path: root/usr/src/lib/libdwarf/common/dwarf_elf_access.c

/*
  Copyright (C) 2000-2005 Silicon Graphics, Inc.  All Rights Reserved.
  Portions Copyright 2007-2010 Sun Microsystems, Inc. All rights reserved.
  Portions Copyright 2008-2010 Arxan Technologies, Inc. All Rights Reserved.
  Portions Copyright 2009-2010 David Anderson. All rights reserved.
  Portions Copyright 2009-2010 Novell Inc. All rights reserved.

  This program is free software; you can redistribute it and/or modify it
  under the terms of version 2.1 of the GNU Lesser General Public License 
  as published by the Free Software Foundation.

  This program is distributed in the hope that it would be useful, but
  WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  

  Further, this software is distributed without any warranty that it is
  free of the rightful claim of any third person regarding infringement 
  or the like.  Any license provided herein, whether implied or 
  otherwise, applies only to this software file.  Patent licenses, if
  any, provided herein do not apply to combinations of this program with 
  other software, or any other product whatsoever.  

  You should have received a copy of the GNU Lesser General Public 
  License along with this program; if not, write the Free Software 
  Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston MA 02110-1301,
  USA.

  Contact information:  Silicon Graphics, Inc., 1500 Crittenden Lane,
  Mountain View, CA 94043, or:

  http://www.sgi.com

  For further information regarding this notice, see:

  http://oss.sgi.com/projects/GenInfo/NoticeExplan

*/

#include "config.h"
#include "dwarf_incl.h"
#include "dwarf_elf_access.h"

#ifdef HAVE_ELF_H
#include <elf.h>
#endif
#ifdef HAVE_LIBELF_H
#include <libelf.h>
#else
#ifdef HAVE_LIBELF_LIBELF_H
#include <libelf/libelf.h>
#endif
#endif

#include <stdio.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <string.h>
#include <stdlib.h>

#define FALSE 0
#define TRUE  1

#ifndef EM_MIPS
/* This is the standard elf value EM_MIPS. */
#define EM_MIPS 8
#endif


#ifdef HAVE_ELF64_GETEHDR
extern Elf64_Ehdr *elf64_getehdr(Elf *);
#endif
#ifdef HAVE_ELF64_GETSHDR
extern Elf64_Shdr *elf64_getshdr(Elf_Scn *);
#endif
#ifdef WORDS_BIGENDIAN
#define WRITE_UNALIGNED(dbg,dest,source, srclength,len_out) \
    { \
      dbg->de_copy_word(dest, \
                        ((char *)source) +srclength-len_out,  \
                        len_out) ; \
    }


#else /* LITTLE ENDIAN */

#define WRITE_UNALIGNED(dbg,dest,source, srclength,len_out) \
    { \
      dbg->de_copy_word( (dest) , \
                        ((char *)source) ,  \
                        len_out) ; \
    }
#endif



typedef struct {
    dwarf_elf_handle elf;
    int              is_64bit;
    Dwarf_Small      length_size;
    Dwarf_Small      pointer_size;
    Dwarf_Unsigned   section_count;
    Dwarf_Endianness endianness;
    Dwarf_Small      machine;
    int              libdwarf_owns_elf;
    Elf32_Ehdr *ehdr32;

#ifdef HAVE_ELF64_GETEHDR
    Elf64_Ehdr *ehdr64;
#endif
    /* Elf symtab and its strtab.  Initialized at first
       call to do relocations, the actual data is in the Dwarf_Debug
       struct, not allocated locally here. */
    struct Dwarf_Section_s *symtab; 
    struct Dwarf_Section_s *strtab; 

} dwarf_elf_object_access_internals_t;

struct Dwarf_Elf_Rela {
    Dwarf_ufixed64 r_offset;
    /*Dwarf_ufixed64 r_info; */
    Dwarf_ufixed64 r_type;
    Dwarf_ufixed64 r_symidx;
    Dwarf_ufixed64 r_addend; 
};


static int dwarf_elf_object_access_load_section(void* obj_in, 
    Dwarf_Half section_index, 
    Dwarf_Small** section_data, 
    int* error);

/*
    dwarf_elf_object_access_internals_init()
 */
static int 
dwarf_elf_object_access_internals_init(void* obj_in, 
                              dwarf_elf_handle elf, 
                              int* error)
{
    dwarf_elf_object_access_internals_t*obj = 
        (dwarf_elf_object_access_internals_t*)obj_in;
    char *ehdr_ident = 0;
    Dwarf_Half machine = 0;
    obj->elf = elf;

    if ((ehdr_ident = elf_getident(elf, NULL)) == NULL) {
        *error = DW_DLE_ELF_GETIDENT_ERROR;
        return DW_DLV_ERROR;
    }

    obj->is_64bit = (ehdr_ident[EI_CLASS] == ELFCLASS64);


    if(ehdr_ident[EI_DATA] == ELFDATA2LSB){
        obj->endianness = DW_OBJECT_LSB;
    }
    else if(ehdr_ident[EI_DATA] == ELFDATA2MSB){
        obj->endianness = DW_OBJECT_MSB;
    }

    if (obj->is_64bit) {
#ifdef HAVE_ELF64_GETEHDR
        obj->ehdr64 = elf64_getehdr(elf);
        if (obj->ehdr64 == NULL) {
            *error = DW_DLE_ELF_GETEHDR_ERROR;
            return DW_DLV_ERROR;
        }
        obj->section_count = obj->ehdr64->e_shnum;
        machine = obj->ehdr64->e_machine;
        obj->machine = machine;
#else
        *error = DW_DLE_NO_ELF64_SUPPORT;
        return DW_DLV_ERROR;
#endif
    } 
    else {
        obj->ehdr32 = elf32_getehdr(elf);
        if (obj->ehdr32 == NULL) {
           *error = DW_DLE_ELF_GETEHDR_ERROR;
           return DW_DLV_ERROR;
        }
        obj->section_count = obj->ehdr32->e_shnum;
        machine = obj->ehdr32->e_machine;
        obj->machine = machine;
    }

    /* The following length_size is Not Too Significant. Only used
       one calculation, and an approximate one at that. */
    obj->length_size = obj->is_64bit ? 8 : 4;
    obj->pointer_size = obj->is_64bit ? 8 : 4;    

    if (obj->is_64bit && machine != EM_MIPS) {
        /* MIPS/IRIX makes pointer size and length size 8 for -64.
           Other platforms make length 4 always. */
        /* 4 here supports 32bit-offset dwarf2, as emitted by cygnus
           tools, and the dwarfv2.1 64bit extension setting. 
           This is not the same as the size-of-an-offset, which
           is 4 in 32bit dwarf and 8 in 64bit dwarf.  */
        obj->length_size = 4;
    }
    return DW_DLV_OK;
}

/*
    dwarf_elf_object_access_get_byte_order
 */
static
Dwarf_Endianness 
dwarf_elf_object_access_get_byte_order(void* obj_in)
{
    dwarf_elf_object_access_internals_t*obj = 
        (dwarf_elf_object_access_internals_t*)obj_in;
    return obj->endianness;
}

/*
    dwarf_elf_object_access_get_section_count()
 */
static
Dwarf_Unsigned 
dwarf_elf_object_access_get_section_count(void * obj_in)
{
    dwarf_elf_object_access_internals_t*obj = 
        (dwarf_elf_object_access_internals_t*)obj_in;
    return obj->section_count;
}


/*
    dwarf_elf_object_access_get_section()
 */
static 
int 
dwarf_elf_object_access_get_section_info(
    void* obj_in, 
    Dwarf_Half section_index, 
    Dwarf_Obj_Access_Section* ret_scn, 
    int* error)
{
    dwarf_elf_object_access_internals_t*obj = 
        (dwarf_elf_object_access_internals_t*)obj_in;

    Elf32_Shdr *shdr32 = 0;

#ifdef HAVE_ELF64_GETSHDR
    Elf64_Shdr *shdr64 = 0;
#endif
    Elf_Scn *scn = 0;


    scn = elf_getscn(obj->elf, section_index);
    if (scn == NULL) {
        *error = DW_DLE_MDE;
        return DW_DLV_ERROR;
    }
    if (obj->is_64bit) {
#ifdef HAVE_ELF64_GETSHDR
        shdr64 = elf64_getshdr(scn);
        if (shdr64 == NULL) {
            *error = DW_DLE_ELF_GETSHDR_ERROR;
            return DW_DLV_ERROR;
        }

        ret_scn->size = shdr64->sh_size;
        ret_scn->addr = shdr64->sh_addr;
        ret_scn->link = shdr64->sh_link;

        ret_scn->name = elf_strptr(obj->elf, obj->ehdr64->e_shstrndx,
                                        shdr64->sh_name);
        if(ret_scn->name == NULL) {
            *error = DW_DLE_ELF_STRPTR_ERROR;
            return DW_DLV_ERROR;
        }
        return DW_DLV_OK;
#else
        *error = DW_DLE_MISSING_ELF64_SUPPORT;
        return DW_DLV_ERROR;
#endif /* HAVE_ELF64_GETSHDR */
    } 
    if ((shdr32 = elf32_getshdr(scn)) == NULL) {
        *error = DW_DLE_ELF_GETSHDR_ERROR;
        return DW_DLV_ERROR;
    }

    ret_scn->size = shdr32->sh_size;
    ret_scn->addr = shdr32->sh_addr;
    ret_scn->link = shdr32->sh_link;

    ret_scn->name = elf_strptr(obj->elf, obj->ehdr32->e_shstrndx,
        shdr32->sh_name);
    if (ret_scn->name == NULL) {
        *error = DW_DLE_ELF_STRPTR_ERROR;
        return DW_DLV_ERROR;
    }
    return DW_DLV_OK;
}

/*
    dwarf_elf_object_access_get_length_size
 */
static
Dwarf_Small 
dwarf_elf_object_access_get_length_size(void* obj_in)
{
    dwarf_elf_object_access_internals_t*obj = 
        (dwarf_elf_object_access_internals_t*)obj_in;
    return obj->length_size;
}

/*
    dwarf_elf_object_access_get_pointer_size
 */
static
Dwarf_Small 
dwarf_elf_object_access_get_pointer_size(void* obj_in)
{
    dwarf_elf_object_access_internals_t*obj = 
        (dwarf_elf_object_access_internals_t*)obj_in;
    return obj->pointer_size;
}

#define MATCH_REL_SEC(i_,s_,r_)  \
if(i_ == s_.dss_index) { \
    *r_ = &s_;            \
    return DW_DLV_OK;    \
}

static int
find_section_to_relocate(Dwarf_Debug dbg,Dwarf_Half section_index,
   struct Dwarf_Section_s **relocatablesec, int *error)
{
    MATCH_REL_SEC(section_index,dbg->de_debug_info,relocatablesec);
    MATCH_REL_SEC(section_index,dbg->de_debug_abbrev,relocatablesec);
    MATCH_REL_SEC(section_index,dbg->de_debug_line,relocatablesec);
    MATCH_REL_SEC(section_index,dbg->de_debug_loc,relocatablesec);
    MATCH_REL_SEC(section_index,dbg->de_debug_aranges,relocatablesec);
    MATCH_REL_SEC(section_index,dbg->de_debug_macinfo,relocatablesec);
    MATCH_REL_SEC(section_index,dbg->de_debug_pubnames,relocatablesec);
    MATCH_REL_SEC(section_index,dbg->de_debug_ranges,relocatablesec);
    MATCH_REL_SEC(section_index,dbg->de_debug_frame,relocatablesec);
    MATCH_REL_SEC(section_index,dbg->de_debug_frame_eh_gnu,relocatablesec);
    MATCH_REL_SEC(section_index,dbg->de_debug_pubtypes,relocatablesec);
    MATCH_REL_SEC(section_index,dbg->de_debug_funcnames,relocatablesec);
    MATCH_REL_SEC(section_index,dbg->de_debug_typenames,relocatablesec);
    MATCH_REL_SEC(section_index,dbg->de_debug_varnames,relocatablesec);
    MATCH_REL_SEC(section_index,dbg->de_debug_weaknames,relocatablesec);
    /* dbg-> de_debug_str,syms); */
    /* de_elf_symtab,syms); */
    /* de_elf_strtab,syms); */
    *error = DW_DLE_RELOC_SECTION_MISMATCH;
    return DW_DLV_ERROR;
   
}
#undef MATCH_REL_SEC

static void
get_rela_elf32(Dwarf_Small *data, unsigned int i,
  int endianness,
  int machine, struct Dwarf_Elf_Rela *relap)
{
    Elf32_Rela *relp = (Elf32_Rela*)(data + (i * sizeof(Elf32_Rela)));
    relap->r_offset = relp->r_offset;
    /*
    relap->r_info = relp->r_info;
   */
    relap->r_type = ELF32_R_TYPE(relp->r_info);
    relap->r_symidx = ELF32_R_SYM(relp->r_info);
    relap->r_addend = relp->r_addend;
}

static void
get_rela_elf64(Dwarf_Small *data, unsigned int i, 
  int endianness,
  int machine,struct Dwarf_Elf_Rela *relap)
{
#ifdef HAVE_ELF64_RELA
    Elf64_Rela * relp = (Elf64_Rela*)(data + (i * sizeof(Elf64_Rela)));
    relap->r_offset = relp->r_offset;
    /*
    relap->r_info = relp->r_info;
    */
    if(machine == EM_MIPS && endianness == DW_OBJECT_LSB ) {
        /* This is really wierd. Treat this very specially. 
           The Elf64 LE MIPS object used for
           testing (that has rela) wants the
           values as  sym  ssym type3 type2 type, treating
           each value as independent value. But libelf xlate
           treats it as something else so we fudge here.  
           It is unclear
           how to precisely characterize where these relocations
           were used.
           SGI MIPS on IRIX never used .rela relocations.
           The BE 64bit elf MIPS test object with rela uses traditional
           elf relocation layouts, not this special case.  */
#define ELF64MIPS_REL_SYM(i) ((i) & 0xffffffff)
#define ELF64MIPS_REL_TYPE(i) ((i >> 56) &0xff)
        /* We ignore the special TYPE2 and TYPE3, they should be
           value R_MIPS_NONE in rela. */
        relap->r_type = ELF64MIPS_REL_TYPE(relp->r_info);
        relap->r_symidx = ELF64MIPS_REL_SYM(relp->r_info);
#undef MIPS64SYM
#undef MIPS64TYPE
    } else 
    {
        relap->r_type = ELF64_R_TYPE(relp->r_info);
        relap->r_symidx = ELF64_R_SYM(relp->r_info);
    }
    relap->r_addend = relp->r_addend;
#endif
}

static void
get_relocations_array(Dwarf_Bool is_64bit, 
    int endianness,
    int machine,
    Dwarf_Small *data, 
    unsigned int num_relocations, 
    struct Dwarf_Elf_Rela *relap)
{
    unsigned int i = 0;
    void (*get_relocations)(Dwarf_Small *data, unsigned int i, 
         int endianness,
         int machine,
         struct Dwarf_Elf_Rela *relap);

    /* Handle 32/64 bit issue
     */
    if (is_64bit) {
        get_relocations = get_rela_elf64;
    } else {
        get_relocations = get_rela_elf32;
    }

    for (i=0; i < num_relocations; i++) {
       get_relocations(data, i,endianness,machine, &(relap[i]));
    }

}

static int
get_relocation_entries(Dwarf_Bool is_64bit,
    int endianness,
    int machine,
    Dwarf_Small *relocation_section,
    Dwarf_Unsigned relocation_section_size,
    struct Dwarf_Elf_Rela **relas,
    unsigned int *nrelas,
    int *error)
{
    unsigned int relocation_size = 0;

    if (is_64bit) {
#ifdef HAVE_ELF64_RELA
        relocation_size = sizeof(Elf64_Rela);
#else
        *error = DW_DLE_MISSING_ELF64_SUPPORT;
        return DW_DLV_ERROR;
#endif
    } else {
        relocation_size = sizeof(Elf32_Rela);
    }

    if (relocation_section == NULL) {
        *error = DW_DLE_RELOC_SECTION_PTR_NULL;
        return(DW_DLV_ERROR);
    }

    if ((relocation_section_size != 0)) {
        size_t bytescount = 0;
        if(relocation_section_size%relocation_size) {
            *error = DW_DLE_RELOC_SECTION_LENGTH_ODD;
            return DW_DLV_ERROR;
        }
        *nrelas = relocation_section_size/relocation_size;
        bytescount = (*nrelas) * sizeof(struct Dwarf_Elf_Rela);
        *relas = malloc(bytescount);
        if (!*relas) {
            *error = DW_DLE_MAF;
            return(DW_DLV_ERROR);
        }
        memset(*relas,0,bytescount);
        get_relocations_array(is_64bit,endianness,machine, relocation_section, 
            *nrelas, *relas);
    }
    return(DW_DLV_OK);
}

static Dwarf_Bool
is_32bit_abs_reloc(unsigned int type, Dwarf_Half machine) 
{
    Dwarf_Bool r = 0;
    switch (machine) {
#if defined(EM_MIPS) && defined (R_MIPS_32)
    case EM_MIPS:
         r = (type == R_MIPS_32);
         break;
#endif
#if defined(EM_SPARC32PLUS)  && defined (R_SPARC_UA32)
    case EM_SPARC32PLUS:
         r =  (type == R_SPARC_UA32);
         break;
#endif
#if defined(EM_SPARCV9)  && defined (R_SPARC_UA32)
    case EM_SPARCV9:
         r =  (type == R_SPARC_UA32);
         break;
#endif
#if defined(EM_SPARC) && defined (R_SPARC_UA32)
    case EM_SPARC:
         r =  (type == R_SPARC_UA32);
         break;
#endif
#if defined(EM_386) && defined (R_386_32)
    case EM_386:
        r =  (type == R_386_32);
        break;
#endif
#if defined(EM_IA_64) && defined (R_IA64_SECREL32LSB)
    case EM_IA_64:
        r =  (type == R_IA64_SECREL32LSB);
        break;
#endif
#if defined(EM_PPC64) && defined (R_PPC64_ADDR32)
    case EM_PPC64:
        r =  (type == R_PPC64_ADDR32);
        break;
#endif
#if defined(EM_PPC) && defined (R_PPC_ADDR32)
    case EM_PPC:
        r =  (type == R_PPC_ADDR32);
        break;
#endif
#if defined(EM_S390) && defined (R_390_32)
    case EM_S390:
        r =  (type == R_390_32);
        break;
#endif
#if defined(EM_X86_64) && defined (R_X86_64_32)
    case EM_X86_64:
        r = (type == R_X86_64_32);
        break;
#endif
    }
    return r;
}

static Dwarf_Bool
is_64bit_abs_reloc(unsigned int type, Dwarf_Half machine) 
{
    Dwarf_Bool r = 0;
    switch (machine) {
#if defined(EM_MIPS) && defined (R_MIPS_64)
    case EM_MIPS:
        r =  (type == R_MIPS_64);
        break;
#endif
#if defined(EM_SPARC32PLUS) && defined (R_SPARC_UA64)
    case EM_SPARC32PLUS:
        r =  (type == R_SPARC_UA64);
        break;
#endif
#if defined(EM_SPARCV9) && defined (R_SPARC_UA64)
    case EM_SPARCV9:
        r = (type == R_SPARC_UA64);
        break;
#endif
#if defined(EM_SPARC) && defined (R_SPARC_UA64)
    case EM_SPARC:
        r = (type == R_SPARC_UA64);
        break;
#endif
#if defined(EM_IA_64) && defined (R_IA64_SECREL32LSB)
    case EM_IA_64:
        r =  (type == R_IA64_DIR64LSB);
        break;
#endif
#if defined(EM_PPC64) && defined (R_PPC64_ADDR64)
    case EM_PPC64:
        r =  (type == R_PPC64_ADDR64);
        break;
#endif
#if defined(EM_S390) && defined (R_390_64)
    case EM_S390:
        r =  (type == R_390_64);
        break;
#endif
#if defined(EM_X86_64) && defined (R_X86_64_64)
    case EM_X86_64:
        r =  (type == R_X86_64_64);
        break;
#endif
    }
    return r;
}


static void
update_entry(Dwarf_Debug dbg,
    Dwarf_Bool is_64bit, Dwarf_Endianness endianess,
    Dwarf_Half machine, struct Dwarf_Elf_Rela *rela,
    Dwarf_Small *target_section, Dwarf_Small *section_data)
{
    unsigned int type = 0; 
    unsigned int sym_idx = 0;
#ifdef HAVE_ELF64_SYM
    Elf64_Sym sym_buf;
    Elf64_Sym *sym = 0;
#else
    Elf32_Sym sym_buf;
    Elf32_Sym *sym = 0; 
#endif
    Elf32_Sym *sym32 = 0;
    Dwarf_ufixed64 offset = 0;
    Dwarf_sfixed64 addend = 0;
    Dwarf_Unsigned reloc_size = 0;


    /* Dwarf_Elf_Rela dereferencing */
    offset = rela->r_offset;
    addend = rela->r_addend;
    type = rela->r_type;
    sym_idx = rela->r_symidx;

    if (is_64bit) {
#ifdef HAVE_ELF64_SYM
       sym = &((Elf64_Sym*)section_data)[sym_idx];
#endif
    } else {
       sym32 = &((Elf32_Sym*)section_data)[sym_idx];

       /* Convert Elf32_Sym struct to Elf64_Sym struct. We point at
        * an Elf64_Sym local variable (sym_buf) to allow us to use the
        * same pointer (sym) for both 32-bit and 64-bit instances.
        */
       sym = &sym_buf;
       sym->st_name = sym32->st_name;
       sym->st_info = sym32->st_info;
       sym->st_other = sym32->st_other;
       sym->st_shndx = sym32->st_shndx;
       sym->st_value = sym32->st_value;
       sym->st_size = sym32->st_size;
    }

    /* Determine relocation size */
    if (is_32bit_abs_reloc(type, machine)) {
        reloc_size = 4;
    } else if (is_64bit_abs_reloc(type, machine)) {
        reloc_size = 8;
    } else {
        return;
    }


    {
        /* Assuming we do not need to do a READ_UNALIGNED here
           at target_section + offset and add its value to
           outval.  Some ABIs say no read (for example MIPS),
           but if some do then which ones? */
        Dwarf_Unsigned outval = sym->st_value + addend;
        WRITE_UNALIGNED(dbg,target_section + offset,
                  &outval,sizeof(outval),reloc_size);
    }
}



static int 
apply_rela_entries(Dwarf_Debug dbg,
    Dwarf_Bool is_64bit,
    Dwarf_Endianness endianess,
    Dwarf_Half machine,
    Dwarf_Small *target_section,
    Dwarf_Small *symtab_section,
    struct Dwarf_Elf_Rela *relas, unsigned int nrelas,
    int *error)
{
    if ((target_section != NULL)  && (relas != NULL)) {
        unsigned int i;
        for (i = 0; i < nrelas; i++) {
            update_entry(dbg, is_64bit,
                endianess,
                machine,
                &(relas)[i],
                target_section,
                symtab_section);
        }
    }
    return DW_DLV_OK;
}


static int
loop_through_relocations(
   Dwarf_Debug dbg,
   dwarf_elf_object_access_internals_t* obj,
   struct Dwarf_Section_s *relocatablesec,
   int *error)
{
    Dwarf_Small *target_section = 0;
    Dwarf_Small *symtab_section = obj->symtab->dss_data;
    Dwarf_Small *relocation_section  = relocatablesec->dss_reloc_data;
    Dwarf_Unsigned relocation_section_size =
              relocatablesec->dss_reloc_size;
    int ret = DW_DLV_ERROR;
    struct Dwarf_Elf_Rela *relas = 0;
    unsigned int nrelas = 0;
    Dwarf_Small *mspace = 0;

    ret = get_relocation_entries(obj->is_64bit,
        obj->endianness,
        obj->machine,
        relocation_section, 
        relocation_section_size, 
        &relas, &nrelas, error);
    if(ret != DW_DLV_OK) {
        free(relas);
        return ret;
    }

    /* Some systems read Elf in read-only memory via mmap or the like.
       So the only safe thing is to copy the current data into
       malloc space and refer to the malloc space instead of the
       space returned by the elf library */
    mspace = malloc(relocatablesec->dss_size);
    if(!mspace) {
        *error = DW_DLE_RELOC_SECTION_MALLOC_FAIL;
        return DW_DLV_ERROR;
    }
    memcpy(mspace,relocatablesec->dss_data,relocatablesec->dss_size);
    relocatablesec->dss_data = mspace;
    target_section = relocatablesec->dss_data;
    relocatablesec->dss_data_was_malloc = 1;

    ret = apply_rela_entries(
        dbg,
        obj->is_64bit,
        obj->endianness, obj->machine, 
        target_section, 
        symtab_section,
        relas, nrelas, error);

    free(relas);

    return ret;
}

/*
    Find the section data in dbg and find all the relevant
    sections.  Then do relocations.
*/
static int
dwarf_elf_object_relocate_a_section(void* obj_in,
    Dwarf_Half section_index,
    Dwarf_Debug dbg,
    int* error)
{
    int res = DW_DLV_ERROR;
    dwarf_elf_object_access_internals_t*obj = 0; 
    struct Dwarf_Section_s * relocatablesec = 0;
    if (section_index == 0) {
        return DW_DLV_NO_ENTRY;
    }
    obj = (dwarf_elf_object_access_internals_t*)obj_in;

    /* The section to relocate must already be loaded into memory. */
    res = find_section_to_relocate(dbg, section_index,&relocatablesec,error);
    if(res != DW_DLV_OK) {
         return res;
    }

    /* Sun and possibly others do not always set sh_link in .debug_* sections. 
       So we cannot do full  consistency checks. */
    if(relocatablesec->dss_reloc_index == 0 ) {
        /* Something is wrong. */
        *error = DW_DLE_RELOC_SECTION_MISSING_INDEX;
        return DW_DLV_ERROR;
    }
    /* Now load the relocations themselves. */
    res =  dwarf_elf_object_access_load_section(obj_in,
            relocatablesec->dss_reloc_index,
            &relocatablesec->dss_reloc_data, error);
    if(res != DW_DLV_OK) {
            return res;
    }

    /* Now get the symtab. */
    if  (!obj->symtab) {
       obj->symtab = &dbg->de_elf_symtab;
       obj->strtab = &dbg->de_elf_strtab;
    }
    if( obj->symtab->dss_index != relocatablesec->dss_reloc_link) {
        /* Something is wrong. */
        *error = DW_DLE_RELOC_MISMATCH_RELOC_INDEX;
        return DW_DLV_ERROR;
    }
    if( obj->strtab->dss_index != obj->symtab->dss_link) {
        /* Something is wrong. */
        *error = DW_DLE_RELOC_MISMATCH_STRTAB_INDEX;
        return DW_DLV_ERROR;
    }
    if(!obj->symtab->dss_data) {
        /* Now load the symtab */
        res =  dwarf_elf_object_access_load_section(obj_in,
            obj->symtab->dss_index,
            &obj->symtab->dss_data, error);
        if(res != DW_DLV_OK) {
            return res;
        }
    }
    if(! obj->strtab->dss_data) {
        /* Now load the strtab */
        res = dwarf_elf_object_access_load_section(obj_in, 
            obj->strtab->dss_index,
            &obj->strtab->dss_data,error);
        if(res != DW_DLV_OK){
            return res;
        }
    }

    /* We have all the data we need in memory. */
    res = loop_through_relocations(dbg,obj,relocatablesec,error);

    return res;
}

/* 
    dwarf_elf_object_access_load_section
 */
static int 
dwarf_elf_object_access_load_section(void* obj_in, 
    Dwarf_Half section_index, 
    Dwarf_Small** section_data, 
    int* error)
{
    dwarf_elf_object_access_internals_t*obj = 
        (dwarf_elf_object_access_internals_t*)obj_in;
    if (section_index == 0) {
        return DW_DLV_NO_ENTRY;
    }

    {
        Elf_Scn *scn = 0;
        Elf_Data *data = 0;

        scn = elf_getscn(obj->elf, section_index);
        if (scn == NULL) {
            *error = DW_DLE_MDE;
            return DW_DLV_ERROR;
        }

        /* 
           When using libelf as a producer, section data may be stored
           in multiple buffers. In libdwarf however, we only use libelf
           as a consumer (there is a dwarf producer API, but it doesn't
           use libelf). Because of this, this single call to elf_getdata
           will retrieve the entire section in a single contiguous
           buffer. */
        data = elf_getdata(scn, NULL);
        if (data == NULL) {
                  *error = DW_DLE_MDE;
                  return DW_DLV_ERROR;
        }
        *section_data = data->d_buf;
    }
    return DW_DLV_OK;
}


/* dwarf_elf_access method table. */
static const struct Dwarf_Obj_Access_Methods_s dwarf_elf_object_access_methods = 
{
    dwarf_elf_object_access_get_section_info,
    dwarf_elf_object_access_get_byte_order,
    dwarf_elf_object_access_get_length_size,
    dwarf_elf_object_access_get_pointer_size,
    dwarf_elf_object_access_get_section_count,
    dwarf_elf_object_access_load_section,
    dwarf_elf_object_relocate_a_section 
};


/*
    Interface for the ELF object file implementation.
 */
int 
dwarf_elf_object_access_init(dwarf_elf_handle elf, 
    int libdwarf_owns_elf,
    Dwarf_Obj_Access_Interface** ret_obj,
    int *err)
{
    int res = 0;
    dwarf_elf_object_access_internals_t *internals = 0;
    Dwarf_Obj_Access_Interface *intfc = 0;

    internals = malloc(sizeof(dwarf_elf_object_access_internals_t));
    if(!internals) {
        /* Impossible case, we hope. Give up. */
        return DW_DLV_ERROR;
    }
    memset(internals,0,sizeof(*internals));
    res = dwarf_elf_object_access_internals_init(internals, elf, err);
    if(res != DW_DLV_OK){
        free(internals);
        return DW_DLV_ERROR;
    }
    internals->libdwarf_owns_elf = libdwarf_owns_elf;
    
    intfc = malloc(sizeof(Dwarf_Obj_Access_Interface));
    if(!intfc) {
        /* Impossible case, we hope. Give up. */
        free(internals);
        return DW_DLV_ERROR;
    }
    /* Initialize the interface struct */
    intfc->object = internals;
    intfc->methods = &dwarf_elf_object_access_methods;

    *ret_obj = intfc;
    return DW_DLV_OK;
}



/*
    Clean up the Dwarf_Obj_Access_Interface returned by elf_access_init.
 */
void 
dwarf_elf_object_access_finish(Dwarf_Obj_Access_Interface* obj)
{
    if(!obj) {
        return;
    }
    if(obj->object) {
        dwarf_elf_object_access_internals_t *internals = 
            (dwarf_elf_object_access_internals_t *)obj->object;
        if(internals->libdwarf_owns_elf){
            elf_end(internals->elf);
        }
    }
    free(obj->object);
    free(obj);
}

/*
    This function returns the Elf * pointer
    associated with a Dwarf_Debug.

    This function only makes sense if ELF is implied.
 */
int
dwarf_get_elf(Dwarf_Debug dbg, dwarf_elf_handle * elf,
              Dwarf_Error * error)
{   
    struct Dwarf_Obj_Access_Interface_s * obj = 0;
    if (dbg == NULL) {
        _dwarf_error(NULL, error, DW_DLE_DBG_NULL);
        return (DW_DLV_ERROR);
    }

    obj = dbg->de_obj_file; 
    if(obj) {
       dwarf_elf_object_access_internals_t *internals =
           (dwarf_elf_object_access_internals_t*)obj->object;
       if(internals->elf == NULL) {
           _dwarf_error(dbg, error, DW_DLE_FNO);
           return (DW_DLV_ERROR);
       }
       *elf = internals->elf;
       return DW_DLV_OK;
       
    }
    _dwarf_error(dbg, error, DW_DLE_FNO);
    return DW_DLV_ERROR;
}