path: root/fs/pstore/blk.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Implements pstore backend driver that write to block (or non-block) storage
 * devices, using the pstore/zone API.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/kernel.h>
#include <linux/module.h>
#include "../../block/blk.h"
#include <linux/blkdev.h>
#include <linux/string.h>
#include <linux/of.h>
#include <linux/of_address.h>
#include <linux/platform_device.h>
#include <linux/pstore_blk.h>
#include <linux/mount.h>
#include <linux/uio.h>

static long kmsg_size = CONFIG_PSTORE_BLK_KMSG_SIZE;
module_param(kmsg_size, long, 0400);
MODULE_PARM_DESC(kmsg_size, "kmsg dump record size in kbytes");

static int max_reason = CONFIG_PSTORE_BLK_MAX_REASON;
module_param(max_reason, int, 0400);
MODULE_PARM_DESC(max_reason,
		 "maximum reason for kmsg dump (default 2: Oops and Panic)");

/*
 * blkdev - the block device to use for pstore storage
 *
 * Usually, this will be a partition of a block device.
 *
 * blkdev accepts the following variants:
 * 1) <hex_major><hex_minor> device number in hexadecimal representation,
 *    with no leading 0x, for example b302.
 * 2) /dev/<disk_name> represents the device number of disk
 * 3) /dev/<disk_name><decimal> represents the device number
 *    of partition - device number of disk plus the partition number
 * 4) /dev/<disk_name>p<decimal> - same as the above, that form is
 *    used when disk name of partitioned disk ends on a digit.
 * 5) PARTUUID=00112233-4455-6677-8899-AABBCCDDEEFF representing the
 *    unique id of a partition if the partition table provides it.
 *    The UUID may be either an EFI/GPT UUID, or refer to an MSDOS
 *    partition using the format SSSSSSSS-PP, where SSSSSSSS is a zero-
 *    filled hex representation of the 32-bit "NT disk signature", and PP
 *    is a zero-filled hex representation of the 1-based partition number.
 * 6) PARTUUID=<UUID>/PARTNROFF=<int> to select a partition in relation to
 *    a partition with a known unique id.
 * 7) <major>:<minor> major and minor number of the device separated by
 *    a colon.
 */
static char blkdev[80] = CONFIG_PSTORE_BLK_BLKDEV;
module_param_string(blkdev, blkdev, 80, 0400);
MODULE_PARM_DESC(blkdev, "block device for pstore storage");

/*
 * All globals must only be accessed under the pstore_blk_lock
 * during the register/unregister functions.
 */
static DEFINE_MUTEX(pstore_blk_lock);
static struct block_device *psblk_bdev;
static struct pstore_zone_info *pstore_zone_info;
static pstore_blk_panic_write_op blkdev_panic_write;

struct bdev_info {
	dev_t devt;
	sector_t nr_sects;
	sector_t start_sect;
};

/**
 * struct pstore_device_info - back-end pstore/blk driver structure.
 *
 * @total_size: The total size in bytes pstore/blk can use. It must be greater
 *		than 4096 and be multiple of 4096.
 * @flags:	Refer to macro starting with PSTORE_FLAGS defined in
 *		linux/pstore.h. It means what front-ends this device support.
 *		Zero means all backends for compatible.
 * @read:	The general read operation. Both of the function parameters
 *		@size and @offset are relative value to bock device (not the
 *		whole disk).
 *		On success, the number of bytes should be returned, others
 *		means error.
 * @write:	The same as @read.
 * @panic_write:The write operation only used for panic case. It's optional
 *		if you do not care panic log. The parameters and return value
 *		are the same as @read.
 */
struct pstore_device_info {
	unsigned long total_size;
	unsigned int flags;
	pstore_zone_read_op read;
	pstore_zone_write_op write;
	pstore_zone_write_op panic_write;
};

static int psblk_register_do(struct pstore_device_info *dev)
{
	int ret;

	if (!dev || !dev->total_size || !dev->read || !dev->write)
		return -EINVAL;

	mutex_lock(&pstore_blk_lock);

	/* someone already registered before */
	if (pstore_zone_info) {
		mutex_unlock(&pstore_blk_lock);
		return -EBUSY;
	}
	pstore_zone_info = kzalloc(sizeof(struct pstore_zone_info), GFP_KERNEL);
	if (!pstore_zone_info) {
		mutex_unlock(&pstore_blk_lock);
		return -ENOMEM;
	}

	/* zero means not limit on which backends to attempt to store. */
	if (!dev->flags)
		dev->flags = UINT_MAX;

#define verify_size(name, alignsize, enabled) {				\
		long _##name_ = (enabled) ? (name) : 0;			\
		_##name_ = _##name_ <= 0 ? 0 : (_##name_ * 1024);	\
		if (_##name_ & ((alignsize) - 1)) {			\
			pr_info(#name " must align to %d\n",		\
					(alignsize));			\
			_##name_ = ALIGN(name, (alignsize));		\
		}							\
		name = _##name_ / 1024;					\
		pstore_zone_info->name = _##name_;			\
	}

	verify_size(kmsg_size, 4096, dev->flags & PSTORE_FLAGS_DMESG);
#undef verify_size

	pstore_zone_info->total_size = dev->total_size;
	pstore_zone_info->max_reason = max_reason;
	pstore_zone_info->read = dev->read;
	pstore_zone_info->write = dev->write;
	pstore_zone_info->panic_write = dev->panic_write;
	pstore_zone_info->name = KBUILD_MODNAME;
	pstore_zone_info->owner = THIS_MODULE;

	ret = register_pstore_zone(pstore_zone_info);
	if (ret) {
		kfree(pstore_zone_info);
		pstore_zone_info = NULL;
	}
	mutex_unlock(&pstore_blk_lock);
	return ret;
}

static void psblk_unregister_do(struct pstore_device_info *dev)
{
	mutex_lock(&pstore_blk_lock);
	if (pstore_zone_info && pstore_zone_info->read == dev->read) {
		unregister_pstore_zone(pstore_zone_info);
		kfree(pstore_zone_info);
		pstore_zone_info = NULL;
	}
	mutex_unlock(&pstore_blk_lock);
}

/**
 * psblk_get_bdev() - open block device
 *
 * @holder:	Exclusive holder identifier
 * @info:	Information about bdev to fill in
 *
 * Return: pointer to block device on success and others on error.
 *
 * On success, the returned block_device has reference count of one.
 */
static struct block_device *psblk_get_bdev(void *holder,
					   struct bdev_info *info)
{
	struct block_device *bdev = ERR_PTR(-ENODEV);
	fmode_t mode = FMODE_READ | FMODE_WRITE;
	sector_t nr_sects;

	lockdep_assert_held(&pstore_blk_lock);

	if (pstore_zone_info)
		return ERR_PTR(-EBUSY);

	if (!blkdev[0])
		return ERR_PTR(-ENODEV);

	if (holder)
		mode |= FMODE_EXCL;
	bdev = blkdev_get_by_path(blkdev, mode, holder);
	if (IS_ERR(bdev)) {
		dev_t devt;

		devt = name_to_dev_t(blkdev);
		if (devt == 0)
			return ERR_PTR(-ENODEV);
		bdev = blkdev_get_by_dev(devt, mode, holder);
		if (IS_ERR(bdev))
			return bdev;
	}

	nr_sects = part_nr_sects_read(bdev->bd_part);
	if (!nr_sects) {
		pr_err("not enough space for '%s'\n", blkdev);
		blkdev_put(bdev, mode);
		return ERR_PTR(-ENOSPC);
	}

	if (info) {
		info->devt = bdev->bd_dev;
		info->nr_sects = nr_sects;
		info->start_sect = get_start_sect(bdev);
	}

	return bdev;
}

static void psblk_put_bdev(struct block_device *bdev, void *holder)
{
	fmode_t mode = FMODE_READ | FMODE_WRITE;

	lockdep_assert_held(&pstore_blk_lock);

	if (!bdev)
		return;

	if (holder)
		mode |= FMODE_EXCL;
	blkdev_put(bdev, mode);
}

static ssize_t psblk_generic_blk_read(char *buf, size_t bytes, loff_t pos)
{
	struct block_device *bdev = psblk_bdev;
	struct file file;
	struct kiocb kiocb;
	struct iov_iter iter;
	struct kvec iov = {.iov_base = buf, .iov_len = bytes};

	if (!bdev)
		return -ENODEV;

	memset(&file, 0, sizeof(struct file));
	file.f_mapping = bdev->bd_inode->i_mapping;
	file.f_flags = O_DSYNC | __O_SYNC | O_NOATIME;
	file.f_inode = bdev->bd_inode;
	file_ra_state_init(&file.f_ra, file.f_mapping);

	init_sync_kiocb(&kiocb, &file);
	kiocb.ki_pos = pos;
	iov_iter_kvec(&iter, READ, &iov, 1, bytes);

	return generic_file_read_iter(&kiocb, &iter);
}

static ssize_t psblk_generic_blk_write(const char *buf, size_t bytes,
		loff_t pos)
{
	struct block_device *bdev = psblk_bdev;
	struct iov_iter iter;
	struct kiocb kiocb;
	struct file file;
	ssize_t ret;
	struct kvec iov = {.iov_base = (void *)buf, .iov_len = bytes};

	if (!bdev)
		return -ENODEV;

	/* Console/Ftrace backend may handle buffer until flush dirty zones */
	if (in_interrupt() || irqs_disabled())
		return -EBUSY;

	memset(&file, 0, sizeof(struct file));
	file.f_mapping = bdev->bd_inode->i_mapping;
	file.f_flags = O_DSYNC | __O_SYNC | O_NOATIME;
	file.f_inode = bdev->bd_inode;

	init_sync_kiocb(&kiocb, &file);
	kiocb.ki_pos = pos;
	iov_iter_kvec(&iter, WRITE, &iov, 1, bytes);

	inode_lock(bdev->bd_inode);
	ret = generic_write_checks(&kiocb, &iter);
	if (ret > 0)
		ret = generic_perform_write(&file, &iter, pos);
	inode_unlock(bdev->bd_inode);

	if (likely(ret > 0)) {
		const struct file_operations f_op = {.fsync = blkdev_fsync};

		file.f_op = &f_op;
		kiocb.ki_pos += ret;
		ret = generic_write_sync(&kiocb, ret);
	}
	return ret;
}

static ssize_t psblk_blk_panic_write(const char *buf, size_t size,
		loff_t off)
{
	int ret;

	if (!blkdev_panic_write)
		return -EOPNOTSUPP;

	/* size and off must align to SECTOR_SIZE for block device */
	ret = blkdev_panic_write(buf, off >> SECTOR_SHIFT,
			size >> SECTOR_SHIFT);
	return ret ? -EIO : size;
}

static int __register_pstore_blk(struct pstore_blk_info *info)
{
	char bdev_name[BDEVNAME_SIZE];
	struct block_device *bdev;
	struct pstore_device_info dev;
	struct bdev_info binfo;
	void *holder = blkdev;
	int ret = -ENODEV;

	lockdep_assert_held(&pstore_blk_lock);

	/* hold bdev exclusively */
	memset(&binfo, 0, sizeof(binfo));
	bdev = psblk_get_bdev(holder, &binfo);
	if (IS_ERR(bdev)) {
		pr_err("failed to open '%s'!\n", blkdev);
		return PTR_ERR(bdev);
	}

	/* only allow driver matching the @blkdev */
	if (!binfo.devt || MAJOR(binfo.devt) != info->major) {
		pr_debug("invalid major %u (expect %u)\n",
				info->major, MAJOR(binfo.devt));
		ret = -ENODEV;
		goto err_put_bdev;
	}

	/* psblk_bdev must be assigned before register to pstore/blk */
	psblk_bdev = bdev;
	blkdev_panic_write = info->panic_write;

	/* Copy back block device details. */
	info->devt = binfo.devt;
	info->nr_sects = binfo.nr_sects;
	info->start_sect = binfo.start_sect;

	memset(&dev, 0, sizeof(dev));
	dev.total_size = info->nr_sects << SECTOR_SHIFT;
	dev.flags = info->flags;
	dev.read = psblk_generic_blk_read;
	dev.write = psblk_generic_blk_write;
	dev.panic_write = info->panic_write ? psblk_blk_panic_write : NULL;

	ret = psblk_register_do(&dev);
	if (ret)
		goto err_put_bdev;

	bdevname(bdev, bdev_name);
	pr_info("attached %s%s\n", bdev_name,
		info->panic_write ? "" : " (no dedicated panic_write!)");
	return 0;

err_put_bdev:
	psblk_bdev = NULL;
	blkdev_panic_write = NULL;
	psblk_put_bdev(bdev, holder);
	return ret;
}

/**
 * register_pstore_blk() - register block device to pstore/blk
 *
 * @info: details on the desired block device interface
 *
 * Return:
 * * 0		- OK
 * * Others	- something error.
 */
int register_pstore_blk(struct pstore_blk_info *info)
{
	int ret;

	mutex_lock(&pstore_blk_lock);
	ret = __register_pstore_blk(info);
	mutex_unlock(&pstore_blk_lock);

	return ret;
}
EXPORT_SYMBOL_GPL(register_pstore_blk);

static void __unregister_pstore_blk(unsigned int major)
{
	struct pstore_device_info dev = { .read = psblk_generic_blk_read };
	void *holder = blkdev;

	lockdep_assert_held(&pstore_blk_lock);
	if (psblk_bdev && MAJOR(psblk_bdev->bd_dev) == major) {
		psblk_unregister_do(&dev);
		psblk_put_bdev(psblk_bdev, holder);
		blkdev_panic_write = NULL;
		psblk_bdev = NULL;
	}
}

/**
 * unregister_pstore_blk() - unregister block device from pstore/blk
 *
 * @major: the major device number of device
 */
void unregister_pstore_blk(unsigned int major)
{
	mutex_lock(&pstore_blk_lock);
	__unregister_pstore_blk(major);
	mutex_unlock(&pstore_blk_lock);
}
EXPORT_SYMBOL_GPL(unregister_pstore_blk);

static void __exit pstore_blk_exit(void)
{
	mutex_lock(&pstore_blk_lock);
	if (psblk_bdev)
		__unregister_pstore_blk(MAJOR(psblk_bdev->bd_dev));
	mutex_unlock(&pstore_blk_lock);
}
module_exit(pstore_blk_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("WeiXiong Liao <liaoweixiong@allwinnertech.com>");
MODULE_AUTHOR("Kees Cook <keescook@chromium.org>");
MODULE_DESCRIPTION("pstore backend for block devices");