This patch adds pretty print support to the basic arraymap. Support for other bpf maps can be added later. This patch adds new attrs to the BPF_MAP_CREATE command to allow specifying the btf_fd, btf_key_id and btf_value_id. The BPF_MAP_CREATE can then associate the btf to the map if the creating map supports BTF. A BTF supported map needs to implement two new map ops, map_seq_show_elem() and map_check_btf(). This patch has implemented these new map ops for the basic arraymap. It also adds file_operations, bpffs_map_fops, to the pinned map such that the pinned map can be opened and read. After that, the user has an intuitive way to do "cat bpffs/pathto/a-pinned-map" instead of getting an error. bpffs_map_fops should not be extended further to support other operations. Other operations (e.g. write/key-lookup...) should be realized by the userspace tools (e.g. bpftool) through the BPF_OBJ_GET_INFO_BY_FD, map's lookup/update interface...etc. Follow up patches will allow the userspace to obtain the BTF from a map-fd. Here is a sample output when reading a pinned arraymap with the following map's value: struct map_value { int count_a; int count_b; }; cat /sys/fs/bpf/pinned_array_map: 0: {1,2} 1: {3,4} 2: {5,6} ...
Showing the changes to kernel/bpf/arraymap.c (1 of 5 files). Show all
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| @@ -11,11 +11,13 @@ · 10 unmodified lines | ||
| 11 | 11 | * General Public License for more details. |
| 12 | 12 | */ |
| 13 | 13 | #include <linux/bpf.h> |
| 14 | +#include <linux/btf.h> | |
| 14 | 15 | #include <linux/err.h> |
| 15 | 16 | #include <linux/slab.h> |
| 16 | 17 | #include <linux/mm.h> |
| 17 | 18 | #include <linux/filter.h> |
| 18 | 19 | #include <linux/perf_event.h> |
| 20 | +#include <uapi/linux/btf.h> | |
| 19 | 21 | |
| 20 | 22 | #include "map_in_map.h" |
| 21 | 23 | |
| @@ -336,6 +338,52 @@ static void array_map_free(struct bpf_map *map) · 314 unmodified lines | ||
| 336 | 338 | bpf_map_area_free(array); |
| 337 | 339 | } |
| 338 | 340 | |
| 341 | +static void array_map_seq_show_elem(struct bpf_map *map, void *key, | |
| 342 | + struct seq_file *m) | |
| 343 | +{ | |
| 344 | + void *value; | |
| 345 | + | |
| 346 | + rcu_read_lock(); | |
| 347 | + | |
| 348 | + value = array_map_lookup_elem(map, key); | |
| 349 | + if (!value) { | |
| 350 | + rcu_read_unlock(); | |
| 351 | + return; | |
| 352 | + } | |
| 353 | + | |
| 354 | + seq_printf(m, "%u: ", *(u32 *)key); | |
| 355 | + btf_type_seq_show(map->btf, map->btf_value_id, value, m); | |
| 356 | + seq_puts(m, "\n"); | |
| 357 | + | |
| 358 | + rcu_read_unlock(); | |
| 359 | +} | |
| 360 | + | |
| 361 | +static int array_map_check_btf(const struct bpf_map *map, const struct btf *btf, | |
| 362 | + u32 btf_key_id, u32 btf_value_id) | |
| 363 | +{ | |
| 364 | + const struct btf_type *key_type, *value_type; | |
| 365 | + u32 key_size, value_size; | |
| 366 | + u32 int_data; | |
| 367 | + | |
| 368 | + key_type = btf_type_id_size(btf, &btf_key_id, &key_size); | |
| 369 | + if (!key_type || BTF_INFO_KIND(key_type->info) != BTF_KIND_INT) | |
| 370 | + return -EINVAL; | |
| 371 | + | |
| 372 | + int_data = *(u32 *)(key_type + 1); | |
| 373 | + /* bpf array can only take a u32 key. This check makes | |
| 374 | + * sure that the btf matches the attr used during map_create. | |
| 375 | + */ | |
| 376 | + if (BTF_INT_BITS(int_data) != 32 || key_size != 4 || | |
| 377 | + BTF_INT_OFFSET(int_data)) | |
| 378 | + return -EINVAL; | |
| 379 | + | |
| 380 | + value_type = btf_type_id_size(btf, &btf_value_id, &value_size); | |
| 381 | + if (!value_type || value_size > map->value_size) | |
| 382 | + return -EINVAL; | |
| 383 | + | |
| 384 | + return 0; | |
| 385 | +} | |
| 386 | + | |
| 339 | 387 | const struct bpf_map_ops array_map_ops = { |
| 340 | 388 | .map_alloc_check = array_map_alloc_check, |
| 341 | 389 | .map_alloc = array_map_alloc, |
| @@ -345,6 +393,8 @@ const struct bpf_map_ops array_map_ops = { · 3 unmodified lines | ||
| 345 | 393 | .map_update_elem = array_map_update_elem, |
| 346 | 394 | .map_delete_elem = array_map_delete_elem, |
| 347 | 395 | .map_gen_lookup = array_map_gen_lookup, |
| 396 | + .map_seq_show_elem = array_map_seq_show_elem, | |
| 397 | + .map_check_btf = array_map_check_btf, | |
| 348 | 398 | }; |
| 349 | 399 | |
| 350 | 400 | const struct bpf_map_ops percpu_array_map_ops = { |