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 #include <limits.h> 26 27 #ifndef ARRAY_SIZE 28 #define ARRAY_SIZE(arr) (sizeof(arr) / sizeof(arr[0])) 29 #endif 30 31 #define KSYM_NAME_LEN 128 32 33 struct sym_entry { 34 unsigned long long addr; 35 unsigned int len; 36 unsigned int start_pos; 37 unsigned char *sym; 38 unsigned int percpu_absolute; 39 }; 40 41 struct addr_range { 42 const char *start_sym, *end_sym; 43 unsigned long long start, end; 44 }; 45 46 static unsigned long long _text; 47 static unsigned long long relative_base; 48 static struct addr_range text_ranges[] = { 49 { "_stext", "_etext" }, 50 { "_sinittext", "_einittext" }, 51 { "_stext_l1", "_etext_l1" }, /* Blackfin on-chip L1 inst SRAM */ 52 { "_stext_l2", "_etext_l2" }, /* Blackfin on-chip L2 SRAM */ 53 }; 54 #define text_range_text (&text_ranges[0]) 55 #define text_range_inittext (&text_ranges[1]) 56 57 static struct addr_range percpu_range = { 58 "__per_cpu_start", "__per_cpu_end", -1ULL, 0 59 }; 60 61 static struct sym_entry *table; 62 static unsigned int table_size, table_cnt; 63 static int all_symbols = 0; 64 static int absolute_percpu = 0; 65 static int base_relative = 0; 66 67 int token_profit[0x10000]; 68 69 /* the table that holds the result of the compression */ 70 unsigned char best_table[256][2]; 71 unsigned char best_table_len[256]; 72 73 74 static void usage(void) 75 { 76 fprintf(stderr, "Usage: kallsyms [--all-symbols] " 77 "[--base-relative] < in.map > out.S\n"); 78 exit(1); 79 } 80 81 /* 82 * This ignores the intensely annoying "mapping symbols" found 83 * in ARM ELF files: $a, $t and $d. 84 */ 85 static inline int is_arm_mapping_symbol(const char *str) 86 { 87 return str[0] == '$' && strchr("axtd", str[1]) 88 && (str[2] == '\0' || str[2] == '.'); 89 } 90 91 static int check_symbol_range(const char *sym, unsigned long long addr, 92 struct addr_range *ranges, int entries) 93 { 94 size_t i; 95 struct addr_range *ar; 96 97 for (i = 0; i < entries; ++i) { 98 ar = &ranges[i]; 99 100 if (strcmp(sym, ar->start_sym) == 0) { 101 ar->start = addr; 102 return 0; 103 } else if (strcmp(sym, ar->end_sym) == 0) { 104 ar->end = addr; 105 return 0; 106 } 107 } 108 109 return 1; 110 } 111 112 static int read_symbol(FILE *in, struct sym_entry *s) 113 { 114 char sym[500], stype; 115 int rc; 116 117 rc = fscanf(in, "%llx %c %499s\n", &s->addr, &stype, sym); 118 if (rc != 3) { 119 if (rc != EOF && fgets(sym, 500, in) == NULL) 120 fprintf(stderr, "Read error or end of file.\n"); 121 return -1; 122 } 123 if (strlen(sym) > KSYM_NAME_LEN) { 124 fprintf(stderr, "Symbol %s too long for kallsyms (%zu vs %d).\n" 125 "Please increase KSYM_NAME_LEN both in kernel and kallsyms.c\n", 126 sym, strlen(sym), KSYM_NAME_LEN); 127 return -1; 128 } 129 130 /* Ignore most absolute/undefined (?) symbols. */ 131 if (strcmp(sym, "_text") == 0) 132 _text = s->addr; 133 else if (check_symbol_range(sym, s->addr, text_ranges, 134 ARRAY_SIZE(text_ranges)) == 0) 135 /* nothing to do */; 136 else if (toupper(stype) == 'A') 137 { 138 /* Keep these useful absolute symbols */ 139 if (strcmp(sym, "__kernel_syscall_via_break") && 140 strcmp(sym, "__kernel_syscall_via_epc") && 141 strcmp(sym, "__kernel_sigtramp") && 142 strcmp(sym, "__gp")) 143 return -1; 144 145 } 146 else if (toupper(stype) == 'U' || 147 is_arm_mapping_symbol(sym)) 148 return -1; 149 /* exclude also MIPS ELF local symbols ($L123 instead of .L123) */ 150 else if (sym[0] == '$') 151 return -1; 152 /* exclude debugging symbols */ 153 else if (stype == 'N' || stype == 'n') 154 return -1; 155 156 /* include the type field in the symbol name, so that it gets 157 * compressed together */ 158 s->len = strlen(sym) + 1; 159 s->sym = malloc(s->len + 1); 160 if (!s->sym) { 161 fprintf(stderr, "kallsyms failure: " 162 "unable to allocate required amount of memory\n"); 163 exit(EXIT_FAILURE); 164 } 165 strcpy((char *)s->sym + 1, sym); 166 s->sym[0] = stype; 167 168 s->percpu_absolute = 0; 169 170 /* Record if we've found __per_cpu_start/end. */ 171 check_symbol_range(sym, s->addr, &percpu_range, 1); 172 173 return 0; 174 } 175 176 static int symbol_in_range(struct sym_entry *s, struct addr_range *ranges, 177 int entries) 178 { 179 size_t i; 180 struct addr_range *ar; 181 182 for (i = 0; i < entries; ++i) { 183 ar = &ranges[i]; 184 185 if (s->addr >= ar->start && s->addr <= ar->end) 186 return 1; 187 } 188 189 return 0; 190 } 191 192 static int symbol_valid(struct sym_entry *s) 193 { 194 /* Symbols which vary between passes. Passes 1 and 2 must have 195 * identical symbol lists. The kallsyms_* symbols below are only added 196 * after pass 1, they would be included in pass 2 when --all-symbols is 197 * specified so exclude them to get a stable symbol list. 198 */ 199 static char *special_symbols[] = { 200 "kallsyms_addresses", 201 "kallsyms_offsets", 202 "kallsyms_relative_base", 203 "kallsyms_num_syms", 204 "kallsyms_names", 205 "kallsyms_markers", 206 "kallsyms_token_table", 207 "kallsyms_token_index", 208 209 /* Exclude linker generated symbols which vary between passes */ 210 "_SDA_BASE_", /* ppc */ 211 "_SDA2_BASE_", /* ppc */ 212 NULL }; 213 214 static char *special_prefixes[] = { 215 "__crc_", /* modversions */ 216 "__efistub_", /* arm64 EFI stub namespace */ 217 NULL }; 218 219 static char *special_suffixes[] = { 220 "_veneer", /* arm */ 221 "_from_arm", /* arm */ 222 "_from_thumb", /* arm */ 223 NULL }; 224 225 int i; 226 char *sym_name = (char *)s->sym + 1; 227 228 /* if --all-symbols is not specified, then symbols outside the text 229 * and inittext sections are discarded */ 230 if (!all_symbols) { 231 if (symbol_in_range(s, text_ranges, 232 ARRAY_SIZE(text_ranges)) == 0) 233 return 0; 234 /* Corner case. Discard any symbols with the same value as 235 * _etext _einittext; they can move between pass 1 and 2 when 236 * the kallsyms data are added. If these symbols move then 237 * they may get dropped in pass 2, which breaks the kallsyms 238 * rules. 239 */ 240 if ((s->addr == text_range_text->end && 241 strcmp(sym_name, 242 text_range_text->end_sym)) || 243 (s->addr == text_range_inittext->end && 244 strcmp(sym_name, 245 text_range_inittext->end_sym))) 246 return 0; 247 } 248 249 /* Exclude symbols which vary between passes. */ 250 for (i = 0; special_symbols[i]; i++) 251 if (strcmp(sym_name, special_symbols[i]) == 0) 252 return 0; 253 254 for (i = 0; special_prefixes[i]; i++) { 255 int l = strlen(special_prefixes[i]); 256 257 if (l <= strlen(sym_name) && 258 strncmp(sym_name, special_prefixes[i], l) == 0) 259 return 0; 260 } 261 262 for (i = 0; special_suffixes[i]; i++) { 263 int l = strlen(sym_name) - strlen(special_suffixes[i]); 264 265 if (l >= 0 && strcmp(sym_name + l, special_suffixes[i]) == 0) 266 return 0; 267 } 268 269 return 1; 270 } 271 272 static void read_map(FILE *in) 273 { 274 while (!feof(in)) { 275 if (table_cnt >= table_size) { 276 table_size += 10000; 277 table = realloc(table, sizeof(*table) * table_size); 278 if (!table) { 279 fprintf(stderr, "out of memory\n"); 280 exit (1); 281 } 282 } 283 if (read_symbol(in, &table[table_cnt]) == 0) { 284 table[table_cnt].start_pos = table_cnt; 285 table_cnt++; 286 } 287 } 288 } 289 290 static void output_label(char *label) 291 { 292 printf(".globl %s\n", label); 293 printf("\tALGN\n"); 294 printf("%s:\n", label); 295 } 296 297 /* uncompress a compressed symbol. When this function is called, the best table 298 * might still be compressed itself, so the function needs to be recursive */ 299 static int expand_symbol(unsigned char *data, int len, char *result) 300 { 301 int c, rlen, total=0; 302 303 while (len) { 304 c = *data; 305 /* if the table holds a single char that is the same as the one 306 * we are looking for, then end the search */ 307 if (best_table[c][0]==c && best_table_len[c]==1) { 308 *result++ = c; 309 total++; 310 } else { 311 /* if not, recurse and expand */ 312 rlen = expand_symbol(best_table[c], best_table_len[c], result); 313 total += rlen; 314 result += rlen; 315 } 316 data++; 317 len--; 318 } 319 *result=0; 320 321 return total; 322 } 323 324 static int symbol_absolute(struct sym_entry *s) 325 { 326 return s->percpu_absolute; 327 } 328 329 static void write_src(void) 330 { 331 unsigned int i, k, off; 332 unsigned int best_idx[256]; 333 unsigned int *markers; 334 char buf[KSYM_NAME_LEN]; 335 336 printf("#include <asm/types.h>\n"); 337 printf("#if BITS_PER_LONG == 64\n"); 338 printf("#define PTR .quad\n"); 339 printf("#define ALGN .align 8\n"); 340 printf("#else\n"); 341 printf("#define PTR .long\n"); 342 printf("#define ALGN .align 4\n"); 343 printf("#endif\n"); 344 345 printf("\t.section .rodata, \"a\"\n"); 346 347 /* Provide proper symbols relocatability by their relativeness 348 * to a fixed anchor point in the runtime image, either '_text' 349 * for absolute address tables, in which case the linker will 350 * emit the final addresses at build time. Otherwise, use the 351 * offset relative to the lowest value encountered of all relative 352 * symbols, and emit non-relocatable fixed offsets that will be fixed 353 * up at runtime. 354 * 355 * The symbol names cannot be used to construct normal symbol 356 * references as the list of symbols contains symbols that are 357 * declared static and are private to their .o files. This prevents 358 * .tmp_kallsyms.o or any other object from referencing them. 359 */ 360 if (!base_relative) 361 output_label("kallsyms_addresses"); 362 else 363 output_label("kallsyms_offsets"); 364 365 for (i = 0; i < table_cnt; i++) { 366 if (base_relative) { 367 long long offset; 368 int overflow; 369 370 if (!absolute_percpu) { 371 offset = table[i].addr - relative_base; 372 overflow = (offset < 0 || offset > UINT_MAX); 373 } else if (symbol_absolute(&table[i])) { 374 offset = table[i].addr; 375 overflow = (offset < 0 || offset > INT_MAX); 376 } else { 377 offset = relative_base - table[i].addr - 1; 378 overflow = (offset < INT_MIN || offset >= 0); 379 } 380 if (overflow) { 381 fprintf(stderr, "kallsyms failure: " 382 "%s symbol value %#llx out of range in relative mode\n", 383 symbol_absolute(&table[i]) ? "absolute" : "relative", 384 table[i].addr); 385 exit(EXIT_FAILURE); 386 } 387 printf("\t.long\t%#x\n", (int)offset); 388 } else if (!symbol_absolute(&table[i])) { 389 if (_text <= table[i].addr) 390 printf("\tPTR\t_text + %#llx\n", 391 table[i].addr - _text); 392 else 393 printf("\tPTR\t_text - %#llx\n", 394 _text - table[i].addr); 395 } else { 396 printf("\tPTR\t%#llx\n", table[i].addr); 397 } 398 } 399 printf("\n"); 400 401 if (base_relative) { 402 output_label("kallsyms_relative_base"); 403 printf("\tPTR\t_text - %#llx\n", _text - relative_base); 404 printf("\n"); 405 } 406 407 output_label("kallsyms_num_syms"); 408 printf("\tPTR\t%u\n", table_cnt); 409 printf("\n"); 410 411 /* table of offset markers, that give the offset in the compressed stream 412 * every 256 symbols */ 413 markers = malloc(sizeof(unsigned int) * ((table_cnt + 255) / 256)); 414 if (!markers) { 415 fprintf(stderr, "kallsyms failure: " 416 "unable to allocate required memory\n"); 417 exit(EXIT_FAILURE); 418 } 419 420 output_label("kallsyms_names"); 421 off = 0; 422 for (i = 0; i < table_cnt; i++) { 423 if ((i & 0xFF) == 0) 424 markers[i >> 8] = off; 425 426 printf("\t.byte 0x%02x", table[i].len); 427 for (k = 0; k < table[i].len; k++) 428 printf(", 0x%02x", table[i].sym[k]); 429 printf("\n"); 430 431 off += table[i].len + 1; 432 } 433 printf("\n"); 434 435 output_label("kallsyms_markers"); 436 for (i = 0; i < ((table_cnt + 255) >> 8); i++) 437 printf("\tPTR\t%d\n", markers[i]); 438 printf("\n"); 439 440 free(markers); 441 442 output_label("kallsyms_token_table"); 443 off = 0; 444 for (i = 0; i < 256; i++) { 445 best_idx[i] = off; 446 expand_symbol(best_table[i], best_table_len[i], buf); 447 printf("\t.asciz\t\"%s\"\n", buf); 448 off += strlen(buf) + 1; 449 } 450 printf("\n"); 451 452 output_label("kallsyms_token_index"); 453 for (i = 0; i < 256; i++) 454 printf("\t.short\t%d\n", best_idx[i]); 455 printf("\n"); 456 } 457 458 459 /* table lookup compression functions */ 460 461 /* count all the possible tokens in a symbol */ 462 static void learn_symbol(unsigned char *symbol, int len) 463 { 464 int i; 465 466 for (i = 0; i < len - 1; i++) 467 token_profit[ symbol[i] + (symbol[i + 1] << 8) ]++; 468 } 469 470 /* decrease the count for all the possible tokens in a symbol */ 471 static void forget_symbol(unsigned char *symbol, int len) 472 { 473 int i; 474 475 for (i = 0; i < len - 1; i++) 476 token_profit[ symbol[i] + (symbol[i + 1] << 8) ]--; 477 } 478 479 /* remove all the invalid symbols from the table and do the initial token count */ 480 static void build_initial_tok_table(void) 481 { 482 unsigned int i, pos; 483 484 pos = 0; 485 for (i = 0; i < table_cnt; i++) { 486 if ( symbol_valid(&table[i]) ) { 487 if (pos != i) 488 table[pos] = table[i]; 489 learn_symbol(table[pos].sym, table[pos].len); 490 pos++; 491 } 492 } 493 table_cnt = pos; 494 } 495 496 static void *find_token(unsigned char *str, int len, unsigned char *token) 497 { 498 int i; 499 500 for (i = 0; i < len - 1; i++) { 501 if (str[i] == token[0] && str[i+1] == token[1]) 502 return &str[i]; 503 } 504 return NULL; 505 } 506 507 /* replace a given token in all the valid symbols. Use the sampled symbols 508 * to update the counts */ 509 static void compress_symbols(unsigned char *str, int idx) 510 { 511 unsigned int i, len, size; 512 unsigned char *p1, *p2; 513 514 for (i = 0; i < table_cnt; i++) { 515 516 len = table[i].len; 517 p1 = table[i].sym; 518 519 /* find the token on the symbol */ 520 p2 = find_token(p1, len, str); 521 if (!p2) continue; 522 523 /* decrease the counts for this symbol's tokens */ 524 forget_symbol(table[i].sym, len); 525 526 size = len; 527 528 do { 529 *p2 = idx; 530 p2++; 531 size -= (p2 - p1); 532 memmove(p2, p2 + 1, size); 533 p1 = p2; 534 len--; 535 536 if (size < 2) break; 537 538 /* find the token on the symbol */ 539 p2 = find_token(p1, size, str); 540 541 } while (p2); 542 543 table[i].len = len; 544 545 /* increase the counts for this symbol's new tokens */ 546 learn_symbol(table[i].sym, len); 547 } 548 } 549 550 /* search the token with the maximum profit */ 551 static int find_best_token(void) 552 { 553 int i, best, bestprofit; 554 555 bestprofit=-10000; 556 best = 0; 557 558 for (i = 0; i < 0x10000; i++) { 559 if (token_profit[i] > bestprofit) { 560 best = i; 561 bestprofit = token_profit[i]; 562 } 563 } 564 return best; 565 } 566 567 /* this is the core of the algorithm: calculate the "best" table */ 568 static void optimize_result(void) 569 { 570 int i, best; 571 572 /* using the '\0' symbol last allows compress_symbols to use standard 573 * fast string functions */ 574 for (i = 255; i >= 0; i--) { 575 576 /* if this table slot is empty (it is not used by an actual 577 * original char code */ 578 if (!best_table_len[i]) { 579 580 /* find the token with the best profit value */ 581 best = find_best_token(); 582 if (token_profit[best] == 0) 583 break; 584 585 /* place it in the "best" table */ 586 best_table_len[i] = 2; 587 best_table[i][0] = best & 0xFF; 588 best_table[i][1] = (best >> 8) & 0xFF; 589 590 /* replace this token in all the valid symbols */ 591 compress_symbols(best_table[i], i); 592 } 593 } 594 } 595 596 /* start by placing the symbols that are actually used on the table */ 597 static void insert_real_symbols_in_table(void) 598 { 599 unsigned int i, j, c; 600 601 memset(best_table, 0, sizeof(best_table)); 602 memset(best_table_len, 0, sizeof(best_table_len)); 603 604 for (i = 0; i < table_cnt; i++) { 605 for (j = 0; j < table[i].len; j++) { 606 c = table[i].sym[j]; 607 best_table[c][0]=c; 608 best_table_len[c]=1; 609 } 610 } 611 } 612 613 static void optimize_token_table(void) 614 { 615 build_initial_tok_table(); 616 617 insert_real_symbols_in_table(); 618 619 /* When valid symbol is not registered, exit to error */ 620 if (!table_cnt) { 621 fprintf(stderr, "No valid symbol.\n"); 622 exit(1); 623 } 624 625 optimize_result(); 626 } 627 628 /* guess for "linker script provide" symbol */ 629 static int may_be_linker_script_provide_symbol(const struct sym_entry *se) 630 { 631 const char *symbol = (char *)se->sym + 1; 632 int len = se->len - 1; 633 634 if (len < 8) 635 return 0; 636 637 if (symbol[0] != '_' || symbol[1] != '_') 638 return 0; 639 640 /* __start_XXXXX */ 641 if (!memcmp(symbol + 2, "start_", 6)) 642 return 1; 643 644 /* __stop_XXXXX */ 645 if (!memcmp(symbol + 2, "stop_", 5)) 646 return 1; 647 648 /* __end_XXXXX */ 649 if (!memcmp(symbol + 2, "end_", 4)) 650 return 1; 651 652 /* __XXXXX_start */ 653 if (!memcmp(symbol + len - 6, "_start", 6)) 654 return 1; 655 656 /* __XXXXX_end */ 657 if (!memcmp(symbol + len - 4, "_end", 4)) 658 return 1; 659 660 return 0; 661 } 662 663 static int prefix_underscores_count(const char *str) 664 { 665 const char *tail = str; 666 667 while (*tail == '_') 668 tail++; 669 670 return tail - str; 671 } 672 673 static int compare_symbols(const void *a, const void *b) 674 { 675 const struct sym_entry *sa; 676 const struct sym_entry *sb; 677 int wa, wb; 678 679 sa = a; 680 sb = b; 681 682 /* sort by address first */ 683 if (sa->addr > sb->addr) 684 return 1; 685 if (sa->addr < sb->addr) 686 return -1; 687 688 /* sort by "weakness" type */ 689 wa = (sa->sym[0] == 'w') || (sa->sym[0] == 'W'); 690 wb = (sb->sym[0] == 'w') || (sb->sym[0] == 'W'); 691 if (wa != wb) 692 return wa - wb; 693 694 /* sort by "linker script provide" type */ 695 wa = may_be_linker_script_provide_symbol(sa); 696 wb = may_be_linker_script_provide_symbol(sb); 697 if (wa != wb) 698 return wa - wb; 699 700 /* sort by the number of prefix underscores */ 701 wa = prefix_underscores_count((const char *)sa->sym + 1); 702 wb = prefix_underscores_count((const char *)sb->sym + 1); 703 if (wa != wb) 704 return wa - wb; 705 706 /* sort by initial order, so that other symbols are left undisturbed */ 707 return sa->start_pos - sb->start_pos; 708 } 709 710 static void sort_symbols(void) 711 { 712 qsort(table, table_cnt, sizeof(struct sym_entry), compare_symbols); 713 } 714 715 static void make_percpus_absolute(void) 716 { 717 unsigned int i; 718 719 for (i = 0; i < table_cnt; i++) 720 if (symbol_in_range(&table[i], &percpu_range, 1)) { 721 /* 722 * Keep the 'A' override for percpu symbols to 723 * ensure consistent behavior compared to older 724 * versions of this tool. 725 */ 726 table[i].sym[0] = 'A'; 727 table[i].percpu_absolute = 1; 728 } 729 } 730 731 /* find the minimum non-absolute symbol address */ 732 static void record_relative_base(void) 733 { 734 unsigned int i; 735 736 relative_base = -1ULL; 737 for (i = 0; i < table_cnt; i++) 738 if (!symbol_absolute(&table[i]) && 739 table[i].addr < relative_base) 740 relative_base = table[i].addr; 741 } 742 743 int main(int argc, char **argv) 744 { 745 if (argc >= 2) { 746 int i; 747 for (i = 1; i < argc; i++) { 748 if(strcmp(argv[i], "--all-symbols") == 0) 749 all_symbols = 1; 750 else if (strcmp(argv[i], "--absolute-percpu") == 0) 751 absolute_percpu = 1; 752 else if (strcmp(argv[i], "--base-relative") == 0) 753 base_relative = 1; 754 else 755 usage(); 756 } 757 } else if (argc != 1) 758 usage(); 759 760 read_map(stdin); 761 if (absolute_percpu) 762 make_percpus_absolute(); 763 if (base_relative) 764 record_relative_base(); 765 sort_symbols(); 766 optimize_token_table(); 767 write_src(); 768 769 return 0; 770 } 771