[dpdk-dev] [PATCH v14 00/12] Arm build options rework

[Juraj Linkeš]

> -----Original Message-----
> From: Bruce Richardson <bruce.richardson at intel.com>
> Sent: Friday, January 29, 2021 10:46 AM
> To: Juraj Linkeš <juraj.linkes at pantheon.tech>
> Cc: Andrew Boyer <aboyer at pensando.io>; Honnappa Nagarahalli
> <Honnappa.Nagarahalli at arm.com>; thomas at monjalon.net; Ruifeng Wang
> <Ruifeng.Wang at arm.com>; Phil Yang <Phil.Yang at arm.com>;
> vcchunga at amazon.com; Dharmik Thakkar <Dharmik.Thakkar at arm.com>;
> jerinjacobk at gmail.com; hemant.agrawal at nxp.com; Ajit Khaparde
> (ajit.khaparde at broadcom.com) <ajit.khaparde at broadcom.com>;
> ferruh.yigit at intel.com; dev at dpdk.org; nd <nd at arm.com>
> Subject: Re: [dpdk-dev] [PATCH v14 00/12] Arm build options rework
> 
> On Fri, Jan 29, 2021 at 08:41:45AM +0000, Juraj Linkeš wrote:
> > > > 3) We need to build kni against the aarch64 kernel headers, but it
> > > > fails. It appears that kernel/linux/kni/meson.build doesn’t pass
> > > > any cross-compile flags in the make command it creates. The diff
> > > > below shows how I hardcoded it to get it to work for now. Thoughts
> > > > on how to do this right? meson has the path (in $PATH) and the
> > > > binary prefixs (in ‘[binaries]’ in the cross file). It must know
> > > > the arch, too.
> > > >
> > > > --- a/kernel/linux/kni/meson.build +++
> > > > b/kernel/linux/kni/meson.build @@ -14,6 +14,8 @@
> > > > custom_target('rte_kni', input: kni_sources,
> > > > output: 'rte_kni.ko', command: ['make', '-j4', '-C', kernel_dir +
> > > > '/build', + +
> > > > 'CROSS_COMPILE=/tool/toolchain/aarch64-1.1/bin/aarch64-linux-
> > > > gnu-',
> > > > +               'ARCH=aarch64', 'M=' + meson.current_build_dir(),
> > > > 'src=' + meson.current_source_dir(), 'MODULE_CFLAGS=-include ' +
> > > > meson.source_root() + '/config/rte_config.h' +
> > > >
> > >
> > > Yes, Meson should know these. I'll submit this separately (in a new
> > > series), as this series is getting pretty big and this fix is
> > > actually unrelated.
> > >
> >
> > I tried to figure out how to implement this and I've ran into a brick
> > wall - there's no way to figure out the full name of the cross-compiler.
> > I found only one way to get the cross compiler:
> > meson.get_compiler('c',
> > native:false).get_id()
> >
> > But that only retuns 'gcc', not the full binary name (c =
> > 'aarch64-linux-gnu-gcc' in cross file).
> >
> > Bruce, any ideas on how to get the full name? If I understand the
> > sources right, we aren't able to access arbitrary object attributes,
> > just those, which are specifically exposed.
> >
> > Maybe we could do a workaround? Either if cross compiling and the
> > compiler is gcc, use the 'aarch64-linux-gnu-' prefix or just put the
> > prefix into the cross file as an additional property?
> >
> According to the cross-file/native-file documentation[1], the files in the binaries
> section can be queried using the "find_program()" call. That then returns an
> external program object rather than a compiler one, so the full path can be got.
> Unfortunately, find_program('c') doesn't seem to work for the non-cross-
> compiled case, so it will need to be conditional on cross-compilation.
> 

Thanks, this is great, I'll use this.
We don't need it for native builds. But it's strange that it doesn't work for those - the docs say it does.

> Example I tested:
> 
> <code change added>
> +myc = find_program('c')
> +message('find_program(\'c\') = ' + myc.full_path())
> +
> 
> <output when run>
> ~/dpdk.org/__BUILDS/build-arm64-host-clang$ ninja [0/1] Regenerating build
> files.
> ....
> Target machine cpu family: aarch64
> Target machine cpu: armv8-a
> Program aarch64-linux-gnu-gcc found: YES
> WARNING: Project targeting '>= 0.47.1' but tried to use feature introduced in
> '0.55.0': ExternalProgram.full_path.
> Message: find_program('c') = /home/bruce/Downloads/gcc-arm-8.3-2019.03-
> x86_64-aarch64-linux-gnu/bin/aarch64-linux-gnu-gcc
> ...
> 
> /Bruce
> 
> 
> [1] https://mesonbuild.com/Machine-files.html#binaries