GetMetadata fetches the process's metadata of type t and writes it into buf.

Cmdline represents /proc/[pid]/cmdline.

Environ represents /proc/[pid]/environ.

Name is the default filesystem name.

FilesystemType is the factory class for procfs.

InternalData contains internal data passed in to the procfs mount via vfs.GetFilesystemOptions.InternalData.

MetadataType enumerates the types of metadata that is exposed through proc.