NAME
mod - module information and loading of symbols and debugging data
SYNOPSIS
mod -s module [objfile] | -d module | -S [directory] [-D|-t|-r|-R|-o|-g]
DESCRIPTION
With no arguments, this command displays basic information of the currently
installed modules, consisting of the module address, name, base address,
size, the object file name (if known), and whether the module was compiled
with CONFIG_KALLSYMS.
The arguments are concerned with with the loading or deleting of symbolic
and debugging data from a module's object file. A modules's object file
always contains symbolic data (symbol names and addresses), but contains
debugging data only if the module was compiled with the -g CFLAG. In
addition, the module may have compiled with CONFIG_KALLSYMS, which means
that the module's symbolic data will have been loaded into the kernel's
address space when it was installed. If the module was not compiled with
CONFIG_KALLSYMS, then only the module's exported symbols will be loaded
into the kernel's address space. Therefore, for the purpose of this
command, it should noted that a kernel module may have been compiled in
one of following manners:
1. If the module was built without CONFIG_KALLSYMS and without the -g CFLAG,
then the loading of the module's additional non-exported symbols can
be accomplished with this command.
2. If the module was built with CONFIG_KALLSYMS, but without the -g CFLAG,
then there is no benefit in loading the symbols from the module object
file, because all of the module's symbols will have been loaded into the
kernel's address space when it was installed.
3. If the module was built with CONFIG_KALLSYMS and with the the -g CFLAG,
then the loading of the module's debugging data can be accomplished
with this command.
4. If the module was built without CONFIG_KALLSYMS but with the -g CFLAG,
then the loading of the both module's symbolic and debugging data can
be accomplished with this command.
-s module [objfile] Loads symbolic and debugging data from the object file
for the module specified. If no objfile argument is
appended, a search will be made for an object file
consisting of the module name with a .o or .ko suffix,
starting at the /lib/modules/<release> directory on
the host system, or if not found there, starting at the
directory containing the kernel namelist file. If an
objfile argument is appended, then that file will be
used.
-d module Deletes the symbolic and debugging data of the module
specified.
-S [directory] Load symbolic and debugging data from the object file
for all loaded modules. For each module, a search
will be made for an object file consisting of the
module name with a .o or .ko suffix, starting at the
/lib/modules/<release> directory of the host system,
or if not found there, starting at the directory
containing the kernel namelist file. If a directory
argument is appended, then the search will be restricted
to that directory.
-D Deletes the symbolic and debugging data of all modules.
-t Display the contents of the module's "taints" bitmask
if it is non-zero. When possible, the "taints" bits
are translated to symbolic letters of the taint type;
otherwise the hexadecimal value is shown. In older
kernels, the contents of the "license_gplok" field is
displayed in hexadecimal; the field may be either a
bitmask or a boolean, depending upon the kernel version.
The relevant kernel sources should be consulted for the
meaning of the letter(s) or hexadecimal bit value(s).
For modules that have a "gpgsig_ok" field that is zero
(unsigned), the notation "(U)" is shown.
-r Passes the -readnow flag to the embedded gdb module,
which will override the two-stage strategy that it uses
for reading symbol tables from module object files.
-R Reinitialize module data. All currently-loaded symbolic
and debugging data will be deleted, and the installed
module list will be updated (live system only).
-g When used with -s or -S, add a module object's section
start and end addresses to its symbol list.
-o Load module symbols with old mechanism.
If the crash session was invoked with the "--mod <directory>" option, or
a CRASH_MODULE_PATH environment variable exists, then /lib/modules/<release>
will be overridden as the default directory tree that is searched for module
object files.
After symbolic and debugging data have been loaded, backtraces and text
disassembly will be displayed appropriately. Depending upon the processor
architecture, data may also printed symbolically with the "p" command;
at a minimum, the "rd" command may be used with module data symbols.
If crash can recognize that the set of modules has changed while running a
session on a live kernel, the module data will be reinitialized the next
time this command is run; the -r option forces the reinitialization.
EXAMPLES
Display the currently-installed modules:
crash> mod
MODULE NAME BASE SIZE OBJECT FILE
f7e44c20 dm_mod f7e34000 88568 (not loaded)
f7e5a8a0 dm_log f7e59000 8354 (not loaded)
f7e66420 dm_region_hash f7e65000 9708 (not loaded)
f7e76b60 dm_mirror f7e74000 12609 (not loaded)
f7e8b8e0 ata_piix f7e87000 20637 (not loaded)
...
Display the currently-installed modules on a system where all modules were
compiled with CONFIG_KALLSYMS:
crash> mod
MODULE NAME BASE SIZE OBJECT FILE
f7e44c20 dm_mod f7e34000 88568 (not loaded) [CONFIG_KALLSYMS]
f7e5a8a0 dm_log f7e59000 8354 (not loaded) [CONFIG_KALLSYMS]
f7e66420 dm_region_hash f7e65000 9708 (not loaded) [CONFIG_KALLSYMS]
f7e76b60 dm_mirror f7e74000 12609 (not loaded) [CONFIG_KALLSYMS]
f7e8b8e0 ata_piix f7e87000 20637 (not loaded) [CONFIG_KALLSYMS]
...
Load the symbolic and debugging data of all modules:
crash> mod -S
MODULE NAME BASE SIZE OBJECT FILE
f7e44c20 dm_mod f7e34000 88568 /lib/modules/2.6.32/kernel/drivers/md/dm-mod.ko
f7e5a8a0 dm_log f7e59000 8354 /lib/modules/2.6.32/kernel/drivers/md/dm-log.ko
f7e66420 dm_region_hash f7e65000 9708 /lib/modules/2.6.32/kernel/drivers/md/dm-region-hash.ko
f7e76b60 dm_mirror f7e74000 12609 /lib/modules/2.6.32/kernel/drivers/md/dm-mirror.ko
f7e8b8e0 ata_piix f7e87000 20637 /lib/modules/2.6.32/kernel/drivers/ata/ata_piix.ko
...
Load the symbolic and debugging data of the dm_mod module from its
known location:
crash> mod -s dm_mod
MODULE NAME BASE SIZE OBJECT FILE
f7e44c20 dm_mod f7e34000 88568 /lib/modules/2.6.32/kernel/drivers/md/dm-mod.ko
Delete the current symbolic and debugging data of the dm_mod module,
and then re-load it from a specified object file:
crash> mod -d dm_mod
crash> mod -s dm_mod /tmp/dm_mod.ko
MODULE NAME BASE SIZE OBJECT FILE
f7e44c20 dm_mod f7e34000 88568 /tmp/dm-mod.ko
After installing a new kernel module on a live system, reinitialize the
installed module list:
crash> !modprobe soundcore
crash> mod
mod: NOTE: modules have changed on this system -- reinitializing
MODULE NAME BASE SIZE OBJECT FILE
f7e44c20 dm_mod f7e34000 88568 (not loaded)
f7e5a8a0 dm_log f7e59000 8354 (not loaded)
f7e62e40 soundcore f7e62000 6390 (not loaded)
f7e66420 dm_region_hash f7e65000 9708 (not loaded)
f7e76b60 dm_mirror f7e74000 12609 (not loaded)
f7e8b8e0 ata_piix f7e87000 20637 (not loaded)
...
Display modules that are "tainted", where in this case
where they are proprietary and unsigned:
crash> mod -t
NAME TAINT
vxspec P(U)
vxportal P(U)
fdd P(U)
vxfs P(U)
vxdmp P(U)
vxio P(U)
vxglm P(U)
vxgms P(U)
vxodm P(U)
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