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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
       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

       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

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       project,  information  about  reporting  bugs, and the latest version of this page, can be
       found at https://www.kernel.org/doc/man-pages/.