source: bootcd/isolinux/syslinux-6.03/gpxe/src/core/nvo.c

/*
 * Copyright (C) 2006 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.
 */

FILE_LICENCE ( GPL2_OR_LATER );

#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <gpxe/dhcp.h>
#include <gpxe/nvs.h>
#include <gpxe/nvo.h>

/** @file
 *
 * Non-volatile stored options
 *
 */

/**
 * Calculate checksum over non-volatile stored options
 *
 * @v nvo               Non-volatile options block
 * @ret sum             Checksum
 */
static unsigned int nvo_checksum ( struct nvo_block *nvo ) {
        uint8_t *data = nvo->data;
        uint8_t sum = 0;
        unsigned int i;

        for ( i = 0 ; i < nvo->total_len ; i++ ) {
                sum += *(data++);
        }
        return sum;
}

/**
 * Load non-volatile stored options from non-volatile storage device
 *
 * @v nvo               Non-volatile options block
 * @ret rc              Return status code
 */
static int nvo_load ( struct nvo_block *nvo ) {
        void *data = nvo->data;
        struct nvo_fragment *frag;
        int rc;

        /* Read data a fragment at a time */
        for ( frag = nvo->fragments ; frag->len ; frag++ ) {
                if ( ( rc = nvs_read ( nvo->nvs, frag->address, data,
                                       frag->len ) ) != 0 ) {
                        DBGC ( nvo, "NVO %p could not read %zd bytes at "
                               "%#04x\n", nvo, frag->len, frag->address );
                        return rc;
                }
                data += frag->len;
        }

        DBGC ( nvo, "NVO %p loaded from non-volatile storage\n", nvo );
        return 0;
}

/**
 * Save non-volatile stored options back to non-volatile storage device
 *
 * @v nvo               Non-volatile options block
 * @ret rc              Return status code
 */
static int nvo_save ( struct nvo_block *nvo ) {
        void *data = nvo->data;
        uint8_t *checksum = data;
        struct nvo_fragment *frag;
        int rc;

        /* Recalculate checksum */
        *checksum -= nvo_checksum ( nvo );

        /* Write data a fragment at a time */
        for ( frag = nvo->fragments ; frag->len ; frag++ ) {
                if ( ( rc = nvs_write ( nvo->nvs, frag->address, data,
                                        frag->len ) ) != 0 ) {
                        DBGC ( nvo, "NVO %p could not write %zd bytes at "
                               "%#04x\n", nvo, frag->len, frag->address );
                        return rc;
                }
                data += frag->len;
        }

        DBGC ( nvo, "NVO %p saved to non-volatile storage\n", nvo );
        return 0;
}

/**
 * Parse stored options
 *
 * @v nvo               Non-volatile options block
 *
 * Verifies that the options data is valid, and configures the DHCP
 * options block.  If the data is not valid, it is replaced with an
 * empty options block.
 */
static void nvo_init_dhcpopts ( struct nvo_block *nvo ) {
        uint8_t *options_data;
        size_t options_len;

        /* Steal one byte for the checksum */
        options_data = ( nvo->data + 1 );
        options_len = ( nvo->total_len - 1 );

        /* If checksum fails, or options data starts with a zero,
         * assume the whole block is invalid.  This should capture the
         * case of random initial contents.
         */
        if ( ( nvo_checksum ( nvo ) != 0 ) || ( options_data[0] == 0 ) ) {
                DBGC ( nvo, "NVO %p has checksum %02x and initial byte %02x; "
                       "assuming empty\n", nvo, nvo_checksum ( nvo ),
                       options_data[0] );
                memset ( nvo->data, 0, nvo->total_len );
        }

        dhcpopt_init ( &nvo->dhcpopts, options_data, options_len );
}

/**
 * Store value of NVO 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 nvo_store ( struct settings *settings, struct setting *setting,
                       const void *data, size_t len ) {
        struct nvo_block *nvo =
                container_of ( settings, struct nvo_block, settings );
        int rc;

        /* Update stored options */
        if ( ( rc = dhcpopt_store ( &nvo->dhcpopts, setting->tag,
                                    data, len ) ) != 0 ) {
                DBGC ( nvo, "NVO %p could not store %zd bytes: %s\n",
                       nvo, len, strerror ( rc ) );
                return rc;
        }

        /* Save updated options to NVS */
        if ( ( rc = nvo_save ( nvo ) ) != 0 )
                return rc;

        return 0;
}

/**
 * Fetch value of NVO setting
 *
 * @v settings          Settings block
 * @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
 *
 * The actual length of the setting will be returned even if
 * the buffer was too small.
 */
static int nvo_fetch ( struct settings *settings, struct setting *setting,
                       void *data, size_t len ) {
        struct nvo_block *nvo =
                container_of ( settings, struct nvo_block, settings );

        return dhcpopt_fetch ( &nvo->dhcpopts, setting->tag, data, len );
}

/** NVO settings operations */
static struct settings_operations nvo_settings_operations = {
        .store = nvo_store,
        .fetch = nvo_fetch,
};

/**
 * Initialise non-volatile stored options
 *
 * @v nvo               Non-volatile options block
 * @v nvs               Underlying non-volatile storage device
 * @v fragments         List of option-containing fragments
 * @v refcnt            Containing object reference counter, or NULL
 */
void nvo_init ( struct nvo_block *nvo, struct nvs_device *nvs,
                struct nvo_fragment *fragments, struct refcnt *refcnt ) {
        nvo->nvs = nvs;
        nvo->fragments = fragments;
        settings_init ( &nvo->settings, &nvo_settings_operations, refcnt,
                        "nvo", 0 );
}

/**
 * Register non-volatile stored options
 *
 * @v nvo               Non-volatile options block
 * @v parent            Parent settings block, or NULL
 * @ret rc              Return status code
 */
int register_nvo ( struct nvo_block *nvo, struct settings *parent ) {
        struct nvo_fragment *fragment = nvo->fragments;
        int rc;

        /* Calculate total length of all fragments */
        for ( fragment = nvo->fragments ; fragment->len ; fragment++ )
                nvo->total_len += fragment->len;

        /* Allocate memory for options and read in from NVS */
        nvo->data = malloc ( nvo->total_len );
        if ( ! nvo->data ) {
                DBGC ( nvo, "NVO %p could not allocate %zd bytes\n",
                       nvo, nvo->total_len );
                rc = -ENOMEM;
                goto err_malloc;
        }
        if ( ( rc = nvo_load ( nvo ) ) != 0 )
                goto err_load;

        /* Verify and register options */
        nvo_init_dhcpopts ( nvo );
        if ( ( rc = register_settings ( &nvo->settings, parent ) ) != 0 )
                goto err_register;

        DBGC ( nvo, "NVO %p registered\n", nvo );
        return 0;
        
 err_register:
 err_load:
        free ( nvo->data );
        nvo->data = NULL;
 err_malloc:
        return rc;
}

/**
 * Unregister non-volatile stored options
 *
 * @v nvo               Non-volatile options block
 */
void unregister_nvo ( struct nvo_block *nvo ) {
        unregister_settings ( &nvo->settings );
        free ( nvo->data );
        nvo->data = NULL;
        DBGC ( nvo, "NVO %p unregistered\n", nvo );
}