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: 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
  26 #ifndef ARRAY_SIZE
  27 #define ARRAY_SIZE(arr) (sizeof(arr) / sizeof(arr[0]))
  28 #endif
  29
  30 #define KSYM_NAME_LEN           128
  31
  32 struct sym_entry {
  33         unsigned long long addr;
  34         unsigned int len;
  35         unsigned int start_pos;
  36         unsigned char *sym;
  37 };
  38
  39 struct text_range {
  40         const char *stext, *etext;
  41         unsigned long long start, end;
  42 };
  43
  44 static unsigned long long _text;
  45 static struct text_range text_ranges[] = {
  46         { "_stext",     "_etext"     },
  47         { "_sinittext", "_einittext" },
  48         { "_stext_l1",  "_etext_l1"  }, /* Blackfin on-chip L1 inst SRAM */
  49         { "_stext_l2",  "_etext_l2"  }, /* Blackfin on-chip L2 SRAM */
  50 };
  51 #define text_range_text     (&text_ranges[0])
  52 #define text_range_inittext (&text_ranges[1])
  53
  54 static struct sym_entry *table;
  55 static unsigned int table_size, table_cnt;
  56 static int all_symbols = 0;
  57 static char symbol_prefix_char = '\0';
  58
  59 int token_profit[0x10000];
  60
  61 /* the table that holds the result of the compression */
  62 unsigned char best_table[256][2];
  63 unsigned char best_table_len[256];
  64
  65
  66 static void usage(void)
  67 {
  68         fprintf(stderr, "Usage: kallsyms [--all-symbols] [--symbol-prefix=<prefix char>] < in.map > out.S\n");
  69         exit(1);
  70 }
  71
  72 /*
  73  * This ignores the intensely annoying "mapping symbols" found
  74  * in ARM ELF files: $a, $t and $d.
  75  */
  76 static inline int is_arm_mapping_symbol(const char *str)
  77 {
  78         return str[0] == '$' && strchr("atd", str[1])
  79                && (str[2] == '\0' || str[2] == '.');
  80 }
  81
  82 static int read_symbol_tr(const char *sym, unsigned long long addr)
  83 {
  84         size_t i;
  85         struct text_range *tr;
  86
  87         for (i = 0; i < ARRAY_SIZE(text_ranges); ++i) {
  88                 tr = &text_ranges[i];
  89
  90                 if (strcmp(sym, tr->stext) == 0) {
  91                         tr->start = addr;
  92                         return 0;
  93                 } else if (strcmp(sym, tr->etext) == 0) {
  94                         tr->end = addr;
  95                         return 0;
  96                 }
  97         }
  98
  99         return 1;
 100 }
 101
 102 static int read_symbol(FILE *in, struct sym_entry *s)
 103 {
 104         char str[500];
 105         char *sym, stype;
 106         int rc;
 107
 108         rc = fscanf(in, "%llx %c %499s\n", &s->addr, &stype, str);
 109         if (rc != 3) {
 110                 if (rc != EOF) {
 111                         /* skip line */
 112                         fgets(str, 500, in);
 113                 }
 114                 return -1;
 115         }
 116
 117         sym = str;
 118         /* skip prefix char */
 119         if (symbol_prefix_char && str[0] == symbol_prefix_char)
 120                 sym++;
 121
 122         /* Ignore most absolute/undefined (?) symbols. */
 123         if (strcmp(sym, "_text") == 0)
 124                 _text = s->addr;
 125         else if (read_symbol_tr(sym, s->addr) == 0)
 126                 /* nothing to do */;
 127         else if (toupper(stype) == 'A')
 128         {
 129                 /* Keep these useful absolute symbols */
 130                 if (strcmp(sym, "__kernel_syscall_via_break") &&
 131                     strcmp(sym, "__kernel_syscall_via_epc") &&
 132                     strcmp(sym, "__kernel_sigtramp") &&
 133                     strcmp(sym, "__gp"))
 134                         return -1;
 135
 136         }
 137         else if (toupper(stype) == 'U' ||
 138                  is_arm_mapping_symbol(sym))
 139                 return -1;
 140         /* exclude also MIPS ELF local symbols ($L123 instead of .L123) */
 141         else if (str[0] == '$')
 142                 return -1;
 143         /* exclude debugging symbols */
 144         else if (stype == 'N')
 145                 return -1;
 146
 147         /* include the type field in the symbol name, so that it gets
 148          * compressed together */
 149         s->len = strlen(str) + 1;
 150         s->sym = malloc(s->len + 1);
 151         if (!s->sym) {
 152                 fprintf(stderr, "kallsyms failure: "
 153                         "unable to allocate required amount of memory\n");
 154                 exit(EXIT_FAILURE);
 155         }
 156         strcpy((char *)s->sym + 1, str);
 157         s->sym[0] = stype;
 158
 159         return 0;
 160 }
 161
 162 static int symbol_valid_tr(struct sym_entry *s)
 163 {
 164         size_t i;
 165         struct text_range *tr;
 166
 167         for (i = 0; i < ARRAY_SIZE(text_ranges); ++i) {
 168                 tr = &text_ranges[i];
 169
 170                 if (s->addr >= tr->start && s->addr <= tr->end)
 171                         return 1;
 172         }
 173
 174         return 0;
 175 }
 176
 177 static int symbol_valid(struct sym_entry *s)
 178 {
 179         /* Symbols which vary between passes.  Passes 1 and 2 must have
 180          * identical symbol lists.  The kallsyms_* symbols below are only added
 181          * after pass 1, they would be included in pass 2 when --all-symbols is
 182          * specified so exclude them to get a stable symbol list.
 183          */
 184         static char *special_symbols[] = {
 185                 "kallsyms_addresses",
 186                 "kallsyms_num_syms",
 187                 "kallsyms_names",
 188                 "kallsyms_markers",
 189                 "kallsyms_token_table",
 190                 "kallsyms_token_index",
 191
 192         /* Exclude linker generated symbols which vary between passes */
 193                 "_SDA_BASE_",           /* ppc */
 194                 "_SDA2_BASE_",          /* ppc */
 195                 NULL };
 196         int i;
 197         int offset = 1;
 198
 199         /* skip prefix char */
 200         if (symbol_prefix_char && *(s->sym + 1) == symbol_prefix_char)
 201                 offset++;
 202
 203         /* if --all-symbols is not specified, then symbols outside the text
 204          * and inittext sections are discarded */
 205         if (!all_symbols) {
 206                 if (symbol_valid_tr(s) == 0)
 207                         return 0;
 208                 /* Corner case.  Discard any symbols with the same value as
 209                  * _etext _einittext; they can move between pass 1 and 2 when
 210                  * the kallsyms data are added.  If these symbols move then
 211                  * they may get dropped in pass 2, which breaks the kallsyms
 212                  * rules.
 213                  */
 214                 if ((s->addr == text_range_text->end &&
 215                                 strcmp((char *)s->sym + offset, text_range_text->etext)) ||
 216                     (s->addr == text_range_inittext->end &&
 217                                 strcmp((char *)s->sym + offset, text_range_inittext->etext)))
 218                         return 0;
 219         }
 220
 221         /* Exclude symbols which vary between passes. */
 222         if (strstr((char *)s->sym + offset, "_compiled."))
 223                 return 0;
 224
 225         for (i = 0; special_symbols[i]; i++)
 226                 if( strcmp((char *)s->sym + offset, special_symbols[i]) == 0 )
 227                         return 0;
 228
 229         return 1;
 230 }
 231
 232 static void read_map(FILE *in)
 233 {
 234         while (!feof(in)) {
 235                 if (table_cnt >= table_size) {
 236                         table_size += 10000;
 237                         table = realloc(table, sizeof(*table) * table_size);
 238                         if (!table) {
 239                                 fprintf(stderr, "out of memory\n");
 240                                 exit (1);
 241                         }
 242                 }
 243                 if (read_symbol(in, &table[table_cnt]) == 0) {
 244                         table[table_cnt].start_pos = table_cnt;
 245                         table_cnt++;
 246                 }
 247         }
 248 }
 249
 250 static void output_label(char *label)
 251 {
 252         if (symbol_prefix_char)
 253                 printf(".globl %c%s\n", symbol_prefix_char, label);
 254         else
 255                 printf(".globl %s\n", label);
 256         printf("\tALGN\n");
 257         if (symbol_prefix_char)
 258                 printf("%c%s:\n", symbol_prefix_char, label);
 259         else
 260                 printf("%s:\n", label);
 261 }
 262
 263 /* uncompress a compressed symbol. When this function is called, the best table
 264  * might still be compressed itself, so the function needs to be recursive */
 265 static int expand_symbol(unsigned char *data, int len, char *result)
 266 {
 267         int c, rlen, total=0;
 268
 269         while (len) {
 270                 c = *data;
 271                 /* if the table holds a single char that is the same as the one
 272                  * we are looking for, then end the search */
 273                 if (best_table[c][0]==c && best_table_len[c]==1) {
 274                         *result++ = c;
 275                         total++;
 276                 } else {
 277                         /* if not, recurse and expand */
 278                         rlen = expand_symbol(best_table[c], best_table_len[c], result);
 279                         total += rlen;
 280                         result += rlen;
 281                 }
 282                 data++;
 283                 len--;
 284         }
 285         *result=0;
 286
 287         return total;
 288 }
 289
 290 static void write_src(void)
 291 {
 292         unsigned int i, k, off;
 293         unsigned int best_idx[256];
 294         unsigned int *markers;
 295         char buf[KSYM_NAME_LEN];
 296
 297         printf("#include <asm/types.h>\n");
 298         printf("#if BITS_PER_LONG == 64\n");
 299         printf("#define PTR .quad\n");
 300         printf("#define ALGN .align 8\n");
 301         printf("#else\n");
 302         printf("#define PTR .long\n");
 303         printf("#define ALGN .align 4\n");
 304         printf("#endif\n");
 305
 306         printf("\t.section .rodata, \"a\"\n");
 307
 308         /* Provide proper symbols relocatability by their '_text'
 309          * relativeness.  The symbol names cannot be used to construct
 310          * normal symbol references as the list of symbols contains
 311          * symbols that are declared static and are private to their
 312          * .o files.  This prevents .tmp_kallsyms.o or any other
 313          * object from referencing them.
 314          */
 315         output_label("kallsyms_addresses");
 316         for (i = 0; i < table_cnt; i++) {
 317                 if (toupper(table[i].sym[0]) != 'A') {
 318                         if (_text <= table[i].addr)
 319                                 printf("\tPTR\t_text + %#llx\n",
 320                                         table[i].addr - _text);
 321                         else
 322                                 printf("\tPTR\t_text - %#llx\n",
 323                                         _text - table[i].addr);
 324                 } else {
 325                         printf("\tPTR\t%#llx\n", table[i].addr);
 326                 }
 327         }
 328         printf("\n");
 329
 330         output_label("kallsyms_num_syms");
 331         printf("\tPTR\t%d\n", table_cnt);
 332         printf("\n");
 333
 334         /* table of offset markers, that give the offset in the compressed stream
 335          * every 256 symbols */
 336         markers = malloc(sizeof(unsigned int) * ((table_cnt + 255) / 256));
 337         if (!markers) {
 338                 fprintf(stderr, "kallsyms failure: "
 339                         "unable to allocate required memory\n");
 340                 exit(EXIT_FAILURE);
 341         }
 342
 343         output_label("kallsyms_names");
 344         off = 0;
 345         for (i = 0; i < table_cnt; i++) {
 346                 if ((i & 0xFF) == 0)
 347                         markers[i >> 8] = off;
 348
 349                 printf("\t.byte 0x%02x", table[i].len);
 350                 for (k = 0; k < table[i].len; k++)
 351                         printf(", 0x%02x", table[i].sym[k]);
 352                 printf("\n");
 353
 354                 off += table[i].len + 1;
 355         }
 356         printf("\n");
 357
 358         output_label("kallsyms_markers");
 359         for (i = 0; i < ((table_cnt + 255) >> 8); i++)
 360                 printf("\tPTR\t%d\n", markers[i]);
 361         printf("\n");
 362
 363         free(markers);
 364
 365         output_label("kallsyms_token_table");
 366         off = 0;
 367         for (i = 0; i < 256; i++) {
 368                 best_idx[i] = off;
 369                 expand_symbol(best_table[i], best_table_len[i], buf);
 370                 printf("\t.asciz\t\"%s\"\n", buf);
 371                 off += strlen(buf) + 1;
 372         }
 373         printf("\n");
 374
 375         output_label("kallsyms_token_index");
 376         for (i = 0; i < 256; i++)
 377                 printf("\t.short\t%d\n", best_idx[i]);
 378         printf("\n");
 379 }
 380
 381
 382 /* table lookup compression functions */
 383
 384 /* count all the possible tokens in a symbol */
 385 static void learn_symbol(unsigned char *symbol, int len)
 386 {
 387         int i;
 388
 389         for (i = 0; i < len - 1; i++)
 390                 token_profit[ symbol[i] + (symbol[i + 1] << 8) ]++;
 391 }
 392
 393 /* decrease the count for all the possible tokens in a symbol */
 394 static void forget_symbol(unsigned char *symbol, int len)
 395 {
 396         int i;
 397
 398         for (i = 0; i < len - 1; i++)
 399                 token_profit[ symbol[i] + (symbol[i + 1] << 8) ]--;
 400 }
 401
 402 /* remove all the invalid symbols from the table and do the initial token count */
 403 static void build_initial_tok_table(void)
 404 {
 405         unsigned int i, pos;
 406
 407         pos = 0;
 408         for (i = 0; i < table_cnt; i++) {
 409                 if ( symbol_valid(&table[i]) ) {
 410                         if (pos != i)
 411                                 table[pos] = table[i];
 412                         learn_symbol(table[pos].sym, table[pos].len);
 413                         pos++;
 414                 }
 415         }
 416         table_cnt = pos;
 417 }
 418
 419 static void *find_token(unsigned char *str, int len, unsigned char *token)
 420 {
 421         int i;
 422
 423         for (i = 0; i < len - 1; i++) {
 424                 if (str[i] == token[0] && str[i+1] == token[1])
 425                         return &str[i];
 426         }
 427         return NULL;
 428 }
 429
 430 /* replace a given token in all the valid symbols. Use the sampled symbols
 431  * to update the counts */
 432 static void compress_symbols(unsigned char *str, int idx)
 433 {
 434         unsigned int i, len, size;
 435         unsigned char *p1, *p2;
 436
 437         for (i = 0; i < table_cnt; i++) {
 438
 439                 len = table[i].len;
 440                 p1 = table[i].sym;
 441
 442                 /* find the token on the symbol */
 443                 p2 = find_token(p1, len, str);
 444                 if (!p2) continue;
 445
 446                 /* decrease the counts for this symbol's tokens */
 447                 forget_symbol(table[i].sym, len);
 448
 449                 size = len;
 450
 451                 do {
 452                         *p2 = idx;
 453                         p2++;
 454                         size -= (p2 - p1);
 455                         memmove(p2, p2 + 1, size);
 456                         p1 = p2;
 457                         len--;
 458
 459                         if (size < 2) break;
 460
 461                         /* find the token on the symbol */
 462                         p2 = find_token(p1, size, str);
 463
 464                 } while (p2);
 465
 466                 table[i].len = len;
 467
 468                 /* increase the counts for this symbol's new tokens */
 469                 learn_symbol(table[i].sym, len);
 470         }
 471 }
 472
 473 /* search the token with the maximum profit */
 474 static int find_best_token(void)
 475 {
 476         int i, best, bestprofit;
 477
 478         bestprofit=-10000;
 479         best = 0;
 480
 481         for (i = 0; i < 0x10000; i++) {
 482                 if (token_profit[i] > bestprofit) {
 483                         best = i;
 484                         bestprofit = token_profit[i];
 485                 }
 486         }
 487         return best;
 488 }
 489
 490 /* this is the core of the algorithm: calculate the "best" table */
 491 static void optimize_result(void)
 492 {
 493         int i, best;
 494
 495         /* using the '\0' symbol last allows compress_symbols to use standard
 496          * fast string functions */
 497         for (i = 255; i >= 0; i--) {
 498
 499                 /* if this table slot is empty (it is not used by an actual
 500                  * original char code */
 501                 if (!best_table_len[i]) {
 502
 503                         /* find the token with the breates profit value */
 504                         best = find_best_token();
 505
 506                         /* place it in the "best" table */
 507                         best_table_len[i] = 2;
 508                         best_table[i][0] = best & 0xFF;
 509                         best_table[i][1] = (best >> 8) & 0xFF;
 510
 511                         /* replace this token in all the valid symbols */
 512                         compress_symbols(best_table[i], i);
 513                 }
 514         }
 515 }
 516
 517 /* start by placing the symbols that are actually used on the table */
 518 static void insert_real_symbols_in_table(void)
 519 {
 520         unsigned int i, j, c;
 521
 522         memset(best_table, 0, sizeof(best_table));
 523         memset(best_table_len, 0, sizeof(best_table_len));
 524
 525         for (i = 0; i < table_cnt; i++) {
 526                 for (j = 0; j < table[i].len; j++) {
 527                         c = table[i].sym[j];
 528                         best_table[c][0]=c;
 529                         best_table_len[c]=1;
 530                 }
 531         }
 532 }
 533
 534 static void optimize_token_table(void)
 535 {
 536         build_initial_tok_table();
 537
 538         insert_real_symbols_in_table();
 539
 540         /* When valid symbol is not registered, exit to error */
 541         if (!table_cnt) {
 542                 fprintf(stderr, "No valid symbol.\n");
 543                 exit(1);
 544         }
 545
 546         optimize_result();
 547 }
 548
 549 /* guess for "linker script provide" symbol */
 550 static int may_be_linker_script_provide_symbol(const struct sym_entry *se)
 551 {
 552         const char *symbol = (char *)se->sym + 1;
 553         int len = se->len - 1;
 554
 555         if (len < 8)
 556                 return 0;
 557
 558         if (symbol[0] != '_' || symbol[1] != '_')
 559                 return 0;
 560
 561         /* __start_XXXXX */
 562         if (!memcmp(symbol + 2, "start_", 6))
 563                 return 1;
 564
 565         /* __stop_XXXXX */
 566         if (!memcmp(symbol + 2, "stop_", 5))
 567                 return 1;
 568
 569         /* __end_XXXXX */
 570         if (!memcmp(symbol + 2, "end_", 4))
 571                 return 1;
 572
 573         /* __XXXXX_start */
 574         if (!memcmp(symbol + len - 6, "_start", 6))
 575                 return 1;
 576
 577         /* __XXXXX_end */
 578         if (!memcmp(symbol + len - 4, "_end", 4))
 579                 return 1;
 580
 581         return 0;
 582 }
 583
 584 static int prefix_underscores_count(const char *str)
 585 {
 586         const char *tail = str;
 587
 588         while (*tail == '_')
 589                 tail++;
 590
 591         return tail - str;
 592 }
 593
 594 static int compare_symbols(const void *a, const void *b)
 595 {
 596         const struct sym_entry *sa;
 597         const struct sym_entry *sb;
 598         int wa, wb;
 599
 600         sa = a;
 601         sb = b;
 602
 603         /* sort by address first */
 604         if (sa->addr > sb->addr)
 605                 return 1;
 606         if (sa->addr < sb->addr)
 607                 return -1;
 608
 609         /* sort by "weakness" type */
 610         wa = (sa->sym[0] == 'w') || (sa->sym[0] == 'W');
 611         wb = (sb->sym[0] == 'w') || (sb->sym[0] == 'W');
 612         if (wa != wb)
 613                 return wa - wb;
 614
 615         /* sort by "linker script provide" type */
 616         wa = may_be_linker_script_provide_symbol(sa);
 617         wb = may_be_linker_script_provide_symbol(sb);
 618         if (wa != wb)
 619                 return wa - wb;
 620
 621         /* sort by the number of prefix underscores */
 622         wa = prefix_underscores_count((const char *)sa->sym + 1);
 623         wb = prefix_underscores_count((const char *)sb->sym + 1);
 624         if (wa != wb)
 625                 return wa - wb;
 626
 627         /* sort by initial order, so that other symbols are left undisturbed */
 628         return sa->start_pos - sb->start_pos;
 629 }
 630
 631 static void sort_symbols(void)
 632 {
 633         qsort(table, table_cnt, sizeof(struct sym_entry), compare_symbols);
 634 }
 635
 636 int main(int argc, char **argv)
 637 {
 638         if (argc >= 2) {
 639                 int i;
 640                 for (i = 1; i < argc; i++) {
 641                         if(strcmp(argv[i], "--all-symbols") == 0)
 642                                 all_symbols = 1;
 643                         else if (strncmp(argv[i], "--symbol-prefix=", 16) == 0) {
 644                                 char *p = &argv[i][16];
 645                                 /* skip quote */
 646                                 if ((*p == '"' && *(p+2) == '"') || (*p == '\'' && *(p+2) == '\''))
 647                                         p++;
 648                                 symbol_prefix_char = *p;
 649                         } else
 650                                 usage();
 651                 }
 652         } else if (argc != 1)
 653                 usage();
 654
 655         read_map(stdin);
 656         sort_symbols();
 657         optimize_token_table();
 658         write_src();
 659
 660         return 0;
 661 }