.\" Copyright (C) 2012 Michael Kerrisk .\" A few fragments remain from a version .\" Copyright (C) 1996 Free Software Foundation, Inc. .\" .\" %%%LICENSE_START(VERBATIM) .\" Permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" Permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" Since the Linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. The author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. The author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" Formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%LICENSE_END .\" .TH INIT_MODULE 2 2016-03-15 "Linux" "Linux Programmer's Manual" .SH NAME init_module, finit_module \- load a kernel module .SH SYNOPSIS .nf .BI "int init_module(void *" module_image ", unsigned long " len , .BI " const char *" param_values ); .BI "int finit_module(int " fd ", const char *" param_values , .BI " int " flags ); .fi .IR Note : glibc provides no header file declaration of .BR init_module () and no wrapper function for .BR finit_module (); see NOTES. .SH DESCRIPTION .BR init_module () loads an ELF image into kernel space, performs any necessary symbol relocations, initializes module parameters to values provided by the caller, and then runs the module's .I init function. This system call requires privilege. The .I module_image argument points to a buffer containing the binary image to be loaded; .I len specifies the size of that buffer. The module image should be a valid ELF image, built for the running kernel. The .I param_values argument is a string containing space-delimited specifications of the values for module parameters (defined inside the module using .BR module_param () and .BR module_param_array ()). The kernel parses this string and initializes the specified parameters. Each of the parameter specifications has the form: .RI " " name [\c .BI = value\c .RB [ ,\c .IR value ...]] The parameter .I name is one of those defined within the module using .IR module_param () (see the Linux kernel source file .IR include/linux/moduleparam.h ). The parameter .I value is optional in the case of .I bool and .I invbool parameters. Values for array parameters are specified as a comma-separated list. .SS finit_module() The .BR finit_module () .\" commit 34e1169d996ab148490c01b65b4ee371cf8ffba2 .\" https://lwn.net/Articles/519010/ system call is like .BR init_module (), but reads the module to be loaded from the file descriptor .IR 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 .I param_values argument is as for .BR init_module (). The .I flags argument modifies the operation of .BR finit_module (). It is a bit mask value created by ORing together zero or more of the following flags: .\" commit 2f3238aebedb243804f58d62d57244edec4149b2 .TP .B MODULE_INIT_IGNORE_MODVERSIONS Ignore symbol version hashes. .TP .B MODULE_INIT_IGNORE_VERMAGIC Ignore kernel version magic. .PP There are some safety checks built into a module to ensure that it matches the kernel against which it is loaded. .\" http://www.tldp.org/HOWTO/Module-HOWTO/basekerncompat.html .\" is dated, but informative 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 .B 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 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 .B MODULE_INIT_IGNORE_VERMAGIC flag indicates that the "vermagic" string is to be ignored, and the .B 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 .BR CONFIG_MODULE_FORCE_LOAD ), then loading will continue, otherwise it will fail with .B ENOEXEC as expected for malformed modules. .SH RETURN VALUE On success, these system calls return 0. On error, \-1 is returned and .I errno is set appropriately. .SH ERRORS .TP .BR EBADMSG " (since Linux 3.7)" Module signature is misformatted. .TP .B EBUSY Timeout while trying to resolve a symbol reference by this module. .TP .B EFAULT An address argument referred to a location that is outside the process's accessible address space. .TP .BR ENOKEY " (since Linux 3.7)" .\" commit 48ba2462ace6072741fd8d0058207d630ce93bf1 .\" commit 1d0059f3a468825b5fc5405c636a2f6e02707ffa .\" commit 106a4ee258d14818467829bf0e12aeae14c16cd7 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 .BR CONFIG_MODULE_SIG_FORCE ; if the kernel was not configured with this option, then an invalid or unsigned module simply taints the kernel. .TP .B ENOMEM Out of memory. .TP .B EPERM The caller was not privileged (did not have the .B CAP_SYS_MODULE capability), or module loading is disabled (see .IR /proc/sys/kernel/modules_disabled in .BR proc (5)). .PP The following errors may additionally occur for .BR init_module (): .TP .B EEXIST A module with this name is already loaded. .TP .B EINVAL .I param_values is invalid, or some part of the ELF image in .IR module_image contains inconsistencies. .\" .TP .\" .BR EINVAL " (Linux 2.4 and earlier)" .\" Some .\" .I image .\" slot is filled in incorrectly, .\" .I image\->name .\" does not correspond to the original module name, some .\" .I image\->deps .\" entry does not correspond to a loaded module, .\" or some other similar inconsistency. .TP .B ENOEXEC The binary image supplied in .I module_image is not an ELF image, or is an ELF image that is invalid or for a different architecture. .PP The following errors may additionally occur for .BR finit_module (): .TP .B EBADF The file referred to by .I fd is not opened for reading. .TP .B EFBIG The file referred to by .I fd is too large. .TP .B EINVAL .I flags is invalid. .TP .B ENOEXEC .I fd does not refer to an open file. .PP In addition to the above errors, if the module's .I init function is executed and returns an error, then .BR init_module () or .BR finit_module () fails and .I errno is set to the value returned by the .I init function. .SH VERSIONS .BR finit_module () is available since Linux 3.8. .SH CONFORMING TO .BR init_module () and .BR finit_module () are Linux-specific. .SH NOTES The .BR init_module () system call is not supported by glibc. No declaration is provided in glibc headers, but, through a quirk of history, glibc versions before 2.23 did export an ABI for this system call. Therefore, in order to employ this system call, it is (before glibc 2.23) sufficient to manually declare the interface in your code; alternatively, you can invoke the system call using .BR syscall (2). Glibc does not provide a wrapper for .BR finit_module (); call it using .BR syscall (2). Information about currently loaded modules can be found in .IR /proc/modules and in the file trees under the per-module subdirectories under .IR /sys/module . See the Linux kernel source file .I include/linux/module.h for some useful background information. .SS Linux 2.4 and earlier .PP In Linux 2.4 and earlier, the .BR init_module () system call was rather different: .B " #include " .BI " int init_module(const char *" name ", struct module *" image ); (User-space applications can detect which version of .BR init_module () is available by calling .BR query_module (); the latter call fails with the error .BR ENOSYS on Linux 2.6 and later.) The older version of the system call loads the relocated module image pointed to by .I image into kernel space and runs the module's .I init function. The caller is responsible for providing the relocated image (since Linux 2.6, the .BR init_module () system call does the relocation). .PP 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: .PP .in +4n .nf 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 }; .fi .in .PP All of the pointer fields, with the exception of .I next and .IR refs , are expected to point within the module body and be initialized as appropriate for kernel space, that is, relocated with the rest of the module. .SH SEE ALSO .BR create_module (2), .BR delete_module (2), .BR query_module (2), .BR lsmod (8), .BR modprobe (8) .SH COLOPHON This page is part of release 4.10 of the Linux .I man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/.