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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};
41
42static struct dentry *anon_inodefs_mount(struct file_system_type *fs_type,
43 int flags, const char *dev_name, void *data)
44{
45 return mount_pseudo(fs_type, "anon_inode:", NULL,
46 &anon_inodefs_dentry_operations, ANON_INODE_FS_MAGIC);
47}
48
49static struct file_system_type anon_inode_fs_type = {
50 .name = "anon_inodefs",
51 .mount = anon_inodefs_mount,
52 .kill_sb = kill_anon_super,
53};
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58
59static int anon_set_page_dirty(struct page *page)
60{
61 return 0;
62};
63
64static const struct address_space_operations anon_aops = {
65 .set_page_dirty = anon_set_page_dirty,
66};
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84struct file *anon_inode_getfile(const char *name,
85 const struct file_operations *fops,
86 void *priv, int flags)
87{
88 struct qstr this;
89 struct path path;
90 struct file *file;
91 int error;
92
93 if (IS_ERR(anon_inode_inode))
94 return ERR_PTR(-ENODEV);
95
96 if (fops->owner && !try_module_get(fops->owner))
97 return ERR_PTR(-ENOENT);
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102
103 error = -ENOMEM;
104 this.name = name;
105 this.len = strlen(name);
106 this.hash = 0;
107 path.dentry = d_alloc_pseudo(anon_inode_mnt->mnt_sb, &this);
108 if (!path.dentry)
109 goto err_module;
110
111 path.mnt = mntget(anon_inode_mnt);
112
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115
116 ihold(anon_inode_inode);
117
118 d_instantiate(path.dentry, anon_inode_inode);
119
120 error = -ENFILE;
121 file = alloc_file(&path, OPEN_FMODE(flags), fops);
122 if (!file)
123 goto err_dput;
124 file->f_mapping = anon_inode_inode->i_mapping;
125
126 file->f_pos = 0;
127 file->f_flags = flags & (O_ACCMODE | O_NONBLOCK);
128 file->f_version = 0;
129 file->private_data = priv;
130
131 return file;
132
133err_dput:
134 path_put(&path);
135err_module:
136 module_put(fops->owner);
137 return ERR_PTR(error);
138}
139EXPORT_SYMBOL_GPL(anon_inode_getfile);
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157int anon_inode_getfd(const char *name, const struct file_operations *fops,
158 void *priv, int flags)
159{
160 int error, fd;
161 struct file *file;
162
163 error = get_unused_fd_flags(flags);
164 if (error < 0)
165 return error;
166 fd = error;
167
168 file = anon_inode_getfile(name, fops, priv, flags);
169 if (IS_ERR(file)) {
170 error = PTR_ERR(file);
171 goto err_put_unused_fd;
172 }
173 fd_install(fd, file);
174
175 return fd;
176
177err_put_unused_fd:
178 put_unused_fd(fd);
179 return error;
180}
181EXPORT_SYMBOL_GPL(anon_inode_getfd);
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187
188static struct inode *anon_inode_mkinode(void)
189{
190 struct inode *inode = new_inode(anon_inode_mnt->mnt_sb);
191
192 if (!inode)
193 return ERR_PTR(-ENOMEM);
194
195 inode->i_ino = get_next_ino();
196 inode->i_fop = &anon_inode_fops;
197
198 inode->i_mapping->a_ops = &anon_aops;
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206 inode->i_state = I_DIRTY;
207 inode->i_mode = S_IRUSR | S_IWUSR;
208 inode->i_uid = current_fsuid();
209 inode->i_gid = current_fsgid();
210 inode->i_flags |= S_PRIVATE;
211 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
212 return inode;
213}
214
215static int __init anon_inode_init(void)
216{
217 int error;
218
219 error = register_filesystem(&anon_inode_fs_type);
220 if (error)
221 goto err_exit;
222 anon_inode_mnt = kern_mount(&anon_inode_fs_type);
223 if (IS_ERR(anon_inode_mnt)) {
224 error = PTR_ERR(anon_inode_mnt);
225 goto err_unregister_filesystem;
226 }
227 anon_inode_inode = anon_inode_mkinode();
228 if (IS_ERR(anon_inode_inode)) {
229 error = PTR_ERR(anon_inode_inode);
230 goto err_mntput;
231 }
232
233 return 0;
234
235err_mntput:
236 mntput(anon_inode_mnt);
237err_unregister_filesystem:
238 unregister_filesystem(&anon_inode_fs_type);
239err_exit:
240 panic(KERN_ERR "anon_inode_init() failed (%d)\n", error);
241}
242
243fs_initcall(anon_inode_init);
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245