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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | CONFORMING TO | NOTES | SEE ALSO | COLOPHON |
DELETE_MODULE(2) Linux Programmer's Manual DELETE_MODULE(2)
delete_module - unload a kernel module
int delete_module(const char *name, int flags);
Note: No declaration of this system call is provided in glibc
headers; see NOTES.
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).
On success, zero is returned. On error, -1 is returned and errno is
set appropriately.
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.
delete_module() is Linux-specific.
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.
create_module(2), init_module(2), query_module(2), lsmod(8),
modprobe(8), rmmod(8)
This page is part of release 4.12 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/.
Linux 2016-03-15 DELETE_MODULE(2)
Pages that refer to this page: create_module(2), get_kernel_syms(2), init_module(2), query_module(2), syscalls(2), unimplemented(2), systemd.exec(5), capabilities(7)