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 if (strlen(str) > KSYM_NAME_LEN) { 119 fprintf(stderr, "Symbol %s too long for kallsyms (%zu vs %d).\n" 120 "Please increase KSYM_NAME_LEN both in kernel and kallsyms.c\n", 121 str, strlen(str), KSYM_NAME_LEN); 122 return -1; 123 } 124 125 sym = str; 126 /* skip prefix char */ 127 if (symbol_prefix_char && str[0] == symbol_prefix_char) 128 sym++; 129 130 /* Ignore most absolute/undefined (?) symbols. */ 131 if (strcmp(sym, "_text") == 0) 132 _text = s->addr; 133 else if (read_symbol_tr(sym, s->addr) == 0) 134 /* nothing to do */; 135 else if (toupper(stype) == 'A') 136 { 137 /* Keep these useful absolute symbols */ 138 if (strcmp(sym, "__kernel_syscall_via_break") && 139 strcmp(sym, "__kernel_syscall_via_epc") && 140 strcmp(sym, "__kernel_sigtramp") && 141 strcmp(sym, "__gp")) 142 return -1; 143 144 } 145 else if (toupper(stype) == 'U' || 146 is_arm_mapping_symbol(sym)) 147 return -1; 148 /* exclude also MIPS ELF local symbols ($L123 instead of .L123) */ 149 else if (str[0] == '$') 150 return -1; 151 /* exclude debugging symbols */ 152 else if (stype == 'N') 153 return -1; 154 155 /* include the type field in the symbol name, so that it gets 156 * compressed together */ 157 s->len = strlen(str) + 1; 158 s->sym = malloc(s->len + 1); 159 if (!s->sym) { 160 fprintf(stderr, "kallsyms failure: " 161 "unable to allocate required amount of memory\n"); 162 exit(EXIT_FAILURE); 163 } 164 strcpy((char *)s->sym + 1, str); 165 s->sym[0] = stype; 166 167 return 0; 168 } 169 170 static int symbol_valid_tr(struct sym_entry *s) 171 { 172 size_t i; 173 struct text_range *tr; 174 175 for (i = 0; i < ARRAY_SIZE(text_ranges); ++i) { 176 tr = &text_ranges[i]; 177 178 if (s->addr >= tr->start && s->addr <= tr->end) 179 return 1; 180 } 181 182 return 0; 183 } 184 185 static int symbol_valid(struct sym_entry *s) 186 { 187 /* Symbols which vary between passes. Passes 1 and 2 must have 188 * identical symbol lists. The kallsyms_* symbols below are only added 189 * after pass 1, they would be included in pass 2 when --all-symbols is 190 * specified so exclude them to get a stable symbol list. 191 */ 192 static char *special_symbols[] = { 193 "kallsyms_addresses", 194 "kallsyms_num_syms", 195 "kallsyms_names", 196 "kallsyms_markers", 197 "kallsyms_token_table", 198 "kallsyms_token_index", 199 200 /* Exclude linker generated symbols which vary between passes */ 201 "_SDA_BASE_", /* ppc */ 202 "_SDA2_BASE_", /* ppc */ 203 NULL }; 204 int i; 205 int offset = 1; 206 207 if (s->addr < kernel_start_addr) 208 return 0; 209 210 /* skip prefix char */ 211 if (symbol_prefix_char && *(s->sym + 1) == symbol_prefix_char) 212 offset++; 213 214 /* if --all-symbols is not specified, then symbols outside the text 215 * and inittext sections are discarded */ 216 if (!all_symbols) { 217 if (symbol_valid_tr(s) == 0) 218 return 0; 219 /* Corner case. Discard any symbols with the same value as 220 * _etext _einittext; they can move between pass 1 and 2 when 221 * the kallsyms data are added. If these symbols move then 222 * they may get dropped in pass 2, which breaks the kallsyms 223 * rules. 224 */ 225 if ((s->addr == text_range_text->end && 226 strcmp((char *)s->sym + offset, text_range_text->etext)) || 227 (s->addr == text_range_inittext->end && 228 strcmp((char *)s->sym + offset, text_range_inittext->etext))) 229 return 0; 230 } 231 232 /* Exclude symbols which vary between passes. */ 233 if (strstr((char *)s->sym + offset, "_compiled.")) 234 return 0; 235 236 for (i = 0; special_symbols[i]; i++) 237 if( strcmp((char *)s->sym + offset, special_symbols[i]) == 0 ) 238 return 0; 239 240 return 1; 241 } 242 243 static void read_map(FILE *in) 244 { 245 while (!feof(in)) { 246 if (table_cnt >= table_size) { 247 table_size += 10000; 248 table = realloc(table, sizeof(*table) * table_size); 249 if (!table) { 250 fprintf(stderr, "out of memory\n"); 251 exit (1); 252 } 253 } 254 if (read_symbol(in, &table[table_cnt]) == 0) { 255 table[table_cnt].start_pos = table_cnt; 256 table_cnt++; 257 } 258 } 259 } 260 261 static void output_label(char *label) 262 { 263 if (symbol_prefix_char) 264 printf(".globl %c%s\n", symbol_prefix_char, label); 265 else 266 printf(".globl %s\n", label); 267 printf("\tALGN\n"); 268 if (symbol_prefix_char) 269 printf("%c%s:\n", symbol_prefix_char, label); 270 else 271 printf("%s:\n", label); 272 } 273 274 /* uncompress a compressed symbol. When this function is called, the best table 275 * might still be compressed itself, so the function needs to be recursive */ 276 static int expand_symbol(unsigned char *data, int len, char *result) 277 { 278 int c, rlen, total=0; 279 280 while (len) { 281 c = *data; 282 /* if the table holds a single char that is the same as the one 283 * we are looking for, then end the search */ 284 if (best_table[c][0]==c && best_table_len[c]==1) { 285 *result++ = c; 286 total++; 287 } else { 288 /* if not, recurse and expand */ 289 rlen = expand_symbol(best_table[c], best_table_len[c], result); 290 total += rlen; 291 result += rlen; 292 } 293 data++; 294 len--; 295 } 296 *result=0; 297 298 return total; 299 } 300 301 static void write_src(void) 302 { 303 unsigned int i, k, off; 304 unsigned int best_idx[256]; 305 unsigned int *markers; 306 char buf[KSYM_NAME_LEN]; 307 308 printf("#include <asm/types.h>\n"); 309 printf("#if BITS_PER_LONG == 64\n"); 310 printf("#define PTR .quad\n"); 311 printf("#define ALGN .align 8\n"); 312 printf("#else\n"); 313 printf("#define PTR .long\n"); 314 printf("#define ALGN .align 4\n"); 315 printf("#endif\n"); 316 317 printf("\t.section .rodata, \"a\"\n"); 318 319 /* Provide proper symbols relocatability by their '_text' 320 * relativeness. The symbol names cannot be used to construct 321 * normal symbol references as the list of symbols contains 322 * symbols that are declared static and are private to their 323 * .o files. This prevents .tmp_kallsyms.o or any other 324 * object from referencing them. 325 */ 326 output_label("kallsyms_addresses"); 327 for (i = 0; i < table_cnt; i++) { 328 if (toupper(table[i].sym[0]) != 'A') { 329 if (_text <= table[i].addr) 330 printf("\tPTR\t_text + %#llx\n", 331 table[i].addr - _text); 332 else 333 printf("\tPTR\t_text - %#llx\n", 334 _text - table[i].addr); 335 } else { 336 printf("\tPTR\t%#llx\n", table[i].addr); 337 } 338 } 339 printf("\n"); 340 341 output_label("kallsyms_num_syms"); 342 printf("\tPTR\t%d\n", table_cnt); 343 printf("\n"); 344 345 /* table of offset markers, that give the offset in the compressed stream 346 * every 256 symbols */ 347 markers = malloc(sizeof(unsigned int) * ((table_cnt + 255) / 256)); 348 if (!markers) { 349 fprintf(stderr, "kallsyms failure: " 350 "unable to allocate required memory\n"); 351 exit(EXIT_FAILURE); 352 } 353 354 output_label("kallsyms_names"); 355 off = 0; 356 for (i = 0; i < table_cnt; i++) { 357 if ((i & 0xFF) == 0) 358 markers[i >> 8] = off; 359 360 printf("\t.byte 0x%02x", table[i].len); 361 for (k = 0; k < table[i].len; k++) 362 printf(", 0x%02x", table[i].sym[k]); 363 printf("\n"); 364 365 off += table[i].len + 1; 366 } 367 printf("\n"); 368 369 output_label("kallsyms_markers"); 370 for (i = 0; i < ((table_cnt + 255) >> 8); i++) 371 printf("\tPTR\t%d\n", markers[i]); 372 printf("\n"); 373 374 free(markers); 375 376 output_label("kallsyms_token_table"); 377 off = 0; 378 for (i = 0; i < 256; i++) { 379 best_idx[i] = off; 380 expand_symbol(best_table[i], best_table_len[i], buf); 381 printf("\t.asciz\t\"%s\"\n", buf); 382 off += strlen(buf) + 1; 383 } 384 printf("\n"); 385 386 output_label("kallsyms_token_index"); 387 for (i = 0; i < 256; i++) 388 printf("\t.short\t%d\n", best_idx[i]); 389 printf("\n"); 390 } 391 392 393 /* table lookup compression functions */ 394 395 /* count all the possible tokens in a symbol */ 396 static void learn_symbol(unsigned char *symbol, int len) 397 { 398 int i; 399 400 for (i = 0; i < len - 1; i++) 401 token_profit[ symbol[i] + (symbol[i + 1] << 8) ]++; 402 } 403 404 /* decrease the count for all the possible tokens in a symbol */ 405 static void forget_symbol(unsigned char *symbol, int len) 406 { 407 int i; 408 409 for (i = 0; i < len - 1; i++) 410 token_profit[ symbol[i] + (symbol[i + 1] << 8) ]--; 411 } 412 413 /* remove all the invalid symbols from the table and do the initial token count */ 414 static void build_initial_tok_table(void) 415 { 416 unsigned int i, pos; 417 418 pos = 0; 419 for (i = 0; i < table_cnt; i++) { 420 if ( symbol_valid(&table[i]) ) { 421 if (pos != i) 422 table[pos] = table[i]; 423 learn_symbol(table[pos].sym, table[pos].len); 424 pos++; 425 } 426 } 427 table_cnt = pos; 428 } 429 430 static void *find_token(unsigned char *str, int len, unsigned char *token) 431 { 432 int i; 433 434 for (i = 0; i < len - 1; i++) { 435 if (str[i] == token[0] && str[i+1] == token[1]) 436 return &str[i]; 437 } 438 return NULL; 439 } 440 441 /* replace a given token in all the valid symbols. Use the sampled symbols 442 * to update the counts */ 443 static void compress_symbols(unsigned char *str, int idx) 444 { 445 unsigned int i, len, size; 446 unsigned char *p1, *p2; 447 448 for (i = 0; i < table_cnt; i++) { 449 450 len = table[i].len; 451 p1 = table[i].sym; 452 453 /* find the token on the symbol */ 454 p2 = find_token(p1, len, str); 455 if (!p2) continue; 456 457 /* decrease the counts for this symbol's tokens */ 458 forget_symbol(table[i].sym, len); 459 460 size = len; 461 462 do { 463 *p2 = idx; 464 p2++; 465 size -= (p2 - p1); 466 memmove(p2, p2 + 1, size); 467 p1 = p2; 468 len--; 469 470 if (size < 2) break; 471 472 /* find the token on the symbol */ 473 p2 = find_token(p1, size, str); 474 475 } while (p2); 476 477 table[i].len = len; 478 479 /* increase the counts for this symbol's new tokens */ 480 learn_symbol(table[i].sym, len); 481 } 482 } 483 484 /* search the token with the maximum profit */ 485 static int find_best_token(void) 486 { 487 int i, best, bestprofit; 488 489 bestprofit=-10000; 490 best = 0; 491 492 for (i = 0; i < 0x10000; i++) { 493 if (token_profit[i] > bestprofit) { 494 best = i; 495 bestprofit = token_profit[i]; 496 } 497 } 498 return best; 499 } 500 501 /* this is the core of the algorithm: calculate the "best" table */ 502 static void optimize_result(void) 503 { 504 int i, best; 505 506 /* using the '\0' symbol last allows compress_symbols to use standard 507 * fast string functions */ 508 for (i = 255; i >= 0; i--) { 509 510 /* if this table slot is empty (it is not used by an actual 511 * original char code */ 512 if (!best_table_len[i]) { 513 514 /* find the token with the breates profit value */ 515 best = find_best_token(); 516 if (token_profit[best] == 0) 517 break; 518 519 /* place it in the "best" table */ 520 best_table_len[i] = 2; 521 best_table[i][0] = best & 0xFF; 522 best_table[i][1] = (best >> 8) & 0xFF; 523 524 /* replace this token in all the valid symbols */ 525 compress_symbols(best_table[i], i); 526 } 527 } 528 } 529 530 /* start by placing the symbols that are actually used on the table */ 531 static void insert_real_symbols_in_table(void) 532 { 533 unsigned int i, j, c; 534 535 memset(best_table, 0, sizeof(best_table)); 536 memset(best_table_len, 0, sizeof(best_table_len)); 537 538 for (i = 0; i < table_cnt; i++) { 539 for (j = 0; j < table[i].len; j++) { 540 c = table[i].sym[j]; 541 best_table[c][0]=c; 542 best_table_len[c]=1; 543 } 544 } 545 } 546 547 static void optimize_token_table(void) 548 { 549 build_initial_tok_table(); 550 551 insert_real_symbols_in_table(); 552 553 /* When valid symbol is not registered, exit to error */ 554 if (!table_cnt) { 555 fprintf(stderr, "No valid symbol.\n"); 556 exit(1); 557 } 558 559 optimize_result(); 560 } 561 562 /* guess for "linker script provide" symbol */ 563 static int may_be_linker_script_provide_symbol(const struct sym_entry *se) 564 { 565 const char *symbol = (char *)se->sym + 1; 566 int len = se->len - 1; 567 568 if (len < 8) 569 return 0; 570 571 if (symbol[0] != '_' || symbol[1] != '_') 572 return 0; 573 574 /* __start_XXXXX */ 575 if (!memcmp(symbol + 2, "start_", 6)) 576 return 1; 577 578 /* __stop_XXXXX */ 579 if (!memcmp(symbol + 2, "stop_", 5)) 580 return 1; 581 582 /* __end_XXXXX */ 583 if (!memcmp(symbol + 2, "end_", 4)) 584 return 1; 585 586 /* __XXXXX_start */ 587 if (!memcmp(symbol + len - 6, "_start", 6)) 588 return 1; 589 590 /* __XXXXX_end */ 591 if (!memcmp(symbol + len - 4, "_end", 4)) 592 return 1; 593 594 return 0; 595 } 596 597 static int prefix_underscores_count(const char *str) 598 { 599 const char *tail = str; 600 601 while (*tail == '_') 602 tail++; 603 604 return tail - str; 605 } 606 607 static int compare_symbols(const void *a, const void *b) 608 { 609 const struct sym_entry *sa; 610 const struct sym_entry *sb; 611 int wa, wb; 612 613 sa = a; 614 sb = b; 615 616 /* sort by address first */ 617 if (sa->addr > sb->addr) 618 return 1; 619 if (sa->addr < sb->addr) 620 return -1; 621 622 /* sort by "weakness" type */ 623 wa = (sa->sym[0] == 'w') || (sa->sym[0] == 'W'); 624 wb = (sb->sym[0] == 'w') || (sb->sym[0] == 'W'); 625 if (wa != wb) 626 return wa - wb; 627 628 /* sort by "linker script provide" type */ 629 wa = may_be_linker_script_provide_symbol(sa); 630 wb = may_be_linker_script_provide_symbol(sb); 631 if (wa != wb) 632 return wa - wb; 633 634 /* sort by the number of prefix underscores */ 635 wa = prefix_underscores_count((const char *)sa->sym + 1); 636 wb = prefix_underscores_count((const char *)sb->sym + 1); 637 if (wa != wb) 638 return wa - wb; 639 640 /* sort by initial order, so that other symbols are left undisturbed */ 641 return sa->start_pos - sb->start_pos; 642 } 643 644 static void sort_symbols(void) 645 { 646 qsort(table, table_cnt, sizeof(struct sym_entry), compare_symbols); 647 } 648 649 int main(int argc, char **argv) 650 { 651 if (argc >= 2) { 652 int i; 653 for (i = 1; i < argc; i++) { 654 if(strcmp(argv[i], "--all-symbols") == 0) 655 all_symbols = 1; 656 else if (strncmp(argv[i], "--symbol-prefix=", 16) == 0) { 657 char *p = &argv[i][16]; 658 /* skip quote */ 659 if ((*p == '"' && *(p+2) == '"') || (*p == '\'' && *(p+2) == '\'')) 660 p++; 661 symbol_prefix_char = *p; 662 } else if (strncmp(argv[i], "--page-offset=", 14) == 0) { 663 const char *p = &argv[i][14]; 664 kernel_start_addr = strtoull(p, NULL, 16); 665 } else 666 usage(); 667 } 668 } else if (argc != 1) 669 usage(); 670 671 read_map(stdin); 672 sort_symbols(); 673 optimize_token_table(); 674 write_src(); 675 676 return 0; 677 } 678