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1/*
2 * kallsyms.c: in-kernel printing of symbolic oopses and stack traces.
3 *
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
7 *
8 * ChangeLog:
9 *
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)
13 */
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/compiler.h>
27
28#include <asm/sections.h>
29
30#ifdef CONFIG_KALLSYMS_ALL
31#define all_var 1
32#else
33#define all_var 0
34#endif
35
36/*
37 * These will be re-linked against their real values
38 * during the second link stage.
39 */
40extern const unsigned long kallsyms_addresses[] __weak;
41extern const int kallsyms_offsets[] __weak;
42extern const u8 kallsyms_names[] __weak;
43
44/*
45 * Tell the compiler that the count isn't in the small data section if the arch
46 * has one (eg: FRV).
47 */
48extern const unsigned long kallsyms_num_syms
49__attribute__((weak, section(".rodata")));
50
51extern const unsigned long kallsyms_relative_base
52__attribute__((weak, section(".rodata")));
53
54extern const u8 kallsyms_token_table[] __weak;
55extern const u16 kallsyms_token_index[] __weak;
56
57extern const unsigned long kallsyms_markers[] __weak;
58
59static inline int is_kernel_inittext(unsigned long addr)
60{
61 if (addr >= (unsigned long)_sinittext
62 && addr <= (unsigned long)_einittext)
63 return 1;
64 return 0;
65}
66
67static inline int is_kernel_text(unsigned long addr)
68{
69 if ((addr >= (unsigned long)_stext && addr <= (unsigned long)_etext) ||
70 arch_is_kernel_text(addr))
71 return 1;
72 return in_gate_area_no_mm(addr);
73}
74
75static inline int is_kernel(unsigned long addr)
76{
77 if (addr >= (unsigned long)_stext && addr <= (unsigned long)_end)
78 return 1;
79 return in_gate_area_no_mm(addr);
80}
81
82static int is_ksym_addr(unsigned long addr)
83{
84 if (all_var)
85 return is_kernel(addr);
86
87 return is_kernel_text(addr) || is_kernel_inittext(addr);
88}
89
90/*
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.
94 */
95static unsigned int kallsyms_expand_symbol(unsigned int off,
96 char *result, size_t maxlen)
97{
98 int len, skipped_first = 0;
99 const u8 *tptr, *data;
100
101 /* Get the compressed symbol length from the first symbol byte. */
102 data = &kallsyms_names[off];
103 len = *data;
104 data++;
105
106 /*
107 * Update the offset to return the offset for the next symbol on
108 * the compressed stream.
109 */
110 off += len + 1;
111
112 /*
113 * For every byte on the compressed symbol data, copy the table
114 * entry for that byte.
115 */
116 while (len) {
117 tptr = &kallsyms_token_table[kallsyms_token_index[*data]];
118 data++;
119 len--;
120
121 while (*tptr) {
122 if (skipped_first) {
123 if (maxlen <= 1)
124 goto tail;
125 *result = *tptr;
126 result++;
127 maxlen--;
128 } else
129 skipped_first = 1;
130 tptr++;
131 }
132 }
133
134tail:
135 if (maxlen)
136 *result = '\0';
137
138 /* Return to offset to the next symbol. */
139 return off;
140}
141
142/*
143 * Get symbol type information. This is encoded as a single char at the
144 * beginning of the symbol name.
145 */
146static char kallsyms_get_symbol_type(unsigned int off)
147{
148 /*
149 * Get just the first code, look it up in the token table,
150 * and return the first char from this token.
151 */
152 return kallsyms_token_table[kallsyms_token_index[kallsyms_names[off + 1]]];
153}
154
155
156/*
157 * Find the offset on the compressed stream given and index in the
158 * kallsyms array.
159 */
160static unsigned int get_symbol_offset(unsigned long pos)
161{
162 const u8 *name;
163 int i;
164
165 /*
166 * Use the closest marker we have. We have markers every 256 positions,
167 * so that should be close enough.
168 */
169 name = &kallsyms_names[kallsyms_markers[pos >> 8]];
170
171 /*
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.
176 */
177 for (i = 0; i < (pos & 0xFF); i++)
178 name = name + (*name) + 1;
179
180 return name - kallsyms_names;
181}
182
183static unsigned long kallsyms_sym_address(int idx)
184{
185 if (!IS_ENABLED(CONFIG_KALLSYMS_BASE_RELATIVE))
186 return kallsyms_addresses[idx];
187
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];
191
192 /* ...otherwise, positive offsets are absolute values */
193 if (kallsyms_offsets[idx] >= 0)
194 return kallsyms_offsets[idx];
195
196 /* ...and negative offsets are relative to kallsyms_relative_base - 1 */
197 return kallsyms_relative_base - 1 - kallsyms_offsets[idx];
198}
199
200/* Lookup the address for this symbol. Returns 0 if not found. */
201unsigned long kallsyms_lookup_name(const char *name)
202{
203 char namebuf[KSYM_NAME_LEN];
204 unsigned long i;
205 unsigned int off;
206
207 for (i = 0, off = 0; i < kallsyms_num_syms; i++) {
208 off = kallsyms_expand_symbol(off, namebuf, ARRAY_SIZE(namebuf));
209
210 if (strcmp(namebuf, name) == 0)
211 return kallsyms_sym_address(i);
212 }
213 return module_kallsyms_lookup_name(name);
214}
215EXPORT_SYMBOL_GPL(kallsyms_lookup_name);
216
217int kallsyms_on_each_symbol(int (*fn)(void *, const char *, struct module *,
218 unsigned long),
219 void *data)
220{
221 char namebuf[KSYM_NAME_LEN];
222 unsigned long i;
223 unsigned int off;
224 int ret;
225
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));
229 if (ret != 0)
230 return ret;
231 }
232 return module_kallsyms_on_each_symbol(fn, data);
233}
234EXPORT_SYMBOL_GPL(kallsyms_on_each_symbol);
235
236static unsigned long get_symbol_pos(unsigned long addr,
237 unsigned long *symbolsize,
238 unsigned long *offset)
239{
240 unsigned long symbol_start = 0, symbol_end = 0;
241 unsigned long i, low, high, mid;
242
243 /* This kernel should never had been booted. */
244 if (!IS_ENABLED(CONFIG_KALLSYMS_BASE_RELATIVE))
245 BUG_ON(!kallsyms_addresses);
246 else
247 BUG_ON(!kallsyms_offsets);
248
249 /* Do a binary search on the sorted kallsyms_addresses array. */
250 low = 0;
251 high = kallsyms_num_syms;
252
253 while (high - low > 1) {
254 mid = low + (high - low) / 2;
255 if (kallsyms_sym_address(mid) <= addr)
256 low = mid;
257 else
258 high = mid;
259 }
260
261 /*
262 * Search for the first aliased symbol. Aliased
263 * symbols are symbols with the same address.
264 */
265 while (low && kallsyms_sym_address(low-1) == kallsyms_sym_address(low))
266 --low;
267
268 symbol_start = kallsyms_sym_address(low);
269
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);
274 break;
275 }
276 }
277
278 /* If we found no next symbol, we use the end of the section. */
279 if (!symbol_end) {
280 if (is_kernel_inittext(addr))
281 symbol_end = (unsigned long)_einittext;
282 else if (all_var)
283 symbol_end = (unsigned long)_end;
284 else
285 symbol_end = (unsigned long)_etext;
286 }
287
288 if (symbolsize)
289 *symbolsize = symbol_end - symbol_start;
290 if (offset)
291 *offset = addr - symbol_start;
292
293 return low;
294}
295
296/*
297 * Lookup an address but don't bother to find any names.
298 */
299int kallsyms_lookup_size_offset(unsigned long addr, unsigned long *symbolsize,
300 unsigned long *offset)
301{
302 char namebuf[KSYM_NAME_LEN];
303 if (is_ksym_addr(addr))
304 return !!get_symbol_pos(addr, symbolsize, offset);
305
306 return !!module_address_lookup(addr, symbolsize, offset, NULL, namebuf);
307}
308
309/*
310 * Lookup an address
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.
315 */
316const char *kallsyms_lookup(unsigned long addr,
317 unsigned long *symbolsize,
318 unsigned long *offset,
319 char **modname, char *namebuf)
320{
321 namebuf[KSYM_NAME_LEN - 1] = 0;
322 namebuf[0] = 0;
323
324 if (is_ksym_addr(addr)) {
325 unsigned long pos;
326
327 pos = get_symbol_pos(addr, symbolsize, offset);
328 /* Grab name */
329 kallsyms_expand_symbol(get_symbol_offset(pos),
330 namebuf, KSYM_NAME_LEN);
331 if (modname)
332 *modname = NULL;
333 return namebuf;
334 }
335
336 /* See if it's in a module. */
337 return module_address_lookup(addr, symbolsize, offset, modname,
338 namebuf);
339}
340
341int lookup_symbol_name(unsigned long addr, char *symname)
342{
343 symname[0] = '\0';
344 symname[KSYM_NAME_LEN - 1] = '\0';
345
346 if (is_ksym_addr(addr)) {
347 unsigned long pos;
348
349 pos = get_symbol_pos(addr, NULL, NULL);
350 /* Grab name */
351 kallsyms_expand_symbol(get_symbol_offset(pos),
352 symname, KSYM_NAME_LEN);
353 return 0;
354 }
355 /* See if it's in a module. */
356 return lookup_module_symbol_name(addr, symname);
357}
358
359int lookup_symbol_attrs(unsigned long addr, unsigned long *size,
360 unsigned long *offset, char *modname, char *name)
361{
362 name[0] = '\0';
363 name[KSYM_NAME_LEN - 1] = '\0';
364
365 if (is_ksym_addr(addr)) {
366 unsigned long pos;
367
368 pos = get_symbol_pos(addr, size, offset);
369 /* Grab name */
370 kallsyms_expand_symbol(get_symbol_offset(pos),
371 name, KSYM_NAME_LEN);
372 modname[0] = '\0';
373 return 0;
374 }
375 /* See if it's in a module. */
376 return lookup_module_symbol_attrs(addr, size, offset, modname, name);
377}
378
379/* Look up a kernel symbol and return it in a text buffer. */
380static int __sprint_symbol(char *buffer, unsigned long address,
381 int symbol_offset, int add_offset)
382{
383 char *modname;
384 const char *name;
385 unsigned long offset, size;
386 int len;
387
388 address += symbol_offset;
389 name = kallsyms_lookup(address, &size, &offset, &modname, buffer);
390 if (!name)
391 return sprintf(buffer, "0x%lx", address - symbol_offset);
392
393 if (name != buffer)
394 strcpy(buffer, name);
395 len = strlen(buffer);
396 offset -= symbol_offset;
397
398 if (add_offset)
399 len += sprintf(buffer + len, "+%#lx/%#lx", offset, size);
400
401 if (modname)
402 len += sprintf(buffer + len, " [%s]", modname);
403
404 return len;
405}
406
407/**
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
411 *
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.
415 *
416 * This function returns the number of bytes stored in @buffer.
417 */
418int sprint_symbol(char *buffer, unsigned long address)
419{
420 return __sprint_symbol(buffer, address, 0, 1);
421}
422EXPORT_SYMBOL_GPL(sprint_symbol);
423
424/**
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
428 *
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.
432 *
433 * This function returns the number of bytes stored in @buffer.
434 */
435int sprint_symbol_no_offset(char *buffer, unsigned long address)
436{
437 return __sprint_symbol(buffer, address, 0, 0);
438}
439EXPORT_SYMBOL_GPL(sprint_symbol_no_offset);
440
441/**
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
445 *
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.
452 *
453 * This function returns the number of bytes stored in @buffer.
454 */
455int sprint_backtrace(char *buffer, unsigned long address)
456{
457 return __sprint_symbol(buffer, address, -1, 1);
458}
459
460/* Look up a kernel symbol and print it to the kernel messages. */
461void __print_symbol(const char *fmt, unsigned long address)
462{
463 char buffer[KSYM_SYMBOL_LEN];
464
465 sprint_symbol(buffer, address);
466
467 printk(fmt, buffer);
468}
469EXPORT_SYMBOL(__print_symbol);
470
471/* To avoid using get_symbol_offset for every symbol, we carry prefix along. */
472struct kallsym_iter {
473 loff_t pos;
474 unsigned long value;
475 unsigned int nameoff; /* If iterating in core kernel symbols. */
476 char type;
477 char name[KSYM_NAME_LEN];
478 char module_name[MODULE_NAME_LEN];
479 int exported;
480};
481
482static int get_ksymbol_mod(struct kallsym_iter *iter)
483{
484 if (module_get_kallsym(iter->pos - kallsyms_num_syms, &iter->value,
485 &iter->type, iter->name, iter->module_name,
486 &iter->exported) < 0)
487 return 0;
488 return 1;
489}
490
491/* Returns space to next name. */
492static unsigned long get_ksymbol_core(struct kallsym_iter *iter)
493{
494 unsigned off = iter->nameoff;
495
496 iter->module_name[0] = '\0';
497 iter->value = kallsyms_sym_address(iter->pos);
498
499 iter->type = kallsyms_get_symbol_type(off);
500
501 off = kallsyms_expand_symbol(off, iter->name, ARRAY_SIZE(iter->name));
502
503 return off - iter->nameoff;
504}
505
506static void reset_iter(struct kallsym_iter *iter, loff_t new_pos)
507{
508 iter->name[0] = '\0';
509 iter->nameoff = get_symbol_offset(new_pos);
510 iter->pos = new_pos;
511}
512
513/* Returns false if pos at or past end of file. */
514static int update_iter(struct kallsym_iter *iter, loff_t pos)
515{
516 /* Module symbols can be accessed randomly. */
517 if (pos >= kallsyms_num_syms) {
518 iter->pos = pos;
519 return get_ksymbol_mod(iter);
520 }
521
522 /* If we're not on the desired position, reset to new position. */
523 if (pos != iter->pos)
524 reset_iter(iter, pos);
525
526 iter->nameoff += get_ksymbol_core(iter);
527 iter->pos++;
528
529 return 1;
530}
531
532static void *s_next(struct seq_file *m, void *p, loff_t *pos)
533{
534 (*pos)++;
535
536 if (!update_iter(m->private, *pos))
537 return NULL;
538 return p;
539}
540
541static void *s_start(struct seq_file *m, loff_t *pos)
542{
543 if (!update_iter(m->private, *pos))
544 return NULL;
545 return m->private;
546}
547
548static void s_stop(struct seq_file *m, void *p)
549{
550}
551
552static int s_show(struct seq_file *m, void *p)
553{
554 struct kallsym_iter *iter = m->private;
555
556 /* Some debugging symbols have no name. Ignore them. */
557 if (!iter->name[0])
558 return 0;
559
560 if (iter->module_name[0]) {
561 char type;
562
563 /*
564 * Label it "global" if it is exported,
565 * "local" if not exported.
566 */
567 type = iter->exported ? toupper(iter->type) :
568 tolower(iter->type);
569 seq_printf(m, "%pK %c %s\t[%s]\n", (void *)iter->value,
570 type, iter->name, iter->module_name);
571 } else
572 seq_printf(m, "%pK %c %s\n", (void *)iter->value,
573 iter->type, iter->name);
574 return 0;
575}
576
577static const struct seq_operations kallsyms_op = {
578 .start = s_start,
579 .next = s_next,
580 .stop = s_stop,
581 .show = s_show
582};
583
584static int kallsyms_open(struct inode *inode, struct file *file)
585{
586 /*
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.
590 */
591 struct kallsym_iter *iter;
592 iter = __seq_open_private(file, &kallsyms_op, sizeof(*iter));
593 if (!iter)
594 return -ENOMEM;
595 reset_iter(iter, 0);
596
597 return 0;
598}
599
600#ifdef CONFIG_KGDB_KDB
601const char *kdb_walk_kallsyms(loff_t *pos)
602{
603 static struct kallsym_iter kdb_walk_kallsyms_iter;
604 if (*pos == 0) {
605 memset(&kdb_walk_kallsyms_iter, 0,
606 sizeof(kdb_walk_kallsyms_iter));
607 reset_iter(&kdb_walk_kallsyms_iter, 0);
608 }
609 while (1) {
610 if (!update_iter(&kdb_walk_kallsyms_iter, *pos))
611 return NULL;
612 ++*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;
616 }
617}
618#endif /* CONFIG_KGDB_KDB */
619
620static const struct file_operations kallsyms_operations = {
621 .open = kallsyms_open,
622 .read = seq_read,
623 .llseek = seq_lseek,
624 .release = seq_release_private,
625};
626
627static int __init kallsyms_init(void)
628{
629 proc_create("kallsyms", 0444, NULL, &kallsyms_operations);
630 return 0;
631}
632device_initcall(kallsyms_init);
1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * kallsyms.c: in-kernel printing of symbolic oopses and stack traces.
4 *
5 * Rewritten and vastly simplified by Rusty Russell for in-kernel
6 * module loader:
7 * Copyright 2002 Rusty Russell <rusty@rustcorp.com.au> IBM Corporation
8 *
9 * ChangeLog:
10 *
11 * (25/Aug/2004) Paulo Marques <pmarques@grupopie.com>
12 * Changed the compression method from stem compression to "table lookup"
13 * compression (see scripts/kallsyms.c for a more complete description)
14 */
15#include <linux/kallsyms.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/ctype.h>
24#include <linux/slab.h>
25#include <linux/filter.h>
26#include <linux/ftrace.h>
27#include <linux/kprobes.h>
28#include <linux/compiler.h>
29
30/*
31 * These will be re-linked against their real values
32 * during the second link stage.
33 */
34extern const unsigned long kallsyms_addresses[] __weak;
35extern const int kallsyms_offsets[] __weak;
36extern const u8 kallsyms_names[] __weak;
37
38/*
39 * Tell the compiler that the count isn't in the small data section if the arch
40 * has one (eg: FRV).
41 */
42extern const unsigned int kallsyms_num_syms
43__attribute__((weak, section(".rodata")));
44
45extern const unsigned long kallsyms_relative_base
46__attribute__((weak, section(".rodata")));
47
48extern const char kallsyms_token_table[] __weak;
49extern const u16 kallsyms_token_index[] __weak;
50
51extern const unsigned int kallsyms_markers[] __weak;
52
53/*
54 * Expand a compressed symbol data into the resulting uncompressed string,
55 * if uncompressed string is too long (>= maxlen), it will be truncated,
56 * given the offset to where the symbol is in the compressed stream.
57 */
58static unsigned int kallsyms_expand_symbol(unsigned int off,
59 char *result, size_t maxlen)
60{
61 int len, skipped_first = 0;
62 const char *tptr;
63 const u8 *data;
64
65 /* Get the compressed symbol length from the first symbol byte. */
66 data = &kallsyms_names[off];
67 len = *data;
68 data++;
69
70 /*
71 * Update the offset to return the offset for the next symbol on
72 * the compressed stream.
73 */
74 off += len + 1;
75
76 /*
77 * For every byte on the compressed symbol data, copy the table
78 * entry for that byte.
79 */
80 while (len) {
81 tptr = &kallsyms_token_table[kallsyms_token_index[*data]];
82 data++;
83 len--;
84
85 while (*tptr) {
86 if (skipped_first) {
87 if (maxlen <= 1)
88 goto tail;
89 *result = *tptr;
90 result++;
91 maxlen--;
92 } else
93 skipped_first = 1;
94 tptr++;
95 }
96 }
97
98tail:
99 if (maxlen)
100 *result = '\0';
101
102 /* Return to offset to the next symbol. */
103 return off;
104}
105
106/*
107 * Get symbol type information. This is encoded as a single char at the
108 * beginning of the symbol name.
109 */
110static char kallsyms_get_symbol_type(unsigned int off)
111{
112 /*
113 * Get just the first code, look it up in the token table,
114 * and return the first char from this token.
115 */
116 return kallsyms_token_table[kallsyms_token_index[kallsyms_names[off + 1]]];
117}
118
119
120/*
121 * Find the offset on the compressed stream given and index in the
122 * kallsyms array.
123 */
124static unsigned int get_symbol_offset(unsigned long pos)
125{
126 const u8 *name;
127 int i;
128
129 /*
130 * Use the closest marker we have. We have markers every 256 positions,
131 * so that should be close enough.
132 */
133 name = &kallsyms_names[kallsyms_markers[pos >> 8]];
134
135 /*
136 * Sequentially scan all the symbols up to the point we're searching
137 * for. Every symbol is stored in a [<len>][<len> bytes of data] format,
138 * so we just need to add the len to the current pointer for every
139 * symbol we wish to skip.
140 */
141 for (i = 0; i < (pos & 0xFF); i++)
142 name = name + (*name) + 1;
143
144 return name - kallsyms_names;
145}
146
147static unsigned long kallsyms_sym_address(int idx)
148{
149 if (!IS_ENABLED(CONFIG_KALLSYMS_BASE_RELATIVE))
150 return kallsyms_addresses[idx];
151
152 /* values are unsigned offsets if --absolute-percpu is not in effect */
153 if (!IS_ENABLED(CONFIG_KALLSYMS_ABSOLUTE_PERCPU))
154 return kallsyms_relative_base + (u32)kallsyms_offsets[idx];
155
156 /* ...otherwise, positive offsets are absolute values */
157 if (kallsyms_offsets[idx] >= 0)
158 return kallsyms_offsets[idx];
159
160 /* ...and negative offsets are relative to kallsyms_relative_base - 1 */
161 return kallsyms_relative_base - 1 - kallsyms_offsets[idx];
162}
163
164/* Lookup the address for this symbol. Returns 0 if not found. */
165unsigned long kallsyms_lookup_name(const char *name)
166{
167 char namebuf[KSYM_NAME_LEN];
168 unsigned long i;
169 unsigned int off;
170
171 for (i = 0, off = 0; i < kallsyms_num_syms; i++) {
172 off = kallsyms_expand_symbol(off, namebuf, ARRAY_SIZE(namebuf));
173
174 if (strcmp(namebuf, name) == 0)
175 return kallsyms_sym_address(i);
176 }
177 return module_kallsyms_lookup_name(name);
178}
179
180int kallsyms_on_each_symbol(int (*fn)(void *, const char *, struct module *,
181 unsigned long),
182 void *data)
183{
184 char namebuf[KSYM_NAME_LEN];
185 unsigned long i;
186 unsigned int off;
187 int ret;
188
189 for (i = 0, off = 0; i < kallsyms_num_syms; i++) {
190 off = kallsyms_expand_symbol(off, namebuf, ARRAY_SIZE(namebuf));
191 ret = fn(data, namebuf, NULL, kallsyms_sym_address(i));
192 if (ret != 0)
193 return ret;
194 }
195 return module_kallsyms_on_each_symbol(fn, data);
196}
197
198static unsigned long get_symbol_pos(unsigned long addr,
199 unsigned long *symbolsize,
200 unsigned long *offset)
201{
202 unsigned long symbol_start = 0, symbol_end = 0;
203 unsigned long i, low, high, mid;
204
205 /* This kernel should never had been booted. */
206 if (!IS_ENABLED(CONFIG_KALLSYMS_BASE_RELATIVE))
207 BUG_ON(!kallsyms_addresses);
208 else
209 BUG_ON(!kallsyms_offsets);
210
211 /* Do a binary search on the sorted kallsyms_addresses array. */
212 low = 0;
213 high = kallsyms_num_syms;
214
215 while (high - low > 1) {
216 mid = low + (high - low) / 2;
217 if (kallsyms_sym_address(mid) <= addr)
218 low = mid;
219 else
220 high = mid;
221 }
222
223 /*
224 * Search for the first aliased symbol. Aliased
225 * symbols are symbols with the same address.
226 */
227 while (low && kallsyms_sym_address(low-1) == kallsyms_sym_address(low))
228 --low;
229
230 symbol_start = kallsyms_sym_address(low);
231
232 /* Search for next non-aliased symbol. */
233 for (i = low + 1; i < kallsyms_num_syms; i++) {
234 if (kallsyms_sym_address(i) > symbol_start) {
235 symbol_end = kallsyms_sym_address(i);
236 break;
237 }
238 }
239
240 /* If we found no next symbol, we use the end of the section. */
241 if (!symbol_end) {
242 if (is_kernel_inittext(addr))
243 symbol_end = (unsigned long)_einittext;
244 else if (IS_ENABLED(CONFIG_KALLSYMS_ALL))
245 symbol_end = (unsigned long)_end;
246 else
247 symbol_end = (unsigned long)_etext;
248 }
249
250 if (symbolsize)
251 *symbolsize = symbol_end - symbol_start;
252 if (offset)
253 *offset = addr - symbol_start;
254
255 return low;
256}
257
258/*
259 * Lookup an address but don't bother to find any names.
260 */
261int kallsyms_lookup_size_offset(unsigned long addr, unsigned long *symbolsize,
262 unsigned long *offset)
263{
264 char namebuf[KSYM_NAME_LEN];
265
266 if (is_ksym_addr(addr)) {
267 get_symbol_pos(addr, symbolsize, offset);
268 return 1;
269 }
270 return !!module_address_lookup(addr, symbolsize, offset, NULL, namebuf) ||
271 !!__bpf_address_lookup(addr, symbolsize, offset, namebuf);
272}
273
274/*
275 * Lookup an address
276 * - modname is set to NULL if it's in the kernel.
277 * - We guarantee that the returned name is valid until we reschedule even if.
278 * It resides in a module.
279 * - We also guarantee that modname will be valid until rescheduled.
280 */
281const char *kallsyms_lookup(unsigned long addr,
282 unsigned long *symbolsize,
283 unsigned long *offset,
284 char **modname, char *namebuf)
285{
286 const char *ret;
287
288 namebuf[KSYM_NAME_LEN - 1] = 0;
289 namebuf[0] = 0;
290
291 if (is_ksym_addr(addr)) {
292 unsigned long pos;
293
294 pos = get_symbol_pos(addr, symbolsize, offset);
295 /* Grab name */
296 kallsyms_expand_symbol(get_symbol_offset(pos),
297 namebuf, KSYM_NAME_LEN);
298 if (modname)
299 *modname = NULL;
300 return namebuf;
301 }
302
303 /* See if it's in a module or a BPF JITed image. */
304 ret = module_address_lookup(addr, symbolsize, offset,
305 modname, namebuf);
306 if (!ret)
307 ret = bpf_address_lookup(addr, symbolsize,
308 offset, modname, namebuf);
309
310 if (!ret)
311 ret = ftrace_mod_address_lookup(addr, symbolsize,
312 offset, modname, namebuf);
313 return ret;
314}
315
316int lookup_symbol_name(unsigned long addr, char *symname)
317{
318 symname[0] = '\0';
319 symname[KSYM_NAME_LEN - 1] = '\0';
320
321 if (is_ksym_addr(addr)) {
322 unsigned long pos;
323
324 pos = get_symbol_pos(addr, NULL, NULL);
325 /* Grab name */
326 kallsyms_expand_symbol(get_symbol_offset(pos),
327 symname, KSYM_NAME_LEN);
328 return 0;
329 }
330 /* See if it's in a module. */
331 return lookup_module_symbol_name(addr, symname);
332}
333
334int lookup_symbol_attrs(unsigned long addr, unsigned long *size,
335 unsigned long *offset, char *modname, char *name)
336{
337 name[0] = '\0';
338 name[KSYM_NAME_LEN - 1] = '\0';
339
340 if (is_ksym_addr(addr)) {
341 unsigned long pos;
342
343 pos = get_symbol_pos(addr, size, offset);
344 /* Grab name */
345 kallsyms_expand_symbol(get_symbol_offset(pos),
346 name, KSYM_NAME_LEN);
347 modname[0] = '\0';
348 return 0;
349 }
350 /* See if it's in a module. */
351 return lookup_module_symbol_attrs(addr, size, offset, modname, name);
352}
353
354/* Look up a kernel symbol and return it in a text buffer. */
355static int __sprint_symbol(char *buffer, unsigned long address,
356 int symbol_offset, int add_offset)
357{
358 char *modname;
359 const char *name;
360 unsigned long offset, size;
361 int len;
362
363 address += symbol_offset;
364 name = kallsyms_lookup(address, &size, &offset, &modname, buffer);
365 if (!name)
366 return sprintf(buffer, "0x%lx", address - symbol_offset);
367
368 if (name != buffer)
369 strcpy(buffer, name);
370 len = strlen(buffer);
371 offset -= symbol_offset;
372
373 if (add_offset)
374 len += sprintf(buffer + len, "+%#lx/%#lx", offset, size);
375
376 if (modname)
377 len += sprintf(buffer + len, " [%s]", modname);
378
379 return len;
380}
381
382/**
383 * sprint_symbol - Look up a kernel symbol and return it in a text buffer
384 * @buffer: buffer to be stored
385 * @address: address to lookup
386 *
387 * This function looks up a kernel symbol with @address and stores its name,
388 * offset, size and module name to @buffer if possible. If no symbol was found,
389 * just saves its @address as is.
390 *
391 * This function returns the number of bytes stored in @buffer.
392 */
393int sprint_symbol(char *buffer, unsigned long address)
394{
395 return __sprint_symbol(buffer, address, 0, 1);
396}
397EXPORT_SYMBOL_GPL(sprint_symbol);
398
399/**
400 * sprint_symbol_no_offset - Look up a kernel symbol and return it in a text buffer
401 * @buffer: buffer to be stored
402 * @address: address to lookup
403 *
404 * This function looks up a kernel symbol with @address and stores its name
405 * and module name to @buffer if possible. If no symbol was found, just saves
406 * its @address as is.
407 *
408 * This function returns the number of bytes stored in @buffer.
409 */
410int sprint_symbol_no_offset(char *buffer, unsigned long address)
411{
412 return __sprint_symbol(buffer, address, 0, 0);
413}
414EXPORT_SYMBOL_GPL(sprint_symbol_no_offset);
415
416/**
417 * sprint_backtrace - Look up a backtrace symbol and return it in a text buffer
418 * @buffer: buffer to be stored
419 * @address: address to lookup
420 *
421 * This function is for stack backtrace and does the same thing as
422 * sprint_symbol() but with modified/decreased @address. If there is a
423 * tail-call to the function marked "noreturn", gcc optimized out code after
424 * the call so that the stack-saved return address could point outside of the
425 * caller. This function ensures that kallsyms will find the original caller
426 * by decreasing @address.
427 *
428 * This function returns the number of bytes stored in @buffer.
429 */
430int sprint_backtrace(char *buffer, unsigned long address)
431{
432 return __sprint_symbol(buffer, address, -1, 1);
433}
434
435/* To avoid using get_symbol_offset for every symbol, we carry prefix along. */
436struct kallsym_iter {
437 loff_t pos;
438 loff_t pos_arch_end;
439 loff_t pos_mod_end;
440 loff_t pos_ftrace_mod_end;
441 loff_t pos_bpf_end;
442 unsigned long value;
443 unsigned int nameoff; /* If iterating in core kernel symbols. */
444 char type;
445 char name[KSYM_NAME_LEN];
446 char module_name[MODULE_NAME_LEN];
447 int exported;
448 int show_value;
449};
450
451int __weak arch_get_kallsym(unsigned int symnum, unsigned long *value,
452 char *type, char *name)
453{
454 return -EINVAL;
455}
456
457static int get_ksymbol_arch(struct kallsym_iter *iter)
458{
459 int ret = arch_get_kallsym(iter->pos - kallsyms_num_syms,
460 &iter->value, &iter->type,
461 iter->name);
462
463 if (ret < 0) {
464 iter->pos_arch_end = iter->pos;
465 return 0;
466 }
467
468 return 1;
469}
470
471static int get_ksymbol_mod(struct kallsym_iter *iter)
472{
473 int ret = module_get_kallsym(iter->pos - iter->pos_arch_end,
474 &iter->value, &iter->type,
475 iter->name, iter->module_name,
476 &iter->exported);
477 if (ret < 0) {
478 iter->pos_mod_end = iter->pos;
479 return 0;
480 }
481
482 return 1;
483}
484
485/*
486 * ftrace_mod_get_kallsym() may also get symbols for pages allocated for ftrace
487 * purposes. In that case "__builtin__ftrace" is used as a module name, even
488 * though "__builtin__ftrace" is not a module.
489 */
490static int get_ksymbol_ftrace_mod(struct kallsym_iter *iter)
491{
492 int ret = ftrace_mod_get_kallsym(iter->pos - iter->pos_mod_end,
493 &iter->value, &iter->type,
494 iter->name, iter->module_name,
495 &iter->exported);
496 if (ret < 0) {
497 iter->pos_ftrace_mod_end = iter->pos;
498 return 0;
499 }
500
501 return 1;
502}
503
504static int get_ksymbol_bpf(struct kallsym_iter *iter)
505{
506 int ret;
507
508 strlcpy(iter->module_name, "bpf", MODULE_NAME_LEN);
509 iter->exported = 0;
510 ret = bpf_get_kallsym(iter->pos - iter->pos_ftrace_mod_end,
511 &iter->value, &iter->type,
512 iter->name);
513 if (ret < 0) {
514 iter->pos_bpf_end = iter->pos;
515 return 0;
516 }
517
518 return 1;
519}
520
521/*
522 * This uses "__builtin__kprobes" as a module name for symbols for pages
523 * allocated for kprobes' purposes, even though "__builtin__kprobes" is not a
524 * module.
525 */
526static int get_ksymbol_kprobe(struct kallsym_iter *iter)
527{
528 strlcpy(iter->module_name, "__builtin__kprobes", MODULE_NAME_LEN);
529 iter->exported = 0;
530 return kprobe_get_kallsym(iter->pos - iter->pos_bpf_end,
531 &iter->value, &iter->type,
532 iter->name) < 0 ? 0 : 1;
533}
534
535/* Returns space to next name. */
536static unsigned long get_ksymbol_core(struct kallsym_iter *iter)
537{
538 unsigned off = iter->nameoff;
539
540 iter->module_name[0] = '\0';
541 iter->value = kallsyms_sym_address(iter->pos);
542
543 iter->type = kallsyms_get_symbol_type(off);
544
545 off = kallsyms_expand_symbol(off, iter->name, ARRAY_SIZE(iter->name));
546
547 return off - iter->nameoff;
548}
549
550static void reset_iter(struct kallsym_iter *iter, loff_t new_pos)
551{
552 iter->name[0] = '\0';
553 iter->nameoff = get_symbol_offset(new_pos);
554 iter->pos = new_pos;
555 if (new_pos == 0) {
556 iter->pos_arch_end = 0;
557 iter->pos_mod_end = 0;
558 iter->pos_ftrace_mod_end = 0;
559 iter->pos_bpf_end = 0;
560 }
561}
562
563/*
564 * The end position (last + 1) of each additional kallsyms section is recorded
565 * in iter->pos_..._end as each section is added, and so can be used to
566 * determine which get_ksymbol_...() function to call next.
567 */
568static int update_iter_mod(struct kallsym_iter *iter, loff_t pos)
569{
570 iter->pos = pos;
571
572 if ((!iter->pos_arch_end || iter->pos_arch_end > pos) &&
573 get_ksymbol_arch(iter))
574 return 1;
575
576 if ((!iter->pos_mod_end || iter->pos_mod_end > pos) &&
577 get_ksymbol_mod(iter))
578 return 1;
579
580 if ((!iter->pos_ftrace_mod_end || iter->pos_ftrace_mod_end > pos) &&
581 get_ksymbol_ftrace_mod(iter))
582 return 1;
583
584 if ((!iter->pos_bpf_end || iter->pos_bpf_end > pos) &&
585 get_ksymbol_bpf(iter))
586 return 1;
587
588 return get_ksymbol_kprobe(iter);
589}
590
591/* Returns false if pos at or past end of file. */
592static int update_iter(struct kallsym_iter *iter, loff_t pos)
593{
594 /* Module symbols can be accessed randomly. */
595 if (pos >= kallsyms_num_syms)
596 return update_iter_mod(iter, pos);
597
598 /* If we're not on the desired position, reset to new position. */
599 if (pos != iter->pos)
600 reset_iter(iter, pos);
601
602 iter->nameoff += get_ksymbol_core(iter);
603 iter->pos++;
604
605 return 1;
606}
607
608static void *s_next(struct seq_file *m, void *p, loff_t *pos)
609{
610 (*pos)++;
611
612 if (!update_iter(m->private, *pos))
613 return NULL;
614 return p;
615}
616
617static void *s_start(struct seq_file *m, loff_t *pos)
618{
619 if (!update_iter(m->private, *pos))
620 return NULL;
621 return m->private;
622}
623
624static void s_stop(struct seq_file *m, void *p)
625{
626}
627
628static int s_show(struct seq_file *m, void *p)
629{
630 void *value;
631 struct kallsym_iter *iter = m->private;
632
633 /* Some debugging symbols have no name. Ignore them. */
634 if (!iter->name[0])
635 return 0;
636
637 value = iter->show_value ? (void *)iter->value : NULL;
638
639 if (iter->module_name[0]) {
640 char type;
641
642 /*
643 * Label it "global" if it is exported,
644 * "local" if not exported.
645 */
646 type = iter->exported ? toupper(iter->type) :
647 tolower(iter->type);
648 seq_printf(m, "%px %c %s\t[%s]\n", value,
649 type, iter->name, iter->module_name);
650 } else
651 seq_printf(m, "%px %c %s\n", value,
652 iter->type, iter->name);
653 return 0;
654}
655
656static const struct seq_operations kallsyms_op = {
657 .start = s_start,
658 .next = s_next,
659 .stop = s_stop,
660 .show = s_show
661};
662
663static inline int kallsyms_for_perf(void)
664{
665#ifdef CONFIG_PERF_EVENTS
666 extern int sysctl_perf_event_paranoid;
667 if (sysctl_perf_event_paranoid <= 1)
668 return 1;
669#endif
670 return 0;
671}
672
673/*
674 * We show kallsyms information even to normal users if we've enabled
675 * kernel profiling and are explicitly not paranoid (so kptr_restrict
676 * is clear, and sysctl_perf_event_paranoid isn't set).
677 *
678 * Otherwise, require CAP_SYSLOG (assuming kptr_restrict isn't set to
679 * block even that).
680 */
681bool kallsyms_show_value(const struct cred *cred)
682{
683 switch (kptr_restrict) {
684 case 0:
685 if (kallsyms_for_perf())
686 return true;
687 fallthrough;
688 case 1:
689 if (security_capable(cred, &init_user_ns, CAP_SYSLOG,
690 CAP_OPT_NOAUDIT) == 0)
691 return true;
692 fallthrough;
693 default:
694 return false;
695 }
696}
697
698static int kallsyms_open(struct inode *inode, struct file *file)
699{
700 /*
701 * We keep iterator in m->private, since normal case is to
702 * s_start from where we left off, so we avoid doing
703 * using get_symbol_offset for every symbol.
704 */
705 struct kallsym_iter *iter;
706 iter = __seq_open_private(file, &kallsyms_op, sizeof(*iter));
707 if (!iter)
708 return -ENOMEM;
709 reset_iter(iter, 0);
710
711 /*
712 * Instead of checking this on every s_show() call, cache
713 * the result here at open time.
714 */
715 iter->show_value = kallsyms_show_value(file->f_cred);
716 return 0;
717}
718
719#ifdef CONFIG_KGDB_KDB
720const char *kdb_walk_kallsyms(loff_t *pos)
721{
722 static struct kallsym_iter kdb_walk_kallsyms_iter;
723 if (*pos == 0) {
724 memset(&kdb_walk_kallsyms_iter, 0,
725 sizeof(kdb_walk_kallsyms_iter));
726 reset_iter(&kdb_walk_kallsyms_iter, 0);
727 }
728 while (1) {
729 if (!update_iter(&kdb_walk_kallsyms_iter, *pos))
730 return NULL;
731 ++*pos;
732 /* Some debugging symbols have no name. Ignore them. */
733 if (kdb_walk_kallsyms_iter.name[0])
734 return kdb_walk_kallsyms_iter.name;
735 }
736}
737#endif /* CONFIG_KGDB_KDB */
738
739static const struct proc_ops kallsyms_proc_ops = {
740 .proc_open = kallsyms_open,
741 .proc_read = seq_read,
742 .proc_lseek = seq_lseek,
743 .proc_release = seq_release_private,
744};
745
746static int __init kallsyms_init(void)
747{
748 proc_create("kallsyms", 0444, NULL, &kallsyms_proc_ops);
749 return 0;
750}
751device_initcall(kallsyms_init);