[PATCH] VFS: Permit filesystem to override root dentry on mount
[linux-2.6.git] / drivers / oprofile / oprofilefs.c
1 /**
2  * @file oprofilefs.c
3  *
4  * @remark Copyright 2002 OProfile authors
5  * @remark Read the file COPYING
6  *
7  * @author John Levon
8  *
9  * A simple filesystem for configuration and
10  * access of oprofile.
11  */
12
13 #include <linux/init.h>
14 #include <linux/module.h>
15 #include <linux/oprofile.h>
16 #include <linux/fs.h>
17 #include <linux/pagemap.h>
18 #include <asm/uaccess.h>
19
20 #include "oprof.h"
21
22 #define OPROFILEFS_MAGIC 0x6f70726f
23
24 DEFINE_SPINLOCK(oprofilefs_lock);
25
26 static struct inode * oprofilefs_get_inode(struct super_block * sb, int mode)
27 {
28         struct inode * inode = new_inode(sb);
29
30         if (inode) {
31                 inode->i_mode = mode;
32                 inode->i_uid = 0;
33                 inode->i_gid = 0;
34                 inode->i_blksize = PAGE_CACHE_SIZE;
35                 inode->i_blocks = 0;
36                 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
37         }
38         return inode;
39 }
40
41
42 static struct super_operations s_ops = {
43         .statfs         = simple_statfs,
44         .drop_inode     = generic_delete_inode,
45 };
46
47
48 ssize_t oprofilefs_str_to_user(char const * str, char __user * buf, size_t count, loff_t * offset)
49 {
50         return simple_read_from_buffer(buf, count, offset, str, strlen(str));
51 }
52
53
54 #define TMPBUFSIZE 50
55
56 ssize_t oprofilefs_ulong_to_user(unsigned long val, char __user * buf, size_t count, loff_t * offset)
57 {
58         char tmpbuf[TMPBUFSIZE];
59         size_t maxlen = snprintf(tmpbuf, TMPBUFSIZE, "%lu\n", val);
60         if (maxlen > TMPBUFSIZE)
61                 maxlen = TMPBUFSIZE;
62         return simple_read_from_buffer(buf, count, offset, tmpbuf, maxlen);
63 }
64
65
66 int oprofilefs_ulong_from_user(unsigned long * val, char const __user * buf, size_t count)
67 {
68         char tmpbuf[TMPBUFSIZE];
69
70         if (!count)
71                 return 0;
72
73         if (count > TMPBUFSIZE - 1)
74                 return -EINVAL;
75
76         memset(tmpbuf, 0x0, TMPBUFSIZE);
77
78         if (copy_from_user(tmpbuf, buf, count))
79                 return -EFAULT;
80
81         spin_lock(&oprofilefs_lock);
82         *val = simple_strtoul(tmpbuf, NULL, 0);
83         spin_unlock(&oprofilefs_lock);
84         return 0;
85 }
86
87
88 static ssize_t ulong_read_file(struct file * file, char __user * buf, size_t count, loff_t * offset)
89 {
90         unsigned long * val = file->private_data;
91         return oprofilefs_ulong_to_user(*val, buf, count, offset);
92 }
93
94
95 static ssize_t ulong_write_file(struct file * file, char const __user * buf, size_t count, loff_t * offset)
96 {
97         unsigned long * value = file->private_data;
98         int retval;
99
100         if (*offset)
101                 return -EINVAL;
102
103         retval = oprofilefs_ulong_from_user(value, buf, count);
104
105         if (retval)
106                 return retval;
107         return count;
108 }
109
110
111 static int default_open(struct inode * inode, struct file * filp)
112 {
113         if (inode->u.generic_ip)
114                 filp->private_data = inode->u.generic_ip;
115         return 0;
116 }
117
118
119 static struct file_operations ulong_fops = {
120         .read           = ulong_read_file,
121         .write          = ulong_write_file,
122         .open           = default_open,
123 };
124
125
126 static struct file_operations ulong_ro_fops = {
127         .read           = ulong_read_file,
128         .open           = default_open,
129 };
130
131
132 static struct dentry * __oprofilefs_create_file(struct super_block * sb,
133         struct dentry * root, char const * name, const struct file_operations * fops,
134         int perm)
135 {
136         struct dentry * dentry;
137         struct inode * inode;
138
139         dentry = d_alloc_name(root, name);
140         if (!dentry)
141                 return NULL;
142         inode = oprofilefs_get_inode(sb, S_IFREG | perm);
143         if (!inode) {
144                 dput(dentry);
145                 return NULL;
146         }
147         inode->i_fop = fops;
148         d_add(dentry, inode);
149         return dentry;
150 }
151
152
153 int oprofilefs_create_ulong(struct super_block * sb, struct dentry * root,
154         char const * name, unsigned long * val)
155 {
156         struct dentry * d = __oprofilefs_create_file(sb, root, name,
157                                                      &ulong_fops, 0644);
158         if (!d)
159                 return -EFAULT;
160
161         d->d_inode->u.generic_ip = val;
162         return 0;
163 }
164
165
166 int oprofilefs_create_ro_ulong(struct super_block * sb, struct dentry * root,
167         char const * name, unsigned long * val)
168 {
169         struct dentry * d = __oprofilefs_create_file(sb, root, name,
170                                                      &ulong_ro_fops, 0444);
171         if (!d)
172                 return -EFAULT;
173
174         d->d_inode->u.generic_ip = val;
175         return 0;
176 }
177
178
179 static ssize_t atomic_read_file(struct file * file, char __user * buf, size_t count, loff_t * offset)
180 {
181         atomic_t * val = file->private_data;
182         return oprofilefs_ulong_to_user(atomic_read(val), buf, count, offset);
183 }
184  
185
186 static struct file_operations atomic_ro_fops = {
187         .read           = atomic_read_file,
188         .open           = default_open,
189 };
190  
191
192 int oprofilefs_create_ro_atomic(struct super_block * sb, struct dentry * root,
193         char const * name, atomic_t * val)
194 {
195         struct dentry * d = __oprofilefs_create_file(sb, root, name,
196                                                      &atomic_ro_fops, 0444);
197         if (!d)
198                 return -EFAULT;
199
200         d->d_inode->u.generic_ip = val;
201         return 0;
202 }
203
204  
205 int oprofilefs_create_file(struct super_block * sb, struct dentry * root,
206         char const * name, const struct file_operations * fops)
207 {
208         if (!__oprofilefs_create_file(sb, root, name, fops, 0644))
209                 return -EFAULT;
210         return 0;
211 }
212
213
214 int oprofilefs_create_file_perm(struct super_block * sb, struct dentry * root,
215         char const * name, const struct file_operations * fops, int perm)
216 {
217         if (!__oprofilefs_create_file(sb, root, name, fops, perm))
218                 return -EFAULT;
219         return 0;
220 }
221
222
223 struct dentry * oprofilefs_mkdir(struct super_block * sb,
224         struct dentry * root, char const * name)
225 {
226         struct dentry * dentry;
227         struct inode * inode;
228
229         dentry = d_alloc_name(root, name);
230         if (!dentry)
231                 return NULL;
232         inode = oprofilefs_get_inode(sb, S_IFDIR | 0755);
233         if (!inode) {
234                 dput(dentry);
235                 return NULL;
236         }
237         inode->i_op = &simple_dir_inode_operations;
238         inode->i_fop = &simple_dir_operations;
239         d_add(dentry, inode);
240         return dentry;
241 }
242
243
244 static int oprofilefs_fill_super(struct super_block * sb, void * data, int silent)
245 {
246         struct inode * root_inode;
247         struct dentry * root_dentry;
248
249         sb->s_blocksize = PAGE_CACHE_SIZE;
250         sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
251         sb->s_magic = OPROFILEFS_MAGIC;
252         sb->s_op = &s_ops;
253         sb->s_time_gran = 1;
254
255         root_inode = oprofilefs_get_inode(sb, S_IFDIR | 0755);
256         if (!root_inode)
257                 return -ENOMEM;
258         root_inode->i_op = &simple_dir_inode_operations;
259         root_inode->i_fop = &simple_dir_operations;
260         root_dentry = d_alloc_root(root_inode);
261         if (!root_dentry) {
262                 iput(root_inode);
263                 return -ENOMEM;
264         }
265
266         sb->s_root = root_dentry;
267
268         oprofile_create_files(sb, root_dentry);
269
270         // FIXME: verify kill_litter_super removes our dentries
271         return 0;
272 }
273
274
275 static int oprofilefs_get_sb(struct file_system_type *fs_type,
276         int flags, const char *dev_name, void *data, struct vfsmount *mnt)
277 {
278         return get_sb_single(fs_type, flags, data, oprofilefs_fill_super, mnt);
279 }
280
281
282 static struct file_system_type oprofilefs_type = {
283         .owner          = THIS_MODULE,
284         .name           = "oprofilefs",
285         .get_sb         = oprofilefs_get_sb,
286         .kill_sb        = kill_litter_super,
287 };
288
289
290 int __init oprofilefs_register(void)
291 {
292         return register_filesystem(&oprofilefs_type);
293 }
294
295
296 void __exit oprofilefs_unregister(void)
297 {
298         unregister_filesystem(&oprofilefs_type);
299 }