NAME

elf32_newehdr, elf64_newehdr, gelf_newehdr —

retrieve or allocate the object file header

LIBRARY

ELF Access Library (libelf, -lelf)

SYNOPSIS

#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.