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