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/*
* Copyright 2016 General Electric Company
*
* SPDX-License-Identifier: GPL-2.0+
*/
#include "vpd_reader.h"
#include <linux/bch.h>
#include <stdlib.h>
/* BCH configuration */
const struct {
int header_ecc_capability_bits;
int data_ecc_capability_bits;
unsigned int prim_poly;
struct {
int min;
int max;
} galois_field_order;
} bch_configuration = {
.header_ecc_capability_bits = 4,
.data_ecc_capability_bits = 16,
.prim_poly = 0,
.galois_field_order = {
.min = 5,
.max = 15,
},
};
static int calculate_galois_field_order(size_t source_length)
{
int gfo = bch_configuration.galois_field_order.min;
for (; gfo < bch_configuration.galois_field_order.max &&
((((1 << gfo) - 1) - ((int)source_length * 8)) < 0);
gfo++) {
}
if (gfo == bch_configuration.galois_field_order.max) {
return -1;
}
return gfo + 1;
}
static int verify_bch(int ecc_bits, unsigned int prim_poly,
uint8_t * data, size_t data_length,
const uint8_t * ecc, size_t ecc_length)
{
int gfo = calculate_galois_field_order(data_length);
if (gfo < 0) {
return -1;
}
struct bch_control * bch = init_bch(gfo, ecc_bits, prim_poly);
if (!bch) {
return -1;
}
if (bch->ecc_bytes != ecc_length) {
free_bch(bch);
return -1;
}
unsigned * errloc = (unsigned *)calloc(data_length, sizeof(unsigned));
int errors = decode_bch(
bch, data, data_length, ecc, NULL, NULL, errloc);
free_bch(bch);
if (errors < 0) {
free(errloc);
return -1;
}
if (errors > 0) {
for (int n = 0; n < errors; n++) {
if (errloc[n] >= 8 * data_length) {
/* n-th error located in ecc (no need for data correction) */
} else {
/* n-th error located in data */
data[errloc[n] / 8] ^= 1 << (errloc[n] % 8);
}
}
}
free(errloc);
return 0;
}
static const int ID = 0;
static const int LEN = 1;
static const int VER = 2;
static const int TYP = 3;
static const int BLOCK_SIZE = 4;
static const uint8_t HEADER_BLOCK_ID = 0x00;
static const uint8_t HEADER_BLOCK_LEN = 18;
static const uint32_t HEADER_BLOCK_MAGIC = 0xca53ca53;
static const size_t HEADER_BLOCK_VERIFY_LEN = 14;
static const size_t HEADER_BLOCK_ECC_OFF = 14;
static const size_t HEADER_BLOCK_ECC_LEN = 4;
static const uint8_t ECC_BLOCK_ID = 0xFF;
int vpd_reader(
size_t size,
uint8_t * data,
void * userdata,
int (*fn)(
void * userdata,
uint8_t id,
uint8_t version,
uint8_t type,
size_t size,
uint8_t const * data))
{
if ( size < HEADER_BLOCK_LEN
|| data == NULL
|| fn == NULL) {
return -EINVAL;
}
/*
* +--------------------+--------------------+--//--+--------------------+
* | header block | data block | ... | ecc block |
* +--------------------+--------------------+--//--+--------------------+
* : : :
* +------+-------+-----+ +------+-------------+
* | id | magic | ecc | | ... | ecc |
* | len | off | | +------+-------------+
* | ver | size | | :
* | type | | | :
* +------+-------+-----+ :
* : : : :
* <----- [1] ----> <----------- [2] ----------->
*
* Repair (if necessary) the contents of header block [1] by using a
* 4 byte ECC located at the end of the header block. A successful
* return value means that we can trust the header.
*/
int ret = verify_bch(
bch_configuration.header_ecc_capability_bits,
bch_configuration.prim_poly,
data,
HEADER_BLOCK_VERIFY_LEN,
&data[HEADER_BLOCK_ECC_OFF],
HEADER_BLOCK_ECC_LEN);
if (ret < 0) {
return ret;
}
/* Validate header block { id, length, version, type }. */
if ( data[ID] != HEADER_BLOCK_ID
|| data[LEN] != HEADER_BLOCK_LEN
|| data[VER] != 0
|| data[TYP] != 0
|| ntohl(*(uint32_t *)(&data[4])) != HEADER_BLOCK_MAGIC) {
return -EINVAL;
}
uint32_t offset = ntohl(*(uint32_t *)(&data[8]));
uint16_t size_bits = ntohs(*(uint16_t *)(&data[12]));
/* Check that ECC header fits. */
if (offset + 3 >= size) {
return -EINVAL;
}
/* Validate ECC block. */
uint8_t * ecc = &data[offset];
if ( ecc[ID] != ECC_BLOCK_ID
|| ecc[LEN] < BLOCK_SIZE
|| ecc[LEN] + offset > size
|| ecc[LEN] - BLOCK_SIZE != size_bits / 8
|| ecc[VER] != 1
|| ecc[TYP] != 1) {
return -EINVAL;
}
/*
* Use the header block to locate the ECC block and verify the data
* blocks [2] against the ecc block ECC.
*/
ret = verify_bch(
bch_configuration.data_ecc_capability_bits,
bch_configuration.prim_poly,
&data[data[LEN]],
offset - data[LEN],
&data[offset + BLOCK_SIZE],
ecc[LEN] - BLOCK_SIZE);
if (ret < 0) {
return ret;
}
/* Stop after ECC. Ignore possible zero padding. */
size = offset;
for (;;) {
/* Move to next block. */
size -= data[LEN];
data += data[LEN];
if (size == 0) {
/* Finished iterating through blocks. */
return 0;
}
if ( size < BLOCK_SIZE
|| data[LEN] < BLOCK_SIZE) {
/* Not enough data for a header, or short header. */
return -EINVAL;
}
ret = fn(
userdata,
data[ID],
data[VER],
data[TYP],
data[LEN] - BLOCK_SIZE,
&data[BLOCK_SIZE]);
if (ret) {
return ret;
}
}
}
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