xref: /openbmc/linux/fs/pstore/inode.c (revision 93696d8f) 
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 		kvfree(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 
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 
204 static 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 
212 static const struct inode_operations pstore_dir_inode_operations = {
213 	.lookup		= simple_lookup,
214 	.unlink		= pstore_unlink,
215 };
216 
217 static 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 
227 enum {
228 	Opt_kmsg_bytes, Opt_err
229 };
230 
231 static const match_table_t tokens = {
232 	{Opt_kmsg_bytes, "kmsg_bytes=%u"},
233 	{Opt_err, NULL}
234 };
235 
236 static 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  */
264 static 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 
271 static 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 
279 static 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 
287 static 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 
305 int 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  */
335 int 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 
390 fail_private:
391 	free_pstore_private(private);
392 fail_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  */
403 void 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 
415 static 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 
447 static 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 
453 static 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 
465 static 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 
472 int __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 
485 out:
486 	return err;
487 }
488 
489 void __exit pstore_exit_fs(void)
490 {
491 	unregister_filesystem(&pstore_fs_type);
492 	sysfs_remove_mount_point(fs_kobj, "pstore");
493 }
494