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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: There are no glibc wrappers for these system calls; see NOTES.

DESCRIPTION
       init_module() loads an ELF image into kernel space, performs any neces‐
       sary 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 speci‐
       fications  of the values for module parameters (defined inside the mod‐
       ule 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 mod‐
       ule_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_mod‐
       ule().

       The flags argument modifies the operation of finit_module().  It	 is  a
       bit  mask value created by ORing together zero or more of the following
       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 configura‐
       tion 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	 "ver‐
       magic"  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  mod‐
	      ule.

       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
	      configured 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/ker‐
	      nel/modules_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  mod‐
	      ule_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  architec‐
	      ture.

       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 exe‐
       cuted 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
       Glibc  does  not	 provide  a  wrapper for these system calls; call them
       using syscall(2).

       Information about currently loaded modules can be found	in  /proc/mod‐
       ules  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 dif‐
       ferent:

	   #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 func‐
       tion.  The caller is responsible	 for  providing	 the  relocated	 image
       (since Linux 2.6, the init_module() system call does the relocation).

       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 mod‐
       ule.

SEE ALSO
       create_module(2),  delete_module(2),  query_module(2),  lsmod(8),  mod‐
       probe(8)

COLOPHON
       This  page  is  part of release 3.54 of the Linux man-pages project.  A
       description of the project, and information about reporting  bugs,  can
       be found at http://www.kernel.org/doc/man-pages/.

Linux				  2013-01-07			INIT_MODULE(2)
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