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 creating 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 building 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 */
}