On 7/31/15 4:59 AM, Kaixu Xia wrote:
+static int check_func_limit(struct bpf_map **mapp, int func_id)
+{
+       struct bpf_map *map = *mapp;
+
+       if (map && map->map_type == BPF_MAP_TYPE_PROG_ARRAY &&
+           func_id != BPF_FUNC_tail_call)
+               /* prog_array map type needs extra care:
+                * only allow to pass it into bpf_tail_call() for now.
+                * bpf_map_delete_elem() can be allowed in the future,
+                * while bpf_map_update_elem() must only be done via syscall
+                */
+               return -EINVAL;
+
+       if (func_id == BPF_FUNC_tail_call &&
+           map->map_type != BPF_MAP_TYPE_PROG_ARRAY)
+               /* don't allow any other map type to be passed into
+                * bpf_tail_call()
+                */
+               return -EINVAL;
+
+       if (map && map->map_type == BPF_MAP_TYPE_PERF_EVENT_ARRAY &&
+           func_id != BPF_FUNC_perf_event_read)
+               /* perf_event_array map type needs extra care:
+                * only allow to pass it into bpf_perf_event_read() for now.
+                * bpf_map_update/delete_elem() must only be done via syscall
+                */
+               return -EINVAL;
+
+       if (func_id == BPF_FUNC_perf_event_read &&
+           map->map_type != BPF_MAP_TYPE_PERF_EVENT_ARRAY)
+               /* don't allow any other map type to be passed into
+                * bpf_perf_event_read()
+                */
+               return -EINVAL;

copy paste of comments is too much.
The whole thing probably can be better generalized with an array
{{BPF_MAP_TYPE_PROG_ARRAY, BPF_FUNC_tail_call},
 {BPF_MAP_TYPE_PERF_EVENT_ARRAY, BPF_FUNC_perf_event_read},
}
and a loop?

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