[dpdk-dev] [RFC PATCH v1] build: kni gcc cross-compilation support

Bruce Richardson bruce.richardson at intel.com
Fri Jan 29 12:43:40 CET 2021


On Fri, Jan 29, 2021 at 11:29:19AM +0100, Juraj Linkeš wrote:
> The kni linux module is using a custom target for building, which
> doesn't take into account any cross compilation arguments. The arguments
> in question are ARCH and CROSS_COMPILE. Get those from the cross file
> and pass them to the custom target.
> 
> The user supplied path may not contain the 'build' directory, such as
> when using cross-compiled headers, so only append that in the default
> case (when no path is supplied in native builds) and use the unmodified
> path from the user otherwise.
> 
> Signed-off-by: Juraj Linkeš <juraj.linkes at pantheon.tech>
> ---
>  kernel/linux/kni/meson.build |  4 ++--
>  kernel/linux/meson.build     | 33 +++++++++++++++++++++++++++++----
>  2 files changed, 31 insertions(+), 6 deletions(-)
> 
> diff --git a/kernel/linux/kni/meson.build b/kernel/linux/kni/meson.build
> index 07e0c9dae..0fbf52c93 100644
> --- a/kernel/linux/kni/meson.build
> +++ b/kernel/linux/kni/meson.build
> @@ -13,7 +13,7 @@ kni_sources = files(
>  custom_target('rte_kni',
>  	input: kni_sources,
>  	output: 'rte_kni.ko',
> -	command: ['make', '-j4', '-C', kernel_dir + '/build',
> +	command: ['make', '-j4', '-C', kernel_dir,
>  		'M=' + meson.current_build_dir(),
>  		'src=' + meson.current_source_dir(),
>  		'MODULE_CFLAGS=-include ' + meson.source_root() + '/config/rte_config.h' +
> @@ -21,7 +21,7 @@ custom_target('rte_kni',
>  		' -I' + meson.source_root() + '/lib/librte_kni' +
>  		' -I' + meson.build_root() +
>  		' -I' + meson.current_source_dir(),
> -		'modules'],
> +		'modules'] + cross_args,
>  	depends: kni_mkfile,
>  	install: true,
>  	install_dir: kernel_dir + '/extra/dpdk',
> diff --git a/kernel/linux/meson.build b/kernel/linux/meson.build
> index 5c864a465..57ed9bc48 100644
> --- a/kernel/linux/meson.build
> +++ b/kernel/linux/meson.build
> @@ -3,20 +3,45 @@
>  
>  subdirs = ['kni']
>  
> +cross_args = []
>  # if we are cross-compiling we need kernel_dir specified
> -if get_option('kernel_dir') == '' and meson.is_cross_build()
> -	error('Need "kernel_dir" option for kmod compilation when cross-compiling')
> +if meson.is_cross_build()
> +	if get_option('kernel_dir') == ''
> +		error('Need "kernel_dir" option for kmod compilation when cross-compiling')
> +	else
> +		cross_compiler = find_program('c').path()
> +		if cross_compiler.endswith('gcc')
> +			cross_prefix = ''
> +			# remove the 'gcc' suffix
> +			# meson doesn't support removing elements from an array
> +			# nor does it support slicing, so do it on our own
> +			foreach element : cross_compiler.split('-')
> +				if element != 'gcc'
> +					cross_prefix += '@0 at -'.format(element)
> +				endif
> +			endforeach
> +		else
> +			error('Unsupported cross compiler: @0@'.format(cross_compiler))
> +		endif

Rather than splitting manually, might it be better to just define a new
property in the cross-file to hold the prefix? Alternatively, rather than
meson looping, why not just use "run_command" to use shell or python to do
the job, e.g. [untested]

run_command([py3, '-c', 
	'print("-".join("' + cross_compiler + '".split("-")[:-1]))')

run_command('bash', '-c', 
	'echo ' + cross_compiler + ' | sed "s/gcc$//"')

> +		if host_machine.cpu_family() == 'aarch64'
> +			cross_arch = 'arm64'
> +		else
> +			cross_arch = build_machine.cpu_family()
> +		endif
> +		cross_args = ['ARCH=@0@'.format(cross_arch),
> +			'CROSS_COMPILE=@0@'.format(cross_prefix)]
> +	endif
>  endif
>  
>  kernel_dir = get_option('kernel_dir')
>  if kernel_dir == ''
>  	# use default path for native builds
>  	kernel_version = run_command('uname', '-r').stdout().strip()
> -	kernel_dir = '/lib/modules/' + kernel_version
> +	kernel_dir = '/lib/modules/' + kernel_version + '/build'
>  endif

The reason we don't keep the "build" off the kernel_dir is to ensure that
the kernel modules install to the correct place. With this change the
modules will go in "/lib/modules/<version>/build/extra/dpdk", rather than
"/lib/modules/<version>/extra/dpdk".

>  
>  # test running make in kernel directory, using "make kernelversion"
> -make_returncode = run_command('make', '-sC', kernel_dir + '/build',
> +make_returncode = run_command('make', '-sC', kernel_dir,
>  		'kernelversion').returncode()
>  if make_returncode != 0
>  	error('Cannot compile kernel modules as requested - are kernel headers installed?')
> -- 
> 2.20.1
> 


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