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