codinguncut / jsbochs

Emscripten "port" to Javascript of the Bochs PC Emulator, making it possible to run linux or windows in the browser.

jsbochs - Bochs PC Emulator for the Browser

Emscripten "port" to Javascript of the Bochs PC Emulator.

Inspired by Fabrice Bellard's fantastic jslinux.

(Being) Ported by Johannes Ahlmann

Status

The code runs flawlessly under javascript. The only issue is that it runs SLOOOOW. It runs the BIOS code reasonably fast, but then goes down to 0.04MIPS instead of native 30MIPS.

Also, I have almost no output options yet.

This git repo is currently my work bench and a bastadization of the original bochs code. I have removed all files that were not absolutely necessary for compilation in order to get my bearings.

Suggestions for Performance

• -s PRECISE_I64_MATH=0 will likely not work. I am very concerned that doubles > 2^32 may not be monotonic when adding 1.
• -s INLINING_LIMIT=0 compiles very slowly. But I will try to get it compiled (>1h)
• replace 64bit ints with 32bit. Not sure what to replace the instruction counter with since 32bit counter will overflow in (2^32instructions/30,000,000instructions/s/60s =) 2.5 minutes. I will try a clock divider since I don't need instruction-precise timers anyway.

Install

Requirements

• llvm
• emscripten
• possibly node

Building

Simply run the build_it.sh script which will configure and build the bochs.js file.

Alternatively follow the steps below:

emconfigure ./configure --disable-plugins --disable-x86-64 --enable-cpu-level=4 \
--with-term  --disable-large-ramfile --disable-cdrom --disable-debugger-gui \
--disable-readline --disable-iodebug --enable-show-ips --enable-logging \
--disable-idle-hack --disable-debugger --disable-disasm --enable-fpu

emmake make

emcc -O1 bochs.bc -o bochs.js

node launch.js

TODO

• Currently it runs under node in the console. Get main loop running for browser
• Get an output running. Either a nicer terminal output or SDL output in the browser
• Get it to compile with -O2. This would be a tremendous speedup, but currently there are compiler errors about bit arithmetic.

Issues

Resolved Issues

• 64bit pointer casting
• Division error with long double
• Memory Alignment

Open Issues

• Browser main loop
• Compile with closure (bit arithmetic errors)
• Speed

License

• Bochs (and jsbochs) as a whole is released under the GNU Lesser General Public License

• Parts of Bochs have specific licenses which are compatible with the GNU Lesser General Public License. Hence each source file contains its own licensing information.