path: root/fdisks/utils.c

/*
 *  Copyright (C) 2012 Davidlohr Bueso <dave@gnu.org>
 *
 *  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.,
 *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */

#include <errno.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <ctype.h>
#ifdef HAVE_LIBBLKID
#include <blkid.h>
#endif

#include "nls.h"
#include "blkdev.h"
#include "common.h"
#include "fdisk.h"

#include "fdiskdoslabel.h"
#include "fdisksunlabel.h"

int fdisk_debug_mask;

/*
 * Label probing functions.
 */
static const struct fdisk_label *labels[] =
{
	&gpt_label,
	&dos_label,
	&sun_label,
	&sgi_label,
	&aix_label,
	&bsd_label,
	&mac_label,
};


static int __probe_labels(struct fdisk_context *cxt)
{
	size_t i;

	cxt->disklabel = FDISK_DISKLABEL_ANY;

	for (i = 0; i < ARRAY_SIZE(labels); i++) {
		if (!labels[i]->probe || labels[i]->probe(cxt) != 1)
			continue;

		cxt->label = labels[i];

		DBG(LABEL, dbgprint("detected a %s label", cxt->label->name));
		return 0;
	}

	return 1; /* not found */
}

static unsigned long __get_sector_size(int fd)
{
	int sect_sz;

	if (!blkdev_get_sector_size(fd, &sect_sz))
		return (unsigned long) sect_sz;
	return DEFAULT_SECTOR_SIZE;
}

/**
 * fdisk_context_force_sector_size:
 * @cxt: fdisk context
 * @s: required sector size
 *
 * Overwrites logical and physical sector size. Note that the default sector
 * size is discovered by fdisk_new_context_from_device() from device topology.
 *
 * Don't use this function, rely on the default behavioer is more safe.
 *
 * Returns: 0 on success, < 0 on error.
 */
int fdisk_context_force_sector_size(struct fdisk_context *cxt, sector_t s)
{
	if (!cxt)
		return -EINVAL;

	cxt->phy_sector_size = cxt->sector_size = s;
	cxt->min_io_size = cxt->io_size = s;

	fdisk_reset_alignment(cxt);
	return 0;
}

static void recount_geometry(struct fdisk_context *cxt)
{
	cxt->geom.cylinders = cxt->total_sectors /
		(cxt->geom.heads * cxt->geom.sectors);
}

/**
 * fdisk_context_set_user_geometry:
 * @cxt: fdisk context
 * @cylinders: user specified cylinders
 * @heads: user specified heads
 * @sectors: user specified sectors
 *
 * Overrides autodiscovery and apply user specified geometry.
 *
 * Returns: 0 on success, < 0 on error.
 */
int fdisk_context_set_user_geometry(struct fdisk_context *cxt,
				    unsigned int cylinders,
				    unsigned int heads,
				    unsigned int sectors)
{
	if (!cxt)
		return -EINVAL;
	if (heads)
		cxt->geom.heads = heads;
	if (sectors)
		cxt->geom.sectors = sectors;

	if (cylinders)
		cxt->geom.cylinders = cylinders;
	else
		recount_geometry(cxt);

	fdisk_reset_alignment(cxt);
	return 0;
}

/*
 * Generic (label independent) geometry
 */
static int __discover_system_geometry(struct fdisk_context *cxt)
{
	sector_t nsects;
	unsigned int h = 0, s = 0;

	/* get number of 512-byte sectors, and convert it the real sectors */
	if (!blkdev_get_sectors(cxt->dev_fd, &nsects))
		cxt->total_sectors = (nsects / (cxt->sector_size >> 9));

	/* what the kernel/bios thinks the geometry is */
	blkdev_get_geometry(cxt->dev_fd, &h, &s);
	if (!h && !s) {
		/* unable to discover geometry, use default values */
		s = 63;
		h = 255;
	}

	/* obtained heads and sectors */
	cxt->geom.heads = h;
	cxt->geom.sectors = s;
	recount_geometry(cxt);

	DBG(GEOMETRY, dbgprint("geometry discovered for %s: C/H/S: %lld/%d/%lld",
			       cxt->dev_path, cxt->geom.cylinders,
			       cxt->geom.heads, cxt->geom.sectors));
	return 0;
}

static int __discover_topology(struct fdisk_context *cxt)
{
#ifdef HAVE_LIBBLKID
	blkid_probe pr;

	DBG(TOPOLOGY, dbgprint("initialize libblkid prober"));

	pr = blkid_new_probe();
	if (pr && blkid_probe_set_device(pr, cxt->dev_fd, 0, 0) == 0) {
		blkid_topology tp = blkid_probe_get_topology(pr);

		if (tp) {
			cxt->min_io_size = blkid_topology_get_minimum_io_size(tp);
			cxt->optimal_io_size = blkid_topology_get_optimal_io_size(tp);
			cxt->phy_sector_size = blkid_topology_get_physical_sector_size(tp);
			cxt->alignment_offset = blkid_topology_get_alignment_offset(tp);

			/* I/O size used by fdisk */
			cxt->io_size = cxt->optimal_io_size;
			if (!cxt->io_size)
				/* optimal IO is optional, default to minimum IO */
				cxt->io_size = cxt->min_io_size;
		}
	}
	blkid_free_probe(pr);
#endif

	cxt->sector_size = __get_sector_size(cxt->dev_fd);
	if (!cxt->phy_sector_size) /* could not discover physical size */
		cxt->phy_sector_size = cxt->sector_size;

	/* no blkid or error, use default values */
	if (!cxt->min_io_size)
		cxt->min_io_size = cxt->sector_size;
	if (!cxt->io_size)
		cxt->io_size = cxt->sector_size;

	DBG(TOPOLOGY, dbgprint("topology discovered for %s:\n"
			       "\tlogical/physical sector sizes: %ld/%ld\n"
			       "\tfdisk/minimal/optimal io sizes: %ld/%ld/%ld\n",
			       cxt->dev_path, cxt->sector_size, cxt->phy_sector_size,
			       cxt->io_size, cxt->optimal_io_size, cxt->min_io_size));
	return 0;
}

/**
 * fdisk_dev_sectsz_is_default:
 * @cxt: fdisk context
 *
 * Returns 1 if the device's sector size is the default value, otherwise 0.
 */
int fdisk_dev_sectsz_is_default(struct fdisk_context *cxt)
{
	if (!cxt)
		return -EINVAL;

	return cxt->sector_size == DEFAULT_SECTOR_SIZE;
}

/**
 * fdisk_dev_has_topology:
 * @cxt: fdisk context
 *
 * Returns 1 if the device provides topology information, otherwise 0.
 */
int fdisk_dev_has_topology(struct fdisk_context *cxt)
{
	/*
	 * Assume that the device provides topology info if
	 * optimal_io_size is set or alignment_offset is set or
	 * minimum_io_size is not power of 2.
	 */
	if (cxt &&
	    (cxt->optimal_io_size ||
	     cxt->alignment_offset ||
	     !is_power_of_2(cxt->min_io_size)))
		return 1;
	return 0;
}

/*
 * The LBA of the first partition is based on the device geometry and topology.
 * This offset is generic (and recommended) for all labels.
 *
 * Returns: 0 on error or number of logical sectors.
 */
sector_t fdisk_topology_get_first_lba(struct fdisk_context *cxt)
{
	sector_t x = 0, res;

	if (!cxt)
		return 0;

	if (!cxt->io_size)
		__discover_topology(cxt);

	/*
	 * Align the begin of partitions to:
	 *
	 * a) topology
	 *  a2) alignment offset
	 *  a1) or physical sector (minimal_io_size, aka "grain")
	 *
	 * b) or default to 1MiB (2048 sectrors, Windows Vista default)
	 *
	 * c) or for very small devices use 1 phy.sector
	 */
	if (fdisk_dev_has_topology(cxt)) {
		if (cxt->alignment_offset)
			x = cxt->alignment_offset;
		else if (cxt->io_size > 2048 * 512)
			x = cxt->io_size;
	}
	/* default to 1MiB */
	if (!x)
		x = 2048 * 512;

	res = x / cxt->sector_size;

	/* don't use huge offset on small devices */
	if (cxt->total_sectors <= res * 4)
		res = cxt->phy_sector_size / cxt->sector_size;

	return res;
}

/*
 * The LBA of the first partition is based on the device geometry and topology.
 * This offset is generic generic (and recommended) for all labels.
 *
 * Returns: 0 on error or number of bytes.
 */
unsigned long fdisk_topology_get_grain(struct fdisk_context *cxt)
{
	unsigned long res;

	if (!cxt)
		return 0;

	if (!cxt->io_size)
		__discover_topology(cxt);

	res = cxt->io_size;

	/* use 1MiB grain always when possible */
	if (res < 2048 * 512)
		res = 2048 * 512;

	/* don't use huge grain on small devices */
	if (cxt->total_sectors <= (res * 4 / cxt->sector_size))
		res = cxt->phy_sector_size;

	return res;
}

/**
 * fdisk_reset_alignment:
 * @cxt: fdisk context
 *
 * Resets alignment setting to the default or label specific values.
 *
 * Returns: 0 on success, < 0 in case of error.
 */
int fdisk_reset_alignment(struct fdisk_context *cxt)
{
	int rc = 0;

	if (!cxt)
		return -EINVAL;

	/* default */
	cxt->grain = fdisk_topology_get_grain(cxt);
	cxt->first_lba = fdisk_topology_get_first_lba(cxt);

	/* overwrite default by label stuff */
	if (cxt->label && cxt->label->reset_alignment)
		rc = cxt->label->reset_alignment(cxt);

	DBG(LABEL, dbgprint("%s alignment reseted to: "
			    "first LBA=%ju, grain=%lu [rc=%d]",
			    cxt->label ? cxt->label->name : NULL,
			    (uintmax_t) cxt->first_lba,
			    cxt->grain,	rc));
	return rc;
}


/**
 * fdisk_create_disklabel:
 * @cxt: fdisk context
 * @name: label name
 *
 * Creates a new disk label of type @name. If @name is NULL, then it
 * will create a default system label type, either SUN or DOS.
 *
 * Returns 0 on success, otherwise, a corresponding error.
 */
int fdisk_create_disklabel(struct fdisk_context *cxt, const char *name)
{
	if (!cxt)
		return -EINVAL;

	cxt->label = NULL;

	if (!name) { /* use default label creation */
#ifdef __sparc__
		cxt->label = &sun_label;
#else
		cxt->label = &dos_label;
#endif
	} else {
		size_t i;

		for (i = 0; i < ARRAY_SIZE(labels); i++) {
			if (strcmp(name, labels[i]->name) != 0)
				continue;

			cxt->label = labels[i];
			DBG(LABEL, dbgprint("changing to %s label\n", cxt->label->name));
			break;
		}
	}

	if (!cxt->label)
		return -EINVAL;
	if (!cxt->label->create)
		return -ENOSYS;

	fdisk_reset_alignment(cxt);

	return cxt->label->create(cxt);
}

/**
 * fdisk_new_context:
 * @fname: path to the device to be handled
 * @readonly: how to open the device
 *
 * If the @readonly flag is set to false, fdisk will attempt to open
 * the device with read-write mode and will fallback to read-only if
 * unsuccessful.
 *
 * Returns: newly allocated fdisk context or NULL upon failure.
 */
struct fdisk_context *fdisk_new_context_from_filename(const char *fname, int readonly)
{
	int fd, errsv = 0;
	struct fdisk_context *cxt = NULL;

	DBG(CONTEXT, dbgprint("initializing context for %s", fname));

	if (readonly == 1 || (fd = open(fname, O_RDWR)) < 0) {
		if ((fd = open(fname, O_RDONLY)) < 0)
			return NULL;
		readonly = 1;
	}

	cxt = calloc(1, sizeof(*cxt));
	if (!cxt)
		goto fail;

	cxt->dev_fd = fd;
	cxt->dev_path = strdup(fname);
	if (!cxt->dev_path)
		goto fail;

	__discover_topology(cxt);
	__discover_system_geometry(cxt);

	if (fdisk_read_firstsector(cxt) < 0)
		goto fail;

	/* detect labels and apply labes specific stuff (e.g geomery)
	 * to the context */
	__probe_labels(cxt);

	fdisk_reset_alignment(cxt);

	DBG(CONTEXT, dbgprint("context %p initialized for %s [%s]",
			      cxt, fname,
			      readonly ? "READ-ONLY" : "READ-WRITE"));
	return cxt;
fail:
	errsv = errno;
	fdisk_free_context(cxt);
	errno = errsv;

	DBG(CONTEXT, dbgprint("failed to initialize context for %s: %m", fname));
	return NULL;
}

/**
 * fdisk_free_context:
 * @cxt: fdisk context
 *
 * Deallocates context struct.
 */
void fdisk_free_context(struct fdisk_context *cxt)
{
	if (!cxt)
		return;

	DBG(CONTEXT, dbgprint("freeing context %p for %s", cxt, cxt->dev_path));
	close(cxt->dev_fd);
	free(cxt->dev_path);
	free(cxt->firstsector);
	free(cxt);
}