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Linux/fs/pstore/inode.c

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  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 

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