[pxe] Split out platform-independent portions of cachedhcp.c

Split out the portions of cachedhcp.c that can be shared between BIOS
and UEFI (both of which can provide a buffer containing a previously
obtained DHCP packet, and neither of which provide a means to
determine the length of this DHCP packet).

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

src/arch/x86/interface/pcbios/bios_cachedhcp.c

@@ -0,0 +1,76 @@
+/*
+ * Copyright (C) 2013 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 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.
+ *
+ * You can also choose to distribute this program under the terms of
+ * the Unmodified Binary Distribution Licence (as given in the file
+ * COPYING.UBDL), provided that you have satisfied its requirements.
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
+
+#include <stdint.h>
+#include <ipxe/init.h>
+#include <ipxe/cachedhcp.h>
+#include <realmode.h>
+#include <pxe_api.h>
+
+/** @file
+ *
+ * Cached DHCP packet
+ *
+ */
+
+/** Cached DHCPACK physical address
+ *
+ * This can be set by the prefix.
+ */
+uint32_t __bss16 ( cached_dhcpack_phys );
+#define cached_dhcpack_phys __use_data16 ( cached_dhcpack_phys )
+
+/** Colour for debug messages */
+#define colour &cached_dhcpack_phys
+
+/**
+ * Cached DHCPACK initialisation function
+ *
+ */
+static void cachedhcp_init ( void ) {
+	int rc;
+
+	/* Do nothing if no cached DHCPACK is present */
+	if ( ! cached_dhcpack_phys ) {
+		DBGC ( colour, "CACHEDHCP found no cached DHCPACK\n" );
+		return;
+	}
+
+	/* Record cached DHCPACK */
+	if ( ( rc = cachedhcp_record ( phys_to_user ( cached_dhcpack_phys ),
+				       sizeof ( BOOTPLAYER_t ) ) ) != 0 ) {
+		DBGC ( colour, "CACHEDHCP could not record DHCPACK: %s\n",
+		       strerror ( rc ) );
+		return;
+	}
+
+	/* Mark as consumed */
+	cached_dhcpack_phys = 0;
+}
+
+/** Cached DHCPACK initialisation function */
+struct init_fn cachedhcp_init_fn __init_fn ( INIT_NORMAL ) = {
+	.initialise = cachedhcp_init,
+};