kernel modules and 64-bit kernels

kernel modules and 64-bit kernels

[devnetfs]

[posted this query on kernelnewbies@nl.linux.org earlier]

Hello,

Do kernel modules need to be aware that they are running in a 64-bit
kernel or a 32-bit kernel? 

I guess yes, especially interacting with 32-bit userspace programs.
For e.g. if a 32-bit program (running on a 64-bit kernel) passes a
pointer to the kernel module (via an ioctl), how does the kernel/module
know that its a 32-bit address? the sizeof(pointer) changes in
kernel/userspace in this case. So in the ioctl handler the kernel
modules does how many bytes of copy_from_use() to get the ioctl args?

How should be the modules be written so they work both on 32/64-bit
kernel AND can interact with both 32/64-bit userspace programs in
a 64-bit kernel??

Any links, pointers to relevant HOWTO/docs/source will be very useful.

Thanks,
A.

ps: Please Cc: me the reply. I am not on this mailing list.

__________________________________________________
Do you Yahoo!?
Yahoo! Mail Plus - Powerful. Affordable. Sign up now.
http://mailplus.yahoo.com

Re: kernel modules and 64-bit kernels

[Andi Kleen]

devnetfs <devnetfs@yahoo.com> writes:

> Do kernel modules need to be aware that they are running in a 64-bit
> kernel or a 32-bit kernel? 

Yes, if they want to support 32bit programs in a 64bit kernel they 
usually need ioctl translation and sometimes syscall translation
(if they have own ioctls or syscalls) 


> How should be the modules be written so they work both on 32/64-bit
> kernel AND can interact with both 32/64-bit userspace programs in
> a 64-bit kernel??

http://www.firstfloor.org/~andi/writing-ioctl32


-Andi