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 :
33 : /*
34 : * These will be re-linked against their real values
35 : * during the second link stage.
36 : */
37 : extern const unsigned long kallsyms_addresses[] __weak;
38 : extern const int kallsyms_offsets[] __weak;
39 : extern 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 : */
45 : extern const unsigned int kallsyms_num_syms
46 : __section(".rodata") __attribute__((weak));
47 :
48 : extern const unsigned long kallsyms_relative_base
49 : __section(".rodata") __attribute__((weak));
50 :
51 : extern const char kallsyms_token_table[] __weak;
52 : extern const u16 kallsyms_token_index[] __weak;
53 :
54 : extern 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 : */
61 58 : static unsigned int kallsyms_expand_symbol(unsigned int off,
62 : char *result, size_t maxlen)
63 : {
64 58 : 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 58 : data = &kallsyms_names[off];
70 58 : len = *data;
71 58 : data++;
72 :
73 : /*
74 : * Update the offset to return the offset for the next symbol on
75 : * the compressed stream.
76 : */
77 58 : off += len + 1;
78 :
79 : /*
80 : * For every byte on the compressed symbol data, copy the table
81 : * entry for that byte.
82 : */
83 630 : while (len) {
84 514 : tptr = &kallsyms_token_table[kallsyms_token_index[*data]];
85 514 : data++;
86 514 : len--;
87 :
88 1906 : while (*tptr) {
89 878 : if (skipped_first) {
90 820 : if (maxlen <= 1)
91 : goto tail;
92 820 : *result = *tptr;
93 820 : result++;
94 820 : maxlen--;
95 : } else
96 : skipped_first = 1;
97 878 : tptr++;
98 : }
99 : }
100 :
101 : tail:
102 58 : if (maxlen)
103 58 : *result = '\0';
104 :
105 : /* Return to offset to the next symbol. */
106 58 : 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 : */
113 : static 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 0 : 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 : */
127 : static 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 58 : 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 6984 : for (i = 0; i < (pos & 0xFF); i++)
145 6926 : name = name + (*name) + 1;
146 :
147 58 : return name - kallsyms_names;
148 : }
149 :
150 : static 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 1084 : 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 : static bool cleanup_symbol_name(char *s)
168 : {
169 : char *res;
170 :
171 : if (!IS_ENABLED(CONFIG_LTO_CLANG))
172 : return false;
173 :
174 : /*
175 : * LLVM appends various suffixes for local functions and variables that
176 : * must be promoted to global scope as part of LTO. This can break
177 : * hooking of static functions with kprobes. '.' is not a valid
178 : * character in an identifier in C. Suffixes observed:
179 : * - foo.llvm.[0-9a-f]+
180 : * - foo.[0-9a-f]+
181 : * - foo.[0-9a-f]+.cfi_jt
182 : */
183 : res = strchr(s, '.');
184 : if (res) {
185 : *res = '\0';
186 : return true;
187 : }
188 :
189 : if (!IS_ENABLED(CONFIG_CFI_CLANG) ||
190 : !IS_ENABLED(CONFIG_LTO_CLANG_THIN) ||
191 : CONFIG_CLANG_VERSION >= 130000)
192 : return false;
193 :
194 : /*
195 : * Prior to LLVM 13, the following suffixes were observed when thinLTO
196 : * and CFI are both enabled:
197 : * - foo$[0-9]+
198 : */
199 : res = strrchr(s, '$');
200 : if (res) {
201 : *res = '\0';
202 : return true;
203 : }
204 :
205 : return false;
206 : }
207 :
208 : /* Lookup the address for this symbol. Returns 0 if not found. */
209 0 : unsigned long kallsyms_lookup_name(const char *name)
210 : {
211 : char namebuf[KSYM_NAME_LEN];
212 : unsigned long i;
213 : unsigned int off;
214 :
215 : /* Skip the search for empty string. */
216 0 : if (!*name)
217 : return 0;
218 :
219 0 : for (i = 0, off = 0; i < kallsyms_num_syms; i++) {
220 0 : off = kallsyms_expand_symbol(off, namebuf, ARRAY_SIZE(namebuf));
221 :
222 0 : if (strcmp(namebuf, name) == 0)
223 0 : return kallsyms_sym_address(i);
224 :
225 0 : if (cleanup_symbol_name(namebuf) && strcmp(namebuf, name) == 0)
226 : return kallsyms_sym_address(i);
227 : }
228 : return module_kallsyms_lookup_name(name);
229 : }
230 :
231 : #ifdef CONFIG_LIVEPATCH
232 : /*
233 : * Iterate over all symbols in vmlinux. For symbols from modules use
234 : * module_kallsyms_on_each_symbol instead.
235 : */
236 : int kallsyms_on_each_symbol(int (*fn)(void *, const char *, struct module *,
237 : unsigned long),
238 : void *data)
239 : {
240 : char namebuf[KSYM_NAME_LEN];
241 : unsigned long i;
242 : unsigned int off;
243 : int ret;
244 :
245 : for (i = 0, off = 0; i < kallsyms_num_syms; i++) {
246 : off = kallsyms_expand_symbol(off, namebuf, ARRAY_SIZE(namebuf));
247 : ret = fn(data, namebuf, NULL, kallsyms_sym_address(i));
248 : if (ret != 0)
249 : return ret;
250 : cond_resched();
251 : }
252 : return 0;
253 : }
254 : #endif /* CONFIG_LIVEPATCH */
255 :
256 58 : static unsigned long get_symbol_pos(unsigned long addr,
257 : unsigned long *symbolsize,
258 : unsigned long *offset)
259 : {
260 58 : unsigned long symbol_start = 0, symbol_end = 0;
261 : unsigned long i, low, high, mid;
262 :
263 : /* This kernel should never had been booted. */
264 : if (!IS_ENABLED(CONFIG_KALLSYMS_BASE_RELATIVE))
265 : BUG_ON(!kallsyms_addresses);
266 : else
267 58 : BUG_ON(!kallsyms_offsets);
268 :
269 : /* Do a binary search on the sorted kallsyms_addresses array. */
270 58 : low = 0;
271 58 : high = kallsyms_num_syms;
272 :
273 968 : while (high - low > 1) {
274 852 : mid = low + (high - low) / 2;
275 1704 : if (kallsyms_sym_address(mid) <= addr)
276 : low = mid;
277 : else
278 : high = mid;
279 : }
280 :
281 : /*
282 : * Search for the first aliased symbol. Aliased
283 : * symbols are symbols with the same address.
284 : */
285 174 : while (low && kallsyms_sym_address(low-1) == kallsyms_sym_address(low))
286 0 : --low;
287 :
288 116 : symbol_start = kallsyms_sym_address(low);
289 :
290 : /* Search for next non-aliased symbol. */
291 58 : for (i = low + 1; i < kallsyms_num_syms; i++) {
292 116 : if (kallsyms_sym_address(i) > symbol_start) {
293 : symbol_end = kallsyms_sym_address(i);
294 : break;
295 : }
296 : }
297 :
298 : /* If we found no next symbol, we use the end of the section. */
299 58 : if (!symbol_end) {
300 0 : if (is_kernel_inittext(addr))
301 0 : symbol_end = (unsigned long)_einittext;
302 : else if (IS_ENABLED(CONFIG_KALLSYMS_ALL))
303 : symbol_end = (unsigned long)_end;
304 : else
305 0 : symbol_end = (unsigned long)_etext;
306 : }
307 :
308 58 : if (symbolsize)
309 58 : *symbolsize = symbol_end - symbol_start;
310 58 : if (offset)
311 58 : *offset = addr - symbol_start;
312 :
313 58 : return low;
314 : }
315 :
316 : /*
317 : * Lookup an address but don't bother to find any names.
318 : */
319 0 : int kallsyms_lookup_size_offset(unsigned long addr, unsigned long *symbolsize,
320 : unsigned long *offset)
321 : {
322 : char namebuf[KSYM_NAME_LEN];
323 :
324 0 : if (is_ksym_addr(addr)) {
325 0 : get_symbol_pos(addr, symbolsize, offset);
326 0 : return 1;
327 : }
328 : return !!module_address_lookup(addr, symbolsize, offset, NULL, NULL, namebuf) ||
329 : !!__bpf_address_lookup(addr, symbolsize, offset, namebuf);
330 : }
331 :
332 58 : static const char *kallsyms_lookup_buildid(unsigned long addr,
333 : unsigned long *symbolsize,
334 : unsigned long *offset, char **modname,
335 : const unsigned char **modbuildid, char *namebuf)
336 : {
337 : const char *ret;
338 :
339 58 : namebuf[KSYM_NAME_LEN - 1] = 0;
340 58 : namebuf[0] = 0;
341 :
342 58 : if (is_ksym_addr(addr)) {
343 : unsigned long pos;
344 :
345 58 : pos = get_symbol_pos(addr, symbolsize, offset);
346 : /* Grab name */
347 58 : kallsyms_expand_symbol(get_symbol_offset(pos),
348 : namebuf, KSYM_NAME_LEN);
349 58 : if (modname)
350 58 : *modname = NULL;
351 58 : if (modbuildid)
352 58 : *modbuildid = NULL;
353 :
354 : ret = namebuf;
355 : goto found;
356 : }
357 :
358 : /* See if it's in a module or a BPF JITed image. */
359 : ret = module_address_lookup(addr, symbolsize, offset,
360 : modname, modbuildid, namebuf);
361 : if (!ret)
362 : ret = bpf_address_lookup(addr, symbolsize,
363 : offset, modname, namebuf);
364 :
365 : if (!ret)
366 : ret = ftrace_mod_address_lookup(addr, symbolsize,
367 : offset, modname, namebuf);
368 :
369 : found:
370 58 : cleanup_symbol_name(namebuf);
371 58 : return ret;
372 : }
373 :
374 : /*
375 : * Lookup an address
376 : * - modname is set to NULL if it's in the kernel.
377 : * - We guarantee that the returned name is valid until we reschedule even if.
378 : * It resides in a module.
379 : * - We also guarantee that modname will be valid until rescheduled.
380 : */
381 0 : const char *kallsyms_lookup(unsigned long addr,
382 : unsigned long *symbolsize,
383 : unsigned long *offset,
384 : char **modname, char *namebuf)
385 : {
386 0 : return kallsyms_lookup_buildid(addr, symbolsize, offset, modname,
387 : NULL, namebuf);
388 : }
389 :
390 0 : int lookup_symbol_name(unsigned long addr, char *symname)
391 : {
392 : int res;
393 :
394 0 : symname[0] = '\0';
395 0 : symname[KSYM_NAME_LEN - 1] = '\0';
396 :
397 0 : if (is_ksym_addr(addr)) {
398 : unsigned long pos;
399 :
400 0 : pos = get_symbol_pos(addr, NULL, NULL);
401 : /* Grab name */
402 0 : kallsyms_expand_symbol(get_symbol_offset(pos),
403 : symname, KSYM_NAME_LEN);
404 : goto found;
405 : }
406 : /* See if it's in a module. */
407 : res = lookup_module_symbol_name(addr, symname);
408 : if (res)
409 : return res;
410 :
411 : found:
412 0 : cleanup_symbol_name(symname);
413 0 : return 0;
414 : }
415 :
416 0 : int lookup_symbol_attrs(unsigned long addr, unsigned long *size,
417 : unsigned long *offset, char *modname, char *name)
418 : {
419 : int res;
420 :
421 0 : name[0] = '\0';
422 0 : name[KSYM_NAME_LEN - 1] = '\0';
423 :
424 0 : if (is_ksym_addr(addr)) {
425 : unsigned long pos;
426 :
427 0 : pos = get_symbol_pos(addr, size, offset);
428 : /* Grab name */
429 0 : kallsyms_expand_symbol(get_symbol_offset(pos),
430 : name, KSYM_NAME_LEN);
431 0 : modname[0] = '\0';
432 : goto found;
433 : }
434 : /* See if it's in a module. */
435 : res = lookup_module_symbol_attrs(addr, size, offset, modname, name);
436 : if (res)
437 : return res;
438 :
439 : found:
440 0 : cleanup_symbol_name(name);
441 0 : return 0;
442 : }
443 :
444 : /* Look up a kernel symbol and return it in a text buffer. */
445 58 : static int __sprint_symbol(char *buffer, unsigned long address,
446 : int symbol_offset, int add_offset, int add_buildid)
447 : {
448 : char *modname;
449 : const unsigned char *buildid;
450 : const char *name;
451 : unsigned long offset, size;
452 : int len;
453 :
454 58 : address += symbol_offset;
455 58 : name = kallsyms_lookup_buildid(address, &size, &offset, &modname, &buildid,
456 : buffer);
457 58 : if (!name)
458 0 : return sprintf(buffer, "0x%lx", address - symbol_offset);
459 :
460 58 : if (name != buffer)
461 0 : strcpy(buffer, name);
462 58 : len = strlen(buffer);
463 58 : offset -= symbol_offset;
464 :
465 58 : if (add_offset)
466 58 : len += sprintf(buffer + len, "+%#lx/%#lx", offset, size);
467 :
468 58 : if (modname) {
469 0 : len += sprintf(buffer + len, " [%s", modname);
470 : #if IS_ENABLED(CONFIG_STACKTRACE_BUILD_ID)
471 : if (add_buildid && buildid) {
472 : /* build ID should match length of sprintf */
473 : #if IS_ENABLED(CONFIG_MODULES)
474 : static_assert(sizeof(typeof_member(struct module, build_id)) == 20);
475 : #endif
476 : len += sprintf(buffer + len, " %20phN", buildid);
477 : }
478 : #endif
479 0 : len += sprintf(buffer + len, "]");
480 : }
481 :
482 : return len;
483 : }
484 :
485 : /**
486 : * sprint_symbol - Look up a kernel symbol and return it in a text buffer
487 : * @buffer: buffer to be stored
488 : * @address: address to lookup
489 : *
490 : * This function looks up a kernel symbol with @address and stores its name,
491 : * offset, size and module name to @buffer if possible. If no symbol was found,
492 : * just saves its @address as is.
493 : *
494 : * This function returns the number of bytes stored in @buffer.
495 : */
496 58 : int sprint_symbol(char *buffer, unsigned long address)
497 : {
498 58 : return __sprint_symbol(buffer, address, 0, 1, 0);
499 : }
500 : EXPORT_SYMBOL_GPL(sprint_symbol);
501 :
502 : /**
503 : * sprint_symbol_build_id - Look up a kernel symbol and return it in a text buffer
504 : * @buffer: buffer to be stored
505 : * @address: address to lookup
506 : *
507 : * This function looks up a kernel symbol with @address and stores its name,
508 : * offset, size, module name and module build ID to @buffer if possible. If no
509 : * symbol was found, just saves its @address as is.
510 : *
511 : * This function returns the number of bytes stored in @buffer.
512 : */
513 0 : int sprint_symbol_build_id(char *buffer, unsigned long address)
514 : {
515 0 : return __sprint_symbol(buffer, address, 0, 1, 1);
516 : }
517 : EXPORT_SYMBOL_GPL(sprint_symbol_build_id);
518 :
519 : /**
520 : * sprint_symbol_no_offset - Look up a kernel symbol and return it in a text buffer
521 : * @buffer: buffer to be stored
522 : * @address: address to lookup
523 : *
524 : * This function looks up a kernel symbol with @address and stores its name
525 : * and module name to @buffer if possible. If no symbol was found, just saves
526 : * its @address as is.
527 : *
528 : * This function returns the number of bytes stored in @buffer.
529 : */
530 0 : int sprint_symbol_no_offset(char *buffer, unsigned long address)
531 : {
532 0 : return __sprint_symbol(buffer, address, 0, 0, 0);
533 : }
534 : EXPORT_SYMBOL_GPL(sprint_symbol_no_offset);
535 :
536 : /**
537 : * sprint_backtrace - Look up a backtrace symbol and return it in a text buffer
538 : * @buffer: buffer to be stored
539 : * @address: address to lookup
540 : *
541 : * This function is for stack backtrace and does the same thing as
542 : * sprint_symbol() but with modified/decreased @address. If there is a
543 : * tail-call to the function marked "noreturn", gcc optimized out code after
544 : * the call so that the stack-saved return address could point outside of the
545 : * caller. This function ensures that kallsyms will find the original caller
546 : * by decreasing @address.
547 : *
548 : * This function returns the number of bytes stored in @buffer.
549 : */
550 0 : int sprint_backtrace(char *buffer, unsigned long address)
551 : {
552 0 : return __sprint_symbol(buffer, address, -1, 1, 0);
553 : }
554 :
555 : /**
556 : * sprint_backtrace_build_id - Look up a backtrace symbol and return it in a text buffer
557 : * @buffer: buffer to be stored
558 : * @address: address to lookup
559 : *
560 : * This function is for stack backtrace and does the same thing as
561 : * sprint_symbol() but with modified/decreased @address. If there is a
562 : * tail-call to the function marked "noreturn", gcc optimized out code after
563 : * the call so that the stack-saved return address could point outside of the
564 : * caller. This function ensures that kallsyms will find the original caller
565 : * by decreasing @address. This function also appends the module build ID to
566 : * the @buffer if @address is within a kernel module.
567 : *
568 : * This function returns the number of bytes stored in @buffer.
569 : */
570 0 : int sprint_backtrace_build_id(char *buffer, unsigned long address)
571 : {
572 0 : return __sprint_symbol(buffer, address, -1, 1, 1);
573 : }
574 :
575 : /* To avoid using get_symbol_offset for every symbol, we carry prefix along. */
576 : struct kallsym_iter {
577 : loff_t pos;
578 : loff_t pos_arch_end;
579 : loff_t pos_mod_end;
580 : loff_t pos_ftrace_mod_end;
581 : loff_t pos_bpf_end;
582 : unsigned long value;
583 : unsigned int nameoff; /* If iterating in core kernel symbols. */
584 : char type;
585 : char name[KSYM_NAME_LEN];
586 : char module_name[MODULE_NAME_LEN];
587 : int exported;
588 : int show_value;
589 : };
590 :
591 0 : int __weak arch_get_kallsym(unsigned int symnum, unsigned long *value,
592 : char *type, char *name)
593 : {
594 0 : return -EINVAL;
595 : }
596 :
597 0 : static int get_ksymbol_arch(struct kallsym_iter *iter)
598 : {
599 0 : int ret = arch_get_kallsym(iter->pos - kallsyms_num_syms,
600 : &iter->value, &iter->type,
601 0 : iter->name);
602 :
603 0 : if (ret < 0) {
604 0 : iter->pos_arch_end = iter->pos;
605 0 : return 0;
606 : }
607 :
608 : return 1;
609 : }
610 :
611 : static int get_ksymbol_mod(struct kallsym_iter *iter)
612 : {
613 0 : int ret = module_get_kallsym(iter->pos - iter->pos_arch_end,
614 : &iter->value, &iter->type,
615 0 : iter->name, iter->module_name,
616 : &iter->exported);
617 : if (ret < 0) {
618 0 : iter->pos_mod_end = iter->pos;
619 : return 0;
620 : }
621 :
622 : return 1;
623 : }
624 :
625 : /*
626 : * ftrace_mod_get_kallsym() may also get symbols for pages allocated for ftrace
627 : * purposes. In that case "__builtin__ftrace" is used as a module name, even
628 : * though "__builtin__ftrace" is not a module.
629 : */
630 : static int get_ksymbol_ftrace_mod(struct kallsym_iter *iter)
631 : {
632 0 : int ret = ftrace_mod_get_kallsym(iter->pos - iter->pos_mod_end,
633 : &iter->value, &iter->type,
634 0 : iter->name, iter->module_name,
635 : &iter->exported);
636 : if (ret < 0) {
637 0 : iter->pos_ftrace_mod_end = iter->pos;
638 : return 0;
639 : }
640 :
641 : return 1;
642 : }
643 :
644 : static int get_ksymbol_bpf(struct kallsym_iter *iter)
645 : {
646 : int ret;
647 :
648 0 : strlcpy(iter->module_name, "bpf", MODULE_NAME_LEN);
649 0 : iter->exported = 0;
650 0 : ret = bpf_get_kallsym(iter->pos - iter->pos_ftrace_mod_end,
651 : &iter->value, &iter->type,
652 0 : iter->name);
653 : if (ret < 0) {
654 0 : iter->pos_bpf_end = iter->pos;
655 : return 0;
656 : }
657 :
658 : return 1;
659 : }
660 :
661 : /*
662 : * This uses "__builtin__kprobes" as a module name for symbols for pages
663 : * allocated for kprobes' purposes, even though "__builtin__kprobes" is not a
664 : * module.
665 : */
666 : static int get_ksymbol_kprobe(struct kallsym_iter *iter)
667 : {
668 0 : strlcpy(iter->module_name, "__builtin__kprobes", MODULE_NAME_LEN);
669 0 : iter->exported = 0;
670 0 : return kprobe_get_kallsym(iter->pos - iter->pos_bpf_end,
671 : &iter->value, &iter->type,
672 0 : iter->name) < 0 ? 0 : 1;
673 : }
674 :
675 : /* Returns space to next name. */
676 0 : static unsigned long get_ksymbol_core(struct kallsym_iter *iter)
677 : {
678 0 : unsigned off = iter->nameoff;
679 :
680 0 : iter->module_name[0] = '\0';
681 0 : iter->value = kallsyms_sym_address(iter->pos);
682 :
683 0 : iter->type = kallsyms_get_symbol_type(off);
684 :
685 0 : off = kallsyms_expand_symbol(off, iter->name, ARRAY_SIZE(iter->name));
686 :
687 0 : return off - iter->nameoff;
688 : }
689 :
690 : static void reset_iter(struct kallsym_iter *iter, loff_t new_pos)
691 : {
692 0 : iter->name[0] = '\0';
693 0 : iter->nameoff = get_symbol_offset(new_pos);
694 0 : iter->pos = new_pos;
695 0 : if (new_pos == 0) {
696 0 : iter->pos_arch_end = 0;
697 0 : iter->pos_mod_end = 0;
698 0 : iter->pos_ftrace_mod_end = 0;
699 0 : iter->pos_bpf_end = 0;
700 : }
701 : }
702 :
703 : /*
704 : * The end position (last + 1) of each additional kallsyms section is recorded
705 : * in iter->pos_..._end as each section is added, and so can be used to
706 : * determine which get_ksymbol_...() function to call next.
707 : */
708 0 : static int update_iter_mod(struct kallsym_iter *iter, loff_t pos)
709 : {
710 0 : iter->pos = pos;
711 :
712 0 : if ((!iter->pos_arch_end || iter->pos_arch_end > pos) &&
713 0 : get_ksymbol_arch(iter))
714 : return 1;
715 :
716 0 : if ((!iter->pos_mod_end || iter->pos_mod_end > pos) &&
717 0 : get_ksymbol_mod(iter))
718 : return 1;
719 :
720 0 : if ((!iter->pos_ftrace_mod_end || iter->pos_ftrace_mod_end > pos) &&
721 0 : get_ksymbol_ftrace_mod(iter))
722 : return 1;
723 :
724 0 : if ((!iter->pos_bpf_end || iter->pos_bpf_end > pos) &&
725 0 : get_ksymbol_bpf(iter))
726 : return 1;
727 :
728 0 : return get_ksymbol_kprobe(iter);
729 : }
730 :
731 : /* Returns false if pos at or past end of file. */
732 0 : static int update_iter(struct kallsym_iter *iter, loff_t pos)
733 : {
734 : /* Module symbols can be accessed randomly. */
735 0 : if (pos >= kallsyms_num_syms)
736 0 : return update_iter_mod(iter, pos);
737 :
738 : /* If we're not on the desired position, reset to new position. */
739 0 : if (pos != iter->pos)
740 : reset_iter(iter, pos);
741 :
742 0 : iter->nameoff += get_ksymbol_core(iter);
743 0 : iter->pos++;
744 :
745 0 : return 1;
746 : }
747 :
748 0 : static void *s_next(struct seq_file *m, void *p, loff_t *pos)
749 : {
750 0 : (*pos)++;
751 :
752 0 : if (!update_iter(m->private, *pos))
753 : return NULL;
754 0 : return p;
755 : }
756 :
757 0 : static void *s_start(struct seq_file *m, loff_t *pos)
758 : {
759 0 : if (!update_iter(m->private, *pos))
760 : return NULL;
761 0 : return m->private;
762 : }
763 :
764 0 : static void s_stop(struct seq_file *m, void *p)
765 : {
766 0 : }
767 :
768 0 : static int s_show(struct seq_file *m, void *p)
769 : {
770 : void *value;
771 0 : struct kallsym_iter *iter = m->private;
772 :
773 : /* Some debugging symbols have no name. Ignore them. */
774 0 : if (!iter->name[0])
775 : return 0;
776 :
777 0 : value = iter->show_value ? (void *)iter->value : NULL;
778 :
779 0 : if (iter->module_name[0]) {
780 : char type;
781 :
782 : /*
783 : * Label it "global" if it is exported,
784 : * "local" if not exported.
785 : */
786 0 : type = iter->exported ? toupper(iter->type) :
787 0 : tolower(iter->type);
788 0 : seq_printf(m, "%px %c %s\t[%s]\n", value,
789 0 : type, iter->name, iter->module_name);
790 : } else
791 0 : seq_printf(m, "%px %c %s\n", value,
792 0 : iter->type, iter->name);
793 : return 0;
794 : }
795 :
796 : static const struct seq_operations kallsyms_op = {
797 : .start = s_start,
798 : .next = s_next,
799 : .stop = s_stop,
800 : .show = s_show
801 : };
802 :
803 : static inline int kallsyms_for_perf(void)
804 : {
805 : #ifdef CONFIG_PERF_EVENTS
806 : extern int sysctl_perf_event_paranoid;
807 : if (sysctl_perf_event_paranoid <= 1)
808 : return 1;
809 : #endif
810 : return 0;
811 : }
812 :
813 : /*
814 : * We show kallsyms information even to normal users if we've enabled
815 : * kernel profiling and are explicitly not paranoid (so kptr_restrict
816 : * is clear, and sysctl_perf_event_paranoid isn't set).
817 : *
818 : * Otherwise, require CAP_SYSLOG (assuming kptr_restrict isn't set to
819 : * block even that).
820 : */
821 0 : bool kallsyms_show_value(const struct cred *cred)
822 : {
823 0 : switch (kptr_restrict) {
824 : case 0:
825 : if (kallsyms_for_perf())
826 : return true;
827 : fallthrough;
828 : case 1:
829 0 : if (security_capable(cred, &init_user_ns, CAP_SYSLOG,
830 : CAP_OPT_NOAUDIT) == 0)
831 : return true;
832 : fallthrough;
833 : default:
834 : return false;
835 : }
836 : }
837 :
838 0 : static int kallsyms_open(struct inode *inode, struct file *file)
839 : {
840 : /*
841 : * We keep iterator in m->private, since normal case is to
842 : * s_start from where we left off, so we avoid doing
843 : * using get_symbol_offset for every symbol.
844 : */
845 : struct kallsym_iter *iter;
846 0 : iter = __seq_open_private(file, &kallsyms_op, sizeof(*iter));
847 0 : if (!iter)
848 : return -ENOMEM;
849 0 : reset_iter(iter, 0);
850 :
851 : /*
852 : * Instead of checking this on every s_show() call, cache
853 : * the result here at open time.
854 : */
855 0 : iter->show_value = kallsyms_show_value(file->f_cred);
856 0 : return 0;
857 : }
858 :
859 : #ifdef CONFIG_KGDB_KDB
860 : const char *kdb_walk_kallsyms(loff_t *pos)
861 : {
862 : static struct kallsym_iter kdb_walk_kallsyms_iter;
863 : if (*pos == 0) {
864 : memset(&kdb_walk_kallsyms_iter, 0,
865 : sizeof(kdb_walk_kallsyms_iter));
866 : reset_iter(&kdb_walk_kallsyms_iter, 0);
867 : }
868 : while (1) {
869 : if (!update_iter(&kdb_walk_kallsyms_iter, *pos))
870 : return NULL;
871 : ++*pos;
872 : /* Some debugging symbols have no name. Ignore them. */
873 : if (kdb_walk_kallsyms_iter.name[0])
874 : return kdb_walk_kallsyms_iter.name;
875 : }
876 : }
877 : #endif /* CONFIG_KGDB_KDB */
878 :
879 : static const struct proc_ops kallsyms_proc_ops = {
880 : .proc_open = kallsyms_open,
881 : .proc_read = seq_read,
882 : .proc_lseek = seq_lseek,
883 : .proc_release = seq_release_private,
884 : };
885 :
886 1 : static int __init kallsyms_init(void)
887 : {
888 1 : proc_create("kallsyms", 0444, NULL, &kallsyms_proc_ops);
889 1 : return 0;
890 : }
891 : device_initcall(kallsyms_init);
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