// Attach to the given jail, if any. The system call also changes the
	// process' root and working directories to the jail's path directory.
	if sys.Jail > 0 {
		_, _, err1 = RawSyscall(SYS_JAIL_ATTACH, uintptr(sys.Jail), 0, 0)
		if err1 != 0 {
			goto childerror
		}
	}

	// Enable tracing if requested.
	if sys.Ptrace {
		_, _, err1 = RawSyscall(SYS_PTRACE, uintptr(PTRACE_TRACEME), 0, 0)

	SYS__UMTX_LOCK               = 434 // { int _umtx_lock(struct umtx *umtx); }
	SYS__UMTX_UNLOCK             = 435 // { int _umtx_unlock(struct umtx *umtx); }
	SYS_JAIL_ATTACH              = 436 // { int jail_attach(int jid); }
	SYS_EXTATTR_LIST_FD          = 437 // { ssize_t extattr_list_fd(int fd, \
	SYS_EXTATTR_LIST_FILE        = 438 // { ssize_t extattr_list_file( \

	SYS__UMTX_LOCK               = 434 // { int _umtx_lock(struct umtx *umtx); }
	SYS__UMTX_UNLOCK             = 435 // { int _umtx_unlock(struct umtx *umtx); }
	SYS_JAIL_ATTACH              = 436 // { int jail_attach(int jid); }
	SYS_EXTATTR_LIST_FD          = 437 // { ssize_t extattr_list_fd(int fd, \
	SYS_EXTATTR_LIST_FILE        = 438 // { ssize_t extattr_list_file( \

	SYS__UMTX_LOCK               = 434 // { int _umtx_lock(struct umtx *umtx); }
	SYS__UMTX_UNLOCK             = 435 // { int _umtx_unlock(struct umtx *umtx); }
	SYS_JAIL_ATTACH              = 436 // { int jail_attach(int jid); }
	SYS_EXTATTR_LIST_FD          = 437 // { ssize_t extattr_list_fd(int fd, \
	SYS_EXTATTR_LIST_FILE        = 438 // { ssize_t extattr_list_file( \

	SYS_UMTX_SLEEP             = 469 // { int umtx_sleep(volatile const int *ptr, int value, int timeout); }
	SYS_UMTX_WAKEUP            = 470 // { int umtx_wakeup(volatile const int *ptr, int count); }
	SYS_JAIL_ATTACH            = 471 // { int jail_attach(int jid); }
	SYS_SET_TLS_AREA           = 472 // { int set_tls_area(int which, struct tls_info *info, size_t infosize); }

	SYS_UMTX_SLEEP             = 469 // { int umtx_sleep(volatile const int *ptr, int value, int timeout); }
	SYS_UMTX_WAKEUP            = 470 // { int umtx_wakeup(volatile const int *ptr, int count); }
	SYS_JAIL_ATTACH            = 471 // { int jail_attach(int jid); }
	SYS_SET_TLS_AREA           = 472 // { int set_tls_area(int which, struct tls_info *info, size_t infosize); }

	SYS_THR_EXIT                 = 431 // { void thr_exit(long *state); }
	SYS_THR_SELF                 = 432 // { int thr_self(long *id); }
	SYS_THR_KILL                 = 433 // { int thr_kill(long id, int sig); }
	SYS_JAIL_ATTACH              = 436 // { int jail_attach(int jid); }
	SYS_EXTATTR_LIST_FD          = 437 // { ssize_t extattr_list_fd(int fd, int attrnamespace, void *data, size_t nbytes); }

	SYS_THR_EXIT                 = 431 // { void thr_exit(long *state); }
	SYS_THR_SELF                 = 432 // { int thr_self(long *id); }
	SYS_THR_KILL                 = 433 // { int thr_kill(long id, int sig); }
	SYS_JAIL_ATTACH              = 436 // { int jail_attach(int jid); }
	SYS_EXTATTR_LIST_FD          = 437 // { ssize_t extattr_list_fd(int fd, int attrnamespace, void *data, size_t nbytes); }

	SYS_THR_EXIT                 = 431 // { void thr_exit(long *state); }
	SYS_THR_SELF                 = 432 // { int thr_self(long *id); }
	SYS_THR_KILL                 = 433 // { int thr_kill(long id, int sig); }
	SYS_JAIL_ATTACH              = 436 // { int jail_attach(int jid); }
	SYS_EXTATTR_LIST_FD          = 437 // { ssize_t extattr_list_fd(int fd, int attrnamespace, void *data, size_t nbytes); }

	SYS_THR_EXIT                 = 431 // { void thr_exit(long *state); }
	SYS_THR_SELF                 = 432 // { int thr_self(long *id); }
	SYS_THR_KILL                 = 433 // { int thr_kill(long id, int sig); }
	SYS_JAIL_ATTACH              = 436 // { int jail_attach(int jid); }
	SYS_EXTATTR_LIST_FD          = 437 // { ssize_t extattr_list_fd(int fd, int attrnamespace, void *data, size_t nbytes); }