Root/kernel/kallsyms.c

1/*
2 * kallsyms.c: in-kernel printing of symbolic oopses and stack traces.
3 *
4 * Rewritten and vastly simplified by Rusty Russell for in-kernel
5 * module loader:
6 * Copyright 2002 Rusty Russell <rusty@rustcorp.com.au> IBM Corporation
7 *
8 * ChangeLog:
9 *
10 * (25/Aug/2004) Paulo Marques <pmarques@grupopie.com>
11 * Changed the compression method from stem compression to "table lookup"
12 * compression (see scripts/kallsyms.c for a more complete description)
13 */
14#include <linux/kallsyms.h>
15#include <linux/module.h>
16#include <linux/init.h>
17#include <linux/seq_file.h>
18#include <linux/fs.h>
19#include <linux/kdb.h>
20#include <linux/err.h>
21#include <linux/proc_fs.h>
22#include <linux/sched.h> /* for cond_resched */
23#include <linux/mm.h>
24#include <linux/ctype.h>
25#include <linux/slab.h>
26#include <linux/compiler.h>
27
28#include <asm/sections.h>
29
30#ifdef CONFIG_KALLSYMS_ALL
31#define all_var 1
32#else
33#define all_var 0
34#endif
35
36/*
37 * These will be re-linked against their real values
38 * during the second link stage.
39 */
40extern const unsigned long kallsyms_addresses[] __weak;
41extern const u8 kallsyms_names[] __weak;
42
43/*
44 * Tell the compiler that the count isn't in the small data section if the arch
45 * has one (eg: FRV).
46 */
47extern const unsigned long kallsyms_num_syms
48__attribute__((weak, section(".rodata")));
49
50extern const u8 kallsyms_token_table[] __weak;
51extern const u16 kallsyms_token_index[] __weak;
52
53extern const unsigned long kallsyms_markers[] __weak;
54
55static inline int is_kernel_inittext(unsigned long addr)
56{
57    if (addr >= (unsigned long)_sinittext
58        && addr <= (unsigned long)_einittext)
59        return 1;
60    return 0;
61}
62
63static inline int is_kernel_text(unsigned long addr)
64{
65    if ((addr >= (unsigned long)_stext && addr <= (unsigned long)_etext) ||
66        arch_is_kernel_text(addr))
67        return 1;
68    return in_gate_area_no_mm(addr);
69}
70
71static inline int is_kernel(unsigned long addr)
72{
73    if (addr >= (unsigned long)_stext && addr <= (unsigned long)_end)
74        return 1;
75    return in_gate_area_no_mm(addr);
76}
77
78static int is_ksym_addr(unsigned long addr)
79{
80    if (all_var)
81        return is_kernel(addr);
82
83    return is_kernel_text(addr) || is_kernel_inittext(addr);
84}
85
86/*
87 * Expand a compressed symbol data into the resulting uncompressed string,
88 * if uncompressed string is too long (>= maxlen), it will be truncated,
89 * given the offset to where the symbol is in the compressed stream.
90 */
91static unsigned int kallsyms_expand_symbol(unsigned int off,
92                       char *result, size_t maxlen)
93{
94    int len, skipped_first = 0;
95    const u8 *tptr, *data;
96
97    /* Get the compressed symbol length from the first symbol byte. */
98    data = &kallsyms_names[off];
99    len = *data;
100    data++;
101
102    /*
103     * Update the offset to return the offset for the next symbol on
104     * the compressed stream.
105     */
106    off += len + 1;
107
108    /*
109     * For every byte on the compressed symbol data, copy the table
110     * entry for that byte.
111     */
112    while (len) {
113        tptr = &kallsyms_token_table[kallsyms_token_index[*data]];
114        data++;
115        len--;
116
117        while (*tptr) {
118            if (skipped_first) {
119                if (maxlen <= 1)
120                    goto tail;
121                *result = *tptr;
122                result++;
123                maxlen--;
124            } else
125                skipped_first = 1;
126            tptr++;
127        }
128    }
129
130tail:
131    if (maxlen)
132        *result = '\0';
133
134    /* Return to offset to the next symbol. */
135    return off;
136}
137
138/*
139 * Get symbol type information. This is encoded as a single char at the
140 * beginning of the symbol name.
141 */
142static char kallsyms_get_symbol_type(unsigned int off)
143{
144    /*
145     * Get just the first code, look it up in the token table,
146     * and return the first char from this token.
147     */
148    return kallsyms_token_table[kallsyms_token_index[kallsyms_names[off + 1]]];
149}
150
151
152/*
153 * Find the offset on the compressed stream given and index in the
154 * kallsyms array.
155 */
156static unsigned int get_symbol_offset(unsigned long pos)
157{
158    const u8 *name;
159    int i;
160
161    /*
162     * Use the closest marker we have. We have markers every 256 positions,
163     * so that should be close enough.
164     */
165    name = &kallsyms_names[kallsyms_markers[pos >> 8]];
166
167    /*
168     * Sequentially scan all the symbols up to the point we're searching
169     * for. Every symbol is stored in a [<len>][<len> bytes of data] format,
170     * so we just need to add the len to the current pointer for every
171     * symbol we wish to skip.
172     */
173    for (i = 0; i < (pos & 0xFF); i++)
174        name = name + (*name) + 1;
175
176    return name - kallsyms_names;
177}
178
179/* Lookup the address for this symbol. Returns 0 if not found. */
180unsigned long kallsyms_lookup_name(const char *name)
181{
182    char namebuf[KSYM_NAME_LEN];
183    unsigned long i;
184    unsigned int off;
185
186    for (i = 0, off = 0; i < kallsyms_num_syms; i++) {
187        off = kallsyms_expand_symbol(off, namebuf, ARRAY_SIZE(namebuf));
188
189        if (strcmp(namebuf, name) == 0)
190            return kallsyms_addresses[i];
191    }
192    return module_kallsyms_lookup_name(name);
193}
194EXPORT_SYMBOL_GPL(kallsyms_lookup_name);
195
196int kallsyms_on_each_symbol(int (*fn)(void *, const char *, struct module *,
197                      unsigned long),
198                void *data)
199{
200    char namebuf[KSYM_NAME_LEN];
201    unsigned long i;
202    unsigned int off;
203    int ret;
204
205    for (i = 0, off = 0; i < kallsyms_num_syms; i++) {
206        off = kallsyms_expand_symbol(off, namebuf, ARRAY_SIZE(namebuf));
207        ret = fn(data, namebuf, NULL, kallsyms_addresses[i]);
208        if (ret != 0)
209            return ret;
210    }
211    return module_kallsyms_on_each_symbol(fn, data);
212}
213EXPORT_SYMBOL_GPL(kallsyms_on_each_symbol);
214
215static unsigned long get_symbol_pos(unsigned long addr,
216                    unsigned long *symbolsize,
217                    unsigned long *offset)
218{
219    unsigned long symbol_start = 0, symbol_end = 0;
220    unsigned long i, low, high, mid;
221
222    /* This kernel should never had been booted. */
223    BUG_ON(!kallsyms_addresses);
224
225    /* Do a binary search on the sorted kallsyms_addresses array. */
226    low = 0;
227    high = kallsyms_num_syms;
228
229    while (high - low > 1) {
230        mid = low + (high - low) / 2;
231        if (kallsyms_addresses[mid] <= addr)
232            low = mid;
233        else
234            high = mid;
235    }
236
237    /*
238     * Search for the first aliased symbol. Aliased
239     * symbols are symbols with the same address.
240     */
241    while (low && kallsyms_addresses[low-1] == kallsyms_addresses[low])
242        --low;
243
244    symbol_start = kallsyms_addresses[low];
245
246    /* Search for next non-aliased symbol. */
247    for (i = low + 1; i < kallsyms_num_syms; i++) {
248        if (kallsyms_addresses[i] > symbol_start) {
249            symbol_end = kallsyms_addresses[i];
250            break;
251        }
252    }
253
254    /* If we found no next symbol, we use the end of the section. */
255    if (!symbol_end) {
256        if (is_kernel_inittext(addr))
257            symbol_end = (unsigned long)_einittext;
258        else if (all_var)
259            symbol_end = (unsigned long)_end;
260        else
261            symbol_end = (unsigned long)_etext;
262    }
263
264    if (symbolsize)
265        *symbolsize = symbol_end - symbol_start;
266    if (offset)
267        *offset = addr - symbol_start;
268
269    return low;
270}
271
272/*
273 * Lookup an address but don't bother to find any names.
274 */
275int kallsyms_lookup_size_offset(unsigned long addr, unsigned long *symbolsize,
276                unsigned long *offset)
277{
278    char namebuf[KSYM_NAME_LEN];
279    if (is_ksym_addr(addr))
280        return !!get_symbol_pos(addr, symbolsize, offset);
281
282    return !!module_address_lookup(addr, symbolsize, offset, NULL, namebuf);
283}
284
285/*
286 * Lookup an address
287 * - modname is set to NULL if it's in the kernel.
288 * - We guarantee that the returned name is valid until we reschedule even if.
289 * It resides in a module.
290 * - We also guarantee that modname will be valid until rescheduled.
291 */
292const char *kallsyms_lookup(unsigned long addr,
293                unsigned long *symbolsize,
294                unsigned long *offset,
295                char **modname, char *namebuf)
296{
297    namebuf[KSYM_NAME_LEN - 1] = 0;
298    namebuf[0] = 0;
299
300    if (is_ksym_addr(addr)) {
301        unsigned long pos;
302
303        pos = get_symbol_pos(addr, symbolsize, offset);
304        /* Grab name */
305        kallsyms_expand_symbol(get_symbol_offset(pos),
306                       namebuf, KSYM_NAME_LEN);
307        if (modname)
308            *modname = NULL;
309        return namebuf;
310    }
311
312    /* See if it's in a module. */
313    return module_address_lookup(addr, symbolsize, offset, modname,
314                     namebuf);
315}
316
317int lookup_symbol_name(unsigned long addr, char *symname)
318{
319    symname[0] = '\0';
320    symname[KSYM_NAME_LEN - 1] = '\0';
321
322    if (is_ksym_addr(addr)) {
323        unsigned long pos;
324
325        pos = get_symbol_pos(addr, NULL, NULL);
326        /* Grab name */
327        kallsyms_expand_symbol(get_symbol_offset(pos),
328                       symname, KSYM_NAME_LEN);
329        return 0;
330    }
331    /* See if it's in a module. */
332    return lookup_module_symbol_name(addr, symname);
333}
334
335int lookup_symbol_attrs(unsigned long addr, unsigned long *size,
336            unsigned long *offset, char *modname, char *name)
337{
338    name[0] = '\0';
339    name[KSYM_NAME_LEN - 1] = '\0';
340
341    if (is_ksym_addr(addr)) {
342        unsigned long pos;
343
344        pos = get_symbol_pos(addr, size, offset);
345        /* Grab name */
346        kallsyms_expand_symbol(get_symbol_offset(pos),
347                       name, KSYM_NAME_LEN);
348        modname[0] = '\0';
349        return 0;
350    }
351    /* See if it's in a module. */
352    return lookup_module_symbol_attrs(addr, size, offset, modname, name);
353}
354
355/* Look up a kernel symbol and return it in a text buffer. */
356static int __sprint_symbol(char *buffer, unsigned long address,
357               int symbol_offset, int add_offset)
358{
359    char *modname;
360    const char *name;
361    unsigned long offset, size;
362    int len;
363
364    address += symbol_offset;
365    name = kallsyms_lookup(address, &size, &offset, &modname, buffer);
366    if (!name)
367        return sprintf(buffer, "0x%lx", address);
368
369    if (name != buffer)
370        strcpy(buffer, name);
371    len = strlen(buffer);
372    offset -= symbol_offset;
373
374    if (add_offset)
375        len += sprintf(buffer + len, "+%#lx/%#lx", offset, size);
376
377    if (modname)
378        len += sprintf(buffer + len, " [%s]", modname);
379
380    return len;
381}
382
383/**
384 * sprint_symbol - Look up a kernel symbol and return it in a text buffer
385 * @buffer: buffer to be stored
386 * @address: address to lookup
387 *
388 * This function looks up a kernel symbol with @address and stores its name,
389 * offset, size and module name to @buffer if possible. If no symbol was found,
390 * just saves its @address as is.
391 *
392 * This function returns the number of bytes stored in @buffer.
393 */
394int sprint_symbol(char *buffer, unsigned long address)
395{
396    return __sprint_symbol(buffer, address, 0, 1);
397}
398EXPORT_SYMBOL_GPL(sprint_symbol);
399
400/**
401 * sprint_symbol_no_offset - Look up a kernel symbol and return it in a text buffer
402 * @buffer: buffer to be stored
403 * @address: address to lookup
404 *
405 * This function looks up a kernel symbol with @address and stores its name
406 * and module name to @buffer if possible. If no symbol was found, just saves
407 * its @address as is.
408 *
409 * This function returns the number of bytes stored in @buffer.
410 */
411int sprint_symbol_no_offset(char *buffer, unsigned long address)
412{
413    return __sprint_symbol(buffer, address, 0, 0);
414}
415EXPORT_SYMBOL_GPL(sprint_symbol_no_offset);
416
417/**
418 * sprint_backtrace - Look up a backtrace symbol and return it in a text buffer
419 * @buffer: buffer to be stored
420 * @address: address to lookup
421 *
422 * This function is for stack backtrace and does the same thing as
423 * sprint_symbol() but with modified/decreased @address. If there is a
424 * tail-call to the function marked "noreturn", gcc optimized out code after
425 * the call so that the stack-saved return address could point outside of the
426 * caller. This function ensures that kallsyms will find the original caller
427 * by decreasing @address.
428 *
429 * This function returns the number of bytes stored in @buffer.
430 */
431int sprint_backtrace(char *buffer, unsigned long address)
432{
433    return __sprint_symbol(buffer, address, -1, 1);
434}
435
436/* Look up a kernel symbol and print it to the kernel messages. */
437void __print_symbol(const char *fmt, unsigned long address)
438{
439    char buffer[KSYM_SYMBOL_LEN];
440
441    sprint_symbol(buffer, address);
442
443    printk(fmt, buffer);
444}
445EXPORT_SYMBOL(__print_symbol);
446
447/* To avoid using get_symbol_offset for every symbol, we carry prefix along. */
448struct kallsym_iter {
449    loff_t pos;
450    unsigned long value;
451    unsigned int nameoff; /* If iterating in core kernel symbols. */
452    char type;
453    char name[KSYM_NAME_LEN];
454    char module_name[MODULE_NAME_LEN];
455    int exported;
456};
457
458static int get_ksymbol_mod(struct kallsym_iter *iter)
459{
460    if (module_get_kallsym(iter->pos - kallsyms_num_syms, &iter->value,
461                &iter->type, iter->name, iter->module_name,
462                &iter->exported) < 0)
463        return 0;
464    return 1;
465}
466
467/* Returns space to next name. */
468static unsigned long get_ksymbol_core(struct kallsym_iter *iter)
469{
470    unsigned off = iter->nameoff;
471
472    iter->module_name[0] = '\0';
473    iter->value = kallsyms_addresses[iter->pos];
474
475    iter->type = kallsyms_get_symbol_type(off);
476
477    off = kallsyms_expand_symbol(off, iter->name, ARRAY_SIZE(iter->name));
478
479    return off - iter->nameoff;
480}
481
482static void reset_iter(struct kallsym_iter *iter, loff_t new_pos)
483{
484    iter->name[0] = '\0';
485    iter->nameoff = get_symbol_offset(new_pos);
486    iter->pos = new_pos;
487}
488
489/* Returns false if pos at or past end of file. */
490static int update_iter(struct kallsym_iter *iter, loff_t pos)
491{
492    /* Module symbols can be accessed randomly. */
493    if (pos >= kallsyms_num_syms) {
494        iter->pos = pos;
495        return get_ksymbol_mod(iter);
496    }
497
498    /* If we're not on the desired position, reset to new position. */
499    if (pos != iter->pos)
500        reset_iter(iter, pos);
501
502    iter->nameoff += get_ksymbol_core(iter);
503    iter->pos++;
504
505    return 1;
506}
507
508static void *s_next(struct seq_file *m, void *p, loff_t *pos)
509{
510    (*pos)++;
511
512    if (!update_iter(m->private, *pos))
513        return NULL;
514    return p;
515}
516
517static void *s_start(struct seq_file *m, loff_t *pos)
518{
519    if (!update_iter(m->private, *pos))
520        return NULL;
521    return m->private;
522}
523
524static void s_stop(struct seq_file *m, void *p)
525{
526}
527
528static int s_show(struct seq_file *m, void *p)
529{
530    struct kallsym_iter *iter = m->private;
531
532    /* Some debugging symbols have no name. Ignore them. */
533    if (!iter->name[0])
534        return 0;
535
536    if (iter->module_name[0]) {
537        char type;
538
539        /*
540         * Label it "global" if it is exported,
541         * "local" if not exported.
542         */
543        type = iter->exported ? toupper(iter->type) :
544                    tolower(iter->type);
545        seq_printf(m, "%pK %c %s\t[%s]\n", (void *)iter->value,
546               type, iter->name, iter->module_name);
547    } else
548        seq_printf(m, "%pK %c %s\n", (void *)iter->value,
549               iter->type, iter->name);
550    return 0;
551}
552
553static const struct seq_operations kallsyms_op = {
554    .start = s_start,
555    .next = s_next,
556    .stop = s_stop,
557    .show = s_show
558};
559
560static int kallsyms_open(struct inode *inode, struct file *file)
561{
562    /*
563     * We keep iterator in m->private, since normal case is to
564     * s_start from where we left off, so we avoid doing
565     * using get_symbol_offset for every symbol.
566     */
567    struct kallsym_iter *iter;
568    int ret;
569
570    iter = kmalloc(sizeof(*iter), GFP_KERNEL);
571    if (!iter)
572        return -ENOMEM;
573    reset_iter(iter, 0);
574
575    ret = seq_open(file, &kallsyms_op);
576    if (ret == 0)
577        ((struct seq_file *)file->private_data)->private = iter;
578    else
579        kfree(iter);
580    return ret;
581}
582
583#ifdef CONFIG_KGDB_KDB
584const char *kdb_walk_kallsyms(loff_t *pos)
585{
586    static struct kallsym_iter kdb_walk_kallsyms_iter;
587    if (*pos == 0) {
588        memset(&kdb_walk_kallsyms_iter, 0,
589               sizeof(kdb_walk_kallsyms_iter));
590        reset_iter(&kdb_walk_kallsyms_iter, 0);
591    }
592    while (1) {
593        if (!update_iter(&kdb_walk_kallsyms_iter, *pos))
594            return NULL;
595        ++*pos;
596        /* Some debugging symbols have no name. Ignore them. */
597        if (kdb_walk_kallsyms_iter.name[0])
598            return kdb_walk_kallsyms_iter.name;
599    }
600}
601#endif /* CONFIG_KGDB_KDB */
602
603static const struct file_operations kallsyms_operations = {
604    .open = kallsyms_open,
605    .read = seq_read,
606    .llseek = seq_lseek,
607    .release = seq_release_private,
608};
609
610static int __init kallsyms_init(void)
611{
612    proc_create("kallsyms", 0444, NULL, &kallsyms_operations);
613    return 0;
614}
615device_initcall(kallsyms_init);
616

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