kallsyms.c

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