selftests/bpf: Add weak/typeless ksym test for light skeleton

Also, avoid using CO-RE features, as lskel doesn't support CO-RE, yet.
Include both light and libbpf skeleton in same file to test both of them
together.

In c48e51c8b07a ("bpf: selftests: Add selftests for module kfunc support"),
I added support for generating both lskel and libbpf skel for a BPF
object, however the name parameter for bpftool caused collisions when
included in same file together. This meant that every test needed a
separate file for a libbpf/light skeleton separation instead of
subtests.

Change that by appending a "_lskel" suffix to the name for files using
light skeleton, and convert all existing users.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20211028063501.2239335-7-memxor@gmail.com

selftests/bpf: Convert few tests to light skeleton.

Convert few tests that don't use CO-RE to light skeleton.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210514003623.28033-19-alexei.starovoitov@gmail.com

selftests/bpf: Silence clang compilation warnings

With clang compiler:
make -j60 LLVM=1 LLVM_IAS=1 <=== compile kernel
make -j60 -C tools/testing/selftests/bpf LLVM=1 LLVM_IAS=1
Some linker flags are not used/effective for some binaries and
we have warnings like:
warning: -lelf: 'linker' input unused [-Wunused-command-line-argument]

We also have warnings like:
.../selftests/bpf/prog_tests/ns_current_pid_tgid.c:74:57: note: treat the string as an argument to avoid this
if (CHECK(waitpid(cpid, &wstatus, 0) == -1, "waitpid", strerror(errno)))
^
"%s",
.../selftests/bpf/test_progs.h:129:35: note: expanded from macro 'CHECK'
_CHECK(condition, tag, duration, format)
^
.../selftests/bpf/test_progs.h:108:21: note: expanded from macro '_CHECK'
fprintf(stdout, ##format); \
^
The first warning can be silenced with clang option -Wno-unused-command-line-argument.
For the second warning, source codes are modified as suggested by the compiler
to silence the warning. Since gcc does not support the option
-Wno-unused-command-line-argument and the warning only happens with clang
compiler, the option -Wno-unused-command-line-argument is enabled only when
clang compiler is used.

Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210413153429.3029377-1-yhs@fb.com

selftest/bpf: Add a test to check trampoline freeing logic.

Add a selftest for commit e21aa341785c ("bpf: Fix fexit trampoline.")
to make sure that attaching fexit prog to a sleeping kernel function
will trigger appropriate trampoline and program destruction.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20210318004523.55908-1-alexei.starovoitov@gmail.com