On Wed, Dec 16, 2020 at 09:44:53AM +0000, Maciej W. Rozycki wrote: > On Wed, 16 Dec 2020, Al Viro wrote: > > > > It may be worth pushing through GDB's gdb.threads/tls-core.exp test case, > > > making sure no UNSUPPORTED results have been produced due to resource > > > limits preventing a core from being dumped (and no FAILs, of course), with > > > o32/n32 native GDB. This should guarantee our output is still as expected > > > by an interpreter. Sadly I'm currently not set up for such testing though > > > eventually I mean to. > > > > Umm... What triple does one use for n32 gdb? > > I don't think there's a standardised one, just configure with CC/CXX set > for n32 compilation, e.g.: > > $ /path/to/configure CC="gcc -mabi=n32" CXX="g++ -mabi=n32" > > (and any other options set as usually). This has to be with CC/CXX rather > than CFLAGS/CXXFLAGS so that it is guaranteed to be never overridden with > any logic that might do any fiddling with compilation options. This will > set up the test suite accordingly. > > NB this may already be the compiler's default, depending on how it was > configured, i.e. if `--with-abi=n32' was used, in which case no extra > options will be required. I don't know if any standard MIPS distribution > does it though; 64-bit MIPS/Debian might. This will be reported with `gcc > --help -v', somewhere along the way. > > Let me know if there are issues with this approach. FWIW, on debian/mips64el (both stretch and buster) the test fails with the distro kernels (4.9- and 4.19-based) as well as with 5.10-rc1 and 5.10-rc1+that series, all in the same way: [Current thread is 1 (LWP 4154)] (gdb) p/x foo Cannot find thread-local storage for LWP 4154, executable file <pathname> Cannot find thread-local variables on this target buster has libc6-2.28, so that should be fine for the test in question (libthread_db definitely recent enough). That was n32 gdb; considering how much time it had taken to build that sucker I hadn't tried o32 yet. Note that it's not just with native coredumps - gcore-produced ones give the same result. That was gdb from binutils-gdb.git; I'm not familiar with gdb guts to start debugging it, so if you have any suggestions in that direction that do not include a full rebuild... In any case, I won't get around to that until the next week. Incidentally, build time is bloody awful - 3 days, with qemu-3.1 on 3.5GHz amd64 host, all spent pretty much entirely in userland (both from guest and host POV). g++-8 is atrociously slow... That said, I don't see what in that series could possibly mess the things up for tls, while leaving the registers working; the only thing that realistically might've been fucked up is prstatus layout (and possibly size), and that would've screwed the registers as well.
