itszn / chrome-wasm-debugger

A chrome extension to provide a slightly easier debugging UI for WASM modules

This is a pretty feature bare gdb style debugger for WASM webpages. It works by using proxies to hook WASM module operations and providing a gdb view to set breakpoints and inspect memory.

This is currently only has a few features but works alright for some debugging some WASM memory corruption. The main feature is the easy of reading module memory.

How To

• Enable the extension
• Go to the page you want to debug and open the dev tools, the proxy hooks should start working.
• Click the extension icon to open the debugger
• Reload the page you want to debug. The debugger should say it loaded some wasm functions
• Now you can set breakpoints in the debugger
• Refreshing the original page will keep breakpoints and rerun the wasm

Features

• i f to get a list of functions
• disassemble <function name or number> Print the disassembly (via chrome) of the function. Can use function index number instead of name.
• break <function>:<line> Set a break point on a given line of the disassembly (via chrome)
• si Single step
• c Continue execution
• x/<num>[bhw][xd] <address> Examine memory like gdb. Must be broken to use.
• Printing stack values on step

Limitiations

• Many
• Cannot see locals
• Currently only works for a single page. If you change debug targets you will have to reload the plugin
• Cannot catch crashes
• Not sure how it would handle thread stuff but might be ok
• No removing breakpoints atm