root/scripts/kallsyms.c

DEFINITIONS

1. usage
2. is_arm_mapping_symbol
3. check_symbol_range
4. read_symbol
5. symbol_in_range
6. symbol_valid
7. read_map
8. output_label
9. expand_symbol
10. symbol_absolute
11. write_src
12. learn_symbol
13. forget_symbol
14. build_initial_tok_table
15. find_token
16. compress_symbols
17. find_best_token
18. optimize_result
19. insert_real_symbols_in_table
20. optimize_token_table
21. may_be_linker_script_provide_symbol
22. prefix_underscores_count
23. compare_symbols
24. sort_symbols
25. make_percpus_absolute
26. record_relative_base
27. main

   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 };
  52 #define text_range_text     (&text_ranges[0])
  53 #define text_range_inittext (&text_ranges[1])
  54 
  55 static struct addr_range percpu_range = {
  56         "__per_cpu_start", "__per_cpu_end", -1ULL, 0
  57 };
  58 
  59 static struct sym_entry *table;
  60 static unsigned int table_size, table_cnt;
  61 static int all_symbols = 0;
  62 static int absolute_percpu = 0;
  63 static int base_relative = 0;
  64 
  65 static int token_profit[0x10000];
  66 
  67 /* the table that holds the result of the compression */
  68 static unsigned char best_table[256][2];
  69 static unsigned char best_table_len[256];
  70 
  71 
  72 static void usage(void)
  73 {
  74         fprintf(stderr, "Usage: kallsyms [--all-symbols] "
  75                         "[--base-relative] < in.map > out.S\n");
  76         exit(1);
  77 }
  78 
  79 /*
  80  * This ignores the intensely annoying "mapping symbols" found
  81  * in ARM ELF files: $a, $t and $d.
  82  */
  83 static int is_arm_mapping_symbol(const char *str)
  84 {
  85         return str[0] == '$' && strchr("axtd", str[1])
  86                && (str[2] == '\0' || str[2] == '.');
  87 }
  88 
  89 static int check_symbol_range(const char *sym, unsigned long long addr,
  90                               struct addr_range *ranges, int entries)
  91 {
  92         size_t i;
  93         struct addr_range *ar;
  94 
  95         for (i = 0; i < entries; ++i) {
  96                 ar = &ranges[i];
  97 
  98                 if (strcmp(sym, ar->start_sym) == 0) {
  99                         ar->start = addr;
 100                         return 0;
 101                 } else if (strcmp(sym, ar->end_sym) == 0) {
 102                         ar->end = addr;
 103                         return 0;
 104                 }
 105         }
 106 
 107         return 1;
 108 }
 109 
 110 static int read_symbol(FILE *in, struct sym_entry *s)
 111 {
 112         char sym[500], stype;
 113         int rc;
 114 
 115         rc = fscanf(in, "%llx %c %499s\n", &s->addr, &stype, sym);
 116         if (rc != 3) {
 117                 if (rc != EOF && fgets(sym, 500, in) == NULL)
 118                         fprintf(stderr, "Read error or end of file.\n");
 119                 return -1;
 120         }
 121         if (strlen(sym) >= KSYM_NAME_LEN) {
 122                 fprintf(stderr, "Symbol %s too long for kallsyms (%zu >= %d).\n"
 123                                 "Please increase KSYM_NAME_LEN both in kernel and kallsyms.c\n",
 124                         sym, strlen(sym), KSYM_NAME_LEN);
 125                 return -1;
 126         }
 127 
 128         /* Ignore most absolute/undefined (?) symbols. */
 129         if (strcmp(sym, "_text") == 0)
 130                 _text = s->addr;
 131         else if (check_symbol_range(sym, s->addr, text_ranges,
 132                                     ARRAY_SIZE(text_ranges)) == 0)
 133                 /* nothing to do */;
 134         else if (toupper(stype) == 'A')
 135         {
 136                 /* Keep these useful absolute symbols */
 137                 if (strcmp(sym, "__kernel_syscall_via_break") &&
 138                     strcmp(sym, "__kernel_syscall_via_epc") &&
 139                     strcmp(sym, "__kernel_sigtramp") &&
 140                     strcmp(sym, "__gp"))
 141                         return -1;
 142 
 143         }
 144         else if (toupper(stype) == 'U' ||
 145                  is_arm_mapping_symbol(sym))
 146                 return -1;
 147         /* exclude also MIPS ELF local symbols ($L123 instead of .L123) */
 148         else if (sym[0] == '$')
 149                 return -1;
 150         /* exclude debugging symbols */
 151         else if (stype == 'N' || stype == 'n')
 152                 return -1;
 153         /* exclude s390 kasan local symbols */
 154         else if (!strncmp(sym, ".LASANPC", 8))
 155                 return -1;
 156 
 157         /* include the type field in the symbol name, so that it gets
 158          * compressed together */
 159         s->len = strlen(sym) + 1;
 160         s->sym = malloc(s->len + 1);
 161         if (!s->sym) {
 162                 fprintf(stderr, "kallsyms failure: "
 163                         "unable to allocate required amount of memory\n");
 164                 exit(EXIT_FAILURE);
 165         }
 166         strcpy((char *)s->sym + 1, sym);
 167         s->sym[0] = stype;
 168 
 169         s->percpu_absolute = 0;
 170 
 171         /* Record if we've found __per_cpu_start/end. */
 172         check_symbol_range(sym, s->addr, &percpu_range, 1);
 173 
 174         return 0;
 175 }
 176 
 177 static int symbol_in_range(struct sym_entry *s, struct addr_range *ranges,
 178                            int entries)
 179 {
 180         size_t i;
 181         struct addr_range *ar;
 182 
 183         for (i = 0; i < entries; ++i) {
 184                 ar = &ranges[i];
 185 
 186                 if (s->addr >= ar->start && s->addr <= ar->end)
 187                         return 1;
 188         }
 189 
 190         return 0;
 191 }
 192 
 193 static int symbol_valid(struct sym_entry *s)
 194 {
 195         /* Symbols which vary between passes.  Passes 1 and 2 must have
 196          * identical symbol lists.  The kallsyms_* symbols below are only added
 197          * after pass 1, they would be included in pass 2 when --all-symbols is
 198          * specified so exclude them to get a stable symbol list.
 199          */
 200         static char *special_symbols[] = {
 201                 "kallsyms_addresses",
 202                 "kallsyms_offsets",
 203                 "kallsyms_relative_base",
 204                 "kallsyms_num_syms",
 205                 "kallsyms_names",
 206                 "kallsyms_markers",
 207                 "kallsyms_token_table",
 208                 "kallsyms_token_index",
 209 
 210         /* Exclude linker generated symbols which vary between passes */
 211                 "_SDA_BASE_",           /* ppc */
 212                 "_SDA2_BASE_",          /* ppc */
 213                 NULL };
 214 
 215         static char *special_prefixes[] = {
 216                 "__crc_",               /* modversions */
 217                 "__efistub_",           /* arm64 EFI stub namespace */
 218                 NULL };
 219 
 220         static char *special_suffixes[] = {
 221                 "_veneer",              /* arm */
 222                 "_from_arm",            /* arm */
 223                 "_from_thumb",          /* arm */
 224                 NULL };
 225 
 226         int i;
 227         char *sym_name = (char *)s->sym + 1;
 228 
 229         /* if --all-symbols is not specified, then symbols outside the text
 230          * and inittext sections are discarded */
 231         if (!all_symbols) {
 232                 if (symbol_in_range(s, text_ranges,
 233                                     ARRAY_SIZE(text_ranges)) == 0)
 234                         return 0;
 235                 /* Corner case.  Discard any symbols with the same value as
 236                  * _etext _einittext; they can move between pass 1 and 2 when
 237                  * the kallsyms data are added.  If these symbols move then
 238                  * they may get dropped in pass 2, which breaks the kallsyms
 239                  * rules.
 240                  */
 241                 if ((s->addr == text_range_text->end &&
 242                                 strcmp(sym_name,
 243                                        text_range_text->end_sym)) ||
 244                     (s->addr == text_range_inittext->end &&
 245                                 strcmp(sym_name,
 246                                        text_range_inittext->end_sym)))
 247                         return 0;
 248         }
 249 
 250         /* Exclude symbols which vary between passes. */
 251         for (i = 0; special_symbols[i]; i++)
 252                 if (strcmp(sym_name, special_symbols[i]) == 0)
 253                         return 0;
 254 
 255         for (i = 0; special_prefixes[i]; i++) {
 256                 int l = strlen(special_prefixes[i]);
 257 
 258                 if (l <= strlen(sym_name) &&
 259                     strncmp(sym_name, special_prefixes[i], l) == 0)
 260                         return 0;
 261         }
 262 
 263         for (i = 0; special_suffixes[i]; i++) {
 264                 int l = strlen(sym_name) - strlen(special_suffixes[i]);
 265 
 266                 if (l >= 0 && strcmp(sym_name + l, special_suffixes[i]) == 0)
 267                         return 0;
 268         }
 269 
 270         return 1;
 271 }
 272 
 273 static void read_map(FILE *in)
 274 {
 275         while (!feof(in)) {
 276                 if (table_cnt >= table_size) {
 277                         table_size += 10000;
 278                         table = realloc(table, sizeof(*table) * table_size);
 279                         if (!table) {
 280                                 fprintf(stderr, "out of memory\n");
 281                                 exit (1);
 282                         }
 283                 }
 284                 if (read_symbol(in, &table[table_cnt]) == 0) {
 285                         table[table_cnt].start_pos = table_cnt;
 286                         table_cnt++;
 287                 }
 288         }
 289 }
 290 
 291 static void output_label(char *label)
 292 {
 293         printf(".globl %s\n", label);
 294         printf("\tALGN\n");
 295         printf("%s:\n", label);
 296 }
 297 
 298 /* uncompress a compressed symbol. When this function is called, the best table
 299  * might still be compressed itself, so the function needs to be recursive */
 300 static int expand_symbol(unsigned char *data, int len, char *result)
 301 {
 302         int c, rlen, total=0;
 303 
 304         while (len) {
 305                 c = *data;
 306                 /* if the table holds a single char that is the same as the one
 307                  * we are looking for, then end the search */
 308                 if (best_table[c][0]==c && best_table_len[c]==1) {
 309                         *result++ = c;
 310                         total++;
 311                 } else {
 312                         /* if not, recurse and expand */
 313                         rlen = expand_symbol(best_table[c], best_table_len[c], result);
 314                         total += rlen;
 315                         result += rlen;
 316                 }
 317                 data++;
 318                 len--;
 319         }
 320         *result=0;
 321 
 322         return total;
 323 }
 324 
 325 static int symbol_absolute(struct sym_entry *s)
 326 {
 327         return s->percpu_absolute;
 328 }
 329 
 330 static void write_src(void)
 331 {
 332         unsigned int i, k, off;
 333         unsigned int best_idx[256];
 334         unsigned int *markers;
 335         char buf[KSYM_NAME_LEN];
 336 
 337         printf("#include <asm/bitsperlong.h>\n");
 338         printf("#if BITS_PER_LONG == 64\n");
 339         printf("#define PTR .quad\n");
 340         printf("#define ALGN .balign 8\n");
 341         printf("#else\n");
 342         printf("#define PTR .long\n");
 343         printf("#define ALGN .balign 4\n");
 344         printf("#endif\n");
 345 
 346         printf("\t.section .rodata, \"a\"\n");
 347 
 348         /* Provide proper symbols relocatability by their relativeness
 349          * to a fixed anchor point in the runtime image, either '_text'
 350          * for absolute address tables, in which case the linker will
 351          * emit the final addresses at build time. Otherwise, use the
 352          * offset relative to the lowest value encountered of all relative
 353          * symbols, and emit non-relocatable fixed offsets that will be fixed
 354          * up at runtime.
 355          *
 356          * The symbol names cannot be used to construct normal symbol
 357          * references as the list of symbols contains symbols that are
 358          * declared static and are private to their .o files.  This prevents
 359          * .tmp_kallsyms.o or any other object from referencing them.
 360          */
 361         if (!base_relative)
 362                 output_label("kallsyms_addresses");
 363         else
 364                 output_label("kallsyms_offsets");
 365 
 366         for (i = 0; i < table_cnt; i++) {
 367                 if (base_relative) {
 368                         long long offset;
 369                         int overflow;
 370 
 371                         if (!absolute_percpu) {
 372                                 offset = table[i].addr - relative_base;
 373                                 overflow = (offset < 0 || offset > UINT_MAX);
 374                         } else if (symbol_absolute(&table[i])) {
 375                                 offset = table[i].addr;
 376                                 overflow = (offset < 0 || offset > INT_MAX);
 377                         } else {
 378                                 offset = relative_base - table[i].addr - 1;
 379                                 overflow = (offset < INT_MIN || offset >= 0);
 380                         }
 381                         if (overflow) {
 382                                 fprintf(stderr, "kallsyms failure: "
 383                                         "%s symbol value %#llx out of range in relative mode\n",
 384                                         symbol_absolute(&table[i]) ? "absolute" : "relative",
 385                                         table[i].addr);
 386                                 exit(EXIT_FAILURE);
 387                         }
 388                         printf("\t.long\t%#x\n", (int)offset);
 389                 } else if (!symbol_absolute(&table[i])) {
 390                         if (_text <= table[i].addr)
 391                                 printf("\tPTR\t_text + %#llx\n",
 392                                         table[i].addr - _text);
 393                         else
 394                                 printf("\tPTR\t_text - %#llx\n",
 395                                         _text - table[i].addr);
 396                 } else {
 397                         printf("\tPTR\t%#llx\n", table[i].addr);
 398                 }
 399         }
 400         printf("\n");
 401 
 402         if (base_relative) {
 403                 output_label("kallsyms_relative_base");
 404                 printf("\tPTR\t_text - %#llx\n", _text - relative_base);
 405                 printf("\n");
 406         }
 407 
 408         output_label("kallsyms_num_syms");
 409         printf("\t.long\t%u\n", table_cnt);
 410         printf("\n");
 411 
 412         /* table of offset markers, that give the offset in the compressed stream
 413          * every 256 symbols */
 414         markers = malloc(sizeof(unsigned int) * ((table_cnt + 255) / 256));
 415         if (!markers) {
 416                 fprintf(stderr, "kallsyms failure: "
 417                         "unable to allocate required memory\n");
 418                 exit(EXIT_FAILURE);
 419         }
 420 
 421         output_label("kallsyms_names");
 422         off = 0;
 423         for (i = 0; i < table_cnt; i++) {
 424                 if ((i & 0xFF) == 0)
 425                         markers[i >> 8] = off;
 426 
 427                 printf("\t.byte 0x%02x", table[i].len);
 428                 for (k = 0; k < table[i].len; k++)
 429                         printf(", 0x%02x", table[i].sym[k]);
 430                 printf("\n");
 431 
 432                 off += table[i].len + 1;
 433         }
 434         printf("\n");
 435 
 436         output_label("kallsyms_markers");
 437         for (i = 0; i < ((table_cnt + 255) >> 8); i++)
 438                 printf("\t.long\t%u\n", markers[i]);
 439         printf("\n");
 440 
 441         free(markers);
 442 
 443         output_label("kallsyms_token_table");
 444         off = 0;
 445         for (i = 0; i < 256; i++) {
 446                 best_idx[i] = off;
 447                 expand_symbol(best_table[i], best_table_len[i], buf);
 448                 printf("\t.asciz\t\"%s\"\n", buf);
 449                 off += strlen(buf) + 1;
 450         }
 451         printf("\n");
 452 
 453         output_label("kallsyms_token_index");
 454         for (i = 0; i < 256; i++)
 455                 printf("\t.short\t%d\n", best_idx[i]);
 456         printf("\n");
 457 }
 458 
 459 
 460 /* table lookup compression functions */
 461 
 462 /* count all the possible tokens in a symbol */
 463 static void learn_symbol(unsigned char *symbol, int len)
 464 {
 465         int i;
 466 
 467         for (i = 0; i < len - 1; i++)
 468                 token_profit[ symbol[i] + (symbol[i + 1] << 8) ]++;
 469 }
 470 
 471 /* decrease the count for all the possible tokens in a symbol */
 472 static void forget_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 /* remove all the invalid symbols from the table and do the initial token count */
 481 static void build_initial_tok_table(void)
 482 {
 483         unsigned int i, pos;
 484 
 485         pos = 0;
 486         for (i = 0; i < table_cnt; i++) {
 487                 if ( symbol_valid(&table[i]) ) {
 488                         if (pos != i)
 489                                 table[pos] = table[i];
 490                         learn_symbol(table[pos].sym, table[pos].len);
 491                         pos++;
 492                 } else {
 493                         free(table[i].sym);
 494                 }
 495         }
 496         table_cnt = pos;
 497 }
 498 
 499 static void *find_token(unsigned char *str, int len, unsigned char *token)
 500 {
 501         int i;
 502 
 503         for (i = 0; i < len - 1; i++) {
 504                 if (str[i] == token[0] && str[i+1] == token[1])
 505                         return &str[i];
 506         }
 507         return NULL;
 508 }
 509 
 510 /* replace a given token in all the valid symbols. Use the sampled symbols
 511  * to update the counts */
 512 static void compress_symbols(unsigned char *str, int idx)
 513 {
 514         unsigned int i, len, size;
 515         unsigned char *p1, *p2;
 516 
 517         for (i = 0; i < table_cnt; i++) {
 518 
 519                 len = table[i].len;
 520                 p1 = table[i].sym;
 521 
 522                 /* find the token on the symbol */
 523                 p2 = find_token(p1, len, str);
 524                 if (!p2) continue;
 525 
 526                 /* decrease the counts for this symbol's tokens */
 527                 forget_symbol(table[i].sym, len);
 528 
 529                 size = len;
 530 
 531                 do {
 532                         *p2 = idx;
 533                         p2++;
 534                         size -= (p2 - p1);
 535                         memmove(p2, p2 + 1, size);
 536                         p1 = p2;
 537                         len--;
 538 
 539                         if (size < 2) break;
 540 
 541                         /* find the token on the symbol */
 542                         p2 = find_token(p1, size, str);
 543 
 544                 } while (p2);
 545 
 546                 table[i].len = len;
 547 
 548                 /* increase the counts for this symbol's new tokens */
 549                 learn_symbol(table[i].sym, len);
 550         }
 551 }
 552 
 553 /* search the token with the maximum profit */
 554 static int find_best_token(void)
 555 {
 556         int i, best, bestprofit;
 557 
 558         bestprofit=-10000;
 559         best = 0;
 560 
 561         for (i = 0; i < 0x10000; i++) {
 562                 if (token_profit[i] > bestprofit) {
 563                         best = i;
 564                         bestprofit = token_profit[i];
 565                 }
 566         }
 567         return best;
 568 }
 569 
 570 /* this is the core of the algorithm: calculate the "best" table */
 571 static void optimize_result(void)
 572 {
 573         int i, best;
 574 
 575         /* using the '\0' symbol last allows compress_symbols to use standard
 576          * fast string functions */
 577         for (i = 255; i >= 0; i--) {
 578 
 579                 /* if this table slot is empty (it is not used by an actual
 580                  * original char code */
 581                 if (!best_table_len[i]) {
 582 
 583                         /* find the token with the best profit value */
 584                         best = find_best_token();
 585                         if (token_profit[best] == 0)
 586                                 break;
 587 
 588                         /* place it in the "best" table */
 589                         best_table_len[i] = 2;
 590                         best_table[i][0] = best & 0xFF;
 591                         best_table[i][1] = (best >> 8) & 0xFF;
 592 
 593                         /* replace this token in all the valid symbols */
 594                         compress_symbols(best_table[i], i);
 595                 }
 596         }
 597 }
 598 
 599 /* start by placing the symbols that are actually used on the table */
 600 static void insert_real_symbols_in_table(void)
 601 {
 602         unsigned int i, j, c;
 603 
 604         for (i = 0; i < table_cnt; i++) {
 605                 for (j = 0; j < table[i].len; j++) {
 606                         c = table[i].sym[j];
 607                         best_table[c][0]=c;
 608                         best_table_len[c]=1;
 609                 }
 610         }
 611 }
 612 
 613 static void optimize_token_table(void)
 614 {
 615         build_initial_tok_table();
 616 
 617         insert_real_symbols_in_table();
 618 
 619         /* When valid symbol is not registered, exit to error */
 620         if (!table_cnt) {
 621                 fprintf(stderr, "No valid symbol.\n");
 622                 exit(1);
 623         }
 624 
 625         optimize_result();
 626 }
 627 
 628 /* guess for "linker script provide" symbol */
 629 static int may_be_linker_script_provide_symbol(const struct sym_entry *se)
 630 {
 631         const char *symbol = (char *)se->sym + 1;
 632         int len = se->len - 1;
 633 
 634         if (len < 8)
 635                 return 0;
 636 
 637         if (symbol[0] != '_' || symbol[1] != '_')
 638                 return 0;
 639 
 640         /* __start_XXXXX */
 641         if (!memcmp(symbol + 2, "start_", 6))
 642                 return 1;
 643 
 644         /* __stop_XXXXX */
 645         if (!memcmp(symbol + 2, "stop_", 5))
 646                 return 1;
 647 
 648         /* __end_XXXXX */
 649         if (!memcmp(symbol + 2, "end_", 4))
 650                 return 1;
 651 
 652         /* __XXXXX_start */
 653         if (!memcmp(symbol + len - 6, "_start", 6))
 654                 return 1;
 655 
 656         /* __XXXXX_end */
 657         if (!memcmp(symbol + len - 4, "_end", 4))
 658                 return 1;
 659 
 660         return 0;
 661 }
 662 
 663 static int prefix_underscores_count(const char *str)
 664 {
 665         const char *tail = str;
 666 
 667         while (*tail == '_')
 668                 tail++;
 669 
 670         return tail - str;
 671 }
 672 
 673 static int compare_symbols(const void *a, const void *b)
 674 {
 675         const struct sym_entry *sa;
 676         const struct sym_entry *sb;
 677         int wa, wb;
 678 
 679         sa = a;
 680         sb = b;
 681 
 682         /* sort by address first */
 683         if (sa->addr > sb->addr)
 684                 return 1;
 685         if (sa->addr < sb->addr)
 686                 return -1;
 687 
 688         /* sort by "weakness" type */
 689         wa = (sa->sym[0] == 'w') || (sa->sym[0] == 'W');
 690         wb = (sb->sym[0] == 'w') || (sb->sym[0] == 'W');
 691         if (wa != wb)
 692                 return wa - wb;
 693 
 694         /* sort by "linker script provide" type */
 695         wa = may_be_linker_script_provide_symbol(sa);
 696         wb = may_be_linker_script_provide_symbol(sb);
 697         if (wa != wb)
 698                 return wa - wb;
 699 
 700         /* sort by the number of prefix underscores */
 701         wa = prefix_underscores_count((const char *)sa->sym + 1);
 702         wb = prefix_underscores_count((const char *)sb->sym + 1);
 703         if (wa != wb)
 704                 return wa - wb;
 705 
 706         /* sort by initial order, so that other symbols are left undisturbed */
 707         return sa->start_pos - sb->start_pos;
 708 }
 709 
 710 static void sort_symbols(void)
 711 {
 712         qsort(table, table_cnt, sizeof(struct sym_entry), compare_symbols);
 713 }
 714 
 715 static void make_percpus_absolute(void)
 716 {
 717         unsigned int i;
 718 
 719         for (i = 0; i < table_cnt; i++)
 720                 if (symbol_in_range(&table[i], &percpu_range, 1)) {
 721                         /*
 722                          * Keep the 'A' override for percpu symbols to
 723                          * ensure consistent behavior compared to older
 724                          * versions of this tool.
 725                          */
 726                         table[i].sym[0] = 'A';
 727                         table[i].percpu_absolute = 1;
 728                 }
 729 }
 730 
 731 /* find the minimum non-absolute symbol address */
 732 static void record_relative_base(void)
 733 {
 734         unsigned int i;
 735 
 736         relative_base = -1ULL;
 737         for (i = 0; i < table_cnt; i++)
 738                 if (!symbol_absolute(&table[i]) &&
 739                     table[i].addr < relative_base)
 740                         relative_base = table[i].addr;
 741 }
 742 
 743 int main(int argc, char **argv)
 744 {
 745         if (argc >= 2) {
 746                 int i;
 747                 for (i = 1; i < argc; i++) {
 748                         if(strcmp(argv[i], "--all-symbols") == 0)
 749                                 all_symbols = 1;
 750                         else if (strcmp(argv[i], "--absolute-percpu") == 0)
 751                                 absolute_percpu = 1;
 752                         else if (strcmp(argv[i], "--base-relative") == 0)
 753                                 base_relative = 1;
 754                         else
 755                                 usage();
 756                 }
 757         } else if (argc != 1)
 758                 usage();
 759 
 760         read_map(stdin);
 761         if (absolute_percpu)
 762                 make_percpus_absolute();
 763         if (base_relative)
 764                 record_relative_base();
 765         sort_symbols();
 766         optimize_token_table();
 767         write_src();
 768 
 769         return 0;
 770 }