xref: /kernel/linux/linux-5.10/fs/pstore/inode.c (revision 8c2ecf20) 
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		kfree(private->record->buf);
58		kfree(private->record);
59	}
60	kfree(private);
61}
62
63static void *pstore_ftrace_seq_start(struct seq_file *s, loff_t *pos)
64{
65	struct pstore_private *ps = s->private;
66	struct pstore_ftrace_seq_data *data;
67
68	data = kzalloc(sizeof(*data), GFP_KERNEL);
69	if (!data)
70		return NULL;
71
72	data->off = ps->total_size % REC_SIZE;
73	data->off += *pos * REC_SIZE;
74	if (data->off + REC_SIZE > ps->total_size) {
75		kfree(data);
76		return NULL;
77	}
78
79	return data;
80
81}
82
83static void pstore_ftrace_seq_stop(struct seq_file *s, void *v)
84{
85	kfree(v);
86}
87
88static void *pstore_ftrace_seq_next(struct seq_file *s, void *v, loff_t *pos)
89{
90	struct pstore_private *ps = s->private;
91	struct pstore_ftrace_seq_data *data = v;
92
93	(*pos)++;
94	data->off += REC_SIZE;
95	if (data->off + REC_SIZE > ps->total_size)
96		return NULL;
97
98	return data;
99}
100
101static int pstore_ftrace_seq_show(struct seq_file *s, void *v)
102{
103	struct pstore_private *ps = s->private;
104	struct pstore_ftrace_seq_data *data = v;
105	struct pstore_ftrace_record *rec;
106
107	if (!data)
108		return 0;
109
110	rec = (struct pstore_ftrace_record *)(ps->record->buf + data->off);
111
112	seq_printf(s, "CPU:%d ts:%llu %08lx  %08lx  %ps <- %pS\n",
113		   pstore_ftrace_decode_cpu(rec),
114		   pstore_ftrace_read_timestamp(rec),
115		   rec->ip, rec->parent_ip, (void *)rec->ip,
116		   (void *)rec->parent_ip);
117
118	return 0;
119}
120
121static const struct seq_operations pstore_ftrace_seq_ops = {
122	.start	= pstore_ftrace_seq_start,
123	.next	= pstore_ftrace_seq_next,
124	.stop	= pstore_ftrace_seq_stop,
125	.show	= pstore_ftrace_seq_show,
126};
127
128static ssize_t pstore_file_read(struct file *file, char __user *userbuf,
129						size_t count, loff_t *ppos)
130{
131	struct seq_file *sf = file->private_data;
132	struct pstore_private *ps = sf->private;
133
134	if (ps->record->type == PSTORE_TYPE_FTRACE)
135		return seq_read(file, userbuf, count, ppos);
136	return simple_read_from_buffer(userbuf, count, ppos,
137				       ps->record->buf, ps->total_size);
138}
139
140static int pstore_file_open(struct inode *inode, struct file *file)
141{
142	struct pstore_private *ps = inode->i_private;
143	struct seq_file *sf;
144	int err;
145	const struct seq_operations *sops = NULL;
146
147	if (ps->record->type == PSTORE_TYPE_FTRACE)
148		sops = &pstore_ftrace_seq_ops;
149
150	err = seq_open(file, sops);
151	if (err < 0)
152		return err;
153
154	sf = file->private_data;
155	sf->private = ps;
156
157	return 0;
158}
159
160static loff_t pstore_file_llseek(struct file *file, loff_t off, int whence)
161{
162	struct seq_file *sf = file->private_data;
163
164	if (sf->op)
165		return seq_lseek(file, off, whence);
166	return default_llseek(file, off, whence);
167}
168
169static const struct file_operations pstore_file_operations = {
170	.open		= pstore_file_open,
171	.read		= pstore_file_read,
172	.llseek		= pstore_file_llseek,
173	.release	= seq_release,
174};
175
176/*
177 * When a file is unlinked from our file system we call the
178 * platform driver to erase the record from persistent store.
179 */
180static int pstore_unlink(struct inode *dir, struct dentry *dentry)
181{
182	struct pstore_private *p = d_inode(dentry)->i_private;
183	struct pstore_record *record = p->record;
184	int rc = 0;
185
186	if (!record->psi->erase)
187		return -EPERM;
188
189	/* Make sure we can't race while removing this file. */
190	mutex_lock(&records_list_lock);
191	if (!list_empty(&p->list))
192		list_del_init(&p->list);
193	else
194		rc = -ENOENT;
195	p->dentry = NULL;
196	mutex_unlock(&records_list_lock);
197	if (rc)
198		return rc;
199
200	mutex_lock(&record->psi->read_mutex);
201	record->psi->erase(record);
202	mutex_unlock(&record->psi->read_mutex);
203
204	return simple_unlink(dir, dentry);
205}
206
207static void pstore_evict_inode(struct inode *inode)
208{
209	struct pstore_private	*p = inode->i_private;
210
211	clear_inode(inode);
212	free_pstore_private(p);
213}
214
215static const struct inode_operations pstore_dir_inode_operations = {
216	.lookup		= simple_lookup,
217	.unlink		= pstore_unlink,
218};
219
220static struct inode *pstore_get_inode(struct super_block *sb)
221{
222	struct inode *inode = new_inode(sb);
223	if (inode) {
224		inode->i_ino = get_next_ino();
225		inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
226	}
227	return inode;
228}
229
230enum {
231	Opt_kmsg_bytes, Opt_err
232};
233
234static const match_table_t tokens = {
235	{Opt_kmsg_bytes, "kmsg_bytes=%u"},
236	{Opt_err, NULL}
237};
238
239static void parse_options(char *options)
240{
241	char		*p;
242	substring_t	args[MAX_OPT_ARGS];
243	int		option;
244
245	if (!options)
246		return;
247
248	while ((p = strsep(&options, ",")) != NULL) {
249		int token;
250
251		if (!*p)
252			continue;
253
254		token = match_token(p, tokens, args);
255		switch (token) {
256		case Opt_kmsg_bytes:
257			if (!match_int(&args[0], &option))
258				pstore_set_kmsg_bytes(option);
259			break;
260		}
261	}
262}
263
264/*
265 * Display the mount options in /proc/mounts.
266 */
267static int pstore_show_options(struct seq_file *m, struct dentry *root)
268{
269	if (kmsg_bytes != PSTORE_DEFAULT_KMSG_BYTES)
270		seq_printf(m, ",kmsg_bytes=%lu", kmsg_bytes);
271	return 0;
272}
273
274static int pstore_remount(struct super_block *sb, int *flags, char *data)
275{
276	sync_filesystem(sb);
277	parse_options(data);
278
279	return 0;
280}
281
282static const struct super_operations pstore_ops = {
283	.statfs		= simple_statfs,
284	.drop_inode	= generic_delete_inode,
285	.evict_inode	= pstore_evict_inode,
286	.remount_fs	= pstore_remount,
287	.show_options	= pstore_show_options,
288};
289
290static struct dentry *psinfo_lock_root(void)
291{
292	struct dentry *root;
293
294	mutex_lock(&pstore_sb_lock);
295	/*
296	 * Having no backend is fine -- no records appear.
297	 * Not being mounted is fine -- nothing to do.
298	 */
299	if (!psinfo || !pstore_sb) {
300		mutex_unlock(&pstore_sb_lock);
301		return NULL;
302	}
303
304	root = pstore_sb->s_root;
305	inode_lock(d_inode(root));
306	mutex_unlock(&pstore_sb_lock);
307
308	return root;
309}
310
311int pstore_put_backend_records(struct pstore_info *psi)
312{
313	struct pstore_private *pos, *tmp;
314	struct dentry *root;
315
316	root = psinfo_lock_root();
317	if (!root)
318		return 0;
319
320	mutex_lock(&records_list_lock);
321	list_for_each_entry_safe(pos, tmp, &records_list, list) {
322		if (pos->record->psi == psi) {
323			list_del_init(&pos->list);
324			d_invalidate(pos->dentry);
325			simple_unlink(d_inode(root), pos->dentry);
326			pos->dentry = NULL;
327		}
328	}
329	mutex_unlock(&records_list_lock);
330
331	inode_unlock(d_inode(root));
332
333	return 0;
334}
335
336/*
337 * Make a regular file in the root directory of our file system.
338 * Load it up with "size" bytes of data from "buf".
339 * Set the mtime & ctime to the date that this record was originally stored.
340 */
341int pstore_mkfile(struct dentry *root, struct pstore_record *record)
342{
343	struct dentry		*dentry;
344	struct inode		*inode;
345	int			rc = 0;
346	char			name[PSTORE_NAMELEN];
347	struct pstore_private	*private, *pos;
348	size_t			size = record->size + record->ecc_notice_size;
349
350	if (WARN_ON(!inode_is_locked(d_inode(root))))
351		return -EINVAL;
352
353	rc = -EEXIST;
354	/* Skip records that are already present in the filesystem. */
355	mutex_lock(&records_list_lock);
356	list_for_each_entry(pos, &records_list, list) {
357		if (pos->record->type == record->type &&
358		    pos->record->id == record->id &&
359		    pos->record->psi == record->psi)
360			goto fail;
361	}
362
363	rc = -ENOMEM;
364	inode = pstore_get_inode(root->d_sb);
365	if (!inode)
366		goto fail;
367	inode->i_mode = S_IFREG | 0444;
368	inode->i_fop = &pstore_file_operations;
369	scnprintf(name, sizeof(name), "%s-%s-%llu%s",
370			pstore_type_to_name(record->type),
371			record->psi->name, record->id,
372			record->compressed ? ".enc.z" : "");
373
374	private = kzalloc(sizeof(*private), GFP_KERNEL);
375	if (!private)
376		goto fail_inode;
377
378	dentry = d_alloc_name(root, name);
379	if (!dentry)
380		goto fail_private;
381
382	private->dentry = dentry;
383	private->record = record;
384	inode->i_size = private->total_size = size;
385	inode->i_private = private;
386
387	if (record->time.tv_sec)
388		inode->i_mtime = inode->i_ctime = record->time;
389
390	d_add(dentry, inode);
391
392	list_add(&private->list, &records_list);
393	mutex_unlock(&records_list_lock);
394
395	return 0;
396
397fail_private:
398	free_pstore_private(private);
399fail_inode:
400	iput(inode);
401fail:
402	mutex_unlock(&records_list_lock);
403	return rc;
404}
405
406/*
407 * Read all the records from the persistent store. Create
408 * files in our filesystem.  Don't warn about -EEXIST errors
409 * when we are re-scanning the backing store looking to add new
410 * error records.
411 */
412void pstore_get_records(int quiet)
413{
414	struct dentry *root;
415
416	root = psinfo_lock_root();
417	if (!root)
418		return;
419
420	pstore_get_backend_records(psinfo, root, quiet);
421	inode_unlock(d_inode(root));
422}
423
424static int pstore_fill_super(struct super_block *sb, void *data, int silent)
425{
426	struct inode *inode;
427
428	sb->s_maxbytes		= MAX_LFS_FILESIZE;
429	sb->s_blocksize		= PAGE_SIZE;
430	sb->s_blocksize_bits	= PAGE_SHIFT;
431	sb->s_magic		= PSTOREFS_MAGIC;
432	sb->s_op		= &pstore_ops;
433	sb->s_time_gran		= 1;
434
435	parse_options(data);
436
437	inode = pstore_get_inode(sb);
438	if (inode) {
439		inode->i_mode = S_IFDIR | 0750;
440		inode->i_op = &pstore_dir_inode_operations;
441		inode->i_fop = &simple_dir_operations;
442		inc_nlink(inode);
443	}
444	sb->s_root = d_make_root(inode);
445	if (!sb->s_root)
446		return -ENOMEM;
447
448	mutex_lock(&pstore_sb_lock);
449	pstore_sb = sb;
450	mutex_unlock(&pstore_sb_lock);
451
452	pstore_get_records(0);
453
454	return 0;
455}
456
457static struct dentry *pstore_mount(struct file_system_type *fs_type,
458	int flags, const char *dev_name, void *data)
459{
460	return mount_single(fs_type, flags, data, pstore_fill_super);
461}
462
463static void pstore_kill_sb(struct super_block *sb)
464{
465	mutex_lock(&pstore_sb_lock);
466	WARN_ON(pstore_sb && pstore_sb != sb);
467
468	kill_litter_super(sb);
469	pstore_sb = NULL;
470
471	mutex_lock(&records_list_lock);
472	INIT_LIST_HEAD(&records_list);
473	mutex_unlock(&records_list_lock);
474
475	mutex_unlock(&pstore_sb_lock);
476}
477
478static struct file_system_type pstore_fs_type = {
479	.owner          = THIS_MODULE,
480	.name		= "pstore",
481	.mount		= pstore_mount,
482	.kill_sb	= pstore_kill_sb,
483};
484
485int __init pstore_init_fs(void)
486{
487	int err;
488
489	/* Create a convenient mount point for people to access pstore */
490	err = sysfs_create_mount_point(fs_kobj, "pstore");
491	if (err)
492		goto out;
493
494	err = register_filesystem(&pstore_fs_type);
495	if (err < 0)
496		sysfs_remove_mount_point(fs_kobj, "pstore");
497
498out:
499	return err;
500}
501
502void __exit pstore_exit_fs(void)
503{
504	unregister_filesystem(&pstore_fs_type);
505	sysfs_remove_mount_point(fs_kobj, "pstore");
506}
507