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, i;
 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   for (i = 1; argv[i]; i++)
 398     {
 399       char *a = argv[i];
 400       if (a[0] == '-' && a[1] == 'v' && a[2] == '\0')
 401         {
 402           for (i = 0; argv[i]; i++)
 403             fprintf (stderr, "%s ", argv[i]);
 404           fprintf (stderr, "\n");
 405           break;
 406         }
 407     }
 408
 409   new_argv[0] = argv[0];
 410   new_argv[1] = at_args;
 411   new_argv[2] = NULL;
 412
 413   if (debug)
 414     {
 415       for (i = 0; new_argv[i]; i++)
 416         fprintf (stderr, "%s ", new_argv[i]);
 417       fprintf (stderr, "\n");
 418     }
 419
 420
 421   pex = pex_init (PEX_USE_PIPES, "lto-wrapper", NULL);
 422   check (pex != NULL, LDPL_FATAL, "could not pex_init lto-wrapper");
 423
 424   errmsg = pex_run (pex, 0, new_argv[0], new_argv, NULL, NULL, &t);
 425   check (errmsg == NULL, LDPL_FATAL, "could not run lto-wrapper");
 426   check (t == 0, LDPL_FATAL, "could not run lto-wrapper");
 427
 428   wrapper_output = pex_read_output (pex, 0);
 429   check (wrapper_output, LDPL_FATAL, "could not read lto-wrapper output");
 430
 431   add_output_files (wrapper_output);
 432
 433   t = pex_get_status (pex, 1, &status);
 434   check (t == 1, LDPL_FATAL, "could not get lto-wrapper exit status");
 435   check (WIFEXITED (status) && WEXITSTATUS (status) == 0, LDPL_FATAL,
 436          "lto-wrapper failed");
 437
 438   pex_free (pex);
 439
 440   free (at_args);
 441 }
 442
 443 /* Pass the original files back to the linker. */
 444
 445 static void
 446 use_original_files (void)
 447 {
 448   unsigned i;
 449   for (i = 0; i < num_claimed_files; i++)
 450     {
 451       struct plugin_file_info *info = &claimed_files[i];
 452       add_input_file (info->name);
 453     }
 454 }
 455
 456
 457 /* Called by the linker once all symbols have been read. */
 458
 459 static enum ld_plugin_status
 460 all_symbols_read_handler (void)
 461 {
 462   unsigned i;
 463   unsigned num_lto_args = num_claimed_files + lto_wrapper_num_args + 2 + 1;
 464   char **lto_argv;
 465   const char **lto_arg_ptr;
 466   if (num_claimed_files == 0)
 467     return LDPS_OK;
 468
 469   if (nop)
 470     {
 471       use_original_files ();
 472       return LDPS_OK;
 473     }
 474
 475   lto_argv = (char **) calloc (sizeof (char *), num_lto_args);
 476   lto_arg_ptr = (const char **) lto_argv;
 477   assert (lto_wrapper_argv);
 478
 479   resolution_file = make_temp_file ("");
 480
 481   write_resolution ();
 482
 483   free_1 ();
 484
 485   for (i = 0; i < lto_wrapper_num_args; i++)
 486     *lto_arg_ptr++ = lto_wrapper_argv[i];
 487
 488   *lto_arg_ptr++ = "-fresolution";
 489   *lto_arg_ptr++ = resolution_file;
 490
 491   for (i = 0; i < num_claimed_files; i++)
 492     {
 493       struct plugin_file_info *info = &claimed_files[i];
 494
 495       *lto_arg_ptr++ = info->name;
 496     }
 497
 498   *lto_arg_ptr++ = NULL;
 499   exec_lto_wrapper (lto_argv);
 500
 501   free (lto_argv);
 502
 503   if (pass_through_items)
 504     {
 505       unsigned int i;
 506       for (i = 0; i < num_pass_through_items; i++)
 507         {
 508           if (strncmp (pass_through_items[i], "-l", 2) == 0)
 509             add_input_library (pass_through_items[i] + 2);
 510           else
 511             add_input_file (pass_through_items[i]);
 512           free (pass_through_items[i]);
 513           pass_through_items[i] = NULL;
 514         }
 515       free (pass_through_items);
 516       pass_through_items = NULL;
 517     }
 518
 519   return LDPS_OK;
 520 }
 521
 522 /* Remove temporary files at the end of the link. */
 523
 524 static enum ld_plugin_status
 525 cleanup_handler (void)
 526 {
 527   unsigned int i;
 528   int t;
 529
 530   if (debug)
 531     return LDPS_OK;
 532
 533   if (arguments_file_name)
 534     {
 535       t = unlink (arguments_file_name);
 536       check (t == 0, LDPL_FATAL, "could not unlink arguments file");
 537     }
 538
 539   if (resolution_file)
 540     {
 541       t = unlink (resolution_file);
 542       check (t == 0, LDPL_FATAL, "could not unlink resolution file");
 543     }
 544
 545   for (i = 0; i < num_output_files; i++)
 546     {
 547       t = unlink (output_files[i]);
 548       check (t == 0, LDPL_FATAL, "could not unlink output file");
 549     }
 550
 551   free_2 ();
 552   return LDPS_OK;
 553 }
 554
 555 /* Callback used by gold to check if the plugin will claim FILE. Writes
 556    the result in CLAIMED. */
 557
 558 static enum ld_plugin_status
 559 claim_file_handler (const struct ld_plugin_input_file *file, int *claimed)
 560 {
 561   enum ld_plugin_status status;
 562   Elf *elf;
 563   struct plugin_file_info lto_file;
 564   Elf_Data *symtab;
 565
 566   if (file->offset != 0)
 567     {
 568       char *objname;
 569       Elf *archive;
 570       off_t offset;
 571       /* We pass the offset of the actual file, not the archive header. */
 572       int t = asprintf (&objname, "%s@0x%" PRIx64, file->name,
 573                         (int64_t) file->offset);
 574       check (t >= 0, LDPL_FATAL, "asprintf failed");
 575       lto_file.name = objname;
 576
 577       archive = elf_begin (file->fd, ELF_C_READ, NULL);
 578       check (elf_kind (archive) == ELF_K_AR, LDPL_FATAL,
 579              "Not an archive and offset not 0");
 580
 581       /* elf_rand expects the offset to point to the ar header, not the
 582          object itself. Subtract the size of the ar header (60 bytes).
 583          We don't uses sizeof (struct ar_hd) to avoid including ar.h */
 584
 585       offset = file->offset - 60;
 586       check (offset == elf_rand (archive, offset), LDPL_FATAL,
 587              "could not seek in archive");
 588       elf = elf_begin (file->fd, ELF_C_READ, archive);
 589       check (elf != NULL, LDPL_FATAL, "could not find archive member");
 590       elf_end (archive);
 591     }
 592   else
 593     {
 594       lto_file.name = strdup (file->name);
 595       elf = elf_begin (file->fd, ELF_C_READ, NULL);
 596     }
 597   lto_file.handle = file->handle;
 598
 599   *claimed = 0;
 600
 601   if (!elf)
 602     goto err;
 603
 604   symtab = get_symtab (elf);
 605   if (!symtab)
 606     goto err;
 607
 608   translate (symtab, &lto_file.symtab);
 609
 610   status = add_symbols (file->handle, lto_file.symtab.nsyms,
 611                         lto_file.symtab.syms);
 612   check (status == LDPS_OK, LDPL_FATAL, "could not add symbols");
 613
 614   *claimed = 1;
 615   num_claimed_files++;
 616   claimed_files =
 617     realloc (claimed_files,
 618              num_claimed_files * sizeof (struct plugin_file_info));
 619   claimed_files[num_claimed_files - 1] = lto_file;
 620
 621   goto cleanup;
 622
 623  err:
 624   free (lto_file.name);
 625
 626  cleanup:
 627   if (elf)
 628     elf_end (elf);
 629
 630   return LDPS_OK;
 631 }
 632
 633 /* Parse the plugin options. */
 634
 635 static void
 636 process_option (const char *option)
 637 {
 638   if (strcmp (option, "-debug") == 0)
 639     debug = 1;
 640   else if (strcmp (option, "-nop") == 0)
 641     nop = 1;
 642   else if (!strncmp (option, "-pass-through=", strlen("-pass-through=")))
 643     {
 644       num_pass_through_items++;
 645       pass_through_items = realloc (pass_through_items,
 646                                     num_pass_through_items * sizeof (char *));
 647       pass_through_items[num_pass_through_items - 1] =
 648           strdup (option + strlen ("-pass-through="));
 649     }
 650   else
 651     {
 652       int size;
 653       lto_wrapper_num_args += 1;
 654       size = lto_wrapper_num_args * sizeof (char *);
 655       lto_wrapper_argv = (char **) realloc (lto_wrapper_argv, size);
 656       lto_wrapper_argv[lto_wrapper_num_args - 1] = strdup(option);
 657     }
 658 }
 659
 660 /* Called by gold after loading the plugin. TV is the transfer vector. */
 661
 662 enum ld_plugin_status
 663 onload (struct ld_plugin_tv *tv)
 664 {
 665   struct ld_plugin_tv *p;
 666   enum ld_plugin_status status;
 667
 668   unsigned version = elf_version (EV_CURRENT);
 669   check (version != EV_NONE, LDPL_FATAL, "invalid ELF version");
 670
 671   p = tv;
 672   while (p->tv_tag)
 673     {
 674       switch (p->tv_tag)
 675         {
 676         case LDPT_MESSAGE:
 677           message = p->tv_u.tv_message;
 678           break;
 679         case LDPT_REGISTER_CLAIM_FILE_HOOK:
 680           register_claim_file = p->tv_u.tv_register_claim_file;
 681           break;
 682         case LDPT_ADD_SYMBOLS:
 683           add_symbols = p->tv_u.tv_add_symbols;
 684           break;
 685         case LDPT_REGISTER_ALL_SYMBOLS_READ_HOOK:
 686           register_all_symbols_read = p->tv_u.tv_register_all_symbols_read;
 687           break;
 688         case LDPT_GET_SYMBOLS:
 689           get_symbols = p->tv_u.tv_get_symbols;
 690           break;
 691         case LDPT_REGISTER_CLEANUP_HOOK:
 692           register_cleanup = p->tv_u.tv_register_cleanup;
 693           break;
 694         case LDPT_ADD_INPUT_FILE:
 695           add_input_file = p->tv_u.tv_add_input_file;
 696           break;
 697         case LDPT_ADD_INPUT_LIBRARY:
 698           add_input_library = p->tv_u.tv_add_input_library;
 699           break;
 700         case LDPT_OPTION:
 701           process_option (p->tv_u.tv_string);
 702           break;
 703         default:
 704           break;
 705         }
 706       p++;
 707     }
 708
 709   check (register_claim_file, LDPL_FATAL, "register_claim_file not found");
 710   check (add_symbols, LDPL_FATAL, "add_symbols not found");
 711   status = register_claim_file (claim_file_handler);
 712   check (status == LDPS_OK, LDPL_FATAL,
 713          "could not register the claim_file callback");
 714
 715   if (register_cleanup)
 716     {
 717       status = register_cleanup (cleanup_handler);
 718       check (status == LDPS_OK, LDPL_FATAL,
 719              "could not register the cleanup callback");
 720     }
 721
 722   if (register_all_symbols_read)
 723     {
 724       check (get_symbols, LDPL_FATAL, "get_symbols not found");
 725       status = register_all_symbols_read (all_symbols_read_handler);
 726       check (status == LDPS_OK, LDPL_FATAL,
 727              "could not register the all_symbols_read callback");
 728     }
 729
 730   return LDPS_OK;
 731 }