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NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | STANDARDS | HISTORY | NOTES | SEE ALSO | COLOPHON |
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delete_module(2) System Calls Manual delete_module(2)
delete_module - unload a kernel module
Standard C library (libc, -lc)
#include <fcntl.h> /* Definition of O_* constants */
#include <sys/syscall.h> /* Definition of SYS_* constants */
#include <unistd.h>
int syscall(SYS_delete_module, const char *name, unsigned int flags);
Note: glibc provides no wrapper for delete_module(),
necessitating the use of syscall(2).
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 fails. 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 to indicate the error.
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.
Linux.
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 glibc 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).
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.
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.
create_module(2), init_module(2), query_module(2), lsmod(8),
modprobe(8), rmmod(8)
This page is part of the man-pages (Linux kernel and C library
user-space interface documentation) project. Information about
the project can be found at
⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report
for this manual page, see
⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.
This page was obtained from the tarball man-pages-6.9.1.tar.gz
fetched from
⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on
2024-06-26. If you discover any rendering problems in this HTML
version of the page, or you believe there is a better or more up-
to-date source for the page, or you have corrections or
improvements to the information in this COLOPHON (which is not
part of the original manual page), send a mail to
man-pages@man7.org
Linux man-pages 6.9.1 2024-05-02 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)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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