This macro emits an SD_ELF_NOTE_DLOPEN note so that calling sites,
and not just libsystemd-shared, get the ELF stamped with the notes
documenting the dependency. Currently most of the dlopen notes end
up in libsystemd-shared, and executables have no way to document
the optional dependencies they need. With this new macro, this
issue can be fixed.
Co-developed-by: Claude Opus 4.8 <noreply@anthropic.com>
Renames src/shared/bpf-dlopen.{c,h} to src/shared/bpf-util.{c,h} and
folds the former src/shared/bpf-compat.h (struct forward decl and
compat_bpf_map_create() helper) into the new header.
Aligns dlopen_bpf() with the standard wrapper pattern: drops the
manual dlopen_safe()/dlsym_many_or_warn()/TAKE_PTR(dl) plumbing and
the bespoke 'cached' int in favor of dlopen_many_sym_or_warn() inside
a FOREACH_STRING() soname-fallback loop.
Unifies declaration of the version-specific symbols (bpf_create_map,
bpf_map_create, bpf_object__next_map, bpf_token_create) into a single
DISABLE_WARNING_REDUNDANT_DECLS block in the header, and alphabetically
merges the DLSYM_PROTOTYPE list. DLSYM_OPTIONAL is used to load each
one — call sites already handle NULL (compat_bpf_map_create() and the
sym_bpf_object__next_map guard in userns-restrict.c). bpf_token_create
additionally defaults to a missing_bpf_token_create() stub returning
-ENOSYS, so callers can branch on the errno instead of NULL-checking
the pointer.
Updates test-bpf-token to match: drops the compile-time
LIBBPF_MAJOR_VERSION ≥ 1.5 gate and the direct <bpf/bpf.h> include in
favor of dlopen_bpf() + sym_bpf_token_create(), and treats -ENOSYS as
the test-skip path (covering both 'libbpf too old' and 'kernel lacks
BPF_TOKEN_CREATE support').
Luca Boccassi
Daan De Meyer