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elf_getdata.c

/* Return the next data element from the section after possibly converting it.
   Copyright (C) 1998-2005, 2006 Red Hat, Inc.
   This file is part of Red Hat elfutils.
   Written by Ulrich Drepper <drepper@redhat.com>, 1998.

   Red Hat elfutils is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by the
   Free Software Foundation; version 2 of the License.

   Red Hat 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 a copy of the GNU General Public License along
   with Red Hat elfutils; if not, write to the Free Software Foundation,
   Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301 USA.

   In addition, as a special exception, Red Hat, Inc. gives You the
   additional right to link the code of Red Hat elfutils with code licensed
   under any Open Source Initiative certified open source license
   (http://www.opensource.org/licenses/index.php) which requires the
   distribution of source code with any binary distribution and to
   distribute linked combinations of the two.  Non-GPL Code permitted under
   this exception must only link to the code of Red Hat elfutils through
   those well defined interfaces identified in the file named EXCEPTION
   found in the source code files (the "Approved Interfaces").  The files
   of Non-GPL Code may instantiate templates or use macros or inline
   functions from the Approved Interfaces without causing the resulting
   work to be covered by the GNU General Public License.  Only Red Hat,
   Inc. may make changes or additions to the list of Approved Interfaces.
   Red Hat's grant of this exception is conditioned upon your not adding
   any new exceptions.  If you wish to add a new Approved Interface or
   exception, please contact Red Hat.  You must obey the GNU General Public
   License in all respects for all of the Red Hat elfutils code and other
   code used in conjunction with Red Hat elfutils except the Non-GPL Code
   covered by this exception.  If you modify this file, you may extend this
   exception to your version of the file, but you are not obligated to do
   so.  If you do not wish to provide this exception without modification,
   you must delete this exception statement from your version and license
   this file solely under the GPL without exception.

   Red Hat elfutils is an included package of the Open Invention Network.
   An included package of the Open Invention Network is a package for which
   Open Invention Network licensees cross-license their patents.  No patent
   license is granted, either expressly or impliedly, by designation as an
   included package.  Should you wish to participate in the Open Invention
   Network licensing program, please visit www.openinventionnetwork.com
   <http://www.openinventionnetwork.com>.  */

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

#include <errno.h>
#include <stddef.h>
#include <string.h>
#include <unistd.h>

#include "libelfP.h"
#include <system.h>
#include "common.h"
#include "elf-knowledge.h"


#if _STRING_ARCH_unaligned
# define ALLOW_ALIGNED  1
#else
# define ALLOW_ALIGNED  0
#endif


#define TYPEIDX(Sh_Type) \
  (Sh_Type >= SHT_NULL && Sh_Type < SHT_NUM                             \
   ? Sh_Type                                                      \
   : (Sh_Type >= SHT_GNU_HASH && Sh_Type <= SHT_HISUNW                        \
      ? SHT_NUM + Sh_Type - SHT_GNU_HASH                          \
      : 0))

static const struct
{
  Elf_Type type;
  size_t size;
#if ALLOW_ALIGNED
# define AL(val)
#else
  size_t align;
# define AL(val), val
#endif
} shtype_map[EV_NUM - 1][ELFCLASSNUM - 1][TYPEIDX (SHT_HISUNW) + 1] =
{
  [EV_CURRENT - 1] =
  {
    [ELFCLASS32 - 1] =
    {
      /* Associate section types with libelf types, their sizes and
       alignment.  SHT_GNU_verdef is special since the section does
       not contain entries of only one size.  */
#define DEFINE(Bits) \
      [SHT_SYMTAB] = { ELF_T_SYM, sizeof (ElfW2(Bits,Sym))              \
                   AL (__alignof__ (ElfW2(Bits,Sym))) },                \
      [SHT_RELA] = { ELF_T_RELA, sizeof (ElfW2(Bits,Rela))              \
                   AL (__alignof__ (ElfW2(Bits,Rela))) },               \
      [SHT_HASH] = { ELF_T_WORD, sizeof (ElfW2(Bits,Word))              \
                   AL (__alignof__ (ElfW2(Bits,Word))) },               \
      [SHT_DYNAMIC] = { ELF_T_DYN, sizeof (ElfW2(Bits,Dyn))             \
                   AL (__alignof__ (ElfW2(Bits,Dyn))) },                \
      [SHT_REL] = { ELF_T_REL, sizeof (ElfW2(Bits,Rel))                       \
                   AL (__alignof__ (ElfW2(Bits,Rel))) },                \
      [SHT_DYNSYM] = { ELF_T_SYM, sizeof (ElfW2(Bits,Sym))              \
                   AL (__alignof__ (ElfW2(Bits,Sym))) },                \
      [SHT_INIT_ARRAY] = { ELF_T_ADDR, sizeof (ElfW2(Bits,Addr))        \
                     AL (__alignof__ (ElfW2(Bits,Addr))) },       \
      [SHT_FINI_ARRAY] = { ELF_T_ADDR, sizeof (ElfW2(Bits,Addr))        \
                     AL (__alignof__ (ElfW2(Bits,Addr))) },       \
      [SHT_PREINIT_ARRAY] = { ELF_T_ADDR, sizeof (ElfW2(Bits,Addr))           \
                        AL (__alignof__ (ElfW2(Bits,Addr))) },          \
      [SHT_GROUP] = { ELF_T_WORD, sizeof (Elf32_Word)                   \
                  AL (__alignof__ (Elf32_Word)) },                      \
      [SHT_SYMTAB_SHNDX] = { ELF_T_WORD, sizeof (Elf32_Word)                  \
                       AL (__alignof__ (Elf32_Word)) },                 \
      [TYPEIDX (SHT_GNU_verdef)] = { ELF_T_VDEF, 1 AL (1) },                  \
      [TYPEIDX (SHT_GNU_verneed)] = { ELF_T_VNEED,                      \
                              sizeof (ElfW2(Bits,Verneed))        \
                              AL (__alignof__ (ElfW2(Bits,Verneed)))},\
      [TYPEIDX (SHT_GNU_versym)] = { ELF_T_HALF, sizeof (ElfW2(Bits,Versym))  \
                             AL (__alignof__ (ElfW2(Bits,Versym))) }, \
      [TYPEIDX (SHT_SUNW_syminfo)] = { ELF_T_SYMINFO,                   \
                               sizeof (ElfW2(Bits,Syminfo))       \
                               AL(__alignof__ (ElfW2(Bits,Syminfo)))},\
      [TYPEIDX (SHT_SUNW_move)] = { ELF_T_MOVE, sizeof (ElfW2(Bits,Move))     \
                            AL (__alignof__ (ElfW2(Bits,Move))) },    \
      [TYPEIDX (SHT_GNU_LIBLIST)] = { ELF_T_LIB, sizeof (ElfW2(Bits,Lib))     \
                              AL (__alignof__ (ElfW2(Bits,Lib))) }
      DEFINE (32),
      [TYPEIDX (SHT_GNU_HASH)] = { ELF_T_WORD, sizeof (Elf32_Word)
                           AL (__alignof__ (Elf32_Word)) }
    },
    [ELFCLASS64 - 1] =
    {
      DEFINE (64),
      [TYPEIDX (SHT_GNU_HASH)] = { ELF_T_GNUHASH, 1
                           AL (__alignof__ (Elf64_Xword)) }
    }
  }
};


/* Convert the data in the current section.  */
static void
convert_data (Elf_Scn *scn, int version __attribute__ ((unused)), int eclass,
            int data, size_t size, size_t type)
{
#if ALLOW_ALIGNED
  /* No need to compute the alignment requirement of the host.  */
  const size_t align = 1;
#else
# if EV_NUM != 2
  size_t align = shtype_map[version - 1][eclass - 1][type].align;
# else
  size_t align = shtype_map[0][eclass - 1][type].align;
# endif
#endif

  if (data == MY_ELFDATA)
    {
      if (ALLOW_ALIGNED
        || (((size_t) ((char *) scn->rawdata_base)) & (align - 1)) == 0)
      /* No need to copy, we can use the raw data.  */
      scn->data_base = scn->rawdata_base;
      else
      {
        scn->data_base = (char *) malloc (size);
        if (scn->data_base == NULL)
          {
            __libelf_seterrno (ELF_E_NOMEM);
            return;
          }

        /* The copy will be appropriately aligned for direct access.  */
        memcpy (scn->data_base, scn->rawdata_base, size);
      }
    }
  else
    {
      xfct_t fp;

      scn->data_base = (char *) malloc (size);
      if (scn->data_base == NULL)
      {
        __libelf_seterrno (ELF_E_NOMEM);
        return;
      }

      /* Get the conversion function.  */
#if EV_NUM != 2
      fp = __elf_xfctstom[version - 1][__libelf_version - 1][eclass - 1][type];
#else
      fp = __elf_xfctstom[0][0][eclass - 1][type];
#endif

      fp (scn->data_base, scn->rawdata_base, size, 0);
    }

  scn->data_list.data.d.d_buf = scn->data_base;
  scn->data_list.data.d.d_size = size;
  scn->data_list.data.d.d_type = type;
  scn->data_list.data.d.d_off = scn->rawdata.d.d_off;
  scn->data_list.data.d.d_align = scn->rawdata.d.d_align;
  scn->data_list.data.d.d_version = scn->rawdata.d.d_version;

  scn->data_list.data.s = scn;
}


/* Store the information for the raw data in the `rawdata' element.  */
int
internal_function
__libelf_set_rawdata (Elf_Scn *scn)
{
  size_t offset;
  size_t size;
  size_t align;
  int type;
  Elf *elf = scn->elf;

  if (elf->class == ELFCLASS32)
    {
      Elf32_Shdr *shdr = scn->shdr.e32 ?: INTUSE(elf32_getshdr) (scn);

      if (shdr == NULL)
      /* Something went terribly wrong.  */
      return 1;

      offset = shdr->sh_offset;
      size = shdr->sh_size;
      type = shdr->sh_type;
      align = shdr->sh_addralign;
    }
  else
    {
      Elf64_Shdr *shdr = scn->shdr.e64 ?: INTUSE(elf64_getshdr) (scn);

      if (shdr == NULL)
      /* Something went terribly wrong.  */
      return 1;

      offset = shdr->sh_offset;
      size = shdr->sh_size;
      type = shdr->sh_type;
      align = shdr->sh_addralign;
    }

  /* If the section has no data (for whatever reason), leave the `d_buf'
     pointer NULL.  */
  if (size != 0 && type != SHT_NOBITS)
    {
      /* First a test whether the section is valid at all.  */
      size_t entsize;

      if (type == SHT_HASH)
      {
        GElf_Ehdr ehdr_mem;

        entsize = SH_ENTSIZE_HASH (INTUSE(gelf_getehdr) (elf, &ehdr_mem));
      }
      else
      {
#if EV_NUM != 2
        entsize = shtype_map[__libelf_version - 1][elf->class - 1][TYPEIDX (type)].size;
#else
        entsize = shtype_map[0][elf->class - 1][TYPEIDX (type)].size;
#endif
      }

      /* We assume it is an array of bytes if it is none of the structured
       sections we know of.  */
      if (entsize == 0)
      entsize = 1;

      if (unlikely (size % entsize != 0))
      {
        __libelf_seterrno (ELF_E_INVALID_DATA);
        return 1;
      }

      /* We can use the mapped or loaded data if available.  */
      if (elf->map_address != NULL)
      {
        /* First see whether the information in the section header is
           valid and it does not ask for too much.  */
        if (unlikely (offset + size > elf->maximum_size))
          {
            /* Something is wrong.  */
            __libelf_seterrno (ELF_E_INVALID_SECTION_HEADER);
            return 1;
          }

        scn->rawdata_base = scn->rawdata.d.d_buf
          = (char *) elf->map_address + elf->start_offset + offset;
      }
      else if (likely (elf->fildes != -1))
      {
        /* We have to read the data from the file.  Allocate the needed
           memory.  */
        scn->rawdata_base = scn->rawdata.d.d_buf
          = (char *) malloc (size);
        if (scn->rawdata.d.d_buf == NULL)
          {
            __libelf_seterrno (ELF_E_NOMEM);
            return 1;
          }

        ssize_t n = pread_retry (elf->fildes, scn->rawdata.d.d_buf, size,
                           elf->start_offset + offset);
        if (unlikely ((size_t) n != size))
          {
            /* Cannot read the data.  */
            free (scn->rawdata.d.d_buf);
            scn->rawdata_base = scn->rawdata.d.d_buf = NULL;
            __libelf_seterrno (ELF_E_READ_ERROR);
            return 1;
          }
      }
      else
      {
        /* The file descriptor is already closed, we cannot get the data
           anymore.  */
        __libelf_seterrno (ELF_E_FD_DISABLED);
        return 1;
      }
    }

  scn->rawdata.d.d_size = size;
  /* Some broken ELF ABI for 64-bit machines use the wrong hash table
     entry size.  See elf-knowledge.h for more information.  */
  if (type == SHT_HASH && elf->class == ELFCLASS64)
    {
      GElf_Ehdr ehdr_mem;

      scn->rawdata.d.d_type
      = (SH_ENTSIZE_HASH (INTUSE(gelf_getehdr) (elf, &ehdr_mem)) == 4
         ? ELF_T_WORD : ELF_T_XWORD);
    }
  else
    {
#if EV_NUM != 2
      scn->rawdata.d.d_type =
      shtype_map[__libelf_version - 1][elf->class - 1][TYPEIDX (type)].type;
#else
      scn->rawdata.d.d_type =
      shtype_map[0][elf->class - 1][TYPEIDX (type)].type;
#endif
    }
  scn->rawdata.d.d_off = 0;
  scn->rawdata.d.d_align = align;
  if (elf->class == ELFCLASS32
      || (offsetof (struct Elf, state.elf32.ehdr)
        == offsetof (struct Elf, state.elf64.ehdr)))
    scn->rawdata.d.d_version =
      elf->state.elf32.ehdr->e_ident[EI_VERSION];
  else
    scn->rawdata.d.d_version =
      elf->state.elf64.ehdr->e_ident[EI_VERSION];

  scn->rawdata.s = scn;

  scn->data_read = 1;

  /* We actually read data from the file.  At least we tried.  */
  scn->flags |= ELF_F_FILEDATA;

  return 0;
}


Elf_Data *
elf_getdata (scn, data)
     Elf_Scn *scn;
     Elf_Data *data;
{
  Elf_Data *result = NULL;
  Elf *elf;

  if (scn == NULL)
    return NULL;

  if (unlikely (scn->elf->kind != ELF_K_ELF))
    {
      __libelf_seterrno (ELF_E_INVALID_HANDLE);
      return NULL;
    }

  /* We will need this multiple times later on.  */
  elf = scn->elf;

  rwlock_rdlock (elf->lock);

  /* If `data' is not NULL this means we are not addressing the initial
     data in the file.  But this also means this data is already read
     (since otherwise it is not possible to have a valid `data' pointer)
     and all the data structures are initialized as well.  In this case
     we can simply walk the list of data records.  */
  if (data != NULL)
    {
      Elf_Data_List *runp;

      /* It is not possible that if DATA is not NULL the first entry is
       returned.  But this also means that there must be a first data
       entry.  */
      if (scn->data_list_rear == NULL
        /* The section the reference data is for must match the section
           parameter.  */
        || unlikely (((Elf_Data_Scn *) data)->s != scn))
      {
        __libelf_seterrno (ELF_E_DATA_MISMATCH);
        goto out;
      }

      /* We start searching with the first entry.  */
      runp = &scn->data_list;

      while (1)
      {
        /* If `data' does not match any known record punt.  */
        if (runp == NULL)
          {
            __libelf_seterrno (ELF_E_DATA_MISMATCH);
            goto out;
          }

        if (&runp->data.d == data)
          /* Found the entry.  */
          break;

        runp = runp->next;
      }

      /* Return the data for the next data record.  */
      result = runp->next ? &runp->next->data.d : NULL;
      goto out;
    }

  /* If the data for this section was not yet initialized do it now.  */
  if (scn->data_read == 0)
    {
      /* We cannot acquire a write lock while we are holding a read
         lock.  Therefore give up the read lock and then get the write
         lock.  But this means that the data could meanwhile be
         modified, therefore start the tests again.  */
      rwlock_unlock (elf->lock);
      rwlock_wrlock (elf->lock);

      /* Read the data from the file.  There is always a file (or
       memory region) associated with this descriptor since
       otherwise the `data_read' flag would be set.  */
      if (scn->data_read == 0 && __libelf_set_rawdata (scn) != 0)
      /* Something went wrong.  The error value is already set.  */
      goto out;
    }

  /* At this point we know the raw data is available.  But it might be
     empty in case the section has size zero (for whatever reason).
     Now create the converted data in case this is necessary.  */
  if (scn->data_list_rear == NULL)
    {
      if (scn->rawdata.d.d_buf != NULL && scn->rawdata.d.d_size > 0)
      /* Convert according to the version and the type.   */
      convert_data (scn, __libelf_version, elf->class,
                  (elf->class == ELFCLASS32
                   || (offsetof (struct Elf, state.elf32.ehdr)
                     == offsetof (struct Elf, state.elf64.ehdr))
                   ? elf->state.elf32.ehdr->e_ident[EI_DATA]
                   : elf->state.elf64.ehdr->e_ident[EI_DATA]),
                  scn->rawdata.d.d_size, scn->rawdata.d.d_type);
      else
      /* This is an empty or NOBITS section.  There is no buffer but
         the size information etc is important.  */
      scn->data_list.data.d = scn->rawdata.d;

      scn->data_list_rear = &scn->data_list;
    }

  /* If no data is present we cannot return any.  */
  if (scn->data_list_rear != NULL)
    /* Return the first data element in the list.  */
    result = &scn->data_list.data.d;

 out:
  rwlock_unlock (elf->lock);

  return result;
}
INTDEF(elf_getdata)

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