procfs: new helper - PDE_DATA(inode)

[mirror_ubuntu-bionic-kernel.git] / fs / proc / generic.c

/*
 * proc/fs/generic.c --- generic routines for the proc-fs
 *
 * This file contains generic proc-fs routines for handling
 * directories and files.
 * 
 * Copyright (C) 1991, 1992 Linus Torvalds.
 * Copyright (C) 1997 Theodore Ts'o
 */

#include <linux/errno.h>
#include <linux/time.h>
#include <linux/proc_fs.h>
#include <linux/stat.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/printk.h>
#include <linux/mount.h>
#include <linux/init.h>
#include <linux/idr.h>
#include <linux/namei.h>
#include <linux/bitops.h>
#include <linux/spinlock.h>
#include <linux/completion.h>
#include <asm/uaccess.h>

#include "internal.h"

DEFINE_SPINLOCK(proc_subdir_lock);

static int proc_match(unsigned int len, const char *name, struct proc_dir_entry *de)
{
        if (de->namelen != len)
                return 0;
        return !memcmp(name, de->name, len);
}

/* buffer size is one page but our output routines use some slack for overruns */
#define PROC_BLOCK_SIZE (PAGE_SIZE - 1024)

static ssize_t
__proc_file_read(struct file *file, char __user *buf, size_t nbytes,
               loff_t *ppos)
{
        struct inode * inode = file_inode(file);
        char    *page;
        ssize_t retval=0;
        int     eof=0;
        ssize_t n, count;
        char    *start;
        struct proc_dir_entry * dp;
        unsigned long long pos;

        /*
         * Gaah, please just use "seq_file" instead. The legacy /proc
         * interfaces cut loff_t down to off_t for reads, and ignore
         * the offset entirely for writes..
         */
        pos = *ppos;
        if (pos > MAX_NON_LFS)
                return 0;
        if (nbytes > MAX_NON_LFS - pos)
                nbytes = MAX_NON_LFS - pos;

        dp = PDE(inode);
        if (!(page = (char*) __get_free_page(GFP_TEMPORARY)))
                return -ENOMEM;

        while ((nbytes > 0) && !eof) {
                count = min_t(size_t, PROC_BLOCK_SIZE, nbytes);

                start = NULL;
                if (dp->read_proc) {
                        /*
                         * How to be a proc read function
                         * ------------------------------
                         * Prototype:
                         *    int f(char *buffer, char **start, off_t offset,
                         *          int count, int *peof, void *dat)
                         *
                         * Assume that the buffer is "count" bytes in size.
                         *
                         * If you know you have supplied all the data you
                         * have, set *peof.
                         *
                         * You have three ways to return data:
                         * 0) Leave *start = NULL.  (This is the default.)
                         *    Put the data of the requested offset at that
                         *    offset within the buffer.  Return the number (n)
                         *    of bytes there are from the beginning of the
                         *    buffer up to the last byte of data.  If the
                         *    number of supplied bytes (= n - offset) is 
                         *    greater than zero and you didn't signal eof
                         *    and the reader is prepared to take more data
                         *    you will be called again with the requested
                         *    offset advanced by the number of bytes 
                         *    absorbed.  This interface is useful for files
                         *    no larger than the buffer.
                         * 1) Set *start = an unsigned long value less than
                         *    the buffer address but greater than zero.
                         *    Put the data of the requested offset at the
                         *    beginning of the buffer.  Return the number of
                         *    bytes of data placed there.  If this number is
                         *    greater than zero and you didn't signal eof
                         *    and the reader is prepared to take more data
                         *    you will be called again with the requested
                         *    offset advanced by *start.  This interface is
                         *    useful when you have a large file consisting
                         *    of a series of blocks which you want to count
                         *    and return as wholes.
                         *    (Hack by Paul.Russell@rustcorp.com.au)
                         * 2) Set *start = an address within the buffer.
                         *    Put the data of the requested offset at *start.
                         *    Return the number of bytes of data placed there.
                         *    If this number is greater than zero and you
                         *    didn't signal eof and the reader is prepared to
                         *    take more data you will be called again with the
                         *    requested offset advanced by the number of bytes
                         *    absorbed.
                         */
                        n = dp->read_proc(page, &start, *ppos,
                                          count, &eof, dp->data);
                } else
                        break;

                if (n == 0)   /* end of file */
                        break;
                if (n < 0) {  /* error */
                        if (retval == 0)
                                retval = n;
                        break;
                }

                if (start == NULL) {
                        if (n > PAGE_SIZE)      /* Apparent buffer overflow */
                                n = PAGE_SIZE;
                        n -= *ppos;
                        if (n <= 0)
                                break;
                        if (n > count)
                                n = count;
                        start = page + *ppos;
                } else if (start < page) {
                        if (n > PAGE_SIZE)      /* Apparent buffer overflow */
                                n = PAGE_SIZE;
                        if (n > count) {
                                /*
                                 * Don't reduce n because doing so might
                                 * cut off part of a data block.
                                 */
                                pr_warn("proc_file_read: count exceeded\n");
                        }
                } else /* start >= page */ {
                        unsigned long startoff = (unsigned long)(start - page);
                        if (n > (PAGE_SIZE - startoff)) /* buffer overflow? */
                                n = PAGE_SIZE - startoff;
                        if (n > count)
                                n = count;
                }
                
                n -= copy_to_user(buf, start < page ? page : start, n);
                if (n == 0) {
                        if (retval == 0)
                                retval = -EFAULT;
                        break;
                }

                *ppos += start < page ? (unsigned long)start : n;
                nbytes -= n;
                buf += n;
                retval += n;
        }
        free_page((unsigned long) page);
        return retval;
}

static ssize_t
proc_file_read(struct file *file, char __user *buf, size_t nbytes,
               loff_t *ppos)
{
        struct proc_dir_entry *pde = PDE(file_inode(file));
        ssize_t rv = -EIO;

        spin_lock(&pde->pde_unload_lock);
        if (!pde->proc_fops) {
                spin_unlock(&pde->pde_unload_lock);
                return rv;
        }
        pde->pde_users++;
        spin_unlock(&pde->pde_unload_lock);

        rv = __proc_file_read(file, buf, nbytes, ppos);

        pde_users_dec(pde);
        return rv;
}

static loff_t
proc_file_lseek(struct file *file, loff_t offset, int orig)
{
        loff_t retval = -EINVAL;
        switch (orig) {
        case 1:
                offset += file->f_pos;
        /* fallthrough */
        case 0:
                if (offset < 0 || offset > MAX_NON_LFS)
                        break;
                file->f_pos = retval = offset;
        }
        return retval;
}

static const struct file_operations proc_file_operations = {
        .llseek         = proc_file_lseek,
        .read           = proc_file_read,
};

static int proc_notify_change(struct dentry *dentry, struct iattr *iattr)
{
        struct inode *inode = dentry->d_inode;
        struct proc_dir_entry *de = PDE(inode);
        int error;

        error = inode_change_ok(inode, iattr);
        if (error)
                return error;

        setattr_copy(inode, iattr);
        mark_inode_dirty(inode);

        de->uid = inode->i_uid;
        de->gid = inode->i_gid;
        de->mode = inode->i_mode;
        return 0;
}

static int proc_getattr(struct vfsmount *mnt, struct dentry *dentry,
                        struct kstat *stat)
{
        struct inode *inode = dentry->d_inode;
        struct proc_dir_entry *de = PROC_I(inode)->pde;
        if (de && de->nlink)
                set_nlink(inode, de->nlink);

        generic_fillattr(inode, stat);
        return 0;
}

static const struct inode_operations proc_file_inode_operations = {
        .setattr        = proc_notify_change,
};

/*
 * This function parses a name such as "tty/driver/serial", and
 * returns the struct proc_dir_entry for "/proc/tty/driver", and
 * returns "serial" in residual.
 */
static int __xlate_proc_name(const char *name, struct proc_dir_entry **ret,
                             const char **residual)
{
        const char              *cp = name, *next;
        struct proc_dir_entry   *de;
        unsigned int            len;

        de = *ret;
        if (!de)
                de = &proc_root;

        while (1) {
                next = strchr(cp, '/');
                if (!next)
                        break;

                len = next - cp;
                for (de = de->subdir; de ; de = de->next) {
                        if (proc_match(len, cp, de))
                                break;
                }
                if (!de) {
                        WARN(1, "name '%s'\n", name);
                        return -ENOENT;
                }
                cp += len + 1;
        }
        *residual = cp;
        *ret = de;
        return 0;
}

static int xlate_proc_name(const char *name, struct proc_dir_entry **ret,
                           const char **residual)
{
        int rv;

        spin_lock(&proc_subdir_lock);
        rv = __xlate_proc_name(name, ret, residual);
        spin_unlock(&proc_subdir_lock);
        return rv;
}

static DEFINE_IDA(proc_inum_ida);
static DEFINE_SPINLOCK(proc_inum_lock); /* protects the above */

#define PROC_DYNAMIC_FIRST 0xF0000000U

/*
 * Return an inode number between PROC_DYNAMIC_FIRST and
 * 0xffffffff, or zero on failure.
 */
int proc_alloc_inum(unsigned int *inum)
{
        unsigned int i;
        int error;

retry:
        if (!ida_pre_get(&proc_inum_ida, GFP_KERNEL))
                return -ENOMEM;

        spin_lock_irq(&proc_inum_lock);
        error = ida_get_new(&proc_inum_ida, &i);
        spin_unlock_irq(&proc_inum_lock);
        if (error == -EAGAIN)
                goto retry;
        else if (error)
                return error;

        if (i > UINT_MAX - PROC_DYNAMIC_FIRST) {
                spin_lock_irq(&proc_inum_lock);
                ida_remove(&proc_inum_ida, i);
                spin_unlock_irq(&proc_inum_lock);
                return -ENOSPC;
        }
        *inum = PROC_DYNAMIC_FIRST + i;
        return 0;
}

void proc_free_inum(unsigned int inum)
{
        unsigned long flags;
        spin_lock_irqsave(&proc_inum_lock, flags);
        ida_remove(&proc_inum_ida, inum - PROC_DYNAMIC_FIRST);
        spin_unlock_irqrestore(&proc_inum_lock, flags);
}

static void *proc_follow_link(struct dentry *dentry, struct nameidata *nd)
{
        nd_set_link(nd, PDE_DATA(dentry->d_inode));
        return NULL;
}

static const struct inode_operations proc_link_inode_operations = {
        .readlink       = generic_readlink,
        .follow_link    = proc_follow_link,
};

/*
 * As some entries in /proc are volatile, we want to 
 * get rid of unused dentries.  This could be made 
 * smarter: we could keep a "volatile" flag in the 
 * inode to indicate which ones to keep.
 */
static int proc_delete_dentry(const struct dentry * dentry)
{
        return 1;
}

static const struct dentry_operations proc_dentry_operations =
{
        .d_delete       = proc_delete_dentry,
};

/*
 * Don't create negative dentries here, return -ENOENT by hand
 * instead.
 */
struct dentry *proc_lookup_de(struct proc_dir_entry *de, struct inode *dir,
                struct dentry *dentry)
{
        struct inode *inode;

        spin_lock(&proc_subdir_lock);
        for (de = de->subdir; de ; de = de->next) {
                if (de->namelen != dentry->d_name.len)
                        continue;
                if (!memcmp(dentry->d_name.name, de->name, de->namelen)) {
                        pde_get(de);
                        spin_unlock(&proc_subdir_lock);
                        inode = proc_get_inode(dir->i_sb, de);
                        if (!inode)
                                return ERR_PTR(-ENOMEM);
                        d_set_d_op(dentry, &proc_dentry_operations);
                        d_add(dentry, inode);
                        return NULL;
                }
        }
        spin_unlock(&proc_subdir_lock);
        return ERR_PTR(-ENOENT);
}

struct dentry *proc_lookup(struct inode *dir, struct dentry *dentry,
                unsigned int flags)
{
        return proc_lookup_de(PDE(dir), dir, dentry);
}

/*
 * This returns non-zero if at EOF, so that the /proc
 * root directory can use this and check if it should
 * continue with the <pid> entries..
 *
 * Note that the VFS-layer doesn't care about the return
 * value of the readdir() call, as long as it's non-negative
 * for success..
 */
int proc_readdir_de(struct proc_dir_entry *de, struct file *filp, void *dirent,
                filldir_t filldir)
{
        unsigned int ino;
        int i;
        struct inode *inode = file_inode(filp);
        int ret = 0;

        ino = inode->i_ino;
        i = filp->f_pos;
        switch (i) {
                case 0:
                        if (filldir(dirent, ".", 1, i, ino, DT_DIR) < 0)
                                goto out;
                        i++;
                        filp->f_pos++;
                        /* fall through */
                case 1:
                        if (filldir(dirent, "..", 2, i,
                                    parent_ino(filp->f_path.dentry),
                                    DT_DIR) < 0)
                                goto out;
                        i++;
                        filp->f_pos++;
                        /* fall through */
                default:
                        spin_lock(&proc_subdir_lock);
                        de = de->subdir;
                        i -= 2;
                        for (;;) {
                                if (!de) {
                                        ret = 1;
                                        spin_unlock(&proc_subdir_lock);
                                        goto out;
                                }
                                if (!i)
                                        break;
                                de = de->next;
                                i--;
                        }

                        do {
                                struct proc_dir_entry *next;

                                /* filldir passes info to user space */
                                pde_get(de);
                                spin_unlock(&proc_subdir_lock);
                                if (filldir(dirent, de->name, de->namelen, filp->f_pos,
                                            de->low_ino, de->mode >> 12) < 0) {
                                        pde_put(de);
                                        goto out;
                                }
                                spin_lock(&proc_subdir_lock);
                                filp->f_pos++;
                                next = de->next;
                                pde_put(de);
                                de = next;
                        } while (de);
                        spin_unlock(&proc_subdir_lock);
        }
        ret = 1;
out:
        return ret;     
}

int proc_readdir(struct file *filp, void *dirent, filldir_t filldir)
{
        struct inode *inode = file_inode(filp);

        return proc_readdir_de(PDE(inode), filp, dirent, filldir);
}

/*
 * These are the generic /proc directory operations. They
 * use the in-memory "struct proc_dir_entry" tree to parse
 * the /proc directory.
 */
static const struct file_operations proc_dir_operations = {
        .llseek                 = generic_file_llseek,
        .read                   = generic_read_dir,
        .readdir                = proc_readdir,
};

/*
 * proc directories can do almost nothing..
 */
static const struct inode_operations proc_dir_inode_operations = {
        .lookup         = proc_lookup,
        .getattr        = proc_getattr,
        .setattr        = proc_notify_change,
};

static int proc_register(struct proc_dir_entry * dir, struct proc_dir_entry * dp)
{
        struct proc_dir_entry *tmp;
        int ret;
        
        ret = proc_alloc_inum(&dp->low_ino);
        if (ret)
                return ret;

        if (S_ISDIR(dp->mode)) {
                dp->proc_fops = &proc_dir_operations;
                dp->proc_iops = &proc_dir_inode_operations;
                dir->nlink++;
        } else if (S_ISLNK(dp->mode)) {
                dp->proc_iops = &proc_link_inode_operations;
        } else if (S_ISREG(dp->mode)) {
                if (dp->proc_fops == NULL)
                        dp->proc_fops = &proc_file_operations;
                dp->proc_iops = &proc_file_inode_operations;
        } else {
                WARN_ON(1);
                return -EINVAL;
        }

        spin_lock(&proc_subdir_lock);

        for (tmp = dir->subdir; tmp; tmp = tmp->next)
                if (strcmp(tmp->name, dp->name) == 0) {
                        WARN(1, "proc_dir_entry '%s/%s' already registered\n",
                                dir->name, dp->name);
                        break;
                }

        dp->next = dir->subdir;
        dp->parent = dir;
        dir->subdir = dp;
        spin_unlock(&proc_subdir_lock);

        return 0;
}

static struct proc_dir_entry *__proc_create(struct proc_dir_entry **parent,
                                          const char *name,
                                          umode_t mode,
                                          nlink_t nlink)
{
        struct proc_dir_entry *ent = NULL;
        const char *fn = name;
        unsigned int len;

        /* make sure name is valid */
        if (!name || !strlen(name))
                goto out;

        if (xlate_proc_name(name, parent, &fn) != 0)
                goto out;

        /* At this point there must not be any '/' characters beyond *fn */
        if (strchr(fn, '/'))
                goto out;

        len = strlen(fn);

        ent = kzalloc(sizeof(struct proc_dir_entry) + len + 1, GFP_KERNEL);
        if (!ent)
                goto out;

        memcpy(ent->name, fn, len + 1);
        ent->namelen = len;
        ent->mode = mode;
        ent->nlink = nlink;
        atomic_set(&ent->count, 1);
        spin_lock_init(&ent->pde_unload_lock);
        INIT_LIST_HEAD(&ent->pde_openers);
out:
        return ent;
}

struct proc_dir_entry *proc_symlink(const char *name,
                struct proc_dir_entry *parent, const char *dest)
{
        struct proc_dir_entry *ent;

        ent = __proc_create(&parent, name,
                          (S_IFLNK | S_IRUGO | S_IWUGO | S_IXUGO),1);

        if (ent) {
                ent->data = kmalloc((ent->size=strlen(dest))+1, GFP_KERNEL);
                if (ent->data) {
                        strcpy((char*)ent->data,dest);
                        if (proc_register(parent, ent) < 0) {
                                kfree(ent->data);
                                kfree(ent);
                                ent = NULL;
                        }
                } else {
                        kfree(ent);
                        ent = NULL;
                }
        }
        return ent;
}
EXPORT_SYMBOL(proc_symlink);

struct proc_dir_entry *proc_mkdir_mode(const char *name, umode_t mode,
                struct proc_dir_entry *parent)
{
        struct proc_dir_entry *ent;

        ent = __proc_create(&parent, name, S_IFDIR | mode, 2);
        if (ent) {
                if (proc_register(parent, ent) < 0) {
                        kfree(ent);
                        ent = NULL;
                }
        }
        return ent;
}
EXPORT_SYMBOL(proc_mkdir_mode);

struct proc_dir_entry *proc_net_mkdir(struct net *net, const char *name,
                struct proc_dir_entry *parent)
{
        struct proc_dir_entry *ent;

        ent = __proc_create(&parent, name, S_IFDIR | S_IRUGO | S_IXUGO, 2);
        if (ent) {
                ent->data = net;
                if (proc_register(parent, ent) < 0) {
                        kfree(ent);
                        ent = NULL;
                }
        }
        return ent;
}
EXPORT_SYMBOL_GPL(proc_net_mkdir);

struct proc_dir_entry *proc_mkdir(const char *name,
                struct proc_dir_entry *parent)
{
        return proc_mkdir_mode(name, S_IRUGO | S_IXUGO, parent);
}
EXPORT_SYMBOL(proc_mkdir);

struct proc_dir_entry *create_proc_entry(const char *name, umode_t mode,
                                         struct proc_dir_entry *parent)
{
        struct proc_dir_entry *ent;

        if ((mode & S_IFMT) == 0)
                mode |= S_IFREG;

        if (!S_ISREG(mode)) {
                WARN_ON(1);     /* use proc_mkdir(), damnit */
                return NULL;
        }

        if ((mode & S_IALLUGO) == 0)
                mode |= S_IRUGO;

        ent = __proc_create(&parent, name, mode, 1);
        if (ent) {
                if (proc_register(parent, ent) < 0) {
                        kfree(ent);
                        ent = NULL;
                }
        }
        return ent;
}
EXPORT_SYMBOL(create_proc_entry);

struct proc_dir_entry *proc_create_data(const char *name, umode_t mode,
                                        struct proc_dir_entry *parent,
                                        const struct file_operations *proc_fops,
                                        void *data)
{
        struct proc_dir_entry *pde;
        if ((mode & S_IFMT) == 0)
                mode |= S_IFREG;

        if (!S_ISREG(mode)) {
                WARN_ON(1);     /* use proc_mkdir() */
                return NULL;
        }

        if ((mode & S_IALLUGO) == 0)
                mode |= S_IRUGO;
        pde = __proc_create(&parent, name, mode, 1);
        if (!pde)
                goto out;
        pde->proc_fops = proc_fops;
        pde->data = data;
        if (proc_register(parent, pde) < 0)
                goto out_free;
        return pde;
out_free:
        kfree(pde);
out:
        return NULL;
}
EXPORT_SYMBOL(proc_create_data);

static void free_proc_entry(struct proc_dir_entry *de)
{
        proc_free_inum(de->low_ino);

        if (S_ISLNK(de->mode))
                kfree(de->data);
        kfree(de);
}

void pde_put(struct proc_dir_entry *pde)
{
        if (atomic_dec_and_test(&pde->count))
                free_proc_entry(pde);
}

static void entry_rundown(struct proc_dir_entry *de)
{
        spin_lock(&de->pde_unload_lock);
        /*
         * Stop accepting new callers into module. If you're
         * dynamically allocating ->proc_fops, save a pointer somewhere.
         */
        de->proc_fops = NULL;
        /* Wait until all existing callers into module are done. */
        if (de->pde_users > 0) {
                DECLARE_COMPLETION_ONSTACK(c);

                if (!de->pde_unload_completion)
                        de->pde_unload_completion = &c;

                spin_unlock(&de->pde_unload_lock);

                wait_for_completion(de->pde_unload_completion);

                spin_lock(&de->pde_unload_lock);
        }

        while (!list_empty(&de->pde_openers)) {
                struct pde_opener *pdeo;

                pdeo = list_first_entry(&de->pde_openers, struct pde_opener, lh);
                list_del(&pdeo->lh);
                spin_unlock(&de->pde_unload_lock);
                pdeo->release(pdeo->inode, pdeo->file);
                kfree(pdeo);
                spin_lock(&de->pde_unload_lock);
        }
        spin_unlock(&de->pde_unload_lock);
}

/*
 * Remove a /proc entry and free it if it's not currently in use.
 */
void remove_proc_entry(const char *name, struct proc_dir_entry *parent)
{
        struct proc_dir_entry **p;
        struct proc_dir_entry *de = NULL;
        const char *fn = name;
        unsigned int len;

        spin_lock(&proc_subdir_lock);
        if (__xlate_proc_name(name, &parent, &fn) != 0) {
                spin_unlock(&proc_subdir_lock);
                return;
        }
        len = strlen(fn);

        for (p = &parent->subdir; *p; p=&(*p)->next ) {
                if (proc_match(len, fn, *p)) {
                        de = *p;
                        *p = de->next;
                        de->next = NULL;
                        break;
                }
        }
        spin_unlock(&proc_subdir_lock);
        if (!de) {
                WARN(1, "name '%s'\n", name);
                return;
        }

        entry_rundown(de);

        if (S_ISDIR(de->mode))
                parent->nlink--;
        de->nlink = 0;
        WARN(de->subdir, "%s: removing non-empty directory "
                         "'%s/%s', leaking at least '%s'\n", __func__,
                         de->parent->name, de->name, de->subdir->name);
        pde_put(de);
}
EXPORT_SYMBOL(remove_proc_entry);

int remove_proc_subtree(const char *name, struct proc_dir_entry *parent)
{
        struct proc_dir_entry **p;
        struct proc_dir_entry *root = NULL, *de, *next;
        const char *fn = name;
        unsigned int len;

        spin_lock(&proc_subdir_lock);
        if (__xlate_proc_name(name, &parent, &fn) != 0) {
                spin_unlock(&proc_subdir_lock);
                return -ENOENT;
        }
        len = strlen(fn);

        for (p = &parent->subdir; *p; p=&(*p)->next ) {
                if (proc_match(len, fn, *p)) {
                        root = *p;
                        *p = root->next;
                        root->next = NULL;
                        break;
                }
        }
        if (!root) {
                spin_unlock(&proc_subdir_lock);
                return -ENOENT;
        }
        de = root;
        while (1) {
                next = de->subdir;
                if (next) {
                        de->subdir = next->next;
                        next->next = NULL;
                        de = next;
                        continue;
                }
                spin_unlock(&proc_subdir_lock);

                entry_rundown(de);
                next = de->parent;
                if (S_ISDIR(de->mode))
                        next->nlink--;
                de->nlink = 0;
                if (de == root)
                        break;
                pde_put(de);

                spin_lock(&proc_subdir_lock);
                de = next;
        }
        pde_put(root);
        return 0;
}
EXPORT_SYMBOL(remove_proc_subtree);