Copy protection: DecryptGameBinary

       Name: DecryptGameBinary                                       [Show more]
       Type: Subroutine
   Category: Copy protection
    Summary: Placeholder routine to decrypt game code to &8000 so it can be run
    Context: See this subroutine in context in the source code
 References: This subroutine is called as follows:
             * RunImageEntry calls DecryptGameBinary


.DecryptGameBinary

 LDR     R0, gameCodeAddr           \ Set R0 to the address of the game code

 LDR     R1, absoluteAddr           \ Set R1 to the address of the start of the
                                    \ Absolute file

 LDR     R2, gameCodeEndAddr        \ Set R2 to the address of the end of the
                                    \ game code

.decr1

 LDR     R12, [R0], #4              \ Copy a word from R0 to R1, updating the
 STR     R12, [R1], #4              \ addresses as we go (this is where the
                                    \ decryption process would work, but
                                    \ currently it is just a copy)

 CMP     R0, R2                     \ Loop back until we have copied the whole
 BNE     decr1                      \ game

 B       Entry                      \ Start the game by jumping to the Entry
                                    \ routine