@@ -1363,7 +1363,7 @@ CLEAN_DIRS += $(MODVERDIR) include/ksym
CLEAN_FILES += modules.builtin.modinfo
# Directories & files removed with 'make mrproper'
-MRPROPER_DIRS += include/config usr/include include/generated \
+MRPROPER_DIRS += include/config include/generated \
arch/$(SRCARCH)/include/generated .tmp_objdiff
MRPROPER_FILES += .config .config.old .version \
Module.symvers tags TAGS cscope* GPATH GTAGS GRTAGS GSYMS \
@@ -105,6 +105,17 @@ config HEADER_TEST
If you are a developer or tester and want to ensure the requested
headers are self-contained, say Y here. Otherwise, choose N.
+config UAPI_HEADER_TEST
+ bool "Compile test UAPI headers"
+ depends on HEADER_TEST && HEADERS_INSTALL
+ depends on $(success,$(srctree)/scripts/cc-system-headers.sh $(CC))
+ help
+ Compile test headers exported to user-space to ensure they are
+ self-contained, i.e. compilable as standalone units.
+
+ If you are a developer or tester and want to ensure the UAPI
+ headers are self-contained, say Y here. Otherwise, choose N.
+
config LOCALVERSION
string "Local version - append to kernel release"
help
new file mode 100755
@@ -0,0 +1,8 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0-only
+
+cat << "END" | $@ -E -x c - -o /dev/null >/dev/null 2>&1
+#include <stdlib.h>
+#include <sys/ioctl.h>
+#include <sys/time.h>
+END
@@ -7,4 +7,3 @@ initramfs_data.cpio.gz
initramfs_data.cpio.bz2
initramfs_data.cpio.lzma
initramfs_list
-include
@@ -56,3 +56,5 @@ $(deps_initramfs): klibcdirs
$(obj)/$(datafile_y): $(obj)/gen_init_cpio $(deps_initramfs) klibcdirs
$(Q)$(initramfs) -l $(ramfs-input) > $(obj)/$(datafile_d_y)
$(call if_changed,initfs)
+
+subdir-$(CONFIG_UAPI_HEADER_TEST) += include
new file mode 100644
@@ -0,0 +1,3 @@
+*
+!.gitignore
+!Makefile
new file mode 100644
@@ -0,0 +1,132 @@
+# SPDX-License-Identifier: GPL-2.0-only
+
+# Unlike the kernel space, uapi headers are written in more strict C.
+# - Forbid C++ style comments
+# - Use '__inline', '__asm__' instead of 'inline', 'asm'
+#
+# -std=c90 (equivalent to -ansi) catches the violation of those.
+# We cannot go as far as adding -Wpedantic since it emits too many warnings.
+#
+# REVISIT: re-consider the proper set of compiler flags for uapi compile-test.
+
+UAPI_CFLAGS := -std=c90 -Wall -Werror=implicit-function-declaration
+
+override c_flags = $(UAPI_CFLAGS) -Wp,-MD,$(depfile) -I$(objtree)/usr/include
+
+# We want to compile as many headers as possible. We collect all headers
+# by using the wildcard, then filter-out some later.
+all-uapi-headers = $(shell cd $(obj) && find * -name '*.h')
+
+# asm-generic/*.h is used by asm/*.h, and should not be included directly
+no-header-test += asm-generic/%.h
+
+# The following are excluded for now just because they fail to build.
+# The cause of errors are mostly missing include directives.
+# Check one by one, and send a patch to each subsystem.
+#
+# Do not add a new header to the list without legitimate reason.
+# Please consider to fix the header first.
+no-header-test += asm/ipcbuf.h
+no-header-test += asm/msgbuf.h
+no-header-test += asm/sembuf.h
+no-header-test += asm/shmbuf.h
+no-header-test += asm/signal.h
+no-header-test += asm/ucontext.h
+no-header-test += drm/vmwgfx_drm.h
+no-header-test += linux/am437x-vpfe.h
+no-header-test += linux/android/binderfs.h
+no-header-test += linux/android/binder.h
+no-header-test += linux/coda.h
+no-header-test += linux/coda_psdev.h
+no-header-test += linux/dvb/audio.h
+no-header-test += linux/dvb/osd.h
+no-header-test += linux/elfcore.h
+no-header-test += linux/errqueue.h
+no-header-test += linux/fsmap.h
+no-header-test += linux/hdlc/ioctl.h
+no-header-test += linux/jffs2.h
+no-header-test += linux/kexec.h
+no-header-test += linux/matroxfb.h
+no-header-test += linux/netfilter_bridge/ebtables.h
+no-header-test += linux/netfilter_ipv4/ipt_LOG.h
+no-header-test += linux/netfilter_ipv6/ip6t_LOG.h
+no-header-test += linux/nfc.h
+no-header-test += linux/nilfs2_ondisk.h
+no-header-test += linux/omap3isp.h
+no-header-test += linux/omapfb.h
+no-header-test += linux/patchkey.h
+no-header-test += linux/phonet.h
+no-header-test += linux/reiserfs_xattr.h
+no-header-test += linux/scc.h
+no-header-test += linux/sctp.h
+no-header-test += linux/signal.h
+no-header-test += linux/sysctl.h
+no-header-test += linux/usb/audio.h
+no-header-test += linux/ivtv.h
+no-header-test += linux/v4l2-mediabus.h
+no-header-test += linux/v4l2-subdev.h
+no-header-test += linux/videodev2.h
+no-header-test += linux/vm_sockets.h
+no-header-test += misc/ocxl.h
+no-header-test += scsi/scsi_bsg_fc.h
+no-header-test += scsi/scsi_netlink_fc.h
+no-header-test += scsi/scsi_netlink.h
+no-header-test += sound/asequencer.h
+no-header-test += sound/asound.h
+no-header-test += sound/asoc.h
+no-header-test += sound/compress_offload.h
+no-header-test += sound/emu10k1.h
+no-header-test += sound/sfnt_info.h
+no-header-test += sound/sof/eq.h
+no-header-test += sound/sof/fw.h
+no-header-test += sound/sof/header.h
+no-header-test += sound/sof/manifest.h
+no-header-test += sound/sof/trace.h
+no-header-test += xen/evtchn.h
+no-header-test += xen/gntdev.h
+no-header-test += xen/privcmd.h
+
+# more headers are broken in some architectures
+
+ifeq ($(SRCARCH),arc)
+no-header-test += linux/bpf_perf_event.h
+endif
+
+ifeq ($(SRCARCH),ia64)
+no-header-test += asm/setup.h
+no-header-test += asm/sigcontext.h
+no-header-test += asm/perfmon.h
+no-header-test += asm/perfmon_default_smpl.h
+no-header-test += linux/if_bonding.h
+endif
+
+ifeq ($(SRCARCH),mips)
+no-header-test += asm/stat.h
+endif
+
+ifeq ($(SRCARCH),powerpc)
+no-header-test += asm/stat.h
+no-header-test += linux/bpf_perf_event.h
+endif
+
+ifeq ($(SRCARCH),riscv)
+no-header-test += linux/bpf_perf_event.h
+endif
+
+ifeq ($(SRCARCH),s390)
+no-header-test += asm/runtime_instr.h
+no-header-test += asm/zcrypt.h
+endif
+
+ifeq ($(SRCARCH),sparc)
+no-header-test += asm/stat.h
+no-header-test += asm/uctx.h
+no-header-test += asm/fbio.h
+no-header-test += asm/openpromio.h
+endif
+
+# Use '=' instead of ':=' to avoid $(shell ...) evaluation when cleaning
+header-test-y = $(filter-out $(no-header-test), $(all-uapi-headers))
+
+# Use '=' instead of ':=' to avoid $(shell ...) evaluation when building
+clean-dirs = $(shell cd $(obj) 2>/dev/null && find * -maxdepth 0 -type d)
Multiple people have suggested compile-testing UAPI headers to ensure they can be really included from user-space. "make headers_check" is obviously not enough to catch bugs, and we often leak references to kernel-space definition to user-space. The most recent patch I know is David Howells' work: https://patchwork.kernel.org/patch/10590203/ While I agree that we should do this, we must consider how it can be integrated cleanly. That is why it has not been supported in the mainline yet. The idea that has been in my mind is to compile every UAPI header so that it can be included without relying on any include order. Please note usr/include/ is built with a completely different set of compiler flags. The header search path is set to $(objtree)/usr/include since UAPI headers should not include unexported headers. We use -std=gnu89 for the kernel space since the kernel code highly depends on GNU extensions. On the other hand, UAPI headers should be written in somewhat strict C, so they are compiled with -std=c89. This will catch C++ style comments, the keyword 'inline', etc. ('__inline__' should be used instead). There is additional compiler requirement for building under usr/include. because many of UAPI headers include <stdlib.h>, <sys/ioctl.h>, <sys/time.h>, etc. directly or indirectly. You can use kernel.org prebuilt toolchains for building the kernel (https://mirrors.edge.kernel.org/pub/tools/crosstool/index.html) but they do not provide <stdlib.h> etc. If you want to compile test UAPI headers, you need to use full-featured compilers, which are usually provided by distributions. I added scripts/cc-system-headers.sh to check if necessary system headers are available, which CONFIG_UAPI_HEADER_TEST depends on. For now, a lot of headers need to be excluded because they cannot be compiled standalone, but this is a good start point. Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com> --- Makefile | 2 +- init/Kconfig | 11 +++ scripts/cc-system-headers.sh | 8 +++ usr/.gitignore | 1 - usr/Makefile | 2 + usr/include/.gitignore | 3 + usr/include/Makefile | 132 +++++++++++++++++++++++++++++++++++ 7 files changed, 157 insertions(+), 2 deletions(-) create mode 100755 scripts/cc-system-headers.sh create mode 100644 usr/include/.gitignore create mode 100644 usr/include/Makefile