kallsyms.c 13 KB
Newer Older
Linus Torvalds's avatar
Linus Torvalds committed
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
/* 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>

26
#define KSYM_NAME_LEN		128
Linus Torvalds's avatar
Linus Torvalds committed
27 28 29

struct sym_entry {
	unsigned long long addr;
30
	unsigned int len;
31
	unsigned int start_pos;
Linus Torvalds's avatar
Linus Torvalds committed
32 33 34 35
	unsigned char *sym;
};

static struct sym_entry *table;
36
static unsigned int table_size, table_cnt;
37
static unsigned long long _text, _stext, _etext, _sinittext, _einittext;
Linus Torvalds's avatar
Linus Torvalds committed
38
static int all_symbols = 0;
39
static char symbol_prefix_char = '\0';
Linus Torvalds's avatar
Linus Torvalds committed
40

41
int token_profit[0x10000];
Linus Torvalds's avatar
Linus Torvalds committed
42 43

/* the table that holds the result of the compression */
44
unsigned char best_table[256][2];
Linus Torvalds's avatar
Linus Torvalds committed
45 46 47
unsigned char best_table_len[256];


48
static void usage(void)
Linus Torvalds's avatar
Linus Torvalds committed
49
{
50
	fprintf(stderr, "Usage: kallsyms [--all-symbols] [--symbol-prefix=<prefix char>] < in.map > out.S\n");
Linus Torvalds's avatar
Linus Torvalds committed
51 52 53 54 55 56 57
	exit(1);
}

/*
 * This ignores the intensely annoying "mapping symbols" found
 * in ARM ELF files: $a, $t and $d.
 */
58
static inline int is_arm_mapping_symbol(const char *str)
Linus Torvalds's avatar
Linus Torvalds committed
59 60 61 62 63
{
	return str[0] == '$' && strchr("atd", str[1])
	       && (str[2] == '\0' || str[2] == '.');
}

64
static int read_symbol(FILE *in, struct sym_entry *s)
Linus Torvalds's avatar
Linus Torvalds committed
65 66
{
	char str[500];
67
	char *sym, stype;
Linus Torvalds's avatar
Linus Torvalds committed
68 69
	int rc;

70
	rc = fscanf(in, "%llx %c %499s\n", &s->addr, &stype, str);
Linus Torvalds's avatar
Linus Torvalds committed
71 72 73 74 75 76 77 78
	if (rc != 3) {
		if (rc != EOF) {
			/* skip line */
			fgets(str, 500, in);
		}
		return -1;
	}

79 80 81 82 83
	sym = str;
	/* skip prefix char */
	if (symbol_prefix_char && str[0] == symbol_prefix_char)
		sym++;

Linus Torvalds's avatar
Linus Torvalds committed
84
	/* Ignore most absolute/undefined (?) symbols. */
85 86 87
	if (strcmp(sym, "_text") == 0)
		_text = s->addr;
	else if (strcmp(sym, "_stext") == 0)
Linus Torvalds's avatar
Linus Torvalds committed
88
		_stext = s->addr;
89
	else if (strcmp(sym, "_etext") == 0)
Linus Torvalds's avatar
Linus Torvalds committed
90
		_etext = s->addr;
91
	else if (strcmp(sym, "_sinittext") == 0)
Linus Torvalds's avatar
Linus Torvalds committed
92
		_sinittext = s->addr;
93
	else if (strcmp(sym, "_einittext") == 0)
Linus Torvalds's avatar
Linus Torvalds committed
94
		_einittext = s->addr;
95
	else if (toupper(stype) == 'A')
Linus Torvalds's avatar
Linus Torvalds committed
96 97
	{
		/* Keep these useful absolute symbols */
98 99 100 101
		if (strcmp(sym, "__kernel_syscall_via_break") &&
		    strcmp(sym, "__kernel_syscall_via_epc") &&
		    strcmp(sym, "__kernel_sigtramp") &&
		    strcmp(sym, "__gp"))
Linus Torvalds's avatar
Linus Torvalds committed
102 103 104
			return -1;

	}
105
	else if (toupper(stype) == 'U' ||
106
		 is_arm_mapping_symbol(sym))
Linus Torvalds's avatar
Linus Torvalds committed
107
		return -1;
108 109 110
	/* exclude also MIPS ELF local symbols ($L123 instead of .L123) */
	else if (str[0] == '$')
		return -1;
111 112 113
	/* exclude debugging symbols */
	else if (stype == 'N')
		return -1;
Linus Torvalds's avatar
Linus Torvalds committed
114 115 116 117

	/* include the type field in the symbol name, so that it gets
	 * compressed together */
	s->len = strlen(str) + 1;
118
	s->sym = malloc(s->len + 1);
119 120 121 122 123
	if (!s->sym) {
		fprintf(stderr, "kallsyms failure: "
			"unable to allocate required amount of memory\n");
		exit(EXIT_FAILURE);
	}
124 125
	strcpy((char *)s->sym + 1, str);
	s->sym[0] = stype;
Linus Torvalds's avatar
Linus Torvalds committed
126 127 128 129

	return 0;
}

130
static int symbol_valid(struct sym_entry *s)
Linus Torvalds's avatar
Linus Torvalds committed
131 132
{
	/* Symbols which vary between passes.  Passes 1 and 2 must have
133
	 * identical symbol lists.
Linus Torvalds's avatar
Linus Torvalds committed
134 135 136 137 138 139 140
	 */
	static char *special_symbols[] = {
	/* Exclude linker generated symbols which vary between passes */
		"_SDA_BASE_",		/* ppc */
		"_SDA2_BASE_",		/* ppc */
		NULL };
	int i;
141 142 143 144 145
	int offset = 1;

	/* skip prefix char */
	if (symbol_prefix_char && *(s->sym + 1) == symbol_prefix_char)
		offset++;
Linus Torvalds's avatar
Linus Torvalds committed
146 147 148 149 150

	/* if --all-symbols is not specified, then symbols outside the text
	 * and inittext sections are discarded */
	if (!all_symbols) {
		if ((s->addr < _stext || s->addr > _etext)
151
		    && (s->addr < _sinittext || s->addr > _einittext))
Linus Torvalds's avatar
Linus Torvalds committed
152 153
			return 0;
		/* Corner case.  Discard any symbols with the same value as
154 155 156 157
		 * _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.
Linus Torvalds's avatar
Linus Torvalds committed
158
		 */
159 160 161 162
		if ((s->addr == _etext &&
				strcmp((char *)s->sym + offset, "_etext")) ||
		    (s->addr == _einittext &&
				strcmp((char *)s->sym + offset, "_einittext")))
Linus Torvalds's avatar
Linus Torvalds committed
163 164 165 166
			return 0;
	}

	/* Exclude symbols which vary between passes. */
167 168 169
	if (strstr((char *)s->sym + offset, "_compiled.") ||
	    strncmp((char*)s->sym + offset, "__compound_literal.", 19) == 0 ||
	    strncmp((char*)s->sym + offset, "__compound_literal$", 19) == 0)
Linus Torvalds's avatar
Linus Torvalds committed
170 171 172
		return 0;

	for (i = 0; special_symbols[i]; i++)
173
		if( strcmp((char *)s->sym + offset, special_symbols[i]) == 0 )
Linus Torvalds's avatar
Linus Torvalds committed
174 175 176 177 178
			return 0;

	return 1;
}

179
static void read_map(FILE *in)
Linus Torvalds's avatar
Linus Torvalds committed
180 181
{
	while (!feof(in)) {
182 183 184
		if (table_cnt >= table_size) {
			table_size += 10000;
			table = realloc(table, sizeof(*table) * table_size);
Linus Torvalds's avatar
Linus Torvalds committed
185 186 187 188 189
			if (!table) {
				fprintf(stderr, "out of memory\n");
				exit (1);
			}
		}
190 191
		if (read_symbol(in, &table[table_cnt]) == 0) {
			table[table_cnt].start_pos = table_cnt;
192
			table_cnt++;
193
		}
Linus Torvalds's avatar
Linus Torvalds committed
194 195 196 197 198
	}
}

static void output_label(char *label)
{
199 200 201 202
	if (symbol_prefix_char)
		printf(".globl %c%s\n", symbol_prefix_char, label);
	else
		printf(".globl %s\n", label);
Linus Torvalds's avatar
Linus Torvalds committed
203
	printf("\tALGN\n");
204 205 206 207
	if (symbol_prefix_char)
		printf("%c%s:\n", symbol_prefix_char, label);
	else
		printf("%s:\n", label);
Linus Torvalds's avatar
Linus Torvalds committed
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
}

/* 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;
}

237
static void write_src(void)
Linus Torvalds's avatar
Linus Torvalds committed
238
{
239
	unsigned int i, k, off;
Linus Torvalds's avatar
Linus Torvalds committed
240 241
	unsigned int best_idx[256];
	unsigned int *markers;
242
	char buf[KSYM_NAME_LEN];
Linus Torvalds's avatar
Linus Torvalds committed
243 244 245 246 247 248 249 250 251 252

	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");

253
	printf("\t.section .rodata, \"a\"\n");
Linus Torvalds's avatar
Linus Torvalds committed
254

255 256 257 258 259 260 261
	/* 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.
	 */
Linus Torvalds's avatar
Linus Torvalds committed
262
	output_label("kallsyms_addresses");
263
	for (i = 0; i < table_cnt; i++) {
264
		if (toupper(table[i].sym[0]) != 'A') {
265 266 267 268 269 270
			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);
271 272 273
		} else {
			printf("\tPTR\t%#llx\n", table[i].addr);
		}
Linus Torvalds's avatar
Linus Torvalds committed
274 275 276 277
	}
	printf("\n");

	output_label("kallsyms_num_syms");
278
	printf("\tPTR\t%d\n", table_cnt);
Linus Torvalds's avatar
Linus Torvalds committed
279 280 281 282
	printf("\n");

	/* table of offset markers, that give the offset in the compressed stream
	 * every 256 symbols */
283 284 285 286 287 288
	markers = malloc(sizeof(unsigned int) * ((table_cnt + 255) / 256));
	if (!markers) {
		fprintf(stderr, "kallsyms failure: "
			"unable to allocate required memory\n");
		exit(EXIT_FAILURE);
	}
Linus Torvalds's avatar
Linus Torvalds committed
289 290 291

	output_label("kallsyms_names");
	off = 0;
292 293 294
	for (i = 0; i < table_cnt; i++) {
		if ((i & 0xFF) == 0)
			markers[i >> 8] = off;
Linus Torvalds's avatar
Linus Torvalds committed
295 296 297 298 299 300 301 302 303 304 305

		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");
306
	for (i = 0; i < ((table_cnt + 255) >> 8); i++)
Linus Torvalds's avatar
Linus Torvalds committed
307 308 309 310 311 312 313 314 315
		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;
316
		expand_symbol(best_table[i], best_table_len[i], buf);
Linus Torvalds's avatar
Linus Torvalds committed
317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336
		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++)
337
		token_profit[ symbol[i] + (symbol[i + 1] << 8) ]++;
Linus Torvalds's avatar
Linus Torvalds committed
338 339 340 341 342 343 344 345
}

/* 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++)
346
		token_profit[ symbol[i] + (symbol[i + 1] << 8) ]--;
Linus Torvalds's avatar
Linus Torvalds committed
347 348
}

349
/* remove all the invalid symbols from the table and do the initial token count */
Linus Torvalds's avatar
Linus Torvalds committed
350 351
static void build_initial_tok_table(void)
{
352
	unsigned int i, pos;
Linus Torvalds's avatar
Linus Torvalds committed
353

354 355
	pos = 0;
	for (i = 0; i < table_cnt; i++) {
Linus Torvalds's avatar
Linus Torvalds committed
356
		if ( symbol_valid(&table[i]) ) {
357 358 359 360
			if (pos != i)
				table[pos] = table[i];
			learn_symbol(table[pos].sym, table[pos].len);
			pos++;
Linus Torvalds's avatar
Linus Torvalds committed
361 362
		}
	}
363
	table_cnt = pos;
Linus Torvalds's avatar
Linus Torvalds committed
364 365
}

366 367 368 369 370 371 372 373 374 375 376
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;
}

Linus Torvalds's avatar
Linus Torvalds committed
377 378
/* replace a given token in all the valid symbols. Use the sampled symbols
 * to update the counts */
379
static void compress_symbols(unsigned char *str, int idx)
Linus Torvalds's avatar
Linus Torvalds committed
380
{
381 382
	unsigned int i, len, size;
	unsigned char *p1, *p2;
Linus Torvalds's avatar
Linus Torvalds committed
383

384
	for (i = 0; i < table_cnt; i++) {
Linus Torvalds's avatar
Linus Torvalds committed
385 386

		len = table[i].len;
387 388 389
		p1 = table[i].sym;

		/* find the token on the symbol */
390
		p2 = find_token(p1, len, str);
391 392 393 394 395 396
		if (!p2) continue;

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

		size = len;
Linus Torvalds's avatar
Linus Torvalds committed
397 398

		do {
399 400 401 402 403 404 405 406 407
			*p2 = idx;
			p2++;
			size -= (p2 - p1);
			memmove(p2, p2 + 1, size);
			p1 = p2;
			len--;

			if (size < 2) break;

Linus Torvalds's avatar
Linus Torvalds committed
408
			/* find the token on the symbol */
409
			p2 = find_token(p1, size, str);
Linus Torvalds's avatar
Linus Torvalds committed
410

411
		} while (p2);
Linus Torvalds's avatar
Linus Torvalds committed
412

413
		table[i].len = len;
Linus Torvalds's avatar
Linus Torvalds committed
414

415 416
		/* increase the counts for this symbol's new tokens */
		learn_symbol(table[i].sym, len);
Linus Torvalds's avatar
Linus Torvalds committed
417 418 419 420
	}
}

/* search the token with the maximum profit */
421
static int find_best_token(void)
Linus Torvalds's avatar
Linus Torvalds committed
422
{
423
	int i, best, bestprofit;
Linus Torvalds's avatar
Linus Torvalds committed
424 425

	bestprofit=-10000;
426
	best = 0;
Linus Torvalds's avatar
Linus Torvalds committed
427

428 429 430 431
	for (i = 0; i < 0x10000; i++) {
		if (token_profit[i] > bestprofit) {
			best = i;
			bestprofit = token_profit[i];
Linus Torvalds's avatar
Linus Torvalds committed
432 433 434 435 436 437 438 439
		}
	}
	return best;
}

/* this is the core of the algorithm: calculate the "best" table */
static void optimize_result(void)
{
440
	int i, best;
Linus Torvalds's avatar
Linus Torvalds committed
441 442 443 444 445 446 447 448 449 450 451 452 453

	/* 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 */
454 455 456
			best_table_len[i] = 2;
			best_table[i][0] = best & 0xFF;
			best_table[i][1] = (best >> 8) & 0xFF;
Linus Torvalds's avatar
Linus Torvalds committed
457 458

			/* replace this token in all the valid symbols */
459
			compress_symbols(best_table[i], i);
Linus Torvalds's avatar
Linus Torvalds committed
460 461 462 463 464 465 466
		}
	}
}

/* start by placing the symbols that are actually used on the table */
static void insert_real_symbols_in_table(void)
{
467
	unsigned int i, j, c;
Linus Torvalds's avatar
Linus Torvalds committed
468 469 470 471

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

472 473 474 475 476
	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;
Linus Torvalds's avatar
Linus Torvalds committed
477 478 479 480 481 482 483 484 485 486
		}
	}
}

static void optimize_token_table(void)
{
	build_initial_tok_table();

	insert_real_symbols_in_table();

487
	/* When valid symbol is not registered, exit to error */
488
	if (!table_cnt) {
489 490 491 492
		fprintf(stderr, "No valid symbol.\n");
		exit(1);
	}

Linus Torvalds's avatar
Linus Torvalds committed
493 494 495
	optimize_result();
}

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
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 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);
}
Linus Torvalds's avatar
Linus Torvalds committed
525

526
int main(int argc, char **argv)
Linus Torvalds's avatar
Linus Torvalds committed
527
{
528 529 530 531 532 533 534 535 536 537 538 539 540 541 542
	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)
Linus Torvalds's avatar
Linus Torvalds committed
543 544 545
		usage();

	read_map(stdin);
546 547 548 549
	if (table_cnt) {
		sort_symbols();
		optimize_token_table();
	}
Linus Torvalds's avatar
Linus Torvalds committed
550 551 552 553
	write_src();

	return 0;
}