[PATCH bpf-next 2/3] bpf: implement map_update_elem to init relay file
From: Philo Lu <hidden>
Date: 2023-12-22 12:21:54
Also in:
bpf
Subsystem:
bpf [general] (safe dynamic programs and tools), the rest · Maintainers:
Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko, Eduard Zingerman, Kumar Kartikeya Dwivedi, Linus Torvalds
map_update_elem is used to create relay files and bind them with the relay channel, which is created with BPF_MAP_CREATE. This allows users to set a custom directory name. It must be used with key=NULL and flag=0. Here is an example:
struct {
__uint(type, BPF_MAP_TYPE_RELAY);
__uint(max_entries, 4096);
} my_relay SEC(".maps");
...
char dir_name[] = "relay_test";
bpf_map_update_elem(map_fd, NULL, dir_name, 0);
Then, directory `/sys/kerenl/debug/relay_test` will be created, which includes files of my_relay0...my_relay[#cpu]. Each represents a per-cpu buffer with size 8 * 4096 B (there are 8 subbufs by default, each with size 4096B). Signed-off-by: Philo Lu <redacted> --- kernel/bpf/relaymap.c | 32 +++++++++++++++++++++++++++++++- 1 file changed, 31 insertions(+), 1 deletion(-)
diff --git a/kernel/bpf/relaymap.c b/kernel/bpf/relaymap.c
index d0adc7f67758..588c8de0a4bd 100644
--- a/kernel/bpf/relaymap.c
+++ b/kernel/bpf/relaymap.c@@ -117,7 +117,37 @@ static void *relay_map_lookup_elem(struct bpf_map *map, void *key) static long relay_map_update_elem(struct bpf_map *map, void *key, void *value, u64 flags) { - return -EOPNOTSUPP; + struct bpf_relay_map *rmap; + struct dentry *parent; + int err; + + if (unlikely(flags)) + return -EINVAL; + + if (unlikely(key)) + return -EINVAL; + + rmap = container_of(map, struct bpf_relay_map, map); + + /* The directory already exists */ + if (rmap->relay_chan->has_base_filename) + return -EEXIST; + + /* Setup relay files. Note that the directory name passed as value should + * not be longer than map->value_size, including the '\0' at the end. + */ + ((char *)value)[map->value_size - 1] = '\0'; + parent = debugfs_create_dir(value, NULL); + if (IS_ERR_OR_NULL(parent)) + return PTR_ERR(parent); + + err = relay_late_setup_files(rmap->relay_chan, map->name, parent); + if (err) { + debugfs_remove_recursive(parent); + return err; + } + + return 0; } static long relay_map_delete_elem(struct bpf_map *map, void *key)
--
2.32.0.3.g01195cf9f