Index: sys/riscv/riscv/trap.c
===================================================================
--- sys/riscv/riscv/trap.c
+++ sys/riscv/riscv/trap.c
@@ -46,6 +46,7 @@
 #include <sys/ptrace.h>
 #include <sys/syscall.h>
 #include <sys/sysent.h>
+#include <sys/sysproto.h>
 #ifdef KDB
 #include <sys/kdb.h>
 #endif
@@ -95,32 +96,31 @@
 int
 cpu_fetch_syscall_args(struct thread *td)
 {
-	struct proc *p;
-	register_t *ap, *dst_ap;
+	struct sysentvec *sv;
 	struct syscall_args *sa;
+	register_t *ap;
 
-	p = td->td_proc;
 	sa = &td->td_sa;
+	sv = td->td_proc->p_sysent;
 	ap = &td->td_frame->tf_a[0];
-	dst_ap = &sa->args[0];
 
 	sa->code = td->td_frame->tf_t[0];
 
-	if (__predict_false(sa->code == SYS_syscall || sa->code == SYS___syscall)) {
-		sa->code = *ap++;
-	} else {
-		*dst_ap++ = *ap++;
-	}
-
-	if (__predict_false(sa->code >= p->p_sysent->sv_size))
-		sa->callp = &p->p_sysent->sv_table[0];
+	if (__predict_false(sa->code >= sv->sv_size))
+		sa->callp = &sv->sv_table[0];
 	else
-		sa->callp = &p->p_sysent->sv_table[sa->code];
+		sa->callp = &sv->sv_table[sa->code];
 
 	KASSERT(sa->callp->sy_narg <= nitems(sa->args),
 	    ("Syscall %d takes too many arguments", sa->code));
 
-	memcpy(dst_ap, ap, (NARGREG - 1) * sizeof(register_t));
+	if (__predict_false(sa->callp->sy_call == (sy_call_t *)nosys) &&
+	    (sa->code == SYS_syscall || sa->code == SYS___syscall)) {
+		sa->code = td->td_frame->tf_a[0];
+		memcpy(sa->args, ap + 1, (NARGREG - 1) * sizeof(register_t));
+	} else {
+		memcpy(sa->args, ap, NARGREG * sizeof(register_t));
+	}
 
 	td->td_retval[0] = 0;
 	td->td_retval[1] = 0;