netdev - [PATCHv3 bpf-next] libbpf: Add names for auxiliary maps

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Date:   Thu, 11 Aug 2022 11:40:20 +0800
From:   Hangbin Liu <liuhangbin@...il.com>
To:     netdev@...r.kernel.org
Cc:     Quentin Monnet <quentin@...valent.com>,
        Andrii Nakryiko <andrii@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Martin KaFai Lau <martin.lau@...ux.dev>,
        Song Liu <song@...nel.org>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Stanislav Fomichev <sdf@...gle.com>,
        Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>,
        bpf@...r.kernel.org, Hangbin Liu <liuhangbin@...il.com>
Subject: [PATCHv3 bpf-next] 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 disscussed[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@...il.com>
---
v3: let bpf_map_create ignore the name if kernel doesn't support
v2: rename the wrapper with proper name
---
 tools/lib/bpf/bpf.c    | 2 +-
 tools/lib/bpf/libbpf.c | 6 +++---
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
index efcc06dafbd9..6a96e665dc5d 100644
--- 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 f7364ea82ac1..a075211b3730 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -4432,7 +4432,7 @@ 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));
@@ -4565,7 +4565,7 @@ 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);
 }
 
@@ -4612,7 +4612,7 @@ 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));
-- 
2.35.3