validateMaps fails for eBPF map without property 'value'

[havefuncoding1]

Almost all yaml files under examples point to eBPF maps with 'value' property defined. Here is an example from accept-latency:

struct {
    __uint(type, BPF_MAP_TYPE_HASH);
    __uint(max_entries, (MAX_LATENCY_SLOT + 1) * MAX_PORTS);
    __type(key, struct socket_latency_key_t);
    __type(value, u64);
} accept_latency_seconds SEC(".maps");

One exception is that oomkill. Here is the map definition which has no 'value'. Instead, it is value_size.

struct {
    __uint(type, BPF_MAP_TYPE_PERF_EVENT_ARRAY);
    __uint(key_size, sizeof(u32));
    __uint(value_size, sizeof(u32));
} oom_kills_total SEC(".maps");

Running this example results in runtime failure

Error attaching exporter: error validating maps for config "oomkill": value size for map "oom_kills_total" is not expected 8 bytes (u64), it is 4 bytes

And this is caused by the check in validateMap. What would be the solution here? Is replacing 'fmt.Errorf' with a warning message reasonable? We can add a 'value' to the map, but per my understanding there shouldn't be a 'value' property for BPF_MAP_TYPE_PERF_EVENT_ARRAY. Here is reference from Nakryiko's blog. Thanks.

valueSize := m.ValueSize()
if valueSize != 8 {
	return fmt.Errorf("value size for map %q is not expected 8 bytes (u64), it is %d bytes", name, valueSize)
}

[bobrik]

Thanks for the report. I opened #322 to both fix this and prevent it from breaking again.