base-linux ram dataspace file descriptor usage

[Johannes Kliemann]

Hi all,

I'm struggling with modifying the Ram_dataspace in base-linux.
I have replaced the file descriptor opened in
> void Ram_dataspace_factory::_export_ram_ds(Dataspace_component *ds)
in base-linux/src/core/ram_daraspace_support.cc by opening a special
device file that provides mappable ram.

I have attached the exact diff that causes the segfault. The kernel
module that provides the device file and the ioctl is available at [1].
I have tested it on a Linux system and mapping memory and
reading/writing it worked flawlessly.

With this change each component creates a segmentation fault. I was not
able to trace it, I couldn't even find out in which file it occurs.
The instruction pointer randomly appeared in
repos/base/src/lib/base/lock.cc or in repos/base/src/lib/base/heap.cc. I
have touched neither of these files.

Is there any information about where this is used exactly? I was unable
to trace the usage of the mapped memory beyond Region_map_mmap::attach.
I have also traced the calls inside the kernel module and it looks as it
only uses open, mmap and close so there shouldn't a problem.
I'd like to give you further information about this but I have
absolutely no idea by myself.

Regards,
Johannes

[1]:
https://github.com/jklmnn/hwiodev/blob/0f5d367162812ee015434e5b97fdf208ef362215/hwio.c
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