Question

I have a program. I want it to be able to mmap a particular region of memory over different runs.

I have the source code of the program. C/C++
I control how the program is compiled. gcc
I control how the program is linked. gcc
I control how the program is run (Linux).

I just want to have this particular region of memory, say 0xabcdabcd to 0xdeadbeef that I mmap to a particular file. Is there anyway to guarantee this? (I have to somehow make sure that other things aren t loaded into this particular region).

EDIT:

How do I make sure that nothing else takes this particular region in memory?

Answer 1

You cannot make sure that nothing else takes that area of memory - first come, first served. However, as you need a particular part of the memory, I m guessing that you have a pretty specialized environment, so you simply need to make sure that you are first (using start scripts)

Answer 2

You need to do two things:

Specify the starting address as the first argument to mmap.
Include the MAP_FIXED flag.

For the starting address, you need to make sure it s a multiple of the pagesize. To get the pagesize, use the call sysconf(_SC_PAGESIZE) (that s the appropriate call on Linux, other platforms may be different).

Answer 3

Pass the address to map in addr. Try to get it on a 8KB boundary. You could try mlock() instead though.

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