Porting/Tor Browser

Early efforts to port Tor Browser to POWER are underway. The primary challenge is that Tor Browser uses an unusual build system (rbm) in order to ensure reproducible builds. While Tor's configuration of rbm can cross-compile for Windows and macOS targets, it is not configured out of the box to cross-compile for GNU/Linux targets. As a result, our early efforts are focused on modifying Tor's rbm configuration to support cross-compiling for non-x86 GNU/Linux targets; it is expected that this will be useful not only for POWER but also for targets like ARM.

Current source code is at: https://notabug.org/JeremyRand/tor-browser-build/src/armhf-esr60 (armhf-esr60 branch)

If you're interested in joining the effort, talk to Jeremy_Rand or Jeremy_Rand_Talos in #talos-workstation.

Build instructions

./rbm/rbm build firefox --target nightly --target torbrowser-linux-arm
./rbm/rbm build tor --target nightly --target torbrowser-linux-arm

Errors / Troubleshooting

Unfixed

Missing libssp.so.0

./firefox: error while loading shared libraries: libssp.so.0: cannot open shared object file: No such file or directory

• Workaround: add the Browser directory to your LD_LIBRARY_PATH in order for Tor Browser to find the library.
• This should be fixable by porting the non-Firefox projects (one of which is responsible for setting the LD_LIBRARY_PATH).

Fixed

• /var/tmp/build/firefox-f8f42fea2af3/js/src/jsnativestack.cpp:69:31: error: 'syscall' was not declared in this scope
  • This is because jsnativestack.cpp forgot to #include <unistd.h>. This is fixed in all releases of Tor Browser based on ESR 60. Since we're still using ESR 52 for now, I fixed it by applying a short patch to add the missing include.
• /var/tmp/build/firefox-f8f42fea2af3/js/src/jsnativestack.cpp:77:27: error: 'getpid' was not declared in this scope
  • Also caused by missing #include <unistd.h> in jsnativestack.cpp; same fixes as above.
• ./firefox: error while loading shared libraries: libssp.so.0: cannot open shared object file: No such file or directory
  • Workaround: copy libssp.so* from the gcc-cross output tar into the Browser directory of the firefox output.
  • Fixed in the Firefox rbm build script as of 2018 Oct 10.
• Segfault immediately on startup in libxul.so
  • Only affects ESR 60; ESR 52 unaffected
  • Fixed by doing all of these:
    • Upgrade to gcc 7.3.0 / binutils 2.29.1
    • Build with ac_add_options --disable-elf-hack
    • Build with ac_add_options --disable-stylo
  • Possibly related bugs:
    • https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=902231
    • https://bugs.launchpad.net/ubuntu/+source/firefox/+bug/1711337
    • https://bugzilla.mozilla.org/show_bug.cgi?id=1452128

Task list

• (DONE!) Finish porting this to Firefox ESR 60.
• (DONE!) Build openssl without errors.
• (DONE!) Build libevent without errors.
• (DONE!) Build tor without errors.
• Test the openssl, libevent, and tor binaries.
• Build the projects besides firefox and tor.
• Fine-tune the compiler settings. (Are we inadvertently excluding some ARM devices that we want to support? Should we enable Neon?)
• Generalize the GNU/Linux cross-compiling changes so that they work on target arches besides armhf. (ppc64be, ppc64le, and aarch64 are all likely to be useful.)

Upstream Tickets

• http://ea5faa5po25cf7fb.onion/projects/tor/ticket/12631