src/elf_update.c

   1 /* Update data structures for changes and write them out.
   2    Copyright (C) 1999, 2000, 2001, 2002, 2004, 2005, 2006 Red Hat, Inc.
   3    This file is part of elfutils.
   4    Contributed by Ulrich Drepper <drepper@redhat.com>, 1999.
   5
   6    This file is free software; you can redistribute it and/or modify
   7    it under the terms of either
   8
   9      * the GNU Lesser General Public License as published by the Free
  10        Software Foundation; either version 3 of the License, or (at
  11        your option) any later version
  12
  13    or
  14
  15      * the GNU General Public License as published by the Free
  16        Software Foundation; either version 2 of the License, or (at
  17        your option) any later version
  18
  19    or both in parallel, as here.
  20
  21    elfutils is distributed in the hope that it will be useful, but
  22    WITHOUT ANY WARRANTY; without even the implied warranty of
  23    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  24    General Public License for more details.
  25
  26    You should have received copies of the GNU General Public License and
  27    the GNU Lesser General Public License along with this program.  If
  28    not, see <http://www.gnu.org/licenses/>.  */
  29
  30 #ifdef HAVE_CONFIG_H
  31 # include <config.h>
  32 #endif
  33
  34 #include <unistd.h>
  35 #include <sys/mman.h>
  36 #include <sys/stat.h>
  37
  38 #include "libelf.h"
  39 #include "libelfP.h"
  40
  41
  42 static off_t
  43 write_file (Elf *elf, off_t size, int change_bo, size_t shnum)
  44 {
  45   int class = elf->class;
  46
  47   /* Check the mode bits now, before modification might change them.  */
  48   struct stat st;
  49   if (unlikely (fstat (elf->fildes, &st) != 0))
  50     {
  51       __libelf_seterrno (ELF_E_WRITE_ERROR);
  52       return -1;
  53     }
  54
  55   /* Adjust the size in any case.  We do this even if we use `write'.
  56      We cannot do this if this file is in an archive.  We also don't
  57      do it *now* if we are shortening the file since this would
  58      prevent programs to use the data of the file in generating the
  59      new file.  We truncate the file later in this case.  */
  60   if (elf->parent == NULL
  61       && (elf->maximum_size == ~((size_t) 0)
  62           || (size_t) size > elf->maximum_size)
  63       && unlikely (ftruncate (elf->fildes, size) != 0))
  64     {
  65       __libelf_seterrno (ELF_E_WRITE_ERROR);
  66       return -1;
  67     }
  68
  69   /* Try to map the file if this isn't done yet.  */
  70   if (elf->map_address == NULL && elf->cmd == ELF_C_WRITE_MMAP)
  71     {
  72 #if _MUDFLAP
  73       /* Mudflap doesn't grok that our mmap'd data is ok.  */
  74 #else
  75       elf->map_address = mmap (NULL, size, PROT_READ | PROT_WRITE,
  76                                MAP_SHARED, elf->fildes, 0);
  77       if (unlikely (elf->map_address == MAP_FAILED))
  78         elf->map_address = NULL;
  79 #endif
  80     }
  81
  82   if (elf->map_address != NULL)
  83     {
  84       /* The file is mmaped.  */
  85       if ((class == ELFCLASS32
  86            ? __elf32_updatemmap (elf, change_bo, shnum)
  87            : __elf64_updatemmap (elf, change_bo, shnum)) != 0)
  88         /* Some problem while writing.  */
  89         size = -1;
  90     }
  91   else
  92     {
  93       /* The file is not mmaped.  */
  94       if ((class == ELFCLASS32
  95            ? __elf32_updatefile (elf, change_bo, shnum)
  96            : __elf64_updatefile (elf, change_bo, shnum)) != 0)
  97         /* Some problem while writing.  */
  98         size = -1;
  99     }
 100
 101   if (size != -1
 102       && elf->parent == NULL
 103       && elf->maximum_size != ~((size_t) 0)
 104       && (size_t) size < elf->maximum_size
 105       && unlikely (ftruncate (elf->fildes, size) != 0))
 106     {
 107       __libelf_seterrno (ELF_E_WRITE_ERROR);
 108       size = -1;
 109     }
 110
 111   /* POSIX says that ftruncate and write may clear the S_ISUID and S_ISGID
 112      mode bits.  So make sure we restore them afterwards if they were set.
 113      This is not atomic if someone else chmod's the file while we operate.  */
 114   if (size != -1
 115       && unlikely (st.st_mode & (S_ISUID | S_ISGID))
 116       /* fchmod ignores the bits we cannot change.  */
 117       && unlikely (fchmod (elf->fildes, st.st_mode) != 0))
 118     {
 119       __libelf_seterrno (ELF_E_WRITE_ERROR);
 120       size = -1;
 121     }
 122
 123   if (size != -1 && elf->parent == NULL)
 124     elf->maximum_size = size;
 125
 126   return size;
 127 }
 128
 129
 130 off_t
 131 elf_update (elf, cmd)
 132      Elf *elf;
 133      Elf_Cmd cmd;
 134 {
 135   size_t shnum;
 136   off_t size;
 137   int change_bo = 0;
 138
 139   if (cmd != ELF_C_NULL
 140       && cmd != ELF_C_WRITE
 141       && unlikely (cmd != ELF_C_WRITE_MMAP))
 142     {
 143       __libelf_seterrno (ELF_E_INVALID_CMD);
 144       return -1;
 145     }
 146
 147   if (elf == NULL)
 148     return -1;
 149
 150   if (elf->kind != ELF_K_ELF)
 151     {
 152       __libelf_seterrno (ELF_E_INVALID_HANDLE);
 153       return -1;
 154     }
 155
 156   rwlock_wrlock (elf->lock);
 157
 158   /* Make sure we have an ELF header.  */
 159   if (elf->state.elf.ehdr == NULL)
 160     {
 161       __libelf_seterrno (ELF_E_WRONG_ORDER_EHDR);
 162       size = -1;
 163       goto out;
 164     }
 165
 166   /* Determine the number of sections.  */
 167   shnum = (elf->state.elf.scns_last->cnt == 0
 168            ? 0
 169            : 1 + elf->state.elf.scns_last->data[elf->state.elf.scns_last->cnt - 1].index);
 170
 171   /* Update the ELF descriptor.  First, place the program header.  It
 172      will come right after the ELF header.  The count the size of all
 173      sections and finally place the section table.  */
 174   size = (elf->class == ELFCLASS32
 175           ? __elf32_updatenull_wrlock (elf, &change_bo, shnum)
 176           : __elf64_updatenull_wrlock (elf, &change_bo, shnum));
 177   if (likely (size != -1)
 178       /* See whether we actually have to write out the data.  */
 179       && (cmd == ELF_C_WRITE || cmd == ELF_C_WRITE_MMAP))
 180     {
 181       if (elf->cmd != ELF_C_RDWR
 182           && elf->cmd != ELF_C_RDWR_MMAP
 183           && elf->cmd != ELF_C_WRITE
 184           && unlikely (elf->cmd != ELF_C_WRITE_MMAP))
 185         {
 186           __libelf_seterrno (ELF_E_UPDATE_RO);
 187           size = -1;
 188         }
 189       else if (unlikely (elf->fildes == -1))
 190         {
 191           /* We closed the file already.  */
 192           __libelf_seterrno (ELF_E_FD_DISABLED);
 193           size = -1;
 194         }
 195       else
 196         size = write_file (elf, size, change_bo, shnum);
 197     }
 198
 199  out:
 200   rwlock_unlock (elf->lock);
 201
 202   return size;
 203 }