/src/util-linux/libblkid/src/probe.c

Source
/*
 * Low-level libblkid probing API
 *
 * Copyright (C) 2008-2009 Karel Zak <kzak@redhat.com>
 *
 * This file may be redistributed under the terms of the
 * GNU Lesser General Public License.
 */

/**
 * SECTION: lowprobe
 * @title: Low-level probing
 * @short_description: low-level prober initialization
 *
 * The low-level probing routines always and directly read information from
 * the selected (see blkid_probe_set_device()) device.
 *
 * The probing routines are grouped together into separate chains. Currently,
 * the library provides superblocks, partitions and topology chains.
 *
 * The probing routines is possible to filter (enable/disable) by type (e.g.
 * fstype "vfat" or partype "gpt") or by usage flags (e.g. BLKID_USAGE_RAID).
 * These filters are per-chain. Note that always when you touch the chain
 * filter the current probing position is reset and probing starts from
 * scratch.  It means that the chain filter should not be modified during
 * probing, for example in loop where you call blkid_do_probe().
 *
 * For more details see the chain specific documentation.
 *
 * The low-level API provides two ways how access to probing results.
 *
 *   1. The NAME=value (tag) interface. This interface is older and returns all data
 *      as strings. This interface is generic for all chains.
 *
 *   2. The binary interfaces. These interfaces return data in the native formats.
 *      The interface is always specific to the probing chain.
 *
 *  Note that the previous probing result (binary or NAME=value) is always
 *  zeroized when a chain probing function is called. For example:
 *
 * <informalexample>
 *   <programlisting>
 *     blkid_probe_enable_partitions(pr, TRUE);
 *     blkid_probe_enable_superblocks(pr, FALSE);
 *
 *     blkid_do_safeprobe(pr);
 *   </programlisting>
 * </informalexample>
 *
 * overwrites the previous probing result for the partitions chain, the superblocks
 * result is not modified.
 */

/**
 * SECTION: lowprobe-tags
 * @title: Low-level tags
 * @short_description: generic NAME=value interface.
 *
 * The probing routines inside the chain are mutually exclusive by default --
 * only few probing routines are marked as "tolerant". The "tolerant" probing
 * routines are used for filesystem which can share the same device with any
 * other filesystem. The blkid_do_safeprobe() checks for the "tolerant" flag.
 *
 * The SUPERBLOCKS chain is enabled by default. The all others chains is
 * necessary to enable by blkid_probe_enable_'CHAINNAME'(). See chains specific
 * documentation.
 *
 * The blkid_do_probe() function returns a result from only one probing
 * routine, and the next call from the next probing routine. It means you need
 * to call the function in loop, for example:
 *
 * <informalexample>
 *   <programlisting>
 *  while((blkid_do_probe(pr) == BLKID_PROBE_OK)
 *    ... use result ...
 *   </programlisting>
 * </informalexample>
 *
 * The blkid_do_safeprobe() is the same as blkid_do_probe(), but returns only
 * first probing result for every enabled chain. This function checks for
 * ambivalent results (e.g. more "intolerant" filesystems superblocks on the
 * device).
 *
 * The probing result is set of NAME=value pairs (the NAME is always unique).
 */

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <ctype.h>
#include <sys/mman.h>
#include <sys/types.h>
#ifdef HAVE_LINUX_CDROM_H
#include <linux/cdrom.h>
#endif
#ifdef HAVE_LINUX_BLKZONED_H
#include <linux/blkzoned.h>
#endif
#ifdef HAVE_SYS_STAT_H
#include <sys/stat.h>
#endif
#ifdef HAVE_ERRNO_H
#include <errno.h>
#endif
#ifdef HAVE_LINUX_FD_H
#include <linux/fd.h>
#endif
#include <inttypes.h>
#include <stdint.h>
#include <stdarg.h>
#include <limits.h>
#ifdef HAVE_OPAL_GET_STATUS
#include <linux/sed-opal.h>
#endif

#include "blkidP.h"
#include "all-io.h"
#include "sysfs.h"
#include "strutils.h"
#include "list.h"
#include "fileutils.h"

/*
 * All supported chains
 */
static const struct blkid_chaindrv *const chains_drvs[] = {
  [BLKID_CHAIN_SUBLKS] = &superblocks_drv,
  [BLKID_CHAIN_TOPLGY] = &topology_drv,
  [BLKID_CHAIN_PARTS] = &partitions_drv
};

static void blkid_probe_reset_values(blkid_probe pr);

/**
 * blkid_new_probe:
 *
 * Returns: a pointer to the newly allocated probe struct or NULL in case of error.
 */
blkid_probe blkid_new_probe(void)
{
  int i;
  blkid_probe pr;

  pr = calloc(1, sizeof(struct blkid_struct_probe));
  if (!pr)
    return NULL;

  DBG(LOWPROBE, ul_debug("allocate a new probe"));

  /* initialize chains */
  for (i = 0; i < BLKID_NCHAINS; i++) {
    pr->chains[i].driver = chains_drvs[i];
    pr->chains[i].flags = chains_drvs[i]->dflt_flags;
    pr->chains[i].enabled = chains_drvs[i]->dflt_enabled;
  }
  INIT_LIST_HEAD(&pr->buffers);
  INIT_LIST_HEAD(&pr->prunable_buffers);
  INIT_LIST_HEAD(&pr->values);
  INIT_LIST_HEAD(&pr->hints);
  return pr;
}

/*
 * Clone @parent, the new clone shares all, but except:
 *
 *  - probing result
 *  - buffers if another device (or offset) is set to the prober
 */
blkid_probe blkid_clone_probe(blkid_probe parent)
{
  blkid_probe pr;

  if (!parent)
    return NULL;

  DBG(LOWPROBE, ul_debug("allocate a probe clone"));

  pr = blkid_new_probe();
  if (!pr)
    return NULL;

  pr->fd = parent->fd;
  pr->off = parent->off;
  pr->size = parent->size;
  pr->io_size = parent->io_size;
  pr->devno = parent->devno;
  pr->disk_devno = parent->disk_devno;
  pr->blkssz = parent->blkssz;
  pr->flags = parent->flags;
  pr->zone_size = parent->zone_size;
  pr->parent = parent;

  pr->flags &= ~BLKID_FL_PRIVATE_FD;

  if (parent->vfs) {
    pr->vfs = ul_vfs_copy(parent->vfs);
    if (!pr->vfs) {
      blkid_free_probe(pr);
      return NULL;
    }
  }

  return pr;
}

/**
 * blkid_probe_open_device:
 * @pr: probe
 * @filename: device or regular file
 * @flags: open(2) flags or 0 for default (O_RDONLY|O_CLOEXEC|O_NONBLOCK)
 *
 * Opens the @filename and assigns it to the probe. This is equivalent to
 * calling open() and blkid_probe_set_device(), but uses VFS operations
 * if previously set by blkid_probe_set_vfs().
 *
 * This allows probe setup before the device is opened:
 *
 *   blkid_new_probe() → blkid_probe_set_vfs() → blkid_probe_open_device()
 *
 * The @filename is closed by blkid_free_probe() or by the
 * blkid_probe_set_device() call.
 *
 * Since: 2.43
 *
 * Returns: 0 on success, or <0 in case of error.
 */
int blkid_probe_open_device(blkid_probe pr, const char *filename, int flags)
{
  int fd;
  struct stat sb;

  if (stat(filename, &sb) == 0 && S_ISBLK(sb.st_mode) &&
      sysfs_devno_is_dm_hidden(sb.st_rdev, NULL, pr->vfs)) {
    DBG(LOWPROBE, ul_debug("ignore hidden device mapper device"));
    errno = EINVAL;
    return -EINVAL;
  }

  if (!flags)
    flags = O_RDONLY | O_CLOEXEC | O_NONBLOCK;

  fd = ul_vfs_open(pr->vfs, filename, flags, 0);
  if (fd < 0)
    return -errno;

  if (blkid_probe_set_device(pr, fd, 0, 0)) {
    ul_vfs_close(pr->vfs, fd);
    return -errno ? -errno : -EINVAL;
  }

  pr->flags |= BLKID_FL_PRIVATE_FD;
  return 0;
}

/**
 * blkid_new_probe_from_filename:
 * @filename: device or regular file
 *
 * This function is same as call open(filename), blkid_new_probe() and
 * blkid_probe_set_device(pr, fd, 0, 0).
 *
 * The @filename is closed by blkid_free_probe() or by the
 * blkid_probe_set_device() call.
 *
 * Returns: a pointer to the newly allocated probe struct or NULL in case of
 * error.
 */
blkid_probe blkid_new_probe_from_filename(const char *filename)
{
  blkid_probe pr;

  pr = blkid_new_probe();
  if (!pr)
    return NULL;

  if (blkid_probe_open_device(pr, filename, 0)) {
    blkid_free_probe(pr);
    return NULL;
  }

  return pr;
}

/**
 * blkid_free_probe:
 * @pr: probe
 *
 * Deallocates the probe struct, buffers and all allocated
 * data that are associated with this probing control struct.
 */
void blkid_free_probe(blkid_probe pr)
{
  int i;

  if (!pr)
    return;

  for (i = 0; i < BLKID_NCHAINS; i++) {
    struct blkid_chain *ch = &pr->chains[i];

    if (ch->driver->free_data)
      ch->driver->free_data(pr, ch->data);
    free(ch->fltr);
    ch->fltr = NULL;
  }

  if ((pr->flags & BLKID_FL_PRIVATE_FD) && pr->fd >= 0)
    ul_vfs_close(pr->vfs, pr->fd);
  blkid_probe_reset_buffers(pr);
  blkid_probe_reset_values(pr);
  blkid_probe_reset_hints(pr);
  blkid_free_probe(pr->disk_probe);

  DBG(LOWPROBE, ul_debug("free probe"));
  free(pr->vfs);
  free(pr);
}

void blkid_probe_free_value(struct blkid_prval *v)
{
  if (!v)
    return;

  list_del(&v->prvals);
  free(v->data);

  DBG(LOWPROBE, ul_debug(" free value %s", v->name));
  free(v);
}

/*
 * Removes chain values from probing result.
 */
void blkid_probe_chain_reset_values(blkid_probe pr, struct blkid_chain *chn)
{

  struct list_head *p, *pnext;

  if (list_empty(&pr->values))
    return;

  DBG(LOWPROBE, ul_debug("Resetting %s values", chn->driver->name));

  list_for_each_safe(p, pnext, &pr->values) {
    struct blkid_prval *v = list_entry(p,
            struct blkid_prval, prvals);

    if (v->chain == chn)
      blkid_probe_free_value(v);
  }
}

static void blkid_probe_chain_reset_position(struct blkid_chain *chn)
{
  chn->idx = -1;
}

/*
 * Move chain values from probing result to @vals
 */
int blkid_probe_chain_save_values(blkid_probe pr, struct blkid_chain *chn,
        struct list_head *vals)
{
  struct list_head *p, *pnext;
  struct blkid_prval *v;

  DBG(LOWPROBE, ul_debug("saving %s values", chn->driver->name));

  list_for_each_safe(p, pnext, &pr->values) {

    v = list_entry(p, struct blkid_prval, prvals);
    if (v->chain != chn)
      continue;

    list_del_init(&v->prvals);
    list_add_tail(&v->prvals, vals);
  }
  return 0;
}

/*
 * Appends values from @vals to the probing result
 */
void blkid_probe_append_values_list(blkid_probe pr, struct list_head *vals)
{
  DBG(LOWPROBE, ul_debug("appending values"));

  list_splice(vals, &pr->values);
  INIT_LIST_HEAD(vals);
}


void blkid_probe_free_values_list(struct list_head *vals)
{
  if (!vals)
    return;

  DBG(LOWPROBE, ul_debug("freeing values list"));

  while (!list_empty(vals)) {
    struct blkid_prval *v = list_entry(vals->next, struct blkid_prval, prvals);
    blkid_probe_free_value(v);
  }
}

struct blkid_chain *blkid_probe_get_chain(blkid_probe pr)
{
  return pr->cur_chain;
}

static const char *blkid_probe_get_probername(blkid_probe pr)
{
  struct blkid_chain *chn = blkid_probe_get_chain(pr);

  if (chn && chn->idx >= 0 && (unsigned)chn->idx < chn->driver->nidinfos)
    return chn->driver->idinfos[chn->idx]->name;

  return NULL;
}

void *blkid_probe_get_binary_data(blkid_probe pr, struct blkid_chain *chn)
{
  int rc, org_prob_flags;
  struct blkid_chain *org_chn;

  /* save the current setting -- the binary API has to be completely
   * independent on the current probing status
   */
  org_chn = pr->cur_chain;
  org_prob_flags = pr->prob_flags;

  pr->cur_chain = chn;
  pr->prob_flags = 0;
  chn->binary = TRUE;
  blkid_probe_chain_reset_position(chn);

  rc = chn->driver->probe(pr, chn);

  chn->binary = FALSE;
  blkid_probe_chain_reset_position(chn);

  /* restore the original setting
   */
  pr->cur_chain = org_chn;
  pr->prob_flags = org_prob_flags;

  if (rc != 0)
    return NULL;

  DBG(LOWPROBE, ul_debug("returning %s binary data", chn->driver->name));
  return chn->data;
}


/**
 * blkid_reset_probe:
 * @pr: probe
 *
 * Zeroize probing results and resets the current probing (this has impact to
 * blkid_do_probe() only). This function does not touch probing filters and
 * keeps assigned device.
 */
void blkid_reset_probe(blkid_probe pr)
{
  int i;

  blkid_probe_reset_values(pr);
  blkid_probe_set_wiper(pr, 0, 0);

  pr->cur_chain = NULL;

  for (i = 0; i < BLKID_NCHAINS; i++)
    blkid_probe_chain_reset_position(&pr->chains[i]);
}

/***
static int blkid_probe_dump_filter(blkid_probe pr, int chain)
{
  struct blkid_chain *chn;
  int i;

  if (!pr || chain < 0 || chain >= BLKID_NCHAINS)
    return -1;

  chn = &pr->chains[chain];

  if (!chn->fltr)
    return -1;

  for (i = 0; i < chn->driver->nidinfos; i++) {
    const struct blkid_idinfo *id = chn->driver->idinfos[i];

    DBG(LOWPROBE, ul_debug("%d: %s: %s",
      i,
      id->name,
      blkid_bmp_get_item(chn->fltr, i)
        ? "disabled" : "enabled <--"));
  }
  return 0;
}
***/

/*
 * Returns properly initialized chain filter
 */
unsigned long *blkid_probe_get_filter(blkid_probe pr, int chain, int create)
{
  struct blkid_chain *chn;

  if (chain < 0 || chain >= BLKID_NCHAINS)
    return NULL;

  chn = &pr->chains[chain];

  /* always when you touch the chain filter all indexes are reset and
   * probing starts from scratch
   */
  blkid_probe_chain_reset_position(chn);
  pr->cur_chain = NULL;

  if (!chn->driver->has_fltr || (!chn->fltr && !create))
    return NULL;

  if (!chn->fltr)
    chn->fltr = calloc(1, blkid_bmp_nbytes(chn->driver->nidinfos));
  else
    memset(chn->fltr, 0, blkid_bmp_nbytes(chn->driver->nidinfos));

  /* blkid_probe_dump_filter(pr, chain); */
  return chn->fltr;
}

/*
 * Generic private functions for filter setting
 */
int __blkid_probe_invert_filter(blkid_probe pr, int chain)
{
  size_t i;
  struct blkid_chain *chn;

  chn = &pr->chains[chain];

  if (!chn->driver->has_fltr || !chn->fltr)
    return -1;

  for (i = 0; i < blkid_bmp_nwords(chn->driver->nidinfos); i++)
    chn->fltr[i] = ~chn->fltr[i];

  DBG(LOWPROBE, ul_debug("probing filter inverted"));
  /* blkid_probe_dump_filter(pr, chain); */
  return 0;
}

int __blkid_probe_reset_filter(blkid_probe pr, int chain)
{
  return blkid_probe_get_filter(pr, chain, FALSE) ? 0 : -1;
}

int __blkid_probe_filter_types(blkid_probe pr, int chain, int flag, char *names[])
{
  unsigned long *fltr;
  struct blkid_chain *chn;
  size_t i;

  fltr = blkid_probe_get_filter(pr, chain, TRUE);
  if (!fltr)
    return -1;

  chn = &pr->chains[chain];

  for (i = 0; i < chn->driver->nidinfos; i++) {
    int has = 0;
    const struct blkid_idinfo *id = chn->driver->idinfos[i];
    char **n;

    for (n = names; *n; n++) {
      if (!strcmp(id->name, *n)) {
        has = 1;
        break;
      }
    }
    if (has) {
      if (flag & BLKID_FLTR_NOTIN)
        blkid_bmp_set_item(fltr, i);
    } else if (flag & BLKID_FLTR_ONLYIN)
      blkid_bmp_set_item(fltr, i);
  }

  DBG(LOWPROBE, ul_debug("%s: a new probing type-filter initialized",
    chn->driver->name));
  /* blkid_probe_dump_filter(pr, chain); */
  return 0;
}

static void remove_buffer(struct blkid_bufinfo *bf)
{
  list_del(&bf->bufs);

  DBG(BUFFER, ul_debug(" remove buffer: [off=%"PRIu64", len=%"PRIu64"]",
        bf->off, bf->len));
  munmap(bf->data, bf->len);
  free(bf);
}

static struct blkid_bufinfo *read_buffer(blkid_probe pr, uint64_t real_off, uint64_t len)
{
  ssize_t ret;
  struct blkid_bufinfo *bf = NULL;

  if (ul_vfs_lseek(pr->vfs, pr->fd, real_off, SEEK_SET) == (off_t) -1) {
    errno = 0;
    return NULL;
  }

  /* someone trying to overflow some buffers? */
  if (len > ULONG_MAX - sizeof(struct blkid_bufinfo)) {
    errno = ENOMEM;
    return NULL;
  }

  /* allocate info and space for data by one malloc call */
  bf = calloc(1, sizeof(struct blkid_bufinfo));
  if (!bf) {
    errno = ENOMEM;
    return NULL;
  }

  bf->data = mmap(NULL, len, PROT_READ | PROT_WRITE,
      MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
  if (bf->data == MAP_FAILED) {
    free(bf);
    errno = ENOMEM;
    return NULL;
  }

  bf->len = len;
  bf->off = real_off;
  INIT_LIST_HEAD(&bf->bufs);

  DBG(LOWPROBE, ul_debug("\tread: off=%"PRIu64" len=%"PRIu64"",
                         real_off, len));

  ret = ul_vfs_read(pr->vfs, pr->fd, bf->data, len);
  if (ret != (ssize_t) len) {
    DBG(LOWPROBE, ul_debug("\tread failed: %m"));
    remove_buffer(bf);

    /* I/O errors on CDROMs are non-fatal to work with hybrid
     * audio+data disks */
    if (ret >= 0 || blkid_probe_is_cdrom(pr) || blkdid_probe_is_opal_locked(pr))
      errno = 0;

    return NULL;
  }

  if (mprotect(bf->data, len, PROT_READ))
    DBG(LOWPROBE, ul_debug("\tmprotect failed: %m"));

  return bf;
}

/*
 * Search in buffers we already have in memory
 */
static struct blkid_bufinfo *get_cached_buffer(blkid_probe pr, uint64_t off, uint64_t len)
{
  uint64_t real_off = pr->off + off;
  struct list_head *p;

  list_for_each(p, &pr->buffers) {
    struct blkid_bufinfo *x =
        list_entry(p, struct blkid_bufinfo, bufs);

    if (real_off >= x->off && real_off + len <= x->off + x->len) {
      DBG(BUFFER, ul_debug("\treuse: off=%"PRIu64" len=%"PRIu64" (for off=%"PRIu64" len=%"PRIu64")",
            x->off, x->len, real_off, len));
      return x;
    }
  }
  return NULL;
}

/*
 * Mark smaller buffers that can be satisfied by bf as prunable
 */
static void mark_prunable_buffers(blkid_probe pr, const struct blkid_bufinfo *bf)
{
  struct list_head *p, *next;

  list_for_each_safe(p, next, &pr->buffers) {
    struct blkid_bufinfo *x =
        list_entry(p, struct blkid_bufinfo, bufs);

    if (bf->off <= x->off && bf->off + bf->len >= x->off + x->len) {
      list_del(&x->bufs);
      list_add(&x->bufs, &pr->prunable_buffers);
    }
  }
}

/*
 * Remove buffers that are marked as prunable
 */
void blkid_probe_prune_buffers(blkid_probe pr)
{
  struct list_head *p, *next;

  list_for_each_safe(p, next, &pr->prunable_buffers) {
    struct blkid_bufinfo *x =
        list_entry(p, struct blkid_bufinfo, bufs);

    remove_buffer(x);
  }
}

/*
 * Zeroize in-memory data in already read buffer. The next blkid_probe_get_buffer()
 * will return modified buffer. This is usable when you want to call the same probing
 * function more than once and hide previously detected magic strings.
 *
 * See blkid_probe_hide_range().
 */
static int hide_buffer(blkid_probe pr, uint64_t off, uint64_t len)
{
  uint64_t real_off = pr->off + off;
  struct list_head *p;
  int ct = 0;

  if (UINT64_MAX - len < off) {
    DBG(BUFFER, ul_debug("\t  hide-buffer overflow (ignore)"));
    return -EINVAL;
  }

  list_for_each(p, &pr->buffers) {
    struct blkid_bufinfo *x =
      list_entry(p, struct blkid_bufinfo, bufs);
    unsigned char *data;

    if (real_off >= x->off && real_off + len <= x->off + x->len) {

      assert(x->off <= real_off);
      assert(x->off + x->len >= real_off + len);

      data = real_off ? x->data + (real_off - x->off) : x->data;

      DBG(BUFFER, ul_debug("\thiding: off=%"PRIu64" len=%"PRIu64,
            off, len));
      mprotect(x->data, x->len, PROT_READ | PROT_WRITE);
      memset(data, 0, len);
      mprotect(x->data, x->len, PROT_READ);
      ct++;
    }
  }
  return ct == 0 ? -EINVAL : 0;
}


/*
 * Note that @off is offset within probing area, the probing area is defined by
 * pr->off and pr->size.
 */
const unsigned char *blkid_probe_get_buffer(blkid_probe pr, uint64_t off, uint64_t len)
{
  struct blkid_bufinfo *bf = NULL;
  uint64_t real_off, bias, len_align;

  bias = off % pr->io_size;
  off -= bias;
  len += bias;

  if (len % pr->io_size) {
    len_align = pr->io_size - (len % pr->io_size);

    if (pr->off + off + len + len_align <= pr->size)
      len += len_align;
  }

  real_off = pr->off + off;

  /*
  DBG(BUFFER, ul_debug("\t>>>> off=%ju, real-off=%ju (probe <%ju..%ju>, len=%ju",
        off, real_off, pr->off, pr->off + pr->size, len));
  */
  if (pr->size == 0 || pr->io_size == 0) {
    errno = EINVAL;
    return NULL;
  }

  if (UINT64_MAX - len < off || UINT64_MAX - len < real_off) {
    DBG(BUFFER, ul_debug("\t  read-buffer overflow (ignore)"));
    return NULL;
  }

  if (len > 8388608 /* 8 Mib */ ) {
    DBG(BUFFER, ul_debug("\t  too large read request (ignore)"));
    return NULL;
  }

  if (len == 0
      || (!S_ISCHR(pr->mode) && (pr->size < off || pr->size < len))
      || (!S_ISCHR(pr->mode) && (pr->off + pr->size < real_off + len))) {
    DBG(BUFFER, ul_debug("\t  read-buffer out of probing area (ignore)"));
    errno = 0;
    return NULL;
  }

  if (pr->parent &&
      pr->parent->devno == pr->devno &&
      pr->parent->off <= pr->off &&
      pr->parent->off + pr->parent->size >= pr->off + pr->size) {
    /*
     * This is a cloned prober and points to the same area as
     * parent. Let's use parent's buffers.
     *
     * Note that pr->off (and pr->parent->off) is always from the
     * begin of the device.
     */
    return blkid_probe_get_buffer(pr->parent,
        pr->off + off + bias - pr->parent->off, len);
  }

  /* try buffers we already have in memory or read from device */
  bf = get_cached_buffer(pr, off, len);
  if (!bf) {
    bf = read_buffer(pr, real_off, len);
    if (!bf)
      return NULL;

    mark_prunable_buffers(pr, bf);
    list_add_tail(&bf->bufs, &pr->buffers);
  }

  assert(bf->off <= real_off);
  assert(bf->off + bf->len >= real_off + len);

  errno = 0;
  return real_off ? bf->data + (real_off - bf->off + bias) : bf->data + bias;
}

#ifdef O_DIRECT
/*
 * This is blkid_probe_get_buffer with the read done as an O_DIRECT operation.
 * Note that @off is offset within probing area, the probing area is defined by
 * pr->off and pr->size.
 */
const unsigned char *blkid_probe_get_buffer_direct(blkid_probe pr, uint64_t off, uint64_t len)
{
  const unsigned char *ret = NULL;
  int flags, rc, olderrno;

  flags = fcntl(pr->fd, F_GETFL);
  rc = fcntl(pr->fd, F_SETFL, flags | O_DIRECT);
  if (rc) {
    DBG(LOWPROBE, ul_debug("fcntl F_SETFL failed to set O_DIRECT"));
    errno = 0;
    return NULL;
  }
  ret = blkid_probe_get_buffer(pr, off, len);
  olderrno = errno;
  rc = fcntl(pr->fd, F_SETFL, flags);
  if (rc) {
    DBG(LOWPROBE, ul_debug("fcntl F_SETFL failed to clear O_DIRECT"));
    errno = olderrno;
  }
  return ret;
}
#endif

/**
 * blkid_probe_reset_buffers:
 * @pr: prober
 *
 * libblkid reuse all already read buffers from the device. The buffers may be
 * modified by blkid_probe_hide_range(). This function reset and free all
 * cached buffers. The next blkid_do_probe() will read all data from the
 * device.
 *
 * Since: 2.31
 *
 * Returns: <0 in case of failure, or 0 on success.
 */
int blkid_probe_reset_buffers(blkid_probe pr)
{
  uint64_t ct = 0, len = 0;

  pr->flags &= ~BLKID_FL_MODIF_BUFF;

  blkid_probe_prune_buffers(pr);

  if (list_empty(&pr->buffers))
    return 0;

  DBG(BUFFER, ul_debug("Resetting probing buffers"));

  while (!list_empty(&pr->buffers)) {
    struct blkid_bufinfo *bf = list_entry(pr->buffers.next,
            struct blkid_bufinfo, bufs);
    ct++;
    len += bf->len;

    remove_buffer(bf);
  }

  DBG(LOWPROBE, ul_debug(" buffers summary: %"PRIu64" bytes by %"PRIu64" read() calls",
      len, ct));

  INIT_LIST_HEAD(&pr->buffers);

  return 0;
}

/**
 * blkid_probe_hide_range:
 * @pr: prober
 * @off: start of the range
 * @len: size of the range
 *
 * This function modifies in-memory cached data from the device. The specified
 * range is zeroized. This is usable together with blkid_probe_step_back().
 * The next blkid_do_probe() will not see specified area.
 *
 * Note that this is usable for already (by library) read data, and this
 * function is not a way how to hide any large areas on your device.
 *
 * The function blkid_probe_reset_buffers() reverts all.
 *
 * Since: 2.31
 *
 * Returns: <0 in case of failure, or 0 on success.
 */
int blkid_probe_hide_range(blkid_probe pr, uint64_t off, uint64_t len)
{
  int rc = hide_buffer(pr, off, len);

  if (rc == 0)
    pr->flags |= BLKID_FL_MODIF_BUFF;
  return rc;
}


static void blkid_probe_reset_values(blkid_probe pr)
{
  if (list_empty(&pr->values))
    return;

  DBG(LOWPROBE, ul_debug("resetting results"));

  while (!list_empty(&pr->values)) {
    struct blkid_prval *v = list_entry(pr->values.next,
            struct blkid_prval, prvals);
    blkid_probe_free_value(v);
  }

  INIT_LIST_HEAD(&pr->values);
}

/*
 * Small devices need a special care.
 */
int blkid_probe_is_tiny(blkid_probe pr)
{
  return (pr->flags & BLKID_FL_TINY_DEV);
}

/*
 * CDROMs may fail when probed for RAID (last sector problem)
 */
int blkid_probe_is_cdrom(blkid_probe pr)
{
  return (pr->flags & BLKID_FL_CDROM_DEV);
}

int blkdid_probe_is_opal_locked(blkid_probe pr)
{
  if (!(pr->flags & BLKID_FL_OPAL_CHECKED)) {
    pr->flags |= BLKID_FL_OPAL_CHECKED;

#ifdef HAVE_OPAL_GET_STATUS
    ssize_t ret;
    struct opal_status st = { };
    int errsv = errno;

    /* If the device is locked with OPAL, we'll fail to read with I/O
     * errors when probing deep into the block device. */
    ret = ioctl(pr->fd, IOC_OPAL_GET_STATUS, &st);
    if (ret == 0 && (st.flags & OPAL_FL_LOCKED)) {
      pr->flags |= BLKID_FL_OPAL_LOCKED;
    }

    errno = errsv;
#endif
  }

  return (pr->flags & BLKID_FL_OPAL_LOCKED);
}

#ifdef CDROM_GET_CAPABILITY

static int is_sector_readable(blkid_probe pr, uint64_t sector)
{
  char buf[512];
  ssize_t sz;

  if (ul_vfs_lseek(pr->vfs, pr->fd, sector * 512, SEEK_SET) == (off_t) -1)
    goto failed;

  sz = ul_vfs_read(pr->vfs, pr->fd, buf, sizeof(buf));
  if (sz != (ssize_t) sizeof(buf))
    goto failed;

  return 1;
failed:
  DBG(LOWPROBE, ul_debug("CDROM: read sector %"PRIu64" failed %m", sector));
  errno = 0;
  return 0;
}

/*
 * Linux kernel reports (BLKGETSIZE) cdrom device size greater than area
 * readable by read(2). We have to reduce the probing area to avoid unwanted
 * I/O errors in probing functions. It seems that unreadable are always last 2
 * or 3 CD blocks (CD block size is 2048 bytes, it means 12 in 512-byte
 * sectors). Linux kernel reports (CDROM_LAST_WRITTEN) also location of last
 * written block, so we will reduce size based on it too.
 */
static void cdrom_size_correction(blkid_probe pr, uint64_t last_written)
{
  uint64_t n, nsectors = pr->size >> 9;

  if (last_written && nsectors > ((last_written+1) << 2))
    nsectors = (last_written+1) << 2;

  for (n = nsectors - 12; n < nsectors; n++) {
    if (!is_sector_readable(pr, n))
      goto failed;
  }

  DBG(LOWPROBE, ul_debug("CDROM: full size available"));
  return;
failed:
  /* 'n' is the failed sector, reduce device size to n-1; */
  DBG(LOWPROBE, ul_debug("CDROM: reduce size from %ju to %ju.",
        (uintmax_t) pr->size,
        (uintmax_t) n << 9));
  pr->size = n << 9;
}

#endif

static uint64_t blkid_get_io_size(int fd)
{
  static const int ioctls[] = {
#ifdef BLKIOOPT
    BLKIOOPT,
#endif
#ifdef BLKIOMIN
    BLKIOMIN,
#endif
#ifdef BLKBSZGET
    BLKBSZGET,
#endif
  };
  unsigned int s;
  size_t i;
  int r;

  for (i = 0; i < ARRAY_SIZE(ioctls); i++) {
    r = ioctl(fd, ioctls[i], &s);
    if (r == 0 && is_power_of_2(s) && s >= DEFAULT_SECTOR_SIZE)
      return min(s, 1U << 16);
  }

  return DEFAULT_SECTOR_SIZE;
}

/**
 * blkid_probe_set_device:
 * @pr: probe
 * @fd: device file descriptor
 * @off: begin of probing area
 * @size: size of probing area (zero means whole device/file)
 *
 * Assigns the device to probe control struct, resets internal buffers, resets
 * the current probing, and close previously associated device (if open by
 * libblkid).
 *
 * If @fd is < 0 than only resets the prober and returns 1. Note that
 * blkid_reset_probe() keeps the device associated with the prober, but
 * blkid_probe_set_device() does complete reset.
 *
 * Returns: -1 in case of failure, 0 on success and 1 on reset.
 */
int blkid_probe_set_device(blkid_probe pr, int fd,
    blkid_loff_t off, blkid_loff_t size)
{
  struct stat sb;
  uint64_t devsiz = 0;
  char *dm_uuid = NULL;
  int is_floppy = 0;

  blkid_reset_probe(pr);
  blkid_probe_reset_buffers(pr);

  if ((pr->flags & BLKID_FL_PRIVATE_FD) && pr->fd >= 0)
    ul_vfs_close(pr->vfs, pr->fd);

  if (pr->disk_probe) {
    blkid_free_probe(pr->disk_probe);
    pr->disk_probe = NULL;
  }

  pr->flags &= ~BLKID_FL_PRIVATE_FD;
  pr->flags &= ~BLKID_FL_TINY_DEV;
  pr->flags &= ~BLKID_FL_CDROM_DEV;
  pr->prob_flags = 0;
  pr->fd = fd;
  pr->off = (uint64_t) off;
  pr->size = 0;
  pr->io_size = DEFAULT_SECTOR_SIZE;
  pr->devno = 0;
  pr->disk_devno = 0;
  pr->mode = 0;
  pr->blkssz = 0;
  pr->wipe_off = 0;
  pr->wipe_size = 0;
  pr->wipe_chain = NULL;
  pr->zone_size = 0;

  if (fd < 0)
    return 1;


#if defined(POSIX_FADV_RANDOM) && defined(HAVE_POSIX_FADVISE)
  /* Disable read-ahead */
  posix_fadvise(fd, 0, 0, POSIX_FADV_RANDOM);
#endif
  if (fstat(fd, &sb))
    goto err;

  if (!S_ISBLK(sb.st_mode) && !S_ISCHR(sb.st_mode) && !S_ISREG(sb.st_mode)) {
    errno = EINVAL;
    goto err;
  }

  pr->mode = sb.st_mode;
  if (S_ISBLK(sb.st_mode) || S_ISCHR(sb.st_mode))
    pr->devno = sb.st_rdev;

  if (S_ISBLK(sb.st_mode)) {
    if (blkdev_get_size(fd, (unsigned long long *) &devsiz)) {
      DBG(LOWPROBE, ul_debug("failed to get device size"));
      goto err;
    }
  } else if (S_ISCHR(sb.st_mode)) {
    char buf[PATH_MAX];

    if (!sysfs_chrdev_devno_to_devname(sb.st_rdev, buf, sizeof(buf))
        || strncmp(buf, "ubi", 3) != 0) {
      DBG(LOWPROBE, ul_debug("no UBI char device"));
      errno = EINVAL;
      goto err;
    }
    devsiz = 1;   /* UBI devices are char... */
  } else if (S_ISREG(sb.st_mode))
    devsiz = sb.st_size; /* regular file */

  pr->size = size ? (uint64_t)size : devsiz;

  if (off && size == 0)
    /* only offset without size specified */
    pr->size -= (uint64_t) off;

  if (pr->off + pr->size > devsiz) {
    DBG(LOWPROBE, ul_debug("area specified by offset and size is bigger than device"));
    errno = EINVAL;
    goto err;
  }

  if (pr->size <= 1440 * 1024 && !S_ISCHR(sb.st_mode))
    pr->flags |= BLKID_FL_TINY_DEV;

#ifdef FDGETFDCSTAT
  if (S_ISBLK(sb.st_mode)) {
    /*
     * Re-open without O_NONBLOCK for floppy device.
     *
     * Since kernel commit c7e9d0020361f4308a70cdfd6d5335e273eb8717
     * floppy drive works bad when opened with O_NONBLOCK.
     */
    struct floppy_fdc_state flst;

    if (ioctl(fd, FDGETFDCSTAT, &flst) >= 0) {
      int flags = fcntl(fd, F_GETFL, 0);

      if (flags < 0)
        goto err;
      if (flags & O_NONBLOCK) {
        flags &= ~O_NONBLOCK;

        fd = ul_reopen(fd, flags | O_CLOEXEC);
        if (fd < 0)
          goto err;

        pr->flags |= BLKID_FL_PRIVATE_FD;
        pr->fd = fd;
      }
      is_floppy = 1;
    }
    errno = 0;
  }
#endif
  if (S_ISBLK(sb.st_mode) &&
      !is_floppy &&
      sysfs_devno_is_dm_private(sb.st_rdev, &dm_uuid, pr->vfs)) {
    DBG(LOWPROBE, ul_debug("ignore private device mapper device"));
    pr->flags |= BLKID_FL_NOSCAN_DEV;
  }

#ifdef CDROM_GET_CAPABILITY
  else if (S_ISBLK(sb.st_mode) &&
      !blkid_probe_is_tiny(pr) &&
      !dm_uuid &&
      !is_floppy &&
      blkid_probe_is_wholedisk(pr)) {

    long last_written = 0;

    /*
     * pktcdvd.ko accepts only these ioctls:
     *   CDROMEJECT CDROMMULTISESSION CDROMREADTOCENTRY
     *   CDROM_LAST_WRITTEN CDROM_SEND_PACKET SCSI_IOCTL_SEND_COMMAND
     * So CDROM_GET_CAPABILITY cannot be used for detecting pktcdvd
     * devices. But CDROM_GET_CAPABILITY and CDROM_DRIVE_STATUS are
     * fast so use them for detecting if medium is present. In any
     * case use last written block form CDROM_LAST_WRITTEN.
     */

    if (ioctl(fd, CDROM_GET_CAPABILITY, NULL) >= 0) {
# ifdef CDROM_DRIVE_STATUS
      switch (ioctl(fd, CDROM_DRIVE_STATUS, CDSL_CURRENT)) {
      case CDS_TRAY_OPEN:
      case CDS_NO_DISC:
        errno = ENOMEDIUM;
        goto err;
      }
# endif
      pr->flags |= BLKID_FL_CDROM_DEV;
    }

# ifdef CDROM_LAST_WRITTEN
    if (ioctl(fd, CDROM_LAST_WRITTEN, &last_written) == 0) {
      pr->flags |= BLKID_FL_CDROM_DEV;
    } else {
      if (errno == ENOMEDIUM)
        goto err;
    }
# endif

    if (pr->flags & BLKID_FL_CDROM_DEV) {
      cdrom_size_correction(pr, last_written);

# ifdef CDROMMULTISESSION
      if (!pr->off && blkid_probe_get_hint(pr, "session_offset", NULL) < 0) {
        struct cdrom_multisession multisession = { .addr_format = CDROM_LBA };
        if (ioctl(fd, CDROMMULTISESSION, &multisession) == 0 && multisession.xa_flag)
          blkid_probe_set_hint(pr, "session_offset", (multisession.addr.lba << 11));
      }
# endif
    }
  }
#endif
  free(dm_uuid);

# ifdef BLKGETZONESZ
  if (S_ISBLK(sb.st_mode) && !is_floppy) {
    uint32_t zone_size_sector;

    if (!ioctl(pr->fd, BLKGETZONESZ, &zone_size_sector))
      pr->zone_size = zone_size_sector << 9;
  }
# endif

  if (S_ISBLK(sb.st_mode) && !is_floppy && !blkid_probe_is_tiny(pr))
    pr->io_size = blkid_get_io_size(fd);

  DBG(LOWPROBE, ul_debug("ready for low-probing, offset=%"PRIu64", size=%"PRIu64", zonesize=%"PRIu64", iosize=%"PRIu64,
        pr->off, pr->size, pr->zone_size, pr->io_size));
  DBG(LOWPROBE, ul_debug("whole-disk: %s, regfile: %s",
    blkid_probe_is_wholedisk(pr) ?"YES" : "NO",
    S_ISREG(pr->mode) ? "YES" : "NO"));

  return 0;
err:
  DBG(LOWPROBE, ul_debug("failed to prepare a device for low-probing"));
  return -1;

}

int blkid_probe_get_dimension(blkid_probe pr, uint64_t *off, uint64_t *size)
{
  *off = pr->off;
  *size = pr->size;
  return 0;
}

int blkid_probe_set_dimension(blkid_probe pr, uint64_t off, uint64_t size)
{
  DBG(LOWPROBE, ul_debug(
    "changing probing area: size=%"PRIu64", off=%"PRIu64" "
    "-to-> size=%"PRIu64", off=%"PRIu64"",
    pr->size, pr->off, size, off));

  pr->off = off;
  pr->size = size;
  pr->flags &= ~BLKID_FL_TINY_DEV;

  if (pr->size <= 1440ULL * 1024ULL && !S_ISCHR(pr->mode))
    pr->flags |= BLKID_FL_TINY_DEV;

  blkid_probe_reset_buffers(pr);

  return 0;
}

const unsigned char *blkid_probe_get_sb_buffer(blkid_probe pr, const struct blkid_idmag *mag, size_t size)
{
  uint64_t hint_offset, off;

  if (mag->kboff >= 0) {
    if (!mag->hoff || blkid_probe_get_hint(pr, mag->hoff, &hint_offset) < 0)
      hint_offset = 0;

    off = hint_offset + (mag->kboff << 10);
  } else {
    off = pr->size - (-mag->kboff << 10);
  }

  return blkid_probe_get_buffer(pr, off, size);
}

uint64_t blkid_probe_get_idmag_off(blkid_probe pr, const struct blkid_idmag *mag)
{
  if (mag->kboff >= 0)
    return mag->kboff << 10;
  else
    return pr->size - (-mag->kboff << 10);
}

/*
 * Check for matching magic value.
 * Returns BLKID_PROBE_OK if found, BLKID_PROBE_NONE if not found
 * or no magic present, or negative value on error.
 */
int blkid_probe_get_idmag(blkid_probe pr, const struct blkid_idinfo *id,
      uint64_t *offset, const struct blkid_idmag **res)
{
  const struct blkid_idmag *mag = NULL;
  uint64_t off = 0;

  if (id)
    mag = &id->magics[0];
  if (res)
    *res = NULL;

  /* try to detect by magic string */
  while(mag && mag->magic) {
    const unsigned char *buf;
    long kboff;
    uint64_t hint_offset;

    if (!mag->hoff || blkid_probe_get_hint(pr, mag->hoff, &hint_offset) < 0)
      hint_offset = 0;

    /* If the magic is for zoned device, skip non-zoned device */
    if (mag->is_zoned && !pr->zone_size) {
      mag++;
      continue;
    }

    if (!mag->is_zoned)
      kboff = mag->kboff;
    else
      kboff = ((mag->zonenum * pr->zone_size) >> 10) + mag->kboff_inzone;

    if (kboff >= 0)
      off = hint_offset + (kboff << 10) + mag->sboff;
    else
      off = pr->size - (-kboff << 10) + mag->sboff;
    buf = blkid_probe_get_buffer(pr, off, mag->len);

    if (!buf && errno)
      return -errno;

    if (buf && !memcmp(mag->magic, buf, mag->len)) {
      DBG(LOWPROBE, ul_debug("\tmagic sboff=%u, kboff=%ld",
        mag->sboff, kboff));
      if (offset)
        *offset = off;
      if (res)
        *res = mag;
      return BLKID_PROBE_OK;
    }
    mag++;
  }

  if (id && id->magics[0].magic)
    /* magic string(s) defined, but not found */
    return BLKID_PROBE_NONE;

  return BLKID_PROBE_OK;
}

static inline void blkid_probe_start(blkid_probe pr)
{
  DBG(LOWPROBE, ul_debug("start probe"));
  pr->cur_chain = NULL;
  pr->prob_flags = 0;
  blkid_probe_set_wiper(pr, 0, 0);
}

static inline void blkid_probe_end(blkid_probe pr)
{
  DBG(LOWPROBE, ul_debug("end probe"));
  pr->cur_chain = NULL;
  pr->prob_flags = 0;
  blkid_probe_set_wiper(pr, 0, 0);
}

/**
 * blkid_do_probe:
 * @pr: prober
 *
 * Calls probing functions in all enabled chains. The superblocks chain is
 * enabled by default. The blkid_do_probe() stores result from only one
 * probing function. It's necessary to call this routine in a loop to get
 * results from all probing functions in all chains. The probing is reset
 * by blkid_reset_probe() or by filter functions.
 *
 * This is string-based NAME=value interface only.
 *
 * <example>
 *   <title>basic case - use the first result only</title>
 *   <programlisting>
 *  if (blkid_do_probe(pr) == BLKID_PROBE_OK) {
 *    int nvals = blkid_probe_numof_values(pr);
 *    for (n = 0; n < nvals; n++) {
 *      if (blkid_probe_get_value(pr, n, &name, &data, &len) == 0)
 *        printf("%s = %s\n", name, data);
 *    }
 *  }
 *  </programlisting>
 * </example>
 *
 * <example>
 *   <title>advanced case - probe for all signatures</title>
 *   <programlisting>
 *  while (blkid_do_probe(pr) == BLKID_PROBE_OK) {
 *    int nvals = blkid_probe_numof_values(pr);
 *    ...
 *  }
 *  </programlisting>
 * </example>
 *
 * See also blkid_reset_probe().
 *
 * Returns: 0 on success, 1 when probing is done and -1 in case of error.
 */
int blkid_do_probe(blkid_probe pr)
{
  int rc = 1;

  if (pr->flags & BLKID_FL_NOSCAN_DEV)
    return BLKID_PROBE_NONE;

  do {
    struct blkid_chain *chn = pr->cur_chain;

    if (!chn) {
      blkid_probe_start(pr);
      chn = pr->cur_chain = &pr->chains[0];
    }
    /* we go to the next chain only when the previous probing
     * result was nothing (rc == 1) and when the current chain is
     * disabled or we are at end of the current chain (chain->idx +
     * 1 == sizeof chain) or the current chain bailed out right at
     * the start (chain->idx == -1)
     */
    else if (rc == 1 && (chn->enabled == FALSE ||
             chn->idx + 1 == (int) chn->driver->nidinfos ||
             chn->idx == -1)) {

      size_t idx = chn->driver->id + 1;

      if (idx < BLKID_NCHAINS)
        chn = pr->cur_chain = &pr->chains[idx];
      else {
        blkid_probe_end(pr);
        return BLKID_PROBE_NONE; /* all chains already probed */
      }
    }

    chn->binary = FALSE;   /* for sure... */

    DBG(LOWPROBE, ul_debug("chain probe %s %s (idx=%d)",
        chn->driver->name,
        chn->enabled? "ENABLED" : "DISABLED",
        chn->idx));

    if (!chn->enabled)
      continue;

    /* rc: -1 = error, 0 = success, 1 = no result */
    rc = chn->driver->probe(pr, chn);

  } while (rc == BLKID_PROBE_NONE);

  if (rc < 0)
         return BLKID_PROBE_ERROR;

  return rc;
}

#ifdef HAVE_LINUX_BLKZONED_H
static int is_conventional(blkid_probe pr, uint64_t offset)
{
  struct blk_zone_report *rep = NULL;
  int ret;
  uint64_t zone_mask;

  if (!pr->zone_size)
    return 1;

  zone_mask = ~(pr->zone_size - 1);
  rep = blkdev_get_zonereport(blkid_probe_get_fd(pr),
            (offset & zone_mask) >> 9, 1);
  if (!rep)
    return -1;

  if (rep->zones[0].type == BLK_ZONE_TYPE_CONVENTIONAL)
    ret = 1;
  else
    ret = 0;

  free(rep);

  return ret;
}
#else
static inline int is_conventional(blkid_probe pr __attribute__((__unused__)),
          uint64_t offset __attribute__((__unused__)))
{
  return 1;
}
#endif

/**
 * blkid_do_wipe:
 * @pr: prober
 * @dryrun: if TRUE then don't touch the device.
 *
 * This function erases the current signature detected by @pr. The @pr has to
 * be open in O_RDWR mode, BLKID_SUBLKS_MAGIC or/and BLKID_PARTS_MAGIC flags
 * has to be enabled (if you want to erase also superblock with broken check
 * sums then use BLKID_SUBLKS_BADCSUM too).
 *
 * After successful signature removing the @pr prober will be moved one step
 * back and the next blkid_do_probe() call will again call previously called
 * probing function. All in-memory cached data from the device are always
 * reset.
 *
 *  <example>
 *  <title>wipe all filesystems or raids from the device</title>
 *   <programlisting>
 *      fd = open(devname, O_RDWR|O_CLOEXEC);
 *      blkid_probe_set_device(pr, fd, 0, 0);
 *
 *      blkid_probe_enable_superblocks(pr, 1);
 *      blkid_probe_set_superblocks_flags(pr, BLKID_SUBLKS_MAGIC);
 *
 *  while (blkid_do_probe(pr) == 0)
 *    blkid_do_wipe(pr, FALSE);
 *  </programlisting>
 * </example>
 *
 * See also blkid_probe_step_back() if you cannot use this built-in wipe
 * function, but you want to use libblkid probing as a source for wiping.
 *
 * See also blkid_wipe_all() which works the same as the example above.
 *
 * Returns: 0 on success, and -1 in case of error.
 */
int blkid_do_wipe(blkid_probe pr, int dryrun)
{
  const char *off = NULL;
  size_t len = 0;
  uint64_t offset, magoff;
  int conventional;
  char buf[BUFSIZ];
  int fd, rc = 0;
  struct blkid_chain *chn;

  chn = pr->cur_chain;
  if (!chn)
    return BLKID_PROBE_ERROR;

  switch (chn->driver->id) {
  case BLKID_CHAIN_SUBLKS:
    rc = blkid_probe_lookup_value(pr, "SBMAGIC_OFFSET", &off, NULL);
    if (!rc)
      rc = blkid_probe_lookup_value(pr, "SBMAGIC", NULL, &len);
    break;
  case BLKID_CHAIN_PARTS:
    rc = blkid_probe_lookup_value(pr, "PTMAGIC_OFFSET", &off, NULL);
    if (!rc)
      rc = blkid_probe_lookup_value(pr, "PTMAGIC", NULL, &len);
    break;
  default:
    return BLKID_PROBE_OK;
  }

  if (rc || len == 0 || off == NULL)
    return BLKID_PROBE_OK;

  errno = 0;
  magoff = strtoumax(off, NULL, 10);
  if (errno)
    return BLKID_PROBE_OK;

  offset = magoff + pr->off;
  fd = blkid_probe_get_fd(pr);
  if (fd < 0)
    return BLKID_PROBE_ERROR;

  if (len > sizeof(buf))
    len = sizeof(buf);

  rc = is_conventional(pr, offset);
  if (rc < 0)
    return BLKID_PROBE_ERROR;
  conventional = rc == 1;

  DBG(LOWPROBE, ul_debug(
      "do_wipe [offset=0x%"PRIx64" (%"PRIu64"), len=%zu, chain=%s, idx=%d, dryrun=%s]\n",
      offset, offset, len, chn->driver->name, chn->idx, dryrun ? "yes" : "not"));

  if (ul_vfs_lseek(pr->vfs, fd, offset, SEEK_SET) == (off_t) -1)
    return BLKID_PROBE_ERROR;

  if (!dryrun && len) {
    if (conventional) {
      memset(buf, 0, len);

      /* wipen on device */
      if (ul_vfs_write_all(pr->vfs, fd, buf, len))
        return BLKID_PROBE_ERROR;
      if (ul_vfs_fsync(pr->vfs, fd) != 0)
        return BLKID_PROBE_ERROR;
    } else {
#ifdef HAVE_LINUX_BLKZONED_H
      uint64_t zone_mask = ~(pr->zone_size - 1);
      struct blk_zone_range range = {
        .sector = (offset & zone_mask) >> 9,
        .nr_sectors = pr->zone_size >> 9,
      };

      rc = ioctl(fd, BLKRESETZONE, &range);
      if (rc < 0)
        return BLKID_PROBE_ERROR;
#else
      /* Should not reach here */
      assert(0);
#endif
    }

    pr->flags &= ~BLKID_FL_MODIF_BUFF; /* be paranoid */

    return blkid_probe_step_back(pr);

  }

  if (dryrun) {
    /* wipe in memory only */
    blkid_probe_hide_range(pr, magoff, len);
    return blkid_probe_step_back(pr);
  }

  return BLKID_PROBE_OK;
}

/**
 * blkid_wipe_all:
 * @pr: prober
 *
 * This function erases all detectable signatures from &pr.
 * The @pr has to be open in O_RDWR mode. All other necessary configurations
 * will be enabled automatically.
 *
 *  <example>
 *  <title>wipe all filesystems or raids from the device</title>
 *   <programlisting>
 *      fd = open(devname, O_RDWR|O_CLOEXEC);
 *      blkid_probe_set_device(pr, fd, 0, 0);
 *
 *      blkid_wipe_all(pr);
 *  </programlisting>
 * </example>
 *
 * Returns: 0 on success, and -1 in case of error.
 */
int blkid_wipe_all(blkid_probe pr)
{
  DBG(LOWPROBE, ul_debug("wiping all signatures"));

  blkid_probe_enable_superblocks(pr, 1);
  blkid_probe_set_superblocks_flags(pr, BLKID_SUBLKS_MAGIC |
      BLKID_SUBLKS_BADCSUM);

  blkid_probe_enable_partitions(pr, 1);
  blkid_probe_set_partitions_flags(pr, BLKID_PARTS_MAGIC |
      BLKID_PARTS_FORCE_GPT);

  while (blkid_do_probe(pr) == 0) {
    DBG(LOWPROBE, ul_debug("wiping one signature"));
    blkid_do_wipe(pr, 0);
  }

  return BLKID_PROBE_OK;
}

/**
 * blkid_probe_step_back:
 * @pr: prober
 *
 * This function move pointer to the probing chain one step back -- it means
 * that the previously used probing function will be called again in the next
 * blkid_do_probe() call.
 *
 * This is necessary for example if you erase or modify on-disk superblock
 * according to the current libblkid probing result.
 *
 * Note that blkid_probe_hide_range() changes semantic of this function and
 * cached buffers are not reset, but library uses in-memory modified
 * buffers to call the next probing function.
 *
 * <example>
 *  <title>wipe all superblock, but use libblkid only for probing</title>
 *  <programlisting>
 *      pr = blkid_new_probe_from_filename(devname);
 *
 *      blkid_probe_enable_superblocks(pr, 1);
 *      blkid_probe_set_superblocks_flags(pr, BLKID_SUBLKS_MAGIC);
 *
 *      blkid_probe_enable_partitions(pr, 1);
 *      blkid_probe_set_partitions_flags(pr, BLKID_PARTS_MAGIC);
 *
 *  while (blkid_do_probe(pr) == BLKID_PROBE_OK) {
 *    const char *ostr = NULL;
 *    size_t len = 0;
 *
 *    // superblocks
 *    if (blkid_probe_lookup_value(pr, "SBMAGIC_OFFSET", &ostr, NULL) == 0)
 *      blkid_probe_lookup_value(pr, "SBMAGIC", NULL, &len);
 *
 *    // partition tables
 *    if (len == 0 && blkid_probe_lookup_value(pr, "PTMAGIC_OFFSET", &ostr, NULL) == 0)
 *      blkid_probe_lookup_value(pr, "PTMAGIC", NULL, &len);
 *
 *    if (!len || !str)
 *      continue;
 *
 *    // convert ostr to the real offset by off = strtoll(ostr, NULL, 10);
 *              // use your stuff to erase @len bytes at the @off
 *              ....
 *
 *    // retry the last probing to check for backup superblocks ..etc.
 *              blkid_probe_step_back(pr);
 *  }
 *  </programlisting>
 * </example>
 *
 * Returns: 0 on success, and -1 in case of error.
 */
int blkid_probe_step_back(blkid_probe pr)
{
  struct blkid_chain *chn;

  chn = pr->cur_chain;
  if (!chn)
    return -1;

  if (!(pr->flags & BLKID_FL_MODIF_BUFF))
    blkid_probe_reset_buffers(pr);

  if (chn->idx >= 0) {
    chn->idx--;
    DBG(LOWPROBE, ul_debug("step back: moving %s chain index to %d",
      chn->driver->name,
      chn->idx));
  }

  if (chn->idx == -1) {
    /* blkid_do_probe() goes to the next chain if the index
     * of the current chain is -1, so we have to set the
     * chain pointer to the previous chain.
     */
    size_t idx = chn->driver->id > 0 ? chn->driver->id - 1 : 0;

    DBG(LOWPROBE, ul_debug("step back: moving to previous chain"));

    if (idx > 0)
      pr->cur_chain = &pr->chains[idx];
    else if (idx == 0)
      pr->cur_chain = NULL;
  }

  return 0;
}

/**
 * blkid_do_safeprobe:
 * @pr: prober
 *
 * This function gathers probing results from all enabled chains and checks
 * for ambivalent results (e.g. more filesystems on the device).
 *
 * This is string-based NAME=value interface only.
 *
 * Note about superblocks chain -- the function does not check for filesystems
 * when a RAID signature is detected.  The function also does not check for
 * collision between RAIDs. The first detected RAID is returned. The function
 * checks for collision between partition table and RAID signature -- it's
 * recommended to enable partitions chain together with superblocks chain.
 *
 * Returns: 0 on success, 1 if nothing is detected, -2 if ambivalent result is
 * detected and -1 on case of error.
 */
int blkid_do_safeprobe(blkid_probe pr)
{
  int i, count = 0, rc = 0;

  if (pr->flags & BLKID_FL_NOSCAN_DEV)
    return BLKID_PROBE_NONE;

  blkid_probe_start(pr);
  pr->prob_flags |= BLKID_PROBE_FL_SAFEPROBE;

  for (i = 0; i < BLKID_NCHAINS; i++) {
    struct blkid_chain *chn;

    chn = pr->cur_chain = &pr->chains[i];
    chn->binary = FALSE;   /* for sure... */

    DBG(LOWPROBE, ul_debug("chain safeprobe %s %s",
        chn->driver->name,
        chn->enabled? "ENABLED" : "DISABLED"));

    if (!chn->enabled)
      continue;

    blkid_probe_chain_reset_position(chn);

    rc = chn->driver->safeprobe(pr, chn);

    blkid_probe_chain_reset_position(chn);

    /* rc: -2 ambivalent, -1 = error, 0 = success, 1 = no result */
    if (rc < 0)
      goto done;  /* error */
    if (rc == 0)
      count++; /* success */
  }

done:
  blkid_probe_end(pr);
  if (rc < 0)
    return BLKID_PROBE_ERROR;

  return count == 0 ? BLKID_PROBE_NONE : BLKID_PROBE_OK;
}

/**
 * blkid_do_fullprobe:
 * @pr: prober
 *
 * This function gathers probing results from all enabled chains. Same as
 * blkid_do_safeprobe() but does not check for collision between probing
 * result.
 *
 * This is string-based NAME=value interface only.
 *
 * Returns: 0 on success, 1 if nothing is detected or -1 on case of error.
 */
int blkid_do_fullprobe(blkid_probe pr)
{
  int i, count = 0, rc = 0;

  if (pr->flags & BLKID_FL_NOSCAN_DEV)
    return BLKID_PROBE_NONE;

  blkid_probe_start(pr);

  for (i = 0; i < BLKID_NCHAINS; i++) {
    struct blkid_chain *chn;

    chn = pr->cur_chain = &pr->chains[i];
    chn->binary = FALSE;   /* for sure... */

    DBG(LOWPROBE, ul_debug("chain fullprobe %s: %s",
        chn->driver->name,
        chn->enabled? "ENABLED" : "DISABLED"));

    if (!chn->enabled)
      continue;

    blkid_probe_chain_reset_position(chn);

    rc = chn->driver->probe(pr, chn);

    blkid_probe_chain_reset_position(chn);

    /* rc: -1 = error, 0 = success, 1 = no result */
    if (rc < 0)
      goto done; /* error */
    if (rc == 0)
      count++; /* success */
  }

done:
  blkid_probe_end(pr);
  if (rc < 0)
    return BLKID_PROBE_ERROR;

  return count == 0 ? BLKID_PROBE_NONE : BLKID_PROBE_OK;
}

/* same sa blkid_probe_get_buffer() but works with 512-sectors */
const unsigned char *blkid_probe_get_sector(blkid_probe pr, unsigned int sector)
{
  return blkid_probe_get_buffer(pr, ((uint64_t) sector) << 9, 0x200);
}

struct blkid_prval *blkid_probe_assign_value(blkid_probe pr, const char *name)
{
  struct blkid_prval *v;

  v = calloc(1, sizeof(struct blkid_prval));
  if (!v)
    return NULL;

  INIT_LIST_HEAD(&v->prvals);
  v->name = name;
  v->chain = pr->cur_chain;
  list_add_tail(&v->prvals, &pr->values);

  DBG(LOWPROBE, ul_debug("assigning %s [%s]", name, v->chain->driver->name));
  return v;
}

/* Note that value data is always terminated by zero to keep things robust,
 * this extra zero is not count to the value length. It's caller responsibility
 * to set proper value length (for strings we count terminator to the length,
 * for binary data it's without terminator).
 */
int blkid_probe_value_set_data(struct blkid_prval *v,
    const unsigned char *data, size_t len)
{
  v->data = calloc(1, len + 1); /* always terminate by \0 */

  if (!v->data)
    return -ENOMEM;
  memcpy(v->data, data, len);
  v->len = len;
  return 0;
}

int blkid_probe_set_value(blkid_probe pr, const char *name,
    const unsigned char *data, size_t len)
{
  struct blkid_prval *v;

  v = blkid_probe_assign_value(pr, name);
  if (!v)
    return -1;

  return blkid_probe_value_set_data(v, data, len);
}

int blkid_probe_vsprintf_value(blkid_probe pr, const char *name,
    const char *fmt, va_list ap)
{
  struct blkid_prval *v;
  ssize_t len;

  v = blkid_probe_assign_value(pr, name);
  if (!v)
    return -ENOMEM;

  len = vasprintf((char **) &v->data, fmt, ap);

  if (len <= 0) {
    blkid_probe_free_value(v);
    return len == 0 ? -EINVAL : -ENOMEM;
  }
  v->len = len + 1;
  return 0;
}

int blkid_probe_sprintf_value(blkid_probe pr, const char *name,
    const char *fmt, ...)
{
  int rc;
  va_list ap;

  va_start(ap, fmt);
  rc = blkid_probe_vsprintf_value(pr, name, fmt, ap);
  va_end(ap);

  return rc;
}

int blkid_probe_set_magic(blkid_probe pr, uint64_t offset,
      size_t len, const unsigned char *magic)
{
  int rc = 0;
  struct blkid_chain *chn = blkid_probe_get_chain(pr);

  if (!chn || !len || chn->binary)
    return 0;

  switch (chn->driver->id) {
  case BLKID_CHAIN_SUBLKS:
    if (!(chn->flags & BLKID_SUBLKS_MAGIC))
      return 0;
    rc = blkid_probe_set_value(pr, "SBMAGIC", magic, len);
    if (!rc)
      rc = blkid_probe_sprintf_value(pr,
          "SBMAGIC_OFFSET", "%llu", (unsigned long long)offset);
    break;
  case BLKID_CHAIN_PARTS:
    if (!(chn->flags & BLKID_PARTS_MAGIC))
      return 0;
    rc = blkid_probe_set_value(pr, "PTMAGIC", magic, len);
    if (!rc)
      rc = blkid_probe_sprintf_value(pr,
          "PTMAGIC_OFFSET", "%llu", (unsigned long long)offset);
    break;
  default:
    break;
  }

  return rc;
}

static void blkid_probe_log_csum_mismatch(blkid_probe pr, size_t n, const void *csum,
    const void *expected)
{
  char csum_hex[256 + 1] = "";
  char expected_hex[sizeof(csum_hex)] = "";
  int hex_size = min(sizeof(csum_hex) - 1, n * 2);

  for (int i = 0; i < hex_size; i+=2) {
    snprintf(&csum_hex[i], sizeof(csum_hex) - i, "%02X", ((const unsigned char *) csum)[i / 2]);
    snprintf(&expected_hex[i], sizeof(expected_hex) - i, "%02X", ((const unsigned char *) expected)[i / 2]);
  }

  DBG(LOWPROBE, ul_debug(
    "incorrect checksum for type %s,"
    " got %s, expected %s",
    blkid_probe_get_probername(pr),
    csum_hex, expected_hex));
}


int blkid_probe_verify_csum_buf(blkid_probe pr, size_t n, const void *csum,
    const void *expected)
{
  if (memcmp(csum, expected, n) != 0) {
    struct blkid_chain *chn = blkid_probe_get_chain(pr);

    ON_DBG(LOWPROBE, blkid_probe_log_csum_mismatch(pr, n, csum, expected));

    /*
     * Accept bad checksum if BLKID_SUBLKS_BADCSUM flags is set
     */
    if (chn && chn->driver->id == BLKID_CHAIN_SUBLKS
        && (chn->flags & BLKID_SUBLKS_BADCSUM)) {
      blkid_probe_set_value(pr, "SBBADCSUM", (unsigned char *) "1", 2);
      goto accept;
    }
    return 0; /* bad checksum */
  }

accept:
  return 1;
}

int blkid_probe_verify_csum(blkid_probe pr, uint64_t csum, uint64_t expected)
{
  return blkid_probe_verify_csum_buf(pr, sizeof(csum), &csum, &expected);
}

/**
 * blkid_probe_get_devno:
 * @pr: probe
 *
 * Returns: block device number, or 0 for regular files.
 */
dev_t blkid_probe_get_devno(blkid_probe pr)
{
  return pr->devno;
}

/**
 * blkid_probe_get_wholedisk_devno:
 * @pr: probe
 *
 * Returns: device number of the wholedisk, or 0 for regular files.
 */
dev_t blkid_probe_get_wholedisk_devno(blkid_probe pr)
{
  if (!pr->disk_devno) {
    dev_t devno, disk_devno = 0;

    devno = blkid_probe_get_devno(pr);
    if (!devno)
      return 0;

    if (blkid_devno_to_wholedisk(devno, NULL, 0, &disk_devno) == 0)
      pr->disk_devno = disk_devno;
  }
  return pr->disk_devno;
}

/**
 * blkid_probe_is_wholedisk:
 * @pr: probe
 *
 * Returns: 1 if the device is whole-disk or 0.
 */
int blkid_probe_is_wholedisk(blkid_probe pr)
{
  dev_t devno, disk_devno;

  devno = blkid_probe_get_devno(pr);
  if (!devno)
    return 0;

  disk_devno = blkid_probe_get_wholedisk_devno(pr);
  if (!disk_devno)
    return 0;

  return devno == disk_devno;
}

blkid_probe blkid_probe_get_wholedisk_probe(blkid_probe pr)
{
  dev_t disk;

  if (blkid_probe_is_wholedisk(pr))
    return NULL;     /* this is not partition */

  if (pr->parent)
    /* this is cloned blkid_probe, use parent's stuff */
    return blkid_probe_get_wholedisk_probe(pr->parent);

  disk = blkid_probe_get_wholedisk_devno(pr);

  if (pr->disk_probe && pr->disk_probe->devno != disk) {
    /* we have disk prober, but for another disk... close it */
    blkid_free_probe(pr->disk_probe);
    pr->disk_probe = NULL;
  }

  if (!pr->disk_probe) {
    /* Open a new disk prober */
    char *disk_path = blkid_devno_to_devname(disk);
    int flags;

    if (!disk_path)
      return NULL;

    DBG(LOWPROBE, ul_debug("allocate a wholedisk probe"));

    pr->disk_probe = blkid_new_probe_from_filename(disk_path);

    free(disk_path);

    if (!pr->disk_probe)
      return NULL; /* ENOMEM? */

    flags = blkid_probe_get_partitions_flags(pr);
    if (flags & BLKID_PARTS_FORCE_GPT)
      blkid_probe_set_partitions_flags(pr->disk_probe,
               BLKID_PARTS_FORCE_GPT);
  }

  return pr->disk_probe;
}

/**
 * blkid_probe_get_size:
 * @pr: probe
 *
 * This function returns size of probing area as defined by blkid_probe_set_device().
 * If the size of the probing area is unrestricted then this function returns
 * the real size of device. See also blkid_get_dev_size().
 *
 * Returns: size in bytes or -1 in case of error.
 */
blkid_loff_t blkid_probe_get_size(blkid_probe pr)
{
  return (blkid_loff_t) pr->size;
}

/**
 * blkid_probe_get_offset:
 * @pr: probe
 *
 * This function returns offset of probing area as defined by blkid_probe_set_device().
 *
 * Returns: offset in bytes or -1 in case of error.
 */
blkid_loff_t blkid_probe_get_offset(blkid_probe pr)
{
  return (blkid_loff_t) pr->off;
}

/**
 * blkid_probe_get_fd:
 * @pr: probe
 *
 * Returns: file descriptor for assigned device/file or -1 in case of error.
 */
int blkid_probe_get_fd(blkid_probe pr)
{
  return pr->fd;
}

/**
 * blkid_probe_get_sectorsize:
 * @pr: probe or NULL (for NULL returns 512)
 *
 * Returns: block device logical sector size (BLKSSZGET ioctl, default 512).
 */
unsigned int blkid_probe_get_sectorsize(blkid_probe pr)
{
  if (pr->blkssz)
    return pr->blkssz;

  if (S_ISBLK(pr->mode) &&
      blkdev_get_sector_size(pr->fd, (int *) &pr->blkssz) == 0)
    return pr->blkssz;

  pr->blkssz = DEFAULT_SECTOR_SIZE;
  return pr->blkssz;
}

/**
 * blkid_probe_set_sectorsize:
 * @pr: probe
 * @sz: new size (to overwrite system default)
 *
 * Note that blkid_probe_set_device() resets this setting. Use it after
 * blkid_probe_set_device() and before any probing call.
 *
 * Since: 2.30
 *
 * Returns: 0 or <0 in case of error
 */
int blkid_probe_set_sectorsize(blkid_probe pr, unsigned int sz)
{
  pr->blkssz = sz;
  return 0;
}

/**
 * blkid_probe_set_vfs:
 * @pr: probe
 * @ops: VFS operations or NULL to reset to defaults
 *
 * Sets custom I/O operations for the probe. This allows replacing
 * standard read/write/lseek/etc. with custom implementations
 * (e.g., fiber-aware I/O).
 *
 * The @ops struct is copied into a private allocation owned by the
 * probe. The caller sets ops->size to sizeof(struct ul_vfs_ops) to
 * enable forward/backward compatibility. NULL function pointers fall
 * back to standard syscalls. Passing @ops as NULL frees the private
 * copy and resets the probe to default (direct syscall) I/O.
 *
 * Note: blkid_new_probe_from_filename() opens the device before VFS
 * can be set. VFS users should use blkid_new_probe(), then
 * blkid_probe_set_vfs(), then blkid_probe_open_device().
 *
 * Since: 2.43
 *
 * Returns: 0 on success, or <0 in case of error.
 */
int blkid_probe_set_vfs(blkid_probe pr, const struct ul_vfs_ops *ops)
{
  if (!ops) {
    free(pr->vfs);
    pr->vfs = NULL;
    return 0;
  }
  if (!pr->vfs) {
    pr->vfs = calloc(1, sizeof(*pr->vfs));
    if (!pr->vfs)
      return -ENOMEM;
  }
  ul_vfs_init(pr->vfs, ops);
  return 0;
}

/**
 * blkid_probe_get_sectors:
 * @pr: probe
 *
 * Returns: 512-byte sector count or -1 in case of error.
 */
blkid_loff_t blkid_probe_get_sectors(blkid_probe pr)
{
  return (blkid_loff_t) (pr->size >> 9);
}

/**
 * blkid_probe_numof_values:
 * @pr: probe
 *
 * Returns: number of values in probing result or -1 in case of error.
 */
int blkid_probe_numof_values(blkid_probe pr)
{
  int i = 0;
  struct list_head *p;

  list_for_each(p, &pr->values)
    ++i;
  return i;
}

/**
 * blkid_probe_get_value:
 * @pr: probe
 * @num: wanted value in range 0..N, where N is blkid_probe_numof_values() - 1
 * @name: pointer to return value name or NULL
 * @data: pointer to return value data or NULL
 * @len: pointer to return value length or NULL
 *
 * Note, the @len returns length of the @data, including the terminating
 * '\0' character.
 *
 * Returns: 0 on success, or -1 in case of error.
 */
int blkid_probe_get_value(blkid_probe pr, int num, const char **name,
      const char **data, size_t *len)
{
  struct blkid_prval *v = __blkid_probe_get_value(pr, num);

  if (!v)
    return -1;
  if (name)
    *name = v->name;
  if (data)
    *data = (char *) v->data;
  if (len)
    *len = v->len;

  DBG(LOWPROBE, ul_debug("returning %s value", v->name));
  return 0;
}

/**
 * blkid_probe_lookup_value:
 * @pr: probe
 * @name: name of value
 * @data: pointer to return value data or NULL
 * @len: pointer to return value length or NULL
 *
 * Note, the @len returns length of the @data, including the terminating
 * '\0' character.
 *
 * Returns: 0 on success, or -1 in case of error.
 */
int blkid_probe_lookup_value(blkid_probe pr, const char *name,
      const char **data, size_t *len)
{
  struct blkid_prval *v = __blkid_probe_lookup_value(pr, name);

  if (!v)
    return -1;
  if (data)
    *data = (char *) v->data;
  if (len)
    *len = v->len;
  return 0;
}

/**
 * blkid_probe_has_value:
 * @pr: probe
 * @name: name of value
 *
 * Returns: 1 if value exist in probing result, otherwise 0.
 */
int blkid_probe_has_value(blkid_probe pr, const char *name)
{
  if (blkid_probe_lookup_value(pr, name, NULL, NULL) == 0)
    return 1;
  return 0;
}

struct blkid_prval *__blkid_probe_get_value(blkid_probe pr, int num)
{
  int i = 0;
  struct list_head *p;

  if (num < 0)
    return NULL;

  list_for_each(p, &pr->values) {
    if (i++ != num)
      continue;
    return list_entry(p, struct blkid_prval, prvals);
  }
  return NULL;
}

struct blkid_prval *__blkid_probe_lookup_value(blkid_probe pr, const char *name)
{
  struct list_head *p;

  if (list_empty(&pr->values))
    return NULL;

  list_for_each(p, &pr->values) {
    struct blkid_prval *v = list_entry(p, struct blkid_prval,
            prvals);

    if (v->name && strcmp(name, v->name) == 0) {
      DBG(LOWPROBE, ul_debug("returning %s value", v->name));
      return v;
    }
  }
  return NULL;
}


/* converts DCE UUID (uuid[16]) to human readable string
 * - the @len should be always 37 */
void blkid_unparse_uuid(const unsigned char *uuid, char *str, size_t len)
{
  snprintf(str, len,
    "%02x%02x%02x%02x-%02x%02x-%02x%02x-%02x%02x-%02x%02x%02x%02x%02x%02x",
    uuid[0], uuid[1], uuid[2], uuid[3],
    uuid[4], uuid[5],
    uuid[6], uuid[7],
    uuid[8], uuid[9],
    uuid[10], uuid[11], uuid[12], uuid[13], uuid[14],uuid[15]);
}

/* like uuid_is_null() from libuuid, but works with arbitrary size of UUID */
int blkid_uuid_is_empty(const unsigned char *buf, size_t len)
{
  size_t i;

  for (i = 0; i < len; i++)
    if (buf[i])
      return 0;
  return 1;
}

/* Removes whitespace from the right-hand side of a string (trailing
 * whitespace).
 *
 * Returns size of the new string (without \0).
 */
size_t blkid_rtrim_whitespace(unsigned char *str)
{
  return rtrim_whitespace(str);
}

/* Removes whitespace from the left-hand side of a string.
 *
 * Returns size of the new string (without \0).
 */
size_t blkid_ltrim_whitespace(unsigned char *str)
{
  return ltrim_whitespace(str);
}

/*
 * Some mkfs-like utils wipe some parts (usually begin) of the device.
 * For example LVM (pvcreate) or mkswap(8). This information could be used
 * for later resolution to conflicts between superblocks.
 *
 * For example we found valid LVM superblock, LVM wipes 8KiB at the begin of
 * the device. If we found another signature (for example MBR) within the
 * wiped area then the signature has been added later and LVM superblock
 * should be ignore.
 *
 * Note that this heuristic is not 100% reliable, for example "pvcreate --zero n"
 * can be used to keep the begin of the device unmodified. It's probably better
 * to use this heuristic for conflicts between superblocks and partition tables
 * than for conflicts between filesystem superblocks -- existence of unwanted
 * partition table is very unusual, because PT is pretty visible (parsed and
 * interpreted by kernel).
 *
 * Note that we usually expect only one signature on the device, it means that
 * we have to remember only one wiped area from previously successfully
 * detected signature.
 *
 * blkid_probe_set_wiper() -- defines wiped area (e.g. LVM)
 * blkid_probe_use_wiper() -- try to use area (e.g. MBR)
 *
 * Note that there is not relation between _wiper and blkid_to_wipe().
 *
 */
void blkid_probe_set_wiper(blkid_probe pr, uint64_t off, uint64_t size)
{
  struct blkid_chain *chn;

  if (!size) {
    DBG(LOWPROBE, ul_debug("zeroize wiper"));
    pr->wipe_size = pr->wipe_off = 0;
    pr->wipe_chain = NULL;
    return;
  }

  chn = pr->cur_chain;

  if (!chn || !chn->driver ||
      chn->idx < 0 || (size_t) chn->idx >= chn->driver->nidinfos)
    return;

  pr->wipe_size = size;
  pr->wipe_off = off;
  pr->wipe_chain = chn;

  DBG(LOWPROBE,
    ul_debug("wiper set to %s::%s off=%"PRIu64" size=%"PRIu64"",
      chn->driver->name,
      chn->driver->idinfos[chn->idx]->name,
      pr->wipe_off, pr->wipe_size));
}

/*
 * Returns 1 if the <@off,@size> area was wiped
 */
int blkid_probe_is_wiped(blkid_probe pr, struct blkid_chain **chn, uint64_t off, uint64_t size)
{
  if (!size)
    return 0;

  if (pr->wipe_off <= off && off + size <= pr->wipe_off + pr->wipe_size) {
    *chn = pr->wipe_chain;
    return 1;
  }
  return 0;
}

/*
 *  Try to use any area -- if the area has been previously wiped then the
 *  previous probing result should be ignored (reset).
 */
void blkid_probe_use_wiper(blkid_probe pr, uint64_t off, uint64_t size)
{
  struct blkid_chain *chn = NULL;

  if (blkid_probe_is_wiped(pr, &chn, off, size) && chn) {
    DBG(LOWPROBE, ul_debug("previously wiped area modified "
               " -- ignore previous results"));
    blkid_probe_set_wiper(pr, 0, 0);
    blkid_probe_chain_reset_values(pr, chn);
  }
}

static struct blkid_hint *get_hint(blkid_probe pr, const char *name)
{
  struct list_head *p;

  if (list_empty(&pr->hints))
    return NULL;

  list_for_each(p, &pr->hints) {
    struct blkid_hint *h = list_entry(p, struct blkid_hint, hints);

    if (h->name && strcmp(name, h->name) == 0)
      return h;
  }
  return NULL;
}

/**
 * blkid_probe_set_hint:
 * @pr: probe
 * @name: hint name or NAME=value
 * @value: offset or another number
 *
 * Sets extra hint for low-level prober. If the hint is set by NAME=value
 * notation than @value is ignored. The functions blkid_probe_set_device()
 * and blkid_reset_probe() resets all hints.
 *
 * The hints are optional way how to force libblkid probing functions to check
 * for example another location.
 *
 * Returns: 0 on success, or -1 in case of error.
 */
int blkid_probe_set_hint(blkid_probe pr, const char *name, uint64_t value)
{
  struct blkid_hint *hint = NULL;
  char *n = NULL, *v = NULL;

  if (strchr(name, '=')) {
    char *end = NULL;

    if (blkid_parse_tag_string(name, &n, &v) != 0)
      goto done;

    errno = 0;
    value = strtoumax(v, &end, 10);

    if (errno || v == end || (end && *end))
      goto done;
  }

  hint = get_hint(pr, n ? n : name);
  if (hint) {
    /* alter old hint */
    hint->value = value;
    DBG(LOWPROBE,
      ul_debug("updated hint '%s' to %"PRIu64"", hint->name, hint->value));
  } else {
    /* add a new hint */
    if (!n) {
      n = strdup(name);
      if (!n)
        goto done;
    }
    hint = malloc(sizeof(*hint));
    if (!hint)
      goto done;

    hint->name = n;
    hint->value = value;

    INIT_LIST_HEAD(&hint->hints);
    list_add_tail(&hint->hints, &pr->hints);

    DBG(LOWPROBE,
      ul_debug("new hint '%s' is %"PRIu64"", hint->name, hint->value));
    n = NULL;
  }
done:
  free(n);
  free(v);

  if (!hint)
    return errno ? -errno : -EINVAL;
  return 0;
}

int blkid_probe_get_hint(blkid_probe pr, const char *name, uint64_t *value)
{
  struct blkid_hint *h = get_hint(pr, name);

  if (!h)
    return -EINVAL;
  if (value)
    *value = h->value;
  return 0;
}

/**
 * blkid_probe_reset_hints:
 * @pr: probe
 *
 * Removes all previously defined probinig hints. See also blkid_probe_set_hint().
 */
void blkid_probe_reset_hints(blkid_probe pr)
{
  if (list_empty(&pr->hints))
    return;

  DBG(LOWPROBE, ul_debug("resetting hints"));

  while (!list_empty(&pr->hints)) {
    struct blkid_hint *h = list_entry(pr->hints.next,
            struct blkid_hint, hints);
    list_del(&h->hints);
    free(h->name);
    free(h);
  }

  INIT_LIST_HEAD(&pr->hints);
}

Coverage Report

Created: 2026-07-16 06:59