在 2025/1/25 00:27, Jiri Olsa 写道:
On Fri, Jan 24, 2025 at 10:44:10PM +0800, Tao Chen 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. Signed-off-by: Tao Chen <chen.dylane@xxxxxxxxx> --- tools/lib/bpf/libbpf.h | 17 ++++++++++++++++- tools/lib/bpf/libbpf.map | 1 + tools/lib/bpf/libbpf_probes.c | 30 ++++++++++++++++++++++++++++++ 3 files changed, 47 insertions(+), 1 deletion(-) diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h index 3020ee45303a..035829e22099 100644 --- a/tools/lib/bpf/libbpf.h +++ b/tools/lib/bpf/libbpf.h @@ -1680,7 +1680,22 @@ 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 btf_fd The module BTF FD, 0 for vmlinux + * @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, __s16 btf_fd, 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. diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map index a8b2936a1646..e93fae101efd 100644 --- a/tools/lib/bpf/libbpf.map +++ b/tools/lib/bpf/libbpf.map @@ -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; diff --git a/tools/lib/bpf/libbpf_probes.c b/tools/lib/bpf/libbpf_probes.c index b73345977b4e..cd7d16c1cc49 100644 --- a/tools/lib/bpf/libbpf_probes.c +++ b/tools/lib/bpf/libbpf_probes.c @@ -446,6 +446,36 @@ static int probe_func_comm(enum bpf_prog_type prog_type, struct bpf_insn insn, return 0; }+int libbpf_probe_bpf_kfunc(enum bpf_prog_type prog_type, int kfunc_id,+ __s16 btf_fd, const void *opts) +{ + struct bpf_insn insn; + int err; + char buf[4096]; + + if (opts) + return libbpf_err(-EINVAL); + + insn.code = BPF_JMP | BPF_CALL; + insn.src_reg = BPF_PSEUDO_KFUNC_CALL; + insn.imm = kfunc_id; + insn.off = btf_fd;nit, you could use struct bpf_insn insns[] = { BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, BPF_PSEUDO_KFUNC_CALL, off, imm), BPF_EXIT_INSN(), }; jirka
Yeah, it looks more concise, i will send it in v4. Thanks.
+ + err = probe_func_comm(prog_type, insn, buf, sizeof(buf)); + if (err) + return 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) { -- 2.43.0
-- Best Regards Dylane Chen
