在 2025/2/10 21:47, Jiri Olsa 写道:
On Mon, Feb 10, 2025 at 01:59:44PM +0800, Tao Chen wrote:
SNIP
diff --git a/tools/lib/bpf/libbpf_probes.c b/tools/lib/bpf/libbpf_probes.c
index e142130cb83c..53f1196394bf 100644
--- a/tools/lib/bpf/libbpf_probes.c
+++ b/tools/lib/bpf/libbpf_probes.c
@@ -433,6 +433,54 @@ static bool can_probe_prog_type(enum bpf_prog_type prog_type)
return true;
}
+int libbpf_probe_bpf_kfunc(enum bpf_prog_type prog_type, int kfunc_id, int btf_fd,
+ const void *opts)
+{
+ struct bpf_insn insns[] = {
+ BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, BPF_PSEUDO_KFUNC_CALL, 1, kfunc_id),
+ BPF_EXIT_INSN(),
+ };
+ const size_t insn_cnt = ARRAY_SIZE(insns);
+ char buf[4096];
+ int fd_array[2] = {-1};
+ int ret;
+
+ if (opts)
+ return libbpf_err(-EINVAL);
+
+ if (!can_probe_prog_type(prog_type))
+ return -EOPNOTSUPP;
+
+ if (btf_fd >= 0) {
+ fd_array[1] = btf_fd;
+ } else if (btf_fd == -1) {
+ /* insn.off = 0, means vmlinux btf */
+ insns[0].off = 0;
+ } else {
+ return libbpf_err(-EINVAL);
+ }
+
+ buf[0] = '\0';
+ ret = probe_prog_load(prog_type, insns, insn_cnt, btf_fd >= 0 ? fd_array : NULL,
+ 0, buf, sizeof(buf));
hum, you pass fd_array_cnt as 0, which IIUC will work properly
but I guess then we don't need to have fd_array_cnt argument in
probe_prog_load if all callers pass 0 ?
jirka
Hi, jiri
In fact, 0 is indeed used everywhere here. I was just thinking about
whether we might need it in the future. Anyway, it seems better to
remove it. I'll make the modifications in the next version.
+ if (ret < 0)
+ return libbpf_err(ret);
+
+ /* 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 btf fd
+ * invalid in module btf, it will emit "invalid module BTF fd specified" or
+ * "negative offset disallowed for kernel module function call"
+ */
+ if (ret == 0 && (strstr(buf, "not allowed") || strstr(buf, "not a function") ||
+ (strstr(buf, "invalid module BTF fd")) ||
+ (strstr(buf, "negative offset disallowed"))))
+ 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)
{
--
2.43.0
--
Best Regards
Dylane Chen
