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 _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, "_stext") == 0) 95 _stext = s->addr; 96 else if (strcmp(sym, "_etext") == 0) 97 _etext = s->addr; 98 else if (strcmp(sym, "_sinittext") == 0) 99 _sinittext = s->addr; 100 else if (strcmp(sym, "_einittext") == 0) 101 _einittext = s->addr; 102 else if (strcmp(sym, "_sextratext") == 0) 103 _sextratext = s->addr; 104 else if (strcmp(sym, "_eextratext") == 0) 105 _eextratext = s->addr; 106 else if (toupper(stype) == 'A') 107 { 108 /* Keep these useful absolute symbols */ 109 if (strcmp(sym, "__kernel_syscall_via_break") && 110 strcmp(sym, "__kernel_syscall_via_epc") && 111 strcmp(sym, "__kernel_sigtramp") && 112 strcmp(sym, "__gp")) 113 return -1; 114 115 } 116 else if (toupper(stype) == 'U' || 117 is_arm_mapping_symbol(sym)) 118 return -1; 119 /* exclude also MIPS ELF local symbols ($L123 instead of .L123) */ 120 else if (str[0] == '$') 121 return -1; 122 123 /* include the type field in the symbol name, so that it gets 124 * compressed together */ 125 s->len = strlen(str) + 1; 126 s->sym = malloc(s->len + 1); 127 if (!s->sym) { 128 fprintf(stderr, "kallsyms failure: " 129 "unable to allocate required amount of memory\n"); 130 exit(EXIT_FAILURE); 131 } 132 strcpy((char *)s->sym + 1, str); 133 s->sym[0] = stype; 134 135 return 0; 136 } 137 138 static int symbol_valid(struct sym_entry *s) 139 { 140 /* Symbols which vary between passes. Passes 1 and 2 must have 141 * identical symbol lists. The kallsyms_* symbols below are only added 142 * after pass 1, they would be included in pass 2 when --all-symbols is 143 * specified so exclude them to get a stable symbol list. 144 */ 145 static char *special_symbols[] = { 146 "kallsyms_addresses", 147 "kallsyms_num_syms", 148 "kallsyms_names", 149 "kallsyms_markers", 150 "kallsyms_token_table", 151 "kallsyms_token_index", 152 153 /* Exclude linker generated symbols which vary between passes */ 154 "_SDA_BASE_", /* ppc */ 155 "_SDA2_BASE_", /* ppc */ 156 NULL }; 157 int i; 158 int offset = 1; 159 160 /* skip prefix char */ 161 if (symbol_prefix_char && *(s->sym + 1) == symbol_prefix_char) 162 offset++; 163 164 /* if --all-symbols is not specified, then symbols outside the text 165 * and inittext sections are discarded */ 166 if (!all_symbols) { 167 if ((s->addr < _stext || s->addr > _etext) 168 && (s->addr < _sinittext || s->addr > _einittext) 169 && (s->addr < _sextratext || s->addr > _eextratext)) 170 return 0; 171 /* Corner case. Discard any symbols with the same value as 172 * _etext _einittext or _eextratext; they can move between pass 173 * 1 and 2 when the kallsyms data are added. If these symbols 174 * move then they may get dropped in pass 2, which breaks the 175 * kallsyms rules. 176 */ 177 if ((s->addr == _etext && strcmp((char*)s->sym + offset, "_etext")) || 178 (s->addr == _einittext && strcmp((char*)s->sym + offset, "_einittext")) || 179 (s->addr == _eextratext && strcmp((char*)s->sym + offset, "_eextratext"))) 180 return 0; 181 } 182 183 /* Exclude symbols which vary between passes. */ 184 if (strstr((char *)s->sym + offset, "_compiled.")) 185 return 0; 186 187 for (i = 0; special_symbols[i]; i++) 188 if( strcmp((char *)s->sym + offset, special_symbols[i]) == 0 ) 189 return 0; 190 191 return 1; 192 } 193 194 static void read_map(FILE *in) 195 { 196 while (!feof(in)) { 197 if (table_cnt >= table_size) { 198 table_size += 10000; 199 table = realloc(table, sizeof(*table) * table_size); 200 if (!table) { 201 fprintf(stderr, "out of memory\n"); 202 exit (1); 203 } 204 } 205 if (read_symbol(in, &table[table_cnt]) == 0) 206 table_cnt++; 207 } 208 } 209 210 static void output_label(char *label) 211 { 212 if (symbol_prefix_char) 213 printf(".globl %c%s\n", symbol_prefix_char, label); 214 else 215 printf(".globl %s\n", label); 216 printf("\tALGN\n"); 217 if (symbol_prefix_char) 218 printf("%c%s:\n", symbol_prefix_char, label); 219 else 220 printf("%s:\n", label); 221 } 222 223 /* uncompress a compressed symbol. When this function is called, the best table 224 * might still be compressed itself, so the function needs to be recursive */ 225 static int expand_symbol(unsigned char *data, int len, char *result) 226 { 227 int c, rlen, total=0; 228 229 while (len) { 230 c = *data; 231 /* if the table holds a single char that is the same as the one 232 * we are looking for, then end the search */ 233 if (best_table[c][0]==c && best_table_len[c]==1) { 234 *result++ = c; 235 total++; 236 } else { 237 /* if not, recurse and expand */ 238 rlen = expand_symbol(best_table[c], best_table_len[c], result); 239 total += rlen; 240 result += rlen; 241 } 242 data++; 243 len--; 244 } 245 *result=0; 246 247 return total; 248 } 249 250 static void write_src(void) 251 { 252 unsigned int i, k, off; 253 unsigned int best_idx[256]; 254 unsigned int *markers; 255 char buf[KSYM_NAME_LEN+1]; 256 257 printf("#include <asm/types.h>\n"); 258 printf("#if BITS_PER_LONG == 64\n"); 259 printf("#define PTR .quad\n"); 260 printf("#define ALGN .align 8\n"); 261 printf("#else\n"); 262 printf("#define PTR .long\n"); 263 printf("#define ALGN .align 4\n"); 264 printf("#endif\n"); 265 266 printf(".data\n"); 267 268 output_label("kallsyms_addresses"); 269 for (i = 0; i < table_cnt; i++) { 270 printf("\tPTR\t%#llx\n", table[i].addr); 271 } 272 printf("\n"); 273 274 output_label("kallsyms_num_syms"); 275 printf("\tPTR\t%d\n", table_cnt); 276 printf("\n"); 277 278 /* table of offset markers, that give the offset in the compressed stream 279 * every 256 symbols */ 280 markers = malloc(sizeof(unsigned int) * ((table_cnt + 255) / 256)); 281 if (!markers) { 282 fprintf(stderr, "kallsyms failure: " 283 "unable to allocate required memory\n"); 284 exit(EXIT_FAILURE); 285 } 286 287 output_label("kallsyms_names"); 288 off = 0; 289 for (i = 0; i < table_cnt; i++) { 290 if ((i & 0xFF) == 0) 291 markers[i >> 8] = off; 292 293 printf("\t.byte 0x%02x", table[i].len); 294 for (k = 0; k < table[i].len; k++) 295 printf(", 0x%02x", table[i].sym[k]); 296 printf("\n"); 297 298 off += table[i].len + 1; 299 } 300 printf("\n"); 301 302 output_label("kallsyms_markers"); 303 for (i = 0; i < ((table_cnt + 255) >> 8); i++) 304 printf("\tPTR\t%d\n", markers[i]); 305 printf("\n"); 306 307 free(markers); 308 309 output_label("kallsyms_token_table"); 310 off = 0; 311 for (i = 0; i < 256; i++) { 312 best_idx[i] = off; 313 expand_symbol(best_table[i], best_table_len[i], buf); 314 printf("\t.asciz\t\"%s\"\n", buf); 315 off += strlen(buf) + 1; 316 } 317 printf("\n"); 318 319 output_label("kallsyms_token_index"); 320 for (i = 0; i < 256; i++) 321 printf("\t.short\t%d\n", best_idx[i]); 322 printf("\n"); 323 } 324 325 326 /* table lookup compression functions */ 327 328 /* count all the possible tokens in a symbol */ 329 static void learn_symbol(unsigned char *symbol, int len) 330 { 331 int i; 332 333 for (i = 0; i < len - 1; i++) 334 token_profit[ symbol[i] + (symbol[i + 1] << 8) ]++; 335 } 336 337 /* decrease the count for all the possible tokens in a symbol */ 338 static void forget_symbol(unsigned char *symbol, int len) 339 { 340 int i; 341 342 for (i = 0; i < len - 1; i++) 343 token_profit[ symbol[i] + (symbol[i + 1] << 8) ]--; 344 } 345 346 /* remove all the invalid symbols from the table and do the initial token count */ 347 static void build_initial_tok_table(void) 348 { 349 unsigned int i, pos; 350 351 pos = 0; 352 for (i = 0; i < table_cnt; i++) { 353 if ( symbol_valid(&table[i]) ) { 354 if (pos != i) 355 table[pos] = table[i]; 356 learn_symbol(table[pos].sym, table[pos].len); 357 pos++; 358 } 359 } 360 table_cnt = pos; 361 } 362 363 /* replace a given token in all the valid symbols. Use the sampled symbols 364 * to update the counts */ 365 static void compress_symbols(unsigned char *str, int idx) 366 { 367 unsigned int i, len, size; 368 unsigned char *p1, *p2; 369 370 for (i = 0; i < table_cnt; i++) { 371 372 len = table[i].len; 373 p1 = table[i].sym; 374 375 /* find the token on the symbol */ 376 p2 = memmem(p1, len, str, 2); 377 if (!p2) continue; 378 379 /* decrease the counts for this symbol's tokens */ 380 forget_symbol(table[i].sym, len); 381 382 size = len; 383 384 do { 385 *p2 = idx; 386 p2++; 387 size -= (p2 - p1); 388 memmove(p2, p2 + 1, size); 389 p1 = p2; 390 len--; 391 392 if (size < 2) break; 393 394 /* find the token on the symbol */ 395 p2 = memmem(p1, size, str, 2); 396 397 } while (p2); 398 399 table[i].len = len; 400 401 /* increase the counts for this symbol's new tokens */ 402 learn_symbol(table[i].sym, len); 403 } 404 } 405 406 /* search the token with the maximum profit */ 407 static int find_best_token(void) 408 { 409 int i, best, bestprofit; 410 411 bestprofit=-10000; 412 best = 0; 413 414 for (i = 0; i < 0x10000; i++) { 415 if (token_profit[i] > bestprofit) { 416 best = i; 417 bestprofit = token_profit[i]; 418 } 419 } 420 return best; 421 } 422 423 /* this is the core of the algorithm: calculate the "best" table */ 424 static void optimize_result(void) 425 { 426 int i, best; 427 428 /* using the '\0' symbol last allows compress_symbols to use standard 429 * fast string functions */ 430 for (i = 255; i >= 0; i--) { 431 432 /* if this table slot is empty (it is not used by an actual 433 * original char code */ 434 if (!best_table_len[i]) { 435 436 /* find the token with the breates profit value */ 437 best = find_best_token(); 438 439 /* place it in the "best" table */ 440 best_table_len[i] = 2; 441 best_table[i][0] = best & 0xFF; 442 best_table[i][1] = (best >> 8) & 0xFF; 443 444 /* replace this token in all the valid symbols */ 445 compress_symbols(best_table[i], i); 446 } 447 } 448 } 449 450 /* start by placing the symbols that are actually used on the table */ 451 static void insert_real_symbols_in_table(void) 452 { 453 unsigned int i, j, c; 454 455 memset(best_table, 0, sizeof(best_table)); 456 memset(best_table_len, 0, sizeof(best_table_len)); 457 458 for (i = 0; i < table_cnt; i++) { 459 for (j = 0; j < table[i].len; j++) { 460 c = table[i].sym[j]; 461 best_table[c][0]=c; 462 best_table_len[c]=1; 463 } 464 } 465 } 466 467 static void optimize_token_table(void) 468 { 469 build_initial_tok_table(); 470 471 insert_real_symbols_in_table(); 472 473 /* When valid symbol is not registered, exit to error */ 474 if (!table_cnt) { 475 fprintf(stderr, "No valid symbol.\n"); 476 exit(1); 477 } 478 479 optimize_result(); 480 } 481 482 483 int main(int argc, char **argv) 484 { 485 if (argc >= 2) { 486 int i; 487 for (i = 1; i < argc; i++) { 488 if(strcmp(argv[i], "--all-symbols") == 0) 489 all_symbols = 1; 490 else if (strncmp(argv[i], "--symbol-prefix=", 16) == 0) { 491 char *p = &argv[i][16]; 492 /* skip quote */ 493 if ((*p == '"' && *(p+2) == '"') || (*p == '\'' && *(p+2) == '\'')) 494 p++; 495 symbol_prefix_char = *p; 496 } else 497 usage(); 498 } 499 } else if (argc != 1) 500 usage(); 501 502 read_map(stdin); 503 optimize_token_table(); 504 write_src(); 505 506 return 0; 507 } 508