@@ -1680,7 +1680,21 @@ LIBBPF_API int libbpf_probe_bpf_map_type(enum bpf_map_type map_type, const void
*/
LIBBPF_API int libbpf_probe_bpf_helper(enum bpf_prog_type prog_type,
enum bpf_func_id helper_id, const void *opts);
-
+/**
+ * @brief **libbpf_probe_bpf_kfunc()** detects if host kernel supports the
+ * use of a given BPF kfunc from specified BPF program type.
+ * @param prog_type BPF program type used to check the support of BPF kfunc
+ * @param kfunc_id The btf ID of BPF kfunc to check support for
+ * @param opts reserved for future extensibility, should be NULL
+ * @return 1, if given combination of program type and kfunc is supported; 0,
+ * if the combination is not supported; negative error code if feature
+ * detection for provided input arguments failed or can't be performed
+ *
+ * Make sure the process has required set of CAP_* permissions (or runs as
+ * root) when performing feature checking.
+ */
+LIBBPF_API int libbpf_probe_bpf_kfunc(enum bpf_prog_type prog_type,
+ int kfunc_id, const void *opts);
/**
* @brief **libbpf_num_possible_cpus()** is a helper function to get the
* number of possible CPUs that the host kernel supports and expects.
@@ -436,4 +436,5 @@ LIBBPF_1.6.0 {
bpf_linker__add_buf;
bpf_linker__add_fd;
bpf_linker__new_fd;
+ libbpf_probe_bpf_kfunc;
} LIBBPF_1.5.0;
@@ -413,6 +413,42 @@ int libbpf_probe_bpf_map_type(enum bpf_map_type map_type, const void *opts)
return libbpf_err(ret);
}
+int libbpf_probe_bpf_kfunc(enum bpf_prog_type prog_type, int kfunc_id,
+ const void *opts)
+{
+ 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);
+
+ insns[0].code = BPF_JMP | BPF_CALL;
+ insns[0].src_reg = BPF_PSEUDO_KFUNC_CALL;
+ insns[0].imm = kfunc_id;
+
+ /* Now only support kfunc from vmlinux */
+ insns[0].off = 0;
+
+ 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 (err == 0 && strstr(buf, "not allowed"))
+ 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)
{
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. Signed-off-by: Tao Chen <chen.dylane@gmail.com> --- tools/lib/bpf/libbpf.h | 16 +++++++++++++++- tools/lib/bpf/libbpf.map | 1 + tools/lib/bpf/libbpf_probes.c | 36 +++++++++++++++++++++++++++++++++++ 3 files changed, 52 insertions(+), 1 deletion(-)