linux/fs/proc/inode.c
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   1/*
   2 *  linux/fs/proc/inode.c
   3 *
   4 *  Copyright (C) 1991, 1992  Linus Torvalds
   5 */
   6
   7#include <linux/time.h>
   8#include <linux/proc_fs.h>
   9#include <linux/kernel.h>
  10#include <linux/mm.h>
  11#include <linux/string.h>
  12#include <linux/stat.h>
  13#include <linux/completion.h>
  14#include <linux/poll.h>
  15#include <linux/file.h>
  16#include <linux/limits.h>
  17#include <linux/init.h>
  18#include <linux/module.h>
  19#include <linux/sysctl.h>
  20#include <linux/slab.h>
  21
  22#include <asm/system.h>
  23#include <asm/uaccess.h>
  24
  25#include "internal.h"
  26
  27static void proc_evict_inode(struct inode *inode)
  28{
  29        struct proc_dir_entry *de;
  30        struct ctl_table_header *head;
  31        const struct proc_ns_operations *ns_ops;
  32
  33        truncate_inode_pages(&inode->i_data, 0);
  34        end_writeback(inode);
  35
  36        /* Stop tracking associated processes */
  37        put_pid(PROC_I(inode)->pid);
  38
  39        /* Let go of any associated proc directory entry */
  40        de = PROC_I(inode)->pde;
  41        if (de)
  42                pde_put(de);
  43        head = PROC_I(inode)->sysctl;
  44        if (head) {
  45                rcu_assign_pointer(PROC_I(inode)->sysctl, NULL);
  46                sysctl_head_put(head);
  47        }
  48        /* Release any associated namespace */
  49        ns_ops = PROC_I(inode)->ns_ops;
  50        if (ns_ops && ns_ops->put)
  51                ns_ops->put(PROC_I(inode)->ns);
  52}
  53
  54static struct kmem_cache * proc_inode_cachep;
  55
  56static struct inode *proc_alloc_inode(struct super_block *sb)
  57{
  58        struct proc_inode *ei;
  59        struct inode *inode;
  60
  61        ei = (struct proc_inode *)kmem_cache_alloc(proc_inode_cachep, GFP_KERNEL);
  62        if (!ei)
  63                return NULL;
  64        ei->pid = NULL;
  65        ei->fd = 0;
  66        ei->op.proc_get_link = NULL;
  67        ei->pde = NULL;
  68        ei->sysctl = NULL;
  69        ei->sysctl_entry = NULL;
  70        ei->ns = NULL;
  71        ei->ns_ops = NULL;
  72        inode = &ei->vfs_inode;
  73        inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
  74        return inode;
  75}
  76
  77static void proc_i_callback(struct rcu_head *head)
  78{
  79        struct inode *inode = container_of(head, struct inode, i_rcu);
  80        INIT_LIST_HEAD(&inode->i_dentry);
  81        kmem_cache_free(proc_inode_cachep, PROC_I(inode));
  82}
  83
  84static void proc_destroy_inode(struct inode *inode)
  85{
  86        call_rcu(&inode->i_rcu, proc_i_callback);
  87}
  88
  89static void init_once(void *foo)
  90{
  91        struct proc_inode *ei = (struct proc_inode *) foo;
  92
  93        inode_init_once(&ei->vfs_inode);
  94}
  95
  96void __init proc_init_inodecache(void)
  97{
  98        proc_inode_cachep = kmem_cache_create("proc_inode_cache",
  99                                             sizeof(struct proc_inode),
 100                                             0, (SLAB_RECLAIM_ACCOUNT|
 101                                                SLAB_MEM_SPREAD|SLAB_PANIC),
 102                                             init_once);
 103}
 104
 105static const struct super_operations proc_sops = {
 106        .alloc_inode    = proc_alloc_inode,
 107        .destroy_inode  = proc_destroy_inode,
 108        .drop_inode     = generic_delete_inode,
 109        .evict_inode    = proc_evict_inode,
 110        .statfs         = simple_statfs,
 111};
 112
 113static void __pde_users_dec(struct proc_dir_entry *pde)
 114{
 115        pde->pde_users--;
 116        if (pde->pde_unload_completion && pde->pde_users == 0)
 117                complete(pde->pde_unload_completion);
 118}
 119
 120void pde_users_dec(struct proc_dir_entry *pde)
 121{
 122        spin_lock(&pde->pde_unload_lock);
 123        __pde_users_dec(pde);
 124        spin_unlock(&pde->pde_unload_lock);
 125}
 126
 127static loff_t proc_reg_llseek(struct file *file, loff_t offset, int whence)
 128{
 129        struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
 130        loff_t rv = -EINVAL;
 131        loff_t (*llseek)(struct file *, loff_t, int);
 132
 133        spin_lock(&pde->pde_unload_lock);
 134        /*
 135         * remove_proc_entry() is going to delete PDE (as part of module
 136         * cleanup sequence). No new callers into module allowed.
 137         */
 138        if (!pde->proc_fops) {
 139                spin_unlock(&pde->pde_unload_lock);
 140                return rv;
 141        }
 142        /*
 143         * Bump refcount so that remove_proc_entry will wail for ->llseek to
 144         * complete.
 145         */
 146        pde->pde_users++;
 147        /*
 148         * Save function pointer under lock, to protect against ->proc_fops
 149         * NULL'ifying right after ->pde_unload_lock is dropped.
 150         */
 151        llseek = pde->proc_fops->llseek;
 152        spin_unlock(&pde->pde_unload_lock);
 153
 154        if (!llseek)
 155                llseek = default_llseek;
 156        rv = llseek(file, offset, whence);
 157
 158        pde_users_dec(pde);
 159        return rv;
 160}
 161
 162static ssize_t proc_reg_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
 163{
 164        struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
 165        ssize_t rv = -EIO;
 166        ssize_t (*read)(struct file *, char __user *, size_t, loff_t *);
 167
 168        spin_lock(&pde->pde_unload_lock);
 169        if (!pde->proc_fops) {
 170                spin_unlock(&pde->pde_unload_lock);
 171                return rv;
 172        }
 173        pde->pde_users++;
 174        read = pde->proc_fops->read;
 175        spin_unlock(&pde->pde_unload_lock);
 176
 177        if (read)
 178                rv = read(file, buf, count, ppos);
 179
 180        pde_users_dec(pde);
 181        return rv;
 182}
 183
 184static ssize_t proc_reg_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
 185{
 186        struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
 187        ssize_t rv = -EIO;
 188        ssize_t (*write)(struct file *, const char __user *, size_t, loff_t *);
 189
 190        spin_lock(&pde->pde_unload_lock);
 191        if (!pde->proc_fops) {
 192                spin_unlock(&pde->pde_unload_lock);
 193                return rv;
 194        }
 195        pde->pde_users++;
 196        write = pde->proc_fops->write;
 197        spin_unlock(&pde->pde_unload_lock);
 198
 199        if (write)
 200                rv = write(file, buf, count, ppos);
 201
 202        pde_users_dec(pde);
 203        return rv;
 204}
 205
 206static unsigned int proc_reg_poll(struct file *file, struct poll_table_struct *pts)
 207{
 208        struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
 209        unsigned int rv = DEFAULT_POLLMASK;
 210        unsigned int (*poll)(struct file *, struct poll_table_struct *);
 211
 212        spin_lock(&pde->pde_unload_lock);
 213        if (!pde->proc_fops) {
 214                spin_unlock(&pde->pde_unload_lock);
 215                return rv;
 216        }
 217        pde->pde_users++;
 218        poll = pde->proc_fops->poll;
 219        spin_unlock(&pde->pde_unload_lock);
 220
 221        if (poll)
 222                rv = poll(file, pts);
 223
 224        pde_users_dec(pde);
 225        return rv;
 226}
 227
 228static long proc_reg_unlocked_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 229{
 230        struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
 231        long rv = -ENOTTY;
 232        long (*ioctl)(struct file *, unsigned int, unsigned long);
 233
 234        spin_lock(&pde->pde_unload_lock);
 235        if (!pde->proc_fops) {
 236                spin_unlock(&pde->pde_unload_lock);
 237                return rv;
 238        }
 239        pde->pde_users++;
 240        ioctl = pde->proc_fops->unlocked_ioctl;
 241        spin_unlock(&pde->pde_unload_lock);
 242
 243        if (ioctl)
 244                rv = ioctl(file, cmd, arg);
 245
 246        pde_users_dec(pde);
 247        return rv;
 248}
 249
 250#ifdef CONFIG_COMPAT
 251static long proc_reg_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 252{
 253        struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
 254        long rv = -ENOTTY;
 255        long (*compat_ioctl)(struct file *, unsigned int, unsigned long);
 256
 257        spin_lock(&pde->pde_unload_lock);
 258        if (!pde->proc_fops) {
 259                spin_unlock(&pde->pde_unload_lock);
 260                return rv;
 261        }
 262        pde->pde_users++;
 263        compat_ioctl = pde->proc_fops->compat_ioctl;
 264        spin_unlock(&pde->pde_unload_lock);
 265
 266        if (compat_ioctl)
 267                rv = compat_ioctl(file, cmd, arg);
 268
 269        pde_users_dec(pde);
 270        return rv;
 271}
 272#endif
 273
 274static int proc_reg_mmap(struct file *file, struct vm_area_struct *vma)
 275{
 276        struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
 277        int rv = -EIO;
 278        int (*mmap)(struct file *, struct vm_area_struct *);
 279
 280        spin_lock(&pde->pde_unload_lock);
 281        if (!pde->proc_fops) {
 282                spin_unlock(&pde->pde_unload_lock);
 283                return rv;
 284        }
 285        pde->pde_users++;
 286        mmap = pde->proc_fops->mmap;
 287        spin_unlock(&pde->pde_unload_lock);
 288
 289        if (mmap)
 290                rv = mmap(file, vma);
 291
 292        pde_users_dec(pde);
 293        return rv;
 294}
 295
 296static int proc_reg_open(struct inode *inode, struct file *file)
 297{
 298        struct proc_dir_entry *pde = PDE(inode);
 299        int rv = 0;
 300        int (*open)(struct inode *, struct file *);
 301        int (*release)(struct inode *, struct file *);
 302        struct pde_opener *pdeo;
 303
 304        /*
 305         * What for, you ask? Well, we can have open, rmmod, remove_proc_entry
 306         * sequence. ->release won't be called because ->proc_fops will be
 307         * cleared. Depending on complexity of ->release, consequences vary.
 308         *
 309         * We can't wait for mercy when close will be done for real, it's
 310         * deadlockable: rmmod foo </proc/foo . So, we're going to do ->release
 311         * by hand in remove_proc_entry(). For this, save opener's credentials
 312         * for later.
 313         */
 314        pdeo = kmalloc(sizeof(struct pde_opener), GFP_KERNEL);
 315        if (!pdeo)
 316                return -ENOMEM;
 317
 318        spin_lock(&pde->pde_unload_lock);
 319        if (!pde->proc_fops) {
 320                spin_unlock(&pde->pde_unload_lock);
 321                kfree(pdeo);
 322                return -ENOENT;
 323        }
 324        pde->pde_users++;
 325        open = pde->proc_fops->open;
 326        release = pde->proc_fops->release;
 327        spin_unlock(&pde->pde_unload_lock);
 328
 329        if (open)
 330                rv = open(inode, file);
 331
 332        spin_lock(&pde->pde_unload_lock);
 333        if (rv == 0 && release) {
 334                /* To know what to release. */
 335                pdeo->inode = inode;
 336                pdeo->file = file;
 337                /* Strictly for "too late" ->release in proc_reg_release(). */
 338                pdeo->release = release;
 339                list_add(&pdeo->lh, &pde->pde_openers);
 340        } else
 341                kfree(pdeo);
 342        __pde_users_dec(pde);
 343        spin_unlock(&pde->pde_unload_lock);
 344        return rv;
 345}
 346
 347static struct pde_opener *find_pde_opener(struct proc_dir_entry *pde,
 348                                        struct inode *inode, struct file *file)
 349{
 350        struct pde_opener *pdeo;
 351
 352        list_for_each_entry(pdeo, &pde->pde_openers, lh) {
 353                if (pdeo->inode == inode && pdeo->file == file)
 354                        return pdeo;
 355        }
 356        return NULL;
 357}
 358
 359static int proc_reg_release(struct inode *inode, struct file *file)
 360{
 361        struct proc_dir_entry *pde = PDE(inode);
 362        int rv = 0;
 363        int (*release)(struct inode *, struct file *);
 364        struct pde_opener *pdeo;
 365
 366        spin_lock(&pde->pde_unload_lock);
 367        pdeo = find_pde_opener(pde, inode, file);
 368        if (!pde->proc_fops) {
 369                /*
 370                 * Can't simply exit, __fput() will think that everything is OK,
 371                 * and move on to freeing struct file. remove_proc_entry() will
 372                 * find slacker in opener's list and will try to do non-trivial
 373                 * things with struct file. Therefore, remove opener from list.
 374                 *
 375                 * But if opener is removed from list, who will ->release it?
 376                 */
 377                if (pdeo) {
 378                        list_del(&pdeo->lh);
 379                        spin_unlock(&pde->pde_unload_lock);
 380                        rv = pdeo->release(inode, file);
 381                        kfree(pdeo);
 382                } else
 383                        spin_unlock(&pde->pde_unload_lock);
 384                return rv;
 385        }
 386        pde->pde_users++;
 387        release = pde->proc_fops->release;
 388        if (pdeo) {
 389                list_del(&pdeo->lh);
 390                kfree(pdeo);
 391        }
 392        spin_unlock(&pde->pde_unload_lock);
 393
 394        if (release)
 395                rv = release(inode, file);
 396
 397        pde_users_dec(pde);
 398        return rv;
 399}
 400
 401static const struct file_operations proc_reg_file_ops = {
 402        .llseek         = proc_reg_llseek,
 403        .read           = proc_reg_read,
 404        .write          = proc_reg_write,
 405        .poll           = proc_reg_poll,
 406        .unlocked_ioctl = proc_reg_unlocked_ioctl,
 407#ifdef CONFIG_COMPAT
 408        .compat_ioctl   = proc_reg_compat_ioctl,
 409#endif
 410        .mmap           = proc_reg_mmap,
 411        .open           = proc_reg_open,
 412        .release        = proc_reg_release,
 413};
 414
 415#ifdef CONFIG_COMPAT
 416static const struct file_operations proc_reg_file_ops_no_compat = {
 417        .llseek         = proc_reg_llseek,
 418        .read           = proc_reg_read,
 419        .write          = proc_reg_write,
 420        .poll           = proc_reg_poll,
 421        .unlocked_ioctl = proc_reg_unlocked_ioctl,
 422        .mmap           = proc_reg_mmap,
 423        .open           = proc_reg_open,
 424        .release        = proc_reg_release,
 425};
 426#endif
 427
 428struct inode *proc_get_inode(struct super_block *sb, struct proc_dir_entry *de)
 429{
 430        struct inode * inode;
 431
 432        inode = iget_locked(sb, de->low_ino);
 433        if (!inode)
 434                return NULL;
 435        if (inode->i_state & I_NEW) {
 436                inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
 437                PROC_I(inode)->fd = 0;
 438                PROC_I(inode)->pde = de;
 439
 440                if (de->mode) {
 441                        inode->i_mode = de->mode;
 442                        inode->i_uid = de->uid;
 443                        inode->i_gid = de->gid;
 444                }
 445                if (de->size)
 446                        inode->i_size = de->size;
 447                if (de->nlink)
 448                        set_nlink(inode, de->nlink);
 449                if (de->proc_iops)
 450                        inode->i_op = de->proc_iops;
 451                if (de->proc_fops) {
 452                        if (S_ISREG(inode->i_mode)) {
 453#ifdef CONFIG_COMPAT
 454                                if (!de->proc_fops->compat_ioctl)
 455                                        inode->i_fop =
 456                                                &proc_reg_file_ops_no_compat;
 457                                else
 458#endif
 459                                        inode->i_fop = &proc_reg_file_ops;
 460                        } else {
 461                                inode->i_fop = de->proc_fops;
 462                        }
 463                }
 464                unlock_new_inode(inode);
 465        } else
 466               pde_put(de);
 467        return inode;
 468}                       
 469
 470int proc_fill_super(struct super_block *s)
 471{
 472        struct inode * root_inode;
 473
 474        s->s_flags |= MS_NODIRATIME | MS_NOSUID | MS_NOEXEC;
 475        s->s_blocksize = 1024;
 476        s->s_blocksize_bits = 10;
 477        s->s_magic = PROC_SUPER_MAGIC;
 478        s->s_op = &proc_sops;
 479        s->s_time_gran = 1;
 480        
 481        pde_get(&proc_root);
 482        root_inode = proc_get_inode(s, &proc_root);
 483        if (!root_inode)
 484                goto out_no_root;
 485        root_inode->i_uid = 0;
 486        root_inode->i_gid = 0;
 487        s->s_root = d_alloc_root(root_inode);
 488        if (!s->s_root)
 489                goto out_no_root;
 490        return 0;
 491
 492out_no_root:
 493        printk("proc_read_super: get root inode failed\n");
 494        iput(root_inode);
 495        pde_put(&proc_root);
 496        return -ENOMEM;
 497}
 498