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      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 Red Hat elfutils.
      4    Contributed by Ulrich Drepper <drepper (at) redhat.com>, 1999.
      5 
      6    Red Hat elfutils is free software; you can redistribute it and/or modify
      7    it under the terms of the GNU General Public License as published by the
      8    Free Software Foundation; version 2 of the License.
      9 
     10    Red Hat elfutils 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 along
     16    with Red Hat elfutils; if not, write to the Free Software Foundation,
     17    Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301 USA.
     18 
     19    In addition, as a special exception, Red Hat, Inc. gives You the
     20    additional right to link the code of Red Hat elfutils with code licensed
     21    under any Open Source Initiative certified open source license
     22    (http://www.opensource.org/licenses/index.php) which requires the
     23    distribution of source code with any binary distribution and to
     24    distribute linked combinations of the two.  Non-GPL Code permitted under
     25    this exception must only link to the code of Red Hat elfutils through
     26    those well defined interfaces identified in the file named EXCEPTION
     27    found in the source code files (the "Approved Interfaces").  The files
     28    of Non-GPL Code may instantiate templates or use macros or inline
     29    functions from the Approved Interfaces without causing the resulting
     30    work to be covered by the GNU General Public License.  Only Red Hat,
     31    Inc. may make changes or additions to the list of Approved Interfaces.
     32    Red Hat's grant of this exception is conditioned upon your not adding
     33    any new exceptions.  If you wish to add a new Approved Interface or
     34    exception, please contact Red Hat.  You must obey the GNU General Public
     35    License in all respects for all of the Red Hat elfutils code and other
     36    code used in conjunction with Red Hat elfutils except the Non-GPL Code
     37    covered by this exception.  If you modify this file, you may extend this
     38    exception to your version of the file, but you are not obligated to do
     39    so.  If you do not wish to provide this exception without modification,
     40    you must delete this exception statement from your version and license
     41    this file solely under the GPL without exception.
     42 
     43    Red Hat elfutils is an included package of the Open Invention Network.
     44    An included package of the Open Invention Network is a package for which
     45    Open Invention Network licensees cross-license their patents.  No patent
     46    license is granted, either expressly or impliedly, by designation as an
     47    included package.  Should you wish to participate in the Open Invention
     48    Network licensing program, please visit www.openinventionnetwork.com
     49    <http://www.openinventionnetwork.com>.  */
     50 
     51 #ifdef HAVE_CONFIG_H
     52 # include <config.h>
     53 #endif
     54 
     55 #include <libelf.h>
     56 #include <unistd.h>
     57 #include <sys/mman.h>
     58 #include <sys/stat.h>
     59 
     60 #include "libelfP.h"
     61 
     62 
     63 static off_t
     64 write_file (Elf *elf, off_t size, int change_bo, size_t shnum)
     65 {
     66   int class = elf->class;
     67 
     68   /* Check the mode bits now, before modification might change them.  */
     69   struct stat st;
     70   if (unlikely (fstat (elf->fildes, &st) != 0))
     71     {
     72       __libelf_seterrno (ELF_E_WRITE_ERROR);
     73       return -1;
     74     }
     75 
     76   /* Adjust the size in any case.  We do this even if we use `write'.
     77      We cannot do this if this file is in an archive.  We also don't
     78      do it *now* if we are shortening the file since this would
     79      prevent programs to use the data of the file in generating the
     80      new file.  We truncate the file later in this case.  */
     81   if (elf->parent == NULL
     82       && (elf->maximum_size == ~((size_t) 0)
     83 	  || (size_t) size > elf->maximum_size)
     84       && unlikely (ftruncate (elf->fildes, size) != 0))
     85     {
     86       __libelf_seterrno (ELF_E_WRITE_ERROR);
     87       return -1;
     88     }
     89 
     90   /* Try to map the file if this isn't done yet.  */
     91   if (elf->map_address == NULL && elf->cmd == ELF_C_WRITE_MMAP)
     92     {
     93 #if _MUDFLAP
     94       /* Mudflap doesn't grok that our mmap'd data is ok.  */
     95 #else
     96       elf->map_address = mmap (NULL, size, PROT_READ | PROT_WRITE,
     97 			       MAP_SHARED, elf->fildes, 0);
     98       if (unlikely (elf->map_address == MAP_FAILED))
     99 	elf->map_address = NULL;
    100 #endif
    101     }
    102 
    103   if (elf->map_address != NULL)
    104     {
    105       /* The file is mmaped.  */
    106       if ((class == ELFCLASS32
    107 	   ? __elf32_updatemmap (elf, change_bo, shnum)
    108 	   : __elf64_updatemmap (elf, change_bo, shnum)) != 0)
    109 	/* Some problem while writing.  */
    110 	size = -1;
    111     }
    112   else
    113     {
    114       /* The file is not mmaped.  */
    115       if ((class == ELFCLASS32
    116 	   ? __elf32_updatefile (elf, change_bo, shnum)
    117 	   : __elf64_updatefile (elf, change_bo, shnum)) != 0)
    118 	/* Some problem while writing.  */
    119 	size = -1;
    120     }
    121 
    122   if (size != -1
    123       && elf->parent == NULL
    124       && elf->maximum_size != ~((size_t) 0)
    125       && (size_t) size < elf->maximum_size
    126       && unlikely (ftruncate (elf->fildes, size) != 0))
    127     {
    128       __libelf_seterrno (ELF_E_WRITE_ERROR);
    129       size = -1;
    130     }
    131 
    132   /* POSIX says that ftruncate and write may clear the S_ISUID and S_ISGID
    133      mode bits.  So make sure we restore them afterwards if they were set.
    134      This is not atomic if someone else chmod's the file while we operate.  */
    135   if (size != -1
    136       && unlikely (st.st_mode & (S_ISUID | S_ISGID))
    137       /* fchmod ignores the bits we cannot change.  */
    138       && unlikely (fchmod (elf->fildes, st.st_mode) != 0))
    139     {
    140       __libelf_seterrno (ELF_E_WRITE_ERROR);
    141       size = -1;
    142     }
    143 
    144   if (size != -1 && elf->parent == NULL)
    145     elf->maximum_size = size;
    146 
    147   return size;
    148 }
    149 
    150 
    151 off_t
    152 elf_update (elf, cmd)
    153      Elf *elf;
    154      Elf_Cmd cmd;
    155 {
    156   size_t shnum;
    157   off_t size;
    158   int change_bo = 0;
    159 
    160   if (cmd != ELF_C_NULL
    161       && cmd != ELF_C_WRITE
    162       && unlikely (cmd != ELF_C_WRITE_MMAP))
    163     {
    164       __libelf_seterrno (ELF_E_INVALID_CMD);
    165       return -1;
    166     }
    167 
    168   if (elf == NULL)
    169     return -1;
    170 
    171   if (elf->kind != ELF_K_ELF)
    172     {
    173       __libelf_seterrno (ELF_E_INVALID_HANDLE);
    174       return -1;
    175     }
    176 
    177   rwlock_wrlock (elf->lock);
    178 
    179   /* Make sure we have an ELF header.  */
    180   if (elf->state.elf.ehdr == NULL)
    181     {
    182       __libelf_seterrno (ELF_E_WRONG_ORDER_EHDR);
    183       size = -1;
    184       goto out;
    185     }
    186 
    187   /* Determine the number of sections.  */
    188   shnum = (elf->state.elf.scns_last->cnt == 0
    189 	   ? 0
    190 	   : 1 + elf->state.elf.scns_last->data[elf->state.elf.scns_last->cnt - 1].index);
    191 
    192   /* Update the ELF descriptor.  First, place the program header.  It
    193      will come right after the ELF header.  The count the size of all
    194      sections and finally place the section table.  */
    195   size = (elf->class == ELFCLASS32
    196 	  ? __elf32_updatenull_wrlock (elf, &change_bo, shnum)
    197 	  : __elf64_updatenull_wrlock (elf, &change_bo, shnum));
    198   if (likely (size != -1)
    199       /* See whether we actually have to write out the data.  */
    200       && (cmd == ELF_C_WRITE || cmd == ELF_C_WRITE_MMAP))
    201     {
    202       if (elf->cmd != ELF_C_RDWR
    203 	  && elf->cmd != ELF_C_RDWR_MMAP
    204 	  && elf->cmd != ELF_C_WRITE
    205 	  && unlikely (elf->cmd != ELF_C_WRITE_MMAP))
    206 	{
    207 	  __libelf_seterrno (ELF_E_UPDATE_RO);
    208 	  size = -1;
    209 	}
    210       else if (unlikely (elf->fildes == -1))
    211 	{
    212 	  /* We closed the file already.  */
    213 	  __libelf_seterrno (ELF_E_FD_DISABLED);
    214 	  size = -1;
    215 	}
    216       else
    217 	size = write_file (elf, size, change_bo, shnum);
    218     }
    219 
    220  out:
    221   rwlock_unlock (elf->lock);
    222 
    223   return size;
    224 }
    225