scripts/kallsyms.c

   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: kallsyms [--all-symbols] [--absolute-percpu]
   9  *                         [--base-relative] [--lto-clang] in.map > out.S
  10  *
  11  *      Table compression uses all the unused char codes on the symbols and
  12  *  maps these to the most used substrings (tokens). For instance, it might
  13  *  map char code 0xF7 to represent "write_" and then in every symbol where
  14  *  "write_" appears it can be replaced by 0xF7, saving 5 bytes.
  15  *      The used codes themselves are also placed in the table so that the
  16  *  decompresion can work without "special cases".
  17  *      Applied to kernel symbols, this usually produces a compression ratio
  18  *  of about 50%.
  19  *
  20  */
  21
  22 #include <errno.h>
  23 #include <getopt.h>
  24 #include <stdbool.h>
  25 #include <stdio.h>
  26 #include <stdlib.h>
  27 #include <string.h>
  28 #include <ctype.h>
  29 #include <limits.h>
  30
  31 #define ARRAY_SIZE(arr) (sizeof(arr) / sizeof(arr[0]))
  32
  33 #define KSYM_NAME_LEN           512
  34
  35 struct sym_entry {
  36         unsigned long long addr;
  37         unsigned int len;
  38         unsigned int seq;
  39         unsigned int start_pos;
  40         unsigned int percpu_absolute;
  41         unsigned char sym[];
  42 };
  43
  44 struct addr_range {
  45         const char *start_sym, *end_sym;
  46         unsigned long long start, end;
  47 };
  48
  49 static unsigned long long _text;
  50 static unsigned long long relative_base;
  51 static struct addr_range text_ranges[] = {
  52         { "_stext",     "_etext"     },
  53         { "_sinittext", "_einittext" },
  54 };
  55 #define text_range_text     (&text_ranges[0])
  56 #define text_range_inittext (&text_ranges[1])
  57
  58 static struct addr_range percpu_range = {
  59         "__per_cpu_start", "__per_cpu_end", -1ULL, 0
  60 };
  61
  62 static struct sym_entry **table;
  63 static unsigned int table_size, table_cnt;
  64 static int all_symbols;
  65 static int absolute_percpu;
  66 static int base_relative;
  67 static int lto_clang;
  68
  69 static int token_profit[0x10000];
  70
  71 /* the table that holds the result of the compression */
  72 static unsigned char best_table[256][2];
  73 static unsigned char best_table_len[256];
  74
  75
  76 static void usage(void)
  77 {
  78         fprintf(stderr, "Usage: kallsyms [--all-symbols] [--absolute-percpu] "
  79                         "[--base-relative] [--lto-clang] in.map > out.S\n");
  80         exit(1);
  81 }
  82
  83 static char *sym_name(const struct sym_entry *s)
  84 {
  85         return (char *)s->sym + 1;
  86 }
  87
  88 static bool is_ignored_symbol(const char *name, char type)
  89 {
  90         if (type == 'u' || type == 'n')
  91                 return true;
  92
  93         if (toupper(type) == 'A') {
  94                 /* Keep these useful absolute symbols */
  95                 if (strcmp(name, "__kernel_syscall_via_break") &&
  96                     strcmp(name, "__kernel_syscall_via_epc") &&
  97                     strcmp(name, "__kernel_sigtramp") &&
  98                     strcmp(name, "__gp"))
  99                         return true;
 100         }
 101
 102         return false;
 103 }
 104
 105 static void check_symbol_range(const char *sym, unsigned long long addr,
 106                                struct addr_range *ranges, int entries)
 107 {
 108         size_t i;
 109         struct addr_range *ar;
 110
 111         for (i = 0; i < entries; ++i) {
 112                 ar = &ranges[i];
 113
 114                 if (strcmp(sym, ar->start_sym) == 0) {
 115                         ar->start = addr;
 116                         return;
 117                 } else if (strcmp(sym, ar->end_sym) == 0) {
 118                         ar->end = addr;
 119                         return;
 120                 }
 121         }
 122 }
 123
 124 static struct sym_entry *read_symbol(FILE *in, char **buf, size_t *buf_len)
 125 {
 126         char *name, type, *p;
 127         unsigned long long addr;
 128         size_t len;
 129         ssize_t readlen;
 130         struct sym_entry *sym;
 131
 132         readlen = getline(buf, buf_len, in);
 133         if (readlen < 0) {
 134                 if (errno) {
 135                         perror("read_symbol");
 136                         exit(EXIT_FAILURE);
 137                 }
 138                 return NULL;
 139         }
 140
 141         if ((*buf)[readlen - 1] == '\n')
 142                 (*buf)[readlen - 1] = 0;
 143
 144         addr = strtoull(*buf, &p, 16);
 145
 146         if (*buf == p || *p++ != ' ' || !isascii((type = *p++)) || *p++ != ' ') {
 147                 fprintf(stderr, "line format error\n");
 148                 exit(EXIT_FAILURE);
 149         }
 150
 151         name = p;
 152         len = strlen(name);
 153
 154         if (len >= KSYM_NAME_LEN) {
 155                 fprintf(stderr, "Symbol %s too long for kallsyms (%zu >= %d).\n"
 156                                 "Please increase KSYM_NAME_LEN both in kernel and kallsyms.c\n",
 157                         name, len, KSYM_NAME_LEN);
 158                 return NULL;
 159         }
 160
 161         if (strcmp(name, "_text") == 0)
 162                 _text = addr;
 163
 164         /* Ignore most absolute/undefined (?) symbols. */
 165         if (is_ignored_symbol(name, type))
 166                 return NULL;
 167
 168         check_symbol_range(name, addr, text_ranges, ARRAY_SIZE(text_ranges));
 169         check_symbol_range(name, addr, &percpu_range, 1);
 170
 171         /* include the type field in the symbol name, so that it gets
 172          * compressed together */
 173         len++;
 174
 175         sym = malloc(sizeof(*sym) + len + 1);
 176         if (!sym) {
 177                 fprintf(stderr, "kallsyms failure: "
 178                         "unable to allocate required amount of memory\n");
 179                 exit(EXIT_FAILURE);
 180         }
 181         sym->addr = addr;
 182         sym->len = len;
 183         sym->sym[0] = type;
 184         strcpy(sym_name(sym), name);
 185         sym->percpu_absolute = 0;
 186
 187         return sym;
 188 }
 189
 190 static int symbol_in_range(const struct sym_entry *s,
 191                            const struct addr_range *ranges, int entries)
 192 {
 193         size_t i;
 194         const struct addr_range *ar;
 195
 196         for (i = 0; i < entries; ++i) {
 197                 ar = &ranges[i];
 198
 199                 if (s->addr >= ar->start && s->addr <= ar->end)
 200                         return 1;
 201         }
 202
 203         return 0;
 204 }
 205
 206 static int symbol_valid(const struct sym_entry *s)
 207 {
 208         const char *name = sym_name(s);
 209
 210         /* if --all-symbols is not specified, then symbols outside the text
 211          * and inittext sections are discarded */
 212         if (!all_symbols) {
 213                 if (symbol_in_range(s, text_ranges,
 214                                     ARRAY_SIZE(text_ranges)) == 0)
 215                         return 0;
 216                 /* Corner case.  Discard any symbols with the same value as
 217                  * _etext _einittext; they can move between pass 1 and 2 when
 218                  * the kallsyms data are added.  If these symbols move then
 219                  * they may get dropped in pass 2, which breaks the kallsyms
 220                  * rules.
 221                  */
 222                 if ((s->addr == text_range_text->end &&
 223                      strcmp(name, text_range_text->end_sym)) ||
 224                     (s->addr == text_range_inittext->end &&
 225                      strcmp(name, text_range_inittext->end_sym)))
 226                         return 0;
 227         }
 228
 229         return 1;
 230 }
 231
 232 /* remove all the invalid symbols from the table */
 233 static void shrink_table(void)
 234 {
 235         unsigned int i, pos;
 236
 237         pos = 0;
 238         for (i = 0; i < table_cnt; i++) {
 239                 if (symbol_valid(table[i])) {
 240                         if (pos != i)
 241                                 table[pos] = table[i];
 242                         pos++;
 243                 } else {
 244                         free(table[i]);
 245                 }
 246         }
 247         table_cnt = pos;
 248
 249         /* When valid symbol is not registered, exit to error */
 250         if (!table_cnt) {
 251                 fprintf(stderr, "No valid symbol.\n");
 252                 exit(1);
 253         }
 254 }
 255
 256 static void read_map(const char *in)
 257 {
 258         FILE *fp;
 259         struct sym_entry *sym;
 260         char *buf = NULL;
 261         size_t buflen = 0;
 262
 263         fp = fopen(in, "r");
 264         if (!fp) {
 265                 perror(in);
 266                 exit(1);
 267         }
 268
 269         while (!feof(fp)) {
 270                 sym = read_symbol(fp, &buf, &buflen);
 271                 if (!sym)
 272                         continue;
 273
 274                 sym->start_pos = table_cnt;
 275
 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                                 fclose(fp);
 282                                 exit (1);
 283                         }
 284                 }
 285
 286                 table[table_cnt++] = sym;
 287         }
 288
 289         free(buf);
 290         fclose(fp);
 291 }
 292
 293 static void output_label(const char *label)
 294 {
 295         printf(".globl %s\n", label);
 296         printf("\tALGN\n");
 297         printf("%s:\n", label);
 298 }
 299
 300 /* Provide proper symbols relocatability by their '_text' relativeness. */
 301 static void output_address(unsigned long long addr)
 302 {
 303         if (_text <= addr)
 304                 printf("\tPTR\t_text + %#llx\n", addr - _text);
 305         else
 306                 printf("\tPTR\t_text - %#llx\n", _text - addr);
 307 }
 308
 309 /* uncompress a compressed symbol. When this function is called, the best table
 310  * might still be compressed itself, so the function needs to be recursive */
 311 static int expand_symbol(const unsigned char *data, int len, char *result)
 312 {
 313         int c, rlen, total=0;
 314
 315         while (len) {
 316                 c = *data;
 317                 /* if the table holds a single char that is the same as the one
 318                  * we are looking for, then end the search */
 319                 if (best_table[c][0]==c && best_table_len[c]==1) {
 320                         *result++ = c;
 321                         total++;
 322                 } else {
 323                         /* if not, recurse and expand */
 324                         rlen = expand_symbol(best_table[c], best_table_len[c], result);
 325                         total += rlen;
 326                         result += rlen;
 327                 }
 328                 data++;
 329                 len--;
 330         }
 331         *result=0;
 332
 333         return total;
 334 }
 335
 336 static int symbol_absolute(const struct sym_entry *s)
 337 {
 338         return s->percpu_absolute;
 339 }
 340
 341 static void cleanup_symbol_name(char *s)
 342 {
 343         char *p;
 344
 345         /*
 346          * ASCII[.]   = 2e
 347          * ASCII[0-9] = 30,39
 348          * ASCII[A-Z] = 41,5a
 349          * ASCII[_]   = 5f
 350          * ASCII[a-z] = 61,7a
 351          *
 352          * As above, replacing '.' with '\0' does not affect the main sorting,
 353          * but it helps us with subsorting.
 354          */
 355         p = strchr(s, '.');
 356         if (p)
 357                 *p = '\0';
 358 }
 359
 360 static int compare_names(const void *a, const void *b)
 361 {
 362         int ret;
 363         const struct sym_entry *sa = *(const struct sym_entry **)a;
 364         const struct sym_entry *sb = *(const struct sym_entry **)b;
 365
 366         ret = strcmp(sym_name(sa), sym_name(sb));
 367         if (!ret) {
 368                 if (sa->addr > sb->addr)
 369                         return 1;
 370                 else if (sa->addr < sb->addr)
 371                         return -1;
 372
 373                 /* keep old order */
 374                 return (int)(sa->seq - sb->seq);
 375         }
 376
 377         return ret;
 378 }
 379
 380 static void sort_symbols_by_name(void)
 381 {
 382         qsort(table, table_cnt, sizeof(table[0]), compare_names);
 383 }
 384
 385 static void write_src(void)
 386 {
 387         unsigned int i, k, off;
 388         unsigned int best_idx[256];
 389         unsigned int *markers;
 390         char buf[KSYM_NAME_LEN];
 391
 392         printf("#include <asm/bitsperlong.h>\n");
 393         printf("#if BITS_PER_LONG == 64\n");
 394         printf("#define PTR .quad\n");
 395         printf("#define ALGN .balign 8\n");
 396         printf("#else\n");
 397         printf("#define PTR .long\n");
 398         printf("#define ALGN .balign 4\n");
 399         printf("#endif\n");
 400
 401         printf("\t.section .rodata, \"a\"\n");
 402
 403         output_label("kallsyms_num_syms");
 404         printf("\t.long\t%u\n", table_cnt);
 405         printf("\n");
 406
 407         /* table of offset markers, that give the offset in the compressed stream
 408          * every 256 symbols */
 409         markers = malloc(sizeof(unsigned int) * ((table_cnt + 255) / 256));
 410         if (!markers) {
 411                 fprintf(stderr, "kallsyms failure: "
 412                         "unable to allocate required memory\n");
 413                 exit(EXIT_FAILURE);
 414         }
 415
 416         output_label("kallsyms_names");
 417         off = 0;
 418         for (i = 0; i < table_cnt; i++) {
 419                 if ((i & 0xFF) == 0)
 420                         markers[i >> 8] = off;
 421                 table[i]->seq = i;
 422
 423                 /* There cannot be any symbol of length zero. */
 424                 if (table[i]->len == 0) {
 425                         fprintf(stderr, "kallsyms failure: "
 426                                 "unexpected zero symbol length\n");
 427                         exit(EXIT_FAILURE);
 428                 }
 429
 430                 /* Only lengths that fit in up-to-two-byte ULEB128 are supported. */
 431                 if (table[i]->len > 0x3FFF) {
 432                         fprintf(stderr, "kallsyms failure: "
 433                                 "unexpected huge symbol length\n");
 434                         exit(EXIT_FAILURE);
 435                 }
 436
 437                 /* Encode length with ULEB128. */
 438                 if (table[i]->len <= 0x7F) {
 439                         /* Most symbols use a single byte for the length. */
 440                         printf("\t.byte 0x%02x", table[i]->len);
 441                         off += table[i]->len + 1;
 442                 } else {
 443                         /* "Big" symbols use two bytes. */
 444                         printf("\t.byte 0x%02x, 0x%02x",
 445                                 (table[i]->len & 0x7F) | 0x80,
 446                                 (table[i]->len >> 7) & 0x7F);
 447                         off += table[i]->len + 2;
 448                 }
 449                 for (k = 0; k < table[i]->len; k++)
 450                         printf(", 0x%02x", table[i]->sym[k]);
 451                 printf("\n");
 452         }
 453         printf("\n");
 454
 455         /*
 456          * Now that we wrote out the compressed symbol names, restore the
 457          * original names, which are needed in some of the later steps.
 458          */
 459         for (i = 0; i < table_cnt; i++) {
 460                 expand_symbol(table[i]->sym, table[i]->len, buf);
 461                 strcpy((char *)table[i]->sym, buf);
 462         }
 463
 464         output_label("kallsyms_markers");
 465         for (i = 0; i < ((table_cnt + 255) >> 8); i++)
 466                 printf("\t.long\t%u\n", markers[i]);
 467         printf("\n");
 468
 469         free(markers);
 470
 471         output_label("kallsyms_token_table");
 472         off = 0;
 473         for (i = 0; i < 256; i++) {
 474                 best_idx[i] = off;
 475                 expand_symbol(best_table[i], best_table_len[i], buf);
 476                 printf("\t.asciz\t\"%s\"\n", buf);
 477                 off += strlen(buf) + 1;
 478         }
 479         printf("\n");
 480
 481         output_label("kallsyms_token_index");
 482         for (i = 0; i < 256; i++)
 483                 printf("\t.short\t%d\n", best_idx[i]);
 484         printf("\n");
 485
 486         if (!base_relative)
 487                 output_label("kallsyms_addresses");
 488         else
 489                 output_label("kallsyms_offsets");
 490
 491         for (i = 0; i < table_cnt; i++) {
 492                 if (base_relative) {
 493                         /*
 494                          * Use the offset relative to the lowest value
 495                          * encountered of all relative symbols, and emit
 496                          * non-relocatable fixed offsets that will be fixed
 497                          * up at runtime.
 498                          */
 499
 500                         long long offset;
 501                         int overflow;
 502
 503                         if (!absolute_percpu) {
 504                                 offset = table[i]->addr - relative_base;
 505                                 overflow = (offset < 0 || offset > UINT_MAX);
 506                         } else if (symbol_absolute(table[i])) {
 507                                 offset = table[i]->addr;
 508                                 overflow = (offset < 0 || offset > INT_MAX);
 509                         } else {
 510                                 offset = relative_base - table[i]->addr - 1;
 511                                 overflow = (offset < INT_MIN || offset >= 0);
 512                         }
 513                         if (overflow) {
 514                                 fprintf(stderr, "kallsyms failure: "
 515                                         "%s symbol value %#llx out of range in relative mode\n",
 516                                         symbol_absolute(table[i]) ? "absolute" : "relative",
 517                                         table[i]->addr);
 518                                 exit(EXIT_FAILURE);
 519                         }
 520                         printf("\t.long\t%#x    /* %s */\n", (int)offset, table[i]->sym);
 521                 } else if (!symbol_absolute(table[i])) {
 522                         output_address(table[i]->addr);
 523                 } else {
 524                         printf("\tPTR\t%#llx\n", table[i]->addr);
 525                 }
 526         }
 527         printf("\n");
 528
 529         if (base_relative) {
 530                 output_label("kallsyms_relative_base");
 531                 output_address(relative_base);
 532                 printf("\n");
 533         }
 534
 535         if (lto_clang)
 536                 for (i = 0; i < table_cnt; i++)
 537                         cleanup_symbol_name((char *)table[i]->sym);
 538
 539         sort_symbols_by_name();
 540         output_label("kallsyms_seqs_of_names");
 541         for (i = 0; i < table_cnt; i++)
 542                 printf("\t.byte 0x%02x, 0x%02x, 0x%02x\n",
 543                         (unsigned char)(table[i]->seq >> 16),
 544                         (unsigned char)(table[i]->seq >> 8),
 545                         (unsigned char)(table[i]->seq >> 0));
 546         printf("\n");
 547 }
 548
 549
 550 /* table lookup compression functions */
 551
 552 /* count all the possible tokens in a symbol */
 553 static void learn_symbol(const unsigned char *symbol, int len)
 554 {
 555         int i;
 556
 557         for (i = 0; i < len - 1; i++)
 558                 token_profit[ symbol[i] + (symbol[i + 1] << 8) ]++;
 559 }
 560
 561 /* decrease the count for all the possible tokens in a symbol */
 562 static void forget_symbol(const unsigned char *symbol, int len)
 563 {
 564         int i;
 565
 566         for (i = 0; i < len - 1; i++)
 567                 token_profit[ symbol[i] + (symbol[i + 1] << 8) ]--;
 568 }
 569
 570 /* do the initial token count */
 571 static void build_initial_token_table(void)
 572 {
 573         unsigned int i;
 574
 575         for (i = 0; i < table_cnt; i++)
 576                 learn_symbol(table[i]->sym, table[i]->len);
 577 }
 578
 579 static unsigned char *find_token(unsigned char *str, int len,
 580                                  const unsigned char *token)
 581 {
 582         int i;
 583
 584         for (i = 0; i < len - 1; i++) {
 585                 if (str[i] == token[0] && str[i+1] == token[1])
 586                         return &str[i];
 587         }
 588         return NULL;
 589 }
 590
 591 /* replace a given token in all the valid symbols. Use the sampled symbols
 592  * to update the counts */
 593 static void compress_symbols(const unsigned char *str, int idx)
 594 {
 595         unsigned int i, len, size;
 596         unsigned char *p1, *p2;
 597
 598         for (i = 0; i < table_cnt; i++) {
 599
 600                 len = table[i]->len;
 601                 p1 = table[i]->sym;
 602
 603                 /* find the token on the symbol */
 604                 p2 = find_token(p1, len, str);
 605                 if (!p2) continue;
 606
 607                 /* decrease the counts for this symbol's tokens */
 608                 forget_symbol(table[i]->sym, len);
 609
 610                 size = len;
 611
 612                 do {
 613                         *p2 = idx;
 614                         p2++;
 615                         size -= (p2 - p1);
 616                         memmove(p2, p2 + 1, size);
 617                         p1 = p2;
 618                         len--;
 619
 620                         if (size < 2) break;
 621
 622                         /* find the token on the symbol */
 623                         p2 = find_token(p1, size, str);
 624
 625                 } while (p2);
 626
 627                 table[i]->len = len;
 628
 629                 /* increase the counts for this symbol's new tokens */
 630                 learn_symbol(table[i]->sym, len);
 631         }
 632 }
 633
 634 /* search the token with the maximum profit */
 635 static int find_best_token(void)
 636 {
 637         int i, best, bestprofit;
 638
 639         bestprofit=-10000;
 640         best = 0;
 641
 642         for (i = 0; i < 0x10000; i++) {
 643                 if (token_profit[i] > bestprofit) {
 644                         best = i;
 645                         bestprofit = token_profit[i];
 646                 }
 647         }
 648         return best;
 649 }
 650
 651 /* this is the core of the algorithm: calculate the "best" table */
 652 static void optimize_result(void)
 653 {
 654         int i, best;
 655
 656         /* using the '\0' symbol last allows compress_symbols to use standard
 657          * fast string functions */
 658         for (i = 255; i >= 0; i--) {
 659
 660                 /* if this table slot is empty (it is not used by an actual
 661                  * original char code */
 662                 if (!best_table_len[i]) {
 663
 664                         /* find the token with the best profit value */
 665                         best = find_best_token();
 666                         if (token_profit[best] == 0)
 667                                 break;
 668
 669                         /* place it in the "best" table */
 670                         best_table_len[i] = 2;
 671                         best_table[i][0] = best & 0xFF;
 672                         best_table[i][1] = (best >> 8) & 0xFF;
 673
 674                         /* replace this token in all the valid symbols */
 675                         compress_symbols(best_table[i], i);
 676                 }
 677         }
 678 }
 679
 680 /* start by placing the symbols that are actually used on the table */
 681 static void insert_real_symbols_in_table(void)
 682 {
 683         unsigned int i, j, c;
 684
 685         for (i = 0; i < table_cnt; i++) {
 686                 for (j = 0; j < table[i]->len; j++) {
 687                         c = table[i]->sym[j];
 688                         best_table[c][0]=c;
 689                         best_table_len[c]=1;
 690                 }
 691         }
 692 }
 693
 694 static void optimize_token_table(void)
 695 {
 696         build_initial_token_table();
 697
 698         insert_real_symbols_in_table();
 699
 700         optimize_result();
 701 }
 702
 703 /* guess for "linker script provide" symbol */
 704 static int may_be_linker_script_provide_symbol(const struct sym_entry *se)
 705 {
 706         const char *symbol = sym_name(se);
 707         int len = se->len - 1;
 708
 709         if (len < 8)
 710                 return 0;
 711
 712         if (symbol[0] != '_' || symbol[1] != '_')
 713                 return 0;
 714
 715         /* __start_XXXXX */
 716         if (!memcmp(symbol + 2, "start_", 6))
 717                 return 1;
 718
 719         /* __stop_XXXXX */
 720         if (!memcmp(symbol + 2, "stop_", 5))
 721                 return 1;
 722
 723         /* __end_XXXXX */
 724         if (!memcmp(symbol + 2, "end_", 4))
 725                 return 1;
 726
 727         /* __XXXXX_start */
 728         if (!memcmp(symbol + len - 6, "_start", 6))
 729                 return 1;
 730
 731         /* __XXXXX_end */
 732         if (!memcmp(symbol + len - 4, "_end", 4))
 733                 return 1;
 734
 735         return 0;
 736 }
 737
 738 static int compare_symbols(const void *a, const void *b)
 739 {
 740         const struct sym_entry *sa = *(const struct sym_entry **)a;
 741         const struct sym_entry *sb = *(const struct sym_entry **)b;
 742         int wa, wb;
 743
 744         /* sort by address first */
 745         if (sa->addr > sb->addr)
 746                 return 1;
 747         if (sa->addr < sb->addr)
 748                 return -1;
 749
 750         /* sort by "weakness" type */
 751         wa = (sa->sym[0] == 'w') || (sa->sym[0] == 'W');
 752         wb = (sb->sym[0] == 'w') || (sb->sym[0] == 'W');
 753         if (wa != wb)
 754                 return wa - wb;
 755
 756         /* sort by "linker script provide" type */
 757         wa = may_be_linker_script_provide_symbol(sa);
 758         wb = may_be_linker_script_provide_symbol(sb);
 759         if (wa != wb)
 760                 return wa - wb;
 761
 762         /* sort by the number of prefix underscores */
 763         wa = strspn(sym_name(sa), "_");
 764         wb = strspn(sym_name(sb), "_");
 765         if (wa != wb)
 766                 return wa - wb;
 767
 768         /* sort by initial order, so that other symbols are left undisturbed */
 769         return sa->start_pos - sb->start_pos;
 770 }
 771
 772 static void sort_symbols(void)
 773 {
 774         qsort(table, table_cnt, sizeof(table[0]), compare_symbols);
 775 }
 776
 777 static void make_percpus_absolute(void)
 778 {
 779         unsigned int i;
 780
 781         for (i = 0; i < table_cnt; i++)
 782                 if (symbol_in_range(table[i], &percpu_range, 1)) {
 783                         /*
 784                          * Keep the 'A' override for percpu symbols to
 785                          * ensure consistent behavior compared to older
 786                          * versions of this tool.
 787                          */
 788                         table[i]->sym[0] = 'A';
 789                         table[i]->percpu_absolute = 1;
 790                 }
 791 }
 792
 793 /* find the minimum non-absolute symbol address */
 794 static void record_relative_base(void)
 795 {
 796         unsigned int i;
 797
 798         for (i = 0; i < table_cnt; i++)
 799                 if (!symbol_absolute(table[i])) {
 800                         /*
 801                          * The table is sorted by address.
 802                          * Take the first non-absolute symbol value.
 803                          */
 804                         relative_base = table[i]->addr;
 805                         return;
 806                 }
 807 }
 808
 809 int main(int argc, char **argv)
 810 {
 811         while (1) {
 812                 static const struct option long_options[] = {
 813                         {"all-symbols",     no_argument, &all_symbols,     1},
 814                         {"absolute-percpu", no_argument, &absolute_percpu, 1},
 815                         {"base-relative",   no_argument, &base_relative,   1},
 816                         {"lto-clang",       no_argument, &lto_clang,       1},
 817                         {},
 818                 };
 819
 820                 int c = getopt_long(argc, argv, "", long_options, NULL);
 821
 822                 if (c == -1)
 823                         break;
 824                 if (c != 0)
 825                         usage();
 826         }
 827
 828         if (optind >= argc)
 829                 usage();
 830
 831         read_map(argv[optind]);
 832         shrink_table();
 833         if (absolute_percpu)
 834                 make_percpus_absolute();
 835         sort_symbols();
 836         if (base_relative)
 837                 record_relative_base();
 838         optimize_token_table();
 839         write_src();
 840
 841         return 0;
 842 }