[Vm-dev] OSVM on WebAssembly

[Manuel Leuenberger]

Hi,

Ever since WebAssembly became a thing, I was wondering if this could become a target for VMs. People are already compiling FFMPEG and other complex tools. So I thought I would try as well.

So here I am to report to whom it may concern: OSVM compiles to WebAssembly, starts up (nearly), then looping infinitely
Meaning: The VM mmaps the image file, loads plugins (SecurityPlugin made EXTERNAL), starts interpreter loop, but then loops the same bytecode sequence forever

Code lives at https://github.com/maenu/opensmalltalk-vm/tree/Cog/building/minheadless.cmake/x86/pharo.stack.spur.wasm <https://github.com/maenu/opensmalltalk-vm/tree/Cog/building/minheadless.cmake/x86/pharo.stack.spur.wasm> if you want to try it out.

Below is the current Readme, including a short list of issues. Maybe some of you could give me a hint?

Cheers,
Manuel

pharo.stack.spur.wasm

Compiles OSVM Stack interpreter to WebAssembly using the Emscripten compiler. Emscripten can be used as a drop-in replacement for gcc/clang and cmake. Based on MinHeadless Linux 32bit sources, as Emscripten provides Linux-like environment (pthreads, nanosleep, dlopen, file system). Check the latest few commits of maenu to see changed files.

 <https://github.com/maenu/opensmalltalk-vm/tree/Cog/building/minheadless.cmake/x86/pharo.stack.spur.wasm#current-issues>Current issues

Most adjustments are just putting EMSCRIPTEN in a macro or script. Should be fine, but should be tested to not interfere with other builds.

Compiles and runs, but seems to be stuck in initial GC and Heartbeat. Those could be related to incorrect get/set64() implementation.

Removed mmap address hint, as it caused errors.

Using argv eval '1 + 3' to do a simple eval does not terminate.

Interpreter repeats these bytecodes forever (what is this?):

332
384
​385
​348
​501
​339
320
401
272
380
 <https://github.com/maenu/opensmalltalk-vm/tree/Cog/building/minheadless.cmake/x86/pharo.stack.spur.wasm#build--run>Build & Run

 <https://github.com/maenu/opensmalltalk-vm/tree/Cog/building/minheadless.cmake/x86/pharo.stack.spur.wasm#1-install-emscripten>1. Install Emscripten

I installed Emscripten SDK <https://emscripten.org/docs/getting_started/downloads.html> to get an all-in-one package.

 <https://github.com/maenu/opensmalltalk-vm/tree/Cog/building/minheadless.cmake/x86/pharo.stack.spur.wasm#2-grab-an-image>2. Grab an image

Grab a 32bit Smalltalk image and but it in the image folder. I used Pharo 9.

cd building/minheadless.cmake/x86/pharo.stack.spur.wasm
mkdir image
cd image
curl https://get.pharo.org/32/90 | bash
 <https://github.com/maenu/opensmalltalk-vm/tree/Cog/building/minheadless.cmake/x86/pharo.stack.spur.wasm#3-build-vm>3. Build VM

./mvm_configure_variant debug Debug && make -C debug install

 <https://github.com/maenu/opensmalltalk-vm/tree/Cog/building/minheadless.cmake/x86/pharo.stack.spur.wasm#4-run-a-web-server>4. Run a web server

emrun --port 9090 --serve_root ../../../../ --no_browser .

 <https://github.com/maenu/opensmalltalk-vm/tree/Cog/building/minheadless.cmake/x86/pharo.stack.spur.wasm#5-launch-vm>5. Launch VM

http://localhost:9090/building/minheadless.cmake/x86/pharo.stack.spur.wasm/debug/dist/squeak.html <http://localhost:9090/building/minheadless.cmake/x86/pharo.stack.spur.wasm/debug/dist/squeak.html>
 <https://github.com/maenu/opensmalltalk-vm/tree/Cog/building/minheadless.cmake/x86/pharo.stack.spur.wasm#6-inspect-running-vm>6. Inspect running VM

The VM is compiled with DWARF debug information, which is understood by the Chrome debugger. So we can step through the C sources of the WebAssembly, pretty nifty.

 <https://github.com/maenu/opensmalltalk-vm/tree/Cog/building/minheadless.cmake/x86/pharo.stack.spur.wasm#resources>Resources

Inspect WebAssembly (at the bottom) <https://webassembly.org/getting-started/developers-guide/>
Emscripten doc (Porting) <https://emscripten.org/docs/porting/index.html>
Emscripten settings <https://emsettings.surma.technology/>

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