drivers/xen/xenfs/super.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  *  xenfs.c - a filesystem for passing info between the a domain and
   4  *  the hypervisor.
   5  *
   6  * 2008-10-07  Alex Zeffertt    Replaced /proc/xen/xenbus with xenfs filesystem
   7  *                              and /proc/xen compatibility mount point.
   8  *                              Turned xenfs into a loadable module.
   9  */
  10
  11 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  12
  13 #include <linux/kernel.h>
  14 #include <linux/errno.h>
  15 #include <linux/module.h>
  16 #include <linux/fs.h>
  17 #include <linux/magic.h>
  18
  19 #include <xen/xen.h>
  20 #include <xen/xenbus.h>
  21
  22 #include "xenfs.h"
  23 #include "../privcmd.h"
  24
  25 #include <asm/xen/hypervisor.h>
  26
  27 MODULE_DESCRIPTION("Xen filesystem");
  28 MODULE_LICENSE("GPL");
  29
  30 static ssize_t capabilities_read(struct file *file, char __user *buf,
  31                                  size_t size, loff_t *off)
  32 {
  33         char *tmp = "";
  34
  35         if (xen_initial_domain())
  36                 tmp = "control_d\n";
  37
  38         return simple_read_from_buffer(buf, size, off, tmp, strlen(tmp));
  39 }
  40
  41 static const struct file_operations capabilities_file_ops = {
  42         .read = capabilities_read,
  43         .llseek = default_llseek,
  44 };
  45
  46 static int xenfs_fill_super(struct super_block *sb, void *data, int silent)
  47 {
  48         static const struct tree_descr xenfs_files[] = {
  49                 [2] = { "xenbus", &xen_xenbus_fops, S_IRUSR|S_IWUSR },
  50                 { "capabilities", &capabilities_file_ops, S_IRUGO },
  51                 { "privcmd", &xen_privcmd_fops, S_IRUSR|S_IWUSR },
  52                 {""},
  53         };
  54
  55         static const struct tree_descr xenfs_init_files[] = {
  56                 [2] = { "xenbus", &xen_xenbus_fops, S_IRUSR|S_IWUSR },
  57                 { "capabilities", &capabilities_file_ops, S_IRUGO },
  58                 { "privcmd", &xen_privcmd_fops, S_IRUSR|S_IWUSR },
  59                 { "xsd_kva", &xsd_kva_file_ops, S_IRUSR|S_IWUSR},
  60                 { "xsd_port", &xsd_port_file_ops, S_IRUSR|S_IWUSR},
  61 #ifdef CONFIG_XEN_SYMS
  62                 { "xensyms", &xensyms_ops, S_IRUSR},
  63 #endif
  64                 {""},
  65         };
  66
  67         return simple_fill_super(sb, XENFS_SUPER_MAGIC,
  68                         xen_initial_domain() ? xenfs_init_files : xenfs_files);
  69 }
  70
  71 static struct dentry *xenfs_mount(struct file_system_type *fs_type,
  72                                   int flags, const char *dev_name,
  73                                   void *data)
  74 {
  75         return mount_single(fs_type, flags, data, xenfs_fill_super);
  76 }
  77
  78 static struct file_system_type xenfs_type = {
  79         .owner =        THIS_MODULE,
  80         .name =         "xenfs",
  81         .mount =        xenfs_mount,
  82         .kill_sb =      kill_litter_super,
  83 };
  84 MODULE_ALIAS_FS("xenfs");
  85
  86 static int __init xenfs_init(void)
  87 {
  88         if (xen_domain())
  89                 return register_filesystem(&xenfs_type);
  90
  91         return 0;
  92 }
  93
  94 static void __exit xenfs_exit(void)
  95 {
  96         if (xen_domain())
  97                 unregister_filesystem(&xenfs_type);
  98 }
  99
 100 module_init(xenfs_init);
 101 module_exit(xenfs_exit);
 102