Line data Source code
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 : #include <linux/bsearch.h>
33 : #include <linux/btf_ids.h>
34 :
35 : #include "kallsyms_internal.h"
36 :
37 : /*
38 : * Expand a compressed symbol data into the resulting uncompressed string,
39 : * if uncompressed string is too long (>= maxlen), it will be truncated,
40 : * given the offset to where the symbol is in the compressed stream.
41 : */
42 236 : static unsigned int kallsyms_expand_symbol(unsigned int off,
43 : char *result, size_t maxlen)
44 : {
45 236 : int len, skipped_first = 0;
46 : const char *tptr;
47 : const u8 *data;
48 :
49 : /* Get the compressed symbol length from the first symbol byte. */
50 236 : data = &kallsyms_names[off];
51 236 : len = *data;
52 236 : data++;
53 236 : off++;
54 :
55 : /* If MSB is 1, it is a "big" symbol, so needs an additional byte. */
56 236 : if ((len & 0x80) != 0) {
57 0 : len = (len & 0x7F) | (*data << 7);
58 0 : data++;
59 0 : off++;
60 : }
61 :
62 : /*
63 : * Update the offset to return the offset for the next symbol on
64 : * the compressed stream.
65 : */
66 236 : off += len;
67 :
68 : /*
69 : * For every byte on the compressed symbol data, copy the table
70 : * entry for that byte.
71 : */
72 2614 : while (len) {
73 2142 : tptr = &kallsyms_token_table[kallsyms_token_index[*data]];
74 2142 : data++;
75 2142 : len--;
76 :
77 7992 : while (*tptr) {
78 3708 : if (skipped_first) {
79 3472 : if (maxlen <= 1)
80 : goto tail;
81 3472 : *result = *tptr;
82 3472 : result++;
83 3472 : maxlen--;
84 : } else
85 : skipped_first = 1;
86 3708 : tptr++;
87 : }
88 : }
89 :
90 : tail:
91 236 : if (maxlen)
92 236 : *result = '\0';
93 :
94 : /* Return to offset to the next symbol. */
95 236 : return off;
96 : }
97 :
98 : /*
99 : * Get symbol type information. This is encoded as a single char at the
100 : * beginning of the symbol name.
101 : */
102 : static char kallsyms_get_symbol_type(unsigned int off)
103 : {
104 : /*
105 : * Get just the first code, look it up in the token table,
106 : * and return the first char from this token.
107 : */
108 0 : return kallsyms_token_table[kallsyms_token_index[kallsyms_names[off + 1]]];
109 : }
110 :
111 :
112 : /*
113 : * Find the offset on the compressed stream given and index in the
114 : * kallsyms array.
115 : */
116 : static unsigned int get_symbol_offset(unsigned long pos)
117 : {
118 : const u8 *name;
119 : int i, len;
120 :
121 : /*
122 : * Use the closest marker we have. We have markers every 256 positions,
123 : * so that should be close enough.
124 : */
125 236 : name = &kallsyms_names[kallsyms_markers[pos >> 8]];
126 :
127 : /*
128 : * Sequentially scan all the symbols up to the point we're searching
129 : * for. Every symbol is stored in a [<len>][<len> bytes of data] format,
130 : * so we just need to add the len to the current pointer for every
131 : * symbol we wish to skip.
132 : */
133 27798 : for (i = 0; i < (pos & 0xFF); i++) {
134 27562 : len = *name;
135 :
136 : /*
137 : * If MSB is 1, it is a "big" symbol, so we need to look into
138 : * the next byte (and skip it, too).
139 : */
140 27562 : if ((len & 0x80) != 0)
141 0 : len = ((len & 0x7F) | (name[1] << 7)) + 1;
142 :
143 27562 : name = name + len + 1;
144 : }
145 :
146 236 : return name - kallsyms_names;
147 : }
148 :
149 0 : unsigned long kallsyms_sym_address(int idx)
150 : {
151 : if (!IS_ENABLED(CONFIG_KALLSYMS_BASE_RELATIVE))
152 : return kallsyms_addresses[idx];
153 :
154 : /* values are unsigned offsets if --absolute-percpu is not in effect */
155 : if (!IS_ENABLED(CONFIG_KALLSYMS_ABSOLUTE_PERCPU))
156 4214 : return kallsyms_relative_base + (u32)kallsyms_offsets[idx];
157 :
158 : /* ...otherwise, positive offsets are absolute values */
159 : if (kallsyms_offsets[idx] >= 0)
160 : return kallsyms_offsets[idx];
161 :
162 : /* ...and negative offsets are relative to kallsyms_relative_base - 1 */
163 : return kallsyms_relative_base - 1 - kallsyms_offsets[idx];
164 : }
165 :
166 : static bool cleanup_symbol_name(char *s)
167 : {
168 : char *res;
169 :
170 : if (!IS_ENABLED(CONFIG_LTO_CLANG))
171 : return false;
172 :
173 : /*
174 : * LLVM appends various suffixes for local functions and variables that
175 : * must be promoted to global scope as part of LTO. This can break
176 : * hooking of static functions with kprobes. '.' is not a valid
177 : * character in an identifier in C. Suffixes observed:
178 : * - foo.llvm.[0-9a-f]+
179 : * - foo.[0-9a-f]+
180 : */
181 : res = strchr(s, '.');
182 : if (res) {
183 : *res = '\0';
184 : return true;
185 : }
186 :
187 : return false;
188 : }
189 :
190 : static int compare_symbol_name(const char *name, char *namebuf)
191 : {
192 : int ret;
193 :
194 0 : ret = strcmp(name, namebuf);
195 : if (!ret)
196 : return ret;
197 :
198 : if (cleanup_symbol_name(namebuf) && !strcmp(name, namebuf))
199 : return 0;
200 :
201 : return ret;
202 : }
203 :
204 : static unsigned int get_symbol_seq(int index)
205 : {
206 0 : unsigned int i, seq = 0;
207 :
208 0 : for (i = 0; i < 3; i++)
209 0 : seq = (seq << 8) | kallsyms_seqs_of_names[3 * index + i];
210 :
211 : return seq;
212 : }
213 :
214 0 : static int kallsyms_lookup_names(const char *name,
215 : unsigned int *start,
216 : unsigned int *end)
217 : {
218 : int ret;
219 : int low, mid, high;
220 : unsigned int seq, off;
221 : char namebuf[KSYM_NAME_LEN];
222 :
223 0 : low = 0;
224 0 : high = kallsyms_num_syms - 1;
225 :
226 0 : while (low <= high) {
227 0 : mid = low + (high - low) / 2;
228 0 : seq = get_symbol_seq(mid);
229 0 : off = get_symbol_offset(seq);
230 0 : kallsyms_expand_symbol(off, namebuf, ARRAY_SIZE(namebuf));
231 0 : ret = compare_symbol_name(name, namebuf);
232 0 : if (ret > 0)
233 0 : low = mid + 1;
234 0 : else if (ret < 0)
235 0 : high = mid - 1;
236 : else
237 : break;
238 : }
239 :
240 0 : if (low > high)
241 : return -ESRCH;
242 :
243 : low = mid;
244 0 : while (low) {
245 0 : seq = get_symbol_seq(low - 1);
246 0 : off = get_symbol_offset(seq);
247 0 : kallsyms_expand_symbol(off, namebuf, ARRAY_SIZE(namebuf));
248 0 : if (compare_symbol_name(name, namebuf))
249 : break;
250 : low--;
251 : }
252 0 : *start = low;
253 :
254 0 : if (end) {
255 : high = mid;
256 0 : while (high < kallsyms_num_syms - 1) {
257 0 : seq = get_symbol_seq(high + 1);
258 0 : off = get_symbol_offset(seq);
259 0 : kallsyms_expand_symbol(off, namebuf, ARRAY_SIZE(namebuf));
260 0 : if (compare_symbol_name(name, namebuf))
261 : break;
262 : high++;
263 : }
264 0 : *end = high;
265 : }
266 :
267 : return 0;
268 : }
269 :
270 : /* Lookup the address for this symbol. Returns 0 if not found. */
271 0 : unsigned long kallsyms_lookup_name(const char *name)
272 : {
273 : int ret;
274 : unsigned int i;
275 :
276 : /* Skip the search for empty string. */
277 0 : if (!*name)
278 : return 0;
279 :
280 0 : ret = kallsyms_lookup_names(name, &i, NULL);
281 0 : if (!ret)
282 0 : return kallsyms_sym_address(get_symbol_seq(i));
283 :
284 : return module_kallsyms_lookup_name(name);
285 : }
286 :
287 : /*
288 : * Iterate over all symbols in vmlinux. For symbols from modules use
289 : * module_kallsyms_on_each_symbol instead.
290 : */
291 0 : int kallsyms_on_each_symbol(int (*fn)(void *, const char *, struct module *,
292 : unsigned long),
293 : void *data)
294 : {
295 : char namebuf[KSYM_NAME_LEN];
296 : unsigned long i;
297 : unsigned int off;
298 : int ret;
299 :
300 0 : for (i = 0, off = 0; i < kallsyms_num_syms; i++) {
301 0 : off = kallsyms_expand_symbol(off, namebuf, ARRAY_SIZE(namebuf));
302 0 : ret = fn(data, namebuf, NULL, kallsyms_sym_address(i));
303 0 : if (ret != 0)
304 : return ret;
305 0 : cond_resched();
306 : }
307 : return 0;
308 : }
309 :
310 0 : int kallsyms_on_each_match_symbol(int (*fn)(void *, unsigned long),
311 : const char *name, void *data)
312 : {
313 : int ret;
314 : unsigned int i, start, end;
315 :
316 0 : ret = kallsyms_lookup_names(name, &start, &end);
317 0 : if (ret)
318 : return 0;
319 :
320 0 : for (i = start; !ret && i <= end; i++) {
321 0 : ret = fn(data, kallsyms_sym_address(get_symbol_seq(i)));
322 0 : cond_resched();
323 : }
324 :
325 : return ret;
326 : }
327 :
328 236 : static unsigned long get_symbol_pos(unsigned long addr,
329 : unsigned long *symbolsize,
330 : unsigned long *offset)
331 : {
332 236 : unsigned long symbol_start = 0, symbol_end = 0;
333 : unsigned long i, low, high, mid;
334 :
335 : /* This kernel should never had been booted. */
336 : if (!IS_ENABLED(CONFIG_KALLSYMS_BASE_RELATIVE))
337 : BUG_ON(!kallsyms_addresses);
338 : else
339 236 : BUG_ON(!kallsyms_offsets);
340 :
341 : /* Do a binary search on the sorted kallsyms_addresses array. */
342 236 : low = 0;
343 236 : high = kallsyms_num_syms;
344 :
345 3742 : while (high - low > 1) {
346 3270 : mid = low + (high - low) / 2;
347 6540 : if (kallsyms_sym_address(mid) <= addr)
348 : low = mid;
349 : else
350 : high = mid;
351 : }
352 :
353 : /*
354 : * Search for the first aliased symbol. Aliased
355 : * symbols are symbols with the same address.
356 : */
357 708 : while (low && kallsyms_sym_address(low-1) == kallsyms_sym_address(low))
358 0 : --low;
359 :
360 472 : symbol_start = kallsyms_sym_address(low);
361 :
362 : /* Search for next non-aliased symbol. */
363 236 : for (i = low + 1; i < kallsyms_num_syms; i++) {
364 472 : if (kallsyms_sym_address(i) > symbol_start) {
365 : symbol_end = kallsyms_sym_address(i);
366 : break;
367 : }
368 : }
369 :
370 : /* If we found no next symbol, we use the end of the section. */
371 236 : if (!symbol_end) {
372 0 : if (is_kernel_inittext(addr))
373 0 : symbol_end = (unsigned long)_einittext;
374 : else if (IS_ENABLED(CONFIG_KALLSYMS_ALL))
375 : symbol_end = (unsigned long)_end;
376 : else
377 0 : symbol_end = (unsigned long)_etext;
378 : }
379 :
380 236 : if (symbolsize)
381 236 : *symbolsize = symbol_end - symbol_start;
382 236 : if (offset)
383 236 : *offset = addr - symbol_start;
384 :
385 236 : return low;
386 : }
387 :
388 : /*
389 : * Lookup an address but don't bother to find any names.
390 : */
391 0 : int kallsyms_lookup_size_offset(unsigned long addr, unsigned long *symbolsize,
392 : unsigned long *offset)
393 : {
394 : char namebuf[KSYM_NAME_LEN];
395 :
396 0 : if (is_ksym_addr(addr)) {
397 0 : get_symbol_pos(addr, symbolsize, offset);
398 0 : return 1;
399 : }
400 : return !!module_address_lookup(addr, symbolsize, offset, NULL, NULL, namebuf) ||
401 : !!__bpf_address_lookup(addr, symbolsize, offset, namebuf);
402 : }
403 :
404 236 : static const char *kallsyms_lookup_buildid(unsigned long addr,
405 : unsigned long *symbolsize,
406 : unsigned long *offset, char **modname,
407 : const unsigned char **modbuildid, char *namebuf)
408 : {
409 : const char *ret;
410 :
411 236 : namebuf[KSYM_NAME_LEN - 1] = 0;
412 236 : namebuf[0] = 0;
413 :
414 236 : if (is_ksym_addr(addr)) {
415 : unsigned long pos;
416 :
417 236 : pos = get_symbol_pos(addr, symbolsize, offset);
418 : /* Grab name */
419 236 : kallsyms_expand_symbol(get_symbol_offset(pos),
420 : namebuf, KSYM_NAME_LEN);
421 236 : if (modname)
422 236 : *modname = NULL;
423 236 : if (modbuildid)
424 236 : *modbuildid = NULL;
425 :
426 : ret = namebuf;
427 : goto found;
428 : }
429 :
430 : /* See if it's in a module or a BPF JITed image. */
431 : ret = module_address_lookup(addr, symbolsize, offset,
432 : modname, modbuildid, namebuf);
433 : if (!ret)
434 : ret = bpf_address_lookup(addr, symbolsize,
435 : offset, modname, namebuf);
436 :
437 : if (!ret)
438 : ret = ftrace_mod_address_lookup(addr, symbolsize,
439 : offset, modname, namebuf);
440 :
441 : found:
442 236 : cleanup_symbol_name(namebuf);
443 236 : return ret;
444 : }
445 :
446 : /*
447 : * Lookup an address
448 : * - modname is set to NULL if it's in the kernel.
449 : * - We guarantee that the returned name is valid until we reschedule even if.
450 : * It resides in a module.
451 : * - We also guarantee that modname will be valid until rescheduled.
452 : */
453 0 : const char *kallsyms_lookup(unsigned long addr,
454 : unsigned long *symbolsize,
455 : unsigned long *offset,
456 : char **modname, char *namebuf)
457 : {
458 0 : return kallsyms_lookup_buildid(addr, symbolsize, offset, modname,
459 : NULL, namebuf);
460 : }
461 :
462 0 : int lookup_symbol_name(unsigned long addr, char *symname)
463 : {
464 : int res;
465 :
466 0 : symname[0] = '\0';
467 0 : symname[KSYM_NAME_LEN - 1] = '\0';
468 :
469 0 : if (is_ksym_addr(addr)) {
470 : unsigned long pos;
471 :
472 0 : pos = get_symbol_pos(addr, NULL, NULL);
473 : /* Grab name */
474 0 : kallsyms_expand_symbol(get_symbol_offset(pos),
475 : symname, KSYM_NAME_LEN);
476 : goto found;
477 : }
478 : /* See if it's in a module. */
479 : res = lookup_module_symbol_name(addr, symname);
480 : if (res)
481 : return res;
482 :
483 : found:
484 0 : cleanup_symbol_name(symname);
485 0 : return 0;
486 : }
487 :
488 0 : int lookup_symbol_attrs(unsigned long addr, unsigned long *size,
489 : unsigned long *offset, char *modname, char *name)
490 : {
491 : int res;
492 :
493 0 : name[0] = '\0';
494 0 : name[KSYM_NAME_LEN - 1] = '\0';
495 :
496 0 : if (is_ksym_addr(addr)) {
497 : unsigned long pos;
498 :
499 0 : pos = get_symbol_pos(addr, size, offset);
500 : /* Grab name */
501 0 : kallsyms_expand_symbol(get_symbol_offset(pos),
502 : name, KSYM_NAME_LEN);
503 0 : modname[0] = '\0';
504 : goto found;
505 : }
506 : /* See if it's in a module. */
507 : res = lookup_module_symbol_attrs(addr, size, offset, modname, name);
508 : if (res)
509 : return res;
510 :
511 : found:
512 0 : cleanup_symbol_name(name);
513 0 : return 0;
514 : }
515 :
516 : /* Look up a kernel symbol and return it in a text buffer. */
517 236 : static int __sprint_symbol(char *buffer, unsigned long address,
518 : int symbol_offset, int add_offset, int add_buildid)
519 : {
520 : char *modname;
521 : const unsigned char *buildid;
522 : const char *name;
523 : unsigned long offset, size;
524 : int len;
525 :
526 236 : address += symbol_offset;
527 236 : name = kallsyms_lookup_buildid(address, &size, &offset, &modname, &buildid,
528 : buffer);
529 236 : if (!name)
530 0 : return sprintf(buffer, "0x%lx", address - symbol_offset);
531 :
532 236 : if (name != buffer)
533 0 : strcpy(buffer, name);
534 236 : len = strlen(buffer);
535 236 : offset -= symbol_offset;
536 :
537 236 : if (add_offset)
538 236 : len += sprintf(buffer + len, "+%#lx/%#lx", offset, size);
539 :
540 236 : if (modname) {
541 0 : len += sprintf(buffer + len, " [%s", modname);
542 : #if IS_ENABLED(CONFIG_STACKTRACE_BUILD_ID)
543 : if (add_buildid && buildid) {
544 : /* build ID should match length of sprintf */
545 : #if IS_ENABLED(CONFIG_MODULES)
546 : static_assert(sizeof(typeof_member(struct module, build_id)) == 20);
547 : #endif
548 : len += sprintf(buffer + len, " %20phN", buildid);
549 : }
550 : #endif
551 0 : len += sprintf(buffer + len, "]");
552 : }
553 :
554 : return len;
555 : }
556 :
557 : /**
558 : * sprint_symbol - Look up a kernel symbol and return it in a text buffer
559 : * @buffer: buffer to be stored
560 : * @address: address to lookup
561 : *
562 : * This function looks up a kernel symbol with @address and stores its name,
563 : * offset, size and module name to @buffer if possible. If no symbol was found,
564 : * just saves its @address as is.
565 : *
566 : * This function returns the number of bytes stored in @buffer.
567 : */
568 236 : int sprint_symbol(char *buffer, unsigned long address)
569 : {
570 236 : return __sprint_symbol(buffer, address, 0, 1, 0);
571 : }
572 : EXPORT_SYMBOL_GPL(sprint_symbol);
573 :
574 : /**
575 : * sprint_symbol_build_id - Look up a kernel symbol and return it in a text buffer
576 : * @buffer: buffer to be stored
577 : * @address: address to lookup
578 : *
579 : * This function looks up a kernel symbol with @address and stores its name,
580 : * offset, size, module name and module build ID to @buffer if possible. If no
581 : * symbol was found, just saves its @address as is.
582 : *
583 : * This function returns the number of bytes stored in @buffer.
584 : */
585 0 : int sprint_symbol_build_id(char *buffer, unsigned long address)
586 : {
587 0 : return __sprint_symbol(buffer, address, 0, 1, 1);
588 : }
589 : EXPORT_SYMBOL_GPL(sprint_symbol_build_id);
590 :
591 : /**
592 : * sprint_symbol_no_offset - Look up a kernel symbol and return it in a text buffer
593 : * @buffer: buffer to be stored
594 : * @address: address to lookup
595 : *
596 : * This function looks up a kernel symbol with @address and stores its name
597 : * and module name to @buffer if possible. If no symbol was found, just saves
598 : * its @address as is.
599 : *
600 : * This function returns the number of bytes stored in @buffer.
601 : */
602 0 : int sprint_symbol_no_offset(char *buffer, unsigned long address)
603 : {
604 0 : return __sprint_symbol(buffer, address, 0, 0, 0);
605 : }
606 : EXPORT_SYMBOL_GPL(sprint_symbol_no_offset);
607 :
608 : /**
609 : * sprint_backtrace - Look up a backtrace symbol and return it in a text buffer
610 : * @buffer: buffer to be stored
611 : * @address: address to lookup
612 : *
613 : * This function is for stack backtrace and does the same thing as
614 : * sprint_symbol() but with modified/decreased @address. If there is a
615 : * tail-call to the function marked "noreturn", gcc optimized out code after
616 : * the call so that the stack-saved return address could point outside of the
617 : * caller. This function ensures that kallsyms will find the original caller
618 : * by decreasing @address.
619 : *
620 : * This function returns the number of bytes stored in @buffer.
621 : */
622 0 : int sprint_backtrace(char *buffer, unsigned long address)
623 : {
624 0 : return __sprint_symbol(buffer, address, -1, 1, 0);
625 : }
626 :
627 : /**
628 : * sprint_backtrace_build_id - Look up a backtrace symbol and return it in a text buffer
629 : * @buffer: buffer to be stored
630 : * @address: address to lookup
631 : *
632 : * This function is for stack backtrace and does the same thing as
633 : * sprint_symbol() but with modified/decreased @address. If there is a
634 : * tail-call to the function marked "noreturn", gcc optimized out code after
635 : * the call so that the stack-saved return address could point outside of the
636 : * caller. This function ensures that kallsyms will find the original caller
637 : * by decreasing @address. This function also appends the module build ID to
638 : * the @buffer if @address is within a kernel module.
639 : *
640 : * This function returns the number of bytes stored in @buffer.
641 : */
642 0 : int sprint_backtrace_build_id(char *buffer, unsigned long address)
643 : {
644 0 : return __sprint_symbol(buffer, address, -1, 1, 1);
645 : }
646 :
647 : /* To avoid using get_symbol_offset for every symbol, we carry prefix along. */
648 : struct kallsym_iter {
649 : loff_t pos;
650 : loff_t pos_arch_end;
651 : loff_t pos_mod_end;
652 : loff_t pos_ftrace_mod_end;
653 : loff_t pos_bpf_end;
654 : unsigned long value;
655 : unsigned int nameoff; /* If iterating in core kernel symbols. */
656 : char type;
657 : char name[KSYM_NAME_LEN];
658 : char module_name[MODULE_NAME_LEN];
659 : int exported;
660 : int show_value;
661 : };
662 :
663 0 : int __weak arch_get_kallsym(unsigned int symnum, unsigned long *value,
664 : char *type, char *name)
665 : {
666 0 : return -EINVAL;
667 : }
668 :
669 0 : static int get_ksymbol_arch(struct kallsym_iter *iter)
670 : {
671 0 : int ret = arch_get_kallsym(iter->pos - kallsyms_num_syms,
672 : &iter->value, &iter->type,
673 0 : iter->name);
674 :
675 0 : if (ret < 0) {
676 0 : iter->pos_arch_end = iter->pos;
677 0 : return 0;
678 : }
679 :
680 : return 1;
681 : }
682 :
683 : static int get_ksymbol_mod(struct kallsym_iter *iter)
684 : {
685 0 : int ret = module_get_kallsym(iter->pos - iter->pos_arch_end,
686 : &iter->value, &iter->type,
687 0 : iter->name, iter->module_name,
688 : &iter->exported);
689 : if (ret < 0) {
690 0 : iter->pos_mod_end = iter->pos;
691 : return 0;
692 : }
693 :
694 : return 1;
695 : }
696 :
697 : /*
698 : * ftrace_mod_get_kallsym() may also get symbols for pages allocated for ftrace
699 : * purposes. In that case "__builtin__ftrace" is used as a module name, even
700 : * though "__builtin__ftrace" is not a module.
701 : */
702 : static int get_ksymbol_ftrace_mod(struct kallsym_iter *iter)
703 : {
704 0 : int ret = ftrace_mod_get_kallsym(iter->pos - iter->pos_mod_end,
705 : &iter->value, &iter->type,
706 0 : iter->name, iter->module_name,
707 : &iter->exported);
708 : if (ret < 0) {
709 0 : iter->pos_ftrace_mod_end = iter->pos;
710 : return 0;
711 : }
712 :
713 : return 1;
714 : }
715 :
716 : static int get_ksymbol_bpf(struct kallsym_iter *iter)
717 : {
718 : int ret;
719 :
720 0 : strlcpy(iter->module_name, "bpf", MODULE_NAME_LEN);
721 0 : iter->exported = 0;
722 0 : ret = bpf_get_kallsym(iter->pos - iter->pos_ftrace_mod_end,
723 : &iter->value, &iter->type,
724 0 : iter->name);
725 : if (ret < 0) {
726 0 : iter->pos_bpf_end = iter->pos;
727 : return 0;
728 : }
729 :
730 : return 1;
731 : }
732 :
733 : /*
734 : * This uses "__builtin__kprobes" as a module name for symbols for pages
735 : * allocated for kprobes' purposes, even though "__builtin__kprobes" is not a
736 : * module.
737 : */
738 : static int get_ksymbol_kprobe(struct kallsym_iter *iter)
739 : {
740 0 : strlcpy(iter->module_name, "__builtin__kprobes", MODULE_NAME_LEN);
741 0 : iter->exported = 0;
742 0 : return kprobe_get_kallsym(iter->pos - iter->pos_bpf_end,
743 : &iter->value, &iter->type,
744 0 : iter->name) < 0 ? 0 : 1;
745 : }
746 :
747 : /* Returns space to next name. */
748 0 : static unsigned long get_ksymbol_core(struct kallsym_iter *iter)
749 : {
750 0 : unsigned off = iter->nameoff;
751 :
752 0 : iter->module_name[0] = '\0';
753 0 : iter->value = kallsyms_sym_address(iter->pos);
754 :
755 0 : iter->type = kallsyms_get_symbol_type(off);
756 :
757 0 : off = kallsyms_expand_symbol(off, iter->name, ARRAY_SIZE(iter->name));
758 :
759 0 : return off - iter->nameoff;
760 : }
761 :
762 0 : static void reset_iter(struct kallsym_iter *iter, loff_t new_pos)
763 : {
764 0 : iter->name[0] = '\0';
765 0 : iter->nameoff = get_symbol_offset(new_pos);
766 0 : iter->pos = new_pos;
767 0 : if (new_pos == 0) {
768 0 : iter->pos_arch_end = 0;
769 0 : iter->pos_mod_end = 0;
770 0 : iter->pos_ftrace_mod_end = 0;
771 0 : iter->pos_bpf_end = 0;
772 : }
773 0 : }
774 :
775 : /*
776 : * The end position (last + 1) of each additional kallsyms section is recorded
777 : * in iter->pos_..._end as each section is added, and so can be used to
778 : * determine which get_ksymbol_...() function to call next.
779 : */
780 0 : static int update_iter_mod(struct kallsym_iter *iter, loff_t pos)
781 : {
782 0 : iter->pos = pos;
783 :
784 0 : if ((!iter->pos_arch_end || iter->pos_arch_end > pos) &&
785 0 : get_ksymbol_arch(iter))
786 : return 1;
787 :
788 0 : if ((!iter->pos_mod_end || iter->pos_mod_end > pos) &&
789 0 : get_ksymbol_mod(iter))
790 : return 1;
791 :
792 0 : if ((!iter->pos_ftrace_mod_end || iter->pos_ftrace_mod_end > pos) &&
793 0 : get_ksymbol_ftrace_mod(iter))
794 : return 1;
795 :
796 0 : if ((!iter->pos_bpf_end || iter->pos_bpf_end > pos) &&
797 0 : get_ksymbol_bpf(iter))
798 : return 1;
799 :
800 0 : return get_ksymbol_kprobe(iter);
801 : }
802 :
803 : /* Returns false if pos at or past end of file. */
804 0 : static int update_iter(struct kallsym_iter *iter, loff_t pos)
805 : {
806 : /* Module symbols can be accessed randomly. */
807 0 : if (pos >= kallsyms_num_syms)
808 0 : return update_iter_mod(iter, pos);
809 :
810 : /* If we're not on the desired position, reset to new position. */
811 0 : if (pos != iter->pos)
812 0 : reset_iter(iter, pos);
813 :
814 0 : iter->nameoff += get_ksymbol_core(iter);
815 0 : iter->pos++;
816 :
817 0 : return 1;
818 : }
819 :
820 0 : static void *s_next(struct seq_file *m, void *p, loff_t *pos)
821 : {
822 0 : (*pos)++;
823 :
824 0 : if (!update_iter(m->private, *pos))
825 : return NULL;
826 0 : return p;
827 : }
828 :
829 0 : static void *s_start(struct seq_file *m, loff_t *pos)
830 : {
831 0 : if (!update_iter(m->private, *pos))
832 : return NULL;
833 0 : return m->private;
834 : }
835 :
836 0 : static void s_stop(struct seq_file *m, void *p)
837 : {
838 0 : }
839 :
840 0 : static int s_show(struct seq_file *m, void *p)
841 : {
842 : void *value;
843 0 : struct kallsym_iter *iter = m->private;
844 :
845 : /* Some debugging symbols have no name. Ignore them. */
846 0 : if (!iter->name[0])
847 : return 0;
848 :
849 0 : value = iter->show_value ? (void *)iter->value : NULL;
850 :
851 0 : if (iter->module_name[0]) {
852 : char type;
853 :
854 : /*
855 : * Label it "global" if it is exported,
856 : * "local" if not exported.
857 : */
858 0 : type = iter->exported ? toupper(iter->type) :
859 0 : tolower(iter->type);
860 0 : seq_printf(m, "%px %c %s\t[%s]\n", value,
861 0 : type, iter->name, iter->module_name);
862 : } else
863 0 : seq_printf(m, "%px %c %s\n", value,
864 0 : iter->type, iter->name);
865 : return 0;
866 : }
867 :
868 : static const struct seq_operations kallsyms_op = {
869 : .start = s_start,
870 : .next = s_next,
871 : .stop = s_stop,
872 : .show = s_show
873 : };
874 :
875 : #ifdef CONFIG_BPF_SYSCALL
876 :
877 : struct bpf_iter__ksym {
878 : __bpf_md_ptr(struct bpf_iter_meta *, meta);
879 : __bpf_md_ptr(struct kallsym_iter *, ksym);
880 : };
881 :
882 : static int ksym_prog_seq_show(struct seq_file *m, bool in_stop)
883 : {
884 : struct bpf_iter__ksym ctx;
885 : struct bpf_iter_meta meta;
886 : struct bpf_prog *prog;
887 :
888 : meta.seq = m;
889 : prog = bpf_iter_get_info(&meta, in_stop);
890 : if (!prog)
891 : return 0;
892 :
893 : ctx.meta = &meta;
894 : ctx.ksym = m ? m->private : NULL;
895 : return bpf_iter_run_prog(prog, &ctx);
896 : }
897 :
898 : static int bpf_iter_ksym_seq_show(struct seq_file *m, void *p)
899 : {
900 : return ksym_prog_seq_show(m, false);
901 : }
902 :
903 : static void bpf_iter_ksym_seq_stop(struct seq_file *m, void *p)
904 : {
905 : if (!p)
906 : (void) ksym_prog_seq_show(m, true);
907 : else
908 : s_stop(m, p);
909 : }
910 :
911 : static const struct seq_operations bpf_iter_ksym_ops = {
912 : .start = s_start,
913 : .next = s_next,
914 : .stop = bpf_iter_ksym_seq_stop,
915 : .show = bpf_iter_ksym_seq_show,
916 : };
917 :
918 : static int bpf_iter_ksym_init(void *priv_data, struct bpf_iter_aux_info *aux)
919 : {
920 : struct kallsym_iter *iter = priv_data;
921 :
922 : reset_iter(iter, 0);
923 :
924 : /* cache here as in kallsyms_open() case; use current process
925 : * credentials to tell BPF iterators if values should be shown.
926 : */
927 : iter->show_value = kallsyms_show_value(current_cred());
928 :
929 : return 0;
930 : }
931 :
932 : DEFINE_BPF_ITER_FUNC(ksym, struct bpf_iter_meta *meta, struct kallsym_iter *ksym)
933 :
934 : static const struct bpf_iter_seq_info ksym_iter_seq_info = {
935 : .seq_ops = &bpf_iter_ksym_ops,
936 : .init_seq_private = bpf_iter_ksym_init,
937 : .fini_seq_private = NULL,
938 : .seq_priv_size = sizeof(struct kallsym_iter),
939 : };
940 :
941 : static struct bpf_iter_reg ksym_iter_reg_info = {
942 : .target = "ksym",
943 : .feature = BPF_ITER_RESCHED,
944 : .ctx_arg_info_size = 1,
945 : .ctx_arg_info = {
946 : { offsetof(struct bpf_iter__ksym, ksym),
947 : PTR_TO_BTF_ID_OR_NULL },
948 : },
949 : .seq_info = &ksym_iter_seq_info,
950 : };
951 :
952 : BTF_ID_LIST(btf_ksym_iter_id)
953 : BTF_ID(struct, kallsym_iter)
954 :
955 : static int __init bpf_ksym_iter_register(void)
956 : {
957 : ksym_iter_reg_info.ctx_arg_info[0].btf_id = *btf_ksym_iter_id;
958 : return bpf_iter_reg_target(&ksym_iter_reg_info);
959 : }
960 :
961 : late_initcall(bpf_ksym_iter_register);
962 :
963 : #endif /* CONFIG_BPF_SYSCALL */
964 :
965 : static inline int kallsyms_for_perf(void)
966 : {
967 : #ifdef CONFIG_PERF_EVENTS
968 : extern int sysctl_perf_event_paranoid;
969 : if (sysctl_perf_event_paranoid <= 1)
970 : return 1;
971 : #endif
972 : return 0;
973 : }
974 :
975 : /*
976 : * We show kallsyms information even to normal users if we've enabled
977 : * kernel profiling and are explicitly not paranoid (so kptr_restrict
978 : * is clear, and sysctl_perf_event_paranoid isn't set).
979 : *
980 : * Otherwise, require CAP_SYSLOG (assuming kptr_restrict isn't set to
981 : * block even that).
982 : */
983 0 : bool kallsyms_show_value(const struct cred *cred)
984 : {
985 0 : switch (kptr_restrict) {
986 : case 0:
987 : if (kallsyms_for_perf())
988 : return true;
989 : fallthrough;
990 : case 1:
991 0 : if (security_capable(cred, &init_user_ns, CAP_SYSLOG,
992 : CAP_OPT_NOAUDIT) == 0)
993 : return true;
994 : fallthrough;
995 : default:
996 : return false;
997 : }
998 : }
999 :
1000 0 : static int kallsyms_open(struct inode *inode, struct file *file)
1001 : {
1002 : /*
1003 : * We keep iterator in m->private, since normal case is to
1004 : * s_start from where we left off, so we avoid doing
1005 : * using get_symbol_offset for every symbol.
1006 : */
1007 : struct kallsym_iter *iter;
1008 0 : iter = __seq_open_private(file, &kallsyms_op, sizeof(*iter));
1009 0 : if (!iter)
1010 : return -ENOMEM;
1011 0 : reset_iter(iter, 0);
1012 :
1013 : /*
1014 : * Instead of checking this on every s_show() call, cache
1015 : * the result here at open time.
1016 : */
1017 0 : iter->show_value = kallsyms_show_value(file->f_cred);
1018 0 : return 0;
1019 : }
1020 :
1021 : #ifdef CONFIG_KGDB_KDB
1022 : const char *kdb_walk_kallsyms(loff_t *pos)
1023 : {
1024 : static struct kallsym_iter kdb_walk_kallsyms_iter;
1025 : if (*pos == 0) {
1026 : memset(&kdb_walk_kallsyms_iter, 0,
1027 : sizeof(kdb_walk_kallsyms_iter));
1028 : reset_iter(&kdb_walk_kallsyms_iter, 0);
1029 : }
1030 : while (1) {
1031 : if (!update_iter(&kdb_walk_kallsyms_iter, *pos))
1032 : return NULL;
1033 : ++*pos;
1034 : /* Some debugging symbols have no name. Ignore them. */
1035 : if (kdb_walk_kallsyms_iter.name[0])
1036 : return kdb_walk_kallsyms_iter.name;
1037 : }
1038 : }
1039 : #endif /* CONFIG_KGDB_KDB */
1040 :
1041 : static const struct proc_ops kallsyms_proc_ops = {
1042 : .proc_open = kallsyms_open,
1043 : .proc_read = seq_read,
1044 : .proc_lseek = seq_lseek,
1045 : .proc_release = seq_release_private,
1046 : };
1047 :
1048 1 : static int __init kallsyms_init(void)
1049 : {
1050 1 : proc_create("kallsyms", 0444, NULL, &kallsyms_proc_ops);
1051 1 : return 0;
1052 : }
1053 : device_initcall(kallsyms_init);
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