Where can I get Valgrind?
Linux: http://valgrind.org/ or use your distro's package manager
Mac: sudo port install valgrind
You can also get Valgrind trunk from SVN and build it yourself.
Is there a shared memcheck suppression file for known bugs?
Jesse has one somewhere...
What do I do if the JIT crashes on startup?
Pass the parameter
--smc-check=all to valgrind for now.
Note: this option makes valgrind run much slower. An alternative solution is to turn both the content and chrome JITs off.
Or build Mozilla with