在 2025/1/24 09:34, Eduard Zingerman 写道:
On Fri, 2025-01-24 at 01:05 +0800, Tao Chen wrote:
[...]
+int libbpf_probe_bpf_kfunc(enum bpf_prog_type prog_type, int kfunc_id,
+ __s16 off, const void *opts)
^^^
Nit: maybe name this btf_fd?
Hi Eduard, thank you for your guidance, ack, i will send it in v3.
+{
In v2 function looks identical to libbpf_probe_bpf_helper,
do we want to copy-paste it or introduce a utility:
static int probe_insn(enum bpf_prog_type prog_type, struct bpf_insn insn,
const char **accepted_msgs)
And call it from both libbpf_probe_bpf_{helper,kfunc}?
Yes, it seems much more concise. I will send it in v3. Thanks.
+ struct bpf_insn insns[] = {
+ BPF_EXIT_INSN(),
+ BPF_EXIT_INSN(),
+ };
+ const size_t insn_cnt = ARRAY_SIZE(insns);
+ int err;
+ char buf[4096];
+
+ if (opts)
+ return libbpf_err(-EINVAL);
+
+ /* Same logic as probe_bpf_helper check */
+ switch (prog_type) {
+ case BPF_PROG_TYPE_TRACING:
+ case BPF_PROG_TYPE_EXT:
+ case BPF_PROG_TYPE_LSM:
+ case BPF_PROG_TYPE_STRUCT_OPS:
+ return -EOPNOTSUPP;
+ default:
+ break;
+ }
+
+ insns[0].code = BPF_JMP | BPF_CALL;
+ insns[0].src_reg = BPF_PSEUDO_KFUNC_CALL;
+ insns[0].imm = kfunc_id;
+ insns[0].off = off;
+
+ buf[0] = '\0';
+ err = probe_prog_load(prog_type, insns, insn_cnt, buf, sizeof(buf));
+ if (err < 0)
+ return libbpf_err(err);
+
+ /* If BPF verifier recognizes BPF kfunc but it's not supported for
+ * given BPF program type, it will emit "calling kernel function
+ * bpf_cpumask_create is not allowed", if the kfunc id is invalid,
+ * it will emit "kernel btf_id 4294967295 is not a function"
+ */
+ if (err == 0 && (strstr(buf, "not allowed") || strstr(buf, "not a function")))
+ return 0;
+
+ return 1; /* assume supported */
+}
+
int libbpf_probe_bpf_helper(enum bpf_prog_type prog_type, enum bpf_func_id helper_id,
const void *opts)
{
--
Best Regards
Dylane Chen
