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