ELF_CNTL(3ELF) ELF Library Functions ELF_CNTL(3ELF)

NAME

elf_cntl - control an elf file descriptor

SYNOPSIS

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

int elf_cntl(Elf *elf, Elf_Cmd cmd);

DESCRIPTION

elf_cntl() instructs the library to modify its behavior with respect to
an ELF descriptor, elf. As elf_begin(3ELF) describes, an ELF descriptor
can have multiple activations, and multiple ELF descriptors may share a
single file descriptor. Generally, elf_cntl() commands apply to all
activations of elf. Moreover, if the ELF descriptor is associated with an
archive file, descriptors for members within the archive will also be
affected as described below. Unless stated otherwise, operations on
archive members do not affect the descriptor for the containing archive.


The cmd argument tells what actions to take and may have the following
values:

ELF_C_FDDONE
This value tells the library not to use the file
descriptor associated with elf. A program should use this
command when it has requested all the information it
cares to use and wishes to avoid the overhead of reading
the rest of the file. The memory for all completed
operations remains valid, but later file operations, such
as the initial elf_getdata() for a section, will fail if
the data are not in memory already.


ELF_C_FDREAD
This command is similar to ELF_C_FDDONE, except it forces
the library to read the rest of the file. A program
should use this command when it must close the file
descriptor but has not yet read everything it needs from
the file. After elf_cntl() completes the ELF_C_FDREAD
command, future operations, such as elf_getdata(), will
use the memory version of the file without needing to use
the file descriptor.


If elf_cntl() succeeds, it returns 0. Otherwise elf was NULL or an error
occurred, and the function returns -1.

ATTRIBUTES

See attributes(7) for descriptions of the following attributes:


+--------------------+-----------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+-----------------+
|Interface Stability | Stable |
+--------------------+-----------------+
|MT-Level | MT-Safe |
+--------------------+-----------------+

SEE ALSO

elf(3ELF), elf_begin(3ELF), elf_getdata(3ELF), elf_rawfile(3ELF),
libelf(3LIB), attributes(7)

NOTES

If the program wishes to use the ``raw'' operations (see elf_rawdata(),
which elf_getdata(3ELF) describes, and elf_rawfile(3ELF)) after disabling
the file descriptor with ELF_C_FDDONE or ELF_C_FDREAD, it must execute
the raw operations explicitly beforehand. Otherwise, the raw file
operations will fail. Calling elf_rawfile() makes the entire image
available, thus supporting subsequent elf_rawdata() calls.

July 11, 2001 ELF_CNTL(3ELF)