xref: /kernel/linux/linux-6.6/fs/pstore/inode.c (revision 62306a36) 
1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Persistent Storage - ramfs parts.
4 *
5 * Copyright (C) 2010 Intel Corporation <tony.luck@intel.com>
6 */
7
8#include <linux/module.h>
9#include <linux/fs.h>
10#include <linux/fsnotify.h>
11#include <linux/pagemap.h>
12#include <linux/highmem.h>
13#include <linux/time.h>
14#include <linux/init.h>
15#include <linux/list.h>
16#include <linux/string.h>
17#include <linux/mount.h>
18#include <linux/seq_file.h>
19#include <linux/ramfs.h>
20#include <linux/parser.h>
21#include <linux/sched.h>
22#include <linux/magic.h>
23#include <linux/pstore.h>
24#include <linux/slab.h>
25#include <linux/uaccess.h>
26
27#include "internal.h"
28
29#define	PSTORE_NAMELEN	64
30
31static DEFINE_MUTEX(records_list_lock);
32static LIST_HEAD(records_list);
33
34static DEFINE_MUTEX(pstore_sb_lock);
35static struct super_block *pstore_sb;
36
37struct pstore_private {
38	struct list_head list;
39	struct dentry *dentry;
40	struct pstore_record *record;
41	size_t total_size;
42};
43
44struct pstore_ftrace_seq_data {
45	const void *ptr;
46	size_t off;
47	size_t size;
48};
49
50#define REC_SIZE sizeof(struct pstore_ftrace_record)
51
52static void free_pstore_private(struct pstore_private *private)
53{
54	if (!private)
55		return;
56	if (private->record) {
57		kvfree(private->record->buf);
58		kfree(private->record->priv);
59		kfree(private->record);
60	}
61	kfree(private);
62}
63
64static void *pstore_ftrace_seq_start(struct seq_file *s, loff_t *pos)
65{
66	struct pstore_private *ps = s->private;
67	struct pstore_ftrace_seq_data *data;
68
69	data = kzalloc(sizeof(*data), GFP_KERNEL);
70	if (!data)
71		return NULL;
72
73	data->off = ps->total_size % REC_SIZE;
74	data->off += *pos * REC_SIZE;
75	if (data->off + REC_SIZE > ps->total_size) {
76		kfree(data);
77		return NULL;
78	}
79
80	return data;
81
82}
83
84static void pstore_ftrace_seq_stop(struct seq_file *s, void *v)
85{
86	kfree(v);
87}
88
89static void *pstore_ftrace_seq_next(struct seq_file *s, void *v, loff_t *pos)
90{
91	struct pstore_private *ps = s->private;
92	struct pstore_ftrace_seq_data *data = v;
93
94	(*pos)++;
95	data->off += REC_SIZE;
96	if (data->off + REC_SIZE > ps->total_size)
97		return NULL;
98
99	return data;
100}
101
102static int pstore_ftrace_seq_show(struct seq_file *s, void *v)
103{
104	struct pstore_private *ps = s->private;
105	struct pstore_ftrace_seq_data *data = v;
106	struct pstore_ftrace_record *rec;
107
108	if (!data)
109		return 0;
110
111	rec = (struct pstore_ftrace_record *)(ps->record->buf + data->off);
112
113	seq_printf(s, "CPU:%d ts:%llu %08lx  %08lx  %ps <- %pS\n",
114		   pstore_ftrace_decode_cpu(rec),
115		   pstore_ftrace_read_timestamp(rec),
116		   rec->ip, rec->parent_ip, (void *)rec->ip,
117		   (void *)rec->parent_ip);
118
119	return 0;
120}
121
122static const struct seq_operations pstore_ftrace_seq_ops = {
123	.start	= pstore_ftrace_seq_start,
124	.next	= pstore_ftrace_seq_next,
125	.stop	= pstore_ftrace_seq_stop,
126	.show	= pstore_ftrace_seq_show,
127};
128
129static ssize_t pstore_file_read(struct file *file, char __user *userbuf,
130						size_t count, loff_t *ppos)
131{
132	struct seq_file *sf = file->private_data;
133	struct pstore_private *ps = sf->private;
134
135	if (ps->record->type == PSTORE_TYPE_FTRACE)
136		return seq_read(file, userbuf, count, ppos);
137	return simple_read_from_buffer(userbuf, count, ppos,
138				       ps->record->buf, ps->total_size);
139}
140
141static int pstore_file_open(struct inode *inode, struct file *file)
142{
143	struct pstore_private *ps = inode->i_private;
144	struct seq_file *sf;
145	int err;
146	const struct seq_operations *sops = NULL;
147
148	if (ps->record->type == PSTORE_TYPE_FTRACE)
149		sops = &pstore_ftrace_seq_ops;
150
151	err = seq_open(file, sops);
152	if (err < 0)
153		return err;
154
155	sf = file->private_data;
156	sf->private = ps;
157
158	return 0;
159}
160
161static loff_t pstore_file_llseek(struct file *file, loff_t off, int whence)
162{
163	struct seq_file *sf = file->private_data;
164
165	if (sf->op)
166		return seq_lseek(file, off, whence);
167	return default_llseek(file, off, whence);
168}
169
170static const struct file_operations pstore_file_operations = {
171	.open		= pstore_file_open,
172	.read		= pstore_file_read,
173	.llseek		= pstore_file_llseek,
174	.release	= seq_release,
175};
176
177/*
178 * When a file is unlinked from our file system we call the
179 * platform driver to erase the record from persistent store.
180 */
181static int pstore_unlink(struct inode *dir, struct dentry *dentry)
182{
183	struct pstore_private *p = d_inode(dentry)->i_private;
184	struct pstore_record *record = p->record;
185
186	if (!record->psi->erase)
187		return -EPERM;
188
189	/* Make sure we can't race while removing this file. */
190	scoped_guard(mutex, &records_list_lock) {
191		if (!list_empty(&p->list))
192			list_del_init(&p->list);
193		else
194			return -ENOENT;
195		p->dentry = NULL;
196	}
197
198	scoped_guard(mutex, &record->psi->read_mutex)
199		record->psi->erase(record);
200
201	return simple_unlink(dir, dentry);
202}
203
204static void pstore_evict_inode(struct inode *inode)
205{
206	struct pstore_private	*p = inode->i_private;
207
208	clear_inode(inode);
209	free_pstore_private(p);
210}
211
212static const struct inode_operations pstore_dir_inode_operations = {
213	.lookup		= simple_lookup,
214	.unlink		= pstore_unlink,
215};
216
217static struct inode *pstore_get_inode(struct super_block *sb)
218{
219	struct inode *inode = new_inode(sb);
220	if (inode) {
221		inode->i_ino = get_next_ino();
222		inode->i_atime = inode->i_mtime = inode_set_ctime_current(inode);
223	}
224	return inode;
225}
226
227enum {
228	Opt_kmsg_bytes, Opt_err
229};
230
231static const match_table_t tokens = {
232	{Opt_kmsg_bytes, "kmsg_bytes=%u"},
233	{Opt_err, NULL}
234};
235
236static void parse_options(char *options)
237{
238	char		*p;
239	substring_t	args[MAX_OPT_ARGS];
240	int		option;
241
242	if (!options)
243		return;
244
245	while ((p = strsep(&options, ",")) != NULL) {
246		int token;
247
248		if (!*p)
249			continue;
250
251		token = match_token(p, tokens, args);
252		switch (token) {
253		case Opt_kmsg_bytes:
254			if (!match_int(&args[0], &option))
255				pstore_set_kmsg_bytes(option);
256			break;
257		}
258	}
259}
260
261/*
262 * Display the mount options in /proc/mounts.
263 */
264static int pstore_show_options(struct seq_file *m, struct dentry *root)
265{
266	if (kmsg_bytes != CONFIG_PSTORE_DEFAULT_KMSG_BYTES)
267		seq_printf(m, ",kmsg_bytes=%lu", kmsg_bytes);
268	return 0;
269}
270
271static int pstore_remount(struct super_block *sb, int *flags, char *data)
272{
273	sync_filesystem(sb);
274	parse_options(data);
275
276	return 0;
277}
278
279static const struct super_operations pstore_ops = {
280	.statfs		= simple_statfs,
281	.drop_inode	= generic_delete_inode,
282	.evict_inode	= pstore_evict_inode,
283	.remount_fs	= pstore_remount,
284	.show_options	= pstore_show_options,
285};
286
287static struct dentry *psinfo_lock_root(void)
288{
289	struct dentry *root;
290
291	guard(mutex)(&pstore_sb_lock);
292	/*
293	 * Having no backend is fine -- no records appear.
294	 * Not being mounted is fine -- nothing to do.
295	 */
296	if (!psinfo || !pstore_sb)
297		return NULL;
298
299	root = pstore_sb->s_root;
300	inode_lock(d_inode(root));
301
302	return root;
303}
304
305int pstore_put_backend_records(struct pstore_info *psi)
306{
307	struct pstore_private *pos, *tmp;
308	struct dentry *root;
309
310	root = psinfo_lock_root();
311	if (!root)
312		return 0;
313
314	scoped_guard(mutex, &records_list_lock) {
315		list_for_each_entry_safe(pos, tmp, &records_list, list) {
316			if (pos->record->psi == psi) {
317				list_del_init(&pos->list);
318				d_invalidate(pos->dentry);
319				simple_unlink(d_inode(root), pos->dentry);
320				pos->dentry = NULL;
321			}
322		}
323	}
324
325	inode_unlock(d_inode(root));
326
327	return 0;
328}
329
330/*
331 * Make a regular file in the root directory of our file system.
332 * Load it up with "size" bytes of data from "buf".
333 * Set the mtime & ctime to the date that this record was originally stored.
334 */
335int pstore_mkfile(struct dentry *root, struct pstore_record *record)
336{
337	struct dentry		*dentry;
338	struct inode		*inode;
339	int			rc = 0;
340	char			name[PSTORE_NAMELEN];
341	struct pstore_private	*private, *pos;
342	size_t			size = record->size + record->ecc_notice_size;
343
344	if (WARN_ON(!inode_is_locked(d_inode(root))))
345		return -EINVAL;
346
347	guard(mutex)(&records_list_lock);
348
349	/* Skip records that are already present in the filesystem. */
350	list_for_each_entry(pos, &records_list, list) {
351		if (pos->record->type == record->type &&
352		    pos->record->id == record->id &&
353		    pos->record->psi == record->psi)
354			return -EEXIST;
355	}
356
357	rc = -ENOMEM;
358	inode = pstore_get_inode(root->d_sb);
359	if (!inode)
360		return -ENOMEM;
361	inode->i_mode = S_IFREG | 0444;
362	inode->i_fop = &pstore_file_operations;
363	scnprintf(name, sizeof(name), "%s-%s-%llu%s",
364			pstore_type_to_name(record->type),
365			record->psi->name, record->id,
366			record->compressed ? ".enc.z" : "");
367
368	private = kzalloc(sizeof(*private), GFP_KERNEL);
369	if (!private)
370		goto fail_inode;
371
372	dentry = d_alloc_name(root, name);
373	if (!dentry)
374		goto fail_private;
375
376	private->dentry = dentry;
377	private->record = record;
378	inode->i_size = private->total_size = size;
379	inode->i_private = private;
380
381	if (record->time.tv_sec)
382		inode->i_mtime = inode_set_ctime_to_ts(inode, record->time);
383
384	d_add(dentry, inode);
385
386	list_add(&private->list, &records_list);
387
388	return 0;
389
390fail_private:
391	free_pstore_private(private);
392fail_inode:
393	iput(inode);
394	return rc;
395}
396
397/*
398 * Read all the records from the persistent store. Create
399 * files in our filesystem.  Don't warn about -EEXIST errors
400 * when we are re-scanning the backing store looking to add new
401 * error records.
402 */
403void pstore_get_records(int quiet)
404{
405	struct dentry *root;
406
407	root = psinfo_lock_root();
408	if (!root)
409		return;
410
411	pstore_get_backend_records(psinfo, root, quiet);
412	inode_unlock(d_inode(root));
413}
414
415static int pstore_fill_super(struct super_block *sb, void *data, int silent)
416{
417	struct inode *inode;
418
419	sb->s_maxbytes		= MAX_LFS_FILESIZE;
420	sb->s_blocksize		= PAGE_SIZE;
421	sb->s_blocksize_bits	= PAGE_SHIFT;
422	sb->s_magic		= PSTOREFS_MAGIC;
423	sb->s_op		= &pstore_ops;
424	sb->s_time_gran		= 1;
425
426	parse_options(data);
427
428	inode = pstore_get_inode(sb);
429	if (inode) {
430		inode->i_mode = S_IFDIR | 0750;
431		inode->i_op = &pstore_dir_inode_operations;
432		inode->i_fop = &simple_dir_operations;
433		inc_nlink(inode);
434	}
435	sb->s_root = d_make_root(inode);
436	if (!sb->s_root)
437		return -ENOMEM;
438
439	scoped_guard(mutex, &pstore_sb_lock)
440		pstore_sb = sb;
441
442	pstore_get_records(0);
443
444	return 0;
445}
446
447static struct dentry *pstore_mount(struct file_system_type *fs_type,
448	int flags, const char *dev_name, void *data)
449{
450	return mount_single(fs_type, flags, data, pstore_fill_super);
451}
452
453static void pstore_kill_sb(struct super_block *sb)
454{
455	guard(mutex)(&pstore_sb_lock);
456	WARN_ON(pstore_sb && pstore_sb != sb);
457
458	kill_litter_super(sb);
459	pstore_sb = NULL;
460
461	guard(mutex)(&records_list_lock);
462	INIT_LIST_HEAD(&records_list);
463}
464
465static struct file_system_type pstore_fs_type = {
466	.owner          = THIS_MODULE,
467	.name		= "pstore",
468	.mount		= pstore_mount,
469	.kill_sb	= pstore_kill_sb,
470};
471
472int __init pstore_init_fs(void)
473{
474	int err;
475
476	/* Create a convenient mount point for people to access pstore */
477	err = sysfs_create_mount_point(fs_kobj, "pstore");
478	if (err)
479		goto out;
480
481	err = register_filesystem(&pstore_fs_type);
482	if (err < 0)
483		sysfs_remove_mount_point(fs_kobj, "pstore");
484
485out:
486	return err;
487}
488
489void __exit pstore_exit_fs(void)
490{
491	unregister_filesystem(&pstore_fs_type);
492	sysfs_remove_mount_point(fs_kobj, "pstore");
493}
494