1INIT_MODULE(2)             Linux Programmer's Manual            INIT_MODULE(2)
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NAME

6       init_module, finit_module - load a kernel module
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SYNOPSIS

9       int init_module(void *module_image, unsigned long len,
10                       const char *param_values);
11
12       int finit_module(int fd, const char *param_values,
13                        int flags);
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15       Note: glibc provides no header file declaration of init_module() and no
16       wrapper function for finit_module(); see NOTES.
17

DESCRIPTION

19       init_module() loads an ELF image into kernel space, performs any neces‐
20       sary  symbol  relocations, initializes module parameters to values pro‐
21       vided by the caller, and then runs the module's  init  function.   This
22       system call requires privilege.
23
24       The  module_image  argument  points  to  a buffer containing the binary
25       image to be loaded; len specifies the size of that buffer.  The  module
26       image should be a valid ELF image, built for the running kernel.
27
28       The param_values argument is a string containing space-delimited speci‐
29       fications of the values for module parameters (defined inside the  mod‐
30       ule  using module_param() and module_param_array()).  The kernel parses
31       this string and initializes the  specified  parameters.   Each  of  the
32       parameter specifications has the form:
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34               name[=value[,value...]]
35
36       The parameter name is one of those defined within the module using mod‐
37       ule_param()  (see  the  Linux  kernel  source  file  include/linux/mod‐
38       uleparam.h).   The  parameter value is optional in the case of bool and
39       invbool parameters.  Values for array parameters  are  specified  as  a
40       comma-separated list.
41
42   finit_module()
43       The  finit_module()  system  call  is like init_module(), but reads the
44       module to be loaded from the file descriptor fd.  It is useful when the
45       authenticity  of a kernel module can be determined from its location in
46       the filesystem; in cases where that is possible, the overhead of  using
47       cryptographically  signed  modules  to  determine the authenticity of a
48       module can be avoided.  The param_values argument is as  for  init_mod‐
49       ule().
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51       The  flags  argument modifies the operation of finit_module().  It is a
52       bit mask value created by ORing together zero or more of the  following
53       flags:
54
55       MODULE_INIT_IGNORE_MODVERSIONS
56              Ignore symbol version hashes.
57
58       MODULE_INIT_IGNORE_VERMAGIC
59              Ignore kernel version magic.
60
61       There  are  some  safety  checks  built into a module to ensure that it
62       matches the kernel against  which  it  is  loaded.   These  checks  are
63       recorded  when  the  module  is  built  and verified when the module is
64       loaded.  First, the module records a "vermagic" string  containing  the
65       kernel  version  number  and prominent features (such as the CPU type).
66       Second, if the module was built with the CONFIG_MODVERSIONS  configura‐
67       tion  option  enabled,  a  version hash is recorded for each symbol the
68       module uses.  This hash is based on the  types  of  the  arguments  and
69       return  value  for the function named by the symbol.  In this case, the
70       kernel version number within the "vermagic" string is ignored,  as  the
71       symbol version hashes are assumed to be sufficiently reliable.
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73       Using  the  MODULE_INIT_IGNORE_VERMAGIC  flag  indicates that the "ver‐
74       magic" string is to be ignored, and the  MODULE_INIT_IGNORE_MODVERSIONS
75       flag  indicates  that  the symbol version hashes are to be ignored.  If
76       the kernel is built to permit forced  loading  (i.e.,  configured  with
77       CONFIG_MODULE_FORCE_LOAD),  then  loading continues, otherwise it fails
78       with the error ENOEXEC as expected for malformed modules.
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RETURN VALUE

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

85       EBADMSG (since Linux 3.7)
86              Module signature is misformatted.
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88       EBUSY  Timeout  while trying to resolve a symbol reference by this mod‐
89              ule.
90
91       EFAULT An address argument referred to a location that is  outside  the
92              process's accessible address space.
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94       ENOKEY (since Linux 3.7)
95              Module  signature  is  invalid or the kernel does not have a key
96              for this module.  This error is returned only if the kernel  was
97              configured  with  CONFIG_MODULE_SIG_FORCE; if the kernel was not
98              configured with this option, then an invalid or unsigned  module
99              simply taints the kernel.
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101       ENOMEM Out of memory.
102
103       EPERM  The  caller  was not privileged (did not have the CAP_SYS_MODULE
104              capability), or module loading is disabled  (see  /proc/sys/ker‐
105              nel/modules_disabled in proc(5)).
106
107       The following errors may additionally occur for init_module():
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109       EEXIST A module with this name is already loaded.
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111       EINVAL param_values  is  invalid, or some part of the ELF image in mod‐
112              ule_image contains inconsistencies.
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114       ENOEXEC
115              The binary image supplied in module_image is not an  ELF  image,
116              or  is an ELF image that is invalid or for a different architec‐
117              ture.
118
119       The following errors may additionally occur for finit_module():
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121       EBADF  The file referred to by fd is not opened for reading.
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123       EFBIG  The file referred to by fd is too large.
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125       EINVAL flags is invalid.
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127       ENOEXEC
128              fd does not refer to an open file.
129
130       In addition to the above errors, if the module's init function is  exe‐
131       cuted  and returns an error, then init_module() or finit_module() fails
132       and errno is set to the value returned by the init function.
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VERSIONS

135       finit_module() is available since Linux 3.8.
136

CONFORMING TO

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

141       The init_module() system call is not supported by glibc.   No  declara‐
142       tion  is  provided  in  glibc headers, but, through a quirk of history,
143       glibc versions before 2.23 did export an  ABI  for  this  system  call.
144       Therefore,  in  order  to  employ this system call, it is (before glibc
145       2.23) sufficient to manually declare the interface in your code; alter‐
146       natively, you can invoke the system call using syscall(2).
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148       Glibc  does  not  provide  a  wrapper for finit_module(); call it using
149       syscall(2).
150
151       Information about currently loaded modules can be found  in  /proc/mod‐
152       ules  and  in  the file trees under the per-module subdirectories under
153       /sys/module.
154
155       See the Linux kernel source file include/linux/module.h for some useful
156       background information.
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158   Linux 2.4 and earlier
159       In Linux 2.4 and earlier, the init_module() system call was rather dif‐
160       ferent:
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162           #include <linux/module.h>
163
164           int init_module(const char *name, struct module *image);
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166       (User-space applications can detect which version of  init_module()  is
167       available  by  calling  query_module();  the latter call fails with the
168       error ENOSYS on Linux 2.6 and later.)
169
170       The older version of the system call loads the relocated  module  image
171       pointed  to by image into kernel space and runs the module's init func‐
172       tion.  The caller is responsible  for  providing  the  relocated  image
173       (since Linux 2.6, the init_module() system call does the relocation).
174
175       The module image begins with a module structure and is followed by code
176       and data as appropriate.  Since Linux  2.2,  the  module  structure  is
177       defined as follows:
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179           struct module {
180               unsigned long         size_of_struct;
181               struct module        *next;
182               const char           *name;
183               unsigned long         size;
184               long                  usecount;
185               unsigned long         flags;
186               unsigned int          nsyms;
187               unsigned int          ndeps;
188               struct module_symbol *syms;
189               struct module_ref    *deps;
190               struct module_ref    *refs;
191               int                 (*init)(void);
192               void                (*cleanup)(void);
193               const struct exception_table_entry *ex_table_start;
194               const struct exception_table_entry *ex_table_end;
195           #ifdef __alpha__
196               unsigned long gp;
197           #endif
198           };
199
200       All  of  the  pointer  fields, with the exception of next and refs, are
201       expected to point within the module body and be initialized  as  appro‐
202       priate  for  kernel space, that is, relocated with the rest of the mod‐
203       ule.
204

SEE ALSO

206       create_module(2),  delete_module(2),  query_module(2),  lsmod(8),  mod‐
207       probe(8)
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COLOPHON

210       This  page  is  part of release 4.16 of the Linux man-pages project.  A
211       description of the project, information about reporting bugs,  and  the
212       latest     version     of     this    page,    can    be    found    at
213       https://www.kernel.org/doc/man-pages/.
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217Linux                             2017-09-15                    INIT_MODULE(2)
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