xref: /openbmc/linux/fs/pstore/inode.c (revision 5f66f73b) 
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);
59 	}
60 	kfree(private);
61 }
62 
63 static 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 
83 static void pstore_ftrace_seq_stop(struct seq_file *s, void *v)
84 {
85 	kfree(v);
86 }
87 
88 static 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 
101 static 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 
121 static 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 
128 static 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 
140 static 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 
160 static 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 
169 static 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  */
180 static 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 
207 static 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 
215 static const struct inode_operations pstore_dir_inode_operations = {
216 	.lookup		= simple_lookup,
217 	.unlink		= pstore_unlink,
218 };
219 
220 static 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 
230 enum {
231 	Opt_kmsg_bytes, Opt_err
232 };
233 
234 static const match_table_t tokens = {
235 	{Opt_kmsg_bytes, "kmsg_bytes=%u"},
236 	{Opt_err, NULL}
237 };
238 
239 static 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  */
267 static int pstore_show_options(struct seq_file *m, struct dentry *root)
268 {
269 	if (kmsg_bytes != CONFIG_PSTORE_DEFAULT_KMSG_BYTES)
270 		seq_printf(m, ",kmsg_bytes=%lu", kmsg_bytes);
271 	return 0;
272 }
273 
274 static 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 
282 static 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 
290 static 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 
311 int pstore_put_backend_records(struct pstore_info *psi)
312 {
313 	struct pstore_private *pos, *tmp;
314 	struct dentry *root;
315 	int rc = 0;
316 
317 	root = psinfo_lock_root();
318 	if (!root)
319 		return 0;
320 
321 	mutex_lock(&records_list_lock);
322 	list_for_each_entry_safe(pos, tmp, &records_list, list) {
323 		if (pos->record->psi == psi) {
324 			list_del_init(&pos->list);
325 			rc = simple_unlink(d_inode(root), pos->dentry);
326 			if (WARN_ON(rc))
327 				break;
328 			d_drop(pos->dentry);
329 			dput(pos->dentry);
330 			pos->dentry = NULL;
331 		}
332 	}
333 	mutex_unlock(&records_list_lock);
334 
335 	inode_unlock(d_inode(root));
336 
337 	return rc;
338 }
339 
340 /*
341  * Make a regular file in the root directory of our file system.
342  * Load it up with "size" bytes of data from "buf".
343  * Set the mtime & ctime to the date that this record was originally stored.
344  */
345 int pstore_mkfile(struct dentry *root, struct pstore_record *record)
346 {
347 	struct dentry		*dentry;
348 	struct inode		*inode;
349 	int			rc = 0;
350 	char			name[PSTORE_NAMELEN];
351 	struct pstore_private	*private, *pos;
352 	size_t			size = record->size + record->ecc_notice_size;
353 
354 	if (WARN_ON(!inode_is_locked(d_inode(root))))
355 		return -EINVAL;
356 
357 	rc = -EEXIST;
358 	/* Skip records that are already present in the filesystem. */
359 	mutex_lock(&records_list_lock);
360 	list_for_each_entry(pos, &records_list, list) {
361 		if (pos->record->type == record->type &&
362 		    pos->record->id == record->id &&
363 		    pos->record->psi == record->psi)
364 			goto fail;
365 	}
366 
367 	rc = -ENOMEM;
368 	inode = pstore_get_inode(root->d_sb);
369 	if (!inode)
370 		goto fail;
371 	inode->i_mode = S_IFREG | 0444;
372 	inode->i_fop = &pstore_file_operations;
373 	scnprintf(name, sizeof(name), "%s-%s-%llu%s",
374 			pstore_type_to_name(record->type),
375 			record->psi->name, record->id,
376 			record->compressed ? ".enc.z" : "");
377 
378 	private = kzalloc(sizeof(*private), GFP_KERNEL);
379 	if (!private)
380 		goto fail_inode;
381 
382 	dentry = d_alloc_name(root, name);
383 	if (!dentry)
384 		goto fail_private;
385 
386 	private->dentry = dentry;
387 	private->record = record;
388 	inode->i_size = private->total_size = size;
389 	inode->i_private = private;
390 
391 	if (record->time.tv_sec)
392 		inode->i_mtime = inode->i_ctime = record->time;
393 
394 	d_add(dentry, inode);
395 
396 	list_add(&private->list, &records_list);
397 	mutex_unlock(&records_list_lock);
398 
399 	return 0;
400 
401 fail_private:
402 	free_pstore_private(private);
403 fail_inode:
404 	iput(inode);
405 fail:
406 	mutex_unlock(&records_list_lock);
407 	return rc;
408 }
409 
410 /*
411  * Read all the records from the persistent store. Create
412  * files in our filesystem.  Don't warn about -EEXIST errors
413  * when we are re-scanning the backing store looking to add new
414  * error records.
415  */
416 void pstore_get_records(int quiet)
417 {
418 	struct dentry *root;
419 
420 	root = psinfo_lock_root();
421 	if (!root)
422 		return;
423 
424 	pstore_get_backend_records(psinfo, root, quiet);
425 	inode_unlock(d_inode(root));
426 }
427 
428 static int pstore_fill_super(struct super_block *sb, void *data, int silent)
429 {
430 	struct inode *inode;
431 
432 	sb->s_maxbytes		= MAX_LFS_FILESIZE;
433 	sb->s_blocksize		= PAGE_SIZE;
434 	sb->s_blocksize_bits	= PAGE_SHIFT;
435 	sb->s_magic		= PSTOREFS_MAGIC;
436 	sb->s_op		= &pstore_ops;
437 	sb->s_time_gran		= 1;
438 
439 	parse_options(data);
440 
441 	inode = pstore_get_inode(sb);
442 	if (inode) {
443 		inode->i_mode = S_IFDIR | 0750;
444 		inode->i_op = &pstore_dir_inode_operations;
445 		inode->i_fop = &simple_dir_operations;
446 		inc_nlink(inode);
447 	}
448 	sb->s_root = d_make_root(inode);
449 	if (!sb->s_root)
450 		return -ENOMEM;
451 
452 	mutex_lock(&pstore_sb_lock);
453 	pstore_sb = sb;
454 	mutex_unlock(&pstore_sb_lock);
455 
456 	pstore_get_records(0);
457 
458 	return 0;
459 }
460 
461 static struct dentry *pstore_mount(struct file_system_type *fs_type,
462 	int flags, const char *dev_name, void *data)
463 {
464 	return mount_single(fs_type, flags, data, pstore_fill_super);
465 }
466 
467 static void pstore_kill_sb(struct super_block *sb)
468 {
469 	mutex_lock(&pstore_sb_lock);
470 	WARN_ON(pstore_sb && pstore_sb != sb);
471 
472 	kill_litter_super(sb);
473 	pstore_sb = NULL;
474 
475 	mutex_lock(&records_list_lock);
476 	INIT_LIST_HEAD(&records_list);
477 	mutex_unlock(&records_list_lock);
478 
479 	mutex_unlock(&pstore_sb_lock);
480 }
481 
482 static struct file_system_type pstore_fs_type = {
483 	.owner          = THIS_MODULE,
484 	.name		= "pstore",
485 	.mount		= pstore_mount,
486 	.kill_sb	= pstore_kill_sb,
487 };
488 
489 int __init pstore_init_fs(void)
490 {
491 	int err;
492 
493 	/* Create a convenient mount point for people to access pstore */
494 	err = sysfs_create_mount_point(fs_kobj, "pstore");
495 	if (err)
496 		goto out;
497 
498 	err = register_filesystem(&pstore_fs_type);
499 	if (err < 0)
500 		sysfs_remove_mount_point(fs_kobj, "pstore");
501 
502 out:
503 	return err;
504 }
505 
506 void __exit pstore_exit_fs(void)
507 {
508 	unregister_filesystem(&pstore_fs_type);
509 	sysfs_remove_mount_point(fs_kobj, "pstore");
510 }
511