GELF_NEWEHDR(3)

NAME
elf32_newehdr, elf64_newehdr, gelf_newehdr - retrieve or allocate the object file header

SYNOPSIS
libelf
#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)