Alloc and lock down large amounts of memory

[Bhavana Nagendra]

Hi,

I have a few questions with regards to alloc'ing and locking down memory.
An example 
would be very useful.  Please CC me on any responses.

1. Is there a mechanism to lock down large amounts of memory (>128M, upto
256M).
    Can 256M be allocated using vmalloc, if so is it swappable?
2. Is it possible for a user process and kernel to access the same shared
memory?
3. Can a shared memory have visibility across processes, i.e. can process A
access 
memory that was allocated by process B?
4. When a process exits will it cause a close to occur on the device?

Thanks,
Bhavana