libbpf: Show supported ELF section names when failing to guess prog/attach type

We need to let users check their wrong ELF section name with proper
ELF section names when they fail to get a prog/attach type from it.
Because users can't realize libbpf guess prog/attach types from given
ELF section names. For example, when a 'cgroup' section name of a
BPF program is used, show available ELF section names(types).

Before:

    $ bpftool prog load bpf-prog.o /sys/fs/bpf/prog1
    Error: failed to guess program type based on ELF section name cgroup

After:

    libbpf: failed to guess program type based on ELF section name 'cgroup'
    libbpf: supported section(type) names are: socket kprobe/ kretprobe/ classifier action tracepoint/ raw_tracepoint/ xdp perf_event lwt_in lwt_out lwt_xmit lwt_seg6local cgroup_skb/ingress cgroup_skb/egress cgroup/skb cgroup/sock cgroup/post_bind4 cgroup/post_bind6 cgroup/dev sockops sk_skb/stream_parser sk_skb/stream_verdict sk_skb sk_msg lirc_mode2 flow_dissector cgroup/bind4 cgroup/bind6 cgroup/connect4 cgroup/connect6 cgroup/sendmsg4 cgroup/sendmsg6

Signed-off-by: Taeung Song <treeze.taeung@gmail.com>
Cc: Quentin Monnet <quentin.monnet@netronome.com>
Cc: Jakub Kicinski <jakub.kicinski@netronome.com>
Cc: Andrey Ignatov <rdna@fb.com>
Reviewed-by: Quentin Monnet <quentin.monnet@netronome.com>
Acked-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

diff --git a/tools/bpf/bpftool/prog.c b/tools/bpf/bpftool/prog.c
index 2d1bb7d..0640e9b 100644 (file)
--- a/tools/bpf/bpftool/prog.c
+++ b/tools/bpf/bpftool/prog.c
@@ -930,10 +930,9 @@ static int load_with_options(int argc, char **argv, bool first_prog_only)
                        err = libbpf_prog_type_by_name(type, &attr.prog_type,
                                                       &expected_attach_type);
                        free(type);
-                       if (err < 0) {
-                               p_err("unknown program type '%s'", *argv);
+                       if (err < 0)
                                goto err_free_reuse_maps;
-                       }
+
                        NEXT_ARG();
                } else if (is_prefix(*argv, "map")) {
                        void *new_map_replace;
@@ -1028,11 +1027,8 @@ static int load_with_options(int argc, char **argv, bool first_prog_only)
 
                        err = libbpf_prog_type_by_name(sec_name, &prog_type,
                                                       &expected_attach_type);
-                       if (err < 0) {
-                               p_err("failed to guess program type based on section name %s\n",
-                                     sec_name);
+                       if (err < 0)
                                goto err_close_obj;
-                       }
                }
 
                bpf_program__set_ifindex(pos, ifindex);

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 169e347..2ccde17 100644 (file)
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -2667,9 +2667,38 @@ static const struct {
 #undef BPF_EAPROG_SEC
 #undef BPF_APROG_COMPAT
 
+#define MAX_TYPE_NAME_SIZE 32
+
+static char *libbpf_get_type_names(bool attach_type)
+{
+       int i, len = ARRAY_SIZE(section_names) * MAX_TYPE_NAME_SIZE;
+       char *buf;
+
+       buf = malloc(len);
+       if (!buf)
+               return NULL;
+
+       buf[0] = '\0';
+       /* Forge string buf with all available names */
+       for (i = 0; i < ARRAY_SIZE(section_names); i++) {
+               if (attach_type && !section_names[i].is_attachable)
+                       continue;
+
+               if (strlen(buf) + strlen(section_names[i].sec) + 2 > len) {
+                       free(buf);
+                       return NULL;
+               }
+               strcat(buf, " ");
+               strcat(buf, section_names[i].sec);
+       }
+
+       return buf;
+}
+
 int libbpf_prog_type_by_name(const char *name, enum bpf_prog_type *prog_type,
                             enum bpf_attach_type *expected_attach_type)
 {
+       char *type_names;
        int i;
 
        if (!name)
@@ -2682,12 +2711,20 @@ int libbpf_prog_type_by_name(const char *name, enum bpf_prog_type *prog_type,
                *expected_attach_type = section_names[i].expected_attach_type;
                return 0;
        }
+       pr_warning("failed to guess program type based on ELF section name '%s'\n", name);
+       type_names = libbpf_get_type_names(false);
+       if (type_names != NULL) {
+               pr_info("supported section(type) names are:%s\n", type_names);
+               free(type_names);
+       }
+
        return -EINVAL;
 }
 
 int libbpf_attach_type_by_name(const char *name,
                               enum bpf_attach_type *attach_type)
 {
+       char *type_names;
        int i;
 
        if (!name)
@@ -2701,6 +2738,13 @@ int libbpf_attach_type_by_name(const char *name,
                *attach_type = section_names[i].attach_type;
                return 0;
        }
+       pr_warning("failed to guess attach type based on ELF section name '%s'\n", name);
+       type_names = libbpf_get_type_names(true);
+       if (type_names != NULL) {
+               pr_info("attachable section(type) names are:%s\n", type_names);
+               free(type_names);
+       }
+
        return -EINVAL;
 }
 
@@ -2907,8 +2951,6 @@ int bpf_prog_load_xattr(const struct bpf_prog_load_attr *attr,
                        err = bpf_program__identify_section(prog, &prog_type,
                                                            &expected_attach_type);
                        if (err < 0) {
-                               pr_warning("failed to guess program type based on section name %s\n",
-                                          prog->section_name);
                                bpf_object__close(obj);
                                return -EINVAL;
                        }

diff --git a/tools/testing/selftests/bpf/test_socket_cookie.c b/tools/testing/selftests/bpf/test_socket_cookie.c
index fc7832e..e51d637 100644 (file)
--- a/tools/testing/selftests/bpf/test_socket_cookie.c
+++ b/tools/testing/selftests/bpf/test_socket_cookie.c
@@ -158,10 +158,8 @@ static int run_test(int cgfd)
        bpf_object__for_each_program(prog, pobj) {
                prog_name = bpf_program__title(prog, /*needs_copy*/ false);
 
-               if (libbpf_attach_type_by_name(prog_name, &attach_type)) {
-                       log_err("Unexpected prog: %s", prog_name);
+               if (libbpf_attach_type_by_name(prog_name, &attach_type))
                        goto err;
-               }
 
                err = bpf_prog_attach(bpf_program__fd(prog), cgfd, attach_type,
                                      BPF_F_ALLOW_OVERRIDE);