elf_flag(3elf)

elf_flag: 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 zero 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

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



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

References

Intro(3elf), elf_end(3elf), elf_getdata(3elf), elf_getehdr(3elf), elf_update(3elf)