1/*
2 * lib/dynamic_debug.c
3 *
4 * make pr_debug()/dev_dbg() calls runtime configurable based upon their
5 * source module.
6 *
7 * Copyright (C) 2008 Jason Baron <jbaron@redhat.com>
8 * By Greg Banks <gnb@melbourne.sgi.com>
9 * Copyright (c) 2008 Silicon Graphics Inc.  All Rights Reserved.
10 */
11
12#include <linux/kernel.h>
13#include <linux/module.h>
14#include <linux/moduleparam.h>
15#include <linux/kallsyms.h>
16#include <linux/version.h>
17#include <linux/types.h>
18#include <linux/mutex.h>
19#include <linux/proc_fs.h>
20#include <linux/seq_file.h>
21#include <linux/list.h>
22#include <linux/sysctl.h>
23#include <linux/ctype.h>
24#include <linux/string.h>
25#include <linux/uaccess.h>
26#include <linux/dynamic_debug.h>
27#include <linux/debugfs.h>
28#include <linux/slab.h>
29
30extern struct _ddebug __start___verbose[];
31extern struct _ddebug __stop___verbose[];
32
33/* dynamic_debug_enabled, and dynamic_debug_enabled2 are bitmasks in which
34 * bit n is set to 1 if any modname hashes into the bucket n, 0 otherwise. They
35 * use independent hash functions, to reduce the chance of false positives.
36 */
37long long dynamic_debug_enabled;
38EXPORT_SYMBOL_GPL(dynamic_debug_enabled);
39long long dynamic_debug_enabled2;
40EXPORT_SYMBOL_GPL(dynamic_debug_enabled2);
41
42struct ddebug_table {
43	struct list_head link;
44	char *mod_name;
45	unsigned int num_ddebugs;
46	unsigned int num_enabled;
47	struct _ddebug *ddebugs;
48};
49
50struct ddebug_query {
51	const char *filename;
52	const char *module;
53	const char *function;
54	const char *format;
55	unsigned int first_lineno, last_lineno;
56};
57
58struct ddebug_iter {
59	struct ddebug_table *table;
60	unsigned int idx;
61};
62
63static DEFINE_MUTEX(ddebug_lock);
64static LIST_HEAD(ddebug_tables);
65static int verbose = 0;
66
67/* Return the last part of a pathname */
68static inline const char *basename(const char *path)
69{
70	const char *tail = strrchr(path, '/');
71	return tail ? tail+1 : path;
72}
73
74/* format a string into buf[] which describes the _ddebug's flags */
75static char *ddebug_describe_flags(struct _ddebug *dp, char *buf,
76				    size_t maxlen)
77{
78	char *p = buf;
79
80	BUG_ON(maxlen < 4);
81	if (dp->flags & _DPRINTK_FLAGS_PRINT)
82		*p++ = 'p';
83	if (p == buf)
84		*p++ = '-';
85	*p = '\0';
86
87	return buf;
88}
89
90/*
91 * must be called with ddebug_lock held
92 */
93
94static int disabled_hash(char hash, bool first_table)
95{
96	struct ddebug_table *dt;
97	char table_hash_value;
98
99	list_for_each_entry(dt, &ddebug_tables, link) {
100		if (first_table)
101			table_hash_value = dt->ddebugs->primary_hash;
102		else
103			table_hash_value = dt->ddebugs->secondary_hash;
104		if (dt->num_enabled && (hash == table_hash_value))
105			return 0;
106	}
107	return 1;
108}
109
110/*
111 * Search the tables for _ddebug's which match the given
112 * `query' and apply the `flags' and `mask' to them.  Tells
113 * the user which ddebug's were changed, or whether none
114 * were matched.
115 */
116static void ddebug_change(const struct ddebug_query *query,
117			   unsigned int flags, unsigned int mask)
118{
119	int i;
120	struct ddebug_table *dt;
121	unsigned int newflags;
122	unsigned int nfound = 0;
123	char flagbuf[8];
124
125	/* search for matching ddebugs */
126	mutex_lock(&ddebug_lock);
127	list_for_each_entry(dt, &ddebug_tables, link) {
128
129		/* match against the module name */
130		if (query->module != NULL &&
131		    strcmp(query->module, dt->mod_name))
132			continue;
133
134		for (i = 0 ; i < dt->num_ddebugs ; i++) {
135			struct _ddebug *dp = &dt->ddebugs[i];
136
137			/* match against the source filename */
138			if (query->filename != NULL &&
139			    strcmp(query->filename, dp->filename) &&
140			    strcmp(query->filename, basename(dp->filename)))
141				continue;
142
143			/* match against the function */
144			if (query->function != NULL &&
145			    strcmp(query->function, dp->function))
146				continue;
147
148			/* match against the format */
149			if (query->format != NULL &&
150			    strstr(dp->format, query->format) == NULL)
151				continue;
152
153			/* match against the line number range */
154			if (query->first_lineno &&
155			    dp->lineno < query->first_lineno)
156				continue;
157			if (query->last_lineno &&
158			    dp->lineno > query->last_lineno)
159				continue;
160
161			nfound++;
162
163			newflags = (dp->flags & mask) | flags;
164			if (newflags == dp->flags)
165				continue;
166
167			if (!newflags)
168				dt->num_enabled--;
169			else if (!dp->flags)
170				dt->num_enabled++;
171			dp->flags = newflags;
172			if (newflags) {
173				dynamic_debug_enabled |=
174						(1LL << dp->primary_hash);
175				dynamic_debug_enabled2 |=
176						(1LL << dp->secondary_hash);
177			} else {
178				if (disabled_hash(dp->primary_hash, true))
179					dynamic_debug_enabled &=
180						~(1LL << dp->primary_hash);
181				if (disabled_hash(dp->secondary_hash, false))
182					dynamic_debug_enabled2 &=
183						~(1LL << dp->secondary_hash);
184			}
185			if (verbose)
186				printk(KERN_INFO
187					"ddebug: changed %s:%d [%s]%s %s\n",
188					dp->filename, dp->lineno,
189					dt->mod_name, dp->function,
190					ddebug_describe_flags(dp, flagbuf,
191							sizeof(flagbuf)));
192		}
193	}
194	mutex_unlock(&ddebug_lock);
195
196	if (!nfound && verbose)
197		printk(KERN_INFO "ddebug: no matches for query\n");
198}
199
200/*
201 * Split the buffer `buf' into space-separated words.
202 * Handles simple " and ' quoting, i.e. without nested,
203 * embedded or escaped \".  Return the number of words
204 * or <0 on error.
205 */
206static int ddebug_tokenize(char *buf, char *words[], int maxwords)
207{
208	int nwords = 0;
209
210	while (*buf) {
211		char *end;
212
213		/* Skip leading whitespace */
214		buf = skip_spaces(buf);
215		if (!*buf)
216			break;	/* oh, it was trailing whitespace */
217
218		/* Run `end' over a word, either whitespace separated or quoted */
219		if (*buf == '"' || *buf == '\'') {
220			int quote = *buf++;
221			for (end = buf ; *end && *end != quote ; end++)
222				;
223			if (!*end)
224				return -EINVAL;	/* unclosed quote */
225		} else {
226			for (end = buf ; *end && !isspace(*end) ; end++)
227				;
228			BUG_ON(end == buf);
229		}
230		/* Here `buf' is the start of the word, `end' is one past the end */
231
232		if (nwords == maxwords)
233			return -EINVAL;	/* ran out of words[] before bytes */
234		if (*end)
235			*end++ = '\0';	/* terminate the word */
236		words[nwords++] = buf;
237		buf = end;
238	}
239
240	if (verbose) {
241		int i;
242		printk(KERN_INFO "%s: split into words:", __func__);
243		for (i = 0 ; i < nwords ; i++)
244			printk(" \"%s\"", words[i]);
245		printk("\n");
246	}
247
248	return nwords;
249}
250
251/*
252 * Parse a single line number.  Note that the empty string ""
253 * is treated as a special case and converted to zero, which
254 * is later treated as a "don't care" value.
255 */
256static inline int parse_lineno(const char *str, unsigned int *val)
257{
258	char *end = NULL;
259	BUG_ON(str == NULL);
260	if (*str == '\0') {
261		*val = 0;
262		return 0;
263	}
264	*val = simple_strtoul(str, &end, 10);
265	return end == NULL || end == str || *end != '\0' ? -EINVAL : 0;
266}
267
268/*
269 * Undo octal escaping in a string, inplace.  This is useful to
270 * allow the user to express a query which matches a format
271 * containing embedded spaces.
272 */
273#define isodigit(c)		((c) >= '0' && (c) <= '7')
274static char *unescape(char *str)
275{
276	char *in = str;
277	char *out = str;
278
279	while (*in) {
280		if (*in == '\\') {
281			if (in[1] == '\\') {
282				*out++ = '\\';
283				in += 2;
284				continue;
285			} else if (in[1] == 't') {
286				*out++ = '\t';
287				in += 2;
288				continue;
289			} else if (in[1] == 'n') {
290				*out++ = '\n';
291				in += 2;
292				continue;
293			} else if (isodigit(in[1]) &&
294			         isodigit(in[2]) &&
295			         isodigit(in[3])) {
296				*out++ = ((in[1] - '0')<<6) |
297				          ((in[2] - '0')<<3) |
298				          (in[3] - '0');
299				in += 4;
300				continue;
301			}
302		}
303		*out++ = *in++;
304	}
305	*out = '\0';
306
307	return str;
308}
309
310/*
311 * Parse words[] as a ddebug query specification, which is a series
312 * of (keyword, value) pairs chosen from these possibilities:
313 *
314 * func <function-name>
315 * file <full-pathname>
316 * file <base-filename>
317 * module <module-name>
318 * format <escaped-string-to-find-in-format>
319 * line <lineno>
320 * line <first-lineno>-<last-lineno> // where either may be empty
321 */
322static int ddebug_parse_query(char *words[], int nwords,
323			       struct ddebug_query *query)
324{
325	unsigned int i;
326
327	/* check we have an even number of words */
328	if (nwords % 2 != 0)
329		return -EINVAL;
330	memset(query, 0, sizeof(*query));
331
332	for (i = 0 ; i < nwords ; i += 2) {
333		if (!strcmp(words[i], "func"))
334			query->function = words[i+1];
335		else if (!strcmp(words[i], "file"))
336			query->filename = words[i+1];
337		else if (!strcmp(words[i], "module"))
338			query->module = words[i+1];
339		else if (!strcmp(words[i], "format"))
340			query->format = unescape(words[i+1]);
341		else if (!strcmp(words[i], "line")) {
342			char *first = words[i+1];
343			char *last = strchr(first, '-');
344			if (last)
345				*last++ = '\0';
346			if (parse_lineno(first, &query->first_lineno) < 0)
347				return -EINVAL;
348			if (last != NULL) {
349				/* range <first>-<last> */
350				if (parse_lineno(last, &query->last_lineno) < 0)
351					return -EINVAL;
352			} else {
353				query->last_lineno = query->first_lineno;
354			}
355		} else {
356			if (verbose)
357				printk(KERN_ERR "%s: unknown keyword \"%s\"\n",
358					__func__, words[i]);
359			return -EINVAL;
360		}
361	}
362
363	if (verbose)
364		printk(KERN_INFO "%s: q->function=\"%s\" q->filename=\"%s\" "
365		       "q->module=\"%s\" q->format=\"%s\" q->lineno=%u-%u\n",
366			__func__, query->function, query->filename,
367			query->module, query->format, query->first_lineno,
368			query->last_lineno);
369
370	return 0;
371}
372
373/*
374 * Parse `str' as a flags specification, format [-+=][p]+.
375 * Sets up *maskp and *flagsp to be used when changing the
376 * flags fields of matched _ddebug's.  Returns 0 on success
377 * or <0 on error.
378 */
379static int ddebug_parse_flags(const char *str, unsigned int *flagsp,
380			       unsigned int *maskp)
381{
382	unsigned flags = 0;
383	int op = '=';
384
385	switch (*str) {
386	case '+':
387	case '-':
388	case '=':
389		op = *str++;
390		break;
391	default:
392		return -EINVAL;
393	}
394	if (verbose)
395		printk(KERN_INFO "%s: op='%c'\n", __func__, op);
396
397	for ( ; *str ; ++str) {
398		switch (*str) {
399		case 'p':
400			flags |= _DPRINTK_FLAGS_PRINT;
401			break;
402		default:
403			return -EINVAL;
404		}
405	}
406	if (flags == 0)
407		return -EINVAL;
408	if (verbose)
409		printk(KERN_INFO "%s: flags=0x%x\n", __func__, flags);
410
411	/* calculate final *flagsp, *maskp according to mask and op */
412	switch (op) {
413	case '=':
414		*maskp = 0;
415		*flagsp = flags;
416		break;
417	case '+':
418		*maskp = ~0U;
419		*flagsp = flags;
420		break;
421	case '-':
422		*maskp = ~flags;
423		*flagsp = 0;
424		break;
425	}
426	if (verbose)
427		printk(KERN_INFO "%s: *flagsp=0x%x *maskp=0x%x\n",
428			__func__, *flagsp, *maskp);
429	return 0;
430}
431
432/*
433 * File_ops->write method for <debugfs>/dynamic_debug/conrol.  Gathers the
434 * command text from userspace, parses and executes it.
435 */
436static ssize_t ddebug_proc_write(struct file *file, const char __user *ubuf,
437				  size_t len, loff_t *offp)
438{
439	unsigned int flags = 0, mask = 0;
440	struct ddebug_query query;
441#define MAXWORDS 9
442	int nwords;
443	char *words[MAXWORDS];
444	char tmpbuf[256];
445
446	if (len == 0)
447		return 0;
448	/* we don't check *offp -- multiple writes() are allowed */
449	if (len > sizeof(tmpbuf)-1)
450		return -E2BIG;
451	if (copy_from_user(tmpbuf, ubuf, len))
452		return -EFAULT;
453	tmpbuf[len] = '\0';
454	if (verbose)
455		printk(KERN_INFO "%s: read %d bytes from userspace\n",
456			__func__, (int)len);
457
458	nwords = ddebug_tokenize(tmpbuf, words, MAXWORDS);
459	if (nwords <= 0)
460		return -EINVAL;
461	if (ddebug_parse_query(words, nwords-1, &query))
462		return -EINVAL;
463	if (ddebug_parse_flags(words[nwords-1], &flags, &mask))
464		return -EINVAL;
465
466	/* actually go and implement the change */
467	ddebug_change(&query, flags, mask);
468
469	*offp += len;
470	return len;
471}
472
473/*
474 * Set the iterator to point to the first _ddebug object
475 * and return a pointer to that first object.  Returns
476 * NULL if there are no _ddebugs at all.
477 */
478static struct _ddebug *ddebug_iter_first(struct ddebug_iter *iter)
479{
480	if (list_empty(&ddebug_tables)) {
481		iter->table = NULL;
482		iter->idx = 0;
483		return NULL;
484	}
485	iter->table = list_entry(ddebug_tables.next,
486				 struct ddebug_table, link);
487	iter->idx = 0;
488	return &iter->table->ddebugs[iter->idx];
489}
490
491/*
492 * Advance the iterator to point to the next _ddebug
493 * object from the one the iterator currently points at,
494 * and returns a pointer to the new _ddebug.  Returns
495 * NULL if the iterator has seen all the _ddebugs.
496 */
497static struct _ddebug *ddebug_iter_next(struct ddebug_iter *iter)
498{
499	if (iter->table == NULL)
500		return NULL;
501	if (++iter->idx == iter->table->num_ddebugs) {
502		/* iterate to next table */
503		iter->idx = 0;
504		if (list_is_last(&iter->table->link, &ddebug_tables)) {
505			iter->table = NULL;
506			return NULL;
507		}
508		iter->table = list_entry(iter->table->link.next,
509					 struct ddebug_table, link);
510	}
511	return &iter->table->ddebugs[iter->idx];
512}
513
514/*
515 * Seq_ops start method.  Called at the start of every
516 * read() call from userspace.  Takes the ddebug_lock and
517 * seeks the seq_file's iterator to the given position.
518 */
519static void *ddebug_proc_start(struct seq_file *m, loff_t *pos)
520{
521	struct ddebug_iter *iter = m->private;
522	struct _ddebug *dp;
523	int n = *pos;
524
525	if (verbose)
526		printk(KERN_INFO "%s: called m=%p *pos=%lld\n",
527			__func__, m, (unsigned long long)*pos);
528
529	mutex_lock(&ddebug_lock);
530
531	if (!n)
532		return SEQ_START_TOKEN;
533	if (n < 0)
534		return NULL;
535	dp = ddebug_iter_first(iter);
536	while (dp != NULL && --n > 0)
537		dp = ddebug_iter_next(iter);
538	return dp;
539}
540
541/*
542 * Seq_ops next method.  Called several times within a read()
543 * call from userspace, with ddebug_lock held.  Walks to the
544 * next _ddebug object with a special case for the header line.
545 */
546static void *ddebug_proc_next(struct seq_file *m, void *p, loff_t *pos)
547{
548	struct ddebug_iter *iter = m->private;
549	struct _ddebug *dp;
550
551	if (verbose)
552		printk(KERN_INFO "%s: called m=%p p=%p *pos=%lld\n",
553			__func__, m, p, (unsigned long long)*pos);
554
555	if (p == SEQ_START_TOKEN)
556		dp = ddebug_iter_first(iter);
557	else
558		dp = ddebug_iter_next(iter);
559	++*pos;
560	return dp;
561}
562
563/*
564 * Seq_ops show method.  Called several times within a read()
565 * call from userspace, with ddebug_lock held.  Formats the
566 * current _ddebug as a single human-readable line, with a
567 * special case for the header line.
568 */
569static int ddebug_proc_show(struct seq_file *m, void *p)
570{
571	struct ddebug_iter *iter = m->private;
572	struct _ddebug *dp = p;
573	char flagsbuf[8];
574
575	if (verbose)
576		printk(KERN_INFO "%s: called m=%p p=%p\n",
577			__func__, m, p);
578
579	if (p == SEQ_START_TOKEN) {
580		seq_puts(m,
581			"# filename:lineno [module]function flags format\n");
582		return 0;
583	}
584
585	seq_printf(m, "%s:%u [%s]%s %s \"",
586		   dp->filename, dp->lineno,
587		   iter->table->mod_name, dp->function,
588		   ddebug_describe_flags(dp, flagsbuf, sizeof(flagsbuf)));
589	seq_escape(m, dp->format, "\t\r\n\"");
590	seq_puts(m, "\"\n");
591
592	return 0;
593}
594
595/*
596 * Seq_ops stop method.  Called at the end of each read()
597 * call from userspace.  Drops ddebug_lock.
598 */
599static void ddebug_proc_stop(struct seq_file *m, void *p)
600{
601	if (verbose)
602		printk(KERN_INFO "%s: called m=%p p=%p\n",
603			__func__, m, p);
604	mutex_unlock(&ddebug_lock);
605}
606
607static const struct seq_operations ddebug_proc_seqops = {
608	.start = ddebug_proc_start,
609	.next = ddebug_proc_next,
610	.show = ddebug_proc_show,
611	.stop = ddebug_proc_stop
612};
613
614/*
615 * File_ops->open method for <debugfs>/dynamic_debug/control.  Does the seq_file
616 * setup dance, and also creates an iterator to walk the _ddebugs.
617 * Note that we create a seq_file always, even for O_WRONLY files
618 * where it's not needed, as doing so simplifies the ->release method.
619 */
620static int ddebug_proc_open(struct inode *inode, struct file *file)
621{
622	struct ddebug_iter *iter;
623	int err;
624
625	if (verbose)
626		printk(KERN_INFO "%s: called\n", __func__);
627
628	iter = kzalloc(sizeof(*iter), GFP_KERNEL);
629	if (iter == NULL)
630		return -ENOMEM;
631
632	err = seq_open(file, &ddebug_proc_seqops);
633	if (err) {
634		kfree(iter);
635		return err;
636	}
637	((struct seq_file *) file->private_data)->private = iter;
638	return 0;
639}
640
641static const struct file_operations ddebug_proc_fops = {
642	.owner = THIS_MODULE,
643	.open = ddebug_proc_open,
644	.read = seq_read,
645	.llseek = seq_lseek,
646	.release = seq_release_private,
647	.write = ddebug_proc_write
648};
649
650/*
651 * Allocate a new ddebug_table for the given module
652 * and add it to the global list.
653 */
654int ddebug_add_module(struct _ddebug *tab, unsigned int n,
655			     const char *name)
656{
657	struct ddebug_table *dt;
658	char *new_name;
659
660	dt = kzalloc(sizeof(*dt), GFP_KERNEL);
661	if (dt == NULL)
662		return -ENOMEM;
663	new_name = kstrdup(name, GFP_KERNEL);
664	if (new_name == NULL) {
665		kfree(dt);
666		return -ENOMEM;
667	}
668	dt->mod_name = new_name;
669	dt->num_ddebugs = n;
670	dt->num_enabled = 0;
671	dt->ddebugs = tab;
672
673	mutex_lock(&ddebug_lock);
674	list_add_tail(&dt->link, &ddebug_tables);
675	mutex_unlock(&ddebug_lock);
676
677	if (verbose)
678		printk(KERN_INFO "%u debug prints in module %s\n",
679				 n, dt->mod_name);
680	return 0;
681}
682EXPORT_SYMBOL_GPL(ddebug_add_module);
683
684static void ddebug_table_free(struct ddebug_table *dt)
685{
686	list_del_init(&dt->link);
687	kfree(dt->mod_name);
688	kfree(dt);
689}
690
691/*
692 * Called in response to a module being unloaded.  Removes
693 * any ddebug_table's which point at the module.
694 */
695int ddebug_remove_module(const char *mod_name)
696{
697	struct ddebug_table *dt, *nextdt;
698	int ret = -ENOENT;
699
700	if (verbose)
701		printk(KERN_INFO "%s: removing module \"%s\"\n",
702				__func__, mod_name);
703
704	mutex_lock(&ddebug_lock);
705	list_for_each_entry_safe(dt, nextdt, &ddebug_tables, link) {
706		if (!strcmp(dt->mod_name, mod_name)) {
707			ddebug_table_free(dt);
708			ret = 0;
709		}
710	}
711	mutex_unlock(&ddebug_lock);
712	return ret;
713}
714EXPORT_SYMBOL_GPL(ddebug_remove_module);
715
716static void ddebug_remove_all_tables(void)
717{
718	mutex_lock(&ddebug_lock);
719	while (!list_empty(&ddebug_tables)) {
720		struct ddebug_table *dt = list_entry(ddebug_tables.next,
721						      struct ddebug_table,
722						      link);
723		ddebug_table_free(dt);
724	}
725	mutex_unlock(&ddebug_lock);
726}
727
728static int __init dynamic_debug_init(void)
729{
730	struct dentry *dir, *file;
731	struct _ddebug *iter, *iter_start;
732	const char *modname = NULL;
733	int ret = 0;
734	int n = 0;
735
736	dir = debugfs_create_dir("dynamic_debug", NULL);
737	if (!dir)
738		return -ENOMEM;
739	file = debugfs_create_file("control", 0644, dir, NULL,
740					&ddebug_proc_fops);
741	if (!file) {
742		debugfs_remove(dir);
743		return -ENOMEM;
744	}
745	if (__start___verbose != __stop___verbose) {
746		iter = __start___verbose;
747		modname = iter->modname;
748		iter_start = iter;
749		for (; iter < __stop___verbose; iter++) {
750			if (strcmp(modname, iter->modname)) {
751				ret = ddebug_add_module(iter_start, n, modname);
752				if (ret)
753					goto out_free;
754				n = 0;
755				modname = iter->modname;
756				iter_start = iter;
757			}
758			n++;
759		}
760		ret = ddebug_add_module(iter_start, n, modname);
761	}
762out_free:
763	if (ret) {
764		ddebug_remove_all_tables();
765		debugfs_remove(dir);
766		debugfs_remove(file);
767	}
768	return 0;
769}
770module_init(dynamic_debug_init);
771