Index: sys/kern/subr_syscall.c
===================================================================
--- sys/kern/subr_syscall.c
+++ sys/kern/subr_syscall.c
@@ -68,6 +68,7 @@
 		PROC_LOCK(p);
 		td->td_dbgflags &= ~TDB_USERWR;
 		td->td_dbgflags |= TDB_SCE;
+		td->td_dbgsa = sa;
 		PROC_UNLOCK(p);
 	} else
 		traced = 0;
@@ -157,6 +158,7 @@
 	if (traced) {
 		PROC_LOCK(p);
 		td->td_dbgflags &= ~TDB_SCE;
+		td->td_dbgsa = NULL;
 		PROC_UNLOCK(p);
 	}
 	(p->p_sysent->sv_set_syscall_retval)(td, error);
@@ -164,7 +166,7 @@
 }
 
 static inline void
-syscallret(struct thread *td, int error, struct syscall_args *sa __unused)
+syscallret(struct thread *td, int error, struct syscall_args *sa)
 {
 	struct proc *p, *p2;
 	int traced;
@@ -188,6 +190,7 @@
 		traced = 1;
 		PROC_LOCK(p);
 		td->td_dbgflags |= TDB_SCX;
+		td->td_dbgsa = sa;
 		PROC_UNLOCK(p);
 	} else
 		traced = 0;
@@ -210,6 +213,7 @@
 		    (p->p_stops & S_PT_SCX) != 0))
 			ptracestop(td, SIGTRAP);
 		td->td_dbgflags &= ~(TDB_SCX | TDB_EXEC | TDB_FORK);
+		td->td_dbgsa = NULL;
 		PROC_UNLOCK(p);
 	}
 
Index: sys/kern/sys_process.c
===================================================================
--- sys/kern/sys_process.c
+++ sys/kern/sys_process.c
@@ -97,6 +97,8 @@
 	struct siginfo32 pl_siginfo;	/* siginfo for signal */
 	char	pl_tdname[MAXCOMLEN + 1];	/* LWP name. */
 	int	pl_child_pid;		/* New child pid */
+	u_int		pl_syscall_code;
+	int		pl_syscall_narg;
 };
 
 #endif
@@ -481,6 +483,8 @@
 	siginfo_to_siginfo32(&pl->pl_siginfo, &pl32->pl_siginfo);
 	strcpy(pl32->pl_tdname, pl->pl_tdname);
 	pl32->pl_child_pid = pl->pl_child_pid;
+	pl32->pl_syscall_code = pl->pl_syscall_code;
+	pl32->pl_syscall_narg = pl->pl_syscall_narg;
 }
 #endif /* COMPAT_FREEBSD32 */
 
@@ -1211,6 +1215,13 @@
 		pl->pl_sigmask = td2->td_sigmask;
 		pl->pl_siglist = td2->td_siglist;
 		strcpy(pl->pl_tdname, td2->td_name);
+		if (td2->td_dbgsa != NULL) {
+			pl->pl_syscall_code = td2->td_dbgsa->code;
+			pl->pl_syscall_narg = td2->td_dbgsa->narg;
+		} else {
+			pl->pl_syscall_code = 0;
+			pl->pl_syscall_narg = 0;
+		}
 #ifdef COMPAT_FREEBSD32
 		if (wrap32)
 			ptrace_lwpinfo_to32(pl, pl32);
Index: sys/sys/proc.h
===================================================================
--- sys/sys/proc.h
+++ sys/sys/proc.h
@@ -174,6 +174,7 @@
 struct racct;
 struct sbuf;
 struct sleepqueue;
+struct syscall_args;
 struct td_sched;
 struct thread;
 struct trapframe;
@@ -282,6 +283,7 @@
 	int		td_no_sleeping;	/* (k) Sleeping disabled count. */
 	int		td_dom_rr_idx;	/* (k) RR Numa domain selection. */
 	void		*td_su;		/* (k) FFS SU private */
+	struct syscall_args *td_dbgsa;	/* (c) Debugger system call state. */
 #define	td_endzero td_sigmask
 
 /* Copied during fork1() or create_thread(). */
@@ -979,7 +981,6 @@
 
 void	cpu_exit(struct thread *);
 void	exit1(struct thread *, int, int) __dead2;
-struct syscall_args;
 int	cpu_fetch_syscall_args(struct thread *td, struct syscall_args *sa);
 void	cpu_fork(struct thread *, struct proc *, struct thread *, int);
 void	cpu_set_fork_handler(struct thread *, void (*)(void *), void *);
Index: sys/sys/ptrace.h
===================================================================
--- sys/sys/ptrace.h
+++ sys/sys/ptrace.h
@@ -113,6 +113,8 @@
 	struct __siginfo pl_siginfo;	/* siginfo for signal */
 	char		pl_tdname[MAXCOMLEN + 1]; /* LWP name */
 	int		pl_child_pid;	/* New child pid */
+	u_int		pl_syscall_code;
+	int		pl_syscall_narg;
 };
 
 /* Argument structure for PT_VM_ENTRY. */