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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 necessary symbol reloca-
       tions, initializes module parameters to values provided 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  mod-
       ule_param_array()).   The  kernel parses this string and initializes the specified parame-
       ters.  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/moduleparam.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 over-
       head 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 cre-
       ated 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 veri-
       fied 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 configuration option enabled, a version  hash
       is recorded for each symbol the module uses.  This hash is based on the types of the argu-
       ments 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.,  config-
       ured  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 appro-
       priately.

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  configured  with CONFIG_MOD-
	      ULE_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 mod-
	      ule loading is disabled (see /proc/sys/kernel/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  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
       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/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 infor-
       mation.

   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 pro-
       viding  the relocated image (since Linux 2.6, the init_module() system call does the relo-
       cation).

       The module image begins with a module structure and is followed by code and data as appro-
       priate.	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 appropriate for kernel space, that is,  relo-
       cated with the rest of the module.

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

COLOPHON
       This  page  is  part of release 3.55 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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