GELF_NEWEHDR(3) | Library Functions Manual | GELF_NEWEHDR(3)

# NAME

`elf32_newehdr`, `elf64_newehdr`, `gelf_newehdr` — retrieve or allocate the object file header

# SYNOPSIS

ELF Access Library (libelf, -lelf)
`#include <libelf.h>`

Elf32_Ehdr *
`elf32_newehdr`(Elf *elf);

Elf64_Ehdr *
`elf64_newehdr`(Elf *elf);

`#include <gelf.h>`

void *
`gelf_newehdr`(Elf *elf, int elfclass);

# DESCRIPTION

These functions retrieve the ELF header from the ELF descriptor elf, allocating a new header if needed. File data structures are translated to their in-memory representations as described in elf(3).

Function `elf32_newehdr`() returns a pointer to a 32 bit Elf32_Ehdr structure. Function `elf64_newehdr`() returns a pointer to a 64 bit Elf64_Ehdr structure.

When argument elfclass has value `ELFCLASS32`, function `gelf_newehdr`() returns the value returned by `elf32_newehdr`(elf). When argument elfclass has value `ELFCLASS64`, it returns the value returned by `elf64_newehdr`(elf).

If a fresh header structure is allocated, the members of the structure are initialized as follows:

e_ident[EI_MAG0..EI_MAG3]
  Identification bytes at offsets `EI_MAG0`, `EI_MAG1`, `EI_MAG2` and `EI_MAG3` are set to the ELF signature.
e_ident[EI_CLASS]
  The identification byte at offset `EI_CLASS` is set to the ELF class associated with the function being called or to argument elfclass for function `gelf_newehdr`().
e_ident[EI_DATA]
  The identification byte at offset `EI_DATA` is set to `ELFDATANONE`.
e_ident[EI_VERSION]
  The identification byte at offset `EI_VERSION` is set to the ELF library's operating version set by a prior call to elf_version(3).
e_machine
  is set to `EM_NONE`.
e_type
  is set to `ELF_K_NONE`.
e_version
  is set to the ELF library's operating version set by a prior call to elf_version(3).

Other members of the header are set to zero. The application is responsible for changing these values as needed before calling `elf_update`().

If successful, these three functions set the `ELF_F_DIRTY` flag on ELF descriptor elf.

# RETURN VALUES

These functions return a pointer to a translated header descriptor if successful, or NULL on failure.

# COMPATIBILITY

The `gelf_newehdr`() function uses a type of void * for its returned value. This differs from some other implementations of the elf(3) API, which use an unsigned long return type.

# ERRORS

These functions can fail with the following errors:

[`ELF_E_ARGUMENT`]
  The argument elf was null.
[`ELF_E_ARGUMENT`]
  Argument elf was not a descriptor for an ELF object.
[`ELF_E_ARGUMENT`]
  Argument elfclass had an unsupported value.
[`ELF_E_ARGUMENT`]
  The class of the ELF descriptor elf did not match that of the requested operation.
[`ELF_E_ARGUMENT`]
  For function `gelf_newehdr`(), the class of argument elf was not `ELFCLASSNONE` and did not match the argument elfclass.
[`ELF_E_CLASS`]
  The ELF class of descriptor elf did not match that of the API function being called.
[`ELF_E_HEADER`]
  A malformed ELF header was detected.
[`ELF_E_RESOURCE`]
  An out of memory condition was detected during execution.
[`ELF_E_SECTION`]
  The ELF descriptor in argument elf did not adhere to the conventions used for extended numbering.
[`ELF_E_VERSION`]
  The ELF descriptor elf had an unsupported ELF version number.

# SEE ALSO

elf(3), elf32_getehdr(3), elf64_getehdr(3), elf_flagdata(3), elf_getident(3), elf_update(3), elf_version(3), gelf(3), gelf_getehdr(3), elf(5)

June 12, 2019 | Debian