[Gllug] How to check if module is in kernel ?

salsaman at xs4all.nl salsaman at xs4all.nl
Mon Nov 15 11:57:44 UTC 2010


On Mon, November 15, 2010 12:21, Richard Jones wrote:
> On Mon, Nov 15, 2010 at 12:03:52AM +0100, salsaman at xs4all.nl wrote:
>> On Sun, November 14, 2010 23:53, John Hearns wrote:
>> > /proc/config.gz contains the kernel configuration for the running
>> kernel.
>> > Is that any use?
>>
>> i don't have that file on my system (ubuntu 10.10)
>
> Everyone is confusing two different mechanisms by which the .config
> file from the kernel source is made available at runtime:
>
> Either: (a) the distro packaging system copies this file into
> somewhere under / or /boot.  The exact location is not well-defined
> and varies according to distro packaging whims.
>
> Or: (b) the kernel can be configured so it includes this information
> in the compiled kernel image, and it is made available through
> /proc/config.  However since this increases the size of the kernel
> image significantly, many distros disable this option.
>
> In summary, looking in/for the config file is *not* a reliable way to
> detect if a kernel supports a feature.
>
> Instead the correct way to do it is as follows: look for /dev, /sys or
> /proc devices or files which show evidence of the API, or use the API
> and catch errors from its non-presence.  For some kernel APIs there
> may be API-specific ways to tell if a feature of the API is available.
> I've no idea if this is the case for V4L.
>
> Rich.
>
> --
> Richard Jones
> Red Hat
> --
> Gllug mailing list  -  Gllug at gllug.org.uk
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>
>

What about looking in /proc/kallsyms ? Is that standard ?

With the module loaded, I see e.g.:

ffffffffa0b42478 t cleanup_module	[vloopback]



Regards,
Salsaman.


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