Retry map access with read-only permission, if access was denied when all permissions were requested (open_flags is set to zero). Write access might have been denied by the bpf_map security hook.
Some operations, such as show and dump, don't need write permissions, so there is a good chance of success with retrying.
Prefer this solution to extending the API, as otherwise a new mechanism would need to be implemented to determine the right permissions for an operation.
Signed-off-by: Roberto Sassu roberto.sassu@huawei.com --- tools/lib/bpf/bpf.c | 5 +++++ 1 file changed, 5 insertions(+)
diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c index 240186aac8e6..b4eec39021a4 100644 --- a/tools/lib/bpf/bpf.c +++ b/tools/lib/bpf/bpf.c @@ -1056,6 +1056,11 @@ int bpf_map_get_fd_by_id(__u32 id) attr.map_id = id;
fd = sys_bpf_fd(BPF_MAP_GET_FD_BY_ID, &attr, sizeof(attr)); + if (fd < 0) { + attr.open_flags = BPF_F_RDONLY; + fd = sys_bpf_fd(BPF_MAP_GET_FD_BY_ID, &attr, sizeof(attr)); + } + return libbpf_err_errno(fd); }