[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/interface/smbios/smbios.c

@@ -0,0 +1,178 @@
+/*
+ * 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>
+
+/** @file
+ *
+ * System Management BIOS
+ *
+ */
+
+/** SMBIOS entry point descriptor */
+static struct smbios smbios = {
+	.address = UNULL,
+};
+
+/**
+ * Find SMBIOS strings terminator
+ *
+ * @v offset		Offset to start of strings
+ * @ret offset		Offset to strings terminator, or 0 if not found
+ */
+static size_t find_strings_terminator ( size_t offset ) {
+	size_t max_offset = ( smbios.len - 2 );
+	uint16_t nulnul;
+
+	for ( ; offset <= max_offset ; offset++ ) {
+		copy_from_user ( &nulnul, smbios.address, offset, 2 );
+		if ( nulnul == 0 )
+			return ( offset + 1 );
+	}
+	return 0;
+}
+
+/**
+ * Find specific structure type within SMBIOS
+ *
+ * @v type		Structure type to search for
+ * @v structure		SMBIOS structure descriptor to fill in
+ * @ret rc		Return status code
+ */
+int find_smbios_structure ( unsigned int type,
+			    struct smbios_structure *structure ) {
+	unsigned int count = 0;
+	size_t offset = 0;
+	size_t strings_offset;
+	size_t terminator_offset;
+	int rc;
+
+	/* Find SMBIOS */
+	if ( ( smbios.address == UNULL ) &&
+	     ( ( rc = find_smbios ( &smbios ) ) != 0 ) )
+		return rc;
+	assert ( smbios.address != UNULL );
+
+	/* Scan through list of structures */
+	while ( ( ( offset + sizeof ( structure->header ) ) < smbios.len )
+		&& ( count < smbios.count ) ) {
+
+		/* Read next SMBIOS structure header */
+		copy_from_user ( &structure->header, smbios.address, offset,
+				 sizeof ( structure->header ) );
+
+		/* Determine start and extent of strings block */
+		strings_offset = ( offset + structure->header.len );
+		if ( strings_offset > smbios.len ) {
+			DBG ( "SMBIOS structure at offset %zx with length "
+			      "%x extends beyond SMBIOS\n", offset,
+			      structure->header.len );
+			return -ENOENT;
+		}
+		terminator_offset = find_strings_terminator ( strings_offset );
+		if ( ! terminator_offset ) {
+			DBG ( "SMBIOS structure at offset %zx has "
+			      "unterminated strings section\n", offset );
+			return -ENOENT;
+		}
+		structure->strings_len = ( terminator_offset - strings_offset);
+
+		DBG ( "SMBIOS structure at offset %zx has type %d, length %x, "
+		      "strings length %zx\n", offset, structure->header.type,
+		      structure->header.len, structure->strings_len );
+
+		/* If this is the structure we want, return */
+		if ( structure->header.type == type ) {
+			structure->offset = offset;
+			return 0;
+		}
+
+		/* Move to next SMBIOS structure */
+		offset = ( terminator_offset + 1 );
+		count++;
+	}
+
+	DBG ( "SMBIOS structure type %d not found\n", type );
+	return -ENOENT;
+}
+
+/**
+ * Copy SMBIOS structure
+ *
+ * @v structure		SMBIOS structure descriptor
+ * @v data		Buffer to hold SMBIOS structure
+ * @v len		Length of buffer
+ * @ret rc		Return status code
+ */
+int read_smbios_structure ( struct smbios_structure *structure,
+			    void *data, size_t len ) {
+
+	assert ( smbios.address != UNULL );
+
+	if ( len > structure->header.len )
+		len = structure->header.len;
+	copy_from_user ( data, smbios.address, structure->offset, len );
+	return 0;
+}
+
+/**
+ * Find indexed string within SMBIOS structure
+ *
+ * @v structure		SMBIOS structure descriptor
+ * @v index		String index
+ * @v data		Buffer for string
+ * @v len		Length of string buffer
+ * @ret rc		Length of string, or negative error
+ */
+int read_smbios_string ( struct smbios_structure *structure,
+			 unsigned int index, void *data, size_t len ) {
+	size_t strings_start = ( structure->offset + structure->header.len );
+	size_t strings_end = ( strings_start + structure->strings_len );
+	size_t offset;
+	size_t string_len;
+
+	assert ( smbios.address != UNULL );
+
+	/* String numbers start at 1 (0 is used to indicate "no string") */
+	if ( ! index )
+		return -ENOENT;
+
+	for ( offset = strings_start ; offset < strings_end ;
+	      offset += ( string_len + 1 ) ) {
+		/* Get string length.  This is known safe, since the
+		 * smbios_strings struct is constructed so as to
+		 * always end on a string boundary.
+		 */
+		string_len = strlen_user ( smbios.address, offset );
+		if ( --index == 0 ) {
+			/* Copy string, truncating as necessary. */
+			if ( len > string_len )
+				len = string_len;
+			copy_from_user ( data, smbios.address, offset, len );
+			return string_len;
+		}
+	}
+
+	DBG ( "SMBIOS string index %d not found\n", index );
+	return -ENOENT;
+}