kbuild: compile-test exported headers to ensure they are self-contained

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 unresolved
references to user-space.

Use the new header-test-y syntax to implement it. Please note exported
headers are compile-tested with a completely different set of compiler
flags. The header search path is set to $(objtree)/usr/include since
exported headers should not include unexported ones.

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 more standardized C, so they are compiled with -std=c90.
This will emit errors if C++ style comments, the keyword 'inline', etc.
are used. Please use C style comments (/* ... */), '__inline__', etc.
in UAPI headers.

There is additional compiler requirement to enable this test because
many of UAPI headers include <stdlib.h>, <sys/ioctl.h>, <sys/time.h>,
etc. directly or indirectly. You cannot use kernel.org pre-built
toolchains [1] since they lack <stdlib.h>.

I reused CONFIG_CC_CAN_LINK to check the system header availability.
The intention is slightly different, but a compiler that can link
userspace programs provide system headers.

For now, a lot of headers need to be excluded because they cannot
be compiled standalone, but this is a good start point.

[1] https://mirrors.edge.kernel.org/pub/tools/crosstool/index.html

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
This commit is contained in:
Masahiro Yamada 2019-07-01 09:58:40 +09:00
parent 1a927fd347
commit d6fc9fcbaa
6 changed files with 148 additions and 2 deletions

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@ -1378,7 +1378,7 @@ 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 \

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@ -108,6 +108,16 @@ 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 && CC_CAN_LINK
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 exported
headers are self-contained, say Y here. Otherwise, choose N.
config LOCALVERSION
string "Local version - append to kernel release"
help

1
usr/.gitignore vendored
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@ -7,4 +7,3 @@ initramfs_data.cpio.gz
initramfs_data.cpio.bz2
initramfs_data.cpio.lzma
initramfs_list
include

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@ -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

3
usr/include/.gitignore vendored Normal file
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@ -0,0 +1,3 @@
*
!.gitignore
!Makefile

132
usr/include/Makefile Normal file
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@ -0,0 +1,132 @@
# SPDX-License-Identifier: GPL-2.0-only
# Unlike the kernel space, exported headers are written in standard 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.
UAPI_CFLAGS := -std=c90 -Wall -Werror=implicit-function-declaration
override c_flags = $(UAPI_CFLAGS) -Wp,-MD,$(depfile) -I$(objtree)/usr/include
# The following are excluded for now because they fail to build.
#
# Do not add a new header to the blacklist without legitimate reason.
# Please consider to fix the header first.
#
# Sorted alphabetically.
header-test- += asm/ipcbuf.h
header-test- += asm/msgbuf.h
header-test- += asm/sembuf.h
header-test- += asm/shmbuf.h
header-test- += asm/signal.h
header-test- += asm/ucontext.h
header-test- += drm/vmwgfx_drm.h
header-test- += linux/am437x-vpfe.h
header-test- += linux/android/binder.h
header-test- += linux/android/binderfs.h
header-test-$(CONFIG_CPU_BIG_ENDIAN) += linux/byteorder/big_endian.h
header-test-$(CONFIG_CPU_LITTLE_ENDIAN) += linux/byteorder/little_endian.h
header-test- += linux/coda.h
header-test- += linux/coda_psdev.h
header-test- += linux/dvb/audio.h
header-test- += linux/dvb/osd.h
header-test- += linux/elfcore.h
header-test- += linux/errqueue.h
header-test- += linux/fsmap.h
header-test- += linux/hdlc/ioctl.h
header-test- += linux/ivtv.h
header-test- += linux/jffs2.h
header-test- += linux/kexec.h
header-test- += linux/matroxfb.h
header-test- += linux/netfilter_bridge/ebtables.h
header-test- += linux/netfilter_ipv4/ipt_LOG.h
header-test- += linux/netfilter_ipv6/ip6t_LOG.h
header-test- += linux/nfc.h
header-test- += linux/nilfs2_ondisk.h
header-test- += linux/omap3isp.h
header-test- += linux/omapfb.h
header-test- += linux/patchkey.h
header-test- += linux/phonet.h
header-test- += linux/reiserfs_xattr.h
header-test- += linux/scc.h
header-test- += linux/sctp.h
header-test- += linux/signal.h
header-test- += linux/sysctl.h
header-test- += linux/usb/audio.h
header-test- += linux/v4l2-mediabus.h
header-test- += linux/v4l2-subdev.h
header-test- += linux/videodev2.h
header-test- += linux/vm_sockets.h
header-test- += misc/ocxl.h
header-test- += mtd/mtd-abi.h
header-test- += mtd/mtd-user.h
header-test- += scsi/scsi_bsg_fc.h
header-test- += scsi/scsi_netlink.h
header-test- += scsi/scsi_netlink_fc.h
header-test- += sound/asequencer.h
header-test- += sound/asoc.h
header-test- += sound/asound.h
header-test- += sound/compress_offload.h
header-test- += sound/emu10k1.h
header-test- += sound/sfnt_info.h
header-test- += sound/sof/eq.h
header-test- += sound/sof/fw.h
header-test- += sound/sof/header.h
header-test- += sound/sof/manifest.h
header-test- += sound/sof/trace.h
header-test- += xen/evtchn.h
header-test- += xen/gntdev.h
header-test- += xen/privcmd.h
# More headers are broken in some architectures
ifeq ($(SRCARCH),arc)
header-test- += linux/bpf_perf_event.h
endif
ifeq ($(SRCARCH),ia64)
header-test- += asm/setup.h
header-test- += asm/sigcontext.h
header-test- += asm/perfmon.h
header-test- += asm/perfmon_default_smpl.h
header-test- += linux/if_bonding.h
endif
ifeq ($(SRCARCH),mips)
header-test- += asm/stat.h
endif
ifeq ($(SRCARCH),powerpc)
header-test- += asm/stat.h
header-test- += linux/bpf_perf_event.h
endif
ifeq ($(SRCARCH),riscv)
header-test- += linux/bpf_perf_event.h
endif
ifeq ($(SRCARCH),s390)
header-test- += asm/runtime_instr.h
header-test- += asm/zcrypt.h
endif
ifeq ($(SRCARCH),sparc)
header-test- += asm/stat.h
header-test- += asm/uctx.h
header-test- += asm/fbio.h
header-test- += asm/openpromio.h
endif
# asm-generic/*.h is used by asm/*.h, and should not be included directly
header-test- += asm-generic/%
# The rest are compile-tested
header-test-y += $(filter-out $(header-test-), \
$(patsubst $(obj)/%,%, $(wildcard \
$(addprefix $(obj)/, *.h */*.h */*/*.h */*/*/*.h))))
# For GNU Make <= 4.2.1, $(wildcard $(obj)/*/) matches to not only directories
# but also regular files. Use $(filter %/, ...) just in case.
clean-dirs += $(patsubst $(obj)/%/,%,$(filter %/, $(wildcard $(obj)/*/)))