ELF_GETIDENT(3ELF) ELF Library Functions ELF_GETIDENT(3ELF)


NAME


elf_getident, elf_getphdrnum, elf_getshdrnum, elf_getshdrstrndx,
elf_getphnum, elf_getshnum, elf_getshstrndx - retrieve ELF header data

SYNOPSIS


cc [ flag ... ] file ... -lelf [ library ... ]
#include <libelf.h>

char *elf_getident(Elf *elf, size_t *dst);


int elf_getphdrnum(Elf *elf, size_t *dst);


int elf_getshdrnum(Elf *elf, size_t *dst);


int elf_getshdrstrndx(Elf *elf, size_t *dst);


Obsolete Interfaces


int elf_getphnum(Elf *elf, size_t *dst);


int elf_getshnum(Elf *elf, size_t *dst);


int elf_getshstrndx(Elf *elf, size_t *dst);


DESCRIPTION


As elf(3ELF) explains, ELF provides a framework for various classes of
files, where basic objects might have 32 or 64 bits. To accommodate these
differences, without forcing the larger sizes on smaller machines, the
initial bytes in an ELF file hold identification information common to
all file classes. The e_ident of every ELF header has EI_NIDENT bytes
with interpretations described in the following table.


e_ident Index Value Purpose

EI_MAG0 ELFMAG0 File identification
EI_MAG1 ELFMAG1
EI_MAG2 ELFMAG2
EI_MAG3 ELFMAG3

EI_CLASS ELFCLASSNONE File class
ELFCLASS32
ELFCLASS64

EI_DATA ELFDATANONE Data encoding
ELFDATA2LSB
ELFDATA2MSB

EI_VERSION EV_CURRENT File version

7-15 0 Unused, set to zero


Other kinds of files might have identification data, though they would
not conform to e_ident. See elf_kind(3ELF) for information on other kinds
of files.


The elf_getident() function returns a pointer to the initial bytes of the
file. If the library recognizes the file, a conversion from the file
image to the memory image can occur. The identification bytes are
guaranteed to be unmodified, though the size of the unmodified area
depends on the file type. If the dst argument is non-null, the library
stores the number of identification bytes in the location to which dst
points. If no data are present, elf is NULL, or an error occurs, the
return value is a null pointer, with 0 stored through dst, if dst is non-
null.


The elf_getphdrnum() function obtains the number of program headers
recorded in the ELF file. The number of sections in a file is typically
recorded in the e_phnum field of the ELF header. A file that requires the
ELF extended program header records the value PN_XNUM in the e_phnum
field and records the number of sections in the sh_info field of section
header 0. See USAGE. The dst argument points to the location where the
number of sections is stored. If elf is NULL or an error occurs,
elf_getphdrnum() returns -1.


The elf_getshdrnum() function obtains the number of sections recorded in
the ELF file. The number of sections in a file is typically recorded in
the e_shnum field of the ELF header. A file that requires ELF extended
section records the value 0 in the e_shnum field and records the number
of sections in the sh_size field of section header 0. See USAGE. The dst
argument points to the location where the number of sections is stored.
If a call to elf_newscn(3ELF) that uses the same elf descriptor is
performed, the value obtained by elf_getshnum() is valid only after a
successful call to elf_update(3ELF). If elf is NULL or an error occurs,
elf_getshdrnum() returns -1.


The elf_getshdrstrndx() function obtains the section index of the string
table associated with the section headers in the ELF file. The section
header string table index is typically recorded in the e_shstrndx field
of the ELF header. A file that requires ELF extended section records the
value SHN_XINDEX in the e_shstrndx field and records the string table
index in the sh_link field of section header 0. See USAGE. The dst
argument points to the location where the section header string table
index is stored. If elf is NULL or an error occurs, elf_getshdrstrndx()
returns -1.


The elf_getphnum(), elf_getshnum(), and elf_getshstrndx() functions
behave in a manner similar to elf_getphdrnum(), elf_getshdrnum(), and
elf_getshdrstrndx(), respectively, except that they return 0 if elf is
NULL or an error occurs. Because these return values differ from those
used by some other systems, they are therefore non-portable and their use
is discouraged. The elf_getphdrnum(), elf_getshdrnum(), and
elf_getshdrstrndx() functions should be used instead.

USAGE


ELF extended sections allow an ELF file to contain more than 0xff00
(SHN_LORESERVE) section. ELF extended program headers allow an ELF file
to contain 0xffff (PN_XNUM) or more program headers. See the Linker and
Libraries Guide for more information.

RETURN VALUES


Upon successful completion, the elf_getident() function returns 1.
Otherwise, it return 0.


Upon successful completion, the elf_getphdrnum(), elf_getshdrnum(), and
elf_getshdrstrndx() functions return 0. Otherwise, they return -1.


Upon successful completion, the elf_getphnum(), elf_getshnum(), and
elf_getshstrndx() functions return 1. Otherwise, they return 0.

ATTRIBUTES


See attributes(5) for descriptions of the following attributes:


+--------------------+-----------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+-----------------+
|Interface Stability | See below. |
+--------------------+-----------------+
|MT-Level | MT-Safe |
+--------------------+-----------------+


The elf_getident(), elf_getphdrnum(), elf_getshdrnum(), and
elf_getshdrstrndx() functions are Committed. The elf_getphnum(),
elf_getshnum(), and elf_getshstrndx() functions are Committed
(Obsolete).

SEE ALSO


elf(3ELF), elf32_getehdr(3ELF), elf_begin(3ELF), elf_kind(3ELF),
elf_newscn(3ELF), elf_rawfile(3ELF), elf_update(3ELF), libelf(3LIB),
attributes(5)


Linker and Libraries Guide


June 18, 2009 ELF_GETIDENT(3ELF)