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] 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 <getopt.h>
  23 #include <stdbool.h>
  24 #include <stdio.h>
  25 #include <stdlib.h>
  26 #include <string.h>
  27 #include <ctype.h>
  28 #include <limits.h>
  29
  30 #define ARRAY_SIZE(arr) (sizeof(arr) / sizeof(arr[0]))
  31
  32 #define _stringify_1(x) #x
  33 #define _stringify(x)   _stringify_1(x)
  34
  35 #define KSYM_NAME_LEN           512
  36
  37 /*
  38  * A substantially bigger size than the current maximum.
  39  *
  40  * It cannot be defined as an expression because it gets stringified
  41  * for the fscanf() format string. Therefore, a _Static_assert() is
  42  * used instead to maintain the relationship with KSYM_NAME_LEN.
  43  */
  44 #define KSYM_NAME_LEN_BUFFER    2048
  45 _Static_assert(
  46         KSYM_NAME_LEN_BUFFER == KSYM_NAME_LEN * 4,
  47         "Please keep KSYM_NAME_LEN_BUFFER in sync with KSYM_NAME_LEN"
  48 );
  49
  50 struct sym_entry {
  51         unsigned long long addr;
  52         unsigned int len;
  53         unsigned int seq;
  54         unsigned int start_pos;
  55         unsigned int percpu_absolute;
  56         unsigned char sym[];
  57 };
  58
  59 struct addr_range {
  60         const char *start_sym, *end_sym;
  61         unsigned long long start, end;
  62 };
  63
  64 static unsigned long long _text;
  65 static unsigned long long relative_base;
  66 static struct addr_range text_ranges[] = {
  67         { "_stext",     "_etext"     },
  68         { "_sinittext", "_einittext" },
  69 };
  70 #define text_range_text     (&text_ranges[0])
  71 #define text_range_inittext (&text_ranges[1])
  72
  73 static struct addr_range percpu_range = {
  74         "__per_cpu_start", "__per_cpu_end", -1ULL, 0
  75 };
  76
  77 static struct sym_entry **table;
  78 static unsigned int table_size, table_cnt;
  79 static int all_symbols;
  80 static int absolute_percpu;
  81 static int base_relative;
  82 static int lto_clang;
  83
  84 static int token_profit[0x10000];
  85
  86 /* the table that holds the result of the compression */
  87 static unsigned char best_table[256][2];
  88 static unsigned char best_table_len[256];
  89
  90
  91 static void usage(void)
  92 {
  93         fprintf(stderr, "Usage: kallsyms [--all-symbols] [--absolute-percpu] "
  94                         "[--base-relative] [--lto-clang] in.map > out.S\n");
  95         exit(1);
  96 }
  97
  98 static char *sym_name(const struct sym_entry *s)
  99 {
 100         return (char *)s->sym + 1;
 101 }
 102
 103 static bool is_ignored_symbol(const char *name, char type)
 104 {
 105         /* Symbol names that exactly match to the following are ignored.*/
 106         static const char * const ignored_symbols[] = {
 107                 /*
 108                  * Symbols which vary between passes. Passes 1 and 2 must have
 109                  * identical symbol lists. The kallsyms_* symbols below are
 110                  * only added after pass 1, they would be included in pass 2
 111                  * when --all-symbols is specified so exclude them to get a
 112                  * stable symbol list.
 113                  */
 114                 "kallsyms_addresses",
 115                 "kallsyms_offsets",
 116                 "kallsyms_relative_base",
 117                 "kallsyms_num_syms",
 118                 "kallsyms_names",
 119                 "kallsyms_markers",
 120                 "kallsyms_token_table",
 121                 "kallsyms_token_index",
 122                 /* Exclude linker generated symbols which vary between passes */
 123                 "_SDA_BASE_",           /* ppc */
 124                 "_SDA2_BASE_",          /* ppc */
 125                 NULL
 126         };
 127
 128         /* Symbol names that begin with the following are ignored.*/
 129         static const char * const ignored_prefixes[] = {
 130                 "__efistub_",           /* arm64 EFI stub namespace */
 131                 "__kvm_nvhe_$",         /* arm64 local symbols in non-VHE KVM namespace */
 132                 "__kvm_nvhe_.L",        /* arm64 local symbols in non-VHE KVM namespace */
 133                 "__AArch64ADRPThunk_",  /* arm64 lld */
 134                 "__ARMV5PILongThunk_",  /* arm lld */
 135                 "__ARMV7PILongThunk_",
 136                 "__ThumbV7PILongThunk_",
 137                 "__LA25Thunk_",         /* mips lld */
 138                 "__microLA25Thunk_",
 139                 "__kcfi_typeid_",       /* CFI type identifiers */
 140                 NULL
 141         };
 142
 143         /* Symbol names that end with the following are ignored.*/
 144         static const char * const ignored_suffixes[] = {
 145                 "_from_arm",            /* arm */
 146                 "_from_thumb",          /* arm */
 147                 "_veneer",              /* arm */
 148                 NULL
 149         };
 150
 151         /* Symbol names that contain the following are ignored.*/
 152         static const char * const ignored_matches[] = {
 153                 ".long_branch.",        /* ppc stub */
 154                 ".plt_branch.",         /* ppc stub */
 155                 NULL
 156         };
 157
 158         const char * const *p;
 159
 160         for (p = ignored_symbols; *p; p++)
 161                 if (!strcmp(name, *p))
 162                         return true;
 163
 164         for (p = ignored_prefixes; *p; p++)
 165                 if (!strncmp(name, *p, strlen(*p)))
 166                         return true;
 167
 168         for (p = ignored_suffixes; *p; p++) {
 169                 int l = strlen(name) - strlen(*p);
 170
 171                 if (l >= 0 && !strcmp(name + l, *p))
 172                         return true;
 173         }
 174
 175         for (p = ignored_matches; *p; p++) {
 176                 if (strstr(name, *p))
 177                         return true;
 178         }
 179
 180         if (type == 'U' || type == 'u')
 181                 return true;
 182         /* exclude debugging symbols */
 183         if (type == 'N' || type == 'n')
 184                 return true;
 185
 186         if (toupper(type) == 'A') {
 187                 /* Keep these useful absolute symbols */
 188                 if (strcmp(name, "__kernel_syscall_via_break") &&
 189                     strcmp(name, "__kernel_syscall_via_epc") &&
 190                     strcmp(name, "__kernel_sigtramp") &&
 191                     strcmp(name, "__gp"))
 192                         return true;
 193         }
 194
 195         return false;
 196 }
 197
 198 static void check_symbol_range(const char *sym, unsigned long long addr,
 199                                struct addr_range *ranges, int entries)
 200 {
 201         size_t i;
 202         struct addr_range *ar;
 203
 204         for (i = 0; i < entries; ++i) {
 205                 ar = &ranges[i];
 206
 207                 if (strcmp(sym, ar->start_sym) == 0) {
 208                         ar->start = addr;
 209                         return;
 210                 } else if (strcmp(sym, ar->end_sym) == 0) {
 211                         ar->end = addr;
 212                         return;
 213                 }
 214         }
 215 }
 216
 217 static struct sym_entry *read_symbol(FILE *in)
 218 {
 219         char name[KSYM_NAME_LEN_BUFFER+1], type;
 220         unsigned long long addr;
 221         unsigned int len;
 222         struct sym_entry *sym;
 223         int rc;
 224
 225         rc = fscanf(in, "%llx %c %" _stringify(KSYM_NAME_LEN_BUFFER) "s\n", &addr, &type, name);
 226         if (rc != 3) {
 227                 if (rc != EOF && fgets(name, ARRAY_SIZE(name), in) == NULL)
 228                         fprintf(stderr, "Read error or end of file.\n");
 229                 return NULL;
 230         }
 231         if (strlen(name) >= KSYM_NAME_LEN) {
 232                 fprintf(stderr, "Symbol %s too long for kallsyms (%zu >= %d).\n"
 233                                 "Please increase KSYM_NAME_LEN both in kernel and kallsyms.c\n",
 234                         name, strlen(name), KSYM_NAME_LEN);
 235                 return NULL;
 236         }
 237
 238         if (strcmp(name, "_text") == 0)
 239                 _text = addr;
 240
 241         /* Ignore most absolute/undefined (?) symbols. */
 242         if (is_ignored_symbol(name, type))
 243                 return NULL;
 244
 245         check_symbol_range(name, addr, text_ranges, ARRAY_SIZE(text_ranges));
 246         check_symbol_range(name, addr, &percpu_range, 1);
 247
 248         /* include the type field in the symbol name, so that it gets
 249          * compressed together */
 250
 251         len = strlen(name) + 1;
 252
 253         sym = malloc(sizeof(*sym) + len + 1);
 254         if (!sym) {
 255                 fprintf(stderr, "kallsyms failure: "
 256                         "unable to allocate required amount of memory\n");
 257                 exit(EXIT_FAILURE);
 258         }
 259         sym->addr = addr;
 260         sym->len = len;
 261         sym->sym[0] = type;
 262         strcpy(sym_name(sym), name);
 263         sym->percpu_absolute = 0;
 264
 265         return sym;
 266 }
 267
 268 static int symbol_in_range(const struct sym_entry *s,
 269                            const struct addr_range *ranges, int entries)
 270 {
 271         size_t i;
 272         const struct addr_range *ar;
 273
 274         for (i = 0; i < entries; ++i) {
 275                 ar = &ranges[i];
 276
 277                 if (s->addr >= ar->start && s->addr <= ar->end)
 278                         return 1;
 279         }
 280
 281         return 0;
 282 }
 283
 284 static int symbol_valid(const struct sym_entry *s)
 285 {
 286         const char *name = sym_name(s);
 287
 288         /* if --all-symbols is not specified, then symbols outside the text
 289          * and inittext sections are discarded */
 290         if (!all_symbols) {
 291                 if (symbol_in_range(s, text_ranges,
 292                                     ARRAY_SIZE(text_ranges)) == 0)
 293                         return 0;
 294                 /* Corner case.  Discard any symbols with the same value as
 295                  * _etext _einittext; they can move between pass 1 and 2 when
 296                  * the kallsyms data are added.  If these symbols move then
 297                  * they may get dropped in pass 2, which breaks the kallsyms
 298                  * rules.
 299                  */
 300                 if ((s->addr == text_range_text->end &&
 301                      strcmp(name, text_range_text->end_sym)) ||
 302                     (s->addr == text_range_inittext->end &&
 303                      strcmp(name, text_range_inittext->end_sym)))
 304                         return 0;
 305         }
 306
 307         return 1;
 308 }
 309
 310 /* remove all the invalid symbols from the table */
 311 static void shrink_table(void)
 312 {
 313         unsigned int i, pos;
 314
 315         pos = 0;
 316         for (i = 0; i < table_cnt; i++) {
 317                 if (symbol_valid(table[i])) {
 318                         if (pos != i)
 319                                 table[pos] = table[i];
 320                         pos++;
 321                 } else {
 322                         free(table[i]);
 323                 }
 324         }
 325         table_cnt = pos;
 326
 327         /* When valid symbol is not registered, exit to error */
 328         if (!table_cnt) {
 329                 fprintf(stderr, "No valid symbol.\n");
 330                 exit(1);
 331         }
 332 }
 333
 334 static void read_map(const char *in)
 335 {
 336         FILE *fp;
 337         struct sym_entry *sym;
 338
 339         fp = fopen(in, "r");
 340         if (!fp) {
 341                 perror(in);
 342                 exit(1);
 343         }
 344
 345         while (!feof(fp)) {
 346                 sym = read_symbol(fp);
 347                 if (!sym)
 348                         continue;
 349
 350                 sym->start_pos = table_cnt;
 351
 352                 if (table_cnt >= table_size) {
 353                         table_size += 10000;
 354                         table = realloc(table, sizeof(*table) * table_size);
 355                         if (!table) {
 356                                 fprintf(stderr, "out of memory\n");
 357                                 fclose(fp);
 358                                 exit (1);
 359                         }
 360                 }
 361
 362                 table[table_cnt++] = sym;
 363         }
 364
 365         fclose(fp);
 366 }
 367
 368 static void output_label(const char *label)
 369 {
 370         printf(".globl %s\n", label);
 371         printf("\tALGN\n");
 372         printf("%s:\n", label);
 373 }
 374
 375 /* Provide proper symbols relocatability by their '_text' relativeness. */
 376 static void output_address(unsigned long long addr)
 377 {
 378         if (_text <= addr)
 379                 printf("\tPTR\t_text + %#llx\n", addr - _text);
 380         else
 381                 printf("\tPTR\t_text - %#llx\n", _text - addr);
 382 }
 383
 384 /* uncompress a compressed symbol. When this function is called, the best table
 385  * might still be compressed itself, so the function needs to be recursive */
 386 static int expand_symbol(const unsigned char *data, int len, char *result)
 387 {
 388         int c, rlen, total=0;
 389
 390         while (len) {
 391                 c = *data;
 392                 /* if the table holds a single char that is the same as the one
 393                  * we are looking for, then end the search */
 394                 if (best_table[c][0]==c && best_table_len[c]==1) {
 395                         *result++ = c;
 396                         total++;
 397                 } else {
 398                         /* if not, recurse and expand */
 399                         rlen = expand_symbol(best_table[c], best_table_len[c], result);
 400                         total += rlen;
 401                         result += rlen;
 402                 }
 403                 data++;
 404                 len--;
 405         }
 406         *result=0;
 407
 408         return total;
 409 }
 410
 411 static int symbol_absolute(const struct sym_entry *s)
 412 {
 413         return s->percpu_absolute;
 414 }
 415
 416 static char * s_name(char *buf)
 417 {
 418         /* Skip the symbol type */
 419         return buf + 1;
 420 }
 421
 422 static void cleanup_symbol_name(char *s)
 423 {
 424         char *p;
 425
 426         if (!lto_clang)
 427                 return;
 428
 429         /*
 430          * ASCII[.]   = 2e
 431          * ASCII[0-9] = 30,39
 432          * ASCII[A-Z] = 41,5a
 433          * ASCII[_]   = 5f
 434          * ASCII[a-z] = 61,7a
 435          *
 436          * As above, replacing '.' with '\0' does not affect the main sorting,
 437          * but it helps us with subsorting.
 438          */
 439         p = strchr(s, '.');
 440         if (p)
 441                 *p = '\0';
 442 }
 443
 444 static int compare_names(const void *a, const void *b)
 445 {
 446         int ret;
 447         char sa_namebuf[KSYM_NAME_LEN];
 448         char sb_namebuf[KSYM_NAME_LEN];
 449         const struct sym_entry *sa = *(const struct sym_entry **)a;
 450         const struct sym_entry *sb = *(const struct sym_entry **)b;
 451
 452         expand_symbol(sa->sym, sa->len, sa_namebuf);
 453         expand_symbol(sb->sym, sb->len, sb_namebuf);
 454         cleanup_symbol_name(s_name(sa_namebuf));
 455         cleanup_symbol_name(s_name(sb_namebuf));
 456         ret = strcmp(s_name(sa_namebuf), s_name(sb_namebuf));
 457         if (!ret) {
 458                 if (sa->addr > sb->addr)
 459                         return 1;
 460                 else if (sa->addr < sb->addr)
 461                         return -1;
 462
 463                 /* keep old order */
 464                 return (int)(sa->seq - sb->seq);
 465         }
 466
 467         return ret;
 468 }
 469
 470 static void sort_symbols_by_name(void)
 471 {
 472         qsort(table, table_cnt, sizeof(table[0]), compare_names);
 473 }
 474
 475 static void write_src(void)
 476 {
 477         unsigned int i, k, off;
 478         unsigned int best_idx[256];
 479         unsigned int *markers;
 480         char buf[KSYM_NAME_LEN];
 481
 482         printf("#include <asm/bitsperlong.h>\n");
 483         printf("#if BITS_PER_LONG == 64\n");
 484         printf("#define PTR .quad\n");
 485         printf("#define ALGN .balign 8\n");
 486         printf("#else\n");
 487         printf("#define PTR .long\n");
 488         printf("#define ALGN .balign 4\n");
 489         printf("#endif\n");
 490
 491         printf("\t.section .rodata, \"a\"\n");
 492
 493         if (!base_relative)
 494                 output_label("kallsyms_addresses");
 495         else
 496                 output_label("kallsyms_offsets");
 497
 498         for (i = 0; i < table_cnt; i++) {
 499                 if (base_relative) {
 500                         /*
 501                          * Use the offset relative to the lowest value
 502                          * encountered of all relative symbols, and emit
 503                          * non-relocatable fixed offsets that will be fixed
 504                          * up at runtime.
 505                          */
 506
 507                         long long offset;
 508                         int overflow;
 509
 510                         if (!absolute_percpu) {
 511                                 offset = table[i]->addr - relative_base;
 512                                 overflow = (offset < 0 || offset > UINT_MAX);
 513                         } else if (symbol_absolute(table[i])) {
 514                                 offset = table[i]->addr;
 515                                 overflow = (offset < 0 || offset > INT_MAX);
 516                         } else {
 517                                 offset = relative_base - table[i]->addr - 1;
 518                                 overflow = (offset < INT_MIN || offset >= 0);
 519                         }
 520                         if (overflow) {
 521                                 fprintf(stderr, "kallsyms failure: "
 522                                         "%s symbol value %#llx out of range in relative mode\n",
 523                                         symbol_absolute(table[i]) ? "absolute" : "relative",
 524                                         table[i]->addr);
 525                                 exit(EXIT_FAILURE);
 526                         }
 527                         printf("\t.long\t%#x\n", (int)offset);
 528                 } else if (!symbol_absolute(table[i])) {
 529                         output_address(table[i]->addr);
 530                 } else {
 531                         printf("\tPTR\t%#llx\n", table[i]->addr);
 532                 }
 533         }
 534         printf("\n");
 535
 536         if (base_relative) {
 537                 output_label("kallsyms_relative_base");
 538                 output_address(relative_base);
 539                 printf("\n");
 540         }
 541
 542         output_label("kallsyms_num_syms");
 543         printf("\t.long\t%u\n", table_cnt);
 544         printf("\n");
 545
 546         /* table of offset markers, that give the offset in the compressed stream
 547          * every 256 symbols */
 548         markers = malloc(sizeof(unsigned int) * ((table_cnt + 255) / 256));
 549         if (!markers) {
 550                 fprintf(stderr, "kallsyms failure: "
 551                         "unable to allocate required memory\n");
 552                 exit(EXIT_FAILURE);
 553         }
 554
 555         output_label("kallsyms_names");
 556         off = 0;
 557         for (i = 0; i < table_cnt; i++) {
 558                 if ((i & 0xFF) == 0)
 559                         markers[i >> 8] = off;
 560                 table[i]->seq = i;
 561
 562                 /* There cannot be any symbol of length zero. */
 563                 if (table[i]->len == 0) {
 564                         fprintf(stderr, "kallsyms failure: "
 565                                 "unexpected zero symbol length\n");
 566                         exit(EXIT_FAILURE);
 567                 }
 568
 569                 /* Only lengths that fit in up-to-two-byte ULEB128 are supported. */
 570                 if (table[i]->len > 0x3FFF) {
 571                         fprintf(stderr, "kallsyms failure: "
 572                                 "unexpected huge symbol length\n");
 573                         exit(EXIT_FAILURE);
 574                 }
 575
 576                 /* Encode length with ULEB128. */
 577                 if (table[i]->len <= 0x7F) {
 578                         /* Most symbols use a single byte for the length. */
 579                         printf("\t.byte 0x%02x", table[i]->len);
 580                         off += table[i]->len + 1;
 581                 } else {
 582                         /* "Big" symbols use two bytes. */
 583                         printf("\t.byte 0x%02x, 0x%02x",
 584                                 (table[i]->len & 0x7F) | 0x80,
 585                                 (table[i]->len >> 7) & 0x7F);
 586                         off += table[i]->len + 2;
 587                 }
 588                 for (k = 0; k < table[i]->len; k++)
 589                         printf(", 0x%02x", table[i]->sym[k]);
 590                 printf("\n");
 591         }
 592         printf("\n");
 593
 594         output_label("kallsyms_markers");
 595         for (i = 0; i < ((table_cnt + 255) >> 8); i++)
 596                 printf("\t.long\t%u\n", markers[i]);
 597         printf("\n");
 598
 599         free(markers);
 600
 601         sort_symbols_by_name();
 602         output_label("kallsyms_seqs_of_names");
 603         for (i = 0; i < table_cnt; i++)
 604                 printf("\t.byte 0x%02x, 0x%02x, 0x%02x\n",
 605                         (unsigned char)(table[i]->seq >> 16),
 606                         (unsigned char)(table[i]->seq >> 8),
 607                         (unsigned char)(table[i]->seq >> 0));
 608         printf("\n");
 609
 610         output_label("kallsyms_token_table");
 611         off = 0;
 612         for (i = 0; i < 256; i++) {
 613                 best_idx[i] = off;
 614                 expand_symbol(best_table[i], best_table_len[i], buf);
 615                 printf("\t.asciz\t\"%s\"\n", buf);
 616                 off += strlen(buf) + 1;
 617         }
 618         printf("\n");
 619
 620         output_label("kallsyms_token_index");
 621         for (i = 0; i < 256; i++)
 622                 printf("\t.short\t%d\n", best_idx[i]);
 623         printf("\n");
 624 }
 625
 626
 627 /* table lookup compression functions */
 628
 629 /* count all the possible tokens in a symbol */
 630 static void learn_symbol(const unsigned char *symbol, int len)
 631 {
 632         int i;
 633
 634         for (i = 0; i < len - 1; i++)
 635                 token_profit[ symbol[i] + (symbol[i + 1] << 8) ]++;
 636 }
 637
 638 /* decrease the count for all the possible tokens in a symbol */
 639 static void forget_symbol(const unsigned char *symbol, int len)
 640 {
 641         int i;
 642
 643         for (i = 0; i < len - 1; i++)
 644                 token_profit[ symbol[i] + (symbol[i + 1] << 8) ]--;
 645 }
 646
 647 /* do the initial token count */
 648 static void build_initial_token_table(void)
 649 {
 650         unsigned int i;
 651
 652         for (i = 0; i < table_cnt; i++)
 653                 learn_symbol(table[i]->sym, table[i]->len);
 654 }
 655
 656 static unsigned char *find_token(unsigned char *str, int len,
 657                                  const unsigned char *token)
 658 {
 659         int i;
 660
 661         for (i = 0; i < len - 1; i++) {
 662                 if (str[i] == token[0] && str[i+1] == token[1])
 663                         return &str[i];
 664         }
 665         return NULL;
 666 }
 667
 668 /* replace a given token in all the valid symbols. Use the sampled symbols
 669  * to update the counts */
 670 static void compress_symbols(const unsigned char *str, int idx)
 671 {
 672         unsigned int i, len, size;
 673         unsigned char *p1, *p2;
 674
 675         for (i = 0; i < table_cnt; i++) {
 676
 677                 len = table[i]->len;
 678                 p1 = table[i]->sym;
 679
 680                 /* find the token on the symbol */
 681                 p2 = find_token(p1, len, str);
 682                 if (!p2) continue;
 683
 684                 /* decrease the counts for this symbol's tokens */
 685                 forget_symbol(table[i]->sym, len);
 686
 687                 size = len;
 688
 689                 do {
 690                         *p2 = idx;
 691                         p2++;
 692                         size -= (p2 - p1);
 693                         memmove(p2, p2 + 1, size);
 694                         p1 = p2;
 695                         len--;
 696
 697                         if (size < 2) break;
 698
 699                         /* find the token on the symbol */
 700                         p2 = find_token(p1, size, str);
 701
 702                 } while (p2);
 703
 704                 table[i]->len = len;
 705
 706                 /* increase the counts for this symbol's new tokens */
 707                 learn_symbol(table[i]->sym, len);
 708         }
 709 }
 710
 711 /* search the token with the maximum profit */
 712 static int find_best_token(void)
 713 {
 714         int i, best, bestprofit;
 715
 716         bestprofit=-10000;
 717         best = 0;
 718
 719         for (i = 0; i < 0x10000; i++) {
 720                 if (token_profit[i] > bestprofit) {
 721                         best = i;
 722                         bestprofit = token_profit[i];
 723                 }
 724         }
 725         return best;
 726 }
 727
 728 /* this is the core of the algorithm: calculate the "best" table */
 729 static void optimize_result(void)
 730 {
 731         int i, best;
 732
 733         /* using the '\0' symbol last allows compress_symbols to use standard
 734          * fast string functions */
 735         for (i = 255; i >= 0; i--) {
 736
 737                 /* if this table slot is empty (it is not used by an actual
 738                  * original char code */
 739                 if (!best_table_len[i]) {
 740
 741                         /* find the token with the best profit value */
 742                         best = find_best_token();
 743                         if (token_profit[best] == 0)
 744                                 break;
 745
 746                         /* place it in the "best" table */
 747                         best_table_len[i] = 2;
 748                         best_table[i][0] = best & 0xFF;
 749                         best_table[i][1] = (best >> 8) & 0xFF;
 750
 751                         /* replace this token in all the valid symbols */
 752                         compress_symbols(best_table[i], i);
 753                 }
 754         }
 755 }
 756
 757 /* start by placing the symbols that are actually used on the table */
 758 static void insert_real_symbols_in_table(void)
 759 {
 760         unsigned int i, j, c;
 761
 762         for (i = 0; i < table_cnt; i++) {
 763                 for (j = 0; j < table[i]->len; j++) {
 764                         c = table[i]->sym[j];
 765                         best_table[c][0]=c;
 766                         best_table_len[c]=1;
 767                 }
 768         }
 769 }
 770
 771 static void optimize_token_table(void)
 772 {
 773         build_initial_token_table();
 774
 775         insert_real_symbols_in_table();
 776
 777         optimize_result();
 778 }
 779
 780 /* guess for "linker script provide" symbol */
 781 static int may_be_linker_script_provide_symbol(const struct sym_entry *se)
 782 {
 783         const char *symbol = sym_name(se);
 784         int len = se->len - 1;
 785
 786         if (len < 8)
 787                 return 0;
 788
 789         if (symbol[0] != '_' || symbol[1] != '_')
 790                 return 0;
 791
 792         /* __start_XXXXX */
 793         if (!memcmp(symbol + 2, "start_", 6))
 794                 return 1;
 795
 796         /* __stop_XXXXX */
 797         if (!memcmp(symbol + 2, "stop_", 5))
 798                 return 1;
 799
 800         /* __end_XXXXX */
 801         if (!memcmp(symbol + 2, "end_", 4))
 802                 return 1;
 803
 804         /* __XXXXX_start */
 805         if (!memcmp(symbol + len - 6, "_start", 6))
 806                 return 1;
 807
 808         /* __XXXXX_end */
 809         if (!memcmp(symbol + len - 4, "_end", 4))
 810                 return 1;
 811
 812         return 0;
 813 }
 814
 815 static int compare_symbols(const void *a, const void *b)
 816 {
 817         const struct sym_entry *sa = *(const struct sym_entry **)a;
 818         const struct sym_entry *sb = *(const struct sym_entry **)b;
 819         int wa, wb;
 820
 821         /* sort by address first */
 822         if (sa->addr > sb->addr)
 823                 return 1;
 824         if (sa->addr < sb->addr)
 825                 return -1;
 826
 827         /* sort by "weakness" type */
 828         wa = (sa->sym[0] == 'w') || (sa->sym[0] == 'W');
 829         wb = (sb->sym[0] == 'w') || (sb->sym[0] == 'W');
 830         if (wa != wb)
 831                 return wa - wb;
 832
 833         /* sort by "linker script provide" type */
 834         wa = may_be_linker_script_provide_symbol(sa);
 835         wb = may_be_linker_script_provide_symbol(sb);
 836         if (wa != wb)
 837                 return wa - wb;
 838
 839         /* sort by the number of prefix underscores */
 840         wa = strspn(sym_name(sa), "_");
 841         wb = strspn(sym_name(sb), "_");
 842         if (wa != wb)
 843                 return wa - wb;
 844
 845         /* sort by initial order, so that other symbols are left undisturbed */
 846         return sa->start_pos - sb->start_pos;
 847 }
 848
 849 static void sort_symbols(void)
 850 {
 851         qsort(table, table_cnt, sizeof(table[0]), compare_symbols);
 852 }
 853
 854 static void make_percpus_absolute(void)
 855 {
 856         unsigned int i;
 857
 858         for (i = 0; i < table_cnt; i++)
 859                 if (symbol_in_range(table[i], &percpu_range, 1)) {
 860                         /*
 861                          * Keep the 'A' override for percpu symbols to
 862                          * ensure consistent behavior compared to older
 863                          * versions of this tool.
 864                          */
 865                         table[i]->sym[0] = 'A';
 866                         table[i]->percpu_absolute = 1;
 867                 }
 868 }
 869
 870 /* find the minimum non-absolute symbol address */
 871 static void record_relative_base(void)
 872 {
 873         unsigned int i;
 874
 875         for (i = 0; i < table_cnt; i++)
 876                 if (!symbol_absolute(table[i])) {
 877                         /*
 878                          * The table is sorted by address.
 879                          * Take the first non-absolute symbol value.
 880                          */
 881                         relative_base = table[i]->addr;
 882                         return;
 883                 }
 884 }
 885
 886 int main(int argc, char **argv)
 887 {
 888         while (1) {
 889                 static struct option long_options[] = {
 890                         {"all-symbols",     no_argument, &all_symbols,     1},
 891                         {"absolute-percpu", no_argument, &absolute_percpu, 1},
 892                         {"base-relative",   no_argument, &base_relative,   1},
 893                         {"lto-clang",       no_argument, &lto_clang,       1},
 894                         {},
 895                 };
 896
 897                 int c = getopt_long(argc, argv, "", long_options, NULL);
 898
 899                 if (c == -1)
 900                         break;
 901                 if (c != 0)
 902                         usage();
 903         }
 904
 905         if (optind >= argc)
 906                 usage();
 907
 908         read_map(argv[optind]);
 909         shrink_table();
 910         if (absolute_percpu)
 911                 make_percpus_absolute();
 912         sort_symbols();
 913         if (base_relative)
 914                 record_relative_base();
 915         optimize_token_table();
 916         write_src();
 917
 918         return 0;
 919 }