1 /* 2 * fs/sysfs/symlink.c - operations for initializing and mounting sysfs 3 * 4 * Copyright (c) 2001-3 Patrick Mochel 5 * Copyright (c) 2007 SUSE Linux Products GmbH 6 * Copyright (c) 2007 Tejun Heo <teheo@suse.de> 7 * 8 * This file is released under the GPLv2. 9 * 10 * Please see Documentation/filesystems/sysfs.txt for more information. 11 */ 12 13 #define DEBUG 14 15 #include <linux/fs.h> 16 #include <linux/mount.h> 17 #include <linux/pagemap.h> 18 #include <linux/init.h> 19 #include <linux/module.h> 20 #include <linux/magic.h> 21 #include <linux/slab.h> 22 #include <linux/user_namespace.h> 23 24 #include "sysfs.h" 25 26 27 static struct vfsmount *sysfs_mnt; 28 struct kmem_cache *sysfs_dir_cachep; 29 30 static const struct super_operations sysfs_ops = { 31 .statfs = simple_statfs, 32 .drop_inode = generic_delete_inode, 33 .evict_inode = sysfs_evict_inode, 34 }; 35 36 struct sysfs_dirent sysfs_root = { 37 .s_name = "", 38 .s_count = ATOMIC_INIT(1), 39 .s_flags = SYSFS_DIR | (KOBJ_NS_TYPE_NONE << SYSFS_NS_TYPE_SHIFT), 40 .s_mode = S_IFDIR | S_IRUGO | S_IXUGO, 41 .s_ino = 1, 42 }; 43 44 static int sysfs_fill_super(struct super_block *sb, void *data, int silent) 45 { 46 struct inode *inode; 47 struct dentry *root; 48 49 sb->s_blocksize = PAGE_CACHE_SIZE; 50 sb->s_blocksize_bits = PAGE_CACHE_SHIFT; 51 sb->s_magic = SYSFS_MAGIC; 52 sb->s_op = &sysfs_ops; 53 sb->s_time_gran = 1; 54 55 /* get root inode, initialize and unlock it */ 56 mutex_lock(&sysfs_mutex); 57 inode = sysfs_get_inode(sb, &sysfs_root); 58 mutex_unlock(&sysfs_mutex); 59 if (!inode) { 60 pr_debug("sysfs: could not get root inode\n"); 61 return -ENOMEM; 62 } 63 64 /* instantiate and link root dentry */ 65 root = d_make_root(inode); 66 if (!root) { 67 pr_debug("%s: could not get root dentry!\n",__func__); 68 return -ENOMEM; 69 } 70 root->d_fsdata = &sysfs_root; 71 sb->s_root = root; 72 sb->s_d_op = &sysfs_dentry_ops; 73 return 0; 74 } 75 76 static int sysfs_test_super(struct super_block *sb, void *data) 77 { 78 struct sysfs_super_info *sb_info = sysfs_info(sb); 79 struct sysfs_super_info *info = data; 80 enum kobj_ns_type type; 81 int found = 1; 82 83 for (type = KOBJ_NS_TYPE_NONE; type < KOBJ_NS_TYPES; type++) { 84 if (sb_info->ns[type] != info->ns[type]) 85 found = 0; 86 } 87 return found; 88 } 89 90 static int sysfs_set_super(struct super_block *sb, void *data) 91 { 92 int error; 93 error = set_anon_super(sb, data); 94 if (!error) 95 sb->s_fs_info = data; 96 return error; 97 } 98 99 static void free_sysfs_super_info(struct sysfs_super_info *info) 100 { 101 int type; 102 for (type = KOBJ_NS_TYPE_NONE; type < KOBJ_NS_TYPES; type++) 103 kobj_ns_drop(type, info->ns[type]); 104 kfree(info); 105 } 106 107 static struct dentry *sysfs_mount(struct file_system_type *fs_type, 108 int flags, const char *dev_name, void *data) 109 { 110 struct sysfs_super_info *info; 111 enum kobj_ns_type type; 112 struct super_block *sb; 113 int error; 114 115 if (!(flags & MS_KERNMOUNT) && !current_user_ns()->may_mount_sysfs) 116 return ERR_PTR(-EPERM); 117 118 info = kzalloc(sizeof(*info), GFP_KERNEL); 119 if (!info) 120 return ERR_PTR(-ENOMEM); 121 122 for (type = KOBJ_NS_TYPE_NONE; type < KOBJ_NS_TYPES; type++) 123 info->ns[type] = kobj_ns_grab_current(type); 124 125 sb = sget(fs_type, sysfs_test_super, sysfs_set_super, flags, info); 126 if (IS_ERR(sb) || sb->s_fs_info != info) 127 free_sysfs_super_info(info); 128 if (IS_ERR(sb)) 129 return ERR_CAST(sb); 130 if (!sb->s_root) { 131 error = sysfs_fill_super(sb, data, flags & MS_SILENT ? 1 : 0); 132 if (error) { 133 deactivate_locked_super(sb); 134 return ERR_PTR(error); 135 } 136 sb->s_flags |= MS_ACTIVE; 137 } 138 139 return dget(sb->s_root); 140 } 141 142 static void sysfs_kill_sb(struct super_block *sb) 143 { 144 struct sysfs_super_info *info = sysfs_info(sb); 145 /* Remove the superblock from fs_supers/s_instances 146 * so we can't find it, before freeing sysfs_super_info. 147 */ 148 kill_anon_super(sb); 149 free_sysfs_super_info(info); 150 } 151 152 static struct file_system_type sysfs_fs_type = { 153 .name = "sysfs", 154 .mount = sysfs_mount, 155 .kill_sb = sysfs_kill_sb, 156 .fs_flags = FS_USERNS_MOUNT, 157 }; 158 159 int __init sysfs_init(void) 160 { 161 int err = -ENOMEM; 162 163 sysfs_dir_cachep = kmem_cache_create("sysfs_dir_cache", 164 sizeof(struct sysfs_dirent), 165 0, 0, NULL); 166 if (!sysfs_dir_cachep) 167 goto out; 168 169 err = sysfs_inode_init(); 170 if (err) 171 goto out_err; 172 173 err = register_filesystem(&sysfs_fs_type); 174 if (!err) { 175 sysfs_mnt = kern_mount(&sysfs_fs_type); 176 if (IS_ERR(sysfs_mnt)) { 177 printk(KERN_ERR "sysfs: could not mount!\n"); 178 err = PTR_ERR(sysfs_mnt); 179 sysfs_mnt = NULL; 180 unregister_filesystem(&sysfs_fs_type); 181 goto out_err; 182 } 183 } else 184 goto out_err; 185 out: 186 return err; 187 out_err: 188 kmem_cache_destroy(sysfs_dir_cachep); 189 sysfs_dir_cachep = NULL; 190 goto out; 191 } 192 193 #undef sysfs_get 194 struct sysfs_dirent *sysfs_get(struct sysfs_dirent *sd) 195 { 196 return __sysfs_get(sd); 197 } 198 EXPORT_SYMBOL_GPL(sysfs_get); 199 200 #undef sysfs_put 201 void sysfs_put(struct sysfs_dirent *sd) 202 { 203 __sysfs_put(sd); 204 } 205 EXPORT_SYMBOL_GPL(sysfs_put); 206