kallsyms.c 15.1 KB
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661
/* Generate assembler source containing symbol information
 *
 * Copyright 2002       by Kai Germaschewski
 *
 * This software may be used and distributed according to the terms
 * of the GNU General Public License, incorporated herein by reference.
 *
 * Usage: nm -n vmlinux | scripts/kallsyms [--all-symbols] > symbols.S
 *
 *      Table compression uses all the unused char codes on the symbols and
 *  maps these to the most used substrings (tokens). For instance, it might
 *  map char code 0xF7 to represent "write_" and then in every symbol where
 *  "write_" appears it can be replaced by 0xF7, saving 5 bytes.
 *      The used codes themselves are also placed in the table so that the
 *  decompresion can work without "special cases".
 *      Applied to kernel symbols, this usually produces a compression ratio
 *  of about 50%.
 *
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>

#ifndef ARRAY_SIZE
#define ARRAY_SIZE(arr) (sizeof(arr) / sizeof(arr[0]))
#endif

#define KSYM_NAME_LEN		128

struct sym_entry {
	unsigned long long addr;
	unsigned int len;
	unsigned int start_pos;
	unsigned char *sym;
};

struct text_range {
	const char *stext, *etext;
	unsigned long long start, end;
};

static unsigned long long _text;
static struct text_range text_ranges[] = {
	{ "_stext",     "_etext"     },
	{ "_sinittext", "_einittext" },
	{ "_stext_l1",  "_etext_l1"  },	/* Blackfin on-chip L1 inst SRAM */
	{ "_stext_l2",  "_etext_l2"  },	/* Blackfin on-chip L2 SRAM */
};
#define text_range_text     (&text_ranges[0])
#define text_range_inittext (&text_ranges[1])

static struct sym_entry *table;
static unsigned int table_size, table_cnt;
static int all_symbols = 0;
static char symbol_prefix_char = '\0';

int token_profit[0x10000];

/* the table that holds the result of the compression */
unsigned char best_table[256][2];
unsigned char best_table_len[256];


static void usage(void)
{
	fprintf(stderr, "Usage: kallsyms [--all-symbols] [--symbol-prefix=<prefix char>] < in.map > out.S\n");
	exit(1);
}

/*
 * This ignores the intensely annoying "mapping symbols" found
 * in ARM ELF files: $a, $t and $d.
 */
static inline int is_arm_mapping_symbol(const char *str)
{
	return str[0] == '$' && strchr("atd", str[1])
	       && (str[2] == '\0' || str[2] == '.');
}

static int read_symbol_tr(const char *sym, unsigned long long addr)
{
	size_t i;
	struct text_range *tr;

	for (i = 0; i < ARRAY_SIZE(text_ranges); ++i) {
		tr = &text_ranges[i];

		if (strcmp(sym, tr->stext) == 0) {
			tr->start = addr;
			return 0;
		} else if (strcmp(sym, tr->etext) == 0) {
			tr->end = addr;
			return 0;
		}
	}

	return 1;
}

static int read_symbol(FILE *in, struct sym_entry *s)
{
	char str[500];
	char *sym, stype;
	int rc;

	rc = fscanf(in, "%llx %c %499s\n", &s->addr, &stype, str);
	if (rc != 3) {
		if (rc != EOF) {
			/* skip line */
			fgets(str, 500, in);
		}
		return -1;
	}

	sym = str;
	/* skip prefix char */
	if (symbol_prefix_char && str[0] == symbol_prefix_char)
		sym++;

	/* Ignore most absolute/undefined (?) symbols. */
	if (strcmp(sym, "_text") == 0)
		_text = s->addr;
	else if (read_symbol_tr(sym, s->addr) == 0)
		/* nothing to do */;
	else if (toupper(stype) == 'A')
	{
		/* Keep these useful absolute symbols */
		if (strcmp(sym, "__kernel_syscall_via_break") &&
		    strcmp(sym, "__kernel_syscall_via_epc") &&
		    strcmp(sym, "__kernel_sigtramp") &&
		    strcmp(sym, "__gp"))
			return -1;

	}
	else if (toupper(stype) == 'U' ||
		 is_arm_mapping_symbol(sym))
		return -1;
	/* exclude also MIPS ELF local symbols ($L123 instead of .L123) */
	else if (str[0] == '$')
		return -1;
	/* exclude debugging symbols */
	else if (stype == 'N')
		return -1;

	/* include the type field in the symbol name, so that it gets
	 * compressed together */
	s->len = strlen(str) + 1;
	s->sym = malloc(s->len + 1);
	if (!s->sym) {
		fprintf(stderr, "kallsyms failure: "
			"unable to allocate required amount of memory\n");
		exit(EXIT_FAILURE);
	}
	strcpy((char *)s->sym + 1, str);
	s->sym[0] = stype;

	return 0;
}

static int symbol_valid_tr(struct sym_entry *s)
{
	size_t i;
	struct text_range *tr;

	for (i = 0; i < ARRAY_SIZE(text_ranges); ++i) {
		tr = &text_ranges[i];

		if (s->addr >= tr->start && s->addr <= tr->end)
			return 1;
	}

	return 0;
}

static int symbol_valid(struct sym_entry *s)
{
	/* Symbols which vary between passes.  Passes 1 and 2 must have
	 * identical symbol lists.  The kallsyms_* symbols below are only added
	 * after pass 1, they would be included in pass 2 when --all-symbols is
	 * specified so exclude them to get a stable symbol list.
	 */
	static char *special_symbols[] = {
		"kallsyms_addresses",
		"kallsyms_num_syms",
		"kallsyms_names",
		"kallsyms_markers",
		"kallsyms_token_table",
		"kallsyms_token_index",

	/* Exclude linker generated symbols which vary between passes */
		"_SDA_BASE_",		/* ppc */
		"_SDA2_BASE_",		/* ppc */
		NULL };
	int i;
	int offset = 1;

	/* skip prefix char */
	if (symbol_prefix_char && *(s->sym + 1) == symbol_prefix_char)
		offset++;

	/* if --all-symbols is not specified, then symbols outside the text
	 * and inittext sections are discarded */
	if (!all_symbols) {
		if (symbol_valid_tr(s) == 0)
			return 0;
		/* Corner case.  Discard any symbols with the same value as
		 * _etext _einittext; they can move between pass 1 and 2 when
		 * the kallsyms data are added.  If these symbols move then
		 * they may get dropped in pass 2, which breaks the kallsyms
		 * rules.
		 */
		if ((s->addr == text_range_text->end &&
				strcmp((char *)s->sym + offset, text_range_text->etext)) ||
		    (s->addr == text_range_inittext->end &&
				strcmp((char *)s->sym + offset, text_range_inittext->etext)))
			return 0;
	}

	/* Exclude symbols which vary between passes. */
	if (strstr((char *)s->sym + offset, "_compiled."))
		return 0;

	for (i = 0; special_symbols[i]; i++)
		if( strcmp((char *)s->sym + offset, special_symbols[i]) == 0 )
			return 0;

	return 1;
}

static void read_map(FILE *in)
{
	while (!feof(in)) {
		if (table_cnt >= table_size) {
			table_size += 10000;
			table = realloc(table, sizeof(*table) * table_size);
			if (!table) {
				fprintf(stderr, "out of memory\n");
				exit (1);
			}
		}
		if (read_symbol(in, &table[table_cnt]) == 0) {
			table[table_cnt].start_pos = table_cnt;
			table_cnt++;
		}
	}
}

static void output_label(char *label)
{
	if (symbol_prefix_char)
		printf(".globl %c%s\n", symbol_prefix_char, label);
	else
		printf(".globl %s\n", label);
	printf("\tALGN\n");
	if (symbol_prefix_char)
		printf("%c%s:\n", symbol_prefix_char, label);
	else
		printf("%s:\n", label);
}

/* uncompress a compressed symbol. When this function is called, the best table
 * might still be compressed itself, so the function needs to be recursive */
static int expand_symbol(unsigned char *data, int len, char *result)
{
	int c, rlen, total=0;

	while (len) {
		c = *data;
		/* if the table holds a single char that is the same as the one
		 * we are looking for, then end the search */
		if (best_table[c][0]==c && best_table_len[c]==1) {
			*result++ = c;
			total++;
		} else {
			/* if not, recurse and expand */
			rlen = expand_symbol(best_table[c], best_table_len[c], result);
			total += rlen;
			result += rlen;
		}
		data++;
		len--;
	}
	*result=0;

	return total;
}

static void write_src(void)
{
	unsigned int i, k, off;
	unsigned int best_idx[256];
	unsigned int *markers;
	char buf[KSYM_NAME_LEN];

	printf("#include <asm/types.h>\n");
	printf("#if BITS_PER_LONG == 64\n");
	printf("#define PTR .quad\n");
	printf("#define ALGN .align 8\n");
	printf("#else\n");
	printf("#define PTR .long\n");
	printf("#define ALGN .align 4\n");
	printf("#endif\n");

	printf("\t.section .rodata, \"a\"\n");

	/* Provide proper symbols relocatability by their '_text'
	 * relativeness.  The symbol names cannot be used to construct
	 * normal symbol references as the list of symbols contains
	 * symbols that are declared static and are private to their
	 * .o files.  This prevents .tmp_kallsyms.o or any other
	 * object from referencing them.
	 */
	output_label("kallsyms_addresses");
	for (i = 0; i < table_cnt; i++) {
		if (toupper(table[i].sym[0]) != 'A') {
			if (_text <= table[i].addr)
				printf("\tPTR\t_text + %#llx\n",
					table[i].addr - _text);
			else
				printf("\tPTR\t_text - %#llx\n",
					_text - table[i].addr);
		} else {
			printf("\tPTR\t%#llx\n", table[i].addr);
		}
	}
	printf("\n");

	output_label("kallsyms_num_syms");
	printf("\tPTR\t%d\n", table_cnt);
	printf("\n");

	/* table of offset markers, that give the offset in the compressed stream
	 * every 256 symbols */
	markers = malloc(sizeof(unsigned int) * ((table_cnt + 255) / 256));
	if (!markers) {
		fprintf(stderr, "kallsyms failure: "
			"unable to allocate required memory\n");
		exit(EXIT_FAILURE);
	}

	output_label("kallsyms_names");
	off = 0;
	for (i = 0; i < table_cnt; i++) {
		if ((i & 0xFF) == 0)
			markers[i >> 8] = off;

		printf("\t.byte 0x%02x", table[i].len);
		for (k = 0; k < table[i].len; k++)
			printf(", 0x%02x", table[i].sym[k]);
		printf("\n");

		off += table[i].len + 1;
	}
	printf("\n");

	output_label("kallsyms_markers");
	for (i = 0; i < ((table_cnt + 255) >> 8); i++)
		printf("\tPTR\t%d\n", markers[i]);
	printf("\n");

	free(markers);

	output_label("kallsyms_token_table");
	off = 0;
	for (i = 0; i < 256; i++) {
		best_idx[i] = off;
		expand_symbol(best_table[i], best_table_len[i], buf);
		printf("\t.asciz\t\"%s\"\n", buf);
		off += strlen(buf) + 1;
	}
	printf("\n");

	output_label("kallsyms_token_index");
	for (i = 0; i < 256; i++)
		printf("\t.short\t%d\n", best_idx[i]);
	printf("\n");
}


/* table lookup compression functions */

/* count all the possible tokens in a symbol */
static void learn_symbol(unsigned char *symbol, int len)
{
	int i;

	for (i = 0; i < len - 1; i++)
		token_profit[ symbol[i] + (symbol[i + 1] << 8) ]++;
}

/* decrease the count for all the possible tokens in a symbol */
static void forget_symbol(unsigned char *symbol, int len)
{
	int i;

	for (i = 0; i < len - 1; i++)
		token_profit[ symbol[i] + (symbol[i + 1] << 8) ]--;
}

/* remove all the invalid symbols from the table and do the initial token count */
static void build_initial_tok_table(void)
{
	unsigned int i, pos;

	pos = 0;
	for (i = 0; i < table_cnt; i++) {
		if ( symbol_valid(&table[i]) ) {
			if (pos != i)
				table[pos] = table[i];
			learn_symbol(table[pos].sym, table[pos].len);
			pos++;
		}
	}
	table_cnt = pos;
}

static void *find_token(unsigned char *str, int len, unsigned char *token)
{
	int i;

	for (i = 0; i < len - 1; i++) {
		if (str[i] == token[0] && str[i+1] == token[1])
			return &str[i];
	}
	return NULL;
}

/* replace a given token in all the valid symbols. Use the sampled symbols
 * to update the counts */
static void compress_symbols(unsigned char *str, int idx)
{
	unsigned int i, len, size;
	unsigned char *p1, *p2;

	for (i = 0; i < table_cnt; i++) {

		len = table[i].len;
		p1 = table[i].sym;

		/* find the token on the symbol */
		p2 = find_token(p1, len, str);
		if (!p2) continue;

		/* decrease the counts for this symbol's tokens */
		forget_symbol(table[i].sym, len);

		size = len;

		do {
			*p2 = idx;
			p2++;
			size -= (p2 - p1);
			memmove(p2, p2 + 1, size);
			p1 = p2;
			len--;

			if (size < 2) break;

			/* find the token on the symbol */
			p2 = find_token(p1, size, str);

		} while (p2);

		table[i].len = len;

		/* increase the counts for this symbol's new tokens */
		learn_symbol(table[i].sym, len);
	}
}

/* search the token with the maximum profit */
static int find_best_token(void)
{
	int i, best, bestprofit;

	bestprofit=-10000;
	best = 0;

	for (i = 0; i < 0x10000; i++) {
		if (token_profit[i] > bestprofit) {
			best = i;
			bestprofit = token_profit[i];
		}
	}
	return best;
}

/* this is the core of the algorithm: calculate the "best" table */
static void optimize_result(void)
{
	int i, best;

	/* using the '\0' symbol last allows compress_symbols to use standard
	 * fast string functions */
	for (i = 255; i >= 0; i--) {

		/* if this table slot is empty (it is not used by an actual
		 * original char code */
		if (!best_table_len[i]) {

			/* find the token with the breates profit value */
			best = find_best_token();

			/* place it in the "best" table */
			best_table_len[i] = 2;
			best_table[i][0] = best & 0xFF;
			best_table[i][1] = (best >> 8) & 0xFF;

			/* replace this token in all the valid symbols */
			compress_symbols(best_table[i], i);
		}
	}
}

/* start by placing the symbols that are actually used on the table */
static void insert_real_symbols_in_table(void)
{
	unsigned int i, j, c;

	memset(best_table, 0, sizeof(best_table));
	memset(best_table_len, 0, sizeof(best_table_len));

	for (i = 0; i < table_cnt; i++) {
		for (j = 0; j < table[i].len; j++) {
			c = table[i].sym[j];
			best_table[c][0]=c;
			best_table_len[c]=1;
		}
	}
}

static void optimize_token_table(void)
{
	build_initial_tok_table();

	insert_real_symbols_in_table();

	/* When valid symbol is not registered, exit to error */
	if (!table_cnt) {
		fprintf(stderr, "No valid symbol.\n");
		exit(1);
	}

	optimize_result();
}

/* guess for "linker script provide" symbol */
static int may_be_linker_script_provide_symbol(const struct sym_entry *se)
{
	const char *symbol = (char *)se->sym + 1;
	int len = se->len - 1;

	if (len < 8)
		return 0;

	if (symbol[0] != '_' || symbol[1] != '_')
		return 0;

	/* __start_XXXXX */
	if (!memcmp(symbol + 2, "start_", 6))
		return 1;

	/* __stop_XXXXX */
	if (!memcmp(symbol + 2, "stop_", 5))
		return 1;

	/* __end_XXXXX */
	if (!memcmp(symbol + 2, "end_", 4))
		return 1;

	/* __XXXXX_start */
	if (!memcmp(symbol + len - 6, "_start", 6))
		return 1;

	/* __XXXXX_end */
	if (!memcmp(symbol + len - 4, "_end", 4))
		return 1;

	return 0;
}

static int prefix_underscores_count(const char *str)
{
	const char *tail = str;

	while (*tail == '_')
		tail++;

	return tail - str;
}

static int compare_symbols(const void *a, const void *b)
{
	const struct sym_entry *sa;
	const struct sym_entry *sb;
	int wa, wb;

	sa = a;
	sb = b;

	/* sort by address first */
	if (sa->addr > sb->addr)
		return 1;
	if (sa->addr < sb->addr)
		return -1;

	/* sort by "weakness" type */
	wa = (sa->sym[0] == 'w') || (sa->sym[0] == 'W');
	wb = (sb->sym[0] == 'w') || (sb->sym[0] == 'W');
	if (wa != wb)
		return wa - wb;

	/* sort by "linker script provide" type */
	wa = may_be_linker_script_provide_symbol(sa);
	wb = may_be_linker_script_provide_symbol(sb);
	if (wa != wb)
		return wa - wb;

	/* sort by the number of prefix underscores */
	wa = prefix_underscores_count((const char *)sa->sym + 1);
	wb = prefix_underscores_count((const char *)sb->sym + 1);
	if (wa != wb)
		return wa - wb;

	/* sort by initial order, so that other symbols are left undisturbed */
	return sa->start_pos - sb->start_pos;
}

static void sort_symbols(void)
{
	qsort(table, table_cnt, sizeof(struct sym_entry), compare_symbols);
}

int main(int argc, char **argv)
{
	if (argc >= 2) {
		int i;
		for (i = 1; i < argc; i++) {
			if(strcmp(argv[i], "--all-symbols") == 0)
				all_symbols = 1;
			else if (strncmp(argv[i], "--symbol-prefix=", 16) == 0) {
				char *p = &argv[i][16];
				/* skip quote */
				if ((*p == '"' && *(p+2) == '"') || (*p == '\'' && *(p+2) == '\''))
					p++;
				symbol_prefix_char = *p;
			} else
				usage();
		}
	} else if (argc != 1)
		usage();

	read_map(stdin);
	sort_symbols();
	optimize_token_table();
	write_src();

	return 0;
}