On Fri, Nov 12, 2021 at 8:28 AM Jean-Philippe Brucker
<jean-philippe@xxxxxxxxxx> wrote:
>
> On Fri, Nov 12, 2021 at 04:17:21PM +0000, Quentin Monnet wrote:
> > 2021-11-12 15:51 UTC+0000 ~ Jean-Philippe Brucker <jean-philippe@xxxxxxxxxx>
> > > Commit be79505caf3f ("tools/runqslower: Install libbpf headers when
> > > building") uses the target libbpf to build the host bpftool, which
> > > doesn't work when cross-building:
> > >
> > > make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- -C tools/bpf/runqslower O=/tmp/runqslower
> > > ...
> > > LINK /tmp/runqslower/bpftool/bpftool
> > > /usr/bin/ld: /tmp/runqslower/libbpf/libbpf.a(libbpf-in.o): Relocations in generic ELF (EM: 183)
> > > /usr/bin/ld: /tmp/runqslower/libbpf/libbpf.a: error adding symbols: file in wrong format
> > > collect2: error: ld returned 1 exit status
> > >
> > > When cross-building, the target architecture differs from the host. The
> > > bpftool used for building runqslower is executed on the host, and thus
> > > must use a different libbpf than that used for runqslower itself.
> > > Remove the LIBBPF_OUTPUT and LIBBPF_DESTDIR parameters, so the bpftool
> > > build makes its own library if necessary.
> > >
> > > In the selftests, pass the host bpftool, already a prerequisite for the
> > > runqslower recipe, as BPFTOOL_OUTPUT. The runqslower Makefile will use
> > > the bpftool that's already built for selftests instead of making a new
> > > one.
> > >
> > > Fixes: be79505caf3f ("tools/runqslower: Install libbpf headers when building")
> > > Signed-off-by: Jean-Philippe Brucker <jean-philippe@xxxxxxxxxx>
> > Reviewed-by: Quentin Monnet <quentin@xxxxxxxxxxxxx>
> >
> > I realised too late I should have cc-ed you on those patches, apologies
> > for not doing so. Thank you for the fix!
>
> No worries, I usually try to catch build issues in bpf-next but missed it
> this time. I'm still slowly working towards getting automated testing on
> Arm targets, which will catch regressions quicker.
Are you planning to contribute it to BPF CI? Or you meant you have
your own separate system?
>
> Thanks,
> Jean
