[time] Add Linux time source using gettimeofday()

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/config/defaults/linux.h

 #define SMBIOS_LINUX
 #define SANBOOT_NULL
 #define ENTROPY_LINUX
-#define TIME_NULL
+#define TIME_LINUX
 
 #define DRIVERS_LINUX
 

src/include/ipxe/linux/linux_time.h

+#ifndef _IPXE_LINUX_TIME_H
+#define _IPXE_LINUX_TIME_H
+
+/** @file
+ *
+ * Linux time source
+ *
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER );
+
+#ifdef TIME_LINUX
+#define TIME_PREFIX_linux
+#else
+#define TIME_PREFIX_linux __linux_
+#endif
+
+#endif /* _IPXE_LINUX_TIME_H */

src/include/ipxe/time.h

 
 /* Include all architecture-independent time API headers */
 #include <ipxe/null_time.h>
+#include <ipxe/linux/linux_time.h>
 
 /* Include all architecture-dependent time API headers */
 #include <bits/time.h>

src/include/linux_api.h

 #include <linux/types.h>
 #include <linux/posix_types.h>
 typedef __kernel_pid_t pid_t;
-typedef __kernel_time_t time_t;
 typedef __kernel_suseconds_t suseconds_t;
 typedef __kernel_loff_t loff_t;
 #include <linux/time.h>

src/interface/linux/linux_time.c

+/*
+ * Copyright (C) 2012 Michael Brown <mbrown@fensystems.co.uk>.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA.
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER );
+
+/** @file
+ *
+ * Linux time source
+ *
+ */
+
+#include <stdint.h>
+#include <errno.h>
+#include <linux_api.h>
+#include <ipxe/time.h>
+
+/**
+ * Get current time in seconds
+ *
+ * @ret time		Time, in seconds
+ */
+static time_t linux_now ( void ) {
+	struct timeval now;
+
+	linux_gettimeofday ( &now, NULL );
+	return now.tv_sec;
+}
+
+PROVIDE_TIME ( linux, time_now, linux_now );