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Man Pages


Manual Reference Pages  -  GELF (3)

NAME

GElf - class-independent API for ELF manipulation

CONTENTS

Library
Synopsis
Description
     GElf Data Structures
     GElf Programming Model
     Namespace use
     GElf Programming APIs
See Also
History
Authors

LIBRARY


.Lb libelf

SYNOPSIS


.In gelf.h

DESCRIPTION

This manual page describes a class independent API for manipulating ELF objects. This API allows an application to operate on ELF descriptors without needing to the know the ELF class of the descriptor.

The GElf API may be used alongside the ELF API without restriction.

    GElf Data Structures

The GElf API defines the following class-independent data structures:
Vt GElf_Addr
  A representation of ELF addresses.
Vt GElf_Dyn A class-independent representation of ELF .dynamic section entries.
Vt GElf_Ehdr
  A class-independent representation of an ELF Executable Header.
Vt GElf_Half
  An unsigned 16 bit quantity.
Vt GElf_Off A class-independent representation of a ELF offset.
Vt GElf_Phdr
  A class-independent representation of an ELF Program Header Table entry.
Vt GElf_Rel A class-independent representation of an ELF relocation entry.
Vt GElf_Rela
  A class-independent representation of an ELF relocation entry with addend.
Vt GElf_Shdr
  A class-independent representation of an ELF Section Header Table entry.
Vt GElf_Sword
  A signed 32 bit quantity.
Vt GElf_Sxword
  A signed 64 bit quantity.
Vt GElf_Sym A class-independent representation of an ELF symbol table entry.
Vt GElf_Word
  An unsigned 32 bit quantity.
Vt GElf_Xword
  An unsigned 64 bit quantity.

These data structures are sized to be compatible with the corresponding 64 bit ELF structures, and have the same internal structure as their 64 bit class-dependent counterparts. Class-dependent ELF structures are described in elf(5).

    GElf Programming Model

GElf functions always return a copy of the underlying (class-dependent) ELF data structure. The programming model with GElf is as follows:
  1. An application will retrieve data from an ELF descriptor using a gelf_get_* function. This will copy out data into a private
    .Vt GElf_* data structure.
  2. The application will work with its private copy of the GElf structure.
  3. Once done, the application copies the new values back to the underlying ELF data structure using the gelf_update_* functions.
  4. The application will then use the elf_flag* APIs to indicate to the ELF library that an ELF data structure is dirty.

When updating an underlying 32 bit ELF data structure, the GElf routines will signal an error if a GElf value is out of range for the underlying ELF data type.

    Namespace use

The GElf interface uses the following symbols:
GElf_*
  Class-independent data types.
gelf_*
  For functions defined in the API set.

    GElf Programming APIs

This section provides an overview of the GElf programming APIs. Further information is provided in the manual page of each function listed here.
Allocating ELF Data Structures
 
gelf_newehdr
  Allocate a new ELF Executable Header.
gelf_newphdr
  Allocate a new ELF Program Header Table.
Data Translation
 
gelf_xlatetof
  Translate the native representation of an ELF data structure to its file representation.
gelf_xlatetom
  Translate from the file representation of an ELF data structure to a native representation.
Retrieving ELF Data
 
gelf_getdyn
  Retrieve an ELF .dynamic table entry.
gelf_getehdr
  Retrieve an ELF Executable Header from the underlying ELF descriptor.
gelf_getphdr
  Retrieve an ELF Program Header Table entry from the underlying ELF descriptor.
gelf_getrel
  Retrieve an ELF relocation entry.
gelf_getrela
  Retrieve an ELF relocation entry with addend.
gelf_getshdr
  Retrieve an ELF Section Header Table entry from the underlying ELF descriptor.
gelf_getsym
  Retrieve an ELF symbol table entry.
Queries
 
gelf_checksum
  Retrieves the ELF checksum for an ELF descriptor.
gelf_fsize
  Retrieves the size of the file representation of an ELF type.
gelf_getclass
  Retrieves the ELF class of an ELF descriptor.
Updating ELF Data
 
gelf_update_dyn
  Copy back an ELF .dynamic Table entry.
gelf_update_phdr
  Copy back an ELF Program Header Table entry.
gelf_update_rel
  Copy back an ELF relocation entry.
gelf_update_rela
  Copy back an ELF relocation with addend entry.
gelf_update_shdr
  Copy back an ELF Section Header Table entry.
gelf_update_sym
  Copy back an ELF symbol table entry.

SEE ALSO

elf(3), elf(5)

HISTORY

The GELF(3) API first appeared in System V Release 4. This implementation of the API first appeared in
.Fx 7.0 .

AUTHORS

The GElf API was implemented by
.An Joseph Koshy <jkoshy@FreeBSD.org>.
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