1/* Generate assembler source containing symbol information 2 * 3 * Copyright 2002 by Kai Germaschewski 4 * 5 * This software may be used and distributed according to the terms 6 * of the GNU General Public License, incorporated herein by reference. 7 * 8 * Usage: nm -n vmlinux | scripts/kallsyms [--all-symbols] > symbols.S 9 * 10 * Table compression uses all the unused char codes on the symbols and 11 * maps these to the most used substrings (tokens). For instance, it might 12 * map char code 0xF7 to represent "write_" and then in every symbol where 13 * "write_" appears it can be replaced by 0xF7, saving 5 bytes. 14 * The used codes themselves are also placed in the table so that the 15 * decompresion can work without "special cases". 16 * Applied to kernel symbols, this usually produces a compression ratio 17 * of about 50%. 18 * 19 */ 20 21#include <stdio.h> 22#include <stdlib.h> 23#include <string.h> 24#include <ctype.h> 25 26#ifndef ARRAY_SIZE 27#define ARRAY_SIZE(arr) (sizeof(arr) / sizeof(arr[0])) 28#endif 29 30#define KSYM_NAME_LEN 128 31 32struct sym_entry { 33 unsigned long long addr; 34 unsigned int len; 35 unsigned int start_pos; 36 unsigned char *sym; 37}; 38 39struct text_range { 40 const char *stext, *etext; 41 unsigned long long start, end; 42}; 43 44static unsigned long long _text; 45static struct text_range text_ranges[] = { 46 { "_stext", "_etext" }, 47 { "_sinittext", "_einittext" }, 48 { "_stext_l1", "_etext_l1" }, /* Blackfin on-chip L1 inst SRAM */ 49 { "_stext_l2", "_etext_l2" }, /* Blackfin on-chip L2 SRAM */ 50}; 51#define text_range_text (&text_ranges[0]) 52#define text_range_inittext (&text_ranges[1]) 53 54static struct sym_entry *table; 55static unsigned int table_size, table_cnt; 56static int all_symbols = 0; 57static char symbol_prefix_char = '\0'; 58 59int token_profit[0x10000]; 60 61/* the table that holds the result of the compression */ 62unsigned char best_table[256][2]; 63unsigned char best_table_len[256]; 64 65 66static void usage(void) 67{ 68 fprintf(stderr, "Usage: kallsyms [--all-symbols] [--symbol-prefix=<prefix char>] < in.map > out.S\n"); 69 exit(1); 70} 71 72/* 73 * This ignores the intensely annoying "mapping symbols" found 74 * in ARM ELF files: $a, $t and $d. 75 */ 76static inline int is_arm_mapping_symbol(const char *str) 77{ 78 return str[0] == '$' && strchr("atd", str[1]) 79 && (str[2] == '\0' || str[2] == '.'); 80} 81 82static int read_symbol_tr(const char *sym, unsigned long long addr) 83{ 84 size_t i; 85 struct text_range *tr; 86 87 for (i = 0; i < ARRAY_SIZE(text_ranges); ++i) { 88 tr = &text_ranges[i]; 89 90 if (strcmp(sym, tr->stext) == 0) { 91 tr->start = addr; 92 return 0; 93 } else if (strcmp(sym, tr->etext) == 0) { 94 tr->end = addr; 95 return 0; 96 } 97 } 98 99 return 1; 100} 101 102static int read_symbol(FILE *in, struct sym_entry *s) 103{ 104 char str[500]; 105 char *sym, stype; 106 int rc; 107 108 rc = fscanf(in, "%llx %c %499s\n", &s->addr, &stype, str); 109 if (rc != 3) { 110 if (rc != EOF) { 111 /* skip line. sym is used as dummy to 112 * shut of "warn_unused_result" warning. 113 */ 114 sym = fgets(str, 500, in); 115 } 116 return -1; 117 } 118 119 sym = str; 120 /* skip prefix char */ 121 if (symbol_prefix_char && str[0] == symbol_prefix_char) 122 sym++; 123 124 /* Ignore most absolute/undefined (?) symbols. */ 125 if (strcmp(sym, "_text") == 0) 126 _text = s->addr; 127 else if (read_symbol_tr(sym, s->addr) == 0) 128 /* nothing to do */; 129 else if (toupper(stype) == 'A') 130 { 131 /* Keep these useful absolute symbols */ 132 if (strcmp(sym, "__kernel_syscall_via_break") && 133 strcmp(sym, "__kernel_syscall_via_epc") && 134 strcmp(sym, "__kernel_sigtramp") && 135 strcmp(sym, "__gp")) 136 return -1; 137 138 } 139 else if (toupper(stype) == 'U' || 140 is_arm_mapping_symbol(sym)) 141 return -1; 142 /* exclude also MIPS ELF local symbols ($L123 instead of .L123) */ 143 else if (str[0] == '$') 144 return -1; 145 /* exclude debugging symbols */ 146 else if (stype == 'N') 147 return -1; 148 149 /* include the type field in the symbol name, so that it gets 150 * compressed together */ 151 s->len = strlen(str) + 1; 152 s->sym = malloc(s->len + 1); 153 if (!s->sym) { 154 fprintf(stderr, "kallsyms failure: " 155 "unable to allocate required amount of memory\n"); 156 exit(EXIT_FAILURE); 157 } 158 strcpy((char *)s->sym + 1, str); 159 s->sym[0] = stype; 160 161 return 0; 162} 163 164static int symbol_valid_tr(struct sym_entry *s) 165{ 166 size_t i; 167 struct text_range *tr; 168 169 for (i = 0; i < ARRAY_SIZE(text_ranges); ++i) { 170 tr = &text_ranges[i]; 171 172 if (s->addr >= tr->start && s->addr <= tr->end) 173 return 1; 174 } 175 176 return 0; 177} 178 179static int symbol_valid(struct sym_entry *s) 180{ 181 /* Symbols which vary between passes. Passes 1 and 2 must have 182 * identical symbol lists. The kallsyms_* symbols below are only added 183 * after pass 1, they would be included in pass 2 when --all-symbols is 184 * specified so exclude them to get a stable symbol list. 185 */ 186 static char *special_symbols[] = { 187 "kallsyms_addresses", 188 "kallsyms_num_syms", 189 "kallsyms_names", 190 "kallsyms_markers", 191 "kallsyms_token_table", 192 "kallsyms_token_index", 193 194 /* Exclude linker generated symbols which vary between passes */ 195 "_SDA_BASE_", /* ppc */ 196 "_SDA2_BASE_", /* ppc */ 197 NULL }; 198 int i; 199 int offset = 1; 200 201 /* skip prefix char */ 202 if (symbol_prefix_char && *(s->sym + 1) == symbol_prefix_char) 203 offset++; 204 205 /* if --all-symbols is not specified, then symbols outside the text 206 * and inittext sections are discarded */ 207 if (!all_symbols) { 208 if (symbol_valid_tr(s) == 0) 209 return 0; 210 /* Corner case. Discard any symbols with the same value as 211 * _etext _einittext; they can move between pass 1 and 2 when 212 * the kallsyms data are added. If these symbols move then 213 * they may get dropped in pass 2, which breaks the kallsyms 214 * rules. 215 */ 216 if ((s->addr == text_range_text->end && 217 strcmp((char *)s->sym + offset, text_range_text->etext)) || 218 (s->addr == text_range_inittext->end && 219 strcmp((char *)s->sym + offset, text_range_inittext->etext))) 220 return 0; 221 } 222 223 /* Exclude symbols which vary between passes. */ 224 if (strstr((char *)s->sym + offset, "_compiled.")) 225 return 0; 226 227 for (i = 0; special_symbols[i]; i++) 228 if( strcmp((char *)s->sym + offset, special_symbols[i]) == 0 ) 229 return 0; 230 231 return 1; 232} 233 234static void read_map(FILE *in) 235{ 236 while (!feof(in)) { 237 if (table_cnt >= table_size) { 238 table_size += 10000; 239 table = realloc(table, sizeof(*table) * table_size); 240 if (!table) { 241 fprintf(stderr, "out of memory\n"); 242 exit (1); 243 } 244 } 245 if (read_symbol(in, &table[table_cnt]) == 0) { 246 table[table_cnt].start_pos = table_cnt; 247 table_cnt++; 248 } 249 } 250} 251 252static void output_label(char *label) 253{ 254 if (symbol_prefix_char) 255 printf(".globl %c%s\n", symbol_prefix_char, label); 256 else 257 printf(".globl %s\n", label); 258 printf("\tALGN\n"); 259 if (symbol_prefix_char) 260 printf("%c%s:\n", symbol_prefix_char, label); 261 else 262 printf("%s:\n", label); 263} 264 265/* uncompress a compressed symbol. When this function is called, the best table 266 * might still be compressed itself, so the function needs to be recursive */ 267static int expand_symbol(unsigned char *data, int len, char *result) 268{ 269 int c, rlen, total=0; 270 271 while (len) { 272 c = *data; 273 /* if the table holds a single char that is the same as the one 274 * we are looking for, then end the search */ 275 if (best_table[c][0]==c && best_table_len[c]==1) { 276 *result++ = c; 277 total++; 278 } else { 279 /* if not, recurse and expand */ 280 rlen = expand_symbol(best_table[c], best_table_len[c], result); 281 total += rlen; 282 result += rlen; 283 } 284 data++; 285 len--; 286 } 287 *result=0; 288 289 return total; 290} 291 292static void write_src(void) 293{ 294 unsigned int i, k, off; 295 unsigned int best_idx[256]; 296 unsigned int *markers; 297 char buf[KSYM_NAME_LEN]; 298 299 printf("#include <asm/types.h>\n"); 300 printf("#if BITS_PER_LONG == 64\n"); 301 printf("#define PTR .quad\n"); 302 printf("#define ALGN .align 8\n"); 303 printf("#else\n"); 304 printf("#define PTR .long\n"); 305 printf("#define ALGN .align 4\n"); 306 printf("#endif\n"); 307 308 printf("\t.section .rodata, \"a\"\n"); 309 310 /* Provide proper symbols relocatability by their '_text' 311 * relativeness. The symbol names cannot be used to construct 312 * normal symbol references as the list of symbols contains 313 * symbols that are declared static and are private to their 314 * .o files. This prevents .tmp_kallsyms.o or any other 315 * object from referencing them. 316 */ 317 output_label("kallsyms_addresses"); 318 for (i = 0; i < table_cnt; i++) { 319 if (toupper(table[i].sym[0]) != 'A') { 320 if (_text <= table[i].addr) 321 printf("\tPTR\t_text + %#llx\n", 322 table[i].addr - _text); 323 else 324 printf("\tPTR\t_text - %#llx\n", 325 _text - table[i].addr); 326 } else { 327 printf("\tPTR\t%#llx\n", table[i].addr); 328 } 329 } 330 printf("\n"); 331 332 output_label("kallsyms_num_syms"); 333 printf("\tPTR\t%d\n", table_cnt); 334 printf("\n"); 335 336 /* table of offset markers, that give the offset in the compressed stream 337 * every 256 symbols */ 338 markers = malloc(sizeof(unsigned int) * ((table_cnt + 255) / 256)); 339 if (!markers) { 340 fprintf(stderr, "kallsyms failure: " 341 "unable to allocate required memory\n"); 342 exit(EXIT_FAILURE); 343 } 344 345 output_label("kallsyms_names"); 346 off = 0; 347 for (i = 0; i < table_cnt; i++) { 348 if ((i & 0xFF) == 0) 349 markers[i >> 8] = off; 350 351 printf("\t.byte 0x%02x", table[i].len); 352 for (k = 0; k < table[i].len; k++) 353 printf(", 0x%02x", table[i].sym[k]); 354 printf("\n"); 355 356 off += table[i].len + 1; 357 } 358 printf("\n"); 359 360 output_label("kallsyms_markers"); 361 for (i = 0; i < ((table_cnt + 255) >> 8); i++) 362 printf("\tPTR\t%d\n", markers[i]); 363 printf("\n"); 364 365 free(markers); 366 367 output_label("kallsyms_token_table"); 368 off = 0; 369 for (i = 0; i < 256; i++) { 370 best_idx[i] = off; 371 expand_symbol(best_table[i], best_table_len[i], buf); 372 printf("\t.asciz\t\"%s\"\n", buf); 373 off += strlen(buf) + 1; 374 } 375 printf("\n"); 376 377 output_label("kallsyms_token_index"); 378 for (i = 0; i < 256; i++) 379 printf("\t.short\t%d\n", best_idx[i]); 380 printf("\n"); 381} 382 383 384/* table lookup compression functions */ 385 386/* count all the possible tokens in a symbol */ 387static void learn_symbol(unsigned char *symbol, int len) 388{ 389 int i; 390 391 for (i = 0; i < len - 1; i++) 392 token_profit[ symbol[i] + (symbol[i + 1] << 8) ]++; 393} 394 395/* decrease the count for all the possible tokens in a symbol */ 396static void forget_symbol(unsigned char *symbol, int len) 397{ 398 int i; 399 400 for (i = 0; i < len - 1; i++) 401 token_profit[ symbol[i] + (symbol[i + 1] << 8) ]--; 402} 403 404/* remove all the invalid symbols from the table and do the initial token count */ 405static void build_initial_tok_table(void) 406{ 407 unsigned int i, pos; 408 409 pos = 0; 410 for (i = 0; i < table_cnt; i++) { 411 if ( symbol_valid(&table[i]) ) { 412 if (pos != i) 413 table[pos] = table[i]; 414 learn_symbol(table[pos].sym, table[pos].len); 415 pos++; 416 } 417 } 418 table_cnt = pos; 419} 420 421static void *find_token(unsigned char *str, int len, unsigned char *token) 422{ 423 int i; 424 425 for (i = 0; i < len - 1; i++) { 426 if (str[i] == token[0] && str[i+1] == token[1]) 427 return &str[i]; 428 } 429 return NULL; 430} 431 432/* replace a given token in all the valid symbols. Use the sampled symbols 433 * to update the counts */ 434static void compress_symbols(unsigned char *str, int idx) 435{ 436 unsigned int i, len, size; 437 unsigned char *p1, *p2; 438 439 for (i = 0; i < table_cnt; i++) { 440 441 len = table[i].len; 442 p1 = table[i].sym; 443 444 /* find the token on the symbol */ 445 p2 = find_token(p1, len, str); 446 if (!p2) continue; 447 448 /* decrease the counts for this symbol's tokens */ 449 forget_symbol(table[i].sym, len); 450 451 size = len; 452 453 do { 454 *p2 = idx; 455 p2++; 456 size -= (p2 - p1); 457 memmove(p2, p2 + 1, size); 458 p1 = p2; 459 len--; 460 461 if (size < 2) break; 462 463 /* find the token on the symbol */ 464 p2 = find_token(p1, size, str); 465 466 } while (p2); 467 468 table[i].len = len; 469 470 /* increase the counts for this symbol's new tokens */ 471 learn_symbol(table[i].sym, len); 472 } 473} 474 475/* search the token with the maximum profit */ 476static int find_best_token(void) 477{ 478 int i, best, bestprofit; 479 480 bestprofit=-10000; 481 best = 0; 482 483 for (i = 0; i < 0x10000; i++) { 484 if (token_profit[i] > bestprofit) { 485 best = i; 486 bestprofit = token_profit[i]; 487 } 488 } 489 return best; 490} 491 492/* this is the core of the algorithm: calculate the "best" table */ 493static void optimize_result(void) 494{ 495 int i, best; 496 497 /* using the '\0' symbol last allows compress_symbols to use standard 498 * fast string functions */ 499 for (i = 255; i >= 0; i--) { 500 501 /* if this table slot is empty (it is not used by an actual 502 * original char code */ 503 if (!best_table_len[i]) { 504 505 /* find the token with the breates profit value */ 506 best = find_best_token(); 507 508 /* place it in the "best" table */ 509 best_table_len[i] = 2; 510 best_table[i][0] = best & 0xFF; 511 best_table[i][1] = (best >> 8) & 0xFF; 512 513 /* replace this token in all the valid symbols */ 514 compress_symbols(best_table[i], i); 515 } 516 } 517} 518 519/* start by placing the symbols that are actually used on the table */ 520static void insert_real_symbols_in_table(void) 521{ 522 unsigned int i, j, c; 523 524 memset(best_table, 0, sizeof(best_table)); 525 memset(best_table_len, 0, sizeof(best_table_len)); 526 527 for (i = 0; i < table_cnt; i++) { 528 for (j = 0; j < table[i].len; j++) { 529 c = table[i].sym[j]; 530 best_table[c][0]=c; 531 best_table_len[c]=1; 532 } 533 } 534} 535 536static void optimize_token_table(void) 537{ 538 build_initial_tok_table(); 539 540 insert_real_symbols_in_table(); 541 542 /* When valid symbol is not registered, exit to error */ 543 if (!table_cnt) { 544 fprintf(stderr, "No valid symbol.\n"); 545 exit(1); 546 } 547 548 optimize_result(); 549} 550 551/* guess for "linker script provide" symbol */ 552static int may_be_linker_script_provide_symbol(const struct sym_entry *se) 553{ 554 const char *symbol = (char *)se->sym + 1; 555 int len = se->len - 1; 556 557 if (len < 8) 558 return 0; 559 560 if (symbol[0] != '_' || symbol[1] != '_') 561 return 0; 562 563 /* __start_XXXXX */ 564 if (!memcmp(symbol + 2, "start_", 6)) 565 return 1; 566 567 /* __stop_XXXXX */ 568 if (!memcmp(symbol + 2, "stop_", 5)) 569 return 1; 570 571 /* __end_XXXXX */ 572 if (!memcmp(symbol + 2, "end_", 4)) 573 return 1; 574 575 /* __XXXXX_start */ 576 if (!memcmp(symbol + len - 6, "_start", 6)) 577 return 1; 578 579 /* __XXXXX_end */ 580 if (!memcmp(symbol + len - 4, "_end", 4)) 581 return 1; 582 583 return 0; 584} 585 586static int prefix_underscores_count(const char *str) 587{ 588 const char *tail = str; 589 590 while (*tail == '_') 591 tail++; 592 593 return tail - str; 594} 595 596static int compare_symbols(const void *a, const void *b) 597{ 598 const struct sym_entry *sa; 599 const struct sym_entry *sb; 600 int wa, wb; 601 602 sa = a; 603 sb = b; 604 605 /* sort by address first */ 606 if (sa->addr > sb->addr) 607 return 1; 608 if (sa->addr < sb->addr) 609 return -1; 610 611 /* sort by "weakness" type */ 612 wa = (sa->sym[0] == 'w') || (sa->sym[0] == 'W'); 613 wb = (sb->sym[0] == 'w') || (sb->sym[0] == 'W'); 614 if (wa != wb) 615 return wa - wb; 616 617 /* sort by "linker script provide" type */ 618 wa = may_be_linker_script_provide_symbol(sa); 619 wb = may_be_linker_script_provide_symbol(sb); 620 if (wa != wb) 621 return wa - wb; 622 623 /* sort by the number of prefix underscores */ 624 wa = prefix_underscores_count((const char *)sa->sym + 1); 625 wb = prefix_underscores_count((const char *)sb->sym + 1); 626 if (wa != wb) 627 return wa - wb; 628 629 /* sort by initial order, so that other symbols are left undisturbed */ 630 return sa->start_pos - sb->start_pos; 631} 632 633static void sort_symbols(void) 634{ 635 qsort(table, table_cnt, sizeof(struct sym_entry), compare_symbols); 636} 637 638int main(int argc, char **argv) 639{ 640 if (argc >= 2) { 641 int i; 642 for (i = 1; i < argc; i++) { 643 if(strcmp(argv[i], "--all-symbols") == 0) 644 all_symbols = 1; 645 else if (strncmp(argv[i], "--symbol-prefix=", 16) == 0) { 646 char *p = &argv[i][16]; 647 /* skip quote */ 648 if ((*p == '"' && *(p+2) == '"') || (*p == '\'' && *(p+2) == '\'')) 649 p++; 650 symbol_prefix_char = *p; 651 } else 652 usage(); 653 } 654 } else if (argc != 1) 655 usage(); 656 657 read_map(stdin); 658 sort_symbols(); 659 optimize_token_table(); 660 write_src(); 661 662 return 0; 663} 664