On 22/05/07, Rajat Jain <rajat.noida.india@xxxxxxxxx> wrote:
Hi, > > Not just that, the kernel you build the module for has to be the > *exact* kernel you are running and try to load the module into. That > is, it has to be the exact same version and it has to be build with > the exact same config. > So you are saying that the module should be built with the SAME config as that of running kernel.
Yes.
I understand that this is RECOMMENDED for
Yes, recommended to say the least. Imagine that you build your kernel with SMP support, the module UP, if you could load that module into the kernel bad things would surely happen (and that's just one of many things that could be mismatched and lead to disaster).
obvious reasons, but is it ENFORCED???
It's somewhat enforced, but not 100% enforced, it is possible to trick the kernel into loading a module not build specifically from it, but enough sanity checks are made to make it quite unlikely that you can accidentally load a module that's not compatible. If you read the load_module() function from kernel/module.c you'll see that it checks things like the ELF version, Architecture, version magic numbers, Also, if your kernel was build with module versioning enabled, then the Module.symvers file will, in adition to a list of all exported symbols, contain a CRC of the full prototype of all symbols, that will then also be checked on module load.
How? Config information isn't embedded in the kernel module, right?
A bit actually is, the modmagic/vermagic string - not everything, but a few of the most important bits. See include/linux/vermagic.h Also see Documentation/kbuild/modules.txt -- Jesper Juhl <jesper.juhl@xxxxxxxxx> Don't top-post http://www.catb.org/~esr/jargon/html/T/top-post.html Plain text mails only, please http://www.expita.com/nomime.html -- To unsubscribe from this list: send an email with "unsubscribe kernelnewbies" to ecartis@xxxxxxxxxxxx Please read the FAQ at http://kernelnewbies.org/FAQ
