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 = xstrdup (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 = xstrdup (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 = xrealloc (syms, n * sizeof (struct ld_plugin_symbol));
 237       check (syms, LDPL_FATAL, "could not allocate memory");
 238       slots = xrealloc (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
 299 /*  Writes the relocations to disk. */
 300
 301 static void
 302 write_resolution (void)
 303 {
 304   unsigned int i;
 305   FILE *f;
 306
 307   check (resolution_file, LDPL_FATAL, "resolution file not specified");
 308   f = fopen (resolution_file, "w");
 309   check (f, LDPL_FATAL, "could not open file");
 310
 311   fprintf (f, "%d\n", num_claimed_files);
 312
 313   for (i = 0; i < num_claimed_files; i++)
 314     {
 315       struct plugin_file_info *info = &claimed_files[i];
 316       struct plugin_symtab *symtab = &info->symtab;
 317       struct ld_plugin_symbol *syms = symtab->syms;
 318       unsigned j;
 319
 320       get_symbols (info->handle, symtab->nsyms, syms);
 321
 322       fprintf (f, "%s %d\n", info->name, info->symtab.nsyms);
 323
 324       for (j = 0; j < info->symtab.nsyms; j++)
 325         {
 326           uint32_t slot = symtab->slots[j];
 327           unsigned int resolution = syms[j].resolution;
 328           fprintf (f, "%d %s %s\n", slot, lto_resolution_str[resolution], syms[j].name);
 329         }
 330     }
 331   fclose (f);
 332 }
 333
 334 /* Pass files generated by the lto-wrapper to the linker. FD is lto-wrapper's
 335    stdout. */
 336
 337 static void
 338 add_output_files (FILE *f)
 339 {
 340   for (;;)
 341     {
 342       const unsigned piece = 32;
 343       char *buf, *s = xmalloc (piece);
 344       size_t len;
 345
 346       buf = s;
 347 cont:
 348       if (!fgets (buf, piece, f))
 349         break;
 350       len = strlen (s);
 351       if (s[len - 1] != '\n')
 352         {
 353           s = xrealloc (s, len + piece);
 354           buf = s + len;
 355           goto cont;
 356         }
 357       s[len - 1] = '\0';
 358
 359       num_output_files++;
 360       output_files
 361         = xrealloc (output_files, num_output_files * sizeof (char *));
 362       output_files[num_output_files - 1] = s;
 363       add_input_file (output_files[num_output_files - 1]);
 364     }
 365 }
 366
 367 /* Execute the lto-wrapper. ARGV[0] is the binary. The rest of ARGV is the
 368    argument list. */
 369
 370 static void
 371 exec_lto_wrapper (char *argv[])
 372 {
 373   int t, i;
 374   int status;
 375   char *at_args;
 376   FILE *args;
 377   FILE *wrapper_output;
 378   char *new_argv[3];
 379   struct pex_obj *pex;
 380   const char *errmsg;
 381
 382   /* Write argv to a file to avoid a command line that is too long. */
 383   arguments_file_name = make_temp_file ("");
 384   check (arguments_file_name, LDPL_FATAL,
 385          "Failed to generate a temorary file name");
 386
 387   args = fopen (arguments_file_name, "w");
 388   check (args, LDPL_FATAL, "could not open arguments file");
 389
 390   t = writeargv (&argv[1], args);
 391   check (t == 0, LDPL_FATAL, "could not write arguments");
 392   t = fclose (args);
 393   check (t == 0, LDPL_FATAL, "could not close arguments file");
 394
 395   at_args = concat ("@", arguments_file_name, NULL);
 396   check (at_args, LDPL_FATAL, "could not allocate");
 397
 398   for (i = 1; argv[i]; i++)
 399     {
 400       char *a = argv[i];
 401       if (a[0] == '-' && a[1] == 'v' && a[2] == '\0')
 402         {
 403           for (i = 0; argv[i]; i++)
 404             fprintf (stderr, "%s ", argv[i]);
 405           fprintf (stderr, "\n");
 406           break;
 407         }
 408     }
 409
 410   new_argv[0] = argv[0];
 411   new_argv[1] = at_args;
 412   new_argv[2] = NULL;
 413
 414   if (debug)
 415     {
 416       for (i = 0; new_argv[i]; i++)
 417         fprintf (stderr, "%s ", new_argv[i]);
 418       fprintf (stderr, "\n");
 419     }
 420
 421
 422   pex = pex_init (PEX_USE_PIPES, "lto-wrapper", NULL);
 423   check (pex != NULL, LDPL_FATAL, "could not pex_init lto-wrapper");
 424
 425   errmsg = pex_run (pex, 0, new_argv[0], new_argv, NULL, NULL, &t);
 426   check (errmsg == NULL, LDPL_FATAL, "could not run lto-wrapper");
 427   check (t == 0, LDPL_FATAL, "could not run lto-wrapper");
 428
 429   wrapper_output = pex_read_output (pex, 0);
 430   check (wrapper_output, LDPL_FATAL, "could not read lto-wrapper output");
 431
 432   add_output_files (wrapper_output);
 433
 434   t = pex_get_status (pex, 1, &status);
 435   check (t == 1, LDPL_FATAL, "could not get lto-wrapper exit status");
 436   check (WIFEXITED (status) && WEXITSTATUS (status) == 0, LDPL_FATAL,
 437          "lto-wrapper failed");
 438
 439   pex_free (pex);
 440
 441   free (at_args);
 442 }
 443
 444 /* Pass the original files back to the linker. */
 445
 446 static void
 447 use_original_files (void)
 448 {
 449   unsigned i;
 450   for (i = 0; i < num_claimed_files; i++)
 451     {
 452       struct plugin_file_info *info = &claimed_files[i];
 453       add_input_file (info->name);
 454     }
 455 }
 456
 457
 458 /* Called by the linker once all symbols have been read. */
 459
 460 static enum ld_plugin_status
 461 all_symbols_read_handler (void)
 462 {
 463   unsigned i;
 464   unsigned num_lto_args = num_claimed_files + lto_wrapper_num_args + 1;
 465   char **lto_argv;
 466   const char **lto_arg_ptr;
 467   if (num_claimed_files == 0)
 468     return LDPS_OK;
 469
 470   if (nop)
 471     {
 472       use_original_files ();
 473       return LDPS_OK;
 474     }
 475
 476   lto_argv = (char **) xcalloc (sizeof (char *), num_lto_args);
 477   lto_arg_ptr = (const char **) lto_argv;
 478   assert (lto_wrapper_argv);
 479
 480   write_resolution ();
 481
 482   free_1 ();
 483
 484   for (i = 0; i < lto_wrapper_num_args; i++)
 485     *lto_arg_ptr++ = lto_wrapper_argv[i];
 486
 487   for (i = 0; i < num_claimed_files; i++)
 488     {
 489       struct plugin_file_info *info = &claimed_files[i];
 490
 491       *lto_arg_ptr++ = info->name;
 492     }
 493
 494   *lto_arg_ptr++ = NULL;
 495   exec_lto_wrapper (lto_argv);
 496
 497   free (lto_argv);
 498
 499   if (pass_through_items)
 500     {
 501       unsigned int i;
 502       for (i = 0; i < num_pass_through_items; i++)
 503         {
 504           if (strncmp (pass_through_items[i], "-l", 2) == 0)
 505             add_input_library (pass_through_items[i] + 2);
 506           else
 507             add_input_file (pass_through_items[i]);
 508           free (pass_through_items[i]);
 509           pass_through_items[i] = NULL;
 510         }
 511       free (pass_through_items);
 512       pass_through_items = NULL;
 513     }
 514
 515   return LDPS_OK;
 516 }
 517
 518 /* Remove temporary files at the end of the link. */
 519
 520 static enum ld_plugin_status
 521 cleanup_handler (void)
 522 {
 523   unsigned int i;
 524   int t;
 525
 526   if (debug)
 527     return LDPS_OK;
 528
 529   if (arguments_file_name)
 530     {
 531       t = unlink (arguments_file_name);
 532       check (t == 0, LDPL_FATAL, "could not unlink arguments file");
 533     }
 534
 535   for (i = 0; i < num_output_files; i++)
 536     {
 537       t = unlink (output_files[i]);
 538       check (t == 0, LDPL_FATAL, "could not unlink output file");
 539     }
 540
 541   free_2 ();
 542   return LDPS_OK;
 543 }
 544
 545 /* Callback used by gold to check if the plugin will claim FILE. Writes
 546    the result in CLAIMED. */
 547
 548 static enum ld_plugin_status
 549 claim_file_handler (const struct ld_plugin_input_file *file, int *claimed)
 550 {
 551   enum ld_plugin_status status;
 552   Elf *elf;
 553   struct plugin_file_info lto_file;
 554   Elf_Data *symtab;
 555
 556   if (file->offset != 0)
 557     {
 558       char *objname;
 559       Elf *archive;
 560       off_t offset;
 561       /* We pass the offset of the actual file, not the archive header. */
 562       int t = asprintf (&objname, "%s@0x%" PRIx64, file->name,
 563                         (int64_t) file->offset);
 564       check (t >= 0, LDPL_FATAL, "asprintf failed");
 565       lto_file.name = objname;
 566
 567       archive = elf_begin (file->fd, ELF_C_READ, NULL);
 568       check (elf_kind (archive) == ELF_K_AR, LDPL_FATAL,
 569              "Not an archive and offset not 0");
 570
 571       /* elf_rand expects the offset to point to the ar header, not the
 572          object itself. Subtract the size of the ar header (60 bytes).
 573          We don't uses sizeof (struct ar_hd) to avoid including ar.h */
 574
 575       offset = file->offset - 60;
 576       check (offset == elf_rand (archive, offset), LDPL_FATAL,
 577              "could not seek in archive");
 578       elf = elf_begin (file->fd, ELF_C_READ, archive);
 579       check (elf != NULL, LDPL_FATAL, "could not find archive member");
 580       elf_end (archive);
 581     }
 582   else
 583     {
 584       lto_file.name = xstrdup (file->name);
 585       elf = elf_begin (file->fd, ELF_C_READ, NULL);
 586     }
 587   lto_file.handle = file->handle;
 588
 589   *claimed = 0;
 590
 591   if (!elf)
 592     goto err;
 593
 594   symtab = get_symtab (elf);
 595   if (!symtab)
 596     goto err;
 597
 598   translate (symtab, &lto_file.symtab);
 599
 600   status = add_symbols (file->handle, lto_file.symtab.nsyms,
 601                         lto_file.symtab.syms);
 602   check (status == LDPS_OK, LDPL_FATAL, "could not add symbols");
 603
 604   *claimed = 1;
 605   num_claimed_files++;
 606   claimed_files =
 607     xrealloc (claimed_files,
 608               num_claimed_files * sizeof (struct plugin_file_info));
 609   claimed_files[num_claimed_files - 1] = lto_file;
 610
 611   goto cleanup;
 612
 613  err:
 614   free (lto_file.name);
 615
 616  cleanup:
 617   if (elf)
 618     elf_end (elf);
 619
 620   return LDPS_OK;
 621 }
 622
 623 /* Parse the plugin options. */
 624
 625 static void
 626 process_option (const char *option)
 627 {
 628   if (strcmp (option, "-debug") == 0)
 629     debug = 1;
 630   else if (strcmp (option, "-nop") == 0)
 631     nop = 1;
 632   else if (!strncmp (option, "-pass-through=", strlen("-pass-through=")))
 633     {
 634       num_pass_through_items++;
 635       pass_through_items = xrealloc (pass_through_items,
 636                                      num_pass_through_items * sizeof (char *));
 637       pass_through_items[num_pass_through_items - 1] =
 638           xstrdup (option + strlen ("-pass-through="));
 639     }
 640   else
 641     {
 642       int size;
 643       char *opt = xstrdup (option);
 644       lto_wrapper_num_args += 1;
 645       size = lto_wrapper_num_args * sizeof (char *);
 646       lto_wrapper_argv = (char **) xrealloc (lto_wrapper_argv, size);
 647       lto_wrapper_argv[lto_wrapper_num_args - 1] = opt;
 648       if (strncmp (option, "-fresolution=", sizeof ("-fresolution=") - 1) == 0)
 649         resolution_file = opt + sizeof ("-fresolution=") - 1;
 650     }
 651 }
 652
 653 /* Called by gold after loading the plugin. TV is the transfer vector. */
 654
 655 enum ld_plugin_status
 656 onload (struct ld_plugin_tv *tv)
 657 {
 658   struct ld_plugin_tv *p;
 659   enum ld_plugin_status status;
 660
 661   unsigned version = elf_version (EV_CURRENT);
 662   check (version != EV_NONE, LDPL_FATAL, "invalid ELF version");
 663
 664   p = tv;
 665   while (p->tv_tag)
 666     {
 667       switch (p->tv_tag)
 668         {
 669         case LDPT_MESSAGE:
 670           message = p->tv_u.tv_message;
 671           break;
 672         case LDPT_REGISTER_CLAIM_FILE_HOOK:
 673           register_claim_file = p->tv_u.tv_register_claim_file;
 674           break;
 675         case LDPT_ADD_SYMBOLS:
 676           add_symbols = p->tv_u.tv_add_symbols;
 677           break;
 678         case LDPT_REGISTER_ALL_SYMBOLS_READ_HOOK:
 679           register_all_symbols_read = p->tv_u.tv_register_all_symbols_read;
 680           break;
 681         case LDPT_GET_SYMBOLS:
 682           get_symbols = p->tv_u.tv_get_symbols;
 683           break;
 684         case LDPT_REGISTER_CLEANUP_HOOK:
 685           register_cleanup = p->tv_u.tv_register_cleanup;
 686           break;
 687         case LDPT_ADD_INPUT_FILE:
 688           add_input_file = p->tv_u.tv_add_input_file;
 689           break;
 690         case LDPT_ADD_INPUT_LIBRARY:
 691           add_input_library = p->tv_u.tv_add_input_library;
 692           break;
 693         case LDPT_OPTION:
 694           process_option (p->tv_u.tv_string);
 695           break;
 696         default:
 697           break;
 698         }
 699       p++;
 700     }
 701
 702   check (register_claim_file, LDPL_FATAL, "register_claim_file not found");
 703   check (add_symbols, LDPL_FATAL, "add_symbols not found");
 704   status = register_claim_file (claim_file_handler);
 705   check (status == LDPS_OK, LDPL_FATAL,
 706          "could not register the claim_file callback");
 707
 708   if (register_cleanup)
 709     {
 710       status = register_cleanup (cleanup_handler);
 711       check (status == LDPS_OK, LDPL_FATAL,
 712              "could not register the cleanup callback");
 713     }
 714
 715   if (register_all_symbols_read)
 716     {
 717       check (get_symbols, LDPL_FATAL, "get_symbols not found");
 718       status = register_all_symbols_read (all_symbols_read_handler);
 719       check (status == LDPS_OK, LDPL_FATAL,
 720              "could not register the all_symbols_read callback");
 721     }
 722
 723   return LDPS_OK;
 724 }