mtd_nandecctest.c

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#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/list.h>
#include <linux/random.h>
#include <linux/string.h>
#include <linux/bitops.h>
#include <linux/slab.h>
#include <linux/mtd/nand_ecc.h>

/*
 * Test the implementation for software ECC
 *
 * No actual MTD device is needed, So we don't need to warry about losing
 * important data by human error.
 *
 * This covers possible patterns of corruption which can be reliably corrected
 * or detected.
 */

#if defined(CONFIG_MTD_NAND) || defined(CONFIG_MTD_NAND_MODULE)

struct nand_ecc_test {
    const char *name;
    void (*prepare)(void *, void *, void *, void *, const size_t);
    int (*verify)(void *, void *, void *, const size_t);
};

/*
 * The reason for this __change_bit_le() instead of __change_bit() is to inject
 * bit error properly within the region which is not a multiple of
 * sizeof(unsigned long) on big-endian systems
 */
#ifdef __LITTLE_ENDIAN
#define __change_bit_le(nr, addr) __change_bit(nr, addr)
#elif defined(__BIG_ENDIAN)
#define __change_bit_le(nr, addr) \
        __change_bit((nr) ^ ((BITS_PER_LONG - 1) & ~0x7), addr)
#else
#error "Unknown byte order"
#endif

static void single_bit_error_data(void *error_data, void *correct_data,
                size_t size)
{
    unsigned int offset = random32() % (size * BITS_PER_BYTE);

    memcpy(error_data, correct_data, size);
    __change_bit_le(offset, error_data);
}

static void double_bit_error_data(void *error_data, void *correct_data,
                size_t size)
{
    unsigned int offset[2];

    offset[0] = random32() % (size * BITS_PER_BYTE);
    do {
        offset[1] = random32() % (size * BITS_PER_BYTE);
    } while (offset[0] == offset[1]);

    memcpy(error_data, correct_data, size);

    __change_bit_le(offset[0], error_data);
    __change_bit_le(offset[1], error_data);
}

static unsigned int random_ecc_bit(size_t size)
{
    unsigned int offset = random32() % (3 * BITS_PER_BYTE);

    if (size == 256) {
        /*
         * Don't inject a bit error into the insignificant bits (16th
         * and 17th bit) in ECC code for 256 byte data block
         */
        while (offset == 16 || offset == 17)
            offset = random32() % (3 * BITS_PER_BYTE);
    }

    return offset;
}

static void single_bit_error_ecc(void *error_ecc, void *correct_ecc,
                size_t size)
{
    unsigned int offset = random_ecc_bit(size);

    memcpy(error_ecc, correct_ecc, 3);
    __change_bit_le(offset, error_ecc);
}

static void double_bit_error_ecc(void *error_ecc, void *correct_ecc,
                size_t size)
{
    unsigned int offset[2];

    offset[0] = random_ecc_bit(size);
    do {
        offset[1] = random_ecc_bit(size);
    } while (offset[0] == offset[1]);

    memcpy(error_ecc, correct_ecc, 3);
    __change_bit_le(offset[0], error_ecc);
    __change_bit_le(offset[1], error_ecc);
}

static void no_bit_error(void *error_data, void *error_ecc,
        void *correct_data, void *correct_ecc, const size_t size)
{
    memcpy(error_data, correct_data, size);
    memcpy(error_ecc, correct_ecc, 3);
}

static int no_bit_error_verify(void *error_data, void *error_ecc,
                void *correct_data, const size_t size)
{
    unsigned char calc_ecc[3];
    int ret;

    __nand_calculate_ecc(error_data, size, calc_ecc);
    ret = __nand_correct_data(error_data, error_ecc, calc_ecc, size);
    if (ret == 0 && !memcmp(correct_data, error_data, size))
        return 0;

    return -EINVAL;
}

static void single_bit_error_in_data(void *error_data, void *error_ecc,
        void *correct_data, void *correct_ecc, const size_t size)
{
    single_bit_error_data(error_data, correct_data, size);
    memcpy(error_ecc, correct_ecc, 3);
}

static void single_bit_error_in_ecc(void *error_data, void *error_ecc,
        void *correct_data, void *correct_ecc, const size_t size)
{
    memcpy(error_data, correct_data, size);
    single_bit_error_ecc(error_ecc, correct_ecc, size);
}

static int single_bit_error_correct(void *error_data, void *error_ecc,
                void *correct_data, const size_t size)
{
    unsigned char calc_ecc[3];
    int ret;

    __nand_calculate_ecc(error_data, size, calc_ecc);
    ret = __nand_correct_data(error_data, error_ecc, calc_ecc, size);
    if (ret == 1 && !memcmp(correct_data, error_data, size))
        return 0;

    return -EINVAL;
}

static void double_bit_error_in_data(void *error_data, void *error_ecc,
        void *correct_data, void *correct_ecc, const size_t size)
{
    double_bit_error_data(error_data, correct_data, size);
    memcpy(error_ecc, correct_ecc, 3);
}

static void single_bit_error_in_data_and_ecc(void *error_data, void *error_ecc,
        void *correct_data, void *correct_ecc, const size_t size)
{
    single_bit_error_data(error_data, correct_data, size);
    single_bit_error_ecc(error_ecc, correct_ecc, size);
}

static void double_bit_error_in_ecc(void *error_data, void *error_ecc,
        void *correct_data, void *correct_ecc, const size_t size)
{
    memcpy(error_data, correct_data, size);
    double_bit_error_ecc(error_ecc, correct_ecc, size);
}

static int double_bit_error_detect(void *error_data, void *error_ecc,
                void *correct_data, const size_t size)
{
    unsigned char calc_ecc[3];
    int ret;

    __nand_calculate_ecc(error_data, size, calc_ecc);
    ret = __nand_correct_data(error_data, error_ecc, calc_ecc, size);

    return (ret == -1) ? 0 : -EINVAL;
}

static const struct nand_ecc_test nand_ecc_test[] = {
    {
        .name = "no-bit-error",
        .prepare = no_bit_error,
        .verify = no_bit_error_verify,
    },
    {
        .name = "single-bit-error-in-data-correct",
        .prepare = single_bit_error_in_data,
        .verify = single_bit_error_correct,
    },
    {
        .name = "single-bit-error-in-ecc-correct",
        .prepare = single_bit_error_in_ecc,
        .verify = single_bit_error_correct,
    },
    {
        .name = "double-bit-error-in-data-detect",
        .prepare = double_bit_error_in_data,
        .verify = double_bit_error_detect,
    },
    {
        .name = "single-bit-error-in-data-and-ecc-detect",
        .prepare = single_bit_error_in_data_and_ecc,
        .verify = double_bit_error_detect,
    },
    {
        .name = "double-bit-error-in-ecc-detect",
        .prepare = double_bit_error_in_ecc,
        .verify = double_bit_error_detect,
    },
};

static void dump_data_ecc(void *error_data, void *error_ecc, void *correct_data,
            void *correct_ecc, const size_t size)
{
    pr_info("hexdump of error data:\n");
    print_hex_dump(KERN_INFO, "", DUMP_PREFIX_OFFSET, 16, 4,
            error_data, size, false);
    print_hex_dump(KERN_INFO, "hexdump of error ecc: ",
            DUMP_PREFIX_NONE, 16, 1, error_ecc, 3, false);

    pr_info("hexdump of correct data:\n");
    print_hex_dump(KERN_INFO, "", DUMP_PREFIX_OFFSET, 16, 4,
            correct_data, size, false);
    print_hex_dump(KERN_INFO, "hexdump of correct ecc: ",
            DUMP_PREFIX_NONE, 16, 1, correct_ecc, 3, false);
}

static int nand_ecc_test_run(const size_t size)
{
    int i;
    int err = 0;
    void *error_data;
    void *error_ecc;
    void *correct_data;
    void *correct_ecc;

    error_data = kmalloc(size, GFP_KERNEL);
    error_ecc = kmalloc(3, GFP_KERNEL);
    correct_data = kmalloc(size, GFP_KERNEL);
    correct_ecc = kmalloc(3, GFP_KERNEL);

    if (!error_data || !error_ecc || !correct_data || !correct_ecc) {
        err = -ENOMEM;
        goto error;
    }

    get_random_bytes(correct_data, size);
    __nand_calculate_ecc(correct_data, size, correct_ecc);

    for (i = 0; i < ARRAY_SIZE(nand_ecc_test); i++) {
        nand_ecc_test[i].prepare(error_data, error_ecc,
                correct_data, correct_ecc, size);
        err = nand_ecc_test[i].verify(error_data, error_ecc,
                        correct_data, size);

        if (err) {
            pr_err("mtd_nandecctest: not ok - %s-%zd\n",
                nand_ecc_test[i].name, size);
            dump_data_ecc(error_data, error_ecc,
                correct_data, correct_ecc, size);
            break;
        }
        pr_info("mtd_nandecctest: ok - %s-%zd\n",
            nand_ecc_test[i].name, size);
    }
error:
    kfree(error_data);
    kfree(error_ecc);
    kfree(correct_data);
    kfree(correct_ecc);

    return err;
}

#else

static int nand_ecc_test_run(const size_t size)
{
    return 0;
}

#endif

static int __init ecc_test_init(void)
{
    int err;

    err = nand_ecc_test_run(256);
    if (err)
        return err;

    return nand_ecc_test_run(512);
}

static void __exit ecc_test_exit(void)
{
}

module_init(ecc_test_init);
module_exit(ecc_test_exit);

MODULE_DESCRIPTION("NAND ECC function test module");
MODULE_AUTHOR("Akinobu Mita");
MODULE_LICENSE("GPL");