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

NAME

       init_module, finit_module - load a kernel module

SYNOPSIS

       int init_module(void *module_image, unsigned long len,
		       const char *param_values);

       int finit_module(int fd, const char *param_values,
			int flags);

       Note: glibc provides no header file declaration of init_module() and no wrapper function for finit_module(); see NOTES.

DESCRIPTION

       init_module() loads an ELF image into kernel space, performs any necessary symbol relocations, initializes module parameters to values pro-
       vided by the caller, and then runs the module's init function.  This system call requires privilege.

       The module_image argument points to a buffer containing the binary image to be loaded; len specifies the size of that buffer.   The  module
       image should be a valid ELF image, built for the running kernel.

       The  param_values  argument  is	a string containing space-delimited specifications of the values for module parameters (defined inside the
       module using module_param() and module_param_array()).  The kernel parses this string and initializes the specified  parameters.   Each	of
       the parameter specifications has the form:

	       name[=value[,value...]]

       The  parameter  name  is  one  of those defined within the module using module_param() (see the Linux kernel source file include/linux/mod-
       uleparam.h).  The parameter value is optional in the case of bool and invbool parameters.  Values for array parameters are specified  as  a
       comma-separated list.

   finit_module()
       The finit_module() system call is like init_module(), but reads the module to be loaded from the file descriptor fd.  It is useful when the
       authenticity of a kernel module can be determined from its location in the filesystem; in cases where that is  possible,  the  overhead	of
       using  cryptographically  signed  modules  to  determine  the authenticity of a module can be avoided.  The param_values argument is as for
       init_module().

       The flags argument modifies the operation of finit_module().  It is a bit mask value created by ORing together zero or more of the  follow-
       ing flags:

       MODULE_INIT_IGNORE_MODVERSIONS
	      Ignore symbol version hashes.

       MODULE_INIT_IGNORE_VERMAGIC
	      Ignore kernel version magic.

       There  are  some  safety  checks  built	into  a  module to ensure that it matches the kernel against which it is loaded.  These checks are
       recorded when the module is built and verified when the module is loaded.  First, the module records a  "vermagic"  string  containing  the
       kernel  version number and prominent features (such as the CPU type).  Second, if the module was built with the CONFIG_MODVERSIONS configu-
       ration option enabled, a version hash is recorded for each symbol the module uses.  This hash is based on the types of  the  arguments  and
       return value for the function named by the symbol.  In this case, the kernel version number within the "vermagic" string is ignored, as the
       symbol version hashes are assumed to be sufficiently reliable.

       Using the MODULE_INIT_IGNORE_VERMAGIC flag indicates that the "vermagic" string is to be ignored,  and  the  MODULE_INIT_IGNORE_MODVERSIONS
       flag  indicates	that  the symbol version hashes are to be ignored.  If the kernel is built to permit forced loading (i.e., configured with
       CONFIG_MODULE_FORCE_LOAD), then loading will continue, otherwise it will fail with ENOEXEC as expected for malformed modules.

RETURN VALUE

       On success, these system calls return 0.  On error, -1 is returned and errno is set appropriately.

ERRORS

       EBADMSG (since Linux 3.7)
	      Module signature is misformatted.

       EBUSY  Timeout while trying to resolve a symbol reference by this module.

       EFAULT An address argument referred to a location that is outside the process's accessible address space.

       ENOKEY (since Linux 3.7)
	      Module signature is invalid or the kernel does not have a key for this module.  This error is returned only if the kernel  was  con-
	      figured  with  CONFIG_MODULE_SIG_FORCE; if the kernel was not configured with this option, then an invalid or unsigned module simply
	      taints the kernel.

       ENOMEM Out of memory.

       EPERM  The caller was not privileged (did not have the CAP_SYS_MODULE capability), or module loading is disabled (see /proc/sys/kernel/mod-
	      ules_disabled in proc(5)).

       The following errors may additionally occur for init_module():

       EEXIST A module with this name is already loaded.

       EINVAL param_values is invalid, or some part of the ELF image in module_image contains inconsistencies.

       ENOEXEC
	      The binary image supplied in module_image is not an ELF image, or is an ELF image that is invalid or for a different architecture.

       The following errors may additionally occur for finit_module():

       EBADF  The file referred to by fd is not opened for reading.

       EFBIG  The file referred to by fd is too large.

       EINVAL flags is invalid.

       ENOEXEC
	      fd does not refer to an open file.

       In addition to the above errors, if the module's init function is executed and returns an error, then init_module() or finit_module() fails
       and errno is set to the value returned by the init function.

VERSIONS

       finit_module() is available since Linux 3.8.

CONFORMING TO

       init_module() and finit_module() are Linux-specific.

NOTES

       The init_module() system call is not supported by glibc.  No declaration is provided in glibc headers, but, through  a  quirk  of  history,
       glibc  does  export  an ABI for this system call.  Therefore, in order to employ this system call, it is sufficient to manually declare the
       interface in your code; alternatively, you can invoke the system call using syscall(2).

       Glibc does not provide a wrapper for finit_module(); call it using syscall(2).

       Information about currently loaded modules can be found in /proc/modules and in the file trees under the  per-module  subdirectories  under
       /sys/module.

       See the Linux kernel source file include/linux/module.h for some useful background information.

   Linux 2.4 and earlier
       In Linux 2.4 and earlier, the init_module() system call was rather different:

	   #include <linux/module.h>

	   int init_module(const char *name, struct module *image);

       (User-space  applications  can detect which version of init_module() is available by calling query_module(); the latter call fails with the
       error ENOSYS on Linux 2.6 and later.)

       The older version of the system call loads the relocated module image pointed to by image into kernel space  and  runs  the  module's  init
       function.   The	caller	is  responsible for providing the relocated image (since Linux 2.6, the init_module() system call does the reloca-
       tion).

       The module image begins with a module structure and is followed by code and data as appropriate.  Since Linux 2.2, the module structure	is
       defined as follows:

	   struct module {
	       unsigned long	     size_of_struct;
	       struct module	    *next;
	       const char	    *name;
	       unsigned long	     size;
	       long		     usecount;
	       unsigned long	     flags;
	       unsigned int	     nsyms;
	       unsigned int	     ndeps;
	       struct module_symbol *syms;
	       struct module_ref    *deps;
	       struct module_ref    *refs;
	       int		   (*init)(void);
	       void		   (*cleanup)(void);
	       const struct exception_table_entry *ex_table_start;
	       const struct exception_table_entry *ex_table_end;
	   #ifdef __alpha__
	       unsigned long gp;
	   #endif
	   };

       All  of	the pointer fields, with the exception of next and refs, are expected to point within the module body and be initialized as appro-
       priate for kernel space, that is, relocated with the rest of the module.

SEE ALSO

       create_module(2), delete_module(2), query_module(2), lsmod(8), modprobe(8)

Linux								    2014-05-10							    INIT_MODULE(2)