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Man page of DELETE_MODULE
DELETE_MODULE
Section: Linux Programmer's Manual (2)
Updated: 2016-03-15
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NAME
delete_module - unload a kernel module
SYNOPSIS
int delete_module(const char *name, int flags);
Note:
No declaration of this system call is provided in glibc headers; see NOTES.
DESCRIPTION
The
delete_module()
system call attempts to remove the unused loadable module entry
identified by
name.
If the module has an
exit
function, then that function is executed before unloading the module.
The
flags
argument is used to modify the behavior of the system call,
as described below.
This system call requires privilege.
Module removal is attempted according to the following rules:
- 1.
-
If there are other loaded modules that depend on
(i.e., refer to symbols defined in) this module,
then the call fails.
- 2.
-
Otherwise, if the reference count for the module
(i.e., the number of processes currently using the module)
is zero, then the module is immediately unloaded.
- 3.
-
If a module has a nonzero reference count,
then the behavior depends on the bits set in
flags.
In normal usage (see NOTES), the
O_NONBLOCK
flag is always specified, and the
O_TRUNC
flag may additionally be specified.
The various combinations for
flags
have the following effect:
-
- flags == O_NONBLOCK
-
The call returns immediately, with an error.
- flags == (O_NONBLOCK | O_TRUNC)
-
The module is unloaded immediately,
regardless of whether it has a nonzero reference count.
- (flags & O_NONBLOCK) == 0
-
If
flags
does not specify
O_NONBLOCK,
the following steps occur:
-
- *
-
The module is marked so that no new references are permitted.
- *
-
If the module's reference count is nonzero,
the caller is placed in an uninterruptible sleep state
(TASK_UNINTERRUPTIBLE)
until the reference count is zero, at which point the call unblocks.
- *
-
The module is unloaded in the usual way.
The
O_TRUNC
flag has one further effect on the rules described above.
By default, if a module has an
init
function but no
exit
function, then an attempt to remove the module will fail.
However, if
O_TRUNC
was specified, this requirement is bypassed.
Using the
O_TRUNC
flag is dangerous!
If the kernel was not built with
CONFIG_MODULE_FORCE_UNLOAD,
this flag is silently ignored.
(Normally,
CONFIG_MODULE_FORCE_UNLOAD
is enabled.)
Using this flag taints the kernel (TAINT_FORCED_RMMOD).
RETURN VALUE
On success, zero is returned.
On error, -1 is returned and
errno
is set appropriately.
ERRORS
- EBUSY
-
The module is not "live"
(i.e., it is still being initialized or is already marked for removal);
or, the module has
an
init
function but has no
exit
function, and
O_TRUNC
was not specified in
flags.
- EFAULT
-
name
refers to a location outside the process's accessible address space.
- ENOENT
-
No module by that name exists.
- EPERM
-
The caller was not privileged
(did not have the
CAP_SYS_MODULE
capability),
or module unloading is disabled
(see
/proc/sys/kernel/modules_disabled
in
proc(5)).
- EWOULDBLOCK
-
Other modules depend on this module;
or,
O_NONBLOCK
was specified in
flags,
but the reference count of this module is nonzero and
O_TRUNC
was not specified in
flags.
CONFORMING TO
delete_module()
is Linux-specific.
NOTES
The
delete_module()
system call is not supported by glibc.
No declaration is provided in glibc headers, but, through a quirk of history,
glibc versions before 2.23 did export an ABI for this system call.
Therefore, in order to employ this system call,
it is (before glibc 2.23) sufficient to
manually declare the interface in your code;
alternatively, you can invoke the system call using
syscall(2).
The uninterruptible sleep that may occur if
O_NONBLOCK
is omitted from
flags
is considered undesirable, because the sleeping process is left
in an unkillable state.
As at Linux 3.7, specifying
O_NONBLOCK
is optional, but in future kernels it is likely to become mandatory.
Linux 2.4 and earlier
In Linux 2.4 and earlier, the system call took only one argument:
int delete_module(const char *name);
If
name
is NULL, all unused modules marked auto-clean are removed.
Some further details of differences in the behavior of
delete_module()
in Linux 2.4 and earlier are
not
currently explained in this manual page.
SEE ALSO
create_module(2),
init_module(2),
query_module(2),
lsmod(8),
modprobe(8),
rmmod(8)
COLOPHON
This page is part of release 4.09 of the Linux
man-pages
project.
A description of the project,
information about reporting bugs,
and the latest version of this page,
can be found at
https://www.kernel.org/doc/man-pages/.
Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- RETURN VALUE
-
- ERRORS
-
- CONFORMING TO
-
- NOTES
-
- Linux 2.4 and earlier
-
- SEE ALSO
-
- COLOPHON
-
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Time: 14:28:26 GMT, February 25, 2017