bin/54154: NetBSD gdb does not interoperate with qemu 4.0.0 gdb stub

[gson%gson.org@localhost (Andreas Gustafsson)]

>Number:         54154
>Category:       bin
>Synopsis:       NetBSD gdb does not interoperate with qemu 4.0.0 gdb stub
>Confidential:   no
>Severity:       critical
>Priority:       high
>Responsible:    bin-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Fri May 03 07:45:00 +0000 2019
>Originator:     Andreas Gustafsson
>Release:        NetBSD-current
>Organization:

>Environment:
System: NetBSD
Architecture: i386
Machine: i386
>Description:

When I try to remotely debug NetBSD-current/i386 under qemu 4.0.0 from
pkgsrc, running gdb on a NetBSD-current/i386 system identical to the
target per https://wiki.netbsd.org/kernel_debugging_with_qemu/ 
debugging fails with the error "Remote 'g' packet reply is too long":

  (gdb) target remote guido.araneus.fi:1234
  Remote debugging using guido.araneus.fi:1234
  warning: Can not parse XML target description; XML support was disabled at compile time
  Remote 'g' packet reply is too long (expected 308 bytes, got 344 bytes): 00000000fc3e20adfc3e20ad004072add8af97c9e848470000000000887472ad604311c04600000008000000100000001f000

I have tested this with -current source dates 2019.04.07.08.14.20 and
2018.03.01.03.32.33, and both fail the same way.  Remote debugging of
-current worked for me around 2018.03, so the triggering factor
appears to be a recent qemu, not a recent -current.

I wonder if building gdb with XML support would fix this.

>How-To-Repeat:

>Fix: