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).
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 9.0 |