Playing with the PROM
I've got a socketed series 2.5 around that I have not been using to watch TV lately and I have started digging into the PROM to see what other new and interesting mods could be made. I've been using an external programmer with the original SST37VF010. To save wear and tear on the socket, I could replace it with an SST39VF010. Even though I would be able to flash it in place that would still require frequent reboots so I thought I'd pull interesting parts of the PROM code out and re-assemble them with the gnu assembler. This way I would save on the purchase of another PROM chip, save wear and tear on the socket, and most importantly, save time.
My first section of re-assembled code caused a segfault when attempting to run it. In order to find precisely which address read or write was causing the segfault, I figured gdb would be helpful. After searching, I was unable to locate a MIPS gdb binary and also failed at cross-compiling gdb. I figured including a printf function in my re-assembled code could be a useful alternative to gdb. So I extracted the printf function from the PROM and re-assembled it. I felt like I was making progress because this time it did not segfault but gave a bus error instead.
Please post a link to download a TiVo binary of gdb if anyone has it. I've attached my still not working printf test binary in case anyone wants to look at it and help me find my error(s).