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New versions of bpftool now emit additional link placeholders for BPF maps (struct_ops maps are the only maps right now that support attachment), and set up BPF skeleton in such a way that libbpf will auto-attach BPF maps automatically, assumming libbpf is recent enough (v1.5+). Old libbpf will do nothing with those links and won't attempt to auto-attach maps. This allows user code to handle both pre-v1.5 and v1.5+ versions of libbpf at runtime, if necessary. But if users don't have (or don't want to) control bpftool version that generates skeleton, then they can't just assume that skeleton will have link placeholders. To make this detection possible and easy, let's add the following to generated skeleton header file: #define BPF_SKEL_SUPPORTS_MAP_AUTO_ATTACH 1 This can be used during compilation time to guard code that accesses skel->links.<map> slots. Note, if auto-attachment is undesirable, libbpf allows to disable this through bpf_map__set_autoattach(map, false). This is necessary only on libbpf v1.5+, older libbpf doesn't support map auto-attach anyways. Libbpf version can be detected at compilation time using LIBBPF_MAJOR_VERSION and LIBBPF_MINOR_VERSION macros, or at runtime with libbpf_major_version() and libbpf_minor_version() APIs. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Quentin Monnet <qmo@kernel.org> Link: https://lore.kernel.org/bpf/20240618183832.2535876-1-andrii@kernel.org |
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| .. | ||
| bpftool | ||
| resolve_btfids | ||
| runqslower | ||
| .gitignore | ||
| bpf_asm.c | ||
| bpf_dbg.c | ||
| bpf_exp.l | ||
| bpf_exp.y | ||
| bpf_jit_disasm.c | ||
| Makefile | ||