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path: root/kernel/kallsyms.c (plain)
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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#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 int kallsyms_offsets[] __weak;
42extern const u8 kallsyms_names[] __weak;
43
44/*
45 * Tell the compiler that the count isn't in the small data section if the arch
46 * has one (eg: FRV).
47 */
48extern const unsigned long kallsyms_num_syms
49__attribute__((weak, section(".rodata")));
50
51extern const unsigned long kallsyms_relative_base
52__attribute__((weak, section(".rodata")));
53
54extern const u8 kallsyms_token_table[] __weak;
55extern const u16 kallsyms_token_index[] __weak;
56
57extern const unsigned long kallsyms_markers[] __weak;
58
59static inline int is_kernel_inittext(unsigned long addr)
60{
61 if (addr >= (unsigned long)_sinittext
62 && addr <= (unsigned long)_einittext)
63 return 1;
64 return 0;
65}
66
67static inline int is_kernel_text(unsigned long addr)
68{
69 if ((addr >= (unsigned long)_stext && addr <= (unsigned long)_etext) ||
70 arch_is_kernel_text(addr))
71 return 1;
72 return in_gate_area_no_mm(addr);
73}
74
75static inline int is_kernel(unsigned long addr)
76{
77 if (addr >= (unsigned long)_stext && addr <= (unsigned long)_end)
78 return 1;
79 return in_gate_area_no_mm(addr);
80}
81
82static int is_ksym_addr(unsigned long addr)
83{
84 if (all_var)
85 return is_kernel(addr);
86
87 return is_kernel_text(addr) || is_kernel_inittext(addr);
88}
89
90/*
91 * Expand a compressed symbol data into the resulting uncompressed string,
92 * if uncompressed string is too long (>= maxlen), it will be truncated,
93 * given the offset to where the symbol is in the compressed stream.
94 */
95static unsigned int kallsyms_expand_symbol(unsigned int off,
96 char *result, size_t maxlen)
97{
98 int len, skipped_first = 0;
99 const u8 *tptr, *data;
100
101 /* Get the compressed symbol length from the first symbol byte. */
102 data = &kallsyms_names[off];
103 len = *data;
104 data++;
105
106 /*
107 * Update the offset to return the offset for the next symbol on
108 * the compressed stream.
109 */
110 off += len + 1;
111
112 /*
113 * For every byte on the compressed symbol data, copy the table
114 * entry for that byte.
115 */
116 while (len) {
117 tptr = &kallsyms_token_table[kallsyms_token_index[*data]];
118 data++;
119 len--;
120
121 while (*tptr) {
122 if (skipped_first) {
123 if (maxlen <= 1)
124 goto tail;
125 *result = *tptr;
126 result++;
127 maxlen--;
128 } else
129 skipped_first = 1;
130 tptr++;
131 }
132 }
133
134tail:
135 if (maxlen)
136 *result = '\0';
137
138 /* Return to offset to the next symbol. */
139 return off;
140}
141
142/*
143 * Get symbol type information. This is encoded as a single char at the
144 * beginning of the symbol name.
145 */
146static char kallsyms_get_symbol_type(unsigned int off)
147{
148 /*
149 * Get just the first code, look it up in the token table,
150 * and return the first char from this token.
151 */
152 return kallsyms_token_table[kallsyms_token_index[kallsyms_names[off + 1]]];
153}
154
155
156/*
157 * Find the offset on the compressed stream given and index in the
158 * kallsyms array.
159 */
160static unsigned int get_symbol_offset(unsigned long pos)
161{
162 const u8 *name;
163 int i;
164
165 /*
166 * Use the closest marker we have. We have markers every 256 positions,
167 * so that should be close enough.
168 */
169 name = &kallsyms_names[kallsyms_markers[pos >> 8]];
170
171 /*
172 * Sequentially scan all the symbols up to the point we're searching
173 * for. Every symbol is stored in a [<len>][<len> bytes of data] format,
174 * so we just need to add the len to the current pointer for every
175 * symbol we wish to skip.
176 */
177 for (i = 0; i < (pos & 0xFF); i++)
178 name = name + (*name) + 1;
179
180 return name - kallsyms_names;
181}
182
183static unsigned long kallsyms_sym_address(int idx)
184{
185 if (!IS_ENABLED(CONFIG_KALLSYMS_BASE_RELATIVE))
186 return kallsyms_addresses[idx];
187
188 /* values are unsigned offsets if --absolute-percpu is not in effect */
189 if (!IS_ENABLED(CONFIG_KALLSYMS_ABSOLUTE_PERCPU))
190 return kallsyms_relative_base + (u32)kallsyms_offsets[idx];
191
192 /* ...otherwise, positive offsets are absolute values */
193 if (kallsyms_offsets[idx] >= 0)
194 return kallsyms_offsets[idx];
195
196 /* ...and negative offsets are relative to kallsyms_relative_base - 1 */
197 return kallsyms_relative_base - 1 - kallsyms_offsets[idx];
198}
199
200/* Lookup the address for this symbol. Returns 0 if not found. */
201unsigned long kallsyms_lookup_name(const char *name)
202{
203 char namebuf[KSYM_NAME_LEN];
204 unsigned long i;
205 unsigned int off;
206
207 for (i = 0, off = 0; i < kallsyms_num_syms; i++) {
208 off = kallsyms_expand_symbol(off, namebuf, ARRAY_SIZE(namebuf));
209
210 if (strcmp(namebuf, name) == 0)
211 return kallsyms_sym_address(i);
212 }
213 return module_kallsyms_lookup_name(name);
214}
215EXPORT_SYMBOL_GPL(kallsyms_lookup_name);
216
217int kallsyms_on_each_symbol(int (*fn)(void *, const char *, struct module *,
218 unsigned long),
219 void *data)
220{
221 char namebuf[KSYM_NAME_LEN];
222 unsigned long i;
223 unsigned int off;
224 int ret;
225
226 for (i = 0, off = 0; i < kallsyms_num_syms; i++) {
227 off = kallsyms_expand_symbol(off, namebuf, ARRAY_SIZE(namebuf));
228 ret = fn(data, namebuf, NULL, kallsyms_sym_address(i));
229 if (ret != 0)
230 return ret;
231 }
232 return module_kallsyms_on_each_symbol(fn, data);
233}
234EXPORT_SYMBOL_GPL(kallsyms_on_each_symbol);
235
236static unsigned long get_symbol_pos(unsigned long addr,
237 unsigned long *symbolsize,
238 unsigned long *offset)
239{
240 unsigned long symbol_start = 0, symbol_end = 0;
241 unsigned long i, low, high, mid;
242
243 /* This kernel should never had been booted. */
244 if (!IS_ENABLED(CONFIG_KALLSYMS_BASE_RELATIVE))
245 BUG_ON(!kallsyms_addresses);
246 else
247 BUG_ON(!kallsyms_offsets);
248
249 /* Do a binary search on the sorted kallsyms_addresses array. */
250 low = 0;
251 high = kallsyms_num_syms;
252
253 while (high - low > 1) {
254 mid = low + (high - low) / 2;
255 if (kallsyms_sym_address(mid) <= addr)
256 low = mid;
257 else
258 high = mid;
259 }
260
261 /*
262 * Search for the first aliased symbol. Aliased
263 * symbols are symbols with the same address.
264 */
265 while (low && kallsyms_sym_address(low-1) == kallsyms_sym_address(low))
266 --low;
267
268 symbol_start = kallsyms_sym_address(low);
269
270 /* Search for next non-aliased symbol. */
271 for (i = low + 1; i < kallsyms_num_syms; i++) {
272 if (kallsyms_sym_address(i) > symbol_start) {
273 symbol_end = kallsyms_sym_address(i);
274 break;
275 }
276 }
277
278 /* If we found no next symbol, we use the end of the section. */
279 if (!symbol_end) {
280 if (is_kernel_inittext(addr))
281 symbol_end = (unsigned long)_einittext;
282 else if (all_var)
283 symbol_end = (unsigned long)_end;
284 else
285 symbol_end = (unsigned long)_etext;
286 }
287
288 if (symbolsize)
289 *symbolsize = symbol_end - symbol_start;
290 if (offset)
291 *offset = addr - symbol_start;
292
293 return low;
294}
295
296/*
297 * Lookup an address but don't bother to find any names.
298 */
299int kallsyms_lookup_size_offset(unsigned long addr, unsigned long *symbolsize,
300 unsigned long *offset)
301{
302 char namebuf[KSYM_NAME_LEN];
303 if (is_ksym_addr(addr))
304 return !!get_symbol_pos(addr, symbolsize, offset);
305
306 return !!module_address_lookup(addr, symbolsize, offset, NULL, namebuf);
307}
308
309#ifdef CONFIG_CFI_CLANG
310/*
311 * LLVM appends .cfi to function names when CONFIG_CFI_CLANG is enabled,
312 * which causes confusion and potentially breaks user space tools, so we
313 * will strip the postfix from expanded symbol names.
314 */
315static inline void cleanup_symbol_name(char *s)
316{
317 char *res;
318
319 res = strrchr(s, '.');
320 if (res && !strcmp(res, ".cfi"))
321 *res = '\0';
322}
323#else
324static inline void cleanup_symbol_name(char *s) {}
325#endif
326
327/*
328 * Lookup an address
329 * - modname is set to NULL if it's in the kernel.
330 * - We guarantee that the returned name is valid until we reschedule even if.
331 * It resides in a module.
332 * - We also guarantee that modname will be valid until rescheduled.
333 */
334const char *kallsyms_lookup(unsigned long addr,
335 unsigned long *symbolsize,
336 unsigned long *offset,
337 char **modname, char *namebuf)
338{
339 namebuf[KSYM_NAME_LEN - 1] = 0;
340 namebuf[0] = 0;
341
342 if (is_ksym_addr(addr)) {
343 unsigned long pos;
344
345 pos = get_symbol_pos(addr, symbolsize, offset);
346 /* Grab name */
347 kallsyms_expand_symbol(get_symbol_offset(pos),
348 namebuf, KSYM_NAME_LEN);
349 if (modname)
350 *modname = NULL;
351 goto found;
352 }
353
354 /* See if it's in a module. */
355 if (!module_address_lookup(addr, symbolsize, offset, modname,
356 namebuf))
357 return NULL;
358
359found:
360 cleanup_symbol_name(namebuf);
361 return namebuf;
362}
363
364int lookup_symbol_name(unsigned long addr, char *symname)
365{
366 int res;
367
368 symname[0] = '\0';
369 symname[KSYM_NAME_LEN - 1] = '\0';
370
371 if (is_ksym_addr(addr)) {
372 unsigned long pos;
373
374 pos = get_symbol_pos(addr, NULL, NULL);
375 /* Grab name */
376 kallsyms_expand_symbol(get_symbol_offset(pos),
377 symname, KSYM_NAME_LEN);
378 goto found;
379 }
380 /* See if it's in a module. */
381 res = lookup_module_symbol_name(addr, symname);
382 if (res)
383 return res;
384
385found:
386 cleanup_symbol_name(symname);
387 return 0;
388}
389
390int lookup_symbol_attrs(unsigned long addr, unsigned long *size,
391 unsigned long *offset, char *modname, char *name)
392{
393 int res;
394
395 name[0] = '\0';
396 name[KSYM_NAME_LEN - 1] = '\0';
397
398 if (is_ksym_addr(addr)) {
399 unsigned long pos;
400
401 pos = get_symbol_pos(addr, size, offset);
402 /* Grab name */
403 kallsyms_expand_symbol(get_symbol_offset(pos),
404 name, KSYM_NAME_LEN);
405 modname[0] = '\0';
406 goto found;
407 }
408 /* See if it's in a module. */
409 res = lookup_module_symbol_attrs(addr, size, offset, modname, name);
410 if (res)
411 return res;
412
413found:
414 cleanup_symbol_name(name);
415 return 0;
416}
417
418/* Look up a kernel symbol and return it in a text buffer. */
419static int __sprint_symbol(char *buffer, unsigned long address,
420 int symbol_offset, int add_offset)
421{
422 char *modname;
423 const char *name;
424 unsigned long offset, size;
425 int len;
426
427 address += symbol_offset;
428 name = kallsyms_lookup(address, &size, &offset, &modname, buffer);
429 if (!name)
430 return sprintf(buffer, "0x%lx", address - symbol_offset);
431
432 if (name != buffer)
433 strcpy(buffer, name);
434 len = strlen(buffer);
435 offset -= symbol_offset;
436
437 if (add_offset)
438 len += sprintf(buffer + len, "+%#lx/%#lx", offset, size);
439
440 if (modname)
441 len += sprintf(buffer + len, " [%s]", modname);
442
443 return len;
444}
445
446/**
447 * sprint_symbol - Look up a kernel symbol and return it in a text buffer
448 * @buffer: buffer to be stored
449 * @address: address to lookup
450 *
451 * This function looks up a kernel symbol with @address and stores its name,
452 * offset, size and module name to @buffer if possible. If no symbol was found,
453 * just saves its @address as is.
454 *
455 * This function returns the number of bytes stored in @buffer.
456 */
457int sprint_symbol(char *buffer, unsigned long address)
458{
459 return __sprint_symbol(buffer, address, 0, 1);
460}
461EXPORT_SYMBOL_GPL(sprint_symbol);
462
463/**
464 * sprint_symbol_no_offset - Look up a kernel symbol and return it in a text buffer
465 * @buffer: buffer to be stored
466 * @address: address to lookup
467 *
468 * This function looks up a kernel symbol with @address and stores its name
469 * and module name to @buffer if possible. If no symbol was found, just saves
470 * its @address as is.
471 *
472 * This function returns the number of bytes stored in @buffer.
473 */
474int sprint_symbol_no_offset(char *buffer, unsigned long address)
475{
476 return __sprint_symbol(buffer, address, 0, 0);
477}
478EXPORT_SYMBOL_GPL(sprint_symbol_no_offset);
479
480/**
481 * sprint_backtrace - Look up a backtrace symbol and return it in a text buffer
482 * @buffer: buffer to be stored
483 * @address: address to lookup
484 *
485 * This function is for stack backtrace and does the same thing as
486 * sprint_symbol() but with modified/decreased @address. If there is a
487 * tail-call to the function marked "noreturn", gcc optimized out code after
488 * the call so that the stack-saved return address could point outside of the
489 * caller. This function ensures that kallsyms will find the original caller
490 * by decreasing @address.
491 *
492 * This function returns the number of bytes stored in @buffer.
493 */
494int sprint_backtrace(char *buffer, unsigned long address)
495{
496 return __sprint_symbol(buffer, address, -1, 1);
497}
498
499/* Look up a kernel symbol and print it to the kernel messages. */
500void __print_symbol(const char *fmt, unsigned long address)
501{
502 char buffer[KSYM_SYMBOL_LEN];
503
504 sprint_symbol(buffer, address);
505
506 printk(fmt, buffer);
507}
508EXPORT_SYMBOL(__print_symbol);
509
510/* To avoid using get_symbol_offset for every symbol, we carry prefix along. */
511struct kallsym_iter {
512 loff_t pos;
513 unsigned long value;
514 unsigned int nameoff; /* If iterating in core kernel symbols. */
515 char type;
516 char name[KSYM_NAME_LEN];
517 char module_name[MODULE_NAME_LEN];
518 int exported;
519};
520
521static int get_ksymbol_mod(struct kallsym_iter *iter)
522{
523 if (module_get_kallsym(iter->pos - kallsyms_num_syms, &iter->value,
524 &iter->type, iter->name, iter->module_name,
525 &iter->exported) < 0)
526 return 0;
527 return 1;
528}
529
530/* Returns space to next name. */
531static unsigned long get_ksymbol_core(struct kallsym_iter *iter)
532{
533 unsigned off = iter->nameoff;
534
535 iter->module_name[0] = '\0';
536 iter->value = kallsyms_sym_address(iter->pos);
537
538 iter->type = kallsyms_get_symbol_type(off);
539
540 off = kallsyms_expand_symbol(off, iter->name, ARRAY_SIZE(iter->name));
541
542 return off - iter->nameoff;
543}
544
545static void reset_iter(struct kallsym_iter *iter, loff_t new_pos)
546{
547 iter->name[0] = '\0';
548 iter->nameoff = get_symbol_offset(new_pos);
549 iter->pos = new_pos;
550}
551
552/* Returns false if pos at or past end of file. */
553static int update_iter(struct kallsym_iter *iter, loff_t pos)
554{
555 /* Module symbols can be accessed randomly. */
556 if (pos >= kallsyms_num_syms) {
557 iter->pos = pos;
558 return get_ksymbol_mod(iter);
559 }
560
561 /* If we're not on the desired position, reset to new position. */
562 if (pos != iter->pos)
563 reset_iter(iter, pos);
564
565 iter->nameoff += get_ksymbol_core(iter);
566 iter->pos++;
567
568 return 1;
569}
570
571static void *s_next(struct seq_file *m, void *p, loff_t *pos)
572{
573 (*pos)++;
574
575 if (!update_iter(m->private, *pos))
576 return NULL;
577 return p;
578}
579
580static void *s_start(struct seq_file *m, loff_t *pos)
581{
582 if (!update_iter(m->private, *pos))
583 return NULL;
584 return m->private;
585}
586
587static void s_stop(struct seq_file *m, void *p)
588{
589}
590
591static int s_show(struct seq_file *m, void *p)
592{
593 struct kallsym_iter *iter = m->private;
594
595 /* Some debugging symbols have no name. Ignore them. */
596 if (!iter->name[0])
597 return 0;
598
599 if (iter->module_name[0]) {
600 char type;
601
602 /*
603 * Label it "global" if it is exported,
604 * "local" if not exported.
605 */
606 type = iter->exported ? toupper(iter->type) :
607 tolower(iter->type);
608 seq_printf(m, "%pK %c %s\t[%s]\n", (void *)iter->value,
609 type, iter->name, iter->module_name);
610 } else
611 seq_printf(m, "%pK %c %s\n", (void *)iter->value,
612 iter->type, iter->name);
613 return 0;
614}
615
616static const struct seq_operations kallsyms_op = {
617 .start = s_start,
618 .next = s_next,
619 .stop = s_stop,
620 .show = s_show
621};
622
623static int kallsyms_open(struct inode *inode, struct file *file)
624{
625 /*
626 * We keep iterator in m->private, since normal case is to
627 * s_start from where we left off, so we avoid doing
628 * using get_symbol_offset for every symbol.
629 */
630 struct kallsym_iter *iter;
631 iter = __seq_open_private(file, &kallsyms_op, sizeof(*iter));
632 if (!iter)
633 return -ENOMEM;
634 reset_iter(iter, 0);
635
636 return 0;
637}
638
639#ifdef CONFIG_KGDB_KDB
640const char *kdb_walk_kallsyms(loff_t *pos)
641{
642 static struct kallsym_iter kdb_walk_kallsyms_iter;
643 if (*pos == 0) {
644 memset(&kdb_walk_kallsyms_iter, 0,
645 sizeof(kdb_walk_kallsyms_iter));
646 reset_iter(&kdb_walk_kallsyms_iter, 0);
647 }
648 while (1) {
649 if (!update_iter(&kdb_walk_kallsyms_iter, *pos))
650 return NULL;
651 ++*pos;
652 /* Some debugging symbols have no name. Ignore them. */
653 if (kdb_walk_kallsyms_iter.name[0])
654 return kdb_walk_kallsyms_iter.name;
655 }
656}
657#endif /* CONFIG_KGDB_KDB */
658
659static const struct file_operations kallsyms_operations = {
660 .open = kallsyms_open,
661 .read = seq_read,
662 .llseek = seq_lseek,
663 .release = seq_release_private,
664};
665
666static int __init kallsyms_init(void)
667{
668 proc_create("kallsyms", 0444, NULL, &kallsyms_operations);
669 return 0;
670}
671device_initcall(kallsyms_init);
672
generated by cgit at 2024-05-18 17:54:41 (GMT)