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/*****************************************************************************\
* cmos_ops.c
*****************************************************************************
* This file is part of nvramtool, a utility for reading/writing coreboot
* parameters and displaying information from the coreboot table.
* For details, see https://coreboot.org/nvramtool.
*
* 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.
\*****************************************************************************/
#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, e->config)) != 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:
case CMOS_ENTRY_STRING:
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;
char *memory = NULL;
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((int)(unsigned char)*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;
case CMOS_ENTRY_STRING:
if (e->length < (8 * strlen(value_str)))
return CMOS_OP_VALUE_TOO_WIDE;
memory = malloc(e->length / 8);
memset(memory, 0, e->length / 8);
strcpy(memory, value_str);
out = (unsigned long)memory;
break;
default:
BUG();
}
if ((e->length < (8 * sizeof(*value))) && (out >= (1ull << e->length))) {
if (memory) free(memory);
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);
fprintf(stderr, "Computed checksum: 0x%x. Stored checksum: 0x%x\n",
computed, actual);
exit(1);
}
}
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