Ported the Firefox Profiler to FreeBSD in order to investigate why WebRender has some jank when scrolling some walls of text on my 4K/HiDPI setup.

The profiler code initially looked somewhat scary: some Google Breakpad code is used, a custom stack unwinder called LUL is used on Linux (which also partially derived from Breakpad code)…

Initially, I got it working with “pre-symbolication” (an option to build the goblin ELF parser into Firefox for this purpose) only, ifdef’ing any Breakpad code out.

Turns out:

• the only part of Breakpad used is extracting build IDs from shared objects (and in fact the “base profiler”, a copy (for now) of the Gecko profiler used for profiling during the early startup phase, just copied all the relevant code);
• devel/breakpad was there in FreeBSD Ports (but expires in like three days!), and its patches showed that it’s really trivial to get all it working.

So I got the main symbolication system working. Which, it turns out, runs WebAssembly-compiled goblin in a web worker! Fun stuff. Requires stripping libxul for now tho.

In the end, the patch turned out to be mostly just ifdef’s! The only meaningful parts are: thr_self/thr_kill2 instead of gettid/tgkill, supporting the different mcontext structs, and (for the pre-symbolication code path) ignoring symbol names returned by dladdr because they’re hilariously bad.

BTW, earlier in the dev-tools-on-FreeBSD space: heaptrack! I even used it to find a real memory leak in Wayfire.

Firefox content process sandboxing with Capsicum: it’s alive! Work in progress, but I have WebGL and audio working :)

Current Windows 10 has a feature called “Windows Sandbox” which spawns a tiny Hyper-V VM with allegedly a very smart slim disk image thing that shares the OS files with the host, and smart memory management, and so on.. and virtualized GPU support, like virgl in the free world.

So can it run Crysis, or at least Quake? Is it what we need for isolating old games? Well.. it has the ability to load up the host GPU with work and to show the results, but it’s absolutely unsuitable for gaming in its current state. Seems like it uses regular RDP for the window, and there aren’t any special optimizations that make 3D fast. The frame pacing is awful, framerate is weirdly limited, etc.

Also, this is not obviously found on google right now: if you have a compressed disk, you need to decompress C:\ProgramData\Microsoft\Windows\Containers for it to work.

Was wondering for a month why Firefox on my laptop would forget my GitHub session (and some other sessions) after restarting. Turns out “Delete cookies and site data when Firefox is closed” got enabled somehow. Facepalm.

“Why do programs I compile become all-zero files after rebooting?”

well, maybe that untested filesystem-related kernel patch you applied has something to do with it :D

But seriously, if anyone wants to make a very cursed unix system: apply this diff (note: old version by now) to FreeBSD from around now (say the beginning of 2020 — happy new year!), build programs using clang/lld 9.x and reboot.