Re: lib/55719 (Unwind tables for signal trampoline on amd64 are incorrect)

[Kamil Rytarowski <kamil%netbsd.org@localhost>]

On 12.10.2020 16:01, Kamil Rytarowski wrote:
> On 12.10.2020 08:00, Nikhil Benesch wrote:
>> The following reply was made to PR lib/55719; it has been noted by GNATS.
>>
>> From: Nikhil Benesch <nikhil.benesch%gmail.com@localhost>
>> To: gnats-bugs%netbsd.org@localhost
>> Cc: kamil%netbsd.org@localhost, gnats-admin%netbsd.org@localhost, netbsd-bugs%netbsd.org@localhost
>> Subject: Re: lib/55719 (Unwind tables for signal trampoline on amd64 are incorrect)
>> Date: Mon, 12 Oct 2020 01:57:32 -0400
>>
>>  On Mon, Oct 12, 2020 at 1:05 AM Andrew Cagney <andrew.cagney%gmail.com@localhost> wrote:
>>  >  Code uses the tuple {CFA,FUNCTION_START} to identify a frame.  So if
>>  >  the CFA changes, code will think the frame changed.
>>  >
>>  >  Testing is "easy".  Code up a SIGILL, say, and then breakpoint on the
>>  >  signal handler.  Then instruction-step back to the trapping
>>  >  instruction.  Every single instruction needs to breaktrace correctly.
>>  >  GDB should still have tests (I wrote) that do this.
>>  
>>  Via reverse-debugging, yeah? I couldn't get this to work in the GDB
>>  that ships with NetBSD.
>>  
>>  (gdb) target record-full
>>  Process record: the current architecture doesn't support record function.
>>  
>>  Possibly due to the fact that I'm using a VM? Not sure.

Unfortunately recording and reverse-debugging is still unsupported in
GDB on NetBSD. I would need to research how much of work is needed to
get support and maybe Andrew can shed some light on it too.