// SPDX-License-Identifier: GPL-2.0-only

  /*
   * Persistent Storage - ramfs parts.
   *
   * Copyright (C) 2010 Intel Corporation <tony.luck@intel.com>

   */
  
  #include <linux/module.h>
  #include <linux/fs.h>
  #include <linux/fsnotify.h>
  #include <linux/pagemap.h>
  #include <linux/highmem.h>
  #include <linux/time.h>
  #include <linux/init.h>

  #include <linux/list.h>

  #include <linux/string.h>
  #include <linux/mount.h>

  #include <linux/seq_file.h>

  #include <linux/ramfs.h>

  #include <linux/parser.h>

  #include <linux/sched.h>
  #include <linux/magic.h>
  #include <linux/pstore.h>
  #include <linux/slab.h>
  #include <linux/uaccess.h>
  
  #include "internal.h"
  
  #define	PSTORE_NAMELEN	64

  static DEFINE_MUTEX(records_list_lock);

  static LIST_HEAD(records_list);

  static DEFINE_MUTEX(pstore_sb_lock);
  static struct super_block *pstore_sb;

  struct pstore_private {

  	struct list_head list;

  	struct dentry *dentry;

  	struct pstore_record *record;
  	size_t total_size;

  };

  struct pstore_ftrace_seq_data {
  	const void *ptr;
  	size_t off;
  	size_t size;
  };
  
  #define REC_SIZE sizeof(struct pstore_ftrace_record)

  static void free_pstore_private(struct pstore_private *private)
  {
  	if (!private)
  		return;

  	if (private->record) {
  		kfree(private->record->buf);
  		kfree(private->record);
  	}

  	kfree(private);
  }

  static void *pstore_ftrace_seq_start(struct seq_file *s, loff_t *pos)
  {
  	struct pstore_private *ps = s->private;
  	struct pstore_ftrace_seq_data *data;
  
  	data = kzalloc(sizeof(*data), GFP_KERNEL);
  	if (!data)
  		return NULL;

  	data->off = ps->total_size % REC_SIZE;

  	data->off += *pos * REC_SIZE;

  	if (data->off + REC_SIZE > ps->total_size) {

  		kfree(data);
  		return NULL;
  	}
  
  	return data;
  
  }
  
  static void pstore_ftrace_seq_stop(struct seq_file *s, void *v)
  {
  	kfree(v);
  }
  
  static void *pstore_ftrace_seq_next(struct seq_file *s, void *v, loff_t *pos)
  {
  	struct pstore_private *ps = s->private;
  	struct pstore_ftrace_seq_data *data = v;

  	(*pos)++;

  	data->off += REC_SIZE;

  	if (data->off + REC_SIZE > ps->total_size)

  		return NULL;

  	return data;
  }
  
  static int pstore_ftrace_seq_show(struct seq_file *s, void *v)
  {
  	struct pstore_private *ps = s->private;
  	struct pstore_ftrace_seq_data *data = v;

  	struct pstore_ftrace_record *rec;

  	if (!data)
  		return 0;

  	rec = (struct pstore_ftrace_record *)(ps->record->buf + data->off);

  	seq_printf(s, "CPU:%d ts:%llu %08lx  %08lx  %ps <- %pS
  ",

  		   pstore_ftrace_decode_cpu(rec),
  		   pstore_ftrace_read_timestamp(rec),
  		   rec->ip, rec->parent_ip, (void *)rec->ip,
  		   (void *)rec->parent_ip);

  
  	return 0;
  }
  
  static const struct seq_operations pstore_ftrace_seq_ops = {
  	.start	= pstore_ftrace_seq_start,
  	.next	= pstore_ftrace_seq_next,
  	.stop	= pstore_ftrace_seq_stop,
  	.show	= pstore_ftrace_seq_show,
  };

  static ssize_t pstore_file_read(struct file *file, char __user *userbuf,
  						size_t count, loff_t *ppos)
  {

  	struct seq_file *sf = file->private_data;
  	struct pstore_private *ps = sf->private;

  	if (ps->record->type == PSTORE_TYPE_FTRACE)

  		return seq_read(file, userbuf, count, ppos);

  	return simple_read_from_buffer(userbuf, count, ppos,
  				       ps->record->buf, ps->total_size);

  }

  static int pstore_file_open(struct inode *inode, struct file *file)
  {
  	struct pstore_private *ps = inode->i_private;
  	struct seq_file *sf;
  	int err;
  	const struct seq_operations *sops = NULL;

  	if (ps->record->type == PSTORE_TYPE_FTRACE)

  		sops = &pstore_ftrace_seq_ops;
  
  	err = seq_open(file, sops);
  	if (err < 0)
  		return err;
  
  	sf = file->private_data;
  	sf->private = ps;
  
  	return 0;
  }

  static loff_t pstore_file_llseek(struct file *file, loff_t off, int whence)

  {
  	struct seq_file *sf = file->private_data;
  
  	if (sf->op)

  		return seq_lseek(file, off, whence);
  	return default_llseek(file, off, whence);

  }

  static const struct file_operations pstore_file_operations = {

  	.open		= pstore_file_open,
  	.read		= pstore_file_read,
  	.llseek		= pstore_file_llseek,
  	.release	= seq_release,

  };

  
  /*
   * When a file is unlinked from our file system we call the
   * platform driver to erase the record from persistent store.
   */
  static int pstore_unlink(struct inode *dir, struct dentry *dentry)
  {

  	struct pstore_private *p = d_inode(dentry)->i_private;

  	struct pstore_record *record = p->record;

  	int rc = 0;

  	if (!record->psi->erase)

  		return -EPERM;

  	/* Make sure we can't race while removing this file. */
  	mutex_lock(&records_list_lock);
  	if (!list_empty(&p->list))
  		list_del_init(&p->list);
  	else
  		rc = -ENOENT;

  	p->dentry = NULL;

  	mutex_unlock(&records_list_lock);
  	if (rc)
  		return rc;

  	mutex_lock(&record->psi->read_mutex);
  	record->psi->erase(record);
  	mutex_unlock(&record->psi->read_mutex);

  
  	return simple_unlink(dir, dentry);
  }

  static void pstore_evict_inode(struct inode *inode)
  {

  	struct pstore_private	*p = inode->i_private;

  	clear_inode(inode);

  	free_pstore_private(p);

  }

  static const struct inode_operations pstore_dir_inode_operations = {
  	.lookup		= simple_lookup,
  	.unlink		= pstore_unlink,
  };

  static struct inode *pstore_get_inode(struct super_block *sb)

  {
  	struct inode *inode = new_inode(sb);

  	if (inode) {
  		inode->i_ino = get_next_ino();

  		inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);

  	}
  	return inode;
  }

  enum {
  	Opt_kmsg_bytes, Opt_err
  };
  
  static const match_table_t tokens = {
  	{Opt_kmsg_bytes, "kmsg_bytes=%u"},
  	{Opt_err, NULL}
  };
  
  static void parse_options(char *options)
  {
  	char		*p;
  	substring_t	args[MAX_OPT_ARGS];
  	int		option;
  
  	if (!options)
  		return;
  
  	while ((p = strsep(&options, ",")) != NULL) {
  		int token;
  
  		if (!*p)
  			continue;
  
  		token = match_token(p, tokens, args);
  		switch (token) {
  		case Opt_kmsg_bytes:
  			if (!match_int(&args[0], &option))
  				pstore_set_kmsg_bytes(option);
  			break;
  		}
  	}
  }

  /*
   * Display the mount options in /proc/mounts.
   */
  static int pstore_show_options(struct seq_file *m, struct dentry *root)
  {
  	if (kmsg_bytes != PSTORE_DEFAULT_KMSG_BYTES)
  		seq_printf(m, ",kmsg_bytes=%lu", kmsg_bytes);
  	return 0;
  }

  static int pstore_remount(struct super_block *sb, int *flags, char *data)
  {

  	sync_filesystem(sb);

  	parse_options(data);
  
  	return 0;
  }

  static const struct super_operations pstore_ops = {
  	.statfs		= simple_statfs,
  	.drop_inode	= generic_delete_inode,

  	.evict_inode	= pstore_evict_inode,

  	.remount_fs	= pstore_remount,

  	.show_options	= pstore_show_options,

  };

  static struct dentry *psinfo_lock_root(void)

  {

  	struct dentry *root;
  
  	mutex_lock(&pstore_sb_lock);
  	/*
  	 * Having no backend is fine -- no records appear.
  	 * Not being mounted is fine -- nothing to do.
  	 */
  	if (!psinfo || !pstore_sb) {
  		mutex_unlock(&pstore_sb_lock);
  		return NULL;
  	}
  
  	root = pstore_sb->s_root;
  	inode_lock(d_inode(root));
  	mutex_unlock(&pstore_sb_lock);
  
  	return root;

  }

  int pstore_put_backend_records(struct pstore_info *psi)
  {
  	struct pstore_private *pos, *tmp;
  	struct dentry *root;
  	int rc = 0;
  
  	root = psinfo_lock_root();
  	if (!root)
  		return 0;
  
  	mutex_lock(&records_list_lock);
  	list_for_each_entry_safe(pos, tmp, &records_list, list) {
  		if (pos->record->psi == psi) {
  			list_del_init(&pos->list);
  			rc = simple_unlink(d_inode(root), pos->dentry);
  			if (WARN_ON(rc))
  				break;
  			d_drop(pos->dentry);
  			dput(pos->dentry);
  			pos->dentry = NULL;
  		}
  	}
  	mutex_unlock(&records_list_lock);
  
  	inode_unlock(d_inode(root));
  
  	return rc;
  }

  /*
   * Make a regular file in the root directory of our file system.
   * Load it up with "size" bytes of data from "buf".
   * Set the mtime & ctime to the date that this record was originally stored.
   */

  int pstore_mkfile(struct dentry *root, struct pstore_record *record)

  {

  	struct dentry		*dentry;
  	struct inode		*inode;

  	int			rc = 0;

  	char			name[PSTORE_NAMELEN];

  	struct pstore_private	*private, *pos;

  	size_t			size = record->size + record->ecc_notice_size;

  	if (WARN_ON(!inode_is_locked(d_inode(root))))
  		return -EINVAL;

  	rc = -EEXIST;
  	/* Skip records that are already present in the filesystem. */

  	mutex_lock(&records_list_lock);

  	list_for_each_entry(pos, &records_list, list) {

  		if (pos->record->type == record->type &&
  		    pos->record->id == record->id &&

  		    pos->record->psi == record->psi)
  			goto fail;

  	}

  
  	rc = -ENOMEM;

  	inode = pstore_get_inode(root->d_sb);

  	if (!inode)
  		goto fail;

  	inode->i_mode = S_IFREG | 0444;
  	inode->i_fop = &pstore_file_operations;

  	scnprintf(name, sizeof(name), "%s-%s-%llu%s",
  			pstore_type_to_name(record->type),
  			record->psi->name, record->id,
  			record->compressed ? ".enc.z" : "");

  	private = kzalloc(sizeof(*private), GFP_KERNEL);
  	if (!private)
  		goto fail_inode;

  	dentry = d_alloc_name(root, name);

  	if (!dentry)

  		goto fail_private;

  	private->dentry = dentry;

  	private->record = record;

  	inode->i_size = private->total_size = size;

  	inode->i_private = private;

  	if (record->time.tv_sec)
  		inode->i_mtime = inode->i_ctime = record->time;

  	d_add(dentry, inode);

  	list_add(&private->list, &records_list);

  	mutex_unlock(&records_list_lock);

  	return 0;

  fail_private:

  	free_pstore_private(private);

  fail_inode:

  	iput(inode);

  fail:

  	mutex_unlock(&records_list_lock);

  	return rc;
  }

  /*
   * Read all the records from the persistent store. Create
   * files in our filesystem.  Don't warn about -EEXIST errors
   * when we are re-scanning the backing store looking to add new
   * error records.
   */
  void pstore_get_records(int quiet)
  {

  	struct dentry *root;

  	root = psinfo_lock_root();
  	if (!root)

  		return;

  	pstore_get_backend_records(psinfo, root, quiet);

  	inode_unlock(d_inode(root));
  }

  static int pstore_fill_super(struct super_block *sb, void *data, int silent)

  {

  	struct inode *inode;

  	sb->s_maxbytes		= MAX_LFS_FILESIZE;

  	sb->s_blocksize		= PAGE_SIZE;
  	sb->s_blocksize_bits	= PAGE_SHIFT;

  	sb->s_magic		= PSTOREFS_MAGIC;
  	sb->s_op		= &pstore_ops;
  	sb->s_time_gran		= 1;

  	parse_options(data);

  	inode = pstore_get_inode(sb);

  	if (inode) {

  		inode->i_mode = S_IFDIR | 0750;

  		inode->i_op = &pstore_dir_inode_operations;

  		inode->i_fop = &simple_dir_operations;
  		inc_nlink(inode);

  	}

  	sb->s_root = d_make_root(inode);
  	if (!sb->s_root)
  		return -ENOMEM;

  	mutex_lock(&pstore_sb_lock);
  	pstore_sb = sb;
  	mutex_unlock(&pstore_sb_lock);

  	pstore_get_records(0);

  
  	return 0;

  }

  static struct dentry *pstore_mount(struct file_system_type *fs_type,
  	int flags, const char *dev_name, void *data)

  {

  	return mount_single(fs_type, flags, data, pstore_fill_super);

  }
  
  static void pstore_kill_sb(struct super_block *sb)
  {

  	mutex_lock(&pstore_sb_lock);
  	WARN_ON(pstore_sb != sb);

  	kill_litter_super(sb);
  	pstore_sb = NULL;

  
  	mutex_lock(&records_list_lock);

  	INIT_LIST_HEAD(&records_list);

  	mutex_unlock(&records_list_lock);
  
  	mutex_unlock(&pstore_sb_lock);

  }
  
  static struct file_system_type pstore_fs_type = {

  	.owner          = THIS_MODULE,

  	.name		= "pstore",

  	.mount		= pstore_mount,

  	.kill_sb	= pstore_kill_sb,
  };

  int __init pstore_init_fs(void)

  {

  	int err;

  
  	/* Create a convenient mount point for people to access pstore */

  	err = sysfs_create_mount_point(fs_kobj, "pstore");
  	if (err)

  		goto out;

  
  	err = register_filesystem(&pstore_fs_type);
  	if (err < 0)

  		sysfs_remove_mount_point(fs_kobj, "pstore");

  
  out:
  	return err;

  }

  void __exit pstore_exit_fs(void)

  {
  	unregister_filesystem(&pstore_fs_type);
  	sysfs_remove_mount_point(fs_kobj, "pstore");
  }