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

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

The following reply was made to PR lib/55719; it has been noted by GNATS.

From: Kamil Rytarowski <kamil%netbsd.org@localhost>
To: Kamil Rytarowski <kamil%netbsd.org@localhost>, gnats-bugs%netbsd.org@localhost,
 gnats-admin%netbsd.org@localhost, netbsd-bugs%netbsd.org@localhost, nikhil.benesch%gmail.com@localhost,
 Andrew Cagney <andrew.cagney%gmail.com@localhost>
Cc: 
Subject: Re: lib/55719 (Unwind tables for signal trampoline on amd64 are
 incorrect)
Date: Mon, 12 Oct 2020 16:24:33 +0200

 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.