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 24014 : for (i = 0; i < (pos & 0xFF); i++) {
134 23778 : 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 23778 : if ((len & 0x80) != 0)
141 0 : len = ((len & 0x7F) | (name[1] << 7)) + 1;
142 :
143 23778 : 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 4206 : 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 *, unsigned long),
292 : void *data)
293 : {
294 : char namebuf[KSYM_NAME_LEN];
295 : unsigned long i;
296 : unsigned int off;
297 : int ret;
298 :
299 0 : for (i = 0, off = 0; i < kallsyms_num_syms; i++) {
300 0 : off = kallsyms_expand_symbol(off, namebuf, ARRAY_SIZE(namebuf));
301 0 : ret = fn(data, namebuf, kallsyms_sym_address(i));
302 0 : if (ret != 0)
303 : return ret;
304 0 : cond_resched();
305 : }
306 : return 0;
307 : }
308 :
309 0 : int kallsyms_on_each_match_symbol(int (*fn)(void *, unsigned long),
310 : const char *name, void *data)
311 : {
312 : int ret;
313 : unsigned int i, start, end;
314 :
315 0 : ret = kallsyms_lookup_names(name, &start, &end);
316 0 : if (ret)
317 : return 0;
318 :
319 0 : for (i = start; !ret && i <= end; i++) {
320 0 : ret = fn(data, kallsyms_sym_address(get_symbol_seq(i)));
321 0 : cond_resched();
322 : }
323 :
324 : return ret;
325 : }
326 :
327 236 : static unsigned long get_symbol_pos(unsigned long addr,
328 : unsigned long *symbolsize,
329 : unsigned long *offset)
330 : {
331 236 : unsigned long symbol_start = 0, symbol_end = 0;
332 : unsigned long i, low, high, mid;
333 :
334 : /* This kernel should never had been booted. */
335 : if (!IS_ENABLED(CONFIG_KALLSYMS_BASE_RELATIVE))
336 : BUG_ON(!kallsyms_addresses);
337 : else
338 236 : BUG_ON(!kallsyms_offsets);
339 :
340 : /* Do a binary search on the sorted kallsyms_addresses array. */
341 236 : low = 0;
342 236 : high = kallsyms_num_syms;
343 :
344 3734 : while (high - low > 1) {
345 3262 : mid = low + (high - low) / 2;
346 6524 : if (kallsyms_sym_address(mid) <= addr)
347 : low = mid;
348 : else
349 : high = mid;
350 : }
351 :
352 : /*
353 : * Search for the first aliased symbol. Aliased
354 : * symbols are symbols with the same address.
355 : */
356 708 : while (low && kallsyms_sym_address(low-1) == kallsyms_sym_address(low))
357 0 : --low;
358 :
359 472 : symbol_start = kallsyms_sym_address(low);
360 :
361 : /* Search for next non-aliased symbol. */
362 236 : for (i = low + 1; i < kallsyms_num_syms; i++) {
363 472 : if (kallsyms_sym_address(i) > symbol_start) {
364 : symbol_end = kallsyms_sym_address(i);
365 : break;
366 : }
367 : }
368 :
369 : /* If we found no next symbol, we use the end of the section. */
370 236 : if (!symbol_end) {
371 0 : if (is_kernel_inittext(addr))
372 0 : symbol_end = (unsigned long)_einittext;
373 : else if (IS_ENABLED(CONFIG_KALLSYMS_ALL))
374 : symbol_end = (unsigned long)_end;
375 : else
376 0 : symbol_end = (unsigned long)_etext;
377 : }
378 :
379 236 : if (symbolsize)
380 236 : *symbolsize = symbol_end - symbol_start;
381 236 : if (offset)
382 236 : *offset = addr - symbol_start;
383 :
384 236 : return low;
385 : }
386 :
387 : /*
388 : * Lookup an address but don't bother to find any names.
389 : */
390 0 : int kallsyms_lookup_size_offset(unsigned long addr, unsigned long *symbolsize,
391 : unsigned long *offset)
392 : {
393 : char namebuf[KSYM_NAME_LEN];
394 :
395 0 : if (is_ksym_addr(addr)) {
396 0 : get_symbol_pos(addr, symbolsize, offset);
397 0 : return 1;
398 : }
399 : return !!module_address_lookup(addr, symbolsize, offset, NULL, NULL, namebuf) ||
400 : !!__bpf_address_lookup(addr, symbolsize, offset, namebuf);
401 : }
402 :
403 236 : static const char *kallsyms_lookup_buildid(unsigned long addr,
404 : unsigned long *symbolsize,
405 : unsigned long *offset, char **modname,
406 : const unsigned char **modbuildid, char *namebuf)
407 : {
408 : const char *ret;
409 :
410 236 : namebuf[KSYM_NAME_LEN - 1] = 0;
411 236 : namebuf[0] = 0;
412 :
413 236 : if (is_ksym_addr(addr)) {
414 : unsigned long pos;
415 :
416 236 : pos = get_symbol_pos(addr, symbolsize, offset);
417 : /* Grab name */
418 236 : kallsyms_expand_symbol(get_symbol_offset(pos),
419 : namebuf, KSYM_NAME_LEN);
420 236 : if (modname)
421 236 : *modname = NULL;
422 236 : if (modbuildid)
423 236 : *modbuildid = NULL;
424 :
425 : ret = namebuf;
426 : goto found;
427 : }
428 :
429 : /* See if it's in a module or a BPF JITed image. */
430 : ret = module_address_lookup(addr, symbolsize, offset,
431 : modname, modbuildid, namebuf);
432 : if (!ret)
433 : ret = bpf_address_lookup(addr, symbolsize,
434 : offset, modname, namebuf);
435 :
436 : if (!ret)
437 : ret = ftrace_mod_address_lookup(addr, symbolsize,
438 : offset, modname, namebuf);
439 :
440 : found:
441 236 : cleanup_symbol_name(namebuf);
442 236 : return ret;
443 : }
444 :
445 : /*
446 : * Lookup an address
447 : * - modname is set to NULL if it's in the kernel.
448 : * - We guarantee that the returned name is valid until we reschedule even if.
449 : * It resides in a module.
450 : * - We also guarantee that modname will be valid until rescheduled.
451 : */
452 0 : const char *kallsyms_lookup(unsigned long addr,
453 : unsigned long *symbolsize,
454 : unsigned long *offset,
455 : char **modname, char *namebuf)
456 : {
457 0 : return kallsyms_lookup_buildid(addr, symbolsize, offset, modname,
458 : NULL, namebuf);
459 : }
460 :
461 0 : int lookup_symbol_name(unsigned long addr, char *symname)
462 : {
463 : int res;
464 :
465 0 : symname[0] = '\0';
466 0 : symname[KSYM_NAME_LEN - 1] = '\0';
467 :
468 0 : if (is_ksym_addr(addr)) {
469 : unsigned long pos;
470 :
471 0 : pos = get_symbol_pos(addr, NULL, NULL);
472 : /* Grab name */
473 0 : kallsyms_expand_symbol(get_symbol_offset(pos),
474 : symname, KSYM_NAME_LEN);
475 : goto found;
476 : }
477 : /* See if it's in a module. */
478 : res = lookup_module_symbol_name(addr, symname);
479 : if (res)
480 : return res;
481 :
482 : found:
483 0 : cleanup_symbol_name(symname);
484 0 : return 0;
485 : }
486 :
487 0 : int lookup_symbol_attrs(unsigned long addr, unsigned long *size,
488 : unsigned long *offset, char *modname, char *name)
489 : {
490 : int res;
491 :
492 0 : name[0] = '\0';
493 0 : name[KSYM_NAME_LEN - 1] = '\0';
494 :
495 0 : if (is_ksym_addr(addr)) {
496 : unsigned long pos;
497 :
498 0 : pos = get_symbol_pos(addr, size, offset);
499 : /* Grab name */
500 0 : kallsyms_expand_symbol(get_symbol_offset(pos),
501 : name, KSYM_NAME_LEN);
502 0 : modname[0] = '\0';
503 : goto found;
504 : }
505 : /* See if it's in a module. */
506 : res = lookup_module_symbol_attrs(addr, size, offset, modname, name);
507 : if (res)
508 : return res;
509 :
510 : found:
511 0 : cleanup_symbol_name(name);
512 0 : return 0;
513 : }
514 :
515 : /* Look up a kernel symbol and return it in a text buffer. */
516 236 : static int __sprint_symbol(char *buffer, unsigned long address,
517 : int symbol_offset, int add_offset, int add_buildid)
518 : {
519 : char *modname;
520 : const unsigned char *buildid;
521 : const char *name;
522 : unsigned long offset, size;
523 : int len;
524 :
525 236 : address += symbol_offset;
526 236 : name = kallsyms_lookup_buildid(address, &size, &offset, &modname, &buildid,
527 : buffer);
528 236 : if (!name)
529 0 : return sprintf(buffer, "0x%lx", address - symbol_offset);
530 :
531 236 : if (name != buffer)
532 0 : strcpy(buffer, name);
533 236 : len = strlen(buffer);
534 236 : offset -= symbol_offset;
535 :
536 236 : if (add_offset)
537 236 : len += sprintf(buffer + len, "+%#lx/%#lx", offset, size);
538 :
539 236 : if (modname) {
540 0 : len += sprintf(buffer + len, " [%s", modname);
541 : #if IS_ENABLED(CONFIG_STACKTRACE_BUILD_ID)
542 : if (add_buildid && buildid) {
543 : /* build ID should match length of sprintf */
544 : #if IS_ENABLED(CONFIG_MODULES)
545 : static_assert(sizeof(typeof_member(struct module, build_id)) == 20);
546 : #endif
547 : len += sprintf(buffer + len, " %20phN", buildid);
548 : }
549 : #endif
550 0 : len += sprintf(buffer + len, "]");
551 : }
552 :
553 : return len;
554 : }
555 :
556 : /**
557 : * sprint_symbol - Look up a kernel symbol and return it in a text buffer
558 : * @buffer: buffer to be stored
559 : * @address: address to lookup
560 : *
561 : * This function looks up a kernel symbol with @address and stores its name,
562 : * offset, size and module name to @buffer if possible. If no symbol was found,
563 : * just saves its @address as is.
564 : *
565 : * This function returns the number of bytes stored in @buffer.
566 : */
567 236 : int sprint_symbol(char *buffer, unsigned long address)
568 : {
569 236 : return __sprint_symbol(buffer, address, 0, 1, 0);
570 : }
571 : EXPORT_SYMBOL_GPL(sprint_symbol);
572 :
573 : /**
574 : * sprint_symbol_build_id - Look up a kernel symbol and return it in a text buffer
575 : * @buffer: buffer to be stored
576 : * @address: address to lookup
577 : *
578 : * This function looks up a kernel symbol with @address and stores its name,
579 : * offset, size, module name and module build ID to @buffer if possible. If no
580 : * symbol was found, just saves its @address as is.
581 : *
582 : * This function returns the number of bytes stored in @buffer.
583 : */
584 0 : int sprint_symbol_build_id(char *buffer, unsigned long address)
585 : {
586 0 : return __sprint_symbol(buffer, address, 0, 1, 1);
587 : }
588 : EXPORT_SYMBOL_GPL(sprint_symbol_build_id);
589 :
590 : /**
591 : * sprint_symbol_no_offset - Look up a kernel symbol and return it in a text buffer
592 : * @buffer: buffer to be stored
593 : * @address: address to lookup
594 : *
595 : * This function looks up a kernel symbol with @address and stores its name
596 : * and module name to @buffer if possible. If no symbol was found, just saves
597 : * its @address as is.
598 : *
599 : * This function returns the number of bytes stored in @buffer.
600 : */
601 0 : int sprint_symbol_no_offset(char *buffer, unsigned long address)
602 : {
603 0 : return __sprint_symbol(buffer, address, 0, 0, 0);
604 : }
605 : EXPORT_SYMBOL_GPL(sprint_symbol_no_offset);
606 :
607 : /**
608 : * sprint_backtrace - Look up a backtrace symbol and return it in a text buffer
609 : * @buffer: buffer to be stored
610 : * @address: address to lookup
611 : *
612 : * This function is for stack backtrace and does the same thing as
613 : * sprint_symbol() but with modified/decreased @address. If there is a
614 : * tail-call to the function marked "noreturn", gcc optimized out code after
615 : * the call so that the stack-saved return address could point outside of the
616 : * caller. This function ensures that kallsyms will find the original caller
617 : * by decreasing @address.
618 : *
619 : * This function returns the number of bytes stored in @buffer.
620 : */
621 0 : int sprint_backtrace(char *buffer, unsigned long address)
622 : {
623 0 : return __sprint_symbol(buffer, address, -1, 1, 0);
624 : }
625 :
626 : /**
627 : * sprint_backtrace_build_id - Look up a backtrace symbol and return it in a text buffer
628 : * @buffer: buffer to be stored
629 : * @address: address to lookup
630 : *
631 : * This function is for stack backtrace and does the same thing as
632 : * sprint_symbol() but with modified/decreased @address. If there is a
633 : * tail-call to the function marked "noreturn", gcc optimized out code after
634 : * the call so that the stack-saved return address could point outside of the
635 : * caller. This function ensures that kallsyms will find the original caller
636 : * by decreasing @address. This function also appends the module build ID to
637 : * the @buffer if @address is within a kernel module.
638 : *
639 : * This function returns the number of bytes stored in @buffer.
640 : */
641 0 : int sprint_backtrace_build_id(char *buffer, unsigned long address)
642 : {
643 0 : return __sprint_symbol(buffer, address, -1, 1, 1);
644 : }
645 :
646 : /* To avoid using get_symbol_offset for every symbol, we carry prefix along. */
647 : struct kallsym_iter {
648 : loff_t pos;
649 : loff_t pos_arch_end;
650 : loff_t pos_mod_end;
651 : loff_t pos_ftrace_mod_end;
652 : loff_t pos_bpf_end;
653 : unsigned long value;
654 : unsigned int nameoff; /* If iterating in core kernel symbols. */
655 : char type;
656 : char name[KSYM_NAME_LEN];
657 : char module_name[MODULE_NAME_LEN];
658 : int exported;
659 : int show_value;
660 : };
661 :
662 0 : int __weak arch_get_kallsym(unsigned int symnum, unsigned long *value,
663 : char *type, char *name)
664 : {
665 0 : return -EINVAL;
666 : }
667 :
668 0 : static int get_ksymbol_arch(struct kallsym_iter *iter)
669 : {
670 0 : int ret = arch_get_kallsym(iter->pos - kallsyms_num_syms,
671 : &iter->value, &iter->type,
672 0 : iter->name);
673 :
674 0 : if (ret < 0) {
675 0 : iter->pos_arch_end = iter->pos;
676 0 : return 0;
677 : }
678 :
679 : return 1;
680 : }
681 :
682 : static int get_ksymbol_mod(struct kallsym_iter *iter)
683 : {
684 0 : int ret = module_get_kallsym(iter->pos - iter->pos_arch_end,
685 : &iter->value, &iter->type,
686 0 : iter->name, iter->module_name,
687 : &iter->exported);
688 : if (ret < 0) {
689 0 : iter->pos_mod_end = iter->pos;
690 : return 0;
691 : }
692 :
693 : return 1;
694 : }
695 :
696 : /*
697 : * ftrace_mod_get_kallsym() may also get symbols for pages allocated for ftrace
698 : * purposes. In that case "__builtin__ftrace" is used as a module name, even
699 : * though "__builtin__ftrace" is not a module.
700 : */
701 : static int get_ksymbol_ftrace_mod(struct kallsym_iter *iter)
702 : {
703 0 : int ret = ftrace_mod_get_kallsym(iter->pos - iter->pos_mod_end,
704 : &iter->value, &iter->type,
705 0 : iter->name, iter->module_name,
706 : &iter->exported);
707 : if (ret < 0) {
708 0 : iter->pos_ftrace_mod_end = iter->pos;
709 : return 0;
710 : }
711 :
712 : return 1;
713 : }
714 :
715 : static int get_ksymbol_bpf(struct kallsym_iter *iter)
716 : {
717 : int ret;
718 :
719 0 : strlcpy(iter->module_name, "bpf", MODULE_NAME_LEN);
720 0 : iter->exported = 0;
721 0 : ret = bpf_get_kallsym(iter->pos - iter->pos_ftrace_mod_end,
722 : &iter->value, &iter->type,
723 0 : iter->name);
724 : if (ret < 0) {
725 0 : iter->pos_bpf_end = iter->pos;
726 : return 0;
727 : }
728 :
729 : return 1;
730 : }
731 :
732 : /*
733 : * This uses "__builtin__kprobes" as a module name for symbols for pages
734 : * allocated for kprobes' purposes, even though "__builtin__kprobes" is not a
735 : * module.
736 : */
737 : static int get_ksymbol_kprobe(struct kallsym_iter *iter)
738 : {
739 0 : strlcpy(iter->module_name, "__builtin__kprobes", MODULE_NAME_LEN);
740 0 : iter->exported = 0;
741 0 : return kprobe_get_kallsym(iter->pos - iter->pos_bpf_end,
742 : &iter->value, &iter->type,
743 0 : iter->name) < 0 ? 0 : 1;
744 : }
745 :
746 : /* Returns space to next name. */
747 0 : static unsigned long get_ksymbol_core(struct kallsym_iter *iter)
748 : {
749 0 : unsigned off = iter->nameoff;
750 :
751 0 : iter->module_name[0] = '\0';
752 0 : iter->value = kallsyms_sym_address(iter->pos);
753 :
754 0 : iter->type = kallsyms_get_symbol_type(off);
755 :
756 0 : off = kallsyms_expand_symbol(off, iter->name, ARRAY_SIZE(iter->name));
757 :
758 0 : return off - iter->nameoff;
759 : }
760 :
761 0 : static void reset_iter(struct kallsym_iter *iter, loff_t new_pos)
762 : {
763 0 : iter->name[0] = '\0';
764 0 : iter->nameoff = get_symbol_offset(new_pos);
765 0 : iter->pos = new_pos;
766 0 : if (new_pos == 0) {
767 0 : iter->pos_arch_end = 0;
768 0 : iter->pos_mod_end = 0;
769 0 : iter->pos_ftrace_mod_end = 0;
770 0 : iter->pos_bpf_end = 0;
771 : }
772 0 : }
773 :
774 : /*
775 : * The end position (last + 1) of each additional kallsyms section is recorded
776 : * in iter->pos_..._end as each section is added, and so can be used to
777 : * determine which get_ksymbol_...() function to call next.
778 : */
779 0 : static int update_iter_mod(struct kallsym_iter *iter, loff_t pos)
780 : {
781 0 : iter->pos = pos;
782 :
783 0 : if ((!iter->pos_arch_end || iter->pos_arch_end > pos) &&
784 0 : get_ksymbol_arch(iter))
785 : return 1;
786 :
787 0 : if ((!iter->pos_mod_end || iter->pos_mod_end > pos) &&
788 0 : get_ksymbol_mod(iter))
789 : return 1;
790 :
791 0 : if ((!iter->pos_ftrace_mod_end || iter->pos_ftrace_mod_end > pos) &&
792 0 : get_ksymbol_ftrace_mod(iter))
793 : return 1;
794 :
795 0 : if ((!iter->pos_bpf_end || iter->pos_bpf_end > pos) &&
796 0 : get_ksymbol_bpf(iter))
797 : return 1;
798 :
799 0 : return get_ksymbol_kprobe(iter);
800 : }
801 :
802 : /* Returns false if pos at or past end of file. */
803 0 : static int update_iter(struct kallsym_iter *iter, loff_t pos)
804 : {
805 : /* Module symbols can be accessed randomly. */
806 0 : if (pos >= kallsyms_num_syms)
807 0 : return update_iter_mod(iter, pos);
808 :
809 : /* If we're not on the desired position, reset to new position. */
810 0 : if (pos != iter->pos)
811 0 : reset_iter(iter, pos);
812 :
813 0 : iter->nameoff += get_ksymbol_core(iter);
814 0 : iter->pos++;
815 :
816 0 : return 1;
817 : }
818 :
819 0 : static void *s_next(struct seq_file *m, void *p, loff_t *pos)
820 : {
821 0 : (*pos)++;
822 :
823 0 : if (!update_iter(m->private, *pos))
824 : return NULL;
825 0 : return p;
826 : }
827 :
828 0 : static void *s_start(struct seq_file *m, loff_t *pos)
829 : {
830 0 : if (!update_iter(m->private, *pos))
831 : return NULL;
832 0 : return m->private;
833 : }
834 :
835 0 : static void s_stop(struct seq_file *m, void *p)
836 : {
837 0 : }
838 :
839 0 : static int s_show(struct seq_file *m, void *p)
840 : {
841 : void *value;
842 0 : struct kallsym_iter *iter = m->private;
843 :
844 : /* Some debugging symbols have no name. Ignore them. */
845 0 : if (!iter->name[0])
846 : return 0;
847 :
848 0 : value = iter->show_value ? (void *)iter->value : NULL;
849 :
850 0 : if (iter->module_name[0]) {
851 : char type;
852 :
853 : /*
854 : * Label it "global" if it is exported,
855 : * "local" if not exported.
856 : */
857 0 : type = iter->exported ? toupper(iter->type) :
858 0 : tolower(iter->type);
859 0 : seq_printf(m, "%px %c %s\t[%s]\n", value,
860 0 : type, iter->name, iter->module_name);
861 : } else
862 0 : seq_printf(m, "%px %c %s\n", value,
863 0 : iter->type, iter->name);
864 : return 0;
865 : }
866 :
867 : static const struct seq_operations kallsyms_op = {
868 : .start = s_start,
869 : .next = s_next,
870 : .stop = s_stop,
871 : .show = s_show
872 : };
873 :
874 : #ifdef CONFIG_BPF_SYSCALL
875 :
876 : struct bpf_iter__ksym {
877 : __bpf_md_ptr(struct bpf_iter_meta *, meta);
878 : __bpf_md_ptr(struct kallsym_iter *, ksym);
879 : };
880 :
881 : static int ksym_prog_seq_show(struct seq_file *m, bool in_stop)
882 : {
883 : struct bpf_iter__ksym ctx;
884 : struct bpf_iter_meta meta;
885 : struct bpf_prog *prog;
886 :
887 : meta.seq = m;
888 : prog = bpf_iter_get_info(&meta, in_stop);
889 : if (!prog)
890 : return 0;
891 :
892 : ctx.meta = &meta;
893 : ctx.ksym = m ? m->private : NULL;
894 : return bpf_iter_run_prog(prog, &ctx);
895 : }
896 :
897 : static int bpf_iter_ksym_seq_show(struct seq_file *m, void *p)
898 : {
899 : return ksym_prog_seq_show(m, false);
900 : }
901 :
902 : static void bpf_iter_ksym_seq_stop(struct seq_file *m, void *p)
903 : {
904 : if (!p)
905 : (void) ksym_prog_seq_show(m, true);
906 : else
907 : s_stop(m, p);
908 : }
909 :
910 : static const struct seq_operations bpf_iter_ksym_ops = {
911 : .start = s_start,
912 : .next = s_next,
913 : .stop = bpf_iter_ksym_seq_stop,
914 : .show = bpf_iter_ksym_seq_show,
915 : };
916 :
917 : static int bpf_iter_ksym_init(void *priv_data, struct bpf_iter_aux_info *aux)
918 : {
919 : struct kallsym_iter *iter = priv_data;
920 :
921 : reset_iter(iter, 0);
922 :
923 : /* cache here as in kallsyms_open() case; use current process
924 : * credentials to tell BPF iterators if values should be shown.
925 : */
926 : iter->show_value = kallsyms_show_value(current_cred());
927 :
928 : return 0;
929 : }
930 :
931 : DEFINE_BPF_ITER_FUNC(ksym, struct bpf_iter_meta *meta, struct kallsym_iter *ksym)
932 :
933 : static const struct bpf_iter_seq_info ksym_iter_seq_info = {
934 : .seq_ops = &bpf_iter_ksym_ops,
935 : .init_seq_private = bpf_iter_ksym_init,
936 : .fini_seq_private = NULL,
937 : .seq_priv_size = sizeof(struct kallsym_iter),
938 : };
939 :
940 : static struct bpf_iter_reg ksym_iter_reg_info = {
941 : .target = "ksym",
942 : .feature = BPF_ITER_RESCHED,
943 : .ctx_arg_info_size = 1,
944 : .ctx_arg_info = {
945 : { offsetof(struct bpf_iter__ksym, ksym),
946 : PTR_TO_BTF_ID_OR_NULL },
947 : },
948 : .seq_info = &ksym_iter_seq_info,
949 : };
950 :
951 : BTF_ID_LIST(btf_ksym_iter_id)
952 : BTF_ID(struct, kallsym_iter)
953 :
954 : static int __init bpf_ksym_iter_register(void)
955 : {
956 : ksym_iter_reg_info.ctx_arg_info[0].btf_id = *btf_ksym_iter_id;
957 : return bpf_iter_reg_target(&ksym_iter_reg_info);
958 : }
959 :
960 : late_initcall(bpf_ksym_iter_register);
961 :
962 : #endif /* CONFIG_BPF_SYSCALL */
963 :
964 : static inline int kallsyms_for_perf(void)
965 : {
966 : #ifdef CONFIG_PERF_EVENTS
967 : extern int sysctl_perf_event_paranoid;
968 : if (sysctl_perf_event_paranoid <= 1)
969 : return 1;
970 : #endif
971 : return 0;
972 : }
973 :
974 : /*
975 : * We show kallsyms information even to normal users if we've enabled
976 : * kernel profiling and are explicitly not paranoid (so kptr_restrict
977 : * is clear, and sysctl_perf_event_paranoid isn't set).
978 : *
979 : * Otherwise, require CAP_SYSLOG (assuming kptr_restrict isn't set to
980 : * block even that).
981 : */
982 0 : bool kallsyms_show_value(const struct cred *cred)
983 : {
984 0 : switch (kptr_restrict) {
985 : case 0:
986 : if (kallsyms_for_perf())
987 : return true;
988 : fallthrough;
989 : case 1:
990 0 : if (security_capable(cred, &init_user_ns, CAP_SYSLOG,
991 : CAP_OPT_NOAUDIT) == 0)
992 : return true;
993 : fallthrough;
994 : default:
995 : return false;
996 : }
997 : }
998 :
999 0 : static int kallsyms_open(struct inode *inode, struct file *file)
1000 : {
1001 : /*
1002 : * We keep iterator in m->private, since normal case is to
1003 : * s_start from where we left off, so we avoid doing
1004 : * using get_symbol_offset for every symbol.
1005 : */
1006 : struct kallsym_iter *iter;
1007 0 : iter = __seq_open_private(file, &kallsyms_op, sizeof(*iter));
1008 0 : if (!iter)
1009 : return -ENOMEM;
1010 0 : reset_iter(iter, 0);
1011 :
1012 : /*
1013 : * Instead of checking this on every s_show() call, cache
1014 : * the result here at open time.
1015 : */
1016 0 : iter->show_value = kallsyms_show_value(file->f_cred);
1017 0 : return 0;
1018 : }
1019 :
1020 : #ifdef CONFIG_KGDB_KDB
1021 : const char *kdb_walk_kallsyms(loff_t *pos)
1022 : {
1023 : static struct kallsym_iter kdb_walk_kallsyms_iter;
1024 : if (*pos == 0) {
1025 : memset(&kdb_walk_kallsyms_iter, 0,
1026 : sizeof(kdb_walk_kallsyms_iter));
1027 : reset_iter(&kdb_walk_kallsyms_iter, 0);
1028 : }
1029 : while (1) {
1030 : if (!update_iter(&kdb_walk_kallsyms_iter, *pos))
1031 : return NULL;
1032 : ++*pos;
1033 : /* Some debugging symbols have no name. Ignore them. */
1034 : if (kdb_walk_kallsyms_iter.name[0])
1035 : return kdb_walk_kallsyms_iter.name;
1036 : }
1037 : }
1038 : #endif /* CONFIG_KGDB_KDB */
1039 :
1040 : static const struct proc_ops kallsyms_proc_ops = {
1041 : .proc_open = kallsyms_open,
1042 : .proc_read = seq_read,
1043 : .proc_lseek = seq_lseek,
1044 : .proc_release = seq_release_private,
1045 : };
1046 :
1047 1 : static int __init kallsyms_init(void)
1048 : {
1049 1 : proc_create("kallsyms", 0444, NULL, &kallsyms_proc_ops);
1050 1 : return 0;
1051 : }
1052 : device_initcall(kallsyms_init);
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