[SRU][J][PATCH 0/1] Fix bpf selftests build failure after v5.15.139 update

[Roxana Nicolescu]

BugLink: https://bugs.launchpad.net/bugs/2054567

SRU justification

[Impact]
Upstream v5.15.139 (#lp2049432) brought commit
"selftests/bpf: Test tail call counting with bpf2bpf and data on stack"
that affects one of the bpf kselftests (tailcall_bpf2bpf6).
because LIBBPF_OPTS macro does not exists, it does not compile. Error below.

[Fix]
Initially, I thought cherry-picking commit
"libbpf: Rename DECLARE_LIBBPF_OPTS into LIBBPF_OPTS" would be the best,
but upstream stable just reverted the commit that broke it. Hence the fix
consists of cherry-picking this commit from stable upstream 5.15.49:
Commit 62900d358c48 (Revert "selftests/bpf: Test tail call counting with bpf2bpf and data on stack")

[Test]
This should be solved soon, but compileselftests debian rule does not
compile bpf selftests.
I tested it by using our regression testing tooling, but same results can
be achieved by running:
$ make -C linux/tools/testing/selftests TARGETS=bpf SKIP_TARGETS= clean all KDIR=/usr/src/linux-headers-5.15.0-<verson>-generic
from the linux tree directory

Without the fix, it fails to compile:
  /root/autotest/client/tmp/ubuntu_bpf/src/linux/tools/testing/selftests/bpf/prog_tests/tailcalls.c: In function ‘test_tailcall_bpf2bpf_6’:
  /root/autotest/client/tmp/ubuntu_bpf/src/linux/tools/testing/selftests/bpf/prog_tests/tailcalls.c:822:9: warning: implicit declaration of function ‘LIBBPF_OPTS’; did you mean ‘LIBBPF_API’? [-Wimplicit-function-declaration]
    822 | LIBBPF_OPTS(bpf_test_run_opts, topts,
        | ^~~~~~~~~~~
        | LIBBPF_API
  /root/autotest/client/tmp/ubuntu_bpf/src/linux/tools/testing/selftests/bpf/prog_tests/tailcalls.c:822:21: error: ‘bpf_test_run_opts’ undeclared (first use in this function)
    822 | LIBBPF_OPTS(bpf_test_run_opts, topts,
        | ^~~~~~~~~~~~~~~~~
  /root/autotest/client/tmp/ubuntu_bpf/src/linux/tools/testing/selftests/bpf/prog_tests/tailcalls.c:822:21: note: each undeclared identifier is reported only once for each function it appears in
  /root/autotest/client/tmp/ubuntu_bpf/src/linux/tools/testing/selftests/bpf/prog_tests/tailcalls.c:822:40: error: ‘topts’ undeclared (first use in this function)
    822 | LIBBPF_OPTS(bpf_test_run_opts, topts,
        | ^~~~~
  /root/autotest/client/tmp/ubuntu_bpf/src/linux/tools/testing/selftests/bpf/prog_tests/tailcalls.c:823:17: error: expected expression before ‘.’ token
    823 | .data_in = &pkt_v4,
        | ^
  make[1]: *** [Makefile:471: /root/autotest/client/tmp/ubuntu_bpf/src/linux/tools/testing/selftests/bpf/tailcalls.test.o] Error 1
  make: *** [Makefile:172: all] Error 2

With the fix, it compiles.

[Regression potential]
The only place this is being used is selftests, so the risk is very low.

Samasth Norway Ananda (1):
  Revert "selftests/bpf: Test tail call counting with bpf2bpf and data
    on stack"

 .../selftests/bpf/prog_tests/tailcalls.c      | 55 -------------------
 .../selftests/bpf/progs/tailcall_bpf2bpf6.c   | 42 --------------
 2 files changed, 97 deletions(-)
 delete mode 100644 tools/testing/selftests/bpf/progs/tailcall_bpf2bpf6.c

-- 
2.34.1