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/compiler.h>
28 #include <asm/sections.h>
30 #ifdef CONFIG_KALLSYMS_ALL
37 * These will be re-linked against their real values
38 * during the second link stage.
40 extern const unsigned long kallsyms_addresses[] __weak;
41 extern const int kallsyms_offsets[] __weak;
42 extern const u8 kallsyms_names[] __weak;
45 * Tell the compiler that the count isn't in the small data section if the arch
48 extern const unsigned long kallsyms_num_syms
49 __attribute__((weak, section(".rodata")));
51 extern const unsigned long kallsyms_relative_base
52 __attribute__((weak, section(".rodata")));
54 extern const u8 kallsyms_token_table[] __weak;
55 extern const u16 kallsyms_token_index[] __weak;
57 extern const unsigned long kallsyms_markers[] __weak;
59 static inline int is_kernel_inittext(unsigned long addr)
61 if (addr >= (unsigned long)_sinittext
62 && addr <= (unsigned long)_einittext)
67 static inline int is_kernel_text(unsigned long addr)
69 if ((addr >= (unsigned long)_stext && addr <= (unsigned long)_etext) ||
70 arch_is_kernel_text(addr))
72 return in_gate_area_no_mm(addr);
75 static inline int is_kernel(unsigned long addr)
77 if (addr >= (unsigned long)_stext && addr <= (unsigned long)_end)
79 return in_gate_area_no_mm(addr);
82 static int is_ksym_addr(unsigned long addr)
85 return is_kernel(addr);
87 return is_kernel_text(addr) || is_kernel_inittext(addr);
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.
95 static unsigned int kallsyms_expand_symbol(unsigned int off,
96 char *result, size_t maxlen)
98 int len, skipped_first = 0;
99 const u8 *tptr, *data;
101 /* Get the compressed symbol length from the first symbol byte. */
102 data = &kallsyms_names[off];
107 * Update the offset to return the offset for the next symbol on
108 * the compressed stream.
113 * For every byte on the compressed symbol data, copy the table
114 * entry for that byte.
117 tptr = &kallsyms_token_table[kallsyms_token_index[*data]];
138 /* Return to offset to the next symbol. */
143 * Get symbol type information. This is encoded as a single char at the
144 * beginning of the symbol name.
146 static char kallsyms_get_symbol_type(unsigned int off)
149 * Get just the first code, look it up in the token table,
150 * and return the first char from this token.
152 return kallsyms_token_table[kallsyms_token_index[kallsyms_names[off + 1]]];
157 * Find the offset on the compressed stream given and index in the
160 static unsigned int get_symbol_offset(unsigned long pos)
166 * Use the closest marker we have. We have markers every 256 positions,
167 * so that should be close enough.
169 name = &kallsyms_names[kallsyms_markers[pos >> 8]];
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.
177 for (i = 0; i < (pos & 0xFF); i++)
178 name = name + (*name) + 1;
180 return name - kallsyms_names;
183 static unsigned long kallsyms_sym_address(int idx)
185 if (!IS_ENABLED(CONFIG_KALLSYMS_BASE_RELATIVE))
186 return kallsyms_addresses[idx];
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];
192 /* ...otherwise, positive offsets are absolute values */
193 if (kallsyms_offsets[idx] >= 0)
194 return kallsyms_offsets[idx];
196 /* ...and negative offsets are relative to kallsyms_relative_base - 1 */
197 return kallsyms_relative_base - 1 - kallsyms_offsets[idx];
200 /* Lookup the address for this symbol. Returns 0 if not found. */
201 unsigned long kallsyms_lookup_name(const char *name)
203 char namebuf[KSYM_NAME_LEN];
207 for (i = 0, off = 0; i < kallsyms_num_syms; i++) {
208 off = kallsyms_expand_symbol(off, namebuf, ARRAY_SIZE(namebuf));
210 if (strcmp(namebuf, name) == 0)
211 return kallsyms_sym_address(i);
213 return module_kallsyms_lookup_name(name);
215 EXPORT_SYMBOL_GPL(kallsyms_lookup_name);
217 int kallsyms_on_each_symbol(int (*fn)(void *, const char *, struct module *,
221 char namebuf[KSYM_NAME_LEN];
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));
232 return module_kallsyms_on_each_symbol(fn, data);
234 EXPORT_SYMBOL_GPL(kallsyms_on_each_symbol);
236 static unsigned long get_symbol_pos(unsigned long addr,
237 unsigned long *symbolsize,
238 unsigned long *offset)
240 unsigned long symbol_start = 0, symbol_end = 0;
241 unsigned long i, low, high, mid;
243 /* This kernel should never had been booted. */
244 if (!IS_ENABLED(CONFIG_KALLSYMS_BASE_RELATIVE))
245 BUG_ON(!kallsyms_addresses);
247 BUG_ON(!kallsyms_offsets);
249 /* Do a binary search on the sorted kallsyms_addresses array. */
251 high = kallsyms_num_syms;
253 while (high - low > 1) {
254 mid = low + (high - low) / 2;
255 if (kallsyms_sym_address(mid) <= addr)
262 * Search for the first aliased symbol. Aliased
263 * symbols are symbols with the same address.
265 while (low && kallsyms_sym_address(low-1) == kallsyms_sym_address(low))
268 symbol_start = kallsyms_sym_address(low);
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);
278 /* If we found no next symbol, we use the end of the section. */
280 if (is_kernel_inittext(addr))
281 symbol_end = (unsigned long)_einittext;
283 symbol_end = (unsigned long)_end;
285 symbol_end = (unsigned long)_etext;
289 *symbolsize = symbol_end - symbol_start;
291 *offset = addr - symbol_start;
297 * Lookup an address but don't bother to find any names.
299 int kallsyms_lookup_size_offset(unsigned long addr, unsigned long *symbolsize,
300 unsigned long *offset)
302 char namebuf[KSYM_NAME_LEN];
303 if (is_ksym_addr(addr))
304 return !!get_symbol_pos(addr, symbolsize, offset);
306 return !!module_address_lookup(addr, symbolsize, offset, NULL, namebuf);
311 * - modname is set to NULL if it's in the kernel.
312 * - We guarantee that the returned name is valid until we reschedule even if.
313 * It resides in a module.
314 * - We also guarantee that modname will be valid until rescheduled.
316 const char *kallsyms_lookup(unsigned long addr,
317 unsigned long *symbolsize,
318 unsigned long *offset,
319 char **modname, char *namebuf)
321 namebuf[KSYM_NAME_LEN - 1] = 0;
324 if (is_ksym_addr(addr)) {
327 pos = get_symbol_pos(addr, symbolsize, offset);
329 kallsyms_expand_symbol(get_symbol_offset(pos),
330 namebuf, KSYM_NAME_LEN);
336 /* See if it's in a module. */
337 return module_address_lookup(addr, symbolsize, offset, modname,
341 int lookup_symbol_name(unsigned long addr, char *symname)
344 symname[KSYM_NAME_LEN - 1] = '\0';
346 if (is_ksym_addr(addr)) {
349 pos = get_symbol_pos(addr, NULL, NULL);
351 kallsyms_expand_symbol(get_symbol_offset(pos),
352 symname, KSYM_NAME_LEN);
355 /* See if it's in a module. */
356 return lookup_module_symbol_name(addr, symname);
359 int lookup_symbol_attrs(unsigned long addr, unsigned long *size,
360 unsigned long *offset, char *modname, char *name)
363 name[KSYM_NAME_LEN - 1] = '\0';
365 if (is_ksym_addr(addr)) {
368 pos = get_symbol_pos(addr, size, offset);
370 kallsyms_expand_symbol(get_symbol_offset(pos),
371 name, KSYM_NAME_LEN);
375 /* See if it's in a module. */
376 return lookup_module_symbol_attrs(addr, size, offset, modname, name);
379 /* Look up a kernel symbol and return it in a text buffer. */
380 static int __sprint_symbol(char *buffer, unsigned long address,
381 int symbol_offset, int add_offset)
385 unsigned long offset, size;
388 address += symbol_offset;
389 name = kallsyms_lookup(address, &size, &offset, &modname, buffer);
391 return sprintf(buffer, "0x%lx", address - symbol_offset);
394 strcpy(buffer, name);
395 len = strlen(buffer);
396 offset -= symbol_offset;
399 len += sprintf(buffer + len, "+%#lx/%#lx", offset, size);
402 len += sprintf(buffer + len, " [%s]", modname);
408 * sprint_symbol - Look up a kernel symbol and return it in a text buffer
409 * @buffer: buffer to be stored
410 * @address: address to lookup
412 * This function looks up a kernel symbol with @address and stores its name,
413 * offset, size and module name to @buffer if possible. If no symbol was found,
414 * just saves its @address as is.
416 * This function returns the number of bytes stored in @buffer.
418 int sprint_symbol(char *buffer, unsigned long address)
420 return __sprint_symbol(buffer, address, 0, 1);
422 EXPORT_SYMBOL_GPL(sprint_symbol);
425 * sprint_symbol_no_offset - Look up a kernel symbol and return it in a text buffer
426 * @buffer: buffer to be stored
427 * @address: address to lookup
429 * This function looks up a kernel symbol with @address and stores its name
430 * and module name to @buffer if possible. If no symbol was found, just saves
431 * its @address as is.
433 * This function returns the number of bytes stored in @buffer.
435 int sprint_symbol_no_offset(char *buffer, unsigned long address)
437 return __sprint_symbol(buffer, address, 0, 0);
439 EXPORT_SYMBOL_GPL(sprint_symbol_no_offset);
442 * sprint_backtrace - Look up a backtrace symbol and return it in a text buffer
443 * @buffer: buffer to be stored
444 * @address: address to lookup
446 * This function is for stack backtrace and does the same thing as
447 * sprint_symbol() but with modified/decreased @address. If there is a
448 * tail-call to the function marked "noreturn", gcc optimized out code after
449 * the call so that the stack-saved return address could point outside of the
450 * caller. This function ensures that kallsyms will find the original caller
451 * by decreasing @address.
453 * This function returns the number of bytes stored in @buffer.
455 int sprint_backtrace(char *buffer, unsigned long address)
457 return __sprint_symbol(buffer, address, -1, 1);
460 /* Look up a kernel symbol and print it to the kernel messages. */
461 void __print_symbol(const char *fmt, unsigned long address)
463 char buffer[KSYM_SYMBOL_LEN];
465 sprint_symbol(buffer, address);
469 EXPORT_SYMBOL(__print_symbol);
471 /* To avoid using get_symbol_offset for every symbol, we carry prefix along. */
472 struct kallsym_iter {
475 unsigned int nameoff; /* If iterating in core kernel symbols. */
477 char name[KSYM_NAME_LEN];
478 char module_name[MODULE_NAME_LEN];
482 static int get_ksymbol_mod(struct kallsym_iter *iter)
484 if (module_get_kallsym(iter->pos - kallsyms_num_syms, &iter->value,
485 &iter->type, iter->name, iter->module_name,
486 &iter->exported) < 0)
491 /* Returns space to next name. */
492 static unsigned long get_ksymbol_core(struct kallsym_iter *iter)
494 unsigned off = iter->nameoff;
496 iter->module_name[0] = '\0';
497 iter->value = kallsyms_sym_address(iter->pos);
499 iter->type = kallsyms_get_symbol_type(off);
501 off = kallsyms_expand_symbol(off, iter->name, ARRAY_SIZE(iter->name));
503 return off - iter->nameoff;
506 static void reset_iter(struct kallsym_iter *iter, loff_t new_pos)
508 iter->name[0] = '\0';
509 iter->nameoff = get_symbol_offset(new_pos);
513 /* Returns false if pos at or past end of file. */
514 static int update_iter(struct kallsym_iter *iter, loff_t pos)
516 /* Module symbols can be accessed randomly. */
517 if (pos >= kallsyms_num_syms) {
519 return get_ksymbol_mod(iter);
522 /* If we're not on the desired position, reset to new position. */
523 if (pos != iter->pos)
524 reset_iter(iter, pos);
526 iter->nameoff += get_ksymbol_core(iter);
532 static void *s_next(struct seq_file *m, void *p, loff_t *pos)
536 if (!update_iter(m->private, *pos))
541 static void *s_start(struct seq_file *m, loff_t *pos)
543 if (!update_iter(m->private, *pos))
548 static void s_stop(struct seq_file *m, void *p)
552 static int s_show(struct seq_file *m, void *p)
554 struct kallsym_iter *iter = m->private;
556 /* Some debugging symbols have no name. Ignore them. */
560 if (iter->module_name[0]) {
564 * Label it "global" if it is exported,
565 * "local" if not exported.
567 type = iter->exported ? toupper(iter->type) :
569 seq_printf(m, "%pK %c %s\t[%s]\n", (void *)iter->value,
570 type, iter->name, iter->module_name);
572 seq_printf(m, "%pK %c %s\n", (void *)iter->value,
573 iter->type, iter->name);
577 static const struct seq_operations kallsyms_op = {
584 static int kallsyms_open(struct inode *inode, struct file *file)
587 * We keep iterator in m->private, since normal case is to
588 * s_start from where we left off, so we avoid doing
589 * using get_symbol_offset for every symbol.
591 struct kallsym_iter *iter;
592 iter = __seq_open_private(file, &kallsyms_op, sizeof(*iter));
600 #ifdef CONFIG_KGDB_KDB
601 const char *kdb_walk_kallsyms(loff_t *pos)
603 static struct kallsym_iter kdb_walk_kallsyms_iter;
605 memset(&kdb_walk_kallsyms_iter, 0,
606 sizeof(kdb_walk_kallsyms_iter));
607 reset_iter(&kdb_walk_kallsyms_iter, 0);
610 if (!update_iter(&kdb_walk_kallsyms_iter, *pos))
613 /* Some debugging symbols have no name. Ignore them. */
614 if (kdb_walk_kallsyms_iter.name[0])
615 return kdb_walk_kallsyms_iter.name;
618 #endif /* CONFIG_KGDB_KDB */
620 static const struct file_operations kallsyms_operations = {
621 .open = kallsyms_open,
624 .release = seq_release_private,
627 static int __init kallsyms_init(void)
629 proc_create("kallsyms", 0444, NULL, &kallsyms_operations);
632 device_initcall(kallsyms_init);