lto-plugin/lto-plugin-elf.c

   1 /* LTO plugin for gold.
   2    Copyright (C) 2009, 2010 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 #include <assert.h>
  20 #include <string.h>
  21 #include <stdio.h>
  22 #include <libiberty.h>
  23 #include <stdlib.h>
  24 #include <inttypes.h>
  25
  26 /* The presence of gelf.h is checked by the toplevel configure script.  */
  27 #include <gelf.h>
  28
  29 /* Common definitions that the object format dependent code needs.  */
  30 #include "lto-plugin.h"
  31
  32 /* Process all lto symtabs of file ELF. */
  33
  34 static int
  35 process_symtab (Elf *elf, struct plugin_symtab *out)
  36 {
  37   int found = 0;
  38   Elf_Scn *section = 0;
  39   GElf_Ehdr header;
  40   GElf_Ehdr *t = gelf_getehdr (elf, &header);
  41   if (t == NULL)
  42     return 0;
  43   assert (t == &header);
  44
  45   while ((section = elf_nextscn(elf, section)) != 0)
  46     {
  47       GElf_Shdr shdr;
  48       GElf_Shdr *tshdr = gelf_getshdr (section, &shdr);
  49       Elf_Data *symtab;
  50       const char *t;
  51       assert (tshdr == &shdr);
  52       t = elf_strptr (elf, header.e_shstrndx, shdr.sh_name);
  53       assert (t != NULL);
  54       if (strncmp (t, LTO_SECTION_PREFIX, strlen (LTO_SECTION_PREFIX)) == 0)
  55         {
  56           char *s = strrchr (t, '.');
  57           if (s)
  58               sscanf (s, ".%x", &out->id);
  59           symtab = elf_getdata (section, NULL);
  60           translate (symtab->d_buf, symtab->d_buf + symtab->d_size, out);
  61           found++;
  62         }
  63     }
  64   return found;
  65 }
  66
  67 /* Callback used by gold to check if the plugin will claim FILE. Writes
  68    the result in CLAIMED. */
  69
  70 enum ld_plugin_status
  71 claim_file_handler (const struct ld_plugin_input_file *file, int *claimed)
  72 {
  73   enum ld_plugin_status status;
  74   Elf *elf;
  75   struct plugin_file_info lto_file;
  76   int n;
  77
  78   memset (&lto_file, 0, sizeof (struct plugin_file_info));
  79
  80   if (file->offset != 0)
  81     {
  82       char *objname;
  83       Elf *archive;
  84       off_t offset;
  85       /* We pass the offset of the actual file, not the archive header. */
  86       int t = asprintf (&objname, "%s@0x%" PRIx64, file->name,
  87                         (int64_t) file->offset);
  88       check (t >= 0, LDPL_FATAL, "asprintf failed");
  89       lto_file.name = objname;
  90
  91       archive = elf_begin (file->fd, ELF_C_READ, NULL);
  92       check (elf_kind (archive) == ELF_K_AR, LDPL_FATAL,
  93              "Not an archive and offset not 0");
  94
  95       /* elf_rand expects the offset to point to the ar header, not the
  96          object itself. Subtract the size of the ar header (60 bytes).
  97          We don't uses sizeof (struct ar_hd) to avoid including ar.h */
  98
  99       offset = file->offset - 60;
 100       check (offset == elf_rand (archive, offset), LDPL_FATAL,
 101              "could not seek in archive");
 102       elf = elf_begin (file->fd, ELF_C_READ, archive);
 103       check (elf != NULL, LDPL_FATAL, "could not find archive member");
 104       elf_end (archive);
 105     }
 106   else
 107     {
 108       lto_file.name = xstrdup (file->name);
 109       elf = elf_begin (file->fd, ELF_C_READ, NULL);
 110     }
 111   lto_file.handle = file->handle;
 112
 113   *claimed = 0;
 114
 115   if (!elf)
 116     goto err;
 117
 118   n = process_symtab (elf, &lto_file.symtab);
 119   if (n == 0)
 120     goto err;
 121
 122   if (n > 1)
 123     resolve_conflicts (&lto_file.symtab, &lto_file.conflicts);
 124
 125   status = add_symbols (file->handle, lto_file.symtab.nsyms,
 126                         lto_file.symtab.syms);
 127   check (status == LDPS_OK, LDPL_FATAL, "could not add symbols");
 128
 129   *claimed = 1;
 130   num_claimed_files++;
 131   claimed_files =
 132     xrealloc (claimed_files,
 133               num_claimed_files * sizeof (struct plugin_file_info));
 134   claimed_files[num_claimed_files - 1] = lto_file;
 135
 136   goto cleanup;
 137
 138  err:
 139   free (lto_file.name);
 140
 141  cleanup:
 142   if (elf)
 143     elf_end (elf);
 144
 145   return LDPS_OK;
 146 }
 147
 148 /* Method called first thing at onload time to perform sanity checks.  */
 149
 150 enum ld_plugin_status
 151 onload_format_checks (struct ld_plugin_tv *tv)
 152 {
 153   unsigned version = elf_version (EV_CURRENT);
 154   check (version != EV_NONE, LDPL_FATAL, "invalid ELF version");
 155   return LDPS_OK;
 156 }
 157