projects/linux·blob v7.0 · refs

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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 <[email protected]> IBM Corporation
8 *
9 * ChangeLog:
10 *
11 * (25/Aug/2004) Paulo Marques <[email protected]>
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. If MSB of length
107 * is 1, it is a "big" symbol, so needs an additional byte.
108 */
109 if (kallsyms_names[off] & 0x80)
110 off++;
111 return kallsyms_token_table[kallsyms_token_index[kallsyms_names[off + 1]]];
112}
113
114
115/*
116 * Find the offset on the compressed stream given and index in the
117 * kallsyms array.
118 */
119static unsigned int get_symbol_offset(unsigned long pos)
120{
121 const u8 *name;
122 int i, len;
123
124 /*
125 * Use the closest marker we have. We have markers every 256 positions,
126 * so that should be close enough.
127 */
128 name = &kallsyms_names[kallsyms_markers[pos >> 8]];
129
130 /*
131 * Sequentially scan all the symbols up to the point we're searching
132 * for. Every symbol is stored in a [<len>][<len> bytes of data] format,
133 * so we just need to add the len to the current pointer for every
134 * symbol we wish to skip.
135 */
136 for (i = 0; i < (pos & 0xFF); i++) {
137 len = *name;
138
139 /*
140 * If MSB is 1, it is a "big" symbol, so we need to look into
141 * the next byte (and skip it, too).
142 */
143 if ((len & 0x80) != 0)
144 len = ((len & 0x7F) | (name[1] << 7)) + 1;
145
146 name = name + len + 1;
147 }
148
149 return name - kallsyms_names;
150}
151
152unsigned long kallsyms_sym_address(int idx)
153{
154 /* non-relocatable 32-bit kernels just embed the value directly */
155 if (!IS_ENABLED(CONFIG_64BIT) && !IS_ENABLED(CONFIG_RELOCATABLE))
156 return (u32)kallsyms_offsets[idx];
157 return (unsigned long)offset_to_ptr(kallsyms_offsets + idx);
158}
159
160static unsigned int get_symbol_seq(int index)
161{
162 unsigned int i, seq = 0;
163
164 for (i = 0; i < 3; i++)
165 seq = (seq << 8) | kallsyms_seqs_of_names[3 * index + i];
166
167 return seq;
168}
169
170static int kallsyms_lookup_names(const char *name,
171 unsigned int *start,
172 unsigned int *end)
173{
174 int ret;
175 int low, mid, high;
176 unsigned int seq, off;
177 char namebuf[KSYM_NAME_LEN];
178
179 low = 0;
180 high = kallsyms_num_syms - 1;
181
182 while (low <= high) {
183 mid = low + (high - low) / 2;
184 seq = get_symbol_seq(mid);
185 off = get_symbol_offset(seq);
186 kallsyms_expand_symbol(off, namebuf, ARRAY_SIZE(namebuf));
187 ret = strcmp(name, namebuf);
188 if (ret > 0)
189 low = mid + 1;
190 else if (ret < 0)
191 high = mid - 1;
192 else
193 break;
194 }
195
196 if (low > high)
197 return -ESRCH;
198
199 low = mid;
200 while (low) {
201 seq = get_symbol_seq(low - 1);
202 off = get_symbol_offset(seq);
203 kallsyms_expand_symbol(off, namebuf, ARRAY_SIZE(namebuf));
204 if (strcmp(name, namebuf))
205 break;
206 low--;
207 }
208 *start = low;
209
210 if (end) {
211 high = mid;
212 while (high < kallsyms_num_syms - 1) {
213 seq = get_symbol_seq(high + 1);
214 off = get_symbol_offset(seq);
215 kallsyms_expand_symbol(off, namebuf, ARRAY_SIZE(namebuf));
216 if (strcmp(name, namebuf))
217 break;
218 high++;
219 }
220 *end = high;
221 }
222
223 return 0;
224}
225
226/* Lookup the address for this symbol. Returns 0 if not found. */
227unsigned long kallsyms_lookup_name(const char *name)
228{
229 int ret;
230 unsigned int i;
231
232 /* Skip the search for empty string. */
233 if (!*name)
234 return 0;
235
236 ret = kallsyms_lookup_names(name, &i, NULL);
237 if (!ret)
238 return kallsyms_sym_address(get_symbol_seq(i));
239
240 return module_kallsyms_lookup_name(name);
241}
242
243/*
244 * Iterate over all symbols in vmlinux. For symbols from modules use
245 * module_kallsyms_on_each_symbol instead.
246 */
247int kallsyms_on_each_symbol(int (*fn)(void *, const char *, unsigned long),
248 void *data)
249{
250 char namebuf[KSYM_NAME_LEN];
251 unsigned long i;
252 unsigned int off;
253 int ret;
254
255 for (i = 0, off = 0; i < kallsyms_num_syms; i++) {
256 off = kallsyms_expand_symbol(off, namebuf, ARRAY_SIZE(namebuf));
257 ret = fn(data, namebuf, kallsyms_sym_address(i));
258 if (ret != 0)
259 return ret;
260 cond_resched();
261 }
262 return 0;
263}
264
265int kallsyms_on_each_match_symbol(int (*fn)(void *, unsigned long),
266 const char *name, void *data)
267{
268 int ret;
269 unsigned int i, start, end;
270
271 ret = kallsyms_lookup_names(name, &start, &end);
272 if (ret)
273 return 0;
274
275 for (i = start; !ret && i <= end; i++) {
276 ret = fn(data, kallsyms_sym_address(get_symbol_seq(i)));
277 cond_resched();
278 }
279
280 return ret;
281}
282
283static unsigned long get_symbol_pos(unsigned long addr,
284 unsigned long *symbolsize,
285 unsigned long *offset)
286{
287 unsigned long symbol_start = 0, symbol_end = 0;
288 unsigned long i, low, high, mid;
289
290 /* Do a binary search on the sorted kallsyms_offsets array. */
291 low = 0;
292 high = kallsyms_num_syms;
293
294 while (high - low > 1) {
295 mid = low + (high - low) / 2;
296 if (kallsyms_sym_address(mid) <= addr)
297 low = mid;
298 else
299 high = mid;
300 }
301
302 /*
303 * Search for the first aliased symbol. Aliased
304 * symbols are symbols with the same address.
305 */
306 while (low && kallsyms_sym_address(low-1) == kallsyms_sym_address(low))
307 --low;
308
309 symbol_start = kallsyms_sym_address(low);
310
311 /* Search for next non-aliased symbol. */
312 for (i = low + 1; i < kallsyms_num_syms; i++) {
313 if (kallsyms_sym_address(i) > symbol_start) {
314 symbol_end = kallsyms_sym_address(i);
315 break;
316 }
317 }
318
319 /* If we found no next symbol, we use the end of the section. */
320 if (!symbol_end) {
321 if (is_kernel_inittext(addr))
322 symbol_end = (unsigned long)_einittext;
323 else if (IS_ENABLED(CONFIG_KALLSYMS_ALL))
324 symbol_end = (unsigned long)_end;
325 else
326 symbol_end = (unsigned long)_etext;
327 }
328
329 if (symbolsize)
330 *symbolsize = symbol_end - symbol_start;
331 if (offset)
332 *offset = addr - symbol_start;
333
334 return low;
335}
336
337/*
338 * Lookup an address but don't bother to find any names.
339 */
340int kallsyms_lookup_size_offset(unsigned long addr, unsigned long *symbolsize,
341 unsigned long *offset)
342{
343 char namebuf[KSYM_NAME_LEN];
344
345 if (is_ksym_addr(addr)) {
346 get_symbol_pos(addr, symbolsize, offset);
347 return 1;
348 }
349 return !!module_address_lookup(addr, symbolsize, offset, NULL, NULL, namebuf) ||
350 !!bpf_address_lookup(addr, symbolsize, offset, namebuf);
351}
352
353static int kallsyms_lookup_buildid(unsigned long addr,
354 unsigned long *symbolsize,
355 unsigned long *offset, char **modname,
356 const unsigned char **modbuildid, char *namebuf)
357{
358 int ret;
359
360 /*
361 * kallsyms_lookus() returns pointer to namebuf on success and
362 * NULL on error. But some callers ignore the return value.
363 * Instead they expect @namebuf filled either with valid
364 * or empty string.
365 */
366 namebuf[0] = 0;
367 /*
368 * Initialize the module-related return values. They are not set
369 * when the symbol is in vmlinux or it is a bpf address.
370 */
371 if (modname)
372 *modname = NULL;
373 if (modbuildid)
374 *modbuildid = NULL;
375
376 if (is_ksym_addr(addr)) {
377 unsigned long pos;
378
379 pos = get_symbol_pos(addr, symbolsize, offset);
380 /* Grab name */
381 kallsyms_expand_symbol(get_symbol_offset(pos),
382 namebuf, KSYM_NAME_LEN);
383
384 return strlen(namebuf);
385 }
386
387 /* See if it's in a module or a BPF JITed image. */
388 ret = module_address_lookup(addr, symbolsize, offset,
389 modname, modbuildid, namebuf);
390 if (!ret)
391 ret = bpf_address_lookup(addr, symbolsize, offset, namebuf);
392
393 if (!ret)
394 ret = ftrace_mod_address_lookup(addr, symbolsize, offset,
395 modname, modbuildid, namebuf);
396
397 return ret;
398}
399
400/*
401 * Lookup an address
402 * - modname is set to NULL if it's in the kernel.
403 * - We guarantee that the returned name is valid until we reschedule even if.
404 * It resides in a module.
405 * - We also guarantee that modname will be valid until rescheduled.
406 */
407const char *kallsyms_lookup(unsigned long addr,
408 unsigned long *symbolsize,
409 unsigned long *offset,
410 char **modname, char *namebuf)
411{
412 int ret = kallsyms_lookup_buildid(addr, symbolsize, offset, modname,
413 NULL, namebuf);
414
415 if (!ret)
416 return NULL;
417
418 return namebuf;
419}
420
421int lookup_symbol_name(unsigned long addr, char *symname)
422{
423 symname[0] = '\0';
424 symname[KSYM_NAME_LEN - 1] = '\0';
425
426 if (is_ksym_addr(addr)) {
427 unsigned long pos;
428
429 pos = get_symbol_pos(addr, NULL, NULL);
430 /* Grab name */
431 kallsyms_expand_symbol(get_symbol_offset(pos),
432 symname, KSYM_NAME_LEN);
433 return 0;
434 }
435 /* See if it's in a module. */
436 return lookup_module_symbol_name(addr, symname);
437}
438
439#ifdef CONFIG_STACKTRACE_BUILD_ID
440
441static int append_buildid(char *buffer, const char *modname,
442 const unsigned char *buildid)
443{
444 if (!modname)
445 return 0;
446
447 if (!buildid) {
448 pr_warn_once("Undefined buildid for the module %s\n", modname);
449 return 0;
450 }
451
452 /* build ID should match length of sprintf */
453#ifdef CONFIG_MODULES
454 static_assert(sizeof(typeof_member(struct module, build_id)) == 20);
455#endif
456
457 return sprintf(buffer, " %20phN", buildid);
458}
459
460#else /* CONFIG_STACKTRACE_BUILD_ID */
461
462static int append_buildid(char *buffer, const char *modname,
463 const unsigned char *buildid)
464{
465 return 0;
466}
467
468#endif /* CONFIG_STACKTRACE_BUILD_ID */
469
470/* Look up a kernel symbol and return it in a text buffer. */
471static int __sprint_symbol(char *buffer, unsigned long address,
472 int symbol_offset, int add_offset, int add_buildid)
473{
474 char *modname;
475 const unsigned char *buildid;
476 unsigned long offset, size;
477 int len;
478
479 /* Prevent module removal until modname and modbuildid are printed */
480 guard(rcu)();
481
482 address += symbol_offset;
483 len = kallsyms_lookup_buildid(address, &size, &offset, &modname, &buildid,
484 buffer);
485 if (!len)
486 return sprintf(buffer, "0x%lx", address - symbol_offset);
487
488 offset -= symbol_offset;
489
490 if (add_offset)
491 len += sprintf(buffer + len, "+%#lx/%#lx", offset, size);
492
493 if (modname) {
494 len += sprintf(buffer + len, " [%s", modname);
495 if (add_buildid)
496 len += append_buildid(buffer + len, modname, buildid);
497 len += sprintf(buffer + len, "]");
498 }
499
500 return len;
501}
502
503/**
504 * sprint_symbol - Look up a kernel symbol and return it in a text buffer
505 * @buffer: buffer to be stored
506 * @address: address to lookup
507 *
508 * This function looks up a kernel symbol with @address and stores its name,
509 * offset, size and module name to @buffer if possible. If no symbol was found,
510 * just saves its @address as is.
511 *
512 * This function returns the number of bytes stored in @buffer.
513 */
514int sprint_symbol(char *buffer, unsigned long address)
515{
516 return __sprint_symbol(buffer, address, 0, 1, 0);
517}
518EXPORT_SYMBOL_GPL(sprint_symbol);
519
520/**
521 * sprint_symbol_build_id - Look up a kernel symbol and return it in a text buffer
522 * @buffer: buffer to be stored
523 * @address: address to lookup
524 *
525 * This function looks up a kernel symbol with @address and stores its name,
526 * offset, size, module name and module build ID to @buffer if possible. If no
527 * symbol was found, just saves its @address as is.
528 *
529 * This function returns the number of bytes stored in @buffer.
530 */
531int sprint_symbol_build_id(char *buffer, unsigned long address)
532{
533 return __sprint_symbol(buffer, address, 0, 1, 1);
534}
535EXPORT_SYMBOL_GPL(sprint_symbol_build_id);
536
537/**
538 * sprint_symbol_no_offset - Look up a kernel symbol and return it in a text buffer
539 * @buffer: buffer to be stored
540 * @address: address to lookup
541 *
542 * This function looks up a kernel symbol with @address and stores its name
543 * and module name to @buffer if possible. If no symbol was found, just saves
544 * its @address as is.
545 *
546 * This function returns the number of bytes stored in @buffer.
547 */
548int sprint_symbol_no_offset(char *buffer, unsigned long address)
549{
550 return __sprint_symbol(buffer, address, 0, 0, 0);
551}
552EXPORT_SYMBOL_GPL(sprint_symbol_no_offset);
553
554/**
555 * sprint_backtrace - Look up a backtrace symbol and return it in a text buffer
556 * @buffer: buffer to be stored
557 * @address: address to lookup
558 *
559 * This function is for stack backtrace and does the same thing as
560 * sprint_symbol() but with modified/decreased @address. If there is a
561 * tail-call to the function marked "noreturn", gcc optimized out code after
562 * the call so that the stack-saved return address could point outside of the
563 * caller. This function ensures that kallsyms will find the original caller
564 * by decreasing @address.
565 *
566 * This function returns the number of bytes stored in @buffer.
567 */
568int sprint_backtrace(char *buffer, unsigned long address)
569{
570 return __sprint_symbol(buffer, address, -1, 1, 0);
571}
572
573/**
574 * sprint_backtrace_build_id - Look up a backtrace symbol and return it in a text buffer
575 * @buffer: buffer to be stored
576 * @address: address to lookup
577 *
578 * This function is for stack backtrace and does the same thing as
579 * sprint_symbol() but with modified/decreased @address. If there is a
580 * tail-call to the function marked "noreturn", gcc optimized out code after
581 * the call so that the stack-saved return address could point outside of the
582 * caller. This function ensures that kallsyms will find the original caller
583 * by decreasing @address. This function also appends the module build ID to
584 * the @buffer if @address is within a kernel module.
585 *
586 * This function returns the number of bytes stored in @buffer.
587 */
588int sprint_backtrace_build_id(char *buffer, unsigned long address)
589{
590 return __sprint_symbol(buffer, address, -1, 1, 1);
591}
592
593/* To avoid using get_symbol_offset for every symbol, we carry prefix along. */
594struct kallsym_iter {
595 loff_t pos;
596 loff_t pos_mod_end;
597 loff_t pos_ftrace_mod_end;
598 loff_t pos_bpf_end;
599 unsigned long value;
600 unsigned int nameoff; /* If iterating in core kernel symbols. */
601 char type;
602 char name[KSYM_NAME_LEN];
603 char module_name[MODULE_NAME_LEN];
604 int exported;
605 int show_value;
606};
607
608static int get_ksymbol_mod(struct kallsym_iter *iter)
609{
610 int ret = module_get_kallsym(iter->pos - kallsyms_num_syms,
611 &iter->value, &iter->type,
612 iter->name, iter->module_name,
613 &iter->exported);
614 if (ret < 0) {
615 iter->pos_mod_end = iter->pos;
616 return 0;
617 }
618
619 return 1;
620}
621
622/*
623 * ftrace_mod_get_kallsym() may also get symbols for pages allocated for ftrace
624 * purposes. In that case "__builtin__ftrace" is used as a module name, even
625 * though "__builtin__ftrace" is not a module.
626 */
627static int get_ksymbol_ftrace_mod(struct kallsym_iter *iter)
628{
629 int ret = ftrace_mod_get_kallsym(iter->pos - iter->pos_mod_end,
630 &iter->value, &iter->type,
631 iter->name, iter->module_name,
632 &iter->exported);
633 if (ret < 0) {
634 iter->pos_ftrace_mod_end = iter->pos;
635 return 0;
636 }
637
638 return 1;
639}
640
641static int get_ksymbol_bpf(struct kallsym_iter *iter)
642{
643 int ret;
644
645 strscpy(iter->module_name, "bpf", MODULE_NAME_LEN);
646 iter->exported = 0;
647 ret = bpf_get_kallsym(iter->pos - iter->pos_ftrace_mod_end,
648 &iter->value, &iter->type,
649 iter->name);
650 if (ret < 0) {
651 iter->pos_bpf_end = iter->pos;
652 return 0;
653 }
654
655 return 1;
656}
657
658/*
659 * This uses "__builtin__kprobes" as a module name for symbols for pages
660 * allocated for kprobes' purposes, even though "__builtin__kprobes" is not a
661 * module.
662 */
663static int get_ksymbol_kprobe(struct kallsym_iter *iter)
664{
665 strscpy(iter->module_name, "__builtin__kprobes", MODULE_NAME_LEN);
666 iter->exported = 0;
667 return kprobe_get_kallsym(iter->pos - iter->pos_bpf_end,
668 &iter->value, &iter->type,
669 iter->name) < 0 ? 0 : 1;
670}
671
672/* Returns space to next name. */
673static unsigned long get_ksymbol_core(struct kallsym_iter *iter)
674{
675 unsigned off = iter->nameoff;
676
677 iter->module_name[0] = '\0';
678 iter->value = kallsyms_sym_address(iter->pos);
679
680 iter->type = kallsyms_get_symbol_type(off);
681
682 off = kallsyms_expand_symbol(off, iter->name, ARRAY_SIZE(iter->name));
683
684 return off - iter->nameoff;
685}
686
687static void reset_iter(struct kallsym_iter *iter, loff_t new_pos)
688{
689 iter->name[0] = '\0';
690 iter->nameoff = get_symbol_offset(new_pos);
691 iter->pos = new_pos;
692 if (new_pos == 0) {
693 iter->pos_mod_end = 0;
694 iter->pos_ftrace_mod_end = 0;
695 iter->pos_bpf_end = 0;
696 }
697}
698
699/*
700 * The end position (last + 1) of each additional kallsyms section is recorded
701 * in iter->pos_..._end as each section is added, and so can be used to
702 * determine which get_ksymbol_...() function to call next.
703 */
704static int update_iter_mod(struct kallsym_iter *iter, loff_t pos)
705{
706 iter->pos = pos;
707
708 if ((!iter->pos_mod_end || iter->pos_mod_end > pos) &&
709 get_ksymbol_mod(iter))
710 return 1;
711
712 if ((!iter->pos_ftrace_mod_end || iter->pos_ftrace_mod_end > pos) &&
713 get_ksymbol_ftrace_mod(iter))
714 return 1;
715
716 if ((!iter->pos_bpf_end || iter->pos_bpf_end > pos) &&
717 get_ksymbol_bpf(iter))
718 return 1;
719
720 return get_ksymbol_kprobe(iter);
721}
722
723/* Returns false if pos at or past end of file. */
724static int update_iter(struct kallsym_iter *iter, loff_t pos)
725{
726 /* Module symbols can be accessed randomly. */
727 if (pos >= kallsyms_num_syms)
728 return update_iter_mod(iter, pos);
729
730 /* If we're not on the desired position, reset to new position. */
731 if (pos != iter->pos)
732 reset_iter(iter, pos);
733
734 iter->nameoff += get_ksymbol_core(iter);
735 iter->pos++;
736
737 return 1;
738}
739
740static void *s_next(struct seq_file *m, void *p, loff_t *pos)
741{
742 (*pos)++;
743
744 if (!update_iter(m->private, *pos))
745 return NULL;
746 return p;
747}
748
749static void *s_start(struct seq_file *m, loff_t *pos)
750{
751 if (!update_iter(m->private, *pos))
752 return NULL;
753 return m->private;
754}
755
756static void s_stop(struct seq_file *m, void *p)
757{
758}
759
760static int s_show(struct seq_file *m, void *p)
761{
762 void *value;
763 struct kallsym_iter *iter = m->private;
764
765 /* Some debugging symbols have no name. Ignore them. */
766 if (!iter->name[0])
767 return 0;
768
769 value = iter->show_value ? (void *)iter->value : NULL;
770
771 if (iter->module_name[0]) {
772 char type;
773
774 /*
775 * Label it "global" if it is exported,
776 * "local" if not exported.
777 */
778 type = iter->exported ? toupper(iter->type) :
779 tolower(iter->type);
780 seq_printf(m, "%px %c %s\t[%s]\n", value,
781 type, iter->name, iter->module_name);
782 } else
783 seq_printf(m, "%px %c %s\n", value,
784 iter->type, iter->name);
785 return 0;
786}
787
788static const struct seq_operations kallsyms_op = {
789 .start = s_start,
790 .next = s_next,
791 .stop = s_stop,
792 .show = s_show
793};
794
795#ifdef CONFIG_BPF_SYSCALL
796
797struct bpf_iter__ksym {
798 __bpf_md_ptr(struct bpf_iter_meta *, meta);
799 __bpf_md_ptr(struct kallsym_iter *, ksym);
800};
801
802static int ksym_prog_seq_show(struct seq_file *m, bool in_stop)
803{
804 struct bpf_iter__ksym ctx;
805 struct bpf_iter_meta meta;
806 struct bpf_prog *prog;
807
808 meta.seq = m;
809 prog = bpf_iter_get_info(&meta, in_stop);
810 if (!prog)
811 return 0;
812
813 ctx.meta = &meta;
814 ctx.ksym = m ? m->private : NULL;
815 return bpf_iter_run_prog(prog, &ctx);
816}
817
818static int bpf_iter_ksym_seq_show(struct seq_file *m, void *p)
819{
820 return ksym_prog_seq_show(m, false);
821}
822
823static void bpf_iter_ksym_seq_stop(struct seq_file *m, void *p)
824{
825 if (!p)
826 (void) ksym_prog_seq_show(m, true);
827 else
828 s_stop(m, p);
829}
830
831static const struct seq_operations bpf_iter_ksym_ops = {
832 .start = s_start,
833 .next = s_next,
834 .stop = bpf_iter_ksym_seq_stop,
835 .show = bpf_iter_ksym_seq_show,
836};
837
838static int bpf_iter_ksym_init(void *priv_data, struct bpf_iter_aux_info *aux)
839{
840 struct kallsym_iter *iter = priv_data;
841
842 reset_iter(iter, 0);
843
844 /* cache here as in kallsyms_open() case; use current process
845 * credentials to tell BPF iterators if values should be shown.
846 */
847 iter->show_value = kallsyms_show_value(current_cred());
848
849 return 0;
850}
851
852DEFINE_BPF_ITER_FUNC(ksym, struct bpf_iter_meta *meta, struct kallsym_iter *ksym)
853
854static const struct bpf_iter_seq_info ksym_iter_seq_info = {
855 .seq_ops = &bpf_iter_ksym_ops,
856 .init_seq_private = bpf_iter_ksym_init,
857 .fini_seq_private = NULL,
858 .seq_priv_size = sizeof(struct kallsym_iter),
859};
860
861static struct bpf_iter_reg ksym_iter_reg_info = {
862 .target = "ksym",
863 .feature = BPF_ITER_RESCHED,
864 .ctx_arg_info_size = 1,
865 .ctx_arg_info = {
866 { offsetof(struct bpf_iter__ksym, ksym),
867 PTR_TO_BTF_ID_OR_NULL },
868 },
869 .seq_info = &ksym_iter_seq_info,
870};
871
872BTF_ID_LIST_SINGLE(btf_ksym_iter_id, struct, kallsym_iter)
873
874static int __init bpf_ksym_iter_register(void)
875{
876 ksym_iter_reg_info.ctx_arg_info[0].btf_id = *btf_ksym_iter_id;
877 return bpf_iter_reg_target(&ksym_iter_reg_info);
878}
879
880late_initcall(bpf_ksym_iter_register);
881
882#endif /* CONFIG_BPF_SYSCALL */
883
884static int kallsyms_open(struct inode *inode, struct file *file)
885{
886 /*
887 * We keep iterator in m->private, since normal case is to
888 * s_start from where we left off, so we avoid doing
889 * using get_symbol_offset for every symbol.
890 */
891 struct kallsym_iter *iter;
892 iter = __seq_open_private(file, &kallsyms_op, sizeof(*iter));
893 if (!iter)
894 return -ENOMEM;
895 reset_iter(iter, 0);
896
897 /*
898 * Instead of checking this on every s_show() call, cache
899 * the result here at open time.
900 */
901 iter->show_value = kallsyms_show_value(file->f_cred);
902 return 0;
903}
904
905#ifdef CONFIG_KGDB_KDB
906const char *kdb_walk_kallsyms(loff_t *pos)
907{
908 static struct kallsym_iter kdb_walk_kallsyms_iter;
909 if (*pos == 0) {
910 memset(&kdb_walk_kallsyms_iter, 0,
911 sizeof(kdb_walk_kallsyms_iter));
912 reset_iter(&kdb_walk_kallsyms_iter, 0);
913 }
914 while (1) {
915 if (!update_iter(&kdb_walk_kallsyms_iter, *pos))
916 return NULL;
917 ++*pos;
918 /* Some debugging symbols have no name. Ignore them. */
919 if (kdb_walk_kallsyms_iter.name[0])
920 return kdb_walk_kallsyms_iter.name;
921 }
922}
923#endif /* CONFIG_KGDB_KDB */
924
925static const struct proc_ops kallsyms_proc_ops = {
926 .proc_open = kallsyms_open,
927 .proc_read = seq_read,
928 .proc_lseek = seq_lseek,
929 .proc_release = seq_release_private,
930};
931
932static int __init kallsyms_init(void)
933{
934 proc_create("kallsyms", 0444, NULL, &kallsyms_proc_ops);
935 return 0;
936}
937device_initcall(kallsyms_init);