kbuild: compile-test exported headers to ensure they are self-contained (d6fc9fcb) · Commits · 戴 / test

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>

Makefile

+1 −1

Original line number	Diff line number	Diff line
		@@ -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 \

init/Kconfig

+10 −0

Original line number	Diff line number	Diff line
		@@ -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

usr/.gitignore

+0 −1

Original line number	Diff line number	Diff line
		@@ -7,4 +7,3 @@ initramfs_data.cpio.gz
		initramfs_data.cpio.bz2
		initramfs_data.cpio.lzma
		initramfs_list
		include

usr/Makefile

+2 −0

Original line number	Diff line number	Diff line
		@@ -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

usr/include/.gitignore

0 → 100644

+3 −0

Original line number	Diff line number	Diff line
		*
		!.gitignore
		!Makefile

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