On Thu, Oct 22, 2015 at 3:38 PM, Jeff Haran <Jeff.Haran@citrix.com> wrote:

From: kernelnewbies-bounces@kernelnewbies.org [mailto:kernelnewbies-bounces@kernelnewbies.org] On Behalf Of Kenneth Adam Miller
Sent: Thursday, October 22, 2015 12:14 PM
To: Kernelnewbies
Subject: Query Hard Memory Addresses

So, previously it was discussed that /dev/mem could be used to mmap a specific hardware memory into a process. Now I need to unit test some userland code that does exactly that, but I need to make sure that the unit test selects a small page that is always free in kernel land. How can I query mem to just grab the location of a free page?

(my development setup is different from my other deployment; in deployment these values are hard coded, in development they occur on a qemu emulator)

I suppose it might work to write a kernel module that allocates a page in its init routine and then provides the address to user space via a /proc entry.

Well see now we're back to where I was before finding out about /dev/mem.

In any case, I think I can isolate my userland tests with some shared memory regions at the process level, and then in the production environment serve up a buffer grabbed by mmap.

Jeff Haran