Re: [PATCH bpf-next 0/6] tools/bpf: Enable cross-building with clang

[Jean-Philippe Brucker <jean-philippe@linaro.org>]

On Fri, Nov 26, 2021 at 08:36:24PM +0000, Quentin Monnet wrote:
> On Mon, 22 Nov 2021 at 19:23, Jean-Philippe Brucker
> <jean-philippe@linaro.org> wrote:
> >
> > Add support for cross-building BPF tools and selftests with clang, by
> > passing LLVM=1 or CC=clang to make, as well as CROSS_COMPILE. A single
> > clang toolchain can generate binaries for multiple architectures, so
> > instead of having prefixes such as aarch64-linux-gnu-gcc, clang uses the
> > -target parameter: `clang -target aarch64-linux-gnu'.
> >
> > Patch 1 adds the parameter in Makefile.include so tools can easily
> > support this. Patch 2 prepares for the libbpf change from patch 3 (keep
> > building resolve_btfids's libbpf in the host arch, when cross-building
> > the kernel with clang). Patches 3-6 enable cross-building BPF tools with
> > clang.
> 
> The set looks good to me. I checked that the tools are still building
> (without cross-compiling). I currently have issues building the
> selftests on my setup, but they don't appear to be related to this
> patchset.
> 
> Acked-by: Quentin Monnet <quentin@isovalent.com>
> 
> Note that on bpf-next, patch 5 (runqslower) has a conflict with
> be79505caf3f ("tools/runqslower: Install libbpf headers when
> building").

Ah right, I have the series on top of "tools/runqslower: Fix cross-build",
which is in bpf/master but not yet in bpf-next. I'll wait for the branches
to synchronize before resending, since the patches conflict either way.

> Did you consider enabling cross-compiling for the BPF samples too? I'm
> asking because the build system is pretty similar to the BPF tools.

Right, the problems seem similar to the selftests (need to build two
libbpfs, pass $(HOSTCC) etc). Samples aren't as crucial as tools but I can
look into it when I find a bit of time.

Thanks,
Jean