,$(KBUILD_CFLAGS))) \ -include $(srctree)/include/linux/kern_levels.h \ -include $(srctree)/$(ARCH_DIR)/include/shared/user.h +NOLIBC_CFLAGS = $(patsubst $(KERNEL_DEFINES),,$(patsubst -I%,,$(KBUILD_CFLAGS))) \
$(ARCH_INCLUDE) $(MODE_INCLUDE) $(filter -I%,$(CFLAGS)) \-I $(srctree)/tools/include \-D__EXPORTED_HEADERS__ \-D__UM_HOST__ \-DNOLIBC_NO_RUNTIME \-DNOLIBC_IGNORE_ERRNO \-nostdlib -nostdinc -static \-I$(srctree)/include/uapi \-I$(srctree)/$(HOST_DIR)/include/uapi \-I$(objtree)/$(HOST_DIR)/include/generated/uapi \-I $(srctree)/tools/include/nolibc \-I $(srctree)/usr/include \
This looks incorrect. The UAPI headers would be installed to $(objtree). But UML does not even use CONFIG_HEADERS_INSTALL. Also the whitespace is inconsistent between different lines.
-include $(objtree)/include/generated/autoconf.h \-include $(srctree)/tools/include/linux/kconfig.h \-include $(srctree)/include/linux/kern_levels.h \-include $(srctree)/$(ARCH_DIR)/include/shared/user.h#This will adjust *FLAGS accordingly to the platform. include $(srctree)/$(ARCH_DIR)/Makefile-os-Linux @@ -160,4 +178,4 @@ archclean: -o -name '*.gcov' ) -type f -print | xargs rm -f $(Q)$(MAKE) -f $(srctree)/Makefile ARCH=$(HEADER_ARCH) clean -export HEADER_ARCH SUBARCH USER_CFLAGS CFLAGS_NO_HARDENING DEV_NULL_PATH +export HEADER_ARCH SUBARCH USER_CFLAGS NOLIBC_CFLAGS CFLAGS_NO_HARDENING DEV_NULL_PATH
(...)