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

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