[efi] Use EFI-native mechanism for accessing SMBIOS table

EFI provides a copy of the SMBIOS table accessible via the EFI system
table, which we should use instead of manually scanning through the
F000:0000 segment.

src/arch/i386/interface/pcbios/bios_smbios.c

@@ -0,0 +1,84 @@
+/*
+ * Copyright (C) 2007 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., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#include <stdint.h>
+#include <string.h>
+#include <errno.h>
+#include <assert.h>
+#include <gpxe/uaccess.h>
+#include <gpxe/smbios.h>
+#include <realmode.h>
+#include <pnpbios.h>
+
+/** @file
+ *
+ * System Management BIOS
+ *
+ */
+
+/**
+ * Find SMBIOS
+ *
+ * @v smbios		SMBIOS entry point descriptor structure to fill in
+ * @ret rc		Return status code
+ */
+static int bios_find_smbios ( struct smbios *smbios ) {
+	union {
+		struct smbios_entry entry;
+		uint8_t bytes[256]; /* 256 is maximum length possible */
+	} u;
+	static unsigned int offset = 0;
+	size_t len;
+	unsigned int i;
+	uint8_t sum;
+
+	/* Try to find SMBIOS */
+	for ( ; offset < 0x10000 ; offset += 0x10 ) {
+
+		/* Read start of header and verify signature */
+		copy_from_real ( &u.entry, BIOS_SEG, offset,
+				 sizeof ( u.entry ));
+		if ( u.entry.signature != SMBIOS_SIGNATURE )
+			continue;
+
+		/* Read whole header and verify checksum */
+		len = u.entry.len;
+		copy_from_real ( &u.bytes, BIOS_SEG, offset, len );
+		for ( i = 0 , sum = 0 ; i < len ; i++ ) {
+			sum += u.bytes[i];
+		}
+		if ( sum != 0 ) {
+			DBG ( "SMBIOS at %04x:%04x has bad checksum %02x\n",
+			      BIOS_SEG, offset, sum );
+			continue;
+		}
+
+		/* Fill result structure */
+		DBG ( "Found SMBIOS v%d.%d entry point at %04x:%04x\n",
+		      u.entry.major, u.entry.minor, BIOS_SEG, offset );
+		smbios->address = phys_to_user ( u.entry.smbios_address );
+		smbios->len = u.entry.smbios_len;
+		smbios->count = u.entry.smbios_count;
+		return 0;
+	}
+
+	DBG ( "No SMBIOS found\n" );
+	return -ENODEV;
+}
+
+PROVIDE_SMBIOS ( pcbios, find_smbios, bios_find_smbios );