super.c

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/*
 *  xenfs.c - a filesystem for passing info between the a domain and
 *  the hypervisor.
 *
 * 2008-10-07  Alex Zeffertt    Replaced /proc/xen/xenbus with xenfs filesystem
 *                              and /proc/xen compatibility mount point.
 *                              Turned xenfs into a loadable module.
 */

#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/magic.h>

#include <xen/xen.h>

#include "xenfs.h"
#include "../privcmd.h"
#include "../xenbus/xenbus_comms.h"

#include <asm/xen/hypervisor.h>

MODULE_DESCRIPTION("Xen filesystem");
MODULE_LICENSE("GPL");

static struct inode *xenfs_make_inode(struct super_block *sb, int mode)
{
    struct inode *ret = new_inode(sb);

    if (ret) {
        ret->i_mode = mode;
        ret->i_uid = GLOBAL_ROOT_UID;
        ret->i_gid = GLOBAL_ROOT_GID;
        ret->i_blocks = 0;
        ret->i_atime = ret->i_mtime = ret->i_ctime = CURRENT_TIME;
    }
    return ret;
}

static struct dentry *xenfs_create_file(struct super_block *sb,
                    struct dentry *parent,
                    const char *name,
                    const struct file_operations *fops,
                    void *data,
                    int mode)
{
    struct dentry *dentry;
    struct inode *inode;

    dentry = d_alloc_name(parent, name);
    if (!dentry)
        return NULL;

    inode = xenfs_make_inode(sb, S_IFREG | mode);
    if (!inode) {
        dput(dentry);
        return NULL;
    }

    inode->i_fop = fops;
    inode->i_private = data;

    d_add(dentry, inode);
    return dentry;
}

static ssize_t capabilities_read(struct file *file, char __user *buf,
                 size_t size, loff_t *off)
{
    char *tmp = "";

    if (xen_initial_domain())
        tmp = "control_d\n";

    return simple_read_from_buffer(buf, size, off, tmp, strlen(tmp));
}

static const struct file_operations capabilities_file_ops = {
    .read = capabilities_read,
    .llseek = default_llseek,
};

static int xenfs_fill_super(struct super_block *sb, void *data, int silent)
{
    static struct tree_descr xenfs_files[] = {
        [1] = {},
        { "xenbus", &xen_xenbus_fops, S_IRUSR|S_IWUSR },
        { "capabilities", &capabilities_file_ops, S_IRUGO },
        { "privcmd", &xen_privcmd_fops, S_IRUSR|S_IWUSR },
        {""},
    };
    int rc;

    rc = simple_fill_super(sb, XENFS_SUPER_MAGIC, xenfs_files);
    if (rc < 0)
        return rc;

    if (xen_initial_domain()) {
        xenfs_create_file(sb, sb->s_root, "xsd_kva",
                  &xsd_kva_file_ops, NULL, S_IRUSR|S_IWUSR);
        xenfs_create_file(sb, sb->s_root, "xsd_port",
                  &xsd_port_file_ops, NULL, S_IRUSR|S_IWUSR);
    }

    return rc;
}

static struct dentry *xenfs_mount(struct file_system_type *fs_type,
                  int flags, const char *dev_name,
                  void *data)
{
    return mount_single(fs_type, flags, data, xenfs_fill_super);
}

static struct file_system_type xenfs_type = {
    .owner =    THIS_MODULE,
    .name =     "xenfs",
    .mount =    xenfs_mount,
    .kill_sb =  kill_litter_super,
};

static int __init xenfs_init(void)
{
    if (xen_domain())
        return register_filesystem(&xenfs_type);

    printk(KERN_INFO "XENFS: not registering filesystem on non-xen platform\n");
    return 0;
}

static void __exit xenfs_exit(void)
{
    if (xen_domain())
        unregister_filesystem(&xenfs_type);
}

module_init(xenfs_init);
module_exit(xenfs_exit);