• Yonghong Song's avatar
    bpf: Change uapi for bpf iterator map elements · 5e7b3020
    Yonghong Song authored
    Commit a5cbe05a ("bpf: Implement bpf iterator for
    map elements") added bpf iterator support for
    map elements. The map element bpf iterator requires
    info to identify a particular map. In the above
    commit, the attr->link_create.target_fd is used
    to carry map_fd and an enum bpf_iter_link_info
    is added to uapi to specify the target_fd actually
    representing a map_fd:
        enum bpf_iter_link_info {
    	BPF_ITER_LINK_UNSPEC = 0,
    	BPF_ITER_LINK_MAP_FD = 1,
    
    	MAX_BPF_ITER_LINK_INFO,
        };
    
    This is an extensible approach as we can grow
    enumerator for pid, cgroup_id, etc. and we can
    unionize target_fd for pid, cgroup_id, etc.
    But in the future, there are chances that
    more complex customization may happen, e.g.,
    for tasks, it could be filtered based on
    both cgroup_id and user_id.
    
    This patch changed the uapi to have fields
    	__aligned_u64	iter_info;
    	__u32		iter_info_len;
    for additional iter_info for link_create.
    The iter_info is defined as
    	union bpf_iter_link_info {
    		struct {
    			__u32   map_fd;
    		} map;
    	};
    
    So future extension for additional customization
    will be easier. The bpf_iter_link_info will be
    passed to target callback to validate and generic
    bpf_iter framework does not need to deal it any
    more.
    
    Note that map_fd = 0 will be considered invalid
    and -EBADF will be returned to user space.
    
    Fixes: a5cbe05a ("bpf: Implement bpf iterator for map elements")
    Signed-off-by: default avatarYonghong Song <yhs@fb.com>
    Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
    Acked-by: default avatarAndrii Nakryiko <andriin@fb.com>
    Acked-by: default avatarJohn Fastabend <john.fastabend@gmail.com>
    Link: https://lore.kernel.org/bpf/20200805055056.1457463-1-yhs@fb.com
    5e7b3020
bpf_iter.c 12.9 KB