[Settings] Expose SMBIOS via settings API

In particular, expose the system UUID as a setting ("smbios/uuid").

src/arch/i386/firmware/pcbios/smbios.c

@@ -18,10 +18,9 @@
 
 #include <stdint.h>
 #include <string.h>
-#include <stdio.h>
 #include <errno.h>
+#include <assert.h>
 #include <gpxe/uaccess.h>
-#include <gpxe/uuid.h>
 #include <realmode.h>
 #include <pnpbios.h>
 #include <smbios.h>
@@ -51,7 +50,7 @@ struct smbios_entry {
 	/** Checksum */
 	uint8_t checksum;
 	/** Length */
-	uint8_t length;
+	uint8_t len;
 	/** Major version */
 	uint8_t major;
 	/** Minor version */
@@ -67,7 +66,7 @@ struct smbios_entry {
 	/** DMI checksum */
 	uint8_t dmi_checksum;
 	/** Structure table length */
-	uint16_t smbios_length;
+	uint16_t smbios_len;
 	/** Structure table address */
 	physaddr_t smbios_address;
 	/** Number of SMBIOS structures */
@@ -86,49 +85,37 @@ struct smbios {
 	/** Start of SMBIOS structures */
 	userptr_t address;
 	/** Length of SMBIOS structures */ 
-	size_t length;
+	size_t len;
 	/** Number of SMBIOS structures */
 	unsigned int count;
 };
 
-/**
- * SMBIOS strings descriptor
- *
- * This is returned as part of the search for an SMBIOS structure, and
- * contains the information needed for extracting the strings within
- * the "unformatted" portion of the structure.
- */
-struct smbios_strings {
-	/** Start of strings data */
-	userptr_t data;
-	/** Length of strings data */
-	size_t length;
+/** SMBIOS entry point descriptor */
+static struct smbios smbios = {
+	.address = UNULL,
 };
 
 /**
  * Find SMBIOS
  *
- * @ret smbios		SMBIOS entry point descriptor, or NULL if not found
+ * @ret rc		Return status code
  */
-static struct smbios * find_smbios ( void ) {
-	static struct smbios smbios = {
-		.address = UNULL,
-	};
+static int find_smbios ( void ) {
 	union {
 		struct smbios_entry entry;
 		uint8_t bytes[256]; /* 256 is maximum length possible */
 	} u;
-	unsigned int offset;
+	static unsigned int offset = 0;
 	size_t len;
 	unsigned int i;
 	uint8_t sum;
 
-	/* Return cached result if available */
+	/* Return cached result if avaiable */
 	if ( smbios.address != UNULL )
-		return &smbios;
+		return 0;
 
 	/* Try to find SMBIOS */
-	for ( offset = 0 ; offset < 0x10000 ; offset += 0x10 ) {
+	for ( ; offset < 0x10000 ; offset += 0x10 ) {
 
 		/* Read start of header and verify signature */
 		copy_from_real ( &u.entry, BIOS_SEG, offset,
@@ -137,7 +124,7 @@ static struct smbios * find_smbios ( void ) {
 			continue;
 
 		/* Read whole header and verify checksum */
-		len = u.entry.length;
+		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];
@@ -152,29 +139,27 @@ static struct smbios * find_smbios ( void ) {
 		DBG ( "Found SMBIOS entry point at %04x:%04x\n",
 		      BIOS_SEG, offset );
 		smbios.address = phys_to_user ( u.entry.smbios_address );
-		smbios.length = u.entry.smbios_length;
+		smbios.len = u.entry.smbios_len;
 		smbios.count = u.entry.smbios_count;
-		return &smbios;
+		return 0;
 	}
 
 	DBG ( "No SMBIOS found\n" );
-	return NULL;
+	return -ENODEV;
 }
 
 /**
  * Find SMBIOS strings terminator
  *
- * @v smbios		SMBIOS entry point descriptor
  * @v offset		Offset to start of strings
  * @ret offset		Offset to strings terminator, or 0 if not found
  */
-static size_t find_strings_terminator ( struct smbios *smbios,
-					size_t offset ) {
-	size_t max_offset = ( smbios->length - 2 );
+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 );
+		copy_from_user ( &nulnul, smbios.address, offset, 2 );
 		if ( nulnul == 0 )
 			return ( offset + 1 );
 	}
@@ -185,66 +170,52 @@ static size_t find_strings_terminator ( struct smbios *smbios,
  * Find specific structure type within SMBIOS
  *
  * @v type		Structure type to search for
- * @v structure		Buffer to fill in with structure
- * @v length		Length of buffer
- * @v strings		Strings descriptor to fill in, or NULL
+ * @v structure		SMBIOS structure descriptor to fill in
  * @ret rc		Return status code
  */
-int find_smbios_structure ( unsigned int type, void *structure,
-			    size_t length, struct smbios_strings *strings ) {
-	struct smbios *smbios;
-	struct smbios_header header;
-	struct smbios_strings temp_strings;
+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;
 
-	/* Locate SMBIOS entry point */
-	if ( ! ( smbios = find_smbios() ) )
-		return -ENOENT;
-
-	/* Ensure that we have a usable strings descriptor buffer */
-	if ( ! strings )
-		strings = &temp_strings;
+	/* Find SMBIOS */
+	if ( ( rc = find_smbios() ) != 0 )
+		return rc;
 
 	/* Scan through list of structures */
-	while ( ( ( offset + sizeof ( header ) ) < smbios->length ) &&
-		( count < smbios->count ) ) {
+	while ( ( ( offset + sizeof ( structure->header ) ) < smbios.len )
+		&& ( count < smbios.count ) ) {
 
 		/* Read next SMBIOS structure header */
-		copy_from_user ( &header, smbios->address, offset,
-				 sizeof ( header ) );
+		copy_from_user ( &structure->header, smbios.address, offset,
+				 sizeof ( structure->header ) );
 
 		/* Determine start and extent of strings block */
-		strings_offset = ( offset + header.length );
-		if ( strings_offset > smbios->length ) {
+		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,
-			      header.length );
+			      structure->header.len );
 			return -ENOENT;
 		}
-		terminator_offset =
-			find_strings_terminator ( smbios, strings_offset );
+		terminator_offset = find_strings_terminator ( strings_offset );
 		if ( ! terminator_offset ) {
 			DBG ( "SMBIOS structure at offset %zx has "
 			      "unterminated strings section\n", offset );
 			return -ENOENT;
 		}
-		strings->data = userptr_add ( smbios->address,
-					      strings_offset );
-		strings->length = ( terminator_offset - strings_offset );
+		structure->strings_len = ( terminator_offset - strings_offset);
 
-		DBG ( "SMBIOS structure at offset %zx has type %d, "
-		      "length %x, strings length %zx\n",
-		      offset, header.type, header.length, strings->length );
+		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 ( header.type == type ) {
-			if ( length > header.length )
-				length = header.length;
-			copy_from_user ( structure, smbios->address,
-					 offset, length );
+		if ( structure->header.type == type ) {
+			structure->offset = offset;
 			return 0;
 		}
 
@@ -257,67 +228,65 @@ int find_smbios_structure ( unsigned int type, void *structure,
 	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 strings		SMBIOS strings descriptor
+ * @v structure		SMBIOS structure descriptor
  * @v index		String index
- * @v buffer		Buffer for string
- * @v length		Length of string buffer
- * @ret rc		Return status code
+ * @v data		Buffer for string
+ * @v len		Length of string buffer
+ * @ret rc		Length of string, or negative error
  */
-int find_smbios_string ( struct smbios_strings *strings, unsigned int index,
-			 char *buffer, size_t length ) {
-	size_t offset = 0;
+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;
 
-	/* Zero buffer.  This ensures that a valid NUL terminator is
-	 * always present (unless length==0).
-	 */
-	memset ( buffer, 0, length );
-	   
+	assert ( smbios.address != UNULL );
+
 	/* String numbers start at 1 (0 is used to indicate "no string") */
 	if ( ! index )
-		return 0;
+		return -ENOENT;
 
-	while ( offset < strings->length ) {
+	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 ( strings->data, offset );
+		string_len = strlen_user ( smbios.address,
+					   ( structure->offset + offset ) );
 		if ( --index == 0 ) {
 			/* Copy string, truncating as necessary. */
-			if ( string_len >= length )
-				string_len = ( length - 1 );
-			copy_from_user ( buffer, strings->data,
-					 offset, string_len );
-			return 0;
+			if ( len > string_len )
+				len = string_len;
+			copy_from_user ( data, smbios.address,
+					 ( structure->offset + offset ), len );
+			return string_len;
 		}
-		offset += ( string_len + 1 );
 	}
 
 	DBG ( "SMBIOS string index %d not found\n", index );
 	return -ENOENT;
 }
-
-/**
- * Get UUID from SMBIOS
- *
- * @v uuid		UUID to fill in
- * @ret rc		Return status code
- */
-int smbios_get_uuid ( union uuid *uuid ) {
-	struct smbios_system_information sysinfo;
-	int rc;
-
-	if ( ( rc = find_smbios_structure ( SMBIOS_TYPE_SYSTEM_INFORMATION,
-					    &sysinfo, sizeof ( sysinfo ),
-					    NULL ) ) != 0 )
-		return rc;
-
-	memcpy ( uuid, sysinfo.uuid, sizeof ( *uuid ) );
-	DBG ( "SMBIOS found UUID %s\n", uuid_ntoa ( uuid ) );
-
-	return 0;
-}

src/arch/i386/firmware/pcbios/smbios_settings.c

@@ -0,0 +1,158 @@
+/*
+ * Copyright (C) 2008 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 <gpxe/settings.h>
+#include <gpxe/init.h>
+#include <gpxe/uuid.h>
+#include <smbios.h>
+
+/**
+ * Construct SMBIOS raw-data tag
+ *
+ * @v _type		SMBIOS structure type number
+ * @v _structure	SMBIOS structure data type
+ * @v _field		Field within SMBIOS structure data type
+ * @ret tag		SMBIOS setting tag
+ */
+#define SMBIOS_RAW_TAG( _type, _structure, _field )		\
+	( ( (_type) << 16 ) |					\
+	  ( offsetof ( _structure, _field ) << 8 ) |		\
+	  ( sizeof ( ( ( _structure * ) 0 )->_field ) ) )
+
+/**
+ * Construct SMBIOS string tag
+ *
+ * @v _type		SMBIOS structure type number
+ * @v _structure	SMBIOS structure data type
+ * @v _field		Field within SMBIOS structure data type
+ * @ret tag		SMBIOS setting tag
+ */
+#define SMBIOS_STRING_TAG( _type, _structure, _field )		\
+	( ( (_type) << 16 ) |					\
+	  ( offsetof ( _structure, _field ) << 8 ) )
+
+/**
+ * Store value of SMBIOS setting
+ *
+ * @v settings		Settings block
+ * @v setting		Setting to store
+ * @v data		Setting data, or NULL to clear setting
+ * @v len		Length of setting data
+ * @ret rc		Return status code
+ */
+static int smbios_store ( struct settings *settings __unused,
+			  struct setting *setting __unused,
+			  const void *data __unused, size_t len __unused ) {
+	/* Cannot write data into SMBIOS */
+	return -ENOTSUP;
+}
+
+/**
+ * Fetch value of SMBIOS setting
+ *
+ * @v settings		Settings block, or NULL to search all blocks
+ * @v setting		Setting to fetch
+ * @v data		Buffer to fill with setting data
+ * @v len		Length of buffer
+ * @ret len		Length of setting data, or negative error
+ */
+static int smbios_fetch ( struct settings *settings __unused,
+			  struct setting *setting,
+			  void *data, size_t len ) {
+	struct smbios_structure structure;
+	unsigned int tag_type;
+	unsigned int tag_offset;
+	unsigned int tag_len;
+	int rc;
+
+	/* Split tag into type, offset and length */
+	tag_type = ( setting->tag >> 16 );
+	tag_offset = ( ( setting->tag >> 8 ) & 0xff );
+	tag_len = ( setting->tag & 0xff );
+	if ( ! tag_type )
+		return -ENOENT;
+
+	/* Find SMBIOS structure */
+	if ( ( rc = find_smbios_structure ( tag_type, &structure ) ) != 0 )
+		return rc;
+
+	{
+		uint8_t buf[structure.header.len];
+
+		/* Read SMBIOS structure */
+		if ( ( rc = read_smbios_structure ( &structure, buf,
+						    sizeof ( buf ) ) ) != 0 )
+			return rc;
+
+		if ( tag_len == 0 ) {
+			/* String */
+			return read_smbios_string ( &structure,
+						    buf[tag_offset],
+						    data, len );
+		} else {
+			/* Raw data */
+			if ( len > tag_len )
+				len = tag_len;
+			memcpy ( data, &buf[tag_offset], len );
+			return tag_len;
+		}
+	}
+}
+
+/** SMBIOS settings operations */
+static struct settings_operations smbios_settings_operations = {
+	.store = smbios_store,
+	.fetch = smbios_fetch,
+};
+
+/** SMBIOS settings */
+static struct settings smbios_settings = {
+	.refcnt = NULL,
+	.name = "smbios",
+	.siblings = LIST_HEAD_INIT ( smbios_settings.siblings ),
+	.children = LIST_HEAD_INIT ( smbios_settings.children ),
+	.op = &smbios_settings_operations,
+};
+
+/** Initialise SMBIOS settings */
+static void smbios_init ( void ) {
+	int rc;
+
+	if ( ( rc = register_settings ( &smbios_settings, NULL ) ) != 0 ) {
+		DBG ( "SMBIOS could not register settings: %s\n",
+		      strerror ( rc ) );
+		return;
+	}
+}
+
+/** SMBIOS settings initialiser */
+struct init_fn smbios_init_fn __init_fn ( INIT_NORMAL ) = {
+	.initialise = smbios_init,
+};
+
+/** UUID setting obtained via SMBIOS */
+struct setting uuid_setting __setting = {
+	.name = "uuid",
+	.description = "UUID",
+	.tag = SMBIOS_RAW_TAG ( SMBIOS_TYPE_SYSTEM_INFORMATION,
+				struct smbios_system_information, uuid ),
+	.type = &setting_type_uuid,
+};

src/arch/i386/include/bits/errfile.h

@@ -12,6 +12,7 @@
 #define ERRFILE_smbios		( ERRFILE_ARCH | ERRFILE_CORE | 0x00030000 )
 #define ERRFILE_biosint		( ERRFILE_ARCH | ERRFILE_CORE | 0x00040000 )
 #define ERRFILE_int13		( ERRFILE_ARCH | ERRFILE_CORE | 0x00050000 )
+#define ERRFILE_smbios_settings	( ERRFILE_ARCH | ERRFILE_CORE | 0x00060000 )
 
 #define ERRFILE_bootsector     ( ERRFILE_ARCH | ERRFILE_IMAGE | 0x00000000 )
 #define ERRFILE_bzimage	       ( ERRFILE_ARCH | ERRFILE_IMAGE | 0x00010000 )

src/arch/i386/include/bits/uuid.h

@@ -1,10 +0,0 @@
-#ifndef _I386_UUID_H
-#define _I386_UUID_H
-
-#include <smbios.h>
-
-static inline int get_uuid ( union uuid *uuid ) {
-	return smbios_get_uuid ( uuid );
-}
-
-#endif /* _I386_UUID_H */

src/arch/i386/include/smbios.h

@@ -13,11 +13,21 @@ struct smbios_header {
 	/** Type */
 	uint8_t type;
 	/** Length */
-	uint8_t length;
+	uint8_t len;
 	/** Handle */
 	uint16_t handle;
 } __attribute__ (( packed ));
 
+/** SMBIOS structure descriptor */
+struct smbios_structure {
+	/** Copy of SMBIOS structure header */
+	struct smbios_header header;
+	/** Offset of structure within SMBIOS */
+	size_t offset;
+	/** Length of strings section */
+	size_t strings_len;
+};
+
 /** SMBIOS system information structure */
 struct smbios_system_information {
 	/** SMBIOS structure header */
@@ -39,13 +49,12 @@ struct smbios_system_information {
 /** SMBIOS system information structure type */
 #define SMBIOS_TYPE_SYSTEM_INFORMATION 1
 
-struct smbios_strings;
 extern int find_smbios_structure ( unsigned int type,
-				   void *structure, size_t length,
-				   struct smbios_strings *strings );
-extern int find_smbios_string ( struct smbios_strings *strings,
+				   struct smbios_structure *structure );
+extern int read_smbios_structure ( struct smbios_structure *structure,
+				   void *data, size_t len );
+extern int read_smbios_string ( struct smbios_structure *structure,
 				unsigned int index,
-				char *buffer, size_t length );
-extern int smbios_get_uuid ( union uuid *uuid );
+				void *data, size_t len );
 
 #endif /* _SMBIOS_H */

src/core/settings.c

@@ -27,6 +27,7 @@
 #include <gpxe/in.h>
 #include <gpxe/vsprintf.h>
 #include <gpxe/dhcp.h>
+#include <gpxe/uuid.h>
 #include <gpxe/settings.h>
 
 /** @file
@@ -487,6 +488,26 @@ unsigned long fetch_uintz_setting ( struct settings *settings,
 	return value;
 }
 
+/**
+ * Fetch value of UUID setting
+ *
+ * @v settings		Settings block, or NULL to search all blocks
+ * @v setting		Setting to fetch
+ * @v uuid		UUID to fill in
+ * @ret len		Length of setting, or negative error
+ */
+int fetch_uuid_setting ( struct settings *settings, struct setting *setting,
+			 union uuid *uuid ) {
+	int len;
+
+	len = fetch_setting ( settings, setting, uuid, sizeof ( *uuid ) );
+	if ( len < 0 )
+		return len;
+	if ( len != sizeof ( *uuid ) )
+		return -ERANGE;
+	return len;
+}
+
 /**
  * Compare two settings
  *
@@ -752,11 +773,11 @@ static int storef_ipv4 ( struct settings *settings, struct setting *setting,
 static int fetchf_ipv4 ( struct settings *settings, struct setting *setting,
 			 char *buf, size_t len ) {
 	struct in_addr ipv4;
-	int rc;
+	int raw_len;
 
-	if ( ( rc = fetch_ipv4_setting ( settings, setting, &ipv4 ) ) < 0 )
-		return rc;
-	return snprintf ( buf, len, inet_ntoa ( ipv4 ) );
+	if ( ( raw_len = fetch_ipv4_setting ( settings, setting, &ipv4 ) ) < 0)
+		return raw_len;
+	return snprintf ( buf, len, "%s", inet_ntoa ( ipv4 ) );
 }
 
 /** An IPv4 address setting type */
@@ -985,6 +1006,46 @@ struct setting_type setting_type_hex __setting_type = {
 	.fetchf = fetchf_hex,
 };
 
+/**
+ * Parse and store value of UUID setting
+ *
+ * @v settings		Settings block
+ * @v setting		Setting to store
+ * @v value		Formatted setting data
+ * @ret rc		Return status code
+ */
+static int storef_uuid ( struct settings *settings __unused,
+			 struct setting *setting __unused,
+			 const char *value __unused ) {
+	return -ENOTSUP;
+}
+
+/**
+ * Fetch and format value of UUID setting
+ *
+ * @v settings		Settings block, or NULL to search all blocks
+ * @v setting		Setting to fetch
+ * @v buf		Buffer to contain formatted value
+ * @v len		Length of buffer
+ * @ret len		Length of formatted value, or negative error
+ */
+static int fetchf_uuid ( struct settings *settings, struct setting *setting,
+			 char *buf, size_t len ) {
+	union uuid uuid;
+	int raw_len;
+
+	if ( ( raw_len = fetch_uuid_setting ( settings, setting, &uuid ) ) < 0)
+		return raw_len;
+	return snprintf ( buf, len, "%s", uuid_ntoa ( &uuid ) );
+}
+
+/** UUID setting type */
+struct setting_type setting_type_uuid __setting_type = {
+	.name = "uuid",
+	.storef = storef_uuid,
+	.fetchf = fetchf_uuid,
+};
+
 /******************************************************************************
  *
  * Settings

src/include/gpxe/settings.h

@@ -15,6 +15,7 @@
 
 struct settings;
 struct in_addr;
+union uuid;
 
 /** A setting */
 struct setting {
@@ -177,6 +178,8 @@ extern long fetch_intz_setting ( struct settings *settings,
 				 struct setting *setting );
 extern unsigned long fetch_uintz_setting ( struct settings *settings,
 					   struct setting *setting );
+extern int fetch_uuid_setting ( struct settings *settings,
+				struct setting *setting, union uuid *uuid );
 extern int setting_cmp ( struct setting *a, struct setting *b );
 
 extern struct settings * find_child_settings ( struct settings *parent,
@@ -198,6 +201,7 @@ extern struct setting_type setting_type_uint8 __setting_type;
 extern struct setting_type setting_type_uint16 __setting_type;
 extern struct setting_type setting_type_uint32 __setting_type;
 extern struct setting_type setting_type_hex __setting_type;
+extern struct setting_type setting_type_uuid __setting_type;
 
 extern struct setting ip_setting __setting;
 extern struct setting netmask_setting __setting;
@@ -210,6 +214,7 @@ extern struct setting username_setting __setting;
 extern struct setting password_setting __setting;
 extern struct setting priority_setting __setting;
 extern struct setting bios_drive_setting __setting;
+extern struct setting uuid_setting __setting;
 
 /**
  * Initialise a settings block

src/include/gpxe/uuid.h

@@ -8,9 +8,6 @@
 
 #include <stdint.h>
 
-union uuid;
-#include <bits/uuid.h>
-
 /** A universally unique ID */
 union uuid {
 	/** Canonical form (00000000-0000-0000-0000-000000000000) */

src/net/udp/dhcp.c

@@ -214,7 +214,7 @@ static int dhcpset_store ( struct settings *settings, struct setting *setting,
 }
 
 /**
- * Fetch value of setting
+ * Fetch value of DHCP setting
  *
  * @v settings		Settings block, or NULL to search all blocks
  * @v setting		Setting to fetch
@@ -517,7 +517,8 @@ int dhcp_create_request ( struct dhcp_packet *dhcppkt,
 
 	/* Add client UUID, if we have one.  Required for PXE. */
 	client_uuid.type = DHCP_CLIENT_UUID_TYPE;
-	if ( ( rc = get_uuid ( &client_uuid.uuid ) ) == 0 ) {
+	if ( ( rc = fetch_uuid_setting ( NULL, &uuid_setting,
+					 &client_uuid.uuid ) ) >= 0 ) {
 		if ( ( rc = dhcppkt_store ( dhcppkt, DHCP_CLIENT_UUID,
 					    &client_uuid,
 					    sizeof ( client_uuid ) ) ) != 0 ) {