HP-UX Reference (11i v2 03/08) - 3 Library Functions A-M (vol 6)

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elf_getscn(3E) elf_getscn(3E)

NAME

elf_getscn, elf_ndxscn, elf_newscn, elf_nextscn - get section information

SYNOPSIS

cc [ﬂag... ] ﬁle...

-lelf [library ] ...

#include <libelf.h>

Elf_Scn *elf_getscn(Elf *elf, size_t index);

size_t elf_ndxscn(Elf_Scn *scn);

Elf_Scn *elf_newscn(Elf *elf);

Elf_Scn *elf_nextscn(Elf *elf, Elf_Scn *scn);

DESCRIPTION

These functions provide indexed and sequential access to the sections associated with the ELF descriptor

elf. If the program is building a new ﬁle, it is responsible for creating the ﬁle’s ELF header before creat-

ing sections; see elf_getehdr (3E).

elf_getscn returns a section descriptor, given an index into the ﬁle’s section header table. Note the

ﬁrst ‘‘real’’ section has index 1. Although a program can get a section descriptor for the section whose

index is 0 (

SHN_UNDEF, the undeﬁned section), the section has no data and the section header is ‘‘empty’’

(though present). If the speciﬁed section does not exist, an error occurs, or elf is null,

elf_getscn

returns a null pointer.

elf_newscn creates a new section and appends it to the list for elf. Because the SHN_UNDEF

section is

required and not ‘‘interesting’’ to applications, the library creates it automatically. Thus the ﬁrst call to

elf_newscn for an ELF descriptor with no existing sections returns a descriptor for section 1. If an

error occurs or elf is null, elf_newscn returns a null pointer.

After creating a new section descriptor, the program can use

elf_getshdr to retrieve the newly

created, ‘‘clean’’ section header. The new section descriptor will have no associated data (see

elf_getdata (3E)). When creating a new section in this way, the library updates the e_shnum member of

the ELF header and sets the ELF_F_DIRTY bit for the section (see elf_ﬂag(3E)). If the program is build-

ing a new ﬁle, it is responsible for creating the ﬁle’s ELF header (see elf_getehdr (3E)) before creating new

sections.

elf_nextscn takes an existing section descriptor, scn, and returns a section descriptor for the next

higher section. One may use a null scn to obtain a section descriptor for the section whose index is 1

(skipping the section whose index is SHN_UNDEF). If no further sections are present or an error occurs,

elf_nextscn returns a null pointer.

elf_ndxscn takes an existing section descriptor, scn, and returns its section table index. If scn is null

or an error occurs,

elf_ndxscn returns SHN_UNDEF.

EXAMPLES

An example of sequential access appears below. Each pass through the loop processes the next section in

the ﬁle; the loop terminates when all sections have been processed.

scn=0;

while ((scn = elf_nextscn(elf, scn)) != 0)

{

/* process section */

}