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11#include <linux/cred.h>
12#include <linux/file.h>
13#include <linux/poll.h>
14#include <linux/sched.h>
15#include <linux/init.h>
16#include <linux/fs.h>
17#include <linux/mount.h>
18#include <linux/module.h>
19#include <linux/kernel.h>
20#include <linux/magic.h>
21#include <linux/anon_inodes.h>
22
23#include <asm/uaccess.h>
24
25static struct vfsmount *anon_inode_mnt __read_mostly;
26static struct inode *anon_inode_inode;
27static const struct file_operations anon_inode_fops;
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31
32static char *anon_inodefs_dname(struct dentry *dentry, char *buffer, int buflen)
33{
34 return dynamic_dname(dentry, buffer, buflen, "anon_inode:%s",
35 dentry->d_name.name);
36}
37
38static const struct dentry_operations anon_inodefs_dentry_operations = {
39 .d_dname = anon_inodefs_dname,
40};
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45
46static int anon_set_page_dirty(struct page *page)
47{
48 return 0;
49};
50
51static const struct address_space_operations anon_aops = {
52 .set_page_dirty = anon_set_page_dirty,
53};
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59
60static struct inode *anon_inode_mkinode(struct super_block *s)
61{
62 struct inode *inode = new_inode_pseudo(s);
63
64 if (!inode)
65 return ERR_PTR(-ENOMEM);
66
67 inode->i_ino = get_next_ino();
68 inode->i_fop = &anon_inode_fops;
69
70 inode->i_mapping->a_ops = &anon_aops;
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78 inode->i_state = I_DIRTY;
79 inode->i_mode = S_IRUSR | S_IWUSR;
80 inode->i_uid = current_fsuid();
81 inode->i_gid = current_fsgid();
82 inode->i_flags |= S_PRIVATE;
83 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
84 return inode;
85}
86
87static struct dentry *anon_inodefs_mount(struct file_system_type *fs_type,
88 int flags, const char *dev_name, void *data)
89{
90 struct dentry *root;
91 root = mount_pseudo(fs_type, "anon_inode:", NULL,
92 &anon_inodefs_dentry_operations, ANON_INODE_FS_MAGIC);
93 if (!IS_ERR(root)) {
94 struct super_block *s = root->d_sb;
95 anon_inode_inode = anon_inode_mkinode(s);
96 if (IS_ERR(anon_inode_inode)) {
97 dput(root);
98 deactivate_locked_super(s);
99 root = ERR_CAST(anon_inode_inode);
100 }
101 }
102 return root;
103}
104
105static struct file_system_type anon_inode_fs_type = {
106 .name = "anon_inodefs",
107 .mount = anon_inodefs_mount,
108 .kill_sb = kill_anon_super,
109};
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127struct file *anon_inode_getfile(const char *name,
128 const struct file_operations *fops,
129 void *priv, int flags)
130{
131 struct qstr this;
132 struct path path;
133 struct file *file;
134
135 if (IS_ERR(anon_inode_inode))
136 return ERR_PTR(-ENODEV);
137
138 if (fops->owner && !try_module_get(fops->owner))
139 return ERR_PTR(-ENOENT);
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144
145 file = ERR_PTR(-ENOMEM);
146 this.name = name;
147 this.len = strlen(name);
148 this.hash = 0;
149 path.dentry = d_alloc_pseudo(anon_inode_mnt->mnt_sb, &this);
150 if (!path.dentry)
151 goto err_module;
152
153 path.mnt = mntget(anon_inode_mnt);
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158 ihold(anon_inode_inode);
159
160 d_instantiate(path.dentry, anon_inode_inode);
161
162 file = alloc_file(&path, OPEN_FMODE(flags), fops);
163 if (IS_ERR(file))
164 goto err_dput;
165 file->f_mapping = anon_inode_inode->i_mapping;
166
167 file->f_flags = flags & (O_ACCMODE | O_NONBLOCK);
168 file->private_data = priv;
169
170 return file;
171
172err_dput:
173 path_put(&path);
174err_module:
175 module_put(fops->owner);
176 return file;
177}
178EXPORT_SYMBOL_GPL(anon_inode_getfile);
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196int anon_inode_getfd(const char *name, const struct file_operations *fops,
197 void *priv, int flags)
198{
199 int error, fd;
200 struct file *file;
201
202 error = get_unused_fd_flags(flags);
203 if (error < 0)
204 return error;
205 fd = error;
206
207 file = anon_inode_getfile(name, fops, priv, flags);
208 if (IS_ERR(file)) {
209 error = PTR_ERR(file);
210 goto err_put_unused_fd;
211 }
212 fd_install(fd, file);
213
214 return fd;
215
216err_put_unused_fd:
217 put_unused_fd(fd);
218 return error;
219}
220EXPORT_SYMBOL_GPL(anon_inode_getfd);
221
222static int __init anon_inode_init(void)
223{
224 int error;
225
226 error = register_filesystem(&anon_inode_fs_type);
227 if (error)
228 goto err_exit;
229 anon_inode_mnt = kern_mount(&anon_inode_fs_type);
230 if (IS_ERR(anon_inode_mnt)) {
231 error = PTR_ERR(anon_inode_mnt);
232 goto err_unregister_filesystem;
233 }
234 return 0;
235
236err_unregister_filesystem:
237 unregister_filesystem(&anon_inode_fs_type);
238err_exit:
239 panic(KERN_ERR "anon_inode_init() failed (%d)\n", error);
240}
241
242fs_initcall(anon_inode_init);
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244