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	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
 166static bool cleanup_symbol_name(char *s)
 167{
 168	char *res;
 169
 170	if (!IS_ENABLED(CONFIG_LTO_CLANG))
 171		return false;
 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 observed:
 178	 * - foo.llvm.[0-9a-f]+
 179	 * - foo.[0-9a-f]+
 180	 */
 181	res = strchr(s, '.');
 182	if (res) {
 183		*res = '\0';
 184		return true;
 185	}
 186
 187	return false;
 188}
 189
 190static int compare_symbol_name(const char *name, char *namebuf)
 191{
 192	int ret;
 193
 194	ret = strcmp(name, namebuf);
 195	if (!ret)
 196		return ret;
 197
 198	if (cleanup_symbol_name(namebuf) && !strcmp(name, namebuf))
 199		return 0;
 200
 201	return ret;
 202}
 203
 204static unsigned int get_symbol_seq(int index)
 205{
 206	unsigned int i, seq = 0;
 207
 208	for (i = 0; i < 3; i++)
 209		seq = (seq << 8) | kallsyms_seqs_of_names[3 * index + i];
 210
 211	return seq;
 212}
 213
 214static int kallsyms_lookup_names(const char *name,
 215				 unsigned int *start,
 216				 unsigned int *end)
 217{
 218	int ret;
 219	int low, mid, high;
 220	unsigned int seq, off;
 221	char namebuf[KSYM_NAME_LEN];
 222
 223	low = 0;
 224	high = kallsyms_num_syms - 1;
 225
 226	while (low <= high) {
 227		mid = low + (high - low) / 2;
 228		seq = get_symbol_seq(mid);
 229		off = get_symbol_offset(seq);
 230		kallsyms_expand_symbol(off, namebuf, ARRAY_SIZE(namebuf));
 231		ret = compare_symbol_name(name, namebuf);
 232		if (ret > 0)
 233			low = mid + 1;
 234		else if (ret < 0)
 235			high = mid - 1;
 236		else
 237			break;
 238	}
 239
 240	if (low > high)
 241		return -ESRCH;
 242
 243	low = mid;
 244	while (low) {
 245		seq = get_symbol_seq(low - 1);
 246		off = get_symbol_offset(seq);
 247		kallsyms_expand_symbol(off, namebuf, ARRAY_SIZE(namebuf));
 248		if (compare_symbol_name(name, namebuf))
 249			break;
 250		low--;
 251	}
 252	*start = low;
 253
 254	if (end) {
 255		high = mid;
 256		while (high < kallsyms_num_syms - 1) {
 257			seq = get_symbol_seq(high + 1);
 258			off = get_symbol_offset(seq);
 259			kallsyms_expand_symbol(off, namebuf, ARRAY_SIZE(namebuf));
 260			if (compare_symbol_name(name, namebuf))
 261				break;
 262			high++;
 263		}
 264		*end = high;
 265	}
 266
 267	return 0;
 268}
 269
 270/* Lookup the address for this symbol. Returns 0 if not found. */
 271unsigned long kallsyms_lookup_name(const char *name)
 272{
 273	int ret;
 274	unsigned int i;
 275
 276	/* Skip the search for empty string. */
 277	if (!*name)
 278		return 0;
 279
 280	ret = kallsyms_lookup_names(name, &i, NULL);
 281	if (!ret)
 282		return kallsyms_sym_address(get_symbol_seq(i));
 283
 
 
 
 284	return module_kallsyms_lookup_name(name);
 285}
 
 286
 287/*
 288 * Iterate over all symbols in vmlinux.  For symbols from modules use
 289 * module_kallsyms_on_each_symbol instead.
 290 */
 291int kallsyms_on_each_symbol(int (*fn)(void *, const char *, struct module *,
 292				      unsigned long),
 293			    void *data)
 294{
 295	char namebuf[KSYM_NAME_LEN];
 296	unsigned long i;
 297	unsigned int off;
 298	int ret;
 299
 300	for (i = 0, off = 0; i < kallsyms_num_syms; i++) {
 301		off = kallsyms_expand_symbol(off, namebuf, ARRAY_SIZE(namebuf));
 302		ret = fn(data, namebuf, NULL, kallsyms_sym_address(i));
 303		if (ret != 0)
 304			return ret;
 305		cond_resched();
 306	}
 307	return 0;
 308}
 309
 310int kallsyms_on_each_match_symbol(int (*fn)(void *, unsigned long),
 311				  const char *name, void *data)
 312{
 313	int ret;
 314	unsigned int i, start, end;
 315
 316	ret = kallsyms_lookup_names(name, &start, &end);
 317	if (ret)
 318		return 0;
 319
 320	for (i = start; !ret && i <= end; i++) {
 321		ret = fn(data, kallsyms_sym_address(get_symbol_seq(i)));
 322		cond_resched();
 323	}
 324
 325	return ret;
 326}
 
 327
 328static unsigned long get_symbol_pos(unsigned long addr,
 329				    unsigned long *symbolsize,
 330				    unsigned long *offset)
 331{
 332	unsigned long symbol_start = 0, symbol_end = 0;
 333	unsigned long i, low, high, mid;
 334
 335	/* This kernel should never had been booted. */
 336	if (!IS_ENABLED(CONFIG_KALLSYMS_BASE_RELATIVE))
 337		BUG_ON(!kallsyms_addresses);
 338	else
 339		BUG_ON(!kallsyms_offsets);
 340
 341	/* Do a binary search on the sorted kallsyms_addresses array. */
 342	low = 0;
 343	high = kallsyms_num_syms;
 344
 345	while (high - low > 1) {
 346		mid = low + (high - low) / 2;
 347		if (kallsyms_sym_address(mid) <= addr)
 348			low = mid;
 349		else
 350			high = mid;
 351	}
 352
 353	/*
 354	 * Search for the first aliased symbol. Aliased
 355	 * symbols are symbols with the same address.
 356	 */
 357	while (low && kallsyms_sym_address(low-1) == kallsyms_sym_address(low))
 358		--low;
 359
 360	symbol_start = kallsyms_sym_address(low);
 361
 362	/* Search for next non-aliased symbol. */
 363	for (i = low + 1; i < kallsyms_num_syms; i++) {
 364		if (kallsyms_sym_address(i) > symbol_start) {
 365			symbol_end = kallsyms_sym_address(i);
 366			break;
 367		}
 368	}
 369
 370	/* If we found no next symbol, we use the end of the section. */
 371	if (!symbol_end) {
 372		if (is_kernel_inittext(addr))
 373			symbol_end = (unsigned long)_einittext;
 374		else if (IS_ENABLED(CONFIG_KALLSYMS_ALL))
 375			symbol_end = (unsigned long)_end;
 376		else
 377			symbol_end = (unsigned long)_etext;
 378	}
 379
 380	if (symbolsize)
 381		*symbolsize = symbol_end - symbol_start;
 382	if (offset)
 383		*offset = addr - symbol_start;
 384
 385	return low;
 386}
 387
 388/*
 389 * Lookup an address but don't bother to find any names.
 390 */
 391int kallsyms_lookup_size_offset(unsigned long addr, unsigned long *symbolsize,
 392				unsigned long *offset)
 393{
 394	char namebuf[KSYM_NAME_LEN];
 
 
 395
 396	if (is_ksym_addr(addr)) {
 397		get_symbol_pos(addr, symbolsize, offset);
 398		return 1;
 399	}
 400	return !!module_address_lookup(addr, symbolsize, offset, NULL, NULL, namebuf) ||
 401	       !!__bpf_address_lookup(addr, symbolsize, offset, namebuf);
 402}
 403
 404static const char *kallsyms_lookup_buildid(unsigned long addr,
 405			unsigned long *symbolsize,
 406			unsigned long *offset, char **modname,
 407			const unsigned char **modbuildid, char *namebuf)
 
 
 
 
 
 
 
 408{
 409	const char *ret;
 410
 411	namebuf[KSYM_NAME_LEN - 1] = 0;
 412	namebuf[0] = 0;
 413
 414	if (is_ksym_addr(addr)) {
 415		unsigned long pos;
 416
 417		pos = get_symbol_pos(addr, symbolsize, offset);
 418		/* Grab name */
 419		kallsyms_expand_symbol(get_symbol_offset(pos),
 420				       namebuf, KSYM_NAME_LEN);
 421		if (modname)
 422			*modname = NULL;
 423		if (modbuildid)
 424			*modbuildid = NULL;
 425
 426		ret = namebuf;
 427		goto found;
 428	}
 429
 430	/* See if it's in a module or a BPF JITed image. */
 431	ret = module_address_lookup(addr, symbolsize, offset,
 432				    modname, modbuildid, namebuf);
 433	if (!ret)
 434		ret = bpf_address_lookup(addr, symbolsize,
 435					 offset, modname, namebuf);
 436
 437	if (!ret)
 438		ret = ftrace_mod_address_lookup(addr, symbolsize,
 439						offset, modname, namebuf);
 440
 441found:
 442	cleanup_symbol_name(namebuf);
 443	return ret;
 444}
 445
 446/*
 447 * Lookup an address
 448 * - modname is set to NULL if it's in the kernel.
 449 * - We guarantee that the returned name is valid until we reschedule even if.
 450 *   It resides in a module.
 451 * - We also guarantee that modname will be valid until rescheduled.
 452 */
 453const char *kallsyms_lookup(unsigned long addr,
 454			    unsigned long *symbolsize,
 455			    unsigned long *offset,
 456			    char **modname, char *namebuf)
 457{
 458	return kallsyms_lookup_buildid(addr, symbolsize, offset, modname,
 459				       NULL, namebuf);
 460}
 461
 462int lookup_symbol_name(unsigned long addr, char *symname)
 463{
 464	int res;
 465
 466	symname[0] = '\0';
 467	symname[KSYM_NAME_LEN - 1] = '\0';
 468
 469	if (is_ksym_addr(addr)) {
 470		unsigned long pos;
 471
 472		pos = get_symbol_pos(addr, NULL, NULL);
 473		/* Grab name */
 474		kallsyms_expand_symbol(get_symbol_offset(pos),
 475				       symname, KSYM_NAME_LEN);
 476		goto found;
 477	}
 478	/* See if it's in a module. */
 479	res = lookup_module_symbol_name(addr, symname);
 480	if (res)
 481		return res;
 482
 483found:
 484	cleanup_symbol_name(symname);
 485	return 0;
 486}
 487
 488int lookup_symbol_attrs(unsigned long addr, unsigned long *size,
 489			unsigned long *offset, char *modname, char *name)
 490{
 491	int res;
 492
 493	name[0] = '\0';
 494	name[KSYM_NAME_LEN - 1] = '\0';
 495
 496	if (is_ksym_addr(addr)) {
 497		unsigned long pos;
 498
 499		pos = get_symbol_pos(addr, size, offset);
 500		/* Grab name */
 501		kallsyms_expand_symbol(get_symbol_offset(pos),
 502				       name, KSYM_NAME_LEN);
 503		modname[0] = '\0';
 504		goto found;
 505	}
 506	/* See if it's in a module. */
 507	res = lookup_module_symbol_attrs(addr, size, offset, modname, name);
 508	if (res)
 509		return res;
 510
 511found:
 512	cleanup_symbol_name(name);
 513	return 0;
 514}
 515
 516/* Look up a kernel symbol and return it in a text buffer. */
 517static int __sprint_symbol(char *buffer, unsigned long address,
 518			   int symbol_offset, int add_offset, int add_buildid)
 519{
 520	char *modname;
 521	const unsigned char *buildid;
 522	const char *name;
 523	unsigned long offset, size;
 524	int len;
 525
 526	address += symbol_offset;
 527	name = kallsyms_lookup_buildid(address, &size, &offset, &modname, &buildid,
 528				       buffer);
 529	if (!name)
 530		return sprintf(buffer, "0x%lx", address - symbol_offset);
 531
 532	if (name != buffer)
 533		strcpy(buffer, name);
 534	len = strlen(buffer);
 535	offset -= symbol_offset;
 536
 537	if (add_offset)
 538		len += sprintf(buffer + len, "+%#lx/%#lx", offset, size);
 539
 540	if (modname) {
 541		len += sprintf(buffer + len, " [%s", modname);
 542#if IS_ENABLED(CONFIG_STACKTRACE_BUILD_ID)
 543		if (add_buildid && buildid) {
 544			/* build ID should match length of sprintf */
 545#if IS_ENABLED(CONFIG_MODULES)
 546			static_assert(sizeof(typeof_member(struct module, build_id)) == 20);
 547#endif
 548			len += sprintf(buffer + len, " %20phN", buildid);
 549		}
 550#endif
 551		len += sprintf(buffer + len, "]");
 552	}
 553
 554	return len;
 555}
 556
 557/**
 558 * sprint_symbol - Look up a kernel symbol and return it in a text buffer
 559 * @buffer: buffer to be stored
 560 * @address: address to lookup
 561 *
 562 * This function looks up a kernel symbol with @address and stores its name,
 563 * offset, size and module name to @buffer if possible. If no symbol was found,
 564 * just saves its @address as is.
 565 *
 566 * This function returns the number of bytes stored in @buffer.
 567 */
 568int sprint_symbol(char *buffer, unsigned long address)
 569{
 570	return __sprint_symbol(buffer, address, 0, 1, 0);
 571}
 572EXPORT_SYMBOL_GPL(sprint_symbol);
 573
 574/**
 575 * sprint_symbol_build_id - Look up a kernel symbol and return it in a text buffer
 576 * @buffer: buffer to be stored
 577 * @address: address to lookup
 578 *
 579 * This function looks up a kernel symbol with @address and stores its name,
 580 * offset, size, module name and module build ID to @buffer if possible. If no
 581 * symbol was found, just saves its @address as is.
 582 *
 583 * This function returns the number of bytes stored in @buffer.
 584 */
 585int sprint_symbol_build_id(char *buffer, unsigned long address)
 586{
 587	return __sprint_symbol(buffer, address, 0, 1, 1);
 588}
 589EXPORT_SYMBOL_GPL(sprint_symbol_build_id);
 590
 591/**
 592 * sprint_symbol_no_offset - Look up a kernel symbol and return it in a text buffer
 593 * @buffer: buffer to be stored
 594 * @address: address to lookup
 595 *
 596 * This function looks up a kernel symbol with @address and stores its name
 597 * and module name to @buffer if possible. If no symbol was found, just saves
 598 * its @address as is.
 599 *
 600 * This function returns the number of bytes stored in @buffer.
 601 */
 602int sprint_symbol_no_offset(char *buffer, unsigned long address)
 603{
 604	return __sprint_symbol(buffer, address, 0, 0, 0);
 605}
 606EXPORT_SYMBOL_GPL(sprint_symbol_no_offset);
 607
 608/**
 609 * sprint_backtrace - Look up a backtrace symbol and return it in a text buffer
 610 * @buffer: buffer to be stored
 611 * @address: address to lookup
 612 *
 613 * This function is for stack backtrace and does the same thing as
 614 * sprint_symbol() but with modified/decreased @address. If there is a
 615 * tail-call to the function marked "noreturn", gcc optimized out code after
 616 * the call so that the stack-saved return address could point outside of the
 617 * caller. This function ensures that kallsyms will find the original caller
 618 * by decreasing @address.
 619 *
 620 * This function returns the number of bytes stored in @buffer.
 621 */
 622int sprint_backtrace(char *buffer, unsigned long address)
 623{
 624	return __sprint_symbol(buffer, address, -1, 1, 0);
 625}
 626
 627/**
 628 * sprint_backtrace_build_id - Look up a backtrace symbol and return it in a text buffer
 629 * @buffer: buffer to be stored
 630 * @address: address to lookup
 631 *
 632 * This function is for stack backtrace and does the same thing as
 633 * sprint_symbol() but with modified/decreased @address. If there is a
 634 * tail-call to the function marked "noreturn", gcc optimized out code after
 635 * the call so that the stack-saved return address could point outside of the
 636 * caller. This function ensures that kallsyms will find the original caller
 637 * by decreasing @address. This function also appends the module build ID to
 638 * the @buffer if @address is within a kernel module.
 639 *
 640 * This function returns the number of bytes stored in @buffer.
 641 */
 642int sprint_backtrace_build_id(char *buffer, unsigned long address)
 643{
 644	return __sprint_symbol(buffer, address, -1, 1, 1);
 
 
 
 
 645}
 
 646
 647/* To avoid using get_symbol_offset for every symbol, we carry prefix along. */
 648struct kallsym_iter {
 649	loff_t pos;
 650	loff_t pos_arch_end;
 651	loff_t pos_mod_end;
 652	loff_t pos_ftrace_mod_end;
 653	loff_t pos_bpf_end;
 654	unsigned long value;
 655	unsigned int nameoff; /* If iterating in core kernel symbols. */
 656	char type;
 657	char name[KSYM_NAME_LEN];
 658	char module_name[MODULE_NAME_LEN];
 659	int exported;
 660	int show_value;
 661};
 662
 663int __weak arch_get_kallsym(unsigned int symnum, unsigned long *value,
 664			    char *type, char *name)
 665{
 666	return -EINVAL;
 667}
 668
 669static int get_ksymbol_arch(struct kallsym_iter *iter)
 670{
 671	int ret = arch_get_kallsym(iter->pos - kallsyms_num_syms,
 672				   &iter->value, &iter->type,
 673				   iter->name);
 674
 675	if (ret < 0) {
 676		iter->pos_arch_end = iter->pos;
 677		return 0;
 678	}
 679
 680	return 1;
 681}
 682
 683static int get_ksymbol_mod(struct kallsym_iter *iter)
 684{
 685	int ret = module_get_kallsym(iter->pos - iter->pos_arch_end,
 686				     &iter->value, &iter->type,
 687				     iter->name, iter->module_name,
 688				     &iter->exported);
 689	if (ret < 0) {
 690		iter->pos_mod_end = iter->pos;
 691		return 0;
 692	}
 693
 694	return 1;
 695}
 696
 697/*
 698 * ftrace_mod_get_kallsym() may also get symbols for pages allocated for ftrace
 699 * purposes. In that case "__builtin__ftrace" is used as a module name, even
 700 * though "__builtin__ftrace" is not a module.
 701 */
 702static int get_ksymbol_ftrace_mod(struct kallsym_iter *iter)
 703{
 704	int ret = ftrace_mod_get_kallsym(iter->pos - iter->pos_mod_end,
 705					 &iter->value, &iter->type,
 706					 iter->name, iter->module_name,
 707					 &iter->exported);
 708	if (ret < 0) {
 709		iter->pos_ftrace_mod_end = iter->pos;
 710		return 0;
 711	}
 712
 713	return 1;
 714}
 715
 716static int get_ksymbol_bpf(struct kallsym_iter *iter)
 717{
 718	int ret;
 719
 720	strlcpy(iter->module_name, "bpf", MODULE_NAME_LEN);
 721	iter->exported = 0;
 722	ret = bpf_get_kallsym(iter->pos - iter->pos_ftrace_mod_end,
 723			      &iter->value, &iter->type,
 724			      iter->name);
 725	if (ret < 0) {
 726		iter->pos_bpf_end = iter->pos;
 727		return 0;
 728	}
 729
 730	return 1;
 731}
 732
 733/*
 734 * This uses "__builtin__kprobes" as a module name for symbols for pages
 735 * allocated for kprobes' purposes, even though "__builtin__kprobes" is not a
 736 * module.
 737 */
 738static int get_ksymbol_kprobe(struct kallsym_iter *iter)
 739{
 740	strlcpy(iter->module_name, "__builtin__kprobes", MODULE_NAME_LEN);
 741	iter->exported = 0;
 742	return kprobe_get_kallsym(iter->pos - iter->pos_bpf_end,
 743				  &iter->value, &iter->type,
 744				  iter->name) < 0 ? 0 : 1;
 745}
 746
 747/* Returns space to next name. */
 748static unsigned long get_ksymbol_core(struct kallsym_iter *iter)
 749{
 750	unsigned off = iter->nameoff;
 751
 752	iter->module_name[0] = '\0';
 753	iter->value = kallsyms_sym_address(iter->pos);
 754
 755	iter->type = kallsyms_get_symbol_type(off);
 756
 757	off = kallsyms_expand_symbol(off, iter->name, ARRAY_SIZE(iter->name));
 758
 759	return off - iter->nameoff;
 760}
 761
 762static void reset_iter(struct kallsym_iter *iter, loff_t new_pos)
 763{
 764	iter->name[0] = '\0';
 765	iter->nameoff = get_symbol_offset(new_pos);
 766	iter->pos = new_pos;
 767	if (new_pos == 0) {
 768		iter->pos_arch_end = 0;
 769		iter->pos_mod_end = 0;
 770		iter->pos_ftrace_mod_end = 0;
 771		iter->pos_bpf_end = 0;
 772	}
 773}
 774
 775/*
 776 * The end position (last + 1) of each additional kallsyms section is recorded
 777 * in iter->pos_..._end as each section is added, and so can be used to
 778 * determine which get_ksymbol_...() function to call next.
 779 */
 780static int update_iter_mod(struct kallsym_iter *iter, loff_t pos)
 781{
 782	iter->pos = pos;
 783
 784	if ((!iter->pos_arch_end || iter->pos_arch_end > pos) &&
 785	    get_ksymbol_arch(iter))
 786		return 1;
 787
 788	if ((!iter->pos_mod_end || iter->pos_mod_end > pos) &&
 789	    get_ksymbol_mod(iter))
 790		return 1;
 791
 792	if ((!iter->pos_ftrace_mod_end || iter->pos_ftrace_mod_end > pos) &&
 793	    get_ksymbol_ftrace_mod(iter))
 794		return 1;
 795
 796	if ((!iter->pos_bpf_end || iter->pos_bpf_end > pos) &&
 797	    get_ksymbol_bpf(iter))
 798		return 1;
 799
 800	return get_ksymbol_kprobe(iter);
 801}
 802
 803/* Returns false if pos at or past end of file. */
 804static int update_iter(struct kallsym_iter *iter, loff_t pos)
 805{
 806	/* Module symbols can be accessed randomly. */
 807	if (pos >= kallsyms_num_syms)
 808		return update_iter_mod(iter, pos);
 
 
 809
 810	/* If we're not on the desired position, reset to new position. */
 811	if (pos != iter->pos)
 812		reset_iter(iter, pos);
 813
 814	iter->nameoff += get_ksymbol_core(iter);
 815	iter->pos++;
 816
 817	return 1;
 818}
 819
 820static void *s_next(struct seq_file *m, void *p, loff_t *pos)
 821{
 822	(*pos)++;
 823
 824	if (!update_iter(m->private, *pos))
 825		return NULL;
 826	return p;
 827}
 828
 829static void *s_start(struct seq_file *m, loff_t *pos)
 830{
 831	if (!update_iter(m->private, *pos))
 832		return NULL;
 833	return m->private;
 834}
 835
 836static void s_stop(struct seq_file *m, void *p)
 837{
 838}
 839
 840static int s_show(struct seq_file *m, void *p)
 841{
 842	void *value;
 843	struct kallsym_iter *iter = m->private;
 844
 845	/* Some debugging symbols have no name.  Ignore them. */
 846	if (!iter->name[0])
 847		return 0;
 848
 849	value = iter->show_value ? (void *)iter->value : NULL;
 850
 851	if (iter->module_name[0]) {
 852		char type;
 853
 854		/*
 855		 * Label it "global" if it is exported,
 856		 * "local" if not exported.
 857		 */
 858		type = iter->exported ? toupper(iter->type) :
 859					tolower(iter->type);
 860		seq_printf(m, "%px %c %s\t[%s]\n", value,
 861			   type, iter->name, iter->module_name);
 862	} else
 863		seq_printf(m, "%px %c %s\n", value,
 864			   iter->type, iter->name);
 865	return 0;
 866}
 867
 868static const struct seq_operations kallsyms_op = {
 869	.start = s_start,
 870	.next = s_next,
 871	.stop = s_stop,
 872	.show = s_show
 873};
 874
 875#ifdef CONFIG_BPF_SYSCALL
 876
 877struct bpf_iter__ksym {
 878	__bpf_md_ptr(struct bpf_iter_meta *, meta);
 879	__bpf_md_ptr(struct kallsym_iter *, ksym);
 880};
 881
 882static int ksym_prog_seq_show(struct seq_file *m, bool in_stop)
 883{
 884	struct bpf_iter__ksym ctx;
 885	struct bpf_iter_meta meta;
 886	struct bpf_prog *prog;
 887
 888	meta.seq = m;
 889	prog = bpf_iter_get_info(&meta, in_stop);
 890	if (!prog)
 891		return 0;
 892
 893	ctx.meta = &meta;
 894	ctx.ksym = m ? m->private : NULL;
 895	return bpf_iter_run_prog(prog, &ctx);
 896}
 897
 898static int bpf_iter_ksym_seq_show(struct seq_file *m, void *p)
 899{
 900	return ksym_prog_seq_show(m, false);
 901}
 902
 903static void bpf_iter_ksym_seq_stop(struct seq_file *m, void *p)
 904{
 905	if (!p)
 906		(void) ksym_prog_seq_show(m, true);
 907	else
 908		s_stop(m, p);
 909}
 910
 911static const struct seq_operations bpf_iter_ksym_ops = {
 912	.start = s_start,
 913	.next = s_next,
 914	.stop = bpf_iter_ksym_seq_stop,
 915	.show = bpf_iter_ksym_seq_show,
 916};
 917
 918static int bpf_iter_ksym_init(void *priv_data, struct bpf_iter_aux_info *aux)
 919{
 920	struct kallsym_iter *iter = priv_data;
 921
 922	reset_iter(iter, 0);
 923
 924	/* cache here as in kallsyms_open() case; use current process
 925	 * credentials to tell BPF iterators if values should be shown.
 926	 */
 927	iter->show_value = kallsyms_show_value(current_cred());
 928
 929	return 0;
 930}
 931
 932DEFINE_BPF_ITER_FUNC(ksym, struct bpf_iter_meta *meta, struct kallsym_iter *ksym)
 933
 934static const struct bpf_iter_seq_info ksym_iter_seq_info = {
 935	.seq_ops		= &bpf_iter_ksym_ops,
 936	.init_seq_private	= bpf_iter_ksym_init,
 937	.fini_seq_private	= NULL,
 938	.seq_priv_size		= sizeof(struct kallsym_iter),
 939};
 940
 941static struct bpf_iter_reg ksym_iter_reg_info = {
 942	.target                 = "ksym",
 943	.feature		= BPF_ITER_RESCHED,
 944	.ctx_arg_info_size	= 1,
 945	.ctx_arg_info		= {
 946		{ offsetof(struct bpf_iter__ksym, ksym),
 947		  PTR_TO_BTF_ID_OR_NULL },
 948	},
 949	.seq_info		= &ksym_iter_seq_info,
 950};
 951
 952BTF_ID_LIST(btf_ksym_iter_id)
 953BTF_ID(struct, kallsym_iter)
 954
 955static int __init bpf_ksym_iter_register(void)
 956{
 957	ksym_iter_reg_info.ctx_arg_info[0].btf_id = *btf_ksym_iter_id;
 958	return bpf_iter_reg_target(&ksym_iter_reg_info);
 959}
 960
 961late_initcall(bpf_ksym_iter_register);
 962
 963#endif /* CONFIG_BPF_SYSCALL */
 964
 965static inline int kallsyms_for_perf(void)
 966{
 967#ifdef CONFIG_PERF_EVENTS
 968	extern int sysctl_perf_event_paranoid;
 969	if (sysctl_perf_event_paranoid <= 1)
 970		return 1;
 971#endif
 972	return 0;
 973}
 974
 975/*
 976 * We show kallsyms information even to normal users if we've enabled
 977 * kernel profiling and are explicitly not paranoid (so kptr_restrict
 978 * is clear, and sysctl_perf_event_paranoid isn't set).
 979 *
 980 * Otherwise, require CAP_SYSLOG (assuming kptr_restrict isn't set to
 981 * block even that).
 982 */
 983bool kallsyms_show_value(const struct cred *cred)
 984{
 985	switch (kptr_restrict) {
 986	case 0:
 987		if (kallsyms_for_perf())
 988			return true;
 989		fallthrough;
 990	case 1:
 991		if (security_capable(cred, &init_user_ns, CAP_SYSLOG,
 992				     CAP_OPT_NOAUDIT) == 0)
 993			return true;
 994		fallthrough;
 995	default:
 996		return false;
 997	}
 998}
 999
1000static int kallsyms_open(struct inode *inode, struct file *file)
1001{
1002	/*
1003	 * We keep iterator in m->private, since normal case is to
1004	 * s_start from where we left off, so we avoid doing
1005	 * using get_symbol_offset for every symbol.
1006	 */
1007	struct kallsym_iter *iter;
1008	iter = __seq_open_private(file, &kallsyms_op, sizeof(*iter));
1009	if (!iter)
1010		return -ENOMEM;
1011	reset_iter(iter, 0);
1012
1013	/*
1014	 * Instead of checking this on every s_show() call, cache
1015	 * the result here at open time.
1016	 */
1017	iter->show_value = kallsyms_show_value(file->f_cred);
1018	return 0;
1019}
1020
1021#ifdef	CONFIG_KGDB_KDB
1022const char *kdb_walk_kallsyms(loff_t *pos)
1023{
1024	static struct kallsym_iter kdb_walk_kallsyms_iter;
1025	if (*pos == 0) {
1026		memset(&kdb_walk_kallsyms_iter, 0,
1027		       sizeof(kdb_walk_kallsyms_iter));
1028		reset_iter(&kdb_walk_kallsyms_iter, 0);
1029	}
1030	while (1) {
1031		if (!update_iter(&kdb_walk_kallsyms_iter, *pos))
1032			return NULL;
1033		++*pos;
1034		/* Some debugging symbols have no name.  Ignore them. */
1035		if (kdb_walk_kallsyms_iter.name[0])
1036			return kdb_walk_kallsyms_iter.name;
1037	}
1038}
1039#endif	/* CONFIG_KGDB_KDB */
1040
1041static const struct proc_ops kallsyms_proc_ops = {
1042	.proc_open	= kallsyms_open,
1043	.proc_read	= seq_read,
1044	.proc_lseek	= seq_lseek,
1045	.proc_release	= seq_release_private,
1046};
1047
1048static int __init kallsyms_init(void)
1049{
1050	proc_create("kallsyms", 0444, NULL, &kallsyms_proc_ops);
1051	return 0;
1052}
1053device_initcall(kallsyms_init);