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

Tor Bug Tracker & Wiki blackhole at torproject.org
Wed Jan 8 11:04:34 UTC 2020


#23719: Make sure WebExtensions are spared from JIT disabling in higher security
settings (Medium-High)
-------------------------------------------------+-------------------------
 Reporter:  cypherpunks                          |          Owner:  acat
     Type:  defect                               |         Status:
                                                 |  assigned
 Priority:  Medium                               |      Milestone:
Component:  Applications/Tor Browser             |        Version:
 Severity:  Major                                |     Resolution:
 Keywords:  tbb-performance, GeorgKoppen201911,  |  Actual Points:  0.5
  TorBrowserTeam202001                           |
Parent ID:                                       |         Points:  1
 Reviewer:                                       |        Sponsor:
-------------------------------------------------+-------------------------

Comment (by acat):

 I wanted to test on the same device the patch that enables `ion` on
 `WebExtensions` from https://bugzilla.mozilla.org/show_bug.cgi?id=1599226.
 I quickly backported it (might have missed something) in branch
 https://github.com/acatarineu/tor-browser/commits/23719+1, after the wasm
 patches. The resulting apk is in
 https://people.torproject.org/~acat/builds/tor-browser-9.5a4-android-armv7
 -multi-qa_23719+1.apk.

 Unfortunately, it seems the patches still do not solve the issue. After
 testing the tor browser build, I tried some prefs combinations in a
 regular fennec with https everywhere:

 `baselinejit = false`, `ion = false` -> too slow, prompt shown
 `baselinejit = false`, `ion = true` -> too slow, prompt shown
 `baselinejit = true`, `ion = false` -> fast enough, prompt not shown
 `baselinejit = true`, `ion = false` -> faster, prompt not shown

 Then I checked the code in the patch and realized that the `IsIonEnabled`
 function in https://phabricator.services.mozilla.com/D56987  returns
 {{{
 IsBaselineJitEnabled() && prefEnabled;
 }}}
 so it seems for `ion` to be enabled the `baselinejit` must also be, which
 I think makes sense.

 So, do we also need to be able to selectively enable the `baselinejit` on
 extensions, or would there be a simpler way?

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/23719#comment:30>
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