Calculator Community > HP Calculators
HP Prime Emulator
gigi1237:
Hey guys, I'm new here. I've been working on an emulator for the HP Prime as to better understand how it's OS works and possibly develop something like ndless for the Prime. Right now the emulator it's in it's super early stages, no input, display or anything at all for that matter. Just some of the Prime's armfir.elf (the main OS file) code running and not yet doing aything useful.
I've approached the emulator from a relativley high level perspective. I'm not trying to emulate it at a hardware level and instead I'm emulating the systemcalls that the Prime makes. Right now I'm targeting the earliest public Prime OS available (20130808) as it contains the most debug info. All the code is hosted on Github https://github.com/Gigi1237/PrimeU . Check it out and hit me up if any of you would be interested in contributing. ;)
Eeems:
If you aren't actually emulating the hardware but just the system calls I'd describe your projects more as a compatibility layer (like Wine). If I had time I'd be interested in helping even though I don't have an HP Prime.
You may also want to cross-post this on Cemetech as they have more c++ developers over there.
That said if you need help with higher level planning or want someone to go over your designs and give feedback feel free to post about it here, or to tag me in the github issue/pr and I'll give it a once over the best I can.
Jean-Baptiste Boric:
I'm the author of Rip'em, one (the only?) third-party firmware for the HP Prime. My efforts stalled when flashing the calculator under Windows over and over got really old, so I am interested in a HP Prime hardware emulator. It's been a while, but I'm still probably the guy most familiar with the HP Prime hardware outside of HP.
I did not attempt to write an emulator earlier because I'm not motivated enough to make one from scratch and QEMU's source code gives me headaches. However, I've discovered the Unicorn CPU emulator by browsing your source code. That might be enough to get me started.
While I'm here: as soon as someone circumvents the exam mode, you can bet HP will lock down the bootloader in the next firmware version to put a stop to that. Please don't nuke exam mode, whether directly or indirectly.
gigi1237:
hey kinda forgot about this post and the forum. Anyways i've been busy so I had not time to work on aything HP prime related.
--- Quote from: Eeems on May 08, 2017, 03:32:19 pm ---If you aren't actually emulating the hardware but just the system calls I'd describe your projects more as a compatibility layer (like Wine). If I had time I'd be interested in helping even though I don't have an HP Prime.
You may also want to cross-post this on Cemetech as they have more c++ developers over there.
That said if you need help with higher level planning or want someone to go over your designs and give feedback feel free to post about it here, or to tag me in the github issue/pr and I'll give it a once over the best I can.
--- End quote ---
You're absoloutley right it's absoloutley a compatibility layer. I just decided to call it emulator because there is actual CPU instructuor emulation going on, unlike wine which does not allow cross arch executables. I opted to go for a compatbility layer as I was interested in the inner workings of armfir.elf and wanted some way to debug it without using jtag. Considering the limited (~300) number of syscalls armfir makes this sounded like a much better idea compared to a full blown hardware emulator.
I hadn't though of Cemetech though iirc I did cross-post to another forum, now if I only remembered which... :banghead:
Thanks for the offer, some feedback could definetley come in useful as I'm quite new at this.
--- Quote from: Jean-Baptiste Boric on May 09, 2017, 11:56:14 am ---I'm the author of Rip'em, one (the only?) third-party firmware for the HP Prime. My efforts stalled when flashing the calculator under Windows over and over got really old, so I am interested in a HP Prime hardware emulator. It's been a while, but I'm still probably the guy most familiar with the HP Prime hardware outside of HP.
I did not attempt to write an emulator earlier because I'm not motivated enough to make one from scratch and QEMU's source code gives me headaches. However, I've discovered the Unicorn CPU emulator by browsing your source code. That might be enough to get me started.
While I'm here: as soon as someone circumvents the exam mode, you can bet HP will lock down the bootloader in the next firmware version to put a stop to that. Please don't nuke exam mode, whether directly or indirectly.
--- End quote ---
I tested out your firmware and found it quite interesting, albeit it was not what I was interested in. But nonetheless a hardware emulator would benefit me as much, if not more than what I was currently creating. One question, were you ever able to debug the code running on the calc itself? Whether JTAG or something similar.
You're right about qemu being a massive headache, I to build on that initially but just found the source too incomprehensible and time consuming to edit. Even if theoretically it would be perfect for a hardware emulator. Did you end up starting with a Unicorn-engine based emulator? If you have I'd be more than glad to take a look and possibly contribute.
Also you're absoloutley right about exam mode. I was intending to stay as far away from that as possible to not have any issues. But nonetheless from my understaing of the Prime's firmware it feels like it would be extremley hard to lock it down anywhere as tighlty as the nspire, it has no built in encryption capability and all it's memory can be written to so even if HP would decide to lock it down (hopefully thid does not happen ever) it'd be quite easy to circumvent, even if just by overwriting the key they'd use to sign their firmware. Am I completley wrong here? All my knowledge of embeded devices and calculators come from reverse engeneering and a minimal amount of google.
Jean-Baptiste Boric:
I haven't tried to create a hardware emulator yet, mostly because I'm thoroughly overworked with an internship, sysadmin freelance work and a GSoC student to mentor. I don't expect a saner workload until September. Also, my C++ is rusty and my knowledge of Qt is nil, even though Qt Creator looks slick as heck.
I did not attempt to use JTAG. I did all my debugging with the UART. I wrote a GDB stub to poke stuff around, but without interrupts it is rather limited.
About exam mode: unlike TI hardware, there is no root of trust inside the HP Prime hardware. You can always program whatever you want into the first 8 KiB of Flash and the S3C2416 will happily run it. While HP could introduce crypto checks and obfuscate things in an update, it's nothing some reverse-engineering and a soldering iron can't reverse. Fixing that hole for real would require at the very least a new hardware revision.
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