xref: /linux/fs/pstore/inode.c (revision 17cfcb68af3bc7d5e8ae08779b1853310a2949f3) 
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/spinlock.h>
26 #include <linux/uaccess.h>
27 
28 #include "internal.h"
29 
30 #define	PSTORE_NAMELEN	64
31 
32 static DEFINE_SPINLOCK(allpstore_lock);
33 static LIST_HEAD(allpstore);
34 
35 struct pstore_private {
36 	struct list_head list;
37 	struct pstore_record *record;
38 	size_t total_size;
39 };
40 
41 struct pstore_ftrace_seq_data {
42 	const void *ptr;
43 	size_t off;
44 	size_t size;
45 };
46 
47 #define REC_SIZE sizeof(struct pstore_ftrace_record)
48 
49 static void free_pstore_private(struct pstore_private *private)
50 {
51 	if (!private)
52 		return;
53 	if (private->record) {
54 		kfree(private->record->buf);
55 		kfree(private->record);
56 	}
57 	kfree(private);
58 }
59 
60 static void *pstore_ftrace_seq_start(struct seq_file *s, loff_t *pos)
61 {
62 	struct pstore_private *ps = s->private;
63 	struct pstore_ftrace_seq_data *data;
64 
65 	data = kzalloc(sizeof(*data), GFP_KERNEL);
66 	if (!data)
67 		return NULL;
68 
69 	data->off = ps->total_size % REC_SIZE;
70 	data->off += *pos * REC_SIZE;
71 	if (data->off + REC_SIZE > ps->total_size) {
72 		kfree(data);
73 		return NULL;
74 	}
75 
76 	return data;
77 
78 }
79 
80 static void pstore_ftrace_seq_stop(struct seq_file *s, void *v)
81 {
82 	kfree(v);
83 }
84 
85 static void *pstore_ftrace_seq_next(struct seq_file *s, void *v, loff_t *pos)
86 {
87 	struct pstore_private *ps = s->private;
88 	struct pstore_ftrace_seq_data *data = v;
89 
90 	data->off += REC_SIZE;
91 	if (data->off + REC_SIZE > ps->total_size)
92 		return NULL;
93 
94 	(*pos)++;
95 	return data;
96 }
97 
98 static int pstore_ftrace_seq_show(struct seq_file *s, void *v)
99 {
100 	struct pstore_private *ps = s->private;
101 	struct pstore_ftrace_seq_data *data = v;
102 	struct pstore_ftrace_record *rec;
103 
104 	rec = (struct pstore_ftrace_record *)(ps->record->buf + data->off);
105 
106 	seq_printf(s, "CPU:%d ts:%llu %08lx  %08lx  %ps <- %pS\n",
107 		   pstore_ftrace_decode_cpu(rec),
108 		   pstore_ftrace_read_timestamp(rec),
109 		   rec->ip, rec->parent_ip, (void *)rec->ip,
110 		   (void *)rec->parent_ip);
111 
112 	return 0;
113 }
114 
115 static const struct seq_operations pstore_ftrace_seq_ops = {
116 	.start	= pstore_ftrace_seq_start,
117 	.next	= pstore_ftrace_seq_next,
118 	.stop	= pstore_ftrace_seq_stop,
119 	.show	= pstore_ftrace_seq_show,
120 };
121 
122 static ssize_t pstore_file_read(struct file *file, char __user *userbuf,
123 						size_t count, loff_t *ppos)
124 {
125 	struct seq_file *sf = file->private_data;
126 	struct pstore_private *ps = sf->private;
127 
128 	if (ps->record->type == PSTORE_TYPE_FTRACE)
129 		return seq_read(file, userbuf, count, ppos);
130 	return simple_read_from_buffer(userbuf, count, ppos,
131 				       ps->record->buf, ps->total_size);
132 }
133 
134 static int pstore_file_open(struct inode *inode, struct file *file)
135 {
136 	struct pstore_private *ps = inode->i_private;
137 	struct seq_file *sf;
138 	int err;
139 	const struct seq_operations *sops = NULL;
140 
141 	if (ps->record->type == PSTORE_TYPE_FTRACE)
142 		sops = &pstore_ftrace_seq_ops;
143 
144 	err = seq_open(file, sops);
145 	if (err < 0)
146 		return err;
147 
148 	sf = file->private_data;
149 	sf->private = ps;
150 
151 	return 0;
152 }
153 
154 static loff_t pstore_file_llseek(struct file *file, loff_t off, int whence)
155 {
156 	struct seq_file *sf = file->private_data;
157 
158 	if (sf->op)
159 		return seq_lseek(file, off, whence);
160 	return default_llseek(file, off, whence);
161 }
162 
163 static const struct file_operations pstore_file_operations = {
164 	.open		= pstore_file_open,
165 	.read		= pstore_file_read,
166 	.llseek		= pstore_file_llseek,
167 	.release	= seq_release,
168 };
169 
170 /*
171  * When a file is unlinked from our file system we call the
172  * platform driver to erase the record from persistent store.
173  */
174 static int pstore_unlink(struct inode *dir, struct dentry *dentry)
175 {
176 	struct pstore_private *p = d_inode(dentry)->i_private;
177 	struct pstore_record *record = p->record;
178 
179 	if (!record->psi->erase)
180 		return -EPERM;
181 
182 	mutex_lock(&record->psi->read_mutex);
183 	record->psi->erase(record);
184 	mutex_unlock(&record->psi->read_mutex);
185 
186 	return simple_unlink(dir, dentry);
187 }
188 
189 static void pstore_evict_inode(struct inode *inode)
190 {
191 	struct pstore_private	*p = inode->i_private;
192 	unsigned long		flags;
193 
194 	clear_inode(inode);
195 	if (p) {
196 		spin_lock_irqsave(&allpstore_lock, flags);
197 		list_del(&p->list);
198 		spin_unlock_irqrestore(&allpstore_lock, flags);
199 		free_pstore_private(p);
200 	}
201 }
202 
203 static const struct inode_operations pstore_dir_inode_operations = {
204 	.lookup		= simple_lookup,
205 	.unlink		= pstore_unlink,
206 };
207 
208 static struct inode *pstore_get_inode(struct super_block *sb)
209 {
210 	struct inode *inode = new_inode(sb);
211 	if (inode) {
212 		inode->i_ino = get_next_ino();
213 		inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
214 	}
215 	return inode;
216 }
217 
218 enum {
219 	Opt_kmsg_bytes, Opt_err
220 };
221 
222 static const match_table_t tokens = {
223 	{Opt_kmsg_bytes, "kmsg_bytes=%u"},
224 	{Opt_err, NULL}
225 };
226 
227 static void parse_options(char *options)
228 {
229 	char		*p;
230 	substring_t	args[MAX_OPT_ARGS];
231 	int		option;
232 
233 	if (!options)
234 		return;
235 
236 	while ((p = strsep(&options, ",")) != NULL) {
237 		int token;
238 
239 		if (!*p)
240 			continue;
241 
242 		token = match_token(p, tokens, args);
243 		switch (token) {
244 		case Opt_kmsg_bytes:
245 			if (!match_int(&args[0], &option))
246 				pstore_set_kmsg_bytes(option);
247 			break;
248 		}
249 	}
250 }
251 
252 /*
253  * Display the mount options in /proc/mounts.
254  */
255 static int pstore_show_options(struct seq_file *m, struct dentry *root)
256 {
257 	if (kmsg_bytes != PSTORE_DEFAULT_KMSG_BYTES)
258 		seq_printf(m, ",kmsg_bytes=%lu", kmsg_bytes);
259 	return 0;
260 }
261 
262 static int pstore_remount(struct super_block *sb, int *flags, char *data)
263 {
264 	sync_filesystem(sb);
265 	parse_options(data);
266 
267 	return 0;
268 }
269 
270 static const struct super_operations pstore_ops = {
271 	.statfs		= simple_statfs,
272 	.drop_inode	= generic_delete_inode,
273 	.evict_inode	= pstore_evict_inode,
274 	.remount_fs	= pstore_remount,
275 	.show_options	= pstore_show_options,
276 };
277 
278 static struct super_block *pstore_sb;
279 
280 bool pstore_is_mounted(void)
281 {
282 	return pstore_sb != NULL;
283 }
284 
285 /*
286  * Make a regular file in the root directory of our file system.
287  * Load it up with "size" bytes of data from "buf".
288  * Set the mtime & ctime to the date that this record was originally stored.
289  */
290 int pstore_mkfile(struct dentry *root, struct pstore_record *record)
291 {
292 	struct dentry		*dentry;
293 	struct inode		*inode;
294 	int			rc = 0;
295 	char			name[PSTORE_NAMELEN];
296 	struct pstore_private	*private, *pos;
297 	unsigned long		flags;
298 	size_t			size = record->size + record->ecc_notice_size;
299 
300 	WARN_ON(!inode_is_locked(d_inode(root)));
301 
302 	spin_lock_irqsave(&allpstore_lock, flags);
303 	list_for_each_entry(pos, &allpstore, list) {
304 		if (pos->record->type == record->type &&
305 		    pos->record->id == record->id &&
306 		    pos->record->psi == record->psi) {
307 			rc = -EEXIST;
308 			break;
309 		}
310 	}
311 	spin_unlock_irqrestore(&allpstore_lock, flags);
312 	if (rc)
313 		return rc;
314 
315 	rc = -ENOMEM;
316 	inode = pstore_get_inode(root->d_sb);
317 	if (!inode)
318 		goto fail;
319 	inode->i_mode = S_IFREG | 0444;
320 	inode->i_fop = &pstore_file_operations;
321 	scnprintf(name, sizeof(name), "%s-%s-%llu%s",
322 			pstore_type_to_name(record->type),
323 			record->psi->name, record->id,
324 			record->compressed ? ".enc.z" : "");
325 
326 	private = kzalloc(sizeof(*private), GFP_KERNEL);
327 	if (!private)
328 		goto fail_inode;
329 
330 	dentry = d_alloc_name(root, name);
331 	if (!dentry)
332 		goto fail_private;
333 
334 	private->record = record;
335 	inode->i_size = private->total_size = size;
336 	inode->i_private = private;
337 
338 	if (record->time.tv_sec)
339 		inode->i_mtime = inode->i_ctime = record->time;
340 
341 	d_add(dentry, inode);
342 
343 	spin_lock_irqsave(&allpstore_lock, flags);
344 	list_add(&private->list, &allpstore);
345 	spin_unlock_irqrestore(&allpstore_lock, flags);
346 
347 	return 0;
348 
349 fail_private:
350 	free_pstore_private(private);
351 fail_inode:
352 	iput(inode);
353 
354 fail:
355 	return rc;
356 }
357 
358 /*
359  * Read all the records from the persistent store. Create
360  * files in our filesystem.  Don't warn about -EEXIST errors
361  * when we are re-scanning the backing store looking to add new
362  * error records.
363  */
364 void pstore_get_records(int quiet)
365 {
366 	struct pstore_info *psi = psinfo;
367 	struct dentry *root;
368 
369 	if (!psi || !pstore_sb)
370 		return;
371 
372 	root = pstore_sb->s_root;
373 
374 	inode_lock(d_inode(root));
375 	pstore_get_backend_records(psi, root, quiet);
376 	inode_unlock(d_inode(root));
377 }
378 
379 static int pstore_fill_super(struct super_block *sb, void *data, int silent)
380 {
381 	struct inode *inode;
382 
383 	pstore_sb = sb;
384 
385 	sb->s_maxbytes		= MAX_LFS_FILESIZE;
386 	sb->s_blocksize		= PAGE_SIZE;
387 	sb->s_blocksize_bits	= PAGE_SHIFT;
388 	sb->s_magic		= PSTOREFS_MAGIC;
389 	sb->s_op		= &pstore_ops;
390 	sb->s_time_gran		= 1;
391 
392 	parse_options(data);
393 
394 	inode = pstore_get_inode(sb);
395 	if (inode) {
396 		inode->i_mode = S_IFDIR | 0750;
397 		inode->i_op = &pstore_dir_inode_operations;
398 		inode->i_fop = &simple_dir_operations;
399 		inc_nlink(inode);
400 	}
401 	sb->s_root = d_make_root(inode);
402 	if (!sb->s_root)
403 		return -ENOMEM;
404 
405 	pstore_get_records(0);
406 
407 	return 0;
408 }
409 
410 static struct dentry *pstore_mount(struct file_system_type *fs_type,
411 	int flags, const char *dev_name, void *data)
412 {
413 	return mount_single(fs_type, flags, data, pstore_fill_super);
414 }
415 
416 static void pstore_kill_sb(struct super_block *sb)
417 {
418 	kill_litter_super(sb);
419 	pstore_sb = NULL;
420 }
421 
422 static struct file_system_type pstore_fs_type = {
423 	.owner          = THIS_MODULE,
424 	.name		= "pstore",
425 	.mount		= pstore_mount,
426 	.kill_sb	= pstore_kill_sb,
427 };
428 
429 int __init pstore_init_fs(void)
430 {
431 	int err;
432 
433 	/* Create a convenient mount point for people to access pstore */
434 	err = sysfs_create_mount_point(fs_kobj, "pstore");
435 	if (err)
436 		goto out;
437 
438 	err = register_filesystem(&pstore_fs_type);
439 	if (err < 0)
440 		sysfs_remove_mount_point(fs_kobj, "pstore");
441 
442 out:
443 	return err;
444 }
445 
446 void __exit pstore_exit_fs(void)
447 {
448 	unregister_filesystem(&pstore_fs_type);
449 	sysfs_remove_mount_point(fs_kobj, "pstore");
450 }
451