libelf/elf32_getshdr.c

/* Return section header.
   Copyright (C) 1998-2002, 2005, 2007, 2009, 2012, 2014, 2015 Red Hat, Inc.
   This file is part of elfutils.
   Written by Ulrich Drepper <drepper@redhat.com>, 1998.

   This file is free software; you can redistribute it and/or modify
   it under the terms of either

     * the GNU Lesser General Public License as published by the Free
       Software Foundation; either version 3 of the License, or (at
       your option) any later version

   or

     * the GNU General Public License as published by the Free
       Software Foundation; either version 2 of the License, or (at
       your option) any later version

   or both in parallel, as here.

   elfutils is distributed in the hope that it will be useful, but
   WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   General Public License for more details.

   You should have received copies of the GNU General Public License and
   the GNU Lesser General Public License along with this program.  If
   not, see <http://www.gnu.org/licenses/>.  */

#ifdef HAVE_CONFIG_H
# include <config.h>
#endif

#include <assert.h>
#include <errno.h>
#include <stdbool.h>
#include <unistd.h>

#include <system.h>
#include "libelfP.h"
#include "common.h"

#ifndef LIBELFBITS
# define LIBELFBITS 32
#endif


static ElfW2(LIBELFBITS,Shdr) *
load_shdr_wrlock (Elf_Scn *scn)
{
  ElfW2(LIBELFBITS,Shdr) *result;

  /* Read the section header table.  */
  Elf *elf = scn->elf;
  ElfW2(LIBELFBITS,Ehdr) *ehdr = elf->state.ELFW(elf,LIBELFBITS).ehdr;

  /* Try again, maybe the data is there now.  */
  result = scn->shdr.ELFW(e,LIBELFBITS);
  if (result != NULL)
    goto out;

  size_t shnum;
  if (__elf_getshdrnum_rdlock (elf, &shnum) != 0
      || shnum > SIZE_MAX / sizeof (ElfW2(LIBELFBITS,Shdr)))
    goto out;
  size_t size = shnum * sizeof (ElfW2(LIBELFBITS,Shdr));

  /* Allocate memory for the section headers.  We know the number
     of entries from the ELF header.  */
  ElfW2(LIBELFBITS,Shdr) *shdr = elf->state.ELFW(elf,LIBELFBITS).shdr =
    (ElfW2(LIBELFBITS,Shdr) *) malloc (size);
  if (elf->state.ELFW(elf,LIBELFBITS).shdr == NULL)
    {
      __libelf_seterrno (ELF_E_NOMEM);
      goto out;
    }
  elf->state.ELFW(elf,LIBELFBITS).shdr_malloced = 1;

  if (elf->map_address != NULL)
    {
      /* First see whether the information in the ELF header is
	 valid and it does not ask for too much.  */
      if (unlikely (ehdr->e_shoff >= elf->maximum_size)
	  || unlikely (elf->maximum_size - ehdr->e_shoff < size))
	{
	  /* Something is wrong.  */
	  __libelf_seterrno (ELF_E_INVALID_SECTION_HEADER);
	  goto free_and_out;
	}

      ElfW2(LIBELFBITS,Shdr) *notcvt;

      /* All the data is already mapped.  If we could use it
	 directly this would already have happened.  Unless
	 we allocated the memory ourselves and the ELF_F_MALLOCED
	 flag is set.  */
      void *file_shdr = ((char *) elf->map_address
			 + elf->start_offset + ehdr->e_shoff);

      assert ((elf->flags & ELF_F_MALLOCED)
	      || ehdr->e_ident[EI_DATA] != MY_ELFDATA
	      || elf->cmd == ELF_C_READ_MMAP
	      || (! ALLOW_UNALIGNED
		  && ((uintptr_t) file_shdr
		      & (__alignof__ (ElfW2(LIBELFBITS,Shdr)) - 1)) != 0));

      /* Now copy the data and at the same time convert the byte order.  */
      if (ehdr->e_ident[EI_DATA] == MY_ELFDATA)
	{
	  assert ((elf->flags & ELF_F_MALLOCED)
		  || elf->cmd == ELF_C_READ_MMAP
		  || ! ALLOW_UNALIGNED);
	  memcpy (shdr, file_shdr, size);
	}
      else
	{
	  bool copy = ! (ALLOW_UNALIGNED
			 || ((uintptr_t) file_shdr
			     & (__alignof__ (ElfW2(LIBELFBITS,Shdr)) - 1))
			     == 0);
	  if (! copy)
	    notcvt = (ElfW2(LIBELFBITS,Shdr) *)
	      ((char *) elf->map_address
	       + elf->start_offset + ehdr->e_shoff);
	  else
	    {
	      notcvt = (ElfW2(LIBELFBITS,Shdr) *) malloc (size);
	      if (unlikely (notcvt == NULL))
		{
		  __libelf_seterrno (ELF_E_NOMEM);
		  goto out;
		}
	      memcpy (notcvt, ((char *) elf->map_address
			       + elf->start_offset + ehdr->e_shoff),
		      size);
	    }

	  for (size_t cnt = 0; cnt < shnum; ++cnt)
	    {
	      CONVERT_TO (shdr[cnt].sh_name, notcvt[cnt].sh_name);
	      CONVERT_TO (shdr[cnt].sh_type, notcvt[cnt].sh_type);
	      CONVERT_TO (shdr[cnt].sh_flags, notcvt[cnt].sh_flags);
	      CONVERT_TO (shdr[cnt].sh_addr, notcvt[cnt].sh_addr);
	      CONVERT_TO (shdr[cnt].sh_offset, notcvt[cnt].sh_offset);
	      CONVERT_TO (shdr[cnt].sh_size, notcvt[cnt].sh_size);
	      CONVERT_TO (shdr[cnt].sh_link, notcvt[cnt].sh_link);
	      CONVERT_TO (shdr[cnt].sh_info, notcvt[cnt].sh_info);
	      CONVERT_TO (shdr[cnt].sh_addralign,
			  notcvt[cnt].sh_addralign);
	      CONVERT_TO (shdr[cnt].sh_entsize, notcvt[cnt].sh_entsize);

	      /* If this is a section with an extended index add a
		 reference in the section which uses the extended
		 index.  */
	      if (shdr[cnt].sh_type == SHT_SYMTAB_SHNDX
		  && shdr[cnt].sh_link < shnum)
		elf->state.ELFW(elf,LIBELFBITS).scns.data[shdr[cnt].sh_link].shndx_index
		  = cnt;

	      /* Set the own shndx_index field in case it has not yet
		 been set.  */
	      if (elf->state.ELFW(elf,LIBELFBITS).scns.data[cnt].shndx_index == 0)
		elf->state.ELFW(elf,LIBELFBITS).scns.data[cnt].shndx_index
		  = -1;
	    }

	  if (copy)
	    free (notcvt);
	}
    }
  else if (likely (elf->fildes != -1))
    {
      /* Read the header.  */
      ssize_t n = pread_retry (elf->fildes,
			       elf->state.ELFW(elf,LIBELFBITS).shdr, size,
			       elf->start_offset + ehdr->e_shoff);
      if (unlikely ((size_t) n != size))
	{
	  /* Severe problems.  We cannot read the data.  */
	  __libelf_seterrno (ELF_E_READ_ERROR);
	  goto free_and_out;
	}

      /* If the byte order of the file is not the same as the one
	 of the host convert the data now.  */
      if (ehdr->e_ident[EI_DATA] != MY_ELFDATA)
	for (size_t cnt = 0; cnt < shnum; ++cnt)
	  {
	    CONVERT (shdr[cnt].sh_name);
	    CONVERT (shdr[cnt].sh_type);
	    CONVERT (shdr[cnt].sh_flags);
	    CONVERT (shdr[cnt].sh_addr);
	    CONVERT (shdr[cnt].sh_offset);
	    CONVERT (shdr[cnt].sh_size);
	    CONVERT (shdr[cnt].sh_link);
	    CONVERT (shdr[cnt].sh_info);
	    CONVERT (shdr[cnt].sh_addralign);
	    CONVERT (shdr[cnt].sh_entsize);
	  }
    }
  else
    {
      /* The file descriptor was already enabled and not all data was
	 read.  Undo the allocation.  */
      __libelf_seterrno (ELF_E_FD_DISABLED);

    free_and_out:
      free (shdr);
      elf->state.ELFW(elf,LIBELFBITS).shdr = NULL;
      elf->state.ELFW(elf,LIBELFBITS).shdr_malloced = 0;

      goto out;
    }

  /* Set the pointers in the `scn's.  */
  for (size_t cnt = 0; cnt < shnum; ++cnt)
    elf->state.ELFW(elf,LIBELFBITS).scns.data[cnt].shdr.ELFW(e,LIBELFBITS)
      = &elf->state.ELFW(elf,LIBELFBITS).shdr[cnt];

  result = scn->shdr.ELFW(e,LIBELFBITS);
  assert (result != NULL);

out:
  return result;
}

static bool
scn_valid (Elf_Scn *scn)
{
  if (scn == NULL)
    return false;

  if (unlikely (scn->elf->state.elf.ehdr == NULL))
    {
      __libelf_seterrno (ELF_E_WRONG_ORDER_EHDR);
      return false;
    }

  if (unlikely (scn->elf->class != ELFW(ELFCLASS,LIBELFBITS)))
    {
      __libelf_seterrno (ELF_E_INVALID_CLASS);
      return false;
    }

  return true;
}

ElfW2(LIBELFBITS,Shdr) *
internal_function
__elfw2(LIBELFBITS,getshdr_rdlock) (Elf_Scn *scn)
{
  ElfW2(LIBELFBITS,Shdr) *result;

  if (!scn_valid (scn))
    return NULL;

  result = scn->shdr.ELFW(e,LIBELFBITS);
  if (result == NULL)
    {
      rwlock_unlock (scn->elf->lock);
      rwlock_wrlock (scn->elf->lock);
      result = scn->shdr.ELFW(e,LIBELFBITS);
      if (result == NULL)
	result = load_shdr_wrlock (scn);
    }

  return result;
}

ElfW2(LIBELFBITS,Shdr) *
internal_function
__elfw2(LIBELFBITS,getshdr_wrlock) (Elf_Scn *scn)
{
  ElfW2(LIBELFBITS,Shdr) *result;

  if (!scn_valid (scn))
    return NULL;

  result = scn->shdr.ELFW(e,LIBELFBITS);
  if (result == NULL)
    result = load_shdr_wrlock (scn);

  return result;
}

ElfW2(LIBELFBITS,Shdr) *
elfw2(LIBELFBITS,getshdr) (Elf_Scn *scn)
{
  ElfW2(LIBELFBITS,Shdr) *result;

  if (!scn_valid (scn))
    return NULL;

  rwlock_rdlock (scn->elf->lock);
  result = __elfw2(LIBELFBITS,getshdr_rdlock) (scn);
  rwlock_unlock (scn->elf->lock);

  return result;
}