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 59 int token_profit[0x10000]; 60 61 /* the table that holds the result of the compression */ 62 unsigned char best_table[256][2]; 63 unsigned char best_table_len[256]; 64 65 66 static void usage(void) 67 { 68 fprintf(stderr, "Usage: kallsyms [--all-symbols] [--symbol-prefix=<prefix char>] < in.map > out.S\n"); 69 exit(1); 70 } 71 72 /* 73 * This ignores the intensely annoying "mapping symbols" found 74 * in ARM ELF files: $a, $t and $d. 75 */ 76 static inline int is_arm_mapping_symbol(const char *str) 77 { 78 return str[0] == '$' && strchr("atd", str[1]) 79 && (str[2] == '\0' || str[2] == '.'); 80 } 81 82 static int read_symbol_tr(const char *sym, unsigned long long addr) 83 { 84 size_t i; 85 struct text_range *tr; 86 87 for (i = 0; i < ARRAY_SIZE(text_ranges); ++i) { 88 tr = &text_ranges[i]; 89 90 if (strcmp(sym, tr->stext) == 0) { 91 tr->start = addr; 92 return 0; 93 } else if (strcmp(sym, tr->etext) == 0) { 94 tr->end = addr; 95 return 0; 96 } 97 } 98 99 return 1; 100 } 101 102 static int read_symbol(FILE *in, struct sym_entry *s) 103 { 104 char str[500]; 105 char *sym, stype; 106 int rc; 107 108 rc = fscanf(in, "%llx %c %499s\n", &s->addr, &stype, str); 109 if (rc != 3) { 110 if (rc != EOF && fgets(str, 500, in) == NULL) 111 fprintf(stderr, "Read error or end of file.\n"); 112 return -1; 113 } 114 115 sym = str; 116 /* skip prefix char */ 117 if (symbol_prefix_char && str[0] == symbol_prefix_char) 118 sym++; 119 120 /* Ignore most absolute/undefined (?) symbols. */ 121 if (strcmp(sym, "_text") == 0) 122 _text = s->addr; 123 else if (read_symbol_tr(sym, s->addr) == 0) 124 /* nothing to do */; 125 else if (toupper(stype) == 'A') 126 { 127 /* Keep these useful absolute symbols */ 128 if (strcmp(sym, "__kernel_syscall_via_break") && 129 strcmp(sym, "__kernel_syscall_via_epc") && 130 strcmp(sym, "__kernel_sigtramp") && 131 strcmp(sym, "__gp")) 132 return -1; 133 134 } 135 else if (toupper(stype) == 'U' || 136 is_arm_mapping_symbol(sym)) 137 return -1; 138 /* exclude also MIPS ELF local symbols ($L123 instead of .L123) */ 139 else if (str[0] == '$') 140 return -1; 141 /* exclude debugging symbols */ 142 else if (stype == 'N') 143 return -1; 144 145 /* include the type field in the symbol name, so that it gets 146 * compressed together */ 147 s->len = strlen(str) + 1; 148 s->sym = malloc(s->len + 1); 149 if (!s->sym) { 150 fprintf(stderr, "kallsyms failure: " 151 "unable to allocate required amount of memory\n"); 152 exit(EXIT_FAILURE); 153 } 154 strcpy((char *)s->sym + 1, str); 155 s->sym[0] = stype; 156 157 return 0; 158 } 159 160 static int symbol_valid_tr(struct sym_entry *s) 161 { 162 size_t i; 163 struct text_range *tr; 164 165 for (i = 0; i < ARRAY_SIZE(text_ranges); ++i) { 166 tr = &text_ranges[i]; 167 168 if (s->addr >= tr->start && s->addr <= tr->end) 169 return 1; 170 } 171 172 return 0; 173 } 174 175 static int symbol_valid(struct sym_entry *s) 176 { 177 /* Symbols which vary between passes. Passes 1 and 2 must have 178 * identical symbol lists. The kallsyms_* symbols below are only added 179 * after pass 1, they would be included in pass 2 when --all-symbols is 180 * specified so exclude them to get a stable symbol list. 181 */ 182 static char *special_symbols[] = { 183 "kallsyms_addresses", 184 "kallsyms_num_syms", 185 "kallsyms_names", 186 "kallsyms_markers", 187 "kallsyms_token_table", 188 "kallsyms_token_index", 189 190 /* Exclude linker generated symbols which vary between passes */ 191 "_SDA_BASE_", /* ppc */ 192 "_SDA2_BASE_", /* ppc */ 193 NULL }; 194 int i; 195 int offset = 1; 196 197 /* skip prefix char */ 198 if (symbol_prefix_char && *(s->sym + 1) == symbol_prefix_char) 199 offset++; 200 201 /* if --all-symbols is not specified, then symbols outside the text 202 * and inittext sections are discarded */ 203 if (!all_symbols) { 204 if (symbol_valid_tr(s) == 0) 205 return 0; 206 /* Corner case. Discard any symbols with the same value as 207 * _etext _einittext; they can move between pass 1 and 2 when 208 * the kallsyms data are added. If these symbols move then 209 * they may get dropped in pass 2, which breaks the kallsyms 210 * rules. 211 */ 212 if ((s->addr == text_range_text->end && 213 strcmp((char *)s->sym + offset, text_range_text->etext)) || 214 (s->addr == text_range_inittext->end && 215 strcmp((char *)s->sym + offset, text_range_inittext->etext))) 216 return 0; 217 } 218 219 /* Exclude symbols which vary between passes. */ 220 if (strstr((char *)s->sym + offset, "_compiled.")) 221 return 0; 222 223 for (i = 0; special_symbols[i]; i++) 224 if( strcmp((char *)s->sym + offset, special_symbols[i]) == 0 ) 225 return 0; 226 227 return 1; 228 } 229 230 static void read_map(FILE *in) 231 { 232 while (!feof(in)) { 233 if (table_cnt >= table_size) { 234 table_size += 10000; 235 table = realloc(table, sizeof(*table) * table_size); 236 if (!table) { 237 fprintf(stderr, "out of memory\n"); 238 exit (1); 239 } 240 } 241 if (read_symbol(in, &table[table_cnt]) == 0) { 242 table[table_cnt].start_pos = table_cnt; 243 table_cnt++; 244 } 245 } 246 } 247 248 static void output_label(char *label) 249 { 250 if (symbol_prefix_char) 251 printf(".globl %c%s\n", symbol_prefix_char, label); 252 else 253 printf(".globl %s\n", label); 254 printf("\tALGN\n"); 255 if (symbol_prefix_char) 256 printf("%c%s:\n", symbol_prefix_char, label); 257 else 258 printf("%s:\n", label); 259 } 260 261 /* uncompress a compressed symbol. When this function is called, the best table 262 * might still be compressed itself, so the function needs to be recursive */ 263 static int expand_symbol(unsigned char *data, int len, char *result) 264 { 265 int c, rlen, total=0; 266 267 while (len) { 268 c = *data; 269 /* if the table holds a single char that is the same as the one 270 * we are looking for, then end the search */ 271 if (best_table[c][0]==c && best_table_len[c]==1) { 272 *result++ = c; 273 total++; 274 } else { 275 /* if not, recurse and expand */ 276 rlen = expand_symbol(best_table[c], best_table_len[c], result); 277 total += rlen; 278 result += rlen; 279 } 280 data++; 281 len--; 282 } 283 *result=0; 284 285 return total; 286 } 287 288 static void write_src(void) 289 { 290 unsigned int i, k, off; 291 unsigned int best_idx[256]; 292 unsigned int *markers; 293 char buf[KSYM_NAME_LEN]; 294 295 printf("#include <asm/types.h>\n"); 296 printf("#if BITS_PER_LONG == 64\n"); 297 printf("#define PTR .quad\n"); 298 printf("#define ALGN .align 8\n"); 299 printf("#else\n"); 300 printf("#define PTR .long\n"); 301 printf("#define ALGN .align 4\n"); 302 printf("#endif\n"); 303 304 printf("\t.section .rodata, \"a\"\n"); 305 306 /* Provide proper symbols relocatability by their '_text' 307 * relativeness. The symbol names cannot be used to construct 308 * normal symbol references as the list of symbols contains 309 * symbols that are declared static and are private to their 310 * .o files. This prevents .tmp_kallsyms.o or any other 311 * object from referencing them. 312 */ 313 output_label("kallsyms_addresses"); 314 for (i = 0; i < table_cnt; i++) { 315 if (toupper(table[i].sym[0]) != 'A') { 316 if (_text <= table[i].addr) 317 printf("\tPTR\t_text + %#llx\n", 318 table[i].addr - _text); 319 else 320 printf("\tPTR\t_text - %#llx\n", 321 _text - table[i].addr); 322 } else { 323 printf("\tPTR\t%#llx\n", table[i].addr); 324 } 325 } 326 printf("\n"); 327 328 output_label("kallsyms_num_syms"); 329 printf("\tPTR\t%d\n", table_cnt); 330 printf("\n"); 331 332 /* table of offset markers, that give the offset in the compressed stream 333 * every 256 symbols */ 334 markers = malloc(sizeof(unsigned int) * ((table_cnt + 255) / 256)); 335 if (!markers) { 336 fprintf(stderr, "kallsyms failure: " 337 "unable to allocate required memory\n"); 338 exit(EXIT_FAILURE); 339 } 340 341 output_label("kallsyms_names"); 342 off = 0; 343 for (i = 0; i < table_cnt; i++) { 344 if ((i & 0xFF) == 0) 345 markers[i >> 8] = off; 346 347 printf("\t.byte 0x%02x", table[i].len); 348 for (k = 0; k < table[i].len; k++) 349 printf(", 0x%02x", table[i].sym[k]); 350 printf("\n"); 351 352 off += table[i].len + 1; 353 } 354 printf("\n"); 355 356 output_label("kallsyms_markers"); 357 for (i = 0; i < ((table_cnt + 255) >> 8); i++) 358 printf("\tPTR\t%d\n", markers[i]); 359 printf("\n"); 360 361 free(markers); 362 363 output_label("kallsyms_token_table"); 364 off = 0; 365 for (i = 0; i < 256; i++) { 366 best_idx[i] = off; 367 expand_symbol(best_table[i], best_table_len[i], buf); 368 printf("\t.asciz\t\"%s\"\n", buf); 369 off += strlen(buf) + 1; 370 } 371 printf("\n"); 372 373 output_label("kallsyms_token_index"); 374 for (i = 0; i < 256; i++) 375 printf("\t.short\t%d\n", best_idx[i]); 376 printf("\n"); 377 } 378 379 380 /* table lookup compression functions */ 381 382 /* count all the possible tokens in a symbol */ 383 static void learn_symbol(unsigned char *symbol, int len) 384 { 385 int i; 386 387 for (i = 0; i < len - 1; i++) 388 token_profit[ symbol[i] + (symbol[i + 1] << 8) ]++; 389 } 390 391 /* decrease the count for all the possible tokens in a symbol */ 392 static void forget_symbol(unsigned char *symbol, int len) 393 { 394 int i; 395 396 for (i = 0; i < len - 1; i++) 397 token_profit[ symbol[i] + (symbol[i + 1] << 8) ]--; 398 } 399 400 /* remove all the invalid symbols from the table and do the initial token count */ 401 static void build_initial_tok_table(void) 402 { 403 unsigned int i, pos; 404 405 pos = 0; 406 for (i = 0; i < table_cnt; i++) { 407 if ( symbol_valid(&table[i]) ) { 408 if (pos != i) 409 table[pos] = table[i]; 410 learn_symbol(table[pos].sym, table[pos].len); 411 pos++; 412 } 413 } 414 table_cnt = pos; 415 } 416 417 static void *find_token(unsigned char *str, int len, unsigned char *token) 418 { 419 int i; 420 421 for (i = 0; i < len - 1; i++) { 422 if (str[i] == token[0] && str[i+1] == token[1]) 423 return &str[i]; 424 } 425 return NULL; 426 } 427 428 /* replace a given token in all the valid symbols. Use the sampled symbols 429 * to update the counts */ 430 static void compress_symbols(unsigned char *str, int idx) 431 { 432 unsigned int i, len, size; 433 unsigned char *p1, *p2; 434 435 for (i = 0; i < table_cnt; i++) { 436 437 len = table[i].len; 438 p1 = table[i].sym; 439 440 /* find the token on the symbol */ 441 p2 = find_token(p1, len, str); 442 if (!p2) continue; 443 444 /* decrease the counts for this symbol's tokens */ 445 forget_symbol(table[i].sym, len); 446 447 size = len; 448 449 do { 450 *p2 = idx; 451 p2++; 452 size -= (p2 - p1); 453 memmove(p2, p2 + 1, size); 454 p1 = p2; 455 len--; 456 457 if (size < 2) break; 458 459 /* find the token on the symbol */ 460 p2 = find_token(p1, size, str); 461 462 } while (p2); 463 464 table[i].len = len; 465 466 /* increase the counts for this symbol's new tokens */ 467 learn_symbol(table[i].sym, len); 468 } 469 } 470 471 /* search the token with the maximum profit */ 472 static int find_best_token(void) 473 { 474 int i, best, bestprofit; 475 476 bestprofit=-10000; 477 best = 0; 478 479 for (i = 0; i < 0x10000; i++) { 480 if (token_profit[i] > bestprofit) { 481 best = i; 482 bestprofit = token_profit[i]; 483 } 484 } 485 return best; 486 } 487 488 /* this is the core of the algorithm: calculate the "best" table */ 489 static void optimize_result(void) 490 { 491 int i, best; 492 493 /* using the '\0' symbol last allows compress_symbols to use standard 494 * fast string functions */ 495 for (i = 255; i >= 0; i--) { 496 497 /* if this table slot is empty (it is not used by an actual 498 * original char code */ 499 if (!best_table_len[i]) { 500 501 /* find the token with the breates profit value */ 502 best = find_best_token(); 503 if (token_profit[best] == 0) 504 break; 505 506 /* place it in the "best" table */ 507 best_table_len[i] = 2; 508 best_table[i][0] = best & 0xFF; 509 best_table[i][1] = (best >> 8) & 0xFF; 510 511 /* replace this token in all the valid symbols */ 512 compress_symbols(best_table[i], i); 513 } 514 } 515 } 516 517 /* start by placing the symbols that are actually used on the table */ 518 static void insert_real_symbols_in_table(void) 519 { 520 unsigned int i, j, c; 521 522 memset(best_table, 0, sizeof(best_table)); 523 memset(best_table_len, 0, sizeof(best_table_len)); 524 525 for (i = 0; i < table_cnt; i++) { 526 for (j = 0; j < table[i].len; j++) { 527 c = table[i].sym[j]; 528 best_table[c][0]=c; 529 best_table_len[c]=1; 530 } 531 } 532 } 533 534 static void optimize_token_table(void) 535 { 536 build_initial_tok_table(); 537 538 insert_real_symbols_in_table(); 539 540 /* When valid symbol is not registered, exit to error */ 541 if (!table_cnt) { 542 fprintf(stderr, "No valid symbol.\n"); 543 exit(1); 544 } 545 546 optimize_result(); 547 } 548 549 /* guess for "linker script provide" symbol */ 550 static int may_be_linker_script_provide_symbol(const struct sym_entry *se) 551 { 552 const char *symbol = (char *)se->sym + 1; 553 int len = se->len - 1; 554 555 if (len < 8) 556 return 0; 557 558 if (symbol[0] != '_' || symbol[1] != '_') 559 return 0; 560 561 /* __start_XXXXX */ 562 if (!memcmp(symbol + 2, "start_", 6)) 563 return 1; 564 565 /* __stop_XXXXX */ 566 if (!memcmp(symbol + 2, "stop_", 5)) 567 return 1; 568 569 /* __end_XXXXX */ 570 if (!memcmp(symbol + 2, "end_", 4)) 571 return 1; 572 573 /* __XXXXX_start */ 574 if (!memcmp(symbol + len - 6, "_start", 6)) 575 return 1; 576 577 /* __XXXXX_end */ 578 if (!memcmp(symbol + len - 4, "_end", 4)) 579 return 1; 580 581 return 0; 582 } 583 584 static int prefix_underscores_count(const char *str) 585 { 586 const char *tail = str; 587 588 while (*tail == '_') 589 tail++; 590 591 return tail - str; 592 } 593 594 static int compare_symbols(const void *a, const void *b) 595 { 596 const struct sym_entry *sa; 597 const struct sym_entry *sb; 598 int wa, wb; 599 600 sa = a; 601 sb = b; 602 603 /* sort by address first */ 604 if (sa->addr > sb->addr) 605 return 1; 606 if (sa->addr < sb->addr) 607 return -1; 608 609 /* sort by "weakness" type */ 610 wa = (sa->sym[0] == 'w') || (sa->sym[0] == 'W'); 611 wb = (sb->sym[0] == 'w') || (sb->sym[0] == 'W'); 612 if (wa != wb) 613 return wa - wb; 614 615 /* sort by "linker script provide" type */ 616 wa = may_be_linker_script_provide_symbol(sa); 617 wb = may_be_linker_script_provide_symbol(sb); 618 if (wa != wb) 619 return wa - wb; 620 621 /* sort by the number of prefix underscores */ 622 wa = prefix_underscores_count((const char *)sa->sym + 1); 623 wb = prefix_underscores_count((const char *)sb->sym + 1); 624 if (wa != wb) 625 return wa - wb; 626 627 /* sort by initial order, so that other symbols are left undisturbed */ 628 return sa->start_pos - sb->start_pos; 629 } 630 631 static void sort_symbols(void) 632 { 633 qsort(table, table_cnt, sizeof(struct sym_entry), compare_symbols); 634 } 635 636 int main(int argc, char **argv) 637 { 638 if (argc >= 2) { 639 int i; 640 for (i = 1; i < argc; i++) { 641 if(strcmp(argv[i], "--all-symbols") == 0) 642 all_symbols = 1; 643 else if (strncmp(argv[i], "--symbol-prefix=", 16) == 0) { 644 char *p = &argv[i][16]; 645 /* skip quote */ 646 if ((*p == '"' && *(p+2) == '"') || (*p == '\'' && *(p+2) == '\'')) 647 p++; 648 symbol_prefix_char = *p; 649 } else 650 usage(); 651 } 652 } else if (argc != 1) 653 usage(); 654 655 read_map(stdin); 656 sort_symbols(); 657 optimize_token_table(); 658 write_src(); 659 660 return 0; 661 } 662