Messages in this thread | | | From | Andrii Nakryiko <> | Date | Mon, 11 Jul 2022 14:51:59 -0700 | Subject | Re: [PATCH] libbpf: fix the name of a reused map |
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On Mon, Jul 11, 2022 at 3:25 AM anquan.wu <leiqi96@hotmail.com> wrote: > > BPF map name was limited to BPF_OBJ_NAME_LEN. > If a map name is defined as being longer than BPF_OBJ_NAME_LEN, > it will be truncated to BPF_OBJ_NAME_LEN > when a userspace program calls libbpf to create the map. > A pinned map also generates a path in the /sys. > If the previous program wanted to reuse the map,it can not get bpf_map > by name, because the name of the map is only partially the same as > the name which get from pinned path. > > The syscall information below show that map name > "process_pinned_map" is truncated to process_pinned_" > > bpf(BPF_OBJ_GET, {pathname="/sys/fs/bpf/process_pinned_map", > bpf_fd=0, file_flags=0}, 144) = -1 ENOENT (No such file or directory) > > bpf(BPF_MAP_CREATE, {map_type=BPF_MAP_TYPE_HASH, key_size=4, value_size=4, > max_entries=1024, map_flags=0, inner_map_fd=0, map_name="process_pinned_", > map_ifindex=0, btf_fd=3, btf_key_type_id=6, btf_value_type_id=10, > btf_vmlinux_value_type_id=0}, 72) = 4 > > This patch check that if the name of pinned map are the same as the > actual name for the first (BPF_OBJ_NAME_LEN - 1), > bpf map still uses the name which is included in bpf object. > > Signed-off-by: anquan.wu <leiqi96@hotmail.com>
please use your complete and capitalized name in Signed-off-by
Overall, looks good, I have a few stylistical nits, see below. But also you forgot to cc bpf@vger.kernel.org, please send v2 and don't forget to add mailing list. Without that our CI can't test your patch properly.
> --- > tools/lib/bpf/libbpf.c | 8 +++++++- > 1 file changed, 7 insertions(+), 1 deletion(-) > > diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c > index e89cc9c885b3..5ad52a8accd1 100644 > --- a/tools/lib/bpf/libbpf.c > +++ b/tools/lib/bpf/libbpf.c > @@ -4328,6 +4328,7 @@ int bpf_map__reuse_fd(struct bpf_map *map, int fd) > { > struct bpf_map_info info = {}; > __u32 len = sizeof(info); > + __u32 name_len;
nit: __u32 len = sizeof(info), name_len;
> int new_fd, err; > char *new_name; > > @@ -4337,7 +4338,12 @@ int bpf_map__reuse_fd(struct bpf_map *map, int fd) > if (err) > return libbpf_err(err); > > - new_name = strdup(info.name); > + name_len = strlen(info.name); > + if ((BPF_OBJ_NAME_LEN - 1) == name_len && !strncmp(map->name, info.name, name_len))
nit, unnecessary () around BPF_OBJ_NAME_LEN, plus the order is a bit weird. I also have general preference with strncmp/strcmp to compare against zero explicitly, so can you rewrite this as:
if (name_len == BPF_OBJ_NAME_LEN - 1 && strncmp(map->name, info.name, name_len) == 0)
?
> + new_name = strdup(map->name); > + else > + new_name = strdup(info.name); > + > if (!new_name) > return libbpf_err(-errno); > > -- > 2.32.0 >
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