xref: /openbmc/linux/fs/pstore/inode.c (revision 76426e23) 
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 	(*pos)++;
91 	data->off += REC_SIZE;
92 	if (data->off + REC_SIZE > ps->total_size)
93 		return NULL;
94 
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 	if (!data)
105 		return 0;
106 
107 	rec = (struct pstore_ftrace_record *)(ps->record->buf + data->off);
108 
109 	seq_printf(s, "CPU:%d ts:%llu %08lx  %08lx  %ps <- %pS\n",
110 		   pstore_ftrace_decode_cpu(rec),
111 		   pstore_ftrace_read_timestamp(rec),
112 		   rec->ip, rec->parent_ip, (void *)rec->ip,
113 		   (void *)rec->parent_ip);
114 
115 	return 0;
116 }
117 
118 static const struct seq_operations pstore_ftrace_seq_ops = {
119 	.start	= pstore_ftrace_seq_start,
120 	.next	= pstore_ftrace_seq_next,
121 	.stop	= pstore_ftrace_seq_stop,
122 	.show	= pstore_ftrace_seq_show,
123 };
124 
125 static ssize_t pstore_file_read(struct file *file, char __user *userbuf,
126 						size_t count, loff_t *ppos)
127 {
128 	struct seq_file *sf = file->private_data;
129 	struct pstore_private *ps = sf->private;
130 
131 	if (ps->record->type == PSTORE_TYPE_FTRACE)
132 		return seq_read(file, userbuf, count, ppos);
133 	return simple_read_from_buffer(userbuf, count, ppos,
134 				       ps->record->buf, ps->total_size);
135 }
136 
137 static int pstore_file_open(struct inode *inode, struct file *file)
138 {
139 	struct pstore_private *ps = inode->i_private;
140 	struct seq_file *sf;
141 	int err;
142 	const struct seq_operations *sops = NULL;
143 
144 	if (ps->record->type == PSTORE_TYPE_FTRACE)
145 		sops = &pstore_ftrace_seq_ops;
146 
147 	err = seq_open(file, sops);
148 	if (err < 0)
149 		return err;
150 
151 	sf = file->private_data;
152 	sf->private = ps;
153 
154 	return 0;
155 }
156 
157 static loff_t pstore_file_llseek(struct file *file, loff_t off, int whence)
158 {
159 	struct seq_file *sf = file->private_data;
160 
161 	if (sf->op)
162 		return seq_lseek(file, off, whence);
163 	return default_llseek(file, off, whence);
164 }
165 
166 static const struct file_operations pstore_file_operations = {
167 	.open		= pstore_file_open,
168 	.read		= pstore_file_read,
169 	.llseek		= pstore_file_llseek,
170 	.release	= seq_release,
171 };
172 
173 /*
174  * When a file is unlinked from our file system we call the
175  * platform driver to erase the record from persistent store.
176  */
177 static int pstore_unlink(struct inode *dir, struct dentry *dentry)
178 {
179 	struct pstore_private *p = d_inode(dentry)->i_private;
180 	struct pstore_record *record = p->record;
181 
182 	if (!record->psi->erase)
183 		return -EPERM;
184 
185 	mutex_lock(&record->psi->read_mutex);
186 	record->psi->erase(record);
187 	mutex_unlock(&record->psi->read_mutex);
188 
189 	return simple_unlink(dir, dentry);
190 }
191 
192 static void pstore_evict_inode(struct inode *inode)
193 {
194 	struct pstore_private	*p = inode->i_private;
195 	unsigned long		flags;
196 
197 	clear_inode(inode);
198 	if (p) {
199 		spin_lock_irqsave(&allpstore_lock, flags);
200 		list_del(&p->list);
201 		spin_unlock_irqrestore(&allpstore_lock, flags);
202 		free_pstore_private(p);
203 	}
204 }
205 
206 static const struct inode_operations pstore_dir_inode_operations = {
207 	.lookup		= simple_lookup,
208 	.unlink		= pstore_unlink,
209 };
210 
211 static struct inode *pstore_get_inode(struct super_block *sb)
212 {
213 	struct inode *inode = new_inode(sb);
214 	if (inode) {
215 		inode->i_ino = get_next_ino();
216 		inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
217 	}
218 	return inode;
219 }
220 
221 enum {
222 	Opt_kmsg_bytes, Opt_err
223 };
224 
225 static const match_table_t tokens = {
226 	{Opt_kmsg_bytes, "kmsg_bytes=%u"},
227 	{Opt_err, NULL}
228 };
229 
230 static void parse_options(char *options)
231 {
232 	char		*p;
233 	substring_t	args[MAX_OPT_ARGS];
234 	int		option;
235 
236 	if (!options)
237 		return;
238 
239 	while ((p = strsep(&options, ",")) != NULL) {
240 		int token;
241 
242 		if (!*p)
243 			continue;
244 
245 		token = match_token(p, tokens, args);
246 		switch (token) {
247 		case Opt_kmsg_bytes:
248 			if (!match_int(&args[0], &option))
249 				pstore_set_kmsg_bytes(option);
250 			break;
251 		}
252 	}
253 }
254 
255 /*
256  * Display the mount options in /proc/mounts.
257  */
258 static int pstore_show_options(struct seq_file *m, struct dentry *root)
259 {
260 	if (kmsg_bytes != PSTORE_DEFAULT_KMSG_BYTES)
261 		seq_printf(m, ",kmsg_bytes=%lu", kmsg_bytes);
262 	return 0;
263 }
264 
265 static int pstore_remount(struct super_block *sb, int *flags, char *data)
266 {
267 	sync_filesystem(sb);
268 	parse_options(data);
269 
270 	return 0;
271 }
272 
273 static const struct super_operations pstore_ops = {
274 	.statfs		= simple_statfs,
275 	.drop_inode	= generic_delete_inode,
276 	.evict_inode	= pstore_evict_inode,
277 	.remount_fs	= pstore_remount,
278 	.show_options	= pstore_show_options,
279 };
280 
281 static struct super_block *pstore_sb;
282 
283 bool pstore_is_mounted(void)
284 {
285 	return pstore_sb != NULL;
286 }
287 
288 /*
289  * Make a regular file in the root directory of our file system.
290  * Load it up with "size" bytes of data from "buf".
291  * Set the mtime & ctime to the date that this record was originally stored.
292  */
293 int pstore_mkfile(struct dentry *root, struct pstore_record *record)
294 {
295 	struct dentry		*dentry;
296 	struct inode		*inode;
297 	int			rc = 0;
298 	char			name[PSTORE_NAMELEN];
299 	struct pstore_private	*private, *pos;
300 	unsigned long		flags;
301 	size_t			size = record->size + record->ecc_notice_size;
302 
303 	WARN_ON(!inode_is_locked(d_inode(root)));
304 
305 	spin_lock_irqsave(&allpstore_lock, flags);
306 	list_for_each_entry(pos, &allpstore, list) {
307 		if (pos->record->type == record->type &&
308 		    pos->record->id == record->id &&
309 		    pos->record->psi == record->psi) {
310 			rc = -EEXIST;
311 			break;
312 		}
313 	}
314 	spin_unlock_irqrestore(&allpstore_lock, flags);
315 	if (rc)
316 		return rc;
317 
318 	rc = -ENOMEM;
319 	inode = pstore_get_inode(root->d_sb);
320 	if (!inode)
321 		goto fail;
322 	inode->i_mode = S_IFREG | 0444;
323 	inode->i_fop = &pstore_file_operations;
324 	scnprintf(name, sizeof(name), "%s-%s-%llu%s",
325 			pstore_type_to_name(record->type),
326 			record->psi->name, record->id,
327 			record->compressed ? ".enc.z" : "");
328 
329 	private = kzalloc(sizeof(*private), GFP_KERNEL);
330 	if (!private)
331 		goto fail_inode;
332 
333 	dentry = d_alloc_name(root, name);
334 	if (!dentry)
335 		goto fail_private;
336 
337 	private->record = record;
338 	inode->i_size = private->total_size = size;
339 	inode->i_private = private;
340 
341 	if (record->time.tv_sec)
342 		inode->i_mtime = inode->i_ctime = record->time;
343 
344 	d_add(dentry, inode);
345 
346 	spin_lock_irqsave(&allpstore_lock, flags);
347 	list_add(&private->list, &allpstore);
348 	spin_unlock_irqrestore(&allpstore_lock, flags);
349 
350 	return 0;
351 
352 fail_private:
353 	free_pstore_private(private);
354 fail_inode:
355 	iput(inode);
356 
357 fail:
358 	return rc;
359 }
360 
361 /*
362  * Read all the records from the persistent store. Create
363  * files in our filesystem.  Don't warn about -EEXIST errors
364  * when we are re-scanning the backing store looking to add new
365  * error records.
366  */
367 void pstore_get_records(int quiet)
368 {
369 	struct pstore_info *psi = psinfo;
370 	struct dentry *root;
371 
372 	if (!psi || !pstore_sb)
373 		return;
374 
375 	root = pstore_sb->s_root;
376 
377 	inode_lock(d_inode(root));
378 	pstore_get_backend_records(psi, root, quiet);
379 	inode_unlock(d_inode(root));
380 }
381 
382 static int pstore_fill_super(struct super_block *sb, void *data, int silent)
383 {
384 	struct inode *inode;
385 
386 	pstore_sb = sb;
387 
388 	sb->s_maxbytes		= MAX_LFS_FILESIZE;
389 	sb->s_blocksize		= PAGE_SIZE;
390 	sb->s_blocksize_bits	= PAGE_SHIFT;
391 	sb->s_magic		= PSTOREFS_MAGIC;
392 	sb->s_op		= &pstore_ops;
393 	sb->s_time_gran		= 1;
394 
395 	parse_options(data);
396 
397 	inode = pstore_get_inode(sb);
398 	if (inode) {
399 		inode->i_mode = S_IFDIR | 0750;
400 		inode->i_op = &pstore_dir_inode_operations;
401 		inode->i_fop = &simple_dir_operations;
402 		inc_nlink(inode);
403 	}
404 	sb->s_root = d_make_root(inode);
405 	if (!sb->s_root)
406 		return -ENOMEM;
407 
408 	pstore_get_records(0);
409 
410 	return 0;
411 }
412 
413 static struct dentry *pstore_mount(struct file_system_type *fs_type,
414 	int flags, const char *dev_name, void *data)
415 {
416 	return mount_single(fs_type, flags, data, pstore_fill_super);
417 }
418 
419 static void pstore_kill_sb(struct super_block *sb)
420 {
421 	kill_litter_super(sb);
422 	pstore_sb = NULL;
423 }
424 
425 static struct file_system_type pstore_fs_type = {
426 	.owner          = THIS_MODULE,
427 	.name		= "pstore",
428 	.mount		= pstore_mount,
429 	.kill_sb	= pstore_kill_sb,
430 };
431 
432 int __init pstore_init_fs(void)
433 {
434 	int err;
435 
436 	/* Create a convenient mount point for people to access pstore */
437 	err = sysfs_create_mount_point(fs_kobj, "pstore");
438 	if (err)
439 		goto out;
440 
441 	err = register_filesystem(&pstore_fs_type);
442 	if (err < 0)
443 		sysfs_remove_mount_point(fs_kobj, "pstore");
444 
445 out:
446 	return err;
447 }
448 
449 void __exit pstore_exit_fs(void)
450 {
451 	unregister_filesystem(&pstore_fs_type);
452 	sysfs_remove_mount_point(fs_kobj, "pstore");
453 }
454