Function userland_sysctl

freebsd/kern/kern_sysctl.c:2363–2434

* This is used from various compatibility syscalls too. That's why name * must be in kernel space. */

 * must be in kernel space.
 */
int
userland_sysctl(struct thread *td, int *name, u_int namelen, void *old,
    size_t *oldlenp, int inkernel, const void *new, size_t newlen,
    size_t *retval, int flags)
{
	int error = 0, memlocked;
	struct sysctl_req req;

	bzero(&req, sizeof req);

	req.td = td;
	req.flags = flags;

	if (oldlenp) {
		if (inkernel) {
			req.oldlen = *oldlenp;
		} else {
			error = copyin(oldlenp, &req.oldlen, sizeof(*oldlenp));
			if (error)
				return (error);
		}
	}
	req.validlen = req.oldlen;
	req.oldptr = old;

	if (new != NULL) {
		req.newlen = newlen;
		req.newptr = new;
	}

	req.oldfunc = sysctl_old_user;
	req.newfunc = sysctl_new_user;
	req.lock = REQ_UNWIRED;

#ifdef KTRACE
	if (KTRPOINT(curthread, KTR_SYSCTL))
		ktrsysctl(name, namelen);
#endif
	memlocked = 0;
	if (req.oldptr && req.oldlen > 4 * PAGE_SIZE) {
		memlocked = 1;
		sx_xlock(&sysctlmemlock);
	}
	CURVNET_SET(TD_TO_VNET(td));

	for (;;) {
		req.oldidx = 0;
		req.newidx = 0;
		error = sysctl_root(0, name, namelen, &req);
		if (error != EAGAIN)
			break;
		kern_yield(PRI_USER);
	}

	CURVNET_RESTORE();

	if (req.lock == REQ_WIRED && req.validlen > 0)
		vsunlock(req.oldptr, req.validlen);