xref: /openbmc/linux/kernel/kallsyms.c (revision 76903a96)
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  */
kallsyms_expand_symbol(unsigned int off,char * result,size_t maxlen)42 static 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 
90 tail:
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  */
kallsyms_get_symbol_type(unsigned int off)102 static 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  */
get_symbol_offset(unsigned long pos)116 static 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 
kallsyms_sym_address(int idx)149 unsigned long kallsyms_sym_address(int idx)
150 {
151 	if (!IS_ENABLED(CONFIG_KALLSYMS_BASE_RELATIVE))
152 		return kallsyms_addresses[idx];
153 
154 	/* values are unsigned offsets if --absolute-percpu is not in effect */
155 	if (!IS_ENABLED(CONFIG_KALLSYMS_ABSOLUTE_PERCPU))
156 		return kallsyms_relative_base + (u32)kallsyms_offsets[idx];
157 
158 	/* ...otherwise, positive offsets are absolute values */
159 	if (kallsyms_offsets[idx] >= 0)
160 		return kallsyms_offsets[idx];
161 
162 	/* ...and negative offsets are relative to kallsyms_relative_base - 1 */
163 	return kallsyms_relative_base - 1 - kallsyms_offsets[idx];
164 }
165 
cleanup_symbol_name(char * s)166 static void cleanup_symbol_name(char *s)
167 {
168 	char *res;
169 
170 	if (!IS_ENABLED(CONFIG_LTO_CLANG))
171 		return;
172 
173 	/*
174 	 * LLVM appends various suffixes for local functions and variables that
175 	 * must be promoted to global scope as part of LTO.  This can break
176 	 * hooking of static functions with kprobes. '.' is not a valid
177 	 * character in an identifier in C. Suffixes only in LLVM LTO observed:
178 	 * - foo.llvm.[0-9a-f]+
179 	 */
180 	res = strstr(s, ".llvm.");
181 	if (res)
182 		*res = '\0';
183 
184 	return;
185 }
186 
compare_symbol_name(const char * name,char * namebuf)187 static int compare_symbol_name(const char *name, char *namebuf)
188 {
189 	/* The kallsyms_seqs_of_names is sorted based on names after
190 	 * cleanup_symbol_name() (see scripts/kallsyms.c) if clang lto is enabled.
191 	 * To ensure correct bisection in kallsyms_lookup_names(), do
192 	 * cleanup_symbol_name(namebuf) before comparing name and namebuf.
193 	 */
194 	cleanup_symbol_name(namebuf);
195 	return strcmp(name, namebuf);
196 }
197 
get_symbol_seq(int index)198 static unsigned int get_symbol_seq(int index)
199 {
200 	unsigned int i, seq = 0;
201 
202 	for (i = 0; i < 3; i++)
203 		seq = (seq << 8) | kallsyms_seqs_of_names[3 * index + i];
204 
205 	return seq;
206 }
207 
kallsyms_lookup_names(const char * name,unsigned int * start,unsigned int * end)208 static int kallsyms_lookup_names(const char *name,
209 				 unsigned int *start,
210 				 unsigned int *end)
211 {
212 	int ret;
213 	int low, mid, high;
214 	unsigned int seq, off;
215 	char namebuf[KSYM_NAME_LEN];
216 
217 	low = 0;
218 	high = kallsyms_num_syms - 1;
219 
220 	while (low <= high) {
221 		mid = low + (high - low) / 2;
222 		seq = get_symbol_seq(mid);
223 		off = get_symbol_offset(seq);
224 		kallsyms_expand_symbol(off, namebuf, ARRAY_SIZE(namebuf));
225 		ret = compare_symbol_name(name, namebuf);
226 		if (ret > 0)
227 			low = mid + 1;
228 		else if (ret < 0)
229 			high = mid - 1;
230 		else
231 			break;
232 	}
233 
234 	if (low > high)
235 		return -ESRCH;
236 
237 	low = mid;
238 	while (low) {
239 		seq = get_symbol_seq(low - 1);
240 		off = get_symbol_offset(seq);
241 		kallsyms_expand_symbol(off, namebuf, ARRAY_SIZE(namebuf));
242 		if (compare_symbol_name(name, namebuf))
243 			break;
244 		low--;
245 	}
246 	*start = low;
247 
248 	if (end) {
249 		high = mid;
250 		while (high < kallsyms_num_syms - 1) {
251 			seq = get_symbol_seq(high + 1);
252 			off = get_symbol_offset(seq);
253 			kallsyms_expand_symbol(off, namebuf, ARRAY_SIZE(namebuf));
254 			if (compare_symbol_name(name, namebuf))
255 				break;
256 			high++;
257 		}
258 		*end = high;
259 	}
260 
261 	return 0;
262 }
263 
264 /* Lookup the address for this symbol. Returns 0 if not found. */
kallsyms_lookup_name(const char * name)265 unsigned long kallsyms_lookup_name(const char *name)
266 {
267 	int ret;
268 	unsigned int i;
269 
270 	/* Skip the search for empty string. */
271 	if (!*name)
272 		return 0;
273 
274 	ret = kallsyms_lookup_names(name, &i, NULL);
275 	if (!ret)
276 		return kallsyms_sym_address(get_symbol_seq(i));
277 
278 	return module_kallsyms_lookup_name(name);
279 }
280 
281 /*
282  * Iterate over all symbols in vmlinux.  For symbols from modules use
283  * module_kallsyms_on_each_symbol instead.
284  */
kallsyms_on_each_symbol(int (* fn)(void *,const char *,unsigned long),void * data)285 int kallsyms_on_each_symbol(int (*fn)(void *, const char *, unsigned long),
286 			    void *data)
287 {
288 	char namebuf[KSYM_NAME_LEN];
289 	unsigned long i;
290 	unsigned int off;
291 	int ret;
292 
293 	for (i = 0, off = 0; i < kallsyms_num_syms; i++) {
294 		off = kallsyms_expand_symbol(off, namebuf, ARRAY_SIZE(namebuf));
295 		ret = fn(data, namebuf, kallsyms_sym_address(i));
296 		if (ret != 0)
297 			return ret;
298 		cond_resched();
299 	}
300 	return 0;
301 }
302 
kallsyms_on_each_match_symbol(int (* fn)(void *,unsigned long),const char * name,void * data)303 int kallsyms_on_each_match_symbol(int (*fn)(void *, unsigned long),
304 				  const char *name, void *data)
305 {
306 	int ret;
307 	unsigned int i, start, end;
308 
309 	ret = kallsyms_lookup_names(name, &start, &end);
310 	if (ret)
311 		return 0;
312 
313 	for (i = start; !ret && i <= end; i++) {
314 		ret = fn(data, kallsyms_sym_address(get_symbol_seq(i)));
315 		cond_resched();
316 	}
317 
318 	return ret;
319 }
320 
get_symbol_pos(unsigned long addr,unsigned long * symbolsize,unsigned long * offset)321 static unsigned long get_symbol_pos(unsigned long addr,
322 				    unsigned long *symbolsize,
323 				    unsigned long *offset)
324 {
325 	unsigned long symbol_start = 0, symbol_end = 0;
326 	unsigned long i, low, high, mid;
327 
328 	/* This kernel should never had been booted. */
329 	if (!IS_ENABLED(CONFIG_KALLSYMS_BASE_RELATIVE))
330 		BUG_ON(!kallsyms_addresses);
331 	else
332 		BUG_ON(!kallsyms_offsets);
333 
334 	/* Do a binary search on the sorted kallsyms_addresses array. */
335 	low = 0;
336 	high = kallsyms_num_syms;
337 
338 	while (high - low > 1) {
339 		mid = low + (high - low) / 2;
340 		if (kallsyms_sym_address(mid) <= addr)
341 			low = mid;
342 		else
343 			high = mid;
344 	}
345 
346 	/*
347 	 * Search for the first aliased symbol. Aliased
348 	 * symbols are symbols with the same address.
349 	 */
350 	while (low && kallsyms_sym_address(low-1) == kallsyms_sym_address(low))
351 		--low;
352 
353 	symbol_start = kallsyms_sym_address(low);
354 
355 	/* Search for next non-aliased symbol. */
356 	for (i = low + 1; i < kallsyms_num_syms; i++) {
357 		if (kallsyms_sym_address(i) > symbol_start) {
358 			symbol_end = kallsyms_sym_address(i);
359 			break;
360 		}
361 	}
362 
363 	/* If we found no next symbol, we use the end of the section. */
364 	if (!symbol_end) {
365 		if (is_kernel_inittext(addr))
366 			symbol_end = (unsigned long)_einittext;
367 		else if (IS_ENABLED(CONFIG_KALLSYMS_ALL))
368 			symbol_end = (unsigned long)_end;
369 		else
370 			symbol_end = (unsigned long)_etext;
371 	}
372 
373 	if (symbolsize)
374 		*symbolsize = symbol_end - symbol_start;
375 	if (offset)
376 		*offset = addr - symbol_start;
377 
378 	return low;
379 }
380 
381 /*
382  * Lookup an address but don't bother to find any names.
383  */
kallsyms_lookup_size_offset(unsigned long addr,unsigned long * symbolsize,unsigned long * offset)384 int kallsyms_lookup_size_offset(unsigned long addr, unsigned long *symbolsize,
385 				unsigned long *offset)
386 {
387 	char namebuf[KSYM_NAME_LEN];
388 
389 	if (is_ksym_addr(addr)) {
390 		get_symbol_pos(addr, symbolsize, offset);
391 		return 1;
392 	}
393 	return !!module_address_lookup(addr, symbolsize, offset, NULL, NULL, namebuf) ||
394 	       !!__bpf_address_lookup(addr, symbolsize, offset, namebuf);
395 }
396 
kallsyms_lookup_buildid(unsigned long addr,unsigned long * symbolsize,unsigned long * offset,char ** modname,const unsigned char ** modbuildid,char * namebuf)397 static const char *kallsyms_lookup_buildid(unsigned long addr,
398 			unsigned long *symbolsize,
399 			unsigned long *offset, char **modname,
400 			const unsigned char **modbuildid, char *namebuf)
401 {
402 	const char *ret;
403 
404 	namebuf[KSYM_NAME_LEN - 1] = 0;
405 	namebuf[0] = 0;
406 
407 	if (is_ksym_addr(addr)) {
408 		unsigned long pos;
409 
410 		pos = get_symbol_pos(addr, symbolsize, offset);
411 		/* Grab name */
412 		kallsyms_expand_symbol(get_symbol_offset(pos),
413 				       namebuf, KSYM_NAME_LEN);
414 		if (modname)
415 			*modname = NULL;
416 		if (modbuildid)
417 			*modbuildid = NULL;
418 
419 		ret = namebuf;
420 		goto found;
421 	}
422 
423 	/* See if it's in a module or a BPF JITed image. */
424 	ret = module_address_lookup(addr, symbolsize, offset,
425 				    modname, modbuildid, namebuf);
426 	if (!ret)
427 		ret = bpf_address_lookup(addr, symbolsize,
428 					 offset, modname, namebuf);
429 
430 	if (!ret)
431 		ret = ftrace_mod_address_lookup(addr, symbolsize,
432 						offset, modname, namebuf);
433 
434 found:
435 	cleanup_symbol_name(namebuf);
436 	return ret;
437 }
438 
439 /*
440  * Lookup an address
441  * - modname is set to NULL if it's in the kernel.
442  * - We guarantee that the returned name is valid until we reschedule even if.
443  *   It resides in a module.
444  * - We also guarantee that modname will be valid until rescheduled.
445  */
kallsyms_lookup(unsigned long addr,unsigned long * symbolsize,unsigned long * offset,char ** modname,char * namebuf)446 const char *kallsyms_lookup(unsigned long addr,
447 			    unsigned long *symbolsize,
448 			    unsigned long *offset,
449 			    char **modname, char *namebuf)
450 {
451 	return kallsyms_lookup_buildid(addr, symbolsize, offset, modname,
452 				       NULL, namebuf);
453 }
454 
lookup_symbol_name(unsigned long addr,char * symname)455 int lookup_symbol_name(unsigned long addr, char *symname)
456 {
457 	int res;
458 
459 	symname[0] = '\0';
460 	symname[KSYM_NAME_LEN - 1] = '\0';
461 
462 	if (is_ksym_addr(addr)) {
463 		unsigned long pos;
464 
465 		pos = get_symbol_pos(addr, NULL, NULL);
466 		/* Grab name */
467 		kallsyms_expand_symbol(get_symbol_offset(pos),
468 				       symname, KSYM_NAME_LEN);
469 		goto found;
470 	}
471 	/* See if it's in a module. */
472 	res = lookup_module_symbol_name(addr, symname);
473 	if (res)
474 		return res;
475 
476 found:
477 	cleanup_symbol_name(symname);
478 	return 0;
479 }
480 
481 /* Look up a kernel symbol and return it in a text buffer. */
__sprint_symbol(char * buffer,unsigned long address,int symbol_offset,int add_offset,int add_buildid)482 static int __sprint_symbol(char *buffer, unsigned long address,
483 			   int symbol_offset, int add_offset, int add_buildid)
484 {
485 	char *modname;
486 	const unsigned char *buildid;
487 	const char *name;
488 	unsigned long offset, size;
489 	int len;
490 
491 	address += symbol_offset;
492 	name = kallsyms_lookup_buildid(address, &size, &offset, &modname, &buildid,
493 				       buffer);
494 	if (!name)
495 		return sprintf(buffer, "0x%lx", address - symbol_offset);
496 
497 	if (name != buffer)
498 		strcpy(buffer, name);
499 	len = strlen(buffer);
500 	offset -= symbol_offset;
501 
502 	if (add_offset)
503 		len += sprintf(buffer + len, "+%#lx/%#lx", offset, size);
504 
505 	if (modname) {
506 		len += sprintf(buffer + len, " [%s", modname);
507 #if IS_ENABLED(CONFIG_STACKTRACE_BUILD_ID)
508 		if (add_buildid && buildid) {
509 			/* build ID should match length of sprintf */
510 #if IS_ENABLED(CONFIG_MODULES)
511 			static_assert(sizeof(typeof_member(struct module, build_id)) == 20);
512 #endif
513 			len += sprintf(buffer + len, " %20phN", buildid);
514 		}
515 #endif
516 		len += sprintf(buffer + len, "]");
517 	}
518 
519 	return len;
520 }
521 
522 /**
523  * sprint_symbol - Look up a kernel symbol and return it in a text buffer
524  * @buffer: buffer to be stored
525  * @address: address to lookup
526  *
527  * This function looks up a kernel symbol with @address and stores its name,
528  * offset, size and module name to @buffer if possible. If no symbol was found,
529  * just saves its @address as is.
530  *
531  * This function returns the number of bytes stored in @buffer.
532  */
sprint_symbol(char * buffer,unsigned long address)533 int sprint_symbol(char *buffer, unsigned long address)
534 {
535 	return __sprint_symbol(buffer, address, 0, 1, 0);
536 }
537 EXPORT_SYMBOL_GPL(sprint_symbol);
538 
539 /**
540  * sprint_symbol_build_id - Look up a kernel symbol and return it in a text buffer
541  * @buffer: buffer to be stored
542  * @address: address to lookup
543  *
544  * This function looks up a kernel symbol with @address and stores its name,
545  * offset, size, module name and module build ID to @buffer if possible. If no
546  * symbol was found, just saves its @address as is.
547  *
548  * This function returns the number of bytes stored in @buffer.
549  */
sprint_symbol_build_id(char * buffer,unsigned long address)550 int sprint_symbol_build_id(char *buffer, unsigned long address)
551 {
552 	return __sprint_symbol(buffer, address, 0, 1, 1);
553 }
554 EXPORT_SYMBOL_GPL(sprint_symbol_build_id);
555 
556 /**
557  * sprint_symbol_no_offset - Look up a kernel symbol and return it in a text buffer
558  * @buffer: buffer to be stored
559  * @address: address to lookup
560  *
561  * This function looks up a kernel symbol with @address and stores its name
562  * and module name to @buffer if possible. If no symbol was found, just saves
563  * its @address as is.
564  *
565  * This function returns the number of bytes stored in @buffer.
566  */
sprint_symbol_no_offset(char * buffer,unsigned long address)567 int sprint_symbol_no_offset(char *buffer, unsigned long address)
568 {
569 	return __sprint_symbol(buffer, address, 0, 0, 0);
570 }
571 EXPORT_SYMBOL_GPL(sprint_symbol_no_offset);
572 
573 /**
574  * sprint_backtrace - 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.
584  *
585  * This function returns the number of bytes stored in @buffer.
586  */
sprint_backtrace(char * buffer,unsigned long address)587 int sprint_backtrace(char *buffer, unsigned long address)
588 {
589 	return __sprint_symbol(buffer, address, -1, 1, 0);
590 }
591 
592 /**
593  * sprint_backtrace_build_id - Look up a backtrace symbol and return it in a text buffer
594  * @buffer: buffer to be stored
595  * @address: address to lookup
596  *
597  * This function is for stack backtrace and does the same thing as
598  * sprint_symbol() but with modified/decreased @address. If there is a
599  * tail-call to the function marked "noreturn", gcc optimized out code after
600  * the call so that the stack-saved return address could point outside of the
601  * caller. This function ensures that kallsyms will find the original caller
602  * by decreasing @address. This function also appends the module build ID to
603  * the @buffer if @address is within a kernel module.
604  *
605  * This function returns the number of bytes stored in @buffer.
606  */
sprint_backtrace_build_id(char * buffer,unsigned long address)607 int sprint_backtrace_build_id(char *buffer, unsigned long address)
608 {
609 	return __sprint_symbol(buffer, address, -1, 1, 1);
610 }
611 
612 /* To avoid using get_symbol_offset for every symbol, we carry prefix along. */
613 struct kallsym_iter {
614 	loff_t pos;
615 	loff_t pos_mod_end;
616 	loff_t pos_ftrace_mod_end;
617 	loff_t pos_bpf_end;
618 	unsigned long value;
619 	unsigned int nameoff; /* If iterating in core kernel symbols. */
620 	char type;
621 	char name[KSYM_NAME_LEN];
622 	char module_name[MODULE_NAME_LEN];
623 	int exported;
624 	int show_value;
625 };
626 
get_ksymbol_mod(struct kallsym_iter * iter)627 static int get_ksymbol_mod(struct kallsym_iter *iter)
628 {
629 	int ret = module_get_kallsym(iter->pos - kallsyms_num_syms,
630 				     &iter->value, &iter->type,
631 				     iter->name, iter->module_name,
632 				     &iter->exported);
633 	if (ret < 0) {
634 		iter->pos_mod_end = iter->pos;
635 		return 0;
636 	}
637 
638 	return 1;
639 }
640 
641 /*
642  * ftrace_mod_get_kallsym() may also get symbols for pages allocated for ftrace
643  * purposes. In that case "__builtin__ftrace" is used as a module name, even
644  * though "__builtin__ftrace" is not a module.
645  */
get_ksymbol_ftrace_mod(struct kallsym_iter * iter)646 static int get_ksymbol_ftrace_mod(struct kallsym_iter *iter)
647 {
648 	int ret = ftrace_mod_get_kallsym(iter->pos - iter->pos_mod_end,
649 					 &iter->value, &iter->type,
650 					 iter->name, iter->module_name,
651 					 &iter->exported);
652 	if (ret < 0) {
653 		iter->pos_ftrace_mod_end = iter->pos;
654 		return 0;
655 	}
656 
657 	return 1;
658 }
659 
get_ksymbol_bpf(struct kallsym_iter * iter)660 static int get_ksymbol_bpf(struct kallsym_iter *iter)
661 {
662 	int ret;
663 
664 	strscpy(iter->module_name, "bpf", MODULE_NAME_LEN);
665 	iter->exported = 0;
666 	ret = bpf_get_kallsym(iter->pos - iter->pos_ftrace_mod_end,
667 			      &iter->value, &iter->type,
668 			      iter->name);
669 	if (ret < 0) {
670 		iter->pos_bpf_end = iter->pos;
671 		return 0;
672 	}
673 
674 	return 1;
675 }
676 
677 /*
678  * This uses "__builtin__kprobes" as a module name for symbols for pages
679  * allocated for kprobes' purposes, even though "__builtin__kprobes" is not a
680  * module.
681  */
get_ksymbol_kprobe(struct kallsym_iter * iter)682 static int get_ksymbol_kprobe(struct kallsym_iter *iter)
683 {
684 	strscpy(iter->module_name, "__builtin__kprobes", MODULE_NAME_LEN);
685 	iter->exported = 0;
686 	return kprobe_get_kallsym(iter->pos - iter->pos_bpf_end,
687 				  &iter->value, &iter->type,
688 				  iter->name) < 0 ? 0 : 1;
689 }
690 
691 /* Returns space to next name. */
get_ksymbol_core(struct kallsym_iter * iter)692 static unsigned long get_ksymbol_core(struct kallsym_iter *iter)
693 {
694 	unsigned off = iter->nameoff;
695 
696 	iter->module_name[0] = '\0';
697 	iter->value = kallsyms_sym_address(iter->pos);
698 
699 	iter->type = kallsyms_get_symbol_type(off);
700 
701 	off = kallsyms_expand_symbol(off, iter->name, ARRAY_SIZE(iter->name));
702 
703 	return off - iter->nameoff;
704 }
705 
reset_iter(struct kallsym_iter * iter,loff_t new_pos)706 static void reset_iter(struct kallsym_iter *iter, loff_t new_pos)
707 {
708 	iter->name[0] = '\0';
709 	iter->nameoff = get_symbol_offset(new_pos);
710 	iter->pos = new_pos;
711 	if (new_pos == 0) {
712 		iter->pos_mod_end = 0;
713 		iter->pos_ftrace_mod_end = 0;
714 		iter->pos_bpf_end = 0;
715 	}
716 }
717 
718 /*
719  * The end position (last + 1) of each additional kallsyms section is recorded
720  * in iter->pos_..._end as each section is added, and so can be used to
721  * determine which get_ksymbol_...() function to call next.
722  */
update_iter_mod(struct kallsym_iter * iter,loff_t pos)723 static int update_iter_mod(struct kallsym_iter *iter, loff_t pos)
724 {
725 	iter->pos = pos;
726 
727 	if ((!iter->pos_mod_end || iter->pos_mod_end > pos) &&
728 	    get_ksymbol_mod(iter))
729 		return 1;
730 
731 	if ((!iter->pos_ftrace_mod_end || iter->pos_ftrace_mod_end > pos) &&
732 	    get_ksymbol_ftrace_mod(iter))
733 		return 1;
734 
735 	if ((!iter->pos_bpf_end || iter->pos_bpf_end > pos) &&
736 	    get_ksymbol_bpf(iter))
737 		return 1;
738 
739 	return get_ksymbol_kprobe(iter);
740 }
741 
742 /* Returns false if pos at or past end of file. */
update_iter(struct kallsym_iter * iter,loff_t pos)743 static int update_iter(struct kallsym_iter *iter, loff_t pos)
744 {
745 	/* Module symbols can be accessed randomly. */
746 	if (pos >= kallsyms_num_syms)
747 		return update_iter_mod(iter, pos);
748 
749 	/* If we're not on the desired position, reset to new position. */
750 	if (pos != iter->pos)
751 		reset_iter(iter, pos);
752 
753 	iter->nameoff += get_ksymbol_core(iter);
754 	iter->pos++;
755 
756 	return 1;
757 }
758 
s_next(struct seq_file * m,void * p,loff_t * pos)759 static void *s_next(struct seq_file *m, void *p, loff_t *pos)
760 {
761 	(*pos)++;
762 
763 	if (!update_iter(m->private, *pos))
764 		return NULL;
765 	return p;
766 }
767 
s_start(struct seq_file * m,loff_t * pos)768 static void *s_start(struct seq_file *m, loff_t *pos)
769 {
770 	if (!update_iter(m->private, *pos))
771 		return NULL;
772 	return m->private;
773 }
774 
s_stop(struct seq_file * m,void * p)775 static void s_stop(struct seq_file *m, void *p)
776 {
777 }
778 
s_show(struct seq_file * m,void * p)779 static int s_show(struct seq_file *m, void *p)
780 {
781 	void *value;
782 	struct kallsym_iter *iter = m->private;
783 
784 	/* Some debugging symbols have no name.  Ignore them. */
785 	if (!iter->name[0])
786 		return 0;
787 
788 	value = iter->show_value ? (void *)iter->value : NULL;
789 
790 	if (iter->module_name[0]) {
791 		char type;
792 
793 		/*
794 		 * Label it "global" if it is exported,
795 		 * "local" if not exported.
796 		 */
797 		type = iter->exported ? toupper(iter->type) :
798 					tolower(iter->type);
799 		seq_printf(m, "%px %c %s\t[%s]\n", value,
800 			   type, iter->name, iter->module_name);
801 	} else
802 		seq_printf(m, "%px %c %s\n", value,
803 			   iter->type, iter->name);
804 	return 0;
805 }
806 
807 static const struct seq_operations kallsyms_op = {
808 	.start = s_start,
809 	.next = s_next,
810 	.stop = s_stop,
811 	.show = s_show
812 };
813 
814 #ifdef CONFIG_BPF_SYSCALL
815 
816 struct bpf_iter__ksym {
817 	__bpf_md_ptr(struct bpf_iter_meta *, meta);
818 	__bpf_md_ptr(struct kallsym_iter *, ksym);
819 };
820 
ksym_prog_seq_show(struct seq_file * m,bool in_stop)821 static int ksym_prog_seq_show(struct seq_file *m, bool in_stop)
822 {
823 	struct bpf_iter__ksym ctx;
824 	struct bpf_iter_meta meta;
825 	struct bpf_prog *prog;
826 
827 	meta.seq = m;
828 	prog = bpf_iter_get_info(&meta, in_stop);
829 	if (!prog)
830 		return 0;
831 
832 	ctx.meta = &meta;
833 	ctx.ksym = m ? m->private : NULL;
834 	return bpf_iter_run_prog(prog, &ctx);
835 }
836 
bpf_iter_ksym_seq_show(struct seq_file * m,void * p)837 static int bpf_iter_ksym_seq_show(struct seq_file *m, void *p)
838 {
839 	return ksym_prog_seq_show(m, false);
840 }
841 
bpf_iter_ksym_seq_stop(struct seq_file * m,void * p)842 static void bpf_iter_ksym_seq_stop(struct seq_file *m, void *p)
843 {
844 	if (!p)
845 		(void) ksym_prog_seq_show(m, true);
846 	else
847 		s_stop(m, p);
848 }
849 
850 static const struct seq_operations bpf_iter_ksym_ops = {
851 	.start = s_start,
852 	.next = s_next,
853 	.stop = bpf_iter_ksym_seq_stop,
854 	.show = bpf_iter_ksym_seq_show,
855 };
856 
bpf_iter_ksym_init(void * priv_data,struct bpf_iter_aux_info * aux)857 static int bpf_iter_ksym_init(void *priv_data, struct bpf_iter_aux_info *aux)
858 {
859 	struct kallsym_iter *iter = priv_data;
860 
861 	reset_iter(iter, 0);
862 
863 	/* cache here as in kallsyms_open() case; use current process
864 	 * credentials to tell BPF iterators if values should be shown.
865 	 */
866 	iter->show_value = kallsyms_show_value(current_cred());
867 
868 	return 0;
869 }
870 
871 DEFINE_BPF_ITER_FUNC(ksym, struct bpf_iter_meta *meta, struct kallsym_iter *ksym)
872 
873 static const struct bpf_iter_seq_info ksym_iter_seq_info = {
874 	.seq_ops		= &bpf_iter_ksym_ops,
875 	.init_seq_private	= bpf_iter_ksym_init,
876 	.fini_seq_private	= NULL,
877 	.seq_priv_size		= sizeof(struct kallsym_iter),
878 };
879 
880 static struct bpf_iter_reg ksym_iter_reg_info = {
881 	.target                 = "ksym",
882 	.feature		= BPF_ITER_RESCHED,
883 	.ctx_arg_info_size	= 1,
884 	.ctx_arg_info		= {
885 		{ offsetof(struct bpf_iter__ksym, ksym),
886 		  PTR_TO_BTF_ID_OR_NULL },
887 	},
888 	.seq_info		= &ksym_iter_seq_info,
889 };
890 
891 BTF_ID_LIST(btf_ksym_iter_id)
BTF_ID(struct,kallsym_iter)892 BTF_ID(struct, kallsym_iter)
893 
894 static int __init bpf_ksym_iter_register(void)
895 {
896 	ksym_iter_reg_info.ctx_arg_info[0].btf_id = *btf_ksym_iter_id;
897 	return bpf_iter_reg_target(&ksym_iter_reg_info);
898 }
899 
900 late_initcall(bpf_ksym_iter_register);
901 
902 #endif /* CONFIG_BPF_SYSCALL */
903 
kallsyms_open(struct inode * inode,struct file * file)904 static int kallsyms_open(struct inode *inode, struct file *file)
905 {
906 	/*
907 	 * We keep iterator in m->private, since normal case is to
908 	 * s_start from where we left off, so we avoid doing
909 	 * using get_symbol_offset for every symbol.
910 	 */
911 	struct kallsym_iter *iter;
912 	iter = __seq_open_private(file, &kallsyms_op, sizeof(*iter));
913 	if (!iter)
914 		return -ENOMEM;
915 	reset_iter(iter, 0);
916 
917 	/*
918 	 * Instead of checking this on every s_show() call, cache
919 	 * the result here at open time.
920 	 */
921 	iter->show_value = kallsyms_show_value(file->f_cred);
922 	return 0;
923 }
924 
925 #ifdef	CONFIG_KGDB_KDB
kdb_walk_kallsyms(loff_t * pos)926 const char *kdb_walk_kallsyms(loff_t *pos)
927 {
928 	static struct kallsym_iter kdb_walk_kallsyms_iter;
929 	if (*pos == 0) {
930 		memset(&kdb_walk_kallsyms_iter, 0,
931 		       sizeof(kdb_walk_kallsyms_iter));
932 		reset_iter(&kdb_walk_kallsyms_iter, 0);
933 	}
934 	while (1) {
935 		if (!update_iter(&kdb_walk_kallsyms_iter, *pos))
936 			return NULL;
937 		++*pos;
938 		/* Some debugging symbols have no name.  Ignore them. */
939 		if (kdb_walk_kallsyms_iter.name[0])
940 			return kdb_walk_kallsyms_iter.name;
941 	}
942 }
943 #endif	/* CONFIG_KGDB_KDB */
944 
945 static const struct proc_ops kallsyms_proc_ops = {
946 	.proc_open	= kallsyms_open,
947 	.proc_read	= seq_read,
948 	.proc_lseek	= seq_lseek,
949 	.proc_release	= seq_release_private,
950 };
951 
kallsyms_init(void)952 static int __init kallsyms_init(void)
953 {
954 	proc_create("kallsyms", 0444, NULL, &kallsyms_proc_ops);
955 	return 0;
956 }
957 device_initcall(kallsyms_init);
958