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/init.h>
16#include <linux/seq_file.h>
17#include <linux/fs.h>
18#include <linux/kdb.h>
19#include <linux/err.h>
20#include <linux/proc_fs.h>
21#include <linux/sched.h> /* for cond_resched */
22#include <linux/ctype.h>
23#include <linux/slab.h>
24#include <linux/filter.h>
25#include <linux/ftrace.h>
26#include <linux/compiler.h>
27
28/*
29 * These will be re-linked against their real values
30 * during the second link stage.
31 */
32extern const unsigned long kallsyms_addresses[] __weak;
33extern const int kallsyms_offsets[] __weak;
34extern const u8 kallsyms_names[] __weak;
35
36/*
37 * Tell the compiler that the count isn't in the small data section if the arch
38 * has one (eg: FRV).
39 */
40extern const unsigned int kallsyms_num_syms
41__attribute__((weak, section(".rodata")));
42
43extern const unsigned long kallsyms_relative_base
44__attribute__((weak, section(".rodata")));
45
46extern const u8 kallsyms_token_table[] __weak;
47extern const u16 kallsyms_token_index[] __weak;
48
49extern const unsigned int kallsyms_markers[] __weak;
50
51/*
52 * Expand a compressed symbol data into the resulting uncompressed string,
53 * if uncompressed string is too long (>= maxlen), it will be truncated,
54 * given the offset to where the symbol is in the compressed stream.
55 */
56static unsigned int kallsyms_expand_symbol(unsigned int off,
57 char *result, size_t maxlen)
58{
59 int len, skipped_first = 0;
60 const u8 *tptr, *data;
61
62 /* Get the compressed symbol length from the first symbol byte. */
63 data = &kallsyms_names[off];
64 len = *data;
65 data++;
66
67 /*
68 * Update the offset to return the offset for the next symbol on
69 * the compressed stream.
70 */
71 off += len + 1;
72
73 /*
74 * For every byte on the compressed symbol data, copy the table
75 * entry for that byte.
76 */
77 while (len) {
78 tptr = &kallsyms_token_table[kallsyms_token_index[*data]];
79 data++;
80 len--;
81
82 while (*tptr) {
83 if (skipped_first) {
84 if (maxlen <= 1)
85 goto tail;
86 *result = *tptr;
87 result++;
88 maxlen--;
89 } else
90 skipped_first = 1;
91 tptr++;
92 }
93 }
94
95tail:
96 if (maxlen)
97 *result = '\0';
98
99 /* Return to offset to the next symbol. */
100 return off;
101}
102
103/*
104 * Get symbol type information. This is encoded as a single char at the
105 * beginning of the symbol name.
106 */
107static char kallsyms_get_symbol_type(unsigned int off)
108{
109 /*
110 * Get just the first code, look it up in the token table,
111 * and return the first char from this token.
112 */
113 return kallsyms_token_table[kallsyms_token_index[kallsyms_names[off + 1]]];
114}
115
116
117/*
118 * Find the offset on the compressed stream given and index in the
119 * kallsyms array.
120 */
121static unsigned int get_symbol_offset(unsigned long pos)
122{
123 const u8 *name;
124 int i;
125
126 /*
127 * Use the closest marker we have. We have markers every 256 positions,
128 * so that should be close enough.
129 */
130 name = &kallsyms_names[kallsyms_markers[pos >> 8]];
131
132 /*
133 * Sequentially scan all the symbols up to the point we're searching
134 * for. Every symbol is stored in a [<len>][<len> bytes of data] format,
135 * so we just need to add the len to the current pointer for every
136 * symbol we wish to skip.
137 */
138 for (i = 0; i < (pos & 0xFF); i++)
139 name = name + (*name) + 1;
140
141 return name - kallsyms_names;
142}
143
144static unsigned long kallsyms_sym_address(int idx)
145{
146 if (!IS_ENABLED(CONFIG_KALLSYMS_BASE_RELATIVE))
147 return kallsyms_addresses[idx];
148
149 /* values are unsigned offsets if --absolute-percpu is not in effect */
150 if (!IS_ENABLED(CONFIG_KALLSYMS_ABSOLUTE_PERCPU))
151 return kallsyms_relative_base + (u32)kallsyms_offsets[idx];
152
153 /* ...otherwise, positive offsets are absolute values */
154 if (kallsyms_offsets[idx] >= 0)
155 return kallsyms_offsets[idx];
156
157 /* ...and negative offsets are relative to kallsyms_relative_base - 1 */
158 return kallsyms_relative_base - 1 - kallsyms_offsets[idx];
159}
160
161/* Lookup the address for this symbol. Returns 0 if not found. */
162unsigned long kallsyms_lookup_name(const char *name)
163{
164 char namebuf[KSYM_NAME_LEN];
165 unsigned long i;
166 unsigned int off;
167
168 for (i = 0, off = 0; i < kallsyms_num_syms; i++) {
169 off = kallsyms_expand_symbol(off, namebuf, ARRAY_SIZE(namebuf));
170
171 if (strcmp(namebuf, name) == 0)
172 return kallsyms_sym_address(i);
173 }
174 return module_kallsyms_lookup_name(name);
175}
176EXPORT_SYMBOL_GPL(kallsyms_lookup_name);
177
178int kallsyms_on_each_symbol(int (*fn)(void *, const char *, struct module *,
179 unsigned long),
180 void *data)
181{
182 char namebuf[KSYM_NAME_LEN];
183 unsigned long i;
184 unsigned int off;
185 int ret;
186
187 for (i = 0, off = 0; i < kallsyms_num_syms; i++) {
188 off = kallsyms_expand_symbol(off, namebuf, ARRAY_SIZE(namebuf));
189 ret = fn(data, namebuf, NULL, kallsyms_sym_address(i));
190 if (ret != 0)
191 return ret;
192 }
193 return module_kallsyms_on_each_symbol(fn, data);
194}
195EXPORT_SYMBOL_GPL(kallsyms_on_each_symbol);
196
197static unsigned long get_symbol_pos(unsigned long addr,
198 unsigned long *symbolsize,
199 unsigned long *offset)
200{
201 unsigned long symbol_start = 0, symbol_end = 0;
202 unsigned long i, low, high, mid;
203
204 /* This kernel should never had been booted. */
205 if (!IS_ENABLED(CONFIG_KALLSYMS_BASE_RELATIVE))
206 BUG_ON(!kallsyms_addresses);
207 else
208 BUG_ON(!kallsyms_offsets);
209
210 /* Do a binary search on the sorted kallsyms_addresses array. */
211 low = 0;
212 high = kallsyms_num_syms;
213
214 while (high - low > 1) {
215 mid = low + (high - low) / 2;
216 if (kallsyms_sym_address(mid) <= addr)
217 low = mid;
218 else
219 high = mid;
220 }
221
222 /*
223 * Search for the first aliased symbol. Aliased
224 * symbols are symbols with the same address.
225 */
226 while (low && kallsyms_sym_address(low-1) == kallsyms_sym_address(low))
227 --low;
228
229 symbol_start = kallsyms_sym_address(low);
230
231 /* Search for next non-aliased symbol. */
232 for (i = low + 1; i < kallsyms_num_syms; i++) {
233 if (kallsyms_sym_address(i) > symbol_start) {
234 symbol_end = kallsyms_sym_address(i);
235 break;
236 }
237 }
238
239 /* If we found no next symbol, we use the end of the section. */
240 if (!symbol_end) {
241 if (is_kernel_inittext(addr))
242 symbol_end = (unsigned long)_einittext;
243 else if (IS_ENABLED(CONFIG_KALLSYMS_ALL))
244 symbol_end = (unsigned long)_end;
245 else
246 symbol_end = (unsigned long)_etext;
247 }
248
249 if (symbolsize)
250 *symbolsize = symbol_end - symbol_start;
251 if (offset)
252 *offset = addr - symbol_start;
253
254 return low;
255}
256
257/*
258 * Lookup an address but don't bother to find any names.
259 */
260int kallsyms_lookup_size_offset(unsigned long addr, unsigned long *symbolsize,
261 unsigned long *offset)
262{
263 char namebuf[KSYM_NAME_LEN];
264
265 if (is_ksym_addr(addr))
266 return !!get_symbol_pos(addr, symbolsize, offset);
267 return !!module_address_lookup(addr, symbolsize, offset, NULL, namebuf) ||
268 !!__bpf_address_lookup(addr, symbolsize, offset, namebuf);
269}
270
271/*
272 * Lookup an address
273 * - modname is set to NULL if it's in the kernel.
274 * - We guarantee that the returned name is valid until we reschedule even if.
275 * It resides in a module.
276 * - We also guarantee that modname will be valid until rescheduled.
277 */
278const char *kallsyms_lookup(unsigned long addr,
279 unsigned long *symbolsize,
280 unsigned long *offset,
281 char **modname, char *namebuf)
282{
283 const char *ret;
284
285 namebuf[KSYM_NAME_LEN - 1] = 0;
286 namebuf[0] = 0;
287
288 if (is_ksym_addr(addr)) {
289 unsigned long pos;
290
291 pos = get_symbol_pos(addr, symbolsize, offset);
292 /* Grab name */
293 kallsyms_expand_symbol(get_symbol_offset(pos),
294 namebuf, KSYM_NAME_LEN);
295 if (modname)
296 *modname = NULL;
297 return namebuf;
298 }
299
300 /* See if it's in a module or a BPF JITed image. */
301 ret = module_address_lookup(addr, symbolsize, offset,
302 modname, namebuf);
303 if (!ret)
304 ret = bpf_address_lookup(addr, symbolsize,
305 offset, modname, namebuf);
306
307 if (!ret)
308 ret = ftrace_mod_address_lookup(addr, symbolsize,
309 offset, modname, namebuf);
310 return ret;
311}
312
313int lookup_symbol_name(unsigned long addr, char *symname)
314{
315 symname[0] = '\0';
316 symname[KSYM_NAME_LEN - 1] = '\0';
317
318 if (is_ksym_addr(addr)) {
319 unsigned long pos;
320
321 pos = get_symbol_pos(addr, NULL, NULL);
322 /* Grab name */
323 kallsyms_expand_symbol(get_symbol_offset(pos),
324 symname, KSYM_NAME_LEN);
325 return 0;
326 }
327 /* See if it's in a module. */
328 return lookup_module_symbol_name(addr, symname);
329}
330
331int lookup_symbol_attrs(unsigned long addr, unsigned long *size,
332 unsigned long *offset, char *modname, char *name)
333{
334 name[0] = '\0';
335 name[KSYM_NAME_LEN - 1] = '\0';
336
337 if (is_ksym_addr(addr)) {
338 unsigned long pos;
339
340 pos = get_symbol_pos(addr, size, offset);
341 /* Grab name */
342 kallsyms_expand_symbol(get_symbol_offset(pos),
343 name, KSYM_NAME_LEN);
344 modname[0] = '\0';
345 return 0;
346 }
347 /* See if it's in a module. */
348 return lookup_module_symbol_attrs(addr, size, offset, modname, name);
349}
350
351/* Look up a kernel symbol and return it in a text buffer. */
352static int __sprint_symbol(char *buffer, unsigned long address,
353 int symbol_offset, int add_offset)
354{
355 char *modname;
356 const char *name;
357 unsigned long offset, size;
358 int len;
359
360 address += symbol_offset;
361 name = kallsyms_lookup(address, &size, &offset, &modname, buffer);
362 if (!name)
363 return sprintf(buffer, "0x%lx", address - symbol_offset);
364
365 if (name != buffer)
366 strcpy(buffer, name);
367 len = strlen(buffer);
368 offset -= symbol_offset;
369
370 if (add_offset)
371 len += sprintf(buffer + len, "+%#lx/%#lx", offset, size);
372
373 if (modname)
374 len += sprintf(buffer + len, " [%s]", modname);
375
376 return len;
377}
378
379/**
380 * sprint_symbol - Look up a kernel symbol and return it in a text buffer
381 * @buffer: buffer to be stored
382 * @address: address to lookup
383 *
384 * This function looks up a kernel symbol with @address and stores its name,
385 * offset, size and module name to @buffer if possible. If no symbol was found,
386 * just saves its @address as is.
387 *
388 * This function returns the number of bytes stored in @buffer.
389 */
390int sprint_symbol(char *buffer, unsigned long address)
391{
392 return __sprint_symbol(buffer, address, 0, 1);
393}
394EXPORT_SYMBOL_GPL(sprint_symbol);
395
396/**
397 * sprint_symbol_no_offset - Look up a kernel symbol and return it in a text buffer
398 * @buffer: buffer to be stored
399 * @address: address to lookup
400 *
401 * This function looks up a kernel symbol with @address and stores its name
402 * and module name to @buffer if possible. If no symbol was found, just saves
403 * its @address as is.
404 *
405 * This function returns the number of bytes stored in @buffer.
406 */
407int sprint_symbol_no_offset(char *buffer, unsigned long address)
408{
409 return __sprint_symbol(buffer, address, 0, 0);
410}
411EXPORT_SYMBOL_GPL(sprint_symbol_no_offset);
412
413/**
414 * sprint_backtrace - Look up a backtrace symbol and return it in a text buffer
415 * @buffer: buffer to be stored
416 * @address: address to lookup
417 *
418 * This function is for stack backtrace and does the same thing as
419 * sprint_symbol() but with modified/decreased @address. If there is a
420 * tail-call to the function marked "noreturn", gcc optimized out code after
421 * the call so that the stack-saved return address could point outside of the
422 * caller. This function ensures that kallsyms will find the original caller
423 * by decreasing @address.
424 *
425 * This function returns the number of bytes stored in @buffer.
426 */
427int sprint_backtrace(char *buffer, unsigned long address)
428{
429 return __sprint_symbol(buffer, address, -1, 1);
430}
431
432/* To avoid using get_symbol_offset for every symbol, we carry prefix along. */
433struct kallsym_iter {
434 loff_t pos;
435 loff_t pos_arch_end;
436 loff_t pos_mod_end;
437 loff_t pos_ftrace_mod_end;
438 unsigned long value;
439 unsigned int nameoff; /* If iterating in core kernel symbols. */
440 char type;
441 char name[KSYM_NAME_LEN];
442 char module_name[MODULE_NAME_LEN];
443 int exported;
444 int show_value;
445};
446
447int __weak arch_get_kallsym(unsigned int symnum, unsigned long *value,
448 char *type, char *name)
449{
450 return -EINVAL;
451}
452
453static int get_ksymbol_arch(struct kallsym_iter *iter)
454{
455 int ret = arch_get_kallsym(iter->pos - kallsyms_num_syms,
456 &iter->value, &iter->type,
457 iter->name);
458
459 if (ret < 0) {
460 iter->pos_arch_end = iter->pos;
461 return 0;
462 }
463
464 return 1;
465}
466
467static int get_ksymbol_mod(struct kallsym_iter *iter)
468{
469 int ret = module_get_kallsym(iter->pos - iter->pos_arch_end,
470 &iter->value, &iter->type,
471 iter->name, iter->module_name,
472 &iter->exported);
473 if (ret < 0) {
474 iter->pos_mod_end = iter->pos;
475 return 0;
476 }
477
478 return 1;
479}
480
481static int get_ksymbol_ftrace_mod(struct kallsym_iter *iter)
482{
483 int ret = ftrace_mod_get_kallsym(iter->pos - iter->pos_mod_end,
484 &iter->value, &iter->type,
485 iter->name, iter->module_name,
486 &iter->exported);
487 if (ret < 0) {
488 iter->pos_ftrace_mod_end = iter->pos;
489 return 0;
490 }
491
492 return 1;
493}
494
495static int get_ksymbol_bpf(struct kallsym_iter *iter)
496{
497 strlcpy(iter->module_name, "bpf", MODULE_NAME_LEN);
498 iter->exported = 0;
499 return bpf_get_kallsym(iter->pos - iter->pos_ftrace_mod_end,
500 &iter->value, &iter->type,
501 iter->name) < 0 ? 0 : 1;
502}
503
504/* Returns space to next name. */
505static unsigned long get_ksymbol_core(struct kallsym_iter *iter)
506{
507 unsigned off = iter->nameoff;
508
509 iter->module_name[0] = '\0';
510 iter->value = kallsyms_sym_address(iter->pos);
511
512 iter->type = kallsyms_get_symbol_type(off);
513
514 off = kallsyms_expand_symbol(off, iter->name, ARRAY_SIZE(iter->name));
515
516 return off - iter->nameoff;
517}
518
519static void reset_iter(struct kallsym_iter *iter, loff_t new_pos)
520{
521 iter->name[0] = '\0';
522 iter->nameoff = get_symbol_offset(new_pos);
523 iter->pos = new_pos;
524 if (new_pos == 0) {
525 iter->pos_arch_end = 0;
526 iter->pos_mod_end = 0;
527 iter->pos_ftrace_mod_end = 0;
528 }
529}
530
531/*
532 * The end position (last + 1) of each additional kallsyms section is recorded
533 * in iter->pos_..._end as each section is added, and so can be used to
534 * determine which get_ksymbol_...() function to call next.
535 */
536static int update_iter_mod(struct kallsym_iter *iter, loff_t pos)
537{
538 iter->pos = pos;
539
540 if ((!iter->pos_arch_end || iter->pos_arch_end > pos) &&
541 get_ksymbol_arch(iter))
542 return 1;
543
544 if ((!iter->pos_mod_end || iter->pos_mod_end > pos) &&
545 get_ksymbol_mod(iter))
546 return 1;
547
548 if ((!iter->pos_ftrace_mod_end || iter->pos_ftrace_mod_end > pos) &&
549 get_ksymbol_ftrace_mod(iter))
550 return 1;
551
552 return get_ksymbol_bpf(iter);
553}
554
555/* Returns false if pos at or past end of file. */
556static int update_iter(struct kallsym_iter *iter, loff_t pos)
557{
558 /* Module symbols can be accessed randomly. */
559 if (pos >= kallsyms_num_syms)
560 return update_iter_mod(iter, pos);
561
562 /* If we're not on the desired position, reset to new position. */
563 if (pos != iter->pos)
564 reset_iter(iter, pos);
565
566 iter->nameoff += get_ksymbol_core(iter);
567 iter->pos++;
568
569 return 1;
570}
571
572static void *s_next(struct seq_file *m, void *p, loff_t *pos)
573{
574 (*pos)++;
575
576 if (!update_iter(m->private, *pos))
577 return NULL;
578 return p;
579}
580
581static void *s_start(struct seq_file *m, loff_t *pos)
582{
583 if (!update_iter(m->private, *pos))
584 return NULL;
585 return m->private;
586}
587
588static void s_stop(struct seq_file *m, void *p)
589{
590}
591
592static int s_show(struct seq_file *m, void *p)
593{
594 void *value;
595 struct kallsym_iter *iter = m->private;
596
597 /* Some debugging symbols have no name. Ignore them. */
598 if (!iter->name[0])
599 return 0;
600
601 value = iter->show_value ? (void *)iter->value : NULL;
602
603 if (iter->module_name[0]) {
604 char type;
605
606 /*
607 * Label it "global" if it is exported,
608 * "local" if not exported.
609 */
610 type = iter->exported ? toupper(iter->type) :
611 tolower(iter->type);
612 seq_printf(m, "%px %c %s\t[%s]\n", value,
613 type, iter->name, iter->module_name);
614 } else
615 seq_printf(m, "%px %c %s\n", value,
616 iter->type, iter->name);
617 return 0;
618}
619
620static const struct seq_operations kallsyms_op = {
621 .start = s_start,
622 .next = s_next,
623 .stop = s_stop,
624 .show = s_show
625};
626
627static inline int kallsyms_for_perf(void)
628{
629#ifdef CONFIG_PERF_EVENTS
630 extern int sysctl_perf_event_paranoid;
631 if (sysctl_perf_event_paranoid <= 1)
632 return 1;
633#endif
634 return 0;
635}
636
637/*
638 * We show kallsyms information even to normal users if we've enabled
639 * kernel profiling and are explicitly not paranoid (so kptr_restrict
640 * is clear, and sysctl_perf_event_paranoid isn't set).
641 *
642 * Otherwise, require CAP_SYSLOG (assuming kptr_restrict isn't set to
643 * block even that).
644 */
645int kallsyms_show_value(void)
646{
647 switch (kptr_restrict) {
648 case 0:
649 if (kallsyms_for_perf())
650 return 1;
651 /* fallthrough */
652 case 1:
653 if (has_capability_noaudit(current, CAP_SYSLOG))
654 return 1;
655 /* fallthrough */
656 default:
657 return 0;
658 }
659}
660
661static int kallsyms_open(struct inode *inode, struct file *file)
662{
663 /*
664 * We keep iterator in m->private, since normal case is to
665 * s_start from where we left off, so we avoid doing
666 * using get_symbol_offset for every symbol.
667 */
668 struct kallsym_iter *iter;
669 iter = __seq_open_private(file, &kallsyms_op, sizeof(*iter));
670 if (!iter)
671 return -ENOMEM;
672 reset_iter(iter, 0);
673
674 iter->show_value = kallsyms_show_value();
675 return 0;
676}
677
678#ifdef CONFIG_KGDB_KDB
679const char *kdb_walk_kallsyms(loff_t *pos)
680{
681 static struct kallsym_iter kdb_walk_kallsyms_iter;
682 if (*pos == 0) {
683 memset(&kdb_walk_kallsyms_iter, 0,
684 sizeof(kdb_walk_kallsyms_iter));
685 reset_iter(&kdb_walk_kallsyms_iter, 0);
686 }
687 while (1) {
688 if (!update_iter(&kdb_walk_kallsyms_iter, *pos))
689 return NULL;
690 ++*pos;
691 /* Some debugging symbols have no name. Ignore them. */
692 if (kdb_walk_kallsyms_iter.name[0])
693 return kdb_walk_kallsyms_iter.name;
694 }
695}
696#endif /* CONFIG_KGDB_KDB */
697
698static const struct file_operations kallsyms_operations = {
699 .open = kallsyms_open,
700 .read = seq_read,
701 .llseek = seq_lseek,
702 .release = seq_release_private,
703};
704
705static int __init kallsyms_init(void)
706{
707 proc_create("kallsyms", 0444, NULL, &kallsyms_operations);
708 return 0;
709}
710device_initcall(kallsyms_init);
711