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MODCTL(2) NetBSD System Calls Manual MODCTL(2)
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modctl -- module control
Standard C Library (libc, -lc)
modctl(int operation, void *argp);
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 per-
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
· an array of modstat_t structures, one per loaded mod-
· a series of NUL-terminated strings containing the mod-
ules' 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 con-
sider the sysctl kern.module.autoload.
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.
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 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 pro-
plib dictionary larger than this size will return ENOMEM.
The modstat_t structure used with MODCTL_STAT contains the following ele-
ments, which are filled in by the kernel:
The name of the module.
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
MODULE_SOURCE_FILESYS The module was loaded from the file sys-
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.
The load address within the kernel. (This value is available
only for privileged users.)
Loaded size of the module's text section. (This value is
available only for privileged users.)
Current number of live references to this module.
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 operat-
The offset (in bytes) from the beginning of the required-module
Upon successful completion, the value returned is 0.
Otherwise, a value of -1 is returned and errno is set to indicate the
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.
module(7), sysctl(7), module(9)
The modctl() function call first appeared in NetBSD 5.0.
NetBSD 9.3 December 4, 2019 NetBSD 9.3