MODCTL(2)

NAME
modctl - module control

LIBRARY
libc

SYNOPSIS
#include <sys/module.h>
int
modctl(int operation, void *argp);

DESCRIPTION
modctl() provides control over loaded kernel modules. The argument operation is one of MODCTL_LOAD, MODCTL_UNLOAD, MODCTL_STAT, or MODCTL_EXISTS. The argument argp depends on the operation to be performed.

Operations are:

MODCTL_LOAD
    Load a module. The argp argument should be a pointer to a modctl_load_t structure, described below.

MODCTL_UNLOAD
    Unload a module. In this case, argp should be a string containing the name of the module to be unloaded.

MODCTL_STAT
    Return a list of loaded modules. In this case, the argp argument should be a struct iovec pointing to a suitable block of memory. The kernel will fill this block with

    •   a count of the number of modules loaded (including aliases),

    •   an array of modstat_t structures, one per loaded module, and

    •   a series of NUL-terminated strings containing the modules' required modules lists.

    If the block is not large enough, the data returned will be truncated to fit. The kernel will then update the iov_len member of the iovec to reflect the size of the complete report, regardless of whether this is larger or smaller than the size passed in.

MODCTL_EXISTS
    Test to see if the kernel was compiled with “options MODULAR” and whether or not modules may be loaded at the moment. In this case, argp should be an integer. It should be “0” to test if a user can load a module via MODCTL_LOAD, or it should be “1” to test if the system can autoload modules. Note that this test does not consider the sysctl kern.module.autoload.

  Data Types
The modctl_load_t structure used with MODCTL_LOAD contains the following elements, which should be filled in by the caller:

const char *ml_filename
    The name/path of the module to load.

int ml_flags
    Zero or more of the following flag values:
    MODCTL_NO_PROP
        Don't load <module>.plist.
    MODCTL_LOAD_FORCE
        Ignore kernel version mismatch.

const char *ml_props
    Externalized proplib dictionary to pass to module.

size_t ml_propslen
    Size of the dictionary blob. ml_props may be NULL in which case ml_propslen must be 0. An upper limit of 4096 bytes is imposed on the value of ml_propslen. Attempting to load a proplib dictionary larger than this size will return ENOMEM.

The modstat_t structure used with MODCTL_STAT contains the following elements, which are filled in by the kernel:

char ms_name[MAXMODNAME]
    The name of the module.

modsrc_t ms_source
    One of the following enumerated constants:
    MODULE_SOURCE_KERNEL
        The module is compiled into the kernel.
    MODULE_SOURCE_BOOT
        The module was provided by the bootstrap loader.
    MODULE_SOURCE_FILESYS
        The module was loaded from the file system.

modclass_t ms_class
    One of the following enumerated constants:
    MODULE_CLASS_SECMODEL
        Security model.
    MODULE_CLASS_VFS
        File system.
    MODULE_CLASS_DRIVER
        Device driver.
    MODULE_CLASS_EXEC
        Executable file format.
    MODULE_CLASS_MISC
        Miscellaneous.

uint64_t ms_addr
    The load address within the kernel. (This value is available only for privileged users.)

u_int ms_size
    Loaded size of the module's text section. (This value is available only for privileged users.)

u_int ms_refcnt
    Current number of live references to this module.

u_int ms_flags
    The module's flags:
    MODFLAG_MUST_FORCE
        The "force" flag must be specified to reload this module.
    MODFLAG_AUTO_LOADED
        The module was auto-loaded by the operating system.

uint_ms_reqoffset
    The offset (in bytes) from the beginning of the required-module data.

RETURN VALUES
Upon successful completion, the value returned is 0.

Otherwise, a value of -1 is returned and errno is set to indicate the error.

ERRORS
modctl() will fail if:

[EBUSY]
    The argument operation is MODCTL_UNLOAD and the module is in use or the module is compiled into the kernel.

[EDEADLK]
    The argument operation is MODCTL_LOAD and there is a circular dependency in the module's dependency chain.

[EEXIST]
    The argument operation is MODCTL_LOAD and the module is already loaded.

[EFAULT]
    A bad address was given for argp.

[EFBIG]
    The argument operation is MODCTL_LOAD, the specified module resides in the file system, and the module's default proplib file was too large.

[EINVAL]
    The argument operation is invalid.

    The argument operation is MODCTL_LOAD and ml_props is not NULL and “ml_propslen” is 0, or ml_props is NULL and “ml_propslen” is not 0. The kernel is unable to internalize the plist. Or, there is a problem with the module or <module>.plist.

[EMLINK]
    The argument operation is MODCTL_LOAD and the module has too many dependencies.

[ENAMETOOLONG]
    A module name/path is too long.

[ENOENT]
    The argument operation is MODCTL_LOAD and the module or a dependency can't be found.

    The argument operation is MODCTL_UNLOAD and no module by the name of argp is loaded.

[ENOEXEC]
    The argument operation is MODCTL_LOAD and the module is not a valid object for the system. Most likely, one or more undefined symbols could not be resolved by the in-kernel linker.

[ENOMEM]
    There was not enough memory to perform the operation.

[EPERM]
    Not allowed to perform the operation.

[EPROGMISMATCH]
    The argument operation is MODCTL_LOAD, the ml_flags field in the modctl_load_t structure does not include MODCTL_LOAD_FORCE, and the requested module does not match the current kernel's version information.

SEE ALSO
module(7), sysctl(7), module(9)

HISTORY
The modctl() function call first appeared in NetBSD 5.0.