Tribblix: manual page: elf

ELF_FLAGDATA(3ELF) ELF Library Functions ELF_FLAGDATA(3ELF)

NAME

elf_flagdata, elf_flagehdr, elf_flagelf, elf_flagphdr, elf_flagscn,
elf_flagshdr - manipulate flags

SYNOPSIS

cc [ flag ... ] file ... -lelf [ library ... ]
#include <libelf.h>

unsigned elf_flagdata(Elf_Data *data, Elf_Cmd cmd, unsigned flags);

unsigned elf_flagehdr(Elf *elf, Elf_Cmd cmd, unsigned flags);

unsigned elf_flagelf(Elf *elf, Elf_Cmd cmd, unsigned flags);

unsigned elf_flagphdr(Elf *elf, Elf_Cmd cmd, unsigned flags);

unsigned elf_flagscn(Elf_Scn *scn, Elf_Cmd cmd, unsigned flags);

unsigned elf_flagshdr(Elf_Scn *scn, Elf_Cmd cmd, unsigned flags);

DESCRIPTION

These functions manipulate the flags associated with various
structures of an ELF file. Given an ELF descriptor (elf), a data
descriptor (data), or a section descriptor (scn), the functions may
set or clear the associated status bits, returning the updated bits.
A null descriptor is allowed, to simplify error handling; all
functions return 0 for this degenerate case.

cmd may have the following values:

ELF_C_CLR
The functions clear the bits that are asserted in flags.
Only the non-zero bits in flags are cleared; zero bits
do not change the status of the descriptor.

ELF_C_SET
The functions set the bits that are asserted in flags.
Only the non-zero bits in flags are set; zero bits do
not change the status of the descriptor.

Descriptions of the defined flags bits appear below:

ELF_F_DIRTY
When the program intends to write an ELF file, this
flag asserts the associated information needs to be
written to the file. Thus, for example, a program
that wished to update the ELF header of an existing
file would call elf_flagehdr() with this bit set in
flags and cmd equal to ELF_C_SET. A later call to
elf_update() would write the marked header to the
file.

ELF_F_LAYOUT
Normally, the library decides how to arrange an
output file. That is, it automatically decides where
to place sections, how to align them in the file,
etc. If this bit is set for an ELF descriptor, the
program assumes responsibility for determining all
file positions. This bit is meaningful only for
elf_flagelf() and applies to the entire file
associated with the descriptor.

When a flag bit is set for an item, it affects all the subitems as
well. Thus, for example, if the program sets the ELF_F_DIRTY bit with
elf_flagelf(), the entire logical file is ``dirty.''

EXAMPLES

Example 1: A sample display of calling the elf_flagdata() function.

The following fragment shows how one might mark the ELF header to be
written to the output file:

/* dirty ehdr ... */
ehdr = elf32_getehdr(elf);
elf_flagehdr(elf, ELF_C_SET, ELF_F_DIRTY);