Linux 4.15.6
[linux/fpc-iii.git] / kernel / kallsyms.c
blobd5fa4116688aff6f9d5c3c58787b4e848be4dc0a
1 /*
2 * kallsyms.c: in-kernel printing of symbolic oopses and stack traces.
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
8 * ChangeLog:
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)
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/filter.h>
27 #include <linux/ftrace.h>
28 #include <linux/compiler.h>
30 #include <asm/sections.h>
33 * These will be re-linked against their real values
34 * during the second link stage.
36 extern const unsigned long kallsyms_addresses[] __weak;
37 extern const int kallsyms_offsets[] __weak;
38 extern const u8 kallsyms_names[] __weak;
41 * Tell the compiler that the count isn't in the small data section if the arch
42 * has one (eg: FRV).
44 extern const unsigned long kallsyms_num_syms
45 __attribute__((weak, section(".rodata")));
47 extern const unsigned long kallsyms_relative_base
48 __attribute__((weak, section(".rodata")));
50 extern const u8 kallsyms_token_table[] __weak;
51 extern const u16 kallsyms_token_index[] __weak;
53 extern const unsigned long kallsyms_markers[] __weak;
55 static inline int is_kernel_inittext(unsigned long addr)
57 if (addr >= (unsigned long)_sinittext
58 && addr <= (unsigned long)_einittext)
59 return 1;
60 return 0;
63 static inline int is_kernel_text(unsigned long addr)
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);
71 static inline int is_kernel(unsigned long addr)
73 if (addr >= (unsigned long)_stext && addr <= (unsigned long)_end)
74 return 1;
75 return in_gate_area_no_mm(addr);
78 static int is_ksym_addr(unsigned long addr)
80 if (IS_ENABLED(CONFIG_KALLSYMS_ALL))
81 return is_kernel(addr);
83 return is_kernel_text(addr) || is_kernel_inittext(addr);
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.
91 static unsigned int kallsyms_expand_symbol(unsigned int off,
92 char *result, size_t maxlen)
94 int len, skipped_first = 0;
95 const u8 *tptr, *data;
97 /* Get the compressed symbol length from the first symbol byte. */
98 data = &kallsyms_names[off];
99 len = *data;
100 data++;
103 * Update the offset to return the offset for the next symbol on
104 * the compressed stream.
106 off += len + 1;
109 * For every byte on the compressed symbol data, copy the table
110 * entry for that byte.
112 while (len) {
113 tptr = &kallsyms_token_table[kallsyms_token_index[*data]];
114 data++;
115 len--;
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++;
130 tail:
131 if (maxlen)
132 *result = '\0';
134 /* Return to offset to the next symbol. */
135 return off;
139 * Get symbol type information. This is encoded as a single char at the
140 * beginning of the symbol name.
142 static char kallsyms_get_symbol_type(unsigned int off)
145 * Get just the first code, look it up in the token table,
146 * and return the first char from this token.
148 return kallsyms_token_table[kallsyms_token_index[kallsyms_names[off + 1]]];
153 * Find the offset on the compressed stream given and index in the
154 * kallsyms array.
156 static unsigned int get_symbol_offset(unsigned long pos)
158 const u8 *name;
159 int i;
162 * Use the closest marker we have. We have markers every 256 positions,
163 * so that should be close enough.
165 name = &kallsyms_names[kallsyms_markers[pos >> 8]];
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.
173 for (i = 0; i < (pos & 0xFF); i++)
174 name = name + (*name) + 1;
176 return name - kallsyms_names;
179 static unsigned long kallsyms_sym_address(int idx)
181 if (!IS_ENABLED(CONFIG_KALLSYMS_BASE_RELATIVE))
182 return kallsyms_addresses[idx];
184 /* values are unsigned offsets if --absolute-percpu is not in effect */
185 if (!IS_ENABLED(CONFIG_KALLSYMS_ABSOLUTE_PERCPU))
186 return kallsyms_relative_base + (u32)kallsyms_offsets[idx];
188 /* ...otherwise, positive offsets are absolute values */
189 if (kallsyms_offsets[idx] >= 0)
190 return kallsyms_offsets[idx];
192 /* ...and negative offsets are relative to kallsyms_relative_base - 1 */
193 return kallsyms_relative_base - 1 - kallsyms_offsets[idx];
196 /* Lookup the address for this symbol. Returns 0 if not found. */
197 unsigned long kallsyms_lookup_name(const char *name)
199 char namebuf[KSYM_NAME_LEN];
200 unsigned long i;
201 unsigned int off;
203 for (i = 0, off = 0; i < kallsyms_num_syms; i++) {
204 off = kallsyms_expand_symbol(off, namebuf, ARRAY_SIZE(namebuf));
206 if (strcmp(namebuf, name) == 0)
207 return kallsyms_sym_address(i);
209 return module_kallsyms_lookup_name(name);
211 EXPORT_SYMBOL_GPL(kallsyms_lookup_name);
213 int kallsyms_on_each_symbol(int (*fn)(void *, const char *, struct module *,
214 unsigned long),
215 void *data)
217 char namebuf[KSYM_NAME_LEN];
218 unsigned long i;
219 unsigned int off;
220 int ret;
222 for (i = 0, off = 0; i < kallsyms_num_syms; i++) {
223 off = kallsyms_expand_symbol(off, namebuf, ARRAY_SIZE(namebuf));
224 ret = fn(data, namebuf, NULL, kallsyms_sym_address(i));
225 if (ret != 0)
226 return ret;
228 return module_kallsyms_on_each_symbol(fn, data);
230 EXPORT_SYMBOL_GPL(kallsyms_on_each_symbol);
232 static unsigned long get_symbol_pos(unsigned long addr,
233 unsigned long *symbolsize,
234 unsigned long *offset)
236 unsigned long symbol_start = 0, symbol_end = 0;
237 unsigned long i, low, high, mid;
239 /* This kernel should never had been booted. */
240 if (!IS_ENABLED(CONFIG_KALLSYMS_BASE_RELATIVE))
241 BUG_ON(!kallsyms_addresses);
242 else
243 BUG_ON(!kallsyms_offsets);
245 /* Do a binary search on the sorted kallsyms_addresses array. */
246 low = 0;
247 high = kallsyms_num_syms;
249 while (high - low > 1) {
250 mid = low + (high - low) / 2;
251 if (kallsyms_sym_address(mid) <= addr)
252 low = mid;
253 else
254 high = mid;
258 * Search for the first aliased symbol. Aliased
259 * symbols are symbols with the same address.
261 while (low && kallsyms_sym_address(low-1) == kallsyms_sym_address(low))
262 --low;
264 symbol_start = kallsyms_sym_address(low);
266 /* Search for next non-aliased symbol. */
267 for (i = low + 1; i < kallsyms_num_syms; i++) {
268 if (kallsyms_sym_address(i) > symbol_start) {
269 symbol_end = kallsyms_sym_address(i);
270 break;
274 /* If we found no next symbol, we use the end of the section. */
275 if (!symbol_end) {
276 if (is_kernel_inittext(addr))
277 symbol_end = (unsigned long)_einittext;
278 else if (IS_ENABLED(CONFIG_KALLSYMS_ALL))
279 symbol_end = (unsigned long)_end;
280 else
281 symbol_end = (unsigned long)_etext;
284 if (symbolsize)
285 *symbolsize = symbol_end - symbol_start;
286 if (offset)
287 *offset = addr - symbol_start;
289 return low;
293 * Lookup an address but don't bother to find any names.
295 int kallsyms_lookup_size_offset(unsigned long addr, unsigned long *symbolsize,
296 unsigned long *offset)
298 char namebuf[KSYM_NAME_LEN];
300 if (is_ksym_addr(addr))
301 return !!get_symbol_pos(addr, symbolsize, offset);
302 return !!module_address_lookup(addr, symbolsize, offset, NULL, namebuf) ||
303 !!__bpf_address_lookup(addr, symbolsize, offset, namebuf);
307 * Lookup an address
308 * - modname is set to NULL if it's in the kernel.
309 * - We guarantee that the returned name is valid until we reschedule even if.
310 * It resides in a module.
311 * - We also guarantee that modname will be valid until rescheduled.
313 const char *kallsyms_lookup(unsigned long addr,
314 unsigned long *symbolsize,
315 unsigned long *offset,
316 char **modname, char *namebuf)
318 const char *ret;
320 namebuf[KSYM_NAME_LEN - 1] = 0;
321 namebuf[0] = 0;
323 if (is_ksym_addr(addr)) {
324 unsigned long pos;
326 pos = get_symbol_pos(addr, symbolsize, offset);
327 /* Grab name */
328 kallsyms_expand_symbol(get_symbol_offset(pos),
329 namebuf, KSYM_NAME_LEN);
330 if (modname)
331 *modname = NULL;
332 return namebuf;
335 /* See if it's in a module or a BPF JITed image. */
336 ret = module_address_lookup(addr, symbolsize, offset,
337 modname, namebuf);
338 if (!ret)
339 ret = bpf_address_lookup(addr, symbolsize,
340 offset, modname, namebuf);
342 if (!ret)
343 ret = ftrace_mod_address_lookup(addr, symbolsize,
344 offset, modname, namebuf);
345 return ret;
348 int lookup_symbol_name(unsigned long addr, char *symname)
350 symname[0] = '\0';
351 symname[KSYM_NAME_LEN - 1] = '\0';
353 if (is_ksym_addr(addr)) {
354 unsigned long pos;
356 pos = get_symbol_pos(addr, NULL, NULL);
357 /* Grab name */
358 kallsyms_expand_symbol(get_symbol_offset(pos),
359 symname, KSYM_NAME_LEN);
360 return 0;
362 /* See if it's in a module. */
363 return lookup_module_symbol_name(addr, symname);
366 int lookup_symbol_attrs(unsigned long addr, unsigned long *size,
367 unsigned long *offset, char *modname, char *name)
369 name[0] = '\0';
370 name[KSYM_NAME_LEN - 1] = '\0';
372 if (is_ksym_addr(addr)) {
373 unsigned long pos;
375 pos = get_symbol_pos(addr, size, offset);
376 /* Grab name */
377 kallsyms_expand_symbol(get_symbol_offset(pos),
378 name, KSYM_NAME_LEN);
379 modname[0] = '\0';
380 return 0;
382 /* See if it's in a module. */
383 return lookup_module_symbol_attrs(addr, size, offset, modname, name);
386 /* Look up a kernel symbol and return it in a text buffer. */
387 static int __sprint_symbol(char *buffer, unsigned long address,
388 int symbol_offset, int add_offset)
390 char *modname;
391 const char *name;
392 unsigned long offset, size;
393 int len;
395 address += symbol_offset;
396 name = kallsyms_lookup(address, &size, &offset, &modname, buffer);
397 if (!name)
398 return sprintf(buffer, "0x%lx", address - symbol_offset);
400 if (name != buffer)
401 strcpy(buffer, name);
402 len = strlen(buffer);
403 offset -= symbol_offset;
405 if (add_offset)
406 len += sprintf(buffer + len, "+%#lx/%#lx", offset, size);
408 if (modname)
409 len += sprintf(buffer + len, " [%s]", modname);
411 return len;
415 * sprint_symbol - Look up a kernel symbol and return it in a text buffer
416 * @buffer: buffer to be stored
417 * @address: address to lookup
419 * This function looks up a kernel symbol with @address and stores its name,
420 * offset, size and module name to @buffer if possible. If no symbol was found,
421 * just saves its @address as is.
423 * This function returns the number of bytes stored in @buffer.
425 int sprint_symbol(char *buffer, unsigned long address)
427 return __sprint_symbol(buffer, address, 0, 1);
429 EXPORT_SYMBOL_GPL(sprint_symbol);
432 * sprint_symbol_no_offset - Look up a kernel symbol and return it in a text buffer
433 * @buffer: buffer to be stored
434 * @address: address to lookup
436 * This function looks up a kernel symbol with @address and stores its name
437 * and module name to @buffer if possible. If no symbol was found, just saves
438 * its @address as is.
440 * This function returns the number of bytes stored in @buffer.
442 int sprint_symbol_no_offset(char *buffer, unsigned long address)
444 return __sprint_symbol(buffer, address, 0, 0);
446 EXPORT_SYMBOL_GPL(sprint_symbol_no_offset);
449 * sprint_backtrace - Look up a backtrace symbol and return it in a text buffer
450 * @buffer: buffer to be stored
451 * @address: address to lookup
453 * This function is for stack backtrace and does the same thing as
454 * sprint_symbol() but with modified/decreased @address. If there is a
455 * tail-call to the function marked "noreturn", gcc optimized out code after
456 * the call so that the stack-saved return address could point outside of the
457 * caller. This function ensures that kallsyms will find the original caller
458 * by decreasing @address.
460 * This function returns the number of bytes stored in @buffer.
462 int sprint_backtrace(char *buffer, unsigned long address)
464 return __sprint_symbol(buffer, address, -1, 1);
467 /* Look up a kernel symbol and print it to the kernel messages. */
468 void __print_symbol(const char *fmt, unsigned long address)
470 char buffer[KSYM_SYMBOL_LEN];
472 sprint_symbol(buffer, address);
474 printk(fmt, buffer);
476 EXPORT_SYMBOL(__print_symbol);
478 /* To avoid using get_symbol_offset for every symbol, we carry prefix along. */
479 struct kallsym_iter {
480 loff_t pos;
481 loff_t pos_mod_end;
482 loff_t pos_ftrace_mod_end;
483 unsigned long value;
484 unsigned int nameoff; /* If iterating in core kernel symbols. */
485 char type;
486 char name[KSYM_NAME_LEN];
487 char module_name[MODULE_NAME_LEN];
488 int exported;
489 int show_value;
492 static int get_ksymbol_mod(struct kallsym_iter *iter)
494 int ret = module_get_kallsym(iter->pos - kallsyms_num_syms,
495 &iter->value, &iter->type,
496 iter->name, iter->module_name,
497 &iter->exported);
498 if (ret < 0) {
499 iter->pos_mod_end = iter->pos;
500 return 0;
503 return 1;
506 static int get_ksymbol_ftrace_mod(struct kallsym_iter *iter)
508 int ret = ftrace_mod_get_kallsym(iter->pos - iter->pos_mod_end,
509 &iter->value, &iter->type,
510 iter->name, iter->module_name,
511 &iter->exported);
512 if (ret < 0) {
513 iter->pos_ftrace_mod_end = iter->pos;
514 return 0;
517 return 1;
520 static int get_ksymbol_bpf(struct kallsym_iter *iter)
522 iter->module_name[0] = '\0';
523 iter->exported = 0;
524 return bpf_get_kallsym(iter->pos - iter->pos_ftrace_mod_end,
525 &iter->value, &iter->type,
526 iter->name) < 0 ? 0 : 1;
529 /* Returns space to next name. */
530 static unsigned long get_ksymbol_core(struct kallsym_iter *iter)
532 unsigned off = iter->nameoff;
534 iter->module_name[0] = '\0';
535 iter->value = kallsyms_sym_address(iter->pos);
537 iter->type = kallsyms_get_symbol_type(off);
539 off = kallsyms_expand_symbol(off, iter->name, ARRAY_SIZE(iter->name));
541 return off - iter->nameoff;
544 static void reset_iter(struct kallsym_iter *iter, loff_t new_pos)
546 iter->name[0] = '\0';
547 iter->nameoff = get_symbol_offset(new_pos);
548 iter->pos = new_pos;
549 if (new_pos == 0) {
550 iter->pos_mod_end = 0;
551 iter->pos_ftrace_mod_end = 0;
555 static int update_iter_mod(struct kallsym_iter *iter, loff_t pos)
557 iter->pos = pos;
559 if (iter->pos_ftrace_mod_end > 0 &&
560 iter->pos_ftrace_mod_end < iter->pos)
561 return get_ksymbol_bpf(iter);
563 if (iter->pos_mod_end > 0 &&
564 iter->pos_mod_end < iter->pos) {
565 if (!get_ksymbol_ftrace_mod(iter))
566 return get_ksymbol_bpf(iter);
567 return 1;
570 if (!get_ksymbol_mod(iter)) {
571 if (!get_ksymbol_ftrace_mod(iter))
572 return get_ksymbol_bpf(iter);
575 return 1;
578 /* Returns false if pos at or past end of file. */
579 static int update_iter(struct kallsym_iter *iter, loff_t pos)
581 /* Module symbols can be accessed randomly. */
582 if (pos >= kallsyms_num_syms)
583 return update_iter_mod(iter, pos);
585 /* If we're not on the desired position, reset to new position. */
586 if (pos != iter->pos)
587 reset_iter(iter, pos);
589 iter->nameoff += get_ksymbol_core(iter);
590 iter->pos++;
592 return 1;
595 static void *s_next(struct seq_file *m, void *p, loff_t *pos)
597 (*pos)++;
599 if (!update_iter(m->private, *pos))
600 return NULL;
601 return p;
604 static void *s_start(struct seq_file *m, loff_t *pos)
606 if (!update_iter(m->private, *pos))
607 return NULL;
608 return m->private;
611 static void s_stop(struct seq_file *m, void *p)
615 static int s_show(struct seq_file *m, void *p)
617 void *value;
618 struct kallsym_iter *iter = m->private;
620 /* Some debugging symbols have no name. Ignore them. */
621 if (!iter->name[0])
622 return 0;
624 value = iter->show_value ? (void *)iter->value : NULL;
626 if (iter->module_name[0]) {
627 char type;
630 * Label it "global" if it is exported,
631 * "local" if not exported.
633 type = iter->exported ? toupper(iter->type) :
634 tolower(iter->type);
635 seq_printf(m, "%px %c %s\t[%s]\n", value,
636 type, iter->name, iter->module_name);
637 } else
638 seq_printf(m, "%px %c %s\n", value,
639 iter->type, iter->name);
640 return 0;
643 static const struct seq_operations kallsyms_op = {
644 .start = s_start,
645 .next = s_next,
646 .stop = s_stop,
647 .show = s_show
650 static inline int kallsyms_for_perf(void)
652 #ifdef CONFIG_PERF_EVENTS
653 extern int sysctl_perf_event_paranoid;
654 if (sysctl_perf_event_paranoid <= 1)
655 return 1;
656 #endif
657 return 0;
661 * We show kallsyms information even to normal users if we've enabled
662 * kernel profiling and are explicitly not paranoid (so kptr_restrict
663 * is clear, and sysctl_perf_event_paranoid isn't set).
665 * Otherwise, require CAP_SYSLOG (assuming kptr_restrict isn't set to
666 * block even that).
668 int kallsyms_show_value(void)
670 switch (kptr_restrict) {
671 case 0:
672 if (kallsyms_for_perf())
673 return 1;
674 /* fallthrough */
675 case 1:
676 if (has_capability_noaudit(current, CAP_SYSLOG))
677 return 1;
678 /* fallthrough */
679 default:
680 return 0;
684 static int kallsyms_open(struct inode *inode, struct file *file)
687 * We keep iterator in m->private, since normal case is to
688 * s_start from where we left off, so we avoid doing
689 * using get_symbol_offset for every symbol.
691 struct kallsym_iter *iter;
692 iter = __seq_open_private(file, &kallsyms_op, sizeof(*iter));
693 if (!iter)
694 return -ENOMEM;
695 reset_iter(iter, 0);
697 iter->show_value = kallsyms_show_value();
698 return 0;
701 #ifdef CONFIG_KGDB_KDB
702 const char *kdb_walk_kallsyms(loff_t *pos)
704 static struct kallsym_iter kdb_walk_kallsyms_iter;
705 if (*pos == 0) {
706 memset(&kdb_walk_kallsyms_iter, 0,
707 sizeof(kdb_walk_kallsyms_iter));
708 reset_iter(&kdb_walk_kallsyms_iter, 0);
710 while (1) {
711 if (!update_iter(&kdb_walk_kallsyms_iter, *pos))
712 return NULL;
713 ++*pos;
714 /* Some debugging symbols have no name. Ignore them. */
715 if (kdb_walk_kallsyms_iter.name[0])
716 return kdb_walk_kallsyms_iter.name;
719 #endif /* CONFIG_KGDB_KDB */
721 static const struct file_operations kallsyms_operations = {
722 .open = kallsyms_open,
723 .read = seq_read,
724 .llseek = seq_lseek,
725 .release = seq_release_private,
728 static int __init kallsyms_init(void)
730 proc_create("kallsyms", 0444, NULL, &kallsyms_operations);
731 return 0;
733 device_initcall(kallsyms_init);