util/lxbios/cmos_ops.c

/*****************************************************************************\
 * cmos_ops.c
 * $Id: cmos_ops.c,v 1.3 2006/01/24 00:25:40 dsp_llnl Exp $
 *****************************************************************************
 *  Copyright (C) 2002-2005 The Regents of the University of California.
 *  Produced at the Lawrence Livermore National Laboratory.
 *  Written by David S. Peterson <dsp@llnl.gov> <dave_peterson@pobox.com>.
 *  UCRL-CODE-2003-012
 *  All rights reserved.
 *
 *  This file is part of lxbios, a utility for reading/writing coreboot
 *  parameters and displaying information from the coreboot table.
 *  For details, see <http://www.llnl.gov/linux/lxbios/>.
 *
 *  Please also read the file DISCLAIMER which is included in this software
 *  distribution.
 *
 *  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) version 2, dated June 1991.
 *
 *  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 terms and
 *  conditions of 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.,
 *  59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
\*****************************************************************************/

#include "common.h"
#include "cmos_ops.h"
#include "cmos_lowlevel.h"

static int prepare_cmos_op_common (const cmos_entry_t *e);

/****************************************************************************
 * prepare_cmos_op_common
 *
 * Perform a few checks common to both reads and writes.
 ****************************************************************************/
static int prepare_cmos_op_common (const cmos_entry_t *e)
 { int result;

   if (e->config == CMOS_ENTRY_RESERVED)
      /* Access to reserved parameters is not permitted. */
      return CMOS_OP_RESERVED;

   if ((result = verify_cmos_op(e->bit, e->length)) != OK)
      return result;

   assert(e->length > 0);
   return OK;
 }

/****************************************************************************
 * prepare_cmos_read
 *
 * The caller wishes to read a CMOS parameter represented by 'e'.  Perform
 * sanity checking on 'e'.  If a problem was found with e, return an error
 * code.  Else return OK.
 ****************************************************************************/
int prepare_cmos_read (const cmos_entry_t *e)
 { int result;

   if ((result = prepare_cmos_op_common(e)) != OK)
      return result;

   switch (e->config)
    { case CMOS_ENTRY_ENUM:
      case CMOS_ENTRY_HEX:
         break;

      default:
         BUG();
    }

   return OK;
 }

/****************************************************************************
 * prepare_cmos_write
 *
 * The caller wishes to set a CMOS parameter represented by 'e' to a value
 * whose string representation is stored in 'value_str'.  Perform sanity
 * checking on 'value_str'.  On error, return an error code.  Else store the
 * numeric equivalent of 'value_str' in '*value' and return OK.
 ****************************************************************************/
int prepare_cmos_write (const cmos_entry_t *e, const char value_str[],
                        unsigned long long *value)
 { const cmos_enum_t *q;
   unsigned long long out;
   const char *p;
   int negative, result, found_one;

   if ((result = prepare_cmos_op_common(e)) != OK)
      return result;

   switch (e->config)
    { case CMOS_ENTRY_ENUM:
         /* Make sure the user's input corresponds to a valid option. */
         for (q = first_cmos_enum_id(e->config_id), found_one = 0;
              q != NULL;
              q = next_cmos_enum_id(q))
          { found_one = 1;

            if (!strncmp(q->text, value_str, CMOS_MAX_TEXT_LENGTH))
               break;
          }

         if (!found_one)
            return CMOS_OP_NO_MATCHING_ENUM;

         if (q == NULL)
            return CMOS_OP_BAD_ENUM_VALUE;

         out = q->value;
         break;

      case CMOS_ENTRY_HEX:
         /* See if the first character of 'value_str' (excluding any initial
          * whitespace) is a minus sign.
          */
         for (p = value_str; isspace(*p); p++);
         negative = (*p == '-');

         out = strtoull(value_str, (char **) &p, 0);

         if (*p)
            return CMOS_OP_INVALID_INT;

         /* If we get this far, the user specified a valid integer.  However
          * we do not currently support the use of negative numbers as CMOS
          * parameter values.
          */
         if (negative)
            return CMOS_OP_NEGATIVE_INT;

         break;

      default:
         BUG();
    }

   if ((e->length < (8 * sizeof(*value))) &&
       (out >= (1ull << e->length)))
      return CMOS_OP_VALUE_TOO_WIDE;

   *value = out;
   return OK;
 }

/****************************************************************************
 * cmos_checksum_read
 *
 * Read the checksum for the coreboot parameters stored in CMOS and return
 * this value.
 ****************************************************************************/
uint16_t cmos_checksum_read (void)
 { uint16_t lo, hi;

   /* The checksum is stored in a big-endian format. */
   hi = cmos_read_byte(cmos_checksum_index);
   lo = cmos_read_byte(cmos_checksum_index + 1);
   return (hi << 8) + lo;
 }

/****************************************************************************
 * cmos_checksum_write
 *
 * Set the checksum for the coreboot parameters stored in CMOS to
 * 'checksum'.
 ****************************************************************************/
void cmos_checksum_write (uint16_t checksum)
 { unsigned char lo, hi;

   /* The checksum is stored in a big-endian format. */
   hi = (unsigned char) (checksum >> 8);
   lo = (unsigned char) (checksum & 0x00ff);
   cmos_write_byte(cmos_checksum_index, hi);
   cmos_write_byte(cmos_checksum_index + 1, lo);
 }

/****************************************************************************
 * cmos_checksum_compute
 *
 * Compute a checksum for the coreboot parameter values currently stored in
 * CMOS and return this checksum.
 ****************************************************************************/
uint16_t cmos_checksum_compute (void)
 { unsigned i, sum;

   sum = 0;

   for (i = cmos_checksum_start; i <= cmos_checksum_end; i++)
      sum += cmos_read_byte(i);

   return ~((uint16_t) (sum & 0xffff));
 }

/****************************************************************************
 * cmos_checksum_verify
 *
 * Verify that the coreboot CMOS checksum is valid.  If checksum is not
 * valid then print warning message and exit.
 ****************************************************************************/
void cmos_checksum_verify (void)
 { uint16_t computed, actual;

   set_iopl(3);
   computed = cmos_checksum_compute();
   actual = cmos_checksum_read();
   set_iopl(0);

   if (computed != actual)
    { fprintf(stderr, "%s: Warning: Coreboot CMOS checksum is bad.\n",
              prog_name);
      exit(1);
    }
 }