521 lines
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HTML
521 lines
12 KiB
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<HTML><HEAD><TITLE>Man page of INIT_MODULE</TITLE>
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</HEAD><BODY>
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<H1>INIT_MODULE</H1>
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Section: Linux Programmer's Manual (2)<BR>Updated: 2017-09-15<BR><A HREF="#index">Index</A>
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<A HREF="/cgi-bin/man/man2html">Return to Main Contents</A><HR>
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<A NAME="lbAB"> </A>
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<H2>NAME</H2>
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init_module, finit_module - load a kernel module
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<A NAME="lbAC"> </A>
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<H2>SYNOPSIS</H2>
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<PRE>
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<B>int init_module(void *</B><I>module_image</I><B>, unsigned long </B><I>len</I><B>,</B>
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<B> const char *</B><I>param_values</I><B>);</B>
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<B>int finit_module(int </B><I>fd</I><B>, const char *</B><I>param_values</I><B>,</B>
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<B> int </B><I>flags</I><B>);</B>
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</PRE>
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<P>
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<I>Note</I>:
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glibc provides no header file declaration of
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<B>init_module</B>()
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and no wrapper function for
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<B>finit_module</B>();
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see NOTES.
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<A NAME="lbAD"> </A>
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<H2>DESCRIPTION</H2>
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<B>init_module</B>()
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loads an ELF image into kernel space,
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performs any necessary symbol relocations,
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initializes module parameters to values provided by the caller,
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and then runs the module's
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<I>init</I>
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function.
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This system call requires privilege.
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<P>
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The
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<I>module_image</I>
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argument points to a buffer containing the binary image
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to be loaded;
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<I>len</I>
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specifies the size of that buffer.
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The module image should be a valid ELF image, built for the running kernel.
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<P>
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The
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<I>param_values</I>
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argument is a string containing space-delimited specifications of the
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values for module parameters (defined inside the module using
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<B>module_param</B>()
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and
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<B>module_param_array</B>()).
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The kernel parses this string and initializes the specified
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parameters.
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Each of the parameter specifications has the form:
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<P>
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<I>name</I>[<B>=</B><I>value</I>[<B>,</B><I>value</I>...]]
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<P>
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The parameter
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<I>name</I>
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is one of those defined within the module using
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<I>module_param</I>()
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(see the Linux kernel source file
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<I>include/linux/moduleparam.h</I>).
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The parameter
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<I>value</I>
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is optional in the case of
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<I>bool</I>
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and
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<I>invbool</I>
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parameters.
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Values for array parameters are specified as a comma-separated list.
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<A NAME="lbAE"> </A>
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<H3>finit_module()</H3>
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The
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<B>finit_module</B>()
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system call is like
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<B>init_module</B>(),
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but reads the module to be loaded from the file descriptor
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<I>fd</I>.
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It is useful when the authenticity of a kernel module
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can be determined from its location in the filesystem;
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in cases where that is possible,
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the overhead of using cryptographically signed modules to
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determine the authenticity of a module can be avoided.
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The
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<I>param_values</I>
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argument is as for
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<B>init_module</B>().
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<P>
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The
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<I>flags</I>
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argument modifies the operation of
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<B>finit_module</B>().
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It is a bit mask value created by ORing
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together zero or more of the following flags:
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<DL COMPACT>
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<DT id="1"><B>MODULE_INIT_IGNORE_MODVERSIONS</B>
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<DD>
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Ignore symbol version hashes.
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<DT id="2"><B>MODULE_INIT_IGNORE_VERMAGIC</B>
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<DD>
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Ignore kernel version magic.
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</DL>
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<P>
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There are some safety checks built into a module to ensure that
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it matches the kernel against which it is loaded.
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These checks are recorded when the module is built and
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verified when the module is loaded.
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First, the module records a "vermagic" string containing
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the kernel version number and prominent features (such as the CPU type).
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Second, if the module was built with the
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<B>CONFIG_MODVERSIONS</B>
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configuration option enabled,
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a version hash is recorded for each symbol the module uses.
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This hash is based on the types of the arguments and return value
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for the function named by the symbol.
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In this case, the kernel version number within the
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"vermagic" string is ignored,
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as the symbol version hashes are assumed to be sufficiently reliable.
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<P>
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Using the
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<B>MODULE_INIT_IGNORE_VERMAGIC</B>
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flag indicates that the "vermagic" string is to be ignored, and the
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<B>MODULE_INIT_IGNORE_MODVERSIONS</B>
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flag indicates that the symbol version hashes are to be ignored.
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If the kernel is built to permit forced loading (i.e., configured with
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<B>CONFIG_MODULE_FORCE_LOAD</B>),
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then loading continues, otherwise it fails with the error
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<B>ENOEXEC</B>
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as expected for malformed modules.
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<A NAME="lbAF"> </A>
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<H2>RETURN VALUE</H2>
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On success, these system calls return 0.
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On error, -1 is returned and
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<I>errno</I>
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is set appropriately.
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<A NAME="lbAG"> </A>
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<H2>ERRORS</H2>
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<DL COMPACT>
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<DT id="3"><B>EBADMSG</B> (since Linux 3.7)
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<DD>
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Module signature is misformatted.
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<DT id="4"><B>EBUSY</B>
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<DD>
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Timeout while trying to resolve a symbol reference by this module.
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<DT id="5"><B>EFAULT</B>
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<DD>
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An address argument referred to a location that
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is outside the process's accessible address space.
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<DT id="6"><B>ENOKEY</B> (since Linux 3.7)
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<DD>
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Module signature is invalid or
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the kernel does not have a key for this module.
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This error is returned only if the kernel was configured with
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<B>CONFIG_MODULE_SIG_FORCE</B>;
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if the kernel was not configured with this option,
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then an invalid or unsigned module simply taints the kernel.
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<DT id="7"><B>ENOMEM</B>
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<DD>
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Out of memory.
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<DT id="8"><B>EPERM</B>
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<DD>
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The caller was not privileged
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(did not have the
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<B>CAP_SYS_MODULE</B>
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capability),
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or module loading is disabled
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(see
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<I>/proc/sys/kernel/modules_disabled</I>
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in
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<B><A HREF="/cgi-bin/man/man2html?5+proc">proc</A></B>(5)).
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</DL>
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<P>
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The following errors may additionally occur for
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<B>init_module</B>():
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<DL COMPACT>
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<DT id="9"><B>EEXIST</B>
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<DD>
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A module with this name is already loaded.
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<DT id="10"><B>EINVAL</B>
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<DD>
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<I>param_values</I>
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is invalid, or some part of the ELF image in
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<I>module_image</I>
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contains inconsistencies.
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<DT id="11"><B>ENOEXEC</B>
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<DD>
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The binary image supplied in
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<I>module_image</I>
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is not an ELF image,
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or is an ELF image that is invalid or for a different architecture.
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</DL>
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<P>
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The following errors may additionally occur for
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<B>finit_module</B>():
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<DL COMPACT>
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<DT id="12"><B>EBADF</B>
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<DD>
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The file referred to by
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<I>fd</I>
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is not opened for reading.
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<DT id="13"><B>EFBIG</B>
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<DD>
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The file referred to by
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<I>fd</I>
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is too large.
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<DT id="14"><B>EINVAL</B>
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<DD>
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<I>flags</I>
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is invalid.
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<DT id="15"><B>ENOEXEC</B>
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<DD>
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<I>fd</I>
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does not refer to an open file.
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</DL>
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<P>
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In addition to the above errors, if the module's
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<I>init</I>
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function is executed and returns an error, then
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<B>init_module</B>()
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or
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<B>finit_module</B>()
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fails and
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<I>errno</I>
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is set to the value returned by the
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<I>init</I>
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function.
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<A NAME="lbAH"> </A>
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<H2>VERSIONS</H2>
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<B>finit_module</B>()
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is available since Linux 3.8.
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<A NAME="lbAI"> </A>
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<H2>CONFORMING TO</H2>
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<B>init_module</B>()
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and
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<B>finit_module</B>()
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are Linux-specific.
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<A NAME="lbAJ"> </A>
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<H2>NOTES</H2>
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The
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<B>init_module</B>()
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system call is not supported by glibc.
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No declaration is provided in glibc headers, but, through a quirk of history,
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glibc versions before 2.23 did export an ABI for this system call.
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Therefore, in order to employ this system call,
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it is (before glibc 2.23) sufficient to
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manually declare the interface in your code;
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alternatively, you can invoke the system call using
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<B><A HREF="/cgi-bin/man/man2html?2+syscall">syscall</A></B>(2).
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<P>
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Glibc does not provide a wrapper for
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<B>finit_module</B>();
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call it using
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<B><A HREF="/cgi-bin/man/man2html?2+syscall">syscall</A></B>(2).
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<P>
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Information about currently loaded modules can be found in
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<I>/proc/modules</I>
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and in the file trees under the per-module subdirectories under
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<I>/sys/module</I>.
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<P>
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See the Linux kernel source file
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<I>include/linux/module.h</I>
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for some useful background information.
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<A NAME="lbAK"> </A>
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<H3>Linux 2.4 and earlier</H3>
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<P>
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In Linux 2.4 and earlier, the
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<B>init_module</B>()
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system call was rather different:
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<P>
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<B> #include <<A HREF="file:///usr/include/linux/module.h">linux/module.h</A>></B>
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<P>
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<B> int init_module(const char *</B><I>name</I><B>, struct module *</B><I>image</I><B>);</B>
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<P>
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(User-space applications can detect which version of
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<B>init_module</B>()
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is available by calling
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<B>query_module</B>();
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the latter call fails with the error
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<B>ENOSYS</B>
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on Linux 2.6 and later.)
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<P>
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The older version of the system call
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loads the relocated module image pointed to by
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<I>image</I>
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into kernel space and runs the module's
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<I>init</I>
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function.
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The caller is responsible for providing the relocated image (since
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Linux 2.6, the
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<B>init_module</B>()
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system call does the relocation).
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<P>
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The module image begins with a module structure and is followed by
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code and data as appropriate.
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Since Linux 2.2, the module structure is defined as follows:
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<P>
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struct module {
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<BR> unsigned long size_of_struct;
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<BR> struct module *next;
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<BR> const char *name;
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<BR> unsigned long size;
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<BR> long usecount;
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<BR> unsigned long flags;
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<BR> unsigned int nsyms;
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<BR> unsigned int ndeps;
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<BR> struct module_symbol *syms;
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<BR> struct module_ref *deps;
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<BR> struct module_ref *refs;
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<BR> int (*init)(void);
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<BR> void (*cleanup)(void);
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<BR> const struct exception_table_entry *ex_table_start;
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<BR> const struct exception_table_entry *ex_table_end;
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#ifdef __alpha__
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<BR> unsigned long gp;
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#endif
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};
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<P>
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All of the pointer fields, with the exception of
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<I>next</I>
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and
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<I>refs</I>,
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are expected to point within the module body and be
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initialized as appropriate for kernel space, that is, relocated with
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the rest of the module.
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<A NAME="lbAL"> </A>
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<H2>SEE ALSO</H2>
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<B><A HREF="/cgi-bin/man/man2html?2+create_module">create_module</A></B>(2),
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<B><A HREF="/cgi-bin/man/man2html?2+delete_module">delete_module</A></B>(2),
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<B><A HREF="/cgi-bin/man/man2html?2+query_module">query_module</A></B>(2),
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<B><A HREF="/cgi-bin/man/man2html?8+lsmod">lsmod</A></B>(8),
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<B><A HREF="/cgi-bin/man/man2html?8+modprobe">modprobe</A></B>(8)
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<A NAME="lbAM"> </A>
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<H2>COLOPHON</H2>
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This page is part of release 5.05 of the Linux
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<I>man-pages</I>
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project.
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A description of the project,
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information about reporting bugs,
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and the latest version of this page,
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can be found at
|
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<A HREF="https://www.kernel.org/doc/man-pages/.">https://www.kernel.org/doc/man-pages/.</A>
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<P>
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<HR>
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<A NAME="index"> </A><H2>Index</H2>
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<DL>
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<DT id="16"><A HREF="#lbAB">NAME</A><DD>
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<DT id="17"><A HREF="#lbAC">SYNOPSIS</A><DD>
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<DT id="18"><A HREF="#lbAD">DESCRIPTION</A><DD>
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<DL>
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<DT id="19"><A HREF="#lbAE">finit_module()</A><DD>
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</DL>
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<DT id="20"><A HREF="#lbAF">RETURN VALUE</A><DD>
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<DT id="21"><A HREF="#lbAG">ERRORS</A><DD>
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<DT id="22"><A HREF="#lbAH">VERSIONS</A><DD>
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<DT id="23"><A HREF="#lbAI">CONFORMING TO</A><DD>
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<DT id="24"><A HREF="#lbAJ">NOTES</A><DD>
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<DL>
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<DT id="25"><A HREF="#lbAK">Linux 2.4 and earlier</A><DD>
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</DL>
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<DT id="26"><A HREF="#lbAL">SEE ALSO</A><DD>
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<DT id="27"><A HREF="#lbAM">COLOPHON</A><DD>
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</DL>
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<HR>
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This document was created by
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<A HREF="/cgi-bin/man/man2html">man2html</A>,
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using the manual pages.<BR>
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Time: 00:05:32 GMT, March 31, 2021
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</BODY>
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</HTML>
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