[ltt-dev] gdb-7.2 can't build with lttng-ust-0.12

Tom Tromey tromey@redhat.com
Tue Apr 26 18:47:00 GMT 2011


>>>>> "Dexuan" == Cui, Dexuan <dexuan.cui@intel.com> writes:

Mathieu> Also, we should reopen the discussion on the way the UST Markers
Mathieu> collect the registers for GDB, because the current way involves a
Mathieu> _lot_ of ugly assembly code. It should be possible to only use a
Mathieu> volatile inline asm to specify input constraints on the target marker
Mathieu> parameters, and keep the instruction pointer address that corresponds
Mathieu> to this inline asm in a section known by gdb (so gdb could use the
Mathieu> drawf info to fetch data from registers/memory). If you can ensure
Mathieu> that this would fit gdb's requirements, I could clean up the marker
Mathieu> code and we could resync the APIs together. We could also provide
Mathieu> this for UST Tracepoints in the same go, with pretty much the same
Mathieu> interface as we'd use for UST Markers. I am aware that this would
Mathieu> require change on the GDB side, but I think it's better to
Mathieu> synchronise our effort rather than to shoot at different targets.

I am not totally clear on the proposal here.

If this means reusing the <sys/sdt.h> stuff, then there are gdb patches
already submitted to fully support that; and updating the existing code
to also use it should not be very difficult.  See gdb-patches from the
last month or two.

If instead you mean something else, it would be useful to have more
information.  From your description it sounds like this may be a
different design from SDT v3; but note that SDT v2 tried to use DWARF to
access the parameters and ran into various problems.  I can get details
on the failure modes if this is what you intend.

Dexuan> Unluckily I'm pretty new to gdb and know few about this now.
Dexuan> Let me Cc the gdb mailing list for more thoughts(hope this cross-posting
Dexuan> wouldn't bother people).

Cross-posting in cases like this is fine, even preferable.

I don't know anything about the gdbserver bits here.  It seems to me
that it would be reasonable to have gdbserver compile against various
versions of UST.

Tom



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