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 */
42static unsigned int kallsyms_expand_symbol(unsigned int off,
43 char *result, size_t maxlen)
44{
45 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 data = &kallsyms_names[off];
51 len = *data;
52 data++;
53 off++;
54
55 /* If MSB is 1, it is a "big" symbol, so needs an additional byte. */
56 if ((len & 0x80) != 0) {
57 len = (len & 0x7F) | (*data << 7);
58 data++;
59 off++;
60 }
61
62 /*
63 * Update the offset to return the offset for the next symbol on
64 * the compressed stream.
65 */
66 off += len;
67
68 /*
69 * For every byte on the compressed symbol data, copy the table
70 * entry for that byte.
71 */
72 while (len) {
73 tptr = &kallsyms_token_table[kallsyms_token_index[*data]];
74 data++;
75 len--;
76
77 while (*tptr) {
78 if (skipped_first) {
79 if (maxlen <= 1)
80 goto tail;
81 *result = *tptr;
82 result++;
83 maxlen--;
84 } else
85 skipped_first = 1;
86 tptr++;
87 }
88 }
89
90tail:
91 if (maxlen)
92 *result = '\0';
93
94 /* Return to offset to the next symbol. */
95 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 */
102static 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 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 */
116static 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 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 for (i = 0; i < (pos & 0xFF); i++) {
134 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 if ((len & 0x80) != 0)
141 len = ((len & 0x7F) | (name[1] << 7)) + 1;
142
143 name = name + len + 1;
144 }
145
146 return name - kallsyms_names;
147}
148
149unsigned long kallsyms_sym_address(int idx)
150{
151 /* values are unsigned offsets */
152 return kallsyms_relative_base + (u32)kallsyms_offsets[idx];
153}
154
155static unsigned int get_symbol_seq(int index)
156{
157 unsigned int i, seq = 0;
158
159 for (i = 0; i < 3; i++)
160 seq = (seq << 8) | kallsyms_seqs_of_names[3 * index + i];
161
162 return seq;
163}
164
165static int kallsyms_lookup_names(const char *name,
166 unsigned int *start,
167 unsigned int *end)
168{
169 int ret;
170 int low, mid, high;
171 unsigned int seq, off;
172 char namebuf[KSYM_NAME_LEN];
173
174 low = 0;
175 high = kallsyms_num_syms - 1;
176
177 while (low <= high) {
178 mid = low + (high - low) / 2;
179 seq = get_symbol_seq(index: mid);
180 off = get_symbol_offset(pos: seq);
181 kallsyms_expand_symbol(off, result: namebuf, ARRAY_SIZE(namebuf));
182 ret = strcmp(name, namebuf);
183 if (ret > 0)
184 low = mid + 1;
185 else if (ret < 0)
186 high = mid - 1;
187 else
188 break;
189 }
190
191 if (low > high)
192 return -ESRCH;
193
194 low = mid;
195 while (low) {
196 seq = get_symbol_seq(index: low - 1);
197 off = get_symbol_offset(pos: seq);
198 kallsyms_expand_symbol(off, result: namebuf, ARRAY_SIZE(namebuf));
199 if (strcmp(name, namebuf))
200 break;
201 low--;
202 }
203 *start = low;
204
205 if (end) {
206 high = mid;
207 while (high < kallsyms_num_syms - 1) {
208 seq = get_symbol_seq(index: high + 1);
209 off = get_symbol_offset(pos: seq);
210 kallsyms_expand_symbol(off, result: namebuf, ARRAY_SIZE(namebuf));
211 if (strcmp(name, namebuf))
212 break;
213 high++;
214 }
215 *end = high;
216 }
217
218 return 0;
219}
220
221/* Lookup the address for this symbol. Returns 0 if not found. */
222unsigned long kallsyms_lookup_name(const char *name)
223{
224 int ret;
225 unsigned int i;
226
227 /* Skip the search for empty string. */
228 if (!*name)
229 return 0;
230
231 ret = kallsyms_lookup_names(name, start: &i, NULL);
232 if (!ret)
233 return kallsyms_sym_address(idx: get_symbol_seq(index: i));
234
235 return module_kallsyms_lookup_name(name);
236}
237
238/*
239 * Iterate over all symbols in vmlinux. For symbols from modules use
240 * module_kallsyms_on_each_symbol instead.
241 */
242int kallsyms_on_each_symbol(int (*fn)(void *, const char *, unsigned long),
243 void *data)
244{
245 char namebuf[KSYM_NAME_LEN];
246 unsigned long i;
247 unsigned int off;
248 int ret;
249
250 for (i = 0, off = 0; i < kallsyms_num_syms; i++) {
251 off = kallsyms_expand_symbol(off, result: namebuf, ARRAY_SIZE(namebuf));
252 ret = fn(data, namebuf, kallsyms_sym_address(idx: i));
253 if (ret != 0)
254 return ret;
255 cond_resched();
256 }
257 return 0;
258}
259
260int kallsyms_on_each_match_symbol(int (*fn)(void *, unsigned long),
261 const char *name, void *data)
262{
263 int ret;
264 unsigned int i, start, end;
265
266 ret = kallsyms_lookup_names(name, start: &start, end: &end);
267 if (ret)
268 return 0;
269
270 for (i = start; !ret && i <= end; i++) {
271 ret = fn(data, kallsyms_sym_address(idx: get_symbol_seq(index: i)));
272 cond_resched();
273 }
274
275 return ret;
276}
277
278static unsigned long get_symbol_pos(unsigned long addr,
279 unsigned long *symbolsize,
280 unsigned long *offset)
281{
282 unsigned long symbol_start = 0, symbol_end = 0;
283 unsigned long i, low, high, mid;
284
285 /* Do a binary search on the sorted kallsyms_offsets array. */
286 low = 0;
287 high = kallsyms_num_syms;
288
289 while (high - low > 1) {
290 mid = low + (high - low) / 2;
291 if (kallsyms_sym_address(idx: mid) <= addr)
292 low = mid;
293 else
294 high = mid;
295 }
296
297 /*
298 * Search for the first aliased symbol. Aliased
299 * symbols are symbols with the same address.
300 */
301 while (low && kallsyms_sym_address(idx: low-1) == kallsyms_sym_address(idx: low))
302 --low;
303
304 symbol_start = kallsyms_sym_address(idx: low);
305
306 /* Search for next non-aliased symbol. */
307 for (i = low + 1; i < kallsyms_num_syms; i++) {
308 if (kallsyms_sym_address(idx: i) > symbol_start) {
309 symbol_end = kallsyms_sym_address(idx: i);
310 break;
311 }
312 }
313
314 /* If we found no next symbol, we use the end of the section. */
315 if (!symbol_end) {
316 if (is_kernel_inittext(addr))
317 symbol_end = (unsigned long)_einittext;
318 else if (IS_ENABLED(CONFIG_KALLSYMS_ALL))
319 symbol_end = (unsigned long)_end;
320 else
321 symbol_end = (unsigned long)_etext;
322 }
323
324 if (symbolsize)
325 *symbolsize = symbol_end - symbol_start;
326 if (offset)
327 *offset = addr - symbol_start;
328
329 return low;
330}
331
332/*
333 * Lookup an address but don't bother to find any names.
334 */
335int kallsyms_lookup_size_offset(unsigned long addr, unsigned long *symbolsize,
336 unsigned long *offset)
337{
338 char namebuf[KSYM_NAME_LEN];
339
340 if (is_ksym_addr(addr)) {
341 get_symbol_pos(addr, symbolsize, offset);
342 return 1;
343 }
344 return !!module_address_lookup(addr, symbolsize, offset, NULL, NULL, namebuf) ||
345 !!__bpf_address_lookup(addr, size: symbolsize, off: offset, sym: namebuf);
346}
347
348static int kallsyms_lookup_buildid(unsigned long addr,
349 unsigned long *symbolsize,
350 unsigned long *offset, char **modname,
351 const unsigned char **modbuildid, char *namebuf)
352{
353 int ret;
354
355 namebuf[KSYM_NAME_LEN - 1] = 0;
356 namebuf[0] = 0;
357
358 if (is_ksym_addr(addr)) {
359 unsigned long pos;
360
361 pos = get_symbol_pos(addr, symbolsize, offset);
362 /* Grab name */
363 kallsyms_expand_symbol(off: get_symbol_offset(pos),
364 result: namebuf, KSYM_NAME_LEN);
365 if (modname)
366 *modname = NULL;
367 if (modbuildid)
368 *modbuildid = NULL;
369
370 return strlen(namebuf);
371 }
372
373 /* See if it's in a module or a BPF JITed image. */
374 ret = module_address_lookup(addr, symbolsize, offset,
375 modname, modbuildid, namebuf);
376 if (!ret)
377 ret = bpf_address_lookup(addr, size: symbolsize,
378 off: offset, modname, sym: namebuf);
379
380 if (!ret)
381 ret = ftrace_mod_address_lookup(addr, size: symbolsize,
382 off: offset, modname, sym: namebuf);
383
384 return ret;
385}
386
387/*
388 * Lookup an address
389 * - modname is set to NULL if it's in the kernel.
390 * - We guarantee that the returned name is valid until we reschedule even if.
391 * It resides in a module.
392 * - We also guarantee that modname will be valid until rescheduled.
393 */
394const char *kallsyms_lookup(unsigned long addr,
395 unsigned long *symbolsize,
396 unsigned long *offset,
397 char **modname, char *namebuf)
398{
399 int ret = kallsyms_lookup_buildid(addr, symbolsize, offset, modname,
400 NULL, namebuf);
401
402 if (!ret)
403 return NULL;
404
405 return namebuf;
406}
407
408int lookup_symbol_name(unsigned long addr, char *symname)
409{
410 symname[0] = '\0';
411 symname[KSYM_NAME_LEN - 1] = '\0';
412
413 if (is_ksym_addr(addr)) {
414 unsigned long pos;
415
416 pos = get_symbol_pos(addr, NULL, NULL);
417 /* Grab name */
418 kallsyms_expand_symbol(off: get_symbol_offset(pos),
419 result: symname, KSYM_NAME_LEN);
420 return 0;
421 }
422 /* See if it's in a module. */
423 return lookup_module_symbol_name(addr, symname);
424}
425
426/* Look up a kernel symbol and return it in a text buffer. */
427static int __sprint_symbol(char *buffer, unsigned long address,
428 int symbol_offset, int add_offset, int add_buildid)
429{
430 char *modname;
431 const unsigned char *buildid;
432 unsigned long offset, size;
433 int len;
434
435 address += symbol_offset;
436 len = kallsyms_lookup_buildid(addr: address, symbolsize: &size, offset: &offset, modname: &modname, modbuildid: &buildid,
437 namebuf: buffer);
438 if (!len)
439 return sprintf(buf: buffer, fmt: "0x%lx", address - symbol_offset);
440
441 offset -= symbol_offset;
442
443 if (add_offset)
444 len += sprintf(buf: buffer + len, fmt: "+%#lx/%#lx", offset, size);
445
446 if (modname) {
447 len += sprintf(buf: buffer + len, fmt: " [%s", modname);
448#if IS_ENABLED(CONFIG_STACKTRACE_BUILD_ID)
449 if (add_buildid && buildid) {
450 /* build ID should match length of sprintf */
451#if IS_ENABLED(CONFIG_MODULES)
452 static_assert(sizeof(typeof_member(struct module, build_id)) == 20);
453#endif
454 len += sprintf(buf: buffer + len, fmt: " %20phN", buildid);
455 }
456#endif
457 len += sprintf(buf: buffer + len, fmt: "]");
458 }
459
460 return len;
461}
462
463/**
464 * sprint_symbol - Look up a kernel symbol and return it in a text buffer
465 * @buffer: buffer to be stored
466 * @address: address to lookup
467 *
468 * This function looks up a kernel symbol with @address and stores its name,
469 * offset, size and module name to @buffer if possible. If no symbol was found,
470 * just saves its @address as is.
471 *
472 * This function returns the number of bytes stored in @buffer.
473 */
474int sprint_symbol(char *buffer, unsigned long address)
475{
476 return __sprint_symbol(buffer, address, symbol_offset: 0, add_offset: 1, add_buildid: 0);
477}
478EXPORT_SYMBOL_GPL(sprint_symbol);
479
480/**
481 * sprint_symbol_build_id - Look up a kernel symbol and return it in a text buffer
482 * @buffer: buffer to be stored
483 * @address: address to lookup
484 *
485 * This function looks up a kernel symbol with @address and stores its name,
486 * offset, size, module name and module build ID to @buffer if possible. If no
487 * symbol was found, just saves its @address as is.
488 *
489 * This function returns the number of bytes stored in @buffer.
490 */
491int sprint_symbol_build_id(char *buffer, unsigned long address)
492{
493 return __sprint_symbol(buffer, address, symbol_offset: 0, add_offset: 1, add_buildid: 1);
494}
495EXPORT_SYMBOL_GPL(sprint_symbol_build_id);
496
497/**
498 * sprint_symbol_no_offset - Look up a kernel symbol and return it in a text buffer
499 * @buffer: buffer to be stored
500 * @address: address to lookup
501 *
502 * This function looks up a kernel symbol with @address and stores its name
503 * and module name to @buffer if possible. If no symbol was found, just saves
504 * its @address as is.
505 *
506 * This function returns the number of bytes stored in @buffer.
507 */
508int sprint_symbol_no_offset(char *buffer, unsigned long address)
509{
510 return __sprint_symbol(buffer, address, symbol_offset: 0, add_offset: 0, add_buildid: 0);
511}
512EXPORT_SYMBOL_GPL(sprint_symbol_no_offset);
513
514/**
515 * sprint_backtrace - Look up a backtrace symbol and return it in a text buffer
516 * @buffer: buffer to be stored
517 * @address: address to lookup
518 *
519 * This function is for stack backtrace and does the same thing as
520 * sprint_symbol() but with modified/decreased @address. If there is a
521 * tail-call to the function marked "noreturn", gcc optimized out code after
522 * the call so that the stack-saved return address could point outside of the
523 * caller. This function ensures that kallsyms will find the original caller
524 * by decreasing @address.
525 *
526 * This function returns the number of bytes stored in @buffer.
527 */
528int sprint_backtrace(char *buffer, unsigned long address)
529{
530 return __sprint_symbol(buffer, address, symbol_offset: -1, add_offset: 1, add_buildid: 0);
531}
532
533/**
534 * sprint_backtrace_build_id - Look up a backtrace symbol and return it in a text buffer
535 * @buffer: buffer to be stored
536 * @address: address to lookup
537 *
538 * This function is for stack backtrace and does the same thing as
539 * sprint_symbol() but with modified/decreased @address. If there is a
540 * tail-call to the function marked "noreturn", gcc optimized out code after
541 * the call so that the stack-saved return address could point outside of the
542 * caller. This function ensures that kallsyms will find the original caller
543 * by decreasing @address. This function also appends the module build ID to
544 * the @buffer if @address is within a kernel module.
545 *
546 * This function returns the number of bytes stored in @buffer.
547 */
548int sprint_backtrace_build_id(char *buffer, unsigned long address)
549{
550 return __sprint_symbol(buffer, address, symbol_offset: -1, add_offset: 1, add_buildid: 1);
551}
552
553/* To avoid using get_symbol_offset for every symbol, we carry prefix along. */
554struct kallsym_iter {
555 loff_t pos;
556 loff_t pos_mod_end;
557 loff_t pos_ftrace_mod_end;
558 loff_t pos_bpf_end;
559 unsigned long value;
560 unsigned int nameoff; /* If iterating in core kernel symbols. */
561 char type;
562 char name[KSYM_NAME_LEN];
563 char module_name[MODULE_NAME_LEN];
564 int exported;
565 int show_value;
566};
567
568static int get_ksymbol_mod(struct kallsym_iter *iter)
569{
570 int ret = module_get_kallsym(symnum: iter->pos - kallsyms_num_syms,
571 value: &iter->value, type: &iter->type,
572 name: iter->name, module_name: iter->module_name,
573 exported: &iter->exported);
574 if (ret < 0) {
575 iter->pos_mod_end = iter->pos;
576 return 0;
577 }
578
579 return 1;
580}
581
582/*
583 * ftrace_mod_get_kallsym() may also get symbols for pages allocated for ftrace
584 * purposes. In that case "__builtin__ftrace" is used as a module name, even
585 * though "__builtin__ftrace" is not a module.
586 */
587static int get_ksymbol_ftrace_mod(struct kallsym_iter *iter)
588{
589 int ret = ftrace_mod_get_kallsym(symnum: iter->pos - iter->pos_mod_end,
590 value: &iter->value, type: &iter->type,
591 name: iter->name, module_name: iter->module_name,
592 exported: &iter->exported);
593 if (ret < 0) {
594 iter->pos_ftrace_mod_end = iter->pos;
595 return 0;
596 }
597
598 return 1;
599}
600
601static int get_ksymbol_bpf(struct kallsym_iter *iter)
602{
603 int ret;
604
605 strscpy(iter->module_name, "bpf", MODULE_NAME_LEN);
606 iter->exported = 0;
607 ret = bpf_get_kallsym(symnum: iter->pos - iter->pos_ftrace_mod_end,
608 value: &iter->value, type: &iter->type,
609 sym: iter->name);
610 if (ret < 0) {
611 iter->pos_bpf_end = iter->pos;
612 return 0;
613 }
614
615 return 1;
616}
617
618/*
619 * This uses "__builtin__kprobes" as a module name for symbols for pages
620 * allocated for kprobes' purposes, even though "__builtin__kprobes" is not a
621 * module.
622 */
623static int get_ksymbol_kprobe(struct kallsym_iter *iter)
624{
625 strscpy(iter->module_name, "__builtin__kprobes", MODULE_NAME_LEN);
626 iter->exported = 0;
627 return kprobe_get_kallsym(symnum: iter->pos - iter->pos_bpf_end,
628 value: &iter->value, type: &iter->type,
629 sym: iter->name) < 0 ? 0 : 1;
630}
631
632/* Returns space to next name. */
633static unsigned long get_ksymbol_core(struct kallsym_iter *iter)
634{
635 unsigned off = iter->nameoff;
636
637 iter->module_name[0] = '\0';
638 iter->value = kallsyms_sym_address(idx: iter->pos);
639
640 iter->type = kallsyms_get_symbol_type(off);
641
642 off = kallsyms_expand_symbol(off, result: iter->name, ARRAY_SIZE(iter->name));
643
644 return off - iter->nameoff;
645}
646
647static void reset_iter(struct kallsym_iter *iter, loff_t new_pos)
648{
649 iter->name[0] = '\0';
650 iter->nameoff = get_symbol_offset(pos: new_pos);
651 iter->pos = new_pos;
652 if (new_pos == 0) {
653 iter->pos_mod_end = 0;
654 iter->pos_ftrace_mod_end = 0;
655 iter->pos_bpf_end = 0;
656 }
657}
658
659/*
660 * The end position (last + 1) of each additional kallsyms section is recorded
661 * in iter->pos_..._end as each section is added, and so can be used to
662 * determine which get_ksymbol_...() function to call next.
663 */
664static int update_iter_mod(struct kallsym_iter *iter, loff_t pos)
665{
666 iter->pos = pos;
667
668 if ((!iter->pos_mod_end || iter->pos_mod_end > pos) &&
669 get_ksymbol_mod(iter))
670 return 1;
671
672 if ((!iter->pos_ftrace_mod_end || iter->pos_ftrace_mod_end > pos) &&
673 get_ksymbol_ftrace_mod(iter))
674 return 1;
675
676 if ((!iter->pos_bpf_end || iter->pos_bpf_end > pos) &&
677 get_ksymbol_bpf(iter))
678 return 1;
679
680 return get_ksymbol_kprobe(iter);
681}
682
683/* Returns false if pos at or past end of file. */
684static int update_iter(struct kallsym_iter *iter, loff_t pos)
685{
686 /* Module symbols can be accessed randomly. */
687 if (pos >= kallsyms_num_syms)
688 return update_iter_mod(iter, pos);
689
690 /* If we're not on the desired position, reset to new position. */
691 if (pos != iter->pos)
692 reset_iter(iter, new_pos: pos);
693
694 iter->nameoff += get_ksymbol_core(iter);
695 iter->pos++;
696
697 return 1;
698}
699
700static void *s_next(struct seq_file *m, void *p, loff_t *pos)
701{
702 (*pos)++;
703
704 if (!update_iter(iter: m->private, pos: *pos))
705 return NULL;
706 return p;
707}
708
709static void *s_start(struct seq_file *m, loff_t *pos)
710{
711 if (!update_iter(iter: m->private, pos: *pos))
712 return NULL;
713 return m->private;
714}
715
716static void s_stop(struct seq_file *m, void *p)
717{
718}
719
720static int s_show(struct seq_file *m, void *p)
721{
722 void *value;
723 struct kallsym_iter *iter = m->private;
724
725 /* Some debugging symbols have no name. Ignore them. */
726 if (!iter->name[0])
727 return 0;
728
729 value = iter->show_value ? (void *)iter->value : NULL;
730
731 if (iter->module_name[0]) {
732 char type;
733
734 /*
735 * Label it "global" if it is exported,
736 * "local" if not exported.
737 */
738 type = iter->exported ? toupper(iter->type) :
739 tolower(iter->type);
740 seq_printf(m, fmt: "%px %c %s\t[%s]\n", value,
741 type, iter->name, iter->module_name);
742 } else
743 seq_printf(m, fmt: "%px %c %s\n", value,
744 iter->type, iter->name);
745 return 0;
746}
747
748static const struct seq_operations kallsyms_op = {
749 .start = s_start,
750 .next = s_next,
751 .stop = s_stop,
752 .show = s_show
753};
754
755#ifdef CONFIG_BPF_SYSCALL
756
757struct bpf_iter__ksym {
758 __bpf_md_ptr(struct bpf_iter_meta *, meta);
759 __bpf_md_ptr(struct kallsym_iter *, ksym);
760};
761
762static int ksym_prog_seq_show(struct seq_file *m, bool in_stop)
763{
764 struct bpf_iter__ksym ctx;
765 struct bpf_iter_meta meta;
766 struct bpf_prog *prog;
767
768 meta.seq = m;
769 prog = bpf_iter_get_info(meta: &meta, in_stop);
770 if (!prog)
771 return 0;
772
773 ctx.meta = &meta;
774 ctx.ksym = m ? m->private : NULL;
775 return bpf_iter_run_prog(prog, ctx: &ctx);
776}
777
778static int bpf_iter_ksym_seq_show(struct seq_file *m, void *p)
779{
780 return ksym_prog_seq_show(m, in_stop: false);
781}
782
783static void bpf_iter_ksym_seq_stop(struct seq_file *m, void *p)
784{
785 if (!p)
786 (void) ksym_prog_seq_show(m, in_stop: true);
787 else
788 s_stop(m, p);
789}
790
791static const struct seq_operations bpf_iter_ksym_ops = {
792 .start = s_start,
793 .next = s_next,
794 .stop = bpf_iter_ksym_seq_stop,
795 .show = bpf_iter_ksym_seq_show,
796};
797
798static int bpf_iter_ksym_init(void *priv_data, struct bpf_iter_aux_info *aux)
799{
800 struct kallsym_iter *iter = priv_data;
801
802 reset_iter(iter, new_pos: 0);
803
804 /* cache here as in kallsyms_open() case; use current process
805 * credentials to tell BPF iterators if values should be shown.
806 */
807 iter->show_value = kallsyms_show_value(current_cred());
808
809 return 0;
810}
811
812DEFINE_BPF_ITER_FUNC(ksym, struct bpf_iter_meta *meta, struct kallsym_iter *ksym)
813
814static const struct bpf_iter_seq_info ksym_iter_seq_info = {
815 .seq_ops = &bpf_iter_ksym_ops,
816 .init_seq_private = bpf_iter_ksym_init,
817 .fini_seq_private = NULL,
818 .seq_priv_size = sizeof(struct kallsym_iter),
819};
820
821static struct bpf_iter_reg ksym_iter_reg_info = {
822 .target = "ksym",
823 .feature = BPF_ITER_RESCHED,
824 .ctx_arg_info_size = 1,
825 .ctx_arg_info = {
826 { offsetof(struct bpf_iter__ksym, ksym),
827 PTR_TO_BTF_ID_OR_NULL },
828 },
829 .seq_info = &ksym_iter_seq_info,
830};
831
832BTF_ID_LIST(btf_ksym_iter_id)
833BTF_ID(struct, kallsym_iter)
834
835static int __init bpf_ksym_iter_register(void)
836{
837 ksym_iter_reg_info.ctx_arg_info[0].btf_id = *btf_ksym_iter_id;
838 return bpf_iter_reg_target(reg_info: &ksym_iter_reg_info);
839}
840
841late_initcall(bpf_ksym_iter_register);
842
843#endif /* CONFIG_BPF_SYSCALL */
844
845static int kallsyms_open(struct inode *inode, struct file *file)
846{
847 /*
848 * We keep iterator in m->private, since normal case is to
849 * s_start from where we left off, so we avoid doing
850 * using get_symbol_offset for every symbol.
851 */
852 struct kallsym_iter *iter;
853 iter = __seq_open_private(file, &kallsyms_op, sizeof(*iter));
854 if (!iter)
855 return -ENOMEM;
856 reset_iter(iter, new_pos: 0);
857
858 /*
859 * Instead of checking this on every s_show() call, cache
860 * the result here at open time.
861 */
862 iter->show_value = kallsyms_show_value(cred: file->f_cred);
863 return 0;
864}
865
866#ifdef CONFIG_KGDB_KDB
867const char *kdb_walk_kallsyms(loff_t *pos)
868{
869 static struct kallsym_iter kdb_walk_kallsyms_iter;
870 if (*pos == 0) {
871 memset(&kdb_walk_kallsyms_iter, 0,
872 sizeof(kdb_walk_kallsyms_iter));
873 reset_iter(iter: &kdb_walk_kallsyms_iter, new_pos: 0);
874 }
875 while (1) {
876 if (!update_iter(iter: &kdb_walk_kallsyms_iter, pos: *pos))
877 return NULL;
878 ++*pos;
879 /* Some debugging symbols have no name. Ignore them. */
880 if (kdb_walk_kallsyms_iter.name[0])
881 return kdb_walk_kallsyms_iter.name;
882 }
883}
884#endif /* CONFIG_KGDB_KDB */
885
886static const struct proc_ops kallsyms_proc_ops = {
887 .proc_open = kallsyms_open,
888 .proc_read = seq_read,
889 .proc_lseek = seq_lseek,
890 .proc_release = seq_release_private,
891};
892
893static int __init kallsyms_init(void)
894{
895 proc_create(name: "kallsyms", mode: 0444, NULL, proc_ops: &kallsyms_proc_ops);
896 return 0;
897}
898device_initcall(kallsyms_init);
899

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source code of linux/kernel/kallsyms.c