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 * ChangeLog: 11 * 12 * (25/Aug/2004) Paulo Marques <pmarques@grupopie.com> 13 * Changed the compression method from stem compression to "table lookup" 14 * compression 15 * 16 * Table compression uses all the unused char codes on the symbols and 17 * maps these to the most used substrings (tokens). For instance, it might 18 * map char code 0xF7 to represent "write_" and then in every symbol where 19 * "write_" appears it can be replaced by 0xF7, saving 5 bytes. 20 * The used codes themselves are also placed in the table so that the 21 * decompresion can work without "special cases". 22 * Applied to kernel symbols, this usually produces a compression ratio 23 * of about 50%. 24 * 25 */ 26 27 #define _GNU_SOURCE 28 29 #include <stdio.h> 30 #include <stdlib.h> 31 #include <string.h> 32 #include <ctype.h> 33 34 #define KSYM_NAME_LEN 127 35 36 37 struct sym_entry { 38 unsigned long long addr; 39 unsigned int len; 40 unsigned char *sym; 41 }; 42 43 44 static struct sym_entry *table; 45 static unsigned int table_size, table_cnt; 46 static unsigned long long _text, _stext, _etext, _sinittext, _einittext, _sextratext, _eextratext; 47 static int all_symbols = 0; 48 static char symbol_prefix_char = '\0'; 49 50 int token_profit[0x10000]; 51 52 /* the table that holds the result of the compression */ 53 unsigned char best_table[256][2]; 54 unsigned char best_table_len[256]; 55 56 57 static void usage(void) 58 { 59 fprintf(stderr, "Usage: kallsyms [--all-symbols] [--symbol-prefix=<prefix char>] < in.map > out.S\n"); 60 exit(1); 61 } 62 63 /* 64 * This ignores the intensely annoying "mapping symbols" found 65 * in ARM ELF files: $a, $t and $d. 66 */ 67 static inline int is_arm_mapping_symbol(const char *str) 68 { 69 return str[0] == '$' && strchr("atd", str[1]) 70 && (str[2] == '\0' || str[2] == '.'); 71 } 72 73 static int read_symbol(FILE *in, struct sym_entry *s) 74 { 75 char str[500]; 76 char *sym, stype; 77 int rc; 78 79 rc = fscanf(in, "%llx %c %499s\n", &s->addr, &stype, str); 80 if (rc != 3) { 81 if (rc != EOF) { 82 /* skip line */ 83 fgets(str, 500, in); 84 } 85 return -1; 86 } 87 88 sym = str; 89 /* skip prefix char */ 90 if (symbol_prefix_char && str[0] == symbol_prefix_char) 91 sym++; 92 93 /* Ignore most absolute/undefined (?) symbols. */ 94 if (strcmp(sym, "_text") == 0) 95 _text = s->addr; 96 else if (strcmp(sym, "_stext") == 0) 97 _stext = s->addr; 98 else if (strcmp(sym, "_etext") == 0) 99 _etext = s->addr; 100 else if (strcmp(sym, "_sinittext") == 0) 101 _sinittext = s->addr; 102 else if (strcmp(sym, "_einittext") == 0) 103 _einittext = s->addr; 104 else if (strcmp(sym, "_sextratext") == 0) 105 _sextratext = s->addr; 106 else if (strcmp(sym, "_eextratext") == 0) 107 _eextratext = s->addr; 108 else if (toupper(stype) == 'A') 109 { 110 /* Keep these useful absolute symbols */ 111 if (strcmp(sym, "__kernel_syscall_via_break") && 112 strcmp(sym, "__kernel_syscall_via_epc") && 113 strcmp(sym, "__kernel_sigtramp") && 114 strcmp(sym, "__gp")) 115 return -1; 116 117 } 118 else if (toupper(stype) == 'U' || 119 is_arm_mapping_symbol(sym)) 120 return -1; 121 /* exclude also MIPS ELF local symbols ($L123 instead of .L123) */ 122 else if (str[0] == '$') 123 return -1; 124 125 /* include the type field in the symbol name, so that it gets 126 * compressed together */ 127 s->len = strlen(str) + 1; 128 s->sym = malloc(s->len + 1); 129 if (!s->sym) { 130 fprintf(stderr, "kallsyms failure: " 131 "unable to allocate required amount of memory\n"); 132 exit(EXIT_FAILURE); 133 } 134 strcpy((char *)s->sym + 1, str); 135 s->sym[0] = stype; 136 137 return 0; 138 } 139 140 static int symbol_valid(struct sym_entry *s) 141 { 142 /* Symbols which vary between passes. Passes 1 and 2 must have 143 * identical symbol lists. The kallsyms_* symbols below are only added 144 * after pass 1, they would be included in pass 2 when --all-symbols is 145 * specified so exclude them to get a stable symbol list. 146 */ 147 static char *special_symbols[] = { 148 "kallsyms_addresses", 149 "kallsyms_num_syms", 150 "kallsyms_names", 151 "kallsyms_markers", 152 "kallsyms_token_table", 153 "kallsyms_token_index", 154 155 /* Exclude linker generated symbols which vary between passes */ 156 "_SDA_BASE_", /* ppc */ 157 "_SDA2_BASE_", /* ppc */ 158 NULL }; 159 int i; 160 int offset = 1; 161 162 /* skip prefix char */ 163 if (symbol_prefix_char && *(s->sym + 1) == symbol_prefix_char) 164 offset++; 165 166 /* if --all-symbols is not specified, then symbols outside the text 167 * and inittext sections are discarded */ 168 if (!all_symbols) { 169 if ((s->addr < _stext || s->addr > _etext) 170 && (s->addr < _sinittext || s->addr > _einittext) 171 && (s->addr < _sextratext || s->addr > _eextratext)) 172 return 0; 173 /* Corner case. Discard any symbols with the same value as 174 * _etext _einittext or _eextratext; they can move between pass 175 * 1 and 2 when the kallsyms data are added. If these symbols 176 * move then they may get dropped in pass 2, which breaks the 177 * kallsyms rules. 178 */ 179 if ((s->addr == _etext && strcmp((char*)s->sym + offset, "_etext")) || 180 (s->addr == _einittext && strcmp((char*)s->sym + offset, "_einittext")) || 181 (s->addr == _eextratext && strcmp((char*)s->sym + offset, "_eextratext"))) 182 return 0; 183 } 184 185 /* Exclude symbols which vary between passes. */ 186 if (strstr((char *)s->sym + offset, "_compiled.")) 187 return 0; 188 189 for (i = 0; special_symbols[i]; i++) 190 if( strcmp((char *)s->sym + offset, special_symbols[i]) == 0 ) 191 return 0; 192 193 return 1; 194 } 195 196 static void read_map(FILE *in) 197 { 198 while (!feof(in)) { 199 if (table_cnt >= table_size) { 200 table_size += 10000; 201 table = realloc(table, sizeof(*table) * table_size); 202 if (!table) { 203 fprintf(stderr, "out of memory\n"); 204 exit (1); 205 } 206 } 207 if (read_symbol(in, &table[table_cnt]) == 0) 208 table_cnt++; 209 } 210 } 211 212 static void output_label(char *label) 213 { 214 if (symbol_prefix_char) 215 printf(".globl %c%s\n", symbol_prefix_char, label); 216 else 217 printf(".globl %s\n", label); 218 printf("\tALGN\n"); 219 if (symbol_prefix_char) 220 printf("%c%s:\n", symbol_prefix_char, label); 221 else 222 printf("%s:\n", label); 223 } 224 225 /* uncompress a compressed symbol. When this function is called, the best table 226 * might still be compressed itself, so the function needs to be recursive */ 227 static int expand_symbol(unsigned char *data, int len, char *result) 228 { 229 int c, rlen, total=0; 230 231 while (len) { 232 c = *data; 233 /* if the table holds a single char that is the same as the one 234 * we are looking for, then end the search */ 235 if (best_table[c][0]==c && best_table_len[c]==1) { 236 *result++ = c; 237 total++; 238 } else { 239 /* if not, recurse and expand */ 240 rlen = expand_symbol(best_table[c], best_table_len[c], result); 241 total += rlen; 242 result += rlen; 243 } 244 data++; 245 len--; 246 } 247 *result=0; 248 249 return total; 250 } 251 252 static void write_src(void) 253 { 254 unsigned int i, k, off; 255 unsigned int best_idx[256]; 256 unsigned int *markers; 257 char buf[KSYM_NAME_LEN+1]; 258 259 printf("#include <asm/types.h>\n"); 260 printf("#if BITS_PER_LONG == 64\n"); 261 printf("#define PTR .quad\n"); 262 printf("#define ALGN .align 8\n"); 263 printf("#else\n"); 264 printf("#define PTR .long\n"); 265 printf("#define ALGN .align 4\n"); 266 printf("#endif\n"); 267 268 printf("\t.section .rodata, \"a\"\n"); 269 270 /* Provide proper symbols relocatability by their '_text' 271 * relativeness. The symbol names cannot be used to construct 272 * normal symbol references as the list of symbols contains 273 * symbols that are declared static and are private to their 274 * .o files. This prevents .tmp_kallsyms.o or any other 275 * object from referencing them. 276 */ 277 output_label("kallsyms_addresses"); 278 for (i = 0; i < table_cnt; i++) { 279 if (toupper(table[i].sym[0]) != 'A') { 280 if (_text <= table[i].addr) 281 printf("\tPTR\t_text + %#llx\n", 282 table[i].addr - _text); 283 else 284 printf("\tPTR\t_text - %#llx\n", 285 _text - table[i].addr); 286 } else { 287 printf("\tPTR\t%#llx\n", table[i].addr); 288 } 289 } 290 printf("\n"); 291 292 output_label("kallsyms_num_syms"); 293 printf("\tPTR\t%d\n", table_cnt); 294 printf("\n"); 295 296 /* table of offset markers, that give the offset in the compressed stream 297 * every 256 symbols */ 298 markers = malloc(sizeof(unsigned int) * ((table_cnt + 255) / 256)); 299 if (!markers) { 300 fprintf(stderr, "kallsyms failure: " 301 "unable to allocate required memory\n"); 302 exit(EXIT_FAILURE); 303 } 304 305 output_label("kallsyms_names"); 306 off = 0; 307 for (i = 0; i < table_cnt; i++) { 308 if ((i & 0xFF) == 0) 309 markers[i >> 8] = off; 310 311 printf("\t.byte 0x%02x", table[i].len); 312 for (k = 0; k < table[i].len; k++) 313 printf(", 0x%02x", table[i].sym[k]); 314 printf("\n"); 315 316 off += table[i].len + 1; 317 } 318 printf("\n"); 319 320 output_label("kallsyms_markers"); 321 for (i = 0; i < ((table_cnt + 255) >> 8); i++) 322 printf("\tPTR\t%d\n", markers[i]); 323 printf("\n"); 324 325 free(markers); 326 327 output_label("kallsyms_token_table"); 328 off = 0; 329 for (i = 0; i < 256; i++) { 330 best_idx[i] = off; 331 expand_symbol(best_table[i], best_table_len[i], buf); 332 printf("\t.asciz\t\"%s\"\n", buf); 333 off += strlen(buf) + 1; 334 } 335 printf("\n"); 336 337 output_label("kallsyms_token_index"); 338 for (i = 0; i < 256; i++) 339 printf("\t.short\t%d\n", best_idx[i]); 340 printf("\n"); 341 } 342 343 344 /* table lookup compression functions */ 345 346 /* count all the possible tokens in a symbol */ 347 static void learn_symbol(unsigned char *symbol, int len) 348 { 349 int i; 350 351 for (i = 0; i < len - 1; i++) 352 token_profit[ symbol[i] + (symbol[i + 1] << 8) ]++; 353 } 354 355 /* decrease the count for all the possible tokens in a symbol */ 356 static void forget_symbol(unsigned char *symbol, int len) 357 { 358 int i; 359 360 for (i = 0; i < len - 1; i++) 361 token_profit[ symbol[i] + (symbol[i + 1] << 8) ]--; 362 } 363 364 /* remove all the invalid symbols from the table and do the initial token count */ 365 static void build_initial_tok_table(void) 366 { 367 unsigned int i, pos; 368 369 pos = 0; 370 for (i = 0; i < table_cnt; i++) { 371 if ( symbol_valid(&table[i]) ) { 372 if (pos != i) 373 table[pos] = table[i]; 374 learn_symbol(table[pos].sym, table[pos].len); 375 pos++; 376 } 377 } 378 table_cnt = pos; 379 } 380 381 /* replace a given token in all the valid symbols. Use the sampled symbols 382 * to update the counts */ 383 static void compress_symbols(unsigned char *str, int idx) 384 { 385 unsigned int i, len, size; 386 unsigned char *p1, *p2; 387 388 for (i = 0; i < table_cnt; i++) { 389 390 len = table[i].len; 391 p1 = table[i].sym; 392 393 /* find the token on the symbol */ 394 p2 = memmem(p1, len, str, 2); 395 if (!p2) continue; 396 397 /* decrease the counts for this symbol's tokens */ 398 forget_symbol(table[i].sym, len); 399 400 size = len; 401 402 do { 403 *p2 = idx; 404 p2++; 405 size -= (p2 - p1); 406 memmove(p2, p2 + 1, size); 407 p1 = p2; 408 len--; 409 410 if (size < 2) break; 411 412 /* find the token on the symbol */ 413 p2 = memmem(p1, size, str, 2); 414 415 } while (p2); 416 417 table[i].len = len; 418 419 /* increase the counts for this symbol's new tokens */ 420 learn_symbol(table[i].sym, len); 421 } 422 } 423 424 /* search the token with the maximum profit */ 425 static int find_best_token(void) 426 { 427 int i, best, bestprofit; 428 429 bestprofit=-10000; 430 best = 0; 431 432 for (i = 0; i < 0x10000; i++) { 433 if (token_profit[i] > bestprofit) { 434 best = i; 435 bestprofit = token_profit[i]; 436 } 437 } 438 return best; 439 } 440 441 /* this is the core of the algorithm: calculate the "best" table */ 442 static void optimize_result(void) 443 { 444 int i, best; 445 446 /* using the '\0' symbol last allows compress_symbols to use standard 447 * fast string functions */ 448 for (i = 255; i >= 0; i--) { 449 450 /* if this table slot is empty (it is not used by an actual 451 * original char code */ 452 if (!best_table_len[i]) { 453 454 /* find the token with the breates profit value */ 455 best = find_best_token(); 456 457 /* place it in the "best" table */ 458 best_table_len[i] = 2; 459 best_table[i][0] = best & 0xFF; 460 best_table[i][1] = (best >> 8) & 0xFF; 461 462 /* replace this token in all the valid symbols */ 463 compress_symbols(best_table[i], i); 464 } 465 } 466 } 467 468 /* start by placing the symbols that are actually used on the table */ 469 static void insert_real_symbols_in_table(void) 470 { 471 unsigned int i, j, c; 472 473 memset(best_table, 0, sizeof(best_table)); 474 memset(best_table_len, 0, sizeof(best_table_len)); 475 476 for (i = 0; i < table_cnt; i++) { 477 for (j = 0; j < table[i].len; j++) { 478 c = table[i].sym[j]; 479 best_table[c][0]=c; 480 best_table_len[c]=1; 481 } 482 } 483 } 484 485 static void optimize_token_table(void) 486 { 487 build_initial_tok_table(); 488 489 insert_real_symbols_in_table(); 490 491 /* When valid symbol is not registered, exit to error */ 492 if (!table_cnt) { 493 fprintf(stderr, "No valid symbol.\n"); 494 exit(1); 495 } 496 497 optimize_result(); 498 } 499 500 501 int main(int argc, char **argv) 502 { 503 if (argc >= 2) { 504 int i; 505 for (i = 1; i < argc; i++) { 506 if(strcmp(argv[i], "--all-symbols") == 0) 507 all_symbols = 1; 508 else if (strncmp(argv[i], "--symbol-prefix=", 16) == 0) { 509 char *p = &argv[i][16]; 510 /* skip quote */ 511 if ((*p == '"' && *(p+2) == '"') || (*p == '\'' && *(p+2) == '\'')) 512 p++; 513 symbol_prefix_char = *p; 514 } else 515 usage(); 516 } 517 } else if (argc != 1) 518 usage(); 519 520 read_map(stdin); 521 optimize_token_table(); 522 write_src(); 523 524 return 0; 525 } 526