UBI: Unsorted Block Images

UBI (Latin: "where?") manages multiple logical volumes on a single
flash device, specifically supporting NAND flash devices. UBI provides
a flexible partitioning concept which still allows for wear-levelling
across the whole flash device.

In a sense, UBI may be compared to the Logical Volume Manager
(LVM). Whereas LVM maps logical sector numbers to physical HDD sector
numbers, UBI maps logical eraseblocks to physical eraseblocks.

More information may be found at
http://www.linux-mtd.infradead.org/doc/ubi.html

Partitioning/Re-partitioning

  An UBI volume occupies a certain number of erase blocks. This is
  limited by a configured maximum volume size, which could also be
  viewed as the partition size. Each individual UBI volume's size can
  be changed independently of the other UBI volumes, provided that the
  sum of all volume sizes doesn't exceed a certain limit.

  UBI supports dynamic volumes and static volumes. Static volumes are
  read-only and their contents are protected by CRC check sums.

Bad eraseblocks handling

  UBI transparently handles bad eraseblocks. When a physical
  eraseblock becomes bad, it is substituted by a good physical
  eraseblock, and the user does not even notice this.

Scrubbing

  On a NAND flash bit flips can occur on any write operation,
  sometimes also on read. If bit flips persist on the device, at first
  they can still be corrected by ECC, but once they accumulate,
  correction will become impossible. Thus it is best to actively scrub
  the affected eraseblock, by first copying it to a free eraseblock
  and then erasing the original. The UBI layer performs this type of
  scrubbing under the covers, transparently to the UBI volume users.

Erase Counts

  UBI maintains an erase count header per eraseblock. This frees
  higher-level layers (like file systems) from doing this and allows
  for centralized erase count management instead. The erase counts are
  used by the wear-levelling algorithm in the UBI layer. The algorithm
  itself is exchangeable.

Booting from NAND

  For booting directly from NAND flash the hardware must at least be
  capable of fetching and executing a small portion of the NAND
  flash. Some NAND flash controllers have this kind of support. They
  usually limit the window to a few kilobytes in erase block 0. This
  "initial program loader" (IPL) must then contain sufficient logic to
  load and execute the next boot phase.

  Due to bad eraseblocks, which may be randomly scattered over the
  flash device, it is problematic to store the "secondary program
  loader" (SPL) statically. Also, due to bit-flips it may become
  corrupted over time. UBI allows to solve this problem gracefully by
  storing the SPL in a small static UBI volume.

UBI volumes vs. static partitions

  UBI volumes are still very similar to static MTD partitions:

    * both consist of eraseblocks (logical eraseblocks in case of UBI
      volumes, and physical eraseblocks in case of static partitions;
    * both support three basic operations - read, write, erase.

  But UBI volumes have the following advantages over traditional
  static MTD partitions:

    * there are no eraseblock wear-leveling constraints in case of UBI
      volumes, so the user should not care about this;
    * there are no bit-flips and bad eraseblocks in case of UBI volumes.

  So, UBI volumes may be considered as flash devices with relaxed
  restrictions.

Where can it be found?

  Documentation, kernel code and applications can be found in the MTD
  gits.

What are the applications for?

  The applications help to create binary flash images for two purposes: pfi
  files (partial flash images) for in-system update of UBI volumes, and plain
  binary images, with or without OOB data in case of NAND, for a manufacturing
  step. Furthermore some tools are/and will be created that allow flash content
  analysis after a system has crashed..

Who did UBI?

  The original ideas, where UBI is based on, were developed by Andreas
  Arnez, Frank Haverkamp and Thomas Gleixner. Josh W. Boyer and some others
  were involved too. The implementation of the kernel layer was done by Artem
  B. Bityutskiy. The user-space applications and tools were written by Oliver
  Lohmann with contributions from Frank Haverkamp, Andreas Arnez, and Artem.
  Joern Engel contributed a patch which modifies JFFS2 so that it can be run on
  a UBI volume. Thomas Gleixner did modifications to the NAND layer. Alexander
  Schmidt made some testing work as well as core functionality improvements.

Signed-off-by: Artem B. Bityutskiy <dedekind@linutronix.de>
Signed-off-by: Frank Haverkamp <haver@vnet.ibm.com>

1 files changed, 1259 insertions, 0 deletions

diff --git a/drivers/mtd/ubi/io.c b/drivers/mtd/ubi/io.c
new file mode 100644
index 0000000..438914d
--- /dev/null
+++ b/drivers/mtd/ubi/io.c
@@ -0,0 +1,1259 @@
+/*
+ * 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 unit.
+ *
+ * This unit 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 unit
+ * 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 no relevant to the sub-page are 0xFF. So, basically, writing
+ * 4x512 sub-pages is 4 times slower then writing one 2KiB NAND page. Thus, we
+ * prefer to use sub-pages only for EV 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 unit 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 "ubi.h"
+
+#ifdef CONFIG_MTD_UBI_DEBUG_PARANOID
+static int paranoid_check_not_bad(const struct ubi_device *ubi, int pnum);
+static int paranoid_check_peb_ec_hdr(const struct ubi_device *ubi, int pnum);
+static int paranoid_check_ec_hdr(const struct ubi_device *ubi, int pnum,
+				 const struct ubi_ec_hdr *ec_hdr);
+static int paranoid_check_peb_vid_hdr(const struct ubi_device *ubi, int pnum);
+static int paranoid_check_vid_hdr(const struct ubi_device *ubi, int pnum,
+				  const struct ubi_vid_hdr *vid_hdr);
+static int paranoid_check_all_ff(const struct ubi_device *ubi, int pnum,
+				 int offset, int len);
+#else
+#define paranoid_check_not_bad(ubi, pnum) 0
+#define paranoid_check_peb_ec_hdr(ubi, pnum)  0
+#define paranoid_check_ec_hdr(ubi, pnum, ec_hdr)  0
+#define paranoid_check_peb_vid_hdr(ubi, pnum) 0
+#define paranoid_check_vid_hdr(ubi, pnum, vid_hdr) 0
+#define paranoid_check_all_ff(ubi, pnum, offset, len) 0
+#endif
+
+/**
+ * ubi_io_read - read data from a physical eraseblock.
+ * @ubi: UBI device description object
+ * @buf: buffer where to store the read data
+ * @pnum: physical eraseblock number to read from
+ * @offset: offset within the physical eraseblock from where to read
+ * @len: how many bytes to read
+ *
+ * This function reads data from offset @offset of physical eraseblock @pnum
+ * and stores the read data in the @buf buffer. The following return codes are
+ * possible:
+ *
+ * o %0 if all the requested data were successfully read;
+ * o %UBI_IO_BITFLIPS if all the requested data were successfully read, but
+ *   correctable bit-flips were detected; this is harmless but may indicate
+ *   that this eraseblock may become bad soon (but do not have to);
+ * o %-EBADMSG if the MTD subsystem reported about data data integrity
+ *   problems, for example it can me an ECC error in case of NAND; this most
+ *   probably means that the data is corrupted;
+ * o %-EIO if some I/O error occurred;
+ * o other negative error codes in case of other errors.
+ */
+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 = paranoid_check_not_bad(ubi, pnum);
+	if (err)
+		return err > 0 ? -EINVAL : err;
+
+	addr = (loff_t)pnum * ubi->peb_size + offset;
+retry:
+	err = ubi->mtd->read(ubi->mtd, addr, len, &read, buf);
+	if (err) {
+		if (err == -EUCLEAN) {
+			/*
+			 * -EUCLEAN is reported if there was a bit-flip which
+			 * was corrected, so this is harmless.
+			 */
+			ubi_msg("fixable bit-flip detected at PEB %d", pnum);
+			ubi_assert(len == read);
+			return UBI_IO_BITFLIPS;
+		}
+
+		if (read != len && retries++ < UBI_IO_RETRIES) {
+			dbg_io("error %d while reading %d bytes from PEB %d:%d, "
+			       "read only %zd bytes, retry",
+			       err, len, pnum, offset, read);
+			yield();
+			goto retry;
+		}
+
+		ubi_err("error %d while reading %d bytes from PEB %d:%d, "
+			"read %zd bytes", err, len, pnum, offset, read);
+		ubi_dbg_dump_stack();
+	} else {
+		ubi_assert(len == read);
+
+		if (ubi_dbg_is_bitflip()) {
+			dbg_msg("bit-flip (emulated)");
+			err = UBI_IO_BITFLIPS;
+		}
+	}
+
+	return err;
+}
+
+/**
+ * ubi_io_write - write data to a physical eraseblock.
+ * @ubi: UBI device description object
+ * @buf: buffer with the data to write
+ * @pnum: physical eraseblock number to write to
+ * @offset: offset within the physical eraseblock where to write
+ * @len: how many bytes to write
+ *
+ * This function writes @len bytes of data from buffer @buf to offset @offset
+ * of physical eraseblock @pnum. If all the data were successfully written,
+ * zero is returned. If an error occurred, this function returns a negative
+ * error code. If %-EIO is returned, the physical eraseblock most probably went
+ * bad.
+ *
+ * Note, in case of an error, it is possible that something was still written
+ * to the flash media, but may be some garbage.
+ */
+int ubi_io_write(const 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;
+	}
+
+	/* The below has to be compiled out if paranoid checks are disabled */
+
+	err = paranoid_check_not_bad(ubi, pnum);
+	if (err)
+		return err > 0 ? -EINVAL : err;
+
+	/* The area we are writing to has to contain all 0xFF bytes */
+	err = paranoid_check_all_ff(ubi, pnum, offset, len);
+	if (err)
+		return err > 0 ? -EINVAL : 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 = paranoid_check_peb_ec_hdr(ubi, pnum);
+		if (err)
+			return err > 0 ? -EINVAL : err;
+		err = paranoid_check_peb_vid_hdr(ubi, pnum);
+		if (err)
+			return err > 0 ? -EINVAL : err;
+	}
+
+	if (ubi_dbg_is_write_failure()) {
+		dbg_err("cannot write %d bytes to PEB %d:%d "
+			"(emulated)", len, pnum, offset);
+		ubi_dbg_dump_stack();
+		return -EIO;
+	}
+
+	addr = (loff_t)pnum * ubi->peb_size + offset;
+	err = ubi->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);
+		ubi_dbg_dump_stack();
+	} else
+		ubi_assert(written == len);
+
+	return err;
+}
+
+/**
+ * erase_callback - MTD erasure call-back.
+ * @ei: MTD erase information object.
+ *
+ * Note, even though MTD erase interface is asynchronous, all the current
+ * implementations are synchronous anyway.
+ */
+static void erase_callback(struct erase_info *ei)
+{
+	wake_up_interruptible((wait_queue_head_t *)ei->priv);
+}
+
+/**
+ * do_sync_erase - synchronously erase a physical eraseblock.
+ * @ubi: UBI device description object
+ * @pnum: the physical eraseblock number to erase
+ *
+ * This function synchronously erases physical eraseblock @pnum and returns
+ * zero in case of success and a negative error code in case of failure. If
+ * %-EIO is returned, the physical eraseblock most probably went bad.
+ */
+static int do_sync_erase(const 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);
+
+retry:
+	init_waitqueue_head(&wq);
+	memset(&ei, 0, sizeof(struct erase_info));
+
+	ei.mtd      = ubi->mtd;
+	ei.addr     = pnum * ubi->peb_size;
+	ei.len      = ubi->peb_size;
+	ei.callback = erase_callback;
+	ei.priv     = (unsigned long)&wq;
+
+	err = ubi->mtd->erase(ubi->mtd, &ei);
+	if (err) {
+		if (retries++ < UBI_IO_RETRIES) {
+			dbg_io("error %d while erasing PEB %d, retry",
+			       err, pnum);
+			yield();
+			goto retry;
+		}
+		ubi_err("cannot erase PEB %d, error %d", pnum, err);
+		ubi_dbg_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) {
+			dbg_io("error while erasing PEB %d, retry", pnum);
+			yield();
+			goto retry;
+		}
+		ubi_err("cannot erase PEB %d", pnum);
+		ubi_dbg_dump_stack();
+		return -EIO;
+	}
+
+	err = paranoid_check_all_ff(ubi, pnum, 0, ubi->peb_size);
+	if (err)
+		return err > 0 ? -EINVAL : err;
+
+	if (ubi_dbg_is_erase_failure() && !err) {
+		dbg_err("cannot erase PEB %d (emulated)", pnum);
+		return -EIO;
+	}
+
+	return 0;
+}
+
+/**
+ * check_pattern - check if buffer contains only a certain byte pattern.
+ * @buf: buffer to check
+ * @patt: the pattern to check
+ * @size: buffer size in bytes
+ *
+ * This function returns %1 in there are only @patt bytes in @buf, and %0 if
+ * something else was also found.
+ */
+static int check_pattern(const void *buf, uint8_t patt, int size)
+{
+	int i;
+
+	for (i = 0; i < size; i++)
+		if (((const uint8_t *)buf)[i] != patt)
+			return 0;
+	return 1;
+}
+
+/* Patterns to write to a physical eraseblock when torturing it */
+static uint8_t patterns[] = {0xa5, 0x5a, 0x0};
+
+/**
+ * torture_peb - test a supposedly bad physical eraseblock.
+ * @ubi: UBI device description object
+ * @pnum: the physical eraseblock number to test
+ *
+ * This function returns %-EIO if the physical eraseblock did not pass the
+ * test, a positive number of erase operations done if the test was
+ * successfully passed, and other negative error codes in case of other errors.
+ */
+static int torture_peb(const struct ubi_device *ubi, int pnum)
+{
+	void *buf;
+	int err, i, patt_count;
+
+	buf = kmalloc(ubi->peb_size, GFP_KERNEL);
+	if (!buf)
+		return -ENOMEM;
+
+	patt_count = ARRAY_SIZE(patterns);
+	ubi_assert(patt_count > 0);
+
+	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, buf, pnum, 0, ubi->peb_size);
+		if (err)
+			goto out;
+
+		err = check_pattern(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(buf, patterns[i], ubi->peb_size);
+		err = ubi_io_write(ubi, buf, pnum, 0, ubi->peb_size);
+		if (err)
+			goto out;
+
+		memset(buf, ~patterns[i], ubi->peb_size);
+		err = ubi_io_read(ubi, buf, pnum, 0, ubi->peb_size);
+		if (err)
+			goto out;
+
+		err = check_pattern(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;
+
+out:
+	if (err == UBI_IO_BITFLIPS || err == -EBADMSG)
+		/*
+		 * 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.
+		 */
+		err = -EIO;
+	kfree(buf);
+	return err;
+}
+
+/**
+ * ubi_io_sync_erase - synchronously erase a physical eraseblock.
+ * @ubi: UBI device description object
+ * @pnum: physical eraseblock number to erase
+ * @torture: if this physical eraseblock has to be tortured
+ *
+ * This function synchronously erases physical eraseblock @pnum. If @torture
+ * flag is not zero, the physical eraseblock is checked by means of writing
+ * different patterns to it and reading them back. If the torturing is enabled,
+ * the physical eraseblock is erased more then once.
+ *
+ * This function returns the number of erasures made in case of success, %-EIO
+ * if the erasure failed or the torturing test failed, and other negative error
+ * codes in case of other errors. Note, %-EIO means that the physical
+ * eraseblock is bad.
+ */
+int ubi_io_sync_erase(const struct ubi_device *ubi, int pnum, int torture)
+{
+	int err, ret = 0;
+
+	ubi_assert(pnum >= 0 && pnum < ubi->peb_count);
+
+	err = paranoid_check_not_bad(ubi, pnum);
+	if (err != 0)
+		return err > 0 ? -EINVAL : err;
+
+	if (ubi->ro_mode) {
+		ubi_err("read-only mode");
+		return -EROFS;
+	}
+
+	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;
+}
+
+/**
+ * ubi_io_is_bad - check if a physical eraseblock is bad.
+ * @ubi: UBI device description object
+ * @pnum: the physical eraseblock number to check
+ *
+ * This function returns a positive number if the physical eraseblock is bad,
+ * zero if not, and a negative error code if an error occurred.
+ */
+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;
+}
+
+/**
+ * ubi_io_mark_bad - mark a physical eraseblock as bad.
+ * @ubi: UBI device description object
+ * @pnum: the physical eraseblock number to mark
+ *
+ * This function returns zero in case of success and a negative error code in
+ * case of failure.
+ */
+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;
+}
+
+/**
+ * validate_ec_hdr - validate an erase counter header.
+ * @ubi: UBI device description object
+ * @ec_hdr: the erase counter header to check
+ *
+ * This function returns zero if the erase counter header is OK, and %1 if
+ * not.
+ */
+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 = ubi64_to_cpu(ec_hdr->ec);
+	vid_hdr_offset = ubi32_to_cpu(ec_hdr->vid_hdr_offset);
+	leb_start = ubi32_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_dbg_dump_ec_hdr(ec_hdr);
+	ubi_dbg_dump_stack();
+	return 1;
+}
+
+/**
+ * ubi_io_read_ec_hdr - read and check an erase counter header.
+ * @ubi: UBI device description object
+ * @pnum: physical eraseblock to read from
+ * @ec_hdr: a &struct ubi_ec_hdr object where to store the read erase counter
+ * header
+ * @verbose: be verbose if the header is corrupted or was not found
+ *
+ * This function reads erase counter header from physical eraseblock @pnum and
+ * stores it in @ec_hdr. This function also checks CRC checksum of the read
+ * erase counter header. The following codes may be returned:
+ *
+ * o %0 if the CRC checksum is correct and the header was successfully read;
+ * o %UBI_IO_BITFLIPS if the CRC is correct, but bit-flips were detected
+ *   and corrected by the flash driver; this is harmless but may indicate that
+ *   this eraseblock may become bad soon (but may be not);
+ * o %UBI_IO_BAD_EC_HDR if the erase counter header is corrupted (a CRC error);
+ * o %UBI_IO_PEB_EMPTY if the physical eraseblock is empty;
+ * o a negative error code in case of failure.
+ */
+int ubi_io_read_ec_hdr(const struct ubi_device *ubi, int pnum,
+		       struct ubi_ec_hdr *ec_hdr, int verbose)
+{
+	int err, read_err = 0;
+	uint32_t crc, magic, hdr_crc;
+
+	dbg_io("read EC header from PEB %d", pnum);
+	ubi_assert(pnum >= 0 && pnum < ubi->peb_count);
+
+	err = ubi_io_read(ubi, ec_hdr, pnum, 0, UBI_EC_HDR_SIZE);
+	if (err) {
+		if (err != UBI_IO_BITFLIPS && err != -EBADMSG)
+			return err;
+
+		/*
+		 * We read all the data, but either a correctable bit-flip
+		 * occurred, or MTD reported about some data integrity error,
+		 * like an 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.
+		 */
+		read_err = err;
+	}
+
+	magic = ubi32_to_cpu(ec_hdr->magic);
+	if (magic != UBI_EC_HDR_MAGIC) {
+		/*
+		 * The magic field is wrong. Let's check if we have read all
+		 * 0xFF. If yes, this physical eraseblock is assumed to be
+		 * empty.
+		 *
+		 * But if there was a read error, we do not test it for all
+		 * 0xFFs. Even if it does contain all 0xFFs, this error
+		 * indicates that something is still wrong with this physical
+		 * eraseblock and we anyway cannot treat it as empty.
+		 */
+		if (read_err != -EBADMSG &&
+		    check_pattern(ec_hdr, 0xFF, UBI_EC_HDR_SIZE)) {
+			/* The physical eraseblock is supposedly empty */
+
+			/*
+			 * The below is just a paranoid check, it has to be
+			 * compiled out if paranoid checks are disabled.
+			 */
+			err = paranoid_check_all_ff(ubi, pnum, 0,
+						    ubi->peb_size);
+			if (err)
+				return err > 0 ? UBI_IO_BAD_EC_HDR : err;
+
+			if (verbose)
+				ubi_warn("no EC header found at PEB %d, "
+					 "only 0xFF bytes", pnum);
+			return UBI_IO_PEB_EMPTY;
+		}
+
+		/*
+		 * 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_dbg_dump_ec_hdr(ec_hdr);
+		}
+		return UBI_IO_BAD_EC_HDR;
+	}
+
+	crc = crc32(UBI_CRC32_INIT, ec_hdr, UBI_EC_HDR_SIZE_CRC);
+	hdr_crc = ubi32_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_dbg_dump_ec_hdr(ec_hdr);
+		}
+		return UBI_IO_BAD_EC_HDR;
+	}
+
+	/* 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;
+	}
+
+	return read_err ? UBI_IO_BITFLIPS : 0;
+}
+
+/**
+ * ubi_io_write_ec_hdr - write an erase counter header.
+ * @ubi: UBI device description object
+ * @pnum: physical eraseblock to write to
+ * @ec_hdr: the erase counter header to write
+ *
+ * This function writes erase counter header described by @ec_hdr to physical
+ * eraseblock @pnum. It also fills most fields of @ec_hdr before writing, so
+ * the caller do not have to fill them. Callers must only fill the @ec_hdr->ec
+ * field.
+ *
+ * This function returns zero in case of success and a negative error code in
+ * case of failure. If %-EIO is returned, the physical eraseblock most probably
+ * went bad.
+ */
+int ubi_io_write_ec_hdr(const 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_ubi32(UBI_EC_HDR_MAGIC);
+	ec_hdr->version = UBI_VERSION;
+	ec_hdr->vid_hdr_offset = cpu_to_ubi32(ubi->vid_hdr_offset);
+	ec_hdr->data_offset = cpu_to_ubi32(ubi->leb_start);
+	crc = crc32(UBI_CRC32_INIT, ec_hdr, UBI_EC_HDR_SIZE_CRC);
+	ec_hdr->hdr_crc = cpu_to_ubi32(crc);
+
+	err = paranoid_check_ec_hdr(ubi, pnum, ec_hdr);
+	if (err)
+		return -EINVAL;
+
+	err = ubi_io_write(ubi, ec_hdr, pnum, 0, ubi->ec_hdr_alsize);
+	return err;
+}
+
+/**
+ * validate_vid_hdr - validate a volume identifier header.
+ * @ubi: UBI device description object
+ * @vid_hdr: the volume identifier header to check
+ *
+ * This function checks that data stored in the volume identifier header
+ * @vid_hdr. Returns zero if the VID header is OK and %1 if not.
+ */
+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 = ubi32_to_cpu(vid_hdr->vol_id);
+	int lnum = ubi32_to_cpu(vid_hdr->lnum);
+	int compat = vid_hdr->compat;
+	int data_size = ubi32_to_cpu(vid_hdr->data_size);
+	int used_ebs = ubi32_to_cpu(vid_hdr->used_ebs);
+	int data_pad = ubi32_to_cpu(vid_hdr->data_pad);
+	int data_crc = ubi32_to_cpu(vid_hdr->data_crc);
+	int usable_leb_size = ubi->leb_size - data_pad;
+
+	if (copy_flag != 0 && copy_flag != 1) {
+		dbg_err("bad copy_flag");
+		goto bad;
+	}
+
+	if (vol_id < 0 || lnum < 0 || data_size < 0 || used_ebs < 0 ||
+	    data_pad < 0) {
+		dbg_err("negative values");
+		goto bad;
+	}
+
+	if (vol_id >= UBI_MAX_VOLUMES && vol_id < UBI_INTERNAL_VOL_START) {
+		dbg_err("bad vol_id");
+		goto bad;
+	}
+
+	if (vol_id < UBI_INTERNAL_VOL_START && compat != 0) {
+		dbg_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) {
+		dbg_err("bad compat");
+		goto bad;
+	}
+
+	if (vol_type != UBI_VID_DYNAMIC && vol_type != UBI_VID_STATIC) {
+		dbg_err("bad vol_type");
+		goto bad;
+	}
+
+	if (data_pad >= ubi->leb_size / 2) {
+		dbg_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) {
+			dbg_err("zero used_ebs");
+			goto bad;
+		}
+		if (data_size == 0) {
+			dbg_err("zero data_size");
+			goto bad;
+		}
+		if (lnum < used_ebs - 1) {
+			if (data_size != usable_leb_size) {
+				dbg_err("bad data_size");
+				goto bad;
+			}
+		} else if (lnum == used_ebs - 1) {
+			if (data_size == 0) {
+				dbg_err("bad data_size at last LEB");
+				goto bad;
+			}
+		} else {
+			dbg_err("too high lnum");
+			goto bad;
+		}
+	} else {
+		if (copy_flag == 0) {
+			if (data_crc != 0) {
+				dbg_err("non-zero data CRC");
+				goto bad;
+			}
+			if (data_size != 0) {
+				dbg_err("non-zero data_size");
+				goto bad;
+			}
+		} else {
+			if (data_size == 0) {
+				dbg_err("zero data_size of copy");
+				goto bad;
+			}
+		}
+		if (used_ebs != 0) {
+			dbg_err("bad used_ebs");
+			goto bad;
+		}
+	}
+
+	return 0;
+
+bad:
+	ubi_err("bad VID header");
+	ubi_dbg_dump_vid_hdr(vid_hdr);
+	ubi_dbg_dump_stack();
+	return 1;
+}
+
+/**
+ * ubi_io_read_vid_hdr - read and check a volume identifier header.
+ * @ubi: UBI device description object
+ * @pnum: physical eraseblock number to read from
+ * @vid_hdr: &struct ubi_vid_hdr object where to store the read volume
+ * identifier header
+ * @verbose: be verbose if the header is corrupted or wasn't found
+ *
+ * This function reads the volume identifier header from physical eraseblock
+ * @pnum and stores it in @vid_hdr. It also checks CRC checksum of the read
+ * volume identifier header. The following codes may be returned:
+ *
+ * o %0 if the CRC checksum is correct and the header was successfully read;
+ * o %UBI_IO_BITFLIPS if the CRC is correct, but bit-flips were detected
+ *   and corrected by the flash driver; this is harmless but may indicate that
+ *   this eraseblock may become bad soon;
+ * o %UBI_IO_BAD_VID_HRD if the volume identifier header is corrupted (a CRC
+ *   error detected);
+ * o %UBI_IO_PEB_FREE if the physical eraseblock is free (i.e., there is no VID
+ *   header there);
+ * o a negative error code in case of failure.
+ */
+int ubi_io_read_vid_hdr(const struct ubi_device *ubi, int pnum,
+			struct ubi_vid_hdr *vid_hdr, int verbose)
+{
+	int err, read_err = 0;
+	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;
+	err = ubi_io_read(ubi, p, pnum, ubi->vid_hdr_aloffset,
+			  ubi->vid_hdr_alsize);
+	if (err) {
+		if (err != UBI_IO_BITFLIPS && err != -EBADMSG)
+			return err;
+
+		/*
+		 * We read all the data, but either a correctable bit-flip
+		 * occurred, or MTD reported about some data integrity error,
+		 * like an ECC error in case of NAND. The former is harmless,
+		 * the later may mean the read data is corrupted. But we have a
+		 * CRC check-sum and we will identify this. If the VID header is
+		 * still OK, we just report this as there was a bit-flip.
+		 */
+		read_err = err;
+	}
+
+	magic = ubi32_to_cpu(vid_hdr->magic);
+	if (magic != UBI_VID_HDR_MAGIC) {
+		/*
+		 * If we have read all 0xFF bytes, the VID header probably does
+		 * not exist and the physical eraseblock is assumed to be free.
+		 *
+		 * But if there was a read error, we do not test the data for
+		 * 0xFFs. Even if it does contain all 0xFFs, this error
+		 * indicates that something is still wrong with this physical
+		 * eraseblock and it cannot be regarded as free.
+		 */
+		if (read_err != -EBADMSG &&
+		    check_pattern(vid_hdr, 0xFF, UBI_VID_HDR_SIZE)) {
+			/* The physical eraseblock is supposedly free */
+
+			/*
+			 * The below is just a paranoid check, it has to be
+			 * compiled out if paranoid checks are disabled.
+			 */
+			err = paranoid_check_all_ff(ubi, pnum, ubi->leb_start,
+						    ubi->leb_size);
+			if (err)
+				return err > 0 ? UBI_IO_BAD_VID_HDR : err;
+
+			if (verbose)
+				ubi_warn("no VID header found at PEB %d, "
+					 "only 0xFF bytes", pnum);
+			return UBI_IO_PEB_FREE;
+		}
+
+		/*
+		 * This is not a valid VID 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_VID_HDR_MAGIC);
+			ubi_dbg_dump_vid_hdr(vid_hdr);
+		}
+		return UBI_IO_BAD_VID_HDR;
+	}
+
+	crc = crc32(UBI_CRC32_INIT, vid_hdr, UBI_VID_HDR_SIZE_CRC);
+	hdr_crc = ubi32_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_dbg_dump_vid_hdr(vid_hdr);
+		}
+		return UBI_IO_BAD_VID_HDR;
+	}
+
+	/* Validate the VID header that we have just read */
+	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;
+}
+
+/**
+ * ubi_io_write_vid_hdr - write a volume identifier header.
+ * @ubi: UBI device description object
+ * @pnum: the physical eraseblock number to write to
+ * @vid_hdr: the volume identifier header to write
+ *
+ * This function writes the volume identifier header described by @vid_hdr to
+ * physical eraseblock @pnum. This function automatically fills the
+ * @vid_hdr->magic and the @vid_hdr->version fields, as well as calculates
+ * header CRC checksum and stores it at vid_hdr->hdr_crc.
+ *
+ * This function returns zero in case of success and a negative error code in
+ * case of failure. If %-EIO is returned, the physical eraseblock probably went
+ * bad.
+ */
+int ubi_io_write_vid_hdr(const 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 = paranoid_check_peb_ec_hdr(ubi, pnum);
+	if (err)
+		return err > 0 ? -EINVAL: err;
+
+	vid_hdr->magic = cpu_to_ubi32(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_ubi32(crc);
+
+	err = paranoid_check_vid_hdr(ubi, pnum, vid_hdr);
+	if (err)
+		return -EINVAL;
+
+	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;
+}
+
+#ifdef CONFIG_MTD_UBI_DEBUG_PARANOID
+
+/**
+ * paranoid_check_not_bad - ensure that a physical eraseblock is not bad.
+ * @ubi: UBI device description object
+ * @pnum: physical eraseblock number to check
+ *
+ * This function returns zero if the physical eraseblock is good, a positive
+ * number if it is bad and a negative error code if an error occurred.
+ */
+static int paranoid_check_not_bad(const struct ubi_device *ubi, int pnum)
+{
+	int err;
+
+	err = ubi_io_is_bad(ubi, pnum);
+	if (!err)
+		return err;
+
+	ubi_err("paranoid check failed for PEB %d", pnum);
+	ubi_dbg_dump_stack();
+	return err;
+}
+
+/**
+ * paranoid_check_ec_hdr - check if an erase counter header is all right.
+ * @ubi: UBI device description object
+ * @pnum: physical eraseblock number the erase counter header belongs to
+ * @ec_hdr: the erase counter header to check
+ *
+ * This function returns zero if the erase counter header contains valid
+ * values, and %1 if not.
+ */
+static int paranoid_check_ec_hdr(const struct ubi_device *ubi, int pnum,
+				 const struct ubi_ec_hdr *ec_hdr)
+{
+	int err;
+	uint32_t magic;
+
+	magic = ubi32_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("paranoid check failed for PEB %d", pnum);
+		goto fail;
+	}
+
+	return 0;
+
+fail:
+	ubi_dbg_dump_ec_hdr(ec_hdr);
+	ubi_dbg_dump_stack();
+	return 1;
+}
+
+/**
+ * paranoid_check_peb_ec_hdr - check that the erase counter header of a
+ * physical eraseblock is in-place and is all right.
+ * @ubi: UBI device description object
+ * @pnum: the physical eraseblock number to check
+ *
+ * This function returns zero if the erase counter header is all right, %1 if
+ * not, and a negative error code if an error occurred.
+ */
+static int paranoid_check_peb_ec_hdr(const struct ubi_device *ubi, int pnum)
+{
+	int err;
+	uint32_t crc, hdr_crc;
+	struct ubi_ec_hdr *ec_hdr;
+
+	ec_hdr = kzalloc(ubi->ec_hdr_alsize, GFP_KERNEL);
+	if (!ec_hdr)
+		return -ENOMEM;
+
+	err = ubi_io_read(ubi, ec_hdr, pnum, 0, UBI_EC_HDR_SIZE);
+	if (err && err != UBI_IO_BITFLIPS && err != -EBADMSG)
+		goto exit;
+
+	crc = crc32(UBI_CRC32_INIT, ec_hdr, UBI_EC_HDR_SIZE_CRC);
+	hdr_crc = ubi32_to_cpu(ec_hdr->hdr_crc);
+	if (hdr_crc != crc) {
+		ubi_err("bad CRC, calculated %#08x, read %#08x", crc, hdr_crc);
+		ubi_err("paranoid check failed for PEB %d", pnum);
+		ubi_dbg_dump_ec_hdr(ec_hdr);
+		ubi_dbg_dump_stack();
+		err = 1;
+		goto exit;
+	}
+
+	err = paranoid_check_ec_hdr(ubi, pnum, ec_hdr);
+
+exit:
+	kfree(ec_hdr);
+	return err;
+}
+
+/**
+ * paranoid_check_vid_hdr - check that a volume identifier header is all right.
+ * @ubi: UBI device description object
+ * @pnum: physical eraseblock number the volume identifier header belongs to
+ * @vid_hdr: the volume identifier header to check
+ *
+ * This function returns zero if the volume identifier header is all right, and
+ * %1 if not.
+ */
+static int paranoid_check_vid_hdr(const struct ubi_device *ubi, int pnum,
+				  const struct ubi_vid_hdr *vid_hdr)
+{
+	int err;
+	uint32_t magic;
+
+	magic = ubi32_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("paranoid check failed for PEB %d", pnum);
+		goto fail;
+	}
+
+	return err;
+
+fail:
+	ubi_err("paranoid check failed for PEB %d", pnum);
+	ubi_dbg_dump_vid_hdr(vid_hdr);
+	ubi_dbg_dump_stack();
+	return 1;
+
+}
+
+/**
+ * paranoid_check_peb_vid_hdr - check that the volume identifier header of a
+ * physical eraseblock is in-place and is all right.
+ * @ubi: UBI device description object
+ * @pnum: the physical eraseblock number to check
+ *
+ * This function returns zero if the volume identifier header is all right,
+ * %1 if not, and a negative error code if an error occurred.
+ */
+static int paranoid_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;
+
+	vid_hdr = ubi_zalloc_vid_hdr(ubi);
+	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 && err != -EBADMSG)
+		goto exit;
+
+	crc = crc32(UBI_CRC32_INIT, vid_hdr, UBI_EC_HDR_SIZE_CRC);
+	hdr_crc = ubi32_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("paranoid check failed for PEB %d", pnum);
+		ubi_dbg_dump_vid_hdr(vid_hdr);
+		ubi_dbg_dump_stack();
+		err = 1;
+		goto exit;
+	}
+
+	err = paranoid_check_vid_hdr(ubi, pnum, vid_hdr);
+
+exit:
+	ubi_free_vid_hdr(ubi, vid_hdr);
+	return err;
+}
+
+/**
+ * paranoid_check_all_ff - check that a region of flash is empty.
+ * @ubi: UBI device description object
+ * @pnum: the physical eraseblock number to check
+ * @offset: the starting offset within the physical eraseblock to check
+ * @len: the length of the region to check
+ *
+ * This function returns zero if only 0xFF bytes are present at offset
+ * @offset of the physical eraseblock @pnum, %1 if not, and a negative error
+ * code if an error occurred.
+ */
+static int paranoid_check_all_ff(const 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;
+
+	buf = kzalloc(len, GFP_KERNEL);
+	if (!buf)
+		return -ENOMEM;
+
+	err = ubi->mtd->read(ubi->mtd, addr, len, &read, buf);
+	if (err && err != -EUCLEAN) {
+		ubi_err("error %d while reading %d bytes from PEB %d:%d, "
+			"read %zd bytes", err, len, pnum, offset, read);
+		goto error;
+	}
+
+	err = 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;
+	}
+
+	kfree(buf);
+	return 0;
+
+fail:
+	ubi_err("paranoid check failed for PEB %d", pnum);
+	dbg_msg("hex dump of the %d-%d region", offset, offset + len);
+	ubi_dbg_hexdump(buf, len);
+	err = 1;
+error:
+	ubi_dbg_dump_stack();
+	kfree(buf);
+	return err;
+}
+
+#endif /* CONFIG_MTD_UBI_DEBUG_PARANOID */