ubuntu_bpf build failure on Hirsute - incomplete type of core_reloc_existence___err_wrong_arr_kind

[Krzysztof Kozlowski]

On Hirsute v5.11, after adding missing docutils in lp:1931580, the ubuntu_bpf fails to build with:

  make[1]: Leaving directory '/home/azure/autotest/client/tmp/ubuntu_bpf/src/linux/tools/testing/selftests/bpf'
  make: Leaving directory '/home/azure/autotest/client/tmp/ubuntu_bpf/src/linux/tools/testing/selftests'
  stderr:
  Warning: Kernel ABI header at 'tools/include/uapi/linux/netlink.h' differs from latest version at 'include/uapi/linux/netlink.h'
  Warning: Kernel ABI header at 'tools/include/uapi/linux/if_link.h' differs from latest version at 'include/uapi/linux/if_link.h'
  progs/btf__core_reloc_existence___err_wrong_arr_kind.c:3:15: warning: declaration of 'struct core_reloc_existence___err_wrong_arr_kind' will not be visible outside of this function [-Wvisibility]
  void f(struct core_reloc_existence___err_wrong_arr_kind x) {}
                ^
  progs/btf__core_reloc_existence___err_wrong_arr_kind.c:3:57: error: variable has incomplete type 'struct core_reloc_existence___err_wrong_arr_kind'
  void f(struct core_reloc_existence___err_wrong_arr_kind x) {}
                                                          ^
  progs/btf__core_reloc_existence___err_wrong_arr_kind.c:3:15: note: forward declaration of 'struct core_reloc_existence___err_wrong_arr_kind'
  void f(struct core_reloc_existence___err_wrong_arr_kind x) {}
                ^
  1 warning and 1 error generated.
  make[1]: *** [Makefile:394: /home/azure/autotest/client/tmp/ubuntu_bpf/src/linux/tools/testing/selftests/bpf/btf__core_reloc_existence___err_wrong_arr_kind.o] Error 1

[Krzysztof Kozlowski (krzk)]

Bigger piece of build log.

[Thadeu Lima de Souza Cascardo (cascardo)]

The other issue we have found is building the kmod test, which worked just fine as long as we had the linux-headers package installed and ran with KDIR=/lib/modules/`uname -r`/build/. I don't recall if the output was like that, it doesn't strike as it was.

Cascardo.