coreboot-kgpe-d16/util/nvramtool/cmos_lowlevel.c

329 lines
11 KiB
C

/* SPDX-License-Identifier: GPL-2.0-only */
#if defined(__FreeBSD__)
#include <fcntl.h>
#include <unistd.h>
#endif
#include "common.h"
#include "cmos_lowlevel.h"
/* Hardware Abstraction Layer: lowlevel byte-wise write access */
extern cmos_access_t cmos_hal, memory_hal;
static cmos_access_t *current_access =
#ifdef CMOS_HAL
&cmos_hal;
#else
&memory_hal;
#endif
void select_hal(hal_t hal, void *data)
{
switch(hal) {
#ifdef CMOS_HAL
case HAL_CMOS:
current_access = &cmos_hal;
break;
#endif
case HAL_MEMORY:
default:
current_access = &memory_hal;
break;
}
current_access->init(data);
}
/* Bit-level access */
typedef struct {
unsigned byte_index;
unsigned bit_offset;
} cmos_bit_op_location_t;
static unsigned cmos_bit_op_strategy(unsigned bit, unsigned bits_left,
cmos_bit_op_location_t * where);
static unsigned char cmos_read_bits(const cmos_bit_op_location_t * where,
unsigned nr_bits);
static void cmos_write_bits(const cmos_bit_op_location_t * where,
unsigned nr_bits, unsigned char value);
static unsigned char get_bits(unsigned long long value, unsigned bit,
unsigned nr_bits);
static void put_bits(unsigned char value, unsigned bit, unsigned nr_bits,
unsigned long long *result);
/****************************************************************************
* get_bits
*
* Extract a value 'nr_bits' bits wide starting at bit position 'bit' from
* 'value' and return the result. It is assumed that 'nr_bits' is at most 8.
****************************************************************************/
static inline unsigned char get_bits(unsigned long long value, unsigned bit,
unsigned nr_bits)
{
return (value >> bit) & ((unsigned char)((1 << nr_bits) - 1));
}
/****************************************************************************
* put_bits
*
* Extract the low order 'nr_bits' bits from 'value' and store them in the
* value pointed to by 'result' starting at bit position 'bit'. The bit
* positions in 'result' where the result is stored are assumed to be
* initially zero.
****************************************************************************/
static inline void put_bits(unsigned char value, unsigned bit,
unsigned nr_bits, unsigned long long *result)
{
*result += ((unsigned long long)(value &
((unsigned char)((1 << nr_bits) - 1)))) << bit;
}
/****************************************************************************
* cmos_read
*
* Read value from nonvolatile RAM at position given by 'bit' and 'length'
* and return this value. The I/O privilege level of the currently executing
* process must be set appropriately.
*
* Returned value is either (unsigned long long), or malloc()'d (char *)
* cast to (unsigned long long)
****************************************************************************/
unsigned long long cmos_read(const cmos_entry_t * e)
{
cmos_bit_op_location_t where;
unsigned bit = e->bit, length = e->length;
unsigned next_bit, bits_left, nr_bits;
unsigned long long result = 0;
unsigned char value;
assert(!verify_cmos_op(bit, length, e->config));
if (e->config == CMOS_ENTRY_STRING) {
int strsz = (length + 7) / 8 + 1;
char *newstring = malloc(strsz);
unsigned usize = (8 * sizeof(unsigned long long));
if (!newstring) {
out_of_memory();
}
memset(newstring, 0, strsz);
for (next_bit = 0, bits_left = length;
bits_left; next_bit += nr_bits, bits_left -= nr_bits) {
nr_bits = cmos_bit_op_strategy(bit + next_bit,
bits_left > usize ? usize : bits_left, &where);
value = cmos_read_bits(&where, nr_bits);
put_bits(value, next_bit % usize, nr_bits,
&((unsigned long long *)newstring)[next_bit /
usize]);
result = (unsigned long)newstring;
}
} else {
for (next_bit = 0, bits_left = length;
bits_left; next_bit += nr_bits, bits_left -= nr_bits) {
nr_bits =
cmos_bit_op_strategy(bit + next_bit, bits_left,
&where);
value = cmos_read_bits(&where, nr_bits);
put_bits(value, next_bit, nr_bits, &result);
}
}
return result;
}
/****************************************************************************
* cmos_write
*
* Write 'data' to nonvolatile RAM at position given by 'bit' and 'length'.
* The I/O privilege level of the currently executing process must be set
* appropriately.
****************************************************************************/
void cmos_write(const cmos_entry_t * e, unsigned long long value)
{
cmos_bit_op_location_t where;
unsigned bit = e->bit, length = e->length;
unsigned next_bit, bits_left, nr_bits;
assert(!verify_cmos_op(bit, length, e->config));
if (e->config == CMOS_ENTRY_STRING) {
unsigned long long *data =
(unsigned long long *)(unsigned long)value;
unsigned usize = (8 * sizeof(unsigned long long));
for (next_bit = 0, bits_left = length;
bits_left; next_bit += nr_bits, bits_left -= nr_bits) {
nr_bits = cmos_bit_op_strategy(bit + next_bit,
bits_left > usize ? usize : bits_left,
&where);
value = data[next_bit / usize];
cmos_write_bits(&where, nr_bits,
get_bits(value, next_bit % usize, nr_bits));
}
} else {
for (next_bit = 0, bits_left = length;
bits_left; next_bit += nr_bits, bits_left -= nr_bits) {
nr_bits = cmos_bit_op_strategy(bit + next_bit,
bits_left, &where);
cmos_write_bits(&where, nr_bits,
get_bits(value, next_bit, nr_bits));
}
}
}
/****************************************************************************
* cmos_read_byte
*
* Read a byte from nonvolatile RAM at a position given by 'index' and return
* the result. An 'index' value of 0 represents the first byte of
* nonvolatile RAM.
*
* Note: the first 14 bytes of nonvolatile RAM provide an interface to the
* real time clock.
****************************************************************************/
unsigned char cmos_read_byte(unsigned index)
{
return current_access->read(index);
}
/****************************************************************************
* cmos_write_byte
*
* Write 'value' to nonvolatile RAM at a position given by 'index'. An
* 'index' of 0 represents the first byte of nonvolatile RAM.
*
* Note: the first 14 bytes of nonvolatile RAM provide an interface to the
* real time clock. Writing to any of these bytes will therefore
* affect its functioning.
****************************************************************************/
void cmos_write_byte(unsigned index, unsigned char value)
{
current_access->write(index, value);
}
/****************************************************************************
* cmos_read_all
*
* Read all contents of CMOS memory into array 'data'. The first 14 bytes of
* 'data' are set to zero since this corresponds to the real time clock area.
****************************************************************************/
void cmos_read_all(unsigned char data[])
{
unsigned i;
for (i = 0; i < CMOS_RTC_AREA_SIZE; i++)
data[i] = 0;
for (; i < CMOS_SIZE; i++)
data[i] = cmos_read_byte(i);
}
/****************************************************************************
* cmos_write_all
*
* Update all of CMOS memory with the contents of array 'data'. The first 14
* bytes of 'data' are ignored since this corresponds to the real time clock
* area.
****************************************************************************/
void cmos_write_all(unsigned char data[])
{
unsigned i;
for (i = CMOS_RTC_AREA_SIZE; i < CMOS_SIZE; i++)
cmos_write_byte(i, data[i]);
}
/****************************************************************************
* set_iopl
*
* Set the I/O privilege level of the executing process. Root privileges are
* required for performing this action. A sufficient I/O privilege level
* allows the process to access x86 I/O address space and to disable/reenable
* interrupts while executing in user space. Messing with the I/O privilege
* level is therefore somewhat dangerous.
****************************************************************************/
void set_iopl(int level)
{
current_access->set_iopl(level);
}
/****************************************************************************
* verify_cmos_op
*
* 'bit' represents a bit position in the nonvolatile RAM. The first bit
* (i.e. the lowest order bit of the first byte) of nonvolatile RAM is
* labeled as bit 0. 'length' represents the width in bits of a value we
* wish to read or write. Perform sanity checking on 'bit' and 'length'. If
* no problems were encountered, return OK. Else return an error code.
****************************************************************************/
int verify_cmos_op(unsigned bit, unsigned length, cmos_entry_config_t config)
{
if ((bit >= (8 * CMOS_SIZE)) || ((bit + length) > (8 * CMOS_SIZE)))
return CMOS_AREA_OUT_OF_RANGE;
if (bit < (8 * CMOS_RTC_AREA_SIZE))
return CMOS_AREA_OVERLAPS_RTC;
if (config == CMOS_ENTRY_STRING)
return OK;
if (length > (8 * sizeof(unsigned long long)))
return CMOS_AREA_TOO_WIDE;
return OK;
}
/****************************************************************************
* cmos_bit_op_strategy
*
* Helper function used by cmos_read() and cmos_write() to determine which
* bits to read or write next.
****************************************************************************/
static unsigned cmos_bit_op_strategy(unsigned bit, unsigned bits_left,
cmos_bit_op_location_t * where)
{
unsigned max_bits;
where->byte_index = bit >> 3;
where->bit_offset = bit & 0x07;
max_bits = 8 - where->bit_offset;
return (bits_left > max_bits) ? max_bits : bits_left;
}
/****************************************************************************
* cmos_read_bits
*
* Read a chunk of bits from a byte location within CMOS memory. Return the
* value represented by the chunk of bits.
****************************************************************************/
static unsigned char cmos_read_bits(const cmos_bit_op_location_t * where,
unsigned nr_bits)
{
return (cmos_read_byte(where->byte_index) >> where->bit_offset) &
((unsigned char)((1 << nr_bits) - 1));
}
/****************************************************************************
* cmos_write_bits
*
* Write a chunk of bits (the low order 'nr_bits' bits of 'value') to an area
* within a particular byte of CMOS memory.
****************************************************************************/
static void cmos_write_bits(const cmos_bit_op_location_t * where,
unsigned nr_bits, unsigned char value)
{
unsigned char n, mask;
if (nr_bits == 8) {
cmos_write_byte(where->byte_index, value);
return;
}
n = cmos_read_byte(where->byte_index);
mask = ((unsigned char)((1 << nr_bits) - 1)) << where->bit_offset;
n = (n & ~mask) + ((value << where->bit_offset) & mask);
cmos_write_byte(where->byte_index, n);
}