| Message ID | 20250123170555.291896-2-chen.dylane@gmail.com (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | BPF |
| Headers | show |
| Series | Add prog_kfunc feature probe | expand |
| Context | Check | Description |
|---|---|---|
| netdev/tree_selection | success | Clearly marked for bpf-next |
| netdev/apply | fail | Patch does not apply to bpf-next-0 |
| bpf/vmtest-bpf-net-PR | fail | merge-conflict |
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? > +{ 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}? > + 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) > {
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) >> { > >
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h index 3020ee45303a..ac0b46d8d8f9 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 off 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 off, 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 9dfbe7750f56..641b1b008eeb 100644 --- a/tools/lib/bpf/libbpf_probes.c +++ b/tools/lib/bpf/libbpf_probes.c @@ -413,6 +413,53 @@ 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, + __s16 off, 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); + + /* 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) { -- 2.43.0
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 | 17 ++++++++++++- tools/lib/bpf/libbpf.map | 1 + tools/lib/bpf/libbpf_probes.c | 47 +++++++++++++++++++++++++++++++++++ 3 files changed, 64 insertions(+), 1 deletion(-)