[Buildroot] [PATCH v2] linux: Build and install kernel selftests

[Yann E. MORIN <yann.morin.1998@free.fr>]

Cyril, All,

On 2016-01-04 11:59 +1100, Cyril Bur spake thusly:
> This patch simply adds the ability to compile and install the kernel
> selftests into the target at /usr/lib/kselftests. The rationale behind
> /usr/lib is that the selftests have subdirectories where they are installed
> which makes them unsuitable to be placed in /usr/sbin as this would result
> in /usr/sbin/kselftests/x/y/z. While the selftests aren't libraries either,
> they don't achieve much as a standalone binary so they can be considered to
> be a 'library of tests' making /usr/lib sensible.
> 
> The selftests require that the kernel headers be installed into the kernel
> build tree as some of the selftests have a hardcoded CFLAGS to include
> kernel headers (CFLAGS += -I../../../../usr/include/). This is most easily
> achieved by using the make ... headers_install inside the kernel build dir.
> 
> This is likely to be a rarely used debugging/performance feature for
> development and unlikely to be used in a production configuration.

So I finally take some time to review this new iteration; sorry for the
delay... :-/

> Signed-off-by: Cyril Bur <cyrilbur@gmail.com>
> ---
[--SNIP--]
> diff --git a/linux/linux-tool-selftests.mk b/linux/linux-tool-selftests.mk
> new file mode 100644
> index 0000000..b610599
> --- /dev/null
> +++ b/linux/linux-tool-selftests.mk
> @@ -0,0 +1,42 @@
> +################################################################################
> +#
> +# selftests
> +#
> +################################################################################
> +
> +LINUX_TOOLS += selftests
> +
> +ifeq ($(KERNEL_ARCH),x86_64)

For i386, Buildroot sets KERNEL_ARCH=i386, so we may also want to handle
that case, no?

> +SELFTESTS_ARCH=x86

I know the other linux-tools don't, but I think we should call that
linux-selftests (so LINUX_SEFLTESTS_ARCH and so on) to avoid name
clashing with other packages.

> +else
> +SELFTESTS_ARCH=$(KERNEL_ARCH)
> +endif
> +
> +SELFTESTS_DEPENDENCIES = bash

It can also use libcap-ng, so you probably want to depend on it, too:

    /home/ymorin/dev/buildroot/O/host/usr/bin/i686-pc-linux-gnu-gcc -O2 -g
      -std=gnu99 -Wall    validate_cap.c  -lcap-ng -lrt -ldl -o validate_cap
    validate_cap.c:1:20: fatal error: cap-ng.h: No such file or directory

Ditto popt:

    /home/ymorin/dev/buildroot/O/host/opt/ext-toolchain/bin/../lib/gcc/
    i686-pc-linux-gnu/4.7.2/../../../../i686-pc-linux-gnu/bin/ld: cannot
    find -lpopt
    collect2: error: ld returned 1 exit status

However, as you said in the commit log, those are not fatal errors
(although reported as such) and the build goes on successfully for the
rest of the tests:

Reviewed-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Tested-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
[build-tested only, for i386]

Regards,
Yann E. MORIN.

> +SELFTESTS_MAKE_FLAGS = \
> +	$(LINUX_MAKE_FLAGS) \
> +	ARCH=$(SELFTESTS_ARCH)
> +
> +# O must be redefined here to overwrite the one used by Buildroot for
> +# out of tree build. We build the selftests in $(@D)/tools/selftests and
> +# not just $(@D) so that it isn't built in the root directory of the kernel
> +# sources.
> +#
> +# The headers_install step here is important as some kernel selftests use a
> +# hardcoded CFLAGS to find kernel headers e.g:
> +# CFLAGS += -I../../../../usr/include/
> +# The headers_install target will install the kernel headers locally inside
> +# the Linux build dir
> +define SELFTESTS_BUILD_CMDS
> +	$(TARGET_MAKE_ENV) $(MAKE1) -C $(@D) $(SELFTESTS_MAKE_FLAGS) \
> +		headers_install
> +	$(TARGET_MAKE_ENV) $(MAKE1) -C $(@D)/tools/testing/selftests \
> +		$(SELFTESTS_MAKE_FLAGS) O=$(@D)/tools/testing/selftests
> +endef
> +
> +define SELFTESTS_INSTALL_TARGET_CMDS
> +	$(TARGET_MAKE_ENV) $(MAKE1) -C $(@D)/tools/testing/selftests \
> +		$(SELFTESTS_MAKE_FLAGS) O=$(@D)/tools/testing/selftests \
> +		INSTALL_PATH=$(TARGET_DIR)/usr/lib/kselftests install
> +endef
> -- 
> 2.6.4
> 

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