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 unsigned long long kernel_start_addr = 0; 67 static int base_relative = 0; 68 69 int token_profit[0x10000]; 70 71 /* the table that holds the result of the compression */ 72 unsigned char best_table[256][2]; 73 unsigned char best_table_len[256]; 74 75 76 static void usage(void) 77 { 78 fprintf(stderr, "Usage: kallsyms [--all-symbols] " 79 "[--symbol-prefix=<prefix char>] " 80 "[--page-offset=<CONFIG_PAGE_OFFSET>] " 81 "[--base-relative] < in.map > out.S\n"); 82 exit(1); 83 } 84 85 /* 86 * This ignores the intensely annoying "mapping symbols" found 87 * in ARM ELF files: $a, $t and $d. 88 */ 89 static inline int is_arm_mapping_symbol(const char *str) 90 { 91 return str[0] == '$' && strchr("axtd", str[1]) 92 && (str[2] == '\0' || str[2] == '.'); 93 } 94 95 static int check_symbol_range(const char *sym, unsigned long long addr, 96 struct addr_range *ranges, int entries) 97 { 98 size_t i; 99 struct addr_range *ar; 100 101 for (i = 0; i < entries; ++i) { 102 ar = &ranges[i]; 103 104 if (strcmp(sym, ar->start_sym) == 0) { 105 ar->start = addr; 106 return 0; 107 } else if (strcmp(sym, ar->end_sym) == 0) { 108 ar->end = addr; 109 return 0; 110 } 111 } 112 113 return 1; 114 } 115 116 static int read_symbol(FILE *in, struct sym_entry *s) 117 { 118 char str[500]; 119 char *sym, stype; 120 int rc; 121 122 rc = fscanf(in, "%llx %c %499s\n", &s->addr, &stype, str); 123 if (rc != 3) { 124 if (rc != EOF && fgets(str, 500, in) == NULL) 125 fprintf(stderr, "Read error or end of file.\n"); 126 return -1; 127 } 128 if (strlen(str) > KSYM_NAME_LEN) { 129 fprintf(stderr, "Symbol %s too long for kallsyms (%zu vs %d).\n" 130 "Please increase KSYM_NAME_LEN both in kernel and kallsyms.c\n", 131 str, strlen(str), KSYM_NAME_LEN); 132 return -1; 133 } 134 135 sym = str; 136 /* skip prefix char */ 137 if (symbol_prefix_char && str[0] == symbol_prefix_char) 138 sym++; 139 140 /* Ignore most absolute/undefined (?) symbols. */ 141 if (strcmp(sym, "_text") == 0) 142 _text = s->addr; 143 else if (check_symbol_range(sym, s->addr, text_ranges, 144 ARRAY_SIZE(text_ranges)) == 0) 145 /* nothing to do */; 146 else if (toupper(stype) == 'A') 147 { 148 /* Keep these useful absolute symbols */ 149 if (strcmp(sym, "__kernel_syscall_via_break") && 150 strcmp(sym, "__kernel_syscall_via_epc") && 151 strcmp(sym, "__kernel_sigtramp") && 152 strcmp(sym, "__gp")) 153 return -1; 154 155 } 156 else if (toupper(stype) == 'U' || 157 is_arm_mapping_symbol(sym)) 158 return -1; 159 /* exclude also MIPS ELF local symbols ($L123 instead of .L123) */ 160 else if (str[0] == '$') 161 return -1; 162 /* exclude debugging symbols */ 163 else if (stype == 'N') 164 return -1; 165 166 /* include the type field in the symbol name, so that it gets 167 * compressed together */ 168 s->len = strlen(str) + 1; 169 s->sym = malloc(s->len + 1); 170 if (!s->sym) { 171 fprintf(stderr, "kallsyms failure: " 172 "unable to allocate required amount of memory\n"); 173 exit(EXIT_FAILURE); 174 } 175 strcpy((char *)s->sym + 1, str); 176 s->sym[0] = stype; 177 178 s->percpu_absolute = 0; 179 180 /* Record if we've found __per_cpu_start/end. */ 181 check_symbol_range(sym, s->addr, &percpu_range, 1); 182 183 return 0; 184 } 185 186 static int symbol_in_range(struct sym_entry *s, struct addr_range *ranges, 187 int entries) 188 { 189 size_t i; 190 struct addr_range *ar; 191 192 for (i = 0; i < entries; ++i) { 193 ar = &ranges[i]; 194 195 if (s->addr >= ar->start && s->addr <= ar->end) 196 return 1; 197 } 198 199 return 0; 200 } 201 202 static int symbol_valid(struct sym_entry *s) 203 { 204 /* Symbols which vary between passes. Passes 1 and 2 must have 205 * identical symbol lists. The kallsyms_* symbols below are only added 206 * after pass 1, they would be included in pass 2 when --all-symbols is 207 * specified so exclude them to get a stable symbol list. 208 */ 209 static char *special_symbols[] = { 210 "kallsyms_addresses", 211 "kallsyms_offsets", 212 "kallsyms_relative_base", 213 "kallsyms_num_syms", 214 "kallsyms_names", 215 "kallsyms_markers", 216 "kallsyms_token_table", 217 "kallsyms_token_index", 218 219 /* Exclude linker generated symbols which vary between passes */ 220 "_SDA_BASE_", /* ppc */ 221 "_SDA2_BASE_", /* ppc */ 222 NULL }; 223 224 static char *special_suffixes[] = { 225 "_veneer", /* arm */ 226 NULL }; 227 228 int i; 229 char *sym_name = (char *)s->sym + 1; 230 231 232 if (s->addr < kernel_start_addr) 233 return 0; 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_suffixes[i]; i++) { 267 int l = strlen(sym_name) - strlen(special_suffixes[i]); 268 269 if (l >= 0 && strcmp(sym_name + l, special_suffixes[i]) == 0) 270 return 0; 271 } 272 273 return 1; 274 } 275 276 static void read_map(FILE *in) 277 { 278 while (!feof(in)) { 279 if (table_cnt >= table_size) { 280 table_size += 10000; 281 table = realloc(table, sizeof(*table) * table_size); 282 if (!table) { 283 fprintf(stderr, "out of memory\n"); 284 exit (1); 285 } 286 } 287 if (read_symbol(in, &table[table_cnt]) == 0) { 288 table[table_cnt].start_pos = table_cnt; 289 table_cnt++; 290 } 291 } 292 } 293 294 static void output_label(char *label) 295 { 296 if (symbol_prefix_char) 297 printf(".globl %c%s\n", symbol_prefix_char, label); 298 else 299 printf(".globl %s\n", label); 300 printf("\tALGN\n"); 301 if (symbol_prefix_char) 302 printf("%c%s:\n", symbol_prefix_char, label); 303 else 304 printf("%s:\n", label); 305 } 306 307 /* uncompress a compressed symbol. When this function is called, the best table 308 * might still be compressed itself, so the function needs to be recursive */ 309 static int expand_symbol(unsigned char *data, int len, char *result) 310 { 311 int c, rlen, total=0; 312 313 while (len) { 314 c = *data; 315 /* if the table holds a single char that is the same as the one 316 * we are looking for, then end the search */ 317 if (best_table[c][0]==c && best_table_len[c]==1) { 318 *result++ = c; 319 total++; 320 } else { 321 /* if not, recurse and expand */ 322 rlen = expand_symbol(best_table[c], best_table_len[c], result); 323 total += rlen; 324 result += rlen; 325 } 326 data++; 327 len--; 328 } 329 *result=0; 330 331 return total; 332 } 333 334 static int symbol_absolute(struct sym_entry *s) 335 { 336 return s->percpu_absolute; 337 } 338 339 static void write_src(void) 340 { 341 unsigned int i, k, off; 342 unsigned int best_idx[256]; 343 unsigned int *markers; 344 char buf[KSYM_NAME_LEN]; 345 346 printf("#include <asm/types.h>\n"); 347 printf("#if BITS_PER_LONG == 64\n"); 348 printf("#define PTR .quad\n"); 349 printf("#define ALGN .align 8\n"); 350 printf("#else\n"); 351 printf("#define PTR .long\n"); 352 printf("#define ALGN .align 4\n"); 353 printf("#endif\n"); 354 355 printf("\t.section .rodata, \"a\"\n"); 356 357 /* Provide proper symbols relocatability by their relativeness 358 * to a fixed anchor point in the runtime image, either '_text' 359 * for absolute address tables, in which case the linker will 360 * emit the final addresses at build time. Otherwise, use the 361 * offset relative to the lowest value encountered of all relative 362 * symbols, and emit non-relocatable fixed offsets that will be fixed 363 * up at runtime. 364 * 365 * The symbol names cannot be used to construct normal symbol 366 * references as the list of symbols contains symbols that are 367 * declared static and are private to their .o files. This prevents 368 * .tmp_kallsyms.o or any other object from referencing them. 369 */ 370 if (!base_relative) 371 output_label("kallsyms_addresses"); 372 else 373 output_label("kallsyms_offsets"); 374 375 for (i = 0; i < table_cnt; i++) { 376 if (base_relative) { 377 long long offset; 378 int overflow; 379 380 if (!absolute_percpu) { 381 offset = table[i].addr - relative_base; 382 overflow = (offset < 0 || offset > UINT_MAX); 383 } else if (symbol_absolute(&table[i])) { 384 offset = table[i].addr; 385 overflow = (offset < 0 || offset > INT_MAX); 386 } else { 387 offset = relative_base - table[i].addr - 1; 388 overflow = (offset < INT_MIN || offset >= 0); 389 } 390 if (overflow) { 391 fprintf(stderr, "kallsyms failure: " 392 "%s symbol value %#llx out of range in relative mode\n", 393 symbol_absolute(&table[i]) ? "absolute" : "relative", 394 table[i].addr); 395 exit(EXIT_FAILURE); 396 } 397 printf("\t.long\t%#x\n", (int)offset); 398 } else if (!symbol_absolute(&table[i])) { 399 if (_text <= table[i].addr) 400 printf("\tPTR\t_text + %#llx\n", 401 table[i].addr - _text); 402 else 403 printf("\tPTR\t_text - %#llx\n", 404 _text - table[i].addr); 405 } else { 406 printf("\tPTR\t%#llx\n", table[i].addr); 407 } 408 } 409 printf("\n"); 410 411 if (base_relative) { 412 output_label("kallsyms_relative_base"); 413 printf("\tPTR\t_text - %#llx\n", _text - relative_base); 414 printf("\n"); 415 } 416 417 output_label("kallsyms_num_syms"); 418 printf("\tPTR\t%d\n", table_cnt); 419 printf("\n"); 420 421 /* table of offset markers, that give the offset in the compressed stream 422 * every 256 symbols */ 423 markers = malloc(sizeof(unsigned int) * ((table_cnt + 255) / 256)); 424 if (!markers) { 425 fprintf(stderr, "kallsyms failure: " 426 "unable to allocate required memory\n"); 427 exit(EXIT_FAILURE); 428 } 429 430 output_label("kallsyms_names"); 431 off = 0; 432 for (i = 0; i < table_cnt; i++) { 433 if ((i & 0xFF) == 0) 434 markers[i >> 8] = off; 435 436 printf("\t.byte 0x%02x", table[i].len); 437 for (k = 0; k < table[i].len; k++) 438 printf(", 0x%02x", table[i].sym[k]); 439 printf("\n"); 440 441 off += table[i].len + 1; 442 } 443 printf("\n"); 444 445 output_label("kallsyms_markers"); 446 for (i = 0; i < ((table_cnt + 255) >> 8); i++) 447 printf("\tPTR\t%d\n", markers[i]); 448 printf("\n"); 449 450 free(markers); 451 452 output_label("kallsyms_token_table"); 453 off = 0; 454 for (i = 0; i < 256; i++) { 455 best_idx[i] = off; 456 expand_symbol(best_table[i], best_table_len[i], buf); 457 printf("\t.asciz\t\"%s\"\n", buf); 458 off += strlen(buf) + 1; 459 } 460 printf("\n"); 461 462 output_label("kallsyms_token_index"); 463 for (i = 0; i < 256; i++) 464 printf("\t.short\t%d\n", best_idx[i]); 465 printf("\n"); 466 } 467 468 469 /* table lookup compression functions */ 470 471 /* count all the possible tokens in a symbol */ 472 static void learn_symbol(unsigned char *symbol, int len) 473 { 474 int i; 475 476 for (i = 0; i < len - 1; i++) 477 token_profit[ symbol[i] + (symbol[i + 1] << 8) ]++; 478 } 479 480 /* decrease the count for all the possible tokens in a symbol */ 481 static void forget_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 /* remove all the invalid symbols from the table and do the initial token count */ 490 static void build_initial_tok_table(void) 491 { 492 unsigned int i, pos; 493 494 pos = 0; 495 for (i = 0; i < table_cnt; i++) { 496 if ( symbol_valid(&table[i]) ) { 497 if (pos != i) 498 table[pos] = table[i]; 499 learn_symbol(table[pos].sym, table[pos].len); 500 pos++; 501 } 502 } 503 table_cnt = pos; 504 } 505 506 static void *find_token(unsigned char *str, int len, unsigned char *token) 507 { 508 int i; 509 510 for (i = 0; i < len - 1; i++) { 511 if (str[i] == token[0] && str[i+1] == token[1]) 512 return &str[i]; 513 } 514 return NULL; 515 } 516 517 /* replace a given token in all the valid symbols. Use the sampled symbols 518 * to update the counts */ 519 static void compress_symbols(unsigned char *str, int idx) 520 { 521 unsigned int i, len, size; 522 unsigned char *p1, *p2; 523 524 for (i = 0; i < table_cnt; i++) { 525 526 len = table[i].len; 527 p1 = table[i].sym; 528 529 /* find the token on the symbol */ 530 p2 = find_token(p1, len, str); 531 if (!p2) continue; 532 533 /* decrease the counts for this symbol's tokens */ 534 forget_symbol(table[i].sym, len); 535 536 size = len; 537 538 do { 539 *p2 = idx; 540 p2++; 541 size -= (p2 - p1); 542 memmove(p2, p2 + 1, size); 543 p1 = p2; 544 len--; 545 546 if (size < 2) break; 547 548 /* find the token on the symbol */ 549 p2 = find_token(p1, size, str); 550 551 } while (p2); 552 553 table[i].len = len; 554 555 /* increase the counts for this symbol's new tokens */ 556 learn_symbol(table[i].sym, len); 557 } 558 } 559 560 /* search the token with the maximum profit */ 561 static int find_best_token(void) 562 { 563 int i, best, bestprofit; 564 565 bestprofit=-10000; 566 best = 0; 567 568 for (i = 0; i < 0x10000; i++) { 569 if (token_profit[i] > bestprofit) { 570 best = i; 571 bestprofit = token_profit[i]; 572 } 573 } 574 return best; 575 } 576 577 /* this is the core of the algorithm: calculate the "best" table */ 578 static void optimize_result(void) 579 { 580 int i, best; 581 582 /* using the '\0' symbol last allows compress_symbols to use standard 583 * fast string functions */ 584 for (i = 255; i >= 0; i--) { 585 586 /* if this table slot is empty (it is not used by an actual 587 * original char code */ 588 if (!best_table_len[i]) { 589 590 /* find the token with the breates profit value */ 591 best = find_best_token(); 592 if (token_profit[best] == 0) 593 break; 594 595 /* place it in the "best" table */ 596 best_table_len[i] = 2; 597 best_table[i][0] = best & 0xFF; 598 best_table[i][1] = (best >> 8) & 0xFF; 599 600 /* replace this token in all the valid symbols */ 601 compress_symbols(best_table[i], i); 602 } 603 } 604 } 605 606 /* start by placing the symbols that are actually used on the table */ 607 static void insert_real_symbols_in_table(void) 608 { 609 unsigned int i, j, c; 610 611 memset(best_table, 0, sizeof(best_table)); 612 memset(best_table_len, 0, sizeof(best_table_len)); 613 614 for (i = 0; i < table_cnt; i++) { 615 for (j = 0; j < table[i].len; j++) { 616 c = table[i].sym[j]; 617 best_table[c][0]=c; 618 best_table_len[c]=1; 619 } 620 } 621 } 622 623 static void optimize_token_table(void) 624 { 625 build_initial_tok_table(); 626 627 insert_real_symbols_in_table(); 628 629 /* When valid symbol is not registered, exit to error */ 630 if (!table_cnt) { 631 fprintf(stderr, "No valid symbol.\n"); 632 exit(1); 633 } 634 635 optimize_result(); 636 } 637 638 /* guess for "linker script provide" symbol */ 639 static int may_be_linker_script_provide_symbol(const struct sym_entry *se) 640 { 641 const char *symbol = (char *)se->sym + 1; 642 int len = se->len - 1; 643 644 if (len < 8) 645 return 0; 646 647 if (symbol[0] != '_' || symbol[1] != '_') 648 return 0; 649 650 /* __start_XXXXX */ 651 if (!memcmp(symbol + 2, "start_", 6)) 652 return 1; 653 654 /* __stop_XXXXX */ 655 if (!memcmp(symbol + 2, "stop_", 5)) 656 return 1; 657 658 /* __end_XXXXX */ 659 if (!memcmp(symbol + 2, "end_", 4)) 660 return 1; 661 662 /* __XXXXX_start */ 663 if (!memcmp(symbol + len - 6, "_start", 6)) 664 return 1; 665 666 /* __XXXXX_end */ 667 if (!memcmp(symbol + len - 4, "_end", 4)) 668 return 1; 669 670 return 0; 671 } 672 673 static int prefix_underscores_count(const char *str) 674 { 675 const char *tail = str; 676 677 while (*tail == '_') 678 tail++; 679 680 return tail - str; 681 } 682 683 static int compare_symbols(const void *a, const void *b) 684 { 685 const struct sym_entry *sa; 686 const struct sym_entry *sb; 687 int wa, wb; 688 689 sa = a; 690 sb = b; 691 692 /* sort by address first */ 693 if (sa->addr > sb->addr) 694 return 1; 695 if (sa->addr < sb->addr) 696 return -1; 697 698 /* sort by "weakness" type */ 699 wa = (sa->sym[0] == 'w') || (sa->sym[0] == 'W'); 700 wb = (sb->sym[0] == 'w') || (sb->sym[0] == 'W'); 701 if (wa != wb) 702 return wa - wb; 703 704 /* sort by "linker script provide" type */ 705 wa = may_be_linker_script_provide_symbol(sa); 706 wb = may_be_linker_script_provide_symbol(sb); 707 if (wa != wb) 708 return wa - wb; 709 710 /* sort by the number of prefix underscores */ 711 wa = prefix_underscores_count((const char *)sa->sym + 1); 712 wb = prefix_underscores_count((const char *)sb->sym + 1); 713 if (wa != wb) 714 return wa - wb; 715 716 /* sort by initial order, so that other symbols are left undisturbed */ 717 return sa->start_pos - sb->start_pos; 718 } 719 720 static void sort_symbols(void) 721 { 722 qsort(table, table_cnt, sizeof(struct sym_entry), compare_symbols); 723 } 724 725 static void make_percpus_absolute(void) 726 { 727 unsigned int i; 728 729 for (i = 0; i < table_cnt; i++) 730 if (symbol_in_range(&table[i], &percpu_range, 1)) { 731 /* 732 * Keep the 'A' override for percpu symbols to 733 * ensure consistent behavior compared to older 734 * versions of this tool. 735 */ 736 table[i].sym[0] = 'A'; 737 table[i].percpu_absolute = 1; 738 } 739 } 740 741 /* find the minimum non-absolute symbol address */ 742 static void record_relative_base(void) 743 { 744 unsigned int i; 745 746 relative_base = -1ULL; 747 for (i = 0; i < table_cnt; i++) 748 if (!symbol_absolute(&table[i]) && 749 table[i].addr < relative_base) 750 relative_base = table[i].addr; 751 } 752 753 int main(int argc, char **argv) 754 { 755 if (argc >= 2) { 756 int i; 757 for (i = 1; i < argc; i++) { 758 if(strcmp(argv[i], "--all-symbols") == 0) 759 all_symbols = 1; 760 else if (strcmp(argv[i], "--absolute-percpu") == 0) 761 absolute_percpu = 1; 762 else if (strncmp(argv[i], "--symbol-prefix=", 16) == 0) { 763 char *p = &argv[i][16]; 764 /* skip quote */ 765 if ((*p == '"' && *(p+2) == '"') || (*p == '\'' && *(p+2) == '\'')) 766 p++; 767 symbol_prefix_char = *p; 768 } else if (strncmp(argv[i], "--page-offset=", 14) == 0) { 769 const char *p = &argv[i][14]; 770 kernel_start_addr = strtoull(p, NULL, 16); 771 } else if (strcmp(argv[i], "--base-relative") == 0) 772 base_relative = 1; 773 else 774 usage(); 775 } 776 } else if (argc != 1) 777 usage(); 778 779 read_map(stdin); 780 if (absolute_percpu) 781 make_percpus_absolute(); 782 if (base_relative) 783 record_relative_base(); 784 sort_symbols(); 785 optimize_token_table(); 786 write_src(); 787 788 return 0; 789 } 790