xref: /openbmc/linux/fs/seq_file.c (revision d5cb9783536a41df9f9cba5b0a1d78047ed787f7)
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, struct seq_operations *op)
30 {
31 	struct seq_file *p = kmalloc(sizeof(*p), GFP_KERNEL);
32 	if (!p)
33 		return -ENOMEM;
34 	memset(p, 0, sizeof(*p));
35 	sema_init(&p->sem, 1);
36 	p->op = op;
37 	file->private_data = p;
38 
39 	/*
40 	 * Wrappers around seq_open(e.g. swaps_open) need to be
41 	 * aware of this. If they set f_version themselves, they
42 	 * should call seq_open first and then set f_version.
43 	 */
44 	file->f_version = 0;
45 
46 	/* SEQ files support lseek, but not pread/pwrite */
47 	file->f_mode &= ~(FMODE_PREAD | FMODE_PWRITE);
48 	return 0;
49 }
50 EXPORT_SYMBOL(seq_open);
51 
52 /**
53  *	seq_read -	->read() method for sequential files.
54  *	@file: the file to read from
55  *	@buf: the buffer to read to
56  *	@size: the maximum number of bytes to read
57  *	@ppos: the current position in the file
58  *
59  *	Ready-made ->f_op->read()
60  */
61 ssize_t seq_read(struct file *file, char __user *buf, size_t size, loff_t *ppos)
62 {
63 	struct seq_file *m = (struct seq_file *)file->private_data;
64 	size_t copied = 0;
65 	loff_t pos;
66 	size_t n;
67 	void *p;
68 	int err = 0;
69 
70 	down(&m->sem);
71 	/*
72 	 * seq_file->op->..m_start/m_stop/m_next may do special actions
73 	 * or optimisations based on the file->f_version, so we want to
74 	 * pass the file->f_version to those methods.
75 	 *
76 	 * seq_file->version is just copy of f_version, and seq_file
77 	 * methods can treat it simply as file version.
78 	 * It is copied in first and copied out after all operations.
79 	 * It is convenient to have it as  part of structure to avoid the
80 	 * need of passing another argument to all the seq_file methods.
81 	 */
82 	m->version = file->f_version;
83 	/* grab buffer if we didn't have one */
84 	if (!m->buf) {
85 		m->buf = kmalloc(m->size = PAGE_SIZE, GFP_KERNEL);
86 		if (!m->buf)
87 			goto Enomem;
88 	}
89 	/* if not empty - flush it first */
90 	if (m->count) {
91 		n = min(m->count, size);
92 		err = copy_to_user(buf, m->buf + m->from, n);
93 		if (err)
94 			goto Efault;
95 		m->count -= n;
96 		m->from += n;
97 		size -= n;
98 		buf += n;
99 		copied += n;
100 		if (!m->count)
101 			m->index++;
102 		if (!size)
103 			goto Done;
104 	}
105 	/* we need at least one record in buffer */
106 	while (1) {
107 		pos = m->index;
108 		p = m->op->start(m, &pos);
109 		err = PTR_ERR(p);
110 		if (!p || IS_ERR(p))
111 			break;
112 		err = m->op->show(m, p);
113 		if (err)
114 			break;
115 		if (m->count < m->size)
116 			goto Fill;
117 		m->op->stop(m, p);
118 		kfree(m->buf);
119 		m->buf = kmalloc(m->size <<= 1, GFP_KERNEL);
120 		if (!m->buf)
121 			goto Enomem;
122 		m->count = 0;
123 		m->version = 0;
124 	}
125 	m->op->stop(m, p);
126 	m->count = 0;
127 	goto Done;
128 Fill:
129 	/* they want more? let's try to get some more */
130 	while (m->count < size) {
131 		size_t offs = m->count;
132 		loff_t next = pos;
133 		p = m->op->next(m, p, &next);
134 		if (!p || IS_ERR(p)) {
135 			err = PTR_ERR(p);
136 			break;
137 		}
138 		err = m->op->show(m, p);
139 		if (err || m->count == m->size) {
140 			m->count = offs;
141 			break;
142 		}
143 		pos = next;
144 	}
145 	m->op->stop(m, p);
146 	n = min(m->count, size);
147 	err = copy_to_user(buf, m->buf, n);
148 	if (err)
149 		goto Efault;
150 	copied += n;
151 	m->count -= n;
152 	if (m->count)
153 		m->from = n;
154 	else
155 		pos++;
156 	m->index = pos;
157 Done:
158 	if (!copied)
159 		copied = err;
160 	else
161 		*ppos += copied;
162 	file->f_version = m->version;
163 	up(&m->sem);
164 	return copied;
165 Enomem:
166 	err = -ENOMEM;
167 	goto Done;
168 Efault:
169 	err = -EFAULT;
170 	goto Done;
171 }
172 EXPORT_SYMBOL(seq_read);
173 
174 static int traverse(struct seq_file *m, loff_t offset)
175 {
176 	loff_t pos = 0;
177 	int error = 0;
178 	void *p;
179 
180 	m->version = 0;
181 	m->index = 0;
182 	m->count = m->from = 0;
183 	if (!offset)
184 		return 0;
185 	if (!m->buf) {
186 		m->buf = kmalloc(m->size = PAGE_SIZE, GFP_KERNEL);
187 		if (!m->buf)
188 			return -ENOMEM;
189 	}
190 	p = m->op->start(m, &m->index);
191 	while (p) {
192 		error = PTR_ERR(p);
193 		if (IS_ERR(p))
194 			break;
195 		error = m->op->show(m, p);
196 		if (error)
197 			break;
198 		if (m->count == m->size)
199 			goto Eoverflow;
200 		if (pos + m->count > offset) {
201 			m->from = offset - pos;
202 			m->count -= m->from;
203 			break;
204 		}
205 		pos += m->count;
206 		m->count = 0;
207 		if (pos == offset) {
208 			m->index++;
209 			break;
210 		}
211 		p = m->op->next(m, p, &m->index);
212 	}
213 	m->op->stop(m, p);
214 	return error;
215 
216 Eoverflow:
217 	m->op->stop(m, p);
218 	kfree(m->buf);
219 	m->buf = kmalloc(m->size <<= 1, GFP_KERNEL);
220 	return !m->buf ? -ENOMEM : -EAGAIN;
221 }
222 
223 /**
224  *	seq_lseek -	->llseek() method for sequential files.
225  *	@file: the file in question
226  *	@offset: new position
227  *	@origin: 0 for absolute, 1 for relative position
228  *
229  *	Ready-made ->f_op->llseek()
230  */
231 loff_t seq_lseek(struct file *file, loff_t offset, int origin)
232 {
233 	struct seq_file *m = (struct seq_file *)file->private_data;
234 	long long retval = -EINVAL;
235 
236 	down(&m->sem);
237 	m->version = file->f_version;
238 	switch (origin) {
239 		case 1:
240 			offset += file->f_pos;
241 		case 0:
242 			if (offset < 0)
243 				break;
244 			retval = offset;
245 			if (offset != file->f_pos) {
246 				while ((retval=traverse(m, offset)) == -EAGAIN)
247 					;
248 				if (retval) {
249 					/* with extreme prejudice... */
250 					file->f_pos = 0;
251 					m->version = 0;
252 					m->index = 0;
253 					m->count = 0;
254 				} else {
255 					retval = file->f_pos = offset;
256 				}
257 			}
258 	}
259 	up(&m->sem);
260 	file->f_version = m->version;
261 	return retval;
262 }
263 EXPORT_SYMBOL(seq_lseek);
264 
265 /**
266  *	seq_release -	free the structures associated with sequential file.
267  *	@file: file in question
268  *	@inode: file->f_dentry->d_inode
269  *
270  *	Frees the structures associated with sequential file; can be used
271  *	as ->f_op->release() if you don't have private data to destroy.
272  */
273 int seq_release(struct inode *inode, struct file *file)
274 {
275 	struct seq_file *m = (struct seq_file *)file->private_data;
276 	kfree(m->buf);
277 	kfree(m);
278 	return 0;
279 }
280 EXPORT_SYMBOL(seq_release);
281 
282 /**
283  *	seq_escape -	print string into buffer, escaping some characters
284  *	@m:	target buffer
285  *	@s:	string
286  *	@esc:	set of characters that need escaping
287  *
288  *	Puts string into buffer, replacing each occurrence of character from
289  *	@esc with usual octal escape.  Returns 0 in case of success, -1 - in
290  *	case of overflow.
291  */
292 int seq_escape(struct seq_file *m, const char *s, const char *esc)
293 {
294 	char *end = m->buf + m->size;
295         char *p;
296 	char c;
297 
298         for (p = m->buf + m->count; (c = *s) != '\0' && p < end; s++) {
299 		if (!strchr(esc, c)) {
300 			*p++ = c;
301 			continue;
302 		}
303 		if (p + 3 < end) {
304 			*p++ = '\\';
305 			*p++ = '0' + ((c & 0300) >> 6);
306 			*p++ = '0' + ((c & 070) >> 3);
307 			*p++ = '0' + (c & 07);
308 			continue;
309 		}
310 		m->count = m->size;
311 		return -1;
312         }
313 	m->count = p - m->buf;
314         return 0;
315 }
316 EXPORT_SYMBOL(seq_escape);
317 
318 int seq_printf(struct seq_file *m, const char *f, ...)
319 {
320 	va_list args;
321 	int len;
322 
323 	if (m->count < m->size) {
324 		va_start(args, f);
325 		len = vsnprintf(m->buf + m->count, m->size - m->count, f, args);
326 		va_end(args);
327 		if (m->count + len < m->size) {
328 			m->count += len;
329 			return 0;
330 		}
331 	}
332 	m->count = m->size;
333 	return -1;
334 }
335 EXPORT_SYMBOL(seq_printf);
336 
337 int seq_path(struct seq_file *m,
338 	     struct vfsmount *mnt, struct dentry *dentry,
339 	     char *esc)
340 {
341 	if (m->count < m->size) {
342 		char *s = m->buf + m->count;
343 		char *p = d_path(dentry, mnt, s, m->size - m->count);
344 		if (!IS_ERR(p)) {
345 			while (s <= p) {
346 				char c = *p++;
347 				if (!c) {
348 					p = m->buf + m->count;
349 					m->count = s - m->buf;
350 					return s - p;
351 				} else if (!strchr(esc, c)) {
352 					*s++ = c;
353 				} else if (s + 4 > p) {
354 					break;
355 				} else {
356 					*s++ = '\\';
357 					*s++ = '0' + ((c & 0300) >> 6);
358 					*s++ = '0' + ((c & 070) >> 3);
359 					*s++ = '0' + (c & 07);
360 				}
361 			}
362 		}
363 	}
364 	m->count = m->size;
365 	return -1;
366 }
367 EXPORT_SYMBOL(seq_path);
368 
369 static void *single_start(struct seq_file *p, loff_t *pos)
370 {
371 	return NULL + (*pos == 0);
372 }
373 
374 static void *single_next(struct seq_file *p, void *v, loff_t *pos)
375 {
376 	++*pos;
377 	return NULL;
378 }
379 
380 static void single_stop(struct seq_file *p, void *v)
381 {
382 }
383 
384 int single_open(struct file *file, int (*show)(struct seq_file *, void *),
385 		void *data)
386 {
387 	struct seq_operations *op = kmalloc(sizeof(*op), GFP_KERNEL);
388 	int res = -ENOMEM;
389 
390 	if (op) {
391 		op->start = single_start;
392 		op->next = single_next;
393 		op->stop = single_stop;
394 		op->show = show;
395 		res = seq_open(file, op);
396 		if (!res)
397 			((struct seq_file *)file->private_data)->private = data;
398 		else
399 			kfree(op);
400 	}
401 	return res;
402 }
403 EXPORT_SYMBOL(single_open);
404 
405 int single_release(struct inode *inode, struct file *file)
406 {
407 	struct seq_operations *op = ((struct seq_file *)file->private_data)->op;
408 	int res = seq_release(inode, file);
409 	kfree(op);
410 	return res;
411 }
412 EXPORT_SYMBOL(single_release);
413 
414 int seq_release_private(struct inode *inode, struct file *file)
415 {
416 	struct seq_file *seq = file->private_data;
417 
418 	kfree(seq->private);
419 	seq->private = NULL;
420 	return seq_release(inode, file);
421 }
422 EXPORT_SYMBOL(seq_release_private);
423 
424 int seq_putc(struct seq_file *m, char c)
425 {
426 	if (m->count < m->size) {
427 		m->buf[m->count++] = c;
428 		return 0;
429 	}
430 	return -1;
431 }
432 EXPORT_SYMBOL(seq_putc);
433 
434 int seq_puts(struct seq_file *m, const char *s)
435 {
436 	int len = strlen(s);
437 	if (m->count + len < m->size) {
438 		memcpy(m->buf + m->count, s, len);
439 		m->count += len;
440 		return 0;
441 	}
442 	m->count = m->size;
443 	return -1;
444 }
445 EXPORT_SYMBOL(seq_puts);
446