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 char symbol_prefix_char = '\0'; 66 static int base_relative = 0; 67 68 int token_profit[0x10000]; 69 70 /* the table that holds the result of the compression */ 71 unsigned char best_table[256][2]; 72 unsigned char best_table_len[256]; 73 74 75 static void usage(void) 76 { 77 fprintf(stderr, "Usage: kallsyms [--all-symbols] " 78 "[--symbol-prefix=<prefix char>] " 79 "[--base-relative] < in.map > out.S\n"); 80 exit(1); 81 } 82 83 /* 84 * This ignores the intensely annoying "mapping symbols" found 85 * in ARM ELF files: $a, $t and $d. 86 */ 87 static inline int is_arm_mapping_symbol(const char *str) 88 { 89 return str[0] == '$' && strchr("axtd", str[1]) 90 && (str[2] == '\0' || str[2] == '.'); 91 } 92 93 static int check_symbol_range(const char *sym, unsigned long long addr, 94 struct addr_range *ranges, int entries) 95 { 96 size_t i; 97 struct addr_range *ar; 98 99 for (i = 0; i < entries; ++i) { 100 ar = &ranges[i]; 101 102 if (strcmp(sym, ar->start_sym) == 0) { 103 ar->start = addr; 104 return 0; 105 } else if (strcmp(sym, ar->end_sym) == 0) { 106 ar->end = addr; 107 return 0; 108 } 109 } 110 111 return 1; 112 } 113 114 static int read_symbol(FILE *in, struct sym_entry *s) 115 { 116 char str[500]; 117 char *sym, stype; 118 int rc; 119 120 rc = fscanf(in, "%llx %c %499s\n", &s->addr, &stype, str); 121 if (rc != 3) { 122 if (rc != EOF && fgets(str, 500, in) == NULL) 123 fprintf(stderr, "Read error or end of file.\n"); 124 return -1; 125 } 126 if (strlen(str) > KSYM_NAME_LEN) { 127 fprintf(stderr, "Symbol %s too long for kallsyms (%zu vs %d).\n" 128 "Please increase KSYM_NAME_LEN both in kernel and kallsyms.c\n", 129 str, strlen(str), KSYM_NAME_LEN); 130 return -1; 131 } 132 133 sym = str; 134 /* skip prefix char */ 135 if (symbol_prefix_char && str[0] == symbol_prefix_char) 136 sym++; 137 138 /* Ignore most absolute/undefined (?) symbols. */ 139 if (strcmp(sym, "_text") == 0) 140 _text = s->addr; 141 else if (check_symbol_range(sym, s->addr, text_ranges, 142 ARRAY_SIZE(text_ranges)) == 0) 143 /* nothing to do */; 144 else if (toupper(stype) == 'A') 145 { 146 /* Keep these useful absolute symbols */ 147 if (strcmp(sym, "__kernel_syscall_via_break") && 148 strcmp(sym, "__kernel_syscall_via_epc") && 149 strcmp(sym, "__kernel_sigtramp") && 150 strcmp(sym, "__gp")) 151 return -1; 152 153 } 154 else if (toupper(stype) == 'U' || 155 is_arm_mapping_symbol(sym)) 156 return -1; 157 /* exclude also MIPS ELF local symbols ($L123 instead of .L123) */ 158 else if (str[0] == '$') 159 return -1; 160 /* exclude debugging symbols */ 161 else if (stype == 'N' || stype == 'n') 162 return -1; 163 164 /* include the type field in the symbol name, so that it gets 165 * compressed together */ 166 s->len = strlen(str) + 1; 167 s->sym = malloc(s->len + 1); 168 if (!s->sym) { 169 fprintf(stderr, "kallsyms failure: " 170 "unable to allocate required amount of memory\n"); 171 exit(EXIT_FAILURE); 172 } 173 strcpy((char *)s->sym + 1, str); 174 s->sym[0] = stype; 175 176 s->percpu_absolute = 0; 177 178 /* Record if we've found __per_cpu_start/end. */ 179 check_symbol_range(sym, s->addr, &percpu_range, 1); 180 181 return 0; 182 } 183 184 static int symbol_in_range(struct sym_entry *s, struct addr_range *ranges, 185 int entries) 186 { 187 size_t i; 188 struct addr_range *ar; 189 190 for (i = 0; i < entries; ++i) { 191 ar = &ranges[i]; 192 193 if (s->addr >= ar->start && s->addr <= ar->end) 194 return 1; 195 } 196 197 return 0; 198 } 199 200 static int symbol_valid(struct sym_entry *s) 201 { 202 /* Symbols which vary between passes. Passes 1 and 2 must have 203 * identical symbol lists. The kallsyms_* symbols below are only added 204 * after pass 1, they would be included in pass 2 when --all-symbols is 205 * specified so exclude them to get a stable symbol list. 206 */ 207 static char *special_symbols[] = { 208 "kallsyms_addresses", 209 "kallsyms_offsets", 210 "kallsyms_relative_base", 211 "kallsyms_num_syms", 212 "kallsyms_names", 213 "kallsyms_markers", 214 "kallsyms_token_table", 215 "kallsyms_token_index", 216 217 /* Exclude linker generated symbols which vary between passes */ 218 "_SDA_BASE_", /* ppc */ 219 "_SDA2_BASE_", /* ppc */ 220 NULL }; 221 222 static char *special_prefixes[] = { 223 "__crc_", /* modversions */ 224 "__efistub_", /* arm64 EFI stub namespace */ 225 NULL }; 226 227 static char *special_suffixes[] = { 228 "_veneer", /* arm */ 229 "_from_arm", /* arm */ 230 "_from_thumb", /* arm */ 231 NULL }; 232 233 int i; 234 char *sym_name = (char *)s->sym + 1; 235 236 /* skip prefix char */ 237 if (symbol_prefix_char && *sym_name == symbol_prefix_char) 238 sym_name++; 239 240 241 /* if --all-symbols is not specified, then symbols outside the text 242 * and inittext sections are discarded */ 243 if (!all_symbols) { 244 if (symbol_in_range(s, text_ranges, 245 ARRAY_SIZE(text_ranges)) == 0) 246 return 0; 247 /* Corner case. Discard any symbols with the same value as 248 * _etext _einittext; they can move between pass 1 and 2 when 249 * the kallsyms data are added. If these symbols move then 250 * they may get dropped in pass 2, which breaks the kallsyms 251 * rules. 252 */ 253 if ((s->addr == text_range_text->end && 254 strcmp(sym_name, 255 text_range_text->end_sym)) || 256 (s->addr == text_range_inittext->end && 257 strcmp(sym_name, 258 text_range_inittext->end_sym))) 259 return 0; 260 } 261 262 /* Exclude symbols which vary between passes. */ 263 for (i = 0; special_symbols[i]; i++) 264 if (strcmp(sym_name, special_symbols[i]) == 0) 265 return 0; 266 267 for (i = 0; special_prefixes[i]; i++) { 268 int l = strlen(special_prefixes[i]); 269 270 if (l <= strlen(sym_name) && 271 strncmp(sym_name, special_prefixes[i], l) == 0) 272 return 0; 273 } 274 275 for (i = 0; special_suffixes[i]; i++) { 276 int l = strlen(sym_name) - strlen(special_suffixes[i]); 277 278 if (l >= 0 && strcmp(sym_name + l, special_suffixes[i]) == 0) 279 return 0; 280 } 281 282 return 1; 283 } 284 285 static void read_map(FILE *in) 286 { 287 while (!feof(in)) { 288 if (table_cnt >= table_size) { 289 table_size += 10000; 290 table = realloc(table, sizeof(*table) * table_size); 291 if (!table) { 292 fprintf(stderr, "out of memory\n"); 293 exit (1); 294 } 295 } 296 if (read_symbol(in, &table[table_cnt]) == 0) { 297 table[table_cnt].start_pos = table_cnt; 298 table_cnt++; 299 } 300 } 301 } 302 303 static void output_label(char *label) 304 { 305 if (symbol_prefix_char) 306 printf(".globl %c%s\n", symbol_prefix_char, label); 307 else 308 printf(".globl %s\n", label); 309 printf("\tALGN\n"); 310 if (symbol_prefix_char) 311 printf("%c%s:\n", symbol_prefix_char, label); 312 else 313 printf("%s:\n", label); 314 } 315 316 /* uncompress a compressed symbol. When this function is called, the best table 317 * might still be compressed itself, so the function needs to be recursive */ 318 static int expand_symbol(unsigned char *data, int len, char *result) 319 { 320 int c, rlen, total=0; 321 322 while (len) { 323 c = *data; 324 /* if the table holds a single char that is the same as the one 325 * we are looking for, then end the search */ 326 if (best_table[c][0]==c && best_table_len[c]==1) { 327 *result++ = c; 328 total++; 329 } else { 330 /* if not, recurse and expand */ 331 rlen = expand_symbol(best_table[c], best_table_len[c], result); 332 total += rlen; 333 result += rlen; 334 } 335 data++; 336 len--; 337 } 338 *result=0; 339 340 return total; 341 } 342 343 static int symbol_absolute(struct sym_entry *s) 344 { 345 return s->percpu_absolute; 346 } 347 348 static void write_src(void) 349 { 350 unsigned int i, k, off; 351 unsigned int best_idx[256]; 352 unsigned int *markers; 353 char buf[KSYM_NAME_LEN]; 354 355 printf("#include <asm/types.h>\n"); 356 printf("#if BITS_PER_LONG == 64\n"); 357 printf("#define PTR .quad\n"); 358 printf("#define ALGN .align 8\n"); 359 printf("#else\n"); 360 printf("#define PTR .long\n"); 361 printf("#define ALGN .align 4\n"); 362 printf("#endif\n"); 363 364 printf("\t.section .rodata, \"a\"\n"); 365 366 /* Provide proper symbols relocatability by their relativeness 367 * to a fixed anchor point in the runtime image, either '_text' 368 * for absolute address tables, in which case the linker will 369 * emit the final addresses at build time. Otherwise, use the 370 * offset relative to the lowest value encountered of all relative 371 * symbols, and emit non-relocatable fixed offsets that will be fixed 372 * up at runtime. 373 * 374 * The symbol names cannot be used to construct normal symbol 375 * references as the list of symbols contains symbols that are 376 * declared static and are private to their .o files. This prevents 377 * .tmp_kallsyms.o or any other object from referencing them. 378 */ 379 if (!base_relative) 380 output_label("kallsyms_addresses"); 381 else 382 output_label("kallsyms_offsets"); 383 384 for (i = 0; i < table_cnt; i++) { 385 if (base_relative) { 386 long long offset; 387 int overflow; 388 389 if (!absolute_percpu) { 390 offset = table[i].addr - relative_base; 391 overflow = (offset < 0 || offset > UINT_MAX); 392 } else if (symbol_absolute(&table[i])) { 393 offset = table[i].addr; 394 overflow = (offset < 0 || offset > INT_MAX); 395 } else { 396 offset = relative_base - table[i].addr - 1; 397 overflow = (offset < INT_MIN || offset >= 0); 398 } 399 if (overflow) { 400 fprintf(stderr, "kallsyms failure: " 401 "%s symbol value %#llx out of range in relative mode\n", 402 symbol_absolute(&table[i]) ? "absolute" : "relative", 403 table[i].addr); 404 exit(EXIT_FAILURE); 405 } 406 printf("\t.long\t%#x\n", (int)offset); 407 } else if (!symbol_absolute(&table[i])) { 408 if (_text <= table[i].addr) 409 printf("\tPTR\t_text + %#llx\n", 410 table[i].addr - _text); 411 else 412 printf("\tPTR\t_text - %#llx\n", 413 _text - table[i].addr); 414 } else { 415 printf("\tPTR\t%#llx\n", table[i].addr); 416 } 417 } 418 printf("\n"); 419 420 if (base_relative) { 421 output_label("kallsyms_relative_base"); 422 printf("\tPTR\t_text - %#llx\n", _text - relative_base); 423 printf("\n"); 424 } 425 426 output_label("kallsyms_num_syms"); 427 printf("\tPTR\t%d\n", table_cnt); 428 printf("\n"); 429 430 /* table of offset markers, that give the offset in the compressed stream 431 * every 256 symbols */ 432 markers = malloc(sizeof(unsigned int) * ((table_cnt + 255) / 256)); 433 if (!markers) { 434 fprintf(stderr, "kallsyms failure: " 435 "unable to allocate required memory\n"); 436 exit(EXIT_FAILURE); 437 } 438 439 output_label("kallsyms_names"); 440 off = 0; 441 for (i = 0; i < table_cnt; i++) { 442 if ((i & 0xFF) == 0) 443 markers[i >> 8] = off; 444 445 printf("\t.byte 0x%02x", table[i].len); 446 for (k = 0; k < table[i].len; k++) 447 printf(", 0x%02x", table[i].sym[k]); 448 printf("\n"); 449 450 off += table[i].len + 1; 451 } 452 printf("\n"); 453 454 output_label("kallsyms_markers"); 455 for (i = 0; i < ((table_cnt + 255) >> 8); i++) 456 printf("\tPTR\t%d\n", markers[i]); 457 printf("\n"); 458 459 free(markers); 460 461 output_label("kallsyms_token_table"); 462 off = 0; 463 for (i = 0; i < 256; i++) { 464 best_idx[i] = off; 465 expand_symbol(best_table[i], best_table_len[i], buf); 466 printf("\t.asciz\t\"%s\"\n", buf); 467 off += strlen(buf) + 1; 468 } 469 printf("\n"); 470 471 output_label("kallsyms_token_index"); 472 for (i = 0; i < 256; i++) 473 printf("\t.short\t%d\n", best_idx[i]); 474 printf("\n"); 475 } 476 477 478 /* table lookup compression functions */ 479 480 /* count all the possible tokens in a symbol */ 481 static void learn_symbol(unsigned char *symbol, int len) 482 { 483 int i; 484 485 for (i = 0; i < len - 1; i++) 486 token_profit[ symbol[i] + (symbol[i + 1] << 8) ]++; 487 } 488 489 /* decrease the count for all the possible tokens in a symbol */ 490 static void forget_symbol(unsigned char *symbol, int len) 491 { 492 int i; 493 494 for (i = 0; i < len - 1; i++) 495 token_profit[ symbol[i] + (symbol[i + 1] << 8) ]--; 496 } 497 498 /* remove all the invalid symbols from the table and do the initial token count */ 499 static void build_initial_tok_table(void) 500 { 501 unsigned int i, pos; 502 503 pos = 0; 504 for (i = 0; i < table_cnt; i++) { 505 if ( symbol_valid(&table[i]) ) { 506 if (pos != i) 507 table[pos] = table[i]; 508 learn_symbol(table[pos].sym, table[pos].len); 509 pos++; 510 } 511 } 512 table_cnt = pos; 513 } 514 515 static void *find_token(unsigned char *str, int len, unsigned char *token) 516 { 517 int i; 518 519 for (i = 0; i < len - 1; i++) { 520 if (str[i] == token[0] && str[i+1] == token[1]) 521 return &str[i]; 522 } 523 return NULL; 524 } 525 526 /* replace a given token in all the valid symbols. Use the sampled symbols 527 * to update the counts */ 528 static void compress_symbols(unsigned char *str, int idx) 529 { 530 unsigned int i, len, size; 531 unsigned char *p1, *p2; 532 533 for (i = 0; i < table_cnt; i++) { 534 535 len = table[i].len; 536 p1 = table[i].sym; 537 538 /* find the token on the symbol */ 539 p2 = find_token(p1, len, str); 540 if (!p2) continue; 541 542 /* decrease the counts for this symbol's tokens */ 543 forget_symbol(table[i].sym, len); 544 545 size = len; 546 547 do { 548 *p2 = idx; 549 p2++; 550 size -= (p2 - p1); 551 memmove(p2, p2 + 1, size); 552 p1 = p2; 553 len--; 554 555 if (size < 2) break; 556 557 /* find the token on the symbol */ 558 p2 = find_token(p1, size, str); 559 560 } while (p2); 561 562 table[i].len = len; 563 564 /* increase the counts for this symbol's new tokens */ 565 learn_symbol(table[i].sym, len); 566 } 567 } 568 569 /* search the token with the maximum profit */ 570 static int find_best_token(void) 571 { 572 int i, best, bestprofit; 573 574 bestprofit=-10000; 575 best = 0; 576 577 for (i = 0; i < 0x10000; i++) { 578 if (token_profit[i] > bestprofit) { 579 best = i; 580 bestprofit = token_profit[i]; 581 } 582 } 583 return best; 584 } 585 586 /* this is the core of the algorithm: calculate the "best" table */ 587 static void optimize_result(void) 588 { 589 int i, best; 590 591 /* using the '\0' symbol last allows compress_symbols to use standard 592 * fast string functions */ 593 for (i = 255; i >= 0; i--) { 594 595 /* if this table slot is empty (it is not used by an actual 596 * original char code */ 597 if (!best_table_len[i]) { 598 599 /* find the token with the best profit value */ 600 best = find_best_token(); 601 if (token_profit[best] == 0) 602 break; 603 604 /* place it in the "best" table */ 605 best_table_len[i] = 2; 606 best_table[i][0] = best & 0xFF; 607 best_table[i][1] = (best >> 8) & 0xFF; 608 609 /* replace this token in all the valid symbols */ 610 compress_symbols(best_table[i], i); 611 } 612 } 613 } 614 615 /* start by placing the symbols that are actually used on the table */ 616 static void insert_real_symbols_in_table(void) 617 { 618 unsigned int i, j, c; 619 620 memset(best_table, 0, sizeof(best_table)); 621 memset(best_table_len, 0, sizeof(best_table_len)); 622 623 for (i = 0; i < table_cnt; i++) { 624 for (j = 0; j < table[i].len; j++) { 625 c = table[i].sym[j]; 626 best_table[c][0]=c; 627 best_table_len[c]=1; 628 } 629 } 630 } 631 632 static void optimize_token_table(void) 633 { 634 build_initial_tok_table(); 635 636 insert_real_symbols_in_table(); 637 638 /* When valid symbol is not registered, exit to error */ 639 if (!table_cnt) { 640 fprintf(stderr, "No valid symbol.\n"); 641 exit(1); 642 } 643 644 optimize_result(); 645 } 646 647 /* guess for "linker script provide" symbol */ 648 static int may_be_linker_script_provide_symbol(const struct sym_entry *se) 649 { 650 const char *symbol = (char *)se->sym + 1; 651 int len = se->len - 1; 652 653 if (len < 8) 654 return 0; 655 656 if (symbol[0] != '_' || symbol[1] != '_') 657 return 0; 658 659 /* __start_XXXXX */ 660 if (!memcmp(symbol + 2, "start_", 6)) 661 return 1; 662 663 /* __stop_XXXXX */ 664 if (!memcmp(symbol + 2, "stop_", 5)) 665 return 1; 666 667 /* __end_XXXXX */ 668 if (!memcmp(symbol + 2, "end_", 4)) 669 return 1; 670 671 /* __XXXXX_start */ 672 if (!memcmp(symbol + len - 6, "_start", 6)) 673 return 1; 674 675 /* __XXXXX_end */ 676 if (!memcmp(symbol + len - 4, "_end", 4)) 677 return 1; 678 679 return 0; 680 } 681 682 static int prefix_underscores_count(const char *str) 683 { 684 const char *tail = str; 685 686 while (*tail == '_') 687 tail++; 688 689 return tail - str; 690 } 691 692 static int compare_symbols(const void *a, const void *b) 693 { 694 const struct sym_entry *sa; 695 const struct sym_entry *sb; 696 int wa, wb; 697 698 sa = a; 699 sb = b; 700 701 /* sort by address first */ 702 if (sa->addr > sb->addr) 703 return 1; 704 if (sa->addr < sb->addr) 705 return -1; 706 707 /* sort by "weakness" type */ 708 wa = (sa->sym[0] == 'w') || (sa->sym[0] == 'W'); 709 wb = (sb->sym[0] == 'w') || (sb->sym[0] == 'W'); 710 if (wa != wb) 711 return wa - wb; 712 713 /* sort by "linker script provide" type */ 714 wa = may_be_linker_script_provide_symbol(sa); 715 wb = may_be_linker_script_provide_symbol(sb); 716 if (wa != wb) 717 return wa - wb; 718 719 /* sort by the number of prefix underscores */ 720 wa = prefix_underscores_count((const char *)sa->sym + 1); 721 wb = prefix_underscores_count((const char *)sb->sym + 1); 722 if (wa != wb) 723 return wa - wb; 724 725 /* sort by initial order, so that other symbols are left undisturbed */ 726 return sa->start_pos - sb->start_pos; 727 } 728 729 static void sort_symbols(void) 730 { 731 qsort(table, table_cnt, sizeof(struct sym_entry), compare_symbols); 732 } 733 734 static void make_percpus_absolute(void) 735 { 736 unsigned int i; 737 738 for (i = 0; i < table_cnt; i++) 739 if (symbol_in_range(&table[i], &percpu_range, 1)) { 740 /* 741 * Keep the 'A' override for percpu symbols to 742 * ensure consistent behavior compared to older 743 * versions of this tool. 744 */ 745 table[i].sym[0] = 'A'; 746 table[i].percpu_absolute = 1; 747 } 748 } 749 750 /* find the minimum non-absolute symbol address */ 751 static void record_relative_base(void) 752 { 753 unsigned int i; 754 755 relative_base = -1ULL; 756 for (i = 0; i < table_cnt; i++) 757 if (!symbol_absolute(&table[i]) && 758 table[i].addr < relative_base) 759 relative_base = table[i].addr; 760 } 761 762 int main(int argc, char **argv) 763 { 764 if (argc >= 2) { 765 int i; 766 for (i = 1; i < argc; i++) { 767 if(strcmp(argv[i], "--all-symbols") == 0) 768 all_symbols = 1; 769 else if (strcmp(argv[i], "--absolute-percpu") == 0) 770 absolute_percpu = 1; 771 else if (strncmp(argv[i], "--symbol-prefix=", 16) == 0) { 772 char *p = &argv[i][16]; 773 /* skip quote */ 774 if ((*p == '"' && *(p+2) == '"') || (*p == '\'' && *(p+2) == '\'')) 775 p++; 776 symbol_prefix_char = *p; 777 } else if (strcmp(argv[i], "--base-relative") == 0) 778 base_relative = 1; 779 else 780 usage(); 781 } 782 } else if (argc != 1) 783 usage(); 784 785 read_map(stdin); 786 if (absolute_percpu) 787 make_percpus_absolute(); 788 if (base_relative) 789 record_relative_base(); 790 sort_symbols(); 791 optimize_token_table(); 792 write_src(); 793 794 return 0; 795 } 796