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/* Create descriptor from ELF descriptor for processing file.
Copyright (C) 2002, 2003, 2004, 2005, 2007 Red Hat, Inc.
This file is part of Red Hat elfutils.
Written by Ulrich Drepper <>, 2002.
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
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
( 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
<>. */
# include <config.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/stat.h>
#include "libdwP.h"
/* Section names. */
static const char dwarf_scnnames[IDX_last][17] =
[IDX_debug_info] = ".debug_info",
[IDX_debug_abbrev] = ".debug_abbrev",
[IDX_debug_aranges] = ".debug_aranges",
[IDX_debug_line] = ".debug_line",
[IDX_debug_frame] = ".debug_frame",
[IDX_eh_frame] = ".eh_frame",
[IDX_debug_loc] = ".debug_loc",
[IDX_debug_pubnames] = ".debug_pubnames",
[IDX_debug_str] = ".debug_str",
[IDX_debug_funcnames] = ".debug_funcnames",
[IDX_debug_typenames] = ".debug_typenames",
[IDX_debug_varnames] = ".debug_varnames",
[IDX_debug_weaknames] = ".debug_weaknames",
[IDX_debug_macinfo] = ".debug_macinfo",
[IDX_debug_ranges] = ".debug_ranges"
#define ndwarf_scnnames (sizeof (dwarf_scnnames) / sizeof (dwarf_scnnames[0]))
static Dwarf *
check_section (Dwarf *result, GElf_Ehdr *ehdr, Elf_Scn *scn, bool inscngrp)
GElf_Shdr shdr_mem;
GElf_Shdr *shdr;
/* Get the section header data. */
shdr = gelf_getshdr (scn, &shdr_mem);
if (shdr == NULL)
/* This should never happen. If it does something is
wrong in the libelf library. */
abort ();
/* Ignore any SHT_NOBITS sections. Debugging sections should not
have been stripped, but in case of a corrupt file we won't try
to look at the missing data. */
if (unlikely (shdr->sh_type == SHT_NOBITS))
return result;
/* Make sure the section is part of a section group only iff we
really need it. If we are looking for the global (= non-section
group debug info) we have to ignore all the info in section
groups. If we are looking into a section group we cannot look at
a section which isn't part of the section group. */
if (! inscngrp && (shdr->sh_flags & SHF_GROUP) != 0)
/* Ignore the section. */
return result;
/* We recognize the DWARF section by their names. This is not very
safe and stable but the best we can do. */
const char *scnname = elf_strptr (result->elf, ehdr->e_shstrndx,
if (scnname == NULL)
/* The section name must be valid. Otherwise is the ELF file
invalid. */
__libdw_seterrno (DWARF_E_INVALID_ELF);
free (result);
return NULL;
/* Recognize the various sections. Most names start with .debug_. */
size_t cnt;
for (cnt = 0; cnt < ndwarf_scnnames; ++cnt)
if (strcmp (scnname, dwarf_scnnames[cnt]) == 0)
/* Found it. Remember where the data is. */
if (unlikely (result->sectiondata[cnt] != NULL))
/* A section appears twice. That's bad. We ignore the section. */
/* Get the section data. */
Elf_Data *data = elf_getdata (scn, NULL);
if (data != NULL && data->d_size != 0)
/* Yep, there is actually data available. */
result->sectiondata[cnt] = data;
return result;
/* Check whether all the necessary DWARF information is available. */
static Dwarf *
valid_p (Dwarf *result)
/* We looked at all the sections. Now determine whether all the
sections with debugging information we need are there.
XXX Which sections are absolutely necessary? Add tests if
necessary. For now we require only .debug_info. Hopefully this
is correct. */
if (likely (result != NULL)
&& unlikely (result->sectiondata[IDX_debug_info] == NULL))
__libdw_seterrno (DWARF_E_NO_DWARF);
free (result);
result = NULL;
return result;
static Dwarf *
global_read (Dwarf *result, Elf *elf, GElf_Ehdr *ehdr)
Elf_Scn *scn = NULL;
while (result != NULL && (scn = elf_nextscn (elf, scn)) != NULL)
result = check_section (result, ehdr, scn, false);
return valid_p (result);
static Dwarf *
scngrp_read (Dwarf *result, Elf *elf, GElf_Ehdr *ehdr, Elf_Scn *scngrp)
/* SCNGRP is the section descriptor for a section group which might
contain debug sections. */
Elf_Data *data = elf_getdata (scngrp, NULL);
if (data == NULL)
/* We cannot read the section content. Fail! */
free (result);
return NULL;
/* The content of the section is a number of 32-bit words which
represent section indices. The first word is a flag word. */
Elf32_Word *scnidx = (Elf32_Word *) data->d_buf;
size_t cnt;
for (cnt = 1; cnt * sizeof (Elf32_Word) <= data->d_size; ++cnt)
Elf_Scn *scn = elf_getscn (elf, scnidx[cnt]);
if (scn == NULL)
/* A section group refers to a non-existing section. Should
never happen. */
__libdw_seterrno (DWARF_E_INVALID_ELF);
free (result);
return NULL;
result = check_section (result, ehdr, scn, true);
if (result == NULL)
return valid_p (result);
Dwarf *
dwarf_begin_elf (elf, cmd, scngrp)
Elf *elf;
Dwarf_Cmd cmd;
Elf_Scn *scngrp;
GElf_Ehdr *ehdr;
GElf_Ehdr ehdr_mem;
/* Get the ELF header of the file. We need various pieces of
information from it. */
ehdr = gelf_getehdr (elf, &ehdr_mem);
if (ehdr == NULL)
if (elf_kind (elf) != ELF_K_ELF)
__libdw_seterrno (DWARF_E_NOELF);
__libdw_seterrno (DWARF_E_GETEHDR_ERROR);
return NULL;
/* Default memory allocation size. */
size_t mem_default_size = sysconf (_SC_PAGESIZE) - 4 * sizeof (void *);
/* Allocate the data structure. */
Dwarf *result = (Dwarf *) calloc (1, sizeof (Dwarf) + mem_default_size);
if (result == NULL)
__libdw_seterrno (DWARF_E_NOMEM);
return NULL;
/* Fill in some values. */
if ((BYTE_ORDER == LITTLE_ENDIAN && ehdr->e_ident[EI_DATA] == ELFDATA2MSB)
|| (BYTE_ORDER == BIG_ENDIAN && ehdr->e_ident[EI_DATA] == ELFDATA2LSB))
result->other_byte_order = true;
result->elf = elf;
/* Initialize the memory handling. */
result->mem_default_size = mem_default_size;
result->oom_handler = __libdw_oom;
result->mem_tail = (struct libdw_memblock *) (result + 1);
result->mem_tail->size = (result->mem_default_size
- offsetof (struct libdw_memblock, mem));
result->mem_tail->remaining = result->mem_tail->size;
result->mem_tail->prev = NULL;
if (cmd == DWARF_C_READ || cmd == DWARF_C_RDWR)
/* If the caller provides a section group we get the DWARF
sections only from this setion group. Otherwise we search
for the first section with the required name. Further
sections with the name are ignored. The DWARF specification
does not really say this is allowed. */
if (scngrp == NULL)
return global_read (result, elf, ehdr);
return scngrp_read (result, elf, ehdr, scngrp);
else if (cmd == DWARF_C_WRITE)
__libdw_seterrno (DWARF_E_UNIMPL);
free (result);
return NULL;
__libdw_seterrno (DWARF_E_INVALID_CMD);
free (result);
return NULL;