When and where are the standard in, out, and error file descriptors first opened in linux?

Where are stdin, stdout, and stderr (the fds) **first** opened? Is it the kernel that does it? And when and where are the symlinks /dev/std{in,out,err} made? Where is the code that does it? I assume it is in the linux kernel source code but I wasn't able to find where it happens even after a search in the archlinux 6.5.3-arch1-1 linux kernel github repo. edit: please, if you are downvoting this question can you explain why so I can make it better? I would really like to know about this question. It is not easy to find the answer.