xref: /openbmc/linux/fs/seq_file.c (revision e868d61272caa648214046a096e5a6bfc068dc8c)
1 /*
2  * linux/fs/seq_file.c
3  *
4  * helper functions for making synthetic files from sequences of records.
5  * initial implementation -- AV, Oct 2001.
6  */
7 
8 #include <linux/fs.h>
9 #include <linux/module.h>
10 #include <linux/seq_file.h>
11 #include <linux/slab.h>
12 
13 #include <asm/uaccess.h>
14 #include <asm/page.h>
15 
16 /**
17  *	seq_open -	initialize sequential file
18  *	@file: file we initialize
19  *	@op: method table describing the sequence
20  *
21  *	seq_open() sets @file, associating it with a sequence described
22  *	by @op.  @op->start() sets the iterator up and returns the first
23  *	element of sequence. @op->stop() shuts it down.  @op->next()
24  *	returns the next element of sequence.  @op->show() prints element
25  *	into the buffer.  In case of error ->start() and ->next() return
26  *	ERR_PTR(error).  In the end of sequence they return %NULL. ->show()
27  *	returns 0 in case of success and negative number in case of error.
28  */
29 int seq_open(struct file *file, const struct seq_operations *op)
30 {
31 	struct seq_file *p = file->private_data;
32 
33 	if (!p) {
34 		p = kmalloc(sizeof(*p), GFP_KERNEL);
35 		if (!p)
36 			return -ENOMEM;
37 		file->private_data = p;
38 	}
39 	memset(p, 0, sizeof(*p));
40 	mutex_init(&p->lock);
41 	p->op = op;
42 
43 	/*
44 	 * Wrappers around seq_open(e.g. swaps_open) need to be
45 	 * aware of this. If they set f_version themselves, they
46 	 * should call seq_open first and then set f_version.
47 	 */
48 	file->f_version = 0;
49 
50 	/* SEQ files support lseek, but not pread/pwrite */
51 	file->f_mode &= ~(FMODE_PREAD | FMODE_PWRITE);
52 	return 0;
53 }
54 EXPORT_SYMBOL(seq_open);
55 
56 /**
57  *	seq_read -	->read() method for sequential files.
58  *	@file: the file to read from
59  *	@buf: the buffer to read to
60  *	@size: the maximum number of bytes to read
61  *	@ppos: the current position in the file
62  *
63  *	Ready-made ->f_op->read()
64  */
65 ssize_t seq_read(struct file *file, char __user *buf, size_t size, loff_t *ppos)
66 {
67 	struct seq_file *m = (struct seq_file *)file->private_data;
68 	size_t copied = 0;
69 	loff_t pos;
70 	size_t n;
71 	void *p;
72 	int err = 0;
73 
74 	mutex_lock(&m->lock);
75 	/*
76 	 * seq_file->op->..m_start/m_stop/m_next may do special actions
77 	 * or optimisations based on the file->f_version, so we want to
78 	 * pass the file->f_version to those methods.
79 	 *
80 	 * seq_file->version is just copy of f_version, and seq_file
81 	 * methods can treat it simply as file version.
82 	 * It is copied in first and copied out after all operations.
83 	 * It is convenient to have it as  part of structure to avoid the
84 	 * need of passing another argument to all the seq_file methods.
85 	 */
86 	m->version = file->f_version;
87 	/* grab buffer if we didn't have one */
88 	if (!m->buf) {
89 		m->buf = kmalloc(m->size = PAGE_SIZE, GFP_KERNEL);
90 		if (!m->buf)
91 			goto Enomem;
92 	}
93 	/* if not empty - flush it first */
94 	if (m->count) {
95 		n = min(m->count, size);
96 		err = copy_to_user(buf, m->buf + m->from, n);
97 		if (err)
98 			goto Efault;
99 		m->count -= n;
100 		m->from += n;
101 		size -= n;
102 		buf += n;
103 		copied += n;
104 		if (!m->count)
105 			m->index++;
106 		if (!size)
107 			goto Done;
108 	}
109 	/* we need at least one record in buffer */
110 	while (1) {
111 		pos = m->index;
112 		p = m->op->start(m, &pos);
113 		err = PTR_ERR(p);
114 		if (!p || IS_ERR(p))
115 			break;
116 		err = m->op->show(m, p);
117 		if (err)
118 			break;
119 		if (m->count < m->size)
120 			goto Fill;
121 		m->op->stop(m, p);
122 		kfree(m->buf);
123 		m->buf = kmalloc(m->size <<= 1, GFP_KERNEL);
124 		if (!m->buf)
125 			goto Enomem;
126 		m->count = 0;
127 		m->version = 0;
128 	}
129 	m->op->stop(m, p);
130 	m->count = 0;
131 	goto Done;
132 Fill:
133 	/* they want more? let's try to get some more */
134 	while (m->count < size) {
135 		size_t offs = m->count;
136 		loff_t next = pos;
137 		p = m->op->next(m, p, &next);
138 		if (!p || IS_ERR(p)) {
139 			err = PTR_ERR(p);
140 			break;
141 		}
142 		err = m->op->show(m, p);
143 		if (err || m->count == m->size) {
144 			m->count = offs;
145 			break;
146 		}
147 		pos = next;
148 	}
149 	m->op->stop(m, p);
150 	n = min(m->count, size);
151 	err = copy_to_user(buf, m->buf, n);
152 	if (err)
153 		goto Efault;
154 	copied += n;
155 	m->count -= n;
156 	if (m->count)
157 		m->from = n;
158 	else
159 		pos++;
160 	m->index = pos;
161 Done:
162 	if (!copied)
163 		copied = err;
164 	else
165 		*ppos += copied;
166 	file->f_version = m->version;
167 	mutex_unlock(&m->lock);
168 	return copied;
169 Enomem:
170 	err = -ENOMEM;
171 	goto Done;
172 Efault:
173 	err = -EFAULT;
174 	goto Done;
175 }
176 EXPORT_SYMBOL(seq_read);
177 
178 static int traverse(struct seq_file *m, loff_t offset)
179 {
180 	loff_t pos = 0;
181 	int error = 0;
182 	void *p;
183 
184 	m->version = 0;
185 	m->index = 0;
186 	m->count = m->from = 0;
187 	if (!offset)
188 		return 0;
189 	if (!m->buf) {
190 		m->buf = kmalloc(m->size = PAGE_SIZE, GFP_KERNEL);
191 		if (!m->buf)
192 			return -ENOMEM;
193 	}
194 	p = m->op->start(m, &m->index);
195 	while (p) {
196 		error = PTR_ERR(p);
197 		if (IS_ERR(p))
198 			break;
199 		error = m->op->show(m, p);
200 		if (error)
201 			break;
202 		if (m->count == m->size)
203 			goto Eoverflow;
204 		if (pos + m->count > offset) {
205 			m->from = offset - pos;
206 			m->count -= m->from;
207 			break;
208 		}
209 		pos += m->count;
210 		m->count = 0;
211 		if (pos == offset) {
212 			m->index++;
213 			break;
214 		}
215 		p = m->op->next(m, p, &m->index);
216 	}
217 	m->op->stop(m, p);
218 	return error;
219 
220 Eoverflow:
221 	m->op->stop(m, p);
222 	kfree(m->buf);
223 	m->buf = kmalloc(m->size <<= 1, GFP_KERNEL);
224 	return !m->buf ? -ENOMEM : -EAGAIN;
225 }
226 
227 /**
228  *	seq_lseek -	->llseek() method for sequential files.
229  *	@file: the file in question
230  *	@offset: new position
231  *	@origin: 0 for absolute, 1 for relative position
232  *
233  *	Ready-made ->f_op->llseek()
234  */
235 loff_t seq_lseek(struct file *file, loff_t offset, int origin)
236 {
237 	struct seq_file *m = (struct seq_file *)file->private_data;
238 	long long retval = -EINVAL;
239 
240 	mutex_lock(&m->lock);
241 	m->version = file->f_version;
242 	switch (origin) {
243 		case 1:
244 			offset += file->f_pos;
245 		case 0:
246 			if (offset < 0)
247 				break;
248 			retval = offset;
249 			if (offset != file->f_pos) {
250 				while ((retval=traverse(m, offset)) == -EAGAIN)
251 					;
252 				if (retval) {
253 					/* with extreme prejudice... */
254 					file->f_pos = 0;
255 					m->version = 0;
256 					m->index = 0;
257 					m->count = 0;
258 				} else {
259 					retval = file->f_pos = offset;
260 				}
261 			}
262 	}
263 	mutex_unlock(&m->lock);
264 	file->f_version = m->version;
265 	return retval;
266 }
267 EXPORT_SYMBOL(seq_lseek);
268 
269 /**
270  *	seq_release -	free the structures associated with sequential file.
271  *	@file: file in question
272  *	@inode: file->f_path.dentry->d_inode
273  *
274  *	Frees the structures associated with sequential file; can be used
275  *	as ->f_op->release() if you don't have private data to destroy.
276  */
277 int seq_release(struct inode *inode, struct file *file)
278 {
279 	struct seq_file *m = (struct seq_file *)file->private_data;
280 	kfree(m->buf);
281 	kfree(m);
282 	return 0;
283 }
284 EXPORT_SYMBOL(seq_release);
285 
286 /**
287  *	seq_escape -	print string into buffer, escaping some characters
288  *	@m:	target buffer
289  *	@s:	string
290  *	@esc:	set of characters that need escaping
291  *
292  *	Puts string into buffer, replacing each occurrence of character from
293  *	@esc with usual octal escape.  Returns 0 in case of success, -1 - in
294  *	case of overflow.
295  */
296 int seq_escape(struct seq_file *m, const char *s, const char *esc)
297 {
298 	char *end = m->buf + m->size;
299         char *p;
300 	char c;
301 
302         for (p = m->buf + m->count; (c = *s) != '\0' && p < end; s++) {
303 		if (!strchr(esc, c)) {
304 			*p++ = c;
305 			continue;
306 		}
307 		if (p + 3 < end) {
308 			*p++ = '\\';
309 			*p++ = '0' + ((c & 0300) >> 6);
310 			*p++ = '0' + ((c & 070) >> 3);
311 			*p++ = '0' + (c & 07);
312 			continue;
313 		}
314 		m->count = m->size;
315 		return -1;
316         }
317 	m->count = p - m->buf;
318         return 0;
319 }
320 EXPORT_SYMBOL(seq_escape);
321 
322 int seq_printf(struct seq_file *m, const char *f, ...)
323 {
324 	va_list args;
325 	int len;
326 
327 	if (m->count < m->size) {
328 		va_start(args, f);
329 		len = vsnprintf(m->buf + m->count, m->size - m->count, f, args);
330 		va_end(args);
331 		if (m->count + len < m->size) {
332 			m->count += len;
333 			return 0;
334 		}
335 	}
336 	m->count = m->size;
337 	return -1;
338 }
339 EXPORT_SYMBOL(seq_printf);
340 
341 int seq_path(struct seq_file *m,
342 	     struct vfsmount *mnt, struct dentry *dentry,
343 	     char *esc)
344 {
345 	if (m->count < m->size) {
346 		char *s = m->buf + m->count;
347 		char *p = d_path(dentry, mnt, s, m->size - m->count);
348 		if (!IS_ERR(p)) {
349 			while (s <= p) {
350 				char c = *p++;
351 				if (!c) {
352 					p = m->buf + m->count;
353 					m->count = s - m->buf;
354 					return s - p;
355 				} else if (!strchr(esc, c)) {
356 					*s++ = c;
357 				} else if (s + 4 > p) {
358 					break;
359 				} else {
360 					*s++ = '\\';
361 					*s++ = '0' + ((c & 0300) >> 6);
362 					*s++ = '0' + ((c & 070) >> 3);
363 					*s++ = '0' + (c & 07);
364 				}
365 			}
366 		}
367 	}
368 	m->count = m->size;
369 	return -1;
370 }
371 EXPORT_SYMBOL(seq_path);
372 
373 static void *single_start(struct seq_file *p, loff_t *pos)
374 {
375 	return NULL + (*pos == 0);
376 }
377 
378 static void *single_next(struct seq_file *p, void *v, loff_t *pos)
379 {
380 	++*pos;
381 	return NULL;
382 }
383 
384 static void single_stop(struct seq_file *p, void *v)
385 {
386 }
387 
388 int single_open(struct file *file, int (*show)(struct seq_file *, void *),
389 		void *data)
390 {
391 	struct seq_operations *op = kmalloc(sizeof(*op), GFP_KERNEL);
392 	int res = -ENOMEM;
393 
394 	if (op) {
395 		op->start = single_start;
396 		op->next = single_next;
397 		op->stop = single_stop;
398 		op->show = show;
399 		res = seq_open(file, op);
400 		if (!res)
401 			((struct seq_file *)file->private_data)->private = data;
402 		else
403 			kfree(op);
404 	}
405 	return res;
406 }
407 EXPORT_SYMBOL(single_open);
408 
409 int single_release(struct inode *inode, struct file *file)
410 {
411 	const struct seq_operations *op = ((struct seq_file *)file->private_data)->op;
412 	int res = seq_release(inode, file);
413 	kfree(op);
414 	return res;
415 }
416 EXPORT_SYMBOL(single_release);
417 
418 int seq_release_private(struct inode *inode, struct file *file)
419 {
420 	struct seq_file *seq = file->private_data;
421 
422 	kfree(seq->private);
423 	seq->private = NULL;
424 	return seq_release(inode, file);
425 }
426 EXPORT_SYMBOL(seq_release_private);
427 
428 int seq_putc(struct seq_file *m, char c)
429 {
430 	if (m->count < m->size) {
431 		m->buf[m->count++] = c;
432 		return 0;
433 	}
434 	return -1;
435 }
436 EXPORT_SYMBOL(seq_putc);
437 
438 int seq_puts(struct seq_file *m, const char *s)
439 {
440 	int len = strlen(s);
441 	if (m->count + len < m->size) {
442 		memcpy(m->buf + m->count, s, len);
443 		m->count += len;
444 		return 0;
445 	}
446 	m->count = m->size;
447 	return -1;
448 }
449 EXPORT_SYMBOL(seq_puts);
450