elf_update(3E)															    elf_update(3E)

NAME

       elf_update - update an ELF descriptor

SYNOPSIS

       [flag... ] file...  [library] ...

DESCRIPTION

       causes the library to examine the information associated with an ELF descriptor, elf, and to recalculate the structural data needed to gen-
       erate the file's image.

       cmd may have the following values.

       This value tells  to recalculate various values, updating only the ELF descriptor's memory structures.  Any modified structures are flagged
			 with  the  bit.   A  program thus can update the structural information and then reexamine them without changing the file
			 associated with the ELF descriptor.  Because this does not change the file, the ELF descriptor may allow  reading,  writ-
			 ing, or both reading and writing (see elf_begin(3E)).

       If		 cmd  has  this value, duplicates its actions and also writes any ``dirty'' information associated with the ELF descriptor
			 to the file.  That is, when a program has used or the facilities to supply new (or update existing)  information  for	an
			 ELF descriptor, those data will be examined, coordinated, translated if necessary (see elf_xlate(3E)), and written to the
			 file.	When portions of the file are written, any bits are reset, indicating those items no longer need to be written	to
			 the file (see elf_flag(3E)).  The sections' data is written in the order of their section header entries, and the section
			 header table is written to the end of the file.

			 When the ELF descriptor was created with it must have allowed writing the file.  That is,  the  command  must	have  been
			 either or

       If  succeeds,  it returns the total size of the file image (not the memory image), in bytes.  Otherwise an error occurred, and the function
       returns -1.

       When updating the internal structures, sets some members itself.  Members listed below are the application's responsibility and retain  the
       values given by the program.

								    Member   Notes
						     -----------------------------------------------
							  e_ident[EI_DATA]   Library controls other
									     e_ident values
								    e_type
								 e_machine
								 e_version
						     ELF Header    e_entry
								   e_phoff   Only when ELF_F_LAYOUT
									     asserted
								   e_shoff   Only when ELF_F_LAYOUT
									     asserted
								   e_flags
								e_shstrndx
						     -----------------------------------------------

								  Member   Notes
					       -----------------------------------------------------------
								  p_type     The application controls all
								p_offset     program header entries
								 p_vaddr
								 p_paddr
					       Program Header	p_filesz
								 p_memsz
								 p_flags
								 p_align
					       -----------------------------------------------------------

								      Member   Notes
						    --------------------------------------------------
								     sh_name
								     sh_type
								    sh_flags
								     sh_addr
								   sh_offset   Only when ELF_F_LAYOUT
									       asserted
						    Section Header   sh_size   Only when ELF_F_LAYOUT
									       asserted
								     sh_link
								     sh_info
								sh_addralign   Only when ELF_F_LAYOUT
									       asserted
								  sh_entsize
						    --------------------------------------------------

								     Member   Notes
						    -------------------------------------------------
								      d_buf
								     d_type
								     d_size
						    Data Descriptor   d_off   Only when ELF_F_LAYOUT
									      asserted
								    d_align
								  d_version
						    -------------------------------------------------

       Note  the  program is responsible for two particularly important members (among others) in the ELF header.  The member controls the version
       of data structures written to the file.	If the version is the library uses its own internal version.  The entry controls the data encoding
       used  in  the file.  As a special case, the value may be to request the native data encoding for the host machine.  An error occurs in this
       case if the native encoding doesn't match a file encoding known by the library.

       Further note that the program is responsible for the section header member.  Although the library sets it for sections with known types, it
       cannot reliably know the correct value for all sections.  Consequently, the library relies on the program to provide the values for unknown
       section type.  If the entry size is unknown or not applicable, the value should be set to zero.

       When deciding how to build the output file, obeys the alignments of individual data buffers to create output sections.	A  section's  most
       strictly  aligned  data buffer controls the section's alignment.  The library also inserts padding between buffers, as necessary, to ensure
       the proper alignment of each buffer.

   Note
       As mentioned above, the commands translate data as necessary, before writing them to the file.  This translation is not always  transparent
       to  the	application  program.	If  a  program	has obtained pointers to data associated with a file (for example, see elf_getehdr(3E) and
       elf_getdata(3E)), the program should reestablish the pointers after calling

       As elf_begin(3E) describes, a program may ``update'' a COFF file to make the image consistent for ELF. (COFF is an object file format  that
       preceded  ELF  on  some computer architectures (Intel, for example).  When a program calls elf_begin on a COFF file, the library translates
       COFF structures to their ELF equivalents, allowing programs to read (but not to write) a COFF file as if it were ELF. This conversion  hap-
       pens  only  to  the memory image and not to the file itself.)  The command updates only the memory image; one can use the command to modify
       the file as well.  Absolute executable files files) require special alignment, which cannot normally be preserved  between  COFF  and  ELF.
       Consequently, one may not update an executable COFF file with the command (though is allowed).

SEE ALSO

       elf(3E), elf_begin(3E), elf_flag(3E), elf_fsize(3E), elf_getdata(3E), elf_getehdr(3E), elf_getshdr(3E), elf_xlate(3E).

																    elf_update(3E)