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>
27 #include <asm/sections.h>
29 #ifdef CONFIG_KALLSYMS_ALL
36 * These will be re-linked against their real values
37 * during the second link stage.
39 extern const unsigned long kallsyms_addresses[] __attribute__((weak));
40 extern const u8 kallsyms_names[] __attribute__((weak));
43 * Tell the compiler that the count isn't in the small data section if the arch
46 extern const unsigned long kallsyms_num_syms
47 __attribute__((weak, section(".rodata")));
49 extern const u8 kallsyms_token_table[] __attribute__((weak));
50 extern const u16 kallsyms_token_index[] __attribute__((weak));
52 extern const unsigned long kallsyms_markers[] __attribute__((weak));
54 static inline int is_kernel_inittext(unsigned long addr)
56 if (addr >= (unsigned long)_sinittext
57 && addr <= (unsigned long)_einittext)
62 static inline int is_kernel_text(unsigned long addr)
64 if ((addr >= (unsigned long)_stext && addr <= (unsigned long)_etext) ||
65 arch_is_kernel_text(addr))
67 return in_gate_area_no_mm(addr);
70 static inline int is_kernel(unsigned long addr)
72 if (addr >= (unsigned long)_stext && addr <= (unsigned long)_end)
74 return in_gate_area_no_mm(addr);
77 static int is_ksym_addr(unsigned long addr)
80 return is_kernel(addr);
82 return is_kernel_text(addr) || is_kernel_inittext(addr);
86 * Expand a compressed symbol data into the resulting uncompressed string,
87 * given the offset to where the symbol is in the compressed stream.
89 static unsigned int kallsyms_expand_symbol(unsigned int off, char *result)
91 int len, skipped_first = 0;
92 const u8 *tptr, *data;
94 /* Get the compressed symbol length from the first symbol byte. */
95 data = &kallsyms_names[off];
100 * Update the offset to return the offset for the next symbol on
101 * the compressed stream.
106 * For every byte on the compressed symbol data, copy the table
107 * entry for that byte.
110 tptr = &kallsyms_token_table[kallsyms_token_index[*data]];
126 /* Return to offset to the next symbol. */
131 * Get symbol type information. This is encoded as a single char at the
132 * beginning of the symbol name.
134 static char kallsyms_get_symbol_type(unsigned int off)
137 * Get just the first code, look it up in the token table,
138 * and return the first char from this token.
140 return kallsyms_token_table[kallsyms_token_index[kallsyms_names[off + 1]]];
145 * Find the offset on the compressed stream given and index in the
148 static unsigned int get_symbol_offset(unsigned long pos)
154 * Use the closest marker we have. We have markers every 256 positions,
155 * so that should be close enough.
157 name = &kallsyms_names[kallsyms_markers[pos >> 8]];
160 * Sequentially scan all the symbols up to the point we're searching
161 * for. Every symbol is stored in a [<len>][<len> bytes of data] format,
162 * so we just need to add the len to the current pointer for every
163 * symbol we wish to skip.
165 for (i = 0; i < (pos & 0xFF); i++)
166 name = name + (*name) + 1;
168 return name - kallsyms_names;
171 /* Lookup the address for this symbol. Returns 0 if not found. */
172 unsigned long kallsyms_lookup_name(const char *name)
174 char namebuf[KSYM_NAME_LEN];
178 for (i = 0, off = 0; i < kallsyms_num_syms; i++) {
179 off = kallsyms_expand_symbol(off, namebuf);
181 if (strcmp(namebuf, name) == 0)
182 return kallsyms_addresses[i];
184 return module_kallsyms_lookup_name(name);
186 EXPORT_SYMBOL_GPL(kallsyms_lookup_name);
188 int kallsyms_on_each_symbol(int (*fn)(void *, const char *, struct module *,
192 char namebuf[KSYM_NAME_LEN];
197 for (i = 0, off = 0; i < kallsyms_num_syms; i++) {
198 off = kallsyms_expand_symbol(off, namebuf);
199 ret = fn(data, namebuf, NULL, kallsyms_addresses[i]);
203 return module_kallsyms_on_each_symbol(fn, data);
205 EXPORT_SYMBOL_GPL(kallsyms_on_each_symbol);
207 static unsigned long get_symbol_pos(unsigned long addr,
208 unsigned long *symbolsize,
209 unsigned long *offset)
211 unsigned long symbol_start = 0, symbol_end = 0;
212 unsigned long i, low, high, mid;
214 /* This kernel should never had been booted. */
215 BUG_ON(!kallsyms_addresses);
217 /* Do a binary search on the sorted kallsyms_addresses array. */
219 high = kallsyms_num_syms;
221 while (high - low > 1) {
222 mid = low + (high - low) / 2;
223 if (kallsyms_addresses[mid] <= addr)
230 * Search for the first aliased symbol. Aliased
231 * symbols are symbols with the same address.
233 while (low && kallsyms_addresses[low-1] == kallsyms_addresses[low])
236 symbol_start = kallsyms_addresses[low];
238 /* Search for next non-aliased symbol. */
239 for (i = low + 1; i < kallsyms_num_syms; i++) {
240 if (kallsyms_addresses[i] > symbol_start) {
241 symbol_end = kallsyms_addresses[i];
246 /* If we found no next symbol, we use the end of the section. */
248 if (is_kernel_inittext(addr))
249 symbol_end = (unsigned long)_einittext;
251 symbol_end = (unsigned long)_end;
253 symbol_end = (unsigned long)_etext;
257 *symbolsize = symbol_end - symbol_start;
259 *offset = addr - symbol_start;
265 * Lookup an address but don't bother to find any names.
267 int kallsyms_lookup_size_offset(unsigned long addr, unsigned long *symbolsize,
268 unsigned long *offset)
270 char namebuf[KSYM_NAME_LEN];
271 if (is_ksym_addr(addr))
272 return !!get_symbol_pos(addr, symbolsize, offset);
274 return !!module_address_lookup(addr, symbolsize, offset, NULL, namebuf);
279 * - modname is set to NULL if it's in the kernel.
280 * - We guarantee that the returned name is valid until we reschedule even if.
281 * It resides in a module.
282 * - We also guarantee that modname will be valid until rescheduled.
284 const char *kallsyms_lookup(unsigned long addr,
285 unsigned long *symbolsize,
286 unsigned long *offset,
287 char **modname, char *namebuf)
289 namebuf[KSYM_NAME_LEN - 1] = 0;
292 if (is_ksym_addr(addr)) {
295 pos = get_symbol_pos(addr, symbolsize, offset);
297 kallsyms_expand_symbol(get_symbol_offset(pos), namebuf);
303 /* See if it's in a module. */
304 return module_address_lookup(addr, symbolsize, offset, modname,
308 int lookup_symbol_name(unsigned long addr, char *symname)
311 symname[KSYM_NAME_LEN - 1] = '\0';
313 if (is_ksym_addr(addr)) {
316 pos = get_symbol_pos(addr, NULL, NULL);
318 kallsyms_expand_symbol(get_symbol_offset(pos), symname);
321 /* See if it's in a module. */
322 return lookup_module_symbol_name(addr, symname);
325 int lookup_symbol_attrs(unsigned long addr, unsigned long *size,
326 unsigned long *offset, char *modname, char *name)
329 name[KSYM_NAME_LEN - 1] = '\0';
331 if (is_ksym_addr(addr)) {
334 pos = get_symbol_pos(addr, size, offset);
336 kallsyms_expand_symbol(get_symbol_offset(pos), name);
340 /* See if it's in a module. */
341 return lookup_module_symbol_attrs(addr, size, offset, modname, name);
344 /* Look up a kernel symbol and return it in a text buffer. */
345 static int __sprint_symbol(char *buffer, unsigned long address,
350 unsigned long offset, size;
353 address += symbol_offset;
354 name = kallsyms_lookup(address, &size, &offset, &modname, buffer);
356 return sprintf(buffer, "0x%lx", address);
359 strcpy(buffer, name);
360 len = strlen(buffer);
362 offset -= symbol_offset;
365 len += sprintf(buffer, "+%#lx/%#lx [%s]", offset, size, modname);
367 len += sprintf(buffer, "+%#lx/%#lx", offset, size);
373 * sprint_symbol - Look up a kernel symbol and return it in a text buffer
374 * @buffer: buffer to be stored
375 * @address: address to lookup
377 * This function looks up a kernel symbol with @address and stores its name,
378 * offset, size and module name to @buffer if possible. If no symbol was found,
379 * just saves its @address as is.
381 * This function returns the number of bytes stored in @buffer.
383 int sprint_symbol(char *buffer, unsigned long address)
385 return __sprint_symbol(buffer, address, 0);
388 EXPORT_SYMBOL_GPL(sprint_symbol);
391 * sprint_backtrace - Look up a backtrace symbol and return it in a text buffer
392 * @buffer: buffer to be stored
393 * @address: address to lookup
395 * This function is for stack backtrace and does the same thing as
396 * sprint_symbol() but with modified/decreased @address. If there is a
397 * tail-call to the function marked "noreturn", gcc optimized out code after
398 * the call so that the stack-saved return address could point outside of the
399 * caller. This function ensures that kallsyms will find the original caller
400 * by decreasing @address.
402 * This function returns the number of bytes stored in @buffer.
404 int sprint_backtrace(char *buffer, unsigned long address)
406 return __sprint_symbol(buffer, address, -1);
409 /* Look up a kernel symbol and print it to the kernel messages. */
410 void __print_symbol(const char *fmt, unsigned long address)
412 char buffer[KSYM_SYMBOL_LEN];
414 sprint_symbol(buffer, address);
418 EXPORT_SYMBOL(__print_symbol);
420 /* To avoid using get_symbol_offset for every symbol, we carry prefix along. */
421 struct kallsym_iter {
424 unsigned int nameoff; /* If iterating in core kernel symbols. */
426 char name[KSYM_NAME_LEN];
427 char module_name[MODULE_NAME_LEN];
431 static int get_ksymbol_mod(struct kallsym_iter *iter)
433 if (module_get_kallsym(iter->pos - kallsyms_num_syms, &iter->value,
434 &iter->type, iter->name, iter->module_name,
435 &iter->exported) < 0)
440 /* Returns space to next name. */
441 static unsigned long get_ksymbol_core(struct kallsym_iter *iter)
443 unsigned off = iter->nameoff;
445 iter->module_name[0] = '\0';
446 iter->value = kallsyms_addresses[iter->pos];
448 iter->type = kallsyms_get_symbol_type(off);
450 off = kallsyms_expand_symbol(off, iter->name);
452 return off - iter->nameoff;
455 static void reset_iter(struct kallsym_iter *iter, loff_t new_pos)
457 iter->name[0] = '\0';
458 iter->nameoff = get_symbol_offset(new_pos);
462 /* Returns false if pos at or past end of file. */
463 static int update_iter(struct kallsym_iter *iter, loff_t pos)
465 /* Module symbols can be accessed randomly. */
466 if (pos >= kallsyms_num_syms) {
468 return get_ksymbol_mod(iter);
471 /* If we're not on the desired position, reset to new position. */
472 if (pos != iter->pos)
473 reset_iter(iter, pos);
475 iter->nameoff += get_ksymbol_core(iter);
481 static void *s_next(struct seq_file *m, void *p, loff_t *pos)
485 if (!update_iter(m->private, *pos))
490 static void *s_start(struct seq_file *m, loff_t *pos)
492 if (!update_iter(m->private, *pos))
497 static void s_stop(struct seq_file *m, void *p)
501 static int s_show(struct seq_file *m, void *p)
503 struct kallsym_iter *iter = m->private;
505 /* Some debugging symbols have no name. Ignore them. */
509 if (iter->module_name[0]) {
513 * Label it "global" if it is exported,
514 * "local" if not exported.
516 type = iter->exported ? toupper(iter->type) :
518 seq_printf(m, "%pK %c %s\t[%s]\n", (void *)iter->value,
519 type, iter->name, iter->module_name);
521 seq_printf(m, "%pK %c %s\n", (void *)iter->value,
522 iter->type, iter->name);
526 static const struct seq_operations kallsyms_op = {
533 static int kallsyms_open(struct inode *inode, struct file *file)
536 * We keep iterator in m->private, since normal case is to
537 * s_start from where we left off, so we avoid doing
538 * using get_symbol_offset for every symbol.
540 struct kallsym_iter *iter;
543 iter = kmalloc(sizeof(*iter), GFP_KERNEL);
548 ret = seq_open(file, &kallsyms_op);
550 ((struct seq_file *)file->private_data)->private = iter;
556 #ifdef CONFIG_KGDB_KDB
557 const char *kdb_walk_kallsyms(loff_t *pos)
559 static struct kallsym_iter kdb_walk_kallsyms_iter;
561 memset(&kdb_walk_kallsyms_iter, 0,
562 sizeof(kdb_walk_kallsyms_iter));
563 reset_iter(&kdb_walk_kallsyms_iter, 0);
566 if (!update_iter(&kdb_walk_kallsyms_iter, *pos))
569 /* Some debugging symbols have no name. Ignore them. */
570 if (kdb_walk_kallsyms_iter.name[0])
571 return kdb_walk_kallsyms_iter.name;
574 #endif /* CONFIG_KGDB_KDB */
576 static const struct file_operations kallsyms_operations = {
577 .open = kallsyms_open,
580 .release = seq_release_private,
583 static int __init kallsyms_init(void)
585 proc_create("kallsyms", 0444, NULL, &kallsyms_operations);
588 device_initcall(kallsyms_init);