HP-UX Reference (11i v2 04/09) - 3 Library Functions A-M (vol 6)

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elf_update(3E) elf_update(3E)

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 e_version member controls the version of data structures written to the ﬁle. If the ver-

sion is EV_NONE, the library uses its own internal version. The e_ident[EI_DATA]

entry controls the

data encoding used in the ﬁle. As a special case, the value may be

ELFDATANONE

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

sh_entsize

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,

elf_update 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.

NOTICES

As mentioned above, the

ELF_C_WRITE 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 elf_update.

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

happens only to the memory image and not to the ﬁle itself.) The

ELF_C_NULL command updates only

the memory image; one can use the ELF_C_WRITE command to modify the ﬁle as well. Absolute execut-

able ﬁles (a.out ﬁles) require special alignment, which cannot normally be preserved between COFF

and ELF. Consequently, one may not update an executable COFF ﬁle with the ELF_C_WRITE command

(though ELF_C_NULL is allowed).