fs/pstore/inode.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Persistent Storage - ramfs parts.
   4  *
   5  * Copyright (C) 2010 Intel Corporation <[email protected]>
   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 #include <linux/cleanup.h>
  27
  28 #include "internal.h"
  29
  30 #define PSTORE_NAMELEN  64
  31
  32 static DEFINE_MUTEX(records_list_lock);
  33 static LIST_HEAD(records_list);
  34
  35 static DEFINE_MUTEX(pstore_sb_lock);
  36 static struct super_block *pstore_sb;
  37
  38 DEFINE_FREE(pstore_iput, struct inode *, if (_T) iput(_T))
  39
  40 struct pstore_private {
  41         struct list_head list;
  42         struct dentry *dentry;
  43         struct pstore_record *record;
  44         size_t total_size;
  45 };
  46
  47 struct pstore_ftrace_seq_data {
  48         const void *ptr;
  49         size_t off;
  50         size_t size;
  51 };
  52
  53 #define REC_SIZE sizeof(struct pstore_ftrace_record)
  54
  55 static void free_pstore_private(struct pstore_private *private)
  56 {
  57         if (!private)
  58                 return;
  59         if (private->record) {
  60                 kvfree(private->record->buf);
  61                 kfree(private->record->priv);
  62                 kfree(private->record);
  63         }
  64         kfree(private);
  65 }
  66 DEFINE_FREE(pstore_private, struct pstore_private *, free_pstore_private(_T));
  67
  68 static void *pstore_ftrace_seq_start(struct seq_file *s, loff_t *pos)
  69 {
  70         struct pstore_private *ps = s->private;
  71         struct pstore_ftrace_seq_data *data __free(kfree) = NULL;
  72
  73         data = kzalloc(sizeof(*data), GFP_KERNEL);
  74         if (!data)
  75                 return NULL;
  76
  77         data->off = ps->total_size % REC_SIZE;
  78         data->off += *pos * REC_SIZE;
  79         if (data->off + REC_SIZE > ps->total_size)
  80                 return NULL;
  81
  82         return_ptr(data);
  83 }
  84
  85 static void pstore_ftrace_seq_stop(struct seq_file *s, void *v)
  86 {
  87         kfree(v);
  88 }
  89
  90 static void *pstore_ftrace_seq_next(struct seq_file *s, void *v, loff_t *pos)
  91 {
  92         struct pstore_private *ps = s->private;
  93         struct pstore_ftrace_seq_data *data = v;
  94
  95         (*pos)++;
  96         data->off += REC_SIZE;
  97         if (data->off + REC_SIZE > ps->total_size)
  98                 return NULL;
  99
 100         return data;
 101 }
 102
 103 static int pstore_ftrace_seq_show(struct seq_file *s, void *v)
 104 {
 105         struct pstore_private *ps = s->private;
 106         struct pstore_ftrace_seq_data *data = v;
 107         struct pstore_ftrace_record *rec;
 108
 109         if (!data)
 110                 return 0;
 111
 112         rec = (struct pstore_ftrace_record *)(ps->record->buf + data->off);
 113
 114         seq_printf(s, "CPU:%d ts:%llu %08lx  %08lx  %ps <- %pS\n",
 115                    pstore_ftrace_decode_cpu(rec),
 116                    pstore_ftrace_read_timestamp(rec),
 117                    rec->ip, rec->parent_ip, (void *)rec->ip,
 118                    (void *)rec->parent_ip);
 119
 120         return 0;
 121 }
 122
 123 static const struct seq_operations pstore_ftrace_seq_ops = {
 124         .start  = pstore_ftrace_seq_start,
 125         .next   = pstore_ftrace_seq_next,
 126         .stop   = pstore_ftrace_seq_stop,
 127         .show   = pstore_ftrace_seq_show,
 128 };
 129
 130 static ssize_t pstore_file_read(struct file *file, char __user *userbuf,
 131                                                 size_t count, loff_t *ppos)
 132 {
 133         struct seq_file *sf = file->private_data;
 134         struct pstore_private *ps = sf->private;
 135
 136         if (ps->record->type == PSTORE_TYPE_FTRACE)
 137                 return seq_read(file, userbuf, count, ppos);
 138         return simple_read_from_buffer(userbuf, count, ppos,
 139                                        ps->record->buf, ps->total_size);
 140 }
 141
 142 static int pstore_file_open(struct inode *inode, struct file *file)
 143 {
 144         struct pstore_private *ps = inode->i_private;
 145         struct seq_file *sf;
 146         int err;
 147         const struct seq_operations *sops = NULL;
 148
 149         if (ps->record->type == PSTORE_TYPE_FTRACE)
 150                 sops = &pstore_ftrace_seq_ops;
 151
 152         err = seq_open(file, sops);
 153         if (err < 0)
 154                 return err;
 155
 156         sf = file->private_data;
 157         sf->private = ps;
 158
 159         return 0;
 160 }
 161
 162 static loff_t pstore_file_llseek(struct file *file, loff_t off, int whence)
 163 {
 164         struct seq_file *sf = file->private_data;
 165
 166         if (sf->op)
 167                 return seq_lseek(file, off, whence);
 168         return default_llseek(file, off, whence);
 169 }
 170
 171 static const struct file_operations pstore_file_operations = {
 172         .open           = pstore_file_open,
 173         .read           = pstore_file_read,
 174         .llseek         = pstore_file_llseek,
 175         .release        = seq_release,
 176 };
 177
 178 /*
 179  * When a file is unlinked from our file system we call the
 180  * platform driver to erase the record from persistent store.
 181  */
 182 static int pstore_unlink(struct inode *dir, struct dentry *dentry)
 183 {
 184         struct pstore_private *p = d_inode(dentry)->i_private;
 185         struct pstore_record *record = p->record;
 186
 187         if (!record->psi->erase)
 188                 return -EPERM;
 189
 190         /* Make sure we can't race while removing this file. */
 191         scoped_guard(mutex, &records_list_lock) {
 192                 if (!list_empty(&p->list))
 193                         list_del_init(&p->list);
 194                 else
 195                         return -ENOENT;
 196                 p->dentry = NULL;
 197         }
 198
 199         scoped_guard(mutex, &record->psi->read_mutex)
 200                 record->psi->erase(record);
 201
 202         return simple_unlink(dir, dentry);
 203 }
 204
 205 static void pstore_evict_inode(struct inode *inode)
 206 {
 207         struct pstore_private   *p = inode->i_private;
 208
 209         clear_inode(inode);
 210         free_pstore_private(p);
 211 }
 212
 213 static const struct inode_operations pstore_dir_inode_operations = {
 214         .lookup         = simple_lookup,
 215         .unlink         = pstore_unlink,
 216 };
 217
 218 static struct inode *pstore_get_inode(struct super_block *sb)
 219 {
 220         struct inode *inode = new_inode(sb);
 221         if (inode) {
 222                 inode->i_ino = get_next_ino();
 223                 simple_inode_init_ts(inode);
 224         }
 225         return inode;
 226 }
 227
 228 enum {
 229         Opt_kmsg_bytes, Opt_err
 230 };
 231
 232 static const match_table_t tokens = {
 233         {Opt_kmsg_bytes, "kmsg_bytes=%u"},
 234         {Opt_err, NULL}
 235 };
 236
 237 static void parse_options(char *options)
 238 {
 239         char            *p;
 240         substring_t     args[MAX_OPT_ARGS];
 241         int             option;
 242
 243         if (!options)
 244                 return;
 245
 246         while ((p = strsep(&options, ",")) != NULL) {
 247                 int token;
 248
 249                 if (!*p)
 250                         continue;
 251
 252                 token = match_token(p, tokens, args);
 253                 switch (token) {
 254                 case Opt_kmsg_bytes:
 255                         if (!match_int(&args[0], &option))
 256                                 pstore_set_kmsg_bytes(option);
 257                         break;
 258                 }
 259         }
 260 }
 261
 262 /*
 263  * Display the mount options in /proc/mounts.
 264  */
 265 static int pstore_show_options(struct seq_file *m, struct dentry *root)
 266 {
 267         if (kmsg_bytes != CONFIG_PSTORE_DEFAULT_KMSG_BYTES)
 268                 seq_printf(m, ",kmsg_bytes=%lu", kmsg_bytes);
 269         return 0;
 270 }
 271
 272 static int pstore_remount(struct super_block *sb, int *flags, char *data)
 273 {
 274         sync_filesystem(sb);
 275         parse_options(data);
 276
 277         return 0;
 278 }
 279
 280 static const struct super_operations pstore_ops = {
 281         .statfs         = simple_statfs,
 282         .drop_inode     = generic_delete_inode,
 283         .evict_inode    = pstore_evict_inode,
 284         .remount_fs     = pstore_remount,
 285         .show_options   = pstore_show_options,
 286 };
 287
 288 static struct dentry *psinfo_lock_root(void)
 289 {
 290         struct dentry *root;
 291
 292         guard(mutex)(&pstore_sb_lock);
 293         /*
 294          * Having no backend is fine -- no records appear.
 295          * Not being mounted is fine -- nothing to do.
 296          */
 297         if (!psinfo || !pstore_sb)
 298                 return NULL;
 299
 300         root = pstore_sb->s_root;
 301         inode_lock(d_inode(root));
 302
 303         return root;
 304 }
 305
 306 int pstore_put_backend_records(struct pstore_info *psi)
 307 {
 308         struct pstore_private *pos, *tmp;
 309         struct dentry *root;
 310         int rc = 0;
 311
 312         root = psinfo_lock_root();
 313         if (!root)
 314                 return 0;
 315
 316         scoped_guard(mutex, &records_list_lock) {
 317                 list_for_each_entry_safe(pos, tmp, &records_list, list) {
 318                         if (pos->record->psi == psi) {
 319                                 list_del_init(&pos->list);
 320                                 rc = simple_unlink(d_inode(root), pos->dentry);
 321                                 if (WARN_ON(rc))
 322                                         break;
 323                                 d_drop(pos->dentry);
 324                                 dput(pos->dentry);
 325                                 pos->dentry = NULL;
 326                         }
 327                 }
 328         }
 329
 330         inode_unlock(d_inode(root));
 331
 332         return rc;
 333 }
 334
 335 /*
 336  * Make a regular file in the root directory of our file system.
 337  * Load it up with "size" bytes of data from "buf".
 338  * Set the mtime & ctime to the date that this record was originally stored.
 339  */
 340 int pstore_mkfile(struct dentry *root, struct pstore_record *record)
 341 {
 342         struct dentry           *dentry;
 343         struct inode            *inode __free(pstore_iput) = NULL;
 344         char                    name[PSTORE_NAMELEN];
 345         struct pstore_private   *private __free(pstore_private) = NULL, *pos;
 346         size_t                  size = record->size + record->ecc_notice_size;
 347
 348         if (WARN_ON(!inode_is_locked(d_inode(root))))
 349                 return -EINVAL;
 350
 351         guard(mutex)(&records_list_lock);
 352
 353         /* Skip records that are already present in the filesystem. */
 354         list_for_each_entry(pos, &records_list, list) {
 355                 if (pos->record->type == record->type &&
 356                     pos->record->id == record->id &&
 357                     pos->record->psi == record->psi)
 358                         return -EEXIST;
 359         }
 360
 361         inode = pstore_get_inode(root->d_sb);
 362         if (!inode)
 363                 return -ENOMEM;
 364         inode->i_mode = S_IFREG | 0444;
 365         inode->i_fop = &pstore_file_operations;
 366         scnprintf(name, sizeof(name), "%s-%s-%llu%s",
 367                         pstore_type_to_name(record->type),
 368                         record->psi->name, record->id,
 369                         record->compressed ? ".enc.z" : "");
 370
 371         private = kzalloc(sizeof(*private), GFP_KERNEL);
 372         if (!private)
 373                 return -ENOMEM;
 374
 375         dentry = d_alloc_name(root, name);
 376         if (!dentry)
 377                 return -ENOMEM;
 378
 379         private->dentry = dentry;
 380         private->record = record;
 381         inode->i_size = private->total_size = size;
 382         inode->i_private = private;
 383
 384         if (record->time.tv_sec)
 385                 inode_set_mtime_to_ts(inode,
 386                                       inode_set_ctime_to_ts(inode, record->time));
 387
 388         d_add(dentry, no_free_ptr(inode));
 389
 390         list_add(&(no_free_ptr(private))->list, &records_list);
 391
 392         return 0;
 393 }
 394
 395 /*
 396  * Read all the records from the persistent store. Create
 397  * files in our filesystem.  Don't warn about -EEXIST errors
 398  * when we are re-scanning the backing store looking to add new
 399  * error records.
 400  */
 401 void pstore_get_records(int quiet)
 402 {
 403         struct dentry *root;
 404
 405         root = psinfo_lock_root();
 406         if (!root)
 407                 return;
 408
 409         pstore_get_backend_records(psinfo, root, quiet);
 410         inode_unlock(d_inode(root));
 411 }
 412
 413 static int pstore_fill_super(struct super_block *sb, void *data, int silent)
 414 {
 415         struct inode *inode;
 416
 417         sb->s_maxbytes          = MAX_LFS_FILESIZE;
 418         sb->s_blocksize         = PAGE_SIZE;
 419         sb->s_blocksize_bits    = PAGE_SHIFT;
 420         sb->s_magic             = PSTOREFS_MAGIC;
 421         sb->s_op                = &pstore_ops;
 422         sb->s_time_gran         = 1;
 423
 424         parse_options(data);
 425
 426         inode = pstore_get_inode(sb);
 427         if (inode) {
 428                 inode->i_mode = S_IFDIR | 0750;
 429                 inode->i_op = &pstore_dir_inode_operations;
 430                 inode->i_fop = &simple_dir_operations;
 431                 inc_nlink(inode);
 432         }
 433         sb->s_root = d_make_root(inode);
 434         if (!sb->s_root)
 435                 return -ENOMEM;
 436
 437         scoped_guard(mutex, &pstore_sb_lock)
 438                 pstore_sb = sb;
 439
 440         pstore_get_records(0);
 441
 442         return 0;
 443 }
 444
 445 static struct dentry *pstore_mount(struct file_system_type *fs_type,
 446         int flags, const char *dev_name, void *data)
 447 {
 448         return mount_single(fs_type, flags, data, pstore_fill_super);
 449 }
 450
 451 static void pstore_kill_sb(struct super_block *sb)
 452 {
 453         guard(mutex)(&pstore_sb_lock);
 454         WARN_ON(pstore_sb && pstore_sb != sb);
 455
 456         kill_litter_super(sb);
 457         pstore_sb = NULL;
 458
 459         guard(mutex)(&records_list_lock);
 460         INIT_LIST_HEAD(&records_list);
 461 }
 462
 463 static struct file_system_type pstore_fs_type = {
 464         .owner          = THIS_MODULE,
 465         .name           = "pstore",
 466         .mount          = pstore_mount,
 467         .kill_sb        = pstore_kill_sb,
 468 };
 469
 470 int __init pstore_init_fs(void)
 471 {
 472         int err;
 473
 474         /* Create a convenient mount point for people to access pstore */
 475         err = sysfs_create_mount_point(fs_kobj, "pstore");
 476         if (err)
 477                 goto out;
 478
 479         err = register_filesystem(&pstore_fs_type);
 480         if (err < 0)
 481                 sysfs_remove_mount_point(fs_kobj, "pstore");
 482
 483 out:
 484         return err;
 485 }
 486
 487 void __exit pstore_exit_fs(void)
 488 {
 489         unregister_filesystem(&pstore_fs_type);
 490         sysfs_remove_mount_point(fs_kobj, "pstore");
 491 }