ELF_BEGIN(3) | Library Functions Manual | ELF_BEGIN(3) |
elf_begin
—
#include <libelf.h>
Elf *
elf_begin
(int
fd, Elf_Cmd cmd,
Elf *elf);
elf_begin
() is used to open ELF files and
ar(1) archives for further
processing by other APIs in the
elf(3) library. It is also used to
access individual ELF members of an
ar(1) archive in combination with
the elf_next(3) and
elf_rand(3) APIs.
Argument fd is an open file descriptor
returned from an open(2) system
call. Function elf_begin
() uses argument
fd for reading or writing depending on the value of
argument cmd. Argument elf is
primarily used for iterating through archives.
The argument cmd can have the following values:
elf_begin
() to return
NULL
. Arguments fd and
elf are ignored, and no additional error is
signalled.If argument elf is
NULL
, the library will allocate a new ELF
descriptor for the file being processed. The argument
fd should have been opened for reading.
If argument elf is not
NULL
, and references a regular ELF file
previously opened with elf_begin
(), then the
activation count for the descriptor referenced by argument
elf is incremented. The value in argument
fd should match that used to open the descriptor
argument elf.
If argument elf is not
NULL
, and references a descriptor for an
ar(1) archive opened earlier
with elf_begin
(), a descriptor for an element in
the archive is returned as described in the section
Processing ar(1)
archives below. The value for argument fd
should match that used to open the archive earlier.
If argument elf is not
NULL
, and references an
ar(1) archive opened earlier
with elf_memory
(), then the value of the
argument fd is ignored.
ELF_C_RDWR
Argument fd should have been opened for
reading and writing. If argument elf is
NULL
, the library will allocate a new ELF
descriptor for the file being processed. If the argument
elf is non-null, it should point to a descriptor
previously allocated with elf_begin
() with the
same values for arguments fd and
cmd; in this case the library will increment the
activation count for descriptor elf and return the
same descriptor.
Changes to the in-memory image of the ELF file may be written back to disk using the elf_update(3) function.
ELF_C_WRITE
ELF_C_READ
) using elf_begin
()
or elf_memory
(). The returned ELF descriptor can be
passed into to subsequent calls to elf_begin
() to
access individual members of the archive.
Random access within an opened archive is possible using the elf_next(3) and elf_rand(3) functions.
The symbol table of the archive may be retrieved using elf_getarsym(3).
NULL
if an error occurred.
Elf_Cmd c; Elf *ar_e, *elf_e; ... c = ELF_C_READ; if ((ar_e = elf_begin(fd, c, (Elf *) 0)) == 0) { ... handle error in opening the archive ... } while ((elf_e = elf_begin(fd, c, ar_e)) != 0) { ... process member referenced by elf_e here ... c = elf_next(elf_e); elf_end(elf_e); }
To create a new ELF file, use:
int fd; Elf *e; ... if ((fd = open("filename", O_RDWR|O_TRUNC|O_CREAT, 0666)) < 0) { ... handle the error from open(2) ... } if ((e = elf_begin(fd, ELF_C_WRITE, (Elf *) 0)) == 0) { ... handle the error from elf_begin() ... } ... create the ELF image using other elf(3) APIs ... elf_update(e, ELF_C_WRITE); elf_end(e);
elf_begin
() can fail with the following errors:
ELF_E_ARCHIVE
]ELF_E_ARGUMENT
]ELF_E_ARGUMENT
]ELF_C_RDWR
.ELF_E_ARGUMENT
]ELF_E_ARGUMENT
]ELF_E_ARGUMENT
]ELF_C_RDWR
.ELF_E_ARGUMENT
]ELF_E_ARGUMENT
]ELF_E_IO
]ELF_E_IO
]ELF_E_RESOURCE
]ELF_E_SEQUENCE
]elf_begin
() was called before a working
version was established with
elf_version(3).ELF_E_VERSION
]December 11, 2011 | NetBSD 10.0 |