Comment by LennyHenrysNuts
1 day ago
We were always doing this kind of thing on these platforms. This is how we used to hack copy protection out of games.
Stepping through, line by line, editing the code and adding JMPs to get around the copy protection code after loading the magic numbers into the register...
Happy, happy times.
Then they started loading the protection code from disk doing tricky things. One I cracked recently was a pair of Commodore 1541 sectors that appeared to be the same logical sector (because the drive head is blind). It needed to hit both of them to compile the next portion of the loader. Naturally the segment up to that point was encrypted as well, but nothing survives a VICE breakpoint. https://oldvcr.blogspot.com/2023/08/cracking-designwares-gra...
Obviously this is nothing on things like V-MAX! and Rapidlok which even nowadays have variations that are tough to remaster.
That's how I first learned assembly. Armed with a monitor program that can disassemble and modify memory, I read and modified programs stepping through them. Mostly games, naturally. I never got an actual assembler/linker chain that would work and useful software was hard to come by.