libbpf: Add names for auxiliary maps

The bpftool self-created maps can appear in final map show output due to
deferred removal in kernel. These maps don't have a name, which would make
users confused about where it comes from.

With a libbpf_ prefix name, users could know who created these maps.
It also could make some tests (like test_offload.py, which skip base maps
without names as a workaround) filter them out.

Kernel adds bpf prog/map name support in the same merge
commit fadad670a8ab ("Merge branch 'bpf-extend-info'"). So we can also use
kernel_supports(NULL, FEAT_PROG_NAME) to check if kernel supports map name.

As discussed [1], Let's make bpf_map_create accept non-null
name string, and silently ignore the name if kernel doesn't support.

  [1] https://lore.kernel.org/bpf/CAEf4BzYL1TQwo1231s83pjTdFPk9XWWhfZC5=KzkU-VO0k=0Ug@mail.gmail.com/

Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20220811034020.529685-1-liuhangbin@gmail.com

diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
index efcc06d..6a96e66 100644 (file)
--- a/tools/lib/bpf/bpf.c
+++ b/tools/lib/bpf/bpf.c
@@ -183,7 +183,7 @@ int bpf_map_create(enum bpf_map_type map_type,
                return libbpf_err(-EINVAL);
 
        attr.map_type = map_type;
-       if (map_name)
+       if (map_name && kernel_supports(NULL, FEAT_PROG_NAME))
                libbpf_strlcpy(attr.map_name, map_name, sizeof(attr.map_name));
        attr.key_size = key_size;
        attr.value_size = value_size;

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 917d975..3f01f5c 100644 (file)
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -4437,7 +4437,7 @@ static int probe_kern_global_data(void)
        };
        int ret, map, insn_cnt = ARRAY_SIZE(insns);
 
-       map = bpf_map_create(BPF_MAP_TYPE_ARRAY, NULL, sizeof(int), 32, 1, NULL);
+       map = bpf_map_create(BPF_MAP_TYPE_ARRAY, "libbpf_global", sizeof(int), 32, 1, NULL);
        if (map < 0) {
                ret = -errno;
                cp = libbpf_strerror_r(ret, errmsg, sizeof(errmsg));
@@ -4570,7 +4570,7 @@ static int probe_kern_array_mmap(void)
        LIBBPF_OPTS(bpf_map_create_opts, opts, .map_flags = BPF_F_MMAPABLE);
        int fd;
 
-       fd = bpf_map_create(BPF_MAP_TYPE_ARRAY, NULL, sizeof(int), sizeof(int), 1, &opts);
+       fd = bpf_map_create(BPF_MAP_TYPE_ARRAY, "libbpf_mmap", sizeof(int), sizeof(int), 1, &opts);
        return probe_fd(fd);
 }
 
@@ -4617,7 +4617,7 @@ static int probe_prog_bind_map(void)
        };
        int ret, map, prog, insn_cnt = ARRAY_SIZE(insns);
 
-       map = bpf_map_create(BPF_MAP_TYPE_ARRAY, NULL, sizeof(int), 32, 1, NULL);
+       map = bpf_map_create(BPF_MAP_TYPE_ARRAY, "libbpf_det_bind", sizeof(int), 32, 1, NULL);
        if (map < 0) {
                ret = -errno;
                cp = libbpf_strerror_r(ret, errmsg, sizeof(errmsg));