The 4.3 upgrade just started rolling out for the S3 and now we also have the kernel sources : http://opensource.samsung.com/reception/receptionSub.do?method=search&searchValue=I9300
The “update12″ file is the one you’re looking for, with version XXUGMJ9.
The “update12″ file is the one you’re looking for, with version XXUGMJ9.