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8462e0b46f
Teach bpf_link_create() to fallback to bpf_raw_tracepoint_open() on older kernels for programs that are attachable through BPF_RAW_TRACEPOINT_OPEN. This makes bpf_link_create() more unified and convenient interface for creating bpf_link-based attachments. With this approach end users can just use bpf_link_create() for tp_btf/fentry/fexit/fmod_ret/lsm program attachments without needing to care about kernel support, as libbpf will handle this transparently. On the other hand, as newer features (like BPF cookie) are added to LINK_CREATE interface, they will be readily usable though the same bpf_link_create() API without any major refactoring from user's standpoint. bpf_program__attach_btf_id() is now using bpf_link_create() internally as well and will take advantaged of this unified interface when BPF cookie is added for fentry/fexit. Doing proactive feature detection of LINK_CREATE support for fentry/tp_btf/etc is quite involved. It requires parsing vmlinux BTF, determining some stable and guaranteed to be in all kernels versions target BTF type (either raw tracepoint or fentry target function), actually attaching this program and thus potentially affecting the performance of the host kernel briefly, etc. So instead we are taking much simpler "lazy" approach of falling back to bpf_raw_tracepoint_open() call only if initial LINK_CREATE command fails. For modern kernels this will mean zero added overhead, while older kernels will incur minimal overhead with a single fast-failing LINK_CREATE call. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Reviewed-by: Kui-Feng Lee <kuifeng@fb.com> Link: https://lore.kernel.org/bpf/20220421033945.3602803-3-andrii@kernel.org |
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| .. | ||
| .gitignore | ||
| bpf_core_read.h | ||
| bpf_endian.h | ||
| bpf_gen_internal.h | ||
| bpf_helpers.h | ||
| bpf_prog_linfo.c | ||
| bpf_tracing.h | ||
| bpf.c | ||
| bpf.h | ||
| btf_dump.c | ||
| btf.c | ||
| btf.h | ||
| Build | ||
| gen_loader.c | ||
| hashmap.c | ||
| hashmap.h | ||
| libbpf_common.h | ||
| libbpf_errno.c | ||
| libbpf_internal.h | ||
| libbpf_legacy.h | ||
| libbpf_probes.c | ||
| libbpf_version.h | ||
| libbpf.c | ||
| libbpf.h | ||
| libbpf.map | ||
| libbpf.pc.template | ||
| linker.c | ||
| Makefile | ||
| netlink.c | ||
| nlattr.c | ||
| nlattr.h | ||
| relo_core.c | ||
| relo_core.h | ||
| ringbuf.c | ||
| skel_internal.h | ||
| str_error.c | ||
| str_error.h | ||
| strset.c | ||
| strset.h | ||
| usdt.bpf.h | ||
| usdt.c | ||
| xsk.c | ||
| xsk.h | ||