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

[Yann E. MORIN]

Cyril, All,

Sorry for the delay, but I'm now looking at this patch...

On 2015-11-25 10:53 +1100, Cyril Bur spake thusly:
> This patch simply adds the ability to compile and install the kernel
> selftests into the target.
> 
> This is likely to be a rarely used debugging/performance feature for
> development and unlikely to be used in a production configuration.
> 
> Signed-off-by: Cyril Bur <cyrilbur at gmail.com>
> ---
>  linux/Config.tools.in         | 12 ++++++++++++
>  linux/linux-tool-selftests.mk | 40 ++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 52 insertions(+)
>  create mode 100644 linux/linux-tool-selftests.mk
> 
> diff --git a/linux/Config.tools.in b/linux/Config.tools.in
> index 24ef8cd..68655dc 100644
> --- a/linux/Config.tools.in
> +++ b/linux/Config.tools.in
> @@ -26,4 +26,16 @@ config BR2_LINUX_KERNEL_TOOL_PERF
>  
>  	  https://perf.wiki.kernel.org/
>  
> +config BR2_LINUX_KERNEL_TOOL_SELFTESTS
> +	bool "selftests"

Since the .mk has:
    SELFTESTS_DEPENDENCIES = bash

then you must either depend on bash or select it here. I think a select
is better, so:

    depends on BR2_USE_MMU  # bash
    select BR2_PACKAGE_BASH

> +	help
> +	  Build and install (to /usr/lib/selftests) kernel selftests.

Why do you install in there?

I'm not sure what the kernel selftests are, but two options:
  - if they are executables, they should go into /usr/sbin
  - if they are libraries, they should go in /usr/lib

> +	  Use of this option implies you know the process using and compiling
> +	  the kernel selftests. The Makefile to build and install these is very
> +	  noisy and may appear to cause your build to fail for strange reasons.
> +
> +	  This is very much a use at your risk option and may not work for
> +	  every setup or every architecture.
> +
>  endmenu
> diff --git a/linux/linux-tool-selftests.mk b/linux/linux-tool-selftests.mk
> new file mode 100644
> index 0000000..573ba0c
> --- /dev/null
> +++ b/linux/linux-tool-selftests.mk
> @@ -0,0 +1,40 @@
> +################################################################################
> +#
> +# selftests
> +#
> +################################################################################
> +
> +LINUX_TOOLS += selftests

linux-tool infrastructure. Yeah! :-)

> +ifeq ($(KERNEL_ARCH),x86_64)
> +SELFTESTS_ARCH=x86
> +else
> +SELFTESTS_ARCH=$(KERNEL_ARCH)
> +endif

Not related to your patch, but I wonder if we should not make that a
common conditional, so that all tools do not have to repeat it.

Since there are only two such tool (with selftests) that do it, it can
be put aside for now, and we can revisit it later.

> +SELFTESTS_DEPENDENCIES = bash
> +
> +SELFTESTS_INSTALL_STAGING = YES

Why install it in staging?

> +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.
> +define SELFTESTS_BUILD_CMDS
> +	$(TARGET_MAKE_ENV) $(MAKE1) -C $(@D) headers_install

Headers are target dependent, so I think you also need to pass
$(SELFTESTS_MAKE_FLAGS) in there, no?

Why are headers needed?

> +	$(TARGET_MAKE_ENV) $(MAKE1) $(SELFTESTS_MAKE_FLAGS) \
> +		-C $(@D)/tools/testing/selftests O=$(@D)/tools/testing/selftests

I prefer when the -C args are passed early (if possible first) because
it is then much obvious where the build is taking place:

    $(TARGET_MAKE_ENV) $(MAKE1) -C $(@D)/tools/testing/selftests \
        $(SELFTESTS_MAKE_FLAGS) \
        O=$(@D)/tools/testing/selftests

> +endef
> +
> +define SELFTESTS_INSTALL_STAGING_CMDS
> +	$(TARGET_MAKE_ENV) $(MAKE1) INSTALL_PATH=$(STAGING_DIR)/usr/lib/selftests $(SELFTESTS_MAKE_FLAGS) \
> +		-C $(@D)/tools/testing/selftests install

Line too long, split it to below ~72 chars; also, I prefer we keep the
generic flags early; probably you also have to repeat the O arg:

    $(TARGET_MAKE_ENV) $(MAKE1) -C $(@D)/tools/testing/selftests \
        $(SELFTESTS_MAKE_FLAGS) \
        O=$(@D)/tools/testing/selftests \
        INSTALL_PATH=$(STAGING_DIR)/usr/lib/selftests \
        install

> +endef
> +
> +define SELFTESTS_INSTALL_TARGET_CMDS
> +	$(TARGET_MAKE_ENV) $(MAKE1) INSTALL_PATH=$(TARGET_DIR)/usr/lib/selftests $(SELFTESTS_MAKE_FLAGS) \
> +		-C $(@D)/tools/testing/selftests install

Ditto.

Regards,
Yann E. MORIN.

> +endef
> -- 
> 2.6.2
> 
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