[RFC,v3] build: kni cross-compilation support

  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, CROSS_COMPILE (for gcc, clang) and CC, LD (for
clang). 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. Also modify the install path accordingly.

Signed-off-by: Juraj Linkeš <juraj.linkes@pantheon.tech>
---
 kernel/linux/kni/meson.build |  8 ++--
 kernel/linux/meson.build     | 79 ++++++++++++++++++++++++++++++------
 2 files changed, 70 insertions(+), 17 deletions(-)
  

On Fri, Feb 05, 2021 at 03:46:37PM +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, CROSS_COMPILE (for gcc, clang) and CC, LD (for
> clang). 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. Also modify the install path accordingly.
> 
> Signed-off-by: Juraj Linkeš <juraj.linkes@pantheon.tech>
> ---
>  kernel/linux/kni/meson.build |  8 ++--
>  kernel/linux/meson.build     | 79 ++++++++++++++++++++++++++++++------
>  2 files changed, 70 insertions(+), 17 deletions(-)
> 
> diff --git a/kernel/linux/kni/meson.build b/kernel/linux/kni/meson.build
> index 07e0c9dae7..46b71c7418 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_build_dir,
>  		'M=' + meson.current_build_dir(),
>  		'src=' + meson.current_source_dir(),
>  		'MODULE_CFLAGS=-include ' + meson.source_root() + '/config/rte_config.h' +
> @@ -21,8 +21,8 @@ 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',
> +	install: install,
> +	install_dir: kernel_install_dir,
>  	build_by_default: get_option('enable_kmods'))
> diff --git a/kernel/linux/meson.build b/kernel/linux/meson.build
> index 5c864a4653..4271483329 100644
> --- a/kernel/linux/meson.build
> +++ b/kernel/linux/meson.build
> @@ -3,24 +3,77 @@
>  
>  subdirs = ['kni']
>  
> -# 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')
> -endif
> +kernel_build_dir = get_option('kernel_dir')
> +install = not meson.is_cross_build()
> +cross_args = []
> +kernel_install_dir = ''
>  
> -kernel_dir = get_option('kernel_dir')
> -if kernel_dir == ''
> -	# use default path for native builds
> +if install

I'd suggest using explicit "not meson.is_cross_build" again for
readability.

> +	# native build
>  	kernel_version = run_command('uname', '-r').stdout().strip()
> -	kernel_dir = '/lib/modules/' + kernel_version
> +	kernel_install_dir = '/lib/modules/' + kernel_version + '/extra/dpdk'
> +	if kernel_build_dir == ''
> +		# use default path for native builds
> +		kernel_build_dir = '/lib/modules/' + kernel_version + '/build'
> +	endif
> +
> +	# test running make in kernel directory, using "make kernelversion"
> +	make_returncode = run_command('make', '-sC', kernel_build_dir,
> +			'kernelversion').returncode()
> +	if make_returncode != 0
> +		error('Cannot compile kernel modules as requested - are kernel headers installed?')
> +	endif
> +
> +	# DO ACTUAL MODULE BUILDING
> +	foreach d:subdirs
> +		subdir(d)
> +	endforeach
> +
> +	subdir_done()
>  endif
>  
> -# test running make in kernel directory, using "make kernelversion"
> -make_returncode = run_command('make', '-sC', kernel_dir + '/build',
> -		'kernelversion').returncode()
> -if make_returncode != 0
> -	error('Cannot compile kernel modules as requested - are kernel headers installed?')
> +# cross build
> +# if we are cross-compiling we need kernel_build_dir specified
> +if kernel_build_dir == ''
> +	error('Need "kernel_dir" option for kmod compilation when cross-compiling')
> +endif
> +cross_compiler = find_program('c').path()
> +if cross_compiler.endswith('gcc')
> +	cross_prefix = run_command([py3, '-c', 'print("' + cross_compiler + '"[:-3])']).stdout().strip()
> +elif cross_compiler.endswith('clang')
> +	cross_prefix = ''
> +	found_target = false
> +	# search for '-target' and use the arg that follows
> +	# (i.e. the value of '-target') as cross_prefix
> +	foreach cross_c_arg : meson.get_cross_property('c_args')
> +		if found_target and cross_prefix == ''
> +			cross_prefix = cross_c_arg
> +		endif
> +		if cross_c_arg == '-target'
> +			found_target = true
> +		endif
> +	endforeach
> +	if cross_prefix == ''
> +		error('Didn\'t find -target and its value in' +
> +		      ' c_args in input cross-file.')
> +	endif
> +	linker = 'lld'
> +	foreach cross_c_link_arg : meson.get_cross_property('c_link_args')
> +		if cross_c_link_arg.startswith('-fuse-ld')
> +			linker = cross_c_link_arg.split('=')[1]
> +		endif
> +	endforeach
> +	cross_args += ['CC=@0@'.format(cross_compiler), 'LD=ld.@0@'.format(linker)]
> +else
> +	error('Unsupported cross compiler: @0@'.format(cross_compiler))
> +endif
> +if host_machine.cpu_family() == 'aarch64'
> +	cross_arch = 'arm64'
> +else
> +	cross_arch = build_machine.cpu_family()
>  endif

Is this not meant to be "host_machine.cpu_family()"?
I also think this might be simpler as:

cross_arch = host_machine.cpu_family()
if cross_arch == 'aarch64'
	cross_arch = arm64
endif

> +cross_args += ['ARCH=@0@'.format(cross_arch),
> +	'CROSS_COMPILE=@0@'.format(cross_prefix)]
>  
>  # DO ACTUAL MODULE BUILDING
>  foreach d:subdirs
> -- 
> 2.20.1
>
  

> -----Original Message-----
> From: Bruce Richardson <bruce.richardson@intel.com>
> Sent: Friday, February 5, 2021 3:53 PM
> To: Juraj Linkeš <juraj.linkes@pantheon.tech>
> Cc: thomas@monjalon.net; Ruifeng.Wang@arm.com;
> Honnappa.Nagarahalli@arm.com; jerinjacobk@gmail.com;
> hemant.agrawal@nxp.com; ferruh.yigit@intel.com; aboyer@pensando.io;
> dev@dpdk.org
> Subject: Re: [RFC PATCH v3] build: kni cross-compilation support
> 
> On Fri, Feb 05, 2021 at 03:46:37PM +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, CROSS_COMPILE (for gcc, clang) and CC,
> > LD (for clang). 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. Also modify the install path
> accordingly.
> >
> > Signed-off-by: Juraj Linkeš <juraj.linkes@pantheon.tech>
> > ---
> >  kernel/linux/kni/meson.build |  8 ++--
> >  kernel/linux/meson.build     | 79 ++++++++++++++++++++++++++++++------
> >  2 files changed, 70 insertions(+), 17 deletions(-)
> >
> > diff --git a/kernel/linux/kni/meson.build
> > b/kernel/linux/kni/meson.build index 07e0c9dae7..46b71c7418 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_build_dir,
> >  		'M=' + meson.current_build_dir(),
> >  		'src=' + meson.current_source_dir(),
> >  		'MODULE_CFLAGS=-include ' + meson.source_root() +
> > '/config/rte_config.h' + @@ -21,8 +21,8 @@ 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',
> > +	install: install,
> > +	install_dir: kernel_install_dir,
> >  	build_by_default: get_option('enable_kmods')) diff --git
> > a/kernel/linux/meson.build b/kernel/linux/meson.build index
> > 5c864a4653..4271483329 100644
> > --- a/kernel/linux/meson.build
> > +++ b/kernel/linux/meson.build
> > @@ -3,24 +3,77 @@
> >
> >  subdirs = ['kni']
> >
> > -# 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')
> > -endif
> > +kernel_build_dir = get_option('kernel_dir') install = not
> > +meson.is_cross_build() cross_args = [] kernel_install_dir = ''
> >
> > -kernel_dir = get_option('kernel_dir') -if kernel_dir == ''
> > -	# use default path for native builds
> > +if install
> 
> I'd suggest using explicit "not meson.is_cross_build" again for readability.
> 

Ok.

> > +	# native build
> >  	kernel_version = run_command('uname', '-r').stdout().strip()
> > -	kernel_dir = '/lib/modules/' + kernel_version
> > +	kernel_install_dir = '/lib/modules/' + kernel_version + '/extra/dpdk'
> > +	if kernel_build_dir == ''
> > +		# use default path for native builds
> > +		kernel_build_dir = '/lib/modules/' + kernel_version + '/build'
> > +	endif
> > +
> > +	# test running make in kernel directory, using "make kernelversion"
> > +	make_returncode = run_command('make', '-sC', kernel_build_dir,
> > +			'kernelversion').returncode()
> > +	if make_returncode != 0
> > +		error('Cannot compile kernel modules as requested - are kernel
> headers installed?')
> > +	endif
> > +
> > +	# DO ACTUAL MODULE BUILDING
> > +	foreach d:subdirs
> > +		subdir(d)
> > +	endforeach
> > +
> > +	subdir_done()
> >  endif
> >
> > -# test running make in kernel directory, using "make kernelversion"
> > -make_returncode = run_command('make', '-sC', kernel_dir + '/build',
> > -		'kernelversion').returncode()
> > -if make_returncode != 0
> > -	error('Cannot compile kernel modules as requested - are kernel headers
> installed?')
> > +# cross build
> > +# if we are cross-compiling we need kernel_build_dir specified if
> > +kernel_build_dir == ''
> > +	error('Need "kernel_dir" option for kmod compilation when
> > +cross-compiling') endif cross_compiler = find_program('c').path() if
> > +cross_compiler.endswith('gcc')
> > +	cross_prefix = run_command([py3, '-c', 'print("' + cross_compiler +
> > +'"[:-3])']).stdout().strip() elif cross_compiler.endswith('clang')
> > +	cross_prefix = ''
> > +	found_target = false
> > +	# search for '-target' and use the arg that follows
> > +	# (i.e. the value of '-target') as cross_prefix
> > +	foreach cross_c_arg : meson.get_cross_property('c_args')
> > +		if found_target and cross_prefix == ''
> > +			cross_prefix = cross_c_arg
> > +		endif
> > +		if cross_c_arg == '-target'
> > +			found_target = true
> > +		endif
> > +	endforeach
> > +	if cross_prefix == ''
> > +		error('Didn\'t find -target and its value in' +
> > +		      ' c_args in input cross-file.')
> > +	endif
> > +	linker = 'lld'
> > +	foreach cross_c_link_arg : meson.get_cross_property('c_link_args')
> > +		if cross_c_link_arg.startswith('-fuse-ld')
> > +			linker = cross_c_link_arg.split('=')[1]
> > +		endif
> > +	endforeach
> > +	cross_args += ['CC=@0@'.format(cross_compiler),
> > +'LD=ld.@0@'.format(linker)] else
> > +	error('Unsupported cross compiler: @0@'.format(cross_compiler))
> > +endif if host_machine.cpu_family() == 'aarch64'
> > +	cross_arch = 'arm64'
> > +else
> > +	cross_arch = build_machine.cpu_family()
> >  endif
> 
> Is this not meant to be "host_machine.cpu_family()"?
> I also think this might be simpler as:
> 
> cross_arch = host_machine.cpu_family()
> if cross_arch == 'aarch64'
> 	cross_arch = arm64
> endif
> 

It should, I'll change it.

> > +cross_args += ['ARCH=@0@'.format(cross_arch),
> > +	'CROSS_COMPILE=@0@'.format(cross_prefix)]
> >
> >  # DO ACTUAL MODULE BUILDING
> >  foreach d:subdirs
> > --
> > 2.20.1
> >