hppfs.c

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/*
 * Copyright (C) 2002 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
 * Licensed under the GPL
 */

#include <linux/ctype.h>
#include <linux/dcache.h>
#include <linux/file.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/list.h>
#include <linux/module.h>
#include <linux/mount.h>
#include <linux/slab.h>
#include <linux/statfs.h>
#include <linux/types.h>
#include <linux/pid_namespace.h>
#include <linux/namei.h>
#include <asm/uaccess.h>
#include <os.h>

static struct inode *get_inode(struct super_block *, struct dentry *);

struct hppfs_data {
    struct list_head list;
    char contents[PAGE_SIZE - sizeof(struct list_head)];
};

struct hppfs_private {
    struct file *proc_file;
    int host_fd;
    loff_t len;
    struct hppfs_data *contents;
};

struct hppfs_inode_info {
    struct dentry *proc_dentry;
    struct inode vfs_inode;
};

static inline struct hppfs_inode_info *HPPFS_I(struct inode *inode)
{
    return container_of(inode, struct hppfs_inode_info, vfs_inode);
}

#define HPPFS_SUPER_MAGIC 0xb00000ee

static const struct super_operations hppfs_sbops;

static int is_pid(struct dentry *dentry)
{
    struct super_block *sb;
    int i;

    sb = dentry->d_sb;
    if (dentry->d_parent != sb->s_root)
        return 0;

    for (i = 0; i < dentry->d_name.len; i++) {
        if (!isdigit(dentry->d_name.name[i]))
            return 0;
    }
    return 1;
}

static char *dentry_name(struct dentry *dentry, int extra)
{
    struct dentry *parent;
    char *root, *name;
    const char *seg_name;
    int len, seg_len;

    len = 0;
    parent = dentry;
    while (parent->d_parent != parent) {
        if (is_pid(parent))
            len += strlen("pid") + 1;
        else len += parent->d_name.len + 1;
        parent = parent->d_parent;
    }

    root = "proc";
    len += strlen(root);
    name = kmalloc(len + extra + 1, GFP_KERNEL);
    if (name == NULL)
        return NULL;

    name[len] = '\0';
    parent = dentry;
    while (parent->d_parent != parent) {
        if (is_pid(parent)) {
            seg_name = "pid";
            seg_len = strlen("pid");
        }
        else {
            seg_name = parent->d_name.name;
            seg_len = parent->d_name.len;
        }

        len -= seg_len + 1;
        name[len] = '/';
        strncpy(&name[len + 1], seg_name, seg_len);
        parent = parent->d_parent;
    }
    strncpy(name, root, strlen(root));
    return name;
}

static int file_removed(struct dentry *dentry, const char *file)
{
    char *host_file;
    int extra, fd;

    extra = 0;
    if (file != NULL)
        extra += strlen(file) + 1;

    host_file = dentry_name(dentry, extra + strlen("/remove"));
    if (host_file == NULL) {
        printk(KERN_ERR "file_removed : allocation failed\n");
        return -ENOMEM;
    }

    if (file != NULL) {
        strcat(host_file, "/");
        strcat(host_file, file);
    }
    strcat(host_file, "/remove");

    fd = os_open_file(host_file, of_read(OPENFLAGS()), 0);
    kfree(host_file);
    if (fd > 0) {
        os_close_file(fd);
        return 1;
    }
    return 0;
}

static struct dentry *hppfs_lookup(struct inode *ino, struct dentry *dentry,
                   unsigned int flags)
{
    struct dentry *proc_dentry, *parent;
    struct qstr *name = &dentry->d_name;
    struct inode *inode;
    int err, deleted;

    deleted = file_removed(dentry, NULL);
    if (deleted < 0)
        return ERR_PTR(deleted);
    else if (deleted)
        return ERR_PTR(-ENOENT);

    parent = HPPFS_I(ino)->proc_dentry;
    mutex_lock(&parent->d_inode->i_mutex);
    proc_dentry = lookup_one_len(name->name, parent, name->len);
    mutex_unlock(&parent->d_inode->i_mutex);

    if (IS_ERR(proc_dentry))
        return proc_dentry;

    err = -ENOMEM;
    inode = get_inode(ino->i_sb, proc_dentry);
    if (!inode)
        goto out;

    d_add(dentry, inode);
    return NULL;

 out:
    return ERR_PTR(err);
}

static const struct inode_operations hppfs_file_iops = {
};

static ssize_t read_proc(struct file *file, char __user *buf, ssize_t count,
             loff_t *ppos, int is_user)
{
    ssize_t (*read)(struct file *, char __user *, size_t, loff_t *);
    ssize_t n;

    read = file->f_path.dentry->d_inode->i_fop->read;

    if (!is_user)
        set_fs(KERNEL_DS);

    n = (*read)(file, buf, count, &file->f_pos);

    if (!is_user)
        set_fs(USER_DS);

    if (ppos)
        *ppos = file->f_pos;
    return n;
}

static ssize_t hppfs_read_file(int fd, char __user *buf, ssize_t count)
{
    ssize_t n;
    int cur, err;
    char *new_buf;

    n = -ENOMEM;
    new_buf = kmalloc(PAGE_SIZE, GFP_KERNEL);
    if (new_buf == NULL) {
        printk(KERN_ERR "hppfs_read_file : kmalloc failed\n");
        goto out;
    }
    n = 0;
    while (count > 0) {
        cur = min_t(ssize_t, count, PAGE_SIZE);
        err = os_read_file(fd, new_buf, cur);
        if (err < 0) {
            printk(KERN_ERR "hppfs_read : read failed, "
                   "errno = %d\n", err);
            n = err;
            goto out_free;
        } else if (err == 0)
            break;

        if (copy_to_user(buf, new_buf, err)) {
            n = -EFAULT;
            goto out_free;
        }
        n += err;
        count -= err;
    }
 out_free:
    kfree(new_buf);
 out:
    return n;
}

static ssize_t hppfs_read(struct file *file, char __user *buf, size_t count,
              loff_t *ppos)
{
    struct hppfs_private *hppfs = file->private_data;
    struct hppfs_data *data;
    loff_t off;
    int err;

    if (hppfs->contents != NULL) {
        int rem;

        if (*ppos >= hppfs->len)
            return 0;

        data = hppfs->contents;
        off = *ppos;
        while (off >= sizeof(data->contents)) {
            data = list_entry(data->list.next, struct hppfs_data,
                      list);
            off -= sizeof(data->contents);
        }

        if (off + count > hppfs->len)
            count = hppfs->len - off;
        rem = copy_to_user(buf, &data->contents[off], count);
        *ppos += count - rem;
        if (rem > 0)
            return -EFAULT;
    } else if (hppfs->host_fd != -1) {
        err = os_seek_file(hppfs->host_fd, *ppos);
        if (err) {
            printk(KERN_ERR "hppfs_read : seek failed, "
                   "errno = %d\n", err);
            return err;
        }
        err = hppfs_read_file(hppfs->host_fd, buf, count);
        if (err < 0) {
            printk(KERN_ERR "hppfs_read: read failed: %d\n", err);
            return err;
        }
        count = err;
        if (count > 0)
            *ppos += count;
    }
    else count = read_proc(hppfs->proc_file, buf, count, ppos, 1);

    return count;
}

static ssize_t hppfs_write(struct file *file, const char __user *buf,
               size_t len, loff_t *ppos)
{
    struct hppfs_private *data = file->private_data;
    struct file *proc_file = data->proc_file;
    ssize_t (*write)(struct file *, const char __user *, size_t, loff_t *);

    write = proc_file->f_path.dentry->d_inode->i_fop->write;
    return (*write)(proc_file, buf, len, ppos);
}

static int open_host_sock(char *host_file, int *filter_out)
{
    char *end;
    int fd;

    end = &host_file[strlen(host_file)];
    strcpy(end, "/rw");
    *filter_out = 1;
    fd = os_connect_socket(host_file);
    if (fd > 0)
        return fd;

    strcpy(end, "/r");
    *filter_out = 0;
    fd = os_connect_socket(host_file);
    return fd;
}

static void free_contents(struct hppfs_data *head)
{
    struct hppfs_data *data;
    struct list_head *ele, *next;

    if (head == NULL)
        return;

    list_for_each_safe(ele, next, &head->list) {
        data = list_entry(ele, struct hppfs_data, list);
        kfree(data);
    }
    kfree(head);
}

static struct hppfs_data *hppfs_get_data(int fd, int filter,
                     struct file *proc_file,
                     struct file *hppfs_file,
                     loff_t *size_out)
{
    struct hppfs_data *data, *new, *head;
    int n, err;

    err = -ENOMEM;
    data = kmalloc(sizeof(*data), GFP_KERNEL);
    if (data == NULL) {
        printk(KERN_ERR "hppfs_get_data : head allocation failed\n");
        goto failed;
    }

    INIT_LIST_HEAD(&data->list);

    head = data;
    *size_out = 0;

    if (filter) {
        while ((n = read_proc(proc_file, data->contents,
                      sizeof(data->contents), NULL, 0)) > 0)
            os_write_file(fd, data->contents, n);
        err = os_shutdown_socket(fd, 0, 1);
        if (err) {
            printk(KERN_ERR "hppfs_get_data : failed to shut down "
                   "socket\n");
            goto failed_free;
        }
    }
    while (1) {
        n = os_read_file(fd, data->contents, sizeof(data->contents));
        if (n < 0) {
            err = n;
            printk(KERN_ERR "hppfs_get_data : read failed, "
                   "errno = %d\n", err);
            goto failed_free;
        } else if (n == 0)
            break;

        *size_out += n;

        if (n < sizeof(data->contents))
            break;

        new = kmalloc(sizeof(*data), GFP_KERNEL);
        if (new == 0) {
            printk(KERN_ERR "hppfs_get_data : data allocation "
                   "failed\n");
            err = -ENOMEM;
            goto failed_free;
        }

        INIT_LIST_HEAD(&new->list);
        list_add(&new->list, &data->list);
        data = new;
    }
    return head;

 failed_free:
    free_contents(head);
 failed:
    return ERR_PTR(err);
}

static struct hppfs_private *hppfs_data(void)
{
    struct hppfs_private *data;

    data = kmalloc(sizeof(*data), GFP_KERNEL);
    if (data == NULL)
        return data;

    *data = ((struct hppfs_private ) { .host_fd         = -1,
                       .len         = -1,
                       .contents        = NULL } );
    return data;
}

static int file_mode(int fmode)
{
    if (fmode == (FMODE_READ | FMODE_WRITE))
        return O_RDWR;
    if (fmode == FMODE_READ)
        return O_RDONLY;
    if (fmode == FMODE_WRITE)
        return O_WRONLY;
    return 0;
}

static int hppfs_open(struct inode *inode, struct file *file)
{
    const struct cred *cred = file->f_cred;
    struct hppfs_private *data;
    struct path path;
    char *host_file;
    int err, fd, type, filter;

    err = -ENOMEM;
    data = hppfs_data();
    if (data == NULL)
        goto out;

    host_file = dentry_name(file->f_path.dentry, strlen("/rw"));
    if (host_file == NULL)
        goto out_free2;

    path.mnt = inode->i_sb->s_fs_info;
    path.dentry = HPPFS_I(inode)->proc_dentry;

    /* XXX This isn't closed anywhere */
    data->proc_file = dentry_open(&path, file_mode(file->f_mode), cred);
    err = PTR_ERR(data->proc_file);
    if (IS_ERR(data->proc_file))
        goto out_free1;

    type = os_file_type(host_file);
    if (type == OS_TYPE_FILE) {
        fd = os_open_file(host_file, of_read(OPENFLAGS()), 0);
        if (fd >= 0)
            data->host_fd = fd;
        else
            printk(KERN_ERR "hppfs_open : failed to open '%s', "
                   "errno = %d\n", host_file, -fd);

        data->contents = NULL;
    } else if (type == OS_TYPE_DIR) {
        fd = open_host_sock(host_file, &filter);
        if (fd > 0) {
            data->contents = hppfs_get_data(fd, filter,
                            data->proc_file,
                            file, &data->len);
            if (!IS_ERR(data->contents))
                data->host_fd = fd;
        } else
            printk(KERN_ERR "hppfs_open : failed to open a socket "
                   "in '%s', errno = %d\n", host_file, -fd);
    }
    kfree(host_file);

    file->private_data = data;
    return 0;

 out_free1:
    kfree(host_file);
 out_free2:
    free_contents(data->contents);
    kfree(data);
 out:
    return err;
}

static int hppfs_dir_open(struct inode *inode, struct file *file)
{
    const struct cred *cred = file->f_cred;
    struct hppfs_private *data;
    struct path path;
    int err;

    err = -ENOMEM;
    data = hppfs_data();
    if (data == NULL)
        goto out;

    path.mnt = inode->i_sb->s_fs_info;
    path.dentry = HPPFS_I(inode)->proc_dentry;
    data->proc_file = dentry_open(&path, file_mode(file->f_mode), cred);
    err = PTR_ERR(data->proc_file);
    if (IS_ERR(data->proc_file))
        goto out_free;

    file->private_data = data;
    return 0;

 out_free:
    kfree(data);
 out:
    return err;
}

static loff_t hppfs_llseek(struct file *file, loff_t off, int where)
{
    struct hppfs_private *data = file->private_data;
    struct file *proc_file = data->proc_file;
    loff_t (*llseek)(struct file *, loff_t, int);
    loff_t ret;

    llseek = proc_file->f_path.dentry->d_inode->i_fop->llseek;
    if (llseek != NULL) {
        ret = (*llseek)(proc_file, off, where);
        if (ret < 0)
            return ret;
    }

    return default_llseek(file, off, where);
}

static const struct file_operations hppfs_file_fops = {
    .owner      = NULL,
    .llseek     = hppfs_llseek,
    .read       = hppfs_read,
    .write      = hppfs_write,
    .open       = hppfs_open,
};

struct hppfs_dirent {
    void *vfs_dirent;
    filldir_t filldir;
    struct dentry *dentry;
};

static int hppfs_filldir(void *d, const char *name, int size,
             loff_t offset, u64 inode, unsigned int type)
{
    struct hppfs_dirent *dirent = d;

    if (file_removed(dirent->dentry, name))
        return 0;

    return (*dirent->filldir)(dirent->vfs_dirent, name, size, offset,
                  inode, type);
}

static int hppfs_readdir(struct file *file, void *ent, filldir_t filldir)
{
    struct hppfs_private *data = file->private_data;
    struct file *proc_file = data->proc_file;
    int (*readdir)(struct file *, void *, filldir_t);
    struct hppfs_dirent dirent = ((struct hppfs_dirent)
                              { .vfs_dirent     = ent,
                    .filldir    = filldir,
                    .dentry     = file->f_path.dentry
                      });
    int err;

    readdir = proc_file->f_path.dentry->d_inode->i_fop->readdir;

    proc_file->f_pos = file->f_pos;
    err = (*readdir)(proc_file, &dirent, hppfs_filldir);
    file->f_pos = proc_file->f_pos;

    return err;
}

static int hppfs_fsync(struct file *file, loff_t start, loff_t end,
               int datasync)
{
    return filemap_write_and_wait_range(file->f_mapping, start, end);
}

static const struct file_operations hppfs_dir_fops = {
    .owner      = NULL,
    .readdir    = hppfs_readdir,
    .open       = hppfs_dir_open,
    .fsync      = hppfs_fsync,
    .llseek     = default_llseek,
};

static int hppfs_statfs(struct dentry *dentry, struct kstatfs *sf)
{
    sf->f_blocks = 0;
    sf->f_bfree = 0;
    sf->f_bavail = 0;
    sf->f_files = 0;
    sf->f_ffree = 0;
    sf->f_type = HPPFS_SUPER_MAGIC;
    return 0;
}

static struct inode *hppfs_alloc_inode(struct super_block *sb)
{
    struct hppfs_inode_info *hi;

    hi = kmalloc(sizeof(*hi), GFP_KERNEL);
    if (!hi)
        return NULL;

    hi->proc_dentry = NULL;
    inode_init_once(&hi->vfs_inode);
    return &hi->vfs_inode;
}

void hppfs_evict_inode(struct inode *ino)
{
    clear_inode(ino);
    dput(HPPFS_I(ino)->proc_dentry);
    mntput(ino->i_sb->s_fs_info);
}

static void hppfs_i_callback(struct rcu_head *head)
{
    struct inode *inode = container_of(head, struct inode, i_rcu);
    kfree(HPPFS_I(inode));
}

static void hppfs_destroy_inode(struct inode *inode)
{
    call_rcu(&inode->i_rcu, hppfs_i_callback);
}

static const struct super_operations hppfs_sbops = {
    .alloc_inode    = hppfs_alloc_inode,
    .destroy_inode  = hppfs_destroy_inode,
    .evict_inode    = hppfs_evict_inode,
    .statfs     = hppfs_statfs,
};

static int hppfs_readlink(struct dentry *dentry, char __user *buffer,
              int buflen)
{
    struct dentry *proc_dentry = HPPFS_I(dentry->d_inode)->proc_dentry;
    return proc_dentry->d_inode->i_op->readlink(proc_dentry, buffer,
                            buflen);
}

static void *hppfs_follow_link(struct dentry *dentry, struct nameidata *nd)
{
    struct dentry *proc_dentry = HPPFS_I(dentry->d_inode)->proc_dentry;

    return proc_dentry->d_inode->i_op->follow_link(proc_dentry, nd);
}

static void hppfs_put_link(struct dentry *dentry, struct nameidata *nd,
               void *cookie)
{
    struct dentry *proc_dentry = HPPFS_I(dentry->d_inode)->proc_dentry;

    if (proc_dentry->d_inode->i_op->put_link)
        proc_dentry->d_inode->i_op->put_link(proc_dentry, nd, cookie);
}

static const struct inode_operations hppfs_dir_iops = {
    .lookup     = hppfs_lookup,
};

static const struct inode_operations hppfs_link_iops = {
    .readlink   = hppfs_readlink,
    .follow_link    = hppfs_follow_link,
    .put_link   = hppfs_put_link,
};

static struct inode *get_inode(struct super_block *sb, struct dentry *dentry)
{
    struct inode *proc_ino = dentry->d_inode;
    struct inode *inode = new_inode(sb);

    if (!inode) {
        dput(dentry);
        return NULL;
    }

    if (S_ISDIR(dentry->d_inode->i_mode)) {
        inode->i_op = &hppfs_dir_iops;
        inode->i_fop = &hppfs_dir_fops;
    } else if (S_ISLNK(dentry->d_inode->i_mode)) {
        inode->i_op = &hppfs_link_iops;
        inode->i_fop = &hppfs_file_fops;
    } else {
        inode->i_op = &hppfs_file_iops;
        inode->i_fop = &hppfs_file_fops;
    }

    HPPFS_I(inode)->proc_dentry = dentry;

    inode->i_uid = proc_ino->i_uid;
    inode->i_gid = proc_ino->i_gid;
    inode->i_atime = proc_ino->i_atime;
    inode->i_mtime = proc_ino->i_mtime;
    inode->i_ctime = proc_ino->i_ctime;
    inode->i_ino = proc_ino->i_ino;
    inode->i_mode = proc_ino->i_mode;
    set_nlink(inode, proc_ino->i_nlink);
    inode->i_size = proc_ino->i_size;
    inode->i_blocks = proc_ino->i_blocks;

    return inode;
}

static int hppfs_fill_super(struct super_block *sb, void *d, int silent)
{
    struct inode *root_inode;
    struct vfsmount *proc_mnt;
    int err = -ENOENT;

    proc_mnt = mntget(current->nsproxy->pid_ns->proc_mnt);
    if (IS_ERR(proc_mnt))
        goto out;

    sb->s_blocksize = 1024;
    sb->s_blocksize_bits = 10;
    sb->s_magic = HPPFS_SUPER_MAGIC;
    sb->s_op = &hppfs_sbops;
    sb->s_fs_info = proc_mnt;

    err = -ENOMEM;
    root_inode = get_inode(sb, dget(proc_mnt->mnt_root));
    sb->s_root = d_make_root(root_inode);
    if (!sb->s_root)
        goto out_mntput;

    return 0;

 out_mntput:
    mntput(proc_mnt);
 out:
    return(err);
}

static struct dentry *hppfs_read_super(struct file_system_type *type,
                int flags, const char *dev_name,
                void *data)
{
    return mount_nodev(type, flags, data, hppfs_fill_super);
}

static struct file_system_type hppfs_type = {
    .owner      = THIS_MODULE,
    .name       = "hppfs",
    .mount      = hppfs_read_super,
    .kill_sb    = kill_anon_super,
    .fs_flags   = 0,
};

static int __init init_hppfs(void)
{
    return register_filesystem(&hppfs_type);
}

static void __exit exit_hppfs(void)
{
    unregister_filesystem(&hppfs_type);
}

module_init(init_hppfs)
module_exit(exit_hppfs)
MODULE_LICENSE("GPL");