trunk/lto-plugin/lto-plugin.c

   1 /* LTO plugin for gold.
   2    Copyright (C) 2009 Free Software Foundation, Inc.
   3    Contributed by Rafael Avila de Espindola (espindola@google.com).
   4
   5 This program is free software; you can redistribute it and/or modify
   6 it under the terms of the GNU General Public License as published by
   7 the Free Software Foundation; either version 3, or (at your option)
   8 any later version.
   9
  10 This program is distributed in the hope that it will be useful, but
  11 WITHOUT ANY WARRANTY; without even the implied warranty of
  12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13 General Public License for more details.
  14
  15 You should have received a copy of the GNU General Public License
  16 along with this program; see the file COPYING3.  If not see
  17 <http://www.gnu.org/licenses/>.  */
  18
  19 /* The plugin has only one external function: onload. Gold passes it an array of
  20    function that the plugin uses to communicate back to gold.
  21
  22    With the functions provided by gold, the plugin can be notified when
  23    gold first analyzes a file and pass a symbol table back to gold. The plugin
  24    is also notified when all symbols have been read and it is time to generate
  25    machine code for the necessary symbols.
  26
  27    More information at http://gcc.gnu.org/wiki/whopr/driver.
  28
  29    This plugin should be passed the lto-wrapper options and will forward them.
  30    It also has 2 options of its own:
  31    -debug: Print the command line used to run lto-wrapper.
  32    -nop: Instead of running lto-wrapper, pass the original to the plugin. This
  33    only works if the input files are hybrid.  */
  34
  35 #include <assert.h>
  36 #include <string.h>
  37 #include <stdlib.h>
  38 #include <stdio.h>
  39 #include <inttypes.h>
  40 #include <sys/stat.h>
  41 #include <unistd.h>
  42 #include <fcntl.h>
  43 #include <sys/types.h>
  44 #include <sys/wait.h>
  45 #include <stdbool.h>
  46 #include <libiberty.h>
  47
  48 /* The presence of gelf.h is checked by the toplevel configure script.  */
  49 #include <gelf.h>
  50
  51 #include "plugin-api.h"
  52 #include "../gcc/lto/common.h"
  53
  54 /* The part of the symbol table the plugin has to keep track of. Note that we
  55    must keep SYMS until all_symbols_read is called to give the linker time to
  56    copy the symbol information. */
  57
  58 struct plugin_symtab
  59 {
  60   int nsyms;
  61   uint32_t *slots;
  62   struct ld_plugin_symbol *syms;
  63 };
  64
  65 /* All that we have to remember about a file. */
  66
  67 struct plugin_file_info
  68 {
  69   char *name;
  70   void *handle;
  71   struct plugin_symtab symtab;
  72 };
  73
  74
  75 static char *arguments_file_name;
  76 static ld_plugin_register_claim_file register_claim_file;
  77 static ld_plugin_add_symbols add_symbols;
  78 static ld_plugin_register_all_symbols_read register_all_symbols_read;
  79 static ld_plugin_get_symbols get_symbols;
  80 static ld_plugin_register_cleanup register_cleanup;
  81 static ld_plugin_add_input_file add_input_file;
  82 static ld_plugin_add_input_library add_input_library;
  83 static ld_plugin_message message;
  84
  85 static struct plugin_file_info *claimed_files = NULL;
  86 static unsigned int num_claimed_files = 0;
  87
  88 static char **output_files = NULL;
  89 static unsigned int num_output_files = 0;
  90
  91 static char **lto_wrapper_argv;
  92 static int lto_wrapper_num_args;
  93
  94 static char **pass_through_items = NULL;
  95 static unsigned int num_pass_through_items;
  96
  97 static bool debug;
  98 static bool nop;
  99 static char *resolution_file = NULL;
 100
 101 static void
 102 check (bool gate, enum ld_plugin_level level, const char *text)
 103 {
 104   if (gate)
 105     return;
 106
 107   if (message)
 108     message (level, text);
 109   else
 110     {
 111       /* If there is no nicer way to inform the user, fallback to stderr. */
 112       fprintf (stderr, "%s\n", text);
 113       if (level == LDPL_FATAL)
 114         abort ();
 115     }
 116 }
 117
 118 /* Parse an entry of the IL symbol table. The data to be parsed is pointed
 119    by P and the result is written in ENTRY. The slot number is stored in SLOT.
 120    Returns the address of the next entry. */
 121
 122 static char *
 123 parse_table_entry (char *p, struct ld_plugin_symbol *entry, uint32_t *slot)
 124 {
 125   unsigned char t;
 126   enum ld_plugin_symbol_kind translate_kind[] =
 127     {
 128       LDPK_DEF,
 129       LDPK_WEAKDEF,
 130       LDPK_UNDEF,
 131       LDPK_WEAKUNDEF,
 132       LDPK_COMMON
 133     };
 134
 135   enum ld_plugin_symbol_visibility translate_visibility[] =
 136     {
 137       LDPV_DEFAULT,
 138       LDPV_PROTECTED,
 139       LDPV_INTERNAL,
 140       LDPV_HIDDEN
 141     };
 142
 143   entry->name = strdup (p);
 144   while (*p)
 145     p++;
 146   p++;
 147
 148   entry->version = NULL;
 149
 150   entry->comdat_key = p;
 151   while (*p)
 152     p++;
 153   p++;
 154
 155   if (strlen (entry->comdat_key) == 0)
 156     entry->comdat_key = NULL;
 157   else
 158     entry->comdat_key = strdup (entry->comdat_key);
 159
 160   t = *p;
 161   check (t <= 4, LDPL_FATAL, "invalid symbol kind found");
 162   entry->def = translate_kind[t];
 163   p++;
 164
 165   t = *p;
 166   check (t <= 3, LDPL_FATAL, "invalid symbol visibility found");
 167   entry->visibility = translate_visibility[t];
 168   p++;
 169
 170   entry->size = *(uint64_t *) p;
 171   p += 8;
 172
 173   *slot = *(uint32_t *) p;
 174   p += 4;
 175
 176   entry->resolution = LDPR_UNKNOWN;
 177
 178   return p;
 179 }
 180
 181 /* Return the section in ELF that is named NAME. */
 182
 183 static Elf_Scn *
 184 get_section (Elf *elf, const char *name)
 185 {
 186   Elf_Scn *section = 0;
 187   GElf_Ehdr header;
 188   GElf_Ehdr *t = gelf_getehdr (elf, &header);
 189   if (t == NULL)
 190     return NULL;
 191   assert (t == &header);
 192
 193   while ((section = elf_nextscn(elf, section)) != 0)
 194     {
 195       GElf_Shdr shdr;
 196       GElf_Shdr *tshdr = gelf_getshdr (section, &shdr);
 197       const char *t;
 198       assert (tshdr == &shdr);
 199       t = elf_strptr (elf, header.e_shstrndx, shdr.sh_name);
 200       assert (t != NULL);
 201       if (strcmp (t, name) == 0)
 202         return section;
 203     }
 204   return NULL;
 205 }
 206
 207 /* Returns the IL symbol table of file ELF. */
 208
 209 static Elf_Data *
 210 get_symtab (Elf *elf)
 211 {
 212   Elf_Data *data = 0;
 213   Elf_Scn *section = get_section (elf, ".gnu.lto_.symtab");
 214   if (!section)
 215     return NULL;
 216
 217   data = elf_getdata (section, data);
 218   assert (data);
 219   return data;
 220 }
 221
 222 /* Translate the IL symbol table SYMTAB. Write the slots and symbols in OUT. */
 223
 224 static void
 225 translate (Elf_Data *symtab, struct plugin_symtab *out)
 226 {
 227   uint32_t *slots = NULL;
 228   char *data = symtab->d_buf;
 229   char *end = data + symtab->d_size;
 230   struct ld_plugin_symbol *syms = NULL;
 231   int n = 0;
 232
 233   while (data < end)
 234     {
 235       n++;
 236       syms = realloc (syms, n * sizeof (struct ld_plugin_symbol));
 237       check (syms, LDPL_FATAL, "could not allocate memory");
 238       slots = realloc (slots, n * sizeof (uint32_t));
 239       check (slots, LDPL_FATAL, "could not allocate memory");
 240       data = parse_table_entry (data, &syms[n - 1], &slots[n - 1]);
 241     }
 242
 243   out->nsyms = n;
 244   out->syms = syms;
 245   out->slots = slots;
 246 }
 247
 248 /* Free all memory that is no longer needed after writing the symbol
 249    resolution. */
 250
 251 static void
 252 free_1 (void)
 253 {
 254   unsigned int i;
 255   for (i = 0; i < num_claimed_files; i++)
 256     {
 257       struct plugin_file_info *info = &claimed_files[i];
 258       struct plugin_symtab *symtab = &info->symtab;
 259       unsigned int j;
 260       for (j = 0; j < symtab->nsyms; j++)
 261         {
 262           struct ld_plugin_symbol *s = &symtab->syms[j];
 263           free (s->name);
 264           if (s->comdat_key)
 265             free (s->comdat_key);
 266         }
 267       free (symtab->syms);
 268       symtab->syms = NULL;
 269     }
 270 }
 271
 272 /* Free all remaining memory. */
 273
 274 static void
 275 free_2 (void)
 276 {
 277   unsigned int i;
 278   for (i = 0; i < num_claimed_files; i++)
 279     {
 280       struct plugin_file_info *info = &claimed_files[i];
 281       struct plugin_symtab *symtab = &info->symtab;
 282       free (symtab->slots);
 283       free (info->name);
 284     }
 285
 286   for (i = 0; i < num_output_files; i++)
 287     free (output_files[i]);
 288   free (output_files);
 289
 290   free (claimed_files);
 291   claimed_files = NULL;
 292   num_claimed_files = 0;
 293
 294   if (arguments_file_name)
 295     free (arguments_file_name);
 296   arguments_file_name = NULL;
 297
 298   if (resolution_file)
 299     {
 300       free (resolution_file);
 301       resolution_file = NULL;
 302     }
 303 }
 304
 305 /*  Writes the relocations to disk. */
 306
 307 static void
 308 write_resolution (void)
 309 {
 310   unsigned int i;
 311   FILE *f;
 312
 313   f = fopen (resolution_file, "w");
 314   check (f, LDPL_FATAL, "could not open file");
 315
 316   fprintf (f, "%d\n", num_claimed_files);
 317
 318   for (i = 0; i < num_claimed_files; i++)
 319     {
 320       struct plugin_file_info *info = &claimed_files[i];
 321       struct plugin_symtab *symtab = &info->symtab;
 322       struct ld_plugin_symbol *syms = symtab->syms;
 323       unsigned j;
 324
 325       assert (syms);
 326       get_symbols (info->handle, symtab->nsyms, syms);
 327
 328       fprintf (f, "%s %d\n", info->name, info->symtab.nsyms);
 329
 330       for (j = 0; j < info->symtab.nsyms; j++)
 331         {
 332           uint32_t slot = symtab->slots[j];
 333           unsigned int resolution = syms[j].resolution;
 334           fprintf (f, "%d %s %s\n", slot, lto_resolution_str[resolution], syms[j].name);
 335         }
 336     }
 337   fclose (f);
 338 }
 339
 340 /* Pass files generated by the lto-wrapper to the linker. FD is lto-wrapper's
 341    stdout. */
 342
 343 static void
 344 add_output_files (FILE *f)
 345 {
 346   char fname[1000]; /* FIXME: Remove this restriction. */
 347
 348   for (;;)
 349     {
 350       size_t len;
 351       char *s = fgets (fname, sizeof (fname), f);
 352       if (!s)
 353         break;
 354
 355       len = strlen (s);
 356       check (s[len - 1] == '\n', LDPL_FATAL, "file name too long");
 357       s[len - 1] = '\0';
 358
 359       num_output_files++;
 360       output_files = realloc (output_files, num_output_files * sizeof (char *));
 361       output_files[num_output_files - 1] = strdup (s);
 362       add_input_file (output_files[num_output_files - 1]);
 363     }
 364 }
 365
 366 /* Execute the lto-wrapper. ARGV[0] is the binary. The rest of ARGV is the
 367    argument list. */
 368
 369 static void
 370 exec_lto_wrapper (char *argv[])
 371 {
 372   int t;
 373   int status;
 374   char *at_args;
 375   FILE *args;
 376   FILE *wrapper_output;
 377   char *new_argv[3];
 378   struct pex_obj *pex;
 379   const char *errmsg;
 380
 381   /* Write argv to a file to avoid a command line that is too long. */
 382   arguments_file_name = make_temp_file ("");
 383   check (arguments_file_name, LDPL_FATAL,
 384          "Failed to generate a temorary file name");
 385
 386   args = fopen (arguments_file_name, "w");
 387   check (args, LDPL_FATAL, "could not open arguments file");
 388
 389   t = writeargv (&argv[1], args);
 390   check (t == 0, LDPL_FATAL, "could not write arguments");
 391   t = fclose (args);
 392   check (t == 0, LDPL_FATAL, "could not close arguments file");
 393
 394   at_args = concat ("@", arguments_file_name, NULL);
 395   check (at_args, LDPL_FATAL, "could not allocate");
 396
 397   new_argv[0] = argv[0];
 398   new_argv[1] = at_args;
 399   new_argv[2] = NULL;
 400
 401   if (debug)
 402     {
 403       int i;
 404       for (i = 0; new_argv[i]; i++)
 405         fprintf (stderr, "%s ", new_argv[i]);
 406       fprintf (stderr, "\n");
 407     }
 408
 409
 410   pex = pex_init (PEX_USE_PIPES, "lto-wrapper", NULL);
 411   check (pex != NULL, LDPL_FATAL, "could not pex_init lto-wrapper");
 412
 413   errmsg = pex_run (pex, 0, new_argv[0], new_argv, NULL, NULL, &t);
 414   check (errmsg == NULL, LDPL_FATAL, "could not run lto-wrapper");
 415   check (t == 0, LDPL_FATAL, "could not run lto-wrapper");
 416
 417   wrapper_output = pex_read_output (pex, 0);
 418   check (wrapper_output, LDPL_FATAL, "could not read lto-wrapper output");
 419
 420   add_output_files (wrapper_output);
 421
 422   t = pex_get_status (pex, 1, &status);
 423   check (t == 1, LDPL_FATAL, "could not get lto-wrapper exit status");
 424   check (WIFEXITED (status) && WEXITSTATUS (status) == 0, LDPL_FATAL,
 425          "lto-wrapper failed");
 426
 427   pex_free (pex);
 428
 429   free (at_args);
 430 }
 431
 432 /* Pass the original files back to the linker. */
 433
 434 static void
 435 use_original_files (void)
 436 {
 437   unsigned i;
 438   for (i = 0; i < num_claimed_files; i++)
 439     {
 440       struct plugin_file_info *info = &claimed_files[i];
 441       add_input_file (info->name);
 442     }
 443 }
 444
 445
 446 /* Called by the linker once all symbols have been read. */
 447
 448 static enum ld_plugin_status
 449 all_symbols_read_handler (void)
 450 {
 451   unsigned i;
 452   unsigned num_lto_args = num_claimed_files + lto_wrapper_num_args + 2 + 1;
 453   char **lto_argv;
 454   const char **lto_arg_ptr;
 455   if (num_claimed_files == 0)
 456     return LDPS_OK;
 457
 458   if (nop)
 459     {
 460       use_original_files ();
 461       return LDPS_OK;
 462     }
 463
 464   lto_argv = (char **) calloc (sizeof (char *), num_lto_args);
 465   lto_arg_ptr = (const char **) lto_argv;
 466   assert (lto_wrapper_argv);
 467
 468   resolution_file = make_temp_file ("");
 469
 470   write_resolution ();
 471
 472   free_1 ();
 473
 474   for (i = 0; i < lto_wrapper_num_args; i++)
 475     *lto_arg_ptr++ = lto_wrapper_argv[i];
 476
 477   *lto_arg_ptr++ = "-fresolution";
 478   *lto_arg_ptr++ = resolution_file;
 479
 480   for (i = 0; i < num_claimed_files; i++)
 481     {
 482       struct plugin_file_info *info = &claimed_files[i];
 483
 484       *lto_arg_ptr++ = info->name;
 485     }
 486
 487   *lto_arg_ptr++ = NULL;
 488   exec_lto_wrapper (lto_argv);
 489
 490   free (lto_argv);
 491
 492   if (pass_through_items)
 493     {
 494       unsigned int i;
 495       for (i = 0; i < num_pass_through_items; i++)
 496         {
 497           if (strncmp (pass_through_items[i], "-l", 2) == 0)
 498             add_input_library (pass_through_items[i] + 2);
 499           else
 500             add_input_file (pass_through_items[i]);
 501           free (pass_through_items[i]);
 502           pass_through_items[i] = NULL;
 503         }
 504       free (pass_through_items);
 505       pass_through_items = NULL;
 506     }
 507
 508   return LDPS_OK;
 509 }
 510
 511 /* Remove temporary files at the end of the link. */
 512
 513 static enum ld_plugin_status
 514 cleanup_handler (void)
 515 {
 516   int t;
 517
 518   if (debug)
 519     return LDPS_OK;
 520
 521   if (arguments_file_name)
 522     {
 523       t = unlink (arguments_file_name);
 524       check (t == 0, LDPL_FATAL, "could not unlink arguments file");
 525     }
 526
 527   if (resolution_file)
 528     {
 529       t = unlink (resolution_file);
 530       check (t == 0, LDPL_FATAL, "could not unlink resolution file");
 531     }
 532
 533   free_2 ();
 534   return LDPS_OK;
 535 }
 536
 537 /* Callback used by gold to check if the plugin will claim FILE. Writes
 538    the result in CLAIMED. */
 539
 540 static enum ld_plugin_status
 541 claim_file_handler (const struct ld_plugin_input_file *file, int *claimed)
 542 {
 543   enum ld_plugin_status status;
 544   Elf *elf;
 545   struct plugin_file_info lto_file;
 546   Elf_Data *symtab;
 547
 548   if (file->offset != 0)
 549     {
 550       char *objname;
 551       Elf *archive;
 552       off_t offset;
 553       /* We pass the offset of the actual file, not the archive header. */
 554       int t = asprintf (&objname, "%s@0x%" PRIx64, file->name,
 555                         (int64_t) file->offset);
 556       check (t >= 0, LDPL_FATAL, "asprintf failed");
 557       lto_file.name = objname;
 558
 559       archive = elf_begin (file->fd, ELF_C_READ, NULL);
 560       check (elf_kind (archive) == ELF_K_AR, LDPL_FATAL,
 561              "Not an archive and offset not 0");
 562
 563       /* elf_rand expects the offset to point to the ar header, not the
 564          object itself. Subtract the size of the ar header (60 bytes).
 565          We don't uses sizeof (struct ar_hd) to avoid including ar.h */
 566
 567       offset = file->offset - 60;
 568       check (offset == elf_rand (archive, offset), LDPL_FATAL,
 569              "could not seek in archive");
 570       elf = elf_begin (file->fd, ELF_C_READ, archive);
 571       check (elf != NULL, LDPL_FATAL, "could not find archive member");
 572       elf_end (archive);
 573     }
 574   else
 575     {
 576       lto_file.name = strdup (file->name);
 577       elf = elf_begin (file->fd, ELF_C_READ, NULL);
 578     }
 579   lto_file.handle = file->handle;
 580
 581   *claimed = 0;
 582
 583   if (!elf)
 584     goto err;
 585
 586   symtab = get_symtab (elf);
 587   if (!symtab)
 588     goto err;
 589
 590   translate (symtab, &lto_file.symtab);
 591
 592   status = add_symbols (file->handle, lto_file.symtab.nsyms,
 593                         lto_file.symtab.syms);
 594   check (status == LDPS_OK, LDPL_FATAL, "could not add symbols");
 595
 596   *claimed = 1;
 597   num_claimed_files++;
 598   claimed_files =
 599     realloc (claimed_files,
 600              num_claimed_files * sizeof (struct plugin_file_info));
 601   claimed_files[num_claimed_files - 1] = lto_file;
 602
 603   goto cleanup;
 604
 605  err:
 606   free (lto_file.name);
 607
 608  cleanup:
 609   if (elf)
 610     elf_end (elf);
 611
 612   return LDPS_OK;
 613 }
 614
 615 /* Parse the plugin options. */
 616
 617 static void
 618 process_option (const char *option)
 619 {
 620   if (strcmp (option, "-debug") == 0)
 621     debug = 1;
 622   else if (strcmp (option, "-nop") == 0)
 623     nop = 1;
 624   else if (!strncmp (option, "-pass-through=", strlen("-pass-through=")))
 625     {
 626       num_pass_through_items++;
 627       pass_through_items = realloc (pass_through_items,
 628                                     num_pass_through_items * sizeof (char *));
 629       pass_through_items[num_pass_through_items - 1] =
 630           strdup (option + strlen ("-pass-through="));
 631     }
 632   else
 633     {
 634       int size;
 635       lto_wrapper_num_args += 1;
 636       size = lto_wrapper_num_args * sizeof (char *);
 637       lto_wrapper_argv = (char **) realloc (lto_wrapper_argv, size);
 638       lto_wrapper_argv[lto_wrapper_num_args - 1] = strdup(option);
 639     }
 640 }
 641
 642 /* Called by gold after loading the plugin. TV is the transfer vector. */
 643
 644 enum ld_plugin_status
 645 onload (struct ld_plugin_tv *tv)
 646 {
 647   struct ld_plugin_tv *p;
 648   enum ld_plugin_status status;
 649
 650   unsigned version = elf_version (EV_CURRENT);
 651   check (version != EV_NONE, LDPL_FATAL, "invalid ELF version");
 652
 653   p = tv;
 654   while (p->tv_tag)
 655     {
 656       switch (p->tv_tag)
 657         {
 658         case LDPT_MESSAGE:
 659           message = p->tv_u.tv_message;
 660           break;
 661         case LDPT_REGISTER_CLAIM_FILE_HOOK:
 662           register_claim_file = p->tv_u.tv_register_claim_file;
 663           break;
 664         case LDPT_ADD_SYMBOLS:
 665           add_symbols = p->tv_u.tv_add_symbols;
 666           break;
 667         case LDPT_REGISTER_ALL_SYMBOLS_READ_HOOK:
 668           register_all_symbols_read = p->tv_u.tv_register_all_symbols_read;
 669           break;
 670         case LDPT_GET_SYMBOLS:
 671           get_symbols = p->tv_u.tv_get_symbols;
 672           break;
 673         case LDPT_REGISTER_CLEANUP_HOOK:
 674           register_cleanup = p->tv_u.tv_register_cleanup;
 675           break;
 676         case LDPT_ADD_INPUT_FILE:
 677           add_input_file = p->tv_u.tv_add_input_file;
 678           break;
 679         case LDPT_ADD_INPUT_LIBRARY:
 680           add_input_library = p->tv_u.tv_add_input_library;
 681           break;
 682         case LDPT_OPTION:
 683           process_option (p->tv_u.tv_string);
 684           break;
 685         default:
 686           break;
 687         }
 688       p++;
 689     }
 690
 691   check (register_claim_file, LDPL_FATAL, "register_claim_file not found");
 692   check (add_symbols, LDPL_FATAL, "add_symbols not found");
 693   status = register_claim_file (claim_file_handler);
 694   check (status == LDPS_OK, LDPL_FATAL,
 695          "could not register the claim_file callback");
 696
 697   if (register_cleanup)
 698     {
 699       status = register_cleanup (cleanup_handler);
 700       check (status == LDPS_OK, LDPL_FATAL,
 701              "could not register the cleanup callback");
 702     }
 703
 704   if (register_all_symbols_read)
 705     {
 706       check (get_symbols, LDPL_FATAL, "get_symbols not found");
 707       status = register_all_symbols_read (all_symbols_read_handler);
 708       check (status == LDPS_OK, LDPL_FATAL,
 709              "could not register the all_symbols_read callback");
 710     }
 711
 712   return LDPS_OK;
 713 }