Question about dataspace

Yuxin Ren ryx at
Wed May 14 03:45:46 CEST 2014

For the unmapping stuff, can you tell me a little more in detail.
I do not  understand the parameters of unmap function.
Thank you so much.

On Tue, May 13, 2014 at 3:55 PM, Adam Lackorzynski <
adam at> wrote:

> On Tue May 13, 2014 at 20:56:54 +0800, Yuxin Ren wrote:
> > Can I alloc and free memory without dataspace?
> The quick answer is: no. The reason is that there need to be some
> service (the allocator) which gives you the memory. And that allocator
> would need to talk a different protocol. However, the L4Re ones use
> dataspaces.
> > I know we can do memory mapping over IPC, using L4::Ipc::Snd_fpage
> > and L4::Ipc::Rcv_fpage.
> > So after a client gets a piece of memory mapping in, how does it ummap
> that
> > memory? Still use deattach or anyting else?
> When handling the virtual memory space directly with fpages both
> dataspaces and the region management are out of the game. You should
> still reserve that area with L4Re::Rm::reserve_area to block the area
> from use by the region management.
> Unmapping can be done, for example, via
> L4Re::Env::env()->task()->unmap().
> > Does Fiasco manage memory in user level or kernel level? That is to say,
> > attach and deattach function are just system call or normal
> > IPC invoking some serve in the user level?
> Fiasco just provides the mechanism to established mappings (page table
> entries) to an address space (a task). Managing those mappings is up to
> user-space. So, for example, the region management is completely
> implemented in user-level.
> Adam
> --
> Adam                 adam at
>   Lackorzynski
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