delete_module(2) — Linux manual page


DELETE_MODULE(2)          Linux Programmer's Manual         DELETE_MODULE(2)

NAME         top

       delete_module - unload a kernel module

SYNOPSIS         top

       int delete_module(const char *name, int flags);

       Note: No declaration of this system call is provided in glibc
       headers; see NOTES.

DESCRIPTION         top

       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

                  *  The module is marked so that no new references are

                  *  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).

RETURN VALUE         top

       On success, zero is returned.  On error, -1 is returned and errno is
       set appropriately.

ERRORS         top

       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)).

              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         top

       delete_module() is Linux-specific.

NOTES         top

       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         top

       create_module(2), init_module(2), query_module(2), lsmod(8),
       modprobe(8), rmmod(8)

COLOPHON         top

       This page is part of release 5.08 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

Linux                            2017-09-15                 DELETE_MODULE(2)

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