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