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!
Quentin
