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INSMOD

Section: Linux Module Support (8)
Updated: November 10 2000
Index

NAME

insmod - install loadable kernel module

SYNOPSIS

insmod[-fhkLmnpqrsSvVxXyY] [-e persist_name] [-o module_name][-O blob_name] [-P prefix] module [ symbol=value ... ]

DESCRIPTION

insmodinstalls a loadable module in the running kernel.

insmodtries to link a module into the running kernel by resolving all symbolsfrom the kernel's exported symbol table.

If the module file name is given without directories or extension,insmodwill search for the module in some common default directories.The environment variable MODPATH can be used to override this default.If a module configuration file such as /etc/modules.conf exists,it will override the paths defined in MODPATH.
The environment variable MODULECONF can also be used to select adifferent configuration file from the default /etc/modules.conf (or/etc/conf.modules (deprecated)).This environment variable will override all the definitions above.

OPTIONS

-f --force: Attempt load the module even if the version of the running kernel andthe version of the kernel for which the module was compiled do not match.This only overrides the kernel version check, it has no effect onsymbol name checks. If the symbol names in the module do not match thekernel then there is no way to forceinsmodto load the module.
-h --help: Print the help text.
-k --autoclean: Set the auto-clean flag on the module. This flag will be used bykerneld(8) to remove modules that have not been used in someperiod of time --- usually one minute.
-L --lock: Use flock(2) to prevent simultaneous loads of the same module.
-m --map: Output a load map on stdout, making it easier to debug the module inthe event of a kernel panic.
-n --noload: Dummy run, do everything except load the module into the kernel. Ifrequested by-mor-O,the run will produce a map or blob file. Since the module is notloaded, the real kernel load address is unknown so the map and blobfile are based on an arbitrary load address of 0x12340000.
-p --probe: Probe the module to see if it could be successfully loaded. Thisincludes locating the object file in the module path, checkingversion numbers, and resolving symbols. It does not check therelocations nor does it produce a map or blob file.
-q --quiet: Do not print a list of any unresolved symbols.Do not complain about version mismatch.The problem will only be reflected in the exit status ofinsmod.
-r --root: Some users compile modules under a non-root userid then install themodules as root. This process can leave the modules owned by thenon-root userid, even though the modules directory is owned by root.If the non-root userid is compromised, an intruder can overwriteexisting modules owned by that userid and use this exposure tobootstrap up to root access.
: By default, modutils will reject attempts to use a module that is notowned by root. Specifying -r will toggle the check and allow root toload modules that are not owned by root.Note:the default value for root check can be changed when modutils isconfigured.
: Use of-rto disable root checking or setting the default to "no root check"at configuration time is a major security exposure and is notrecommended.
-s --syslog: Output everything to syslog(3) instead of the terminal.
-S --kallsyms: Force the loaded module to have kallsyms data, even if the kernel doesnot support it. This option is for small systems where the kernel isloaded without kallsyms data but selected modules need kallsyms fordebugging.
-v --verbose: Be verbose.
-X --export, -x --noexport: Do and do not export all of the module's external symbols, respectively.The default is for the symbols to be exported. This option is onlyeffective if the module does not explicitly export its own controlledsymbol table, and thus is deprecated.
-Y --ksymoops, -y --noksymoops: Do and do not add ksymoops symbols to ksyms. These symbols are used byksymoops to provide better debugging if there is an Oops in thismodule. The default is for the ksymoops symbols to be defined. Thisoption is independent of the -X/-x options.
: ksymoops symbols add approximately 260 bytes per loaded module. Unlessyou are really short on kernel space and are trying to reduce ksyms toits minimum size, take the default and get more accurate Oopsdebugging. ksymoops symbols are required to save persistent moduledata.
-o module_name --name=module_name: Explicitly name the module, rather than deriving the name from thebase name of the source object file.
-O blob_name --blob=blob_name: Save the binary object inblob_name.The result is a binary blob (no ELF headers) showing exactly what isloaded into the kernel, after section manipulation and relocation.Option-mis recommended to get a map of the object.
-P prefix --prefix=prefix: This option can be used with versioned modules for an SMP or bigmemkernel, since such modules have an extra prefix added in their symbolnames.If the kernel was built with symbol versions theninsmodwill automatically extract the prefix from the definition of"get_module_symbol" or "inter_module_get", one of which must exist inany kernel that supports modules. If the kernel has no symbol versionsbut the module was built with symbol versions then the user must supply-P.
-e persist_name --persist=persist_name: Specifies where any persistent data for the module is read from on loadand written to when this instantiantion of the module is unloaded.This option is silently ignored if the module has no persistent data.Persistent data is only read byinsmodif this option is present, by defaultinsmoddoes not process persistent data.As a shorthand form,-e"" (an empty string) is interpreted byinsmodas the value ofpersistdir(seemodules.conf(5))followed by the filename of the module, relative to the module searchpath it was found in, minus any trailing '.gz', '.o' and '.mod'. Ifyou specifypersistdir=(i.e. persistdir is an empty field) then this shorthand form issilently ignored.

MODULE PARAMETERS

Some modules accept load-time parameters to customize their operation.These parameters are often I/O port and IRQ numbers that vary frommachine to machine and cannot be determined from the hardware.

In modules built for 2.0 series kernels, any integer or character pointersymbol may be treated as a parameter and modified. Beginning in the2.1 series kernels, symbols are explicitly marked as parameters so thatonly specific values may be changed. Furthermore type information isprovided for checking the values provided at load time.

In the case of integers, all values may be in decimal, octal orhexadecimal a la C: 17, 021 or 0x11. Array elements are specifiedsequence separated by commas; elements can be skipped by omittingthe value.

In 2.0 series modules, values that do not begin with a number areconsidered strings. Beginning in 2.1, the parameter's type informationindicates whether to interpret the value as a string. If the valuebegins with double-quotes ("), the string is interpreted asin C, escape sequences and all. Do note that from the shell prompt,the quotes themselves may need to be protected from shell interpretation.

KSYMOOPS ASSISTANCE

To assist with debugging of kernel Oops when using modules, insmoddefaults to adding some symbols to ksyms, see the -Y option.These symbols start with __insmod_modulename_. Themodulename is required to make the symbols unique, it is legal toload the same object more than once under different module names.Currently defined symbols are

__insmod_modulename_Oobjectfile_Mmtime_Vversion

objectfile is the name of the file that the object was loadedfrom. This ensures that ksymoops can match the code to the correctobject. mtime is the last modified timestamp on that file inhex, zero if stat failed. version is the kernel version thatthe module was compiled for, -1 if no version is available. The_O symbol has the same start address as the module header.

__insmod_modulename_Ssectionname_Llength

This symbol appears at the start of selected ELF sections,currently .text, .rodata, .data and .bss. It only appears if thesection has a non-zero size. sectionname is the name of the ELFsection, length is the length of the section in decimal. Thesesymbols help ksymoops map addresses to sections when no symbols areavailable.

__insmod_modulename_Ppersistent_filename

Only created by insmod if the module has one or more parameters thatare marked as persistent data and a filename to save persistent data(see-eabove) is available.

The other problem with debugging kernel Oops in modules is that thecontents of /proc/ksyms and /proc/modules can change between the Oopsand when you process the log file. To help overcome this problem, ifdirectory /var/log/ksymoops exists then insmod and rmmod willautomatically copy /proc/ksyms and /proc/modules to /var/log/ksymoopswith a prefix of `date +%Y%m%d%H%M%S`.The system administrator can tell ksymoops which snapshot files to usewhen debugging an Oops. There is no switch to disable this automaticcopy, if you do not want it to occur, do not create /var/log/ksymoops.If that directory exists, it should be owned by root and be mode 644 or600 and you should run this script every day or so. The script belowis installed as insmod_ksymoops_clean.

  #!/bin/sh  # Delete saved ksyms and modules not accessed in 2 days  if [ -d /var/log/ksymoops ]  then          set -e          # Make sure there is always at least one version          d=`date +%Y%m%d%H%M%S`          cp -a /proc/ksyms /var/log/ksymoops/${d}.ksyms          cp -a /proc/modules /var/log/ksymoops/${d}.modules          find /var/log/ksymoops -type f -atime +2 -exec rm {} \;  fi

HISTORY

Module support was first conceived by Anonymous
Initial Linux version by Bas Laarhoven <basAATTvimec.nl>
Version 0.99.14 by Jon Tombs <jonAATTgtex02.us.es>
Extended by Bjorn Ekwall <bj0rnAATTblox.se>
Original ELF help from Eric Youngdale <ericAATTaib.com>
Rewritten for 2.1.17 by Richard Henderson <rthAATTtamu.edu>
Extended by Bjorn Ekwall <bj0rnAATTblox.se> for modutils-2.2.*, March 1999
Assistance for ksymoops by Keith Owens <kaosAATTocs.com.au>, May 1999
Maintainer: Keith Owens <kaosAATTocs.com.au>.

Index

NAME

SYNOPSIS

DESCRIPTION

OPTIONS
MODULE PARAMETERS
KSYMOOPS ASSISTANCE

SEE ALSO

HISTORY

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