Function audit_pipe_read

freebsd/security/audit/audit_pipe.c:899–977

* Audit pipe read. Read one or more partial or complete records to user * memory. */

 * memory.
 */
static int
audit_pipe_read(struct cdev *dev, struct uio *uio, int flag)
{
	struct audit_pipe_entry *ape;
	struct audit_pipe *ap;
	u_int toread;
	int error;

	error = devfs_get_cdevpriv((void **)&ap);
	if (error != 0)
		return (error);

	/*
	 * We hold an sx(9) lock over read and flush because we rely on the
	 * stability of a record in the queue during uiomove(9).
	 */
	if (AUDIT_PIPE_SX_XLOCK_SIG(ap) != 0)
		return (EINTR);
	AUDIT_PIPE_LOCK(ap);
	while (TAILQ_EMPTY(&ap->ap_queue)) {
		if (ap->ap_flags & AUDIT_PIPE_NBIO) {
			AUDIT_PIPE_UNLOCK(ap);
			AUDIT_PIPE_SX_XUNLOCK(ap);
			return (EAGAIN);
		}
		error = cv_wait_sig(&ap->ap_cv, AUDIT_PIPE_MTX(ap));
		if (error) {
			AUDIT_PIPE_UNLOCK(ap);
			AUDIT_PIPE_SX_XUNLOCK(ap);
			return (error);
		}
	}

	/*
	 * Copy as many remaining bytes from the current record to userspace
	 * as we can.  Keep processing records until we run out of records in
	 * the queue, or until the user buffer runs out of space.
	 *
	 * Note: we rely on the SX lock to maintain ape's stability here.
	 */
	ap->ap_reads++;
	while ((ape = TAILQ_FIRST(&ap->ap_queue)) != NULL &&
	    uio->uio_resid > 0) {
		AUDIT_PIPE_LOCK_ASSERT(ap);

		KASSERT(ape->ape_record_len > ap->ap_qoffset,
		    ("audit_pipe_read: record_len > qoffset (1)"));
		toread = MIN(ape->ape_record_len - ap->ap_qoffset,
		    uio->uio_resid);
		AUDIT_PIPE_UNLOCK(ap);
		error = uiomove((char *)ape->ape_record + ap->ap_qoffset,
		    toread, uio);
		if (error) {
			AUDIT_PIPE_SX_XUNLOCK(ap);
			return (error);
		}

		/*