On Mon, Feb 24, 2025 at 9:02 AM Tao Chen <chen.dylane@xxxxxxxxx> wrote:
>
> Similarly to libbpf_probe_bpf_helper, the libbpf_probe_bpf_kfunc
> used to test the availability of the different eBPF kfuncs on the
> current system.
>
> Cc: Tao Chen <dylane.chen@xxxxxxxxxxxxxx>
> Reviewed-by: Jiri Olsa <jolsa@xxxxxxxxxx>
> Reviewed-by: Eduard Zingerman <eddyz87@xxxxxxxxx>
> Signed-off-by: Tao Chen <chen.dylane@xxxxxxxxx>
> ---
> tools/lib/bpf/libbpf.h | 19 ++++++++++++-
> tools/lib/bpf/libbpf.map | 1 +
> tools/lib/bpf/libbpf_probes.c | 51 +++++++++++++++++++++++++++++++++++
> 3 files changed, 70 insertions(+), 1 deletion(-)
>
[...]
> + buf[0] = '\0';
> + ret = probe_prog_load(prog_type, insns, insn_cnt, btf_fd >= 0 ? fd_array : NULL,
> + buf, sizeof(buf));
> + if (ret < 0)
> + return libbpf_err(ret);
> +
> + if (ret > 0)
> + return 1; /* assume supported */
> +
> + /* If BPF verifier recognizes BPF kfunc but it's not supported for
> + * given BPF program type, it will emit "calling kernel function
> + * <name> is not allowed". If the kfunc id is invalid,
> + * it will emit "kernel btf_id <id> is not a function". If BTF fd
> + * invalid in module BTF, it will emit "invalid module BTF fd specified" or
> + * "negative offset disallowed for kernel module function call". If
> + * kfunc prog not dev buound, it will emit "metadata kfuncs require
> + * device-bound program".
> + */
> + if (strstr(buf, "not allowed") || strstr(buf, "not a function") ||
> + strstr(buf, "invalid module BTF fd") ||
why is invalid module BTF FD not an error (negative return)?
> + strstr(buf, "negative offset disallowed") ||
> + strstr(buf, "device-bound program"))
> + return 0;
> +
> + return 1;
> +}
> +
> int libbpf_probe_bpf_helper(enum bpf_prog_type prog_type, enum bpf_func_id helper_id,
> const void *opts)
> {
> --
> 2.43.0
>
