LinuxGuruz
  • Last 5 Forum Topics
    Replies
    Views
    Last post


The Web Only This Site
  • BOOKMARK

  • ADD TO FAVORITES

  • REFERENCES


  • MARC

    Mailing list ARChives
    - Search by -
     Subjects
     Authors
     Bodies





    FOLDOC

    Computing Dictionary




  • Text Link Ads






  • LINUX man pages
  • Linux Man Page Viewer


    The following form allows you to view linux man pages.

    Command:

    elf

    
    
    

    SYNOPSIS

           #include <elf.h>
    
    
    

    DESCRIPTION

           The  header  file  <elf.h>  defines the format of ELF executable binary
           files.  Amongst these files are normal  executable  files,  relocatable
           object files, core files and shared libraries.
    
           An executable file using the ELF file format consists of an ELF header,
           followed by a program header table or a section header table, or  both.
           The  ELF  header  is  always  at  offset zero of the file.  The program
           header table and the section header table's  offset  in  the  file  are
           defined  in  the  ELF  header.  The two tables describe the rest of the
           particularities of the file.
    
           This header file describes the above mentioned headers as C  structures
           and  also includes structures for dynamic sections, relocation sections
           and symbol tables.
    
           The following types are used for  N-bit  architectures  (N=32,64,  ElfN
           stands for Elf32 or Elf64, uintN_t stands for uint32_t or uint64_t):
    
               ElfN_Addr       Unsigned program address, uintN_t
               ElfN_Off        Unsigned file offset, uintN_t
               ElfN_Section    Unsigned section index, uint16_t
               ElfN_Versym     Unsigned version symbol information, uint16_t
               Elf_Byte        unsigned char
               ElfN_Half       uint16_t
               ElfN_Sword      int32_t
               ElfN_Word       uint32_t
               ElfN_Sxword     int64_t
               ElfN_Xword      uint64_t
    
           (Note:  The  *BSD  terminology is a bit different.  There Elf64_Half is
           twice as large as Elf32_Half, and Elf64Quarter is  used  for  uint16_t.
           In  order  to avoid confusion these types are replaced by explicit ones
           in the below.)
    
           All data structures that the file format defines follow  the  "natural"
           size  and  alignment  guidelines for the relevant class.  If necessary,
           data structures contain explicit padding to ensure 4-byte alignment for
           4-byte objects, to force structure sizes to a multiple of 4, and so on.
    
           The ELF header is described by the type Elf32_Ehdr or Elf64_Ehdr:
    
               #define EI_NIDENT 16
    
               typedef struct {
                   unsigned char e_ident[EI_NIDENT];
                   uint16_t      e_type;
                   uint16_t      e_machine;
                   uint32_t      e_version;
    
           e_ident     This array of bytes specifies to interpret the file,  inde-
                       pendent  of the processor or the file's remaining contents.
                       Within this array everything  is  named  by  macros,  which
                       start  with  the  prefix  EI_  and may contain values which
                       start with  the  prefix  ELF.   The  following  macros  are
                       defined:
    
                       EI_MAG0     The first byte of the magic number.  It must be
                                   filled with ELFMAG0.  (0: 0x7f)
    
                       EI_MAG1     The second byte of the magic number.   It  must
                                   be filled with ELFMAG1.  (1: 'E')
    
                       EI_MAG2     The third byte of the magic number.  It must be
                                   filled with ELFMAG2.  (2: 'L')
    
                       EI_MAG3     The fourth byte of the magic number.   It  must
                                   be filled with ELFMAG3.  (3: 'F')
    
                       EI_CLASS    The  fifth byte identifies the architecture for
                                   this binary:
    
                                   ELFCLASSNONE  This class is invalid.
                                   ELFCLASS32    This defines the 32-bit architec-
                                                 ture.   It supports machines with
                                                 files and virtual address  spaces
                                                 up to 4 Gigabytes.
                                   ELFCLASS64    This defines the 64-bit architec-
                                                 ture.
    
                       EI_DATA     The sixth byte specifies the data  encoding  of
                                   the  processor-specific data in the file.  Cur-
                                   rently these encodings are supported:
    
                                   ELFDATANONE   Unknown data format.
                                   ELFDATA2LSB   Two's complement,  little-endian.
                                   ELFDATA2MSB   Two's complement, big-endian.
    
                       EI_VERSION  The  seventh  byte is the version number of the
                                   ELF specification:
                                   EV_NONE       Invalid version.
                                   EV_CURRENT    Current version.
    
                       EI_OSABI    The eighth byte identifies the operating system
                                   and  ABI to which the object is targeted.  Some
                                   fields in other ELF structures have  flags  and
                                   values  that  have  platform-specific meanings;
                                   the interpretation of those  fields  is  deter-
                                   mined by the value of this byte.  E.g.:
    
                                   ELFOSABI_NONE       Same as ELFOSABI_SYSV
                                   ELFOSABI_SYSV       UNIX System V ABI.
                                   versions of an ABI.  The interpretation of this
                                   version number is dependent on the ABI  identi-
                                   fied  by the EI_OSABI field.  Applications con-
                                   forming to this specification use the value  0.
    
                       EI_PAD      Start of padding.  These bytes are reserved and
                                   set to zero.  Programs which read  them  should
                                   ignore  them.  The value for EI_PAD will change
                                   in the future if  currently  unused  bytes  are
                                   given meanings.
    
                       EI_NIDENT   The size of the e_ident array.
    
           e_type      This  member  of  the  structure identifies the object file
                       type:
    
                       ET_NONE     An unknown type.
                       ET_REL      A relocatable file.
                       ET_EXEC     An executable file.
                       ET_DYN      A shared object.
                       ET_CORE     A core file.
    
           e_machine   This member specifies  the  required  architecture  for  an
                       individual file.  E.g.:
    
                       EM_NONE     An unknown machine.
                       EM_M32      AT&T WE 32100.
                       EM_SPARC    Sun Microsystems SPARC.
                       EM_386      Intel 80386.
                       EM_68K      Motorola 68000.
                       EM_88K      Motorola 88000.
                       EM_860      Intel 80860.
                       EM_MIPS     MIPS RS3000 (big-endian only).
                       EM_PARISC   HP/PA.
                       EM_SPARC32PLUS
                                   SPARC with enhanced instruction set.
                       EM_PPC      PowerPC.
                       EM_PPC64    PowerPC 64-bit.
                       EM_S390     IBM S/390
                       EM_ARM      Advanced RISC Machines
                       EM_SH       Renesas SuperH
                       EM_SPARCV9  SPARC v9 64-bit.
                       EM_IA_64    Intel Itanium
                       EM_X86_64   AMD x86-64
                       EM_VAX      DEC Vax.
    
           e_version   This member identifies the file version:
    
                       EV_NONE     Invalid version.
                       EV_CURRENT  Current version.
    
           e_entry     This  member  gives the virtual address to which the system
    
           e_ehsize    This member holds the ELF header's size in bytes.
    
           e_phentsize This member holds the size in bytes of  one  entry  in  the
                       file's program header table; all entries are the same size.
    
           e_phnum     This member holds the number  of  entries  in  the  program
                       header  table.  Thus the product of e_phentsize and e_phnum
                       gives the table's size in bytes.  If a file has no  program
                       header, e_phnum holds the value zero.
    
                       If  the  number  of  entries in the program header table is
                       larger than or equal to PN_XNUM (0xffff), this member holds
                       PN_XNUM (0xffff) and the real number of entries in the pro-
                       gram header table is held in the sh_info member of the ini-
                       tial entry in section header table.  Otherwise, the sh_info
                       member of the initial entry contains the value zero.
    
                       PN_XNUM  This is defined  as  0xffff,  the  largest  number
                                e_phnum can have, specifying where the actual num-
                                ber of program headers is assigned.
    
           e_shentsize This member holds a sections header's  size  in  bytes.   A
                       section  header  is  one entry in the section header table;
                       all entries are the same size.
    
           e_shnum     This member holds the number  of  entries  in  the  section
                       header  table.  Thus the product of e_shentsize and e_shnum
                       gives the section header table's size in bytes.  If a  file
                       has  no  section  header  table, e_shnum holds the value of
                       zero.
    
                       If the number of entries in the  section  header  table  is
                       larger  than  or  equal  to SHN_LORESERVE (0xff00), e_shnum
                       holds the value zero and the real number of entries in  the
                       section  header  table is held in the sh_size member of the
                       initial entry in  section  header  table.   Otherwise,  the
                       sh_size  member  of the initial entry in the section header
                       table holds the value zero.
    
           e_shstrndx  This member holds the section header  table  index  of  the
                       entry  associated  with  the section name string table.  If
                       the file has no section  name  string  table,  this  member
                       holds the value SHN_UNDEF.
    
                       If the index of section name string table section is larger
                       than or equal to SHN_LORESERVE (0xff00), this member  holds
                       SHN_XINDEX  (0xffff) and the real index of the section name
                       string table section is held in the sh_link member  of  the
                       initial  entry  in  section  header  table.  Otherwise, the
                       sh_link member of the initial entry in section header table
    
                       SHN_HIPROC    Values less than or equal to  SHN_LOPROC  are
                                     reserved for processor-specific semantics.
    
                       SHN_ABS       This  value specifies absolute values for the
                                     corresponding reference.  For  example,  sym-
                                     bols   defined  relative  to  section  number
                                     SHN_ABS have  absolute  values  and  are  not
                                     affected by relocation.
    
                       SHN_COMMON    Symbols  defined relative to this section are
                                     common symbols, such  as  Fortran  COMMON  or
                                     unallocated C external variables.
    
                       SHN_HIRESERVE This  value  specifies the upper bound of the
                                     range of reserved indices  between  SHN_LORE-
                                     SERVE  and SHN_HIRESERVE, inclusive; the val-
                                     ues do not reference the section  header  ta-
                                     ble.   That is, the section header table does
                                     not contain entries for the reserved indices.
    
           An  executable or shared object file's program header table is an array
           of structures, each describing a segment or other information the  sys-
           tem needs to prepare the program for execution.  An object file segment
           contains one or more sections.  Program headers are meaningful only for
           executable  and  shared object files.  A file specifies its own program
           header size with the ELF header's e_phentsize and e_phnum members.  The
           ELF  program  header  is described by the type Elf32_Phdr or Elf64_Phdr
           depending on the architecture:
    
               typedef struct {
                   uint32_t   p_type;
                   Elf32_Off  p_offset;
                   Elf32_Addr p_vaddr;
                   Elf32_Addr p_paddr;
                   uint32_t   p_filesz;
                   uint32_t   p_memsz;
                   uint32_t   p_flags;
                   uint32_t   p_align;
               } Elf32_Phdr;
    
               typedef struct {
                   uint32_t   p_type;
                   uint32_t   p_flags;
                   Elf64_Off  p_offset;
                   Elf64_Addr p_vaddr;
                   Elf64_Addr p_paddr;
                   uint64_t   p_filesz;
                   uint64_t   p_memsz;
                   uint64_t   p_align;
               } Elf64_Phdr;
    
                                   the memory segment.  If  the  segment's  memory
                                   size  p_memsz  is  larger  than  the  file size
                                   p_filesz, the "extra" bytes are defined to hold
                                   the  value  0  and to follow the segment's ini-
                                   tialized area.  The file size may not be larger
                                   than the memory size.  Loadable segment entries
                                   in the program header table appear in ascending
                                   order, sorted on the p_vaddr member.
    
                       PT_DYNAMIC  The  array  element  specifies  dynamic linking
                                   information.
    
                       PT_INTERP   The array element specifies  the  location  and
                                   size of a null-terminated pathname to invoke as
                                   an interpreter.  This segment type is  meaning-
                                   ful  only  for  executable files (though it may
                                   occur for shared objects).  However it may  not
                                   occur  more  than  once  in  a  file.  If it is
                                   present, it must precede any  loadable  segment
                                   entry.
    
                       PT_NOTE     The  array  element  specifies the location and
                                   size for auxiliary information.
    
                       PT_SHLIB    This segment type is reserved but has  unspeci-
                                   fied semantics.  Programs that contain an array
                                   element of this type do not conform to the ABI.
    
                       PT_PHDR     The  array  element,  if present, specifies the
                                   location and size of the program  header  table
                                   itself,  both  in  the  file  and in the memory
                                   image of the program.  This  segment  type  may
                                   not  occur more than once in a file.  Moreover,
                                   it may occur only if the program  header  table
                                   is part of the memory image of the program.  If
                                   it is present, it  must  precede  any  loadable
                                   segment entry.
    
                       PT_LOPROC   Values  greater  than or equal to PT_HIPROC are
                                   reserved for processor-specific semantics.
    
                       PT_HIPROC   Values less than  or  equal  to  PT_LOPROC  are
                                   reserved for processor-specific semantics.
    
                       PT_GNU_STACK
                                   GNU extension which is used by the Linux kernel
                                   to control the state of the stack via the flags
                                   set in the p_flags member.
    
           p_offset    This member holds the offset from the beginning of the file
                       at which the first byte of the segment resides.
    
                       ment:
    
                       PF_X   An executable segment.
                       PF_W   A writable segment.
                       PF_R   A readable segment.
    
                       A text segment commonly has the flags  PF_X  and  PF_R.   A
                       data segment commonly has PF_X, PF_W and PF_R.
    
           p_align     This  member  holds  the  value  to  which the segments are
                       aligned in  memory  and  in  the  file.   Loadable  process
                       segments  must have congruent values for p_vaddr and p_off-
                       set, modulo the page size.  Values of zero and one mean  no
                       alignment is required.  Otherwise, p_align should be a pos-
                       itive, integral power of  two,  and  p_vaddr  should  equal
                       p_offset, modulo p_align.
    
           A  file's section header table lets one locate all the file's sections.
           The section header table is an array of Elf32_Shdr or Elf64_Shdr struc-
           tures.   The ELF header's e_shoff member gives the byte offset from the
           beginning of the file to the section header table.  e_shnum  holds  the
           number of entries the section header table contains.  e_shentsize holds
           the size in bytes of each entry.
    
           A section header table index is a subscript into this array.  Some sec-
           tion  header  table  indices  are  reserved:  the initial entry and the
           indices between SHN_LORESERVE and SHN_HIRESERVE.  The initial entry  is
           used  in  ELF  extensions  for  e_phnum, e_shnum and e_strndx; in other
           cases, each field in the initial entry is set to zero.  An object  file
           does not have sections for these special indices:
    
                  SHN_UNDEF     This  value  marks  an undefined, missing, irrele-
                                vant, or otherwise meaningless section  reference.
    
                  SHN_LORESERVE This  value specifies the lower bound of the range
                                of reserved indices.
    
                  SHN_LOPROC    Values greater than or  equal  to  SHN_HIPROC  are
                                reserved for processor-specific semantics.
    
                  SHN_HIPROC    Values  less  than  or  equal  to  SHN_LOPROC  are
                                reserved for processor-specific semantics.
    
                  SHN_ABS       This value specifies the absolute  value  for  the
                                corresponding  reference.   For  example, a symbol
                                defined relative to section number SHN_ABS has  an
                                absolute  value and is not affected by relocation.
    
                  SHN_COMMON    Symbols defined relative to this section are  com-
                                mon symbols, such as FORTRAN COMMON or unallocated
                                C external variables.
    
                   uint32_t   sh_size;
                   uint32_t   sh_link;
                   uint32_t   sh_info;
                   uint32_t   sh_addralign;
                   uint32_t   sh_entsize;
               } Elf32_Shdr;
    
               typedef struct {
                   uint32_t   sh_name;
                   uint32_t   sh_type;
                   uint64_t   sh_flags;
                   Elf64_Addr sh_addr;
                   Elf64_Off  sh_offset;
                   uint64_t   sh_size;
                   uint32_t   sh_link;
                   uint32_t   sh_info;
                   uint64_t   sh_addralign;
                   uint64_t   sh_entsize;
               } Elf64_Shdr;
    
           No real differences exist between the 32-bit and 64-bit  section  head-
           ers.
    
           sh_name   This  member specifies the name of the section.  Its value is
                     an index into the section header string table section, giving
                     the location of a null-terminated string.
    
           sh_type   This member categorizes the section's contents and semantics.
    
                     SHT_NULL       This value marks the section header  as  inac-
                                    tive.  It does not have an associated section.
                                    Other members of the section header have unde-
                                    fined values.
    
                     SHT_PROGBITS   This  section holds information defined by the
                                    program, whose format and meaning  are  deter-
                                    mined solely by the program.
    
                     SHT_SYMTAB     This section holds a symbol table.  Typically,
                                    SHT_SYMTAB provides symbols for link  editing,
                                    though  it  may also be used for dynamic link-
                                    ing.  As a complete symbol table, it may  con-
                                    tain  many  symbols  unnecessary  for  dynamic
                                    linking.  An object file can  also  contain  a
                                    SHT_DYNSYM section.
    
                     SHT_STRTAB     This  section holds a string table.  An object
                                    file may have multiple string table  sections.
    
                     SHT_RELA       This  section  holds  relocation  entries with
                                    explicit addends, such as type Elf32_Rela  for
                                    the  32-bit  class of object files.  An object
    
                     SHT_NOBITS     A section of this type occupies  no  space  in
                                    the file but otherwise resembles SHT_PROGBITS.
                                    Although this section contains no  bytes,  the
                                    sh_offset  member contains the conceptual file
                                    offset.
    
                     SHT_REL        This section holds relocation offsets  without
                                    explicit  addends,  such as type Elf32_Rel for
                                    the 32-bit class of object files.   An  object
                                    file may have multiple relocation sections.
    
                     SHT_SHLIB      This  section  is reserved but has unspecified
                                    semantics.
    
                     SHT_DYNSYM     This section holds a minimal  set  of  dynamic
                                    linking symbols.  An object file can also con-
                                    tain a SHT_SYMTAB section.
    
                     SHT_LOPROC     This value up to and including  SHT_HIPROC  is
                                    reserved for processor-specific semantics.
    
                     SHT_HIPROC     This value down to and including SHT_LOPROC is
                                    reserved for processor-specific semantics.
    
                     SHT_LOUSER     This value specifies the lower  bound  of  the
                                    range of indices reserved for application pro-
                                    grams.
    
                     SHT_HIUSER     This value specifies the upper  bound  of  the
                                    range of indices reserved for application pro-
                                    grams.  Section types between  SHT_LOUSER  and
                                    SHT_HIUSER  may  be  used  by the application,
                                    without conflicting  with  current  or  future
                                    system-defined section types.
    
           sh_flags  Sections  support  one-bit  flags that describe miscellaneous
                     attributes.  If a flag bit is set in sh_flags, the  attribute
                     is  "on"  for the section.  Otherwise, the attribute is "off"
                     or does not apply.  Undefined attributes are set to zero.
    
                     SHF_WRITE      This section  contains  data  that  should  be
                                    writable during process execution.
    
                     SHF_ALLOC      This  section  occupies  memory during process
                                    execution.   Some  control  sections  do   not
                                    reside  in the memory image of an object file.
                                    This attribute is off for those sections.
    
                     SHF_EXECINSTR  This  section  contains   executable   machine
                                    instructions.
    
                     SHF_MASKPROC   All  bits  included  in this mask are reserved
                     bytes in the file.  A section of type SHT_NOBITS may  have  a
                     nonzero size, but it occupies no space in the file.
    
           sh_link   This  member  holds  a section header table index link, whose
                     interpretation depends on the section type.
    
           sh_info   This member holds  extra  information,  whose  interpretation
                     depends on the section type.
    
           sh_addralign
                     Some  sections have address alignment constraints.  If a sec-
                     tion holds a doubleword, the system  must  ensure  doubleword
                     alignment  for  the  entire  section.   That is, the value of
                     sh_addr must be  congruent  to  zero,  modulo  the  value  of
                     sh_addralign.   Only zero and positive integral powers of two
                     are allowed.  Values of zero or one mean the section  has  no
                     alignment constraints.
    
           sh_entsize
                     Some  sections hold a table of fixed-sized entries, such as a
                     symbol table.  For such a section, this member gives the size
                     in  bytes  for  each entry.  This member contains zero if the
                     section does not hold a table of fixed-size entries.
    
           Various sections hold program and control information:
    
           .bss      This section holds uninitialized data that contributes to the
                     program's  memory  image.  By definition, the system initial-
                     izes the data with zeros when  the  program  begins  to  run.
                     This  section is of type SHT_NOBITS.  The attribute types are
                     SHF_ALLOC and SHF_WRITE.
    
           .comment  This section holds version control information.  This section
                     is of type SHT_PROGBITS.  No attribute types are used.
    
           .ctors    This  section holds initialized pointers to the C++ construc-
                     tor functions.  This section is of  type  SHT_PROGBITS.   The
                     attribute types are SHF_ALLOC and SHF_WRITE.
    
           .data     This  section  holds  initialized data that contribute to the
                     program's memory image.  This section is  of  type  SHT_PROG-
                     BITS.  The attribute types are SHF_ALLOC and SHF_WRITE.
    
           .data1    This  section  holds  initialized data that contribute to the
                     program's memory image.  This section is  of  type  SHT_PROG-
                     BITS.  The attribute types are SHF_ALLOC and SHF_WRITE.
    
           .debug    This  section  holds information for symbolic debugging.  The
                     contents are unspecified.  This section is of type  SHT_PROG-
                     BITS.  No attribute types are used.
    
           .dtors    This section holds initialized pointers to the C++ destructor
                     section  is  of  type  SHT_DYNSYM.   The  attribute  used  is
                     SHF_ALLOC.
    
           .fini     This section holds executable instructions that contribute to
                     the process termination code.  When a program exits  normally
                     the  system  arranges  to  execute  the code in this section.
                     This section is of type SHT_PROGBITS.   The  attributes  used
                     are SHF_ALLOC and SHF_EXECINSTR.
    
           .gnu.version
                     This  section  holds  the  version  symbol table, an array of
                     ElfN_Half elements.  This section is of type  SHT_GNU_versym.
                     The attribute type used is SHF_ALLOC.
    
           .gnu.version_d
                     This section holds the version symbol definitions, a table of
                     ElfN_Verdef   structures.    This   section   is   of    type
                     SHT_GNU_verdef.  The attribute type used is SHF_ALLOC.
    
           .gnu.version_r
                     This  section holds the version symbol needed elements, a ta-
                     ble of ElfN_Verneed structures.   This  section  is  of  type
                     SHT_GNU_versym.  The attribute type used is SHF_ALLOC.
    
           .got      This  section holds the global offset table.  This section is
                     of type SHT_PROGBITS.  The attributes are processor-specific.
    
           .hash     This  section  holds a symbol hash table.  This section is of
                     type SHT_HASH.  The attribute used is SHF_ALLOC.
    
           .init     This section holds executable instructions that contribute to
                     the  process  initialization  code.  When a program starts to
                     run the system arranges to execute the code in  this  section
                     before calling the main program entry point.  This section is
                     of type SHT_PROGBITS.  The attributes used are SHF_ALLOC  and
                     SHF_EXECINSTR.
    
           .interp   This section holds the pathname of a program interpreter.  If
                     the file has a loadable segment that  includes  the  section,
                     the  section's  attributes  will  include  the SHF_ALLOC bit.
                     Otherwise, that bit will be off.  This  section  is  of  type
                     SHT_PROGBITS.
    
           .line     This  section  holds  line  number  information  for symbolic
                     debugging, which describes  the  correspondence  between  the
                     program  source  and  the  machine  code.   The  contents are
                     unspecified.  This  section  is  of  type  SHT_PROGBITS.   No
                     attribute types are used.
    
           .note     This  section holds information in the "Note Section" format.
                     This section is of type SHT_NOTE.   No  attribute  types  are
                     used.    OpenBSD   native   executables   usually  contain  a
    
           .relNAME  This section holds relocation information as described below.
                     If  the file has a loadable segment that includes relocation,
                     the section's attributes  will  include  the  SHF_ALLOC  bit.
                     Otherwise the bit will be off.  By convention, "NAME" is sup-
                     plied by the section to which the relocations apply.  Thus  a
                     relocation  section  for  .text  normally would have the name
                     .rel.text.  This section is of type SHT_REL.
    
           .relaNAME This section holds relocation information as described below.
                     If  the file has a loadable segment that includes relocation,
                     the section's attributes  will  include  the  SHF_ALLOC  bit.
                     Otherwise the bit will be off.  By convention, "NAME" is sup-
                     plied by the section to which the relocations apply.  Thus  a
                     relocation  section  for  .text  normally would have the name
                     .rela.text.  This section is of type SHT_RELA.
    
           .rodata   This section holds read-only data that typically  contributes
                     to  a nonwritable segment in the process image.  This section
                     is of type SHT_PROGBITS.  The attribute used is SHF_ALLOC.
    
           .rodata1  This section holds read-only data that typically  contributes
                     to  a nonwritable segment in the process image.  This section
                     is of type SHT_PROGBITS.  The attribute used is SHF_ALLOC.
    
           .shstrtab This section holds section names.  This section  is  of  type
                     SHT_STRTAB.  No attribute types are used.
    
           .strtab   This  section  holds  strings, most commonly the strings that
                     represent the names associated with symbol table entries.  If
                     the  file  has  a  loadable  segment that includes the symbol
                     string table,  the  section's  attributes  will  include  the
                     SHF_ALLOC  bit.  Otherwise the bit will be off.  This section
                     is of type SHT_STRTAB.
    
           .symtab   This section holds a symbol table.  If the file has  a  load-
                     able  segment  that  includes the symbol table, the section's
                     attributes will include the SHF_ALLOC bit.  Otherwise the bit
                     will be off.  This section is of type SHT_SYMTAB.
    
           .text     This section holds the "text", or executable instructions, of
                     a program.   This  section  is  of  type  SHT_PROGBITS.   The
                     attributes used are SHF_ALLOC and SHF_EXECINSTR.
    
           String  table  sections  hold null-terminated character sequences, com-
           monly called strings.  The object file uses these strings to  represent
           symbol and section names.  One references a string as an index into the
           string table section.  The first byte, which is index zero, is  defined
           to  hold  a null byte ('\0').  Similarly, a string table's last byte is
           defined to hold a null byte, ensuring null termination for all strings.
    
           An  object  file's  symbol table holds information needed to locate and
           relocate a program's symbolic definitions and references.  A symbol ta-
                   unsigned char st_other;
                   uint16_t      st_shndx;
                   Elf64_Addr    st_value;
                   uint64_t      st_size;
               } Elf64_Sym;
    
           The 32-bit and 64-bit versions have the same members, just in a differ-
           ent order.
    
           st_name   This member holds an index  into  the  object  file's  symbol
                     string  table,  which  holds character representations of the
                     symbol names.  If the  value  is  nonzero,  it  represents  a
                     string  table  index  that gives the symbol name.  Otherwise,
                     the symbol table has no name.
    
           st_value  This member gives the value of the associated symbol.
    
           st_size   Many symbols have associated sizes.  This member  holds  zero
                     if the symbol has no size or an unknown size.
    
           st_info   This   member   specifies   the  symbol's  type  and  binding
                     attributes:
    
                     STT_NOTYPE  The symbol's type is not defined.
    
                     STT_OBJECT  The symbol is associated with a data object.
    
                     STT_FUNC    The symbol is associated with a function or other
                                 executable code.
    
                     STT_SECTION The  symbol is associated with a section.  Symbol
                                 table entries of this type  exist  primarily  for
                                 relocation  and normally have STB_LOCAL bindings.
    
                     STT_FILE    By convention, the symbol's name gives  the  name
                                 of  the  source  file  associated with the object
                                 file.  A file symbol has STB_LOCAL bindings,  its
                                 section  index  is  SHN_ABS,  and it precedes the
                                 other STB_LOCAL symbols of the  file,  if  it  is
                                 present.
    
                     STT_LOPROC  This  value  up  to  and  including STT_HIPROC is
                                 reserved for processor-specific semantics.
    
                     STT_HIPROC  This value down to and  including  STT_LOPROC  is
                                 reserved for processor-specific semantics.
    
                     STB_LOCAL   Local  symbols are not visible outside the object
                                 file containing their definition.  Local  symbols
                                 of  the  same  name  may  exist in multiple files
                                 without interfering with each other.
    
                                 There are macros for packing  and  unpacking  the
                                 binding and type fields:
    
                                 ELF32_ST_BIND(info)     or    ELF64_ST_BIND(info)
                                 extract a binding from an st_info value.
    
                                 ELF32_ST_TYPE(info) or ELF64_ST_TYPE(info)
                                 extract a type from an st_info value.
    
                                 ELF32_ST_INFO(bind, type) or  ELF64_ST_INFO(bind,
                                 type)
                                 convert  a  binding  and  a  type into an st_info
                                 value.
    
           st_other  This member defines the symbol visibility.
    
                     STV_DEFAULT     Default symbol visibility rules.
                     STV_INTERNAL    Processor-specific hidden class.
                     STV_HIDDEN      Symbol is unavailable in other modules.
                     STV_PROTECTED   Not preemptible, not exported.
    
                     There are macros for extracting the visibility type:
    
                     ELF32_ST_VISIBILITY(other) or ELF64_ST_VISIBILITY(other)
    
           st_shndx  Every symbol table entry is "defined"  in  relation  to  some
                     section.  This member holds the relevant section header table
                     index.
    
           Relocation is the process of connecting symbolic references  with  sym-
           bolic  definitions.   Relocatable  files  must  have  information  that
           describes how to modify their  section  contents,  thus  allowing  exe-
           cutable  and  shared  object  files to hold the right information for a
           process's program image.  Relocation entries are these data.
    
           Relocation structures that do not need an addend:
    
               typedef struct {
                   Elf32_Addr r_offset;
                   uint32_t   r_info;
               } Elf32_Rel;
    
               typedef struct {
                   Elf64_Addr r_offset;
                   uint64_t   r_info;
               } Elf64_Rel;
    
           Relocation structures that need an addend:
    
               typedef struct {
                   Elf32_Addr r_offset;
                   uint32_t   r_info;
                       the storage unit affected by the relocation.
    
           r_info      This  member gives both the symbol table index with respect
                       to which the relocation must be made and the type of  relo-
                       cation  to apply.  Relocation types are processor-specific.
                       When the text refers to  a  relocation  entry's  relocation
                       type or symbol table index, it means the result of applying
                       ELF[32|64]_R_TYPE or ELF[32|64]_R_SYM, respectively, to the
                       entry's r_info member.
    
           r_addend    This member specifies a constant addend used to compute the
                       value to be stored into the relocatable field.
    
           The .dynamic section contains a series of structures that hold relevant
           dynamic linking information.  The d_tag member controls the interpreta-
           tion of d_un.
    
               typedef struct {
                   Elf32_Sword    d_tag;
                   union {
                       Elf32_Word d_val;
                       Elf32_Addr d_ptr;
                   } d_un;
               } Elf32_Dyn;
               extern Elf32_Dyn _DYNAMIC[];
    
               typedef struct {
                   Elf64_Sxword    d_tag;
                   union {
                       Elf64_Xword d_val;
                       Elf64_Addr  d_ptr;
                   } d_un;
               } Elf64_Dyn;
               extern Elf64_Dyn _DYNAMIC[];
    
           d_tag     This member may have any of the following values:
    
                     DT_NULL     Marks end of dynamic section
    
                     DT_NEEDED   String table offset to name of a needed library
    
                     DT_PLTRELSZ Size in bytes of PLT relocs
    
                     DT_PLTGOT   Address of PLT and/or GOT
    
                     DT_HASH     Address of symbol hash table
    
                     DT_STRTAB   Address of string table
    
                     DT_SYMTAB   Address of symbol table
    
                     DT_RELA     Address of Rela relocs table
    
                     DT_RPATH    String table offset to library search path  (dep-
                                 recated)
    
                     DT_SYMBOLIC Alert  linker to search this shared object before
                                 the executable for symbols
    
                     DT_REL      Address of Rel relocs table
    
                     DT_RELSZ    Size in bytes of Rel table
    
                     DT_RELENT   Size in bytes of a Rel table entry
    
                     DT_PLTREL   Type of reloc the PLT refers (Rela or Rel)
    
                     DT_DEBUG    Undefined use for debugging
    
                     DT_TEXTREL  Absence of this indicates no relocs should  apply
                                 to a nonwritable segment
    
                     DT_JMPREL   Address of reloc entries solely for the PLT
    
                     DT_BIND_NOW Instruct  dynamic  linker  to  process all relocs
                                 before transferring control to the executable
    
                     DT_RUNPATH  String table offset to library search path
    
                     DT_LOPROC   Start of processor-specific semantics
    
                     DT_HIPROC   End of processor-specific semantics
    
           d_val     This member represents integer values with various  interpre-
                     tations.
    
           d_ptr     This  member  represents  program  virtual  addresses.   When
                     interpreting these addresses, the actual  address  should  be
                     computed  based  on  the  original file value and memory base
                     address.  Files do not contain relocation  entries  to  fixup
                     these addresses.
    
           _DYNAMIC  Array  containing  all the dynamic structures in the .dynamic
                     section.  This is automatically populated by the linker.
    
    
    

    NOTES

           ELF first appeared in System V.  The ELF format is an adopted standard.
    
           The extensions for e_phnum, e_shnum and e_strndx respectively are Linux
           extensions.  Sun, BSD and AMD64 also support them; for further informa-
           tion, look under SEE ALSO.
    
    
    

    SEE ALSO

           as(1), gdb(1), ld(1), objdump(1), execve(2), core(5)
    
    
    

    Linux 2013-04-17 ELF(5)

    
    
  • MORE RESOURCE


  • Linux

    The Distributions





    Linux

    The Software





    Linux

    The News



  • MARKETING






  • Toll Free

webmaster@linuxguruz.com
Copyright © 1999 - 2016 by LinuxGuruz