On Fri, Jan 29, 2021 at 12:33:06PM +0000, Juraj Linkeš wrote:
>
>
> > -----Original Message-----
> > From: Bruce Richardson <bruce.richard...@intel.com>
> > Sent: Friday, January 29, 2021 12:44 PM
> > To: Juraj Linkeš <juraj.lin...@pantheon.tech>
> > Cc: tho...@monjalon.net; ruifeng.w...@arm.com; jerinjac...@gmail.com;
> > hemant.agra...@nxp.com; ferruh.yi...@intel.com; abo...@pensando.io;
> > dev@dpdk.org
> > Subject: Re: [RFC PATCH v1] build: kni gcc cross-compilation support
> >
> > 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.lin...@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@-
> > '.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?
>
> That would by one more unnecessary input, so I don't like that.
>
> > 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$//"')
> >
>
> Since there isn't a better way to do this in Meson, it makes sense to use an
> external tool.
> On top of that, this would save lines and wouldn't need as many code
> comments. I'll change it.
>
> > > + 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".
> >
>
> Ah, I see. The modules will be installed during meson install. This should
> also be changed, then, as we always want to install them to
> '/lib/modules/<version>' (not necessarily to 'kernel_dir', as the user may
> change that) and only for native builds, right?
>
Well, we definitely want it for native builds, but I'd imagine it would be
useful for cross-builds too, no? Can we find some way of getting it working
for both cases. For native builds we want:
* build kernel-dir = /lib/modules/<ver>/build
* install dir = /lib/modules/<ver>/extra/dpdk
What are the expected equivalent paths for cross building?
/Bruce
