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/fs_context.h>
  18 #include <linux/magic.h>
  19
  20 #include <xen/xen.h>
  21 #include <xen/xenbus.h>
  22
  23 #include "xenfs.h"
  24 #include "../privcmd.h"
  25
  26 #include <asm/xen/hypervisor.h>
  27
  28 MODULE_DESCRIPTION("Xen filesystem");
  29 MODULE_LICENSE("GPL");
  30
  31 static ssize_t capabilities_read(struct file *file, char __user *buf,
  32                                  size_t size, loff_t *off)
  33 {
  34         char *tmp = "";
  35
  36         if (xen_initial_domain())
  37                 tmp = "control_d\n";
  38
  39         return simple_read_from_buffer(buf, size, off, tmp, strlen(tmp));
  40 }
  41
  42 static const struct file_operations capabilities_file_ops = {
  43         .read = capabilities_read,
  44         .llseek = default_llseek,
  45 };
  46
  47 static int xenfs_fill_super(struct super_block *sb, struct fs_context *fc)
  48 {
  49         static const struct tree_descr xenfs_files[] = {
  50                 [2] = { "xenbus", &xen_xenbus_fops, S_IRUSR|S_IWUSR },
  51                 { "capabilities", &capabilities_file_ops, S_IRUGO },
  52                 { "privcmd", &xen_privcmd_fops, S_IRUSR|S_IWUSR },
  53                 {""},
  54         };
  55
  56         static const struct tree_descr xenfs_init_files[] = {
  57                 [2] = { "xenbus", &xen_xenbus_fops, S_IRUSR|S_IWUSR },
  58                 { "capabilities", &capabilities_file_ops, S_IRUGO },
  59                 { "privcmd", &xen_privcmd_fops, S_IRUSR|S_IWUSR },
  60                 { "xsd_kva", &xsd_kva_file_ops, S_IRUSR|S_IWUSR},
  61                 { "xsd_port", &xsd_port_file_ops, S_IRUSR|S_IWUSR},
  62 #ifdef CONFIG_XEN_SYMS
  63                 { "xensyms", &xensyms_ops, S_IRUSR},
  64 #endif
  65                 {""},
  66         };
  67
  68         return simple_fill_super(sb, XENFS_SUPER_MAGIC,
  69                         xen_initial_domain() ? xenfs_init_files : xenfs_files);
  70 }
  71
  72 static int xenfs_get_tree(struct fs_context *fc)
  73 {
  74         return get_tree_single(fc, xenfs_fill_super);
  75 }
  76
  77 static const struct fs_context_operations xenfs_context_ops = {
  78         .get_tree       = xenfs_get_tree,
  79 };
  80
  81 static int xenfs_init_fs_context(struct fs_context *fc)
  82 {
  83         fc->ops = &xenfs_context_ops;
  84         return 0;
  85 }
  86
  87 static struct file_system_type xenfs_type = {
  88         .owner =        THIS_MODULE,
  89         .name =         "xenfs",
  90         .init_fs_context = xenfs_init_fs_context,
  91         .kill_sb =      kill_litter_super,
  92 };
  93 MODULE_ALIAS_FS("xenfs");
  94
  95 static int __init xenfs_init(void)
  96 {
  97         if (xen_domain())
  98                 return register_filesystem(&xenfs_type);
  99
 100         return 0;
 101 }
 102
 103 static void __exit xenfs_exit(void)
 104 {
 105         if (xen_domain())
 106                 unregister_filesystem(&xenfs_type);
 107 }
 108
 109 module_init(xenfs_init);
 110 module_exit(xenfs_exit);
 111