Index: sys/compat/netbsd32/netbsd32_compat_16.c
===================================================================
RCS file: /cvsroot/src/sys/compat/netbsd32/netbsd32_compat_16.c,v
retrieving revision 1.4
diff -p -u -r1.4 netbsd32_compat_16.c
--- sys/compat/netbsd32/netbsd32_compat_16.c	26 Nov 2021 08:06:11 -0000	1.4
+++ sys/compat/netbsd32/netbsd32_compat_16.c	1 May 2024 08:08:14 -0000
@@ -36,6 +36,7 @@ __KERNEL_RCSID(0, "$NetBSD: netbsd32_com
 #include <sys/module.h>
 #include <sys/dirent.h>
 #include <sys/exec.h>
+#include <sys/proc.h>
 #include <sys/lwp.h>
 #include <sys/syscallargs.h>
 #include <sys/syscallvar.h>
@@ -47,40 +48,87 @@ __KERNEL_RCSID(0, "$NetBSD: netbsd32_com
 
 struct uvm_object *emul_netbsd32_object;
 
-MODULE(MODULE_CLASS_EXEC, compat_netbsd32_16, "compat_netbsd32_20,compat_16");
+static const struct syscall_package netbsd32_kern_sig_16_syscalls[] = {
+        /* compat_16_netbs32___sigreturn14 is in MD code! */
+        { NETBSD32_SYS_compat_16_netbsd32___sigreturn14, 0,
+            (sy_call_t *)compat_16_netbsd32___sigreturn14 },
+        { 0, 0, NULL }
+};
 
 static int
-compat_netbsd32_16_modcmd(modcmd_t cmd, void *arg)
+compat_netbsd32_16_init(void)
+{
+	int error;
+
+	error = syscall_establish(&emul_netbsd32, netbsd32_kern_sig_16_syscalls);
+	if (error)
+		return error;
+
+	rw_enter(&exec_lock, RW_WRITER);
+	emul_netbsd32.e_sigcode = netbsd32_sigcode;
+	emul_netbsd32.e_esigcode = netbsd32_esigcode;
+	emul_netbsd32.e_sigobject = &emul_netbsd32_object;
+	error = exec_sigcode_alloc(&emul_netbsd);
+	if (error) {
+		emul_netbsd32.e_sigcode = NULL;
+		emul_netbsd32.e_esigcode = NULL;
+		emul_netbsd32.e_sigobject = NULL;
+	}
+	rw_exit(&exec_lock);
+	if (error)
+		return error;
+	netbsd32_machdep_md_16_init();
+	return 0;
+}
+
+static int
+compat_netbsd32_16_fini(void)
 {
+	proc_t *p;
 	int error;
 
+	error = syscall_disestablish(&emul_netbsd32, netbsd32_kern_sig_16_syscalls);
+        if (error)
+                return error;
+        /*
+         * Ensure sendsig_sigcontext() is not being used.
+         * module_lock prevents the flag being set on any
+         * further processes while we are here.  See
+         * sigaction1() for the opposing half.
+         */
+        mutex_enter(&proc_lock);
+        PROCLIST_FOREACH(p, &allproc) {
+                if ((p->p_lflag & PL_SIGCOMPAT) != 0) {
+                        break;
+                }
+        }
+        mutex_exit(&proc_lock);
+        if (p != NULL) {
+                syscall_establish(&emul_netbsd32, netbsd32_kern_sig_16_syscalls);
+                return EBUSY;
+        }
+
+	rw_enter(&exec_lock, RW_WRITER);
+	exec_sigcode_free(&emul_netbsd);
+	emul_netbsd32.e_sigcode = NULL;
+       	emul_netbsd32.e_esigcode = NULL;
+       	emul_netbsd32.e_sigobject = NULL;
+	rw_exit(&exec_lock);
+	netbsd32_machdep_md_16_fini();
+	return 0;
+}
+
+MODULE(MODULE_CLASS_EXEC, compat_netbsd32_16, "compat_netbsd32_20,compat_16");
+
+static int
+compat_netbsd32_16_modcmd(modcmd_t cmd, void *arg)
+{
 	switch (cmd) {
 	case MODULE_CMD_INIT:
-		rw_enter(&exec_lock, RW_WRITER);
-		emul_netbsd32.e_sigcode = netbsd32_sigcode;
-        	emul_netbsd32.e_esigcode = netbsd32_esigcode;
-        	emul_netbsd32.e_sigobject = &emul_netbsd32_object;
-		error = exec_sigcode_alloc(&emul_netbsd);
-		if (error) {
-			emul_netbsd32.e_sigcode = NULL;
-			emul_netbsd32.e_esigcode = NULL;
-			emul_netbsd32.e_sigobject = NULL;
-		}
-		rw_exit(&exec_lock);
-		if (error)
-			return error;
-		netbsd32_machdep_md_16_init();
-		return 0;
+		return compat_netbsd32_16_init();
 
 	case MODULE_CMD_FINI:
-		rw_enter(&exec_lock, RW_WRITER);
-		exec_sigcode_free(&emul_netbsd);
-		emul_netbsd32.e_sigcode = NULL;
-        	emul_netbsd32.e_esigcode = NULL;
-        	emul_netbsd32.e_sigobject = NULL;
-		rw_exit(&exec_lock);
-		netbsd32_machdep_md_16_fini();
-		return 0;
+		return compat_netbsd32_16_fini();
 
 	default:
 		return ENOTTY;