xref: /openbmc/linux/fs/pstore/inode.c (revision 45cc35e8) 
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 
31 static DEFINE_MUTEX(records_list_lock);
32 static LIST_HEAD(records_list);
33 
34 static DEFINE_MUTEX(pstore_sb_lock);
35 static struct super_block *pstore_sb;
36 
37 struct pstore_private {
38 	struct list_head list;
39 	struct dentry *dentry;
40 	struct pstore_record *record;
41 	size_t total_size;
42 };
43 
44 struct 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 
52 static 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->priv);
59 		kfree(private->record);
60 	}
61 	kfree(private);
62 }
63 
64 static 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 
84 static void pstore_ftrace_seq_stop(struct seq_file *s, void *v)
85 {
86 	kfree(v);
87 }
88 
89 static 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 
102 static 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 
122 static 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 
129 static 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 
141 static 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 
161 static 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 
170 static 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  */
181 static 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 	int rc = 0;
186 
187 	if (!record->psi->erase)
188 		return -EPERM;
189 
190 	/* Make sure we can't race while removing this file. */
191 	mutex_lock(&records_list_lock);
192 	if (!list_empty(&p->list))
193 		list_del_init(&p->list);
194 	else
195 		rc = -ENOENT;
196 	p->dentry = NULL;
197 	mutex_unlock(&records_list_lock);
198 	if (rc)
199 		return rc;
200 
201 	mutex_lock(&record->psi->read_mutex);
202 	record->psi->erase(record);
203 	mutex_unlock(&record->psi->read_mutex);
204 
205 	return simple_unlink(dir, dentry);
206 }
207 
208 static void pstore_evict_inode(struct inode *inode)
209 {
210 	struct pstore_private	*p = inode->i_private;
211 
212 	clear_inode(inode);
213 	free_pstore_private(p);
214 }
215 
216 static const struct inode_operations pstore_dir_inode_operations = {
217 	.lookup		= simple_lookup,
218 	.unlink		= pstore_unlink,
219 };
220 
221 static struct inode *pstore_get_inode(struct super_block *sb)
222 {
223 	struct inode *inode = new_inode(sb);
224 	if (inode) {
225 		inode->i_ino = get_next_ino();
226 		inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
227 	}
228 	return inode;
229 }
230 
231 enum {
232 	Opt_kmsg_bytes, Opt_err
233 };
234 
235 static const match_table_t tokens = {
236 	{Opt_kmsg_bytes, "kmsg_bytes=%u"},
237 	{Opt_err, NULL}
238 };
239 
240 static void parse_options(char *options)
241 {
242 	char		*p;
243 	substring_t	args[MAX_OPT_ARGS];
244 	int		option;
245 
246 	if (!options)
247 		return;
248 
249 	while ((p = strsep(&options, ",")) != NULL) {
250 		int token;
251 
252 		if (!*p)
253 			continue;
254 
255 		token = match_token(p, tokens, args);
256 		switch (token) {
257 		case Opt_kmsg_bytes:
258 			if (!match_int(&args[0], &option))
259 				pstore_set_kmsg_bytes(option);
260 			break;
261 		}
262 	}
263 }
264 
265 /*
266  * Display the mount options in /proc/mounts.
267  */
268 static int pstore_show_options(struct seq_file *m, struct dentry *root)
269 {
270 	if (kmsg_bytes != CONFIG_PSTORE_DEFAULT_KMSG_BYTES)
271 		seq_printf(m, ",kmsg_bytes=%lu", kmsg_bytes);
272 	return 0;
273 }
274 
275 static int pstore_remount(struct super_block *sb, int *flags, char *data)
276 {
277 	sync_filesystem(sb);
278 	parse_options(data);
279 
280 	return 0;
281 }
282 
283 static const struct super_operations pstore_ops = {
284 	.statfs		= simple_statfs,
285 	.drop_inode	= generic_delete_inode,
286 	.evict_inode	= pstore_evict_inode,
287 	.remount_fs	= pstore_remount,
288 	.show_options	= pstore_show_options,
289 };
290 
291 static struct dentry *psinfo_lock_root(void)
292 {
293 	struct dentry *root;
294 
295 	mutex_lock(&pstore_sb_lock);
296 	/*
297 	 * Having no backend is fine -- no records appear.
298 	 * Not being mounted is fine -- nothing to do.
299 	 */
300 	if (!psinfo || !pstore_sb) {
301 		mutex_unlock(&pstore_sb_lock);
302 		return NULL;
303 	}
304 
305 	root = pstore_sb->s_root;
306 	inode_lock(d_inode(root));
307 	mutex_unlock(&pstore_sb_lock);
308 
309 	return root;
310 }
311 
312 int pstore_put_backend_records(struct pstore_info *psi)
313 {
314 	struct pstore_private *pos, *tmp;
315 	struct dentry *root;
316 	int rc = 0;
317 
318 	root = psinfo_lock_root();
319 	if (!root)
320 		return 0;
321 
322 	mutex_lock(&records_list_lock);
323 	list_for_each_entry_safe(pos, tmp, &records_list, list) {
324 		if (pos->record->psi == psi) {
325 			list_del_init(&pos->list);
326 			rc = simple_unlink(d_inode(root), pos->dentry);
327 			if (WARN_ON(rc))
328 				break;
329 			d_drop(pos->dentry);
330 			dput(pos->dentry);
331 			pos->dentry = NULL;
332 		}
333 	}
334 	mutex_unlock(&records_list_lock);
335 
336 	inode_unlock(d_inode(root));
337 
338 	return rc;
339 }
340 
341 /*
342  * Make a regular file in the root directory of our file system.
343  * Load it up with "size" bytes of data from "buf".
344  * Set the mtime & ctime to the date that this record was originally stored.
345  */
346 int pstore_mkfile(struct dentry *root, struct pstore_record *record)
347 {
348 	struct dentry		*dentry;
349 	struct inode		*inode;
350 	int			rc = 0;
351 	char			name[PSTORE_NAMELEN];
352 	struct pstore_private	*private, *pos;
353 	size_t			size = record->size + record->ecc_notice_size;
354 
355 	if (WARN_ON(!inode_is_locked(d_inode(root))))
356 		return -EINVAL;
357 
358 	rc = -EEXIST;
359 	/* Skip records that are already present in the filesystem. */
360 	mutex_lock(&records_list_lock);
361 	list_for_each_entry(pos, &records_list, list) {
362 		if (pos->record->type == record->type &&
363 		    pos->record->id == record->id &&
364 		    pos->record->psi == record->psi)
365 			goto fail;
366 	}
367 
368 	rc = -ENOMEM;
369 	inode = pstore_get_inode(root->d_sb);
370 	if (!inode)
371 		goto fail;
372 	inode->i_mode = S_IFREG | 0444;
373 	inode->i_fop = &pstore_file_operations;
374 	scnprintf(name, sizeof(name), "%s-%s-%llu%s",
375 			pstore_type_to_name(record->type),
376 			record->psi->name, record->id,
377 			record->compressed ? ".enc.z" : "");
378 
379 	private = kzalloc(sizeof(*private), GFP_KERNEL);
380 	if (!private)
381 		goto fail_inode;
382 
383 	dentry = d_alloc_name(root, name);
384 	if (!dentry)
385 		goto fail_private;
386 
387 	private->dentry = dentry;
388 	private->record = record;
389 	inode->i_size = private->total_size = size;
390 	inode->i_private = private;
391 
392 	if (record->time.tv_sec)
393 		inode->i_mtime = inode->i_ctime = record->time;
394 
395 	d_add(dentry, inode);
396 
397 	list_add(&private->list, &records_list);
398 	mutex_unlock(&records_list_lock);
399 
400 	return 0;
401 
402 fail_private:
403 	free_pstore_private(private);
404 fail_inode:
405 	iput(inode);
406 fail:
407 	mutex_unlock(&records_list_lock);
408 	return rc;
409 }
410 
411 /*
412  * Read all the records from the persistent store. Create
413  * files in our filesystem.  Don't warn about -EEXIST errors
414  * when we are re-scanning the backing store looking to add new
415  * error records.
416  */
417 void pstore_get_records(int quiet)
418 {
419 	struct dentry *root;
420 
421 	root = psinfo_lock_root();
422 	if (!root)
423 		return;
424 
425 	pstore_get_backend_records(psinfo, root, quiet);
426 	inode_unlock(d_inode(root));
427 }
428 
429 static int pstore_fill_super(struct super_block *sb, void *data, int silent)
430 {
431 	struct inode *inode;
432 
433 	sb->s_maxbytes		= MAX_LFS_FILESIZE;
434 	sb->s_blocksize		= PAGE_SIZE;
435 	sb->s_blocksize_bits	= PAGE_SHIFT;
436 	sb->s_magic		= PSTOREFS_MAGIC;
437 	sb->s_op		= &pstore_ops;
438 	sb->s_time_gran		= 1;
439 
440 	parse_options(data);
441 
442 	inode = pstore_get_inode(sb);
443 	if (inode) {
444 		inode->i_mode = S_IFDIR | 0750;
445 		inode->i_op = &pstore_dir_inode_operations;
446 		inode->i_fop = &simple_dir_operations;
447 		inc_nlink(inode);
448 	}
449 	sb->s_root = d_make_root(inode);
450 	if (!sb->s_root)
451 		return -ENOMEM;
452 
453 	mutex_lock(&pstore_sb_lock);
454 	pstore_sb = sb;
455 	mutex_unlock(&pstore_sb_lock);
456 
457 	pstore_get_records(0);
458 
459 	return 0;
460 }
461 
462 static struct dentry *pstore_mount(struct file_system_type *fs_type,
463 	int flags, const char *dev_name, void *data)
464 {
465 	return mount_single(fs_type, flags, data, pstore_fill_super);
466 }
467 
468 static void pstore_kill_sb(struct super_block *sb)
469 {
470 	mutex_lock(&pstore_sb_lock);
471 	WARN_ON(pstore_sb && pstore_sb != sb);
472 
473 	kill_litter_super(sb);
474 	pstore_sb = NULL;
475 
476 	mutex_lock(&records_list_lock);
477 	INIT_LIST_HEAD(&records_list);
478 	mutex_unlock(&records_list_lock);
479 
480 	mutex_unlock(&pstore_sb_lock);
481 }
482 
483 static struct file_system_type pstore_fs_type = {
484 	.owner          = THIS_MODULE,
485 	.name		= "pstore",
486 	.mount		= pstore_mount,
487 	.kill_sb	= pstore_kill_sb,
488 };
489 
490 int __init pstore_init_fs(void)
491 {
492 	int err;
493 
494 	/* Create a convenient mount point for people to access pstore */
495 	err = sysfs_create_mount_point(fs_kobj, "pstore");
496 	if (err)
497 		goto out;
498 
499 	err = register_filesystem(&pstore_fs_type);
500 	if (err < 0)
501 		sysfs_remove_mount_point(fs_kobj, "pstore");
502 
503 out:
504 	return err;
505 }
506 
507 void __exit pstore_exit_fs(void)
508 {
509 	unregister_filesystem(&pstore_fs_type);
510 	sysfs_remove_mount_point(fs_kobj, "pstore");
511 }
512