I am working on a os and i am using the ms_abi and was wondering how does it pass arguments because i am moving some systemtable info into a register but when i try to call a function using the correct offset it freezes i think this is because of a incorrect use of the abi

i tried using what is on wikipedia but i dont think it was working i could also just be that i am not using the abi correctly can i get help? i tried using rcx and rdx but those are not working i also looked at the gcc documentation but that was no help either
this is what i am trying

mov [Systable], rcx
mov [ImgHandle],rdx