smbios.c

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/*
 * 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., 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 );
FILE_SECBOOT ( PERMITTED );

#include <stdint.h>
#include <string.h>
#include <errno.h>
#include <assert.h>
#include <ipxe/uaccess.h>
#include <ipxe/smbios.h>

/** @file
 *
 * System Management BIOS
 *
 */

/** SMBIOS entry point descriptor */
static struct smbios smbios = {
        .address = NULL,
};

/**
 * Calculate SMBIOS entry point structure checksum
 *
 * @v start             Start address of region
 * @v len               Length of entry point structure
 * @ret sum             Byte checksum
 */
static uint8_t smbios_checksum ( const void *start, size_t len ) {
        const uint8_t *byte = start;
        uint8_t sum = 0;

        /* Compute checksum */
        while ( len-- )
                sum += *(byte++);

        return sum;
}

/**
 * Scan for SMBIOS 32-bit entry point structure
 *
 * @v start             Start address of region to scan
 * @v len               Length of region to scan
 * @ret entry           SMBIOS entry point structure, or NULL if not found
 */
const struct smbios_entry * find_smbios_entry ( const void *start,
                                                size_t len ) {
        static size_t offset = 0; /* Avoid repeated attempts to locate SMBIOS */
        const struct smbios_entry *entry;
        uint8_t sum;

        /* Try to find SMBIOS */
        for ( ; ( offset + sizeof ( *entry ) ) <= len ; offset += 0x10 ) {

                /* Verify signature */
                entry = ( start + offset );
                if ( entry->signature != SMBIOS_SIGNATURE )
                        continue;

                /* Verify length */
                if ( ( entry->len < sizeof ( *entry ) ) ||
                     ( ( offset + entry->len ) > len ) ) {
                        DBGC ( &smbios, "SMBIOS at %#08lx has bad length "
                               "%#02x\n", virt_to_phys ( entry ), entry->len );
                        continue;
                }

                /* Verify checksum */
                if ( ( sum = smbios_checksum ( entry, entry->len ) ) != 0 ) {
                        DBGC ( &smbios, "SMBIOS at %#08lx has bad checksum "
                               "%#02x\n", virt_to_phys ( entry ), sum );
                        continue;
                }

                /* Fill result structure */
                DBGC ( &smbios, "Found SMBIOS v%d.%d entry point at %#08lx\n",
                       entry->major, entry->minor, virt_to_phys ( entry ) );
                return entry;
        }

        DBGC ( &smbios, "No SMBIOS found\n" );
        return NULL;
}

/**
 * Scan for SMBIOS 64-bit entry point structure
 *
 * @v start             Start address of region to scan
 * @v len               Length of region to scan
 * @ret entry           SMBIOS entry point structure, or NULL if not found
 */
const struct smbios3_entry * find_smbios3_entry ( const void *start,
                                                  size_t len ) {
        static size_t offset = 0; /* Avoid repeated attempts to locate SMBIOS */
        const struct smbios3_entry *entry;
        uint8_t sum;

        /* Try to find SMBIOS */
        for ( ; ( offset + sizeof ( *entry ) ) <= len ; offset += 0x10 ) {

                /* Verify signature */
                entry = ( start + offset );
                if ( entry->signature != SMBIOS3_SIGNATURE )
                        continue;

                /* Verify length */
                if ( ( entry->len < sizeof ( *entry ) ) ||
                     ( ( offset + entry->len ) > len ) ) {
                        DBGC ( &smbios, "SMBIOS at %#08lx has bad length "
                               "%#02x\n", virt_to_phys ( entry ), entry->len );
                        continue;
                }

                /* Verify checksum */
                if ( ( sum = smbios_checksum ( entry, entry->len ) ) != 0 ) {
                        DBGC ( &smbios, "SMBIOS3 at %#08lx has bad checksum "
                               "%#02x\n", virt_to_phys ( entry ), sum );
                        continue;
                }

                /* Fill result structure */
                DBGC ( &smbios, "Found SMBIOS3 v%d.%d entry point at %#08lx\n",
                       entry->major, entry->minor, virt_to_phys ( entry ) );
                return entry;
        }

        DBGC ( &smbios, "No SMBIOS3 found\n" );
        return NULL;
}

/**
 * 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 ) {
        const uint16_t *nulnul __attribute__ (( aligned ( 1 ) ));

        /* Sanity checks */
        assert ( smbios.address != NULL );

        /* Check for presence of terminating empty string */
        for ( ; ( offset + sizeof ( *nulnul ) ) <= smbios.len ; offset++ ) {
                nulnul = ( smbios.address + offset );
                if ( *nulnul == 0 )
                        return ( offset + 1 );
        }
        return 0;
}

/**
 * Find specific structure type within SMBIOS
 *
 * @v type              Structure type to search for
 * @v instance          Instance of this type of structure
 * @ret structure       SMBIOS structure header, or NULL if not found
 */
const struct smbios_header * smbios_structure ( unsigned int type,
                                                unsigned int instance ) {
        const struct smbios_header *structure;
        unsigned int count = 0;
        size_t offset = 0;
        size_t strings_offset;
        size_t terminator_offset;
        size_t strings_len;
        int rc;

        /* Find SMBIOS */
        if ( ( smbios.address == NULL ) &&
             ( ( rc = find_smbios ( &smbios ) ) != 0 ) )
                return NULL;
        assert ( smbios.address != NULL );

        /* Scan through list of structures */
        while ( ( ( offset + sizeof ( *structure ) ) < smbios.len ) &&
                ( ( smbios.count == 0 ) || ( count < smbios.count ) ) ) {

                /* Access next SMBIOS structure header */
                structure = ( smbios.address + offset );

                /* Determine start and extent of strings block */
                strings_offset = ( offset + structure->len );
                if ( strings_offset > smbios.len ) {
                        DBGC ( &smbios, "SMBIOS structure at offset %#zx "
                               "with length %#x extends beyond SMBIOS\n",
                               offset, structure->len );
                        return NULL;
                }
                terminator_offset = find_strings_terminator ( strings_offset );
                if ( ! terminator_offset ) {
                        DBGC ( &smbios, "SMBIOS structure at offset %#zx has "
                               "unterminated strings section\n", offset );
                        return NULL;
                }
                strings_len = ( terminator_offset - strings_offset);
                DBGC ( &smbios, "SMBIOS structure at offset %#zx has type %d, "
                       "length %#x, strings length %#zx\n", offset,
                       structure->type, structure->len, strings_len );

                /* Stop if we have reached an end-of-table marker */
                if ( ( smbios.count == 0 ) &&
                     ( structure->type == SMBIOS_TYPE_END ) )
                        break;

                /* If this is the structure we want, return */
                if ( ( structure->type == type ) &&
                     ( instance-- == 0 ) ) {
                        return structure;
                }

                /* Move to next SMBIOS structure */
                offset = ( terminator_offset + 1 );
                count++;
        }

        DBGC ( &smbios, "SMBIOS structure type %d not found\n", type );
        return NULL;
}

/**
 * Get indexed string within SMBIOS structure
 *
 * @v structure         SMBIOS structure header
 * @v index             String index
 * @ret string          SMBIOS string, or NULL if not fond
 */
const char * smbios_string ( const struct smbios_header *structure,
                             unsigned int index ) {
        const char *string;
        unsigned int i;
        size_t len;

        /* Sanity check */
        assert ( smbios.address != NULL );

        /* Step through strings */
        string = ( ( ( const void * ) structure ) + structure->len );
        for ( i = index ; i-- ; ) {
                /* Get string length.  This is known safe, since we
                 * check for the empty-string terminator in
                 * smbios_structure().
                 */
                len = strlen ( string );
                if ( ! len )
                        break;
                if ( i == 0 )
                        return string;
                string += ( len + 1 /* NUL */ );
        }

        DBGC ( &smbios, "SMBIOS string index %d not found\n", index );
        return NULL;
}

/**
 * Get SMBIOS version
 *
 * @ret version         Version, or negative error
 */
int smbios_version ( void ) {
        int rc;

        /* Find SMBIOS */
        if ( ( smbios.address == NULL ) &&
             ( ( rc = find_smbios ( &smbios ) ) != 0 ) )
                return rc;
        assert ( smbios.address != NULL );

        return smbios.version;
}

/**
 * Clear SMBIOS entry point descriptor
 *
 */
void smbios_clear ( void ) {

        /* Clear address */
        smbios.address = NULL;
}