toolchain/56268: GDB backtrace fails for core dump on m68k

[rokuyama.rk%gmail.com@localhost]

>Number:         56268
>Category:       toolchain
>Synopsis:       GDB backtrace fails for core dump on m68k
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    toolchain-manager
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Tue Jun 22 02:50:00 +0000 2021
>Originator:     Rin Okuyama
>Release:        9.99.85
>Organization:
Department of Physics, Meiji University
>Environment:
NetBSD a1200 9.99.85 NetBSD 9.99.85 (A1200_WSCONS) #14: Wed Jun 16 07:44:49 JST 2021  rin@latipes:/sys/arch/amiga/compile/A1200_WSCONS amiga
>Description:
For m68k, GDB fails to backtrace for core dump:

----
$ cat
^\[1]   Quit (core dumped)      cat
$ gdb cat cat.core
GNU gdb (GDB) 11.0.50.20200914-git
...(snip)...
Type "apropos word" to search for commands related to "word"...
Reading symbols from cat...
Reading symbols from /usr/libdata/debug//bin/cat.debug...
[New process 176]
Core was generated by `cat'.
Program terminated with signal SIGQUIT, Quit.
#0  0x0e06c482 in ?? ()
(gdb) bt
#0  0x0e06c482 in ?? ()
#1  0x00003476 in ?? ()
#2  0x00000000 in ?? ()
(gdb)
----

Whereas this one works just fine:

----
$ gdb cat
GNU gdb (GDB) 11.0.50.20200914-git
...(snip)...
Type "apropos word" to search for commands related to "word"...
Reading symbols from cat...
Reading symbols from /usr/libdata/debug//bin/cat.debug...
(gdb) r
Starting program: /bin/cat
^\[New process 1129]

Thread 2 received signal SIGQUIT, Quit.
[Switching to process 1129]
0x0e062482 in read () from /lib/libc.so.12
(gdb) bt
#0  0x0e062482 in read () from /lib/libc.so.12
#1  0x00003476 in raw_cat (rfd=0) at /usr/src/bin/cat/cat.c:313
#2  0x00003608 in raw_args (argv=0xfefffa18) at /usr/src/bin/cat/cat.c:277
#3  0x000039ae in main (argc=<optimized out>, argv=0xfefffa18)
    at /usr/src/bin/cat/cat.c:136
(gdb)
----

This is *NOT* a recent regression; all of GDB 11, 8.3, 8.0.1, 7.12 fail in
the same manner.

Also, I tried kernels and userlands from netbsd-9 and -8, but in vain.
>How-To-Repeat:
Described above.
>Fix:
N/A