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libbpf: Fix reuse of pinned map on older kernel
[ Upstream commit 97eb31384a
]
When loading a BPF program with a pinned map, the loader checks whether
the pinned map can be reused, i.e. their properties match. To derive
such of the pinned map, the loader invokes BPF_OBJ_GET_INFO_BY_FD and
then does the comparison.
Unfortunately, on < 4.12 kernels the BPF_OBJ_GET_INFO_BY_FD is not
available, so loading the program fails with the following error:
libbpf: failed to get map info for map FD 5: Invalid argument
libbpf: couldn't reuse pinned map at
'/sys/fs/bpf/tc/globals/cilium_call_policy': parameter
mismatch"
libbpf: map 'cilium_call_policy': error reusing pinned map
libbpf: map 'cilium_call_policy': failed to create:
Invalid argument(-22)
libbpf: failed to load object 'bpf_overlay.o'
To fix this, fallback to derivation of the map properties via
/proc/$PID/fdinfo/$MAP_FD if BPF_OBJ_GET_INFO_BY_FD fails with EINVAL,
which can be used as an indicator that the kernel doesn't support
the latter.
Signed-off-by: Martynas Pumputis <m@lambda.lt>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20210712125552.58705-1-m@lambda.lt
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
parent
6a985c5794
commit
c327b69e96
1 changed files with 45 additions and 3 deletions
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@ -3613,6 +3613,42 @@ static int bpf_map_find_btf_info(struct bpf_object *obj, struct bpf_map *map)
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return 0;
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return 0;
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}
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}
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static int bpf_get_map_info_from_fdinfo(int fd, struct bpf_map_info *info)
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{
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char file[PATH_MAX], buff[4096];
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FILE *fp;
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__u32 val;
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int err;
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snprintf(file, sizeof(file), "/proc/%d/fdinfo/%d", getpid(), fd);
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memset(info, 0, sizeof(*info));
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fp = fopen(file, "r");
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if (!fp) {
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err = -errno;
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pr_warn("failed to open %s: %d. No procfs support?\n", file,
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err);
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return err;
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}
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while (fgets(buff, sizeof(buff), fp)) {
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if (sscanf(buff, "map_type:\t%u", &val) == 1)
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info->type = val;
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else if (sscanf(buff, "key_size:\t%u", &val) == 1)
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info->key_size = val;
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else if (sscanf(buff, "value_size:\t%u", &val) == 1)
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info->value_size = val;
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else if (sscanf(buff, "max_entries:\t%u", &val) == 1)
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info->max_entries = val;
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else if (sscanf(buff, "map_flags:\t%i", &val) == 1)
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info->map_flags = val;
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}
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fclose(fp);
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return 0;
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}
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int bpf_map__reuse_fd(struct bpf_map *map, int fd)
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int bpf_map__reuse_fd(struct bpf_map *map, int fd)
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{
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{
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struct bpf_map_info info = {};
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struct bpf_map_info info = {};
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@ -3621,6 +3657,8 @@ int bpf_map__reuse_fd(struct bpf_map *map, int fd)
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char *new_name;
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char *new_name;
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err = bpf_obj_get_info_by_fd(fd, &info, &len);
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err = bpf_obj_get_info_by_fd(fd, &info, &len);
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if (err && errno == EINVAL)
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err = bpf_get_map_info_from_fdinfo(fd, &info);
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if (err)
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if (err)
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return err;
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return err;
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@ -4032,12 +4070,16 @@ static bool map_is_reuse_compat(const struct bpf_map *map, int map_fd)
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struct bpf_map_info map_info = {};
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struct bpf_map_info map_info = {};
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char msg[STRERR_BUFSIZE];
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char msg[STRERR_BUFSIZE];
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__u32 map_info_len;
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__u32 map_info_len;
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int err;
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map_info_len = sizeof(map_info);
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map_info_len = sizeof(map_info);
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if (bpf_obj_get_info_by_fd(map_fd, &map_info, &map_info_len)) {
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err = bpf_obj_get_info_by_fd(map_fd, &map_info, &map_info_len);
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pr_warn("failed to get map info for map FD %d: %s\n",
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if (err && errno == EINVAL)
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map_fd, libbpf_strerror_r(errno, msg, sizeof(msg)));
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err = bpf_get_map_info_from_fdinfo(map_fd, &map_info);
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if (err) {
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pr_warn("failed to get map info for map FD %d: %s\n", map_fd,
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libbpf_strerror_r(errno, msg, sizeof(msg)));
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return false;
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return false;
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}
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}
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