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 32 struct sym_entry { 33 unsigned long long addr; 34 unsigned int len; 35 unsigned int start_pos; 36 unsigned char *sym; 37 }; 38 39 struct text_range { 40 const char *stext, *etext; 41 unsigned long long start, end; 42 }; 43 44 static unsigned long long _text; 45 static 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 54 static struct sym_entry *table; 55 static unsigned int table_size, table_cnt; 56 static int all_symbols = 0; 57 static char symbol_prefix_char = '\0'; 58 static unsigned long long kernel_start_addr = 0; 59 60 int token_profit[0x10000]; 61 62 /* the table that holds the result of the compression */ 63 unsigned char best_table[256][2]; 64 unsigned char best_table_len[256]; 65 66 67 static void usage(void) 68 { 69 fprintf(stderr, "Usage: kallsyms [--all-symbols] " 70 "[--symbol-prefix=<prefix char>] " 71 "[--page-offset=<CONFIG_PAGE_OFFSET>] " 72 "< in.map > out.S\n"); 73 exit(1); 74 } 75 76 /* 77 * This ignores the intensely annoying "mapping symbols" found 78 * in ARM ELF files: $a, $t and $d. 79 */ 80 static inline int is_arm_mapping_symbol(const char *str) 81 { 82 return str[0] == '$' && strchr("atd", str[1]) 83 && (str[2] == '\0' || str[2] == '.'); 84 } 85 86 static int read_symbol_tr(const char *sym, unsigned long long addr) 87 { 88 size_t i; 89 struct text_range *tr; 90 91 for (i = 0; i < ARRAY_SIZE(text_ranges); ++i) { 92 tr = &text_ranges[i]; 93 94 if (strcmp(sym, tr->stext) == 0) { 95 tr->start = addr; 96 return 0; 97 } else if (strcmp(sym, tr->etext) == 0) { 98 tr->end = addr; 99 return 0; 100 } 101 } 102 103 return 1; 104 } 105 106 static int read_symbol(FILE *in, struct sym_entry *s) 107 { 108 char str[500]; 109 char *sym, stype; 110 int rc; 111 112 rc = fscanf(in, "%llx %c %499s\n", &s->addr, &stype, str); 113 if (rc != 3) { 114 if (rc != EOF && fgets(str, 500, in) == NULL) 115 fprintf(stderr, "Read error or end of file.\n"); 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 } 163 164 static 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 } 178 179 static 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 if (s->addr < kernel_start_addr) 202 return 0; 203 204 /* skip prefix char */ 205 if (symbol_prefix_char && *(s->sym + 1) == symbol_prefix_char) 206 offset++; 207 208 /* if --all-symbols is not specified, then symbols outside the text 209 * and inittext sections are discarded */ 210 if (!all_symbols) { 211 if (symbol_valid_tr(s) == 0) 212 return 0; 213 /* Corner case. Discard any symbols with the same value as 214 * _etext _einittext; they can move between pass 1 and 2 when 215 * the kallsyms data are added. If these symbols move then 216 * they may get dropped in pass 2, which breaks the kallsyms 217 * rules. 218 */ 219 if ((s->addr == text_range_text->end && 220 strcmp((char *)s->sym + offset, text_range_text->etext)) || 221 (s->addr == text_range_inittext->end && 222 strcmp((char *)s->sym + offset, text_range_inittext->etext))) 223 return 0; 224 } 225 226 /* Exclude symbols which vary between passes. */ 227 if (strstr((char *)s->sym + offset, "_compiled.")) 228 return 0; 229 230 for (i = 0; special_symbols[i]; i++) 231 if( strcmp((char *)s->sym + offset, special_symbols[i]) == 0 ) 232 return 0; 233 234 return 1; 235 } 236 237 static void read_map(FILE *in) 238 { 239 while (!feof(in)) { 240 if (table_cnt >= table_size) { 241 table_size += 10000; 242 table = realloc(table, sizeof(*table) * table_size); 243 if (!table) { 244 fprintf(stderr, "out of memory\n"); 245 exit (1); 246 } 247 } 248 if (read_symbol(in, &table[table_cnt]) == 0) { 249 table[table_cnt].start_pos = table_cnt; 250 table_cnt++; 251 } 252 } 253 } 254 255 static void output_label(char *label) 256 { 257 if (symbol_prefix_char) 258 printf(".globl %c%s\n", symbol_prefix_char, label); 259 else 260 printf(".globl %s\n", label); 261 printf("\tALGN\n"); 262 if (symbol_prefix_char) 263 printf("%c%s:\n", symbol_prefix_char, label); 264 else 265 printf("%s:\n", label); 266 } 267 268 /* uncompress a compressed symbol. When this function is called, the best table 269 * might still be compressed itself, so the function needs to be recursive */ 270 static int expand_symbol(unsigned char *data, int len, char *result) 271 { 272 int c, rlen, total=0; 273 274 while (len) { 275 c = *data; 276 /* if the table holds a single char that is the same as the one 277 * we are looking for, then end the search */ 278 if (best_table[c][0]==c && best_table_len[c]==1) { 279 *result++ = c; 280 total++; 281 } else { 282 /* if not, recurse and expand */ 283 rlen = expand_symbol(best_table[c], best_table_len[c], result); 284 total += rlen; 285 result += rlen; 286 } 287 data++; 288 len--; 289 } 290 *result=0; 291 292 return total; 293 } 294 295 static void write_src(void) 296 { 297 unsigned int i, k, off; 298 unsigned int best_idx[256]; 299 unsigned int *markers; 300 char buf[KSYM_NAME_LEN]; 301 302 printf("#include <asm/types.h>\n"); 303 printf("#if BITS_PER_LONG == 64\n"); 304 printf("#define PTR .quad\n"); 305 printf("#define ALGN .align 8\n"); 306 printf("#else\n"); 307 printf("#define PTR .long\n"); 308 printf("#define ALGN .align 4\n"); 309 printf("#endif\n"); 310 311 printf("\t.section .rodata, \"a\"\n"); 312 313 /* Provide proper symbols relocatability by their '_text' 314 * relativeness. The symbol names cannot be used to construct 315 * normal symbol references as the list of symbols contains 316 * symbols that are declared static and are private to their 317 * .o files. This prevents .tmp_kallsyms.o or any other 318 * object from referencing them. 319 */ 320 output_label("kallsyms_addresses"); 321 for (i = 0; i < table_cnt; i++) { 322 if (toupper(table[i].sym[0]) != 'A') { 323 if (_text <= table[i].addr) 324 printf("\tPTR\t_text + %#llx\n", 325 table[i].addr - _text); 326 else 327 printf("\tPTR\t_text - %#llx\n", 328 _text - table[i].addr); 329 } else { 330 printf("\tPTR\t%#llx\n", table[i].addr); 331 } 332 } 333 printf("\n"); 334 335 output_label("kallsyms_num_syms"); 336 printf("\tPTR\t%d\n", table_cnt); 337 printf("\n"); 338 339 /* table of offset markers, that give the offset in the compressed stream 340 * every 256 symbols */ 341 markers = malloc(sizeof(unsigned int) * ((table_cnt + 255) / 256)); 342 if (!markers) { 343 fprintf(stderr, "kallsyms failure: " 344 "unable to allocate required memory\n"); 345 exit(EXIT_FAILURE); 346 } 347 348 output_label("kallsyms_names"); 349 off = 0; 350 for (i = 0; i < table_cnt; i++) { 351 if ((i & 0xFF) == 0) 352 markers[i >> 8] = off; 353 354 printf("\t.byte 0x%02x", table[i].len); 355 for (k = 0; k < table[i].len; k++) 356 printf(", 0x%02x", table[i].sym[k]); 357 printf("\n"); 358 359 off += table[i].len + 1; 360 } 361 printf("\n"); 362 363 output_label("kallsyms_markers"); 364 for (i = 0; i < ((table_cnt + 255) >> 8); i++) 365 printf("\tPTR\t%d\n", markers[i]); 366 printf("\n"); 367 368 free(markers); 369 370 output_label("kallsyms_token_table"); 371 off = 0; 372 for (i = 0; i < 256; i++) { 373 best_idx[i] = off; 374 expand_symbol(best_table[i], best_table_len[i], buf); 375 printf("\t.asciz\t\"%s\"\n", buf); 376 off += strlen(buf) + 1; 377 } 378 printf("\n"); 379 380 output_label("kallsyms_token_index"); 381 for (i = 0; i < 256; i++) 382 printf("\t.short\t%d\n", best_idx[i]); 383 printf("\n"); 384 } 385 386 387 /* table lookup compression functions */ 388 389 /* count all the possible tokens in a symbol */ 390 static void learn_symbol(unsigned char *symbol, int len) 391 { 392 int i; 393 394 for (i = 0; i < len - 1; i++) 395 token_profit[ symbol[i] + (symbol[i + 1] << 8) ]++; 396 } 397 398 /* decrease the count for all the possible tokens in a symbol */ 399 static void forget_symbol(unsigned char *symbol, int len) 400 { 401 int i; 402 403 for (i = 0; i < len - 1; i++) 404 token_profit[ symbol[i] + (symbol[i + 1] << 8) ]--; 405 } 406 407 /* remove all the invalid symbols from the table and do the initial token count */ 408 static void build_initial_tok_table(void) 409 { 410 unsigned int i, pos; 411 412 pos = 0; 413 for (i = 0; i < table_cnt; i++) { 414 if ( symbol_valid(&table[i]) ) { 415 if (pos != i) 416 table[pos] = table[i]; 417 learn_symbol(table[pos].sym, table[pos].len); 418 pos++; 419 } 420 } 421 table_cnt = pos; 422 } 423 424 static void *find_token(unsigned char *str, int len, unsigned char *token) 425 { 426 int i; 427 428 for (i = 0; i < len - 1; i++) { 429 if (str[i] == token[0] && str[i+1] == token[1]) 430 return &str[i]; 431 } 432 return NULL; 433 } 434 435 /* replace a given token in all the valid symbols. Use the sampled symbols 436 * to update the counts */ 437 static void compress_symbols(unsigned char *str, int idx) 438 { 439 unsigned int i, len, size; 440 unsigned char *p1, *p2; 441 442 for (i = 0; i < table_cnt; i++) { 443 444 len = table[i].len; 445 p1 = table[i].sym; 446 447 /* find the token on the symbol */ 448 p2 = find_token(p1, len, str); 449 if (!p2) continue; 450 451 /* decrease the counts for this symbol's tokens */ 452 forget_symbol(table[i].sym, len); 453 454 size = len; 455 456 do { 457 *p2 = idx; 458 p2++; 459 size -= (p2 - p1); 460 memmove(p2, p2 + 1, size); 461 p1 = p2; 462 len--; 463 464 if (size < 2) break; 465 466 /* find the token on the symbol */ 467 p2 = find_token(p1, size, str); 468 469 } while (p2); 470 471 table[i].len = len; 472 473 /* increase the counts for this symbol's new tokens */ 474 learn_symbol(table[i].sym, len); 475 } 476 } 477 478 /* search the token with the maximum profit */ 479 static int find_best_token(void) 480 { 481 int i, best, bestprofit; 482 483 bestprofit=-10000; 484 best = 0; 485 486 for (i = 0; i < 0x10000; i++) { 487 if (token_profit[i] > bestprofit) { 488 best = i; 489 bestprofit = token_profit[i]; 490 } 491 } 492 return best; 493 } 494 495 /* this is the core of the algorithm: calculate the "best" table */ 496 static void optimize_result(void) 497 { 498 int i, best; 499 500 /* using the '\0' symbol last allows compress_symbols to use standard 501 * fast string functions */ 502 for (i = 255; i >= 0; i--) { 503 504 /* if this table slot is empty (it is not used by an actual 505 * original char code */ 506 if (!best_table_len[i]) { 507 508 /* find the token with the breates profit value */ 509 best = find_best_token(); 510 if (token_profit[best] == 0) 511 break; 512 513 /* place it in the "best" table */ 514 best_table_len[i] = 2; 515 best_table[i][0] = best & 0xFF; 516 best_table[i][1] = (best >> 8) & 0xFF; 517 518 /* replace this token in all the valid symbols */ 519 compress_symbols(best_table[i], i); 520 } 521 } 522 } 523 524 /* start by placing the symbols that are actually used on the table */ 525 static void insert_real_symbols_in_table(void) 526 { 527 unsigned int i, j, c; 528 529 memset(best_table, 0, sizeof(best_table)); 530 memset(best_table_len, 0, sizeof(best_table_len)); 531 532 for (i = 0; i < table_cnt; i++) { 533 for (j = 0; j < table[i].len; j++) { 534 c = table[i].sym[j]; 535 best_table[c][0]=c; 536 best_table_len[c]=1; 537 } 538 } 539 } 540 541 static void optimize_token_table(void) 542 { 543 build_initial_tok_table(); 544 545 insert_real_symbols_in_table(); 546 547 /* When valid symbol is not registered, exit to error */ 548 if (!table_cnt) { 549 fprintf(stderr, "No valid symbol.\n"); 550 exit(1); 551 } 552 553 optimize_result(); 554 } 555 556 /* guess for "linker script provide" symbol */ 557 static int may_be_linker_script_provide_symbol(const struct sym_entry *se) 558 { 559 const char *symbol = (char *)se->sym + 1; 560 int len = se->len - 1; 561 562 if (len < 8) 563 return 0; 564 565 if (symbol[0] != '_' || symbol[1] != '_') 566 return 0; 567 568 /* __start_XXXXX */ 569 if (!memcmp(symbol + 2, "start_", 6)) 570 return 1; 571 572 /* __stop_XXXXX */ 573 if (!memcmp(symbol + 2, "stop_", 5)) 574 return 1; 575 576 /* __end_XXXXX */ 577 if (!memcmp(symbol + 2, "end_", 4)) 578 return 1; 579 580 /* __XXXXX_start */ 581 if (!memcmp(symbol + len - 6, "_start", 6)) 582 return 1; 583 584 /* __XXXXX_end */ 585 if (!memcmp(symbol + len - 4, "_end", 4)) 586 return 1; 587 588 return 0; 589 } 590 591 static int prefix_underscores_count(const char *str) 592 { 593 const char *tail = str; 594 595 while (*tail == '_') 596 tail++; 597 598 return tail - str; 599 } 600 601 static int compare_symbols(const void *a, const void *b) 602 { 603 const struct sym_entry *sa; 604 const struct sym_entry *sb; 605 int wa, wb; 606 607 sa = a; 608 sb = b; 609 610 /* sort by address first */ 611 if (sa->addr > sb->addr) 612 return 1; 613 if (sa->addr < sb->addr) 614 return -1; 615 616 /* sort by "weakness" type */ 617 wa = (sa->sym[0] == 'w') || (sa->sym[0] == 'W'); 618 wb = (sb->sym[0] == 'w') || (sb->sym[0] == 'W'); 619 if (wa != wb) 620 return wa - wb; 621 622 /* sort by "linker script provide" type */ 623 wa = may_be_linker_script_provide_symbol(sa); 624 wb = may_be_linker_script_provide_symbol(sb); 625 if (wa != wb) 626 return wa - wb; 627 628 /* sort by the number of prefix underscores */ 629 wa = prefix_underscores_count((const char *)sa->sym + 1); 630 wb = prefix_underscores_count((const char *)sb->sym + 1); 631 if (wa != wb) 632 return wa - wb; 633 634 /* sort by initial order, so that other symbols are left undisturbed */ 635 return sa->start_pos - sb->start_pos; 636 } 637 638 static void sort_symbols(void) 639 { 640 qsort(table, table_cnt, sizeof(struct sym_entry), compare_symbols); 641 } 642 643 int main(int argc, char **argv) 644 { 645 if (argc >= 2) { 646 int i; 647 for (i = 1; i < argc; i++) { 648 if(strcmp(argv[i], "--all-symbols") == 0) 649 all_symbols = 1; 650 else if (strncmp(argv[i], "--symbol-prefix=", 16) == 0) { 651 char *p = &argv[i][16]; 652 /* skip quote */ 653 if ((*p == '"' && *(p+2) == '"') || (*p == '\'' && *(p+2) == '\'')) 654 p++; 655 symbol_prefix_char = *p; 656 } else if (strncmp(argv[i], "--page-offset=", 14) == 0) { 657 const char *p = &argv[i][14]; 658 kernel_start_addr = strtoull(p, NULL, 16); 659 } else 660 usage(); 661 } 662 } else if (argc != 1) 663 usage(); 664 665 read_map(stdin); 666 sort_symbols(); 667 optimize_token_table(); 668 write_src(); 669 670 return 0; 671 } 672