 @@ -1,14 +1,14 @@
-/*	$NetBSD: kern_syscall.c,v 1.20 2020/05/23 23:42:43 ad Exp $	*/
+/*	$NetBSD: kern_syscall.c,v 1.21 2020/08/31 19:51:30 christos Exp $	*/
 /*-
  * Copyright (c) 2008 The NetBSD Foundation, Inc.
  * All rights reserved.
+ *
  * This code is derived from software developed for The NetBSD Foundation
  * by Andrew Doran.
+ *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
 @@ -20,27 +20,27 @@
  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  * POSSIBILITY OF SUCH DAMAGE.
  */
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: kern_syscall.c,v 1.20 2020/05/23 23:42:43 ad Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_syscall.c,v 1.21 2020/08/31 19:51:30 christos Exp $");
 #ifdef _KERNEL_OPT
 #include "opt_modular.h"
 #include "opt_syscall_debug.h"
 #include "opt_ktrace.h"
 #include "opt_ptrace.h"
 #include "opt_dtrace.h"
 #endif
 /* XXX To get syscall prototypes. */
 #define SYSVSHM
 #define SYSVSEM
 #define SYSVMSG
 @@ -226,42 +226,47 @@ trace_is_enabled(struct proc *p)
 	return (false);
+}
 /*
  * Start trace of particular system call. If process is being traced,
  * this routine is called by MD syscall dispatch code just before
  * a system call is actually executed.
  */
 int
 trace_enter(register_t code, const struct sysent *sy, const void *args)
+{
 	int error = 0;
 #if defined(PTRACE) || defined(KDTRACE_HOOKS)
 	struct proc *p = curlwp->l_proc;
 #endif
 #ifdef KDTRACE_HOOKS
 	if (sy->sy_entry) {
-		struct emul *e = curlwp->l_proc->p_emul;
+		struct emul *e = p->p_emul;
-		(*e->e_dtrace_syscall)(sy->sy_entry, code, sy, args, NULL, 0);
+		if (e->e_dtrace_syscall)
 			(*e->e_dtrace_syscall)(sy->sy_entry, code, sy, args,
 			    NULL, 0);
+	}
 #endif
 #ifdef SYSCALL_DEBUG
 	scdebug_call(code, args);
 #endif /* SYSCALL_DEBUG */
 	ktrsyscall(code, args, sy->sy_narg);
 #ifdef PTRACE
-	if ((curlwp->l_proc->p_slflag & (PSL_SYSCALL|PSL_TRACED)) ==
+	if ((p->p_slflag & (PSL_SYSCALL|PSL_TRACED)) ==
 	    (PSL_SYSCALL|PSL_TRACED)) {
 		proc_stoptrace(TRAP_SCE, code, args, NULL, 0);
 		if (curlwp->l_proc->p_slflag & PSL_SYSCALLEMU) {
 			/* tracer will emulate syscall for us */
 			error = EJUSTRETURN;
+		}
+	}
 #endif
 	return error;
+}
 /*
  * End trace of particular system call. If process is being traced,
 @@ -270,28 +275,30 @@ trace_enter(register_t code, const struc
  * MD caller guarantees the passed 'code' is within the supported
  * system call number range for emulation the process runs under.
  */
 void
 trace_exit(register_t code, const struct sysent *sy, const void *args,
     register_t rval[], int error)
+{
 #if defined(PTRACE) || defined(KDTRACE_HOOKS)
 	struct proc *p = curlwp->l_proc;
 #endif
 #ifdef KDTRACE_HOOKS
 	if (sy->sy_return) {
-		(*p->p_emul->e_dtrace_syscall)(sy->sy_return, code, sy, args,
+		struct emul *e = p->p_emul;
-		    rval, error);
+		if (e->e_dtrace_syscall)
 			(*p->p_emul->e_dtrace_syscall)(sy->sy_return, code, sy,
 			    args, rval, error);
+	}
 #endif
 #ifdef SYSCALL_DEBUG
 	scdebug_ret(code, error, rval);
 #endif /* SYSCALL_DEBUG */
 	ktrsysret(code, error, rval);
 #ifdef PTRACE
 	if ((p->p_slflag & (PSL_SYSCALL|PSL_TRACED|PSL_SYSCALLEMU)) ==
 	    (PSL_SYSCALL|PSL_TRACED)) {
 		proc_stoptrace(TRAP_SCX, code, args, rval, error);