Index: uspace/lib/posix/source/errno.c
===================================================================
--- uspace/lib/posix/source/errno.c	(revision 33c29521d96b892e096419a2fd8beb867e2596f6)
+++ uspace/lib/posix/source/errno.c	(revision 33c29521d96b892e096419a2fd8beb867e2596f6)
@@ -0,0 +1,52 @@
+/*
+ * Copyright (c) 2011 Jiri Zarevucky
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ *   notice, this list of conditions and the following disclaimer.
+ * - Redistributions in binary form must reproduce the above copyright
+ *   notice, this list of conditions and the following disclaimer in the
+ *   documentation and/or other materials provided with the distribution.
+ * - The name of the author may not be used to endorse or promote products
+ *   derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+/** @addtogroup libposix
+ * @{
+ */
+/** @file System error numbers.
+ */
+
+#include "posix/errno.h"
+
+#include "posix/stdlib.h"
+#include "libc/fibril.h"
+
+static fibril_local int _posix_errno;
+
+int *__posix_errno(void)
+{
+	if (*__errno() != 0) {
+		_posix_errno = abs(*__errno());
+		*__errno() = 0;
+	}
+	return &_posix_errno;
+}
+
+/** @}
+ */