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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
27#include <asm/sections.h>
28
29#ifdef CONFIG_KALLSYMS_ALL
30#define all_var 1
31#else
32#define all_var 0
33#endif
34
35/*
36 * These will be re-linked against their real values
37 * during the second link stage.
38 */
39extern const unsigned long kallsyms_addresses[] __attribute__((weak));
40extern const u8 kallsyms_names[] __attribute__((weak));
41
42/*
43 * Tell the compiler that the count isn't in the small data section if the arch
44 * has one (eg: FRV).
45 */
46extern const unsigned long kallsyms_num_syms
47__attribute__((weak, section(".rodata")));
48
49extern const u8 kallsyms_token_table[] __attribute__((weak));
50extern const u16 kallsyms_token_index[] __attribute__((weak));
51
52extern const unsigned long kallsyms_markers[] __attribute__((weak));
53
54static inline int is_kernel_inittext(unsigned long addr)
55{
56 if (addr >= (unsigned long)_sinittext
57 && addr <= (unsigned long)_einittext)
58 return 1;
59 return 0;
60}
61
62static inline int is_kernel_text(unsigned long addr)
63{
64 if ((addr >= (unsigned long)_stext && addr <= (unsigned long)_etext) ||
65 arch_is_kernel_text(addr))
66 return 1;
67 return in_gate_area_no_mm(addr);
68}
69
70static inline int is_kernel(unsigned long addr)
71{
72 if (addr >= (unsigned long)_stext && addr <= (unsigned long)_end)
73 return 1;
74 return in_gate_area_no_mm(addr);
75}
76
77static int is_ksym_addr(unsigned long addr)
78{
79 if (all_var)
80 return is_kernel(addr);
81
82 return is_kernel_text(addr) || is_kernel_inittext(addr);
83}
84
85/*
86 * Expand a compressed symbol data into the resulting uncompressed string,
87 * given the offset to where the symbol is in the compressed stream.
88 */
89static unsigned int kallsyms_expand_symbol(unsigned int off, char *result)
90{
91 int len, skipped_first = 0;
92 const u8 *tptr, *data;
93
94 /* Get the compressed symbol length from the first symbol byte. */
95 data = &kallsyms_names[off];
96 len = *data;
97 data++;
98
99 /*
100 * Update the offset to return the offset for the next symbol on
101 * the compressed stream.
102 */
103 off += len + 1;
104
105 /*
106 * For every byte on the compressed symbol data, copy the table
107 * entry for that byte.
108 */
109 while (len) {
110 tptr = &kallsyms_token_table[kallsyms_token_index[*data]];
111 data++;
112 len--;
113
114 while (*tptr) {
115 if (skipped_first) {
116 *result = *tptr;
117 result++;
118 } else
119 skipped_first = 1;
120 tptr++;
121 }
122 }
123
124 *result = '\0';
125
126 /* Return to offset to the next symbol. */
127 return off;
128}
129
130/*
131 * Get symbol type information. This is encoded as a single char at the
132 * beginning of the symbol name.
133 */
134static char kallsyms_get_symbol_type(unsigned int off)
135{
136 /*
137 * Get just the first code, look it up in the token table,
138 * and return the first char from this token.
139 */
140 return kallsyms_token_table[kallsyms_token_index[kallsyms_names[off + 1]]];
141}
142
143
144/*
145 * Find the offset on the compressed stream given and index in the
146 * kallsyms array.
147 */
148static unsigned int get_symbol_offset(unsigned long pos)
149{
150 const u8 *name;
151 int i;
152
153 /*
154 * Use the closest marker we have. We have markers every 256 positions,
155 * so that should be close enough.
156 */
157 name = &kallsyms_names[kallsyms_markers[pos >> 8]];
158
159 /*
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.
164 */
165 for (i = 0; i < (pos & 0xFF); i++)
166 name = name + (*name) + 1;
167
168 return name - kallsyms_names;
169}
170
171/* Lookup the address for this symbol. Returns 0 if not found. */
172unsigned long kallsyms_lookup_name(const char *name)
173{
174 char namebuf[KSYM_NAME_LEN];
175 unsigned long i;
176 unsigned int off;
177
178 for (i = 0, off = 0; i < kallsyms_num_syms; i++) {
179 off = kallsyms_expand_symbol(off, namebuf);
180
181 if (strcmp(namebuf, name) == 0)
182 return kallsyms_addresses[i];
183 }
184 return module_kallsyms_lookup_name(name);
185}
186EXPORT_SYMBOL_GPL(kallsyms_lookup_name);
187
188int kallsyms_on_each_symbol(int (*fn)(void *, const char *, struct module *,
189 unsigned long),
190 void *data)
191{
192 char namebuf[KSYM_NAME_LEN];
193 unsigned long i;
194 unsigned int off;
195 int ret;
196
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]);
200 if (ret != 0)
201 return ret;
202 }
203 return module_kallsyms_on_each_symbol(fn, data);
204}
205EXPORT_SYMBOL_GPL(kallsyms_on_each_symbol);
206
207static unsigned long get_symbol_pos(unsigned long addr,
208 unsigned long *symbolsize,
209 unsigned long *offset)
210{
211 unsigned long symbol_start = 0, symbol_end = 0;
212 unsigned long i, low, high, mid;
213
214 /* This kernel should never had been booted. */
215 BUG_ON(!kallsyms_addresses);
216
217 /* Do a binary search on the sorted kallsyms_addresses array. */
218 low = 0;
219 high = kallsyms_num_syms;
220
221 while (high - low > 1) {
222 mid = low + (high - low) / 2;
223 if (kallsyms_addresses[mid] <= addr)
224 low = mid;
225 else
226 high = mid;
227 }
228
229 /*
230 * Search for the first aliased symbol. Aliased
231 * symbols are symbols with the same address.
232 */
233 while (low && kallsyms_addresses[low-1] == kallsyms_addresses[low])
234 --low;
235
236 symbol_start = kallsyms_addresses[low];
237
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];
242 break;
243 }
244 }
245
246 /* If we found no next symbol, we use the end of the section. */
247 if (!symbol_end) {
248 if (is_kernel_inittext(addr))
249 symbol_end = (unsigned long)_einittext;
250 else if (all_var)
251 symbol_end = (unsigned long)_end;
252 else
253 symbol_end = (unsigned long)_etext;
254 }
255
256 if (symbolsize)
257 *symbolsize = symbol_end - symbol_start;
258 if (offset)
259 *offset = addr - symbol_start;
260
261 return low;
262}
263
264/*
265 * Lookup an address but don't bother to find any names.
266 */
267int kallsyms_lookup_size_offset(unsigned long addr, unsigned long *symbolsize,
268 unsigned long *offset)
269{
270 char namebuf[KSYM_NAME_LEN];
271 if (is_ksym_addr(addr))
272 return !!get_symbol_pos(addr, symbolsize, offset);
273
274 return !!module_address_lookup(addr, symbolsize, offset, NULL, namebuf);
275}
276
277/*
278 * Lookup an address
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.
283 */
284const char *kallsyms_lookup(unsigned long addr,
285 unsigned long *symbolsize,
286 unsigned long *offset,
287 char **modname, char *namebuf)
288{
289 namebuf[KSYM_NAME_LEN - 1] = 0;
290 namebuf[0] = 0;
291
292 if (is_ksym_addr(addr)) {
293 unsigned long pos;
294
295 pos = get_symbol_pos(addr, symbolsize, offset);
296 /* Grab name */
297 kallsyms_expand_symbol(get_symbol_offset(pos), namebuf);
298 if (modname)
299 *modname = NULL;
300 return namebuf;
301 }
302
303 /* See if it's in a module. */
304 return module_address_lookup(addr, symbolsize, offset, modname,
305 namebuf);
306}
307
308int lookup_symbol_name(unsigned long addr, char *symname)
309{
310 symname[0] = '\0';
311 symname[KSYM_NAME_LEN - 1] = '\0';
312
313 if (is_ksym_addr(addr)) {
314 unsigned long pos;
315
316 pos = get_symbol_pos(addr, NULL, NULL);
317 /* Grab name */
318 kallsyms_expand_symbol(get_symbol_offset(pos), symname);
319 return 0;
320 }
321 /* See if it's in a module. */
322 return lookup_module_symbol_name(addr, symname);
323}
324
325int lookup_symbol_attrs(unsigned long addr, unsigned long *size,
326 unsigned long *offset, char *modname, char *name)
327{
328 name[0] = '\0';
329 name[KSYM_NAME_LEN - 1] = '\0';
330
331 if (is_ksym_addr(addr)) {
332 unsigned long pos;
333
334 pos = get_symbol_pos(addr, size, offset);
335 /* Grab name */
336 kallsyms_expand_symbol(get_symbol_offset(pos), name);
337 modname[0] = '\0';
338 return 0;
339 }
340 /* See if it's in a module. */
341 return lookup_module_symbol_attrs(addr, size, offset, modname, name);
342}
343
344/* Look up a kernel symbol and return it in a text buffer. */
345static int __sprint_symbol(char *buffer, unsigned long address,
346 int symbol_offset, int add_offset)
347{
348 char *modname;
349 const char *name;
350 unsigned long offset, size;
351 int len;
352
353 address += symbol_offset;
354 name = kallsyms_lookup(address, &size, &offset, &modname, buffer);
355 if (!name)
356 return sprintf(buffer, "0x%lx", address);
357
358 if (name != buffer)
359 strcpy(buffer, name);
360 len = strlen(buffer);
361 offset -= symbol_offset;
362
363 if (add_offset)
364 len += sprintf(buffer + len, "+%#lx/%#lx", offset, size);
365
366 if (modname)
367 len += sprintf(buffer + len, " [%s]", modname);
368
369 return len;
370}
371
372/**
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
376 *
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.
380 *
381 * This function returns the number of bytes stored in @buffer.
382 */
383int sprint_symbol(char *buffer, unsigned long address)
384{
385 return __sprint_symbol(buffer, address, 0, 1);
386}
387EXPORT_SYMBOL_GPL(sprint_symbol);
388
389/**
390 * sprint_symbol_no_offset - Look up a kernel symbol and return it in a text buffer
391 * @buffer: buffer to be stored
392 * @address: address to lookup
393 *
394 * This function looks up a kernel symbol with @address and stores its name
395 * and module name to @buffer if possible. If no symbol was found, just saves
396 * its @address as is.
397 *
398 * This function returns the number of bytes stored in @buffer.
399 */
400int sprint_symbol_no_offset(char *buffer, unsigned long address)
401{
402 return __sprint_symbol(buffer, address, 0, 0);
403}
404EXPORT_SYMBOL_GPL(sprint_symbol_no_offset);
405
406/**
407 * sprint_backtrace - Look up a backtrace symbol and return it in a text buffer
408 * @buffer: buffer to be stored
409 * @address: address to lookup
410 *
411 * This function is for stack backtrace and does the same thing as
412 * sprint_symbol() but with modified/decreased @address. If there is a
413 * tail-call to the function marked "noreturn", gcc optimized out code after
414 * the call so that the stack-saved return address could point outside of the
415 * caller. This function ensures that kallsyms will find the original caller
416 * by decreasing @address.
417 *
418 * This function returns the number of bytes stored in @buffer.
419 */
420int sprint_backtrace(char *buffer, unsigned long address)
421{
422 return __sprint_symbol(buffer, address, -1, 1);
423}
424
425/* Look up a kernel symbol and print it to the kernel messages. */
426void __print_symbol(const char *fmt, unsigned long address)
427{
428 char buffer[KSYM_SYMBOL_LEN];
429
430 sprint_symbol(buffer, address);
431
432 printk(fmt, buffer);
433}
434EXPORT_SYMBOL(__print_symbol);
435
436/* To avoid using get_symbol_offset for every symbol, we carry prefix along. */
437struct kallsym_iter {
438 loff_t pos;
439 unsigned long value;
440 unsigned int nameoff; /* If iterating in core kernel symbols. */
441 char type;
442 char name[KSYM_NAME_LEN];
443 char module_name[MODULE_NAME_LEN];
444 int exported;
445};
446
447static int get_ksymbol_mod(struct kallsym_iter *iter)
448{
449 if (module_get_kallsym(iter->pos - kallsyms_num_syms, &iter->value,
450 &iter->type, iter->name, iter->module_name,
451 &iter->exported) < 0)
452 return 0;
453 return 1;
454}
455
456/* Returns space to next name. */
457static unsigned long get_ksymbol_core(struct kallsym_iter *iter)
458{
459 unsigned off = iter->nameoff;
460
461 iter->module_name[0] = '\0';
462 iter->value = kallsyms_addresses[iter->pos];
463
464 iter->type = kallsyms_get_symbol_type(off);
465
466 off = kallsyms_expand_symbol(off, iter->name);
467
468 return off - iter->nameoff;
469}
470
471static void reset_iter(struct kallsym_iter *iter, loff_t new_pos)
472{
473 iter->name[0] = '\0';
474 iter->nameoff = get_symbol_offset(new_pos);
475 iter->pos = new_pos;
476}
477
478/* Returns false if pos at or past end of file. */
479static int update_iter(struct kallsym_iter *iter, loff_t pos)
480{
481 /* Module symbols can be accessed randomly. */
482 if (pos >= kallsyms_num_syms) {
483 iter->pos = pos;
484 return get_ksymbol_mod(iter);
485 }
486
487 /* If we're not on the desired position, reset to new position. */
488 if (pos != iter->pos)
489 reset_iter(iter, pos);
490
491 iter->nameoff += get_ksymbol_core(iter);
492 iter->pos++;
493
494 return 1;
495}
496
497static void *s_next(struct seq_file *m, void *p, loff_t *pos)
498{
499 (*pos)++;
500
501 if (!update_iter(m->private, *pos))
502 return NULL;
503 return p;
504}
505
506static void *s_start(struct seq_file *m, loff_t *pos)
507{
508 if (!update_iter(m->private, *pos))
509 return NULL;
510 return m->private;
511}
512
513static void s_stop(struct seq_file *m, void *p)
514{
515}
516
517static int s_show(struct seq_file *m, void *p)
518{
519 struct kallsym_iter *iter = m->private;
520
521 /* Some debugging symbols have no name. Ignore them. */
522 if (!iter->name[0])
523 return 0;
524
525 if (iter->module_name[0]) {
526 char type;
527
528 /*
529 * Label it "global" if it is exported,
530 * "local" if not exported.
531 */
532 type = iter->exported ? toupper(iter->type) :
533 tolower(iter->type);
534 seq_printf(m, "%pK %c %s\t[%s]\n", (void *)iter->value,
535 type, iter->name, iter->module_name);
536 } else
537 seq_printf(m, "%pK %c %s\n", (void *)iter->value,
538 iter->type, iter->name);
539 return 0;
540}
541
542static const struct seq_operations kallsyms_op = {
543 .start = s_start,
544 .next = s_next,
545 .stop = s_stop,
546 .show = s_show
547};
548
549static int kallsyms_open(struct inode *inode, struct file *file)
550{
551 /*
552 * We keep iterator in m->private, since normal case is to
553 * s_start from where we left off, so we avoid doing
554 * using get_symbol_offset for every symbol.
555 */
556 struct kallsym_iter *iter;
557 int ret;
558
559 iter = kmalloc(sizeof(*iter), GFP_KERNEL);
560 if (!iter)
561 return -ENOMEM;
562 reset_iter(iter, 0);
563
564 ret = seq_open(file, &kallsyms_op);
565 if (ret == 0)
566 ((struct seq_file *)file->private_data)->private = iter;
567 else
568 kfree(iter);
569 return ret;
570}
571
572#ifdef CONFIG_KGDB_KDB
573const char *kdb_walk_kallsyms(loff_t *pos)
574{
575 static struct kallsym_iter kdb_walk_kallsyms_iter;
576 if (*pos == 0) {
577 memset(&kdb_walk_kallsyms_iter, 0,
578 sizeof(kdb_walk_kallsyms_iter));
579 reset_iter(&kdb_walk_kallsyms_iter, 0);
580 }
581 while (1) {
582 if (!update_iter(&kdb_walk_kallsyms_iter, *pos))
583 return NULL;
584 ++*pos;
585 /* Some debugging symbols have no name. Ignore them. */
586 if (kdb_walk_kallsyms_iter.name[0])
587 return kdb_walk_kallsyms_iter.name;
588 }
589}
590#endif /* CONFIG_KGDB_KDB */
591
592static const struct file_operations kallsyms_operations = {
593 .open = kallsyms_open,
594 .read = seq_read,
595 .llseek = seq_lseek,
596 .release = seq_release_private,
597};
598
599static int __init kallsyms_init(void)
600{
601 proc_create("kallsyms", 0444, NULL, &kallsyms_operations);
602 return 0;
603}
604device_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/build_bug.h>
29#include <linux/compiler.h>
30#include <linux/module.h>
31#include <linux/kernel.h>
32
33/*
34 * These will be re-linked against their real values
35 * during the second link stage.
36 */
37extern const unsigned long kallsyms_addresses[] __weak;
38extern const int kallsyms_offsets[] __weak;
39extern const u8 kallsyms_names[] __weak;
40
41/*
42 * Tell the compiler that the count isn't in the small data section if the arch
43 * has one (eg: FRV).
44 */
45extern const unsigned int kallsyms_num_syms
46__section(".rodata") __attribute__((weak));
47
48extern const unsigned long kallsyms_relative_base
49__section(".rodata") __attribute__((weak));
50
51extern const char kallsyms_token_table[] __weak;
52extern const u16 kallsyms_token_index[] __weak;
53
54extern const unsigned int kallsyms_markers[] __weak;
55
56/*
57 * Expand a compressed symbol data into the resulting uncompressed string,
58 * if uncompressed string is too long (>= maxlen), it will be truncated,
59 * given the offset to where the symbol is in the compressed stream.
60 */
61static unsigned int kallsyms_expand_symbol(unsigned int off,
62 char *result, size_t maxlen)
63{
64 int len, skipped_first = 0;
65 const char *tptr;
66 const u8 *data;
67
68 /* Get the compressed symbol length from the first symbol byte. */
69 data = &kallsyms_names[off];
70 len = *data;
71 data++;
72
73 /*
74 * Update the offset to return the offset for the next symbol on
75 * the compressed stream.
76 */
77 off += len + 1;
78
79 /*
80 * For every byte on the compressed symbol data, copy the table
81 * entry for that byte.
82 */
83 while (len) {
84 tptr = &kallsyms_token_table[kallsyms_token_index[*data]];
85 data++;
86 len--;
87
88 while (*tptr) {
89 if (skipped_first) {
90 if (maxlen <= 1)
91 goto tail;
92 *result = *tptr;
93 result++;
94 maxlen--;
95 } else
96 skipped_first = 1;
97 tptr++;
98 }
99 }
100
101tail:
102 if (maxlen)
103 *result = '\0';
104
105 /* Return to offset to the next symbol. */
106 return off;
107}
108
109/*
110 * Get symbol type information. This is encoded as a single char at the
111 * beginning of the symbol name.
112 */
113static char kallsyms_get_symbol_type(unsigned int off)
114{
115 /*
116 * Get just the first code, look it up in the token table,
117 * and return the first char from this token.
118 */
119 return kallsyms_token_table[kallsyms_token_index[kallsyms_names[off + 1]]];
120}
121
122
123/*
124 * Find the offset on the compressed stream given and index in the
125 * kallsyms array.
126 */
127static unsigned int get_symbol_offset(unsigned long pos)
128{
129 const u8 *name;
130 int i;
131
132 /*
133 * Use the closest marker we have. We have markers every 256 positions,
134 * so that should be close enough.
135 */
136 name = &kallsyms_names[kallsyms_markers[pos >> 8]];
137
138 /*
139 * Sequentially scan all the symbols up to the point we're searching
140 * for. Every symbol is stored in a [<len>][<len> bytes of data] format,
141 * so we just need to add the len to the current pointer for every
142 * symbol we wish to skip.
143 */
144 for (i = 0; i < (pos & 0xFF); i++)
145 name = name + (*name) + 1;
146
147 return name - kallsyms_names;
148}
149
150static unsigned long kallsyms_sym_address(int idx)
151{
152 if (!IS_ENABLED(CONFIG_KALLSYMS_BASE_RELATIVE))
153 return kallsyms_addresses[idx];
154
155 /* values are unsigned offsets if --absolute-percpu is not in effect */
156 if (!IS_ENABLED(CONFIG_KALLSYMS_ABSOLUTE_PERCPU))
157 return kallsyms_relative_base + (u32)kallsyms_offsets[idx];
158
159 /* ...otherwise, positive offsets are absolute values */
160 if (kallsyms_offsets[idx] >= 0)
161 return kallsyms_offsets[idx];
162
163 /* ...and negative offsets are relative to kallsyms_relative_base - 1 */
164 return kallsyms_relative_base - 1 - kallsyms_offsets[idx];
165}
166
167#if defined(CONFIG_CFI_CLANG) && defined(CONFIG_LTO_CLANG_THIN)
168/*
169 * LLVM appends a hash to static function names when ThinLTO and CFI are
170 * both enabled, i.e. foo() becomes foo$707af9a22804d33c81801f27dcfe489b.
171 * This causes confusion and potentially breaks user space tools, so we
172 * strip the suffix from expanded symbol names.
173 */
174static inline bool cleanup_symbol_name(char *s)
175{
176 char *res;
177
178 res = strrchr(s, '$');
179 if (res)
180 *res = '\0';
181
182 return res != NULL;
183}
184#else
185static inline bool cleanup_symbol_name(char *s) { return false; }
186#endif
187
188/* Lookup the address for this symbol. Returns 0 if not found. */
189unsigned long kallsyms_lookup_name(const char *name)
190{
191 char namebuf[KSYM_NAME_LEN];
192 unsigned long i;
193 unsigned int off;
194
195 for (i = 0, off = 0; i < kallsyms_num_syms; i++) {
196 off = kallsyms_expand_symbol(off, namebuf, ARRAY_SIZE(namebuf));
197
198 if (strcmp(namebuf, name) == 0)
199 return kallsyms_sym_address(i);
200
201 if (cleanup_symbol_name(namebuf) && strcmp(namebuf, name) == 0)
202 return kallsyms_sym_address(i);
203 }
204 return module_kallsyms_lookup_name(name);
205}
206
207#ifdef CONFIG_LIVEPATCH
208/*
209 * Iterate over all symbols in vmlinux. For symbols from modules use
210 * module_kallsyms_on_each_symbol instead.
211 */
212int kallsyms_on_each_symbol(int (*fn)(void *, const char *, struct module *,
213 unsigned long),
214 void *data)
215{
216 char namebuf[KSYM_NAME_LEN];
217 unsigned long i;
218 unsigned int off;
219 int ret;
220
221 for (i = 0, off = 0; i < kallsyms_num_syms; i++) {
222 off = kallsyms_expand_symbol(off, namebuf, ARRAY_SIZE(namebuf));
223 ret = fn(data, namebuf, NULL, kallsyms_sym_address(i));
224 if (ret != 0)
225 return ret;
226 }
227 return 0;
228}
229#endif /* CONFIG_LIVEPATCH */
230
231static unsigned long get_symbol_pos(unsigned long addr,
232 unsigned long *symbolsize,
233 unsigned long *offset)
234{
235 unsigned long symbol_start = 0, symbol_end = 0;
236 unsigned long i, low, high, mid;
237
238 /* This kernel should never had been booted. */
239 if (!IS_ENABLED(CONFIG_KALLSYMS_BASE_RELATIVE))
240 BUG_ON(!kallsyms_addresses);
241 else
242 BUG_ON(!kallsyms_offsets);
243
244 /* Do a binary search on the sorted kallsyms_addresses array. */
245 low = 0;
246 high = kallsyms_num_syms;
247
248 while (high - low > 1) {
249 mid = low + (high - low) / 2;
250 if (kallsyms_sym_address(mid) <= addr)
251 low = mid;
252 else
253 high = mid;
254 }
255
256 /*
257 * Search for the first aliased symbol. Aliased
258 * symbols are symbols with the same address.
259 */
260 while (low && kallsyms_sym_address(low-1) == kallsyms_sym_address(low))
261 --low;
262
263 symbol_start = kallsyms_sym_address(low);
264
265 /* Search for next non-aliased symbol. */
266 for (i = low + 1; i < kallsyms_num_syms; i++) {
267 if (kallsyms_sym_address(i) > symbol_start) {
268 symbol_end = kallsyms_sym_address(i);
269 break;
270 }
271 }
272
273 /* If we found no next symbol, we use the end of the section. */
274 if (!symbol_end) {
275 if (is_kernel_inittext(addr))
276 symbol_end = (unsigned long)_einittext;
277 else if (IS_ENABLED(CONFIG_KALLSYMS_ALL))
278 symbol_end = (unsigned long)_end;
279 else
280 symbol_end = (unsigned long)_etext;
281 }
282
283 if (symbolsize)
284 *symbolsize = symbol_end - symbol_start;
285 if (offset)
286 *offset = addr - symbol_start;
287
288 return low;
289}
290
291/*
292 * Lookup an address but don't bother to find any names.
293 */
294int kallsyms_lookup_size_offset(unsigned long addr, unsigned long *symbolsize,
295 unsigned long *offset)
296{
297 char namebuf[KSYM_NAME_LEN];
298
299 if (is_ksym_addr(addr)) {
300 get_symbol_pos(addr, symbolsize, offset);
301 return 1;
302 }
303 return !!module_address_lookup(addr, symbolsize, offset, NULL, NULL, namebuf) ||
304 !!__bpf_address_lookup(addr, symbolsize, offset, namebuf);
305}
306
307static const char *kallsyms_lookup_buildid(unsigned long addr,
308 unsigned long *symbolsize,
309 unsigned long *offset, char **modname,
310 const unsigned char **modbuildid, char *namebuf)
311{
312 const char *ret;
313
314 namebuf[KSYM_NAME_LEN - 1] = 0;
315 namebuf[0] = 0;
316
317 if (is_ksym_addr(addr)) {
318 unsigned long pos;
319
320 pos = get_symbol_pos(addr, symbolsize, offset);
321 /* Grab name */
322 kallsyms_expand_symbol(get_symbol_offset(pos),
323 namebuf, KSYM_NAME_LEN);
324 if (modname)
325 *modname = NULL;
326 if (modbuildid)
327 *modbuildid = NULL;
328
329 ret = namebuf;
330 goto found;
331 }
332
333 /* See if it's in a module or a BPF JITed image. */
334 ret = module_address_lookup(addr, symbolsize, offset,
335 modname, modbuildid, namebuf);
336 if (!ret)
337 ret = bpf_address_lookup(addr, symbolsize,
338 offset, modname, namebuf);
339
340 if (!ret)
341 ret = ftrace_mod_address_lookup(addr, symbolsize,
342 offset, modname, namebuf);
343
344found:
345 cleanup_symbol_name(namebuf);
346 return ret;
347}
348
349/*
350 * Lookup an address
351 * - modname is set to NULL if it's in the kernel.
352 * - We guarantee that the returned name is valid until we reschedule even if.
353 * It resides in a module.
354 * - We also guarantee that modname will be valid until rescheduled.
355 */
356const char *kallsyms_lookup(unsigned long addr,
357 unsigned long *symbolsize,
358 unsigned long *offset,
359 char **modname, char *namebuf)
360{
361 return kallsyms_lookup_buildid(addr, symbolsize, offset, modname,
362 NULL, namebuf);
363}
364
365int lookup_symbol_name(unsigned long addr, char *symname)
366{
367 int res;
368
369 symname[0] = '\0';
370 symname[KSYM_NAME_LEN - 1] = '\0';
371
372 if (is_ksym_addr(addr)) {
373 unsigned long pos;
374
375 pos = get_symbol_pos(addr, NULL, NULL);
376 /* Grab name */
377 kallsyms_expand_symbol(get_symbol_offset(pos),
378 symname, KSYM_NAME_LEN);
379 goto found;
380 }
381 /* See if it's in a module. */
382 res = lookup_module_symbol_name(addr, symname);
383 if (res)
384 return res;
385
386found:
387 cleanup_symbol_name(symname);
388 return 0;
389}
390
391int lookup_symbol_attrs(unsigned long addr, unsigned long *size,
392 unsigned long *offset, char *modname, char *name)
393{
394 int res;
395
396 name[0] = '\0';
397 name[KSYM_NAME_LEN - 1] = '\0';
398
399 if (is_ksym_addr(addr)) {
400 unsigned long pos;
401
402 pos = get_symbol_pos(addr, size, offset);
403 /* Grab name */
404 kallsyms_expand_symbol(get_symbol_offset(pos),
405 name, KSYM_NAME_LEN);
406 modname[0] = '\0';
407 goto found;
408 }
409 /* See if it's in a module. */
410 res = lookup_module_symbol_attrs(addr, size, offset, modname, name);
411 if (res)
412 return res;
413
414found:
415 cleanup_symbol_name(name);
416 return 0;
417}
418
419/* Look up a kernel symbol and return it in a text buffer. */
420static int __sprint_symbol(char *buffer, unsigned long address,
421 int symbol_offset, int add_offset, int add_buildid)
422{
423 char *modname;
424 const unsigned char *buildid;
425 const char *name;
426 unsigned long offset, size;
427 int len;
428
429 address += symbol_offset;
430 name = kallsyms_lookup_buildid(address, &size, &offset, &modname, &buildid,
431 buffer);
432 if (!name)
433 return sprintf(buffer, "0x%lx", address - symbol_offset);
434
435 if (name != buffer)
436 strcpy(buffer, name);
437 len = strlen(buffer);
438 offset -= symbol_offset;
439
440 if (add_offset)
441 len += sprintf(buffer + len, "+%#lx/%#lx", offset, size);
442
443 if (modname) {
444 len += sprintf(buffer + len, " [%s", modname);
445#if IS_ENABLED(CONFIG_STACKTRACE_BUILD_ID)
446 if (add_buildid && buildid) {
447 /* build ID should match length of sprintf */
448#if IS_ENABLED(CONFIG_MODULES)
449 static_assert(sizeof(typeof_member(struct module, build_id)) == 20);
450#endif
451 len += sprintf(buffer + len, " %20phN", buildid);
452 }
453#endif
454 len += sprintf(buffer + len, "]");
455 }
456
457 return len;
458}
459
460/**
461 * sprint_symbol - Look up a kernel symbol and return it in a text buffer
462 * @buffer: buffer to be stored
463 * @address: address to lookup
464 *
465 * This function looks up a kernel symbol with @address and stores its name,
466 * offset, size and module name to @buffer if possible. If no symbol was found,
467 * just saves its @address as is.
468 *
469 * This function returns the number of bytes stored in @buffer.
470 */
471int sprint_symbol(char *buffer, unsigned long address)
472{
473 return __sprint_symbol(buffer, address, 0, 1, 0);
474}
475EXPORT_SYMBOL_GPL(sprint_symbol);
476
477/**
478 * sprint_symbol_build_id - Look up a kernel symbol and return it in a text buffer
479 * @buffer: buffer to be stored
480 * @address: address to lookup
481 *
482 * This function looks up a kernel symbol with @address and stores its name,
483 * offset, size, module name and module build ID to @buffer if possible. If no
484 * symbol was found, just saves its @address as is.
485 *
486 * This function returns the number of bytes stored in @buffer.
487 */
488int sprint_symbol_build_id(char *buffer, unsigned long address)
489{
490 return __sprint_symbol(buffer, address, 0, 1, 1);
491}
492EXPORT_SYMBOL_GPL(sprint_symbol_build_id);
493
494/**
495 * sprint_symbol_no_offset - Look up a kernel symbol and return it in a text buffer
496 * @buffer: buffer to be stored
497 * @address: address to lookup
498 *
499 * This function looks up a kernel symbol with @address and stores its name
500 * and module name to @buffer if possible. If no symbol was found, just saves
501 * its @address as is.
502 *
503 * This function returns the number of bytes stored in @buffer.
504 */
505int sprint_symbol_no_offset(char *buffer, unsigned long address)
506{
507 return __sprint_symbol(buffer, address, 0, 0, 0);
508}
509EXPORT_SYMBOL_GPL(sprint_symbol_no_offset);
510
511/**
512 * sprint_backtrace - Look up a backtrace symbol and return it in a text buffer
513 * @buffer: buffer to be stored
514 * @address: address to lookup
515 *
516 * This function is for stack backtrace and does the same thing as
517 * sprint_symbol() but with modified/decreased @address. If there is a
518 * tail-call to the function marked "noreturn", gcc optimized out code after
519 * the call so that the stack-saved return address could point outside of the
520 * caller. This function ensures that kallsyms will find the original caller
521 * by decreasing @address.
522 *
523 * This function returns the number of bytes stored in @buffer.
524 */
525int sprint_backtrace(char *buffer, unsigned long address)
526{
527 return __sprint_symbol(buffer, address, -1, 1, 0);
528}
529
530/**
531 * sprint_backtrace_build_id - Look up a backtrace symbol and return it in a text buffer
532 * @buffer: buffer to be stored
533 * @address: address to lookup
534 *
535 * This function is for stack backtrace and does the same thing as
536 * sprint_symbol() but with modified/decreased @address. If there is a
537 * tail-call to the function marked "noreturn", gcc optimized out code after
538 * the call so that the stack-saved return address could point outside of the
539 * caller. This function ensures that kallsyms will find the original caller
540 * by decreasing @address. This function also appends the module build ID to
541 * the @buffer if @address is within a kernel module.
542 *
543 * This function returns the number of bytes stored in @buffer.
544 */
545int sprint_backtrace_build_id(char *buffer, unsigned long address)
546{
547 return __sprint_symbol(buffer, address, -1, 1, 1);
548}
549
550/* To avoid using get_symbol_offset for every symbol, we carry prefix along. */
551struct kallsym_iter {
552 loff_t pos;
553 loff_t pos_arch_end;
554 loff_t pos_mod_end;
555 loff_t pos_ftrace_mod_end;
556 loff_t pos_bpf_end;
557 unsigned long value;
558 unsigned int nameoff; /* If iterating in core kernel symbols. */
559 char type;
560 char name[KSYM_NAME_LEN];
561 char module_name[MODULE_NAME_LEN];
562 int exported;
563 int show_value;
564};
565
566int __weak arch_get_kallsym(unsigned int symnum, unsigned long *value,
567 char *type, char *name)
568{
569 return -EINVAL;
570}
571
572static int get_ksymbol_arch(struct kallsym_iter *iter)
573{
574 int ret = arch_get_kallsym(iter->pos - kallsyms_num_syms,
575 &iter->value, &iter->type,
576 iter->name);
577
578 if (ret < 0) {
579 iter->pos_arch_end = iter->pos;
580 return 0;
581 }
582
583 return 1;
584}
585
586static int get_ksymbol_mod(struct kallsym_iter *iter)
587{
588 int ret = module_get_kallsym(iter->pos - iter->pos_arch_end,
589 &iter->value, &iter->type,
590 iter->name, iter->module_name,
591 &iter->exported);
592 if (ret < 0) {
593 iter->pos_mod_end = iter->pos;
594 return 0;
595 }
596
597 return 1;
598}
599
600/*
601 * ftrace_mod_get_kallsym() may also get symbols for pages allocated for ftrace
602 * purposes. In that case "__builtin__ftrace" is used as a module name, even
603 * though "__builtin__ftrace" is not a module.
604 */
605static int get_ksymbol_ftrace_mod(struct kallsym_iter *iter)
606{
607 int ret = ftrace_mod_get_kallsym(iter->pos - iter->pos_mod_end,
608 &iter->value, &iter->type,
609 iter->name, iter->module_name,
610 &iter->exported);
611 if (ret < 0) {
612 iter->pos_ftrace_mod_end = iter->pos;
613 return 0;
614 }
615
616 return 1;
617}
618
619static int get_ksymbol_bpf(struct kallsym_iter *iter)
620{
621 int ret;
622
623 strlcpy(iter->module_name, "bpf", MODULE_NAME_LEN);
624 iter->exported = 0;
625 ret = bpf_get_kallsym(iter->pos - iter->pos_ftrace_mod_end,
626 &iter->value, &iter->type,
627 iter->name);
628 if (ret < 0) {
629 iter->pos_bpf_end = iter->pos;
630 return 0;
631 }
632
633 return 1;
634}
635
636/*
637 * This uses "__builtin__kprobes" as a module name for symbols for pages
638 * allocated for kprobes' purposes, even though "__builtin__kprobes" is not a
639 * module.
640 */
641static int get_ksymbol_kprobe(struct kallsym_iter *iter)
642{
643 strlcpy(iter->module_name, "__builtin__kprobes", MODULE_NAME_LEN);
644 iter->exported = 0;
645 return kprobe_get_kallsym(iter->pos - iter->pos_bpf_end,
646 &iter->value, &iter->type,
647 iter->name) < 0 ? 0 : 1;
648}
649
650/* Returns space to next name. */
651static unsigned long get_ksymbol_core(struct kallsym_iter *iter)
652{
653 unsigned off = iter->nameoff;
654
655 iter->module_name[0] = '\0';
656 iter->value = kallsyms_sym_address(iter->pos);
657
658 iter->type = kallsyms_get_symbol_type(off);
659
660 off = kallsyms_expand_symbol(off, iter->name, ARRAY_SIZE(iter->name));
661
662 return off - iter->nameoff;
663}
664
665static void reset_iter(struct kallsym_iter *iter, loff_t new_pos)
666{
667 iter->name[0] = '\0';
668 iter->nameoff = get_symbol_offset(new_pos);
669 iter->pos = new_pos;
670 if (new_pos == 0) {
671 iter->pos_arch_end = 0;
672 iter->pos_mod_end = 0;
673 iter->pos_ftrace_mod_end = 0;
674 iter->pos_bpf_end = 0;
675 }
676}
677
678/*
679 * The end position (last + 1) of each additional kallsyms section is recorded
680 * in iter->pos_..._end as each section is added, and so can be used to
681 * determine which get_ksymbol_...() function to call next.
682 */
683static int update_iter_mod(struct kallsym_iter *iter, loff_t pos)
684{
685 iter->pos = pos;
686
687 if ((!iter->pos_arch_end || iter->pos_arch_end > pos) &&
688 get_ksymbol_arch(iter))
689 return 1;
690
691 if ((!iter->pos_mod_end || iter->pos_mod_end > pos) &&
692 get_ksymbol_mod(iter))
693 return 1;
694
695 if ((!iter->pos_ftrace_mod_end || iter->pos_ftrace_mod_end > pos) &&
696 get_ksymbol_ftrace_mod(iter))
697 return 1;
698
699 if ((!iter->pos_bpf_end || iter->pos_bpf_end > pos) &&
700 get_ksymbol_bpf(iter))
701 return 1;
702
703 return get_ksymbol_kprobe(iter);
704}
705
706/* Returns false if pos at or past end of file. */
707static int update_iter(struct kallsym_iter *iter, loff_t pos)
708{
709 /* Module symbols can be accessed randomly. */
710 if (pos >= kallsyms_num_syms)
711 return update_iter_mod(iter, pos);
712
713 /* If we're not on the desired position, reset to new position. */
714 if (pos != iter->pos)
715 reset_iter(iter, pos);
716
717 iter->nameoff += get_ksymbol_core(iter);
718 iter->pos++;
719
720 return 1;
721}
722
723static void *s_next(struct seq_file *m, void *p, loff_t *pos)
724{
725 (*pos)++;
726
727 if (!update_iter(m->private, *pos))
728 return NULL;
729 return p;
730}
731
732static void *s_start(struct seq_file *m, loff_t *pos)
733{
734 if (!update_iter(m->private, *pos))
735 return NULL;
736 return m->private;
737}
738
739static void s_stop(struct seq_file *m, void *p)
740{
741}
742
743static int s_show(struct seq_file *m, void *p)
744{
745 void *value;
746 struct kallsym_iter *iter = m->private;
747
748 /* Some debugging symbols have no name. Ignore them. */
749 if (!iter->name[0])
750 return 0;
751
752 value = iter->show_value ? (void *)iter->value : NULL;
753
754 if (iter->module_name[0]) {
755 char type;
756
757 /*
758 * Label it "global" if it is exported,
759 * "local" if not exported.
760 */
761 type = iter->exported ? toupper(iter->type) :
762 tolower(iter->type);
763 seq_printf(m, "%px %c %s\t[%s]\n", value,
764 type, iter->name, iter->module_name);
765 } else
766 seq_printf(m, "%px %c %s\n", value,
767 iter->type, iter->name);
768 return 0;
769}
770
771static const struct seq_operations kallsyms_op = {
772 .start = s_start,
773 .next = s_next,
774 .stop = s_stop,
775 .show = s_show
776};
777
778static inline int kallsyms_for_perf(void)
779{
780#ifdef CONFIG_PERF_EVENTS
781 extern int sysctl_perf_event_paranoid;
782 if (sysctl_perf_event_paranoid <= 1)
783 return 1;
784#endif
785 return 0;
786}
787
788/*
789 * We show kallsyms information even to normal users if we've enabled
790 * kernel profiling and are explicitly not paranoid (so kptr_restrict
791 * is clear, and sysctl_perf_event_paranoid isn't set).
792 *
793 * Otherwise, require CAP_SYSLOG (assuming kptr_restrict isn't set to
794 * block even that).
795 */
796bool kallsyms_show_value(const struct cred *cred)
797{
798 switch (kptr_restrict) {
799 case 0:
800 if (kallsyms_for_perf())
801 return true;
802 fallthrough;
803 case 1:
804 if (security_capable(cred, &init_user_ns, CAP_SYSLOG,
805 CAP_OPT_NOAUDIT) == 0)
806 return true;
807 fallthrough;
808 default:
809 return false;
810 }
811}
812
813static int kallsyms_open(struct inode *inode, struct file *file)
814{
815 /*
816 * We keep iterator in m->private, since normal case is to
817 * s_start from where we left off, so we avoid doing
818 * using get_symbol_offset for every symbol.
819 */
820 struct kallsym_iter *iter;
821 iter = __seq_open_private(file, &kallsyms_op, sizeof(*iter));
822 if (!iter)
823 return -ENOMEM;
824 reset_iter(iter, 0);
825
826 /*
827 * Instead of checking this on every s_show() call, cache
828 * the result here at open time.
829 */
830 iter->show_value = kallsyms_show_value(file->f_cred);
831 return 0;
832}
833
834#ifdef CONFIG_KGDB_KDB
835const char *kdb_walk_kallsyms(loff_t *pos)
836{
837 static struct kallsym_iter kdb_walk_kallsyms_iter;
838 if (*pos == 0) {
839 memset(&kdb_walk_kallsyms_iter, 0,
840 sizeof(kdb_walk_kallsyms_iter));
841 reset_iter(&kdb_walk_kallsyms_iter, 0);
842 }
843 while (1) {
844 if (!update_iter(&kdb_walk_kallsyms_iter, *pos))
845 return NULL;
846 ++*pos;
847 /* Some debugging symbols have no name. Ignore them. */
848 if (kdb_walk_kallsyms_iter.name[0])
849 return kdb_walk_kallsyms_iter.name;
850 }
851}
852#endif /* CONFIG_KGDB_KDB */
853
854static const struct proc_ops kallsyms_proc_ops = {
855 .proc_open = kallsyms_open,
856 .proc_read = seq_read,
857 .proc_lseek = seq_lseek,
858 .proc_release = seq_release_private,
859};
860
861static int __init kallsyms_init(void)
862{
863 proc_create("kallsyms", 0444, NULL, &kallsyms_proc_ops);
864 return 0;
865}
866device_initcall(kallsyms_init);