io.c

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/*
 * Copyright (c) International Business Machines Corp., 2006
 * Copyright (c) Nokia Corporation, 2006, 2007
 *
 * 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; either version 2 of the License, or
 * (at your option) any later version.
 *
 * 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 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
 *
 * Author: Artem Bityutskiy (Битюцкий Артём)
 */

/*
 * UBI input/output sub-system.
 *
 * This sub-system provides a uniform way to work with all kinds of the
 * underlying MTD devices. It also implements handy functions for reading and
 * writing UBI headers.
 *
 * We are trying to have a paranoid mindset and not to trust to what we read
 * from the flash media in order to be more secure and robust. So this
 * sub-system validates every single header it reads from the flash media.
 *
 * Some words about how the eraseblock headers are stored.
 *
 * The erase counter header is always stored at offset zero. By default, the
 * VID header is stored after the EC header at the closest aligned offset
 * (i.e. aligned to the minimum I/O unit size). Data starts next to the VID
 * header at the closest aligned offset. But this default layout may be
 * changed. For example, for different reasons (e.g., optimization) UBI may be
 * asked to put the VID header at further offset, and even at an unaligned
 * offset. Of course, if the offset of the VID header is unaligned, UBI adds
 * proper padding in front of it. Data offset may also be changed but it has to
 * be aligned.
 *
 * About minimal I/O units. In general, UBI assumes flash device model where
 * there is only one minimal I/O unit size. E.g., in case of NOR flash it is 1,
 * in case of NAND flash it is a NAND page, etc. This is reported by MTD in the
 * @ubi->mtd->writesize field. But as an exception, UBI admits of using another
 * (smaller) minimal I/O unit size for EC and VID headers to make it possible
 * to do different optimizations.
 *
 * This is extremely useful in case of NAND flashes which admit of several
 * write operations to one NAND page. In this case UBI can fit EC and VID
 * headers at one NAND page. Thus, UBI may use "sub-page" size as the minimal
 * I/O unit for the headers (the @ubi->hdrs_min_io_size field). But it still
 * reports NAND page size (@ubi->min_io_size) as a minimal I/O unit for the UBI
 * users.
 *
 * Example: some Samsung NANDs with 2KiB pages allow 4x 512-byte writes, so
 * although the minimal I/O unit is 2K, UBI uses 512 bytes for EC and VID
 * headers.
 *
 * Q: why not just to treat sub-page as a minimal I/O unit of this flash
 * device, e.g., make @ubi->min_io_size = 512 in the example above?
 *
 * A: because when writing a sub-page, MTD still writes a full 2K page but the
 * bytes which are not relevant to the sub-page are 0xFF. So, basically,
 * writing 4x512 sub-pages is 4 times slower than writing one 2KiB NAND page.
 * Thus, we prefer to use sub-pages only for EC and VID headers.
 *
 * As it was noted above, the VID header may start at a non-aligned offset.
 * For example, in case of a 2KiB page NAND flash with a 512 bytes sub-page,
 * the VID header may reside at offset 1984 which is the last 64 bytes of the
 * last sub-page (EC header is always at offset zero). This causes some
 * difficulties when reading and writing VID headers.
 *
 * Suppose we have a 64-byte buffer and we read a VID header at it. We change
 * the data and want to write this VID header out. As we can only write in
 * 512-byte chunks, we have to allocate one more buffer and copy our VID header
 * to offset 448 of this buffer.
 *
 * The I/O sub-system does the following trick in order to avoid this extra
 * copy. It always allocates a @ubi->vid_hdr_alsize bytes buffer for the VID
 * header and returns a pointer to offset @ubi->vid_hdr_shift of this buffer.
 * When the VID header is being written out, it shifts the VID header pointer
 * back and writes the whole sub-page.
 */

#include <linux/crc32.h>
#include <linux/err.h>
#include <linux/slab.h>
#include "ubi.h"

static int self_check_not_bad(const struct ubi_device *ubi, int pnum);
static int self_check_peb_ec_hdr(const struct ubi_device *ubi, int pnum);
static int self_check_ec_hdr(const struct ubi_device *ubi, int pnum,
                 const struct ubi_ec_hdr *ec_hdr);
static int self_check_peb_vid_hdr(const struct ubi_device *ubi, int pnum);
static int self_check_vid_hdr(const struct ubi_device *ubi, int pnum,
                  const struct ubi_vid_hdr *vid_hdr);
static int self_check_write(struct ubi_device *ubi, const void *buf, int pnum,
                int offset, int len);

int ubi_io_read(const struct ubi_device *ubi, void *buf, int pnum, int offset,
        int len)
{
    int err, retries = 0;
    size_t read;
    loff_t addr;

    dbg_io("read %d bytes from PEB %d:%d", len, pnum, offset);

    ubi_assert(pnum >= 0 && pnum < ubi->peb_count);
    ubi_assert(offset >= 0 && offset + len <= ubi->peb_size);
    ubi_assert(len > 0);

    err = self_check_not_bad(ubi, pnum);
    if (err)
        return err;

    /*
     * Deliberately corrupt the buffer to improve robustness. Indeed, if we
     * do not do this, the following may happen:
     * 1. The buffer contains data from previous operation, e.g., read from
     *    another PEB previously. The data looks like expected, e.g., if we
     *    just do not read anything and return - the caller would not
     *    notice this. E.g., if we are reading a VID header, the buffer may
     *    contain a valid VID header from another PEB.
     * 2. The driver is buggy and returns us success or -EBADMSG or
     *    -EUCLEAN, but it does not actually put any data to the buffer.
     *
     * This may confuse UBI or upper layers - they may think the buffer
     * contains valid data while in fact it is just old data. This is
     * especially possible because UBI (and UBIFS) relies on CRC, and
     * treats data as correct even in case of ECC errors if the CRC is
     * correct.
     *
     * Try to prevent this situation by changing the first byte of the
     * buffer.
     */
    *((uint8_t *)buf) ^= 0xFF;

    addr = (loff_t)pnum * ubi->peb_size + offset;
retry:
    err = mtd_read(ubi->mtd, addr, len, &read, buf);
    if (err) {
        const char *errstr = mtd_is_eccerr(err) ? " (ECC error)" : "";

        if (mtd_is_bitflip(err)) {
            /*
             * -EUCLEAN is reported if there was a bit-flip which
             * was corrected, so this is harmless.
             *
             * We do not report about it here unless debugging is
             * enabled. A corresponding message will be printed
             * later, when it is has been scrubbed.
             */
            ubi_msg("fixable bit-flip detected at PEB %d", pnum);
            ubi_assert(len == read);
            return UBI_IO_BITFLIPS;
        }

        if (retries++ < UBI_IO_RETRIES) {
            ubi_warn("error %d%s while reading %d bytes from PEB %d:%d, read only %zd bytes, retry",
                 err, errstr, len, pnum, offset, read);
            yield();
            goto retry;
        }

        ubi_err("error %d%s while reading %d bytes from PEB %d:%d, read %zd bytes",
            err, errstr, len, pnum, offset, read);
        dump_stack();

        /*
         * The driver should never return -EBADMSG if it failed to read
         * all the requested data. But some buggy drivers might do
         * this, so we change it to -EIO.
         */
        if (read != len && mtd_is_eccerr(err)) {
            ubi_assert(0);
            err = -EIO;
        }
    } else {
        ubi_assert(len == read);

        if (ubi_dbg_is_bitflip(ubi)) {
            dbg_gen("bit-flip (emulated)");
            err = UBI_IO_BITFLIPS;
        }
    }

    return err;
}

int ubi_io_write(struct ubi_device *ubi, const void *buf, int pnum, int offset,
         int len)
{
    int err;
    size_t written;
    loff_t addr;

    dbg_io("write %d bytes to PEB %d:%d", len, pnum, offset);

    ubi_assert(pnum >= 0 && pnum < ubi->peb_count);
    ubi_assert(offset >= 0 && offset + len <= ubi->peb_size);
    ubi_assert(offset % ubi->hdrs_min_io_size == 0);
    ubi_assert(len > 0 && len % ubi->hdrs_min_io_size == 0);

    if (ubi->ro_mode) {
        ubi_err("read-only mode");
        return -EROFS;
    }

    err = self_check_not_bad(ubi, pnum);
    if (err)
        return err;

    /* The area we are writing to has to contain all 0xFF bytes */
    err = ubi_self_check_all_ff(ubi, pnum, offset, len);
    if (err)
        return err;

    if (offset >= ubi->leb_start) {
        /*
         * We write to the data area of the physical eraseblock. Make
         * sure it has valid EC and VID headers.
         */
        err = self_check_peb_ec_hdr(ubi, pnum);
        if (err)
            return err;
        err = self_check_peb_vid_hdr(ubi, pnum);
        if (err)
            return err;
    }

    if (ubi_dbg_is_write_failure(ubi)) {
        ubi_err("cannot write %d bytes to PEB %d:%d (emulated)",
            len, pnum, offset);
        dump_stack();
        return -EIO;
    }

    addr = (loff_t)pnum * ubi->peb_size + offset;
    err = mtd_write(ubi->mtd, addr, len, &written, buf);
    if (err) {
        ubi_err("error %d while writing %d bytes to PEB %d:%d, written %zd bytes",
            err, len, pnum, offset, written);
        dump_stack();
        ubi_dump_flash(ubi, pnum, offset, len);
    } else
        ubi_assert(written == len);

    if (!err) {
        err = self_check_write(ubi, buf, pnum, offset, len);
        if (err)
            return err;

        /*
         * Since we always write sequentially, the rest of the PEB has
         * to contain only 0xFF bytes.
         */
        offset += len;
        len = ubi->peb_size - offset;
        if (len)
            err = ubi_self_check_all_ff(ubi, pnum, offset, len);
    }

    return err;
}

static void erase_callback(struct erase_info *ei)
{
    wake_up_interruptible((wait_queue_head_t *)ei->priv);
}

static int do_sync_erase(struct ubi_device *ubi, int pnum)
{
    int err, retries = 0;
    struct erase_info ei;
    wait_queue_head_t wq;

    dbg_io("erase PEB %d", pnum);
    ubi_assert(pnum >= 0 && pnum < ubi->peb_count);

    if (ubi->ro_mode) {
        ubi_err("read-only mode");
        return -EROFS;
    }

retry:
    init_waitqueue_head(&wq);
    memset(&ei, 0, sizeof(struct erase_info));

    ei.mtd      = ubi->mtd;
    ei.addr     = (loff_t)pnum * ubi->peb_size;
    ei.len      = ubi->peb_size;
    ei.callback = erase_callback;
    ei.priv     = (unsigned long)&wq;

    err = mtd_erase(ubi->mtd, &ei);
    if (err) {
        if (retries++ < UBI_IO_RETRIES) {
            ubi_warn("error %d while erasing PEB %d, retry",
                 err, pnum);
            yield();
            goto retry;
        }
        ubi_err("cannot erase PEB %d, error %d", pnum, err);
        dump_stack();
        return err;
    }

    err = wait_event_interruptible(wq, ei.state == MTD_ERASE_DONE ||
                       ei.state == MTD_ERASE_FAILED);
    if (err) {
        ubi_err("interrupted PEB %d erasure", pnum);
        return -EINTR;
    }

    if (ei.state == MTD_ERASE_FAILED) {
        if (retries++ < UBI_IO_RETRIES) {
            ubi_warn("error while erasing PEB %d, retry", pnum);
            yield();
            goto retry;
        }
        ubi_err("cannot erase PEB %d", pnum);
        dump_stack();
        return -EIO;
    }

    err = ubi_self_check_all_ff(ubi, pnum, 0, ubi->peb_size);
    if (err)
        return err;

    if (ubi_dbg_is_erase_failure(ubi)) {
        ubi_err("cannot erase PEB %d (emulated)", pnum);
        return -EIO;
    }

    return 0;
}

/* Patterns to write to a physical eraseblock when torturing it */
static uint8_t patterns[] = {0xa5, 0x5a, 0x0};

static int torture_peb(struct ubi_device *ubi, int pnum)
{
    int err, i, patt_count;

    ubi_msg("run torture test for PEB %d", pnum);
    patt_count = ARRAY_SIZE(patterns);
    ubi_assert(patt_count > 0);

    mutex_lock(&ubi->buf_mutex);
    for (i = 0; i < patt_count; i++) {
        err = do_sync_erase(ubi, pnum);
        if (err)
            goto out;

        /* Make sure the PEB contains only 0xFF bytes */
        err = ubi_io_read(ubi, ubi->peb_buf, pnum, 0, ubi->peb_size);
        if (err)
            goto out;

        err = ubi_check_pattern(ubi->peb_buf, 0xFF, ubi->peb_size);
        if (err == 0) {
            ubi_err("erased PEB %d, but a non-0xFF byte found",
                pnum);
            err = -EIO;
            goto out;
        }

        /* Write a pattern and check it */
        memset(ubi->peb_buf, patterns[i], ubi->peb_size);
        err = ubi_io_write(ubi, ubi->peb_buf, pnum, 0, ubi->peb_size);
        if (err)
            goto out;

        memset(ubi->peb_buf, ~patterns[i], ubi->peb_size);
        err = ubi_io_read(ubi, ubi->peb_buf, pnum, 0, ubi->peb_size);
        if (err)
            goto out;

        err = ubi_check_pattern(ubi->peb_buf, patterns[i],
                    ubi->peb_size);
        if (err == 0) {
            ubi_err("pattern %x checking failed for PEB %d",
                patterns[i], pnum);
            err = -EIO;
            goto out;
        }
    }

    err = patt_count;
    ubi_msg("PEB %d passed torture test, do not mark it as bad", pnum);

out:
    mutex_unlock(&ubi->buf_mutex);
    if (err == UBI_IO_BITFLIPS || mtd_is_eccerr(err)) {
        /*
         * If a bit-flip or data integrity error was detected, the test
         * has not passed because it happened on a freshly erased
         * physical eraseblock which means something is wrong with it.
         */
        ubi_err("read problems on freshly erased PEB %d, must be bad",
            pnum);
        err = -EIO;
    }
    return err;
}

static int nor_erase_prepare(struct ubi_device *ubi, int pnum)
{
    int err, err1;
    size_t written;
    loff_t addr;
    uint32_t data = 0;
    /*
     * Note, we cannot generally define VID header buffers on stack,
     * because of the way we deal with these buffers (see the header
     * comment in this file). But we know this is a NOR-specific piece of
     * code, so we can do this. But yes, this is error-prone and we should
     * (pre-)allocate VID header buffer instead.
     */
    struct ubi_vid_hdr vid_hdr;

    /*
     * It is important to first invalidate the EC header, and then the VID
     * header. Otherwise a power cut may lead to valid EC header and
     * invalid VID header, in which case UBI will treat this PEB as
     * corrupted and will try to preserve it, and print scary warnings.
     */
    addr = (loff_t)pnum * ubi->peb_size;
    err = mtd_write(ubi->mtd, addr, 4, &written, (void *)&data);
    if (!err) {
        addr += ubi->vid_hdr_aloffset;
        err = mtd_write(ubi->mtd, addr, 4, &written, (void *)&data);
        if (!err)
            return 0;
    }

    /*
     * We failed to write to the media. This was observed with Spansion
     * S29GL512N NOR flash. Most probably the previously eraseblock erasure
     * was interrupted at a very inappropriate moment, so it became
     * unwritable. In this case we probably anyway have garbage in this
     * PEB.
     */
    err1 = ubi_io_read_vid_hdr(ubi, pnum, &vid_hdr, 0);
    if (err1 == UBI_IO_BAD_HDR_EBADMSG || err1 == UBI_IO_BAD_HDR ||
        err1 == UBI_IO_FF) {
        struct ubi_ec_hdr ec_hdr;

        err1 = ubi_io_read_ec_hdr(ubi, pnum, &ec_hdr, 0);
        if (err1 == UBI_IO_BAD_HDR_EBADMSG || err1 == UBI_IO_BAD_HDR ||
            err1 == UBI_IO_FF)
            /*
             * Both VID and EC headers are corrupted, so we can
             * safely erase this PEB and not afraid that it will be
             * treated as a valid PEB in case of an unclean reboot.
             */
            return 0;
    }

    /*
     * The PEB contains a valid VID header, but we cannot invalidate it.
     * Supposedly the flash media or the driver is screwed up, so return an
     * error.
     */
    ubi_err("cannot invalidate PEB %d, write returned %d read returned %d",
        pnum, err, err1);
    ubi_dump_flash(ubi, pnum, 0, ubi->peb_size);
    return -EIO;
}

int ubi_io_sync_erase(struct ubi_device *ubi, int pnum, int torture)
{
    int err, ret = 0;

    ubi_assert(pnum >= 0 && pnum < ubi->peb_count);

    err = self_check_not_bad(ubi, pnum);
    if (err != 0)
        return err;

    if (ubi->ro_mode) {
        ubi_err("read-only mode");
        return -EROFS;
    }

    if (ubi->nor_flash) {
        err = nor_erase_prepare(ubi, pnum);
        if (err)
            return err;
    }

    if (torture) {
        ret = torture_peb(ubi, pnum);
        if (ret < 0)
            return ret;
    }

    err = do_sync_erase(ubi, pnum);
    if (err)
        return err;

    return ret + 1;
}

int ubi_io_is_bad(const struct ubi_device *ubi, int pnum)
{
    struct mtd_info *mtd = ubi->mtd;

    ubi_assert(pnum >= 0 && pnum < ubi->peb_count);

    if (ubi->bad_allowed) {
        int ret;

        ret = mtd_block_isbad(mtd, (loff_t)pnum * ubi->peb_size);
        if (ret < 0)
            ubi_err("error %d while checking if PEB %d is bad",
                ret, pnum);
        else if (ret)
            dbg_io("PEB %d is bad", pnum);
        return ret;
    }

    return 0;
}

int ubi_io_mark_bad(const struct ubi_device *ubi, int pnum)
{
    int err;
    struct mtd_info *mtd = ubi->mtd;

    ubi_assert(pnum >= 0 && pnum < ubi->peb_count);

    if (ubi->ro_mode) {
        ubi_err("read-only mode");
        return -EROFS;
    }

    if (!ubi->bad_allowed)
        return 0;

    err = mtd_block_markbad(mtd, (loff_t)pnum * ubi->peb_size);
    if (err)
        ubi_err("cannot mark PEB %d bad, error %d", pnum, err);
    return err;
}

static int validate_ec_hdr(const struct ubi_device *ubi,
               const struct ubi_ec_hdr *ec_hdr)
{
    long long ec;
    int vid_hdr_offset, leb_start;

    ec = be64_to_cpu(ec_hdr->ec);
    vid_hdr_offset = be32_to_cpu(ec_hdr->vid_hdr_offset);
    leb_start = be32_to_cpu(ec_hdr->data_offset);

    if (ec_hdr->version != UBI_VERSION) {
        ubi_err("node with incompatible UBI version found: this UBI version is %d, image version is %d",
            UBI_VERSION, (int)ec_hdr->version);
        goto bad;
    }

    if (vid_hdr_offset != ubi->vid_hdr_offset) {
        ubi_err("bad VID header offset %d, expected %d",
            vid_hdr_offset, ubi->vid_hdr_offset);
        goto bad;
    }

    if (leb_start != ubi->leb_start) {
        ubi_err("bad data offset %d, expected %d",
            leb_start, ubi->leb_start);
        goto bad;
    }

    if (ec < 0 || ec > UBI_MAX_ERASECOUNTER) {
        ubi_err("bad erase counter %lld", ec);
        goto bad;
    }

    return 0;

bad:
    ubi_err("bad EC header");
    ubi_dump_ec_hdr(ec_hdr);
    dump_stack();
    return 1;
}

int ubi_io_read_ec_hdr(struct ubi_device *ubi, int pnum,
               struct ubi_ec_hdr *ec_hdr, int verbose)
{
    int err, read_err;
    uint32_t crc, magic, hdr_crc;

    dbg_io("read EC header from PEB %d", pnum);
    ubi_assert(pnum >= 0 && pnum < ubi->peb_count);

    read_err = ubi_io_read(ubi, ec_hdr, pnum, 0, UBI_EC_HDR_SIZE);
    if (read_err) {
        if (read_err != UBI_IO_BITFLIPS && !mtd_is_eccerr(read_err))
            return read_err;

        /*
         * We read all the data, but either a correctable bit-flip
         * occurred, or MTD reported a data integrity error
         * (uncorrectable ECC error in case of NAND). The former is
         * harmless, the later may mean that the read data is
         * corrupted. But we have a CRC check-sum and we will detect
         * this. If the EC header is still OK, we just report this as
         * there was a bit-flip, to force scrubbing.
         */
    }

    magic = be32_to_cpu(ec_hdr->magic);
    if (magic != UBI_EC_HDR_MAGIC) {
        if (mtd_is_eccerr(read_err))
            return UBI_IO_BAD_HDR_EBADMSG;

        /*
         * The magic field is wrong. Let's check if we have read all
         * 0xFF. If yes, this physical eraseblock is assumed to be
         * empty.
         */
        if (ubi_check_pattern(ec_hdr, 0xFF, UBI_EC_HDR_SIZE)) {
            /* The physical eraseblock is supposedly empty */
            if (verbose)
                ubi_warn("no EC header found at PEB %d, only 0xFF bytes",
                     pnum);
            dbg_bld("no EC header found at PEB %d, only 0xFF bytes",
                pnum);
            if (!read_err)
                return UBI_IO_FF;
            else
                return UBI_IO_FF_BITFLIPS;
        }

        /*
         * This is not a valid erase counter header, and these are not
         * 0xFF bytes. Report that the header is corrupted.
         */
        if (verbose) {
            ubi_warn("bad magic number at PEB %d: %08x instead of %08x",
                 pnum, magic, UBI_EC_HDR_MAGIC);
            ubi_dump_ec_hdr(ec_hdr);
        }
        dbg_bld("bad magic number at PEB %d: %08x instead of %08x",
            pnum, magic, UBI_EC_HDR_MAGIC);
        return UBI_IO_BAD_HDR;
    }

    crc = crc32(UBI_CRC32_INIT, ec_hdr, UBI_EC_HDR_SIZE_CRC);
    hdr_crc = be32_to_cpu(ec_hdr->hdr_crc);

    if (hdr_crc != crc) {
        if (verbose) {
            ubi_warn("bad EC header CRC at PEB %d, calculated %#08x, read %#08x",
                 pnum, crc, hdr_crc);
            ubi_dump_ec_hdr(ec_hdr);
        }
        dbg_bld("bad EC header CRC at PEB %d, calculated %#08x, read %#08x",
            pnum, crc, hdr_crc);

        if (!read_err)
            return UBI_IO_BAD_HDR;
        else
            return UBI_IO_BAD_HDR_EBADMSG;
    }

    /* And of course validate what has just been read from the media */
    err = validate_ec_hdr(ubi, ec_hdr);
    if (err) {
        ubi_err("validation failed for PEB %d", pnum);
        return -EINVAL;
    }

    /*
     * If there was %-EBADMSG, but the header CRC is still OK, report about
     * a bit-flip to force scrubbing on this PEB.
     */
    return read_err ? UBI_IO_BITFLIPS : 0;
}

int ubi_io_write_ec_hdr(struct ubi_device *ubi, int pnum,
            struct ubi_ec_hdr *ec_hdr)
{
    int err;
    uint32_t crc;

    dbg_io("write EC header to PEB %d", pnum);
    ubi_assert(pnum >= 0 &&  pnum < ubi->peb_count);

    ec_hdr->magic = cpu_to_be32(UBI_EC_HDR_MAGIC);
    ec_hdr->version = UBI_VERSION;
    ec_hdr->vid_hdr_offset = cpu_to_be32(ubi->vid_hdr_offset);
    ec_hdr->data_offset = cpu_to_be32(ubi->leb_start);
    ec_hdr->image_seq = cpu_to_be32(ubi->image_seq);
    crc = crc32(UBI_CRC32_INIT, ec_hdr, UBI_EC_HDR_SIZE_CRC);
    ec_hdr->hdr_crc = cpu_to_be32(crc);

    err = self_check_ec_hdr(ubi, pnum, ec_hdr);
    if (err)
        return err;

    err = ubi_io_write(ubi, ec_hdr, pnum, 0, ubi->ec_hdr_alsize);
    return err;
}

static int validate_vid_hdr(const struct ubi_device *ubi,
                const struct ubi_vid_hdr *vid_hdr)
{
    int vol_type = vid_hdr->vol_type;
    int copy_flag = vid_hdr->copy_flag;
    int vol_id = be32_to_cpu(vid_hdr->vol_id);
    int lnum = be32_to_cpu(vid_hdr->lnum);
    int compat = vid_hdr->compat;
    int data_size = be32_to_cpu(vid_hdr->data_size);
    int used_ebs = be32_to_cpu(vid_hdr->used_ebs);
    int data_pad = be32_to_cpu(vid_hdr->data_pad);
    int data_crc = be32_to_cpu(vid_hdr->data_crc);
    int usable_leb_size = ubi->leb_size - data_pad;

    if (copy_flag != 0 && copy_flag != 1) {
        ubi_err("bad copy_flag");
        goto bad;
    }

    if (vol_id < 0 || lnum < 0 || data_size < 0 || used_ebs < 0 ||
        data_pad < 0) {
        ubi_err("negative values");
        goto bad;
    }

    if (vol_id >= UBI_MAX_VOLUMES && vol_id < UBI_INTERNAL_VOL_START) {
        ubi_err("bad vol_id");
        goto bad;
    }

    if (vol_id < UBI_INTERNAL_VOL_START && compat != 0) {
        ubi_err("bad compat");
        goto bad;
    }

    if (vol_id >= UBI_INTERNAL_VOL_START && compat != UBI_COMPAT_DELETE &&
        compat != UBI_COMPAT_RO && compat != UBI_COMPAT_PRESERVE &&
        compat != UBI_COMPAT_REJECT) {
        ubi_err("bad compat");
        goto bad;
    }

    if (vol_type != UBI_VID_DYNAMIC && vol_type != UBI_VID_STATIC) {
        ubi_err("bad vol_type");
        goto bad;
    }

    if (data_pad >= ubi->leb_size / 2) {
        ubi_err("bad data_pad");
        goto bad;
    }

    if (vol_type == UBI_VID_STATIC) {
        /*
         * Although from high-level point of view static volumes may
         * contain zero bytes of data, but no VID headers can contain
         * zero at these fields, because they empty volumes do not have
         * mapped logical eraseblocks.
         */
        if (used_ebs == 0) {
            ubi_err("zero used_ebs");
            goto bad;
        }
        if (data_size == 0) {
            ubi_err("zero data_size");
            goto bad;
        }
        if (lnum < used_ebs - 1) {
            if (data_size != usable_leb_size) {
                ubi_err("bad data_size");
                goto bad;
            }
        } else if (lnum == used_ebs - 1) {
            if (data_size == 0) {
                ubi_err("bad data_size at last LEB");
                goto bad;
            }
        } else {
            ubi_err("too high lnum");
            goto bad;
        }
    } else {
        if (copy_flag == 0) {
            if (data_crc != 0) {
                ubi_err("non-zero data CRC");
                goto bad;
            }
            if (data_size != 0) {
                ubi_err("non-zero data_size");
                goto bad;
            }
        } else {
            if (data_size == 0) {
                ubi_err("zero data_size of copy");
                goto bad;
            }
        }
        if (used_ebs != 0) {
            ubi_err("bad used_ebs");
            goto bad;
        }
    }

    return 0;

bad:
    ubi_err("bad VID header");
    ubi_dump_vid_hdr(vid_hdr);
    dump_stack();
    return 1;
}

int ubi_io_read_vid_hdr(struct ubi_device *ubi, int pnum,
            struct ubi_vid_hdr *vid_hdr, int verbose)
{
    int err, read_err;
    uint32_t crc, magic, hdr_crc;
    void *p;

    dbg_io("read VID header from PEB %d", pnum);
    ubi_assert(pnum >= 0 &&  pnum < ubi->peb_count);

    p = (char *)vid_hdr - ubi->vid_hdr_shift;
    read_err = ubi_io_read(ubi, p, pnum, ubi->vid_hdr_aloffset,
              ubi->vid_hdr_alsize);
    if (read_err && read_err != UBI_IO_BITFLIPS && !mtd_is_eccerr(read_err))
        return read_err;

    magic = be32_to_cpu(vid_hdr->magic);
    if (magic != UBI_VID_HDR_MAGIC) {
        if (mtd_is_eccerr(read_err))
            return UBI_IO_BAD_HDR_EBADMSG;

        if (ubi_check_pattern(vid_hdr, 0xFF, UBI_VID_HDR_SIZE)) {
            if (verbose)
                ubi_warn("no VID header found at PEB %d, only 0xFF bytes",
                     pnum);
            dbg_bld("no VID header found at PEB %d, only 0xFF bytes",
                pnum);
            if (!read_err)
                return UBI_IO_FF;
            else
                return UBI_IO_FF_BITFLIPS;
        }

        if (verbose) {
            ubi_warn("bad magic number at PEB %d: %08x instead of %08x",
                 pnum, magic, UBI_VID_HDR_MAGIC);
            ubi_dump_vid_hdr(vid_hdr);
        }
        dbg_bld("bad magic number at PEB %d: %08x instead of %08x",
            pnum, magic, UBI_VID_HDR_MAGIC);
        return UBI_IO_BAD_HDR;
    }

    crc = crc32(UBI_CRC32_INIT, vid_hdr, UBI_VID_HDR_SIZE_CRC);
    hdr_crc = be32_to_cpu(vid_hdr->hdr_crc);

    if (hdr_crc != crc) {
        if (verbose) {
            ubi_warn("bad CRC at PEB %d, calculated %#08x, read %#08x",
                 pnum, crc, hdr_crc);
            ubi_dump_vid_hdr(vid_hdr);
        }
        dbg_bld("bad CRC at PEB %d, calculated %#08x, read %#08x",
            pnum, crc, hdr_crc);
        if (!read_err)
            return UBI_IO_BAD_HDR;
        else
            return UBI_IO_BAD_HDR_EBADMSG;
    }

    err = validate_vid_hdr(ubi, vid_hdr);
    if (err) {
        ubi_err("validation failed for PEB %d", pnum);
        return -EINVAL;
    }

    return read_err ? UBI_IO_BITFLIPS : 0;
}

int ubi_io_write_vid_hdr(struct ubi_device *ubi, int pnum,
             struct ubi_vid_hdr *vid_hdr)
{
    int err;
    uint32_t crc;
    void *p;

    dbg_io("write VID header to PEB %d", pnum);
    ubi_assert(pnum >= 0 &&  pnum < ubi->peb_count);

    err = self_check_peb_ec_hdr(ubi, pnum);
    if (err)
        return err;

    vid_hdr->magic = cpu_to_be32(UBI_VID_HDR_MAGIC);
    vid_hdr->version = UBI_VERSION;
    crc = crc32(UBI_CRC32_INIT, vid_hdr, UBI_VID_HDR_SIZE_CRC);
    vid_hdr->hdr_crc = cpu_to_be32(crc);

    err = self_check_vid_hdr(ubi, pnum, vid_hdr);
    if (err)
        return err;

    p = (char *)vid_hdr - ubi->vid_hdr_shift;
    err = ubi_io_write(ubi, p, pnum, ubi->vid_hdr_aloffset,
               ubi->vid_hdr_alsize);
    return err;
}

static int self_check_not_bad(const struct ubi_device *ubi, int pnum)
{
    int err;

    if (!ubi->dbg->chk_io)
        return 0;

    err = ubi_io_is_bad(ubi, pnum);
    if (!err)
        return err;

    ubi_err("self-check failed for PEB %d", pnum);
    dump_stack();
    return err > 0 ? -EINVAL : err;
}

static int self_check_ec_hdr(const struct ubi_device *ubi, int pnum,
                 const struct ubi_ec_hdr *ec_hdr)
{
    int err;
    uint32_t magic;

    if (!ubi->dbg->chk_io)
        return 0;

    magic = be32_to_cpu(ec_hdr->magic);
    if (magic != UBI_EC_HDR_MAGIC) {
        ubi_err("bad magic %#08x, must be %#08x",
            magic, UBI_EC_HDR_MAGIC);
        goto fail;
    }

    err = validate_ec_hdr(ubi, ec_hdr);
    if (err) {
        ubi_err("self-check failed for PEB %d", pnum);
        goto fail;
    }

    return 0;

fail:
    ubi_dump_ec_hdr(ec_hdr);
    dump_stack();
    return -EINVAL;
}

static int self_check_peb_ec_hdr(const struct ubi_device *ubi, int pnum)
{
    int err;
    uint32_t crc, hdr_crc;
    struct ubi_ec_hdr *ec_hdr;

    if (!ubi->dbg->chk_io)
        return 0;

    ec_hdr = kzalloc(ubi->ec_hdr_alsize, GFP_NOFS);
    if (!ec_hdr)
        return -ENOMEM;

    err = ubi_io_read(ubi, ec_hdr, pnum, 0, UBI_EC_HDR_SIZE);
    if (err && err != UBI_IO_BITFLIPS && !mtd_is_eccerr(err))
        goto exit;

    crc = crc32(UBI_CRC32_INIT, ec_hdr, UBI_EC_HDR_SIZE_CRC);
    hdr_crc = be32_to_cpu(ec_hdr->hdr_crc);
    if (hdr_crc != crc) {
        ubi_err("bad CRC, calculated %#08x, read %#08x", crc, hdr_crc);
        ubi_err("self-check failed for PEB %d", pnum);
        ubi_dump_ec_hdr(ec_hdr);
        dump_stack();
        err = -EINVAL;
        goto exit;
    }

    err = self_check_ec_hdr(ubi, pnum, ec_hdr);

exit:
    kfree(ec_hdr);
    return err;
}

static int self_check_vid_hdr(const struct ubi_device *ubi, int pnum,
                  const struct ubi_vid_hdr *vid_hdr)
{
    int err;
    uint32_t magic;

    if (!ubi->dbg->chk_io)
        return 0;

    magic = be32_to_cpu(vid_hdr->magic);
    if (magic != UBI_VID_HDR_MAGIC) {
        ubi_err("bad VID header magic %#08x at PEB %d, must be %#08x",
            magic, pnum, UBI_VID_HDR_MAGIC);
        goto fail;
    }

    err = validate_vid_hdr(ubi, vid_hdr);
    if (err) {
        ubi_err("self-check failed for PEB %d", pnum);
        goto fail;
    }

    return err;

fail:
    ubi_err("self-check failed for PEB %d", pnum);
    ubi_dump_vid_hdr(vid_hdr);
    dump_stack();
    return -EINVAL;

}

static int self_check_peb_vid_hdr(const struct ubi_device *ubi, int pnum)
{
    int err;
    uint32_t crc, hdr_crc;
    struct ubi_vid_hdr *vid_hdr;
    void *p;

    if (!ubi->dbg->chk_io)
        return 0;

    vid_hdr = ubi_zalloc_vid_hdr(ubi, GFP_NOFS);
    if (!vid_hdr)
        return -ENOMEM;

    p = (char *)vid_hdr - ubi->vid_hdr_shift;
    err = ubi_io_read(ubi, p, pnum, ubi->vid_hdr_aloffset,
              ubi->vid_hdr_alsize);
    if (err && err != UBI_IO_BITFLIPS && !mtd_is_eccerr(err))
        goto exit;

    crc = crc32(UBI_CRC32_INIT, vid_hdr, UBI_EC_HDR_SIZE_CRC);
    hdr_crc = be32_to_cpu(vid_hdr->hdr_crc);
    if (hdr_crc != crc) {
        ubi_err("bad VID header CRC at PEB %d, calculated %#08x, read %#08x",
            pnum, crc, hdr_crc);
        ubi_err("self-check failed for PEB %d", pnum);
        ubi_dump_vid_hdr(vid_hdr);
        dump_stack();
        err = -EINVAL;
        goto exit;
    }

    err = self_check_vid_hdr(ubi, pnum, vid_hdr);

exit:
    ubi_free_vid_hdr(ubi, vid_hdr);
    return err;
}

static int self_check_write(struct ubi_device *ubi, const void *buf, int pnum,
                int offset, int len)
{
    int err, i;
    size_t read;
    void *buf1;
    loff_t addr = (loff_t)pnum * ubi->peb_size + offset;

    if (!ubi->dbg->chk_io)
        return 0;

    buf1 = __vmalloc(len, GFP_NOFS, PAGE_KERNEL);
    if (!buf1) {
        ubi_err("cannot allocate memory to check writes");
        return 0;
    }

    err = mtd_read(ubi->mtd, addr, len, &read, buf1);
    if (err && !mtd_is_bitflip(err))
        goto out_free;

    for (i = 0; i < len; i++) {
        uint8_t c = ((uint8_t *)buf)[i];
        uint8_t c1 = ((uint8_t *)buf1)[i];
        int dump_len;

        if (c == c1)
            continue;

        ubi_err("self-check failed for PEB %d:%d, len %d",
            pnum, offset, len);
        ubi_msg("data differ at position %d", i);
        dump_len = max_t(int, 128, len - i);
        ubi_msg("hex dump of the original buffer from %d to %d",
            i, i + dump_len);
        print_hex_dump(KERN_DEBUG, "", DUMP_PREFIX_OFFSET, 32, 1,
                   buf + i, dump_len, 1);
        ubi_msg("hex dump of the read buffer from %d to %d",
            i, i + dump_len);
        print_hex_dump(KERN_DEBUG, "", DUMP_PREFIX_OFFSET, 32, 1,
                   buf1 + i, dump_len, 1);
        dump_stack();
        err = -EINVAL;
        goto out_free;
    }

    vfree(buf1);
    return 0;

out_free:
    vfree(buf1);
    return err;
}

int ubi_self_check_all_ff(struct ubi_device *ubi, int pnum, int offset, int len)
{
    size_t read;
    int err;
    void *buf;
    loff_t addr = (loff_t)pnum * ubi->peb_size + offset;

    if (!ubi->dbg->chk_io)
        return 0;

    buf = __vmalloc(len, GFP_NOFS, PAGE_KERNEL);
    if (!buf) {
        ubi_err("cannot allocate memory to check for 0xFFs");
        return 0;
    }

    err = mtd_read(ubi->mtd, addr, len, &read, buf);
    if (err && !mtd_is_bitflip(err)) {
        ubi_err("error %d while reading %d bytes from PEB %d:%d, read %zd bytes",
            err, len, pnum, offset, read);
        goto error;
    }

    err = ubi_check_pattern(buf, 0xFF, len);
    if (err == 0) {
        ubi_err("flash region at PEB %d:%d, length %d does not contain all 0xFF bytes",
            pnum, offset, len);
        goto fail;
    }

    vfree(buf);
    return 0;

fail:
    ubi_err("self-check failed for PEB %d", pnum);
    ubi_msg("hex dump of the %d-%d region", offset, offset + len);
    print_hex_dump(KERN_DEBUG, "", DUMP_PREFIX_OFFSET, 32, 1, buf, len, 1);
    err = -EINVAL;
error:
    dump_stack();
    vfree(buf);
    return err;
}