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 u8 kallsyms_names[] __weak;
44 * Tell the compiler that the count isn't in the small data section if the arch
47 extern const unsigned long kallsyms_num_syms
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)
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))
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)
75 return in_gate_area_no_mm(addr);
78 static int is_ksym_addr(unsigned long addr)
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];
103 * Update the offset to return the offset for the next symbol on
104 * the compressed stream.
109 * For every byte on the compressed symbol data, copy the table
110 * entry for that byte.
113 tptr = &kallsyms_token_table[kallsyms_token_index[*data]];
134 /* Return to offset to the next symbol. */
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
156 static unsigned int get_symbol_offset(unsigned long pos)
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 /* Lookup the address for this symbol. Returns 0 if not found. */
180 unsigned long kallsyms_lookup_name(const char *name)
182 char namebuf[KSYM_NAME_LEN];
186 for (i = 0, off = 0; i < kallsyms_num_syms; i++) {
187 off = kallsyms_expand_symbol(off, namebuf, ARRAY_SIZE(namebuf));
189 if (strcmp(namebuf, name) == 0)
190 return kallsyms_addresses[i];
192 return module_kallsyms_lookup_name(name);
194 EXPORT_SYMBOL_GPL(kallsyms_lookup_name);
196 int kallsyms_on_each_symbol(int (*fn)(void *, const char *, struct module *,
200 char namebuf[KSYM_NAME_LEN];
205 for (i = 0, off = 0; i < kallsyms_num_syms; i++) {
206 off = kallsyms_expand_symbol(off, namebuf, ARRAY_SIZE(namebuf));
207 ret = fn(data, namebuf, NULL, kallsyms_addresses[i]);
211 return module_kallsyms_on_each_symbol(fn, data);
213 EXPORT_SYMBOL_GPL(kallsyms_on_each_symbol);
215 static unsigned long get_symbol_pos(unsigned long addr,
216 unsigned long *symbolsize,
217 unsigned long *offset)
219 unsigned long symbol_start = 0, symbol_end = 0;
220 unsigned long i, low, high, mid;
222 /* This kernel should never had been booted. */
223 BUG_ON(!kallsyms_addresses);
225 /* Do a binary search on the sorted kallsyms_addresses array. */
227 high = kallsyms_num_syms;
229 while (high - low > 1) {
230 mid = low + (high - low) / 2;
231 if (kallsyms_addresses[mid] <= addr)
238 * Search for the first aliased symbol. Aliased
239 * symbols are symbols with the same address.
241 while (low && kallsyms_addresses[low-1] == kallsyms_addresses[low])
244 symbol_start = kallsyms_addresses[low];
246 /* Search for next non-aliased symbol. */
247 for (i = low + 1; i < kallsyms_num_syms; i++) {
248 if (kallsyms_addresses[i] > symbol_start) {
249 symbol_end = kallsyms_addresses[i];
254 /* If we found no next symbol, we use the end of the section. */
256 if (is_kernel_inittext(addr))
257 symbol_end = (unsigned long)_einittext;
259 symbol_end = (unsigned long)_end;
261 symbol_end = (unsigned long)_etext;
265 *symbolsize = symbol_end - symbol_start;
267 *offset = addr - symbol_start;
273 * Lookup an address but don't bother to find any names.
275 int kallsyms_lookup_size_offset(unsigned long addr, unsigned long *symbolsize,
276 unsigned long *offset)
278 char namebuf[KSYM_NAME_LEN];
279 if (is_ksym_addr(addr))
280 return !!get_symbol_pos(addr, symbolsize, offset);
282 return !!module_address_lookup(addr, symbolsize, offset, NULL, namebuf);
287 * - modname is set to NULL if it's in the kernel.
288 * - We guarantee that the returned name is valid until we reschedule even if.
289 * It resides in a module.
290 * - We also guarantee that modname will be valid until rescheduled.
292 const char *kallsyms_lookup(unsigned long addr,
293 unsigned long *symbolsize,
294 unsigned long *offset,
295 char **modname, char *namebuf)
297 namebuf[KSYM_NAME_LEN - 1] = 0;
300 if (is_ksym_addr(addr)) {
303 pos = get_symbol_pos(addr, symbolsize, offset);
305 kallsyms_expand_symbol(get_symbol_offset(pos),
306 namebuf, KSYM_NAME_LEN);
312 /* See if it's in a module. */
313 return module_address_lookup(addr, symbolsize, offset, modname,
317 int lookup_symbol_name(unsigned long addr, char *symname)
320 symname[KSYM_NAME_LEN - 1] = '\0';
322 if (is_ksym_addr(addr)) {
325 pos = get_symbol_pos(addr, NULL, NULL);
327 kallsyms_expand_symbol(get_symbol_offset(pos),
328 symname, KSYM_NAME_LEN);
331 /* See if it's in a module. */
332 return lookup_module_symbol_name(addr, symname);
335 int lookup_symbol_attrs(unsigned long addr, unsigned long *size,
336 unsigned long *offset, char *modname, char *name)
339 name[KSYM_NAME_LEN - 1] = '\0';
341 if (is_ksym_addr(addr)) {
344 pos = get_symbol_pos(addr, size, offset);
346 kallsyms_expand_symbol(get_symbol_offset(pos),
347 name, KSYM_NAME_LEN);
351 /* See if it's in a module. */
352 return lookup_module_symbol_attrs(addr, size, offset, modname, name);
355 /* Look up a kernel symbol and return it in a text buffer. */
356 static int __sprint_symbol(char *buffer, unsigned long address,
357 int symbol_offset, int add_offset)
361 unsigned long offset, size;
364 address += symbol_offset;
365 name = kallsyms_lookup(address, &size, &offset, &modname, buffer);
367 return sprintf(buffer, "0x%lx", address);
370 strcpy(buffer, name);
371 len = strlen(buffer);
372 offset -= symbol_offset;
375 len += sprintf(buffer + len, "+%#lx/%#lx", offset, size);
378 len += sprintf(buffer + len, " [%s]", modname);
384 * sprint_symbol - Look up a kernel symbol and return it in a text buffer
385 * @buffer: buffer to be stored
386 * @address: address to lookup
388 * This function looks up a kernel symbol with @address and stores its name,
389 * offset, size and module name to @buffer if possible. If no symbol was found,
390 * just saves its @address as is.
392 * This function returns the number of bytes stored in @buffer.
394 int sprint_symbol(char *buffer, unsigned long address)
396 return __sprint_symbol(buffer, address, 0, 1);
398 EXPORT_SYMBOL_GPL(sprint_symbol);
401 * sprint_symbol_no_offset - Look up a kernel symbol and return it in a text buffer
402 * @buffer: buffer to be stored
403 * @address: address to lookup
405 * This function looks up a kernel symbol with @address and stores its name
406 * and module name to @buffer if possible. If no symbol was found, just saves
407 * its @address as is.
409 * This function returns the number of bytes stored in @buffer.
411 int sprint_symbol_no_offset(char *buffer, unsigned long address)
413 return __sprint_symbol(buffer, address, 0, 0);
415 EXPORT_SYMBOL_GPL(sprint_symbol_no_offset);
418 * sprint_backtrace - Look up a backtrace symbol and return it in a text buffer
419 * @buffer: buffer to be stored
420 * @address: address to lookup
422 * This function is for stack backtrace and does the same thing as
423 * sprint_symbol() but with modified/decreased @address. If there is a
424 * tail-call to the function marked "noreturn", gcc optimized out code after
425 * the call so that the stack-saved return address could point outside of the
426 * caller. This function ensures that kallsyms will find the original caller
427 * by decreasing @address.
429 * This function returns the number of bytes stored in @buffer.
431 int sprint_backtrace(char *buffer, unsigned long address)
433 return __sprint_symbol(buffer, address, -1, 1);
436 /* Look up a kernel symbol and print it to the kernel messages. */
437 void __print_symbol(const char *fmt, unsigned long address)
439 char buffer[KSYM_SYMBOL_LEN];
441 sprint_symbol(buffer, address);
445 EXPORT_SYMBOL(__print_symbol);
447 /* To avoid using get_symbol_offset for every symbol, we carry prefix along. */
448 struct kallsym_iter {
451 unsigned int nameoff; /* If iterating in core kernel symbols. */
453 char name[KSYM_NAME_LEN];
454 char module_name[MODULE_NAME_LEN];
458 static int get_ksymbol_mod(struct kallsym_iter *iter)
460 if (module_get_kallsym(iter->pos - kallsyms_num_syms, &iter->value,
461 &iter->type, iter->name, iter->module_name,
462 &iter->exported) < 0)
467 /* Returns space to next name. */
468 static unsigned long get_ksymbol_core(struct kallsym_iter *iter)
470 unsigned off = iter->nameoff;
472 iter->module_name[0] = '\0';
473 iter->value = kallsyms_addresses[iter->pos];
475 iter->type = kallsyms_get_symbol_type(off);
477 off = kallsyms_expand_symbol(off, iter->name, ARRAY_SIZE(iter->name));
479 return off - iter->nameoff;
482 static void reset_iter(struct kallsym_iter *iter, loff_t new_pos)
484 iter->name[0] = '\0';
485 iter->nameoff = get_symbol_offset(new_pos);
489 /* Returns false if pos at or past end of file. */
490 static int update_iter(struct kallsym_iter *iter, loff_t pos)
492 /* Module symbols can be accessed randomly. */
493 if (pos >= kallsyms_num_syms) {
495 return get_ksymbol_mod(iter);
498 /* If we're not on the desired position, reset to new position. */
499 if (pos != iter->pos)
500 reset_iter(iter, pos);
502 iter->nameoff += get_ksymbol_core(iter);
508 static void *s_next(struct seq_file *m, void *p, loff_t *pos)
512 if (!update_iter(m->private, *pos))
517 static void *s_start(struct seq_file *m, loff_t *pos)
519 if (!update_iter(m->private, *pos))
524 static void s_stop(struct seq_file *m, void *p)
528 static int s_show(struct seq_file *m, void *p)
530 struct kallsym_iter *iter = m->private;
532 /* Some debugging symbols have no name. Ignore them. */
536 if (iter->module_name[0]) {
540 * Label it "global" if it is exported,
541 * "local" if not exported.
543 type = iter->exported ? toupper(iter->type) :
545 seq_printf(m, "%pK %c %s\t[%s]\n", (void *)iter->value,
546 type, iter->name, iter->module_name);
548 seq_printf(m, "%pK %c %s\n", (void *)iter->value,
549 iter->type, iter->name);
553 static const struct seq_operations kallsyms_op = {
560 static int kallsyms_open(struct inode *inode, struct file *file)
563 * We keep iterator in m->private, since normal case is to
564 * s_start from where we left off, so we avoid doing
565 * using get_symbol_offset for every symbol.
567 struct kallsym_iter *iter;
570 iter = kmalloc(sizeof(*iter), GFP_KERNEL);
575 ret = seq_open(file, &kallsyms_op);
577 ((struct seq_file *)file->private_data)->private = iter;
583 #ifdef CONFIG_KGDB_KDB
584 const char *kdb_walk_kallsyms(loff_t *pos)
586 static struct kallsym_iter kdb_walk_kallsyms_iter;
588 memset(&kdb_walk_kallsyms_iter, 0,
589 sizeof(kdb_walk_kallsyms_iter));
590 reset_iter(&kdb_walk_kallsyms_iter, 0);
593 if (!update_iter(&kdb_walk_kallsyms_iter, *pos))
596 /* Some debugging symbols have no name. Ignore them. */
597 if (kdb_walk_kallsyms_iter.name[0])
598 return kdb_walk_kallsyms_iter.name;
601 #endif /* CONFIG_KGDB_KDB */
603 static const struct file_operations kallsyms_operations = {
604 .open = kallsyms_open,
607 .release = seq_release_private,
610 static int __init kallsyms_init(void)
612 proc_create("kallsyms", 0444, NULL, &kallsyms_operations);
615 device_initcall(kallsyms_init);