cdev.c

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/*
 * Copyright (c) International Business Machines Corp., 2006
 *
 * 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)
 */

/*
 * This file includes implementation of UBI character device operations.
 *
 * There are two kinds of character devices in UBI: UBI character devices and
 * UBI volume character devices. UBI character devices allow users to
 * manipulate whole volumes: create, remove, and re-size them. Volume character
 * devices provide volume I/O capabilities.
 *
 * Major and minor numbers are assigned dynamically to both UBI and volume
 * character devices.
 */

#include <linux/module.h>
#include <linux/stat.h>
#include <linux/ioctl.h>
#include <linux/capability.h>
#include <mtd/ubi-user.h>
#include <asm/uaccess.h>
#include <asm/div64.h>
#include "ubi.h"

/*
 * Maximum sequence numbers of UBI and volume character device IOCTLs (direct
 * logical eraseblock erase is a debug-only feature).
 */
#define UBI_CDEV_IOC_MAX_SEQ 2
#ifndef CONFIG_MTD_UBI_DEBUG_USERSPACE_IO
#define VOL_CDEV_IOC_MAX_SEQ 1
#else
#define VOL_CDEV_IOC_MAX_SEQ 2
#endif

/**
 * major_to_device - get UBI device object by character device major number.
 * @major: major number
 *
 * This function returns a pointer to the UBI device object.
 */
static struct ubi_device *major_to_device(int major)
{
	int i;

	for (i = 0; i < ubi_devices_cnt; i++)
		if (ubi_devices[i] && ubi_devices[i]->major == major)
			return ubi_devices[i];
	BUG();
	return NULL;
}

/**
 * get_exclusive - get exclusive access to an UBI volume.
 * @desc: volume descriptor
 *
 * This function changes UBI volume open mode to "exclusive". Returns previous
 * mode value (positive integer) in case of success and a negative error code
 * in case of failure.
 */
static int get_exclusive(struct ubi_volume_desc *desc)
{
	int users, err;
	struct ubi_volume *vol = desc->vol;

	spin_lock(&vol->ubi->volumes_lock);
	users = vol->readers + vol->writers + vol->exclusive;
	ubi_assert(users > 0);
	if (users > 1) {
		dbg_err("%d users for volume %d", users, vol->vol_id);
		err = -EBUSY;
	} else {
		vol->readers = vol->writers = 0;
		vol->exclusive = 1;
		err = desc->mode;
		desc->mode = UBI_EXCLUSIVE;
	}
	spin_unlock(&vol->ubi->volumes_lock);

	return err;
}

/**
 * revoke_exclusive - revoke exclusive mode.
 * @desc: volume descriptor
 * @mode: new mode to switch to
 */
static void revoke_exclusive(struct ubi_volume_desc *desc, int mode)
{
	struct ubi_volume *vol = desc->vol;

	spin_lock(&vol->ubi->volumes_lock);
	ubi_assert(vol->readers == 0 && vol->writers == 0);
	ubi_assert(vol->exclusive == 1 && desc->mode == UBI_EXCLUSIVE);
	vol->exclusive = 0;
	if (mode == UBI_READONLY)
		vol->readers = 1;
	else if (mode == UBI_READWRITE)
		vol->writers = 1;
	else
		vol->exclusive = 1;
	spin_unlock(&vol->ubi->volumes_lock);

	desc->mode = mode;
}

static int vol_cdev_open(struct inode *inode, struct file *file)
{
	struct ubi_volume_desc *desc;
	const struct ubi_device *ubi = major_to_device(imajor(inode));
	int vol_id = iminor(inode) - 1;
	int mode;

	if (file->f_mode & FMODE_WRITE)
		mode = UBI_READWRITE;
	else
		mode = UBI_READONLY;

	dbg_msg("open volume %d, mode %d", vol_id, mode);

	desc = ubi_open_volume(ubi->ubi_num, vol_id, mode);
	if (IS_ERR(desc))
		return PTR_ERR(desc);

	file->private_data = desc;
	return 0;
}

static int vol_cdev_release(struct inode *inode, struct file *file)
{
	struct ubi_volume_desc *desc = file->private_data;
	struct ubi_volume *vol = desc->vol;

	dbg_msg("release volume %d, mode %d", vol->vol_id, desc->mode);

	if (vol->updating) {
		ubi_warn("update of volume %d not finished, volume is damaged",
			 vol->vol_id);
		vol->updating = 0;
		vfree(vol->upd_buf);
	}

	ubi_close_volume(desc);
	return 0;
}

static loff_t vol_cdev_llseek(struct file *file, loff_t offset, int origin)
{
	struct ubi_volume_desc *desc = file->private_data;
	struct ubi_volume *vol = desc->vol;
	loff_t new_offset;

	if (vol->updating) {
		 /* Update is in progress, seeking is prohibited */
		dbg_err("updating");
		return -EBUSY;
	}

	switch (origin) {
	case 0: /* SEEK_SET */
		new_offset = offset;
		break;
	case 1: /* SEEK_CUR */
		new_offset = file->f_pos + offset;
		break;
	case 2: /* SEEK_END */
		new_offset = vol->used_bytes + offset;
		break;
	default:
		return -EINVAL;
	}

	if (new_offset < 0 || new_offset > vol->used_bytes) {
		dbg_err("bad seek %lld", new_offset);
		return -EINVAL;
	}

	dbg_msg("seek volume %d, offset %lld, origin %d, new offset %lld",
		vol->vol_id, offset, origin, new_offset);

	file->f_pos = new_offset;
	return new_offset;
}

static ssize_t vol_cdev_read(struct file *file, __user char *buf, size_t count,
			     loff_t *offp)
{
	struct ubi_volume_desc *desc = file->private_data;
	struct ubi_volume *vol = desc->vol;
	struct ubi_device *ubi = vol->ubi;
	int err, lnum, off, len,  vol_id = desc->vol->vol_id, tbuf_size;
	size_t count_save = count;
	void *tbuf;
	uint64_t tmp;

	dbg_msg("read %zd bytes from offset %lld of volume %d",
		count, *offp, vol_id);

	if (vol->updating) {
		dbg_err("updating");
		return -EBUSY;
	}
	if (vol->upd_marker) {
		dbg_err("damaged volume, update marker is set");
		return -EBADF;
	}
	if (*offp == vol->used_bytes || count == 0)
		return 0;

	if (vol->corrupted)
		dbg_msg("read from corrupted volume %d", vol_id);

	if (*offp + count > vol->used_bytes)
		count_save = count = vol->used_bytes - *offp;

	tbuf_size = vol->usable_leb_size;
	if (count < tbuf_size)
		tbuf_size = ALIGN(count, ubi->min_io_size);
	tbuf = vmalloc(tbuf_size);
	if (!tbuf)
		return -ENOMEM;

	len = count > tbuf_size ? tbuf_size : count;

	tmp = *offp;
	off = do_div(tmp, vol->usable_leb_size);
	lnum = tmp;

	do {
		cond_resched();

		if (off + len >= vol->usable_leb_size)
			len = vol->usable_leb_size - off;

		err = ubi_eba_read_leb(ubi, vol_id, lnum, tbuf, off, len, 0);
		if (err)
			break;

		off += len;
		if (off == vol->usable_leb_size) {
			lnum += 1;
			off -= vol->usable_leb_size;
		}

		count -= len;
		*offp += len;

		err = copy_to_user(buf, tbuf, len);
		if (err) {
			err = -EFAULT;
			break;
		}

		buf += len;
		len = count > tbuf_size ? tbuf_size : count;
	} while (count);

	vfree(tbuf);
	return err ? err : count_save - count;
}

#ifdef CONFIG_MTD_UBI_DEBUG_USERSPACE_IO

/*
 * This function allows to directly write to dynamic UBI volumes, without
 * issuing the volume update operation. Available only as a debugging feature.
 * Very useful for testing UBI.
 */
static ssize_t vol_cdev_direct_write(struct file *file, const char __user *buf,
				     size_t count, loff_t *offp)
{
	struct ubi_volume_desc *desc = file->private_data;
	struct ubi_volume *vol = desc->vol;
	struct ubi_device *ubi = vol->ubi;
	int lnum, off, len, tbuf_size, vol_id = vol->vol_id, err = 0;
	size_t count_save = count;
	char *tbuf;
	uint64_t tmp;

	dbg_msg("requested: write %zd bytes to offset %lld of volume %u",
		count, *offp, desc->vol->vol_id);

	if (vol->vol_type == UBI_STATIC_VOLUME)
		return -EROFS;

	tmp = *offp;
	off = do_div(tmp, vol->usable_leb_size);
	lnum = tmp;

	if (off % ubi->min_io_size) {
		dbg_err("unaligned position");
		return -EINVAL;
	}

	if (*offp + count > vol->used_bytes)
		count_save = count = vol->used_bytes - *offp;

	/* We can write only in fractions of the minimum I/O unit */
	if (count % ubi->min_io_size) {
		dbg_err("unaligned write length");
		return -EINVAL;
	}

	tbuf_size = vol->usable_leb_size;
	if (count < tbuf_size)
		tbuf_size = ALIGN(count, ubi->min_io_size);
	tbuf = vmalloc(tbuf_size);
	if (!tbuf)
		return -ENOMEM;

	len = count > tbuf_size ? tbuf_size : count;

	while (count) {
		cond_resched();

		if (off + len >= vol->usable_leb_size)
			len = vol->usable_leb_size - off;

		err = copy_from_user(tbuf, buf, len);
		if (err) {
			err = -EFAULT;
			break;
		}

		err = ubi_eba_write_leb(ubi, vol_id, lnum, tbuf, off, len,
					UBI_UNKNOWN);
		if (err)
			break;

		off += len;
		if (off == vol->usable_leb_size) {
			lnum += 1;
			off -= vol->usable_leb_size;
		}