[tor-bugs] #23719 [Applications/Tor Browser]: Make sure WebExtensions are spared from JIT disabling in higher security settings (Medium-High)

[Tor Bug Tracker & Wiki]

#23719: Make sure WebExtensions are spared from JIT disabling in higher security
settings (Medium-High)
-------------------------------------------------+-------------------------
 Reporter:  cypherpunks                          |          Owner:  tbb-
                                                 |  team
     Type:  defect                               |         Status:
                                                 |  needs_revision
 Priority:  Medium                               |      Milestone:
Component:  Applications/Tor Browser             |        Version:
 Severity:  Major                                |     Resolution:
 Keywords:  tbb-performance, GeorgKoppen201911,  |  Actual Points:  0.5
  TorBrowserTeam201911                           |
Parent ID:                                       |         Points:  1
 Reviewer:                                       |        Sponsor:
-------------------------------------------------+-------------------------

Comment (by acat):

 Replying to [comment:20 gk]:
 > Replying to [comment:19 gk]:
 > > Do we have a good test making sure the WASM part is actually working
 as expected?
 >
 > I found some "test": On mobile I get a warning now due to an
 unresponsive WASM script. That's pretty bad because users can start
 surfing while HTTPS-E is not ready yet and it gets our fundraising banner
 in a weird shape (not everything is positioned correctly). I am afraid we
 can't ship this as-is.
 >
 > Interestingly, though, we *do have* WASM enabled on the standard level
 in our alpha and nightly builds and I don't have that issue on that level
 on that device. Thus, the problem here is not wasm-on-android per se.

 I could reproduce the https everywhere wasm script warning in Fennec with
 `javascript.options.ion = false` and `javascript.options.baselinejit =
 false`. Without having profiled the extension it looks like the JS code in
 the wasm path is slower than before when JIT is disabled.

 I also tested with a wasm bench function that takes a while (at least 15
 seconds) and just receives an integer as argument and the performance
 seems to be the same independently of `ion` or `baselinejit`, as long as
 `wasm` is enabled.

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/23719#comment:23>
Tor Bug Tracker & Wiki <https://trac.torproject.org/>
The Tor Project: anonymity online