2 * kallsyms.c: in-kernel printing of symbolic oopses and stack traces.
4 * Rewritten and vastly simplified by Rusty Russell for in-kernel
6 * Copyright 2002 Rusty Russell <rusty@rustcorp.com.au> IBM Corporation
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>
19 #include <linux/kdb.h>
20 #include <linux/err.h>
21 #include <linux/proc_fs.h>
22 #include <linux/sched.h> /* for cond_resched */
24 #include <linux/ctype.h>
25 #include <linux/slab.h>
26 #include <linux/filter.h>
27 #include <linux/compiler.h>
29 #include <asm/sections.h>
31 #ifdef CONFIG_KALLSYMS_ALL
38 * These will be re-linked against their real values
39 * during the second link stage.
41 extern const unsigned long kallsyms_addresses[] __weak;
42 extern const int kallsyms_offsets[] __weak;
43 extern const u8 kallsyms_names[] __weak;
46 * Tell the compiler that the count isn't in the small data section if the arch
49 extern const unsigned long kallsyms_num_syms
50 __attribute__((weak, section(".rodata")));
52 extern const unsigned long kallsyms_relative_base
53 __attribute__((weak, section(".rodata")));
55 extern const u8 kallsyms_token_table[] __weak;
56 extern const u16 kallsyms_token_index[] __weak;
58 extern const unsigned long kallsyms_markers[] __weak;
60 static inline int is_kernel_inittext(unsigned long addr)
62 if (addr >= (unsigned long)_sinittext
63 && addr <= (unsigned long)_einittext)
68 static inline int is_kernel_text(unsigned long addr)
70 if ((addr >= (unsigned long)_stext && addr <= (unsigned long)_etext) ||
71 arch_is_kernel_text(addr))
73 return in_gate_area_no_mm(addr);
76 static inline int is_kernel(unsigned long addr)
78 if (addr >= (unsigned long)_stext && addr <= (unsigned long)_end)
80 return in_gate_area_no_mm(addr);
83 static int is_ksym_addr(unsigned long addr)
86 return is_kernel(addr);
88 return is_kernel_text(addr) || is_kernel_inittext(addr);
92 * Expand a compressed symbol data into the resulting uncompressed string,
93 * if uncompressed string is too long (>= maxlen), it will be truncated,
94 * given the offset to where the symbol is in the compressed stream.
96 static unsigned int kallsyms_expand_symbol(unsigned int off,
97 char *result, size_t maxlen)
99 int len, skipped_first = 0;
100 const u8 *tptr, *data;
102 /* Get the compressed symbol length from the first symbol byte. */
103 data = &kallsyms_names[off];
108 * Update the offset to return the offset for the next symbol on
109 * the compressed stream.
114 * For every byte on the compressed symbol data, copy the table
115 * entry for that byte.
118 tptr = &kallsyms_token_table[kallsyms_token_index[*data]];
139 /* Return to offset to the next symbol. */
144 * Get symbol type information. This is encoded as a single char at the
145 * beginning of the symbol name.
147 static char kallsyms_get_symbol_type(unsigned int off)
150 * Get just the first code, look it up in the token table,
151 * and return the first char from this token.
153 return kallsyms_token_table[kallsyms_token_index[kallsyms_names[off + 1]]];
158 * Find the offset on the compressed stream given and index in the
161 static unsigned int get_symbol_offset(unsigned long pos)
167 * Use the closest marker we have. We have markers every 256 positions,
168 * so that should be close enough.
170 name = &kallsyms_names[kallsyms_markers[pos >> 8]];
173 * Sequentially scan all the symbols up to the point we're searching
174 * for. Every symbol is stored in a [<len>][<len> bytes of data] format,
175 * so we just need to add the len to the current pointer for every
176 * symbol we wish to skip.
178 for (i = 0; i < (pos & 0xFF); i++)
179 name = name + (*name) + 1;
181 return name - kallsyms_names;
184 static unsigned long kallsyms_sym_address(int idx)
186 if (!IS_ENABLED(CONFIG_KALLSYMS_BASE_RELATIVE))
187 return kallsyms_addresses[idx];
189 /* values are unsigned offsets if --absolute-percpu is not in effect */
190 if (!IS_ENABLED(CONFIG_KALLSYMS_ABSOLUTE_PERCPU))
191 return kallsyms_relative_base + (u32)kallsyms_offsets[idx];
193 /* ...otherwise, positive offsets are absolute values */
194 if (kallsyms_offsets[idx] >= 0)
195 return kallsyms_offsets[idx];
197 /* ...and negative offsets are relative to kallsyms_relative_base - 1 */
198 return kallsyms_relative_base - 1 - kallsyms_offsets[idx];
201 /* Lookup the address for this symbol. Returns 0 if not found. */
202 unsigned long kallsyms_lookup_name(const char *name)
204 char namebuf[KSYM_NAME_LEN];
208 for (i = 0, off = 0; i < kallsyms_num_syms; i++) {
209 off = kallsyms_expand_symbol(off, namebuf, ARRAY_SIZE(namebuf));
211 if (strcmp(namebuf, name) == 0)
212 return kallsyms_sym_address(i);
214 return module_kallsyms_lookup_name(name);
216 EXPORT_SYMBOL_GPL(kallsyms_lookup_name);
218 int kallsyms_on_each_symbol(int (*fn)(void *, const char *, struct module *,
222 char namebuf[KSYM_NAME_LEN];
227 for (i = 0, off = 0; i < kallsyms_num_syms; i++) {
228 off = kallsyms_expand_symbol(off, namebuf, ARRAY_SIZE(namebuf));
229 ret = fn(data, namebuf, NULL, kallsyms_sym_address(i));
233 return module_kallsyms_on_each_symbol(fn, data);
235 EXPORT_SYMBOL_GPL(kallsyms_on_each_symbol);
237 static unsigned long get_symbol_pos(unsigned long addr,
238 unsigned long *symbolsize,
239 unsigned long *offset)
241 unsigned long symbol_start = 0, symbol_end = 0;
242 unsigned long i, low, high, mid;
244 /* This kernel should never had been booted. */
245 if (!IS_ENABLED(CONFIG_KALLSYMS_BASE_RELATIVE))
246 BUG_ON(!kallsyms_addresses);
248 BUG_ON(!kallsyms_offsets);
250 /* Do a binary search on the sorted kallsyms_addresses array. */
252 high = kallsyms_num_syms;
254 while (high - low > 1) {
255 mid = low + (high - low) / 2;
256 if (kallsyms_sym_address(mid) <= addr)
263 * Search for the first aliased symbol. Aliased
264 * symbols are symbols with the same address.
266 while (low && kallsyms_sym_address(low-1) == kallsyms_sym_address(low))
269 symbol_start = kallsyms_sym_address(low);
271 /* Search for next non-aliased symbol. */
272 for (i = low + 1; i < kallsyms_num_syms; i++) {
273 if (kallsyms_sym_address(i) > symbol_start) {
274 symbol_end = kallsyms_sym_address(i);
279 /* If we found no next symbol, we use the end of the section. */
281 if (is_kernel_inittext(addr))
282 symbol_end = (unsigned long)_einittext;
284 symbol_end = (unsigned long)_end;
286 symbol_end = (unsigned long)_etext;
290 *symbolsize = symbol_end - symbol_start;
292 *offset = addr - symbol_start;
298 * Lookup an address but don't bother to find any names.
300 int kallsyms_lookup_size_offset(unsigned long addr, unsigned long *symbolsize,
301 unsigned long *offset)
303 char namebuf[KSYM_NAME_LEN];
305 if (is_ksym_addr(addr))
306 return !!get_symbol_pos(addr, symbolsize, offset);
307 return !!module_address_lookup(addr, symbolsize, offset, NULL, namebuf) ||
308 !!__bpf_address_lookup(addr, symbolsize, offset, namebuf);
313 * - modname is set to NULL if it's in the kernel.
314 * - We guarantee that the returned name is valid until we reschedule even if.
315 * It resides in a module.
316 * - We also guarantee that modname will be valid until rescheduled.
318 const char *kallsyms_lookup(unsigned long addr,
319 unsigned long *symbolsize,
320 unsigned long *offset,
321 char **modname, char *namebuf)
325 namebuf[KSYM_NAME_LEN - 1] = 0;
328 if (is_ksym_addr(addr)) {
331 pos = get_symbol_pos(addr, symbolsize, offset);
333 kallsyms_expand_symbol(get_symbol_offset(pos),
334 namebuf, KSYM_NAME_LEN);
340 /* See if it's in a module or a BPF JITed image. */
341 ret = module_address_lookup(addr, symbolsize, offset,
344 ret = bpf_address_lookup(addr, symbolsize,
345 offset, modname, namebuf);
349 int lookup_symbol_name(unsigned long addr, char *symname)
352 symname[KSYM_NAME_LEN - 1] = '\0';
354 if (is_ksym_addr(addr)) {
357 pos = get_symbol_pos(addr, NULL, NULL);
359 kallsyms_expand_symbol(get_symbol_offset(pos),
360 symname, KSYM_NAME_LEN);
363 /* See if it's in a module. */
364 return lookup_module_symbol_name(addr, symname);
367 int lookup_symbol_attrs(unsigned long addr, unsigned long *size,
368 unsigned long *offset, char *modname, char *name)
371 name[KSYM_NAME_LEN - 1] = '\0';
373 if (is_ksym_addr(addr)) {
376 pos = get_symbol_pos(addr, size, offset);
378 kallsyms_expand_symbol(get_symbol_offset(pos),
379 name, KSYM_NAME_LEN);
383 /* See if it's in a module. */
384 return lookup_module_symbol_attrs(addr, size, offset, modname, name);
387 /* Look up a kernel symbol and return it in a text buffer. */
388 static int __sprint_symbol(char *buffer, unsigned long address,
389 int symbol_offset, int add_offset)
393 unsigned long offset, size;
396 address += symbol_offset;
397 name = kallsyms_lookup(address, &size, &offset, &modname, buffer);
399 return sprintf(buffer, "0x%lx", address - symbol_offset);
402 strcpy(buffer, name);
403 len = strlen(buffer);
404 offset -= symbol_offset;
407 len += sprintf(buffer + len, "+%#lx/%#lx", offset, size);
410 len += sprintf(buffer + len, " [%s]", modname);
416 * sprint_symbol - Look up a kernel symbol and return it in a text buffer
417 * @buffer: buffer to be stored
418 * @address: address to lookup
420 * This function looks up a kernel symbol with @address and stores its name,
421 * offset, size and module name to @buffer if possible. If no symbol was found,
422 * just saves its @address as is.
424 * This function returns the number of bytes stored in @buffer.
426 int sprint_symbol(char *buffer, unsigned long address)
428 return __sprint_symbol(buffer, address, 0, 1);
430 EXPORT_SYMBOL_GPL(sprint_symbol);
433 * sprint_symbol_no_offset - Look up a kernel symbol and return it in a text buffer
434 * @buffer: buffer to be stored
435 * @address: address to lookup
437 * This function looks up a kernel symbol with @address and stores its name
438 * and module name to @buffer if possible. If no symbol was found, just saves
439 * its @address as is.
441 * This function returns the number of bytes stored in @buffer.
443 int sprint_symbol_no_offset(char *buffer, unsigned long address)
445 return __sprint_symbol(buffer, address, 0, 0);
447 EXPORT_SYMBOL_GPL(sprint_symbol_no_offset);
450 * sprint_backtrace - Look up a backtrace symbol and return it in a text buffer
451 * @buffer: buffer to be stored
452 * @address: address to lookup
454 * This function is for stack backtrace and does the same thing as
455 * sprint_symbol() but with modified/decreased @address. If there is a
456 * tail-call to the function marked "noreturn", gcc optimized out code after
457 * the call so that the stack-saved return address could point outside of the
458 * caller. This function ensures that kallsyms will find the original caller
459 * by decreasing @address.
461 * This function returns the number of bytes stored in @buffer.
463 int sprint_backtrace(char *buffer, unsigned long address)
465 return __sprint_symbol(buffer, address, -1, 1);
468 /* Look up a kernel symbol and print it to the kernel messages. */
469 void __print_symbol(const char *fmt, unsigned long address)
471 char buffer[KSYM_SYMBOL_LEN];
473 sprint_symbol(buffer, address);
477 EXPORT_SYMBOL(__print_symbol);
479 /* To avoid using get_symbol_offset for every symbol, we carry prefix along. */
480 struct kallsym_iter {
484 unsigned int nameoff; /* If iterating in core kernel symbols. */
486 char name[KSYM_NAME_LEN];
487 char module_name[MODULE_NAME_LEN];
491 static int get_ksymbol_mod(struct kallsym_iter *iter)
493 int ret = module_get_kallsym(iter->pos - kallsyms_num_syms,
494 &iter->value, &iter->type,
495 iter->name, iter->module_name,
498 iter->pos_mod_end = iter->pos;
505 static int get_ksymbol_bpf(struct kallsym_iter *iter)
507 iter->module_name[0] = '\0';
509 return bpf_get_kallsym(iter->pos - iter->pos_mod_end,
510 &iter->value, &iter->type,
511 iter->name) < 0 ? 0 : 1;
514 /* Returns space to next name. */
515 static unsigned long get_ksymbol_core(struct kallsym_iter *iter)
517 unsigned off = iter->nameoff;
519 iter->module_name[0] = '\0';
520 iter->value = kallsyms_sym_address(iter->pos);
522 iter->type = kallsyms_get_symbol_type(off);
524 off = kallsyms_expand_symbol(off, iter->name, ARRAY_SIZE(iter->name));
526 return off - iter->nameoff;
529 static void reset_iter(struct kallsym_iter *iter, loff_t new_pos)
531 iter->name[0] = '\0';
532 iter->nameoff = get_symbol_offset(new_pos);
535 iter->pos_mod_end = 0;
538 static int update_iter_mod(struct kallsym_iter *iter, loff_t pos)
542 if (iter->pos_mod_end > 0 &&
543 iter->pos_mod_end < iter->pos)
544 return get_ksymbol_bpf(iter);
546 if (!get_ksymbol_mod(iter))
547 return get_ksymbol_bpf(iter);
552 /* Returns false if pos at or past end of file. */
553 static int update_iter(struct kallsym_iter *iter, loff_t pos)
555 /* Module symbols can be accessed randomly. */
556 if (pos >= kallsyms_num_syms)
557 return update_iter_mod(iter, pos);
559 /* If we're not on the desired position, reset to new position. */
560 if (pos != iter->pos)
561 reset_iter(iter, pos);
563 iter->nameoff += get_ksymbol_core(iter);
569 static void *s_next(struct seq_file *m, void *p, loff_t *pos)
573 if (!update_iter(m->private, *pos))
578 static void *s_start(struct seq_file *m, loff_t *pos)
580 if (!update_iter(m->private, *pos))
585 static void s_stop(struct seq_file *m, void *p)
589 static int s_show(struct seq_file *m, void *p)
591 struct kallsym_iter *iter = m->private;
593 /* Some debugging symbols have no name. Ignore them. */
597 if (iter->module_name[0]) {
601 * Label it "global" if it is exported,
602 * "local" if not exported.
604 type = iter->exported ? toupper(iter->type) :
606 seq_printf(m, "%pK %c %s\t[%s]\n", (void *)iter->value,
607 type, iter->name, iter->module_name);
609 seq_printf(m, "%pK %c %s\n", (void *)iter->value,
610 iter->type, iter->name);
614 static const struct seq_operations kallsyms_op = {
621 static int kallsyms_open(struct inode *inode, struct file *file)
624 * We keep iterator in m->private, since normal case is to
625 * s_start from where we left off, so we avoid doing
626 * using get_symbol_offset for every symbol.
628 struct kallsym_iter *iter;
629 iter = __seq_open_private(file, &kallsyms_op, sizeof(*iter));
637 #ifdef CONFIG_KGDB_KDB
638 const char *kdb_walk_kallsyms(loff_t *pos)
640 static struct kallsym_iter kdb_walk_kallsyms_iter;
642 memset(&kdb_walk_kallsyms_iter, 0,
643 sizeof(kdb_walk_kallsyms_iter));
644 reset_iter(&kdb_walk_kallsyms_iter, 0);
647 if (!update_iter(&kdb_walk_kallsyms_iter, *pos))
650 /* Some debugging symbols have no name. Ignore them. */
651 if (kdb_walk_kallsyms_iter.name[0])
652 return kdb_walk_kallsyms_iter.name;
655 #endif /* CONFIG_KGDB_KDB */
657 static const struct file_operations kallsyms_operations = {
658 .open = kallsyms_open,
661 .release = seq_release_private,
664 static int __init kallsyms_init(void)
666 proc_create("kallsyms", 0444, NULL, &kallsyms_operations);
669 device_initcall(kallsyms_init);