smbios.c

Go to the documentation of this file.

/*
 * 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 );

#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 = UNULL,
};

/**
 * Calculate SMBIOS entry point structure checksum
 *
 * @v start             Start address of region
 * @v offset            Offset of SMBIOS entry point structure
 * @v len               Length of entry point structure
 * @ret sum             Byte checksum
 */
static uint8_t smbios_checksum ( userptr_t start, size_t offset, size_t len ) {
        size_t end = ( offset + len );
        uint8_t sum;
        uint8_t byte;

        for ( sum = 0 ; offset < end ; offset++ ) {
                copy_from_user ( &byte, start, offset, sizeof ( byte ) );
                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
 * @v entry             SMBIOS entry point structure to fill in
 * @ret rc              Return status code
 */
int find_smbios_entry ( userptr_t start, size_t len,
                        struct smbios_entry *entry ) {
        static size_t offset = 0; /* Avoid repeated attempts to locate SMBIOS */
        uint8_t sum;

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

                /* Read start of header and verify signature */
                copy_from_user ( entry, start, offset, sizeof ( *entry ) );
                if ( entry->signature != SMBIOS_SIGNATURE )
                        continue;

                /* Verify checksum */
                if ( ( sum = smbios_checksum ( start, offset,
                                               entry->len ) ) != 0 ) {
                        DBG ( "SMBIOS at %08lx has bad checksum %02x\n",
                              user_to_phys ( start, offset ), sum );
                        continue;
                }

                /* Fill result structure */
                DBG ( "Found SMBIOS v%d.%d entry point at %08lx\n",
                      entry->major, entry->minor,
                      user_to_phys ( start, offset ) );
                return 0;
        }

        DBG ( "No SMBIOS found\n" );
        return -ENODEV;
}

/**
 * Scan for SMBIOS 64-bit entry point structure
 *
 * @v start             Start address of region to scan
 * @v len               Length of region to scan
 * @v entry             SMBIOS entry point structure to fill in
 * @ret rc              Return status code
 */
int find_smbios3_entry ( userptr_t start, size_t len,
                         struct smbios3_entry *entry ) {
        static size_t offset = 0; /* Avoid repeated attempts to locate SMBIOS */
        uint8_t sum;

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

                /* Read start of header and verify signature */
                copy_from_user ( entry, start, offset, sizeof ( *entry ) );
                if ( entry->signature != SMBIOS3_SIGNATURE )
                        continue;

                /* Verify checksum */
                if ( ( sum = smbios_checksum ( start, offset,
                                               entry->len ) ) != 0 ) {
                        DBG ( "SMBIOS3 at %08lx has bad checksum %02x\n",
                              user_to_phys ( start, offset ), sum );
                        continue;
                }

                /* Fill result structure */
                DBG ( "Found SMBIOS3 v%d.%d entry point at %08lx\n",
                      entry->major, entry->minor,
                      user_to_phys ( start, offset ) );
                return 0;
        }

        DBG ( "No SMBIOS3 found\n" );
        return -ENODEV;
}

/**
 * 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 instance          Instance of this type of structure
 * @v structure         SMBIOS structure descriptor to fill in
 * @ret rc              Return status code
 */
int find_smbios_structure ( unsigned int type, unsigned int instance,
                            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 ) &&
                ( ( smbios.count == 0 ) || ( 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 );

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

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

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

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

        return smbios.version;
}

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

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