Function sysctl_wire_old_buffer

freebsd/kern/kern_sysctl.c:2082–2104

* Wire the user space destination buffer. If set to a value greater than * zero, the len parameter limits the maximum amount of wired memory. */

 * zero, the len parameter limits the maximum amount of wired memory.
 */
int
sysctl_wire_old_buffer(struct sysctl_req *req, size_t len)
{
	int ret;
	size_t wiredlen;

	wiredlen = (len > 0 && len < req->oldlen) ? len : req->oldlen;
	ret = 0;
	if (req->lock != REQ_WIRED && req->oldptr &&
	    req->oldfunc == sysctl_old_user) {
		if (wiredlen != 0) {
			ret = vslock(req->oldptr, wiredlen);
			if (ret != 0) {
				if (ret != ENOMEM)
					return (ret);
				wiredlen = 0;
			}
		}
		req->lock = REQ_WIRED;
		req->validlen = wiredlen;
	}
	return (0);
}

int
sysctl_find_oid(int *name, u_int namelen, struct sysctl_oid **noid,