Root/lib/dynamic_debug.c

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

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