kern/56487: binary compat broken for COMPAT_NETBSD32

[martin%NetBSD.org@localhost]

>Number:         56487
>Category:       kern
>Synopsis:       binary compat broken for COMPAT_NETBSD32
>Confidential:   no
>Severity:       critical
>Priority:       high
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Thu Nov 04 14:45:00 +0000 2021
>Originator:     Martin Husemann
>Release:        NetBSD 9.99.92
>Organization:
The NetBSD Foundation, Inc.
>Environment:
System: NetBSD out-of-the-silent-planet.aprisoft.de 9.99.92 NetBSD 9.99.92 (GENERIC64) #226: Sun Oct 24 08:47:00 CEST 2021 martin%seven-days-to-the-wolves.aprisoft.de@localhost:/work/src/sys/arch/evbarm/compile/GENERIC64 evbarm
Architecture: aarch64
Machine: evbarm
>Description:

My test environment chroots for COMPAT_NETBSD32 were broken by recent
sigtramp changes, e.g.:

Reading symbols from /usr/pkg/bin/tcsh...
(No debugging symbols found in /usr/pkg/bin/tcsh)
[New process 6227]
Core was generated by `tcsh'.
Program terminated with signal SIGSYS, Bad system call.
#0  0xf75fb9c8 in __sigtramp_sigcontext_1 () from /usr/lib/libc.so.12
(gdb) bt
#0  0xf75fb9c8 in __sigtramp_sigcontext_1 () from /usr/lib/libc.so.12
#1  0xf75fb9c0 in __vfork14 () from /usr/lib/libc.so.12


>How-To-Repeat:
With a new kernel and new (32bit) userland try to chroot and run some
previously compiled binaries from pkgsrc.

>Fix:
n/a