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