ELF_FLAGELF(3)            Libelf Programmer's Manual            ELF_FLAGELF(3)



NAME
       elf_flagelf, elf_flagdata, elf_flagehdr, elf_flagphdr, elf_flagscn,
       elf_flagshdr - set or clear flags on ELF descriptors and components

SYNOPSIS
       #include <libelf.h>

       unsigned int elf_flagelf(Elf * elf, Elf_Cmd cmd, unsigned int flags);
       unsigned int elf_flagehdr(Elf * elf, Elf_Cmd cmd, unsigned int flags);
       unsigned int elf_flagphdr(Elf * elf, Elf_Cmd cmd, unsigned int flags);
       unsigned int elf_flagscn(Elf_Scn * scn, Elf_Cmd cmd, unsigned int flags);
       unsigned int elf_flagshdr(Elf_Scn * scn, Elf_Cmd cmd, unsigned int flags);
       unsigned int elf_flagdata(Elf_Data * data, Elf_Cmd cmd, unsigned int flags);


DESCRIPTION
       These functions allow the caller to set or clear flags on various ELF
       components managed by libelf .  They are typically used to indicate
       that a component has been modified (dirty), or to control layout
       behavior during output.

       elf_flagelf() modifies flags on the top-level Elf descriptor.

       elf_flagdata() modifies flags on an Elf_Data descriptor, typically
       retrieved using elf_getdata(3) or created with elf_newdata(3).

       elf_flagehdr() modifies flags on the ELF header for a ELF descriptor
       (e.g., the result of gelf_getehdr(3)).

       elf_flagphdr() modifies flags on the program header table of an ELF
       descriptor.

       elf_flagscn() modifies flags on an Elf_Scn (section) descriptor.

       elf_flagshdr() modifies flags on the section header of a given Elf_Scn
       .

       The cmd argument determines whether the given flags should be set (
       ELF_C_SET ) or cleared ( ELF_C_CLR ).

       The following flag values may be passed via the flags parameter:


       ELF_F_DIRTY
              Marks the object as modified. This ensures changes to the
              component is written out during elf_update(3).


       ELF_F_LAYOUT
              Indicates that the layout of the ELF component is managed
              manually. Offsets and sizes will be preserved as provided.  This
              flag is only used with elf_flagelf() and is ignored when used
              with other functions.  If this flag is set the user must set
              Ehdr e_phoff, e_shoff, as well as Elf_Data d_off and Shdr
              sh_offset.  If not set, then these offsets will be recalculated
              when elf_update is called.  If ELF_F_LAYOUT is set then changes
              to phdr offsets will prevent elf_update from automatically
              adjusting shdr offsets.


       ELF_F_PERMISSIVE
              Enables relaxed validation of object structure. This flag
              permits nonstandard layouts without strict checks.  Specifically
              this removes a check in elf_update() that the section sh_size is
              a multiple of the section sh_entsize (if not zero).  This flag
              is only used with elf_flagelf() and is ignored when used with
              other functions.  ELF_F_PERMISSIVE is an elfutils libelf
              extention and may not be available in other libelf
              implementations.


PARAMETERS
       obj    The object to be modified: For elf_flagelf, elf_flagehdr,
              elf_flagphdr, this is an Elf * descriptor.  For elf_flagscn and
              elf_flagshdr , this is an Elf_Scn * descriptor.  For
              elf_flagdata , an Elf_Data * buffer.


       cmd    Must be either: ELF_C_SET to set the given flags, or ELF_C_CLR
              to clear them.


       flags  Bitmask of flags to modify. May include any combination of
              ELF_F_DIRTY , ELF_F_LAYOUT , and ELF_F_PERMISSIVE .

              Note that ELF_F_LAYOUT and ELF_F_PERMISSIVE are only used with
              elf_flagelf() and are ignored for other functions.


RETURN VALUE
       Returns the new value of the flags after the set/clear operation.

       Returns 0 on error, and sets an error code retrievable via
       elf_errmsg(3).  If the first argument is NULL then 0 is return and no
       error code is set.

       If the last flag is cleared, 0 will be returned as the new flag value.
       In this case 0 is not an error indicator and no error code is set.


SEE ALSO
       elf_errmsg(3), elf_update(3), libelf(3), elf(5)


ATTRIBUTES

       +-------------------------------------+---------------+----------------+
       |Interface                            | Attribute     | Value          |
       +-------------------------------------+---------------+----------------+
       |elf_flagelf                          | Thread safety | MT-Unsafe race |
       |(), elf_flagehdr(),                  |               |                |
       |elf_flagphdr(),                      |               |                |
       |elf_flagscn(),                       |               |                |
       |elf_flagshdr(), elf_flagdata()       |               |                |
       +-------------------------------------+---------------+----------------+

REPORTING BUGS
       Report bugs to <elfutils-devel@sourceware.org> or
       https://sourceware.org/bugzilla/.

Libelf                            2025-06-23                    ELF_FLAGELF(3)